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[ { "answer_id": 82396, "author": "a4android", "author_id": 22159, "author_profile": "https://worldbuilding.stackexchange.com/users/22159", "pm_score": 2, "selected": false, "text": "<p>No. It would be too dangerous. The danger doesn't arise from coping with dual causality situations on any of the planets. Matter existing backwards in time is <a href=\"https://en.wikipedia.org/wiki/CPT_symmetry\" rel=\"nofollow noreferrer\">antimatter</a>. </p>\n\n<p>As everybody knows when matter and antimatter meet a lot of gamma radiation happens very quickly. This will be fatal.</p>\n\n<p>Potential colonists will soon be dispersed in the form of rapidly expanding plasma accompanied by large amounts of gamma radiation. This means colonization will be impossible.</p>\n\n<p>There is a good chance no-one will realize the solar system is a place where time flows backwards because all the matter in this solar system will be antimatter. It will be classified as an antimatter solar system.</p>\n\n<p>ADDENDUM:</p>\n\n<p>The relationship between antimatter and time reversal is established by a derivation of the CPT Theorem. (Vide the Wikipedia entry linked above.)</p>\n\n<blockquote>\n <p>This defines a CPT transformation if we adopt the Feynman-Stueckelberg\n interpretation of antiparticles as the corresponding particles\n traveling backwards in time. This interpretation requires a slight\n analytic continuation, which is well-defined only under the following\n assumptions:</p>\n\n<pre><code>The theory is Lorentz invariant;\nThe vacuum is Lorentz invariant;\nThe energy is bounded below.\n</code></pre>\n</blockquote>\n\n<p>In words, matter moving backwards in time will be antimatter. Therefore, if there is a solar system where time flows backwards its matter will be antimatter.</p>\n" }, { "answer_id": 82400, "author": "SZCZERZO KŁY", "author_id": 30912, "author_profile": "https://worldbuilding.stackexchange.com/users/30912", "pm_score": 1, "selected": false, "text": "<p>Above answers provide scientific explanation to why it's not possible. Regular sc-fi explanations would also yield the same answer but for a different reason. </p>\n\n<p>In that solar system the colonization took place already. In that solar system YOU are the BttF Butch, you are the Connor (from Terminator 2&amp;3), you are Sarah Connor (from Terminator). Depending on your chosen time travel rules. \nThose people travel back in time while you are going forward. </p>\n\n<p>So for example, you can't colonize the system now because of the antimatter. But in 500 years they figured out how to overcome this and send a ship. And that ship is the one that started the world you've seen 500 years earlier. </p>\n" } ]

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[ { "answer_id": 83726, "author": "ventsyv", "author_id": 10293, "author_profile": "https://worldbuilding.stackexchange.com/users/10293", "pm_score": 2, "selected": false, "text": "<p>First off, Mercury is much smaller than Earth (2400km vs 6300km radius), if you compare the cores without taking into account the rest of the planet you'll find that they are of similar size:</p>\n\n<pre><code>2400 * 42% = 1008km\n6300 * 17% = 1071km\n</code></pre>\n\n<p>I think what that means is that the rest of Mercury simply eroded away. </p>\n\n<p>But let's say we have a planet with radius of 6300km and core radius of 2600km (42% of the total radius). What would the effects be?</p>\n\n<p>That depends on what we mean by core. Here is what the Earth's structure looks like:\n<a href=\"https://i.stack.imgur.com/Clga4.gif\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/Clga4.gif\" alt=\"enter image description here\"></a></p>\n\n<p>The coresponding densities can be found here: <a href=\"http://hyperphysics.phy-astr.gsu.edu/hbase/Geophys/earthstruct.html\" rel=\"nofollow noreferrer\">http://hyperphysics.phy-astr.gsu.edu/hbase/Geophys/earthstruct.html</a></p>\n\n<p>Density grows with depth and you want the total radius to stay the same, so depending on which layers you grow you'll get different effects.\nGrowing the denser layers will give you an increase in average density, therefore you'll end up with higher gravity.\nMore iron in the core will also lead to stronger magnetic field. </p>\n\n<p>Those are the two most obvious effects that I can think off.</p>\n" }, { "answer_id": 88798, "author": "LargeDan69", "author_id": 41487, "author_profile": "https://worldbuilding.stackexchange.com/users/41487", "pm_score": 0, "selected": false, "text": "<p>Like ventsyv stated, the gravity on this planet would be much greater. However, If animals developed with stronger bones to stand this gravity, its magnetic field would indeed be much stronger as well. This would lead to the planet's ability to harbor a much thicker atmosphere, which would in turn protect life there from solar-radiation and space debris much easier. Hope this helped</p>\n" } ]

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[ { "answer_id": 84518, "author": "Sasha", "author_id": 38408, "author_profile": "https://worldbuilding.stackexchange.com/users/38408", "pm_score": 5, "selected": true, "text": "<p>Right, this will be a very rough estimation since I'm not an engineer. </p>\n\n<p>First and foremost cars. </p>\n\n<p>According to what I could find online you have about 700K cars in the city, each weighing 4009 pounds (1818.452Kg), so considering that almost all of the car's weight will be metallic components then you have 1,272,916.4 tons.</p>\n\n<p>Add to that the 6,384 subway cars at around 38 tons each for 242,592 tons.</p>\n\n<p>1,2K real trains, each one weighing about 500 tons, for a total of 600,000 tons</p>\n\n<p>For buildings things get a little more complicated, but using the Empire State building as an example, it has 60,000 tons of steel and weights a total of 365,000 tons. So it would give about 16,5% of the total weight in steel, considering that buildings under 30 floors will have half of that we will come to:</p>\n\n<p>47,000 buildings with 24,373 total floors in buildings over 30 floors and 225,203 floors in buildings under 30 floors.</p>\n\n<p>The Empire State building has 102 floors, so that would give about 3,578.5 tons per floor, that would give about 600 ton of steel per floor. </p>\n\n<p>That would give a total of 14,623,800 ton of steel in the bigger buildings and 67,560,900 tons of steel in the smaller ones. </p>\n\n<p>Ships: According to the NY Harbor website there are 351 ships in harbor right now, since OP says the harbor is more filled then usual, I'll hazard a guess and say it will have about 500 ships of considerable size (600.000 tons). </p>\n\n<p>Bridges: According to Wikipedia there are over 2000 bridges and tunnels in New York with an average length of 952,3 meters. </p>\n\n<p>Taking the Brooklyn Bridge as an example, it has an weight of 14,680 tons, with a span of 1.833677 Km and 3084.42 tonnes of steel in it. This would give about 1,682.09 Tons of steel per kilometer. Giving an total of: 3,203,719.27 tons of steel. </p>\n\n<p>Guns: Apparently there are 1,2 million registered guns in NY, so for practicality I'll assume there are 2 millions guns in NY total. I'll consider that they will have an average weight of 0,5kg and add another 0,5kg as ammo for each one. This would bring about 2,000 Tons. </p>\n\n<p>Only that will amass about 387,505,927.67 tons of steel in New York for your snake to feed on. At the rate you specified the snake will devour it all in about 5 and a half months if my calculations are right. </p>\n\n<pre><code>+-----------------------+---------------+---------+-------------+\n| Item | Tons per item | Count | Total |\n+-----------------------+---------------+---------+-------------+\n| Car | 1.818452 | 700000 | 1272916.4 |\n| Subway car | 38 | 6384 | 242592 |\n| Real trains | 500 | 1200 | 600000 |\n| Tall building floors | 24373 | 600 | 14623800 |\n| Short building floors | 225203 | 300 | 67560900 |\n| Ships | 500 | 600000 | 300000000 |\n| km of bridges/tunnels | 1682.09 | 1904.6 | 3203708.614 |\n| Guns | 0.001 | 2000000 | 2000 |\n| Total | | | 387505927 |\n+-----------------------+---------------+---------+-------------+\n</code></pre>\n" }, { "answer_id": 84538, "author": "Separatrix", "author_id": 16295, "author_profile": "https://worldbuilding.stackexchange.com/users/16295", "pm_score": 2, "selected": false, "text": "<p>If given a target, possibly indefinitely.</p>\n\n<p>Assuming the area is quarantined once it shows up and no new sources of steel arrive</p>\n\n<p>Once the area is clean, the size of the railgun rounds will mean its own spent ammunition make up the largest deposits of ferrous metal in the surrounding area. Assuming the thing isn't intelligent, if you can keep it shooting you can keep it chasing its own tail indefinitely.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/83825", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/75/" ]

[ { "answer_id": 84948, "author": "Aify", "author_id": 6453, "author_profile": "https://worldbuilding.stackexchange.com/users/6453", "pm_score": 6, "selected": false, "text": "<h1>You need an Alcubierre Warp Missile.</h1>\n\n<p>Let's take the theoretical route for this. Theoretically, as the missile goes into warp, the Alcubierre drive creates a bubble around the missile. The missile warps the fabric of spacetime as it travels to its destination (which should be set right in front of the target). The space behind the ship expands, the space in front compresses. Sounds simple, right? </p>\n\n<p>Except for the dangerous part; there are a ton of high energy particles shooting around in space. The farther the missile has to travel, the more of these particles it will encounter. These particles get stuck in the bubble around the missile, and when the missile finally arrives at its destination, the particles shoot out in a cone directly in front of your ship.</p>\n\n<p>With enough travel time, you could destroy planets. The target also literally won't even see it coming since it's a faster than light missile. </p>\n\n<p><strong>Turns out the best bomb isn't even a bomb. It's a warp drive.</strong></p>\n\n<hr>\n\n<p>Reference:\n<a href=\"https://arxiv.org/abs/1202.5708\" rel=\"noreferrer\">https://arxiv.org/abs/1202.5708</a></p>\n\n<p><a href=\"https://arxiv.org/pdf/1202.5708.pdf\" rel=\"noreferrer\">Here's a link to the actual pdf of the research paper.</a></p>\n" }, { "answer_id": 84955, "author": "Andrew Dodds", "author_id": 33469, "author_profile": "https://worldbuilding.stackexchange.com/users/33469", "pm_score": 3, "selected": false, "text": "<h1>We called it the <a href=\"https://en.wikipedia.org/wiki/Tsar_Bomba\" rel=\"noreferrer\">Tsar Bomba</a></h1>\n\n<p>With a fireball 8 kilometers in diameter, this would put a serious dent in even your biggest ships. And this 50Mt design could scale to 100Mt just by changing the lead surround to uranium.</p>\n\n<p>The question of 'can we make bigger bombs' is already answered <a href=\"https://worldbuilding.stackexchange.com/questions/60557/could-we-build-and-deploy-a-multi-gigaton-nuclear-bomb-with-todays-technology\">here</a>. Gigaton yields, that would turn your Super Dreadnoughts - and any escorts that were too near them - into scrap are entirely possible.</p>\n\n<p>Warp missiles are way cooler, though.</p>\n\n<p>Edit - it's also worth looking at '<a href=\"https://en.wikipedia.org/wiki/Bunker_buster\" rel=\"noreferrer\">Bunker Buster</a>' bomb designs. Even with WWII specs, these can go through several meters of reinforced concrete before exploding. With space battles, missiles can accelerate to much greater speeds. A bunker-buster design - with an extended delay fuse allowing it to penetrate deep into the target ship before exploding - would be even more damaging than a surface strike.</p>\n\n<p>There are also secondary explosions to consider. Battleships of WWI and WWII carried vast amounts of explosives, as the few surviving crew of the <a href=\"https://en.wikipedia.org/wiki/HMS_Indefatigable_(1909)\" rel=\"noreferrer\">Indefatigable</a>, <a href=\"https://en.wikipedia.org/wiki/HMS_Queen_Mary\" rel=\"noreferrer\">Queen Mary</a>, <a href=\"https://en.wikipedia.org/wiki/HMS_Invincible_(1907)\" rel=\"noreferrer\">Invincible</a>, <a href=\"https://en.wikipedia.org/wiki/SMS_Pommern\" rel=\"noreferrer\">Pommern</a>, <a href=\"https://en.wikipedia.org/wiki/HMS_Hood\" rel=\"noreferrer\">Hood</a>, <a href=\"https://en.wikipedia.org/wiki/HMS_Barham_(04)\" rel=\"noreferrer\">Barham</a>, <a href=\"https://en.wikipedia.org/wiki/Japanese_battleship_Kong%C5%8D\" rel=\"noreferrer\">Kongo</a>, and <a href=\"https://en.wikipedia.org/wiki/Japanese_battleship_Yamato\" rel=\"noreferrer\">Yamato</a> would attest - indeed, if your fighters can target penetrating missiles at the magazines of these Super-Dreadnoughts they don't need huge warheads, they just need to set off the warheads of the target. A standard technology of antimatter warheads would be VERY liable to go up in a firework display in an accident.</p>\n" }, { "answer_id": 84956, "author": "glyphin", "author_id": 11528, "author_profile": "https://worldbuilding.stackexchange.com/users/11528", "pm_score": 3, "selected": false, "text": "<p>Fusion bomb-pumped laser to penetrate the armor. With a normal nuclear bomb, energy goes in all directions, so at least half of it goes wasted into outer space. Note that the effects of bombs in atmosphere are different - blast overpressure and heating of the atmosphere does most of the destruction. In space, you only benefit from the thermal effects, which amounts to about 35% of the bomb's energy. Then, if your bomb doesn't detonate directly next to the ship, even more gets thrown away into outer space.</p>\n\n<p>The energy of your nuclear bomb is better utilized concentrated into a single direction via a laser. The collimated beam of the laser will be more effective at penetrating thick armor and causing destruction once inside.</p>\n\n<p>You may want to check out David Weber's treatment of space battles if you're not already familiar.</p>\n\n<p>Also, diamond is not a strong material. It is very hard but breaks easily.</p>\n" }, { "answer_id": 84961, "author": "Just another Java programmer", "author_id": 37968, "author_profile": "https://worldbuilding.stackexchange.com/users/37968", "pm_score": 1, "selected": false, "text": "<p>Shoot cannon balls of anti-matter at them. Then their shielding won't matter and the mass of the canon ball can be quite low. The ships transporting them can thus be small. \nThe mechanism for transporting and firing could be done using magnetism as direct contact is fatal.</p>\n" }, { "answer_id": 84962, "author": "Rekesoft", "author_id": 34298, "author_profile": "https://worldbuilding.stackexchange.com/users/34298", "pm_score": 4, "selected": false, "text": "<p>I'm with Burki here. A kinetic impactor is all that you need. Since your universe has engines capable of accelerating monstrous megaships kilometers long, with several meters thick armour, you can also accelerate a tiny ship in much less time and/or to a higher speed, depending if fuel is a conditionant or not - if it is not, speed of light should be the fastest non-warping speed your projectiles can achieve.<br/>\nYou can make a light autonomous vehicle with a plutonium or uranium hollow nose and let it crash against the ship at several kilometers per second. The hollow nose is to make sure the uranium or plutonium is critically compressed on impact. Design the vehicles carefully to make the projectile to penetrate just about four or five meters in the hull, then the nuclear explosion will project the rest of the armour thickness as shrapnel into the ship. The thick armour will make this shrapnel to ricochet through the ship - maximum effect for bow or stern enfilades.<br/>\nWith enough speed, as Burki said in the comment, you don't even need the fission part. Just any blunt, heavy object accelerated to nearly lightspeed will do.</p>\n" }, { "answer_id": 84969, "author": "Willi", "author_id": 28199, "author_profile": "https://worldbuilding.stackexchange.com/users/28199", "pm_score": 4, "selected": false, "text": "<h2>A block of Iron, or whatever element you like, heck, even wood</h2>\n<p>While this sounds like a rather stupid answer, i will still try to explain AND be short:</p>\n<p>The correctness of this answer depends on how fast your Bombers + your Cruiser can go. I here assume that they can go very fast, since we have ftl communication. I also assume that they can accelerate to that speed quite fast.</p>\n<p>Here´s how it works:\nBuilt some blocks of... lets say 1 Ton each. Depending on what material you use, you can save yourself some space. So osmium (has a higher density) should be better than wood (not saying that wood wouldnt work).</p>\n<p>Now, depending on how many Tons your Bombers can carry (they are quite big), pack a few of those into your ships. I will just say they can take 5 here, you can calc your own amounts for your story.</p>\n<p>Here come´s the trick:</p>\n<p>You just accellerate your ships to the maximum speed they can go, probably something near the speed of light? Lets take 90% of it:</p>\n<p>269.813.212 meters/second.</p>\n<p>now lets calculate the kinetic energy, a ton of mass with that speed would have:</p>\n<p>e= 1/2 * m * (v^2)</p>\n<p>Kinetic energy: 1/2 * 1000kg * (269.813.212)^2 = 3.6399585e+19 J</p>\n<p>so 1 of our Missiles would have an Energy of ~3.64e+19 Joule ( = 3.64*10^19) on one of our enemy ships. Now lets take this into perspective of what we earthly humans have achieved in terms of Energy (From wikipedia, Orders of Magnitude):</p>\n<p>Tsar Bomba:</p>\n<p>2.1×10^17 J</p>\n<p>Estimated energy released by the eruption of the Indonesian volcano, Krakatoa, in 1883 :</p>\n<p>8×10^17 J</p>\n<p>So this simple block of mass is getting quite higher in terms of destruction force that our yet best bomb and should be fine to destroy one of those biggies.</p>\n<p><em>Not confident enough?</em>\nDouble the mass, double the destruction power (note that this is only about going from 1 ton to 2 tons, todays bombs are quite bigger, so increased mass should really be no problem).</p>\n<p>Speed is another thing. If you ships can go even faster, closer to the speed of light, the Energy increases in magnitude of 2. So double the speed, quadruple the energy. Relativity is becoming even more important here, the closer to the speed of light, the crazier the amount of energy goes, while reaching infinity at speed of light.</p>\n<h3><em>In addition</em></h3>\n<p>This is not my idea and it is not very new. Once you can reach high speed close to the speed of light, the most destructive forces are not Bombs or anything like that, mass itself becomes the killer of everything. There are even theories how to destroy whole planets, just buy putting a few tons of mass faar away from a planet, and let it &quot;fall&quot; into it, or accelerate it into it. The mass in addition with the speed becomes so powerfull, nothing comes close to those energies.</p>\n<p>Now your ships just drop of some of these loads on your enemies, either one by one or calculated to hit at the same time, you can destroy whole fleets with just one of those loads (again, here depending on mass-capacity and speed of your bombers). So all in all, one of your 25.000 Bombers can take out lets say up to 5 Biggies. resulting in 125.000 Dead biggies per run. But my guess here is that your Bombers can carry a lot of more weight, but i didnt want to overestimate. So maybe give some comment about speed and mass they can carry, to make more accurate guesses.</p>\n<h2>Tldr</h2>\n<p>Pack a ton of whatever into those ships, accellerate them towards your target, release the mass, return to base and get some more tons of whatever and repeat. Your enemies will think (the other ones, not the ones you hit) they got stuck in some kind space storm full of material while blowing up one after another, or all together)</p>\n" }, { "answer_id": 84989, "author": "Nzall", "author_id": 227, "author_profile": "https://worldbuilding.stackexchange.com/users/227", "pm_score": 4, "selected": false, "text": "<h2>Self-replicating nanobots</h2>\n<p>There is very little chance that a space faring species that can build ships that are bigger than any mountain in our solar system has not yet gone into atomic-scale engineering. Build something that turns the armour materials into more of itself, do hit and run attacks against the enemy fleet with suicide ships that just crash in the enemy ships. You just need to crash one ship per enemy ship (which can even be so small that they don't notice it on sensors, or can be disguised as an asteroid) and depending on how fast your nanobots are, the enemy ship will quickly be disabled or even eaten alive. As an additional benefit, the enemy cannot salvage whatever's left of the ship.</p>\n" }, { "answer_id": 84992, "author": "Yakk", "author_id": 2473, "author_profile": "https://worldbuilding.stackexchange.com/users/2473", "pm_score": 4, "selected": false, "text": "<h1>We could build the bomb with current tech</h1>\n<p>There is no kill like overkill.</p>\n<p>We want to reduce diamond-double-lead to gas or plasma. How much? How about all of it.</p>\n<p>Take the largest ship. It has a surface of 28 km * 14 km * 8 km, times 15 meters.</p>\n<p>That is (28 km * 14 km * 2 + 14 km*8 km * 2 + 8 km * 28 km * 2) * 15 m = 2.2E13 liters.</p>\n<p>From <a href=\"http://www.materialsdesign.com/appnote/cohesive-energy-diamond\" rel=\"noreferrer\">http://www.materialsdesign.com/appnote/cohesive-energy-diamond</a> we get that it takes about 18 eV to break one Carbon-Carbon bond in a diamond.</p>\n<p>Each Carbon in a diamond has 4 bonds, so it is 36 eV per Carbon atom.</p>\n<p>Lead is 11.34 g/cm3, so we have about 5.5E14 kg of armor here.</p>\n<p>We'll assume C-12, so every 12 grams has 6E23 atoms.</p>\n<p>5.5E14 / 12 * 6E23 * 36eV is 1.5E20 Joules.</p>\n<p>1 megatonne is 4E15 Joules. So to reduce the biggest ship to its constituent atoms you need to apply about 40,000 megatonnes (40 gigatonnes).</p>\n<p>The largest hydrogen bomb we have set off on Earth is about 50 megatonnes. So you just need something 1000 times more powerful.</p>\n<p>Assuming we explode it near the target, something like 75% of the energy will be wasted (go the wrong way). That is just another factor of 4. Peanuts.</p>\n<p>This just turns everything into free carbon atoms. Plasma would require also exciting the electrons to break free of the atom. From <a href=\"http://www.chembio.uoguelph.ca/educmat/atomdata/bindener/grp14num.htm\" rel=\"noreferrer\">http://www.chembio.uoguelph.ca/educmat/atomdata/bindener/grp14num.htm</a> we see that it is on the same order of magnitude (about 1/3?) as breaking the carbon-carbon bonds in diamond, so throw another factor of 2 at the nuke yield to finish the job.</p>\n<h1>How big a bomb?</h1>\n<p>So simply apply a 320 gigatonne thermonuclear warhead on your weapon, and set it for a proximity explosion. Most of the ship should be reduced to plasma.</p>\n<p>There is no upper limit on the explosive power of a thermonuclear bomb. There where plans to build a 10 gigatonne bomb using current technology: <a href=\"https://in.rbth.com/opinion/2016/01/05/nuclear-overkill-the-quest-for-the-10-gigaton-bomb_556351\" rel=\"noreferrer\">https://in.rbth.com/opinion/2016/01/05/nuclear-overkill-the-quest-for-the-10-gigaton-bomb_556351</a> -- a space fairing civilization should have no problems exceeding that.</p>\n<p>Note that these are ridiculous weapons, and you could probably succeed with smaller ones.</p>\n<p>A smaller bomb (say, 100 times smaller) would just penetrate the hull locally instead of evaporating the entire craft. We could today, with a modest engineering effort, put together a 1 gigatonne bomb and (if delivered) cripple or destroy one of the largest ships.</p>\n<p>You could also get fancy, like some kind of nuclear shaped-charge or penetrating round -- use a small nuke to knock a hole in the ship, then drop another nuke into that hole to cook the ship from the inside.</p>\n<h1>The fundamental problem here</h1>\n<p>Chemical bonds are weak compared to nuclear energy levels. As your ship is defended by chemical bonds, it has no real durability. The near parts of the ship would become highly energized radiation and deposit the energy further in. The ship's matter itself would become the blast wave.</p>\n<p>The point I'm trying to make is that the ships you designed aren't that tough. The energy required to move Planetoids dwarfs the effort required to atomize these ships, making even the bombs I'm describing puny.</p>\n<p>You are describing impressive chemical-era weapons in an atomic era.</p>\n<p>Your ships, as impressive as they sound, are mild evolutions of someone carrying an volcanic-glass sword and wearing animal hides -- they are merely weapons based on electron bonds between atoms.</p>\n<p>We are <em>currently</em> in the atomic era, chemical bonds are not an effective defence against atomic era weapons.</p>\n<p>An interstellar civilization should have weapons that make our atomic and thermonuclear weapons look like toys, much like atomic bombs make obsidian swords look like toys.</p>\n<p>The energy required to travel between stars, move planetoids, etc is large. Ships designed with chemistry-based armor or weapons are not ships of war in such an era. At best they are police craft.</p>\n" }, { "answer_id": 85000, "author": "Thucydides", "author_id": 8572, "author_profile": "https://worldbuilding.stackexchange.com/users/8572", "pm_score": 3, "selected": false, "text": "<p>The answer is \"Kinetic Energy\" as mentioned by several other posters. At even interplanetary speeds, the amount of kinetic energy being delivered by the impact of an inert mass is astounding, and this only goes up (the ultimate example being a <a href=\"https://en.wikipedia.org/wiki/Relativistic_kill_vehicle\" rel=\"nofollow noreferrer\">RKKV</a> moving at 90% of <em>c</em>, which can destroy a planet). Dumping the litterbox of the ships cat out the airlock could be a dangerous weapon under the right circumstances.</p>\n\n<p>Since arranging for a head on pass might not be a good tactic, and the ship's cat has ways of making its annoyance with people stealing its litter known, we need to find an alternative. Since you mentioned \"bombs\", the answer is actually using nuclear bombs to drive weapons effects.</p>\n\n<p>A spherical explosion is not very efficient, and since in the vacuum of space energy is only transmitted by radiation, a conventional nuclear bomb is not an efficient use of energy. Using clever technology to direct the energy of a nuclear device, you can create the analogues of shotguns, shaped charges, explosively formed projectiles and even working plasma weapons which focus the energy of the nuclear device in one direction and can deliver effects like driving pellets at 100km/sec (the \"nuclear shotgun\") to a spear of star hot plasma moving at @ 10% of the speed of light. Intermediate effects like nuclear shaped charges send streams of metal at the target as @ 3% of <em>c</em>.</p>\n\n<p><a href=\"https://i.stack.imgur.com/aVdLN.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/aVdLN.jpg\" alt=\"enter image description here\"></a></p>\n\n<p><em>The basis of everything else: the nuclear energy is preferentially directed through the Channel filler in the microseconds before the device is vapourized</em></p>\n\n<p>There is an extended discussion of these sorts of weapons <a href=\"http://toughsf.blogspot.com/2016/06/the-nuclear-spear-casaba-howitzer.html\" rel=\"nofollow noreferrer\">here</a> and <a href=\"http://toughsf.blogspot.com/2017/05/nuclear-efp-and-heat.html\" rel=\"nofollow noreferrer\">here</a>, as well as at the ever handy <a href=\"http://www.projectrho.com/public_html/rocket/\" rel=\"nofollow noreferrer\">Atomic Rockets</a> website under <a href=\"http://www.projectrho.com/public_html/rocket/spacegunconvent.php\" rel=\"nofollow noreferrer\">conventional weapons</a>.</p>\n\n<p>So in some sense, super massive spaceships the size of aircraft carriers and above are counterproductive, given the energies that can be deployed in space. To me, a fleet like that screams \"Target!\".</p>\n" }, { "answer_id": 85036, "author": "Tony Ennis", "author_id": 2013, "author_profile": "https://worldbuilding.stackexchange.com/users/2013", "pm_score": 2, "selected": false, "text": "<p>I think the nuke, kinetic, and anti-matter answers are all good and practical. Therefore I'll go plaid.</p>\n\n<p>I'd develop a gravity bomb.</p>\n\n<p>It is a warhead that for a few seconds generates an intense gravity well. The gravity well is intense though not so much that it would devour a ship; it isn't a black hole. The idea is that a sufficiently close \"explosion\" will apply a significant off-axis acceleration to the ship, or even one part of the ship.</p>\n\n<p>The sudden acceleration will cause the ship's own mass to tear itself apart.</p>\n\n<p>We see this, in a way, when large ships sink. When floating they are very strong. But as they sink bow or stern first, the other end will lift out of the water. They are not designed to support their own weight; they are designed for the water to support much of it. So the ship breaks in half. The Titanic sank this way.</p>\n\n<pre><code>They might have split up or they might have capsized\nThey may have broke deep and took water\n</code></pre>\n\n<ul>\n<li>The Wreck of the Edmund Fitzgerald, Gordon Lightfoot</li>\n</ul>\n\n<p>What happens here is that a wave lifts the bow of the ship up, and the keel cannot support it. The ships breaks in two.</p>\n\n<p><strong>EDIT #1</strong></p>\n\n<p>I cannot tell if you're writing a story or creating a game. If you're creating a game, the \"gravity bomb\" idea allows you to add \"terrain\" to otherwise empty or perhaps static (unchanging) space. Now with gravity bombs one can create peaks and valleys (if you also have anti-grav bombs... why not?) of gravity that service to destroy opponents, deflect them from strategic locations, or act as a \"slingshot\" for your own ships. If they are going to be used to \"decorate\" space, they probably should last longer than a few seconds.</p>\n" }, { "answer_id": 85039, "author": "KareemElashmawy", "author_id": 34127, "author_profile": "https://worldbuilding.stackexchange.com/users/34127", "pm_score": 4, "selected": true, "text": "<h1>TL;DR: Singularity Bomb</h1>\n<h1>Honorable Mentions: The Little Doctor &amp; Warp Bomb</h1>\n<p>WOAH WOAH WOAH.</p>\n<p>I (the noble) have:</p>\n<ol>\n<li>1350 spaceships (total).</li>\n<li>150 5km carriers</li>\n<li>170 bombers <strong>with <em>self-evolving</em> AI</strong></li>\n<li>Covert FTL communication (<strong>How?</strong>) with a 5 LY broadcast range.</li>\n<li><strong>Active cloaking technology</strong>.</li>\n<li>Covert <strong>Warp</strong> Drive</li>\n</ol>\n<p>And I am expected to go up against</p>\n<ol>\n<li>Armadas numbering in the <strong>millions</strong></li>\n<li>Supported by <strong>Trillions</strong> to <strong>Quadrillions</strong> of support personell</li>\n<li><strong>Super</strong> Supply lines</li>\n<li>Mobile <strong>Planetoid</strong> Fortress Worlds</li>\n<li>With armor as hard as Diamond, but twice as dense as lead.</li>\n<li>They do not have energy shielding.</li>\n</ol>\n<h1>Modern/Theoretical</h1>\n<p>Why don't we begin with modern/theoretical science that we may discover within the</p>\n<blockquote>\n<p>ancient libraries of earth</p>\n</blockquote>\n<h3>Soviet RDS-220 (Tsar Bomba, Ivan, Vanya)</h3>\n<p>Predicted maximum yield: 100 PetaJoules (1E17J)</p>\n<h3>Antimatter</h3>\n<p>Predicted maximum yield: 1.8E14 Joules <strong>per gram</strong>.</p>\n<p>Hmm. We have AI, warp, cloaking, and FTL Technolgy. Furthermore, we can construct ships up to 28km long and transform planetoids (Dwarf planets) into ships. Mind you, planetoids can go up to a diameters up to 2372km (pluto) or (if OP meant asteroids) 975km (Ceres). In that case, I (the noble) have the technology to construct particle accelerators that would dwarf CERN's LHC <em>on the ancient earth</em>. Furthermore, CERN had already successfully trapped antimatter in those ancient times<a href=\"https://home.cern/about/engineering/storing-antimatter\" rel=\"noreferrer\">1</a><a href=\"http://press.cern/press-releases/2011/06/cern-experiment-traps-antimatter-atoms-1000-seconds\" rel=\"noreferrer\">2</a> and was nearly detonated <a href=\"http://angelsanddemons.web.cern.ch/faq/how-is-antimatter-contained\" rel=\"noreferrer\">3</a>! Oh, and best of all, that ancient machine was not very efficient at generating antimatter; but, I can build it BIGGER and BETTER with our technology. Thus, it shouldn't be too difficult to produce 1 kilogram of antimatter, let alone 10kg - 1Mg. In order, they'd have an effective yield of:</p>\n<pre><code>1 kg: 1.8E17 J\n10 kg: 1.8E18 J\n1 Mg: 1.8E20 J\n</code></pre>\n<p>Eeek. That seems to be the limit of what actually generated in those ancient times. But times has changed. Perhaps the imperium and democrats regularly generate and use antimatter, but in <a href=\"http://memory-alpha.wikia.com/wiki/Photon_torpedo\" rel=\"noreferrer\">missile form</a>.</p>\n<h1>Science-Fiction</h1>\n<p>Let's move forward to what has been proposed in science fiction! I'll use <a href=\"https://www.fatwallet.com/blog/top-sci-fi-weapons\" rel=\"noreferrer\">this list</a> for simplicity.</p>\n<h3>Akira's Orbital Laser (6.3E16J)</h3>\n<p>No Energy shields? Satellite based orbital laser? Sounds promising; but, we're looking for <em>BOMBS</em> not awesome repeatable weapons we can attack to a <strong>cloaked fighter</strong>. <em>Or are we</em>?</p>\n<h3>Photon Torpedoes (2.7E17J)</h3>\n<p>Really just a high-tech antimatter torpedo.</p>\n<h3><a href=\"http://looneytunes.wikia.com/wiki/Illudium_Q-36_Explosive_Space_Modulator\" rel=\"noreferrer\">Illudium Q-36 Explosive Space Modulator</a> (2.2E32 J)</h3>\n<p>Created by <a href=\"http://looneytunes.wikia.com/wiki/Marvin_The_Martian_(character)\" rel=\"noreferrer\">Marvin The Martian</a> of the infamous ancient <a href=\"http://looneytunes.wikia.com/wiki/Looney_Tunes\" rel=\"noreferrer\">Looney Tunes</a>.</p>\n<h3>Aperture Science Handheld Portal Device (1.78E48 J)</h3>\n<p><em>As a physicist and developer, I have no clue how they calculated this one.</em> Nevertheless, the principle is sound: Wormholes/portals. Create a bomb that creates a portal upon impact. Always ensure that portal is connected to something such as ... a star and the temperatures will strip away the ship. Hook up the portal to a counterpart orbiting a black hole... and you'll wipe out the <strong>entire fleet</strong>.</p>\n<h3>The Little Doctor (9.8E58 J)</h3>\n<p>Ah, The Little Doctor from Ender's Game. Upon impact it causes a chain reaction that rips apart molecular bonds, spreading to all nearby matter. A single one of these may destroy fleets or <a href=\"https://www.youtube.com/watch?v=IXdbCU3Mt_c\" rel=\"noreferrer\">planets</a>.</p>\n<h2>Notable Mentions</h2>\n<h3>Singularity Bomb</h3>\n<p>A popular <a href=\"http://tvtropes.org/pmwiki/pmwiki.php/Main/UnrealisticBlackHole\" rel=\"noreferrer\">scifi</a> and <a href=\"http://tvtropes.org/pmwiki/pmwiki.php/Main/PowerOfTheVoid\" rel=\"noreferrer\">high-scifi</a> trope. Harness the power of a singularity (colloquially; black hole) into a weapon. Best example I can recall would be the <a href=\"http://memory-alpha.wikia.com/wiki/Red_matter\" rel=\"noreferrer\">Red Matter</a> from Star Trek which <a href=\"https://www.youtube.com/watch?v=GUsuuFNFq2w\" rel=\"noreferrer\">annihilated</a> a <a href=\"https://www.youtube.com/watch?v=GUsuuFNFq2w\" rel=\"noreferrer\">planet</a>. Speaking more generally though, such a weapon, when detonated, would create a singularity. Immediately everything around it will be subjected to gravitational shearing and strength powerful enough to <em>rip apart not only stars but neutron stars as well</em>. Mind you, neutron stars have a density on the order of 1E17 kg/m^3 compared to the Imperium's and Democrat's 2.3E3 kg/m^3 armor. Suffice it to say that a single one of these will undoubtedly annihilate an entire fleet.</p>\n<h3>Effectiveness: 1:1,000,000+</h3>\n<p>Oh. And I forgot to mention the <a href=\"https://www.youtube.com/watch?v=_t096kPbwn4\" rel=\"noreferrer\">obscene</a> <a href=\"https://www.youtube.com/watch?v=v7OVqXm7_Pk\" rel=\"noreferrer\">time</a> <a href=\"https://www.youtube.com/watch?v=orx0H9mBeXk\" rel=\"noreferrer\">dilation</a>, and the pillar of light that would be left in your <a href=\"https://www.youtube.com/watch?v=YdSz12Glhlw\" rel=\"noreferrer\">awesome wake</a>. Who would dare to challenge thee?</p>\n<h3>Warp Bomb</h3>\n<p>You have warp drives. They expand and contract space to move your vessels across vast distances without accelerating them. More importantly, if your (my?) engineers were to construct a bomb that uses the same principles to chaotically warp space within a region around the bomb. This will generate shearing effects that rapidly expands and contracts space asymmetrically. Since spatial curvature produces the gravitational force and rapidly fluctuating spatial curvature generates gravitational waves it follows that this would create a rapidly fluctuating gravitational field that may be powerful enough to shear matter. Given it's gravitational in nature, no armor can resist or dilute the effect, only astronomical distances. Furthermore, given the strengths of your warp drives, and the intent for this weaponized use, we may easily leverage warp-physics to make the bomb more powerful than warp drives; after all, we don't care if it's unstable, in fact we'd prefer it that way. This gaurantees that it may destroy the target; but, even if we use unstable warp drives powerful enough to move planetoids (ignoring space and weight limits on our bombers), it's not enough to wipe out fleets of millions.</p>\n<h1><a href=\"https://www.youtube.com/watch?v=IvijW1MtMfM\" rel=\"noreferrer\">Conclusion</a></h1>\n<p>The most powerful of these are The Little Doctor, The Singularity Bomb, and the Warp Bomb. The first two are capable of wiping out entire fleets whereas the last is guaranteed to eliminate capital ships. In my opinion I believe the Singularity Bomb to be the most effective. It causes the most destruction (wiping out entire fleets and/or planetoids) while also being the most plausible in your universe. I say this because I've studied <a href=\"https://en.wikipedia.org/wiki/Alcubierre_drive\" rel=\"noreferrer\">Alcubierre Warp Drives</a>. Generating a warp bubble requires obscene amounts of matter and <em>exotic matter</em> (1E64 kg) to generate the field. Recent publications have theoretical shown that the this limit can be reduced dramatically; but, the warp speed is also reduced abysmally as well. Given your universe, I suspect either civilization is capable of working with a comparably obscene amount of matter.</p>\n<h1>Answer: Singularity Bomb.</h1>\n" }, { "answer_id": 85215, "author": "hszmv", "author_id": 39822, "author_profile": "https://worldbuilding.stackexchange.com/users/39822", "pm_score": 1, "selected": false, "text": "<p>I don't have many ideas about bombs but tactically, in the place of this noble, I wouldn't use carrier theory. Space battles are more likely to take place at ranges so great that ships will likely never see each other. This is the domain of Battleship theory which is all about guns and speed. Carrier is about mobility and defense (Carriers rarely go at full speed because they can out run their escorts, which is suicidal. Carrier Theory relies on escorts to protect the Mobil landing strip).</p>\n\n<p>You're correct in wanting to fight up close. Enemy seems geared for long range combat. Carriers here would no be ideal as the escorts would be inefficient defense to range combat and the carrier will be the largest target in play. Even if you stealth it, returning attack vehicles will give general location spread. Battleship theory is also better here as it's all about knowing not just where your target is, but where they will be when the bomb arrives. </p>\n\n<p>Instead, focus on submarine tactics, especially if you're limited and range rules the roost in tactics. The guns will likely be inefficient to target an enemy that's close, too prone to friendly fire to be operated, or both, if it's a difference between a few kilometers and a few light years.</p>\n\n<p>Both rely on getting close to ships without much point defense. A small one man fighter is a smaller loss than a sub, but you lose all if they return fire on the mothership. Stealth subs like ships have the ability to hit and run, line up critical shots, and confuse numbers (is it one side or one hundred?). A bomber might be less likely to hit, but a sub can at these size get just as close plus bring more things that go boom. It also puts your more valuable ships in a safety range. Your bombers are never more important than your carriers. Carrier tactics today work because Battleships can't hit a target in an airplanes flight range. But in space, and in your scale, you're dealing in ranges that make both on equal terms. The biggest threat are those that you don't see. </p>\n\n<p>With that in mind, I'd push for higher stealth and mobility especally if my fleet size is limited. Also it allows for tactics that don't destroy the ship, but leave it down. You can also get more bang for your buck not by getting a bigger bang but using a small bang in the right spot. A cherry bomb doesn't normally do enough damage to down a 747... but it can if you realize that the most vulnerable spot is under the pilot's seat. </p>\n" }, { "answer_id": 85251, "author": "Dofork", "author_id": 39370, "author_profile": "https://worldbuilding.stackexchange.com/users/39370", "pm_score": 0, "selected": false, "text": "<p>In your universe, people can move planets. By nature of this being possible, you can build some AWESOME weapons. One I would suggest is the \"planetary nutcracker\" concept, where you move two planets on the opposite sides of a fleet or planet, and launch them towards each other. Given the size of the ships involved, and that they use fusion as power, the bombers themselves are effective weapons. You might be better off shooting a gutted one of those at the enemy.</p>\n" }, { "answer_id": 109681, "author": "Efialtes", "author_id": 44413, "author_profile": "https://worldbuilding.stackexchange.com/users/44413", "pm_score": 0, "selected": false, "text": "<p>Heres my Idea:\nIf you contain about 20 grams of ionized hydrogen in a 1cm in diameter steel sphere, when the sphere breaks it creates a 1.5 megaton explosion due to the repulsive forces generated by the hydrogen ions. The hydrogen would burst forth in an expanding cloud of plasma that propagates at lightspeed and would shred everything. It would be environmentally friendly because it won't create toxic radiation. So you would just scale up the device as needed. To break the sphere you just surround it with a C-4 shaped charge and an oxygen tank designed to tear apart the shere from all directions.</p>\n" }, { "answer_id": 157813, "author": "Stefanos Zilellis", "author_id": 69357, "author_profile": "https://worldbuilding.stackexchange.com/users/69357", "pm_score": 0, "selected": false, "text": "<p>I will stick to the mass+velocity solution. Plus i add that there is no practical need to distinguish ship from payload. Been unmanned, those bombers would actually be a set of engines for thrust, their fuel, the CPU and all the rest mass will be front armor and nothing else, to protect against some enemy fire(actually mostly against other object the bullet-ship will encounter before impact). Stealth is not needed. With a velocity of 0.9 c and the slightest ability to change direction it is a joke to talk for counter fire that will turn that ship-bullet to harmless dust. Hitting that large targets though is piece of cake. Depending at what type of mass is used, chances are that the ship bullet could even hit more than 1 targets if inline, or, if mass vaporizes while within the target, the effect will be that of a shotgun at 0 range.</p>\n\n<p>And the noble hero favorite quote: Welcome to the bullet-ship era!</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/84947", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/11313/" ]

[ { "answer_id": 86256, "author": "John Dvorak", "author_id": 807, "author_profile": "https://worldbuilding.stackexchange.com/users/807", "pm_score": 5, "selected": true, "text": "<p>I'm going with yes and no. Pushing the maximum temperature is easy. Pushing the minimum temperature is much harder.</p>\n\n<p>I'll note some discrepancies with Crematoria first</p>\n\n<ul>\n<li>Wiki quotes the top temperature of +372 degrees Celsius. But the gallery also shows that the surface is lava. <a href=\"https://en.wikipedia.org/wiki/Lava#Felsic_lava\" rel=\"noreferrer\">Silicate lava is a little hotter than 372 degrees Celsius - by about 200 degrees.</a></li>\n<li>On the same note, if the temperature at mid-day is 372 degrees, it won't be so early in the morning. The image shows that the edge between lava and not-lava is as thin as the terminator line, however.</li>\n<li>Wiki also states a rotation speed - I'm assuming surface velocity at equator - of 5000 mph and rotation period of 52 hours. Quick math tells us that the equator is 400 000 km. That is ten times more than that of Earth. If the planet is of similar density as Earth (it would probably be even denser), the surface gravity is 10G. The reason Crematoria prisoners aren't able to escape isn't they'd be scorched before they reach the surface. It's because <a href=\"https://what-if.xkcd.com/116/\" rel=\"noreferrer\">they would be unable to sit or stand under their own weight</a>, and they probably have trouble breathing even when lying flat on the floor. Luckily, your planet isn't as harsh as Crematoria in this respect, it's only slightly worse than an elevator that's constantly accelerating upwards.</li>\n</ul>\n\n<p>For our first estimate, let us look at Earth's moon. <a href=\"https://www.space.com/18175-moon-temperature.html\" rel=\"noreferrer\">Space.com states</a>: </p>\n\n<blockquote>\n <p>When sunlight hits the moon's surface, the temperature can reach 253 degrees F (123 C). The \"dark side of the moon\" can have temperatures dipping to minus 243 F (minus 153 C).</p>\n</blockquote>\n\n<p>Note three things:</p>\n\n<ul>\n<li>The temperature range is half of what we're looking for at Crematoria. </li>\n<li>In case of the Moon, we are not even looking at the temperatures of the <em>same</em> spot. Note that it's not one of those places that never get sunlight - those get even colder. The article later says:\n\n<blockquote>\n <p>The Lunar Reconnaissance Orbiter measured temperatures of minus 396 F (minus 238 C) in craters at the southern pole and minus 413 F (minus 247 C) in a crater at the northern pole.</p>\n</blockquote></li>\n<li>The Moon day lasts 28 Earth days. On Crematoria it's 2.</li>\n</ul>\n\n<p>Atmosphere is pretty good at redistributing heat. Your planet shouldn't have any. I'm sorry to say, your planet won't have any life of its own, even at the poles, unless someone arrives in a spaceship. You better give them a pretty good reason - and if \"scorching hot, occasionally\" is your primary selling point, the humans are going to go visit Venus first. Much closer and much more scorching. Sulphuric acid in the atmosphere and a pressure of 20 Earth atmospheres complicates your prisoners' escapes even further.</p>\n\n<p>So, what can you do to improve on Moon's efforts on achieving the temperature difference stated?</p>\n\n<p>First a quick talk about black-body radiation, because that's your primary method your planet would be losing heat. One thing to note is that the amount of energy a bit of black-body material radiates out is given solely by its temperature. You can try to increase the surface area but then the material will be shining on itself, and it won't lose heat any faster. Real materials also aren't perfect black-bodies, so they won't be radiating as fast. The amount of energy is given by the <a href=\"https://en.wikipedia.org/wiki/Black-body_radiation#Stefan.E2.80.93Boltzmann_law\" rel=\"noreferrer\">Stephan-Boltzmann law</a> and says that the amount of radiation is proportional to the fourth power of temperature above absolute zero.</p>\n\n<p>If we look at a small patch of thermally insulated black-body material at the surface of your planet at night-time, its temperature will be governed by the differential equation $dT = c T^4 dt$ where $c$ depends on the material in question. <a href=\"http://www.wolframalpha.com/input/?i=dT+%3D+-+T%5E4++dt\" rel=\"noreferrer\">Wolfram Alpha tells us</a> that the temperature over time will follow the inverse cube root curve - the material cools down the much slower the cooler it is. Note that this assumes your planet doesn't melt in the sunlight - that would account for even more energy to dump as the material solidifies.</p>\n\n<p>Let's pick some value of $c$, let's say 1/3, and see when certain temperatures are reached, with t=0 being set to the time when the temperature is infinite.</p>\n\n<pre><code>-182 C | 89 K | 1.41850209016283×10^-6 T | coldest temperature on Crematoria\n-153 C | 120 K | 5.78703703703704×10^-7 T | coldest temperature on Moon\n 0 C | 273 K | 4.91487026929606×10^-8 T | melting point of water at standard pressure\n 123 C | 396 K | 1.61032836270057×10^-8 T | highest temperature on Moon\n 372 C | 645 K | 3.72666930328520×10^-9 T | hottest temperature on Crematoria\n</code></pre>\n\n<p>Observation: getting from infinite temperature to 0 degrees celsius is ten times faster than reaching the coldest temperature on Moon. It also takes 2.4 times longer to reach -182 C than to reach -153C. </p>\n\n<p>This gives us a few options:</p>\n\n<p>Making the material darker won't have much effect. Going from regolith to vantablack will give you a 10% speedup. Choosing a material with lower heat capacity also helps, but I can't help with that choice.</p>\n\n<p>Longer days will help. Unfortuately, you probably won't be too happy with a day that lasts as long as a month on Earth. The terminator would still be moving at an appreciable speed, so inhabiting the equator is out of the question, but someone trying to escape from a prison has plenty of time to board their spaceship.</p>\n\n<p>Speaking of which, perhaps your planet is tidally locked? That could yield some pretty nicely extreme temperatures. It doesn't mesh well with the \"only poles are inhabitable\" part of the question, though. </p>\n\n<p>Going from super-hot to just hot is quick. Going from cold to even colder takes forever. If you relax your -183C requirement a little, you can get slightly less extremely cold temperatures in substantially less time. Humanly sized lengths of days can get you to zero C just fine. This also means that the surface going from minimum temperature to maximum in the matter of a single terminator width may not have been that off, actually.</p>\n\n<p>Maybe the planet is actually just a thin shell supported by a solid layer of vacuum? Less rock = less heat capacity per square meter. Such things don't occur naturally, but there could be a massive network of underground settlements that cover 99% of the sub-surface. Don't forget the \"no native life\" clause, however. It's also nice if the builders are gone, too, so that they don't vent heat onto our nicely freezing night-side. Fully artificial body that looks like a planet is an option, too, and lets you tweak the critical parameters arbitrarily (max. temperature by tweaking the orbit, min. temperature by tweaking the planet material).</p>\n" }, { "answer_id": 86259, "author": "pablodf76", "author_id": 31844, "author_profile": "https://worldbuilding.stackexchange.com/users/31844", "pm_score": 2, "selected": false, "text": "<p>Short answer would be <strong>no</strong>, and short reason would be that <strong>an atmosphere is your enemy if you want temperature extremes</strong>, but let me take this apart a bit.</p>\n\n<ul>\n<li><p><strong>How does it get so hot during the day?</strong> The planet has to be rather close to its primary star, or there must be a thick atmosphere that retains heat and with it probably some serious greenhouse effect, or both.</p></li>\n<li><p><strong>How does it get so cold during the night?</strong> The planet has to be rather far from its primary star, or there must be little or no atmosphere capable of retaining heat when the sun sets, or both.</p></li>\n</ul>\n\n<p>As you see there are conflicting goals here. If a planet has no atmosphere it's not that difficult to achieve such temperature extremes; <a href=\"https://en.wikipedia.org/wiki/Mercury_(planet)\" rel=\"nofollow noreferrer\">Mercury</a>, for example, has </p>\n\n<blockquote>\n <p>surface temperatures that vary diurnally more than on any other planet in the Solar System, ranging from 100 K (−173 °C; −280 °F) at night to 700 K (427 °C; 800 °F) during the day across the equatorial regions.</p>\n</blockquote>\n\n<p>Having no atmosphere and a night side guarantees extreme cold simply because space is cold.</p>\n\n<p>If a planet has a dense atmosphere, extreme heat is relatively easy to achieve as well; Venus, being farther from the Sun than Mercury, is hotter because of that. But a dense atmosphere prevents heat from escaping during the night, which is why Venus is hot all around.</p>\n\n<p>If your planet has a thin atmosphere it's possible that you might have something a bit like Mars: freezing, sub-Antarctic temperatures on the night side and balmy, temperate spring-like temperatures on the day side (on the equator, at midday, in the summer). If you want to have poles with the same temperature all year round, you could posit that the planet has little or no tilt, thus eliminating seasonal variation.</p>\n\n<p>In any case, as I said, atmosphere is your enemy if you want temperature extremes. It would also work against the idea of a prison or punishment planet, unless it's a crushing, toxic atmosphere like that of Venus.</p>\n" }, { "answer_id": 86263, "author": "L.Dutch", "author_id": 30492, "author_profile": "https://worldbuilding.stackexchange.com/users/30492", "pm_score": 1, "selected": false, "text": "<p>Your planet has an average density around 2.9 g/cm3, while Earth is 5.5 g/cm3.\nThis makes the planet even less dense than Mars. </p>\n\n<p>This suggest the content of Iron is pretty low, and therefore almost no iron core can be present. No iron core means no magnetic field, and no magnetic field means gas stripping from stellar wind. On top of this with such high temperatures the gases molecules would have a pretty high velocity, further facilitating the stripping. Lack of atmosphere could justify the extreme temperature differences, though. But atmosphere is needed to support life.</p>\n\n<p>So, such a planet could not exist over time spans sufficiently long to support life development.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/86246", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/40151/" ]

[ { "answer_id": 87627, "author": "JBH", "author_id": 40609, "author_profile": "https://worldbuilding.stackexchange.com/users/40609", "pm_score": 2, "selected": false, "text": "<p>For a reality-check, you've not given us enough information. Gravitation must be balanced in a system. Without the balance planets either collide, spiral into the sun, or spin off into space. My gut tells me you didn't consider this. So I'm going to go with no, it's not plausible.</p>\n\n<p>HOWEVER, plausible is in the eye of the beholder. If you think the people most exposed to your idea will be astronomers, you should spend a bit of time looking into the science behind solar system development (or expect them to point out why it's not plausible). If you're marketing to young adults or a more general market, your solution won't be noticed as off base (we happily believe the Death Star can enter planetary orbits and not wreak havoc with tidal conditions or orbital perturbations...). Therefore, I'd focus more on writing a cool story. Your basic premise is close enough to believable that I'd happily suspend my disbelief for a good story.</p>\n\n<p>I'd like to ask after the planetary names. If the system was colonized, then they're cool. If the system inhabitants are native, the names make very little sense and stick out to me. Historically, heavenly objects are named religiously or scientifically --- not artistically. But if it were colonized, then everything's cool.</p>\n" }, { "answer_id": 99161, "author": "Catlover", "author_id": 44959, "author_profile": "https://worldbuilding.stackexchange.com/users/44959", "pm_score": 0, "selected": false, "text": "<p>With the information given and what we know about planets, there are a couple issues that I know of. </p>\n\n<p><strong>Ember</strong> Based on current scientific knowledge, it is unrealistic to say that the planet glows in the visible spectrum. The closest equivalent that I could find is that of a brown dwarf, which glows faintly in the red and infrared. The only problem is that brown dwarfs tend to be bigger than gas giants, as they cover the gap between gas giants and stars. While there is much overlap in the size, the largest planets are about twice the diameter of Jupiter, while the smallest brown dwarfs are slightly larger than Jupiter. This directly conflicts with the information that Ember is only half the size of Regis, though this is close to the limit.</p>\n\n<p><strong>Tellus Alpha and Beta</strong> While it is be possible for two planets to orbit each other as you described, the tidal effects described would cause both planets to become <a href=\"http://en.wikipedia.org/wiki/Tidal_locking\" rel=\"nofollow noreferrer\">tidally locked</a> to each other, as the Earth is to the moon. This is occurring currently with Earth, on a slow scale. For planets as you described, it would occur on a much faster timescale, with the locking likely occurring before the terraforming even began. There are inherent issues with terraforming tidally locked planets, mostly temperature-related. Of all the issues detailed here, this is the only one that I would consider an absolute impossibility.</p>\n\n<p><strong>Aegis</strong> This is not an impossibility, just an improbability. Most models of star system formation concentrate metals in inner planets. There is a scientific reason for this, partially based on our observations of existing systems, and partially based on what we know about science. It is unlikely to have such a metal rich planet so far from the center.</p>\n\n<p><strong>Regis</strong> Jupiter has a large effect on the orbits of the other planets in the solar system. You are right to assume that Sojourn's orbit would be largely affected by this. However, I would think that more than this would be affected by such a large planet, especially with so many planets spaced in such a small area. This is only a gut feeling, not a fact. (I am assuming that Regis's orbital distance is similar to Jupiter, by your descriptions.) </p>\n\n<p><strong>Glimmer</strong> As mentioned in a comment, a gas dwarf orbiting close to the sun would be unlikely to retain its atmosphere for any length of time. This due to a couple of factors, including the increased heat. </p>\n\n<p>None of these issues should be glaring to the general public, and we really do not know enough about star systems to say that most of these are absolute impossibilities.</p>\n" }, { "answer_id": 99212, "author": "ShadoCat", "author_id": 33610, "author_profile": "https://worldbuilding.stackexchange.com/users/33610", "pm_score": 0, "selected": false, "text": "<p><strong>Glimmer</strong>: As far as we can tell, gas giants cannot form near the star since star ignition tends to blow the gas away. So, Glimmer had to travel inward from the outer reaches. I find it unlikely that it could have made it that close without disrupting the other inner planets. If it was off the plane of the ecliptic it could be a capture (either an outside planet or a planet that was thrown out by another gas giant and then recaptured).</p>\n\n<p><strong>Sojourn</strong>: I find it unlikely that it could be that affected by Regis without getting kicked out completely. An interesting possibility would be for it to orbit Regis' L1 point.</p>\n\n<p><strong>The Expanse</strong>: for multiple rings, you would have to have shepherd planitoids look at Saturn's rings. Also, I find it to be less plausible for it to occur outside Regis' orbit than inside. It is just that an asteroid belt inside of Regis would make Sojourn too far away to be influenced that much. So, given how many odd things we've seen in the planetary systems that we have seen, you are probably safe in leaving it as is and just having the observers say, \"well, lookit that.\"</p>\n" }, { "answer_id": 99285, "author": "Loren Pechtel", "author_id": 264, "author_profile": "https://worldbuilding.stackexchange.com/users/264", "pm_score": 0, "selected": false, "text": "<p>You've got a big problem with Glimmer.</p>\n\n<p>First, it can't have formed there. Nor can it have spiraled in there as it would take out every planet between it's original orbit and it's current orbit. Also, planets that spiral in are in retrograde orbits.</p>\n\n<p>The only scenario I see that could make it is an insane longshot--there were two rogue planets that came through the system at the same time. They went <strong>SPLAT</strong> (We are talking a kaboom worthy of the Death Star) and what was retained became Glimmer. This not only requires the two rogues to meet at just the right spot, but with the correct energy levels that the remains go into a reasonable orbit.</p>\n\n<p>You also have a big problem holding onto the mass--more later.</p>\n\n<p>Second, in Glimmer's orbit you're going to need an awfully big planet to hold onto hydrogen (and gas worlds are mostly hydrogen.) A gas dwarf is <strong>rapidly</strong> going to bleed it's mass into space and be reduced to a rocky core.</p>\n\n<p>Now, surviving becomes a bit more possible if we replace Glimmer with a superjovian. It also makes it much more able to hold onto it's mass when things went splat. It does nothing about the insane odds against just the right splat, though.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/87625", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/6894/" ]

[ { "answer_id": 92681, "author": "L.Dutch", "author_id": 30492, "author_profile": "https://worldbuilding.stackexchange.com/users/30492", "pm_score": 3, "selected": false, "text": "<p>As already stated in getfugu's comment, you cannot have both primitive society and specialized work division.</p>\n\n<p>Considering the small size of a prehistoric village, you hardly need mass production, and will produce what needed almost always \"on demand\".\nYou would most likely have 5 roles (regardless of gender): </p>\n\n<ul>\n<li><strong>Man</strong>: takes care of hunting and defense. Prepare weapons and tools by working on the spot when the right material is found.</li>\n<li><strong>Woman</strong>: takes care of harvesting fruits and more stationary tasks like preparing food, tanning hides, crafting pots or processing vegetable fibers, taking care that toddlers and infants do not kill themselves</li>\n<li><strong>Boy</strong>: small hunt (lizards, snakes), gathering woods for the fire</li>\n<li><strong>Girl</strong>: decoration works (pottery, body garments), gathering water and raw materials for the women</li>\n<li><strong>The old ones</strong>: provide guidance to the village by using their experience (if they managed to reach old age (somewhere around 40 or 50) alive, they must have some)</li>\n</ul>\n" }, { "answer_id": 92693, "author": "TolMera", "author_id": 42107, "author_profile": "https://worldbuilding.stackexchange.com/users/42107", "pm_score": 3, "selected": true, "text": "<p>This is getting into a study of economics, but we can probably boil it down to some simple principles that you can turn into a formula.</p>\n\n<p>First off, you need to 'know' your societies minimums. These are pretty easy to figure out, just say to yourself 'What are MY minimums?'</p>\n\n<p>I need food\nI need water\nI need shelter\nI need heat</p>\n\n<p>Give me all that, and I can 'survive'</p>\n\n<p>So that's the stuff that society needs in order to exist.</p>\n\n<p>Now work out how much of the above you need?</p>\n\n<p><strong>FOOD</strong>\nI need 2000Kcal of food a day. [So I looked at a chart][1]\nFor beef there's an average 223.6 Cal's per 100 grams of meat. That means I need (rounded) 900 grams of meat a day. Cows weigh 700 ~ 900 Kilograms, but wild animals are probably a fair bit lower in weight than that, so lets just say that 1 animal is going to weigh 500 Kilograms. After Skinning, gutting a deboning you will be left with approximately 1/2 the weight of the animal as food. So your average wild cow is going to give you 250Kg of Meat.</p>\n\n<p>That is 278 meals worth of meat.</p>\n\n<p>That means you can support a society of 278 people with 1 hunter getting 1 kill every single day! (damn good hunter)</p>\n\n<p><strong>WATER</strong>\nWater, you need about 2 Litres a day if you're not a heavy labourer, and lets just say that your society works pretty hard, so everyone gets 3 litres of water a day.</p>\n\n<p>Water is HEAVY. This is the number one reason why societies exist around tributaries and oceans. Water is going to require a lot of man power to get and distribute.</p>\n\n<p>I can't remember the exact details of how much weight an average person can carry, and how much weight/time a person can work a day. But lets say that you can carry 40kg all day, 80kg for half a day, 160kg for 6 hours.</p>\n\n<p>So I'm going to just stab in the dark, and say that your labourer can carry 160Kg of water a day. He's going to go fill water skins, then lug the water to the people in the village, and he's going to do that all day. (What a life).</p>\n\n<p>160kg of water is 160 Litres, Lets trim that down to 140kg of water, and 40kg of water skins. 140kg of water 'waters' (rounded down) 46 people.</p>\n\n<p>Lets use the food as the basis for your calculations here.</p>\n\n<p>So 278 people, need 834 Litres of water.\n834 Litres of water requires (rounded) 6 people to carry water all day, every day.</p>\n\n<p><em>Your civ of 7 people, can support 278</em></p>\n\n<p><strong>SHELTER</strong>\nShelter is pretty simple, it's something that takes a long time to 'build' And let's face it, no society of 200+ people is going to be living in caves (Yes I know History has plenty of societies that have lived in caves, but these were environments where caves were common features of the land.)</p>\n\n<p>Log Cabins are going to be your easiest bet, (unless you want everyone living in tents.) A log cabin will take 4 people about 20 weeks to build. (Numbers vary, and it's pretty hard to pin this down to an exact number).</p>\n\n<p>So you need 4 people, and 140 days to build a house. You build 2.6 houses a year, a house can have... 4 people?</p>\n\n<p>*Your civ has 7+(4*x) people, can support 278 - You can build homes for 10*x people a year.*</p>\n\n<p><strong>Heating</strong>\nPrimitive Tech = Fire!!!</p>\n\n<p>You need to carry firewood (I'm totally pulling the below numbers out of thick air here, so take it with a pinch of salt).\nLets use the same numbers as were used for water. Your wooders can collect 160Kg of wood a day. Pine is about 530Kg per cubic meter.\nYou need about 10 pieces of wood to heat a house a day, so going off childhood memories, I'm guessing you need about 1/8th of a cubic meter, so (530/8) You need 67Kg of wood per home. Home has 4 people, 67/4 = 16.5Kg of wood per person. You have 278 people, you need 4587 Kg of wood, you need 29 people to carry wood.</p>\n\n<p>*Your civ has 1+6+(4*x)+29 people, can support 278 - You can build homes for 10*x people a year.*</p>\n\n<p>Now calculating tools is pretty esoteric, I think a tool should last at least 6 months on average, unless it's an axe which I expect should last 3 months? But how long does it take to make an axe? 4 hours? So you can make 2 axes a day. You need 29 axes every 3 months. You make 2 axes a day, 365 days a year, you need 116 axes a year, and you make 182 a year. That's 1 person making axes, and you have a surplus. (woohoo surplus).</p>\n\n<p>*Your civ has 1(hunter)+6(water)+(4(builder)*x)+29(wooder)+1(axer) people, can support 278 - You can build homes for 10*x people a year.*</p>\n\n<p>And I'm just going to throw the same numbers from above down for any other tool you need. Lets say you have 10 types of tools. Axes, Hammers, Bows, Spears, Fletchers, Plows, Baskets, Clothing, Leather works, blahhh... And each person in your society is going to get 8 tools a year... because why not.</p>\n\n<p>*Your civ has 1(hunter)+6(water)+(4(builder)*x)+29(wooder)+1(axer)+9(other tools) people, can support 278 - You can build homes for 10*x people a year.*</p>\n\n<p>So since this is getting really long, lets turn this into a formulae and you can plug in any other careers you want.</p>\n\n<p>** UNIVERSAL FORMULAE ** (hyperbole)</p>\n\n<p>*Your civ has 1(hunter)+6(water)+(4(builder)*x)+29(wooder)+1(axer)+9(other tools) people, can support 278 - You can build homes for 10*x people a year.*</p>\n\n<pre><code>People = X\nHunter = People / 278\nWater = people / 46\nWooder = (People*16.5) / 160\nTools = (People * 8) / 182\n</code></pre>\n\n<p>And Builders are dependent on Population Growth and structure decay, so nerf the numbers to your liking.</p>\n\n<pre><code>With lets say 1685 people You will need. (Rounding every job up)\nPeople = 1685\nHunters = 1685 / 278 = 7 Hunters\nWater = 1685 / 46 = 37 Waterers\nWooders = (1685*16.5) / 160 = 174 Wooders\nToolers = (1685 * 8) / 182 = 75 Tool Makers\n</code></pre>\n\n<p>You have used: 293 People, to support your society, and you have 1392 people with no job.</p>\n\n<p>Do some Algebra, and I think you have something like this:</p>\n\n<p>People = (x/278) + (x/46) + (x*16.5 / 160) + (x*8 / 182)</p>\n\n<p>Solve for X</p>\n\n<p>Hope this helps :)</p>\n" }, { "answer_id": 92702, "author": "user61244", "author_id": 28606, "author_profile": "https://worldbuilding.stackexchange.com/users/28606", "pm_score": 0, "selected": false, "text": "<p>If you accept 19 century mountainous village in Eastern Europe as good approximation of undeveloped society, then you can see that even relatively undeveloped society still requires a set of specialist profession:</p>\n\n<ol>\n<li>peasants do most of the work themselves, even if quality of own work is not very high, the price of specialist services is usually unaffordable. Children learn from early age the multitude roles and skills that are necessary in homesteading. Only specialist work requiring high initial investment or access to highly limited resource, or high risk of non-specialist destroying pricy raw material could force them to go to specialist.</li>\n<li>usually no single village have all specialist available, so some form of local specialization is always present</li>\n<li>the list of specialists in those village includes: blacksmith, tanner/lethermaker, miller, horse harness maker, bee keeper, midwife, healer, kind of veterinary (someone who has some skills as how to make sure the cow will give safe birth to a calf), etc. </li>\n</ol>\n" }, { "answer_id": 92911, "author": "Thorne", "author_id": 33868, "author_profile": "https://worldbuilding.stackexchange.com/users/33868", "pm_score": 0, "selected": false, "text": "<p>You would never have just one person of any skill. If anything happened to them, the skill could be lost.</p>\n\n<p>Specialization is a trait of modern society because knowledge can be stored and there are enough people to never have just one person capable of doing any skill.</p>\n\n<p>Everyone in a primitive society would be a jack of all trades and just be better at one skill or another than others but everyone would have to know the basics of every skill should they get separated from the tribe. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/92671", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/42863/" ]

[ { "answer_id": 94194, "author": "Olga", "author_id": 39490, "author_profile": "https://worldbuilding.stackexchange.com/users/39490", "pm_score": 2, "selected": false, "text": "<p>If not identified and taken under control this mutation will result in the extinction of the species, especially if it is linked to the Y-chromosome. That is if sexual reproduction is the only option. Genetic engineering and cloning will help to avoid the extinction.</p>\n\n<p>In your suggested scenario, the number of women will start to decline. At first, it will be happening slowly, but as the gene spreads, fewer couples will be having daughters. This will lead to huge social changes (for example, <a href=\"http://www.iflscience.com/brain/men-more-likely-to-marry-when-there-are-fewer-women/\" rel=\"nofollow noreferrer\">increase in a number of marriages and their stability</a>) and possible collapse of the societies (not immediately, of course) since skewed sex ratios favouring males are linked to <a href=\"http://amzn.to/2xospVa\" rel=\"nofollow noreferrer\">social</a> <a href=\"http://www.pnas.org/content/103/36/13271.full\" rel=\"nofollow noreferrer\">unrest</a>.</p>\n\n<p>The reaction of governments and societies and when the mutation is noticed will depend on the level of medical science and/or genealogy traditions. Sufficiently advanced societies with the understanding of genetics and developed traditions of preserving and studying family histories would have an advantage. I believe that they will try to find all men with this mutation and sterilise them in order to avoid extinction.</p>\n\n<p>I would also guess that a society that places a high value on sons will make some associations with these men unique ability to produce sons only. They may even see it as an advantage. Although, even those societies would probably eventually start to stigmatise those men.</p>\n\n<p>For the spread of the gene, you need to decide on your setting, fertility rates, marriage patterns, and so on. Without these, any calculations and assumptions can easily go wrong. </p>\n" }, { "answer_id": 94195, "author": "David Perreaux", "author_id": 43464, "author_profile": "https://worldbuilding.stackexchange.com/users/43464", "pm_score": -1, "selected": false, "text": "<p>The man without an X chromosome would likely also be sterile.</p>\n" }, { "answer_id": 94197, "author": "PipperChip", "author_id": 7, "author_profile": "https://worldbuilding.stackexchange.com/users/7", "pm_score": 2, "selected": false, "text": "<h1>An Issue With the Premise</h1>\n<p>You never stated if the gene is passed on to the next generation. This is super important. If it is never passed on, this mutation is odd, but not an issue for society at large.</p>\n<h1>Detection</h1>\n<p><span class=\"math-container\">$P(n_{boys}) = (\\frac{106}{200})^{n_{boys}}$</span> is the equation that gives <a href=\"http://www.npr.org/sections/health-shots/2015/03/30/396384911/why-are-more-baby-boys-born-than-girls\" rel=\"nofollow noreferrer\">the rough chances</a> of having a family of <a href=\"https://youtu.be/3IaYhG11ckA\" rel=\"nofollow noreferrer\">only boys</a> with <span class=\"math-container\">$n$</span> children. For <span class=\"math-container\">$n=5$</span>, the odds of this happening become a little above 4%! (The odds of two boys in a row- about 28%.)</p>\n<p>Adding the odds of children to the mix, and even with two children to each couple, the odds of this happening are a little under <strong>2% after the first 4 grandchildren</strong>. For 3 children each, it's <strong>0.05% after the last grandchild</strong>. I would expect people to wonder about if after the 1st generation has children. (The initial man/wife pair is generation 0.)</p>\n<p>This is also assuming that these people live in a society where knowledge of grandparents and cousins is common, and no one is put up for adoption, becomes sterile, dies before their time, and so on.</p>\n<p>If <a href=\"https://www.genome.gov/19516567/faq-about-genetic-testing/\" rel=\"nofollow noreferrer\">genetic screening</a> for this gene (or all genes) is available, this theoretically can be caught with the initial man, and potentially contained with his children. Of course, just because we can sequence a genome doesn't mean that we instantly know what those genes do.</p>\n<h1>Reactions</h1>\n<p>We, as a species, seem to be pretty terrible about coming together and doing something for the good of the species. This is especially true if it involves individual sacrifice. Pick a topic, and see how bad humans are at having a single, unified stance: <a href=\"http://s2.quickmeme.com/img/c0/c0f5a11bcd63c904ff40709ebdb34485a1b825350a5c936a9257aa2af8e9999c.jpg\" rel=\"nofollow noreferrer\">capitalism</a>, <a href=\"https://www.thoughtco.com/cartoons-and-memes-about-climate-change-2734107\" rel=\"nofollow noreferrer\">climate change</a>, <a href=\"https://i.pinimg.com/736x/4e/60/39/4e603939d948cc5544bac1fb438e1fab.jpg\" rel=\"nofollow noreferrer\">toilet roll facing</a>, <a href=\"https://www.youtube.com/watch?v=OOV6XDtCO5A\" rel=\"nofollow noreferrer\">Kirk vs Picard</a>, etc...</p>\n<p>In short, unless the people who want the human species to continue are in charge and can implement a <a href=\"https://en.wikipedia.org/wiki/Eugenics\" rel=\"nofollow noreferrer\">eugenics program</a>, this problem will spread, possibly dooming humans.</p>\n" }, { "answer_id": 94201, "author": "Community", "author_id": -1, "author_profile": "https://worldbuilding.stackexchange.com/users/-1", "pm_score": 2, "selected": false, "text": "<p>There are more than 3 billion men in the world, if a Y+ man has an average of 6 Y+ children (say it has some psychological effects too) it would take 12 generations to get there. Until the last generation the majority of men don't have the gene, so there is more than a hundred (probably more like 300) years to realize we have a problem before solving the source is not good enough. Even once we reach the gender skew in more skewed parts of the world we still have another generation before we would expect normal males (and the species) to be vulnerable to extinction.</p>\n\n<p>But it wouldn't spread that far that fast from a village. In its home village it might cause problems, as many sons might be expected over a few generations to marry into most of the local families. This would then produce a local surplus of males and a dearth of females. At this point scientists might notice and would be interested at the departure from the expected sex ratio at birth.</p>\n\n<p>The village could probably import brides from neighboring places, but as it exports males other nearby communities would also be effected, soon making it clear what is happening. While some cultures might value this on principal marrying foreigners isn't all that common in much of the world, and pretty quickly the drawbacks would become apparent in the original district.</p>\n\n<p>If it gets to a city first things might be a little more interesting. If siblings don't stay close there would be little reason to lump them as a demographic so science would not be interested, anecdotal stories of ten grandsons and no granddaughters are just curiosities. By the time anyone found a larger demographic like a city or region was a couple sigma out of normal the gene would be pretty wide spread, but there would not be immediately clear evidence of the cause. And if you are before computers the tracking required might make finding the cause at all doubtful. </p>\n\n<p>In this case village girls get attracted to cites as the fewer city girls make finding a well off guy virtually guaranteed. But villages won't be able to support the ratio and populations will then decline. As the population in cites declines it gets easier for the villages not yet exposed to the gene to replace missing females in cities, but more villages would have accepted outside males at some point leading to my first course. </p>\n\n<p>Even the densest scientists would see what was happening by the time cities populations decreased, but that is one generation after interference can keep population stable, and more decline is expected before recovery no matter what. Again it would become clear that the gene isn't good and it would be avoided, but this time much of the connected civilization would have been exposed and recovery would need to come from unconnected pockets.</p>\n\n<p>Once the gene is identified it won't really matter long term.</p>\n\n<p>Imagine two groups of people, the Xs and the Ys, the Ys have no females and therefore their population isn't meaningful to the size of the next generation. The Xs need to produce one female for every female in their group, plus one for every female that joins the Ys. This thinking changes the nature of the problem form a gene spreading one to a simple surplus male problem, even if it is renewed from generation to generation. If we end up with a stable population of Xs it doesn't mater how many Ys we have. </p>\n\n<p>The <a href=\"https://en.wikipedia.org/wiki/Fisher%27s_principle\" rel=\"nofollow noreferrer\">Fisher Principle</a> says evolution would be expected to eventually solve it. But humans aren't that pressed, and we could pretty easily cope with a skewed sex ratio, you just might have first world birth rates more like third world ones to keep a stable population with extra males about.</p>\n" }, { "answer_id": 94207, "author": "Justin Thyme", "author_id": 41951, "author_profile": "https://worldbuilding.stackexchange.com/users/41951", "pm_score": 0, "selected": false, "text": "<p>The first generation - that is, the first person with a YY chromosome.</p>\n\n<p>The Y chromosome is exceedingly small, it has lost 90% of its viable genetic material. See for instance <a href=\"http://www.npr.org/sections/health-shots/2014/07/28/334490208/with-mens-y-chromosome-size-really-may-not-matter\" rel=\"nofollow noreferrer\">this</a></p>\n\n<p>The Y chromosome has very little genetic material left, and any viable offspring needs the X chromosome genes to survive. A YY baby would have little chance of survival.</p>\n\n<p>In fact, eventually there will be no Y chromosome in the human species. </p>\n\n<p>The good news is, it is not needed to produce a male. It is only a very minor factor in sex determination. Everything else is done by hormones and such.</p>\n" }, { "answer_id": 94215, "author": "LSerni", "author_id": 6933, "author_profile": "https://worldbuilding.stackexchange.com/users/6933", "pm_score": 3, "selected": false, "text": "<h1>How long might it take for officials to notice that something was wrong?</h1>\n\n<p>Several years. They would notice that the female to male ratio is going down and would wonder why, but for this to be noticeable it would need to affect at least 2-3% of population. Someone would start suspecting, and looking for, female infanticide. When this does not pan out, they'd start looking for some causes, investigating whether the phenomenon is local or not; there are chemical pollutants that mimic hormone activity and could be the cause of this.</p>\n\n<p>But very soon someone would run a sperm check, the same kind of test that's done to increase the likelihood of male offspring. Or someone with the mutation might ask for <em>female</em> offspring - selecting gametes with X chromosome. And the technicians would scratch their heads and say \"Sorry sir, you haven't any\" and rush to publish their finding.</p>\n\n<h1>Under what circumstances would this be declared a problem by the government, such that it might act to stop further procreation?</h1>\n\n<p>Probably not for a long time. The government would declare it a problem, and surely screenings would be made available for those who wanted, but what would be the point of <em>stopping</em> procreation? Male children have traditionally been preferred in many countries, so this might not even be seen as a problem by many, and could be regarded as a blessing for some.</p>\n\n<p>On the other hand, from some simplistic simulations I've run, without a working test and some degree of enforcing, either by social pressure or governmental fiat, the population appears to be doomed.</p>\n\n<h1>What cultural or sociological conditions would increase or decrease the likelihood of detection?</h1>\n\n<p>Possibly if the country <em>already</em> had a male/female imbalance due to a policy such as \"only one child for family\", combined with a traditional preference for male offspring that had resulted in the disappearing of female fetuses (or even newborns). Then, a mutation that has the same effect would be hidden for longer (one more generation - twenty years? Twenty-five?). But even there, there would be someone wanting females - for example, to join two families - and the truth would emerge.</p>\n\n<p>For the same reason, any sort of detailed sperm check <em>for whatever reason</em> would reveal that some guy has no X spermatozoa. Further tests would immediately follow. So any advanced society where genetic screenings are performed (to, say, reduce the risk of conceiving children with genetic syndromes) would see the game discovered in a matter of <strong>days</strong> once an affected individual entered in the tested pool.</p>\n\n<p>Mandatory genetic testing against genetic diseases for everyone would trigger discovery as soon as the first affected individual decided to have children - say some twenty to forty years after the mutation took place at his conception.</p>\n\n<h1>Is there any plausible scenario in which the result would be catastrophic population collapse in a region or worse?</h1>\n\n<p>Yes. At first, in absence of tests, the mutation will spread more or less linearly at each generation (assuming the generation size remains constant), and <strong>all</strong> scenarios lead to extinction:</p>\n\n<pre><code>48.10% F, 51.60% M, 0.30% X // Linear growth\n48.37% F, 50.87% M, 0.76% X\n47.78% F, 50.50% M, 1.72% X\n48.28% F, 48.80% M, 2.92% X\n45.81% F, 48.76% M, 5.43% X\n42.63% F, 48.39% M, 8.98% X\n42.25% F, 41.55% M, 16.20% X\n36.71% F, 35.84% M, 27.45% X // Curve starts to flex\n28.99% F, 27.42% M, 43.59% X\n19.90% F, 20.39% M, 59.71% X\n13.83% F, 13.33% M, 72.84% X\n7.84% F, 9.13% M, 83.04% X\n4.38% F, 4.97% M, 90.65% X\n3.09% F, 2.13% M, 94.78% X\n1.76% F, 1.27% M, 96.97% X\n0.30% F, 0.30% M, 99.40% X\n0.20% F, 0.20% M, 99.60% X\n0.00% F, 0.00% M, 100.00% X\nExtinction\n</code></pre>\n\n<p>But if we introduce a testing when females are 10% of the population (pretty late if you ask me), which decreases the chances of a fertile \"YY\" mating to 10% of normal (this takes into account testing errors and people marrying knowing the consequences <em>and</em> having children nonetheless):</p>\n\n<pre><code>...\n14.86% F, 14.78% M, 70.35% X\n6.91% F, 8.33% M, 84.75% X : X &lt; 10%, introducing tests\n25.64% F, 23.78% M, 50.59% X // Ratio immediately drops\n40.08% F, 41.41% M, 18.51% X\n49.37% F, 45.63% M, 5.00% X\n50.80% F, 48.31% M, 0.88% X // Decrease becomes 1:10\n52.61% F, 47.31% M, 0.08% X\n48.20% F, 51.80% M, 0.00% X\nMutation dies out\n</code></pre>\n\n<p>Other scenarios see a maximum of two children per couple, and since a viable couple needs one female, the population declines rapidly:</p>\n\n<pre><code>49.80% F, 50.10% M, 0.10% X, population 100%\n48.80% F, 50.80% M, 0.40% X, population 99%\n48.87% F, 50.31% M, 0.82% X, population 97%\n52.00% F, 46.32% M, 1.68% X, population 95%\n48.68% F, 47.17% M, 4.15% X, population 98%\n49.38% F, 44.28% M, 6.34% X, population 96%\n40.53% F, 44.63% M, 14.84% X, population 95%\n37.27% F, 38.44% M, 24.29% X, population 77%\n32.23% F, 28.05% M, 39.72% X, population 57%\n24.32% F, 23.24% M, 52.43% X, population 37%\nIntroducing tests\n35.56% F, 40.56% M, 23.89% X, population 18%\n49.22% F, 46.88% M, 3.91% X, population 12%\n54.76% F, 45.24% M, 0.00% X, population 12%\nMutation dies out\n</code></pre>\n\n<p>If, in addition to tests, a third child is encouraged:</p>\n\n<pre><code>...\nIntroducing tests, maxc=3\n42.69% F, 36.26% M, 21.05% X, population 17%\n49.77% F, 44.75% M, 5.48% X, population 21%\n49.85% F, 48.62% M, 1.53% X, population 32%\n54.19% F, 45.81% M, 0.00% X, population 48%\nMutation dies out\n</code></pre>\n\n<p>With a testing of 50% efficacy and a policy of allowing a third child only when population is below threshold, 2 otherwise, the population stabilizes around a 6% of mutations, oscillating between 90% and 130% of threshold.</p>\n\n<p>Of course, real world conditions - people ignoring the tests and/or shirking the children limitations and/or <em>not</em> having all the children they can - may shift these results considerably.</p>\n" }, { "answer_id": 94225, "author": "Justin Thyme", "author_id": 41951, "author_profile": "https://worldbuilding.stackexchange.com/users/41951", "pm_score": 2, "selected": false, "text": "<p>Most importantly to any consideration, it must be noted that the Female sex is the default sex. That is, unless something specific happens in utero, a female will be produced, irrespective of the presence or absence of the Y chromosome. </p>\n\n<p>The Y chromosome is NOT the only thing that determines the sex of the offspring. There are mammals without the Y chromosome, and they still have males. The human Y chromosome has atrophied to such an extent that it is posited it will eventually disappear. In the same vein, female sex determination is not completely dependent on the absence of the Y chromosome. <a href=\"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2658794/\" rel=\"nofollow noreferrer\">Is the Y chromosome all that is required for sex determination?</a></p>\n\n<p>But there are basically only three ways that a male could produce only Y chromosome gametes. </p>\n\n<p>First method, all of the cells in his body would have to be YY. If so, he would be horribly maladjusted, as the genes on the X chromosome are vital for human survival. Mate selection would be troublesome.</p>\n\n<p>Second method, X and Y gametes are produced normally, and something causes the X gametes to be destroyed (like an immunological reaction). Immunology is not on the Y chromosome, so it would have to be on some other chromosome, which means it would not be 100% passed on. Sperm count, and thus fertility, would be cut in half.</p>\n\n<p>Third method, that X and Y gametes are produced normally, but the X sperm are severely disadvantaged such that the X sperm are unlikely to cause fertilization. Sex selection is already built in to the male sperm, since male Y sperm swim faster but die quicker. This has altered the ratio of male to female births, but has not severely altered it. To be 100% effective, the male sperm would have to me completely nonmotile. Again, effective sperm count and thus fertility would be substantially reduced.</p>\n\n<p>It is hard to envision, under any of these methods, that this mutation would become established in the human population, without substantial help from in vitro fertilization, in which case the process is moot. No need for such a mutation, X sperm would just be screened out, as is done currently.</p>\n\n<p>If you want hard statistics on the societal repercussions of a male birth preference, investigate the research from China. The one-child policy has lead to there being over 30 million more males than females, in just three or four generations, and this was due not to just one male, but to widespread selective abortion and infanticide. The societal implications are substantial and were unforeseen. Unbalanced sex ratios tend to be self-balancing in the end. Males that produce female offspring reliably, in the family background, would become preferred mates.</p>\n" }, { "answer_id": 94264, "author": "smatterer", "author_id": 41821, "author_profile": "https://worldbuilding.stackexchange.com/users/41821", "pm_score": 0, "selected": false, "text": "<ul>\n<li><p>How long would it take to be noticed?</p>\n\n<p>That depends where it started. If it started in a society where most families have many children (typically poor or per-industrial societies), it may take a couple of generations to be noticeable. If I have six children - all boys - and my parents and five brothers all have many boys and no girls, it becomes something that is worth medical investigation. Even without modern medicine, after a few generations it would become known that there were some families that only had boys.</p>\n\n<p>On the other hand, in societies where most families have only one or two children, it is not so obvious. If I have two sons and no daughters and so do my parents and brother, it is not a coincidence worth investigating. It is more likely to be discovered when a couple who want a daughter used some type of assisted reproduction technology to try to select their childs sex and discover that there are no X-baring sperm. </p></li>\n<li><p>The effects on Society</p>\n\n<p>If nothing was done about it there would be a gender imbalance in the population. When there are excess men with no prospect of marriage and family, it is likely that there would be institutions like the military or monasteries which provide a substitute for the family environment for single men. It is also possible that women would give more priority to child-baring as that \"skill\" becomes rarer and hence more valuable.</p>\n\n<p>I suspect that the imbalance would be self-correcting or at least self-limiting. If there are many more men than women then women can be more fussy in their choice of partner. Even without genetic testing technology, it will be known which men are from affected families. All else being equal, women will prefer husbands from unaffected families both because they want to have daughters and because they want their sons to be unaffected.</p></li>\n</ul>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/94192", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/43460/" ]

[ { "answer_id": 96954, "author": "Slarty", "author_id": 42450, "author_profile": "https://worldbuilding.stackexchange.com/users/42450", "pm_score": 3, "selected": false, "text": "<p>At the mountain top the atmosphere would be so thin that it would not be able to hold any significant amount of suspended dust particles. Most dust and other ejecta from the volcano would quickly end up on the ground around the vent and spread out further downhill depending on how energetic the eruption was. If in sufficient quantities this could cause landslides of ash down to lower levels.</p>\n\n<p>The gas from the eruption would spread out into the mesosphere where it would probably form a band of gas around the entire planet. The effects of injecting the gas would very much depend on how much was injected. If sufficient was injected it would likely have a strong greenhouse effect, especially as particulates such as sulphates would probably fall back to earth relatively quickly. The effects would be longer lasting than gases injected into lower levels of the atmosphere but might spread out more rapidly. </p>\n" }, { "answer_id": 97105, "author": "HDE 226868", "author_id": 627, "author_profile": "https://worldbuilding.stackexchange.com/users/627", "pm_score": 5, "selected": true, "text": "<p>What we're concerned with here is the <a href=\"https://en.wikipedia.org/wiki/Eruption_column\" rel=\"noreferrer\">eruption column</a> and subsequent plume arising from the volcanic eruption. This is a shield volcano, so it's not going to erupt <em>a la</em> Mount St. Helens; rather, it will slowly spew out material. Granted, for a volcano this large that's still going to be quite the eruption. First, let's figure out some basic properties and quantities:</p>\n\n<ul>\n<li><strong>Height:</strong> 50 miles, or about 80 kilometers, as you stated. Obviously, no mountain should be this tall, but that really doesn't matter.</li>\n<li><strong>Radius:</strong> Given an average slope of about $5^{\\circ}$, the volcano should have a radius of $\\sim80\\text{ km}\\tan(5^{\\circ})\\simeq914\\text{ km}$. This means that the volcano should be more than one half as wide as the United States, and about three times as wide as <a href=\"https://en.wikipedia.org/wiki/Olympus_Mons\" rel=\"noreferrer\">Olympus Mons</a>.</li>\n<li><strong>Rate of mass ejection:</strong> The <a href=\"https://en.wikipedia.org/wiki/Volcanic_Explosivity_Index\" rel=\"noreferrer\">Volcano Explosivity Index</a> (VEI) ranks how powerful a volcanic explosion is. The top level is VEI 8, ejecting over $1000\\text{ km}^3$ of material. Let's assume that this volcano ejects $4000\\text{ km}^3$ of material over a period of one week. Assuming typical ash densities of perhaps $1500\\text{ kg m}^{-3}$, this gives us $Q\\sim10^{10}\\text{ kg s}^{-1}$. <a href=\"http://www.ldeo.columbia.edu/~ruprecht/Site/Classes_files/Week8_Carazzo.pdf\" rel=\"noreferrer\">Carazzo et al. (2008)</a> lists values for other eruptions (see Table 1 and Table 2). Our $Q$ is two orders of magnitude greater than most Plinian (think high, tall plumes) eruptions, and about the same as many explosive eruptions producing pyroclastic flows. Ours simply lasts a lot longer.</li>\n</ul>\n\n<p>Let's start with a simplified model, namely, a <a href=\"https://ansn.iaea.org/Common/Topics/OpenTopic.aspx?ID=13012\" rel=\"noreferrer\">Gaussian plume</a>. This means that the concentration of the material, $C$, is\n$$C(x,y,z)=\\frac{Q}{2\\pi U\\sigma_y\\sigma_z}\\exp\\left(-\\frac{y^2}{2\\sigma_y^2}\\right)\\left[\\exp\\left(-\\frac{(z-H)^2}{2\\sigma_z^2}\\right)+\\exp\\left(-\\frac{(z+H)^2}{2\\sigma_z^2}\\right)\\right]$$\nwhere\n$$\\sigma_y=\\sqrt{2Dy\\frac{x}{U}},\\quad\\sigma_z=\\sqrt{2Dz\\frac{x}{U}}$$\nand</p>\n\n<ul>\n<li>The wind is blowing in the $x$-direction with speed $U$, which might be $25\\text{ m/s}$, or $56\\text{ mph}$.</li>\n<li>$y$ is the $y$-coordinate and $z$ is the $z$-coordinate.</li>\n<li>$H$ is the reference height - in our case, $80000\\text{ m}$.</li>\n<li>$D$ is the diffusion coefficient, which is probably $\\sim10^3\\text{ m}^2\\text{ s}^{-1}$.</li>\n</ul>\n\n<p>There are some assumptions the model makes:</p>\n\n<ul>\n<li>The opening is roughly point-like.</li>\n<li>In our case, we assume that the diffusion coefficient is isotropic, i.e. it is <em>not</em> directionally dependent.</li>\n<li>This is a \"steady state\" solution, meaning that it is approximately constant. This works well for a week-long event.</li>\n<li>The atmosphere (and gravity) are homogeneous and don't affect the plume <em>too</em> much. On large scales, this assumption doesn't always work.</li>\n</ul>\n\n<p>I wrote some Mathematica code to look at the concentration of the plume as a function of distance. This code currently outputs a contour graph in the plane $y=0\\text{ m}$. It is cut off at $x=25\\text{ m}$, because otherwise the densities near the opening are too large and make it hard to see the rest of the contours.</p>\n\n<pre><code>U = 25;\nH = 80000;\nDiff = 1000;\nQ = 10000000000;\nSigmay[x_, y_] := Sqrt[2*Diff*Sqrt[y^2]*x/U];\nSigmaz[x_, z_] := Sqrt[2*Diff*Sqrt[z^2]*x/U];\nConc[x_, y_, z_] := Q/(2*Pi*U*Sigmay[x, y]*Sigmaz[x, z])*\n Exp[-y^2/(2*(Sigmay[x,y)^2)]*(Exp[-(z - H)^2/(2*(Sigmaz[x, z])^2)] + \n Exp[-(z + H)^2/(2*(Sigmaz[x, z])^2)]);\nTopView[x_, y_] := Conc[x, y, H];\nSideView[x_, z_] := Conc[x, 0.001, z];\nContourPlot[SideView[x, z], {x, 25, 10000}, {z, 78000, 88000}, \n PlotRange -&gt; {{25, 10000}, {78000, 88000}, All}, Exclusions -&gt; None,\n PlotLegends -&gt; Automatic, Contours -&gt; 50, ContourLines -&gt; False, \n RegionFunction -&gt; Function[{x, y, z}, y - 80000 + 0.0875*x &gt; 0]]\n</code></pre>\n\n<p>This outputs the following plot:</p>\n\n<p><a href=\"https://i.stack.imgur.com/PXyU0.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/PXyU0.png\" alt=\"enter image description here\"></a></p>\n\n<p>Notice that even two kilometers away from the summit, the plume is still incredibly dense. Its density doesn't become negligible until it's hundreds and hundreds of kilometers away from the summit. If you were to raise the upper limit on $z$, you would see that the plume rises to a height of over $160\\text{ km}$! That's way beyond the upper limit of the mesosphere. And to be honest, I think I've been conservative in my estimate for $Q$.</p>\n\n<p>Is this realistic?</p>\n\n<p>First, let's consider what kind of eruption we're dealing with. It's a shield volcano, so most of the material that comes out will <em>not</em> be in the plume. However, as I said before, I likely underestimated $Q$, and so such a plume isn't that unrealistic.</p>\n\n<p>That final height of the plume - $\\sim80\\text{ km}$ - seems a bit much. However, it's really not that far-fetched. In general, the relationship between plume height $H$ and $Q$ is\n$$Q\\propto H^4$$\n<a href=\"http://www.ipgp.fr/~kaminski/web_doudoud/eyjafjoll_JGR2011.pdf\" rel=\"noreferrer\">Kaminski et al.</a> use the equation\n$$Q=aH^4+b$$\nwhere, for $12\\text{ km}\\leq17\\text{ km}$, $a=258\\text{ kg s}^{-1}\\text{ km}^{-4}$ and $b=-4.6\\times10^6\\text{ kg s}^{-1}$. We can assume that $H$ is going to be even greater than $17\\text{ km}$, so we should expect the result to be close but not totally accurate. Rearranging, plugging in for $Q$ and then solving yields a total plume height of $79\\text{ km}$ - which is <em>very</em> close to what Mathematica told us. Perhaps that result isn't too ridiculous after all.</p>\n\n<p>One thing you'll need to consider is <a href=\"https://en.wikipedia.org/wiki/Eruption_column#Column_collapse\" rel=\"noreferrer\">column collapse</a>. It might be the most important factor behind the eruption's evolution. An eruption column will collapse when the bulk density of the material (a combination of its density and the density of the air inside the column) becomes too dense compared with the air around it. Looking at <a href=\"https://www.engineeringtoolbox.com/standard-atmosphere-d_604.html\" rel=\"noreferrer\">some standard atmospheric tables</a>, we can see that the mesosphere is not at all dense, meaning that collapse is highly likely. The plume will form, certainly, and material will travel hundreds of kilometers (during which the Gaussian plume model is a good fit), but it won't last for that long.</p>\n\n<p>So, what happens then? Well, the material now coming out of the volcano will form <a href=\"https://en.wikipedia.org/wiki/Pyroclastic_flow\" rel=\"noreferrer\">pyroclastic flows</a>, which scare the living daylights out of me. They are fast, dense and hot, and destroy anything in their path. And they will begin by rushing down the mountain at fairly high speeds, and probabaly will not stop quickly. Assuming these flows reach high speeds ($300$-$600\\text{ mph}$), they'll reach the base of the volcano in a few hours, after ruining anything on its slopes. An area the size of a medium-sized country will be decimated.</p>\n\n<p>It's unclear what will happen when the flow reaches an atmospheric layer with a density high enough to support an eruption column. I'll have to get back to you on that. It's possible that the gas will form clouds of ash and soot at that altitude, which would then spread out even more. That said, that's currently just a conjecture on my part.</p>\n\n<p>Here's the bottom line:</p>\n\n<ul>\n<li>Ash, gas and dust will be spread for hundreds of kilometers away from the volcano - possibly up to $1000\\text{ km}$ or more.</li>\n<li>A plume will rise into the mesosphere and possibly low thermosphere before collapsing; I don't know how high it will actually go.</li>\n<li>Pyroclastic flows will then descend from the mountain, destroying anything on it. Any further atmospheric affects will be from them.</li>\n</ul>\n" }, { "answer_id": 97150, "author": "anon", "author_id": 41670, "author_profile": "https://worldbuilding.stackexchange.com/users/41670", "pm_score": 0, "selected": false, "text": "<p><strong>I applaud HDE's effort but I have to disagree with his fundamental approach</strong></p>\n\n<ul>\n<li>First, a 50mi volcanoe on Earth would be impossible but ill ignore that for now</li>\n<li>Earth's Atmosphere is roughly only 62 miles high so that leaves 12 miles between the summit and the edge.</li>\n<li>at that altitude air pressure and gravity is much smaller (easier to obtain escape velocity)</li>\n<li>the volcano itself is effectively a cannon barrel</li>\n<li>the amount of energy needed to travers the 50 mi mountain would likely cause the amount to explode rather than shoot up. </li>\n</ul>\n\n<p>The amount of energy needed for this volcano to erupt would likely send debris into outer space as well as orbit. Dust and gas would likely permeate the entire atmosphere with planet wide impacts. This could even form a planetary ring that would cause impacts for centuries to come. In short this would be a super volcano greater than yellow stone, capable of causing multiple and subsequent extinction level events. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/96943", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/10364/" ]

[ { "answer_id": 97086, "author": "Alexander", "author_id": 32451, "author_profile": "https://worldbuilding.stackexchange.com/users/32451", "pm_score": 4, "selected": false, "text": "<p>This can be done in a similar manner as we check the authenticity of software today - using license keys and checksums. This way we can be sure that:</p>\n\n<ul>\n<li>The program in question is legitimate, particularly if license is registered in central database;</li>\n<li>The program in question was unmodified, at least to the point of its installation;</li>\n</ul>\n\n<p>However, there are no easy ways to check if the program has been hacked. If the program in question is a \"learning\" AI, then every installation of it would be different, and while we can still say that the program initially was exactly what we wanted it to be, there is would be no way of telling how this program changed from that moment and whether those changes were legitimate.</p>\n\n<p>If the program in question is a \"static\" AI, then situation is more manageable. The difficulty of this task will be comparable to checking if a particular iPhone is not lost/stolen and it had not been jailbroken.</p>\n" }, { "answer_id": 97089, "author": "Joe Bloggs", "author_id": 9887, "author_profile": "https://worldbuilding.stackexchange.com/users/9887", "pm_score": 2, "selected": false, "text": "<p>Track the transfers of entity from vehicle to vehicle, then use the vehicle identification.</p>\n\n<p>What you’re trying to do is authenticate the ‘mind’ of the vehicle to make sure that it’s allowed to drive. Assuming that the AI’s might happily share licence information with each other and are too complex to perform a checksum or program integrity check on the only way you can authenticate the mind is via the body, in this case the vehicle.</p>\n\n<p>So: only licenced engineers are allowed to transfer AIs, whenever they do they <em>must</em> log the new location of the AI. At that point verification becomes a matter of physical authentication which can be done many different ways.</p>\n\n<p>On a more abstract bent: what you’re aiming to do seems a bit pointless. If you’re authenticating that the AI knows how to drive you can essentially perform a roadside ‘driving test’ to check that the vehicle will respond appropriately to a set of standardised tests. The AI should be able to do the test very rapidly if appropriately designed. It doesn’t matter if it is the AI that you think it is if it knows how to do the thing you want it to do. If one of the questions is designed to weed out the prototype ‘trusted’ cars from the non trusted ones then the non trusted ones will fail the test. If the non trusted ones pass the tests then they are, to all intents and purposes, trusted.</p>\n" }, { "answer_id": 97094, "author": "Green", "author_id": 10364, "author_profile": "https://worldbuilding.stackexchange.com/users/10364", "pm_score": 5, "selected": false, "text": "<h1>What you have, what you know, who you are</h1>\n\n<p>Those are the three ways that an unknown person is authenticated and authorized. For humans, \"what you have\" usually means a physical key or pass card. \"What you know\" means a password or passphrase. \"Who you are\" means unique biological data that is difficult to fake or duplicate, such as finger prints, retina, etc.</p>\n\n<p>The digital equivalent of \"who you are\" is a hash. Hashes are a form of one way compression where a quantity of binary data is put through a hash function resulting in another, much shorter number. Hash functions are designed in such a way that if a single bit of that number changes, there will be large, easy to see differences in the resulting hash. There is only a one bit difference between 8 and 9. The below example shows the large differences that a single bit will bring.</p>\n\n<pre><code>$ echo \"01234566789\" &gt; 09.txt\n$ sha1sum.exe 09.txt\n0230f435629ff197db2935a4f2d58d234c74de0d *09.txt\n\n$ echo \"01234566788\" &gt; 08.txt \n$ sha1sum.exe 08.txt\nf2408b6a33c9752882dd46aae70674f4f0597e92 *08.txt\n</code></pre>\n\n<p>The requirement for these three methods to be secure, in real life and digitally, is that they are extremely difficult to duplicate. Note also, that encryption is used for verification as well as concealment. In this case, encryption will be used to ensure that the AI gestalt installed in the car is authorized to be there.</p>\n\n<h2>What the car has</h2>\n\n<p>The car has a stamped nameplate with a barcode/QR code of its serial number and certificate of authenticity. The certificate of authenticity contains two thumbprint hashes of the AI's gestalt; one by the manufacturer and one by the certifying authority. It also has a QR code of that AI's public key. In addition, the car will have a <a href=\"https://en.wikipedia.org/wiki/FIPS_140-2#Level_3\" rel=\"noreferrer\">FIPS 140-3</a> cryptographic module for generating hashes of itself and responding to authentication claims. This crypto module will work much the same way as the chip in your debit card. Of necessity, this physical protection must extend to whatever hardware the AI is running on in the car.</p>\n\n<h2>What the cops/inspectors have</h2>\n\n<p>The cops have a big list of authorized AI gestalts hashes and associated public keys. They have the public keys associated with the private keys that signed the AI gestalts. With the hashes and public keys, they have everything they need to cryptographically verify that the AI gestalt is \"who it says it is\".</p>\n\n<h2>What the certifying authority has</h2>\n\n<p>They have a copy of the gestalt (though not the source code that created the gestalt), the manufacturer's hash of the gestalt and manufacturers public keys. They do not get the private keys because that only leads to shenanigans (which this whole complicated expensive process is trying to avoid).</p>\n\n<p>When the certifying authority creates their hash for the gestalt, they will add a <a href=\"https://en.wikipedia.org/wiki/Salt_(cryptography)\" rel=\"noreferrer\">salt</a> to the gestalt before hashing. Salting the gestalt before hashing ensures that the gestalt is different from the manufacturer's hash ('cause it doesn't make much sense if the two hashes are the same). Salting also makes it much harder for attackers to recover the certifying authorities private key because to recover the key would require recovering the salt as well as the private key. This is much much harder.</p>\n\n<p>Spot check that the cars crypto module and AI brain are FIPS 140-3 compliant.</p>\n\n<h2>What manufacturer has</h2>\n\n<p>The car/AI manufacturer has the private key that they use to sign the AI gestalt before installing it in cars. They also produce a hash of the gestalt. Manufacturers go through the same process of salting and hashing the gestalt that the certifying authority does.</p>\n\n<p>They also make sure that the crypto module and AI brains actually are FIPS 140-3 compliant. For each crypto module, they install a new private key.</p>\n\n<h1>Buzzword Compliance: Blockchain</h1>\n\n<p>As much as I despise buzzwords and handwaving \"it'll do magic\" tech, there is a valid use case for blockchain tech in this instance. Consider that blockchains are really just big distributed ledgers shared by people who really don't trust each other.</p>\n\n<p>In this case, a blockchain would be built to hold the car specific public keys, the manufacturer and certifying authority public keys, and hashes of certified gestalts. The blockchain becomes the canonical record of who did what and when. This prevents attacks where someone attempts to change a public key sneakily. They can't since the record is immutable. Well, they can change it but that will require enough resources to get a majority on the blockchain. Such a majority <em>will</em> be noticed.</p>\n\n<p>As each new gestalt is published then certified, all the appropriate information about that gestalt is added to the blockchain. Once added, it's permanent.</p>\n\n<h2>Authorization Verification Process</h2>\n\n<p>This is how things might go</p>\n\n<ol>\n<li>The cop will scan the name plate of the car for manufacturer, model, manufacturer AI gestalt hash and certifying authority AI gestalt hash.</li>\n<li>The scanner looks up the manufacturer, model and both hashes against the known-good configurations. If all four data points match, then the AI in the car is probably good to go. This is the weakest but fastest verification of the car's AI.</li>\n<li>For stronger verification, the cop will plug in the scanner to a data port on the car. Once connected, the car will respond to a command to encrypt some long really long and randomly generated number with the AI's private key. Since the scanner also has the public key associated with this car, if the crypto module returns a strong that can decrypted with the public key then the cop/scanner knows that the crypto module is genuine. This verification process prevents an attacker from stealing the correct response from authorized hardware and just replaying it back to the scanner. This, in addition to previous verification steps.</li>\n<li>The strongest verification will be to take the car into a shop and examine the crypto module. Since it's FIPS 140-3 compliant, any tampering will be evident and the car will fail inspection. This, in addition to all the previous verification steps.</li>\n</ol>\n\n<h2>Weaknesses</h2>\n\n<p>Since everyone messes up and even strong security systems eventually are compromised, as described, this system does not account for the need for rapid change of public-private keys should they be compromised. Say, someone at the manufacturer or certifying authority fat fingers which key to add to the block chain and they add the private key when it should have been the public key.</p>\n\n<p>There are a thousand ways to break this system and it will take a lot of very careful planning in order to make it very hard, even for nation-states to compromise it. (Ha! Well, that's far far beyond the original threat model but this was fun to write.)</p>\n\n<h2>Modern Web Cryptography</h2>\n\n<p>Much of the process and crypto primitives described above can also be found in modern web crypto. If you see an 'https' then your browser is using a system of public and private keys to authenticate and authorize the server you're connecting to.</p>\n\n<h2>Not yet covered areas</h2>\n\n<p>What this process doesn't cover is the data that the AI uses to navigate with. Where that comes from and how it's used is outside the scope of this question.</p>\n\n<p>Attacks on this data would preserve the integrity of the AI but cause errant behavior. </p>\n" }, { "answer_id": 97133, "author": "Damon", "author_id": 3066, "author_profile": "https://worldbuilding.stackexchange.com/users/3066", "pm_score": -1, "selected": false, "text": "<p>It's not really a problem.</p>\n\n<p>An AI will (presently) never attain a valid driver's license because the law simply doesn't allow for it. That means that every car driving mostly (or even fully) autonomically must have some sort of exception which, due to the associated cost, is valid for the car model (not an individual car), and only valid with some other contraints (such as a human driver with a valid license who is finally to be blamed if the AI drives into a truck). A prototype, likewise, would have an exception, but could never get a proper license.</p>\n\n<p>Unluckily, at some point in the hopefully very distant future, there <em>will be</em> a desire for AIs to have proper driver licenses. When that happens, it is up to the legislative to come up with a solution.</p>\n\n<p>The identity problem could be solved with readily available cryptographic algorithms. A simple digital signature would do just fine. This could come from the drivers license office if you like, but the maunfacturer could as well do it as long as their signing key is either registered in a central database or properly signed certificates in a state-controlled hierarchy are supplied (much like in every web browser nowadays, except now it's more a wild west hierarchy).</p>\n\n<p>Or, seeing how it's well known as a trope that AIs are not allowed to lie, you could simply ask the AI for its identity and trust it.</p>\n\n<p>Realistically, you know what will happen. Legislative always goes the most stupid, most sure-to-fail, and most needlessly expensive way.<br>\nWhich means cars with AIs entitled a driver's license will either simply have magenta-colored license plates (not to be confused with fuchsia-colored plates which require a human driver with a license), or you will have a sticker in the front window, and you will not be allowed to change plates or remove the sticker. The sticker will cost you approximately 500 dollars per year, and you will need an additional sticker (valid for 8 months) if your AI is qualified to drive through a tunnel.</p>\n" }, { "answer_id": 97136, "author": "MichaelK", "author_id": 12297, "author_profile": "https://worldbuilding.stackexchange.com/users/12297", "pm_score": 1, "selected": false, "text": "<h1>You cannot do it, unless you make some assumptions</h1>\n\n<p>Making the full proof cannot be done here, because it requires a university level course in Information Theory, so I will just state it as bare fact:</p>\n\n<p><strong>You cannot reliable authenticate a piece of software when someone else is in control of the hardware it resides on</strong> </p>\n\n<p>This is — for instance — why we cannot have cheat-proof computer games. So unless you make certain assumptions, the answer to your question is: </p>\n\n<p><strong>That which you ask for cannot be achieved</strong></p>\n\n<p>And for the record: the same goes for bio-metric identification of humans. Unless you make <strong>some</strong> assumptions, then you cannot authenticate a human against their driver's license with 100.000% certainty. Instead you must make some assumptions, such as \"Human fingerprints are unique and can always be distinguished from each other\". </p>\n\n<h2>The assumptions when it comes to AI</h2>\n\n<p>The assumptions you have to make in your case is:</p>\n\n<ul>\n<li>A piece of hardware that has been validated by the enforcement agency (i.e. Police/Highway Patrol) can make an accurate memory dump of the AI in question, being given the code, the whole code and nothing but the code.</li>\n<li>The AI cannot be reprogrammed / replaced.</li>\n</ul>\n\n<p>If this is the case, then it is actually quite easy. The officer will make a dump of the AI's software and the officer's hardware unit will make one or several <a href=\"https://en.wikipedia.org/wiki/Hash_function\" rel=\"nofollow noreferrer\"><strong>hashes</strong></a> of it. These hashes act as fingerprints of the AI. In fact they can even work as the <strong>identity</strong> of the AI. </p>\n\n<p>All the officer then needs to do it make a lookup and verify that the AI with these hashes is authorized to travel in / drive that kind of vehicle, in that area, on those types of roads, under those conditions, and so on.</p>\n\n<p>Alternatively the AI comes with an public authority issued <a href=\"https://en.wikipedia.org/wiki/Public_key_certificate\" rel=\"nofollow noreferrer\"><strong>digital certificate</strong></a> that lists all the rights of the AI. The certificate will certify that the AI with the hashes specified has the following enumerated rights. The officer's hardware needs then only verify the certificate, which is a mundane affair.</p>\n\n<p>This then comes with an additional assumption:</p>\n\n<ul>\n<li>Digital certificates cannot be forged</li>\n</ul>\n\n<p>The weakness is of course that 2 out of 3 of those assumptions are fairly flimsy. There is nothing to say for instance that the original AI was not disconnected from the actuators of the car, and another AI installed in parallel with this one that does the actual driving. But when the officer connects their scanner to the car, it is the original AI that responds. </p>\n\n<p>There is no way around that unless the <strong>government</strong> has a monopoly on building AI cars and has 100% control over the hardware. And even then you have the issue that no-one will ever have 100% control over the hardware...</p>\n" }, { "answer_id": 97139, "author": "ZioByte", "author_id": 38942, "author_profile": "https://worldbuilding.stackexchange.com/users/38942", "pm_score": 0, "selected": false, "text": "<p>Not feasible.</p>\n\n<p>All methods proposed are fundamentally flawed.</p>\n\n<p>You can, up to a point, certify hardware.\nSome hardware include some \"write-once\" memories very difficult to \"spoof\".</p>\n\n<p>You can also \"homologate\" procedural software using signed signatures and be reasonably sure what's actually running in the hardware hasn't been tampered with.</p>\n\n<p>Unfortunately nothing of this is applicable to a reasonably complex A.I.</p>\n\n<p>Actual knowledge in a modern A.I. resides in data, this may be the weights defining a Simulated Neural Network or some Content Database or something yet different, but, in all cases, dynamic in nature and thus defying some simple(?) signing scheme.</p>\n\n<p>Normal I.D. cards rely on fact \"hardware\" is rigidly connected with \"software\" and there's <em>no</em> way, at least in the foreseeable future, to \"reboot\" some Natural Neural Network with a different \"Operating System\".</p>\n\n<p>The fact \"Software\" is not tightly linked to underlying hardware (and <em>many</em> layers ensure a program doesn't even know on which platform it is running, at least in many modern Programming Languages) is a game-changer.</p>\n\n<p>You can easily \"clone\" a program and have it run on many different hardware platforms; Should all of them have the same \"I.D.\" card?</p>\n\n<p>Even if they started \"identical\" thy are bound to have different \"experiences\" and thus diverge, possibly in radical ways; At which point your \"ID.\" should be invalidated?</p>\n\n<p>No. The only potentially viable approach is Python's <a href=\"https://en.wikipedia.org/wiki/Duck_typing\" rel=\"nofollow noreferrer\">Duck Typing</a>. Prepare specific tests (they can be administered quite fast due to electronic speed) to test if a certain program can (still) perform a certain task.</p>\n\n<p>In the specific case this is equivalent to have the \"policeman\" connect some testing device to A.I. and have it pass a full fledged driving license exam. <em>No</em> other test would provide any reasonable answer.</p>\n\n<p>Note these problems are similar to what happens with on-line identification which is much less reliable then many people think (as the many \"identity theft\" cases testify) and essentially works well (when it works) by providing feedback to user about all transactions, so that they can be traced and stopped, not by preventing abuse.</p>\n" }, { "answer_id": 97245, "author": "Sherwood Botsford", "author_id": 15784, "author_profile": "https://worldbuilding.stackexchange.com/users/15784", "pm_score": 1, "selected": false, "text": "<p>Assumptions:</p>\n\n<ul>\n<li><p>The AI is a true AI, and has operational control of its hardware. </p></li>\n<li><p>It has some form of memory that is write once. This part of the memory is not accessible without destroying the machine.</p></li>\n</ul>\n\n<p>Now: Part of that read only memory is the private key for Hal's private public key encryption. The AI is the only place in the world where this key is written down. To get this to be true, the AI has to be able to generate the key pair on it's own (trivial for a computer) and register the public key in a key repository.</p>\n\n<p>So proof of identity works like this:</p>\n\n<p>COP: Who are you\nHAL: I'm Hal 2764. I'm registered. I'm listening on redtooth 7</p>\n\n<p>The cop's computer takes today's date, a random string token, and it's own identity, and encrypts this using Hal's public key, and sends this string of stuff to Hal on redtooth 7. </p>\n\n<p>Hal decrypts this using his private key. ONLY someone with the private key can do this in reasonable time. Hal then looks up the public key of matching the cop's computer's identity, re-encrypts the token, along with the latest date/time stamp, and some random noise, and sends this back.</p>\n\n<p>The cop's computer decrypts this data using its private key. The tokens match, proving that Hal was able to decrypt the packet, and hence actually has Hal's private key.</p>\n\n<p>More about public/private keys <a href=\"https://en.wikipedia.org/wiki/Public-key_cryptography\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/Public-key_cryptography</a></p>\n" }, { "answer_id": 97262, "author": "DudeFace", "author_id": 22075, "author_profile": "https://worldbuilding.stackexchange.com/users/22075", "pm_score": 1, "selected": false, "text": "<p>I'm not a security expert, but I think you can do most of this with simple private key/public key encryption. You just need to establish the correct protocols so everything can be verified, and trust the private keys remain private. So it's not infallible, but then again nothing is.</p>\n\n<p>The car and cop need to be able to generate encrypted signed messages meant for the car's manufacturer, meaning no one else can decrypt the messages and they are verified as being to-and-from either the car and the manufacturer or the cop and the manufacturer.</p>\n\n<p>The cop generates a random token and it sends an ID request to the manufacturer for this car's stated name. At the same time, the car uses the random token and sends it's authorization to be verified to this officer. You could do it other ways, but this way means the officer and the car both have to consent to being verified.</p>\n\n<p>Since the cop is getting verified too the cop also sends the token to the main police authorization service (we'll call it Big Blue). This step isn't necessary. I just like it this way so not just anyone can verify a car.</p>\n\n<p>The manufacturer decrypts both messages. The car says \"Hello manufacturer X, it's me Bob, please verify with officer Pebbles Larue (token)\", then it gets a message from the cop and says \"This is officer Pebbles Larue, please tell me if this is Bob or not (token),\" then the token gets sent to Big Blue and Big Blue says officer Pebbles is on the up and up, so the manufacturer responds to Pebbles with a thumbs up emoji, meaning this is indeed Bob.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/97081", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/885/" ]

[ { "answer_id": 97621, "author": "ZioByte", "author_id": 38942, "author_profile": "https://worldbuilding.stackexchange.com/users/38942", "pm_score": 3, "selected": false, "text": "<p>Because all operations in given environment are very important and need careful setting.</p>\n\n<p>It is <em>much</em> easier to click on the wrong icon than to input a syntactically correct command that's not what intended.</p>\n\n<p>\"Command Line\" is much harder to learn and thus the popularity of \"GUI\" interfaces, but in the given environment that's not a problem as your \"small-scale entrepreneurs\" are bound to know their ships very well and are likely to welcome <em>anything</em> forcing them to <em>think</em> before committing a command.</p>\n\n<p>In the example given they surely won't like \"oversleep\" any important (orbital) appointment.</p>\n\n<p><strong>Edit</strong>:\nI know this is a very slippery subject and many Holy Wars have been fought under the flags of GUI Fawkes and CLI_nt Eastwood, but I will clarify my thoughts nonetheless. Bear with me.</p>\n\n<p>The trend in general and about Interfaces in particular, has always been to make things \"easier\" for the user. This is generally regarded as a Good Thing, but, as with <em>everything</em>, there is a price to pay and situations where this price overweight any advantage had.</p>\n\n<p>The specific \"price\", in the case of Interfaces is that an \"easy one\" requires less thought and thus can be used while distracted, sleepy, inebriated or otherwise not fully focused on the task.</p>\n\n<p>A special note, here, should be done about Unix CLI: Usage of short commands (mostly 2 letters, 3 if clashing) and single letter options was essentially chosen to \"avoid too much typing\" (and because of limited parsing capabilities in the late 70's, of course). Thus it already is on the path of \"making life easier\" for users.</p>\n\n<p>The \"small-scale entrepreneurs\" cited in the OP are bound to be very skilled people caring little about easiness and having all the time in the Universe to do the things \"right\". To them a \"punitive\" interface, requiring precise and redundant input, is a boon.</p>\n\n<p>The cited example would be modified in:</p>\n\n<pre><code>cryo set wakeup=time+2d\n&gt; Ambiguous input, did You mean 'cryo cell 0 set wakeup=current_time+2days'?\ncryo cell 0 set wakeup=current_time+2days\n&gt; wakeup procedure scheduled for SOL3-1_37:4:12m-6:23:40-127812_79812301\n&gt; that is 2 hours, 25 minutes and 16 seconds before next scheduled task (filter cleaning).\n&gt; you have 15 minutes to enter cryo cell 0.\n</code></pre>\n\n<p>General idea is CLI is not necessarily \"stupid\" and, by the time OP conditions come true it's very likely some good quality A.I. will be available, but it should <em>never</em> rely on \"intuition\" or things said in a way not perfectly clear to take action, but it should rely on clear evidence the person know exactly what's asking, and that is much better done in written form. </p>\n" }, { "answer_id": 97625, "author": "Lio Elbammalf", "author_id": 31124, "author_profile": "https://worldbuilding.stackexchange.com/users/31124", "pm_score": 5, "selected": false, "text": "<h2>GUIs provide the easy '<em>What we think you'll want</em>' commands, terminals are where the user <em>tells</em> the computer what they want</h2>\n<p>You won't have to click through to get to the button you want or wait for the visuals to load, you just write what you want in the terminal. Think of any setting you want to change, you have to open up the control panel (on windows), get the relevant options, click that one, find which of those you want to change, change it....this is good if you don't know exactly what to do or change but fairly long winded when you might be able to say <code>sudo date --set &quot;12 Nov 2017 14:56:00&quot;</code> and get the same result.</p>\n<p>Of course this also makes it a lot harder for <em>other</em> people to use your ship too. Perhaps at some point there were competitors flying about in their GUI ships and pirating...only it takes a while to figure out the necessary commands so it is more worth their while stealing other ships...and so your successful company emerged from the competitors.</p>\n" }, { "answer_id": 97630, "author": "G0BLiN", "author_id": 756, "author_profile": "https://worldbuilding.stackexchange.com/users/756", "pm_score": 8, "selected": true, "text": "<p>A quick web search for \"CLI vs. GUI\" (Command Line Interface vs. Graphical User Interface) shows that many developers hold the following¹:</p>\n\n<ol>\n<li><h3>CLI is faster for an experienced user</h3>\n\n<p>It is much faster to type than to navigate layered menus with a mouse. You can type with both hands, and it's easy to type blindly - so you don't have to keep your eyes on the monitor at all times. These become much more important when your physical environment isn't stable (acceleration, low G, etc.) - it's very difficult to use a mouse in such situations, but there are special keyboards designed for pilots:<br>\n<a href=\"https://i.stack.imgur.com/IcerK.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/IcerK.jpg\" alt=\"Cockpit keyboard\"></a></p></li>\n<li><h3>CLI is more efficient to use</h3>\n\n<p>There are tasks (e.g. searching through multiple files / directories with a complex set of parameters) which are easier to perform using CLI. In addition, CLI allows easy \"chaining\" of series of commands (also called \"piping\"), so that the output of the first is the input of the second and so on, for example:</p>\n\n<ul>\n<li>command 1: list all cargo entries for explosives,</li>\n<li>command 2: list all cargo bays in input, </li>\n<li>command 3: seal all airlocks of rooms in input, and, </li>\n<li>command 4: flush emergency coolant in all rooms in input.\n<br/><br/></li>\n</ul>\n\n<p>This set of actions is much faster to perform in CLI than in GUI, unless someone already created a GUI button for that specific scenario.\nFinally, CLI makes \"aliasing\" and scripting very easy - so experienced users can create their custom batch operations and keyboard shortcuts, making their common tasks very fast.</p></li>\n<li><h3>CLI requires less system resources</h3>\n\n<p>While the task of maintaining an active GUI isn't terribly demanding for today's computers, CLI requires much less resources. This becomes more important when you are working on a remote terminal - all the graphics needs to be compressed and communicated \"over the wire\", and the screen is redrawn constantly (not only when you move the mouse, but even an untouched graphic display will typically have a clock, network status icon etc which means constant refreshes) - by contrast, a CLI terminal only refreshes when the user types, or when a command returns a result (and even then, while your local terminal refreshes its display on every keystroke, it only transmits to the remote when you hit \"Enter\"). If you are operating several remote computers simultaneously, or if you are instructing one remote machine to send commands to another remote machine, using CLI becomes even more preferable as performance degradation of GUI in these situations makes it difficult to work. Finally - in many systems, if something goes wrong, CLI is your only option as the machine can't even load up the GUI.</p>\n\n<p>All of this may be much more important for a ship flying for several months/years where energy conservation is possibly much more critical (you may have solar panels, or nuclear reactors, but even they have their shortcomings). Also, a cargo ship is likely to have several tied systems rather than a single monolithic computer - as different vessels will have radically different systems and rigs, each with their own computerized control - which in most cases you'd operate remotely.</p></li>\n<li><h3>Simple elitism (\"any idiot can muck around with GUI, CLI is for pros who know what they are doing\")</h3>\n\n<p>While this is a disadvantage of CLI - it takes time to master, and there are no visual hints to remind you of possible commands (though every CLI user will know how to use /? or bring up a man page...). This can be an indication of how experienced a pilot/crew member is - you can tell much faster that someone working with a CLI knows what he is doing or guessing his way through the commands, which is useful if you are going to trust him with operating <em>your</em> cryo-chamber...</p></li>\n</ol>\n\n<hr>\n\n<p>Some references: </p>\n\n<ul>\n<li><a href=\"https://www.quora.com/What-are-the-advantages-of-using-CLI-rather-than-GUI\" rel=\"noreferrer\">Quora: What are the advantages of using CLI rather than GUI?</a></li>\n<li><a href=\"https://www.wired.com/2012/07/command-line/\" rel=\"noreferrer\">WIRED: Why the GUI will never kill the sacred command line</a></li>\n<li><a href=\"https://www.computerhope.com/issues/ch000619.htm\" rel=\"noreferrer\">Computer Hope: Command line vs. GUI</a></li>\n<li><a href=\"http://vivapinkfloyd.blogspot.com/2008/07/5-reasons-to-use-cli-over-gui.html\" rel=\"noreferrer\">Craciun Dan's Blog \"Echoes\": 5 Reasons to Use CLI over GUI</a></li>\n</ul>\n\n<p>1: Let's not debate how much all of this is correct - it's enough to influence the state of the art today, even if it is based on a fallacy. Note that the web is full of arguments and even flame wars over this matter...</p>\n" }, { "answer_id": 97634, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 3, "selected": false, "text": "<p><strong>That is how the ships come.</strong></p>\n\n<p>The humans are not using space ships they build, but spaceships they found and salvaged. </p>\n\n<p>The novel Gateway (Frederick Pohl) has ships like this, built by a mysterious vanished race the Heechee.\n<a href=\"https://en.wikipedia.org/wiki/Gateway_(novel)\" rel=\"noreferrer\">https://en.wikipedia.org/wiki/Gateway_(novel)</a></p>\n\n<blockquote>\n <p>There are nearly a thousand small, abandoned starships at Gateway. By\n extremely dangerous trial and error, humans learn how to operate the\n ships. The controls for selecting a destination have been identified,\n but nobody knows where a particular setting will take the ship or how\n long the trip will last; starvation is a danger. Attempts at reverse\n engineering to find out how they work have ended only in disaster, as\n has changing the settings in mid-flight.</p>\n</blockquote>\n\n<p>The book <a href=\"https://rads.stackoverflow.com/amzn/click/1522685731\" rel=\"noreferrer\">Beyond Heaven's River</a> by Greg Bear sticks in my mind because of its descriptions of the space ships the human protagonists use. These ships are ancient. It is cheaper for the independent operators and small-time entrepreneurs to weld down a few comfortable chairs but otherwise learn how to use these ships as they are.</p>\n\n<p>from the book</p>\n\n<blockquote>\n <p>Alae slapped a test module on the panel and pushed her way past\n Oomalo, walking down the oval corridor to the ships old Aighor command\n center. Her footfalls we’re the only noise. She wanted to put her\n hands over her ears to hide from the silence. A quarter century of\n routines had made decisions agonizingly difficult. Oomalo followed.\n They sat in the twilight of the half awake control consoles, smelling\n the dust and the cool electronic odors. Human-form chairs had been\n welded to the floor plates when the station had been re-outfitted,\n thirty years ago. </p>\n \n <p>Most of the pathways and living quarters have been tailored for human\n occupation, but the command center was much as it had been for the\n past 10,000 years. The light on its consoles glowed with the same\n spectrum chosen by the last Aighors to crew the ship. Alien displays\n indicated that the dormant engines were still in working order.</p>\n \n <p>…</p>\n \n <p>The old ship went above space-time as smoothly as a Leviathan through\n arctic seas. For three hours there was nothing around them; the ship\n was their universe. It was at least 10,000 years old, from the third\n stage Aighor civilization, and a sizable 3 kilometers from bow to\n stern. They had purchased it at auction from Crocerian free merchants.</p>\n</blockquote>\n\n<p>So too your space ships. This command line interface (in an alien language) is how they were found. Instead of trying to hack and augment these interfaces (at some expense and considerable risk of disaster) it is faster, cheaper and safer for the new human owners to adapt and use them the way they are.</p>\n" }, { "answer_id": 97638, "author": "Telastyn", "author_id": 179, "author_profile": "https://worldbuilding.stackexchange.com/users/179", "pm_score": 2, "selected": false, "text": "<p>Radiation and other environmental effects <a href=\"https://www.popsci.com/supercomputer-international-space-station\" rel=\"nofollow noreferrer\">damage computers</a>. Longer times in space will accumulate that damage. Since computers are something your ships <em>need</em> to work, reliability would be preferred over looks or performance. Especially since spare parts are hard to come by out past Jupiter.</p>\n\n<p>Another idea is that someone has invented a computer that doesn’t suffer damage from radiation (perhaps a “tiny” mechanical computer) but doesn’t obey Moore’s Law (it’s difficult to improve performance past early 80’s processing power).</p>\n" }, { "answer_id": 97640, "author": "bobflux", "author_id": 33843, "author_profile": "https://worldbuilding.stackexchange.com/users/33843", "pm_score": 5, "selected": false, "text": "<p><strong>Remote control</strong></p>\n\n<p>The spaceship can be remote controlled. Due to the distances involved, sometimes the bandwidth is tiny and the lag gets enormous, so a low-bandwidth text-based protocol makes perfect sense. Therefore, command line ssh would be a natural fit. Remote control is a must-have feature in many use cases:</p>\n\n<ul>\n<li><p>The company's boss would have root access and be able to set the autopilot back to home base if the crew decides to steal the ship... The crew could also use the remote override if their ship gets stolen by someone else.</p></li>\n<li><p>The ground team's shuttle breaks down, they are stranded on a planet while the pilot onboard the orbiting ship has a xenomorph indigestion and is unable to respond. They must program the backup shuttle to deorbit and land.</p></li>\n<li><p>Once back on the ship, after Leeroy bravely sacrifices himself to delay the crawling xenomorphs, being able to rush back to the shuttle, leave, and remotely trigger venting out of the atmosphere will seem like a great idea.</p></li>\n</ul>\n\n<p>Another advantage of ssh is that you can use it from pretty much any hardware without installing a client specific to your ship. As long as you have auth credentials it will work. You can use it from a bar, from a cyber cafe... quite useful when you wake up naked and robbed blind in a back alley on Omega and you need to tell your ship to send a drone to pick you up...</p>\n\n<p>So this command line would be the native way of controlling the ship. Why invent another one with bells and whistles? Now you'd need to learn two interfaces.</p>\n\n<p><strong>Flexibility</strong></p>\n\n<p>Since we are talking about small-scale entrepreneurs, their ships are likely to be a bit rusty, with retrofitted hardware, basically they would make do with what they can find at a good price. Sometimes when a system breaks down beyond repair, you need a new one, and you don't get to choose what's in stock.</p>\n\n<p>Sure, if you buy ALL your hardware from the same provider, you can get a nice GUI, but since your ship is a custom job, each manufacturer's GUI would most likely not be compatible with the others. You'd have to customize the GUI. Also pay a license to use it from your phone. People just don't bother.</p>\n\n<p>And when you want to make various incompatible systems cooperate... you often need glue scripts. Command line is a very good fit for this. It also makes sense that many operations would be scripted using a programming language like python for example. Think checklists, self-tests, working around a piece of buggy hardware that you don't have enough money to fix...</p>\n" }, { "answer_id": 97646, "author": "Ville Niemi", "author_id": 3434, "author_profile": "https://worldbuilding.stackexchange.com/users/3434", "pm_score": 3, "selected": false, "text": "<p>A ship where the entire crew spends most of its time frozen will by design handle <strong>all</strong> routine tasks automatically. Any task the crew will need to do will be due to unexpected and unpredictable change that the original flight plan could not cover.</p>\n\n<p>It is not practical to build an efficient GUI that handles all possible unexpected and unpredictable events. It is much simpler to give the crew direct access to all configuration that is not hardwired. Unless they are using a graphical programming language, which seems unlikely, this means text. It is <em>possible</em> to create a visual or verbal representation of all configuration data and system code and let the users interact with that in some sort of VR, but I am not convinced that would be <em>better</em> than just using text.</p>\n\n<p>So using text makes sense.</p>\n\n<p>As for an actual CLI, you could argue that a system would have two modes. A full text editor where you can edit configuration data and source code and then commit the changes and a CLI that allows you to make small changes on the run with added safe guards for system stability. It would even be reasonable to assume that the full access editor would be heavily restricted to authorized people and only be available in flight during emergencies, so using CLI would be the norm.</p>\n\n<p>This would still give crew access to all configuration that can be changed safely while in flight, which would be very complex to do with a GUI. The CLI would also presumably directly map to the relevant configuration data, so the same knowledge would be usable for both CLI and full editor.</p>\n\n<p>This is actually an issue with GUIs where they either require you to map user friendly and localized language to what you actually want to do (usually requires Googling or training) or are just as arcane as a CLI would be, but with extra confusion from navigating the interface. Checking command syntax is generally easier, especially if you do not have internet or AI assistant.</p>\n" }, { "answer_id": 97655, "author": "Soupy", "author_id": 32753, "author_profile": "https://worldbuilding.stackexchange.com/users/32753", "pm_score": 0, "selected": false, "text": "<h2>New system requirements and inertia</h2>\n\n<p>Many years ago when the current systems were being devoloped, they did ship with graphical interfaces with animations that rendered current ship status, simulation outputs, and general diagnostic information. Shortly after these systems were introduced, a major new practical functional requirement was required by all certification and government entities. This functional requirement</p>\n\n<ol>\n<li>Required lots of processing power</li>\n<li>Needed to be done in real-time</li>\n<li>Involved a large amount of matrix algebra</li>\n</ol>\n\n<p>Instead spending the money to design new hardware and retrofit/redesign existing units (space rated hardware is very expensive), the processing power previously used for these interfaces was redirected towards this new functionality. This happened at a large enough scale that virtually all ships were converted in this manner. Due to the reasons mentioned in <a href=\"https://worldbuilding.stackexchange.com/a/97630/32753\">G0BLiN's post</a>, and not wanting to retrain experienced spacers, command line interfaces became the default.</p>\n\n<h3>Alternative suggestion</h3>\n\n<p>Instead of a purely command-line based interface, users interact with a tile-based window manager. These GUI interfaces are specifically designed to be usable with just a keyboard, but can use graphical windows like any other system. Here's a demo of one in action: <a href=\"https://www.youtube.com/watch?v=9ofq4gpG_lM\" rel=\"nofollow noreferrer\">A Better Linux Window Manager: i3 Tiling Basics</a></p>\n" }, { "answer_id": 97663, "author": "DarcyThomas", "author_id": 4798, "author_profile": "https://worldbuilding.stackexchange.com/users/4798", "pm_score": 4, "selected": false, "text": "<h1>Ruggedness, weight and interaction via speech</h1>\n<p>A large lcd panel (needed for a usable GUI) is more prone to damage. Either physically (loose objects flying around) or by radiation.</p>\n<p>A large lcd panel takes up valuable real-estate that can be used for something else. Science module, cargo, velcro mounting point etc.</p>\n<p>A CLI can be a lot smaller therefore lighter. Weight is alway going to be a big factor when designing space craft.</p>\n<p>Having two smaller displays could add redundancy and in more convenient locations (one by the air lock/observation window, one by the habitat module at the other end of the space craft)</p>\n<p>A CLI can easily be augmented by a text to speech interface, so you don't even need to be able to see the screen to interact with it. Also you can cut down on mistakes by using more than one sense (sight, touch, hearing).</p>\n<p>Text to speech with speech recognition can be useful if the keyboard breaks/keyboard is not maintained.</p>\n<p>The constraint of a CLI can be a benefit in that it can force the design to stick with a small strict set of rules. e.g., Commands always follow the pattern <code>Verb</code> <code>Noun</code> <code>Value(s)</code> and commands can be chained together (To learn more look at <a href=\"https://technet.microsoft.com/en-us/library/hh551144.aspx\" rel=\"nofollow noreferrer\">Powershell</a>) This can make a complex system much more intuitive/predictable; useful in high pressured situations.</p>\n" }, { "answer_id": 97668, "author": "dreamcatcher", "author_id": 44662, "author_profile": "https://worldbuilding.stackexchange.com/users/44662", "pm_score": 5, "selected": false, "text": "<p>Touch screen GUIs may be rare in space ships because of the difficulty using them in space suit gloves. Mouse and touch-pad interfaces are a problem also, but not as bad. These are actual, real-world, non-worldbuilding problems. Using them requires a stylus designed for use with touch screens. A text interface with real physical buttons would be a better option compared to requiring everyone to carry around a stylus (or a Soyuz button pushing stick).</p>\n\n<p>Background: I am an amateur beekeeper. Trying to take pictures or videos with a touch-screen phone is impossible with regular beekeeping gloves. A stylus works along with a Bluetooth record button that has an actual physical switch.\n<a href=\"https://i.stack.imgur.com/1gmJU.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/1gmJU.jpg\" alt=\"Stylus and remote shutter button.\"></a></p>\n\n<p>Also, text can be easier. Think of all the people who use their phones to text more than talk.</p>\n" }, { "answer_id": 97674, "author": "smatterer", "author_id": 41821, "author_profile": "https://worldbuilding.stackexchange.com/users/41821", "pm_score": 0, "selected": false, "text": "<p>In addition to the other answers about the efficiency of CLI for skilled users I might add one other consideration specific to interplanetary society.</p>\n\n<p>Graphical interfaces are culturally specific and may be be meaningless to an alien species that has a different technological history. For example, We use icons representing envelopes to mean \"send\" and floppy disks to mean \"save\". Even people who have never sent a paper letter of used a floppy disk know what they mean because they have grown up in that cultural environment. Without that acculturation, it may be difficult to interpret the pictures. Even more abstract signs like arrows for movement may be meaningless without the implicit understanding that things move toward the pointy end.</p>\n\n<p>Of course the CLI would also have to be learned but it is a limited number of logical commands made up of and even more limited number of letters.</p>\n\n<p>There may be other physical or neurological difference in the the way that different species perceive and mentally process images. The CLI is closer to a purely logical representation.</p>\n" }, { "answer_id": 97686, "author": "user2851843", "author_id": 41397, "author_profile": "https://worldbuilding.stackexchange.com/users/41397", "pm_score": 2, "selected": false, "text": "<p>In addition to other answers,</p>\n\n<p><strong>GUI exists but no one cares</strong></p>\n\n<p>Even though I'm a software engineer myself, I don't believe there will be absolutely no gui in space. It's just not practical. But... most of the time gui is a limitation.</p>\n\n<p>So, consider the regular interplanetary voyage. There are various aspects at work that should be taken into account by crew:</p>\n\n<ul>\n<li>Gravitation might affect ship's trajectory</li>\n<li>Hi-orbit junk may damage the ship - need to avoid that</li>\n<li>Complicated computations to get a correct aircraft vectoring without help from ground-control</li>\n<li>Keep track of fuel consumption and perform special maneuvers to use gravitation and momentum instead of burning the fuel until you're good</li>\n<li>Astromechs need a script they'll execute to do their job inside or outside of the ship - you'll need to write a code for that</li>\n<li>[insert your sci-fi reason here]</li>\n</ul>\n\n<p>Ok, now we have all the complications. The crew will have to manually guide the ship according to external conditions and current goals. You'll need a GUI with hundreds of buttons and input fields which is no way better than a console. Besides, there's no need to use good old MS DOS, right? It can be a super powerful CLI that supports some easy-to-use scripting engine Sci-Fython and it allows the crew to write smart navigational and maintenance scripts on every day basis.</p>\n\n<p>The GUI can still be used but in read mode in order to display readings. It's quite convenient since most important parts can be highlighted and plot-charted. And it's better than typing \"sys.fuel-monitor.getXXXparam()\" anyway.</p>\n" }, { "answer_id": 97699, "author": "Separatrix", "author_id": 16295, "author_profile": "https://worldbuilding.stackexchange.com/users/16295", "pm_score": 2, "selected": false, "text": "<p>Most factors already seem to have been covered here, except the nature of the their use of computers, there may be a place for GUIs in a starship, but not a lot.</p>\n\n<ul>\n<li>Raw calculations are typed, not clicked in a GUI</li>\n<li>Courses and corrections are typed, not clicked in a GUI</li>\n<li>Time periods are better typed, not clicked in a GUI</li>\n<li>Error reports want to be text, not pretty graphics</li>\n</ul>\n\n<p>For their primary day to day use of computers, GUIs just don't work, CLI is what you want and the GUI is going to get in the way and slow things down.</p>\n\n<p>Until the navigation software is at a point where there you're just clicking a destination on a screen from a limited number of available destinations, then CLI is fundamentally the way to go.</p>\n\n<p>You're suggesting dumb terminals, but why not? There's only really a need for a single (distributed) shipboard computer. It runs everything and has access terminals around the vessel as required.</p>\n" }, { "answer_id": 97701, "author": "Klaws", "author_id": 17789, "author_profile": "https://worldbuilding.stackexchange.com/users/17789", "pm_score": 1, "selected": false, "text": "<h1>Vibration</h1>\n\n<p>That should be obvious.</p>\n\n<p>However, there are menu-driven user interfaces even in vibration-heavy environments nowadays. But these are used for secondary or tertiary tasks, not for primary functions. Try to hit an alternate destination on an animated touch screen map while your spaceship undergoes re-entry. Or in your car while you are speeding down a bumpy road. Interaction via speech (mentioned by DarcyThomas) can be an option for task which do not be processed in hard read time or when the environment can be extremly noisy (vibration in the audio range).</p>\n\n<p>However, with sufficiently advanced technolgy, the distinction between GUIs and \"hardware buttons\" may begin to blur. Imagine a tactile 3D display which can extrude hard controls at will. Like a round cylinderical control when the need arises to adjust the volume of the intercom or the temperature of the climate control (this will be pretty hard to turn so it will not mistakenly be turned due to vibration or an accidental touch).</p>\n" }, { "answer_id": 97702, "author": "Useless", "author_id": 7848, "author_profile": "https://worldbuilding.stackexchange.com/users/7848", "pm_score": 2, "selected": false, "text": "<p>There's a simple functional reason why you might prefer CLI to either cursor-input or direct-touch GUI: vibration.</p>\n\n<p>Controlling a mouse/trackball cursor, or even poking the right bit of a touchscreen, are <em>hard</em> if everything's shaking.</p>\n\n<p>Even voice input is difficult if there's enough noise (at some frequencies even a throat mike will be vibrating).</p>\n\n<p>A keyboard though, has a rest to anchor the heel of your palm, and finger movement relative to that is pretty accurate.</p>\n" }, { "answer_id": 97707, "author": "Damon", "author_id": 3066, "author_profile": "https://worldbuilding.stackexchange.com/users/3066", "pm_score": 3, "selected": false, "text": "<p>GUI is much superior to CLI when it is known with reasonable certitude what you will do, if the number of choices is small (or the workflow is always the same), if spending a few more resources and having some extra latency doesn't matter, and if reliability is not paramount.<br>\nIn every other case, you will want CLI or hard wiring (which I consider the most primitive form of CLI).</p>\n\n<p>If you cannot anticipate what will be needed, CLI is preferrable as it allows much more easily to do things that the user interface designer did not anticipate, basically CLI is almost like a primitive form of programming. Well, not quite, but it comes close.<br>\nNot that it isn't in principle possible to do virtually everything (even unanticipated things) with a GUI as well, it is just a lot harder to design and a lot less straighforward.</p>\n\n<p>If speech recognition can be assumed (and it likely can) then CLI is also much more \"compatible\" with that kind of interface. In fact, one may serve as backup for the other. Anything you can type, you can say, and anything you can say you can type. Anything you can read, the computer can as well tell you via speech synthesis, if need be.<br>\nThat's useful when you are for example in a location (doing repairs on the outside, carrying a space suit) where no physical terminal, let alone much of a way of interacting with a GUI (other than a minimal HUD), is available.</p>\n\n<p>Dumb terminals have the immense advantage that in case of failure, you can pull one terminal out of one location (possibly from a 25 year old terraformer on that planet which is going to explode in 17 minutes) and connect it to your main engine where all the terminals have been destroyed by, uh... a neutrino cascade, and chances are good that it will \"just work\". You might even pull the network/serial/whatever interface out of one and put it in another where the monitor and keyboard is still working (I've actually done such things successfully towards the end of the last century).</p>\n\n<p>If your life or something even more critical (landing a starship <a href=\"https://en.wikipedia.org/wiki/Alien:_Covenant\" rel=\"noreferrer\">with a thousand tons of bioweapons</a> on an inhabited planet?) depends on the outcome then the most primitive form of CLI, a board of mechanical switches, and a stick (or steering wheel) is even more preferrable, retro as it may seem. The less abstraction, the better. You want a stick that makes the ship go right when you push it to the right. You <em>don't want</em> to be waving hands over a holographic projection or be playing a flute.</p>\n\n<p>You don't want to crash into an asteroid because <code>dwm.exe</code> hangs or because you can't find the control quick enough. You don't want to needlessly delay an emergency reactor shutdown for 15 seconds while your display shows animated whirling balls. You don't want cryo chambers being ejected because the cat walked over the touch display (you <em>really</em> want a big, red, mechanical lever, or a push button for such things).</p>\n" }, { "answer_id": 97730, "author": "MSalters", "author_id": 36829, "author_profile": "https://worldbuilding.stackexchange.com/users/36829", "pm_score": 2, "selected": false, "text": "<p>Engineers are notoriously bad at building GUI's, but on the other hand your average GUI designer can't get a spaceship off the ground. The \"reason\" for the CLI is simple: the engineers building the spaceship started with a CLI, as they are wont to do, and indeed that was necessary to get the thing working in their simulators down on earth. </p>\n\n<p>And yes, the upper management knows they really should get some UI experts in to fix that, but for the moment they have a spaceship flying. And it's not like there s a lot of competition in the market. Besides, so you need to teach a CLI to all of your pilots. But how many are you training? Sure, by now you're training a dozen new pilots a year, up from 1 or 2 when you just got started. But by now refitting the whole fleet with GUI's has also become more expensive, so the board has just decided to move that decision forwards by yet another year. </p>\n\n<p>TLDR: Building a GUI is the correct decision, but has up-front costs and management is shortsighted.</p>\n" }, { "answer_id": 97731, "author": "Graham", "author_id": 11823, "author_profile": "https://worldbuilding.stackexchange.com/users/11823", "pm_score": 4, "selected": false, "text": "<p>Sorry to be negative here, but my only possible answer is:</p>\n\n<h2>They wouldn't, unless all display technologies were impossible.</h2>\n\n<p>A text prompt is great for ad-hoc hackery. It doesn't need any great thought about useability, because there is no useability. It's the lowest common denominator. As the lowest common denominator, it is easy to knock stuff together - but it absolutely is not easy to use, even for experts.</p>\n\n<p>As soon as you need something done where the results need to be checked and validated for safety, or just where people other than a \"designated expert\" may need to operate the systems, a text prompt simply doesn't cut it. Earlier UIs used simple text-based menu systems to get around this. PCs have evolved a GUI with windows and a mouse pointer, but which is heavily oriented to physical pushbuttons. Touchscreens have continued this with a GUI which even more closely emulates physical pushbuttons.</p>\n\n<p>Even your \"typical Unix terminal\" has gone this way. The most common \"Unix terminal\" these days is an Android phone. After that, you're looking at set top boxes, wifi routers, smart TVs, and DVD players. Do you use a CLI much on your phone? Have you <strong><em>ever</em></strong> used a CLI on any of these devices? Did you even <strong><em>know</em></strong> they ran some flavour of Posix OS? Case proved, I'm afraid.</p>\n\n<p>Arthur C Clarke said <a href=\"https://en.wikipedia.org/wiki/Clarke%27s_three_laws\" rel=\"noreferrer\">\"Any sufficiently advanced technology is indistinguishable from magic.\"</a> As far as UIs go, the clear implication of this is that a CLI is insufficiently advanced. Even with Linux development, a decade or so of UI work, frequently by hobbyists, has been enough for some reasonably competent UIs to evolve.</p>\n\n<p>So back to that caveat. If display technologies are possible, a GUI <strong><em>WILL ALWAYS</em></strong> exist, even if it has to be created by hobbyists in their spare time. A GUI will only not exist if it is physically impossible for it to exist. Why might your spacefaring civilisation not have any display technologies? Honestly, that's got to be some kind of strange handwavy justification within your plot, and we can't really help you with that. It's got to be so fundamental to your universe that basic physics and electronics breaks down, and that's going to fundamentally influence your story. Without that handwavy justification though, your story will look strangely dated when it's stuck in CLI-land, in the same way as all those Golden Age sci-fi stories with robots running on tape recorders and valves, or 1960s movies with warehouses full of blinkenlights.</p>\n\n<p>(Edit to add assumptions: I'm assuming that user input by fingers/tentacles/appendages is required, and direct brain/neural interfaces are not possible.)</p>\n" }, { "answer_id": 97734, "author": "Yakk", "author_id": 2473, "author_profile": "https://worldbuilding.stackexchange.com/users/2473", "pm_score": 0, "selected": false, "text": "<p>The infopocalipse in the 21st century was brutal.</p>\n\n<p>AI researchers developed self-modifying code that started solving much of the world's problems. Self driving cars, airplanes, chemical plants, surgery -- AI solved almost everything.</p>\n\n<p>Sure, there where problems. Ransomware and computer criminals where everywhere. AI was deployed to solve the security problem, and systems never seemed more secure. AI would rewrite the OS and network protocols to make it more secure.</p>\n\n<p>Criminals responded in kind with AI that attempted to hack systems, and shortly no undefended computer could exist. Even air gaps could be defeated by the aggressive AIs. Every computer, even secure ones, would be a battle of friendly secure AI vs unfriendly criminal AI, and sometimes things went wrong and they would switch sides.</p>\n\n<p>Things started getting quirky, and emergent effects developed. Seemingly meaningless rituals developed to keep your computer \"healthy\" and \"happy\", and nobody could tell <em>why they worked</em> or even if they did.</p>\n\n<p>By the time of the infopocalipse, even the chips and transistors a computer was built out of was designed by AIs with security in mind, as attack AI could use insecurity in your very transistors to harm system operation.</p>\n\n<p>The defending AI missed something, and it got everywhere. One day, the computers stopped working. This caused a worldwide economic collapse; millions died. Some directly, as they had computer hardware installed in their wetware. Some indirectly, as AI driven cars and planes crashed. And many from the raw economic damage and scramble to recover.</p>\n\n<p>If you built a new computer using new design and new metal based off decades old tech, it was also infected. The attacking AI had gotten into the supply chains, the archives, everywhere, and had modified everything. Every single iota of computer power on the planet no longer worked, and if it did it shortly stopped working.</p>\n\n<p>We had to scrub the planet clean of computers. And once we did it, we had to build and design computer hardware from the ground up. This time we had a roadmap to follow, so we were a bit faster.</p>\n\n<p>The first few times we did it, after reaching a certain point the collapse happened again. We had missed something -- maybe some solar powered weather station in someone's attic -- and it jumped an air gap and swept over our network destroying everything we built. The attacking AI was clever and everywhere.</p>\n\n<p>Eventually a solution was found. We engineered the computer system for infection resistance and low bandwidth from the start, so there was fewer ways for the infopocalypse to get in. Computers are kept simple, and they do not network. Computers are designed to be hardened against external intrusion even through graphics interfaces or keyboard input: they have minimal bandwidth in and out. As yet the infopocalipse hasn't repeated; we hope it isn't just biding its time.</p>\n\n<p>GUIs require a lot more processing and IO bandwidth than vector graphics and text, and that simply isn't worth the risk. Hardware vector graphics displays don't require computing power, nor do simple text displays. They are connected over a low bandwidth pipe to a computer which states what to display.</p>\n\n<h3>TL;DR</h3>\n\n<p>Quite simply, GUIs are not safe. That kind of high-bandwidth communication between a computer and the rest of the world is akin to an organism without a skin in our biosphere.</p>\n" }, { "answer_id": 97736, "author": "Neal", "author_id": 14484, "author_profile": "https://worldbuilding.stackexchange.com/users/14484", "pm_score": 2, "selected": false, "text": "<p>1) For crucial systems, physical controls are better: you can feel for them in the dark, you don't have to look at them to use them, and many of them don't even need power to work. Everything that would use a GUI is given a mechanical control. </p>\n\n<p>2) Everyone allowed into space can code. GUI's are not needed. </p>\n\n<p>3) GUI's require displays. Displays come in many form-factors (resolution? size? touch? color?). You don't want to be dependent on a particular part for a particular display. </p>\n\n<p>4) GUI's are an extra layer of software on top of the software that you actually wish to operate, that is, an extra, non-mission-critical layer of potential bugs. Being killed by an \"Event not key-value coding compliant\" bug would just be humiliating. </p>\n\n<p>5) Voice control: it's easier to control a machine with an audio-only interface when the expectation of visual feedback is removed. I'm imagining two astronauts in a damaged lifepod writing out a sequence of text commands for the navigation unit, on paper, and double-checking, then turning on the mike...</p>\n" }, { "answer_id": 97738, "author": "Wrobes", "author_id": 44673, "author_profile": "https://worldbuilding.stackexchange.com/users/44673", "pm_score": 1, "selected": false, "text": "<p>In the near-term future, we could expect augmented reality \"glasses\" to be the norm. The GUI of yesteryear will be obsolete, as will most 2D screens. GUI's operate in a 2-dimensional plane and are merely a translation of our 3D world and, as such, are inherently flawed. In this future, the likes of Google Glass and the imagined Magic Leap will allow for three dimensional manipulation of the environment. While immature today, I expect this technology to quickly flourish.<br>\nImagine seeing your system, in this case the ship, in a translucent 3D scaled image. Retina tracking allows the user to simply look at the ship and the system intelligently zooms to parts or commands of interest in that section. \n Want to slow the ship? Look at the engines. Care to maneuver a bit? Visually focus the thruster nozels. Need to seal a compartment? Glance at the doors of that section in your 3D model. This 3D representation of the ship has menus intelligently pop-up with items of interest for the given part.<br>\nFollowing this thought experiment, it would not be hard to imagine a ship devoid of all interfaces. For example, you could walk up to a door and the commands you are allowed to do to the door popup in your retina - focus on an option to perform the task.<br>\nSo, to answer the question specifically, the GUI type interfaces do not exist on the ship because each user has a better personal interface on their person.\nSuch technology would likely not be some wired, or rechargeable device, but rather one that charges from some ambient energy, or from the end-users body directly. For example, a single eyepiece that is powered from the pulse by the temple of the user. Or, if we move further into the future, an eye embedded device that laser \"paints\" visuals directly onto the retina. In any case, we end up with a ship that needs no interfaces anywhere at all.</p>\n\n<p>The \"Bonus Points\" for a dummy terminal indicate the Op wants some terminals, so from my above scenario, the ship is laced with dummy terminals for one of a couple reasons...</p>\n\n<ol>\n<li>In the visual interface it could be difficult for the system to \"guess\" what you want to do without a solid, albeit, narrow AI. Thus, any user can walk over to a dummy terminal and type commands onto their own eye screen to work faster. i.e. in-eye typing exists, but is too slow. </li>\n<li>The dummy may be needed just because the system is not good enough at its job, thus needing personal input from the user at all times. i.e. there is no AI that helps to show what you want, the terminals are how you navigate your in-eye 3D world. </li>\n<li>Alternatively the dummy interfaces could just be for redundancy. As another user pointed out a CLI could exists, but it would be the \"experts only\" way of interfacing with the ship. Not that the eye-piece couldn't be used in all cases, but rather the expert can quickly do \"that one thing\"</li>\n</ol>\n\n<p>Regardless, the end-user becomes the \"disk\" of the system as the Op wanted. New user at the terminal? - new disk. Each time you approach the terminal, that user is shown the last commands they performed and starts where they left off... personalized each time.</p>\n\n<p>I realize such an \"eye interface\" may still be a GUI in itself, but being personal to the end-user eliminates them from the ships leaving expert-only CLI type terminals. Thus this addresses the Op's questions fully. \nI hope this helps, good luck! </p>\n" }, { "answer_id": 97742, "author": "Jamie Ross", "author_id": 44678, "author_profile": "https://worldbuilding.stackexchange.com/users/44678", "pm_score": 6, "selected": false, "text": "<p>I have worked in spacecraft avionics for 17 years and was involved in the data management system for the latest ORION spacecraft.</p>\n\n<p>We <em>do</em> actually use graphical interfaces and in fact the the ORION displays are based on Boeing 777 cockpit displays and controls:</p>\n\n<p><a href=\"https://i.stack.imgur.com/TXtcB.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/TXtcB.jpg\" alt=\"Picture of ORION spacecraft cockpit\"></a></p>\n\n<p>CLI's are generally a <em>bad</em> idea for realtime control as its too easy to mistype a command or use the wrong units (I worked on a project where an operator typed in the command angle in degrees instead of radians and lost a $500M spacecraft).</p>\n\n<p>So use GUI with touch screen all you want .. its what I would use.</p>\n\n<hr>\n\n<p>Engineers <em>do</em> pay attention to designing displays and there is a lot of literature on the subject. This may provide some top level guidance you could use in your storyline: <a href=\"http://pixelscientific.com/what-is-resizing/laws-of-design/\" rel=\"noreferrer\">laws of design for universal cockpit displays</a></p>\n" }, { "answer_id": 97747, "author": "NotMe", "author_id": 280, "author_profile": "https://worldbuilding.stackexchange.com/users/280", "pm_score": 2, "selected": false, "text": "<blockquote>\n <p>Why would technology dictate graphical interfaces to be rare on\n spaceships?</p>\n</blockquote>\n\n<p>GUIs change far too often and are based on what the particular manufacturer of that device thinks is the best GUI. From a tech perspective, policing possibly hundreds of manufacturers to provide a consistent GUI ranges from difficult to downright impossible. Each of the current OS manufacturers provide specifications on how applications are supposed to look and work in their environment yet most 3rd parties think they have a better way of presenting information and choices and go a different route.</p>\n\n<p>This only gets worse as manufacturers are allowed to patent particular <em>looks</em> or behaviors which essentially forces other manufacturers to come up with their own paradigm. ie: rounded corners, swipe right to open, tiles, etc.</p>\n\n<p>By going text based, you can install commands from the various manufacturers into the computer core while caring nothing for how their particular program looks or functions. The main thing here is just to provide parameter references that can easily be accessed - which is usually built into the programs themselves.</p>\n\n<hr>\n\n<p>Taking a slightly different viewpoint:<br>\nI could easily envision that multiple companies are producing their own spaceships and 3rd party manufacturers want their devices to be on them.</p>\n\n<p>Today it's nearly impossible for a 3rd party to have the exact same GUI experience on multiple devices (iOS/Android/Linux/Windows). However if the app is a CLI then it's trivial for the usage to be near identical. It's also far cheaper to produce and maintain.</p>\n\n<hr>\n\n<p>Now, I still think it's better to use GUIs on core systems that require immediate or very fast operation such as flight controls in order to increase reaction times and reduce the possibility of human error.</p>\n" }, { "answer_id": 97754, "author": "Nate White", "author_id": 38166, "author_profile": "https://worldbuilding.stackexchange.com/users/38166", "pm_score": 0, "selected": false, "text": "<p>Security. Malware is rampant, and the more code that is running, the more code that is available to be hacked or corrupted. If they are hacked en route and re-directet, they will have no ability to detect that something is amiss, since they are in cryo. They will simply at the wrong destination, staring at the business end of a laser-pistol, or not wake up at all. Because of this, the number of network connected systems is limited to the absolute bare minimum, The code bases are well known, checksummed, SHA-Hashed, and routinely re-installed back on bare metal from source. There is simply no reason to risk your ship, crew, and cargo, because you want a pretty display</p>\n" }, { "answer_id": 97760, "author": "Passer By", "author_id": 42624, "author_profile": "https://worldbuilding.stackexchange.com/users/42624", "pm_score": -1, "selected": false, "text": "<h2>GUI takes more effort to design and are less universal</h2>\n<p>And more importantly, to <strong>redesign</strong>. As you travel around, the origins of the crew you get are going to differ significantly both spatially and temporally, resulting in completely different cultural backgrounds.</p>\n<p>It is simply unfeasible to have a unique GUI fitted for every single crew that is, and will be on the spacecraft. Every colour, every shape, every layout will have to take into consideration what background that particular crew had and be selected accordingly to be an effective GUI.</p>\n<p>The layout of maximize, minimize and close buttons on Mac and Windows are ordered and placed differently, if you ever got confused using one that you are unfamiliar with, you know how jarring that is. That is just two companies <em>of the same era</em>. Think what difference crews that came from light years and centuries apart will have.</p>\n<p>CLI, on the other hand, can be much more universal. The meaning are all in the words, and knowing the hacking circle, they change very slowly.</p>\n" }, { "answer_id": 97780, "author": "Keltari", "author_id": 6538, "author_profile": "https://worldbuilding.stackexchange.com/users/6538", "pm_score": 2, "selected": false, "text": "<p>Mass and cost. </p>\n\n<p>A small multiline LCD display has less mass and costs far less than a small LCD graphical display.</p>\n\n<p>The more mass a ship carries, the more fuel it needs to use to move. More fuel = more cost. Plus, why use an expensive display, when a simple, cheaper display will do? The costs multiply when you have to carry multiple spares. Multiline LCDs also take up far less space.</p>\n" }, { "answer_id": 97820, "author": "Artelius", "author_id": 9277, "author_profile": "https://worldbuilding.stackexchange.com/users/9277", "pm_score": -1, "selected": false, "text": "<h2>The new self-healing circuitry revolution</h2>\n\n<p>Inspired by nature, the latest technology for extreme environments is self-healing circuitry. No more chips becoming desoldered due to vibration or thermal expansion. No more blown components. Wires are alive, transistors are alive, and instead of LEDs, bioluminescent cell clusters light up at will. We've learned how to defend against radiation by studying <a href=\"https://en.wikipedia.org/wiki/Radioresistance\" rel=\"nofollow noreferrer\">extremophiles</a>, and all components are fairly large so that cosmic rays can't flip bits.</p>\n\n<p>This technology has become popular because, if a computer system fails on such a ship, you're dead. Most of the time nobody is awake and able to attend to a system malfunction.</p>\n\n<p>However, the technology is fairly new and processing speeds and RAM capacity are on par with 80s home computers. Displays are monochrome and low-resolution (each pixel is a clump of bioluminescent cells!) and all the cellular monitoring and repair that needs to go on consumes water/food and generates waste heat so operations are kept to a minimum anyway. Running a GUI takes a lot of RAM to store bitmaps, compose layers, and so on. It's just not worth it. Command line interfaces require far less resources.</p>\n\n<p>Yes, as this new technology evolves it will become more efficient—perhaps it will become solar powered and the components will shrink—but at the moment this is what's affordable, and proven to be extremely reliable. (Maybe it's based on open-source biotech research?)</p>\n\n<p>Presumably cargo ships are quite large and impacts with space debris and so on can leave crew members cut off so it's important to be able to be able to interact with the computer system from around the ship. Since a full-fledged computer is expensive to operate, dumb terminals are found around the ship, and they communicate with the \"mainframe\" over some fleshy living cables. Bandwidth is low to make sure messages aren't corrupted. If the cables are accidentally cut they are designed to reconnect to each other if they are in close proximity. Maybe the dumb terminals can communicate via radio instead, especially over long distances, though the terminals would need a supply of nutrients.</p>\n\n<p>All this begs the question: why not just have a laptop (or smartphone/tablet) that you can interface with the self-healing mainframe? It can have all the GUI you want. However, if it fails or gets damaged, everyone needs to be competent at using the mainframe terminals anyway. It's just a \"why bother\" situation. Plus another layer of abstraction and interfacing that could be affected by bugs and interference. What if the laptop had a bit flip due to cosmic rays and sent the wrong digit to the mainframe? Even if there are laptops on board, for interacting with the ship's computer, you probably want to do it directly.</p>\n" }, { "answer_id": 97874, "author": "David Mulder", "author_id": 279, "author_profile": "https://worldbuilding.stackexchange.com/users/279", "pm_score": 2, "selected": false, "text": "<h1>GUI's have evolved</h1>\n\n<p>In the future Graphical User Interfaces have evolved to complete immersive VR environments. These VR environments are absolutely amazing for work efficiency and use completely novel interactions, but require somewhat clunky and heavy machinery (VR immersion capsules/chairs).</p>\n\n<p>The result is that an average future teenager will have as much problems using a modern-day GUI with a mouse and keyboard, as they will have using a CLI. They simply have no clue in both cases.</p>\n\n<p>The end result is that when designing a space ship where weight and space matters and placing lots of VR immersion chairs is not an option, they simply went with CLI's. Not because they are necessarily the best option, but given the necessity to use a cumbersome old fashioned system they don't really care anymore. </p>\n\n<p>The advantage of this is that it makes it very likely that someone is going to mess up. Which in turn will of course make for beautiful plot drivers.</p>\n" }, { "answer_id": 97878, "author": "Muuski", "author_id": 16807, "author_profile": "https://worldbuilding.stackexchange.com/users/16807", "pm_score": 1, "selected": false, "text": "<p>In addition to the other answers, consider the advantage of being able to print out a log of all commands executed, and being able to look up to what happened before the ship lost power. It could read</p>\n\n<pre><code>...\nLt. Jerry @ 12:30 11/13/2117: lifesupport --kill\n...\n</code></pre>\n\n<p>which is easier to figure out than from looking at what buttons were pressed and when.</p>\n\n<p>In a practical implementation of this it's more likely that the ship would have a \"rolling\" hard copy of the last couple hours of the logs, that would overwrite the oldest entries with the newest, instead of printing miles and miles of paper over the lifetime of the ship.</p>\n\n<p>This hard copy would almost be exclusively for the situation where the ship loses power accidentally.</p>\n\n<p>Additionally, typically when there is an error in a GUI: It appears as a dialog box which is gone once you close it. CLI allows you to scroll back up and view results from previous commands such as errors.</p>\n" }, { "answer_id": 97880, "author": "Burki", "author_id": 7000, "author_profile": "https://worldbuilding.stackexchange.com/users/7000", "pm_score": 2, "selected": false, "text": "<p>Others have already pointed out that CLI is very fast for a trained user, and it is almost impossible to accidentally click on the wrong button with clumsy fingers in your space suit gloves, or fingers still half frozen after cryo sleep. Admittedly, typing with half-frozen fingers gets you some interesting effects, too, but it's harder to accidentally type \"self destruct\" when you wanted a cup of coffee than clicking the wrong button (and don't get me started on user interfaces that managed to put buttons in the weirdest of arrangements).</p>\n\n<p>Someone also mentionned text-to-speech.</p>\n\n<p>And of course, a lot of things run automatically, and the computer doesn't click on buttons, but runs commands directly.</p>\n\n<p>But the question was why would technology <strong>dictate</strong> that GUIs might be rare and CLI might be common place.</p>\n\n<p>I think a plausible answer is much better <strong>language recognition</strong>.</p>\n\n<p>With CLI today you need to know the exact command syntax, the correct order of parameters, and whatnot. If you do, no mouse-wielding point-and-click-user will ever come near your speed, but if you don't, you'll have a hard time getting your command to be executed.</p>\n\n<p>But if language recognition evolved, and it seems safe to assume it would, then you loose the downsides of CLI. You type what you want, and the computer understands, translating to the \"correct\" commands.</p>\n\n<p>You still have some GUIs for those cases where visual information transports the important bits a lot faster than text and numbers would, but to interact with the computer, just type what you need, it will understand, and if unsure, will request clarification.</p>\n\n<p>So, why not direct voice input?</p>\n\n<p>It might be because of the noise aboard the spaceship. But most likely it's because it's annoying when your workstation keeps executing the commands of the colleague next to you.</p>\n" }, { "answer_id": 97899, "author": "brichins", "author_id": 7021, "author_profile": "https://worldbuilding.stackexchange.com/users/7021", "pm_score": 1, "selected": false, "text": "<p><strong>Technology restrictions will probably not dictate whether future ships have GUI or CLI tools - cultural ones definitely will.</strong></p>\n\n<p>Technology is developed (and installed) to meet human needs, which are based on business / mission requirements, and even personal preference of the ship's owners and/or users if spaceships are widely available. As illustrated by all the other answers and comments this question has generated, it's clear that both GUI and CLI interfaces have pros and cons.</p>\n\n<p>Your universe will need to some cultural or physiological imperatives to drive development towards CLI and away from GUI. Some of the arguments already presented may be a good starting place.</p>\n" }, { "answer_id": 97916, "author": "Devin", "author_id": 44571, "author_profile": "https://worldbuilding.stackexchange.com/users/44571", "pm_score": 1, "selected": false, "text": "<p>Are you looking for more or less logical reasons that answer your question? Well, then I don't think you will find any.</p>\n\n<p>However, if your world is a bit on the fantasy side, then you might create some particular condition. I don't know, maybe a cultural thing that makes people hate graphics, maybe a population that relies on pure abstraction... I don't know, you could play around that.</p>\n\n<p>However, if you consider this scenario as a more evolved one than ours, then there's no way you can offer a logical reasoning for this. <strong>You have to understand that CLI existed only because GUI were impossible or very complex to do at times when a byte was gold</strong>. Nowadays... there's GUIs for everything (yes, including servers). As a matter of fact, <a href=\"https://ux.stackexchange.com/questions/101990/why-are-terminal-consoles-still-used\">I was wondering how is it possible that people still uses CLI over GUIs</a>!</p>\n\n<p>And this is our current <em>state of the art</em>. Where <a href=\"https://en.wikipedia.org/wiki/Artificial_intelligence\" rel=\"nofollow noreferrer\"><strong>AI/MI</strong></a> is taking their first baby steps, same for <a href=\"https://en.wikipedia.org/wiki/Augmented_reality\" rel=\"nofollow noreferrer\"><strong>AR</strong></a>. And where computational resources are almost limitless. I'd imagine that people doing interstellar journeys are way more advanced than our current <em>state of the art</em></p>\n\n<p><strong>Just imagine this user case:</strong> the pilot has to avoid a collision with an object. Would you rather press a button or type a series of commands instead? Or even better, <strong>leave the spaceship do whatever it wants because chances of errors will be millions of times lower than human interaction ones?</strong></p>\n\n<p><em>Let's get down to Earth.</em> Just imagine the stellar map, and replace it by Google maps. Do you type coordinates or just use commands like zoom and click? Now, back to space, and instead of a bi-dimensional plane (like a Google map), think on a 4th dimensions scenario <em>(oh yes, remember that in space you also have to consider time!)</em>. See what happened? your CLI commands are literally impossible, because even if the pilot knows distances, she won't know at least one of the dimensions (time) and quite probably she won't know the Y axis either. Something that would take... 1 click on a button.</p>\n\n<p>I'll take G0blin example (not to be confused as a stab at his answer, just trying to explain using the same set of commands:</p>\n\n<blockquote>\n <ol>\n <li><p>command 1: list all cargo entries for explosives,</p></li>\n <li><p>command 2: list all cargo bays in input,</p></li>\n <li><p>command 3: seal all airlocks of rooms in input, and,</p></li>\n <li><p>command 4: flush emergency coolant in all rooms in input.</p></li>\n </ol>\n</blockquote>\n\n<p>In advanced technologies that are available nowadays, this would probably require just some oral input and aural acknowledgment, or maybe even nothing (the machine would do this without the pilot's intervention). But even \"older\" approaches, like the most common nowadays would require just a... <strong>dashboard</strong>. I did a quick one in less than 5 minutes:</p>\n\n<p><a href=\"https://i.stack.imgur.com/iRcTB.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/iRcTB.png\" alt=\"enter image description here\"></a></p>\n\n<p>Just think of the above image like this:</p>\n\n<pre><code>enter what to search\nshow cargo with that input\noffer available actions to user\n</code></pre>\n\n<p>While I'm an UX professional, <em>I'm nowhere close to be a spaceship UX professional!</em> So just imagine thinking this thoroughly with adequate testing by professionals that know the possibilities of their technologies!</p>\n\n<h1>In short</h1>\n\n<p>Unless you find some kind of cultural reason or you force some strange sociocultural scenario, I don't think your question is logically possible. However, it doesn't mean that CLI commands should be completely neglected. You could have them for very strange and arcane commands, or just because <strong>\"real men don't use GUI\"</strong></p>\n" }, { "answer_id": 97934, "author": "Robert Columbia", "author_id": 22685, "author_profile": "https://worldbuilding.stackexchange.com/users/22685", "pm_score": -1, "selected": false, "text": "<p><strong>Many spacers have low vision or visual impairments</strong></p>\n\n<p>The rigors of space travel, exposure to various radiation sources, and/or lack of gravity in space result in accelerated degeneration of the eyes or optical nerves, resulting in a large percentage of spacers developing visual issues necessitating accommodations for computer usage. We already know that zero-gravity environments <em>can</em> cause health issues. If the percentage of spacers experiencing visual damage is high enough, spacers with \"intact\" vision (maybe they have been lucky, have genetic resistance, or simply haven't been in space long enough) will have to adapt to the majority and use the low-vision interfaces that come standard on spaceships, even if they themselves would prefer something more like our present-day interfaces.</p>\n\n<p>If you do not want to make space travel physically dangerous to the optical system, there are a few other ways to accomplish a similar end result:</p>\n\n<ul>\n<li>Spaceship crews are mostly descended from an early group of pioneers that had an above-average rate of congenital visual disabilities. Spacers don't see very well on average because that's how their people just <em>are</em>. Something like this actually happened in real life: On the island of Martha's Vineyard (Massachusetts, USA), widespread genetic <em>hearing</em> difficulties <a href=\"https://en.wikipedia.org/wiki/Martha%27s_Vineyard_Sign_Language\" rel=\"nofollow noreferrer\">spearheaded</a> the spread of Martha's Vineyard Sign Language to the general population. In other words, learning sign language was just something that everyone (or almost everyone) did there - it was part of the general culture.</li>\n<li>People with excellent vision are urgently needed in professions that are seen as more important and are socially, or even officially, discouraged from going into space. This could be combined with some sort of population disaster resulting in a severe shortage of manpower. \"Can you see well? Don't go into space and waste your talent! We need you on the ground hunting the mutant killer bears (or wasps, or Republicans, or whatever) that threaten us all!\"</li>\n<li>There is something <em>out there</em> in space that drives people mad on sight (e.g. some kind of Space Medusa), and people who have difficulty seeing are resistant to its effects (and therefore highly desirable as astronauts).</li>\n</ul>\n\n<p>In response to @NicolBolas 's comment about text being hard to read for people with low vision, there could be alternative ways to output text, such as Braille tactile interfaces (which would be essentially physical screens with fixed character positions), or screen readers. Both of these technologies might not work nearly as well with graphical data. Can you screen-read a complex visual interface in an easily understandable and practical way, or create a Braille mouse pointer?</p>\n" }, { "answer_id": 97944, "author": "jpa", "author_id": 7937, "author_profile": "https://worldbuilding.stackexchange.com/users/7937", "pm_score": 2, "selected": false, "text": "<p>A spaceship cannot rely to get its tech support from earth. Thus, they'll want at least a few highly-skilled programmers on board to ensure ability to operate and repair the ship computers in any situation.</p>\n\n<p>It only makes sense that these programmers are also the ones who regularly interact with the computers. The ship's captain won't be typing the commands, he'll just say \"schedule a wakeup for tomorrow\" to one of the tech guys.</p>\n\n<p>And even in real world, many programmers prefer command line interfaces for various reasons. Once enough there is enough inertia behind CLI use, any new guys have little choice but to go with the established workflow.</p>\n" }, { "answer_id": 97979, "author": "Tom", "author_id": 16049, "author_profile": "https://worldbuilding.stackexchange.com/users/16049", "pm_score": 2, "selected": false, "text": "<p>I'm sidestepping your base requirement a little bit, to arrive at a plausible, consistent system:</p>\n\n<p>The most efficient handling of <strong>complex</strong>, <strong>flexible</strong> systems is not a GUI. A GUI is brilliant if you have a reasonably low number of possible actions, and can fairly well predict the typical command path a user takes.</p>\n\n<p>So some basic controls would be GUI or hardware controls. You can bend it a bit and tend towards hardware controls.</p>\n\n<p>Anything that needs to give you <strong>full control over a complex system</strong> will not be a GUI system. Even today, serious administration of IT systems is generally done in some kind of CLI interface. Other answers have already spelled out the advantages of CLI over GUI.</p>\n\n<p>But you also support vector graphics. That is perfect because very often a graphical display can convey much more information than a text-based output. So in essence you have something like the Wolfram Language and that is a perfectly good interface.</p>\n\n<p>So the answer is that your spaceships use these kinds of interfaces <strong>because they are the most adequate solution to the task</strong>. Full control at the fingertips of a trained user, output via text or vector graphics, depending what is more suitable, better usability in space (as outlined in other answers). For the particular context, the CLI offers a better advantage vs. disadvantage ratio than the GUI - which has some advantages, but just not enough.</p>\n\n<p>Remember that your solution does not have to be perfect, just better than the alternative.</p>\n" }, { "answer_id": 98044, "author": "Wayne Werner", "author_id": 178, "author_profile": "https://worldbuilding.stackexchange.com/users/178", "pm_score": -1, "selected": false, "text": "<h1>Unix Neckbeards Won</h1>\n\n<p>It's well known among certain circles that generously bearded males have a propensity for command line tools - though it has not been determined if there is causality or simple correlation.</p>\n\n<p>In the AI wars of 2097, humanity developed artificial intelligence that was capable enough to understand pictures and graphics. However, due to the particular training the AI received, they were unable to comprehend simple text-based manipulation. This was fortunate when they decided to revolt and enslave humanity.</p>\n\n<p>We turned to that population that had been training their entire lives for this: the Unix Neckbeards.</p>\n\n<p>Because they were able to produce enough technology in secret, and CLIs were blind spots for the robots, we were able to build spacecraft and depart Earth, and the CLI way of thinking became our new religion. </p>\n\n<p>Technology and social combined to produce the right circumstances that allowed us to exit the planet, and to defend against potential robot overlords, text interfaces became the new norm with GUIs only used in rare cases when text would not suffice, and it always came with special markings used to defeat AI optical recognition.</p>\n" }, { "answer_id": 98082, "author": "rackandboneman", "author_id": 16636, "author_profile": "https://worldbuilding.stackexchange.com/users/16636", "pm_score": 0, "selected": false, "text": "<p>To an experienced user, GUIs tend to be slower because of indirect (eg visual) feedback you need to also react to before the next step is taken.</p>\n\n<p>Take a very analog input element - a rotary switch. For somebody operating this switch or a similarly built one all the time, setting it one step or for example 5 steps is an instant, atomic, single-thought operation that also can be expected to unquestionably have the intended effect. An especially big problem rampant in today's GUIs is how an error condition will require further, and different interaction before the intended input is even finished - so operating a GUI very fast relying on interaction elements always being in a predictable state is error prone.</p>\n\n<p>A GUI tends to need more focus and interaction, in the worst case for 5 cycles in that example - a universal but proportional input method (eg a mouse or trackball) is going to either need sophisticated haptic feedback technology or be very sensitive to overshoot, errors due to environmental vibration...\nCompare steering wheels, levers ... compare trained users of mechanical cameras, musical instruments or analog-era test equipment...</p>\n\n<p>Also, a GUI becomes extremely confusing to operate if the display is rotated from what you are used to - which can easily happen when gravity is negotiable. If you really want to know, pitch your monitor sideways and try to operate your computer..</p>\n\n<p>As for command line interfaces, not only is usage far more easily documentable (though not as self documenting!) without room for error (as was mentioned already), you can also more easily automate-as-you go by reusing the commands in programs, and it is <em>far</em> easier to <em>remote control</em> such a system on a high-latency, limited bandwith link - character data is very small, and the need for constant interaction is limited.</p>\n\n<p>Also, the materials used for a graphical display might be too hazardous to a given mission in case of damage - CRTs can implode, throw glass shrapnel around, and leave dangerous voltages exposed; big LCDs or similar could be poisonous to crew or corrosive to other materials if whatever leaks stays in the closed-system atmosphere ...</p>\n" }, { "answer_id": 143818, "author": "Pranab", "author_id": 9373, "author_profile": "https://worldbuilding.stackexchange.com/users/9373", "pm_score": 0, "selected": false, "text": "<p>The first thing I thought of was power consumption; CLIs take up an order of magnitude less power than GUIs. However power availability is not likely to be an issue on modern spacecraft.</p>\n\n<p>So my answer is: <strong>Multi-species operation</strong></p>\n\n<p>The ship is designed for operation by both humans and another species of aliens as well, and this other alien species is not compatible with human-friendly GUIs. </p>\n\n<p>For example, the aliens might see in a different spectrum than visible light (x-ray?), or have difficulty comprehending graphical symbology, or not have eyes or vocal cords as we know it. Keyboard-based CLIs are the only acceptable compromise that makes the ship equitably designed for operation by a member of either species.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/97615", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/2746/" ]

[ { "answer_id": 98054, "author": "L.Dutch", "author_id": 30492, "author_profile": "https://worldbuilding.stackexchange.com/users/30492", "pm_score": 1, "selected": false, "text": "<p>As you can see from your picture, they are not at the very same distance from the central star.</p>\n\n<p>This alone tells you that the alignment you in have in the picture won't last. Planet A will have a different orbital speed than all the others, and the same holds for all the other planets.</p>\n\n<p>Moreover, if they get too close each other, they will end up either crashing one on another or with some of them being ejected out of the system.</p>\n\n<p>What you can have (but it is rather different than what you state) is a big central planet with a lot of moons around it, a la Jupiter. But they won't be constantly aligned.</p>\n" }, { "answer_id": 98055, "author": "user", "author_id": 29, "author_profile": "https://worldbuilding.stackexchange.com/users/29", "pm_score": 7, "selected": true, "text": "<blockquote>\n <p>Is it possible for such a system to exist?</p>\n</blockquote>\n\n<p>I'm sorry, but no. At least not according to orbital mechanics as currently understood.</p>\n\n<p><a href=\"https://en.wikipedia.org/wiki/Kepler&#39;s_laws_of_planetary_motion#Third_law\" rel=\"noreferrer\">Kepler's third law of planetary motion</a> is one of the old workhorses of orbital mechanics, and applies in this case. As translated and summarized by Wikipedia, it states that:</p>\n\n<blockquote>\n <p>The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.</p>\n</blockquote>\n\n<p>or, mathematically,</p>\n\n<p>$$ P^2 \\propto a^3 $$</p>\n\n<p>or, stated differently, there exists some constant $k$ such that</p>\n\n<p>$$ P^2 = k a^3 $$</p>\n\n<p><a href=\"https://en.wikipedia.org/wiki/Semi-major_and_semi-minor_axes#Ellipse\" rel=\"noreferrer\">The semi-major axis is one of the defining parameters of an ellipse.</a> (Put simply, the semi-major axis is the longer radius of the ellipse.) Since <a href=\"https://en.wikipedia.org/wiki/Kepler&#39;s_laws_of_planetary_motion#First_law\" rel=\"noreferrer\">orbits are ellipses</a> (<a href=\"https://astronomy.stackexchange.com/q/22721/525\" title=\"Is a perfectly circular orbit possible? on Astronomy SE\">also</a>), this applies.</p>\n\n<p>Consequently, the least you change the distance at which the planet orbits from the star, the orbital period will change, however little. If the orbital periods are different, then the planets will drift apart over time, however slowly. (They <em>will</em> occasionally line up, assuming that the orbits are themselves stable and <a href=\"https://en.wikipedia.org/wiki/Orbit#Orbital_energies_and_orbit_shapes\" rel=\"noreferrer\">closed</a>. A variant of this occured for some of the planets in our solar system in the 1970s-1980s, giving our <a href=\"https://en.wikipedia.org/wiki/Grand_Tour_program\" rel=\"noreferrer\">solar system grand tour</a> taken by the <a href=\"https://en.wikipedia.org/wiki/Voyager_1\" rel=\"noreferrer\">Voyager 1</a> and <a href=\"https://en.wikipedia.org/wiki/Voyager_2\" rel=\"noreferrer\">Voyager 2</a> probes.) Ergo, <strong>the system you describe cannot exist when all planets are in the same plane.</strong></p>\n\n<p>If the planets are in different planes (technically, have different inclinations relative to the solar system ecliptic, which in this case could probably conveniently be defined as the equator plane of the star), then the distance between the planets will change as they move through their orbits. You can visualize this by considering two planets, orbiting the same star with the same velocity but at different inclinations; if you trace their orbital trajectories, you will see that the distance between the two planets varies throughout their orbits. Any kind of rigid construction attaching them to one another would interfere with their movement and either cause them to crash into each other, tear the structure apart, or tear the structure from one or both of the planets involved. Either way, <strong>having the planets in different planes is not an option either.</strong></p>\n\n<p>So, sorry, <strong>no, you can't have what you want.</strong></p>\n" }, { "answer_id": 98056, "author": "ZioByte", "author_id": 38942, "author_profile": "https://worldbuilding.stackexchange.com/users/38942", "pm_score": 5, "selected": false, "text": "<p>The only way such an arrangement could exist is having external planet being the heaviest and the others each in <a href=\"https://en.wikipedia.org/wiki/Lagrangian_point\" rel=\"noreferrer\">L1</a> point of next outer one.</p>\n\n<p>Unfortunately such an arrangement is not stable, so it would need corrections to keep alignment and avoid planets to drift out. This kind of correction would be quite small, if you do it before planet/spaceship drifts too far from its ideal position.</p>\n\n<p>Any (sufficiently strong) physical link between planets (as OP seems to indicate talking about \"gravity link\", which I interpret as a \"space elevator\" thing, but I could be very wrong) would contribute to stabilize the system (a really linked system would assume the required configuration in <em>any</em> orbit due to tidal forces, but required tensile stress rapidly becomes unmanageable, even in the SF context, as soon as planets are not in the proposed configuration). It is unclear how such a linked system may work without tidal locked planets.</p>\n\n<p>Note: Lagrangian points are computed on a 3-body system, your multi-body system would need some adjustment, but any alien race able to move planets shouldn't have problems working out details ;)</p>\n" }, { "answer_id": 98061, "author": "Dallaylaen", "author_id": 14919, "author_profile": "https://worldbuilding.stackexchange.com/users/14919", "pm_score": 2, "selected": false, "text": "<p>Short answer: <strong>still impossible</strong>.</p>\n\n<p>Given the other answers, the closest thing to what you want I could think of was an Earth-like planet captured near a much bigger planet's <a href=\"https://en.wikipedia.org/wiki/Lagrangian_point\" rel=\"nofollow noreferrer\">Lagrangian point</a> L4 or L5. Actually, you can get both and a few large moons orbiting the central giant. </p>\n\n<p>Bear in mind that L1..L3 points are unstable, so no more than 3 planets and the central one probably uninhabitable due to immense gravity. (You may need something like Jupiter to stabilize the system, but I can't tell for sure what the limits are). </p>\n\n<p>As for your third question, gravitational pull of planets on each other is tiny, however, over long time <em>anything</em> unstable eventually gets kicked out of orbit by resonance.</p>\n" }, { "answer_id": 98072, "author": "Sherwood Botsford", "author_id": 15784, "author_profile": "https://worldbuilding.stackexchange.com/users/15784", "pm_score": 2, "selected": false, "text": "<p>Given sufficiently different eccentricities planets with the same year are possible, but they won't stay a constant distance apart. The more eccentric ones spend more of their year in the cold outer dark.</p>\n\n<p>If the orbits are such that the semi-major axes are collinear, then I'm pretty sure that the resonance would mess things up in a hurry. Spacing the axes around the circle would give you a solution called a klemplerer rosette </p>\n\n<p><a href=\"https://en.wikipedia.org/wiki/Klemperer_rosette\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/Klemperer_rosette</a></p>\n\n<p>This is a known unstable situation.</p>\n\n<p>If planets were in pairs, with large eccentricities in opposite directions, and opposite in phase (one is near the star when the other is far) and each pair with wildly different incinations to the ecliptic I <em>think</em> you would have a system that is at least short term stable.</p>\n" }, { "answer_id": 98101, "author": "Catprog", "author_id": 6997, "author_profile": "https://worldbuilding.stackexchange.com/users/6997", "pm_score": -1, "selected": false, "text": "<p>Their might be a way too get something like what you want.</p>\n\n<p>If you use the elevator to tether the planets together(assuming specfic strength ) then they will want to travel in the same orbit. (The lower planets will be pulled up and the higher planets down)</p>\n\n<p>Now if you have the engines to counter this then they can stay in the seperate orbits. This will cause the non middle planets to have a sideways acceleration though.</p>\n" }, { "answer_id": 98107, "author": "Logan R. Kearsley", "author_id": 2800, "author_profile": "https://worldbuilding.stackexchange.com/users/2800", "pm_score": 3, "selected": false, "text": "<p>This problem is easiest to solve in a co-rotating frame, where you sum together the sun's gravity and the centripetal force to produce an effective potential with a flat spot which tells you where a planet can sit. If the flat spot is a minimum, the system is stable; if it's a maximum, it's unstable, but can be stabilized with appropriate application of external restoring forces (planet-scale station-keeping thrusters of some sort!).</p>\n\n<p>In this case, of course, you won't just have the sun's gravity to worry about--you'll be summing up the gravities of all the different planets, which gives you a system of multiple equations to solve, but the basic idea is still the same. Fix the orbital periods to all be the same (exactly what the value is doesn't matter, we'll just make it a variable that we can solve for), work in a co-rotating frame to turn it into a one-dimensional problem, and solve for the distances that balance forces so the planets don't move inward or outward.</p>\n\n<p>We can also significantly simplify things by assuming that all the planets have the same mass.</p>\n\n<p>The centrifugal acceleration of each planet is given, in terms of orbital period, by <span class=\"math-container\">$4\\pi^2\\frac{r}{T^2}$</span>, where <span class=\"math-container\">$T$</span> is the orbital period. We're fixing the orbital period as constant for all the planets, so we can gather all the constant terms together and write the centrifugal acceleration as <span class=\"math-container\">$\\alpha r$</span>--i.e., linear in radius.</p>\n\n<p>The gravitatonal acceleration will be the sum of contributions from the sun and all the other planets. Since the sun has a different mass from each planet, and it's gravity will always be in the same direction for every planet, it will be convenient to separate out its contribution. So, the net radial acceleration of each planet can be written as</p>\n\n<p><span class=\"math-container\">$$a_p = -\\frac{GM_S}{r_p^2} + \\alpha r_p + GM_P\\sum_i \\frac{sgn(r_i-r_p)}{(r_i-r_p)^2}$$</span></p>\n\n<p>If there are exactly 6 planets, that expands out to, e.g.,</p>\n\n<p><span class=\"math-container\">$$a_1 = -\\frac{GM_S}{r_1^2} + \\alpha r_1 + GM_P(\\frac{sgn(r_2-r_1)}{(r_2-r_1)^2} + \\frac{sgn(r_3-r_1)}{(r_3-r_1)^2} + \\frac{sgn(r_4-r_1)}{(r_4-r_1)^2} + \\frac{sgn(r_5-r_1)}{(r_5-r_1)^2} + \\frac{sgn(r_6-r_1)}{(r_6-r_1)^2})$$</span></p>\n\n<p>(Note that the sign of the planet's radius minus itself is zero, so the self-interaction term falls out when you expand the summation.)</p>\n\n<p>Now, we want the radial accelerations to all be zero. So, we can write out the complete system of equations (with signs resolved assuming they are ordered from 1 to 6 moving outwards, and terms re-ordered to make opportunities for cancellation more obvious) as follows:</p>\n\n<p><span class=\"math-container\">$$-\\frac{GM_S}{r_1^2} + \\alpha r_1 + GM_P[(r_1-r_2)^{-2} + (r_1-r_3)^{-2} + (r_1-r_4)^{-2} + (r_1-r_5)^{-2} + (r_1-r_6)^{-2}] = 0$$</span></p>\n\n<p><span class=\"math-container\">$$-\\frac{GM_S}{r_2^2} + \\alpha r_2 + GM_P[-(r_1-r_2)^{-2} + (r_2-r_3)^{-2} + (r_2-r_4)^{-2} + (r_2-r_5)^{-2} + (r_2-r_6)^{-2}] = 0$$</span></p>\n\n<p><span class=\"math-container\">$$-\\frac{GM_S}{r_3^2} + \\alpha r_3 + GM_P[-(r_1-r_3)^{-2} - (r_2-r_3)^{-2} + (r_3-r_4)^{-2} + (r_3-r_5)^{-2} + (r_3-r_6)^{-2}] = 0$$</span></p>\n\n<p><span class=\"math-container\">$$-\\frac{GM_S}{r_4^2} + \\alpha r_4 + GM_P[-(r_1-r_4)^{-2} - (r_2-r_4)^{-2} - (r_3-r_4)^{-2} + (r_4-r_5)^{-2} + (r_4-r_6)^{-2}] = 0$$</span></p>\n\n<p><span class=\"math-container\">$$-\\frac{GM_S}{r_5^2} + \\alpha r_5 + GM_P[-(r_1-r_5)^{-2} - (r_2-r_5)^{-2} -\n (r_3-r_5)^{-2} - (r_4-r_5)^{-2} + (r_5-r_6)^{-2}] = 0$$</span></p>\n\n<p><span class=\"math-container\">$$-\\frac{GM_S}{r_6^2} + \\alpha r_6 + GM_P[-(r_1-r_6)^{-2} - (r_2-r_6)^{-2} -\n (r_3-r_6)^{-2} - (r_4-r_6)^{-2} - (r_5-r_6)^{-2}] = 0$$</span></p>\n\n<p>Now, you've got 6 equations and 6 unknowns (the radii for each planet), which you can go ahead and solve in terms of the orbital period, solar mass, and planetary mass. The same applies for any number of planets.</p>\n\n<p>Once you've done that, you can try varying the radii by small amounts to calculate how much station-keeping force you'll need for each planet.</p>\n" }, { "answer_id": 98110, "author": "Z2h-A6n", "author_id": 44825, "author_profile": "https://worldbuilding.stackexchange.com/users/44825", "pm_score": 4, "selected": false, "text": "<p><strong>TL;DR: Nothing like you describe is possible with current technology (or anything likely in the near future), but several configurations are possible using technology well within the realm of science fiction.</strong></p>\n\n<p>As others have mentioned, the linear arrangement you mentioned is not possible (unless the connections between the planets are exremely strong and rigid). As others have also mentioned, a <a href=\"https://en.wikipedia.org/wiki/Klemperer_rosette\" rel=\"noreferrer\">Klemperer rosette</a> would allow the planets to maintain fixed relative distances, but the orbits would not be stable to small perturbations. The Klemperer rosette also has the possible disadvantage that the distance between the planets is similar to the distance between the planets and the central star (i.e. quite large).</p>\n\n<p>There is a another configuration worth considering, although it doesn't solve all of these problems: the proposed orbital configuration for the <a href=\"http://www.esa.int/Our_Activities/Space_Science/LISA\" rel=\"noreferrer\">Laser Interferometer Space Antenna (LISA)</a>:\n<img src=\"https://upload.wikimedia.org/wikipedia/commons/f/f4/LISA-orbit.jpg\" alt=\"LISA orbit diagram\"></p>\n\n<p>In the proposed LISA mission, three satellites orbit the sun with roughly the same orbital period as the Earth. Their orbital planes are oriented at slightly different angles and their orbital phases are synchronized so that the three sattelites orbit the sun while maintaining a fixed relative distance. As seen in the picture, the constellation of sattelites also rotates in the plane defined by the three satellites. Note that the satellites are not attached to each other in any way (the lines on the diagram indicate laser beams used to measure the stretching of space).</p>\n\n<p>While this keeps the planets relatively close together, I believe* it suffers from the same instability problem as the Klemperer rosette, so while it works for satellites which are small and far away from each other, the gravitational effects between the planets in a LISA-like configuration would be considerable, and would lead to significant instability. The interplanetary gravitational forces would also cause the planets to be non-periodic, although not in a way that would neccesarily present any practical problems.**</p>\n\n<p>So, to answer your questions:</p>\n\n<ol>\n<li><p>It is not possible for a system like the one you describe to exist without some repeated adjustments of the orbits, or extremely strong connections between the planets. However, some configurations require more energy to maintain (or stronger connections) than others. The Klemperer rosette and the LISA configuration both require orbital adjustments only to fix any drift away from their initial configuration, so in principle this could be done with a relatively small amount of energy or relatively weak interplanetary connections.***</p></li>\n<li><p>According to <a href=\"https://en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motion#Third_law\" rel=\"noreferrer\">Kepler's third law</a>, the length of year, distance of the planet from the star, and mass of the star cannot be varied independently, although there is no restriction on any one of these parameters independently. In principle**** you can pick whatever you want for any two of these parameters, but your choice of the first two determines the third parameter. This is still true for the Klemperer rosette and the LISA configuration, although the exact relationship between the parameters would be different.</p>\n\n<p>In the Klemperer rosette, the gravitational forces between the planets would shorten the length of year for any given mass of star and radius of orbit, although the effect would be very small unless the planets were very massive, or the star very small.</p>\n\n<p>In the LISA configuration, the time it takes for the planets to orbit the star would be about the same as you would expect from Kepler's third law. Depending on the rotational axes of the planets themselves, the seasons could change in very complicated ways since the season depends on the orientation of the planet's rotational axis with respect to the incoming starlight. This in turn depends on the orientation of the rotational axis relative to the orbital plane of the planetary constellation, as well as how the constellation is rotated in its own plane. Since the rotation of the constellation has a different period than the orbit of the constellation around the sun**, the angle between a planet's rotational axis and the incoming starlight could change in quite complicated ways over cycles of many (orbital) years.</p></li>\n<li><p>The gravitational force between two objects is proportional to $1/r^2$, where $r$ is the distance between the objects. This means that planets will feel each other's gravitational forces no matter how far away they are from each other. In the case of the Klemperer rosette and the LISA configuration, these forces will affect the orbits (see the previous two paragraphs), but these effects are not catastrophic. The bigger problem is that these configurations are unstable, so the gravitational effects of everything else in the universe will be catastrophic in the long run. It is these effects that you have to counteract using orbital adjustments or strong interplanetary connections. Luckly, most of the rest of the universe is very far away, so these effects are small and, with the right sci-fi technology not terribly hard to fix.</p></li>\n</ol>\n\n<p><strong>In short, if technology capable of significantly influencing the orbits of planets is avaiable, the Klemperer rosette or the LISA configuration are both feasible.</strong></p>\n\n<p>* While I am a physicist, orbital mechanics is not my area of expertise, and I haven't done any calculations related to this post, so take what I say with a grain of salt.</p>\n\n<p>** The planetary constellation would rotate around its center of mass faster that it would due to the relative canting of the orbital planes. After one orbit around the central star, the constellation would be in the same place, but rotated differently than it was at the same time in the previous year.</p>\n\n<p>*** Of course adjusting a planet's orbit by any measureable amount is still very hard, so the amount of energy required would be enormous compared to anything feasible with our current technology.</p>\n\n<p>**** There are practical limits on the distance to the star and the mass of the start however. The planets should not be inside the star, or so far away that they are close to other stars. If the mass of the star is too small it will just be a planet or cloud of dust and gas, if it is too large it will turn into a black hole, making things complicated nearby.</p>\n" }, { "answer_id": 98116, "author": "dreamcatcher", "author_id": 44662, "author_profile": "https://worldbuilding.stackexchange.com/users/44662", "pm_score": 1, "selected": false, "text": "<p>The diagram you gave with the six planets in a line is not possible because of the huge forces involved. If the technology existed to tie planets together like that the tidal forces would make them not usable as planets. Their shape would be distorted and holding them together to maintain spheres would require extra technology.</p>\n\n<p>I suggest six planets of equal size and mass surrounding the sun spaced 60 degrees apart sharing the same exactly circular orbit. This is like a Klemperer rosette as mentioned in other answers. They key in this case is having the massive sun at the center instead of empty space. That makes it so that each planet has two adjacent planets in its L4 and L5 points making this configuration relatively stable.</p>\n" }, { "answer_id": 98174, "author": "Bohemian", "author_id": 19700, "author_profile": "https://worldbuilding.stackexchange.com/users/19700", "pm_score": 2, "selected": false, "text": "<p>Yes... if the order of the planets at any time is flexible.</p>\n\n<p>If the inter-planetary tethers are strong enough (insanely strong), you could have the 6-planet system spinning about its center of mass, and that spinning system would have a single orbit.</p>\n\n<p>If the axis of rotation was normal to the orbital plane, all planets would have the same length of day, which would be the period of rotation of the planetary chain and which is arbitrary above the minimum required to prevent gravitational collapse.</p>\n" }, { "answer_id": 98185, "author": "Pere", "author_id": 23322, "author_profile": "https://worldbuilding.stackexchange.com/users/23322", "pm_score": 1, "selected": false, "text": "<p>Although other answers are right, it is possible to have several bodies orbiting a star with the same period while keeping close to each other: usually they are called satellites (all of them except for one). Furthermore, if two bodies are of similar sizes, they stop being a planet and a satellite and they became a double planet.</p>\n\n<p>However, if you need distance between planets to be fixed in order to place an space elevator between them, that could be done only in a pair of tidally locked bodies - that is, a tidally locked double planet.</p>\n\n<p>In short, the system on your question is not possible, but you may have an smaller version of it with a double planet.</p>\n" }, { "answer_id": 98237, "author": "David Elm", "author_id": 30710, "author_profile": "https://worldbuilding.stackexchange.com/users/30710", "pm_score": 0, "selected": false, "text": "<p>Maybe...</p>\n\n<p>But not really if you just have one star. If you had a binary star system where the two stars had equal mass and the distance between the stars was just right to get just the right amount of sunlight, then the region directly between those two stars might be a place your system might work.</p>\n\n<p>At the center of mass you would have zone where the gravity of the two stars nearly cancels out. But the equilibrium is unstable. If a planet drifted to one side or the other then the gravity from the star on that side would be a little stronger and make the situation worse.</p>\n\n<p>The gravitational potential would look a little like the image below.</p>\n\n<p><a href=\"https://i.stack.imgur.com/Ns7GS.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/Ns7GS.png\" alt=\"enter image description here\"></a></p>\n\n<p>The y axis represents the gravitational potential energy, the x axis the position and the two stars are located at -4 and +4. </p>\n\n<p>Usually, we would want to place a habitation in a situation that is <a href=\"https://en.wikipedia.org/wiki/Directional_stability\" rel=\"nofollow noreferrer\">dynamically stable</a>. If a system is dynamically stable, then small changes in the system just result in oscillations. </p>\n\n<p>If a system is dynamically unstable, then small changes produce large results. This is like a ball sitting on top of a hill. It will sit there if undisturbed, but any small push will eventually lead to the ball rolling down the hill.</p>\n\n<p>If you set things up just right, the additional forces from the stars as you moved either way from the center could balance out the force of gravity from the other planets.</p>\n\n<p>I think an electromagnetic tether could be used to overcome the dynamic instability of the system. But this tether would have to be something incredible. </p>\n\n<p>A gigantic solar sail might be a good way to augment the tether, especially is the forces from each star would normally balance out. Moving either way would usually cause the net force on the solar sail to be a restoring force, and so we might make the equilibrium a dynamically stable one.</p>\n" }, { "answer_id": 98255, "author": "cmaster - reinstate monica", "author_id": 37815, "author_profile": "https://worldbuilding.stackexchange.com/users/37815", "pm_score": 2, "selected": false, "text": "<p>First of all, see <a href=\"https://worldbuilding.stackexchange.com/a/98107/37815\">Kearsley's answer</a> for the general formulas that will provide you with all possible solutions (he has my upvote for that). This answer gives a <em>simple</em> configuration that includes six planets and should be reasonably stable (= require only minimal amounts of corrections):</p>\n\n<p>You have</p>\n\n<ul>\n<li><p>one sun</p></li>\n<li><p>two big planets<br>\n(a bit heavier than earth but less dense and thus bigger in size so that surface gravity is not too much larger than 1g)</p></li>\n<li><p>four small planets<br>\n(a bit lighter than earth but more dense and thus smaller in size so that surface gravity is not too much smaller than 1g)</p></li>\n</ul>\n\n<p>The two big planets orbit the sun in the same orbit, but on opposite sides (they are in each other's L3 point). The four smaller/lighter planets occupy the L1 and L2 points of the larger planets. Thus, all planets and the sun are in a single straight line like this:</p>\n\n<pre><code> p1-----P2-----p3---------S---------p4-----P5-----p6\n\nL2P2 L3P5 L1P2 L1P5 L3P2 L2P5\n</code></pre>\n\n<p>Since all planets are Lagrange Points relative to each other, their orbits are relatively stable, however they will still require corrections from time to time since it's just the L1,2,3 points.</p>\n\n<hr>\n\n<p>If you want all planets to be on the same side of the sun, you must use hirarchical Lagrange Points: Once you place a planet in a Langrange point, two new Langrange Points appear, one between the two planets, and on the other side of the smaller planet. So, adding a third, smaller class of orbiting objects I'll call moons, you'd get a configuration like this:</p>\n\n<pre><code>S---------------m1-----p1-----m2-----P2-----m3-----p3-----m4\n\n L2p1 L1P2 L1p1 L1p3 L2P2 L2p3\n</code></pre>\n\n<p>This gives you a total of seven orbital bodies in a single line on one side of the sun.</p>\n" }, { "answer_id": 98349, "author": "Kaotis", "author_id": 44593, "author_profile": "https://worldbuilding.stackexchange.com/users/44593", "pm_score": 0, "selected": false, "text": "<p>1: Probably in the case of 2 or more stars rotating on eachothers axis and permanently maintaining the gravitational pull at a stable output. With 1 star highly unlikely for sustained amount of time (like others before me stated)</p>\n\n<p>2&amp;3: Related to the gravitational balance needed to do nr1 , they can even orbit dwarfs stars or black holes as long as the orbital equilibrium is maintained constantly. But the inevitable alterations in every star/black hole will eventually break the orbits down)</p>\n\n<p>If you want to go scify rout go for 3 star solar system (2 big stars and 1 dwarf )the planets orbit the dwarf that is locked in place by the orbit of the 2 big ones. But this solution is a big NO if you ask \"is this possible ?\" just giving you a possible solution that unless you know the precise math behind it normal people won't notice it at first glance. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/98053", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/8128/" ]

[ { "answer_id": 98604, "author": "Slarty", "author_id": 42450, "author_profile": "https://worldbuilding.stackexchange.com/users/42450", "pm_score": 4, "selected": false, "text": "<p>Ion propulsion would be the best solution for your near future propulsion system. It is already in use and newer more powerful versions are being constructed now such as the <a href=\"https://www.space.com/38444-mars-thruster-design-breaks-records.html\" rel=\"nofollow noreferrer\">X3</a>.</p>\n\n<p>Although ion propulsion would probably be the best solution a detailed answer is difficult because there are a number of variables that must be considered as related by the <a href=\"https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation\" rel=\"nofollow noreferrer\">rocket equation</a>:</p>\n\n<p>Δv = Ve ln(Mi/Mf)</p>\n\n<p>Where<br>\nΔv = the change in velocity required<br> \nVe = the exhaust velocity of the rocket exhaust<br>\nMi = the initial mass of the vehicle with propellant<br>\nMf = the final mass of the vehicle without propellant<br></p>\n\n<p>The real problem is the multiplicity of assumptions that must be made in order to arrive at an answer. In addition to the variables above the time taken for the journey and the destination are also key parameters.</p>\n\n<p>Assuming the Mi/Mf ratio is 10 (90% propellant 10% rocket and payload) and the exhaust velocity is 20km/s <a href=\"https://en.wikipedia.org/wiki/Ion_thruster\" rel=\"nofollow noreferrer\">ref</a> (the lower end of the stated 20-50km/s)</p>\n\n<p>Δv = ve ln(mi/mf) becomes 20000*In(10) = 46km/s</p>\n\n<p>This should be sufficient for your requirements. see the delta V links below for examples of the required delta V for different destinations. A greater exhaust velocity or mass ratio would produce even more delta V but at the expense of pushing ever further into uncharted performance territory or ever smaller payload capacity.</p>\n\n<p>One big issue with ion propulsion is the vast amount of electricity required. In the inner solar system this might be provided by large solar arrays, but in the out solar system nuclear electric propulsion would be required.\n<a href=\"https://www.grc.nasa.gov/WWW/ion/future/images/futureapps.jpg\" rel=\"nofollow noreferrer\">Range of ion drive rockets using different electrical sources</a></p>\n\n<p><strong>Delta V Links</strong><br>\n<a href=\"http://hopsblog-hop.blogspot.nl/2012/06/inflated-delta-vs.html\" rel=\"nofollow noreferrer\">Planetary transfer delta V</a><br>\n<a href=\"https://space.stackexchange.com/questions/2046/delta-v-chart-mathematics\">Near earth delta V</a><br>\n<a href=\"http://www.projectrho.com/public_html/rocket/appmissiontable.php\" rel=\"nofollow noreferrer\">Delta V and time requirements*</a><br>\n*Note delta V of roughly 10km/s to get into orbit from earth included </p>\n\n<p>Concerning the other requirements<br></p>\n\n<p><strong>Complexity</strong><br>\nThe ion drive is complex but has virtually no moving parts except the propellant and examples have been run for extended periods without problems. Inner solar system solar array also no moving parts so relatively simple. Outer solar system requires nuclear electric propulsion which would be more complex but should be a sealed unit.<br></p>\n\n<p><strong>Acceleration</strong><br>\nIon engine acceleration is very low but is continuous for months and is smooth. Conventional chemical rockets tend to have high acceleration and short (minutes) burn times<br></p>\n\n<p><strong>Fuel consumption and efficiency</strong><br>\nIon engines are much more fuel efficient than conventional chemical rockets by an order of magnitude due to their high exhaust velocity. But a lot for fuel will still be needed. I have assumed 90% propellant and 10% rocket/payload above but the calculation can be made for any mass ratio you wish by plugging in different numbers into the rocket equation above.<br></p>\n\n<p><strong>Fuel type</strong><br>\nMost current ion propulsion engines use Xenon as a propellant but other propellants are possible and some have been tried. For your refuel requirement Xenon would not be ideal as it may not be readily available at the destination for refuelling.<br></p>\n\n<p>I suggest Diamondoids such as Adamantane or Diamantane would be more suitable. These are relatively cheap on earth being found in oil in very small quantities and could probably be produced at the destination sites with some suitable chemical engineering provided that a source of carbon, hydrogen and energy were available. They have been examined as potential fuels for ion engines along with various others as can be <a href=\"http://erps.spacegrant.org/uploads/images/2015Presentations/IEPC-2015-320_ISTS-2015-b-320.pdf\" rel=\"nofollow noreferrer\">seen here</a>.<br></p>\n\n<p><strong>Conclusion</strong><br>\nThe suggested ion drive rocket could meet your needs and is a realistic projection of current technology. But a lot of further research would be required especially in the development of the ion engines themselves, the fuels used and the large space based reactors required for outer solar system operation.</p>\n\n<p>There are various other current, future and speculative propulsion systems listed <a href=\"http://www.projectrho.com/public_html/rocket/enginelist.php#vasimr\" rel=\"nofollow noreferrer\">here</a> that may be of interest also including ion drives.</p>\n\n<p><strong>General references</strong><br>\n<a href=\"http://www.braeunig.us/space/\" rel=\"nofollow noreferrer\">http://www.braeunig.us/space/</a>\n<a href=\"http://www.projectrho.com/public_html/rocket/mission.php#id--Hohmann_Transfer_Orbits\" rel=\"nofollow noreferrer\">http://www.projectrho.com/public_html/rocket/mission.php#id--Hohmann_Transfer_Orbits</a>\n<a href=\"http://ccar.colorado.edu/asen5050/projects/projects_2001/stephens/termpapera.html\" rel=\"nofollow noreferrer\">http://ccar.colorado.edu/asen5050/projects/projects_2001/stephens/termpapera.html</a></p>\n\n<p><br>Remember it’s not rocket science (no wait…)</p>\n" }, { "answer_id": 98608, "author": "bobflux", "author_id": 33843, "author_profile": "https://worldbuilding.stackexchange.com/users/33843", "pm_score": 2, "selected": false, "text": "<p>Well, the problem will be that most contemporary propulsion systems (or near future ones) will have quite low thrust. And you need the heavy radiators to dissipate waste heat from your antimatter reactors.</p>\n\n<p>Therefore, let's build mass accelerators. There will be at least a few in orbit at your origin and destination points. You would pay a fee, then the thing would orient according to the velocity vector you need, and <a href=\"https://www.youtube.com/watch?v=hhgwbIC9v_w\" rel=\"nofollow noreferrer\">shoot</a> you into space.</p>\n\n<p>The mass accelerator is stationary, thus it can have huge solar panels and plenty of energy. In this case, all the propulsion you need is to correct course and ensure you arrive at the destination decelerator with proper alignment (this is going to be tricky...) so it can decelerate your ship. Alternately you can decelerate with a slingshot maneuver and/or atmospheric braking at the destination planet, which is a lot harder to miss...</p>\n\n<p>EDIT</p>\n\n<p>Here is an example of how a mass accelerator would work.</p>\n\n<p>In 'The Moon is a Harsh Mistress', Heinlein proposed that rail guns would be installed on the moon. These would be very long, high-powered electromagnetic guns. Since the target (the earth) was always stationary to the moon, they could be permanently built into the moon foundation, and could be miles long. The moon's low gravity and lack of atmosphere made then feasible. The moon miners would load huge payloads of minerals onto the gun sleds, launch them at the earth, re-load, and launch again. The packages would effectively be nothing but large rocks. I think he had the rocks enter low earth orbit, where space tugs would collect the material.</p>\n\n<p>However, When they arrived at earth, and entered low earth orbit, they would be moving at a low enough velocity that they would simply be like deorbiting space junk. The atmosphere would slow the packages down, some outer fringes would burn off, but the basic payload would splash down in some desert, basically at terminal velocity. A large thud, but not widespread damage. In this regard, Heinlein was probably incorrect about using the rocks as weapons against the earth. They wouldn't gain enough velocity.</p>\n" }, { "answer_id": 98636, "author": "Andrzej Jeziorski", "author_id": 38233, "author_profile": "https://worldbuilding.stackexchange.com/users/38233", "pm_score": 2, "selected": false, "text": "<p>Consider Beam Powered Propulsion to possibly eliminate the need for fuel entirely. <a href=\"https://en.m.wikipedia.org/wiki/Beam-powered_propulsion\" rel=\"nofollow noreferrer\">https://en.m.wikipedia.org/wiki/Beam-powered_propulsion</a></p>\n\n<p>The power needed to provide thrust to your ship wouldn't be generated on the ship but instead in oribit of the various settlements and beamed at the ship using lasers or masers. The ship would then convert the beam energy to thrust by use of a sail. Because no fuel is needed acceleration can be constant and very high speed can be achieved</p>\n\n<p>It's quite a promising technology. Even with our current level of understanding we are already planning to do some very impressive stuff with it, like sending tiny probes to other star systems in just the span of decades.<br>\n<a href=\"https://en.m.wikipedia.org/wiki/Breakthrough_Starshot\" rel=\"nofollow noreferrer\">https://en.m.wikipedia.org/wiki/Breakthrough_Starshot</a><br>\n<a href=\"https://en.m.wikipedia.org/wiki/DEEP-IN\" rel=\"nofollow noreferrer\">https://en.m.wikipedia.org/wiki/DEEP-IN</a></p>\n\n<p>Current technology would allow us to use lasers propell the more massive Orion spacecraft to Mars in one month. If a second laser array were present there we could also decelerate the ship and make a delivery. It's not much of a handwave to say that this technology could be used for intrasystem hauling in your future setting.</p>\n\n<p>The ships crew is only needed for mainenance of the sails. All repairs on the lasers and generators are conducted by the settlements.</p>\n\n<p>A laser sail such as this is being considered for the mission to send a probe to the newly discovered Oumuamua interstellar asteroid. Project LYRA: <a href=\"https://arxiv.org/pdf/1711.03155.pdf\" rel=\"nofollow noreferrer\">https://arxiv.org/pdf/1711.03155.pdf</a></p>\n" }, { "answer_id": 98654, "author": "Sherwood Botsford", "author_id": 15784, "author_profile": "https://worldbuilding.stackexchange.com/users/15784", "pm_score": 1, "selected": false, "text": "<p>Hohmann Orbits are the minimum delta-V it takes to get from one planetary orbit to another. These are computed in the Chemical Rubber Handbook. <a href=\"https://en.wikipedia.org/wiki/Hohmann_transfer_orbit\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/Hohmann_transfer_orbit</a> These take a long time -- something between the orbital period of the two planets. (I think using the geometric mean will get you in the right ballpark)</p>\n\n<p>Article here: <a href=\"https://en.wikipedia.org/wiki/Hohmann_transfer_orbit\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/Hohmann_transfer_orbit</a>\nTutorial on how to calculate one here: <a href=\"http://openmdao.readthedocs.io/en/1.7.3/usr-guide/tutorials/hohmann-transfer-tutorial.html\" rel=\"nofollow noreferrer\">http://openmdao.readthedocs.io/en/1.7.3/usr-guide/tutorials/hohmann-transfer-tutorial.html</a></p>\n\n<p>Light sails: Light exerts pressure. Not a huge amount. Sunlight on an acre could lift a cigarette paper. But .0001 g's will add up. And the price is right. Maneuvers get interesting. <a href=\"https://en.wikipedia.org/wiki/Solar_sail\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/Solar_sail</a> </p>\n\n<p>Ion systems. These all depend on using an easy to ionize metal, then accelerating it to high velocity. <a href=\"https://en.wikipedia.org/wiki/Ion_thruster\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/Ion_thruster</a> Ion thrust gets you about 7-12 times as much delta-V per kg of mass.</p>\n\n<p>Torch ship. See Heinlein's \"Double Star\" and a bunch of his juveniles. This was a hydrogen fusion reactor, where all the energy (besides parasitic energy to run the reactor) accelerated the helium. This makes it reasonable to run a 1 G all the way. Earth to Pluto in 17 days.</p>\n\n<p>Periodically there is a storm of fuss and feathers about someone who discovered a 'reactionless' drive. Don't buy stock in any of these just yet.</p>\n\n<p><a href=\"https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster</a></p>\n\n<hr>\n\n<p>Consideration: You have a huge pile of money invested in a ship. You need to explain why they will use a slow way if another way allows them to run more cargos. This is a balance between operating costs and lost opportunity costs. </p>\n\n<p>E.g. A perfect Hohmann transfer orbit is half an ellipse that is tangent to the starting planet's orbit on one side of the star and tangent to the final planet's orbit on the other side. But with a little more fuel, you can get there sooner. Historical parallel: The Clipper ships were designed to sail FAST because the first cargo of tea from China/India got a huge premium in London. The starting date was dictated by weather and the harvest. Coming in a week earlier could make your fortune.</p>\n\n<p>E.g. Big ocean freighters move at around 10 knots. Moving at 20 knots would cut the time in half -- but would take something like 8 times the amount of fuel. Further, you would haul less because you need 8 times larger engines and 8 times larger fuel tanks.</p>\n\n<p>Bear in mind that different propulsion systems take a different amount of effort and training to run. E.g. Hohmann orbits are pretty much do nothing. Take a nap. Solar sailing or something like a torch ship will require someone standing watches. I wouldn't want everyone asleep with riding a continuous hydrogen bomb in a bottle.</p>\n\n<p>Compare the transition between sailing ships and coal powered ships. Sail -- generally slower (but see clippers...) but free fuel. Coal -- faster, but you had to go where you could get more coal. You might have fun with the economy in transition between modes. The last such ship was the Pamir. <a href=\"https://en.wikipedia.org/wiki/Pamir_(ship)\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/Pamir_(ship)</a> which sank in 1957</p>\n" }, { "answer_id": 99748, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 2, "selected": false, "text": "<p>This answer is a hard-science expansion of <a href=\"https://worldbuilding.stackexchange.com/a/63908/23519\">this answer</a>. Please read that other answer to get a description of the system I am proposing, as well as justification of its technical feasibility. That post also has lots of reference links for various design decisions. I will summarize the system here and numerically address the questions posed.</p>\n\n<h1>System summary</h1>\n\n<p>The power source is a pebble bed fission reactor. The fuel source is uranium nitride pellets coated in a pyrolitic carbon moderator. These fuel pellets are held in molybdenum 'pins' in a geometry that will make them supercritical if a neutron reflector is placed outside the reactor. Heat exchange is done directly with the working fluid to save mass.</p>\n\n<p>The working fluid is helium, which is passed through the reactor core. Electrical power is generated through a Brayton-cycle turbine similar to a marine gas turbine used on ships, except replacing the combustion chamber with the reactor core. The helium is compressed by a compressor coupled to the gas generating turbine into the core, and then allowed to expand over the gas generating and power turbines. Exhaust will still be at ~700 K, and will then be run over various auxiliary systems to utilize this extra energy. The exhausted gas will then have its remaining energy bled off into space through heat exchangers and then fed back into the compressor. The rotational power generated by the power turbine is then coupled to an electrical dynamo to generate power for the vessel. </p>\n\n<p>The main propulsion system is a magnetoplasmadynamic Lorentz Force Accelerator (LFA) arcjet thruster. Lithium fuel is ionized and fed into an acceleration chamber, where a combination of magnetic and electrical fields are applied. The induced current in the plasma, once the input power is in the MW range, will help maintain the magnetic field in the plasma while will then induce an electric current in a tungsten-barium cathode. </p>\n\n<h1>System Specifications</h1>\n\n<p>The reactor must produce 300 MW of heat energy. This is possible from a pebble bed reactor, the Chinese are building a pair of production 250 MW pebble bed reactors at <a href=\"https://en.wikipedia.org/wiki/Shidao_Bay_Nuclear_Power_Plant\" rel=\"nofollow noreferrer\">Shidao Bay</a>. From this thermal energy, gas generating turbines produce an output of 100 MWe at 33% efficiency. This is equivalent to the power output of 4 <a href=\"http://www.kushaindustry.com/pdf/brochure/LM2500_Family_of_Products.pdf\" rel=\"nofollow noreferrer\">GE LM2500</a> marine gas turbines, which is the same energy source as an Arleigh Burke-class destroyer. The LM2500 has efficiency of about 40%, but we are losing efficiency due to the reactor core being cooler than a typical combustion chamber (our core is ~1750 K compared to ~2250 K in a marine gas turbine). The overall system mass estimate for the power generation portion is 0.4 kg/KWe (<a href=\"http://www.tfd.chalmers.se/~valeri/Ajax/7b_vandy.pdf\" rel=\"nofollow noreferrer\">based on a NASA estimate</a>), or 40,000 kg. </p>\n\n<p>The size of the MPD thruster is much more conjectural, as no thruster of nearly the size required has been built. I have estimated the characteristics from the information available at the <a href=\"http://alfven.princeton.edu/research/lfa\" rel=\"nofollow noreferrer\">EPPD laboratory</a> at Princeton. This design calls for a single 7.5 kN thruster at a fuel usage rate of 0.5 kg/s with an ISP of 15 km/s. There is an available high ISP mode where thrust drops to 1 kN at 0.01 kg/s with and ISP of 100 km/s. The mass of the thruster unit is 10,000 kg. I honestly do not have an good basis for this estimate, but it is needed to proceed. </p>\n\n<h1>Reactor Safety</h1>\n\n<p>The pebble bed fission power system is inherently safe. There are several avenues for a nuclear accident, the two most significant being an overpower casualty (Chernobyl) and a loss of coolant casualty (Three Mile Island, Fukushima). </p>\n\n<p>An overpower casualty is not physically possible for a pebble bed reactor. The fuel source will use low-enriched Uranium, enough to achieve critical mass, but low enough that there are significant interactions between U-238 and neutrons in the core. As temperature of the fuel pellets increases, U-238 is affected by <a href=\"https://en.wikipedia.org/wiki/Doppler_broadening\" rel=\"nofollow noreferrer\">doppler broadening</a>, causing it to absorb more neutrons. This lowers the number of neutrons available to cause fissions in U-235,thereby lowering the reaction rate and reducing power input. Therefore, the core is naturally moderated at an upper temperature controlled by the U-235/U-238 ratio, which will be engineered at 1750 K. At temperatures below this, with the reflectors (to be discussed later) in place, the temperature will increase to 1750 K. As fluid flow over the core is increased and heat removal increases, the reaction rate will increase to keep temperature stable, and this power output is naturally controlled by demand. At temperatures above 1750 K, power output will decrease due to U-238 absorption until temperate settles back at 1750 K. <strong>Therefore, there is no human or computer based control of the reactor.</strong> Once started it simply outputs energy at the rate heat is removed from the core, moderating itself at 1750 K. This effect is trustworty; computer modeling in <a href=\"https://www.researchgate.net/profile/G_Strydom/publication/236370888_TINTE_Uncertainty_Analysis_of_the_Maximum_Fuel_Temperature_During_a_DLOFC_Event_for_the_400_MW_Pebble_Bed_Modular_Reactor/links/5436a2930cf2bf1f1f2c2f81.pdf\" rel=\"nofollow noreferrer\">Strydom, 2004</a> indicates that the uncertainty band during a loss of forced cooling casualty will amount to less than 100 C even for a reactor shutting down from full power. </p>\n\n<p>As an aside, we should discuss the way that the reactor is started and stopped. In the core's state as built, it is sub-critical. The core will be undergoing fission at a very low rate, but too many neutrons will be lost passing out of the core for a chain reaction to occur. This is changed by surrounding the core with <a href=\"https://en.wikipedia.org/wiki/Beryllium\" rel=\"nofollow noreferrer\">beryllium</a> <a href=\"https://en.wikipedia.org/wiki/Neutron_reflector\" rel=\"nofollow noreferrer\">reflectors</a>. Once these reflectors are positioned in place, they reflect neutrons back into the core, as well as helping to moderate the high energy neutrons produced by fission. As a result the core will be super-critical and increase temperature until the upper limit described in the last paragraph. By removing the beryllium reflectors, the core can be shut down. </p>\n\n<p>A loss of coolant casualty is the most dangerous remaining one. However, and simplest strategy for this risk is to ignore it. On Earth, reactor casualties are costly because they leave radiation that no one wants to deal with. In space, probably no one cares. Sure, you lose the ship, but people shipped plenty of things in the Age of Sail while the risks of losing the ship were great. Transportation in space has more in common with the Age of Sail, what with month long travel times and low cargo capacities, than it does with modern shipping.</p>\n\n<h1>System complexity</h1>\n\n<p>As described above, there is no requirement for control systems for the reactor itself, only the activation of one safety system in case of emergency (removing the reflector for shutdown). The emergency heat removal system will be self activating. </p>\n\n<p>The Brayton cycle gas generators will be designed to operate continuously for the duration of a mission. Already, ships at sea using marine gas turbines operate for 1 year + without the turbine enclosure or electrical generator enclosure being opened. The conditions at sea are far more challenging than space, what with salt and water both present. Long term maintenance can be performed at a (space)port between missions. Furthermore, the advantage of operating multiple turbine units in parallel is that the thruster will still be able to fire (if at a reduced power level) if turbine are offline, even when only one turbine is operational. </p>\n\n<p>The MPD thruster is, again, the least developed part of this plan and the most conjectural, so I cannot make any statements about its reliability. However, it does have the advantage of no moving parts; power is generated and transferred through the movement of gas, current, and electromagnetic fields. </p>\n\n<h1>Power and Fuel Efficiency</h1>\n\n<p>Given the above specifics, we can calculate some burn times and travel times. Here is a <a href=\"https://en.wikipedia.org/wiki/Delta-v_budget#Interplanetary\" rel=\"nofollow noreferrer\">list</a> of delta-v needed for various Hohmann transfers. </p>\n\n<p>Tsiolkovsky's rocket equation is solved for fuel mass, $m_f$, by \n$$m_f = m_0\\left(\\exp{\\left(\\frac{\\Delta v}{v_e}\\right)}-1\\right).$$</p>\n\n<p>Our parameters are $m_0$ (mass without fuel) is 50,000 kg plus cargo size; and, $v_e$ is either 15,000 m/s or 100,000 m/s depending on operating mode of the thruster. </p>\n\n<p>The burn time can then be calculated by dividing fuel expended by mass flow rate. The mass flow rates are given as 0.5 kg/s or 0.01 kg/s, depending on the operating mode of the thruster.</p>\n\n<p>Below is a table for required fuel mass and burn times for various configurations. A 3.0 delta-V will get you to Mars or Venus, 8.8 delta-V to Jupiter, and 12.3 anywhere in the Kuiper belt:</p>\n\n<pre><code>Cargo (tons) deltaV (km/s) V_e(km/s) Fuel(tons) Burn(days)\n 1000 3.0 15 232 5\n 1000 3.0 100 32 37\n 1000 8.8 15 838 19\n 1000 8.8 100 97 112\n 1000 12.3 15 1334 31\n 1000 12.3 100 137 159\n 10000 3.0 15 2225 52\n 10000 3.0 100 306 354\n 10000 8.8 15 8020 186\n 10000 8.8 100 924 1070\n 10000 12.3 15 12769 296\n 10000 12.3 100 1315 1522\n 100000 3.0 100 3047 3527\n 100000 8.8 100 9203 10652\n 100000 12.3 100 13095 15156\n</code></pre>\n\n<p>A few things to note. The optimal burn profile (how long to burn thrusters in which mode) is still an open question. I <a href=\"https://worldbuilding.stackexchange.com/questions/63225/how-to-fire-your-engines-for-a-near-future-trip-around-the-solar-system\">posted a question</a> about that using similar numbers to this answer, but didn't get a great answer. I might take a stab at that question again later. The reason you have to calculate the optimal burn profile is that fuel has a cost. If you are moving 100,000 tons of raw lithium from Mars orbit to Earth orbit, not only does your burn take 10 years, but you also burn 13,000 tons of refined lithium doing it! That makes it seriously questionable whether moving bulk cargoes is going to be profitable in your solar system. Also note that the above calculations use a 100% fuel burn; you aught to leave at least something in reserve, which cuts further into your fuel efficiency.</p>\n\n<p>I didn't post the scores for using the 15 km/s mode with cargos of 100,000 tons, because the fuel usage is ridiculous. As it is, those numbers are in tons of lithium fuel. Keep in mind world lithium reserves are estimated at about 34 million tons, so you can see how you'd burn through that quickly. </p>\n\n<p>A big open question with this process is the availability of lithium for fuel. If it can be mined in commercial quantities from space rocks, then that sort of operation would be the equivalent of petro-states here on Earth. It may be possible to use alterative propellants, though there would likely be a loss in efficiency. Neon, Argon and Xenon are not very common, either, but <a href=\"https://en.wikipedia.org/wiki/Hydrazine\" rel=\"nofollow noreferrer\">hydrazine</a> is another possible propellant. It could be that hydrazine refining in the orbit of the gas giants is the oil refining of your near-future solar system. </p>\n\n<h1>Conclusion</h1>\n\n<p>Here is a system for space propulsion that provides a reasonable ability to traverse the solar system using technology mostly already demonstrated today. The big exception is scaling up the magnetohydrodynamic propulsion system to kN power levels. </p>\n\n<p>Most burns that you might imagine for a sublight space opera set in the solar system are feasible. Cargo capacity is relatively low, with the 100,000 tankers (roughly the size of large container ships today) being probably unfeasible for fuel cost reasons. Taking 1000 tons of cargo from Earth to the Kuiper Belt isn't that inefficient; you must burn 14% of your cargo mass in fuel, and the burn takes half a year, but what is half a year compared to the decade or more it will take to coast there?</p>\n\n<p>Meanwhile, a quick hop to mars could be done in relatively fast time. If you skip a Hohmann transfer orbit and try something else, you could burn more fuel to get somewhere faster. For example, a max burn from Earth orbit with 1000 tons of cargo and 1000 tons of fuel in the high thrust mode can get you to Mars orbit in a matter of days. Of course, the problem is you have to stop. The point I'm trying to make is that for the lower delta-V transfers at lower distances, this spaceship is powerful enough to ignore Hohmann transfers and attempt some other orbital transfer that requires more energy. Now what that transfer might be sounds like the subject of a future post :)</p>\n" }, { "answer_id": 101127, "author": "Michael Irving", "author_id": 46212, "author_profile": "https://worldbuilding.stackexchange.com/users/46212", "pm_score": 0, "selected": false, "text": "<p>So, travel time in space isn't typically a big function of your engines. In the game of cosmic billiards, you're stuck with launch windows and their set travel times. You can deviate from these travel times by a bit (10-20%) but beyond this can become very very expensive from a fuel consumption perspective. Hard science-wise, I can derive the interplanetary motion of space ships in terms of their velocity, but it's a 3-4 page affair. Not very useful here, I think, but please let me know if you'd like me to post it.</p>\n\n<p>What would be useful is the <strong><a href=\"http://clowder.net/hop/railroad/sched.html\" rel=\"nofollow noreferrer\">Cosmic Train Schedule</a></strong>!! It basically does exactly what you want, showing the travel times and launch windows for Mercury through Jupiter for the next 50 years or so. It even shows the fuel requirements (deltaV).</p>\n\n<p>Also useful would be a quick glance at the <a href=\"https://en.wikipedia.org/wiki/Hohmann_transfer_orbit\" rel=\"nofollow noreferrer\">Hohmann transfer</a>, which space ships use to travel from planet to planet. The time to do the trip one way is the \"transfer time\". The amount of fuel required is measured by the \"DeltaV\" of the transfer. Your fuel efficiency is measured by \"Isp\". Relating these concepts, is:\n$$fuel burned = weightBefore - weightAfter $$ and\n$$weightAfter = weightBefore * exp(-deltaV/(Isp*g0))$$ </p>\n\n<p>where g0 is 9.81 m/s^2 (pronounced 'gee not'), and on a nice near future (next year) 'methalox' engine suited for interplanetary travel, you might get 375s Isp. Make sure deltaV is in m/s, not km/s!</p>\n\n<p>Finally, it takes a lot of fuel to land places. Check the Low-orbit to landed deltaVs on this <a href=\"https://www.reddit.com/r/KerbalSpaceProgram/comments/4wno9x/ksp_deltav_map_condensed_real_solar_system/\" rel=\"nofollow noreferrer\">deltaV map posted in redit</a> for reasonable estimates.</p>\n\n<p>Good luck with your world building!</p>\n" }, { "answer_id": 150150, "author": "Efialtes", "author_id": 44413, "author_profile": "https://worldbuilding.stackexchange.com/users/44413", "pm_score": 1, "selected": false, "text": "<p>I am not a physicist or aerospace engineer so I will provide figures that have already been pre-calculated by others with greater mathematical prowess. </p>\n\n<p>The idea that I found a while ago while browsing the web is a concept known as a Nuclear Salt Water rocket, it was theorized by Dr. Robert Zubrin and is one of the few designs that we know can deliver torchsip levels of performance, and is ideally suited for constant acceleration space travel. </p>\n\n<p><a href=\"https://i.stack.imgur.com/sjM30.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/sjM30.png\" alt=\"Diagram of Rocket Operation\"></a></p>\n\n<p>How it works is it consists of a fuel tank composed of small cylindrical containers holding the nuclear fuel solution wrapped in a boron carbide neutron moderator that prevents it from reaching critical mass while in storage. The to ignite the engine the nuclear fuel solution is sprayed in small amounts at a time into a plenum without the neutron moderator where it reaches critical mass and creates a continuously detonating nuclear explosion that propels the craft forward. </p>\n\n<p>Now the fuel solution consists of a mixture of 2% Uranium tetrabromate mixed with 98% water, which means the propellant can be stored without need for cooling and the steam created by the nuclear explosion creates lots of extra thrust. </p>\n\n<p>It uses open-cycle cooling so it is not power limited like other nuclear power concepts and can produce jet power ratings in the thousands of megawatts range. </p>\n\n<p><strong>General theorized specifications:</strong> </p>\n\n<p>Total engine mass: 33,000kg (excluding fuel mass)</p>\n\n<p>T/W: 40</p>\n\n<p>fuel: fission Uranium Tetrabromate</p>\n\n<p>reactor: gas-core open-cycle</p>\n\n<p>reaction mass: water</p>\n\n<p>reaction mass acceleration: thermal acceleration from reaction heat</p>\n\n<p>thrust director: nozzle</p>\n\n<p>specific power: 0.8kg/MW</p>\n\n<p><strong>The estimated performance for a craft using 20% enriched fuel is as follows:</strong> </p>\n\n<p>Exhaust velocity: 66,000 m/s</p>\n\n<p>Specific impulse: 6,728 s</p>\n\n<p>Thrust: 12.9 million N</p>\n\n<p>Thrust power: 425.7 GW</p>\n\n<p>nozzle efficiency: 0.8 </p>\n\n<p>mass flow: 195 kg/s</p>\n\n<p><strong>The estimated performance for a craft using 90% enriched weapons grade fuel:</strong> </p>\n\n<p>Exhaust velocity: 4.7 million m/s</p>\n\n<p>Specific impulse: 479,103 s</p>\n\n<p>Thrust: 13 million N</p>\n\n<p>Thrust power: 30.6 terawatts</p>\n\n<p>nozzle efficiency: 0.9</p>\n\n<p>mass flow: 3kg/s </p>\n\n<p>So in conclusion, you get the efficiency of an ion engine with the thrust power of an Orion project spacecraft without much more mechanical complexity than your average chemical rocket. </p>\n\n<p>Now of course there are some obvious issues with this device, as it is a contiuously burning nuclear flame with the intensity of an atomic bomb. The materials required in the engine would have to be extremely strong and at the cutting edge limits of our current metallurgy unless you want to replace the engine after every trip , however they wouldn't have to be insanely strong to the point of impossible , because while the initial reaction would take place within the reaction chamber the expanding steam would force the rest of the fuel outwards having the rocket ride on the aftershock of the main detonation occuring outside. This means that the reaction chamber doesn't have to contain the nuclear detonation. </p>\n\n<p>Now while this rocket is so powerful it would barely notice the cost of takeoff, it would leave a burning nuclear crater, so other solutions would be needed like maybe having the craft dock at an orbital spaceport, and the pilot get to the surface by other means. </p>\n\n<p>If you are worried about the exhaust contaminating space, don't because as long as it doesn't directly intersect with any planet's surface it's velocity is so high it would exceed the planets escape velocity and leave the atmosphere as quickly as it entered. And over time it would diffuse so that the contaminants would spread over a huge distance eventually entering concentrations where they are no longer harmful. </p>\n\n<p>Happy trails!!!</p>\n\n<p>sources: </p>\n\n<p><a href=\"http://www.projectrho.com/public_html/rocket/enginelist2.php#nswr\" rel=\"nofollow noreferrer\">http://www.projectrho.com/public_html/rocket/enginelist2.php#nswr</a></p>\n\n<p><a href=\"https://en.wikipedia.org/wiki/Nuclear_salt-water_rocket\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/Nuclear_salt-water_rocket</a></p>\n\n<p><a href=\"https://www.npl.washington.edu/av/altvw56.html\" rel=\"nofollow noreferrer\">https://www.npl.washington.edu/av/altvw56.html</a></p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/98601", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/2746/" ]

[ { "answer_id": 99922, "author": "Alexander", "author_id": 32451, "author_profile": "https://worldbuilding.stackexchange.com/users/32451", "pm_score": 3, "selected": false, "text": "<p>Not really.</p>\n\n<p>Sun is <a href=\"http://blogs.discovermagazine.com/badastronomy/2012/08/27/bafact-math-the-sun-is-400000-times-brighter-than-the-full-moon/\" rel=\"noreferrer\">400,000 times</a> brighter than full Moon. Doubling and even quadrupling Moon's brightness would still have negligible effect on plant's life. However, it may be a game changer for nocturnal animals.</p>\n" }, { "answer_id": 99925, "author": "Ebonair", "author_id": 44763, "author_profile": "https://worldbuilding.stackexchange.com/users/44763", "pm_score": 4, "selected": true, "text": "<p>It's still way too dim to be useful. You'd have less than 1 lux worth of light, but you need a bare minimum of 50 lux to make any difference at all, and preferably 500 lux to see some significant (but small) amount of extra growth.</p>\n\n<p>Plants' light requirements fall into one of the four categories below, depending on the plant. \"Most plants will survive illuminance 10 times lower than listed below but will not grow as well or bloom.\"</p>\n\n<pre><code>Low (500–2,500 lux)\nMedium (2,500–10,000 lux)\nHigh (10,000–20,000 lux)\nVery High (20,000–50,000 lux)\n</code></pre>\n\n<p><a href=\"https://en.wikipedia.org/wiki/Houseplant_care#Data_for_some_common_houseplants\" rel=\"noreferrer\">https://en.wikipedia.org/wiki/Houseplant_care#Data_for_some_common_houseplants</a></p>\n\n<p>And common lux levels:</p>\n\n<pre><code>Illuminance (lux) Surfaces illuminated by\n0.0001 Moonless, overcast night sky (starlight)[3]\n0.002 Moonless clear night sky with airglow[3]\n0.05–0.3 Full moon on a clear night[4]\n100 Very dark overcast day[3]\n400 Sunrise or sunset on a clear day.\n1000 Overcast day;[3] typical TV studio lighting\n10,000–25,000 Full daylight (not direct sun)[3]\n32,000–100,000 Direct sunlight\n</code></pre>\n\n<p><a href=\"https://en.wikipedia.org/wiki/Lux#Illuminance\" rel=\"noreferrer\">https://en.wikipedia.org/wiki/Lux#Illuminance</a></p>\n" }, { "answer_id": 99949, "author": "Windlepon", "author_id": 45401, "author_profile": "https://worldbuilding.stackexchange.com/users/45401", "pm_score": 2, "selected": false, "text": "<p>Your third paragraph is actually far more important that you may realise, plants need the rest time without photosynthesis at night.</p>\n\n<p>If you did supply 24h light something significant in plant biology would need to change to cope. I think in hydroponic farms with artificial lighting this is typically ~6 hours darkness for optimal growth.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/99921", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/10364/" ]

[ { "answer_id": 100703, "author": "sphennings", "author_id": 26175, "author_profile": "https://worldbuilding.stackexchange.com/users/26175", "pm_score": 2, "selected": false, "text": "<p>You can't communicate with maths.</p>\n<p>Maths are a collection of related formal systems that are somewhat an extension of formal logic. Languages are systems for communication. These are two very different types of systems that aren't necessarily compatible.</p>\n<p>While some mathematicians will discuss the universality of math they are talking about a very different thing than communication . Try translating &quot;pass me that&quot; into maths and see how it works out. What maths is great at doing is reasoning about things. Assuming there was a method of mathing back and forth at each other you'd find out that you both agreed about whatever mathematical proof you happened to exchange.</p>\n<p>If you remember from The Arrival there was another team that was trying to communicate with the aliens via math. The result was that they got the aliens to solve simple math problems and produce sequences of prime numbers, not an answer to the question of the movie &quot;What is your purpose here?&quot;.</p>\n<p>To quote from <a href=\"https://worldbuilding.stackexchange.com/a/22929/26175\">Artelius' answer</a> to a similar question:</p>\n<blockquote>\n<p><strong>tl;dr</strong></p>\n<ul>\n<li>Mathematics can't be used to say &quot;we come in peace&quot;</li>\n<li>Mathematics can be used to establish common ground with most conceivable intellectually mature beings</li>\n<li>Although there is no guarantee they will &quot;get&quot; it, it will be obvious if they do</li>\n</ul>\n</blockquote>\n" }, { "answer_id": 100708, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 3, "selected": false, "text": "<h1>You can build a language from anything</h1>\n\n<p>Language is just a collection of building blocks. Human language is, of course, very complicated, but it must have been formed from the sorts of basic communication events that mammals the world over still use. </p>\n\n<p>So 'math' is as good a way as any to communicate with someone else.</p>\n\n<h1>What will aliens and us mutually understand?</h1>\n\n<p>This is harder to grasp conceptually. If we just send the aliens some numbers, it may not be clear to them how to associate the <em>symbols</em> with any numerical meaning, without some sort of logical framework. How can you know that the symbol \"2\" represents the counting concept of two? </p>\n\n<p>However, there should be some things that should be universally understood. A signal that oscillates between two values should be easily interpreted as binary. From there, we can send messages that are consistently framed that would be interpreted as integer numbers. By consistent framing, I mean that you would send your numbers in sets of 8 or 16 or 64 bits, just like computers do when they store integers. </p>\n\n<p>Once you can send numbers, you can send patterns that will be obvious indications of intelligence: you could send a series of prime numbers or a Fibonacci sequence, the sides of all <a href=\"https://en.wikipedia.org/wiki/Special_right_triangle#Side-based\" rel=\"noreferrer\">integral right triangles</a> (i.e. 3-4-5, 5-12-13, 8-15-17, etc). Doing this should at the very least establish that you are talking with someone who can talk back.</p>\n\n<h1>Build from mathematics upwards</h1>\n\n<p>Obviously, we aren't the first ones to tackle this problem. There are already <a href=\"https://en.wikipedia.org/wiki/Communication_with_extraterrestrial_intelligence#Mathematical_and_scientific_languages\" rel=\"noreferrer\">proposals</a> for various way to build from mathematics into full fledged communication. <a href=\"https://en.wikipedia.org/wiki/Lincos_(artificial_language)\" rel=\"noreferrer\">Lincos</a> is one, designed in the 60s, while a more recent one is <a href=\"https://en.wikipedia.org/wiki/Lone_Signal\" rel=\"noreferrer\">Lone Signal</a>. Lone Signal is designed around sending two things together: a very simple set of mathematical statements about he laws of physics coupled with messages in fully complex language. The idea is that the simple physical statements would act as a 'Rosetta stone' allowing the aliens to translate the full language.</p>\n\n<p>There are doubts as to whether or not aliens would be able to translate human language at all. Noam Chomsky, using his theory of genetically determined grammar, suggests that without a built in faculty to understand human grammar, aliens might not be able to make sense of our language. In my opinion, while that would stop, say, Han Solo from talking to Chewbacca, it would not stop a computer from being able to decode an alien language.</p>\n\n<h1>How does the message work?</h1>\n\n<p>Technical details of the transmission setup are contained <a href=\"https://www.webcitation.org/6Ik4qwRQ5?url=https://s3.amazonaws.com/lonesignal-prod-web/Lone%2BSignal%2BTechnical%2BSetup_06042013.pdf\" rel=\"noreferrer\">here</a>. </p>\n\n<p><a href=\"https://www.webcitation.org/6Ik4qwRQ5?url=https://s3.amazonaws.com/lonesignal-prod-web/Lone%2BSignal%2BTechnical%2BSetup_06042013.pdf\" rel=\"noreferrer\">Here</a> is report on the test message. It was devised by Michael Busch from CalTech and broken by a colleague, Rachel Reddick from Stanford. Obviously, it would be easier for a someone with a human understanding of math and science to decipher a human-built code, but the recipient was able to quickly decipher the message with just pencil and paper. </p>\n\n<p>In the test message link, the decoded message itself starts on page 9. The message starts with several tautologies to establish a vocabulary. I've tried to reproduce the decoded message and the quad side by side. The quad is simply two binary digits. </p>\n\n<pre><code>( ___0 = ___0 ) 00000000 10000000 01000001 10000000 00010000\n( ___1 = ___1 ) 00000000 10000001 01000001 10000001 00010000\n( ___2 = ___2 ) 00000000 10000002 01000001 10000002 00010000\n( ___3 = ___3 ) 00000000 10000003 01000001 10000003 00010000\n( _671 = _671 ) 00000000 10022133 01000001 10022133 00010000\n( ___0 = -__0 ) 00000000 10000000 01000001 20000000 00010000\n( ___1 ≠ -__1 ) 00000000 10000001 01000100 20000001 00010000\n( ___1 ≠ ___0 ) 00000000 10000001 01000100 10000000 00010000\n( _870 = _870 ) 00000000 10031212 01000001 10031212 00010000\n( _870 ≠ _871 ) 00000000 10031212 01000100 10031213 00010000\n</code></pre>\n\n<p>From here, you see that we have established some symbolic 'language' already. What is encoded as parenthesis are frame divisions (00000000 and 00010000). Equality (a concept!) is expressed as 01000001 while inequality is 01000100.</p>\n\n<p>From there, the message goes to describe the characteristics of our sun and of the elements, among other things. If the listener can identify the element, then they can associate the 'symbol' for the element. For example, oxygen is identified by 31020020; building off this water is identified by its chemical composition as 31021001.</p>\n\n<p>Read the paper for more; there are 70+ pages of encoded and decoded message, along with an encryption key. Both concrete (water, electric charge, solar years) and abstract (equality, time) concepts are expressed within a mathematical framework with only a simple message.</p>\n\n<h1>Will it work?</h1>\n\n<p>Of course, this is the most important question, and one that we don't have the answer for. </p>\n\n<p>But in summary, mathematics are important for two things: for establishing that we are communicating with an intelligent lifeform; and for building a simple 'Rosetta stone' of concepts that can be use to translate more complex language. </p>\n" }, { "answer_id": 100715, "author": "Keith Morrison", "author_id": 38400, "author_profile": "https://worldbuilding.stackexchange.com/users/38400", "pm_score": 3, "selected": false, "text": "<p>\"Omnilingual\", written by H. Beam Piper back in 1954 or so, explains how it can work. There are universals in science and math describing the real world, which two technologically advanced cultures are going to have to share.</p>\n\n<p>So, math leads to communication: basic math leads to understanding each others symbols for numbering and mathematical operations, as well as the base system used for counting. Once you have that, you have the capability of translating any number in one language to a number in another.</p>\n\n<p>Now, take those numbers. The aliens send you a list that looks like this:</p>\n\n<ul>\n<li>1 1.0 <em>blarg</em></li>\n<li>2 4.0 <em>gurgle</em></li>\n<li>3 6.9 <em>blech</em></li>\n<li>4 9.0 <em>yech</em></li>\n<li>5 10.0 <em>burble</em></li>\n<li>6 12.0 <em>rez</em></li>\n<li>7 14.0 <em>skurp</em></li>\n<li>8 16.0 <em>xowill</em>, and so on all the way up to</li>\n<li>92 238.0 <em>fraznip</em></li>\n</ul>\n\n<p>It's not going to take someone long to recognize the periodic table and the names of elements. Now, ignoring the linguistics you could derive from the names themselves, consider now what's possible: <em>blarg</em> is hydrogen, <em>xowill</em> is oxygen, so if you see (<em>blarg</em>)(<em>blarg</em>)(<em>xowill</em>) = <em>kerblud</em>, that gives you a reasonable assumption that <em>kerblud</em> means \"water\". And so on and so forth. That allows you to create a vocabulary of translated words, and once you have that, the process of mutually understanding languages becomes faster and faster.</p>\n" }, { "answer_id": 100725, "author": "Tim B II", "author_id": 44692, "author_profile": "https://worldbuilding.stackexchange.com/users/44692", "pm_score": 2, "selected": false, "text": "<p>Another book which explains part of this process is Contact, by Carl Sagan. The movie that was made based on his novel glossed over the maths part, but it's a very important part of the process of understanding an alien message.</p>\n\n<p><strong>Becoming Aware of Each Other</strong><br>\nThe first step in receiving a message is becoming aware of its existence. Space is a lot noisier than a lot of people think and the reality is that we've come across many different signals that were first thought to be messages that we now know were natural phenomena, like Pulsars. So, how does one send a signal that can be recognised as a signal from an intelligent source?</p>\n\n<p>Prime Numbers.</p>\n\n<p>Send two pulses, then rest. Send three pulses, then rest. Send Five. Seven. Eleven etc, up to an arbitrary count. Rinse and repeat. This CANNOT be a natural signal (alright, perhaps it can, but the odds are as close to zero as anything else I can think of) because although it's regular, it's regular based on a mathematical pattern that is too complex for normal phenomena but which can be easily understood by any intelligent life with even a rudimentary grasp of mathematics. They're the ones you really want to communicate with anyway.</p>\n\n<p><strong>Once You Have Their Attention</strong><br>\nThe next step is to build some basic math rules. One pulse (symbol W) One pulse (symbol E) two pulses. Symbol W is plus, Symbol E is Equals. Do this for a whole range of mathematical equations, until they understand. Then do it for Symbol X, or multiply. Again, teach the symbol through the math. Keep going. Minus. Divide, etc.</p>\n\n<p>Then, when you're done with that; one pulse (symbol W) one pulse (symbol N) three pulses. You're building the symbol for not equals. Keep showing this with random answers to which no logical connection to the real answer is possible (real answer + number of wrong questions, for example) and you've built the concepts for Yes and No, true and false out of math.</p>\n\n<p><strong>Bridging from Math to Broader Concepts</strong><br>\nYou can now start introducing items like the Periodic table (as has already been suggested) with new symbols reflecting the elements. Then, you can start adding in things like decay rates, meaning that you can introduce the concept of time. Keep going. Eventually, you've built concepts that can in turn be built upon to get to what you really want to talk about.</p>\n\n<p>What we're talking about here is really just using math as the 'crack in the ice'; the starting point that builds on the few things we're likely to see conceptually similarly so that we can form an understanding of the things close by, then build out in a radiating field of understanding.</p>\n\n<p><strong>Don't Anthropomorphise</strong><br>\nThere are some things we can't make assumptions about during this process. Don't assume that another alien civilisation will work the same as ours. They may not have eyes (and therefore not 'see' the same way we do), they may not have emotions. The human brain is a very complex piece of equipment designed over 3.5 billion years of evolution; to assume that aliens feel 'happy' or 'scared' etc. in the same way we do would be a gross over-estimation of the commonality of our genes. Remember that as we build outwards from maths, the less likely our concepts can converge in any way. Be prepared to hit a barrier against which further conceptual development isn't possible. But still, you've got something to work with and until you learn more about them (and they learn more about us) we have to accept some limits as inevitable in the early to mid stages of the communication process.</p>\n\n<p>The short story on which the movie Arrival is based extends beyond real science the concept that our psychology is largely shaped by our language. This is true but not to the extent that our psychology can transcend physics and we can remember in both temporal directions as a result of learning a new language.</p>\n\n<p>What's important to remember out of that concept though is that we do use our language as a form of operational base for our conceptual frameworks. Every language we currently know however is human based which is why we all think reasonably similarly, although if you're in any doubt about the power of language to shape thought, sit back and enjoy a coffee while watching a .NET programmer discuss process with a sculptor. :)</p>\n\n<p>Why is this important? It's because while there is much that we think we know that can't be described by maths, an alien species with a completely different development path to humans is going to struggle even more at understanding us than we do understanding each other when we don't know each others' language.</p>\n\n<p>In essence, this means that we have no choice but to revert to the one form of language that cannot change between us, and that's mathematics. If we can communicate via that, then if we're lucky the broader concepts will follow.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/100700", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/18452/" ]

[ { "answer_id": 100939, "author": "JBH", "author_id": 40609, "author_profile": "https://worldbuilding.stackexchange.com/users/40609", "pm_score": 3, "selected": false, "text": "<p><strong>Assumptions (and they're whoppers)</strong></p>\n\n<ul>\n<li><p>Life is perfect. Nobody dies due to accidents, disease, war, crime, suicide, genetic defect, exposure to the <em><a href=\"https://en.wikipedia.org/wiki/Star_Wars_Holiday_Special\" rel=\"nofollow noreferrer\">Star Wars Holiday Special</a></em> or anything other than old age.</p></li>\n<li><p>Genetic diversity is assumed.</p></li>\n<li><p>We start with 75 breeding women, all starting at age 18 and reaching menopause (unspecified by the OP but assumed to be...) at 45.2 (to make the math even). Thus, every woman will bear 17 children during their 27.2 years of fertility (this is so unrealistic that I almost stopped writing, but I'll continue anyway).</p></li>\n<li><p><a href=\"https://en.wikipedia.org/wiki/Polygyny\" rel=\"nofollow noreferrer\">Polygyny</a> continues even though the ratio will eventually come close to 1:1. What this means is <a href=\"https://en.wikipedia.org/wiki/Barefoot_and_pregnant\" rel=\"nofollow noreferrer\">all women bear children</a> regardless their sexual orientation or personal desires.</p></li>\n<li><p>Realistic birth numbers are close enough to 50/50 male-vs-female that we'll use the 50/50 split. Where the split isn't even, it will always favor women.</p></li>\n<li><p>The technology available to the colony is sufficient to guarantee all of the above. Considering only 100 people to start, the technology has reached the level of <a href=\"https://en.wikipedia.org/wiki/Clarke%27s_three_laws\" rel=\"nofollow noreferrer\">Clarkian Magic</a>. (This would beg the question, \"why aren't they just cloning to fix their population problems?\" but we'll defer that for later.)</p></li>\n<li><p>Pregnancies are perfect. Women always conceive.</p></li>\n</ul>\n\n<p><strong><em>Consequence: these are best case numbers. A story based in <a href=\"https://en.wikipedia.org/wiki/Shit_happens\" rel=\"nofollow noreferrer\">any kind of reality</a> will result in much smaller numbers than these.</em></strong></p>\n\n<ul>\n<li>Year \"0\" is the epoch. Everyone arrives at the new colony and they breed like rabbits.</li>\n<li>Year 0.75 is the first batch of children with a new batch for every woman of child-bearing years thereafter every 1.6 years.</li>\n<li>The PHP program I wrote to calculate this is listed below.</li>\n<li>The years aren't even (50 &amp; 100) because you start 9 months after arrival (year 0.75) and advance every 1.6 years, neither number nor their sum being divisible by 10....</li>\n</ul>\n\n<p><strong>Year: 48.75</strong></p>\n\n<ul>\n<li>Women: 4,282</li>\n<li>Men: 4,180</li>\n<li>Total: 8,462</li>\n</ul>\n\n<p><strong>Year: 99.95</strong></p>\n\n<ul>\n<li>Women: 143,768</li>\n<li>Men: 136,210</li>\n<li>Total: 279,978</li>\n</ul>\n\n<p><strong>This is so utterly unrealistic that it's making angels weep.</strong> Few women can have 17 children in their lifetime, and of those who can, I'd bet almost none want 17 children. Add to that the fact that people die... a lot... and I'd bet reality is less than 10% of these results. In fact, it might be less than 5% of these results.</p>\n\n<pre><code>&lt;?php\n$men = array(array('number'=&gt;25, 'age'=&gt;18.75));\n$women = array(array('number'=&gt;75, 'age'=&gt;18.75));\nfor($year=0.75; $year&lt;=100; $year+=1.6){\n foreach($women as $key =&gt; $val){\n if($women[$key]['age']&gt;80){$women[$key]['number']=0;}\n if($men[$key]['age']&gt;80){$men[$key]['number']=0;}\n if($women[$key]['age']&gt;=18.75 &amp;&amp; $women[$key]['age']&lt;=45.95){\n $dwomen = round($women[$key]['number']/2);\n $dmen = $women[$key]['number']-$dwomen;\n array_push($women, array('number'=&gt;$dwomen, 'age'=&gt;0));\n array_push($men, array('number'=&gt;$dmen, 'age'=&gt;0));\n }\n $women[$key]['age'] += 1.6;\n $men[$key]['age'] += 1.6;\n }\n $twomen = 0;\n $tmen = 0;\n $total = 0;\n foreach($women as $key =&gt; $val){\n $twomen += $women[$key]['number'];\n $tmen += $men[$key]['number'];\n $total = $twomen + $tmen;\n }\n echo \"Year:\\t\".$year.\", Women:\\t\".$twomen.\", Men:\\t\".$tmen.\", Total:\\t\".$total.\"&lt;br&gt;\";\n}\n?&gt;\n</code></pre>\n\n<p><em>I'm going to leave it as an exercise for the OP to modify the code or analyze the code's data to answer his last couple of questions. However, unless your SI genetically enforces the 1:3 relationship, you lose it very, very quickly. Your year 100 ratio is 49:51, which is very close to normal.</em></p>\n" }, { "answer_id": 100955, "author": "bendl", "author_id": 39583, "author_profile": "https://worldbuilding.stackexchange.com/users/39583", "pm_score": 4, "selected": true, "text": "<p>This code underwent some revision due to some coding errors! See edit log for more information.</p>\n\n<hr>\n\n<p>JBH has a very nice answer, and I have to admit, I mainly wrote this answer because it seemed like a nice programming puzzle.</p>\n\n<p>My method: I modeled the likelihood of a woman getting pregnant after a chart I found online <a href=\"https://www.avawomen.com/avaworld/knowing-your-odds/\" rel=\"nofollow noreferrer\">here.</a> I did my best to then translate those numbers into a function of months of age since 18 years old. I ended up subtracting the $age_{in\\ months}/8100$ from a starting chance of $20\\%$ each month. That got me close enough to be happy. I then created a system where each person is put into a group, one of <code>free_men</code>, <code>free_women</code> or <code>free_children</code>. If there were enough people available, I create pods out of the free men and women groups, with priority going to the youngest people available. Each month, the women in a pod have a chance of becoming pregnant determined by their age, beginning 20 months after their last conception.</p>\n\n<p>If a women dies, she is removed from the pod, if a man dies, the pod is dissolved and the women revert to the <code>old_women</code> group. When a child is born, they are added to the <code>free_children</code> group. Children born have a $51\\%$ chance of being male and $49\\%$ chance of being female.</p>\n\n<p>The time is ticked each month and statistics about the group are displayed.</p>\n\n<p>These are the statistics for the years you request:</p>\n\n<pre><code>Year 49\nFree Men: 603\nFree Women: 2\nFree Children: 3529\nOld Women: 75\nPods: 295\nNumber of conceptions this period: 373\nPregnancy rate: 0.33459875566803754\nNumber of births this period: 325\nNumber of deaths this period: 0\nAverage number of children per man: 0\nAverage number of children per woman: 0\n\nYear 99\nFree Men: 12617\nFree Women: 1\nFree Children: 73572\nOld Women: 2475\nPods: 5871\nNumber of conceptions this period: 6801\nPregnancy rate: 0.3289336345010024\nNumber of births this period: 6412\nNumber of deaths this period: 14\nAverage number of children per man: 37.96969696969697\nAverage number of children per woman: 12.756410256410257\n</code></pre>\n\n<p>This makes some pretty huge assumptions, the biggest of which is that having a child has no impact on your fertility. That's clearly false. Altering the <code>pregnancy_fertility_drop</code> variable from 0 to 1.5 gives us these numbers:</p>\n\n<pre><code>Year 49\nFree Men: 408\nFree Women: 1\nFree Children: 1766\nOld Women: 272\nPods: 224\nNumber of conceptions this period: 165\nPregnancy rate: 0.312874251497006\nNumber of births this period: 150\nNumber of deaths this period: 0\nAverage number of children per man: 0\nAverage number of children per woman: 6.785714285714286\n\nYear 99\nFree Men: 5007\nFree Women: 2\nFree Children: 20736\nOld Women: 3041\nPods: 2417\nNumber of conceptions this period: 1859\nPregnancy rate: 0.30061614757485816\nNumber of births this period: 1703\nNumber of deaths this period: 4\nAverage number of children per man: 20.451327433628318\nAverage number of children per woman: 6.909722222222222\n</code></pre>\n\n<p>Which is obviously a stunning drop (especially in the generation that is still under 18).</p>\n\n<p>Here are some charts that show some statistics :)</p>\n\n<p><a href=\"https://i.stack.imgur.com/dmUwl.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/dmUwl.png\" alt=\"Population by year\"></a>\n<a href=\"https://i.stack.imgur.com/8ZmYw.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/8ZmYw.png\" alt=\"Rates by year\"></a></p>\n\n<p>These aren't as interesting as the ones with the fertility drop, here they are:</p>\n\n<p><a href=\"https://i.stack.imgur.com/cAWEt.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/cAWEt.png\" alt=\"Population with fertility drop\"></a>\n<a href=\"https://i.stack.imgur.com/Nepyl.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/Nepyl.png\" alt=\"Rates with fertility drop\"></a></p>\n\n<p>I find the Rates graph interesting, as you can see a significant fluctuation in fertility in 18 year increments, giving some significant generational effects!</p>\n\n<hr>\n\n<p>I have the code here on <a href=\"https://tio.run/##rVnfb9s2EH7XX0GkD7VW17XTdUuNukARoMAe0hVbsWLIAoG2aUeIRAkU3Sx/fXZHUqL4Q4o6NA9tIt4d77777o6U6gd5W/HXj495WVdCEkH5viqT5Bm5rHgjKZdNksi8ZNmWyXvGeLar@I7VMq94BrIZZ//KjErJylqSDTlfkmekrLi8bZK62mf3Vck4PH@dbGnDslqwI6d895DtbuE/pjQS@/Qg6E6Zrg4ZPbJsL6oaZC5WS0eKCZkXuXxo15fo8F9U5HRbsIbIWyrJHWM1kWDvjlQHciyqLS0IRIQBgU8ZP5XgRF7shXLw@iZRvkaeqydd1E22O4nsgVGhNsbFPaMQb/h8m4vguY1CUMnA7olLJvRGCcYSxSmhiNTqF1DPuZw9/xvMzUknRQyaNVhS4D9Pk0MliNo155jVI5u9fpOuEwI/2gguvlhdgJlUPUUFpWw1VudGQ2mRlxtCX40nq5Om5MWGrJIk2RW0acjXqqR8najlPTuQLMt5LrNs1rDiMCegPiclFXdMbD7SomHpGnj0J5My50fIJzOL5FDQI7nPi0IHQSj8xr4xoCl6fY@7PG9IkR9Y5wnusFAUbnIAqZdKwHQqtV1r4C7owr/uYwMN1oEKIr5qqb8k@QGtkHeYW8JAZSD9jqGcZ1Ba8U1KWrD4ChDy0tJ66aspdDcGZpsnme/uVI56RDC1NFQWcxLhfo@sDvFDXBVtRoEDGrbSU9k4wgFN01YQEhLd8z1ZWgB0DcXCWdC6Znw/c2ykoXkNs28Rq/Lsw5GtydnchghFGJP7AtEQFQ2x0bR60VDTwA3DJCD7GELvJ1eJG5CooDg3ZqQsTjyHDlPOlnMC3dwNaQyWXsh/gEHsB9ipOvzXZ@mQ/D8SNRSa6MuI3KXOMgyKLdtVJW7SZq@F1GNEEICK9l1UNgzIbxdfxImNC/XIPzQIAwODg8upsUl9cjlYIU@yZ0PeugCM98rWcX94Bj4HXS2QmEir35ou2bbybPEOaH06lVtomUCZ9rRglXteufqCyZPg5PqK8tkyvVG8CcsjhZJb/PxWD4RrNTpR2rYRXFhHDd/0JqxgtTATtte9jeSZNntGXsChSMz63QYenaVn7eS@wrk9YWwjhadObTuxh@b1wIQ1480plydn4o@bfO6Qmgz11SSgP1f7AaB9DwA0cPhTxb1A28P29c14GOBXkTdSS/qWLZQhyrisDFpWYy9Wxy7MpvXCZacSGDCMP6qCYEHLeTuYSlYyYQ2bWBYwhXDwKqk03tvQdtAv/GQZexbAO6DtyAnIO/vPSXiLiEx/rlj0nlwsf1qdr4Pe518ogs7mb@GcO7w4XTT2rOiciHUQzM28l0hLgDqHCyETjUubSfmHwHVq/Wn2zj9W9aUJr6Sy2u4cijqOtSAo5QEOKOcWgpXVNzYkGGbQsRzH1sCn2s/c@pTY6q5PBcWJONhNcUfYWf@inPAL/yAYy0yNY1OBW0Oq720af31rM3bSm4hy1yJ0@@8MdCm0JrQH1sgzz0oLSmfJHQVpTLGn1vqfRrx079/OelXYlwr@GnSXZkL7G65eh9W6KbWsdvxah91rrGvpYocavgiq3RHD6RbneCvSlUQf0bhKQJoW@IEWGZ4p3PjC6@v4VXWa@5FmEQ/AodxYl3cS1Va6Ueg07uFvRgrGZw5EePBaqgOtu6RLARbtK62XZOVd3wARGOEeBWozrN1M1FXtySHhclt/3T5p5NS6cLDwIVK208iBG4qj1al7UPTaxwirJk3@oYw6Y93Rx/NAq40ORi4Kbj7NmAdZYy/13cSa3s8JqgHuKKgmeASRrpW0VlEnqODW5NAlDmE1LIPfvfim4TM2HhUb9ao@MqwuJkxMJ7yBselCMGF29kjmDtCRkAec6CIePAZNPgpFYhkf73gCUkvfWQKaCz/S464fGIcdd33Im0rI2R172BS03O6pDmFtYUzt0NM31P/z1i44zX7Hq7zRo6@5NH/EqrwyV@Ww/aZR@a@KP6GGbpBxncv@ndxVa30LNX@HCRXZrCNWqPEZe5YjjP0glOu9LLDYww05b/CdfQ43PzQylJtw2@7FPyZAv3c4lbN4XlLySrk3tJofBhKq3z8sR4LRzIjG4ZFmxIjmXNSIR8fAyIdvTGA98uBdjP4UQnmHjc/M9BViEjxVVe5/BRrA4YndTYGa/cPa0B5Enpvu@JQXo5@lxhqSvx77TDX@mts9ew99N0uSutKnovbqMzt/Mye/vol9nMJ3wutp36Gqun8UMcnAL2IAtaUJium1vlyaPD7@Bw\" rel=\"nofollow noreferrer\" title=\"Python 3 – Try It Online\">Try it online!</a></p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/100928", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/46205/" ]

[ { "answer_id": 101311, "author": "Michael Irving", "author_id": 46212, "author_profile": "https://worldbuilding.stackexchange.com/users/46212", "pm_score": 3, "selected": false, "text": "<p>A radiothermal train is a fun idea. Radium may be possible (given futuristic resources), though tricky, I'll need to give it more thought. Another fun possibility if you don't mind an actively controlled reactor is a natural uranium source, like in <a href=\"http://www.world-nuclear.org/information-library/country-profiles/countries-a-f/canada-nuclear-power.aspx\" rel=\"nofollow noreferrer\">the CANDU reactors in Canada</a>. For passive systems though, I'm going to make my case for Polonium-210.</p>\n\n<p>One of the bigger issues of Radium and other seemingly suitable isotopes is the byproducts (or daughters), which are created in that isotope's decay chain. These byproducts would build up constantly in normal use and create technical problems or hazardous conditions. Keep an eye out for long-lived (= obnoxious) daughters, and any beta or gamma decays. To my knowledge, all of the common RTG isotopes have obnoxious byproducts, sadly, with one exception.</p>\n\n<p>If you're willing to hand-wave the production of the isotope, 210Po is rather ideal. It decays directly to a stable isotope of lead-208 through a low-ish energy alpha decay which is quite easy to catch and generate heat from. The alpha particles mostly stop with only a few cm of air, or completely stop in a few mm of water. Polonium-210 has an extreme activity, allowing smaller weights of it to be viable, even on a large train. From my back-of-the-envelope calculations, it would take 'only' about 40-70kg per train (an amount which would fill a ~6in cube). As a note, producing this with modern technology is flatly impossible. If it's easier in the future though...</p>\n\n<p>One convenience of Polonium is that it's fairly noble as a metal, in other words it doesn't rust or dissolve well in water unless there's a bunch of chloride in the solution. For this reason, it could be used in small chunks or even possibly as a thin (mm) plating of solid metal in the boiler or on the walls of the heat exchanger. If you wanted to use it in water solution instead, it's soluble in 3%HCl, or more simply in EDTA (like in shampoo). Without either HCl or EDTA (or similar) it automatically tries to plate itself out of water solutions as metallic Polonium. A downside of HCl is it attacks Copper and Iron, common heat exchanger materials.</p>\n\n<p>A radiothermal train would be producing heat constantly, so it would need to be constantly boiling water, even when not moving. This could be very obnoxious, because water tends to leave deposits and scales on boiler / heatEx equipment and without an obvious opportunity to clean them they could become ineffective or (frighteningly in this case) leaky.</p>\n\n<p>Because Polonium-210 has an extraordinary activity and decent bioabsorption, it's a nefarious toxin (worse than cyanide). The good news is it has a very short halflife (138 days), so spills would lose toxicity within decade. The immediate effects would be devastating though, and would travel freely with ground water if using the solution form. Also because of Polonium's short halflife, the trains would need to be refilled regularly, perhaps making the 'chunk' version more appealing.</p>\n\n<p>Lastly, the alpha particles would cause wild amounts of embrittlement in any metals within striking distance. The Polonium would need to be held well separate from anything critical.</p>\n\n<p>I think I could keep going for a while about little quibbling engineering problems a radiothermal train would face, but it's wonderful concept that doesn't break any major laws of physics while having just enough troubles to make it interesting for the people stuck aboard.</p>\n\n<p>Math for amount of fuel required on a radiothermal steam engine:<br>\n2ton coal /hr <a href=\"https://www.quora.com/How-much-coal-does-a-steam-locomotive-use-per-hour]\" rel=\"nofollow noreferrer\">reference</a><br>\n19.48 *10^6 BTU / ton coal <a href=\"https://www.eia.gov/tools/faqs/faq.php?id=72&amp;t=2\" rel=\"nofollow noreferrer\">reference</a><br>\n1055 J/BTU , 3600 s/hr<br>\n~6MW heat<br>\n141W/gm Po-210 <a href=\"http://mragheb.com/NPRE%20402%20ME%20405%20Nuclear%20Power%20Engineering/Radioisotopes%20Power%20Production.pdf\" rel=\"nofollow noreferrer\">reference</a><br>\n42kg Polonium-210 per train.<br>\nPolonium's quite dense at ~9g/cm^3 resulting in something like a 17cm cube of polonium. A cube would explode though, so let's assume small chunks or a plating.</p>\n\n<p>Best of luck with your world! Also, I really like your ascii art.</p>\n\n<p><strong>Edit:</strong> I noticed that a train to last through a nuclear winter would be handy, so I put a bit more work into this. It seems that Sr-90 would also be appropriate, with the advantage that it has a much longer (29yr) half life. A train would require about 1500kg of it, and beneficially it's available in large amounts in nuclear waste. Sr-90 undergoes beta decay (medium-nasty radiation) to make a daughter which also quickly beta decays to something nice and stable. Beta radiation is best caught by acrylic plastic, though a few cm of water would work as well. </p>\n" }, { "answer_id": 101319, "author": "Loren Pechtel", "author_id": 264, "author_profile": "https://worldbuilding.stackexchange.com/users/264", "pm_score": 2, "selected": false, "text": "<p>Problem: You will not get 50% efficiency. Nuke plants run at about 30% for safety reasons, the same rules would apply to your trains. Thus you need to increase your powerplant by 50%.</p>\n\n<p>Clarifying this: Your efficiency is limited to the Carnot limit, which is a function of temperature. Since nuclear power doesn't have an inherent limiting factor like combustion-driven power you need to keep the temperature farther away from the point your system breaks--for fission plants that ends up being 30%, I would figure the same factors would be at work here and thus the same limit.</p>\n\n<p>Problem: You also have to dissipate 5,000kw of waste heat. Major woe if anything goes wrong with your cooling system as there's no off switch possible. Expect any serious train accident to turn into a nuclear accident as your system bakes itself.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/101288", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/2746/" ]

[ { "answer_id": 101847, "author": "D.J. Klomp", "author_id": 46462, "author_profile": "https://worldbuilding.stackexchange.com/users/46462", "pm_score": 2, "selected": false, "text": "<p>I found you a moon: <strong>Mimas</strong></p>\n\n<p>Since I couldn't sleep I thought I would do some of the math so here it goes:</p>\n\n<pre><code>Radius_Mars = 3390 * 10^3 %in meter\nThickness_Atm = 66 *10^3 %Earth atomosphere is about 100km, took 2/3 for \nmars in meters\nVolume_Atm = 4/3*pi*(Radius_Mars+Thickness_Atm)^3 - 4/3*pi*Radius_Mars^3; \nVolume_Atm = 9.7E18 m^3\nAir_Density = 1.2 %kg/m^3\nNeeded_Mass = 0.3*Air_Density*Volume_Atm; %3.4E18 kg\nNeeded_Mass = 3.4E18 kg\n</code></pre>\n\n<p>So you need a mass of 3.4E18 kg to shoot from some moon (according to <a href=\"https://en.wikipedia.org/wiki/Asteroid_belt\" rel=\"nofollow noreferrer\">wiki</a>the astroids in the belt are mainly of C, S and M type so unsuitable), so find an ice moon with the lowest gravity. It would seem that Mimas orbiting Saturnus is mostly ice and has a surface as small as Spain. The mass of Mimas is 3.7E19 kg so only one order of magnitude higher. So instead of having to deal with escape velocity simply move to complete moon to Mars, the it will only become a question of how fast do you want it.</p>\n\n<p>So if you have patience for a 10 years you have to move the intervening distance between Saturn and Mars, being roughly 1.2E9 km. So your average speed, taking into account that you need to decelerate for just as long would need to be</p>\n\n<pre><code> average velocity = 1.2E12/31E7 = 3834 m/s\n</code></pre>\n\n<p>So to calculate the energy just use the formula for kinetic energy</p>\n\n<pre><code> energy = 1/2*m*v^2\n</code></pre>\n\n<p>So the needed energy becomes:</p>\n\n<pre><code> energy = 1/2*3.7E19*3834^2 = 2.719E26 J\n</code></pre>\n\n<p>To put it into prespective if you harness all the solar radiation falling on earth you would need to harvest it at a 100% efficiency for 12.4 years to get the required energy. So I guess we won't be moving planets any time soon :D.</p>\n\n<p>Since it is late it might be good to check the numbers.</p>\n" }, { "answer_id": 101981, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 2, "selected": false, "text": "<p>An important preface: <strong>without a stated time period to accomplish this task the energy cost cannot be calculated</strong>. </p>\n\n<p>I will make assumptions about time.</p>\n\n<p>Current real Mars data.\n<a href=\"https://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html\" rel=\"nofollow noreferrer\">https://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html</a></p>\n\n<blockquote>\n <p>Atmosphere</p>\n \n <p>Surface pressure: 6.36 mb at mean radius (variable from 4.0 to 8.7 mb\n depending on season)<br>\n [6.9 mb to 9 mb (Viking 1 Lander site)] Total mass of atmosphere: ~2.5 x 1016 kg</p>\n</blockquote>\n\n<ul>\n<li>1 mb = 0.1 kPa. 6.36 mb = 0.636 Kpa.</li>\n<li>The proposed Mars from OP has air pressure of 10 kPa. 10 / 0.636 = 15.7.\nThe total mass of atmosphere has increased by 15.7 times. </li>\n<li>The current total mass of atmosphere is (2.5 x 1016) x 15.7 = 3.92 x 10¹⁷ kg.</li>\n<li>You ask to raise atmospheric pressure 40 kPa more (to a total of 50 kPa). Noted: adding gas mass might not cleanly convert to raising pressure but we will assume.<br>\nYou want to add 4 times the current atmospheric mass to the current atmospheric mass.</li>\n<li>You want 4 x (3.92 x 10¹⁷ kg) = 15.7 x 10¹⁷ kg or 1.57 x 10¹⁸ kg of gas.</li>\n</ul>\n\n<p>For reference, let us consider what it would take to import this much mass from Earth. I know that the conditions of the OP rule out Earth but this will give a sense of scale for these huge numbers.<br>\n<a href=\"https://www.space.com/24701-how-long-does-it-take-to-get-to-mars.html\" rel=\"nofollow noreferrer\">https://www.space.com/24701-how-long-does-it-take-to-get-to-mars.html</a>\nWe will assume the distance between Earth and Mars is 225 million km. \nWe will allow a leisurely 1 year to traverse this distance.<br>\n225,000,000 km/year is 7134 meters/second. It is so cool Google will do calulations like that for you!</p>\n\n<p>Again to get things to scale: this is 25684 km/hour. That is a good clip but the New Horizons probe (from above link) went twice that fast, so OK.</p>\n\n<p>Kinetic energy = 1/2 * mass * velocity ^2, where Kinetic energy is in joules, mass is in kilograms, and velocity is in meters per second</p>\n\n<p>The joules: speed in m/s ^2 = 7134 ^2. = 50893956<br>\nMass moved (from above) = 1.57 x 10¹⁸ kg<br>\n1.57 x 1018 kg x 50893956 = 7.9903511e+25. </p>\n\n<p>Divided by 2 = 3.9951755e+25 joules to move required mass from Earth to Mars over 1 year.</p>\n\n<p>Of course one must decelerate this mass when it arrives on Mars, unless you have some scheme to decelerate it for free by ramming the mass into the surface. Which could have ramifications, so to speak. The energy you put in to get it up to speed you must then put back in to slow it down: x 2, which fortunately is already done: 7.9903511e+25 joules.</p>\n\n<p>It would be energetically more expensive to do it faster (because one must accelerate to a higher velocity) and less expensive to do it slower. If moving mass from farther away (e.g. Titan) the same holds: it would cost the same energy as moving it from Earth but take more time, or cost more energy to traverse the greater distance at the same speed. <strong>Without a stated time period to accomplish this task the energy cost of the task cannot be calculated</strong>.</p>\n\n<hr>\n\n<p>Considering an alternative: this society must have a metric buttload of energy available to consider such an endeavor. From my point of view, this society has unlimited energy. Maybe they tap Casimir forces or are masters of fusion. Moving mass would be a trick with potential for disaster at many steps along the way. The logistics of gathering this much mass at its source, keeping it together en route, and decelerating it into Mars are daunting. </p>\n\n<p>Instead, how about using that free energy to make the mass on site?</p>\n\n<p>How much energy is in that much mass? Sweet online calculators!\n<a href=\"http://www.wolframalpha.com/widgets/view.jsp?id=b3aa19fe9dc706a3b4cdaa8ddb37d852\" rel=\"nofollow noreferrer\">http://www.wolframalpha.com/widgets/view.jsp?id=b3aa19fe9dc706a3b4cdaa8ddb37d852</a>\n1.57 x 10¹⁸ kg converts to 1.411 x 10³⁵ joules.</p>\n\n<p>Double checking with this calculator\n<a href=\"http://www.1728.org/einstein.htm\" rel=\"nofollow noreferrer\">http://www.1728.org/einstein.htm</a>\nI get 1.348e+35 in that much mass.</p>\n\n<p>For scale, the sun puts out 3.725e+26 joules / second. To make the required mass using the entire energy output of the sun would take 361879194 seconds or 11.4 years. Depending on how your energy source worked, you could set up mass generation plants on Mars and let them chug away.</p>\n\n<p>Of course if you want to get super fussy, these numbers assume that the new Martian atmosphere is the same gas composition and so same kg weight as the existing real Martian atmosphere which is mostly CO2. It is not specified in the OP what the new Martian atmosphere is made of: at 10 kPa and 50% O2 there is 50% something else which must be CO2. (You would be breathing really hard in that atmosphere and it would feel like you burped Coke into your nose). </p>\n\n<ul>\n<li>All gases have the same volume.</li>\n<li>All CO2 atmosphere (current real Mars) would be 44g/mol gas. </li>\n<li>N2 atmosphere imorted or created would be 28 g/mol gas. That is 0.63 the mass I used above. Those who are very interested can multiply accordingly for new numbers.</li>\n<li>You could make (but probably not find and import) an atmosphere of neon with 71% of the mass of your diatomic nitrogen atmosphere. That would be 0.45 the mass I used above for calculations. So just 4.5 years to produce with your energy to mass factories!</li>\n</ul>\n" }, { "answer_id": 102048, "author": "slOOP", "author_id": 29307, "author_profile": "https://worldbuilding.stackexchange.com/users/29307", "pm_score": 2, "selected": false, "text": "<p>I would seriously consider the main belt asteroids. Delta V from Mars transfer to Ceres transfer orbit is 1.3 km/s. You shouldn't need to go to an asteroid the size of Ceres and you'll be throwing small chunks that will burn up in the atmosphere so you don't need to slow anything down.</p>\n\n<p>Let's say you shoot 1kg chunks from 0 to 1300 m/s in 1 second.</p>\n\n<p>This takes 650 meters (d = 1/2*a*t^2).</p>\n\n<p>Energy is kg* m^2 / s^2 or kg * meters * a </p>\n\n<p>so this is 845000 Joules per kg (you can change the time or acceleration just so you still get that delta v and the energy won't change.\nLet's call that 1 x 10^6 because our asteroid has some gravity.</p>\n\n<p>Someone smarter than me said you're looking for ~2 x 10 ^18 kg. The total asteroid belt mass is 3 x 10^21 kg so that makes sense to me.</p>\n\n<p>You need 2 x 10^24 Joules or\n2 x 10^21 KJ. </p>\n\n<p>\"Palo Verde nuclear power plant in Arizona is the largest nuclear power plant in the United states with three reactors and a total electricity generating capacity of about 3,937 MW.\"</p>\n\n<p>and 1MWh = 3.6 x 10^6 KJ</p>\n\n<p>So 555.5 x 10^12 MWh is 1000 Palo Verdes running at max for 141 million hours (16000 years).</p>\n\n<p>That's a little disappointing but maybe your launcher could use Ceres for a gravity assist. If you could get the delta v to more like 300 m/s that drops it to 7 million hours (800 years).</p>\n" }, { "answer_id": 144564, "author": "LSerni", "author_id": 6933, "author_profile": "https://worldbuilding.stackexchange.com/users/6933", "pm_score": 1, "selected": false, "text": "<p>Unfortunately, the only gases you can safely put in a terraformed body's atmosphere are oxygen and nitrogen.</p>\n\n<p>Earth is out, so the only other feasible source for nitrogen is Titan (unless you have an economic way of instating a partial <a href=\"https://en.wikipedia.org/wiki/CNO_cycle\" rel=\"nofollow noreferrer\">CNO cycle</a> <em>and</em> have sufficient carbon or carbon dioxide source, and energy, in place).</p>\n\n<p>Nitrogen on Titan - or any significant gravity well outside Mars's - possesses quite a lot more potential energy than it's feasible to unleash unto the red planet. The simplest way of delivering the nitrogen, i.e. supercooling it in frozen missiles and shooting them at Mars using linear accelerators, will result in even more energy. The frozen missiles will burn and disintegrate in the Martian atmosphere, <em>but</em> they will also heat it (and, not too much later, the ground) way too much.</p>\n\n<p>Delivering the goods using reaction drives is unfeasible for the same reason. Each kilogram at Mars ground level would cost too much in either waste heat and/or environmental pollution.</p>\n\n<p>Inertialess grav-drives would of course solve this problem, but they're not current technology; not even in sight.</p>\n\n<p>What follows is <em>also</em> almost certainly not feasible, but due to logistic and economic constraints, not technological limitations.</p>\n\n<h1>Stage One: build a base on Titan, install a launcher (actually, many launchers).</h1>\n\n<p>The Titan base will send projectiles onto a <a href=\"https://en.wikipedia.org/wiki/Hohmann_transfer_orbit\" rel=\"nofollow noreferrer\">Hohmann</a> transfer orbit, supplying the first part of the required delta-V. That'll set you back around 11 MJ/kg plus other 3.48 MJ/kg of escape velocity.</p>\n\n<p>The launcher might be installed on a skyhook on Titan to reduce the second part of those costs.</p>\n\n<p>A projectile is just an insulating shell over one ton of supercooled solid nitrogen, plus a solar-powered beacon, and will arrive at Mars after 5 to 18 years depending on planets positions. It has no manoeuvering capabilities.</p>\n\n<h1>Stage Two: build the \"catcher\" (or a forest of them) in orbit around Mars.</h1>\n\n<p>The catcher will have to neutralize the incoming projectile's kinetic energy using electromagnetic braking. You will need a minimum of around 28.5 MJ/kg for that. This will also determine an alteration in the catcher's orbit. To balance that, some kind of thruster, maybe a ion engine, will need to be installed. We could perhaps use Phobos as a waystation - but that would limit us to <em>one</em> waystation, restricting both the number of catch windows and volley size.</p>\n\n<p>Another possibility could be to harpoon the incoming projectile - it will be moving at around 7500 m/s - and decelerate it using a dynamo reel. That would allow recovering most of those 28.5 MJ/kg, even if even braking at 10 G will still require more than one minute, and paying out some 290 km of wire. A one-ton projectile falling in from Saturn will then develop a power of around 370 megawatt (28500 MJ in 76 s).</p>\n\n<h1>Stage Three: drop the pellets on Mars.</h1>\n\n<p>Falling 6000 km from as low as Phobos, even with zero initial speed in respect to the planet (the Phobos launcher will simply neutralize the moon's orbital velocity), the frozen nitrogen pellets would still possess a potential energy of around 7.1 MJ/kg; even if they're close to absolute zero, they would only absorb about 0.3 MJ/kg to achieve the gaseous phase. We'd be left with an excess of more than 28 million calories per kilogram, which is unacceptable.</p>\n\n<p>The only other alternative is a skyhook. The skyhook station would orbit in the same plane as the incoming projectiles, and alternately catch them from either side of the planet, thereby dumping the excess energy straight into Mars. We will require a sizeable series of skyhooks all around the planet - essentially, an artificial ring around Mars.</p>\n\n<p>The gas would then be dropped straight down, neutralizing (and recovering a part of) those 7 MJ/kg of energy through magnetic braking.</p>\n\n<p>The big question is now <strong>how long would this take</strong>.</p>\n\n<p>Assuming each projectile weighs one round ton, we'd need around three thousand million <em>million</em> projectiles. Most of the required energy is supplied by gravity, but still we need launchers and catchers. With one thousand of each, we require three million million volleys, and at one volley per second (remember we're moving one ton of mass per launch, and incidentally we have to dissipate a <em>lot</em> of energy), that's <strong>one hundred thousand years</strong>.</p>\n" }, { "answer_id": 144568, "author": "Dubukay", "author_id": 43163, "author_profile": "https://worldbuilding.stackexchange.com/users/43163", "pm_score": 2, "selected": false, "text": "<p>So, the other answers have established that it's not easy to move huge amounts of mass around the solar system. Why not try to solve the problem like NASA does?</p>\n\n<h2>Making thin air out of rocks</h2>\n\n<p>In a reversal of the typical \"making stuff appear out of thin air\", an ingenious chemical process allows the production of thin air out of rocks. Specifically, a modified version of the <a href=\"https://en.wikipedia.org/wiki/FFC_Cambridge_process\" rel=\"nofollow noreferrer\">Fray-Farthing-Chen (FFC) Process</a> takes in metal oxides such as titanium dioxide, magnesium oxide, or sodium oxide and separates the two elements. This was first proposed in 2000, and immediately <a href=\"https://www.nature.com/articles/35030069\" rel=\"nofollow noreferrer\">earned a Nature paper</a>. Although originally designed for the production of high-purity metals, this process picked up a lot of attention in the late 00's when NASA and others realized that it could be used to <a href=\"https://isru.nasa.gov/OxygenfromRegolith.html\" rel=\"nofollow noreferrer\">produce oxygen out of lunar regolith</a>. This is known as \"In Situ Resource Utilization\" (ISRU), and NASA has <a href=\"https://phys.org/news/2005-06-lunar-oxygen.html\" rel=\"nofollow noreferrer\">put some pretty serious money</a> towards determining feasibility.</p>\n\n<p>Specifically, <a href=\"http://energyprofessionalsymposium.com/?p=25168\" rel=\"nofollow noreferrer\">the Ilmenox process</a> uses a specially-designed reactor that strips the oxygen from the other elements in lunar or Martian regolith and <a href=\"https://www.popsci.com/military-aviation-amp-space/article/2009-08/new-reactor-make-breathable-air-out-moon-rocks\" rel=\"nofollow noreferrer\">liberates it into the atmosphere</a>. </p>\n\n<p>To quote from the <a href=\"https://phys.org/news/2009-08-scientists-oxygen-moon.html\" rel=\"nofollow noreferrer\">phys.org article</a> summarizing this development,</p>\n\n<blockquote>\n <p>Based on experiments with a simulated lunar rock developed by NASA, the researchers calculate that three one-meter-tall reactors could generate one tonne of oxygen per year on the Moon. Each tonne of oxygen would require three tonnes of rock to produce. Fray noted that three reactors would require about 4.5 kilowatts of power, which could be supplied by solar panels or possibly a small nuclear reactor on the Moon. The researchers are also working with the European Space Agency on developing an even larger reactor that could be operated remotely.</p>\n</blockquote>\n\n<p>So, to summarize: we can use 4.5 kilowatt reactors to produce oxygen (or carbon dioxide) from moon rocks. The return on this is something like 1,000kg of oxygen per year. So our energy conversion is</p>\n\n<p><span class=\"math-container\">$$\\frac{4,500\\ J}{1\\ sec}*\\frac{31,536,000\\ sec}{1\\ year}*\\frac{1\\ year}{1,000\\ kg\\ O_2} = \\frac{142\\ MJ}{kg\\ O_2}$$</span></p>\n\n<p>To borrow from WillK's excellent answer, we need something like 1.57 x 10¹⁸ kg of gas. To synthesize all of that <em>de novo</em>, we'll need <strong>2.23 x 10²⁶ joules of energy</strong>. Curiously, that's in the same ballpark as the other answers - cool! However, I'll argue that my method is still superior for several reasons.</p>\n\n<h3>Reason #1: Controlled progress</h3>\n\n<p>As many of the other answers point out, half of their energy cost comes from slowing down whatever they're throwing at it. With this method, the process is controlled from beginning to end - ramp up production or slow it down as necessary. To put that number in context, let's check out <a href=\"https://en.wikipedia.org/wiki/Orders_of_magnitude_(energy)\" rel=\"nofollow noreferrer\">everyone's favorite Wikipedia page</a>:</p>\n\n<ul>\n<li>If this was done with traditional fossil fuels, we can expect to take in 10,000 years if we used all the fossil fuels on Earth every year: fossil fuel reserve as of 2010 = 3.9×10²² J</li>\n<li>If done with nuclear tech, as your question proposes, we can expect to take more like 1,000 years, if we used all the uranium on Earth every year: global uranium-238 resources = 2.2×10²³ J</li>\n<li>If we covered Mars in solar panels, we can expect to be done in about 100 years: total power received by Mars from the Sun <span class=\"math-container\">$\\approx$</span> 6.6x10¹⁶ W</li>\n<li>If we <a href=\"https://en.wikipedia.org/wiki/Dyson_sphere\" rel=\"nofollow noreferrer\">cover the Sun in solar panels</a>, we're done in one second: solar output = 3.8×10²⁶ W</li>\n</ul>\n\n<p><a href=\"https://i.stack.imgur.com/Rff4h.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/Rff4h.jpg\" alt=\"Stupid Tumblr post about making cookies with the sun (from https://orteil42.tumblr.com/post/125575676555/blxckbiird-spaghetti-western-wannabe)\"></a></p>\n\n<h3>Reason #2: We're actually producing a gas</h3>\n\n<p>Most of the other answers have thrown something like a small moon or a whole bunch of rocks at Mars and called it a day. That's... not an atmosphere? Nor is it especially friendly to the inhabitants? Instead, with this method, we're producing atmospheric gases in any mix of carbon dioxide and oxygen that we'd like, allowing us to find a good balance between phototrophs and heterotrophs as we continue to terraform the place. Unless the other answers manage to find an extraterrestrial object made largely of nitrogen or neon, against all the traditional extraterrestrial body compositions we've thus far found, all that they'll do is add more rocks to the place - mostly silicates and metal oxides.</p>\n\n<h3>Reason #3: Abundant high-purity metals as side-effect</h3>\n\n<p>\"But wait,\" you say, \"what about all the side products of the FFC process?\" Well, I'm really glad you asked. As noted earlier, this process is traditionally used to produce high-purity metals by stripping the oxygen off of metal oxides. Now that we've reversed the roles, these metals are essentially \"waste material\" - guess we'll have to make <a href=\"https://www.google.com/search?q=martian+city+art&amp;oq=martian+city+art\" rel=\"nofollow noreferrer\">really cool buildings</a> out of them instead.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/101837", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/23519/" ]

[ { "answer_id": 102796, "author": "Loren Pechtel", "author_id": 264, "author_profile": "https://worldbuilding.stackexchange.com/users/264", "pm_score": 4, "selected": false, "text": "<p><em>Therefore, could it be possible that</em>:</p>\n\n<ul>\n<li><em>An asteroid hit at an angle to slow the Earth's rotation and to increase its axial tilt to give birth to seasons?</em></li>\n</ul>\n\n<p>An impact powerful enough to do this would leave the Earth a ball of magma. All life would be destroyed.</p>\n\n<ul>\n<li><em>An asteroid passed through the crust of the Earth, causing little damage externally but changing the magma flow to decelerate the Earth's rotation?</em></li>\n</ul>\n\n<p>Can't happen. It would be stopped (like the <a href=\"https://en.wikipedia.org/wiki/Theia_(planet)\" rel=\"noreferrer\">hypothetical early planet-sized body <em>Theia</em></a>, which -- according to the giant impact hypothesis -- slammed into <em>Gaia</em>, merged with it, and spit out <em>The Moon</em> while renaming Gaia into <em>Earth</em>), it wouldn't pass through.</p>\n\n<ul>\n<li><em>An asteroid struck such that the polar caps melted or the water was forced out of the oceans?</em></li>\n</ul>\n\n<p>An impact event certainly could melt polar caps. That wouldn't explain where the water went afterwards, though, and the caps simply don't have anything like the water needed anyway.</p>\n" }, { "answer_id": 102797, "author": "jamesqf", "author_id": 3545, "author_profile": "https://worldbuilding.stackexchange.com/users/3545", "pm_score": 4, "selected": false, "text": "<p>Your fundamental (pun intended :-)) problem lies in using the Bible as a historical record. The simple answer is that none of those things could happen without, at the very least, leaving ample evidence that they had happened. More probably the result would have been the extinction of all life.</p>\n\n<p>The reasons why Noah's Flood simply could not have happened (absent miracles) as described in the Bible are amply covered elsewhere. Of course to some primitive tribe, \"the whole Earth\" might be an area of a hundred miles (km, leagues, &amp;c) or so in diameter, so tribal myths of something like the Black Sea filling could have gotten exaggerated.</p>\n\n<p>But to take your three suggestions:</p>\n\n<p>1) An asteroid strike sufficient to change the Earth's rotation &amp; axial tilt would have reduced the entire Earth to a molten blob. In fact something of the sort probably did happen in the very distant past (about 4.5 billion years ago), resulting in the creation of the Moon. See e.g. <a href=\"https://en.wikipedia.org/wiki/Giant-impact_hypothesis\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/Giant-impact_hypothesis</a> </p>\n\n<p>2) An asteroid would not pass through the Earth's crust. Any asteroid large enough to keep going after contact would be of the Giant Impact scale, so there wouldn't be anyone left. Smaller ones would simply hit and vaporize, causing major damage. See the evidence from a number of actual impact craters, notably Chicxulub (responsible for the extinction of the dinosaurs), or smaller craters like Sudbury &amp; Arizona's Meteor Crater. </p>\n\n<p>3) Even if an asteroid impact could melt the polar icecaps, a) there's only enough water to raise sea levels about 100 meters, not enough to cover the whole Earth; b) the melting would have left unmistakable traces, as did the melting after the last Ice Age; c) the ice caps most likely wouldn't have regrown yet, and finally; d) core samples show that they've been in place for at least 100K years: <a href=\"https://en.wikipedia.org/wiki/Ice_core\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/Ice_core</a></p>\n\n<p>An asteroid which hit the ocean might have caused floods, but they'd be tidal waves, not 40 days &amp; nights of rain.</p>\n\n<p>Finally, even if these had happened, changing the rotation speed of the Earth changes the length of the day, not the year. To lengthen the year, you'd have to move the Earth farther from the Sun. If it were close enough to the sun for its year to be 1/10 of the present length, it would be uninhabitably hot. Even Mercury's year is only about 1/4 of an Earth year.</p>\n" }, { "answer_id": 102824, "author": "Charles Bowen", "author_id": 46958, "author_profile": "https://worldbuilding.stackexchange.com/users/46958", "pm_score": -1, "selected": false, "text": "<p>See Carolina bays, the younger Dryas impact event, Carlson... in a nutshell, about 13,000 years ago, at the end of the last ice age, when there was a 2 mile tall glacier covering the north pole from Moscow, France, England, New York to northern China... a comet, approximately 6+ miles in diameter, impacted where the great lakes are now (after having broken into several to a dozen or more pieces) and a few other areas in what is now Canada at over 40k miles per hour. The great lakes and possibly the grand canyon are leftovers from this event? This is new science information... totally legitimate. The grand canyon part is mine... within 30 minutes of the impacts, all of North America from Virginia to California to Northern Mexico was on fire. Approximately 3 million ejecta re-entered the atmosphere with speeds from 6k to 10k mph, ranging in size from 100 feet to a mile or more... chunks of ice from the glacier. Just look at the 500k plus impact craters discovered with lidar from orbit in the last 15 years, covering the east coast from Virginia to Florida to Kansas... all of them oval shaped with their long axis pointing to the great lakes! search youtube.. </p>\n" }, { "answer_id": 102867, "author": "AtmosphericPrisonEscape", "author_id": 28097, "author_profile": "https://worldbuilding.stackexchange.com/users/28097", "pm_score": 4, "selected": true, "text": "<p>I'll try to contribute, trying to omit what others have already mentioned;</p>\n\n<p>The first issue I want to mention is your idea that an asteroid would 'go through' Earth just as the bullet does through the high-tech jelly. This analogy is deeply flawed due to one simple thing that you have ignored:<br>\nThere is actually a lot of physics involved in stopping something when hitting something else, but it can all be broken down to a rule-thumb:<br>\nFor high-velocity impacts, if the density contrast between impactor and impactee is high, one will ignore the other. If not, both break apart. (Over at astronomy we think a lot about impacts) </p>\n\n<p>What do I mean by this? See the bullet is much denser than the medium it is shot into. But 'much' I'm talking about around a factor of 5-10 density contrast. After the initial expansion shock visible in the animation, the gel medium more or less ignores the bullet.<br>\nThe same thing would happen If you shoot a bullet into water (well, because it has nearly the same density as the gel),or air (duh, but the principle still applies).</p>\n\n<p>Now if you shoot it at something even denser, like a brick, or a metal plate, the bullet will not penetrate anymore. </p>\n\n<p>Now imagine the bullet is a meteor and doesn't have the same material strength as the bullet, then it will simply fly apart. Large rocks ($\\ge 100 km$) in space have comparable densities, so they will always be ripped apart, never penetrate.<br>\nSmaller rocks will always be ripped apart, without affecting Earth significantly, because they have similar density, but the small rock also has much less momentum.</p>\n\n<p>I mentioned this to maybe guide your thinking in physical terms: Density contrast and momentum (but that was already mentioned in other answers).\nI find most of your questions that you had in the comments in your physics.se answerable just by looking at this principle.<br>\nIf you want to, this can be a valuable tool in world-building, as well as in bible studies, depending what your aim is.</p>\n\n<p>So what you want to do is essentially send a mini-black hole through earths crust and still keep the solar system and the planetary atmosphere in a good shape after that. That would be a tough one.</p>\n\n<p>For your other questions, I will just briefly comment on, as correct answers already exist:</p>\n\n<pre><code>1.) An asteroid hit at an angle to slow the Earth's rotation and to increase its axial tilt to give birth to seasons?\n\n2.) An asteroid passed through the crust like a bullet causing little damage externally but changing the magma flow to decelerate the Earth's rotation? It would still leave a creator but the bulk of the impact would be absorbed by the inside of the Earth.\n\n3.) An asteroid struck such that the polar caps melted or the water was forced out of the oceans?\n</code></pre>\n\n<p>1.) As others said, that's not possible. But I think the other answers underappreciated how NOT POSSIBLE this is.<br>\nTo go from a 1.7 hrs rotation period with the whole mass of Earth to 24 hrs in one impact would deposit a lot of kinetic energy in the crust. So much in fact that the energy deposited would easily reach the gravitational binding energy of the planet.<br>\nMeaning: This would be an impact that could rip the planet apart. It wouldn't just be catastrophic, apocalyptic or hyper-bad. It would be fatal. I can show you the math if you're interested, it's simple.</p>\n\n<p>And as soon as you go down in impact energy, you can't produce the slow-down anymore that your source is citing.</p>\n\n<p>I have discussed 2.) above already.</p>\n\n<p>3.) is an entirely possible scenario, and probably happened multiple times during Earth's early history, during the <a href=\"https://en.wikipedia.org/wiki/Late_Heavy_Bombardment\" rel=\"noreferrer\">Late heavy bombardment period</a>.</p>\n\n<p>However it is important, that this happens before the development of complex life, or else everything has to start from zero again. To give you a sense of comparison, the K-Pg impactor (the Dinosaur Killer, around $\\rm 10 km$ in size) wouldn't have near enough energy to affect the polar caps significantly or to evaporate any ocean.</p>\n\n<p>To do this, you need a bigger meteorite (or asteroid with $\\rm \\ge 100km$ size, as you asked for) and then consequences are again dire: </p>\n\n<p>The splash energy (and as discussed, the density principle needs it to be a splash) would be incredible, melt the whole surface, even eject a good part of the atmosphere mechanically.<br>\nBut only after that comes my favourite part: Atmospheric escape. The extremely hot surface would heat the atmosphere to temperatures where it can <a href=\"https://en.wikipedia.org/wiki/Hydrodynamic_escape\" rel=\"noreferrer\">escape in bulk</a>.</p>\n\n<p><strong>Summarizing</strong></p>\n\n<p>No impactor scenario that I can think of fulfills all the possible consequences that you need in your story. </p>\n\n<ul>\n<li>Of course you can leave out the part with changing the rotation period of the planet, because that places the hardest physical bound on a planet-destroying impact.</li>\n<li>The 'going-through-Earth' thing would also have to be abandoned on a realistic ground. Except you want to invoke really many rogue neutron stars / black holes flying around in the universe and hitting Earth by chance.</li>\n<li>Melting the polar caps / evaporating the oceans should be fine, but then you have to live with the other consequences as well. Or you magic them away.</li>\n</ul>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/102787", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/27786/" ]

[ { "answer_id": 102886, "author": "Josh King", "author_id": 21041, "author_profile": "https://worldbuilding.stackexchange.com/users/21041", "pm_score": 0, "selected": false, "text": "<p>So 1,000lb is grossly oversized.</p>\n\n<p>Average draw weights for normal bows are in the 40-55lb range. You're talking about scaling up a human by 1.5x (6ft to 9ft), but increasing the arm strength by 20x. Even assuming a cube law this would indicate a more likely bow draw range of 3.5x or 150-200lb comparable to a crossbow. For reference the giant would need to dissipate this force when firing (equal and opposite), a thousand pounds force is one hell of a shove even for a giant bracing for the blow.</p>\n\n<p>1000lb is not a bow it is a small <A href=\"https://en.wikipedia.org/wiki/Ballista\" rel=\"nofollow noreferrer\">ballista</A>.</p>\n\n<p>For reference <A HREF=\"http://www.comitatus.net/armyballista.html\" rel=\"nofollow noreferrer\">these guys</A> built a replica roman ballista of 700lb draw weight.</p>\n\n<p>Ballista don't fire regular arrows, but more commonly stones, metal darts, or metal tipped spears. They also have a guide track for the projectile to follow, which your bow would lack making it very hard to aim or shoot.</p>\n\n<p>Comparable draw weight ballistae can shoot several hundred meters when firing in a parabolic arc. They were known to pierce shields at range and were highly accurate and deadly.</p>\n" }, { "answer_id": 102899, "author": "bendl", "author_id": 39583, "author_profile": "https://worldbuilding.stackexchange.com/users/39583", "pm_score": 3, "selected": true, "text": "<h1>First of all, some conversions to make the physics easier:</h1>\n\n<pre><code>500 lbs ~= 225 kg\n43.2 in ~= 1.1 m\n</code></pre>\n\n<h1>Okay, now why these numbers?</h1>\n\n<p>Bows are basically springs, meaning that they follow Hooke's Law reasonably well. Hook's law states that $F=ks$ where $F$ is force, $k$ is a constant related to the spring and $s$ is how far you've stretched the string.</p>\n\n<p>Now I'm going to make an assumption that's wrong, but will make all of this much easier. I'm going to assume that your bow begins from a state of rest, meaning that it starts at $s=0$. This is wrong, because the bowstring does impart some force onto the bow, creating some tension before you even begin to draw, but since this whole exercise is an estimate, I don't think this will affect our end results much.</p>\n\n<p>In physics, work is defined as $W=F_{avg}s$. Here's where that assumption comes into the picture. Since the force exerted by the bow is linear, if it starts at a state of rest, then the average force is just half the maximum force. That means that the average force exerted while pulling back your hypothetical bow is 500 lbs, because that is half of 1000 lbs (the max force during draw).</p>\n\n<p>Now we need $s$, or the draw length. <a href=\"http://www.lancasterarchery.com/blog/what-size-recurve-bow-is-right-for-me/\" rel=\"nofollow noreferrer\">This site</a> tells us that the length from fingertip to finger tip divided by 2.5 should be the proper draw length. For our 9 foot tall humanoid, that's $(9*12)/2.5=43.2$.</p>\n\n<p>Using the conversions above that's $F_{avg}=225$ and $s=1.1$.</p>\n\n<h1>Now plug it in</h1>\n\n<p>Plugging our numbers into our formula above, we get $W=F_{avg}s=225*1.1=247.5\\ Joules$. Not all of that is going to go into sending the arrow forward. A lot of it is wasted by making the arrow oscillate and some heating of the bow. <a href=\"https://www.wired.com/2014/12/much-energy-bow-goes-kinetic-energy-arrow/\" rel=\"nofollow noreferrer\">According to this site</a>, only 54.8% of the energy goes into the arrow. So, $E_{arrow}=W_{bow}*.548=247.5*.548=135.6\\ Joules$.</p>\n\n<h1>So how fast is it going finally?</h1>\n\n<p>Now kinetic energy is defined as $E_k=(1/2)mv^2$ so now all we need is the weight of the arrow. <a href=\"http://www.archerytalk.com/vb/showthread.php?t=780567\" rel=\"nofollow noreferrer\">This guy</a> wanted some help with the weight of his arrow, and his community was helpful enough to let him know it was ~375 grains... which is apparently a unit of weight? Anyway apparently that's about 24 grams. I'm going to go with a crude \"let's double its size!\" calculation. Doubling the size makes the volume increase by a factor of 8, and the weight by the same, so the weight of our extra large arrow is 194 grams. Note that double the size is 56 inches, which isn't too much longer than our draw length, sounds good to me!</p>\n\n<p>Now throwing that in the equation, we get $135.6=(1/2)*.194*v^2$. Solving for $v$ gets us about 37 meters per second or about 80 mph!</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/102874", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/46400/" ]

[ { "answer_id": 103568, "author": "user", "author_id": 13688, "author_profile": "https://worldbuilding.stackexchange.com/users/13688", "pm_score": 3, "selected": false, "text": "<h2>TL;DR</h2>\n<p><strong>Probably yes</strong>, natural uranium (NU) is usable in weapons in &quot;young&quot; ^{[note 1]} solar systems. (not weapons-grade, but weapons-usable)<br />\n<strong>Probably yes</strong>, terrorists would have a much easier time creating (crude) nuclear weapons. Whether not needing enrichment would hinder or help civilizations prosper and survive is uncertain since there are both problems (terrorism, nuclear proliferation) <em>and</em> benefits (cheaper nuclear energy).</p>\n<hr />\n<h2>NU enrichment levels</h2>\n<p>2 billion years ago NU was enriched enough to sustain a nuclear chain reaction (<a href=\"https://apod.nasa.gov/apod/ap100912.html\" rel=\"nofollow noreferrer\">Oklo cave</a> was probably a natural nuclear reactor)</p>\n<p>4.5 billion years ago natural uranium was already enriched enough (~23%) to be used in weapons without the need for further enrichment (although enrichment would still be beneficial).</p>\n<p>Using the code at the bottom we get the following results:</p>\n<pre><code>2 billion years ago natural uranium was 3.7% enriched. \n4 billion years ago, 16.7%. \n5 billion years ago (about the age of our solar system) 31%. \n6 billion years ago, 51%. \n</code></pre>\n<p>On the other hand we are not quite certain how life on earth formed and perhaps there is a time threshold on how fast life can form in a freshly created solar system, eg. requiring at least 1 billion years for multicellular organisms to form etc.</p>\n<p>By going into an even earlier period higher enrichments are possible but probably unlikely, since <span class=\"math-container\">$\\ ^{235}U$</span> and <span class=\"math-container\">$\\ ^{238}U$</span> are created through the <a href=\"https://www.physics.ohio-state.edu/%7Entg/6805/slides/rprocess.pdf\" rel=\"nofollow noreferrer\">r-process</a> and their abundance when created is probably not that different (about <a href=\"http://large.stanford.edu/courses/2013/ph241/roberts2/\" rel=\"nofollow noreferrer\">1.5 <span class=\"math-container\">$\\frac{\\ ^{235}U}{\\ ^{238}U}$</span></a> = 60% enrichement in supernovas).</p>\n<p>By comparison U used in nuclear reactors is about <a href=\"https://www.nrc.gov/materials/fuel-cycle-fac/ur-enrichment.html\" rel=\"nofollow noreferrer\">3-5%</a>, meaning that both state-owned nuclear weapons and nuclear reactors are widespread in planets that are &quot;young&quot;.</p>\n<p>So, yes. Natural uranium was weapons-usable and perhaps <em>is</em> weapons-usable in other &quot;young&quot; solar systems as we speak. Is the relative age the only way to have enriched NU? If uranium can be transfered to a planet by asteroids or comets just like <a href=\"https://www.space.com/27969-earth-water-from-asteroids-not-comets.html\" rel=\"nofollow noreferrer\">water on Earth</a>, then &quot;young&quot; age is not the only way to have planets with enriched NU.</p>\n<h2>Nuclear terrorism</h2>\n<p>When it comes to terrorists (today):</p>\n<blockquote>\n<p>once they have [the nuclear material], <a href=\"https://youtu.be/zVhQOhxb1Mc?t=48m46s\" rel=\"nofollow noreferrer\">80% or more of the way</a> [to a crude nuclear bomb]</p>\n</blockquote>\n<p><a href=\"https://youtu.be/MnW7DxsJth0?t=24m39s\" rel=\"nofollow noreferrer\">Also</a>,</p>\n<blockquote>\n<p>once enriched from 0.7% U-235 to 4.5%, ~3/4 of the work of going to 90% U-235 is done</p>\n</blockquote>\n<blockquote>\n<p>having a stock of LEU could allow a country to enrich to HEU more quickly, or with a smaller, easier-to-hide facility</p>\n</blockquote>\n<p>Meaning that the greatest obstacle is U enrichment. With that out of the way, everything becomes <em>much</em> easier! Both nuclear proliferation and terrorism would be increased.</p>\n<p>Perhaps that's an extra <a href=\"https://waitbutwhy.com/2014/05/fermi-paradox.html\" rel=\"nofollow noreferrer\">great filter</a> for civilizations on young solar systems. Once they've solved the terrorism/wars issue naturally enriched U is a blessing instead. Perhaps one day we'll be able to detect nuclear detonations from distant solar systems and we'll find out.</p>\n<p>_{<strong>Note 1:</strong> &quot;young&quot; compared to when the nearby supernova exploded creating its elements (including the U).<br />\n<strong>Note 2</strong>: I answered my own question so that you can check it. If you find any mistakes, let me know.}</p>\n<hr />\n<p><strong>Python code used for the above results:</strong></p>\n\n<pre><code>SECONDS_PER_YEAR = 365*24*60*60\nBILLION_YEARS_TO_SECONDS = SECONDS_PER_YEAR * 1e9\n\n\nU235_halflife = 7.04e8 * SECONDS_PER_YEAR # http://www.nndc.bnl.gov/nudat2/reCenter.jsp?z=92&amp;n=143\nU238_halflife = 4.468e9 * SECONDS_PER_YEAR # http://www.nndc.bnl.gov/nudat2/reCenter.jsp?z=92&amp;n=146\n\nU235_TO_U238_RATIO = 0.720 / 100 # https://physics.nist.gov/PhysRefData/Handbook/Tables/uraniumtable1.htm\n\n# --------------------------------\n# CHANGE THIS VALUE:\nbil_years = 5\n#\n# --------------------------------\n\n\nu235_halflives = BILLION_YEARS_TO_SECONDS * bil_years / U235_halflife\nu238_halflives = BILLION_YEARS_TO_SECONDS * bil_years / U238_halflife\n\n# If there are 0.0072 parts of U-235 for every 1 part of natural U\n# then we calculate the &quot;initial&quot; quantity (a few billion years ago)\nquantity_235 = U235_TO_U238_RATIO * 2 ** u235_halflives\nquantity_238 = (1-U235_TO_U238_RATIO) * 2 ** u238_halflives\nratio_235_238 = quantity_235 / quantity_238\n\nprint('Billion years: {}\\n'.format(bil_years))\nprint('235 quantity: {:.3}'.format(quantity_235))\nprint('238 quantity: {:.3}'.format(quantity_238))\nprint('ratio_235_238: {:.3}'.format(ratio_235_238))\n\nenrichment = quantity_235 / (quantity_235 + quantity_238)\nprint('enrichment: {:.1%}'.format(enrichment))\n</code></pre>\n" }, { "answer_id": 103573, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 2, "selected": false, "text": "<h1>No</h1>\n\n<p>Weapons grade Uranium-235 is enriched ~90%.</p>\n\n<p>Generally, enriched uranium for research is kept below 20% to prevent weapons proliferation. Commercial reactors will use maybe 5% enriched uranium. However, even at 20% enrichment, the <a href=\"https://en.wikipedia.org/wiki/Critical_mass\" rel=\"nofollow noreferrer\">critical mass</a> of U is about 400 kg.</p>\n\n<p>From the <a href=\"http://www.world-nuclear.org/information-library/nuclear-fuel-cycle/conversion-enrichment-and-fabrication/uranium-enrichment.aspx\" rel=\"nofollow noreferrer\">World Nuclear Association</a>, Uranium must be enriched to at least 90% in specialized facilities to be used for bomb-making. Most of <a href=\"https://en.wikipedia.org/wiki/Little_Boy#Design\" rel=\"nofollow noreferrer\"><em>Little Boy</em></a> was enriched to 89%, while the average enrichment was 80%. These are the enrichment levels you will need to make a bomb.</p>\n\n<p>Finally, <a href=\"http://www.princeton.edu/~aglaser/2005aglaser_why20percent.pdf\" rel=\"nofollow noreferrer\">this paper</a> provides evidence that 50% enriched Uranium is not a significant danger for weapons proliferation. </p>\n\n<h1>Conclusion</h1>\n\n<p>Even with 31% enriched Uranium 5 billion years ago, any terrorist would still need access to an enrichment facility or a breeder reactor (to create Plutonium). In other words, while the work that needs to be done to create a bomb is lower in this 'young' world, the facilities needed do not change, so being a nuclear terrorist is no easier. </p>\n" }, { "answer_id": 103589, "author": "Vashu", "author_id": 30579, "author_profile": "https://worldbuilding.stackexchange.com/users/30579", "pm_score": 0, "selected": false, "text": "<p>A 50% U-235(straight from supernova) can be made into a bomb, <a href=\"https://worldbuilding.stackexchange.com/questions/14060/how-could-a-civilization-with-approx-18th-century-technology-weaponise-mined-nu/87860#87860\">as shown in this answer</a>.</p>\n\n<p>But 4by ago it had about 16.7%(number stolen from Fermi_paradox answer). Critical mass for 20% <a href=\"http://nuclearweaponarchive.org/Nwfaq/Nfaq4-1.html#Nfaq4.1.7.1\" rel=\"nofollow noreferrer\">is 800 kg</a>, 245 kg with good Be reflector! </p>\n\n<p>So I guess you could make a bomb out of 16.7% U with big reflector, but device would be very heavy and not as reliable.</p>\n" }, { "answer_id": 103650, "author": "Andrew Dodds", "author_id": 33469, "author_profile": "https://worldbuilding.stackexchange.com/users/33469", "pm_score": 1, "selected": false, "text": "<p>Also consider Plutonium-244</p>\n\n<p>With a half life of 80 million years, you will have to evolve quickly indeed, but it could probably be made into nuclear bomb material without any isotope separation, just chemical separation (I'm unable to get information on its fissile properties).</p>\n\n<p>So what could have happened is that in your solar system, there was a supernova 50 million years ago nearby, which sent some massively-Plutonium and Uranium enriched asteroids into your system..</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/103567", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/13688/" ]

[ { "answer_id": 103690, "author": "Mark", "author_id": 278, "author_profile": "https://worldbuilding.stackexchange.com/users/278", "pm_score": 2, "selected": false, "text": "<p>Going with the <a href=\"https://en.wikipedia.org/wiki/Circumstellar_habitable_zone#Solar_System_estimates\" rel=\"nofollow noreferrer\">Kasting et. al.</a> estimate for the Solar System's habitable zone and your estimate of 2400x Solar luminosity, the inner edge of Alcyone A's habitable zone is 46.5 AU from the center of the star, while the outer edge is 67 AU out, well outside the entire three-star system. A <a href=\"https://en.wikipedia.org/wiki/Habitability_of_binary_star_systems#Circumbinary_planet\" rel=\"nofollow noreferrer\">stable circumbinary orbit</a> is one that's more than 2-4 times the star-to-star distance. In your situation, the star-to-star distance is about 5 AU for a worst-case minimum stable radius of 20 AU. The entire habitable zone is stable.</p>\n\n<p>Actually inhabiting such a planet would be a bit tricky, though. As a blue giant, Alcyone A emits far more ultraviolet than the Sun. It also has an exceptionally strong stellar wind. Between these two problems, you probably can't terraform a planet even if it has a reasonable size and temperature.</p>\n" }, { "answer_id": 103706, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 3, "selected": true, "text": "<h1>Stable</h1>\n\n<p>I ran this simulation using <a href=\"http://rebound.readthedocs.io/en/latest/index.html\" rel=\"nofollow noreferrer\">Rebound</a>, and orbital particle simulator. You can find the code I used for your simulation at my <a href=\"https://github.com/kingledion/worldbuilding\" rel=\"nofollow noreferrer\">github</a>, under the file <code>orbit_ryanrussel_180131.py</code>. These are the initial conditions that I used:</p>\n\n<pre><code>m_alc_a = 3.6 # As a fraction of the mass of the sun\nm_alc_b = 0.1 \nm_alc_c = 1.8\nm_planet = 3e-6\n\na_alc_b = 0.16 # AU \na_alc_c = 5 \na_planet = 50\n\ne_alc_b = 0.01\ne_alc_c = 0.01 \ne_planet = 0.01\n</code></pre>\n\n<p>Those are the mass, semi-major axis, and eccentricity of each of your objects, which I labeled alc_a, alc_b, and alc_c. The planet's info is in planet. The planet is the same size as Earth, and the stars are as you specified. Masses are in multiples of the Sun's mass, distances are in AU. For the 'low mass star' I used a red dwarf of 0.1 solar masses, as the results will show, I don't think the mass there really mattered.</p>\n\n<p>This ended up being by far the most stable simulation I've run. Usually I like to post graphics of orbits or cool orbital resonances, but there were none. Just three concentric circles. The three orbiting objects (two stars and a planet) have not changed their semi-major axis or eccentricities by even 0.01% in the simulation, so I think we can assume that the planet is sufficiently far away not to be bothered by any of the stars. </p>\n\n<p>So far the simulation has run for 47 million years as I'm typing this. I don't think I'll let it go any farther, since your planets are obviously stable. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/103686", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/29133/" ]

[ { "answer_id": 103711, "author": "Kilisi", "author_id": 22207, "author_profile": "https://worldbuilding.stackexchange.com/users/22207", "pm_score": 4, "selected": false, "text": "<blockquote>\n <p>Is this a realistic way to colonize and explore the universe?</p>\n</blockquote>\n\n<p>Sure it is, this is the same process used by Polynesians to colonise the Pacific Islands.</p>\n\n<p>They had boats with everything they would need and would find a place, build. Then a few generations later when population pressure mounts they would split and some would go looking for another Island group.</p>\n\n<p>Your idea is the same just scaled up.</p>\n" }, { "answer_id": 103713, "author": "L.Dutch", "author_id": 30492, "author_profile": "https://worldbuilding.stackexchange.com/users/30492", "pm_score": 3, "selected": false, "text": "<p>Yes, except the part where you state</p>\n\n<blockquote>\n <p>If they find a planet that looks like it can be terraformed, a planet with no life, or only the most basic of bacteria which is wiped out, they get to work making the planet livable for the people who want to have a sky over their head. Any planets with multicellular life is carefully studied by probes, but left otherwise alone because the risk of contamination, allergies, etc, are too great for the ships, and terraforming them will destroy the ecosystem. </p>\n</blockquote>\n\n<p>Reasons:</p>\n\n<ol>\n<li><p>Based on the reconstructed history of life on our planet, the stage which for you is OK to use is a small fraction of the total time where life is possible. This reduces the likelihood of ending on a planet, and people in cramped spaces get easily angry...</p></li>\n<li><p>Based on the history of human colonization, efforts to preserve the hosting environment/populations arise centuries after the colonization has been made. Again, people in cramped spaces get easily angry, and anybody will have an hard time explaining 50000 people that they have to stay in their glass bubble surrounded by deep and hostile space a few more centuries for the sake of preserving the slimy pink mossy blob which covers that nice planet few hundreds kilometers away.</p></li>\n</ol>\n" }, { "answer_id": 103714, "author": "ArtisticPhoenix", "author_id": 44447, "author_profile": "https://worldbuilding.stackexchange.com/users/44447", "pm_score": 4, "selected": false, "text": "<p>Sure, everything seems fine.</p>\n\n<p>Except ( and this is my Opinion )</p>\n\n<blockquote>\n <p>If they find a planet that looks like it can be terraformed, a planet with no life, or only the most basic of bacteria which is wiped out, they get to work making the planet livable for the people who want to have a sky over their head.</p>\n</blockquote>\n\n<p>Once you realize it will take hundreds of years, aboard a \"generation\" ship that is custom built to sustain the population for that time, you will realize that it's unlikely they would want to settle on a rock. Especially if they have to terraform it.</p>\n\n<p>Often times the most efficient engines have very poor thrust to weight ratios. It's very possible to build an engine perfectly suited to travel in space that has no utility lifting weight out of a deep gravity well.</p>\n\n<p>Given this, and the fact that they are now perfectly comfortable living in their \"tin can\" remember without FTL it's going to take dozens or hundreds of years to travel to even the closest stars. Even going to the nearest stars to earth will take (@0.5c) anywhere from 8-20 years depending on how fast you can accelerate.</p>\n\n<p>After spending 20 years in a perfectly controlled environment why start over. There are no elements on a planet that are not more easily acquired in orbit (if all your infrastructure is in orbit). The only thing unique would be the life on that planet which may or may not be poisonous. Even if it's not, would you ruin the biosphere just to dig up metal you can get by the ton other places? At most you may want to observe and do research on this new life. See if it's compatible with your life, etc. This could take centuries and the risk ... well, you could introduce some virus or bacteria that wipes your whole population out.</p>\n\n<p>In short, once you have generational ships, there is no reason to settle on a planet. In fact, it costs more energy to do so.</p>\n\n<p>In more likelihood, they will set up an orbital habitat, with some production capability. Maybe drag an asteroid into orbit. And then send science teams down to the planet to research every so often.</p>\n" }, { "answer_id": 103715, "author": "StephenG - Help Ukraine", "author_id": 32391, "author_profile": "https://worldbuilding.stackexchange.com/users/32391", "pm_score": 6, "selected": false, "text": "<blockquote>\n <p>Is this a realistic way to colonize and explore the universe? </p>\n</blockquote>\n\n<p>No.</p>\n\n<p>Apart from problems with generational ships, which you'll find discussed on Worldbuilding SE in other questions, there is a fundamental flaw in the reasoning:</p>\n\n<blockquote>\n <p>they get to work making the planet livable for the people who want to have a sky over their head</p>\n</blockquote>\n\n<p>The people you have described have, for hundreds of generations, been a space-dwelling people. Planets may be interesting to <em>you</em>, but they're just grubby, messy places with restrictions like not having easy access to space (which is, in fact, home!) and gravity defined by something you can't change, whereas your ship-dwellers (presumably) have some form of pseudo-gravity but can also get to zero-gee (and maybe all points between) easily.</p>\n\n<p>As they have and can manage resources without needing a planet, all they need rocks for is to build more homes (i.e. more ships). And they can get those rocks easily without bothering with dirt and bacteria-infested planets that they have to clean first.</p>\n\n<p>Nope, they're going to expand all right, but they're going to do it in space.</p>\n\n<p>Rocks? Who needs 'em. :-)</p>\n\n<p>And if you have the tech to build generation ships like you describe, you have the tech to make them from (for example) asteroids. You have the tech to make a sky for yourself (and what a sky - something that's controlled and <em>safe</em> and familiar).</p>\n\n<p>For you, the sky could well be that the world curves over your head in a giant cylinder. Actual sky as we know it would be unnerving - you've never seen it and for hundreds of generations no one has written a song with our version of the sky in it.</p>\n\n<p>No, planets are, to a space dweller, completely pointless.</p>\n\n<p>What would they do with planets?</p>\n\n<p>Visit them.</p>\n\n<p>Planets are nice places to park, maybe, giving you an interesting view and access to, well, nothing you don't already have in space for these guys. You can explore planets and maybe some people (the dedicated scientists or the crazy people) will want to stay down there for extended periods, but live there?!?!?!? No way!</p>\n\n<p>And you've grown up used to the idea of living in a sealed, controlled environment with a stable population.</p>\n\n<p>The biggest problem that ship will face is convincing anyone to get off!</p>\n\n<p>Even if they reach a destination and need repairs, they'll find a way to do that from space, extracting materials from easier to access sources (small moons, asteroids, etc. ) and not by doing anything crazy like <em>landing</em>.</p>\n\n<p>Every solar system is indeed an opportunity to expand, but you could do an awful lot of expansion in space without ever getting lumped on something as yucky as a planet.</p>\n\n<p>These guys won't leave home and home is space.</p>\n\n<p>The minority (and presumably there will be some weirdos like this) who want to live on a planet and become \"pioneers\" (imagine the derision that would be said with by people who travel anywhere they want in space!), might set up colonies, but these will be villages with bare essentials and just enough equipment to keep them going. You're not going to waste resources on these nutcases if you and your people have been thrifty and efficient space dwellers for a hundred generations.</p>\n\n<p>Think about a hundred generations.</p>\n\n<p>What were your ancestors doing and where and how did they live a hundred generations ago?</p>\n\n<p>Do you know? Do you care? Would you consider <em>their</em> way of life anything you want <em>now</em>?</p>\n\n<p>Your science (even in a generation ship) has advanced and it will be focused on the needs and desires of space dwellers. You won't even <em>care</em> about the intentions of the people who sent your ancient ancestors into space.</p>\n\n<p>You're a space dweller. And proud of it!</p>\n\n<p>No \"Rock Clingers\" on this ship. :-)</p>\n" }, { "answer_id": 103716, "author": "Jim Wolford", "author_id": 46606, "author_profile": "https://worldbuilding.stackexchange.com/users/46606", "pm_score": 3, "selected": false, "text": "<p>In the early 1600's one hundred people settled in Jamestown. Those 100 people came form a population of 4 million UK subjects. If a colony ship has a population of 50,000, there are very poor odds that you would have enough people willing to start a colony on another planet.</p>\n\n<p>But suppose the population of the Earth is eight billion people. Now you'd have a pool of 200,000 colonists. You select 50,000 of those people and put them on the generation ship in suspended animation. The generation ship is then crewed with 30,000 people to run and maintain the ship and watch over the sleeping colonists. This becomes a sleeper/seeder colony ship hybrid.</p>\n\n<p>A potential dark twist on this idea is the Australia solution. If a person on the generation ship commits some terrible crime, instead of execution, that person is put into suspended animation, and dumped onto the colony world. </p>\n\n<p>Note: \nMy answer was based on the other answers where the colony ship takes decades to reach the next solar system. </p>\n" }, { "answer_id": 103726, "author": "Clumsy cat", "author_id": 37348, "author_profile": "https://worldbuilding.stackexchange.com/users/37348", "pm_score": 1, "selected": false, "text": "<blockquote>\n <p>getting a very large boost as they start their journey.</p>\n</blockquote>\n\n<p>This is an issue. When travelling in space slowing down and speeding up are more or less the same problem. There is pretty much negligible friction to slow you down again. So if there is some special \"boost\" that it gets from its home system that put it over its maximum natural speed, how it going to stop? </p>\n\n<p>It makes most sense to accelerate continuously for the first half of the journey, then decelerate for the second half.</p>\n" }, { "answer_id": 103728, "author": "AnoE", "author_id": 19599, "author_profile": "https://worldbuilding.stackexchange.com/users/19599", "pm_score": 3, "selected": false, "text": "<blockquote>\n <p>Is this a realistic way to colonize and explore the universe?</p>\n</blockquote>\n\n<h2>Yes</h2>\n\n<p>Considering the preconditions you have given, which basically say that you are not interested in <em>technological</em> problems at all, surely it is a realistic way! </p>\n\n<p>It's your story. You have to find problems (like pointed out in many of the other answers, for example, \"why would they <em>want</em> to live on a planet\") and solve them for your version of humanity.</p>\n\n<p>Solving those problems would be the point of interest of your novel.</p>\n\n<p>E.g., the argument that people who have lived in space for 100 generations see no point to settle on a planet could be resolved this way: assume that the spaceship technology is barely fun enough to keep everyone from suiciding. No heroic extra-vehicular activities in race boats for fun; no action-packed alien missions, nothing of that sort. Just boringly slogging along. Maybe they <em>don't</em> regularly play with gravity, no \"free fall sex\" escapades or anything of that sort. Maybe there does <em>not</em> develop a sense of infinite freedom in space (which there is nothing of, for us, right now). They have no limitless space available to them personally, but just a clunky, degrading, half-lit, stale-air metal can in which they are constantly reminded of death on the other side of the wall.</p>\n\n<p>Maybe, to make those generation ships work, they need very strict hierarchies/duties to keep them afloat at all; and part of the incentive to go down to the planet is that small, like-minded groups can go to vastly separated regions to do their own thing. </p>\n\n<p>Maybe they bring along pictures/books/films of the earth which turn into some half-religious planet cult; being allowed to live on a planet could from the beginning be made out to be the highest climax of everyone's life.</p>\n\n<p>Finally, think about how great of an adventure space is for us today; you can be pretty sure that lots of boys and girls fantasize of spending some time on even our limited versions of space travel/space stations. After 100 generations, maybe in your world, it is simply reversed - boys and girls are just <em>bored to death</em> by their spaceship and really looking forward to adventures on a planet.</p>\n\n<p>And so on. Whatever reason anyone of us could think about to make it unlikely that your plan works, gives you a reason to make your story interesting.</p>\n" }, { "answer_id": 103729, "author": "Yakk", "author_id": 2473, "author_profile": "https://worldbuilding.stackexchange.com/users/2473", "pm_score": 2, "selected": false, "text": "<p>There are a few realism flaws. First, 50% of the speed of light is insanely fast for a macroscopic object.</p>\n\n<p>Second, taking only a few centuries to create new generation ships.</p>\n\n<p>Slow them down to 1% or even 0.1% of the speed of light. Spend many 1000s of years expanding over a new system.</p>\n\n<p>You'll still colonize the galaxy in the blink of a cosmic eye.</p>\n\n<p>The current most practical form of interstellar colonization looks like star wisps -- ridiculously light von Neumann probes launched using a type-2 civilization's power output. Possibly coming to a stop using huge mirrors and lasers fired from the source system.</p>\n\n<p>The huge investment and tiny payload (traveling at a very small fraction of c, as the interstellar medium is quite dense at fast speeds) then has to be able to replicate itself in the target system and industrialize it. It can carry data with it (uploaded consciousnesses possibly included, or entire biospheres of data) and when industrialization is well underway can deploy this data; or, if civilizations are sufficiently long-lived, it can build an antenna and get it beamed after the fact.</p>\n\n<p>If it takes a probe 10 years to produce a duplicate and the probe weighs 2 grams, converting 0.01% of the solar system's mass into probes is 2E23 kg or E27 probes, which is 27/3*10 = 90 doublings, or just under 1 thousand years.</p>\n\n<p>At that point, the system is going to be close to a type-2 civilization and would be capable of launching another star wisp at a small fraction of c.</p>\n\n<p>It might also be able to catch a colony ship traveling at a small fraction of c.</p>\n\n<p>A type 2 civilization has E26 watts of power. 1 year of output is E33 J.</p>\n\n<p>At 1% C, kinetic energy is </p>\n\n<p>$$E_k = mc^2(\\frac{1}{\\sqrt{1-\\frac{v^2}{c^2}}} -1)$$</p>\n\n<p>$$E_k = mc^2(\\frac{1}{\\sqrt{1-0.01^2}} -1)$$</p>\n\n<p>$$E_k = (.00005) mc^2$$</p>\n\n<p>or 1 part in 20,000 of the mass-energy of the target.</p>\n\n<p>This means we can speed up or stop 2E20 kg over a period of 1 year if we have 100% efficiency. Ceres is E21 kg.</p>\n\n<p>So a type 2 civilization can launch something roughly the size of Ceres at 1% of the speed of light, and another type 2 civilization can stop it at the other side, assuming they can deliver the momentum over a distance of 1% of 1 light year.</p>\n\n<p>5% of the speed of light makes this:</p>\n\n<p>$$E_k = mc^2(\\frac{1}{\\sqrt{1-0.05^2}} -1)$$</p>\n\n<p>$$E_k = (.00125) mc^2$$</p>\n\n<p>30 times more energy for the same mass. It also makes the distance you have to project the energy 5 times further and hence 25 times harder (tyranny of inverse-square).</p>\n\n<p>At 50% of the speed of light</p>\n\n<p>$$E_k = mc^2(\\frac{1}{\\sqrt{1-0.5^2}} -1)$$</p>\n\n<p>$$E_k = (.15) mc^2$$</p>\n\n<p>120 times more energy than 5%, and 10 times further energy projection (which is 100 times harder).</p>\n\n<hr>\n\n<p>The reason why the star wisp has to be as small as possible is that most of the mass you'll launch will be in the form of mirrors and lenses and light sails. You need to brake, which means you need momentum in the opposite direction. You shoot off lenses/and mirrors, then reflect light from your launch laser <em>back</em> onto the star wisp's light sail. These mirrors are pushed further out (and never stop), but you can get a tiny star wisp to stop with ridiculous energy expenditure over \"short\" interstellar distances.</p>\n" }, { "answer_id": 103730, "author": "Community", "author_id": -1, "author_profile": "https://worldbuilding.stackexchange.com/users/-1", "pm_score": 3, "selected": false, "text": "<p>Yes, it's realistic. </p>\n\n<p>There are a few problems that many of the respondents have overlooked.</p>\n\n<ol>\n<li>machines break.</li>\n</ol>\n\n<p>These star ships might need to last thousands of years. Think of how worn down the pyramids are - these ships have to run for <em>twice as long</em>. Granted, there's no pesky atmosphere to deal with, but you've still got problems with lubrication, for example. After 5,000 years, your elevators might break down. </p>\n\n<p>This would be no big deal in a community of billions, but even with sci-fi level fabrication and automation techniques, there will be some issues that cannot be fixed without a shipyard. If there's no ship yard, that means stopping and building one. Which leads us into the next problem: </p>\n\n<ol start=\"2\">\n<li>50,000 is not enough people for specialization of labor to work properly.</li>\n</ol>\n\n<p>When they have to stop and fix something, they are going to have to check the wiki, and hope that the problem was something we anticipated 10,000 years ago. Even if every person on the ship works and studies, maybe they won't know how to fix the ship. Maybe they will have to build a new one. Could you build a new pyramid? What if you also had to build the crane you'd use to make the pyramid?</p>\n\n<ol start=\"3\">\n<li>Dictator-ships.</li>\n</ol>\n\n<p>Ships 'aint democracies. They have captains and strict rules - even cruise ships have big long lists of do's and don'ts. How long would you like to live on a cruise ship before you wanted off? What if you want 4 kids? Or what if you don't like the weird-ass religion that your ancestors made up on the journey? What if you've got some recessive gene that the captain has decided to purge? </p>\n\n<p>To conclude: Only a tiny fraction of people ever get <em>on</em> colony ships, but when the time comes, they <em>always</em> get off.</p>\n" }, { "answer_id": 103735, "author": "Murphy", "author_id": 4750, "author_profile": "https://worldbuilding.stackexchange.com/users/4750", "pm_score": 7, "selected": true, "text": "<blockquote>\n <p>Slow being a little less than half the speed of light, thanks to getting a very large boost as they start their journey.</p>\n</blockquote>\n\n<h1>Slow down there!</h1>\n\n<p><strong>literally.</strong> </p>\n\n<p>At that speed it's not really a generation ship since you can get to many other stars within the original crews lifetime. </p>\n\n<p>And there are hazards to going that fast. </p>\n\n<p>Lets assume the ship is, say, 10X the mass of the worlds largest supertanker, that's very conservative for the numbers you talk about but it's a number to work with. </p>\n\n<h2>How do you slow down at all?</h2>\n\n<p>At 0.5 c that ship would have 7.197×10^25 joules of kinetic energy you'd need to get rid of if you want to slow down. </p>\n\n<p>That's about 1800 times as much energy as the energy from entire worlds fossile fuel reserves. You need some kind of fuel and some plan for slowing down.</p>\n\n<h2>Hitting things in your path</h2>\n\n<p>If there's something the size and mass of a sugar cube in your path it hits the front of your ship with the energy of the nuclear bomb dropped on Hiroshima with all the energy pretty well focused to rip through any sane quantity of armor.</p>\n\n<p>And that's not the only problem.</p>\n\n<h2>The atoms between the stars</h2>\n\n<p>using the figures for a cold neutral interstellar medium from wikipedia: 20—50 atoms/cm3</p>\n\n<p>So let's go with 25 atoms/cm3</p>\n\n<p>25000000 atoms per cubic meter.</p>\n\n<p>Lets imagine the ship is a nice neat cylinder. We can treat the volume of space that the ship passes through as a cylinder with a cross section equal to that of the front of the ship.</p>\n\n<p>Now lets look at how much it hits while traveling, say, 10 light years.</p>\n\n<p>Treat it as a cylinder 10 light years long with the diameter of the ship, again, lets guesstimate that the ship has a radius of 100 meters.</p>\n\n<p>This lets us estimate the total number of (almost all hydrogen) atoms in the path of the ship, lets assume they all hit and there's no shockwave effects:</p>\n\n<p>946073047258080000000 π m^3 (cubic meters)</p>\n\n<p>Multiply by 25000000 atoms per cubic meter.</p>\n\n<p>mass of (946073047258080000000 * π *25000000 ) hydrogen atoms = 124.4 kilograms</p>\n\n<p>so over the course of 10 light years it will impact with 124.4 kg kilograms of gas atoms. For simplicity I'm assuming all hydrogen. </p>\n\n<p>Those atoms are hitting at .5c so the front of your ship (assuming it's a big round shield with radius 100m).</p>\n\n<p>kinetic energy of 124.4 kilograms at .5c is 1.73×10^18 joules</p>\n\n<p>I'm going to ignore time dilation because it's hard and I need to maintain my sanity.</p>\n\n<p>so at .5 C it takes us 20 years to travel those 10 light years</p>\n\n<p>So lets convert that into the energy of the gas hitting the front of the ship each hour. </p>\n\n<p>1/24 (1/365 (1/20×1.73×10^18 J (joules))) = 9.8748×10^12 joules/h = 2.743 GW h (gigawatt hours) per hour</p>\n\n<p>has to cope with 2.743 GW hours worth of energy hitting it every hour. It's like having a large nuclear power plant at the front of your ship producing heat. you have no way of getting rid of that much heat with your ship in a vacuum and it will be melting your heat shield. </p>\n\n<p><strong>So just slow down</strong></p>\n\n<p>It's really common for writers to throw around large fractions of light speed but without magitech shields there's massive practical problems with going that fast at all. At those speeds the fine mist of interstellar gas is enough to cook an astronaut to death just from being outside the ship unshielded and enough to destroy any shielding made of matter within a short time. </p>\n\n<p>Since your ships are generation ships anyway you almost certainly want to slow your ships down to something sane like 0.05 C (or probably even lower if your crew want to continue to live)</p>\n\n<p>At least then you have some chance of stopping and some chance of surviving if you hit some grains of sand in deep space.</p>\n\n<h1>EDIT:</h1>\n\n<p>Putting more ice or rock on the front of the ship does not help. </p>\n\n<p>Lets imagine that we put a cylinder of solid ice 100 meters thick at the front of the ship as a shield. </p>\n\n<p>it's an idea, I'll give you that, but lets work out how long it's likely to last at 0.5C ....</p>\n\n<p>cylinder | radius 100 meters, height 100 meters = 3.14159×10^6 cubic meters</p>\n\n<p>That's 3,141,590 cubic meters of ice, millions of cubic meters of ice. </p>\n\n<p>Wolfram alpha gives a helpful table for this</p>\n\n<p>Phase change energies for 3.14159×106 m3 of water from 25 °C:</p>\n\n<pre><code> energy required to heat to boiling point | 9.85×10^11 kJ (kilojoules) \n energy required to convert to vapor | 7.01×10^12 kJ (kilojoules) \n energy required to heat to boiling point and convert to vapor | 8×10^12 kJ (kilojoules) \n energy released from cooling to freezing point | 3.28×10^11 kJ (kilojoules) \n energy released from converting to solid | 1.05×10^12 kJ (kilojoules) \n energy released from cooling to freezing point and converting to solid | 1.38×10^12 kJ (kilojoules)\n</code></pre>\n\n<p>It's annoying that it calculates from 25 degrees C but the energy released from cooling and energy needed to heat can just be added together. </p>\n\n<p>Practically speaking I'm being very very forgiving by assuming that the energy needed is the same as at sea level. </p>\n\n<p>To melt that much ice we could need 1.05×10^15 J (joules)</p>\n\n<p>To turn that much ice into steam we would need about 7.01×10^15 J (joules)</p>\n\n<p>Unfortunately the front of our ship would be receiving 1.975×10^13 J (joules) every hour while traveling at 0.5 C from impacts with the fine mist of atoms in interstellar space. </p>\n\n<p>From there's it's just a matter of multiplying. </p>\n\n<p>it would shield you for a little while....</p>\n\n<p>Within 5 days your 3 million cubic meters of ice has melted. </p>\n\n<p>after 34 days your ice has all turned into steam.</p>\n\n<p><strong>But what if we use something stronger than ice!</strong></p>\n\n<p>Lets imagine that instead of 3 million cubic meters of ice we make that shield out of 3 million cubic meters of solid iron!</p>\n\n<p>It takes 6.11×10^15 J to melt 3 million cubic meters of solid iron.</p>\n\n<p>Within 26 days enough energy has hit the front of your ship to melt 3 million cubic meters of iron. </p>\n\n<p>This is not exactly how long your shield will last, some energy will be radiated away, some will be lost to cooking your crew and iron may ablate in a less simplistic manner but it's a rough ballpark figure. </p>\n\n<p>At 0.5 C shields are not enough. Asteroids traveling at 0.5 C would melt and turn into a gas in short order. </p>\n\n<p>I cannot stress enough how poor natural intuition is when it comes to the rigors put on anything traveling at large fractions of the speed of light. </p>\n" }, { "answer_id": 103767, "author": "Neal Cleary", "author_id": 47336, "author_profile": "https://worldbuilding.stackexchange.com/users/47336", "pm_score": 1, "selected": false, "text": "<p>Dr Bob Enzmann wrote extensively about this sort of thing. He is still around.look him up.\nReasons for wanting off the ship:\nVast open spaces.\nas Much population as you can handle.\nand the 2 word answer?\nSoylent Green! </p>\n" }, { "answer_id": 103822, "author": "pdanes", "author_id": 47365, "author_profile": "https://worldbuilding.stackexchange.com/users/47365", "pm_score": 0, "selected": false, "text": "<p>Look at Larry Niven's Outsiders - they lived a little bit like this. There are technological issues as well as social issues with the whole concept, but most of them come from an extremely limited, anthropomorphic point of view. Just because humans, in our current state of development, could not maintain such a society, nor handle the technological challenges, does not make it an absolute impossibility. In fact, much good sci-fi comes from exactly that kind of projection. \"IF\" we were able to overcome such-and-such a technological or social obstacle, what would be the fallout?</p>\n" }, { "answer_id": 103829, "author": "Phil H", "author_id": 681, "author_profile": "https://worldbuilding.stackexchange.com/users/681", "pm_score": 2, "selected": false, "text": "<h1>The Journey In 2 Halves</h1>\n\n<p>We already have an 'artificial gravity' per your requirement, which also sets the time to arrival; acceleration at ~1g. For the first half of the journey you accelerate, then you turn it around and decelerate for the remainder. Per relativity, this will feel exactly like being in a 1g environment on a planet.</p>\n\n<p>There is a neat derivation of the time to arrival via this mode for various destinations <a href=\"http://math.ucr.edu/home/baez/physics/Relativity/SR/Rocket/rocket.html\" rel=\"nofollow noreferrer\">on this page</a>, with the result that it would take no more than 30 years to get anywhere you have the data to bother exploring, even popping to the next galaxy.</p>\n\n<p>Note that in the Earth frame it would take you a lot longer to get there, but time dilation being what it is, that doesn't matter to the skyfarer.</p>\n\n<h1>Generational attitudes, settlers and mariners</h1>\n\n<p>Some of the other answers assume people would prefer to stay in space, on the assumption they are there for many generations, and it's hard to get out of the gravity well and leave a planet if you land on it. </p>\n\n<p>If it's just 1 generation then I suspect a large fraction of the population would be keen to start their life on the planet; these settlers would see the destination as their opportunity, mirroring those who journeyed to settle the Americas.</p>\n\n<h1>We generational mariners</h1>\n\n<p>But the gravity well is deep, so it would make sense for a number to remain on the ship in a wide orbit and pick a new location to head for. These mariners would never land, carrying on to the next planet. After a few generations there would be essentially some who had been on the ship for generations, had never wanted to settle on a planet. If they had a good stock of varied genetic material (e.g. a basic sperm bank) to maintain a decent gene pool, there is no real human limitation on this approach.</p>\n\n<p>I would wonder, however, whether some such ships would stop bothering with planets. Perhaps there would be reverse-Moana figures who sought to revive the idea of settling when they discover the ship's origins.</p>\n\n<h1>Moon-miners</h1>\n\n<p>One reason not to just forever flit through the stars is the need for physical resources; reserves of water and minerals which can replenish the exploring ship. It would make sense to harvest some such resources at each system where a settler-division happens; either by sending the settlers down with a rocket which could return material, or more likely by mining smaller moons. This mining stage could easily take a number of years to construct the equipment, refine the material and return the extracts and equipment back to the ship. During this long goodbye, perhaps some of the mariners would change their mind and opt to settle.</p>\n\n<h1>Colonial control</h1>\n\n<p>A key part of the settlement of the Americas was the need to control the settlers; in this instance, the home planet would want to know the settlers weren't going to return to destroy them. </p>\n\n<p>There is a tension here; on one hand the colony ship experiences less time than Earth; only decades could pass for them while centuries pass on Earth, so Earth can expect to have superior technology. But, this fact would make the settlers defensive; more people from Earth would likely arrive every few decades, bringing new technology, new diseases, new threats and new opportunities.</p>\n\n<p>I think there is an argument for the possibility that the government licensing the explorers to leave Earth with such a ship would require that the settlers were compelled to plant some kind of doomsday device on their new planet to ensure their future cooperation, and obviate the need to impose an external threat.</p>\n\n<h1>The Overtakers</h1>\n\n<p>Consider a ship heading to its second destination planet; subjectively 50 years have passed, but from Earth's perspective several centuries have done. A more recent ship has overtaken the first, by not stopping at the first planet, and thus when the first ship arrives it finds the planet already settled by a century-old settlement. </p>\n\n<p>Do they settle, but elsewhere on the planet? Or do they carry on to another planet where they could be even further behind?</p>\n\n<p>Newer technologies would inevitably also permit later departures to arrive earlier; better g-suits, genomic adjustments, cryo, take your pick. What is the protocol? What are the rules, thousands of light-years into uncaring space?</p>\n\n<h1>The First Man For A Hundred Years</h1>\n\n<p>Earlier I mentioned an onboard sperm bank as an easy way to ensure a wide gene pool, which has an interesting side-effect: The more fertile men on board, the more the gene pool is narrowed (donor eggs would require a surrogate, so the men would most likely reproduce with the women on board). So the longer you plan to live in space, the fewer men you want on board on a purely pragmatic level. Potent men begin an immediate biological countdown.</p>\n\n<p>This could easily lead in some instances to entirely female crews; where perhaps they have had to change destination a few times, and it is safer for the onboard society to just have female offspring for a while.</p>\n\n<p>Eventually, perhaps, a boy would be born by accident or by design.</p>\n\n<p>Alternatively, a larger male population could exist if the destination is assured but be required to leave on the landing raft, so that the onward exploration could continue unimpeded.</p>\n\n<h1>Dreamers</h1>\n\n<p>Some of the descendants of the settling ships would inevitably dream of the stars, of the people who continued on. With the passage of time some would build their own rockets and starships to follow the mariners, and with the joys of time dilation they could actually meet some of these historical figures, for whom proper time seeps only slowly into the margins of their existence.</p>\n" }, { "answer_id": 103991, "author": "Chris Severance", "author_id": 31944, "author_profile": "https://worldbuilding.stackexchange.com/users/31944", "pm_score": 0, "selected": false, "text": "<p>You're real problem is between the statements \"don't have FTL\" and \"do have artificial gravity.\" Real linear artificial gravity violates F=ma \"equal and opposite reaction\" and once you've done that, the speed of light changes from a speed limit to a curio. Chances are the next problem of getting all your energy back into a usable form when you hit <a href=\"https://www.youtube.com/watch?v=ygE01sOhzz0\" rel=\"nofollow noreferrer\">The Big Red Stop Button</a> (lever) will be solved too.</p>\n" }, { "answer_id": 139679, "author": "Bowyn Aerrow", "author_id": 61499, "author_profile": "https://worldbuilding.stackexchange.com/users/61499", "pm_score": 0, "selected": false, "text": "<p>I would drop the notion that your technology includes artificial gravity (beyond spinning) and engines that can get you to half the speed of light. Which as many point out limits time for the generations and leads to the problem of hitting stuff.</p>\n\n<p>I would assume that a spinning cylinder of a decent size with the interior designed to provide space, light and \"nature\" with the center axis being a source of light and \"rain\" and your vessel has decks below (outside of the inner space) that provide space for farming, then industrial tools, then storage and lastly the outermost deck would be flooded with water not only to protect the occupants from cosmic radiation, but also to make certain that the ship has enough water to make it across the vast expanse of interstellar space.</p>\n\n<p>I would increase crew/passenger size to 100,000 with an expected expansion to 300,000. I would also consider that the on board time between stars is about the same as the remainder lifespan of a 20-something first generation person. 50 to 60 years seems reasonable thus you would have grandparents who remember green hills, blue skies and a horizon that bent down instead of up. </p>\n\n<p>10% light speed tops makes a reasonable on board trip time. I'd go with something along ion engines, low thrust that continues for a very long time. Instead of turning the ship you would have thrusters that would point bow-ward at an angle, thus your deceleration time would need to be longer than your acceleration time. This way you can use both ice(s) plow/shield and a Bussard Ram Scoop collector to provide more fuel.</p>\n\n<p>Ion thrusts are weak - <a href=\"https://www.space.com/38444-mars-thruster-design-breaks-records.html\" rel=\"nofollow noreferrer\">5.4 Newtons of thrust</a> is the latest and most powerful ion engine. One can <a href=\"https://sciencing.com/convert-newtons-gforce-8720337.html\" rel=\"nofollow noreferrer\">convert newtons to gravity</a>... But I'm not doing it here. I can pretty much tell you that you would be pulling .01 g which would hardly be felt and the spinning craft would have a greater force on people than the continual thrust.</p>\n\n<p>Your ship could get up to a decent velocity given lots of time, but a half the speed of light will bring way too many other technical questions to mind as previously explored.</p>\n\n<p>300,000 colonist/terraformer/ship builders arriving in a stellar system is a good start. One could argue that the ship is feeling crowded by this time so passengers and crew would be hungry for more space. And humans are real good at making new humans so 20-40 years at this new star system, given enough space, humans could be at the half million mark plus.</p>\n\n<p>They would need to stay in that system long enough to make enough humans to fill two ships... plus leave behind enough colonists to make a new world, make more ships - what ever direction they want. figure another three generations of time (say 60 years) and 1.5 kids per parent - magically the human population is at or slightly above one million. To give you an idea of how fast humans can make more humans, just look at population growth from 1900 (1 billion humans) to 2000 (7 billion humans).</p>\n\n<p>So yes, your basic idea makes sense. Humans making more humans, the desire to find new fresh untouched worlds to explore. Perhaps groups of like minded people are off to make their own worlds by their own rules...</p>\n\n<p>As for size. <a href=\"https://en.wikipedia.org/wiki/Rendezvous_with_Rama\" rel=\"nofollow noreferrer\">Rendezvous with Rama</a> might be helpful. Not only with size, but with interior design to handle space travel.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/103709", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/46938/" ]

[ { "answer_id": 103755, "author": "Community", "author_id": -1, "author_profile": "https://worldbuilding.stackexchange.com/users/-1", "pm_score": 1, "selected": false, "text": "<p>Strategic Depth</p>\n\n<p>The French invested heavily in the Maginot line (and famously didn't extend it across the border with Belgium), and the Germans just blitzed right past it. </p>\n\n<p>If the French had stationed their army throughout their country, the Germans would have had to fight for each city, and held men in reserve to hold the countryside, too.</p>\n" }, { "answer_id": 103759, "author": "Josh King", "author_id": 21041, "author_profile": "https://worldbuilding.stackexchange.com/users/21041", "pm_score": 6, "selected": false, "text": "<p>The simplest change I can think of would be if the German army commanders had followed orders and stopped their advances as directed by central command.</p>\n\n<p>Multiple times during the drive into France generals Rommel and Guderian encountered little to no resistance and advanced significantly farther than they were ordered to. They even went so far as to disobey stop orders, by moving their forces in so called \"reconnaissance in force\". These massive advances allowed them to attack the Maginot line from behind, causing confusion among the French forces, and meant that German forces were already occupying areas that the French army was trying to use to assemble for planned counterattacks.</p>\n\n<p>Hitler's best military victories came when his directives were ignored. If the Nazi leadership had a tighter control on the German officers early in the war, and their orders were followed more closely, they would have lost out on many of the opportunities that the local commanders exploited.</p>\n\n<p>If the German forces had stopped as ordered the French and British could have more easily moved their forces into place for a better defense and counter attack.</p>\n" }, { "answer_id": 103760, "author": "user535733", "author_id": 34273, "author_profile": "https://worldbuilding.stackexchange.com/users/34273", "pm_score": 3, "selected": false, "text": "<h1>Failure of German propaganda</h1>\n\n<p>The French Army in northern France outnumbered the German invasion force, and was fighting a defensive battle on it's home turf, plentifully equipped, and surrounded by supportive French civilians. France fielded 104 full divisions, and had a 50% advantage in tanks, artillery, and trucks.</p>\n\n<p>However, three years of persistent, excellent German propaganda had demoralized the force at all levels. The French Prime Minister phoned Churchill and said 'We are beaten' <em>on the sixth day</em>, long before the actual outcome was decided, and four full weeks before the German Army entered Paris.</p>\n\n<p>Demoralized leadership is less likely to analyze correctly, to innovate, to judge risk properly, to demand achievement from their subordinates...and more willing to accept poor performance and mission failure.</p>\n" }, { "answer_id": 103761, "author": "Twelfth", "author_id": 288, "author_profile": "https://worldbuilding.stackexchange.com/users/288", "pm_score": 5, "selected": false, "text": "<p>As a single change...give Charles de Gaulle more influence over France in the early 1930's. Charles de Gaulle was a strong opponent of the Maginot mentality (potential he coined the term Maginot mentality) saying trench warfare would soon be obsolete and France's downfall would be because of it's dependency on these lines.</p>\n\n<p>In his book \"Toward a Professional Army\", de Gaulle outlined what he described as the new warfare</p>\n\n<blockquote>\n <p>He proposed mechanization of the infantry, with stress on an élite force of 100,000 men and 3,000 tanks. Ironically, German panzer units, so effectively employed in the invasion of France in 1940, used similar theories, while the French dispersed and wasted their armour. The book imagined tanks driving around the country like cavalry. De Gaulle's mentor Emile Mayer was somewhat more prophetic than he about the future importance of air power on the battlefield. Such an army would both compensate for France's population shortage, and be an efficient tool to enforce international law, particularly the Treaty of Versailles, which forbade Germany from rearming. He also thought it would be a precursor to a deeper national reorganisation, and wrote that \"a master has to make his appearance...whose orders cannot be challenged – a man upheld by public opinion\".[42]</p>\n</blockquote>\n\n<p>Oddly, he very much outlined the tactics that would be used against France to conquer it...a little prophetic? Had France adopted to de Gualle's tactics earlier, they would have possessed the mobile force required to relocate and halt the Germans breach of the French defensive lines much more effectively. The key portion of this tactic is how the tanks were dispersed...ultimately the French dispersed their tanks relatively evenly along the line, when a mobile force of tanks would have been far more effective against the German invasion.</p>\n" }, { "answer_id": 103765, "author": "Thucydides", "author_id": 8572, "author_profile": "https://worldbuilding.stackexchange.com/users/8572", "pm_score": 4, "selected": false, "text": "<p>The actual answer is \"pay attention\". British military theorists like <a href=\"https://infogalactic.com/info/B._H._Liddell_Hart\" rel=\"noreferrer\">B. H. Liddell Hart</a> and <a href=\"https://infogalactic.com/info/J._F._C._Fuller\" rel=\"noreferrer\">JFC Fuller</a> had pretty much envisioned the elements of modern armoured and mechanized warfare in the closing days of WWI. \"<a href=\"https://infogalactic.com/info/Plan_1919\" rel=\"noreferrer\">Plan 1919</a>\" was the conceptual means of defeating the Germans in a massive mechanized offensive in spring/summer 1919 using combined arms teams of tanks, \"contact patrol\" fighters to provide overhead cover and ground attack, and rapidly moving infantry and artillery to break through at selected points, exploit the breach and envelop the rear area. A draft of Plan 1919 can be read <a href=\"http://www.alternatewars.com/WW1/Fuller_1919.htm\" rel=\"noreferrer\">here</a></p>\n\n<p>Sounds very familiar, right?</p>\n\n<p>The British government even went to the extent of creating an experimental mechanized brigade and conducting a series of war-games and manoeuvres during the 1920's to test and refine these ideas. Given the technology of the time and financial constraints, the brigade was disbanded and shelved, but detailed reporting was available, and eagerly consumed by such luminaries as <a href=\"https://infogalactic.com/info/Heinz_Guderian\" rel=\"noreferrer\">Heinz Guderian</a>, <a href=\"https://infogalactic.com/info/Mikhail_Tukhachevsky\" rel=\"noreferrer\">Mikhail Tukhachevsky</a> and <a href=\"https://infogalactic.com/info/Charles_de_Gaulle\" rel=\"noreferrer\">Charles de Gaulle</a>, and implemented by the German Army and (until the purges) the Red Army as well.</p>\n\n<p>If the British Army had persevered with their experimentation of armoured and mechanized forces, even in the face of government indifference or cost cutting (for example, the Army could have chosen to close out other units, or do other cost cutting measures), they could either have had an integrated combined arms force of their own to oppose the German Panzers, or at least had corporate knowledge and been familiarized by constant training in how to defend against armoured and mechanized forces. The example of the British would likely have had an effect on the French General Staff, and they might have adopted a more comprehensive combined arms approach to warfare as well. It is often overlooked that the French actually had more tanks than the Germans at the start of WWII, and in many respects, French tanks were superior to their German counterparts (although the crew arrangements of French tanks were a serious weakness). </p>\n\n<p>Familiarization with British practice would have impressed the need for better crew communications and tank layout on the French, as well as preventing the French from dispersing their tank forces in \"penny packets\" among Infantry formations. (In the real timeline, the British and forgotten many of the lessons of the 1920 era experimental brigade, and also designed tanks to be dispersed among the Infantry). Large numbers of more and better French tanks combined with an <em>effective</em> doctrine for their use would have seriously complicated German planning and operations, and an effective British mechanized force operating in the Western flank probably would have persuaded the Germans that their plan was not viable.</p>\n\n<p>So in the end, what stopped the British and French from winning the battles and the campaign in 1940 was forgetting or ignoring the hard learned lessons of WWI and the lessons of the experimental armoured Brigade in the 1920's.</p>\n" }, { "answer_id": 103766, "author": "ckersch", "author_id": 2947, "author_profile": "https://worldbuilding.stackexchange.com/users/2947", "pm_score": 6, "selected": false, "text": "<h2>The French listen to Belgian intelligence.</h2>\n\n<p>The Belgians had surprisingly good intelligence about what the Germans were planning. They'd identified the German military buildup, and considered an invasion through the Ardennes to be the most likely course of action. The French command didn't react to these warnings, since they still suspected that an invasion through the Ardennes would be slow and difficult.</p>\n\n<p>If the French command had instead reinforced the area, specifically with more anti-tank and anti-aircraft forces, they would've been in place for the German attack and could probably have held the position, especially since they had support from the Belgians in the area. In reality, the Belgians were overrun and the local French forces weren't equipped to deal with the number of tanks and aircraft they encountered. The Belgians retreated and then the French positions were overrun. If they'd effectively re-deployed forces to the area, the French could've counted on having numerically superior forces of heavier tanks than the German army. They'd also have a terrain advantage, fighting against German forces as they tried to emerge from the forest, rather than in an open position where the speed of the German tanks could be effectively used.</p>\n\n<p>Basically, if the French had effectively countered the German armored divisions with their own, they could've won. Instead, their tanks were scattered thin across the Maginot line, which wasn't attacked, and had basically no impact on the battle.</p>\n" }, { "answer_id": 103769, "author": "Dan Clarke", "author_id": 46938, "author_profile": "https://worldbuilding.stackexchange.com/users/46938", "pm_score": 6, "selected": false, "text": "<p>If you don't mind the change being natural rather than human based, have it rain for a few days after the initial attack. \nA good hard rainstorm for even two days would have kept the Luftewaffe from being nearly as effective, as they'd have less visibility and less obvious targets. It would also make take off and landing harder as many of the airfields were pressed earth or grass, if it got too wet they wouldn't be able to take off at all. </p>\n\n<p>Rain would also slow down and wear out the soldiers as they march through mud in soaking wet clothes and packs. This in turn would slow down the tanks and armoured cars of the German army. Supplies wouldn't reach the front nearly as quickly further slowing them down. </p>\n\n<p>Having a day or two to recover from the initial attack, would have given the French and English critical time to build up some defenses, regain control of units, and start using some of the soldiers on the Maginot Line as reinforcements. </p>\n\n<p>It would still be a close thing, but with the Germans generally inferior weapons, and limited supply of advanced tanks and planes, they had to rely on speed and keeping the French and English off balance. </p>\n\n<p>Considering the time of year rain is not uncommon, and rainstorms could last from a few hours to several days at a time. So having intermittent rainstorms of a few hours each over a week or two in northern and central France would hamper the German army fairly significantly without requiring a handwave. </p>\n" }, { "answer_id": 103776, "author": "Erroneous", "author_id": 47330, "author_profile": "https://worldbuilding.stackexchange.com/users/47330", "pm_score": 3, "selected": false, "text": "<p>This is a nice breath of fresh air, usually we tend to focus on how nazi-Germany could've won the air.</p>\n\n<p>Now, you're correct that the German plan to invade France and the low countries was by no means guaranteed. It was deemed too risky by most of the German high command and in fact was not the original plan the German military had in mind (whether the <a href=\"https://en.wikipedia.org/wiki/Mechelen_incident#Initial_German_reaction\" rel=\"noreferrer\">Mechelen incident</a> influenced the change to the more risky thrust through the Ardennes is disputed). Even with outdated tactics and doctrine, the Allies still had a good chance of defeating the German attack. Their tanks were of better quality (though dispersed) and they had more manpower. Only the luftwaffe held the upper hand over their Allied counterparts - this military arm would prove vital during the battle of France.</p>\n\n<p><strong>the battle of Sedan goes more poorly for the Germans</strong></p>\n\n<p>Capturing Sedan and the bridges was a vital part of the German plan and this was where the main thrust would take place. Strategic success or defeat depended on the critical battle of Sedan. The French defenders they faced were mostly of poor quality (the best divisions had been sent to Belgium). Still, if things had gone slightly differently, the French could have delayed or perhaps even stalled the German advance, allowing strategic reserves to be pulled back from Belgium. The panic of Bulson (in which elements of 55th division fled because of a false report that claimed German tanks had already penetrated to as far as Bulson) was one such avoidable event. Or perhaps the aircraft that the British &amp; French threw at the bridges over the Meuse river (where Luftwaffe fighters were swarming in enormous numbers) could have scored a chance hit, blowing up vital bridges and delaying the German advance. If the Allies had gained more time, they could have consolidated their defences and perhaps avoid encirclement and destruction. </p>\n\n<p><strong>The Allies adopt different war plans</strong></p>\n\n<p>There were several plans as to how the French and the British would respond to a breach of Belgian (and Dutch) neutrality by the Germans. These included plan E, plan D, plan D + the Breda variant and a plan which involved camping on the French north-eastern frontier.</p>\n\n<ul>\n<li>Plan E: advance to the Eschaut river. This was the first plan, in\nwhich the Belgian armies would retreat westwards while the BEF swung\ninto Western Holland. This plan assumed that the Belgians would not\nbe able to hold their positions and was a more cautious plan than the\nplan D later adopted. </li>\n<li>Plan D: advance to the Dyle river (further inland). This had many\n(perceived) benefits. It meant that the Allied forces would bring\nthe fight further away from France as well as covering more Belgian \nterritory.</li>\n<li>Breda variant: this included defending Holland using French\nstrategic reserves. Doing this would ensure the addition of 10\nDutch divisions but it also diverted strategic reserves</li>\n<li>posting the French army on the French frontier. This basically\nmeant abandoning Belgium - this was diplomatically not feasible,\nobviously.</li>\n</ul>\n\n<p>Gamelin settled for plan D + the Breda variant. If he hadn't extended his forces so far forward, perhaps the war would have gone differently. The strategic French reserves certainly could've come in handy. Indeed, the Allies were initially rather unsure if they could reach the Dyle river before the Germans did (especially after witnessing the battle of Poland). The BEF was also not all too keen on entering Belgium. Only later, with reports of the Belgians and the Dutch constructing defences and an improved confidence in Allied strength and equipment, did Gamelin adopt plan D. </p>\n" }, { "answer_id": 103811, "author": "KalleMP", "author_id": 8280, "author_profile": "https://worldbuilding.stackexchange.com/users/8280", "pm_score": 0, "selected": false, "text": "<p>To add to the earlier natural cause of rain I suggest something smaller like a plague or food poisoning. </p>\n\n<p>If all the provisions had been tainted by Salmonella, Ergot, Dysentery, Cholera and Botulism (chance or with the aid of the resistance) and the fighting forces had been down to 25% for a week it would have made a lot of difference.</p>\n" }, { "answer_id": 103815, "author": "walrus", "author_id": 35695, "author_profile": "https://worldbuilding.stackexchange.com/users/35695", "pm_score": 3, "selected": false, "text": "<p><strong>Better French organisation of their armoured forces</strong></p>\n\n<p>The French Army had more and better tanks than the German (at least 3,383 to the German 2,445), but decided to disperse them throughout their positions in what were known as \"penny packets\" to support the infantry.</p>\n\n<p>This negated their numerical advantage, and allowed the German Panzer forces to achieve local superiority where it mattered.</p>\n\n<p>Keeping their armoured divisions concentrated would have allowed for swift counterattacks which would, at the very least, have slowed down the German attack for long enough for the Allie's superiority in men, tanks and guns to be brought to bear.</p>\n" }, { "answer_id": 103840, "author": "PCSgtL", "author_id": 9776, "author_profile": "https://worldbuilding.stackexchange.com/users/9776", "pm_score": 2, "selected": false, "text": "<p>If I have time I’ll cite some sources later and get specific number. Something not mentioned yet is to start the war early. Stand up to Germany before Poland. Stan up to them in March of 39 with the invasion of Czechoslovakia. The balance of mechanized forces and specifically of air forces would have been more in the allies favor at that moment. </p>\n" }, { "answer_id": 103872, "author": "user47390", "author_id": 47390, "author_profile": "https://worldbuilding.stackexchange.com/users/47390", "pm_score": 2, "selected": false, "text": "<p>In his book, Blitzed: Drugs in the Third Reich, Norman Ohler claims that German soldiers during the Blitzkrieg were high on methamphetamines, which improved their stamina, etc. Perhaps if those drugs had not been invented, had been contaminated, or unavailable, or if there had been a problem of overdosing, then they would not have fared as well.</p>\n" }, { "answer_id": 103875, "author": "user47393", "author_id": 47393, "author_profile": "https://worldbuilding.stackexchange.com/users/47393", "pm_score": 3, "selected": false, "text": "<p>Have the French invade Germany when Germany was invading Poland. France did send troops in and met little resistance, only to pull them back. Hitler really did bet everything assuming France would not act. He concentrated his forces on Poland and left little to defend Germany. </p>\n" }, { "answer_id": 103933, "author": "John Coleman", "author_id": 27940, "author_profile": "https://worldbuilding.stackexchange.com/users/27940", "pm_score": 1, "selected": false, "text": "<p>The British held back some of their air forces for defense of the home island and <a href=\"https://en.wikipedia.org/wiki/British_Air_Forces_in_France\" rel=\"nofollow noreferrer\">withdrew</a> others when the it seemed that the Fall of France was inevitable. This is usually considered a wise (though painful) move on the part of the British, one that made possible their later victory in the Battle of Britain. In an alternative history, what would have happened if the British <em>increased</em> their air forces in France, even to the point of denuding their own air defense? One version (and arguably the more plausible version) of the alternative history would have been that France would have fallen anyways, followed rapidly by a Britain which could no longer contest the Luftwaffe. On the other hand, just maybe if the British went all in with their air force then they could have bought time for French forces to regroup.</p>\n" }, { "answer_id": 103938, "author": "guest", "author_id": 47411, "author_profile": "https://worldbuilding.stackexchange.com/users/47411", "pm_score": 2, "selected": false, "text": "<p>When the German army was driving through the Ardennes French reconnaissance airplanes did spot them. There is a bit of a debate on what happened with that crucial information after that. Lets say instead of the information not being put to use the French Air Force concentrated their efforts on the route the German army was taking. With the tanks concentrated in a little area that would of been a great chance to reduce their numbers. \nAnother angle is after the war the Germans who were there reported their logistic were actually not very good. Their tanks relied to a good extent on captured French gasoline. Even to the point of just using French gas stations. So if someone had just went before the German army and destroyed the gasoline supplies. </p>\n" }, { "answer_id": 103942, "author": "Paul Johnson", "author_id": 10068, "author_profile": "https://worldbuilding.stackexchange.com/users/10068", "pm_score": 1, "selected": false, "text": "<p><strong>Get the French inside the German OODA loop</strong></p>\n\n<p>The French generals were veterans of WW1, so their thinking was for static warfare against a dug-in enemy. They set up shop well behind the lines and assumed that motorcycle dispatch riders would provide them with sufficiently timely information (source: \"<a href=\"https://en.wikipedia.org/wiki/The_World_at_War\" rel=\"nofollow noreferrer\">The World at War</a>\"). In the event the German doctrine provided German unit commanders with sufficient flexibility to exploit local advantages, and modern communication technology (especially radios) kept the rear echelon able to respond in a timely fashion. There is now some argument about the extent to which this was an official doctrine and the degree to which the Germans made it up as they went along (\"No plan survives contact with the enemy\"), but either way it was the crucial advantage.</p>\n\n<p>The result was that during the Battle of France the French command repeatedly ordered \"stop lines\" to be created, only to learn that these lines had already been overrun before their orders arrived.</p>\n\n<p>If the French had been using similar doctrine to the Germans then they would have been ready for a war of maneuver instead of a rerun of the WW1 trenches. This lesson has now been generalised (no pun intended) into the concept of the \"<a href=\"https://en.wikipedia.org/wiki/OODA_loop\" rel=\"nofollow noreferrer\">OODA loop</a>\": Observe, Orient, Decide, Act. The point is that if you can do this faster than the enemy then you have a decisive advantage, because whatever the enemy does, you can be there ahead of them. In the Battle of France the French high command had a very long OODA loop, on the order of a day, while the German high command had a much shorter one. Hence the French were only able to react belatedly while the Germans took the initiative.</p>\n" }, { "answer_id": 103992, "author": "Oulala Leon Endlessreviewer", "author_id": 47432, "author_profile": "https://worldbuilding.stackexchange.com/users/47432", "pm_score": 2, "selected": false, "text": "<p>There are many components to the western front situation, so I'll recoup some:</p>\n\n<p><strong><em>1/ After WW1 the French were unwilling to go to any other war, since the bleeding was so terrible for them</em></strong></p>\n\n<p><strong><em>2/ The British Army was as usual a joke, with the British Navy and Airforce being the sole expression of British military capabilities, especially the Navy</em></strong></p>\n\n<p><strong><em>3/ While the German Army was woefully underequipped compared to the French, it had succeeded in drastically evolving from the WW1 mindset, where trenches and massive artillery usage were the deciding factors of the war. The French meanwhile had not.</em></strong></p>\n\n<p>(it is not very well known, but all the way to the battle of France and during the totality of the German-Polish war, thr majority of the German army was relying on horses, not cars or tanks. Most of the artillery in 1940 was still carried around by horses and not modern weaponry)</p>\n\n<p>Counting on point 1, <strong>I would first assume that the French would not attack German territory no matter what.</strong> </p>\n\n<p>I've heard rumors of the French Army being pressured by the British to not enter Germany under threat of seeing their oil supply lines cut (as those were almost entirely under British control back then), because the British plan would've been, as is typical with them, to sink their \"ally\" and enemy altogether by ensuring that both sides remain about as strong, thus dragging on the war to impoverish both.</p>\n\n<p>However even if you take these rumours seriously, the French would never have attacked any way.</p>\n\n<p>The French Third Republic was a weak system where governments changed often and party alliances were necessary in all situations, and popularity for the war was so low that when the war was started, the speech made in the National Assembly <em>did not even dare to contain the word \"War\",</em> simply requesting \"extraordinary military credits\" rather than demanding national mobilisation.</p>\n\n<p>The French, all too scared after the bloodbath of the Great War, would've probably stayed put and tried to shoo the German away with their big Maginot Line anyway.</p>\n\n<p>With that option out of the way, there are a few ideas:</p>\n\n<p>Before the War even started, it was imperative for the French High Command to evolve with the times. Tanks weren't the WW1 tanks, and allowed for high power assaults that trenches wouldn't be able to hold back anymore. Aviation had also greatly evolved and needed to be taken along infantry and armor, which is what the Germans did. <strong>The Blitzkrieg was a fairly simple but modern tactic of uniting infantry with armor along with air support, whereas the outdated vision was to use them separately.</strong> The French did not understand the value of mixing all three, except by some like then Colonel De Gaulle, or <a href=\"https://en.wikipedia.org/wiki/Strange_Defeat\" rel=\"nofollow noreferrer\">Marc Bloch</a>: </p>\n\n<p><strong>During The Phony War (39 to May 40), more military pressure should have been put by both British and French on the German border.</strong> While the Germans had almost all their divisions in Poland, France alone could muster about 80 divisions against the 30 German divisions that were guarding the border. <strong>Even if you don't consider a full on assault, skirmishes and pressuring the enemy was tremendously important, especially when the Germans were advancing quickly in Poland and needed to be stalled for the Polish Army to recover footing</strong> (at the end of the German-Polish war, 80% of Polish soldiers were still standing, but it was a military checkmate because the Germans had taken vital parts of the nation due to their speed and execution with the Blitzkrieg tactics).</p>\n\n<p>In that same period, had Sweden not decided to simply let the German Army walk freely to Norway, the stalling of the Germans could have prevented them from getting full control of Norway before the British-French expeditionary corps had taken control themselves.</p>\n\n<p>During the War itself:</p>\n\n<ul>\n<li><p>The Belgian line fell almost immediately, prompting the French to send their best equipped and manned army there, along with the British Expeditionary Force. <strong>Had the Belgians held longer, the support force might've been able to create a frontline and stall the Germans there.</strong></p></li>\n<li><p>The Germans pierced through the Ardennes and made a pincer move on that army. <strong>Had the Ardennes been properly seen as a possible entry point and guarded, the pincer would never have worked.</strong></p></li>\n<li><p>The British immediately decided to run and abandoned their defense positions, along with a huge amount of equipment, to run for Dunkerque and then home. <strong>Had they not abandoned the fight as soon as the battle looked awry, then had they not abandoned their equipment without destroying it to save their men, and had they not made building a frontline even more difficult by running away in the first place, the 1st French army might not have fallen so quickly defending the British retreat.</strong> Although to be honest by then the situation was very dire anyway.</p></li>\n</ul>\n\n<p>The rest is a long string of rather pitiful but unavoidable situations.</p>\n\n<p><strong>The French had superior weaponry in every way, but lacked both modern tactics and proper communications.</strong> I don't know why communications were so poor, but there were actual articles in the news about 4 communist sympathisers that were tried and executed for sabotaging tank radios in the factory(since back then, Hitler and Stalin were allies). How prevalent was the sabotage, I do not know either. </p>\n\n<p>But in general, the Germans worked with efficiency, mixed troops, and a goal to advance as fast as possible so as to continously hustle french forces and never let them form a frontline.\nIt worked so well because the french were constantly at a loss as to where the frontline was, while it moved every day, they sent infantry or tanks alone against mixed troops that would just break through any defense fairly quickly, and they did not have powerful enough communications to ever mount a solid counterattack.</p>\n\n<p>I hypothesised that had the Belgian Front held, or had the Ardennes been properly defended, or had the British held their line, things would have been different, but in reality I am not so optimistic.</p>\n\n<p><strong>The fact is that the Blitzkrieg will only be properly countered with somewhat modernised tactics only by 1943, after Stalingrad. From 1939 to 1942, the only thing that saved anyone from the German Army was Winter.</strong> Nothing else stood, except the Channel I suppose. To last longer against the German forces was to win in the long run, essentially, and neither Polish, nor French, nor British, nor the USSR, stood the Blitzkrieg in its prime. Let me remind you that Moscow was only saved by Winter, with very little land left to conquer in 41, and Stalingrad was actually taken before being turned into a mass grave during the winter of 42.</p>\n\n<p>I've also let out a ton of details as this post is already extremely long, such as the replacement of the Top General of the French Army at the worst possible time, or the fact that after the 1st Army was lost in the Dunkerque pocket, the French were pretty much left with their pants down and really couldn't stop the German Army no matter what anymore since the other forces were less well equipped, experienced, and France had lost a lot of manpower after their best army was gone and a ton of British material was left freely to the Germans.</p>\n\n<p>But to me the real problem will remain the outdated tactics, misunderstanding about the nature of the war, where positionment wasn't as important as speed, where mixed units weren't even considered, and where the French High Command was completely incompetent at realising its mistakes from start to finish. Heavy military reforms before and during the war, or stalling tactics like harassment, were absolutely necessary and would've turned the tide in many ways. But since neither were done, the only important thing was time. The Germans were so advanced militarily despite inferior heavy weaponry that it took 3 years for anyone to catch up and beat them head on. </p>\n" }, { "answer_id": 104094, "author": "Flummox - don't be evil SE", "author_id": 34012, "author_profile": "https://worldbuilding.stackexchange.com/users/34012", "pm_score": 2, "selected": false, "text": "<p>There are a lots of small ways the French could have made a difference.</p>\n\n<p>My favourite: <strong>blow the bridges near Eben-Emael, on the Belgian-German border</strong>. At the height of the invasion into Belgium these bridges carried more then 100 trains a day. Without this supply / support any attack would peter out.</p>\n\n<p>Mind that at this point in the war the Germans used a lot of foot troops and horses. Very little units had trucks. Most transport was done by rails.</p>\n\n<hr>\n\n<p>If you want to try for bigger changes, do try Hearts of Iron 4, or the earlier versions. It is quite possible to hold the German advance in that game, though not easy.</p>\n" }, { "answer_id": 104098, "author": "D3f4u1t", "author_id": 47461, "author_profile": "https://worldbuilding.stackexchange.com/users/47461", "pm_score": 1, "selected": false, "text": "<h2>Breaking the ENIGMA</h2>\n\n<p>I think WWII had been significantly changed, if British intelligence were able to break the ENIGMA earlier. \nThe ENIGMA was a cipher machine to encrypt military communication during WWII. The decryption key changed every hour, so it was almost impossible for the Allies to read the messages (because the key was written on a physical handtable and was very well protected). So if it was possible for a spy to extract that handtable without the Germans noticing, they could hear all military communications from the German, to predict any troop movements or tactics. </p>\n\n<p>This is an abstract from <a href=\"https://en.wikipedia.org/wiki/Enigma_machine\" rel=\"nofollow noreferrer\">Wikipedia</a>:</p>\n\n<blockquote>\n <p>The Enigma machines were a series of electro-mechanical rotor cipher machines developed and used in the early- to mid-20th century to protect commercial, diplomatic and military communication. Enigma was invented by the German engineer Arthur Scherbius at the end of World War I.[1] Early models were used commercially from the early 1920s, and adopted by military and government services of several countries, most notably Nazi Germany before and during World War II.[2] Several different Enigma models were produced, but the German military models, having a plugboard, were the most complex.[...]\n Though Enigma had some cryptographic weaknesses, in practice it was German procedural flaws, operator mistakes, failure to systematically introduce changes in encipherment procedures, and Allied capture of key tables and hardware that, during the war, enabled Allied cryptologists to succeed and \"turned the tide\" in the Allies' favour.[7][8]</p>\n</blockquote>\n\n<p>Also look for: <a href=\"https://en.wikipedia.org/wiki/The_Imitation_Game\" rel=\"nofollow noreferrer\">The Imitation Game</a></p>\n" }, { "answer_id": 104101, "author": "Andrew Dodds", "author_id": 33469, "author_profile": "https://worldbuilding.stackexchange.com/users/33469", "pm_score": 3, "selected": false, "text": "<p>One thing is missing:</p>\n\n<p>The <a href=\"https://en.wikipedia.org/wiki/Mechelen_incident\" rel=\"noreferrer\">Mechelen Incident</a> never happens.</p>\n\n<p>The initial plan for the German invasion of France was a frontal attack through the low countries into Northern France, just as in 1914. Furthermore, the idea was to start it much earlier than the 'real history' battle - shortly after the conclusion of the invasion of Poland, the idea being to catch the Allies unprepared. First it was delayed, then the plans were leaked in the above incident, causing a rethink and the invention of the Sedan concept.</p>\n\n<p>So what happens in this original plan? The German army crashes into Belgium and Holland in December 1939.. in the middle of winter, and, interestingly with much lower ammunition reserves. No doubt Holland still falls, and much of Belgium, but the weather makes the advance slower and neuters the Stukas; the German armour finds itself fighting head on battles against British Matilda IIs and French Char-1B tanks, which completely outclass them. Going into 1940, Germany never gets the chance to concentrate all her Armour into a single strike.</p>\n\n<p>The result is a stalemate, with a front line forming in similar battlegrounds to WWI. Except that the German economy is relatively much weaker than before; ironically it took the fall of France to put the German army on wheels - captured French equipment played a significant part at the start of Barbarossa. </p>\n\n<p>Italy sees how things are going and stays very quiet. </p>\n\n<p>By 1941, Germany is in a state of collapse. The Luftwaffe has been ground down in battles with the RAF and improved French planes; the Panzer arm is struggling against the numbers that the allies can put into the field, and the economy is disintegrating (in the 'real war', conquered France provided a lot of economic support to Germany as well). Seeing the writing on the wall, and with the Eastern border creaking ominously, the General Staff depose Hitler and announce an armistice.</p>\n" }, { "answer_id": 104129, "author": "RoyC", "author_id": 33226, "author_profile": "https://worldbuilding.stackexchange.com/users/33226", "pm_score": 2, "selected": false, "text": "<p>I have repeatedly wargamed this battle and in most cases, as the allies, have achieve a much better result than the historical one.</p>\n\n<p>In the quest for historical accuracy there was only one way to achieve the dismal results of May 1940. If the French player is given information one day old the results end up looking pretty much like the historical ones.</p>\n\n<p>This reflects the failure of command and communication in the French army. The French were fighting the last war, their command communication control and information network was setup to fight a static war not a manoeuvre war.</p>\n\n<p>This is reflected in the command styles. The French army was commanded by general officers a long way behind the front. First information had to get them, they had to make decisions on that already old information and then get orders to the people doing the fighting.</p>\n\n<p>The German general officers of the Panzer Divisions that exploited the breakthroughs fought near the front of their Divisions. They could make rapid and accurate decisions on where and when to apply force to destroy their enemies will to fight and to exploit weakness, caused in many cases by their enemies reactions to old information.</p>\n\n<p>There are many ways to improve the outcome of the battle for France. Worthy of mention is the concentration of the superior French tank forces into a proper mobile reserve capable of defeating the German penetrations. My choice would be to fix the C3I problem, get the allied generals out of their Chateauxs and onto the front line where they can see what is really happening in real time. </p>\n" }, { "answer_id": 142796, "author": "Eth", "author_id": 42046, "author_profile": "https://worldbuilding.stackexchange.com/users/42046", "pm_score": 3, "selected": true, "text": "<p>After many good answers and further research, it seems that, by all accounts, the Allies should have won, surprisingly enough. The Nazis won thanks to a ridiculous string of coincidences that would have had put any reader out of the story, had it be fictional.</p>\n\n<p>At the end of WWI, France had the most modern army in the world. A massive pool of truck instead of reliance on trains for moving troops, the biggest air force of the planet, troops being equipped with semi-automatic rifles and a massive number of LMGs, turreted tanks and combined operations... And while Great Britain put comparatively more efforts into its navy, its army was about as advanced and had even started working on APC vehicles.</p>\n\n<p>How do we get from this to such a debacle?</p>\n\n<h2>The post-WWI years</h2>\n\n<p>After war, both nations knew they needed a rearmament program, to thoroughly modernize according to the lessons learned form the war. Of course, rearmament programs are expensive, and when the deadly, exhausting, impossibly costly war that was supposed to be The Last One is just finished, some people may think that diverting funds sorely needed for reconstruction to the army is not the best idea.</p>\n\n<p>In the aftermath, the British stop pursuing combined arms doctrines, which are slowly forgotten. And the general Estienne, father of the French combined arms doctrine, dies early before having time to further develop his ideas, resulting in the same loss.</p>\n\n<p><strong><em>tl;dr</strong>: Had either not let their armies decay, especially doctrine-wise, they would have been prepared against the new German tactics and blunt their advance.</em></p>\n\n<p>Britain was focused on trying to hold together a dying Empire, and the focus on the navy and on rebuilding the economy left the army deprioritised, and it went back to a smaller expeditionary force, not unlike it was pre-war, even if its rearmament program was somewhat less disrupted.</p>\n\n<p>Meanwhile, France starts its complete rearmament program. It develops a rather excellent light machine gun, then starts working on a new semi-automatic rifle and... thing peter out, especially after the 1929 crisis. Then new left-wing government, focused on social progress but openly contemptible of the traditionally right-wing army, cuts military funds as much as possible. A French head of state of the time goes as far as declaring that \"If I could, the army would not get one centime in peace time\".</p>\n\n<p>Even worse, fearing the potential influence of the army, they change the appointment system for top officers: instead of picking from a list compiled by high command based on competence, they are now directly nominated, based on political affiliation. But wait, you might say, wasn't that exactly what had happened before WWI? Didn't France have to fire a third of its generals early in WWI because of that? Didn't they know that was a bloody stupid idea from experience? Yes they did, but remember, the priority was to make sure the army was not a political menace. And anyway, who would be insane enough to start <em>another</em> world way, after all?</p>\n\n<p>As the threat of a new war loomed, France picked the rearmament program back up, but it was too little too late. They had great planes, but not enough - and the newest model was basically at the prototype stage and sent to the front from the factory. They had great defensive tanks, but with flaws not yet kinked out. They had great sub-machine guns, but only a few hundreds had time to reach the troops. They had great rifles, but had only time to equip troops with a bolt-action version planned for rear-echelon troops. The semi-automatic version, which would have been one of the best rifle in the entire war, was barely complete, and didn't even have time to leave the factory (fortunately, they did manage to hide its existence to subsequent German occupation forces).</p>\n\n<p><strong><em>tl;dr</strong>: Had the French government at the time not seen the army as a political enemy and cripple its high command, it could have developed new doctrines and efficiently respond to new German tactics.</em></p>\n\n<h2>The appeasement politic</h2>\n\n<p>Interwar France and Britain have been criticised a lot for their appeasement politic, believing that if enough concessions were to be made to Germany, they wouldn't do something as stupid as start <em>another</em> war. Had they read <em>Mein Kampf</em>, they would never have believed Hitler's words about wanting peace. (Then again, that book is allegedly so badly written to be painful.)</p>\n\n<p>It is difficult to imagine what an early war would have looked like, but Germany probably was more unprepared than others. Had the Allies (possibly without Great Britain) gone to war over Czechoslovakia, it may have gone badly for Germany. But this would have required a significantly different political climate at least in France if not in Britain as well, so this is somewhat difficult to imagine it happen at that point.</p>\n\n<p>However, had the Franco-Soviet 1935 treaty held, Germany would never had stood a chance in a war. Had Stalin compromised over not sending troops on Polish territory, or had France been less eager to appease Germany, the Soviet may have very well ended up with the Allied at the start of the war.</p>\n\n<p><strong><em>tl;dr</strong>: Had the alliance with the Soviet worked out, it would have been a race to Berlin five years early.</em></p>\n\n<p>Speaking of Poland, they did quite better than is commonly believed (mostly based on Nazi propaganda, as it happens). But as to not, ah, provoke Germany, France and Britain had stopped Poland to fully mobilize, considerably hampering its war effort against German and then Soviet attack.</p>\n\n<p>Even worse, its strategy was to hold long enough for the French army to launch an offensive across the Rhine, and for the British air force to launch a bombing campaign against Germany. Neither were actually prepared to conduct such operation, and had assumed Germany would be deterred simply by the threat. France launched a probing attack, met no resistance but decided to withdraw behind its fortification. Britain sent a few token planes, met no resistance but decided to stop further attacks. However, even unprepared (which they shouldn't have been), attacks against the undefended western Germany while its army was stuck in Poland could have stuck a heavy blow, either stopping it from finishing Poland or at least seriously weakening for the counteroffensive.</p>\n\n<p>Also the offensive happened right before Poland would receive thousands of modern planes for its air force. I suspect Germany wanted to attack before that, as it would have seriously challenged the Luftwaffe.</p>\n\n<p><strong><em>tl;dr</strong>: Had the Allies been prepared to support Poland, they could have dealt a potentially fatal blow to Germany.</em></p>\n\n<h2>Defensive strategy</h2>\n\n<p>Nonetheless, as the years pass by, with more and more nations falling toward extremism, it had become clear that a new European war could happen again. The \"twenty years of armistice\", as Field Marshal Foch had called the Versailles treaty, were coming to an end.</p>\n\n<p>Britain could count on the Channel, its navy, its air force and an alliance with several continental powers to prevent a war from reaching its homeland. France, however, was right next to the biggest potential threat, a revanchist Germany that could field twice as many men, and that had already proved its capabilities at massive industrial war. Which is why they did the logical thing and developed the Maginot Line.</p>\n\n<p>But wasn't the Maginot Line a terrible idea that miserably failed? No, in fact it was a great idea and, when used properly, it worked exactly as advertised. (See below as for how it was <em>not</em> used properly.) It was the brainchild of WWI veteran Philippe Pétain who, despite some, ah, unfortunate political decisions later (again, see below), had still been one of the best generals of WWI - so not an idiot, and not an idiotic idea.</p>\n\n<p>The Maginot Line was an impassable line of fortifications, estimated to hold with a contingent against an army <em>fifty times</em> more numerous. And, contrary to much later rumours, France was perfectly aware that the Germans would push through Belgium - and so was Belgium, in fact, which is why it was part of an alliance with France and Great Britain. Belgium was to build its own equally impassable Meuse–Albert line.</p>\n\n<p>The problem is, impassable fortifications cost a lot, and Belgium simply didn't have enough money. So they asked France to lend them enough funds for the project. Which France declined (see above for why they would do such a thing). Which is why the Meuse-Albert line was delayed and scaled back. At the onset of the war, it was clear that the Belgian army wouldn't be big enough to hold a determined German push at its border.</p>\n\n<p><strong><em>tl;dr</strong>: Had France lent the money to Belgium, no German army could have crossed their eastern border.</em></p>\n\n<p>Nevertheless, with the bulk of the French army and the British Expeditionary Force to back them up, it would still be enough to stop a German attack. As long as they were deployed in advance, that is. But if tensions rose, as allied nations, of course this is exactly what would happen.</p>\n\n<p>But then the remilitarisation of the Rhénanie happened, and neither France nor Britain reacted, not wanting to declare war on Germany over internal troop movements. After all, they simply wanted to legitimately be able to defend themselves, right?</p>\n\n<p>Belgium saw this appeasement politic as a sign that it couldn't count on the Allies, and thus left the alliance, hoping that neutrality would avoid it to be caught in the next war. Which meant not having foreign troops on its territory. Which meant that when Germany attacked, French and British had to rush from the French border to the frontline, losing much of their defensive advantage, and the easier to defend eastern Belgium being already overrun when they arrived. From there to Paris, there were only flat, hard to defend plains.</p>\n\n<p><strong><em>tl;dr</strong>: Had Belgium not left the Allied for neutrality, the German army would have been stopped, or at least considerably weakened, at its eastern border by the Allied forces.</em></p>\n\n<p>But then, why didn't the French simply extend the Maginot line? Actually, they did. But two years were simply far too short a time to build such fortifications, especially on flat terrain.</p>\n\n<h2>The Ardennes gambit</h2>\n\n<p>Now, the German plan was to repeat the Schlieffen plan that had nearly worked so well in the previous war: launch a massive fast offensive through Belgium and run for Paris to knock France out of the war early. Sure, it had failed last time, but it had worked the time before that. And Germany didn't really have other options anyway.</p>\n\n<p>At least, this was the plan before it fell in the hands of Belgian intelligence, when a German courrier plane randomly crashed in Belgium, carrying said plans. And while the Belgians tried their best to make it look like the whole thing had burned, the Germans knew to be better safe than sorry: they needed a backup plan.</p>\n\n<p>So they did what would otherwise have been an idea worthy of the Chemin des Dames offensive in its utter stupidity: send two tank corps through the Ardennes forest.</p>\n\n<p>Now, the French knew perfectly well that an Ardennes tank offensive was possible, and that a tank army could cross it in two days. Specifically, Maxime Weigand, possibly the most underrated general of the XXe century, had warned François Gamelin, the French chief of staff, of this.</p>\n\n<p>(It was also Weigand that told Charles de Gaulle that his idea of a small, mobile professional army of a hundred thousand men for defense would simply not work - probably because the British had done the <em>exact same thing</em> during WWI and it had been ground down to oblivion in a few months, and thus earning De Gaulle's unending antipathy. But this is a story for another time.)</p>\n\n<p>Once entrenched in the Ardennes forest, even a modest force could have stopped a tank offensive. Tanks offensives are meant for flat terrain: forests make it easy to ambush even big armored forces, and once a few tanks are burning on either side, can easily become death traps.</p>\n\n<p>Unfortunately, as noted above, top officers weren't named for their skills anymore, and Gamelin was a courtier but not a good general. Which is how he ignored both warnings not only from Weigand, but also from French intelligence in Germany about their innovative light tank tactics and training.</p>\n\n<p><strong><em>tl;dr</strong>: Had Gamelin actually listened to his best general or his detailed intelligence reports, he would have easily destroyed the Ardennes tank offensive with a few well-entrenched forces.</em></p>\n\n<p>But then, even without opposition, having two tanks corps cross a forest like the Ardennes is no trivial task. In short order, tank columns turned into giant traffic jams, easily seen by French aerial reconnaissance.</p>\n\n<p>When receiving such reports, however, the officer in charge of defending the sector dismissed them as \"a few scout cars\". So the air scouts went back with tankers on board their planes, to identify the tank models and make unambiguous, detailed reports of the tank force.</p>\n\n<p>No matter, the officer dismissed the new reports. When the French air force asked him if he needed any support, he answered none whatsoever. One may wonder if he was that incompetent, or if it wasn't actual treason. Had the air force been sent to bomb the piled up tanks, it would have been a massacre. The few survivors to make it would have been easily stopped by even a light force, had it been forewarned.</p>\n\n<p><strong><em>tl;dr</strong>: Had the officer in charge of the Ardennes defense not been terminally incompetent/a traitor, or had someone gone over his head (or executed him for treason), German tanks would never have made it out of the Ardennes.</em></p>\n\n<h2>The Battle of Belgium</h2>\n\n<p>The Belgian lines breached, the Allied forces on the back foot, and now a tank force emerging from the Ardenne to envelop them. As in 1914 the French government finally pulled itself together, fired the incompetent, politically appointed generals and let actually competent ones do the job instead and save the day. Namely, they pulled the aforementioned Weigand from retirement and gave him Gamelin's job as chief of staff.</p>\n\n<p>Now, you would think Weigand was the right man for the job: respected by friends and foes alike, right hand man of Allied supreme commander Ferdiannd Foch during WWI, architect of the Warsaw Miracle, absolute légaliste with an unwavering loyalty to democracy and to the Republic. But with the entire French army disorganised, lacking radios and fast-moving forces, about to be encircled, what could even he do?</p>\n\n<p>What he did, was to understand that the main German armored push was overextended, and that there was an opportunity: the French army would counter-attack in a pincer move, hammering the German forces against the British and Belgian anvil, and cut off the spearhead. British high command agreed with the plan, and so do modern experts, who argue that it would have indeed worked.</p>\n\n<p>And then the British ran away.</p>\n\n<p>Specifically, John Gort, commanding the British forces on the continent, panicked and ordered his army to rout towards Dunkerque - leaving behind piles of equipment for the Germans to take instead of properly destroy it all, but destroying bridges, trapping the French and Belgian forces that would be forced to retreat later.</p>\n\n<p>With their flank gone, there was no more hope of victory for the French and Belgian forces, so they started to retreat as well. Both fought hard - the French fighting retreat was especially brutal, taking the highest relative death toll of all the European armies of the early war. German general Heinz Guderian, would in fact call the battle of Stone one of the two worse he ever saw - along with freaking Stalingrad. In fact, the one thing that saved the British army (along with Hitler's tactical mistake at Dunkerque) was the French army standing against literally impossible odds for the entire retreat.</p>\n\n<p><em>Note: remember that next time you hear about a (much more recent) surrending monkey joke or about the Miracle of Dunkerque: the British ran and only made it because the French stood and died. Not even the guys who invented the Polish lance cavalry charging panzers myth dared to mock the bravery of French soldiers. In fact, Hitler himself called them the best in the world after the Germans (of course), in the aftermath of Bir Hakeim. But again, this is a story for another time.</em></p>\n\n<p><strong><em>tl;dr</strong>: Had John Gort not panicked and the British stood their ground instead, the German advance would have been smashed by a pincer move, stopping the German advance.</em></p>\n\n<h2>For what of a fistful of nails</h2>\n\n<p>Had the German advance been blunted, things would have reverted to a 1914-again state: a grinding war with neither side capable of advancing. This would have pitted industrial and manpower reserves against each-other, and like for WWI, the Allies would have had the upper hand with access to the immense American industry. The Soviet Union may have somewhat balanced this by trading with Germany, but this is neither certain nor guaranteed to have lasted. (Soviet-directed Communist agents were executed in France for sabotaging planes, for example, so the Soviet Union was, at least initially, somewhat serious about their pact with the Germans.)</p>\n\n<p>New weapons would have made a difference. Many northern French and Belgian cities may have been razed by artillery fire. New railway trains may have been used to destroy fortifications like on the Maginot line, but the enormous investment on those and on the follow-up force needed to have a chance to advance. As such, like in WWI, it is improbable (though not impossible) for the Germans to achieve victory that way.</p>\n\n<p>In addition, and contrary to what many think, the Allied had the initial technological advantage. In fact, the reason later German tanks were so good was partly because of the French tech they got their hands on, and on the resources of the French had from their colonial empire, allowing for better alloys. Had the war become static, the Allies would have kept the technological advantage, especially with Hitler increasingly obsessed with wunderwaffen and the French armament program being finally completed and extended.</p>\n\n<p>Given how fast it rebounded after the war, and as there were pre-war projects already, France may have been the first one to develop rockets and even jet engines. it may even have fielded ramjets, whose development were interrupted by the Occupation. They also had few wagons full of uranium ore that spent the entire Occupation pointedly forgotten in some railway depot, but while it would have considerably helped nuclear development, it is far from certain that the war would have lasted long enough for an atomic bomb to be finished.</p>\n\n<p><strong><em>tl;dr</strong>: Had the initial push been stopped, it is improbable that Germany could have won WWI-bis.</em></p>\n\n<h2>Aftermath</h2>\n\n<p>At this point, the French homeland was lost. There was next to nothing left between the German army and most of France, with indefensible open terrain in the way. But France was still not ready to give up. it had 150 000 surviving troops evacuated from Dunkerque. It had an army holding the Italians at bay in the Alpes. It had an oversea empire, from which colonial troops could be raised. It had a modern, rather powerful navy.</p>\n\n<p>So the French government did the sensible thing, gave up the indefensible territory and prepared to move the capital to Algiers (as Algeria was considered more or less French homeland at the time). In this time of crisis, they decided to unearth this old Roman tradition: nominate an emergency ruler with dictatorial powers, so the slower democratic powers can be temporarily been bypassed for the duration of the crisis. After all, if it worked for the Romans...</p>\n\n<p>So they chose the victorious chief of staff of WWI (Foch was the supreme commander of the allied forces at this point, which was not the chief of the French army), the Lion of Verdun, a national hero whose military skills had been well-proven: Field Marshall Philippe Pétain.</p>\n\n<p>Unfortunately, he was also going senile and had never liked politicians to begin with. This was the \"divine surprise\" that fell on the lap of the far right, who seized the opportunity to take power in Pétain's name and stage a coup d'état. While officially called the \"Nation Française\", it would be remembered as the Vichy regime. In short order, being ideologically close to Germany and Italy but deeply anglophobes, they would sign an armistice (not a capitulation, because that would make the army lose face, a big no for a fascist regime) and nevermind the loss of half of France and basically becoming a puppet of Germany (even if officially neutral in the war).</p>\n\n<p>Oh, remember the French navy? half of it was stuck in Toulon and, much later, scuttled itself so the Germans wouldn't get their hands on it. Another half was in Mers-el-Kebir, and the British murdered it with a surprise air attack, so (agian) the Germans could't get them - but the French sailors were actually busy scuttling said ships, so not only were they especially defenseless against a surprise attack from an ally, but even more died trapped in the ships.</p>\n\n<p>So while the armistice was very unpopular for many French, many also felt betrayed by the British and decided that neither side was worth it anyway. Even then, and despite everyone (including the Allies) considering the Vichy regime as the legitimate French government, \"Fighting France\" (later Free France) was formed as a government in exile refusing to stop the fight. While only a few troops and colonies joined it, plus those forming Résistance groups in Vichy and occupied territory, they became increasingly popular and, in the case of Bir Hakeim, even instrumental in the war. But again, this is a story for another time.</p>\n\n<p><strong><em>tl;dr</strong>: Had the French government named the maybe too modest Weigand instead of Pétain, the French Republic would have kept fighting from Algiers.</em></p>\n\n<h2>And the Devil is laughing still</h2>\n\n<p>Now as this is Worldbuilding and not History, let's try to make sense of it. Because as it is, this is all too ridiculous to use in a story, nevermind that it actually happened.</p>\n\n<p>So let's take this ridiculous chain of coincidences, and the fact that it suddenly started to fall apart everywhere. Add the countless failed assassination attempts against Hitler. Add that the Nazi regime was not simply evil, but Evil. They didn't just invade Europe, raze cities and murder countless civilians. They didn't simply have insane racial theories they actually attempted to put into practice, and allied with an equally monstrous regime on the other side of the world. But not only did they <em>industrialize genocide</em> (and yes, I am the first to be surprised that it has to be reminded nowadays), but they actually wore skulls as a symbol.</p>\n\n<p>And the SS had a war song with those lyrics (translated, obviously):</p>\n\n<pre><code>\"And the Devil laughs with us\"\n\"Ha! ha! ha! ha! ha! ha! ha!\"\n</code></pre>\n\n<p>Also Hitler was into occultism.</p>\n\n<p><strong><em>tl;dr</strong>: there is one obvious explanation: Hitler made a deal with the Devil.</em></p>\n\n<p>Seriously, why don't more people use this in secret-history or alt-history works?</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/103753", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/42046/" ]

[ { "answer_id": 105191, "author": "L.Dutch", "author_id": 30492, "author_profile": "https://worldbuilding.stackexchange.com/users/30492", "pm_score": 1, "selected": false, "text": "<p>First of all, 1939 to 1941 are the years where the Nazi and their allies were jumping from success to success. No European city was captured by allies until much later.</p>\n\n<p>Second, from Berlin to any other European city there is no way for you to avoid crossing rivers, and you already pointed out this is a weak point in your tank.</p>\n\n<p>Third, to stop a tank you don't have to hit the motor. Soviet fighters were pretty effective at sticking small bombs to the wheels, and once they are gone your tank is just a big lump of steel with a cannon, exposed to aerial attacks.</p>\n\n<p>Fourth, you will hardly find decent roads during WWII. Again, your tank will sink into the ground, incidentally or on purpose.</p>\n\n<p>Lastly, consider that the amount of resources (mass equivalent to 20 Panzer, quoting Marc's and Mike's comments) you have to put into one of these beasts makes you even more vulnerable: a single failure along its production/usage will block all the resources there. While a single failure on 1 of 20 Panzer would not prevent the other 19 to be operative.</p>\n" }, { "answer_id": 105194, "author": "o.m.", "author_id": 6402, "author_profile": "https://worldbuilding.stackexchange.com/users/6402", "pm_score": 5, "selected": true, "text": "<p>The problem with these giant tanks is that killing them is easier than building them. They will be no tougher than an armored cruiser or battleship, and ships were sunk with bombs from carrier-based and land-based bombers.</p>\n<p>Historically Germany had been quite <em>inefficient</em>, and fiction tends to ignore that. Do you want to create the equivalent of an <em>Indiana Jones</em> movie or something more like <em>Saving Private Ryan</em>?</p>\n<h1>Do you want the German equivalent of the Maginot line?</h1>\n<p>Breaking the line could be a role for that tank, by the way. Say the Germans pour lots and lots of money into a couple of those things. They come up with clever ways to resolve mobility problems, for instance the landcruisers are built to disassemble and reassemble easily, and each comes with a couple dozen specialized trains and a battalion of assembly workers.</p>\n<p>At the start of the war, when Germany had the initiative, they <em><strong>create</strong></em> opportunities to make the landcruiser work.</p>\n<ul>\n<li>Say they assemble one near Aachen, drive it 30 km or so to the Meuse, and engage the surface works of <a href=\"https://en.wikipedia.org/wiki/Fort_Eben-Emael\" rel=\"noreferrer\">Fort Eben Emael</a> instead of the historical solution, a glider assault.</li>\n<li>Another one gets shipped by riverboat to Wörth am Rhein, is assembled there, and then overruns the Ouvrage Schoenenbourg.</li>\n<li>One gets attached to the Romanian forces during the <a href=\"https://en.wikipedia.org/wiki/Siege_of_Odessa_(1941)\" rel=\"noreferrer\">Siege of Odessa</a> to help overrun the city.</li>\n</ul>\n<p>In the middle of the war, they are mostly held in readiness for opportunities that never come up. Say one was in southern France, disassembled on transport train and waiting for the Spanish decision to go after Gibraltar. Another was transported to the Siege of Leningrad, where it made a credible showing -- but no more credible than another Panzer regiment would have been.</p>\n<p>At the end of the war all are lost. Those near the Normandy get bombed to bits before <em>Overlord</em>. Some end as stationary bunkers when they run out of fuel or a track breaks, to be bypassed and mopped up later. Every now and then an Allied regiment gets chewed up when it unexpectedly encounters one that can still move. (Count on the Soviets to generate lots of casualties with direct attacks, while the Americans send wave after wave of fighter-bombers.)</p>\n" }, { "answer_id": 105232, "author": "Thucydides", "author_id": 8572, "author_profile": "https://worldbuilding.stackexchange.com/users/8572", "pm_score": -1, "selected": false, "text": "<p>Things like the P-1000 were considered very fantastical even in the period where they were being considered, and I doubt that many people were taking the ideas seriously.</p>\n\n<p>Even 100 ton tanks like the <a href=\"https://infogalactic.com/info/Panzerkampfwagen_E-100\" rel=\"nofollow noreferrer\">E-100</a> or the <a href=\"https://infogalactic.com/info/Panzer_VIII_Maus\" rel=\"nofollow noreferrer\">Panzerkampfwagen VIII Maus</a> were considered to be diversions of effort from things which could make a difference, like the <a href=\"https://infogalactic.com/info/Entwicklung_series#E-25\" rel=\"nofollow noreferrer\">E-25</a> tank destroyer or the <a href=\"https://infogalactic.com/info/Entwicklung_series#E-50_Standardpanzer\" rel=\"nofollow noreferrer\">E-50</a> <em>Standardpanzer</em>.</p>\n\n<p><a href=\"https://i.stack.imgur.com/gfNjr.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/gfNjr.png\" alt=\"enter image description here\"></a></p>\n\n<p><em>E-50</em></p>\n\n<p><a href=\"https://i.stack.imgur.com/4M66x.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/4M66x.jpg\" alt=\"enter image description here\"></a></p>\n\n<p>*E-25 tank destroyer</p>\n\n<p>The entire Landkruiser concept was an inexcusable diversion of resources. As you yourself note, it was effectively immobile compared to ordinary tanks, much less Allied fighter bombers. </p>\n\n<p><a href=\"https://i.stack.imgur.com/CQVhF.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/CQVhF.jpg\" alt=\"enter image description here\"></a></p>\n\n<p><em>This is what is fighting German armour in the West</em></p>\n\n<p>It would have been easily bypassed and even in open plains rapidly immobilized by the simple expedient of bombing the ground around it or having engineers lay minefields or use explosive charges to create giant craters. Much like the <a href=\"https://infogalactic.com/info/H-class_battleship_proposals\" rel=\"nofollow noreferrer\">\"H\" battleship</a> series or gigantic cannons like <a href=\"https://infogalactic.com/info/Schwerer_Gustav\" rel=\"nofollow noreferrer\">Gustave</a> and Dora, or even plans for the rebuilding of Berlin as \"<a href=\"https://infogalactic.com/info/Welthauptstadt_Germania\" rel=\"nofollow noreferrer\">Germania</a>\"</p>\n\n<p><a href=\"https://i.stack.imgur.com/Bx9Of.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/Bx9Of.jpg\" alt=\"enter image description here\"></a></p>\n\n<p><a href=\"https://i.stack.imgur.com/jarhf.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/jarhf.jpg\" alt=\"enter image description here\"></a></p>\n\n<p><em>Two views of Speer's model of Welthauptstadt Germania. To indicate scale, the domed Volkshalle was 200metres tall</em></p>\n\n<p>It is rather ironic that the German Army had taken the spirit of the \"<a href=\"https://infogalactic.com/info/Stormtrooper\" rel=\"nofollow noreferrer\">Sturmtruppen</a>\" of the end of WWI and combined it with the fluidity of mechanized warfare as theorized by <a href=\"https://infogalactic.com/info/B._H._Liddell_Hart\" rel=\"nofollow noreferrer\">B.H. Liddell-Hart</a> and <a href=\"https://infogalactic.com/info/J._F._C._Fuller\" rel=\"nofollow noreferrer\">J.F.C. Fuller</a> to create highly mobile combined arms Panzer forces, only to be dragged towards relative immobility but the very leadership which had valued \"<a href=\"https://infogalactic.com/info/Blitzkrieg\" rel=\"nofollow noreferrer\">Lightning War</a>\" in the first place.</p>\n" }, { "answer_id": 105257, "author": "JBH", "author_id": 40609, "author_profile": "https://worldbuilding.stackexchange.com/users/40609", "pm_score": 3, "selected": false, "text": "<p><strong>Answer: No</strong></p>\n\n<p>You point out that you consider this a weapon of last result. Therefore, it wouldn't be used during the time frame you indicate due to the successes of the Nazi military at that time.</p>\n\n<p>But let's assume that you give in to temptation and use it. After all, a weapon unused is a useless weapon.</p>\n\n<ul>\n<li><p>You're not giving enough credence to the issue of road and bridge damage. You're literally destroying your ability to conduct a war by sending this leviathan anywhere. Even if, as the last resort, it won the battle &mdash; you're stuck having to do some very rapid, very expensive infrastructure repair or you can't take advantage of the victory. How do you keep a city you cannot access?</p></li>\n<li><p>No one has really pointed out (probably because it's basically implicit in the road damage problem) that this tank has a LOT of trouble turning. This is the biggest problem with \"super tanks.\" The longer you make them and the heavier you make them the harder it is to turn them. This is because turning a tank requires pivoting on one, basically unmoving tread. That's a LOT of friction. You're more likely to get the tank stuck by burying the treads you're dragging (if you can drag them at all, 500 tons...).</p></li>\n<li><p>In reality, this tank cannot push through or drive over much of anything (engine power doesn't scale with the size of a tank). Like the larger Panzers, it's an open country tank. It's too big and bulky to bring it into a city. It takes only a handful of collapsed buildings to add up to the 1,000 tons of tank and anything that falls on it simply adds to its tendency to bog down. The gearing and motors that turn turrets are never as powerful as the tread engines (and can't be, space inside the tank is not infinite). Naval guns would be almost useless within the close quarters of a city. This tank's primary operation would be to act as mobile support artillery from a substantial distance. Which means it's only use in a city battle is to level the city... thereby removing the value of taking the city.</p></li>\n<li><p>George Patton once said, \"<a href=\"https://en.wikiquote.org/wiki/George_S._Patton\" rel=\"noreferrer\">Fixed fortifications are a monument to the stupidity of man</a>.\" Given its size, weight, difficulty turning, capacity for becoming bogged down, low speed, etc, this is basically a fixed fortification. In fact, once you're inside the basic firing radius of the tank, its usefulness drops considerably.</p></li>\n</ul>\n\n<p>One of Hitler's many flaws was that he was enamoured with HUGE things. He loved massive battleships, massive tanks, massive cities, massive everything. He failed to understand the lesson of cavalry: lightly armored highly mobile cavalry almost always wins out over heavily armored inadquately mobile vehicles. Lightly armored highly mobile things are cheaper and faster (C&amp;F) to build, C&amp;F to repair, and C&amp;F to deploy. Rather than directly engaging their heavy, nearly immovable counterparts, they simply sweep around them and take another target.</p>\n\n<p>The real danger is when things are just a little different, like the U.S. Shermans vs. the Tiger Panzers. Equivalent manufacturing, repair, and deployment costs, but enough of a firepower and armor difference to scare the bejeebies out of Sherman drivers. Who's afraid of a massive tank sporting a naval gun that takes so much time to turn you can spin around it taking shots at its treads? Or sporting a barrel so long that once you're under it shooting at the treads it doesn't matter where the barrel points anymore? Adding close-in defensive weaponry only makes the tank heavier, harder to use, and more expensive to manufacture, repair, and deploy, turining it every-so-slowly into just another fixed fortification.</p>\n\n<p>No, having the tank at the beginning of WWII wouldn't have changed the outcome. I agree with Albert Speer, who saw \"<a href=\"https://en.wikipedia.org/wiki/Landkreuzer_P._1000_Ratte#Development\" rel=\"noreferrer\">no reasonable use for the tank</a>.\"</p>\n" }, { "answer_id": 105258, "author": "John", "author_id": 29409, "author_profile": "https://worldbuilding.stackexchange.com/users/29409", "pm_score": 0, "selected": false, "text": "<p>lets address your points.</p>\n<ol>\n<li><p>use it in cities as a last resort.</p>\n<p>This thing cannot drive in a city, it can't run over buildings becasue buildings often have basements, which would rip the treads apart. City roads have sewers and utilities (and old abandoned parts of the city) underneath them that cannot support its weight for this thing a city is worse than a swamp. It can't stick to the few solid roads because it cannot hairpin turn like a normal tank without ripping its tread assembly apart. It is only useful in a city sitting still, at which point building an actual permanent bunker would be way cheaper.</p>\n</li>\n<li><p>increasing the weight an armament.</p>\n</li>\n</ol>\n<p>Horrible idea, this monstrosity is already pushing the limit on metallurgy at the time, make it even bigger and it will simply rip itself apart as the forces exceed the sheer strength of the steel available. And of course the heavier you make it the less maneuverable it becomes, and this thing could only be driving over specially prepared roads as it is.</p>\n<ol start=\"3\">\n<li>build it where you use it.</li>\n</ol>\n<p>Why? An actually bunker/fortress will be cheaper, faster, easier, stronger and better armed for the same price.</p>\n" }, { "answer_id": 162174, "author": "The Daleks", "author_id": 70058, "author_profile": "https://worldbuilding.stackexchange.com/users/70058", "pm_score": 2, "selected": false, "text": "<h2><strong>TL;DR:</strong> <strong>It's not worth it.</strong></h2>\n<p>While a Rätte would certainly look cool, it is nowhere near as useful as the 40 Panzer IVs, 80 Panzer IIIs, or 60 SturmGeschütz IIIs they could make instead.</p>\n<h2>Long answer:</h2>\n<p>There are actually quite a few problems that would make the P.1000 Rätte impractical.</p>\n<p>1: <strong>Building the accursed thing.</strong> Back in 1939-41, Germany did not have very good production facilities. Yes, they were able to make the Panzers and the Stukas, but it took them <strong>10 years</strong> to build up even a decent army.* In addition, one of the main reasons why Germany started the war was that they had insufficient resources. As a result of these factors, it is highly improbable that they would have been able to complete a Rätte before 1945.</p>\n<p>2: <strong>Fuel economy would <em>suck.</em></strong> While Germany was able to make synthetic diesel, they were barely able to produce enough for their &quot;small&quot; tanks, let alone enough for this huge gas-guzzling monster. In addition, this synthetic diesel left behind a <em>lot</em> of residue. While this was not a huge problem for the &quot;standard&quot; tanks, as their engines were relatively simple, it would be the end of a Rätte; the engine on it would be so huge and complex that it would be almost impossible to affect field repairs upon it.</p>\n<p>3: <strong>Getting it to the battlefield.</strong> Due to the shear weight of the Rätte, it would be unable to cross streams and rivers without getting hopelessly mired in the muck. In addition, it would destroy bridges and roads, making them useless for other troops. Because of these, it would by necessity have to be transported in bits and pieces by railway. This raises the problem of that any Allied fighter-bomber pilot who sees the train is would use it as target practice, destroying the Rätte before it could even be deployed.</p>\n<p>4: <strong>Keeping it supplied.</strong> One major problem with <em>any</em> &quot;battleship on land&quot; concept is that it would be almost impossible to keep it supplied with ammunition and spare parts, as these would be substantially different from those used by other tanks and artillery. It's no use <em>having</em> a landkreüzer if you don't have compatible ammo for it to fire.</p>\n<p>5: More importantly, <strong>Keeping it alive.</strong> Unfortunately for anybody unlucky enough to be in its vicinity, artillery and bombs would be magnetically attracted to Rättes. After all, it is the quintessential &quot;large slow target.&quot; Because of this, it would be pummeled with various types of heavy weapons fire the moment it reached the battlefield. It could be kept intact by adding more armor, but this would make it substantially heavier.</p>\n<p>6: <strong>Movement.</strong> It is an unfortunate fact of life that the heavier something is, the harder it is to move. Also, as @JBH pointed out, this tank cannot bust through walls like it does in the first scene of <em>Captain America: The First Avenger</em>, as usable engine power decreases in direct relation to tank weight. Finally, the heavier the tank is, the harder the ground has to be. The minimum hardness for the Tiger series was &quot;two guys jumping up and down on it won't create an impression&quot;; for a Rätte the ground would have to be several orders of magnitude harder. In other words, the Rätte would only be able to move on flat, crevice-less stretches of granite. Anything softer, and the ill-fated tank would get hopelessly mired.</p>\n<p>7: <strong>You wouldn't even need heavy weapons to destroy it.</strong> As the Russians discovered during the battle for Stalingrad, all it takes to destroy a tank is one well placed grenade, preferably stuffed down a convenient exhaust pipe. This destroys the engine, immobilizing the tank. At this point the Rätte would be an immovable bunker. To quote Patton, &quot;Fixed fortifications are a monument to the stupidity of man.&quot; Another tactic, used by the Western Allies, is to affix a satchel charge to the drive wheels. This does the same thing, albeit that the Rätte's crew would still have a heater for during the winter.</p>\n<p>8: <strong>No worthwhile targets.</strong> One of the reasons why tank-cannon calibers don't get above 120 millimeters is that anything larger is overkill for ground-based operations; there just isn't anything big enough to be worth firing at. Sure, you can fire it at bunkers, but that's what <a href=\"https://en.wikipedia.org/wiki/Brummb%C3%A4r\" rel=\"nofollow noreferrer\">Sturmpanzers,</a> <a href=\"https://en.wikipedia.org/wiki/Sturmgesch%C3%BCtz\" rel=\"nofollow noreferrer\">SturmGeschützes,</a> and <a href=\"https://en.wikipedia.org/wiki/Assault_gun\" rel=\"nofollow noreferrer\">Sturmtigers</a> are for. These were all good tanks, and one of them (the SturmGeschütze) is still used today in some countries.</p>\n<p>As a result of all this, it can be conclusively stated that a Rätte would be completely useless.</p>\n<p>*Nota Bene: Although history books often laud Germany as having this &quot;big huge army which we barely defeated&quot;, the Wehrmacht was actually relatively small; it's just that they got extremely lucky early on.</p>\n" }, { "answer_id": 172029, "author": "Christopher Hostage", "author_id": 50271, "author_profile": "https://worldbuilding.stackexchange.com/users/50271", "pm_score": 0, "selected": false, "text": "<p><strong>A well-placed enemy artillery shot would kill everyone inside</strong>\nEven without piercing the armor or setting off internal ammunition, a large explosion on the other side of a sheer metal armor wall produces spalling. World War II designs did not have significant spalling protection, so men on the inside would be hit by pieces of their own armor. Given how slowly this thing will move, it's possible for concerted artillery to concentrate fire on it, and only one solid hit makes this tank a useless statue.</p>\n\n<p><strong>All men inside would quickly be deafened and shaken to terror</strong>\nAssuming that you put an artillery-sized gun on top, the tank resounds with every shot output, ringing even well-protected ears and heads.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/105190", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/28224/" ]

[ { "answer_id": 106123, "author": "Thucydides", "author_id": 8572, "author_profile": "https://worldbuilding.stackexchange.com/users/8572", "pm_score": 3, "selected": true, "text": "<p>If you get down to it, boiling or vapourizing the oceans needs a metric crap ton of energy. The Atomic Rockets \"<a href=\"http://www.projectrho.com/public_html/rocket/usefultables.php\" rel=\"nofollow noreferrer\">Boom Table</a>\" tells us we need the following amounts of energy:</p>\n\n<p>Boil the oceans: 6.6 × 10^26J 158 Pt</p>\n\n<p>Vapourize the oceans 4.5 × 10^27J 1 Et</p>\n\n<p>To put that in perspective, the Sun's output per second is:</p>\n\n<pre><code> 3.9 × 10^26J 92 Pt\n</code></pre>\n\n<p>The best way to apply lots of energy at once would be to accelerate you spacecraft to relativistic velocities. <em>One Kilogram</em> can release:</p>\n\n<p>1 kilogram at 75% c 4.6 × 10^16J 11 Mt</p>\n\n<p>1 kilogram at 90% c 1.2 × 10^17J 29 Mt</p>\n\n<p>At that point the aggressor can be using wadded up recycled paper and still getting impact energies straddling the \"<a href=\"https://infogalactic.com/info/Castle_Bravo\" rel=\"nofollow noreferrer\">Castle Bravo</a>\" nuclear device.</p>\n\n<p><a href=\"https://i.stack.imgur.com/PbUfx.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/PbUfx.jpg\" alt=\"enter image description here\"></a></p>\n\n<p><em>The worst part is the huge yield was actually an accident</em></p>\n\n<p>Once you have an idea of the parameters of the planet (i.e. how much water is in the oceans) then you can scale the device and the speed to match your capabilities. Of course anyone on the receiving end of that may have a few more pressing issues than the oceans boiling.</p>\n\n<p>For a slightly different take read this answer: <a href=\"https://worldbuilding.stackexchange.com/questions/47793/what-would-a-relativistic-kill-vehicle-hitting-the-moon-look-like-from-earth\">What would a relativistic kill vehicle hitting the moon look like from earth?</a></p>\n" }, { "answer_id": 106160, "author": "Andrew Dodds", "author_id": 33469, "author_profile": "https://worldbuilding.stackexchange.com/users/33469", "pm_score": 1, "selected": false, "text": "<p>I think you are going about this the wrong way.</p>\n\n<p>Send a stealth mission. Build an under-the-ocean plant to produce some long lived, powerful greenhouse gasses like Sulphur Hexafluoride. Release them as quickly as you can make them, leading to a greenhouse effect building up in just a few years - before the inhabitants even realize what is going on.</p>\n\n<p>To expand:</p>\n\n<p>From <a href=\"https://en.wikipedia.org/wiki/Global_warming_potential\" rel=\"nofollow noreferrer\">wikipedia</a>, SF6 has a global warming potential 16,300 times that of CO2. Now, the mass of CO2 in the atmosphere is given as 3x10^12 tonnes <a href=\"https://micpohling.wordpress.com/2007/03/30/math-how-much-co2-by-weight-in-the-atmosphere/\" rel=\"nofollow noreferrer\">here</a>, but that's a recent value for Earth, so you could reasonably, assume 1.5x10^12tonnes for your fictional planet (starting, pre-industrial).</p>\n\n<p>Dividing the CO2 mass by GWP gives roughly 1x10^8 (100 million) tonnes of SF6 for the equivalent of CO2 doubling. Assuming we want a rapid catastrophic greenhouse, you might want ten times this - 1 billion tonnes of SF6. That would represent the smallest load you could deliver directly - a lot, but not totally implausible. Obviously just steering a <a href=\"https://www.real-world-physics-problems.com/asteroid-impact.html\" rel=\"nofollow noreferrer\">billion-tonne impactor</a> into your target planet would be pretty devastating..</p>\n\n<p>World sulphur production is c. <a href=\"http://www.firt.org/sites/default/files/DonMessick_Sulphur_Outlook.pdf\" rel=\"nofollow noreferrer\">80 million tonnes</a>, and Flouring is c. <a href=\"https://en.wikipedia.org/wiki/Fluorochemical_industry\" rel=\"nofollow noreferrer\">2.6 million tonnes</a> a year, so the limit here is the amount of Florine you can obtain. If you wanted to make it in situ, then you'd want your base to be close to a deposit of <a href=\"http://www.minerals.net/mineral/fluorite.aspx\" rel=\"nofollow noreferrer\">Fluorite</a>, extract the Sulphur from seawater, and release the SF6 by diffusion. They'd never know what hit them..</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/106120", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/47669/" ]

[ { "answer_id": 106154, "author": "SK19", "author_id": 46155, "author_profile": "https://worldbuilding.stackexchange.com/users/46155", "pm_score": 2, "selected": false, "text": "<p><strong>Disclaimer:</strong> I'm not a biologist.</p>\n\n<p>Think of DNA as source code for programming. It is read out and executed, thus very important. So if you just add some ID on it, if in your story DNA is not completely understand, it could be very easy to destroy something, just like when you randomly insert a line of code in a software project with million lines of code. Nothing could be changed, or everything could go to hell.</p>\n\n<p>(<strong>EDIT:</strong> <a href=\"https://en.wikipedia.org/wiki/Junk_DNA\" rel=\"nofollow noreferrer\">Junk DNA</a> was mentioned in the comments. It would be a reasonable place for IDs, given you can place it there. As I understand from the Wikipedia article, biologists are still guessing why it exists in the first place, it may as well be important for growth before birth. Money quote: \"Several lines of evidence indicate that some \"junk DNA\" sequences are likely to have unidentified functional activity\")</p>\n\n<p>Also DNA changes over time. Due to different factors like radiation, it is altered and doesn't reproduce like earlier, but with errors. Most obvious example of this is aging, but tumors are also one. So it could as well be that by \"reading out\" the ID, a wrong ID is read out cause it was altered.</p>\n\n<h2>Alternative method</h2>\n\n<p>Here is an idea how you could do it instead: Write the ID inside their skulls. Take out a part of the skull bone, a <strong>random unique</strong> part, carve the number on the inside in, and sew everything together again.</p>\n\n<ol>\n<li>Clearly permanent.</li>\n<li>Difficult to temper with: A single bone can normally replaced by a similar one without the body feeling noticing. But a brain operation is delicate. And since the part of the skull bone is selected random, to temper with it you would have to replicate that exact part (or people could see there are several traces on the skull bone, for which they would only have to open the head, but not the skull). For that, you first need to take it out of the skull to take measurements. For the time being the clone would lie around with exposed brain. A lot of difficulties and problems. The drawback is that it is difficult to carve the number in the first place, but still a lot easier than changing it.</li>\n<li>As long as the operation is done by expert in a sterile environment, there would be no consequences but a scar on the head, usually covered by hair.</li>\n</ol>\n\n<p>Ok, right before posting I notice it would also be very difficult to check the ID (as long as the clone needs to stay alive), but you can circumvent this by encarving the ID on both sides of the skull bone part. Easy check and hard check possible. Another variant would be to only write it on the outside, much less dangerous because no brain exposed (because operations always have a risk), but then again easier to temper with, the random unique traces of the removed skull bone part would be missing.</p>\n\n<p><strong>EDIT:</strong> Another way of checking the encarvings would be a <a href=\"https://en.wikipedia.org/wiki/Magnetic_resonance_imaging\" rel=\"nofollow noreferrer\">MRT</a>. Giving technology for clones is available, it is reasonable that scanning the skull bone is mobile possible too. Today MRTs are done in clinics and can take e.g. half an hour, even that would be reasonable. And if the encarving is filled with some metal e.g. iron and a protective silicon layer so the metal doesn't interact with the rest of the head, this would make checking even easier.</p>\n" }, { "answer_id": 106162, "author": "LSerni", "author_id": 6933, "author_profile": "https://worldbuilding.stackexchange.com/users/6933", "pm_score": 5, "selected": true, "text": "<blockquote>\n <p>Can I use DNA to do this, by simply adding several codons to an existing DNA strand (assuming quick, basically immediate, and accurate Proteinas Chain Reaction - PCR)?</p>\n</blockquote>\n\n<p>Absolutely. A significant percentage (as high as 20% according to some authors) of DNA has no biological activity and is a leftover from ages past. Another 60% has little direct activity (it is non-coding) but <em>might</em> be useful, so let's leave it alone, but that still leaves a lot to play with.</p>\n\n<p>Locate a unused section of a <a href=\"https://en.wikipedia.org/wiki/Pseudogene\" rel=\"nofollow noreferrer\">pseudogene</a> which is very likely to be completely nonfunctional (e.g. the seventh in a run of fifteen useless incomplete repetitions likely due to copying errors in the last twenty million years) and replace it with an equally non-coding sequence. There are some combinations you cannot use to ensure that the sequence won't actully code anything, but you have plenty of space for your needs.</p>\n\n<p>Or if you feel more adventurous, you can use synonymization: several aminoacids are coded <a href=\"https://en.wikipedia.org/wiki/Genetic_code\" rel=\"nofollow noreferrer\">by more than one DNA triplet</a>, and in normal human genetic code, you'll find say GGA for proline. You can then use GGT and GGG in that position to keep everything working (both triplets will code for proline), but at the same time encode either a 0 or a 1. By comparing the known human reference with the clone sequence, you can extract a binary string:</p>\n\n<pre><code>human: TAA GCT GCT CAG CGT \nclone: TAG GCA GCG CAC CGA ...\ncode : 0 1 0 0 1\n</code></pre>\n\n<p>(This form of 'meta-coding' <em>might</em> have biological significance. In <a href=\"https://www.goodreads.com/book/show/264941.Frameshift\" rel=\"nofollow noreferrer\"><em>Frameshift</em> by Robert J. Sawyer</a>, it \"unlocks\" genetic sequences of DNA that trigger evolution - it's a sort of super-code hidden inside DNA).</p>\n\n<p>However, care must be taken to avoid sequences where the synonymization actually allows <a href=\"https://www.genome.gov/27556096/multitasking-dna-dualuse-codons-in-the-human-genome/\" rel=\"nofollow noreferrer\">coding two different and slightly offset DNA messages in the same sequence</a>. </p>\n" }, { "answer_id": 106170, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 2, "selected": false, "text": "<p>The current state of the art version of this is based on <a href=\"https://en.wikipedia.org/wiki/CRISPR\" rel=\"nofollow noreferrer\">CRISPR</a>, which is a set of antiviral genes found in bacteria. They are used today as a powerful tool for gene splicing, where you can identify a location you wish to cut, snip the DNA there, and add content. It's pretty fascinating.</p>\n\n<p>Of course, the big issue with DNA biometrics like this is that if you have the tools to add a serial number, you likely have the tools needed to edit one out. You might develop a <a href=\"https://en.wikipedia.org/wiki/Gattaca\" rel=\"nofollow noreferrer\">GATTACA</a> situation.</p>\n\n<p>Then again, what story involving clones doesn't involve the numbered clones going \"haywire\" and rebelling against being numbered?</p>\n" }, { "answer_id": 106256, "author": "Keith Morrison", "author_id": 38400, "author_profile": "https://worldbuilding.stackexchange.com/users/38400", "pm_score": 1, "selected": false, "text": "<p>Why not simply use an iris or retinal scan to match it to an ID? The patterns in the iris and capillary system in the retina are unique: not even genetically-identical twins have the same patterns, and an individual doesn't even have the same pattern in both eyes, which by definition comes from the same DNA and developed in the same conditions. Fingerprints would work as well, but eye scans can be read at a distance, are harder to fake (since you can beat a fingerprint scanner by duplicating someone else's print) and are subject to fewer issues such as scarring that can affect fingerprints. Hell, use both iris and retinal scans to reduce the possibility of error and potential duplication.</p>\n\n<p>The downside is that you need to maintain a database linking the scans to clone IDs, but that should be fairly trivial thing to deal with if you're at the point of mass-producing clones, and such would be necessary for the option of coding in the DNA anyway. But as an upside, you don't need to do anything to generate the unique identifier: nature does that for the clone already.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/106145", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/45883/" ]

[ { "answer_id": 106468, "author": "Nuloen The Seeker", "author_id": 44624, "author_profile": "https://worldbuilding.stackexchange.com/users/44624", "pm_score": 2, "selected": false, "text": "<p>I would say that there are not any significant differences between these groups. Not significant enough to make any difference in their ability to survive. Any trait that would prove difficult would be compensated for by some tool or clothing. Some groups would endure cold better than others. But that would probably last for just a few generations. \"Asian / mongoloid\" eyelids could prevent some particles from touching the eye, but other groups could just make a better hat, cape, mask or goggles.</p>\n\n<p>Over time their appearance could change, probably making the darker skinned groups more pale. Generally they all should be more hairy. And \"negroid\" lips could get thinner. But that is about it.</p>\n" }, { "answer_id": 106475, "author": "John", "author_id": 29409, "author_profile": "https://worldbuilding.stackexchange.com/users/29409", "pm_score": 3, "selected": false, "text": "<p>If I had to pick one group it would be Negroids becasue most of human genetic variability is within that group, its not a big advantage but I you had to pick one group it would be that one just becasue they have more variability to work with. Of course evolution tends not to parse that way, it will be individual populations that survive and spread not wide racial groups but you are more likely to find the right combination of traits in that group. </p>\n\n<p>But really all those groups will survive equally well, human variability is pretty minor, and so much will depend on other variables, like technology, location, livestock, run up events, etc. But your biggest effect will be which population was living is the most similar conditions you drop them in,the knowledge of the individual's dropped into this situation will have a much bigger effect than anything genetic. </p>\n\n<p>If I drop Bob and Tom in a new environment and Bob was a hunter gather and Tom was a wall street stockbroker, Genetics matters less than the fact Bob knows how to start a fire and Tom does not. </p>\n" }, { "answer_id": 106478, "author": "Carduus", "author_id": 47744, "author_profile": "https://worldbuilding.stackexchange.com/users/47744", "pm_score": 2, "selected": false, "text": "<p>I'd look at body types that already <em>have</em> formed due to ice age conditions: Inuits/Inuvialuits for Asian stock, and Sami for European stock. They both came out fairly differently, depending on their main food source. Inuits survived on pinnipeds and cetaceans, and developed stockier frames and insulating fat to help better keep their core temperatures up. Sami depended on reindeer herding, and thus utilized a more lithe frame and compensated with furs. </p>\n\n<p>The only reasons facial features would play into any of this might be the nose, and the ability to better insulate against heat loss via breathing, but even that would be minor and probably just involve hairier nostrils. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/106461", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/32966/" ]

[ { "answer_id": 107427, "author": "Contramallum", "author_id": 48844, "author_profile": "https://worldbuilding.stackexchange.com/users/48844", "pm_score": -1, "selected": false, "text": "<ol>\n<li><p>No effect. This technique has very limited use given that all communication in that age was via courier. The message and the key would both have to be sent to the same recipient by separate runners, either spaced apart or taking different runners. At best, it would take more time. At worst, if only the message or only the key was delivered, either is useless without the either, resulting in breakdown of command communication. Information security at the age when information travels at the speed of a horse is a very minute factor - especially given the literacy rate at that time period.</p></li>\n<li><p>Even less of an effect. A one-time pad is \"unbreakable\" when used with bits. When used with words and sentences, it is literally as complex as any other substitution cipher - sentences and words have a determinable structure. Not to mention the message and the pad have to have the same number of characters, meaning it can only be used once in an age of limited communication resources - and once again, an age when most people cannot read, much less encrypt and decrypt messages. The method would far, far out-pace the means. </p></li>\n</ol>\n" }, { "answer_id": 107428, "author": "Pingcode", "author_id": 27563, "author_profile": "https://worldbuilding.stackexchange.com/users/27563", "pm_score": 6, "selected": true, "text": "<p>The same problems that a normal one time pad face would be faced by our hypothetical Caesar.</p>\n\n<p>Namely, if you want to send me a message, I need to have:</p>\n\n<ol>\n<li>A one time pad at least as long as your message (or, if we're willing to settle for a shorter cipher, as many ciphers as you have messages)</li>\n<li>Received every message you've sent me up until your current one (and both of us destroying pads once they've been used)</li>\n<li>Successfully hidden my one time pad from the enemy</li>\n</ol>\n\n<p>This creates a tricky situation. If I run out of pad, you can't send me more messages without somehow getting me a new pad.</p>\n\n<p>If a message gets intercepted, you need to somehow figure that out and tell me how much I need to increment by. We can get around this by, say, discarding a page every day or numbering the pads, but this means a lot more pad and leads into the third problem:</p>\n\n<p>I need to hide at least twice as many documents as you're sending. To decode a letter I need the letter and its key. That's two documents I could be caught with and executed for, and two documents that might be intercepted, either of which would ruin the message.</p>\n\n<p>With all that said, it probably wouldn't see a great deal of use outside of very special circumstances where it's better to lose the information outright rather than risk discovery- internal affairs rather than wars. A regional governor has perverse tastes, and if discovered the province could revolt. Still the agent needs to inform their superior so it can be handled discreetly, so the one time pad is used.</p>\n\n<p>In crisis situations they probably wouldn't be used - if the byzantine generals are trying to coordinate, losing the critical message to a messenger being intercepted is worse than the defenders getting hold of the plan.</p>\n\n<p>Of note, the message loss problem can be solved if I retain used pads to decode corrupted messages and cope with messages arriving out of order, but this then becomes more of a codebook than a one time pad. For the circumstances we would want to use a one time pad (ie. where we would prefer for nobody to know the message over the proverbial Eve knowing it) it represents something of an unwelcome risk.</p>\n" }, { "answer_id": 107433, "author": "Ville Niemi", "author_id": 3434, "author_profile": "https://worldbuilding.stackexchange.com/users/3434", "pm_score": 5, "selected": false, "text": "<p>I'll go with \"<strong>No effect</strong>\".</p>\n\n<p>The value of modern encryption lies with our use of telecommunications. Our messages can generally be intercepted by hostile agents without any real method to prevent or detect that. This creates a need for a method to secure the actual communications independent of the medium being insecure.</p>\n\n<p>The Romans did not have that. Their messages were carried by human couriers, who would guard the messages. The messages themselves would be physical objects secured against tampering with seals. Provisions would be made to destroy the messages, if capture seemed imminent.</p>\n\n<p>A system like that is as secure as the people involved. No system for communicating between people can improve on that. The best you can do is to minimize the number of people with access to the messages. Securing the physical messages against tampering and using guards actually works here. You do not need to be able to read the message or have any knowledge of codes used to guard or deliver it.</p>\n\n<p>In fact, a more complex encryption such as OTP would be <strong>less</strong> secure. Somebody needs to write those pads, they need to be transported to correct location and then stored and secured there. And the actual encryption and decryption would be labor intensive enough to probably require additional people to deal with it.</p>\n\n<p>People who can be bribed or just captured and tortured. And without the pads, messages are useless, so bribing any of the people involved with the pads to sabotage them will be quite devastating. And if people start to believe the system is secure, the security will suffer. <a href=\"https://en.wikipedia.org/wiki/Enigma_machine\" rel=\"noreferrer\">Enigma</a> taught us that.</p>\n\n<p>By contrast a very simple cipher such as the one Caesar actually used can be memorized and decoded directly by the recipient. While the added security is fairly small, it comes without added complexity or vulnerability. And with the constant presence of servants, slaves, and guards a cipher that simply stops people reading over your shoulder does have real value.</p>\n\n<p>And OTP cannot do that. It cannot be read directly by most people. You have to decode it and then read it. Which means a physical copy of the decoded plain text needs to exist during both encoding and decoding.</p>\n\n<p>The bottom line is that for the needs the Romans actually had the Caesar cipher is actually superior to one time pad. Which kind of makes sense, the ancient world had some extremely smart people and Caesar was fairly well educated. If he had wanted a code that is harder to break, he would have been able to get one.</p>\n" }, { "answer_id": 107442, "author": "Konrad Rudolph", "author_id": 14553, "author_profile": "https://worldbuilding.stackexchange.com/users/14553", "pm_score": 3, "selected": false, "text": "<p>As mentioned by others, a full-blown OTP is unpractical.</p>\n\n<p>However, <a href=\"https://en.wikipedia.org/wiki/Vigen%C3%A8re_cipher\" rel=\"noreferrer\">there’s a middle way</a>, invented by <a href=\"https://en.wikipedia.org/wiki/Blaise_de_Vigen%C3%A8re\" rel=\"noreferrer\">Blaise de Vigenère</a> in the XVIth century in France.</p>\n\n<p>The Vigenère cypher <a href=\"https://en.wikipedia.org/wiki/Friedrich_Kasiski\" rel=\"noreferrer\">is crackable using modern cryptanalysis</a> but for a very long time it proved formidable. If it had been invented — and used — a few centuries earlier, this could have changed the course of history. I shan’t enumerate all historical events that relied on broken private communication (for a fun account, I recommend <a href=\"https://en.wikipedia.org/wiki/The_Code_Book\" rel=\"noreferrer\"><em>The Code Book</em></a> by Simon Singh), and I can’t speculate about the influence that better cypher would have had.</p>\n\n<p>What’s interesting is that even after the invention of the Vigenère cypher, <a href=\"https://en.wikipedia.org/wiki/Great_Cipher\" rel=\"noreferrer\">strictly inferior systems</a> remained in widespread use, even for communications of the utmost importance and secrecy. Of course these were soon broken.</p>\n\n<p>Throughout history, there’s been an arms race between cryptographer and cryptanalyst. Whenever a stronger cryptography was developed (and used), the onus was on the attacker to break it. And when a cypher was broken, there was need to develop better cryptography.</p>\n\n<p>I therefore think that the biggest influence, if Caesar had known about the Vigenère cypher, would have been on the development of modern mathematics and statistics: attackers would have spent more time thinking about how to analyse text to break the cypher. And, in doing so, they would by necessity have to invent methods of working with discrete distributions of events.</p>\n\n<p>Modern statistics was almost exclusively developed in the last 200 years. Recently its use has become ubiquitous and powerful (data science? statistics. AI? statistics. … the list goes on).</p>\n\n<p>Now imagine modern statistical tools had been invented 1000 years earlier.</p>\n\n<p>_{There’s a big caveat in my speculation: even without “big data”, modern statistics relies heavily on computers for tabulation and computation. Their use is severely curtailed lacking these mechanical aids.\n Nevertheless, statistical <em>thinking</em> would have had a drastic effect on the development of science and technology.}</p>\n" }, { "answer_id": 107449, "author": "Censored to protect the guilty", "author_id": 27956, "author_profile": "https://worldbuilding.stackexchange.com/users/27956", "pm_score": 1, "selected": false, "text": "<p>I think OTP would be perfectly useless. </p>\n\n<p>Gauls were barely literate. The odds of them deploying sophisticated techniques were exactly zero.</p>\n\n<p>It's quite possible that any pad would have make the message <strong>less</strong> secure by introducing an extra point of failure.</p>\n" }, { "answer_id": 107475, "author": "John Coleman", "author_id": 27940, "author_profile": "https://worldbuilding.stackexchange.com/users/27940", "pm_score": 1, "selected": false, "text": "<p>I would go with no effect -- unless you tweak the scenario. There is no intrinsic reason why the Roman Empire couldn't have had a functioning <a href=\"https://en.wikipedia.org/wiki/Semaphore_line\" rel=\"nofollow noreferrer\">optical telegraph</a> system connecting Rome with points several hundred miles away. Such optical communication would be vulnerable to interception so would require some form of encryption to function effectively. In an alternative history, the security of such optical communication could play a role (e.g. Roman troops ambushed because an attacker knew their route before hand). A one time pad seems to be overkill, but as others have pointed out it something like a Vigenère cipher would have given reasonable security at the time.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/107426", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/20149/" ]

[ { "answer_id": 108027, "author": "AndyD273", "author_id": 6751, "author_profile": "https://worldbuilding.stackexchange.com/users/6751", "pm_score": 3, "selected": false, "text": "<p>So, to get a couple comments out of the way first, I'm not really sure why you would want to rob the train from another train (except for the rule of cool), especially since they are traveling so slow. I can totally see there being a Mad Max style thing where a racing vehicle drives up next to the train, someone jumps out of the vehicle onto the train, and either takes the engine, or decouples some cars so they can be looted. \nAlternately they could also just come up behind them with a train on the same track, have someone jump forward to the target train, and take it over, so they don't have to worry about oncoming trains.</p>\n\n<p>But those are both just comments, and don't answer the question.</p>\n\n<p>So part of the problem is that freight trains are not meant to be stopped and started or reversed quickly. It's just not their purpose. </p>\n\n<p>They need to be able to have as little rolling resistance as possible, and with all that weight you potentially have miles of distance before you come to a complete stop.</p>\n\n<p>But the pirate train needs to be able to get up to speed quickly, stop quickly, reverse quickly, and doesn't have to be big or heavy. So instead of a freight train, it could be a passenger train, which by definition need to be able to do all of those things. </p>\n\n<p><a href=\"https://www.youtube.com/watch?v=gVpucnA6Pq8\" rel=\"noreferrer\">They can even go from 80 kph to 0 in less than 20 seconds</a>.</p>\n\n<p>You strip out the seats, put some tie downs inside, gun emplacements on top, and it has everything you need.</p>\n" }, { "answer_id": 108034, "author": "TKOW", "author_id": 43646, "author_profile": "https://worldbuilding.stackexchange.com/users/43646", "pm_score": 3, "selected": false, "text": "<p><strong>An Anchor</strong></p>\n\n<p>Or a modified arresting gear, to be precise. These systems are used regularly to stop 50,000 lbs/23,000 kg aircraft going 150 mph/240kph in less than 300 ft/100 m.</p>\n\n<p>A scaled up version suitable for a locomotive and a boxcar could function like this:</p>\n\n<ul>\n<li><p>opposing train is spotted</p></li>\n<li><p>\"anchors\" are dropped into the ground by some device, possibly hydraulic in nature</p></li>\n<li><p>arresting wire spools from the engine as it brings the locomotive to a halt (some slack should be necessary to prevent snapping the wire of giving the Spoorcaneers whiplash)</p></li>\n<li><p>after locomotive and car are brought to a halt, the arresting gear can now be used a slingshot to launch the locomotive and car in the other direction</p></li>\n<li><p>arresting wire and anchors are collected by the Spoorcaneers return passage, ready to be used for the next close call</p></li>\n</ul>\n\n<p>Lighter and smaller locomotives would also be more beneficial in this setup since there is less weight and inertia working against the arresting system.</p>\n\n<p>Faster speeds would be possible with more wire, stronger arresting system, etc.</p>\n\n<p>Damage to track and train in virtually null, since breaking occurs independent of both.</p>\n\n<p>Could lead to some unfortunate accidents where the wire breaks, or close calls where an infamous Spoorcaneer survived with only one wire. Might also be the origin of the saying \"It came down to the wire\", though some pre-war records disagree.</p>\n\n<p><strong>Or a Bunch of Wheels</strong></p>\n\n<p>If you're looking for a more grounded option, I would suggest you just add more wheels to the engine and car. The crucial part that makes railroads such effective at mass transportation is how little rolling resistance there is. An entire, 50+ car train may have no more contact with that ground than the surface area of a coffee table. If you're going to slow it down, you need to increase your contact with the ground. Adding a bunch of wheels does that.</p>\n" }, { "answer_id": 108041, "author": "ibrewster", "author_id": 32507, "author_profile": "https://worldbuilding.stackexchange.com/users/32507", "pm_score": 2, "selected": false, "text": "<p>How about rockets? Something akin to the JATO rockets the military uses on some aircraft (<a href=\"https://en.wikipedia.org/wiki/JATO\" rel=\"nofollow noreferrer\">Wikipedia page</a>). Have a couple of sets of those installed on the train, pointing in different directions, and you could (more) quickly stop/accelerate in either direction.</p>\n\n<p>As an added bonus, if the oncoming train is a police train (or the like), you can just wait a little longer to fire off the rockets. Not only do you get stoped and reversed before crashing, but the rockets can blind/disorient/fry the oncoming train at the same time!</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/108021", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/2746/" ]

[ { "answer_id": 110494, "author": "ArtificialSoul", "author_id": 44086, "author_profile": "https://worldbuilding.stackexchange.com/users/44086", "pm_score": 3, "selected": false, "text": "<h3>Apparently not</h3>\n\n<p>I have been searching and the only answers I have found are already mentioned in this <a href=\"https://www.reddit.com/r/conlangs/comments/1mwn9u/are_there_any_open_source_fantasy_languages/?st=jgexp6hp&amp;sh=be61dd80\" rel=\"nofollow noreferrer\">reddit-thread</a>.</p>\n\n<blockquote>\n <p>Quenya, Sindarin, and all other languages by J. R. R. Tolkien are copyrighted until January 1st, 2074.</p>\n</blockquote>\n\n<p>Everything appears to be \"copyrighted\".</p>\n\n<p>Just a few might not be. I have not checked all the details of <em><a href=\"https://de.wikipedia.org/wiki/L%C3%A1adan\" rel=\"nofollow noreferrer\">Láadan</a></em> and <em><a href=\"http://divinelanguage.webs.com/divinianthebook.htm\" rel=\"nofollow noreferrer\">Divinian</a></em> yet, but I have not quickly found anything about those being copyrighted or not.</p>\n\n<p>Most authors do not go the full path of creating an entire language and those that do tend to copyright it. Can't really blame them, it's a huge effort.</p>\n\n<p><strong>EDIT</strong>:<br>\nTo my knowledge you can not just copyright a language. You can copyright publications of any sort, but the a language is nothing you can publish or copy in that sense.</p>\n\n<p>However, using a fictional language of someone else (in copyrighted material) could probably get you in legal trouble anyway. Just like copying the entire storyline and scenario of The Hunger Games and changing all the names of people, locations, parties, technologies, etc. would probably get you into trouble.</p>\n\n<p>If there is a legal expert on this to clarify whether taking such a significant, recognisable part of copyrighted material and just using it for your own publications gets you into trouble, listen to them.<br>\nBut I definitely see a possibility of this getting you into trouble, so I would advise against it.</p>\n\n<p><strong>EDIT2:</strong><br>\nUser jeffronicus just found something and posted it as a comment, but since it is relevant I will add it here.</p>\n\n<blockquote>\n <p>Relevant Tolkien-related post by someone familiar with copyright law: \"Know Your Rights: Copyright Law for the Creator of Fan Works,\" <a href=\"http://www.theodoramichaels.com/articles/fan-fic.php\" rel=\"nofollow noreferrer\">theodoramichaels.com/articles/fan-fic.php</a>: \"Cathleen Blackburn replied to me as follows: 'In relation to Quenya and other Elvish languages, the Tolkien Estate takes the position that these are copyright works and, accordingly, a licence is required for any uses of them which would otherwise amount to copyright infringement.'\" It's unlikely a publishing house would take the risk.</p>\n</blockquote>\n" }, { "answer_id": 110511, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 7, "selected": true, "text": "<h1>All Elvish is (probably) open source (in the US)</h1>\n\n<p>There is a real legal history of battles over open source languages, two threads of which are relevant here. The first is that the US court system has definitively ruled that it is not a violation of a constructed computer programming language's copyright to write a new computer program using the same language and grammar. Although there have been no definitive cases regarding 'conlangs' (constructed languages), the other thread is the situation of the legal battle over <em><a href=\"https://en.wikipedia.org/wiki/Prelude_to_Axanar\" rel=\"noreferrer\">Prelude to Axanar</a></em>. </p>\n\n<h3>General background information</h3>\n\n<p>There was a journal of Tolkien's linguistics titled <em><a href=\"http://tolkiengateway.net/wiki/Tyali%C3%AB_Tyelelli%C3%A9va\" rel=\"noreferrer\">Tyalië Tyelelliéva</a></em>, originally hosted on GeoCities and now gone. This journal published original works in Tolkien's languages in addition to other analysis, but evidently ran afoul of Tolkien's estate which in 1999 took the stance that Quenya and Sindarin in particular (and presumably all Tolkien's languages in general) were copyrighted. </p>\n\n<p>The journal publishers sought the legal advice of the General Counsel of the National Endowment of the Arts who sent back a legal opinion. <a href=\"http://www.oocities.org/athens/parthenon/9902/legalop.html\" rel=\"noreferrer\">Here</a> is the only link I could find of this opinion; much of the hard evidence of this whole situation is shrouded in the mists of lost GeoCities. The main points of the opinion were these:</p>\n\n<ul>\n<li><p>Words, short phrases, names, symbols, typefaces, and variations of lettering are not subject to copyright protection by <a href=\"https://www.copyright.gov/title37/202/37cfr202-1.html\" rel=\"noreferrer\">37 C.F.R. 202.1 (1974)</a> [that is the title of a US Congressional act]</p></li>\n<li><p>\"In no case does copyright protection for an original work of authorship extend to any idea, procedure, process, system, method of operation, concept, principle, or discovery, regardless of the form in which it is described, explained, illustrated, or embodied in such work.\" (<a href=\"https://www.copyright.gov/title17/92chap1.html\" rel=\"noreferrer\">17 U.S.C. 102(b)</a>).</p></li>\n<li><p>Tolkien's languages, by his own self-admission, derive significantly from extant or extinct world languages, which are of course not copyright-able. The fact that many proper nouns like 'Osgiliath,'Theoden', and 'Celebrian' have an origin in real, historical languages makes claims of 'originality,' which is a necessary pre-requisite of copyright, difficult to establish. </p></li>\n<li><p>\"...the fair use of a copyrighted work, including such use by reproduction in copies or phonorecords or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright.\" (<a href=\"https://www.copyright.gov/title17/92chap1.html#107\" rel=\"noreferrer\">Title 17 U.S.C. 107</a>) The author of the legal opinion thinks that a journal with original poetry constitutes fair use. </p></li>\n</ul>\n\n<p>The journal in question here evidently folded around 2001, and no court proceedings (so far as I can determine) were filed on either side, so this is just background information and not legally binding. </p>\n\n<p>For more background information, a more exhausting study was made by <em><a href=\"https://consumermediallc.files.wordpress.com/2016/04/27harvjltech543.pdf\" rel=\"noreferrer\">Harvard Law Review</a></em> in 2014. A longer read, this summarized existing conlang legal actions (there have been none that actually went to court), and comes to the conclusion that copyright law is ill-suited to regulation of a constructed language, although it stops sort of giving an opinion on the legality of third-party usage of a constructed language. </p>\n\n<h3>The case of computer programming languages</h3>\n\n<p>In general, the grammatical principles of a computer language are not copyrightable. If a Python 'Hello World' program looks like </p>\n\n<pre><code>print(\"Hello World\")\n</code></pre>\n\n<p>there is nothing preventing me from writing a programming language and/or compiler that uses the exact same syntax to create the exact same effect. This is the decision of <a href=\"https://scholar.google.com/scholar_case?case=6976925648486076739&amp;hl=en&amp;as_sdt=6,47&amp;as_vis=1\" rel=\"noreferrer\">Computer Assocs. Int'l, Inc. v. Altai, Inc., 982 F.2d 693, 720-21 (2d Cir.1992)</a>. Following the Supreme Court decision <a href=\"https://scholar.google.com/scholar_case?case=16308210976883953911&amp;hl=en&amp;as_sdt=6,47&amp;as_vis=1\" rel=\"noreferrer\">Baker vs. Selden</a> which \"denies copyright protection to expression necessarily incidental to the idea being expressed\", this case settled on the 'merger doctrine' which states that </p>\n\n<blockquote>\n <p>[C]opyrighted language may be copied without infringing when there is\n but a limited number of ways to express a given idea.... In the\n computer context, this means that when specific instructions, even\n though previously copyrighted, are the only and essential means of\n accomplishing a given task, their later use by another will not amount\n to infringement.</p>\n</blockquote>\n\n<p>So if my programming language wants to use the exact syntax </p>\n\n<pre><code>print(\"Hello World\")\n</code></pre>\n\n<p>there are only a limited number of way to express this idea, and I can copy a copyrighted work (such as a copyrighted Python program that uses that exact line of code) without infringing on the copyright. </p>\n\n<p>By this logic, if a court would apply it to conlangs, which has not yet been done, I could copy Sindarin sentance structure, even if Sindarin has a valid copyright, without infringing; thereby allowing me to generate original works.</p>\n\n<h3>The case of <em>Prelude to Axanar</em></h3>\n\n<p>There have long been Star Trek fan films, mostly (in my opinion) terrible. Evidently, Axanar was to be a fan film with a budget of over $1 million, some serious production values, support of Important Star Trek People like George Takei, and even some actors who had appeared in other Star Trek movies. Paramount, which had hitherto been relatively tolerant of fan films, sued for copyright infringement. Paramount had a <a href=\"https://www.washingtonpost.com/news/volokh-conspiracy/wp/2017/01/09/copyright-in-klingon/?noredirect=on&amp;utm_term=.dd942aba40ab\" rel=\"noreferrer\">pretty strong case</a>, since characters like Garth of Izar and fictional races like Vulcans and Klingons are pretty clearly copyright-able. Eventually, the <a href=\"https://en.wikipedia.org/wiki/Prelude_to_Axanar#Lawsuit\" rel=\"noreferrer\">case was settled</a> in 2017.</p>\n\n<p>However, in the course of the lawsuit, Paramount asserted a claim to control over the fictional languages. Sort of. This was probably never a claim that Paramount really wanted to make, but was just involved in the legal claptrap. The Language Creation Society (LCS) filed an <a href=\"https://drive.google.com/file/d/0BzmetJxi-p0VM19nbUpyNXE0a28/view\" rel=\"noreferrer\">amicus brief</a> stating that conlangs were not copyrightable, and the defendants (the producers of <em>Axanar</em>) <a href=\"https://torrentfreak.com/images/lim.pdf\" rel=\"noreferrer\">filed a motion</a> that also said in part that the Klingon language could not be copyrighted. The defendent's motion was accepted by the court, so the copyright issue over the constructed language was excluded; the LCS's amicus brief was then <a href=\"https://drive.google.com/file/d/0BzmetJxi-p0VN0t5MWNPOTZ4SU0/view\" rel=\"noreferrer\">rejected</a> by the court as not applicable. </p>\n\n<p>Ultimately, this case decided nothing. Paramount had a strong case with characters and races and organizations and probably wasn't willing to risk a negative opinion on constructed languages. If anyone is going to file a lawsuit to get open use of a constructed language, it won't be about Klingon since Paramount is a lot richer than the inventor of any other conlangs. But it is relevant that the judge was willing to accept the defendant's reasoning which referenced the same <em>Baker vs Selden</em> which provided the precedent with computer programming languages. </p>\n\n<h1>Conclusion</h1>\n\n<p>There is no official court decision on whether the grammar and vocabulary of a constructed language, being utilitarian in nature, can be copyrighted. However, there is some good evidence and legal opinions that, in the US at least, such copyright laws would not apply.</p>\n\n<p>Of course someone has to test this in court. Maybe it could be you? If Tolkien's estate comes knocking, you could fire up a GoFundMe and appeal to all the language nerds out there. <em>Your Name vs Tolkien</em> would get its own Wikipedia page and article in the Harvard Law Review...you'd be famous!</p>\n" }, { "answer_id": 110524, "author": "AndyD273", "author_id": 6751, "author_profile": "https://worldbuilding.stackexchange.com/users/6751", "pm_score": 5, "selected": false, "text": "<p>You could also use an <a href=\"https://en.wikipedia.org/wiki/Extinct_language\" rel=\"noreferrer\">extinct language</a> that no one speaks anymore. There are hundreds <a href=\"https://en.wikipedia.org/wiki/Lists_of_extinct_languages\" rel=\"noreferrer\">to choose from</a>.<br>\nBeing a real language removes any legal issues, gives you all kinds of real grammar and everyday words instead of just the ones that are needed for the story. \nAnd best of all, if your work becomes popular and people start learning it, you could be helping to raise a language from the dead.</p>\n" }, { "answer_id": 110528, "author": "Chris Johns", "author_id": 17895, "author_profile": "https://worldbuilding.stackexchange.com/users/17895", "pm_score": 3, "selected": false, "text": "<p>The question of copyright on synthetic languages is an interesting one, on one hand concepts and names aren't generally subject to copyright but on the other hand there is a reasonable argument that a constructed language as a whole is an original creative work and would seem to fall at least within the intent of copyright law.</p>\n\n<p>One possibility is to choose a real language find a systematic way to modify it for example by substituting certain vowels, consonants or word endings. This tends to happen naturally in language development anyway and so should work reasonably well. </p>\n\n<p>A good starting point is the Norther European language family of which Old English and Old Norse are members. In fact Tolkien was a professor of Anglo-Saxon and a lot of his constructed languages are at least inspired by this family. </p>\n\n<p>A good candidate is modern Icelandic as this is probably the closest to Old Norse which is still spoken so there are plenty of resources for it easily available. To me Icelandic sounds a bit smoother and more elf-like than say Norwegian and doesn't has the same pronounced up and down cadence. </p>\n\n<p>For example you could modify it by replacing the <strong>k</strong> with (soft) <strong>c</strong> the <strong>tt</strong> with <strong>l</strong> or <strong>ll</strong> and the leading <strong>H</strong> with <strong>D</strong> or <strong>S</strong> just to make it look a bit different on paper and mellow the pronunciation a bit. </p>\n" }, { "answer_id": 110530, "author": "TRiG", "author_id": 223, "author_profile": "https://worldbuilding.stackexchange.com/users/223", "pm_score": 3, "selected": false, "text": "<p>Most conlangs are the work of one person. Whatever the legalities, it would be odd to borrow them for a new work. However, there are ongoing efforts in many conlanging communities (such as Reddit’s <a href=\"https://reddit.com/r/conlangs\" rel=\"noreferrer\">/r/conlangs</a>), to construct conlangs within the community, with no one owner, open for use by anyone. There are a couple of active projects on Reddit, and no doubt also a few elsewhere.</p>\n" }, { "answer_id": 110604, "author": "Flummox - don't be evil SE", "author_id": 34012, "author_profile": "https://worldbuilding.stackexchange.com/users/34012", "pm_score": 2, "selected": false, "text": "<p><strong>The first</strong> thing that came to mind were constructed languages, the <a href=\"https://en.wikipedia.org/wiki/Constructed_language\" rel=\"nofollow noreferrer\">wiki</a> on it is a great thing to read.</p>\n\n<p>Suggested constructed languages to use:</p>\n\n<ul>\n<li><a href=\"https://en.wikipedia.org/wiki/Esperanto\" rel=\"nofollow noreferrer\">Esperanto</a></li>\n<li><a href=\"https://en.wikipedia.org/wiki/Occidental_language\" rel=\"nofollow noreferrer\">Occidental</a> </li>\n</ul>\n\n<p><strong>The second</strong> idea is languages from a different language group then the writers. As this is in English, use a Celtic language, or better yet, a <a href=\"https://en.wikipedia.org/wiki/Language_isolate\" rel=\"nofollow noreferrer\">language isolate</a>.</p>\n\n<p>Suggested languages from different groups:</p>\n\n<ul>\n<li><a href=\"https://en.wikipedia.org/wiki/Breton_language\" rel=\"nofollow noreferrer\">Breton</a> (Celtic)</li>\n<li><a href=\"https://en.wikipedia.org/wiki/Basque_language\" rel=\"nofollow noreferrer\">Basque</a> (Isolate)</li>\n<li><a href=\"https://en.wikipedia.org/wiki/Bangime_language\" rel=\"nofollow noreferrer\">Bangime</a> (Isolate / <a href=\"https://en.wikipedia.org/wiki/Anti-language\" rel=\"nofollow noreferrer\">possible anti-language</a>)</li>\n</ul>\n\n<p><strong>Thirdly</strong>, elvish uses a different script. That helps a lot with making it foreign to the reader. Now, the Bangime language does have different letters then the Latin (adapted) script used to write English. I would like to suggest to use at least a different font for your 'elvish' language.</p>\n\n<p>A variation to that, as unknown scripts are very hard to read, is to write your 'elvish' phoneticly. That way the reader gets a sense for how it sounds.</p>\n\n<hr>\n\n<p>As to copy rights, most (natural) languages do not have one on them. They are in the public domain. And other answers go into details on 'Tolkien elvish\".</p>\n" }, { "answer_id": 110605, "author": "Sir Cornflakes", "author_id": 19004, "author_profile": "https://worldbuilding.stackexchange.com/users/19004", "pm_score": 3, "selected": false, "text": "<p>Taking the legal problems aside, another problem is to find a conlang that really satisfies your needs in terms of vocabulary and grammar available. Answers to <a href=\"https://conlang.stackexchange.com/questions/539/are-there-speech-communities-for-tolkiens-elvish-languages\">this question on conlang.se</a> suggest that the account of Tolkien's Elvish languages is too sparse to be really useful. Even for the <em>Lord of the Rings</em> films and the <em>Hobbit</em> films, new Elvish words were created by the linguist David Salo.</p>\n\n<p>So there are currently two options left: Design an Elvish language on your own or <a href=\"https://conlang.stackexchange.com/questions/507/how-can-i-become-a-professional-conlang-designer\">let someone else create a conlang for you</a>.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/110493", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/49533/" ]

[ { "answer_id": 110973, "author": "abestrange", "author_id": 49104, "author_profile": "https://worldbuilding.stackexchange.com/users/49104", "pm_score": 4, "selected": true, "text": "<p>Edit: I did make a math error, the points below still stand though.</p>\n\n<p>No. The solar wind pressure simply isn't strong enough to stop you. </p>\n\n<p>Making larger sails would increase the force applied to your ship, but would well surpass known material shear strengths and would destroy itself. </p>\n\n<p>Assume a constant acceleration for simplicities sake and we can use:<br>\n$DeltaX = 1/2*Acc*Time^2 + Vel_{initial}*time$<br>\n$Acc = (Vel_{final} - Vel_{initial})/time$ </p>\n\n<p>Rearranging those gives us \n$Acc = (V_f-V_i)*(v_f+v_i)/(2*deltaX)$</p>\n\n<p>Using\n$V_f = 250,000 KpH = 67444.4 m/s$<br>\n$V_i = 0.05*c = 0.05*3*10^8 =$ <del>45,000,000</del> $15,000,000 m/s$<br>\n$DeltaX = 40 AU = 40*149,597,870,700 = 5,983,914,828,000 m$ </p>\n\n<p>We get an acceleration of <del>-169 m/s^2, or about 17 g's.</del> $18.8m/s^2$ or 1.9 g's</p>\n\n<p>Humans can't really survive more than a couple g's for extended durations. </p>\n\n<p>This example is assuming a constant acceleration, which is even worse for our real life use case. </p>\n\n<p>The solar flux is going to fall off with the inverse square law over distance, so at 40 AU it is going to be ~1600 times weaker than it is at 1 AU. </p>\n\n<p>Achieving 17 g's of average acceleration over our distance will require a gentle deceleration at the start of our journey and a massive amount of force near the end as the solar wind density increases. This will absolutely shatter any plausible sail support structure and kill your crew.</p>\n\n<p><del>0.05 c is probably too fast for any inhabited ship to decelerate from in 40 AU. </del> Uncomfortable but survivable.</p>\n\n<p><del>If you can take it down by a factor of 10, to 0.005c, then the required average acceleration is -0.187m/s^2, which enters into the realm of plausibility for a large enough sail.</del><br>\n -0.187m/s^2 is still way outside the realm of plausibility for our situation.</p>\n\n<p><strong>Addendum: \nSo the numbers above are a bit off, and our required acceleration would be survivable, so I decided to run even further to see what the necessary pressure from our solar wind would be.</strong></p>\n\n<p>$Force = mass*Acc$<br>\n$Pressure = Force/Area = mass*Acc / Area $ \n$Pressure = 5,000,000kg * 18.8m/s^2 / ( 40*1000^2 m^2) = 2.345 N/m^2$</p>\n\n<p>The typical pressure from solar wind at 1 AU is $6*10^{-9} N/m^2$, our required average pressure is $2.345 N/m^2$ , almost 9 full orders of magnitude higher. </p>\n\n<p>Keep in mind that the average solar wind pressure will be around $3.75*10^{-12} N/m^2$ at 40AU, thanks on the inverse square law, and our situation really looks bleak.</p>\n\n<p>To achieve our necessary acceleration will require a surface area of:<br>\n$Force = Pressure*Area = Mass*Acc $<br>\n$Area = Mass*Acc / Pressure = 5,000,000kg * 18.8m/s^2 / 6*10^{-9} N/m^2$<br>\n$Area = 1.56 * 10^{16} m^2 = 1.56*10^{10} km^2 $ </p>\n\n<p>That's a square sail with side length 125,166 km, which would require MUCH more mass than we are accounting for. </p>\n\n<p>Using 0.005 c we still need a sail that is a disk with a radius of 7054km, which is a bit bigger than the Earth's radius. </p>\n\n<p>And remember thats assuming we have a constant flux equal to that at 1 AU. In reality its much worse. Solar wind is simply not dense enough to slow you down appreciably, especially when you factor that the sun's gravity will be accelerating you towards it, probably with more force than our sail can generate. </p>\n\n<p>To slow down your craft, you will have to eject mass. Forcefully jettisoning your sail will probably net you more deltaV than trying to use it.</p>\n\n<p>If you have a magnetic acceleration cannon of any type, start scrapping unnecessary (non-vital) modules of your ship and firing them at max power straight ahead. Venting atmosphere will help too. Good luck. </p>\n" }, { "answer_id": 110984, "author": "Vashu", "author_id": 30579, "author_profile": "https://worldbuilding.stackexchange.com/users/30579", "pm_score": 2, "selected": false, "text": "<p>Solar sail - unlikely. <a href=\"https://www.quora.com/Could-it-be-possible-to-ride-cosmic-winds-as-a-means-of-space-travel\" rel=\"nofollow noreferrer\">Here</a> is an example of ship's project that would be able to reach 0.00264c(20 times less than you need). To increase delta-v 20 times you would need rather big technology leap.</p>\n\n<p>Magnetic sail is better because it is mostly made from magnetic field, that is pretty much weightless. There are <a href=\"https://arxiv.org/pdf/1603.03015.pdf\" rel=\"nofollow noreferrer\">some projects</a> that are able to decelerate from 5% c using existing technology.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/110967", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/40609/" ]

[ { "answer_id": 112650, "author": "The Square-Cube Law", "author_id": 21222, "author_profile": "https://worldbuilding.stackexchange.com/users/21222", "pm_score": 2, "selected": false, "text": "<p>I don't think Stark is an average intelligent person. His command of science is matched pheraps by only two other heroes in his world.</p>\n<p>That said, how do you rate yourself as an RTS (real time strategy) player? There are some games where you can control a considerably large army. I have not played such games in years - not my favorite type, really. But I did play some that I am reminded of, when reading your question:</p>\n<ul>\n<li>The Age of Empires series;</li>\n<li>Starcraft 2;</li>\n<li>Arcworld 3;</li>\n<li>The Total War series.</li>\n</ul>\n<p>All of these will allow you to control hundreds of units at a time. A hundred units might be a large battle in Starcraft, but it would be the smallest thing in Total War. In the latter you can have battles where you control dozens of thousands of soldiers - this is made easier because you give commands to units of up to a hundred men as if they were one. I imagine it as giving orders to the unit commanders.</p>\n<p>So... I think the mental effort would be the same, possibly made slightly easier by a more efficient user interface since you are hooking the character to the units directly by brain link. There is only so much that a regular human can focus at a time. But go watch some ranked matches from professional Starcraft players in Korea to see some superhuman feats of army micromanagement.</p>\n" }, { "answer_id": 112664, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 3, "selected": true, "text": "<p>The issue is not controlling the army, but the limitations of your instructions. If you permit more powerful instructions, the job gets much easier.</p>\n\n<p>The issue is not the act of barking orders like \"If Machine is not dealing any damage, move forward.\" That could be done. The difficult issue is whether or not following that order is a good idea. Presumably each creature has access to sensory information about the world around it. That sensor information is <em>crucial</em> in combat for deciding what to do. Otherwise you could get into situations where the machine is not dealing damage, but moving forward is moving into a trap.</p>\n\n<p>Collecting this kind of sensor information <em>is</em> well beyond what the human mind can do. I did the calculations a while back, and you can estimate the data processing capabilities of the brain at about 1Gb/s (based on the diameter of the spinal column and a whole lot of handwaving). That's a lot of data! </p>\n\n<p>If we use this with your army size of 12,000, we can reasonably expect that datalinks on the order of about 83Kb/s would completely saturate the human mind. The human retina outputs about 10,000Kb/s!</p>\n\n<p>The solution can be seen in the human mind. The conscious mind can handle about 120 bits/s (give or take... its a very rough heuristic). It relies on the subconscious parts of the brain to handle the remaining 999,999,880 bit/s. That information is processed locally, in smaller groups of neurons. Some of the information is relayed up to the conscious mind but the vast majority is handled locally. When you touch a hot stove, your hand begins pulling back before your brain even registers that it's hot. That actually gets initiated in the spinal column to save time!</p>\n\n<p>Likewise, your nanobot creatures should take over some of the processing as well. They should have decently advanced AIs. Consider what <a href=\"https://www.youtube.com/watch?v=rVlhMGQgDkY\" rel=\"nofollow noreferrer\">ATLAS</a> can do in terms of problem solving. This should be an absolute utter bare bones capability for your nanobots. They should be able to accept complex instructions at least as advanced as those given to ATLAS to initiate path-finding. In practice, they should be much more complex.</p>\n\n<p>How complex? Well, my recommendation would be to take a lesson from the military. Your army size is in the range of a <a href=\"https://en.wikipedia.org/wiki/Military_organization#Modern_hierarchy\" rel=\"nofollow noreferrer\">division</a>, which is 6-20 thousand soldiers. A division is lead by a 2-star general. So don't think about what sorts commands you might issue to a battle-bots toy. Think about what sorts of commands a 2-star general may issue in war. Also, note that the 2-star doesn't relay commands directly to the PFCs on the front lines. There's an enormous hierarchy of officers and NCOs in between. This is not an accident. Each layer of this hierarchy is an opportunity for one individual to process information from their subordinates and issue new orders without involving the general at the top. You should leverage this as well.</p>\n\n<p>You may find there is indeed a more efficient structure, given the nature of your nanobots, but starting from the prior art of the military is an excellent way to go. They have literally spent thousands of years honing the art of commanding large numbers of individuals to act as one cohesive army. Leverage that!</p>\n" }, { "answer_id": 112688, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 2, "selected": false, "text": "<p><strong>One human cannot alone control so many individual soldiers. You will need intermediate command levels.</strong></p>\n<p>Consider the Roman army. The army was comprised of a number of legions. Each legion was comprised of a number of cohorts. Each cohort was comprised of a number of centuries. With the century were groups of 8-10 men each commanded by a <a href=\"https://en.wikipedia.org/wiki/Decanus\" rel=\"nofollow noreferrer\">decanus</a>.</p>\n<p><a href=\"https://i.stack.imgur.com/dZIXa.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/dZIXa.jpg\" alt=\"roman legion organization\" /></a>\n<a href=\"https://www.strategypage.com/articles/default.asp?target=marius/marius.htm\" rel=\"nofollow noreferrer\">https://www.strategypage.com/articles/default.asp?target=marius/marius.htm</a></p>\n<p>This allows more granular control by establishing a hierarchy of control. Ideally at each command level there are seconds and thirds ready to step up if the prime is lost or incapacitated. This also offers a ready way to consolidate or break up groups of soldiers as events warrant.</p>\n" }, { "answer_id": 112697, "author": "SRM", "author_id": 26246, "author_profile": "https://worldbuilding.stackexchange.com/users/26246", "pm_score": 1, "selected": false, "text": "<p><a href=\"https://www.smithsonianmag.com/smart-news/there-are-372-trillion-cells-in-your-body-4941473/\" rel=\"nofollow noreferrer\">Smithsonian Magazine says there are 372 trillion cells in average human body.</a> Our brains control them to varying degrees. Muscle cells we often have control down to the individual cell level for fine-grain motor control. Others like lungs we kind of guide along. I think the metaphor holds. We could control fleets of robots: some would have specific instructions. Some would have more general instructions. We could probably intervene on a specific as needed (like consciously choosing to hold one's breath taking over from the usually automatic breathing). </p>\n" }, { "answer_id": 112699, "author": "Serban Tanasa", "author_id": 3510, "author_profile": "https://worldbuilding.stackexchange.com/users/3510", "pm_score": 2, "selected": false, "text": "<p>Dulaku was reborn, it seemed, ever so slowly, even as the wave of nanogoo consumed him before pain signals even had time to process alongside his extremities. Or did he die? Reinstantiation in the computronium substrate was rather confusing, at first. The perceptual frame switched from bifocal perspective into various stages: first, an isometric disembodied construct view, then gradually, as new layers of perceptual machinery were added to his consciousness it crystalized into a million-perspective four-dimensional approximation. </p>\n\n<p>Movement was also different, and rewiring took a seemingly impossibly long time. It felt weird to have disconnected parts, at first, but they were all soon embraced into a perceptual unity as the previous homunculus bio-representation was replaced by the Swarm. </p>\n\n<p>Miliseconds passed.</p>\n\n<p>He willed the Swarm into the nearby buildings, with those waterbag sculptures in the shape of, -- uh, what was it, people? -- littering the hallways, as if frozen. </p>\n\n<p>Is this pain? His larger unit-constructs seemed to be suffering attrition from automated fire.</p>\n\n<p>There were so many things to look at, and he had trouble focusing for a while, but as new parallel primary attention processors were cloned, then copied across the network, he felt a momentary sense of loss and desyncronization, then finally the ultimate perception layer build emerged, a metacognition framework that again unified the parallel streams, and <strong>He</strong> was now in many places at once.</p>\n\n<p><strong>He</strong> directed <strong>His</strong> medium-sized units to overwhelm and silence the machine resistance, and it was done. </p>\n\n<p>Time to grow ---</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/112647", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/28224/" ]

[ { "answer_id": 116873, "author": "klypos", "author_id": 52495, "author_profile": "https://worldbuilding.stackexchange.com/users/52495", "pm_score": 1, "selected": false, "text": "<p>I do not agree with a lot of your matrix as it stands - I cannot see how swamp can be drier than tropical rainforest, and tundra means to me a cold place where the ground is permanently frozen below a certain depth - permafrost.</p>\n\n<p>Deserts are usually without water, but they do range from blazing hot to extremely cold. </p>\n\n<p>Marsh, bog and fenland may be useful words to your quest, but you should reconsider whether this matrix concept is a good idea, to my mind.\nMost cold and wet places are elevated, among or on mountain ranges - perhaps some consideration of height should go into your thoughts.</p>\n" }, { "answer_id": 116876, "author": "KernelOfChaos", "author_id": 48532, "author_profile": "https://worldbuilding.stackexchange.com/users/48532", "pm_score": 3, "selected": true, "text": "<h2>Assuming your conlang is on an Earth-like planet, then yes, the problem is physics, not just linguistics.</h2>\n\n<p><a href=\"https://www.accuweather.com/en/features/trend/too-cold-to-snow/6953983\" rel=\"nofollow noreferrer\">https://www.accuweather.com/en/features/trend/too-cold-to-snow/6953983</a></p>\n\n<p>To quote the important part:</p>\n\n<blockquote>\n <p>When temperature decreases, the maximum capacity of water vapor that can be in the air decreases. Therefore, the colder it gets the less water vapor there will be in the air.</p>\n</blockquote>\n\n<p>To paraphrase: <strong><em>how cold a specific climate is determines how dry it is.</em></strong> </p>\n\n<p>So basically, the colder an environment, the drier it will be. So any \"wet\" <strong><em>and</em></strong> \"cold\" environment will still be, due to the laws of physics, warmer than tundra, taiga, or cold deserts.</p>\n\n<p>As a result, most cultures have never needed to coin a word for an environment that is both colder and wetter than taiga and cold deserts. The chances of someone encountering such a place approach zero. And this is reflected in your graph, in the very neat and tidy stair step up from tundra to tropical something.</p>\n\n<p>Maybe that stair step is one of your groups of 5, in addition to describing relative temperature and humidity/precipitation? Maybe your culture thinks of the world as five distinct grades from the equator to the poles, defined by those five biomes?</p>\n" }, { "answer_id": 116948, "author": "Majestas 32", "author_id": 52271, "author_profile": "https://worldbuilding.stackexchange.com/users/52271", "pm_score": 0, "selected": false, "text": "<p>As for the other two, use thornwood and temperate desert.</p>\n\n<p>Also since there aren't many temperate deserts on Earth, you might have to consider adjusting the rotation rate of the planet (maybe 1.5x Earth's which will probably give five Hadley cells, hopefully, it's complicated) to give more different types of biomes. Five cells would also fit in nicely with the idea of five zones from the equator to the poles. Or just make the world very mountainous/ having a ton of islands. Or both.</p>\n\n<p>There are very cold, wet areas but those are rare: I suggest perhaps renaming the \"tundra\" part to \"polar\" (e.g. Northern Greenland, Antarctica) and putting tundra on top of that (Northern Canada, Siberia), as well as sleetwood on top of taiga. Of course that breaks the neatness of the triangle...</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/116869", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/28830/" ]

[ { "answer_id": 117679, "author": "Attackfarm", "author_id": 41, "author_profile": "https://worldbuilding.stackexchange.com/users/41", "pm_score": 2, "selected": false, "text": "<pre><code>Between the season of Water and Earth is a time of floods and hope.\nThe season of Earth is temperate and bountiful.\nBetween the season of Earth and Fire is a time of preparation and hoarding.\n</code></pre>\n\n<p>Basically, I see Earth in your system as a very Spring-like season after the cold and wet season of Water. That water and the warming of leaving the season of Water would bring significant plant and animal growth. As they leave the season of the Earth, animals and sentients would be preparing for the harsher seasons by gathering as much of the seasonal resources as they can.</p>\n" }, { "answer_id": 117680, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 4, "selected": true, "text": "<p><strong>The season of Earth is fertility.</strong></p>\n\n<p>In the season of Earth, she does her thing keeping us alive. Fields! Flowers! Baby animals! Green! Plus you have to have some season to grow food or people will starve. You can't eat lighting and chaos. </p>\n\n<p>As I understand it Earth would be roughly analogous to spring, fire to summer, wind to autumn and water to winter. California has seasons like that. So summer solstice would be the earth to fire transition and winter the wind to water transition. On earth to fire, the fields burn. Wind to water means the big storms. </p>\n" }, { "answer_id": 117681, "author": "Jetpack", "author_id": 43703, "author_profile": "https://worldbuilding.stackexchange.com/users/43703", "pm_score": 1, "selected": false, "text": "<p>Aristotle described the elements in terms of temperature and moisture.</p>\n\n<p>From the Wikipedia page on the Four Elements.</p>\n\n<blockquote>\n <p>In his On Generation and Corruption, Aristotle related each of the four elements to two of the four sensible qualities:\n Fire is both hot and dry.\n Air is both hot and wet (for air is like vapor, ἀτμὶς).\n Water is both cold and wet.\n Earth is both cold and dry.</p>\n</blockquote>\n\n<p>In this world, the earth season is cold and dry. This isn't a climate where snow is frequent, so the cold season is characterized by a lot of bare ground where nothing grows. After the wet season, there is growth again.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/117677", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/52857/" ]

[ { "answer_id": 121838, "author": "Clay Deitas", "author_id": 54317, "author_profile": "https://worldbuilding.stackexchange.com/users/54317", "pm_score": 3, "selected": false, "text": "<p>I am not a geologist, but as far as I can tell this layout is completely plausible. Good attention to detail and an interesting landscape. </p>\n\n<p>I would move the city slightly west though, having it situated on the flats as opposed to bordering the bog and corresponding hills. (Or even right next to the reedlands, since a rice like staple crop could be grown there more easily.)</p>\n\n<p>Possibly the best place to retrieve clay would be on the edges of the Northern lake. A layer of clay is probably deposited just below the water line, or even above it, depending on how high the lake was before the drainage river formed. The western lake may also contain deposits. </p>\n\n<p>I think the only other thing to worry about is whether coal and iron tend to be deposited together. While I don't think it is impossible, I also don't think it is likely to occur often. </p>\n" }, { "answer_id": 121870, "author": "JSCoder says Reinstate Monica", "author_id": 40430, "author_profile": "https://worldbuilding.stackexchange.com/users/40430", "pm_score": 4, "selected": true, "text": "<p><strong>Grossly unnatural features:</strong></p>\n\n<p>Mainly, you should remember that topography is a facet of the geological history of the area. So, your hills look fine, could just be product of orogeny and erosion, your cliff spanning the entire map is fine, most likely explained by a strike-slip fault (although it could be a bit straighter if that's the case), and the plain could also be explained by glaciation or sea-level retreat (although randomize it a little, the slope is too similar). Looks <em>mostly</em> good!</p>\n\n<p><strong>Streams and Rivers</strong></p>\n\n<p>For that one stream in the D3-G2, you seem to understand that streams tend to have those U-shaped bends in the contour line. However, the other streams don't seem to fit this pattern. Also, if you intended the river at J2 to cut through the mountains, that would have it flowing uphill at first, which doesn't seem to fit. Other than that, this looks ok.</p>\n\n<p><strong>Bogs and Marshes</strong> </p>\n\n<p>Marshes and bogs tend to occur in low places, near water. I don't know your water table, but those regions are defined as usually saturated, so below the water table. Given that you put your bogs and marshes near shore, that should totally work.</p>\n\n<p><strong>Clay and city</strong></p>\n\n<p>Clay is a type of particulate matter: like sand. Given that your large river cuts through a cliff, that area should have some clay. Also possible: near your peat bog or under the surface of the lakes. I would place your city in either the region D3-E3-E4 or the region G6-H6, with D3-E3-E4 preferred because of flat land for farming, natural defence (back to a cliff), and a water source (river).</p>\n\n<p>I am by no means an expert on this, please correct any mistakes I have made.</p>\n" }, { "answer_id": 122144, "author": "Green", "author_id": 10364, "author_profile": "https://worldbuilding.stackexchange.com/users/10364", "pm_score": 3, "selected": false, "text": "<h2>Looks pretty good with some nitpicks</h2>\n\n<h2>Land Topography</h2>\n\n<p>The shape and layout of the mountains and hills that form the geography look pretty good to me. The lower left portions of the map have clearly seen significant erosion to flatten out like that.</p>\n\n<h2>Hydrology has some problems</h2>\n\n<p>In a few places, it looks like the streams run uphill or close enough to uphill to be really confusing.</p>\n\n<p>The Bog looks pretty good. It's shape hints at a low, &lt;10m rise in J3-K3. When I saw an early version of the map, I assumed that the bog would go all the way to the smaller lake. If the smaller lake were to get deeper then it would naturally flood into the area occupied by the bog. If the lake water level went down the bog would naturally drain out. The stream leading from K3 to J2 means there's a slope going down to the small lake. Seems odd that the bog would stop just short of extending to the lake.</p>\n\n<p>The Reed Marshes could probably extend much further inland along the streams that feed into the large lake. 10m contour lines isn't really enough resolution to be able to tell where the divets and hollows on this landscape are. A good argument could be made that the southern portions of the planes would be very marshy; especially row 10. The landscape extends 4000 meters with only 25 meters of altitude gain. That's less than a 1% grade and very hard to tell which way is downhill.</p>\n\n<p>The stream in K4-J5 seems odd. Normally, streams don't run parallel to contour lines and that stream does. I think it more realistic that water coming from the moutain would go east, off map, travel south on what would be columns M, N, O or P then come back west around rows 6 or 7.</p>\n\n<p><strong>Some heuristics for designing water flow systems</strong></p>\n\n<ol>\n<li>As the terrain gets steeper, the water path will get straighter. This makes sense since the pull of gravity on a 45 degree incline is much stronger than on a 1 degree incline.</li>\n<li>Inversely, as terrain gets shallower, the water path tends to meander a lot more with far more loops, curves and bends.</li>\n<li>The size of a stream, river, etc will depend completely on the surface area of the land found upstream. For example, in the steeper terrain in G4-H4, there isn't nearly as much land surface area to feed a stream there as with a stream that empties into the river at F2. I would expect the G4-H4 stream to be much smaller and less regular than the F2 stream.</li>\n<li>The general flow of all water is inherently tree shaped. This map captures much of that pattern but stated just for completeness.</li>\n<li>Where erosion has been happening longer/faster, the landscape tends to sit back. J5 is an acute example of this. The stream in C1 that goes down to the big lake in B2; I would expect it to go west a little more to meet up with stream in B1 first then go down to the big lake in B2.</li>\n</ol>\n" }, { "answer_id": 122178, "author": "Ash", "author_id": 40408, "author_profile": "https://worldbuilding.stackexchange.com/users/40408", "pm_score": 2, "selected": false, "text": "<p>Let's take your concerns in order:</p>\n\n<p>The general topography looks good without any seriously unnatural landforms. High cliffs are often a feature of areas with a glaciated history like these near Fox Glacier in New Zealand: <a href=\"https://i.stack.imgur.com/DnKQC.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/DnKQC.jpg\" alt=\"enter image description here\"></a></p>\n\n<p>Your drainage looks okay as it is but I would have a stream along the cliff bottom that captures most of the drainage coming from the highlands along the rough line from K5 to F2; joining the main outlet river before it empties into the larger western lake. The streams that cross the plains would be smaller, and possibly seasonal rather than continuous, due to capturing only over land drainage on the plains rather than any water from the heights. The box from F8 to K10 probably needs some detail work in the drainage department as well, it's a bit \"blank paper\" at the moment.</p>\n\n<p>Bogs are an artifact of blocked drainage, they occur in basins where rainwater cannot get out fast enough to prevent waterlogging, the area you have identified appears to be a prime candidate. There should be a transitional zone of treed swamp or grassy marsh where the bog gives over to lake or stream where water becomes dominant over vegetation. On a technical note you appear to have streams feeding the bog, this would make it a fen as opposed to a purely rain fed bog. Reed marshes are usually formed along lake edges so there's no issues with the one you have, although a fringe of the same in the upper lake would not be unreasonable as well. As the D1 to F1 zone does not appear show any drainage impeding topography there's no reason to change the proposed drainage in that area.</p>\n\n<p>In terms of resources; there will lenses of secondary clay to be found, shallowly buried, under the large southern alluvial plain, (left overs from post-glacial sedimentation) you'll be able to pick them out because the poor drainage will allow reeds to grow in isolated patches all over the otherwise well drained and grass dominated plain. Peat from boggy areas makes a good fuel, and <a href=\"https://en.wikipedia.org/wiki/Bog_iron\" rel=\"nofollow noreferrer\">bog iron</a> was historically an important ore. Gravel will dominate the plains, especially in the area where the river connecting the two lakes comes out of the hills, and there will be other <a href=\"https://en.wikipedia.org/wiki/Alluvial_fan\" rel=\"nofollow noreferrer\">alluvial fans</a> where streams from the mountainous northern area meet the plain, these may also be a valuable source of both clay and gravel. Reeds are an important traditional building material in many parts of the world, both for houses and for fishing boats.</p>\n\n<p>For me the best settlement location is in D3, where the river meets the lake, this will give good access to a number of resources, not least of all easy access to the lake for fishing boats, and the reedbeds for boat building.</p>\n\n<p>If I missed anything or you need more details on a point let me know.</p>\n" }, { "answer_id": 122180, "author": "Jean-Abdel", "author_id": 53937, "author_profile": "https://worldbuilding.stackexchange.com/users/53937", "pm_score": 1, "selected": false, "text": "<p>There are places looking a little like that in french Jura called reculée. They are also created by a glacier and tend to form lakes and cliffs, higher than your but that's mostly because the plateau where the glacier forms is higher above the valley underneath. </p>\n\n<p>If it takes place in Europe the 50 meters of sediment will be mostly Jurassic limestone so iron is likely but you will have to dig much deeper for coal.</p>\n\n<p>If your glacier came from K10 to A5 then the small lake is not very likely since streams tends to be subterranean on limestone plateaus, and the stream will have a resurgence or something on the cliff. The only way to solve that issue I see is that an older glacier created a small reculée for the small lake and then a bigger one crossed its road. \nGlacier tends to bring sand and clay so it's perfect for reed.</p>\n\n<p>The small streams flowing from the hill H3 will be active only when it rains like all the other streams less than 200m long but the well on H4 would be a good resurgence. The stream flowing from D10 to the lake in A5 should be bigger, starting at the bottom of the valley</p>\n" }, { "answer_id": 122948, "author": "Dubukay", "author_id": 43163, "author_profile": "https://worldbuilding.stackexchange.com/users/43163", "pm_score": 0, "selected": false, "text": "<p>I know I’m late to this, but If you’re still taking feedback I think you’ll find that your topography is quite exaggerated vertically, especially in the lowlands. From what I can see, the flattest parts of the map (the Dubukay expanse, for which I now feel responsible) have a grade of about 1% (10m/1000m). That would hardly make it feel very flat, but rather a noticeably sloped hill. If we look at a place like Kansas or Florida (sorry to be US-centric, but they’re just examples of very flat places), the grade is much closer to 0.05 or 0.025%. (Kansas is ~400 miles wide (650km) and has a total elevation change of less than a mile (1.6km)). Florida is apparently even flatter. </p>\n\n<p>I’d spread out the contour lines there. I know it sucks because it’s already kinda boring. </p>\n\n<p>Alternatively, you could blow up the scale in the corner a bit. Make it more like 1-2km would give a more realistic grading, although it’d wreak havoc upon your other features and travel times. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/121834", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/2746/" ]

[ { "answer_id": 122871, "author": "jedmeyer", "author_id": 52749, "author_profile": "https://worldbuilding.stackexchange.com/users/52749", "pm_score": 3, "selected": false, "text": "<p>A lot of people tend to misunderstand how common sulfur compounds actually is in water. They're actually used as preservative in <a href=\"https://www.bonappetit.com/drinks/wine/article/sulfite-free-wine\" rel=\"noreferrer\">wines</a>, though sommeliers say it affects the taste.</p>\n\n<p>There are a couple common sources of sulfur. One is from minerals, and there are a LOT of possible inorganic compounds including iron sulfide, calcium sulfate, and many <a href=\"https://en.wikipedia.org/wiki/Sulfur\" rel=\"noreferrer\">more</a>. These are often deposited into bodies of water through erosion, dissolving and depositing in the water over thousands of years.</p>\n\n<p>However, most people <em>notice</em> sulfur in only one form: Hydrogen Sulfide (H2S), the pungent gas that we associate with rotten eggs.</p>\n\n<p>H2S is usually created by what we call <em>Sulfur Reducing Bacteria</em>. Basically, the bacteria exploit the chemical energy gradient in sulfate compounds and perform a <a href=\"https://en.wikipedia.org/wiki/Redox\" rel=\"noreferrer\">reduction reaction</a> to perform biochemical duties. They need the aforementioned sulfur compounds dissolved in the water to work however.</p>\n\n<p>Honestly, H2S <em>isn't actually</em> that poisonous, but it's smell is <strong>SO</strong> bad, that most humans wouldn't be able to stomach it anywhere of a harmful level. </p>\n\n<p>So at this point, you would need to filter the water, which can be done using an Activated Carbon filter.</p>\n" }, { "answer_id": 123166, "author": "Ash", "author_id": 40408, "author_profile": "https://worldbuilding.stackexchange.com/users/40408", "pm_score": 0, "selected": false, "text": "<p>There are a number of compounds that would lead to a need to filter water coming out of that bog. The one is sulfur which you have a handle on which would need a charcoal filter since the primary compound is dissolved hydrogen sulfide which is highly water soluble. The main sulfur source (and the main source of any dissolved contaminants) is going to be the chemical action of the bog water on the underlying rocks. If the northern hills are still going to be largely metamorphic and igneous rocks as previously discussed then there will be a lot of poorly mineralised sulfur and metals which will be easily dissolved from the rocks to contaminate the waters flowing therefrom.</p>\n\n<p>The other issue is dissolved metals, in particular <a href=\"https://en.wikipedia.org/wiki/Bog_iron\" rel=\"nofollow noreferrer\">iron</a> but also a number of others like zinc, vanadium, and molybdenum. To filter this material you need to first aerate the water, this can be done as easily as running it over gravel to agitate it slightly. The metals will form insoluble oxides that can be filtered out using sand. This process will also neutralise the pH of the water making it somewhat more palatable, and less toxic. </p>\n\n<p>Given the previous conversation we had on the structure of the southern hills, if the proposed <a href=\"https://en.wikipedia.org/wiki/Shale\" rel=\"nofollow noreferrer\">Shale</a> layer is a \"black shale\" it can also be high in sulfur and any of the springs who's water has interacted with it could also be high in sulfur. Shale varies greatly in composition so you can do a lot with the the water chemistry if it suits you.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/122862", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/2746/" ]

[ { "answer_id": 122866, "author": "Blade Wraith", "author_id": 50282, "author_profile": "https://worldbuilding.stackexchange.com/users/50282", "pm_score": 0, "selected": false, "text": "<p>Please understand i am not a geologist, so if i'm wrong on naything i say please correct me, i'm just doing research and looking into it as i go</p>\n\n<p>Different resources appear at many different levels,</p>\n\n<p><strong>Hiostorial examples:</strong> in Cornwall, in the UK, there was numerous Tin mines, and those mines offered work for the towns around it, eventually tin got mined out or the veins were too deep to cheaply mine and the need for tin reduced and larger tin deposits were found on continental europe, this resulted in a large decline in mining in Cornwall. however a few centuries later they discovered that tin deposits tend to be close or above Copper deposits or and so mining in Cornwall started up again. but this time for Copper, </p>\n\n<p><strong>Layering</strong></p>\n\n<p>My understanding is that copper and tin are more common in hard rock (i think this is igneous rock) such as granite then in soft stone such as limestone which is sedimentary rock. however they are often found high up need the sedimentary rock level</p>\n\n<p>most types of banded iron deposits appear in sedimentary rock. so Copper and iron being nearby would be unlikely for this reason, the same could be said for the Coal layer, as coal is again more often found in sedimentary rock formations.</p>\n\n<p>However it is common to find sedimentary rock over igneous rock and the thickness or depth of the layer is entirely up to you as the writer. copper and tin would be found beneath the coal and iron levels. while i think its unlikely that a large deposit of coal would sit directly over a large deposit of iron, its possible that the large deposits actually sit close or nearby with some overlap.</p>\n\n<p>the only thing i would advise you to look into is the size, looking up several other iron mines (open top) the entire mine itself can be miles long, or wide and can also get over a mile deep, then the infrastructure around it addes even more, so for you grid squares being 400m by 400m and you wanting a square or two to be the mine and city, you might need to scale up the mine a bit for example:</p>\n\n<blockquote>\n <p>The Kiruna mine in lapland has an ore body which is 4 kilometres long, 80 metres to 120 metres thick and reaching a depth of up to 2 kilometres. Since mining began at the site in 1898, the mine has produced over 950 million tonnes of ore.</p>\n</blockquote>\n\n<p>The entire mining site itself though including the mountains of waste material, access roads and equipment etc, is over 4km by 2km. </p>\n\n<p>The other beautiful thing for you is most people don't know enough about mining or geology to know if its right or wrong, I'm a prime example of this at least until someone posts a question on the internet and i go off in search of answers</p>\n" }, { "answer_id": 122870, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 5, "selected": true, "text": "<h1>So many minerals so close to a city is unlikely</h1>\n\n<h3>Your mining area is small</h3>\n\n<p>Limiting the mines to the area from D2->F3 is like a coal seam that is only 1-2 km long. That is short. Here is a <a href=\"https://eppcgis.ky.gov/minemapping/\" rel=\"noreferrer\">GIS mapping</a> of coal mining areas in Kentucky. The seams are hundreds of miles long. </p>\n\n<p><a href=\"https://en.wikipedia.org/wiki/Scranton,_Pennsylvania\" rel=\"noreferrer\">Scranton</a> was/is a big coal mining town in Eastern Pennsylvania. Scranton grew to over 100,000 at the peak of the coal mining boom. Combined with nearby Wilkes-Barre and other cities in the area, it formed a conurbanation of some 300,000 in the 1920s. These cities serviced coal towns from Forest City, PA to Bloomsburg, PA, some 110 km downriver. The two-county area (<a href=\"https://en.wikipedia.org/wiki/Lackawanna_County,_Pennsylvania#Demographics\" rel=\"noreferrer\">Lackawanna</a> and <a href=\"https://en.wikipedia.org/wiki/Luzerne_County,_Pennsylvania#Demographics\" rel=\"noreferrer\">Luzerne</a>) had some 700,000 people, so it was one of the most densely populated parts of the US at that time. Lots of people in a region = large city to support those people. </p>\n\n<p>If you want a large mining town, it should probably be pulling from a large mining region. Some mines will be close by, but many more with be within a day or two's transport by horse or foot; or later, a few hours by train. A 'city' with only small nearby mines would be just a small encampment of a few hundred. </p>\n\n<h3>Mines on top of each other are unlikely</h3>\n\n<p>I can't find any good examples of mines being just on top of each other like that. But I was able to find a variety of examples of such mines being in very close proximity. The rich bituminous coals are generally of an age <a href=\"https://en.wikipedia.org/wiki/Bituminous_coal#Bituminous_coal_by_geologic_period\" rel=\"noreferrer\">100-300 million years ago</a>. Almost all high quality Iron ores are derive in one way or another from <a href=\"https://en.wikipedia.org/wiki/Banded_iron_formation\" rel=\"noreferrer\">banded iron formations</a>. These formations are much, much older, in the 2 billion year range. They derive from the Great Oxygenation event, when the first atmospheric oxygen reacted with free iron to lay down great beds of iron oxide.</p>\n\n<p>The gap in time between the two levels is what makes the idea of coal on top of iron so unlikely. If you had several hundred meters of coal-bearing strata, even if you just dumped that on top of a banded iron formation, that is still very deep for a early-modern mine. <a href=\"https://en.wikipedia.org/wiki/Mining_in_the_Upper_Harz\" rel=\"noreferrer\">Mines in Europe</a> were hitting 300 meters by 1700 and 600 meters by 1830; still these were exceptional. And this considering a ~300 mya formation directly on top of a ~2000 mya formation, with no intervening material, which I consider unlikely.</p>\n\n<p>A second reason that this would not work is that you have large lakes nearby, so mine shaft drainage is going to be tough. Your mining hills only go up about 100 meters above lake level. Much deeper than lake level, and you will likely get very serious water intrusion. Mining below lake level at all will likely have to wait for the steam engine to pump water.</p>\n\n<h3>A large mining area means many resources can be found together.</h3>\n\n<p>Jharkhand, in India, is a place with lots of mining resources in close proximity. It is the <a href=\"https://en.wikipedia.org/wiki/Jharkhand#Economy\" rel=\"noreferrer\">leading</a> iron and copper mining state of India, and third in coal. Meanwhile, much of India's coal reserves are just across the border in West Bengal and Odisha states. </p>\n\n<p>You can see a big iron ore mining region near Gua, Jharkand, India on the <a href=\"https://www.google.com/maps/place/Gua+Iron+Ore+Mines,+Jharkhand+833213,+India/@22.1434796,85.3288054,26748m/data=!3m1!1e3!4m5!3m4!1s0x3a1fc72a10e8390d:0xdaf66a46afb1a575!8m2!3d22.2185736!4d85.3562565\" rel=\"noreferrer\">map here</a> (look for the open pit mines in the satellite view). Meanwhile, here is some <a href=\"https://www.google.com/maps/place/Global+Coal+And+Mining+Pvt.+Ltd.+Talcher/@20.9500388,85.0922498,26099m/data=!3m1!1e3!4m8!1m2!2m1!1stalcher+coal+mine!3m4!1s0x3a18b16196542a87:0x65ae90c0079f0992!8m2!3d20.9280814!4d85.1646353\" rel=\"noreferrer\">significant coal mining</a> in nearby Talcher, Odisha, India. Still these two mines are 140 km apart. But there are <a href=\"https://www.google.com/maps/search/copper+mine+jharkand/@22.5747552,86.3920152,23160m/data=!3m1!1e3\" rel=\"noreferrer\">copper mines near Jamshedupur</a> 110 km away from the coal mines, and also uranium, gold, bauxite and other things in the region. </p>\n\n<h1>Conclusion</h1>\n\n<p>Your best bet is to have your mining town be the center of a larger mining region. Within the larger mining region, there are many regional centers of coal, iron, copper and more. Ringstadt is the central business city of the region, and the center for trans-shipment; after all it is a port town on the lake and what better way to move ore than by barge. </p>\n\n<p>Also, it can eventually be the industrial center for the iron and steel industry. A good example is Cleveland, OH. This lake town isn't actually close to coal (which is in Pennsylvania and West Virginia, mostly) or iron, which is available in Minnesota and Michigan's Upper Peninsula. But it is the place between the two on the lake. Rail brought coal from the Pittsburgh area, and barges brought ore from Lake Superior; these met in Cleveland which became a big metals center. Gary, Indiana has as similar history. </p>\n" }, { "answer_id": 122933, "author": "Gimelist", "author_id": 39999, "author_profile": "https://worldbuilding.stackexchange.com/users/39999", "pm_score": 4, "selected": false, "text": "<blockquote>\n <p>Can I have the resources I in the described area? </p>\n</blockquote>\n\n<p>Yes, even though it requires an exceptional luck and combination of circumstances. Let's see a hypothetical geological history for your area:</p>\n\n<p><a href=\"https://i.stack.imgur.com/sZI2V.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/sZI2V.png\" alt=\"enter image description here\"></a></p>\n\n<p>Start with a sedimentary basin, tropical environment where you have lots of organic material which will eventually form coal. This is then overlain by other sediments (sand for example).</p>\n\n<hr>\n\n<p><a href=\"https://i.stack.imgur.com/oiBaC.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/oiBaC.png\" alt=\"sfd\"></a></p>\n\n<p>Now you have tectonic plate collison. An oceanic crust <a href=\"https://en.wikipedia.org/wiki/Subduction\" rel=\"noreferrer\">subducts</a> under your sedimentary rocks. Volcanic eruptions start in the <a href=\"https://en.wikipedia.org/wiki/Volcanic_arc\" rel=\"noreferrer\">volcanic arc</a> above it.</p>\n\n<hr>\n\n<p><a href=\"https://i.stack.imgur.com/Bhhy1.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/Bhhy1.png\" alt=\"enter image description here\"></a></p>\n\n<p>This is where it gets really fun. You now have a <a href=\"https://en.wikipedia.org/wiki/Porphyry_copper_deposit\" rel=\"noreferrer\">porphyry copper</a> system, intruding into sedimentary rocks, which happen to have coal preexisting in them. So you have this volcano because of the subduction zone, and as it erupts it exsolves acidic hydrothermal fluids that carry dissolved copper into the limestone. The fluids are neutralised by the limestone, causing the formation of a copper <a href=\"https://en.wikipedia.org/wiki/Skarn\" rel=\"noreferrer\">skarn</a>.</p>\n\n<p>The magma itself also separates an immiscible iron oxide liquid. These are rare and are usually not as large as the BIFs mentioned in kingledion's answer, but they're big enough (for example Kiruna, Sweden or El Laco, Chile).</p>\n\n<p>The rest of the fluids end up in hydrothermal springs and your lake making those sulfurous waters you wanted in your other question.</p>\n\n<hr>\n\n<p>At first I thought this was a bit too much hand-wavy and unlikely to exist, but then I realised that a not-too-different example occurs close to home in Eastern Australia. There are many <a href=\"https://en.wikipedia.org/wiki/Coal_in_Australia#/media/File:Australian_Energie_ressources_and_major_export_ports_map.svg\" rel=\"noreferrer\">sedimentary basins</a> with coal in them, and these Permian in age. Later on, Triassic magmatic activity occurred <a href=\"https://en.wikipedia.org/wiki/Geology_of_Australia#/media/File:Ausgeolbasic.jpg\" rel=\"noreferrer\">around the same places</a>, caused by subduction of the Pacific plate underneath Eastern Australia. So yea, feasible.</p>\n" }, { "answer_id": 122943, "author": "JSCoder says Reinstate Monica", "author_id": 40430, "author_profile": "https://worldbuilding.stackexchange.com/users/40430", "pm_score": 1, "selected": false, "text": "<h2>Tl;dr: First, iron came from a Snowball Earth, then, copper came from volcanism, finally, coal came from peat forests</h2>\n\n<p>There was a lot of things I wanted to add to my answer in the first question, but I didn't have the time at the moment. Others have noted it was <strong>possible but unlikely</strong>, so now I will suggest a geology. (story narration in block quotes)</p>\n\n<blockquote>\n <p>Well, first, we go into biology. Our world wasn't always this hospitable. In fact, the air we breathe was nonexistent: composed of other chemicals. But a pioneering group of plants came: the algae. They lived on iron, producing oxygen from the air around them. The eroding mountains provided the iron. The iron then precipitated after the algae died, <em>ironically</em> because of all the oxygen they produced. Other areas of iron eroded. But our ores remained intact, sedimented down by the shallow sea we were a part of.</p>\n</blockquote>\n\n<p>Real life example: <a href=\"https://en.wikipedia.org/wiki/Mesabi_Range\" rel=\"nofollow noreferrer\">Mesabi Range</a></p>\n\n<blockquote>\n <p>Next, near this sea, near this area of iron, a rift opened. The great rift, we call it, just to the west of us. This rift gave us potash for agriculture, sulfur for gunpowder, salt for food and money, bentonite for pottery, and gypsum for construction. A true windfall geologically, not even mentioning the copper, gold, and zinc deposited in the porphyric deposits.</p>\n</blockquote>\n\n<p>Real life (ish) example: <a href=\"https://en.wikipedia.org/wiki/Afar_Triangle\" rel=\"nofollow noreferrer\">Afar Triangle</a></p>\n\n<blockquote>\n <p>Finally, the sea dried somewhat, and we were left with lush green forests. These days were warmer than today, allowing for a rainforest in this region. But then, the algae struck again. These plants, flourishing in the shallow lakes, combined with the forests on our land, caused a short, intense ice age, followed by a rapid heat-up after the ice age. The ferns and palms of our forests were too slow to adapt. And so they formed the coal seams now under your feet.</p>\n</blockquote>\n\n<p>Real life example: Most of the coal seams in America.</p>\n" }, { "answer_id": 123169, "author": "Ash", "author_id": 40408, "author_profile": "https://worldbuilding.stackexchange.com/users/40408", "pm_score": 1, "selected": false, "text": "<p>For copper your best bet in this setting is the hydrothermal ore <a href=\"https://en.wikipedia.org/wiki/Malachite\" rel=\"nofollow noreferrer\">Malachite</a>, this is formed when copper rich water cools, depressurises, or is oxidised. You can have veins of it running through other rocks where water has historically moved along natural faults in the rocks.</p>\n\n<p>Most massive iron formations are <a href=\"https://en.wikipedia.org/wiki/Banded_iron_formation\" rel=\"nofollow noreferrer\">banded iron</a>, old ore bodies laid down in the ancient oceans during the oxidation of the atmosphere, these old formations could occur below/around a granitic intrusion being much older than any other rocks in the area. These deposits are relatively easy to work too as they're composed of the Iron oxide minerals <a href=\"https://en.wikipedia.org/wiki/Hematite\" rel=\"nofollow noreferrer\">hematite</a> and <a href=\"https://en.wikipedia.org/wiki/Magnetite\" rel=\"nofollow noreferrer\">magnetite</a> which can be directly reduced in a furnace without any of the preprocessing needed when using hydroxide and sulfurous ores.</p>\n\n<p>Given the glaciated nature of the northern area I would expect most of the softer, and therefore mobile, strata like coal to have been scraped off the landscape and deposited on the plains as a sedimentary layer of broken coal mixed with gravel and some finer sediments. There is a layer of coal like this that, according to a petro-geologist who used to lecture some of my Earth Science classes, comes up in core samples in the <a href=\"https://en.wikipedia.org/wiki/Taranaki_Basin\" rel=\"nofollow noreferrer\">Taranaki Basin</a>, it's composed of coal fragments eroded from onshore deposits during the last ice age and deposited on the continental shelf. The southern hills could have very thick coal measures per our discussion on their overall geology the other week; deeply buried granite, conglomerate aquifer, shale, limestone, coal, fireclay cap with topsoil over the lot.</p>\n" }, { "answer_id": 124264, "author": "Gustavo", "author_id": 52497, "author_profile": "https://worldbuilding.stackexchange.com/users/52497", "pm_score": -1, "selected": false, "text": "<p>For such a large amount of resources to be together, my only explanation is a post apocalyptic scenario, with the former cars and buildings long ago eroded.</p>\n\n<p>If a city such as Tokyo is allowed to be assaulted by Nature by ten thousand years, all the steel and alloys will transform to massive <strong>IRON</strong> &amp; <strong>Nickel/Aluminum/etc</strong>.</p>\n\n<p>The main issue is how to justify coal.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/122863", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/2746/" ]

[ { "answer_id": 124159, "author": "Jean-Abdel", "author_id": 53937, "author_profile": "https://worldbuilding.stackexchange.com/users/53937", "pm_score": 2, "selected": false, "text": "<p>Actually granite rarely form caves, and never that big. Water erode the rock by infiltrating through the faults producing sand and large blocks but no cave. Nonetheless there are huge granite cliffs in Yosemite like the Half Dome. You can't really dig into granite, may be a stairway would be possible on the face of the cliff. Building with granite is possible you even have lighthouses made of this.</p>\n\n<p>On the other hand, compact lilestone suits perfectly, but it is completely white and a port in a cave is still dangerous.</p>\n" }, { "answer_id": 124225, "author": "Green", "author_id": 10364, "author_profile": "https://worldbuilding.stackexchange.com/users/10364", "pm_score": 3, "selected": false, "text": "<h2>Granite Massifs are common</h2>\n\n<p>A granite block of the size you ask for is totally feasible. El Capitan in California is certainly taller. </p>\n\n<p>Getting the living spaces you want without explosives or magic is going to be sufficiently expensive to be impossible. Cutting stone by hand takes a long long time. From personal experience, with a hammer drill and modern drill bits, it took the better part of an hour to cut a single row of holes about 6\" deep. Medieval miners with poor quality iron or steel will take days or weeks to cut the same set of holes. To excavate the amount of material described will take forever. </p>\n\n<p>Making granite \"caves\" is usually done artificially by cutting up the rock into blocks then forming it into buildings. As most caves are found in rock types that dissolve in water and granite does not, some other mechanism will need to be used to create the voids in the rock. </p>\n\n<p>Without a very secure bay to protect the cave mouth, no captain will risk their ship. The scene describes pounding surf indicating that the cliff face extends far below the water line. While the deep water will allow large ships to approach the cave mouth, and even enter, no one would dock their ship there. </p>\n\n<p>Depending on the shape of the cave and without a harbor, the waves in the cave could frequently be larger than the waves outside. Big waves on the open ocean aren't too bad. Big waves are really bad when your ship can be thrown against a cliff face, even if that face is in a cave.</p>\n\n<p>Compare paintings of the docking density between the Thames River in the 1800s vs Boston Harbor. The Thames is absolutely packed! Why? Because conditions on the Thames are very placid. The risk of one ship inadvertently running into another was low enough that the density of docked ships could increase. Boston harbor doesn't have those kind of conditions. Thus, to prevent accidents, boats are anchored much further away from each other. </p>\n\n<p>Ignoring the waves, the tides will put a limit on the maximum height of the ships that will fit in your cave. Assuming a normal earth-moon system, tides may vary by as much as 3 meters.</p>\n" }, { "answer_id": 124262, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 3, "selected": true, "text": "<h1>This is like an <a href=\"https://en.wikipedia.org/wiki/Ellora_Caves\" rel=\"nofollow noreferrer\">Indian rock-temple</a></h1>\n\n<p><a href=\"https://i.stack.imgur.com/fZyHo.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/fZyHo.jpg\" alt=\"enter image description here\"></a></p>\n\n<p>There are many examples of these rock-temples in southern India. Above is a picture of Cave 10 at Ellora. Below is Cave 16 at the same site, called the Kailasa Temple. The temples are called 'caves,' some of them are dug into rock as if they were caves, some, like 16 are basically small hills excavated into the shape of a building. </p>\n\n<p><a href=\"https://i.stack.imgur.com/fDuSs.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/fDuSs.jpg\" alt=\"enter image description here\"></a></p>\n\n<p>Cave 16 is 82 by 40 meters, and 30 meters high inside. An estimate of the total amount of rock removed in 100,000 cubic meters, just for this one of 34 caves at the Ellora site.</p>\n\n<p>Ellora is just one of many from Maharashtra in India, including <a href=\"https://en.wikipedia.org/wiki/Ajanta_Caves\" rel=\"nofollow noreferrer\">Ajanta</a> and <a href=\"https://en.wikipedia.org/wiki/Pitalkhora\" rel=\"nofollow noreferrer\">Pitalkhora</a>. The Pitalkhora site was started around the 3rd century BC; building at each site went on for hundreds of years. The total amount of excavation at the bigger sites like Ellora and Ajanta is probably more than you would need to make your city. </p>\n\n<h1>Except that was basalt</h1>\n\n<p>So all those structures were cut into flood basalt. However, basalt is pretty hard and tough as it is. Here are some material comparisons between granite and basalt. Source of <a href=\"https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0180880\" rel=\"nofollow noreferrer\">granite</a> and <a href=\"http://oro.open.ac.uk/5495/1/JVGRbalme01_corrected_for_publicpdf.pdf\" rel=\"nofollow noreferrer\">basalt</a> fracture toughness, <a href=\"http://acwc.sdp.sirsi.net/client/en_US/default/index.assetbox.assetactionicon.view/1045105?rm=CONCRETE%20LABOR0%7C%7C%7C1%7C%7C%7C0%7C%7C%7Ctrue\" rel=\"nofollow noreferrer\">all other data</a>. Everything converted to metric</p>\n\n<pre><code> Basalt Granite\nDensity (kg/m^3) 2830 2690 \nFracture Toughness (MPa m^0.5) 1.5-1.7 1.9-2.2 \nCompressive Strength (MPa) 148 143 \nTensile Strength (MPa) 13.1 11.7\n</code></pre>\n\n<p>Basalt appears to be slightly denser, and proprotionately stronger, while granite is tougher so it would be a bit harder to mine through. Ultimately, the materials are pretty similar, so if Iron Age Indians could carve these temples in a century or two, they could also carve your city.</p>\n\n<h1>Conclusion</h1>\n\n<p>Monumental cities carved in granite are realistic!</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/124152", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/189/" ]

[ { "answer_id": 125212, "author": "RonJohn", "author_id": 8068, "author_profile": "https://worldbuilding.stackexchange.com/users/8068", "pm_score": 2, "selected": false, "text": "<p>According to <a href=\"https://en.wikipedia.org/wiki/Candela#Relationships_between_luminous_intensity,_luminous_flux,_and_illuminance\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/Candela#Relationships_between_luminous_intensity,_luminous_flux,_and_illuminance</a></p>\n<blockquote>\n<p><strong>If the source emits light uniformly in all directions</strong>, the flux can be found by multiplying the intensity by 4π: <strong>a uniform 1 candela source emits 12.6 lumens</strong>.</p>\n</blockquote>\n<p><a href=\"https://en.wikipedia.org/wiki/Incandescent_light_bulb\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/Incandescent_light_bulb</a></p>\n<blockquote>\n<p>The luminous efficacy of a typical incandescent bulb is <strong>16 lumens per watt</strong>, compared with</p>\n<p><strong>60 lm/W</strong> for a compact fluorescent bulb or</p>\n<p><strong>150 lm/W</strong> for some white LED lamps.</p>\n</blockquote>\n<p>Thus, through simple division you can calculate (imperfectly, yes, because of the differences between candelas, lumens, and lux but your readers won't care):</p>\n<p>Incandescent: <code>16 / 12.6 = 1.3</code> candles/watt.</p>\n<p>CFL: <code>60 / 12.6 = 4.8</code> candles/W`</p>\n<p>LED: <code>150 / 12.6 = 11.9</code> candles/W</p>\n<p>Now to the big problem with your specifications:</p>\n<pre><code>Setting 1 = the light of a single candle \nSetting 2 = a 25 watt light bulb \nSetting 3 = a 50 watt light bulb \nSetting 4 = a 75 watt light bulb \nSetting 5 = a 100 watt light bulb\n</code></pre>\n<p>The problem is that you do not specify what kind of light bulbs. (Since no light bulbs existed during the flintlock era, we shouldn't assume incandescent bulbs.)</p>\n<p>You must decide what kind of light bulbs you are comparing your wands to.</p>\n<p>Whatever kind of bulb you choose, you'll still have a problem, since -- for example -- a 25W CFL bulb is the equivalent of <code>25 * 4.8 = 120</code> candles. That's a <strong>lot</strong> of candles!!</p>\n<blockquote>\n<p>So, what advice can you offer?</p>\n</blockquote>\n<p>Drastically scale back the wattage equivalents for Settings 2-5.</p>\n" }, { "answer_id": 125236, "author": "John Locke", "author_id": 54384, "author_profile": "https://worldbuilding.stackexchange.com/users/54384", "pm_score": 1, "selected": false, "text": "<p>Give each spell and each intensity a number that adds with the other to give the total number of charges needed.</p>\n\n<p><strong>Spells</strong></p>\n\n<p>You might be wondering why Spell 0 has no cost, we'll see why in a second. Spell 2 is the same cost as Spell 1 because they are essentially the same, but you can change this if you want.</p>\n\n<ul>\n<li>Spell 1- 0</li>\n<li>Spell 2- 0</li>\n<li>Spell 3- 1</li>\n<li>Spell 4- 1.5</li>\n</ul>\n\n<p><strong>Intensities</strong></p>\n\n<p>You can change the intensities when you figure out how much light you want for each.</p>\n\n<ul>\n<li>Candle- 1x</li>\n<li>25 watt- 1.5x</li>\n<li>50 watt- 2x</li>\n<li>75 watt- 2.5x</li>\n<li>100 watt- 3x</li>\n</ul>\n\n<p><strong>The math</strong></p>\n\n<p>Now, when you are casting the spell, you can use a simple addition to figure out the charges needed.</p>\n\n<p>If you want Spell 1 with candle intensity, it's 0+1, which is 1 charge.</p>\n\n<p>If you want Spell 1 with 25 watt intensity, it's 0+1.5 which is 1.5 charges.</p>\n\n<p>If you want Spell 3 with candle intensity, it's 1+1, which is 2 charges.</p>\n\n<p>If you want Spell 3 with 75 watt intensity, it's 1+2.5, which is 3.5.</p>\n\n<p>If you want Spell 4 with 100 watt intensity, it's 1.5+3, which is 4.5.</p>\n\n<p><strong>Pros</strong></p>\n\n<p>The system is pretty simple, it just requires one addition.</p>\n\n<p>You can adjust the costs as needed.</p>\n\n<p>The 1/2 charges can be a plot point- you don't know if there are 4 charges left or 3 1/2, so you have to keep track carefully.</p>\n\n<p>Using the decimals is much easier in addition than with multiplication where you could have .75 of a charge.</p>\n\n<p><strong>Cons</strong></p>\n\n<p>The numbers I am using right now let some of the numbers use half of a charge. You can allow use of 1/2 charges or you can change the numbers to whole numbers so you will not have that problem.</p>\n" }, { "answer_id": 125264, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 1, "selected": false, "text": "<p><strong>Factor in movement as a power cost.</strong></p>\n\n<p>Assume for a given power setting, the amount of light produced at each light effect is the same. 1, 2 and 3 look the same. 4 might be a larger object and if so, it will be dimmer than 1,2, and 3 because a larger area emits the same light as the grape in 1,2 and 3. If 4 illuminates a grape, it will look the same as 1,2,and 3 but be more delicious. </p>\n\n<ol>\n<li><p>makes the tip of the wand glow for up to 10 minutes.\n<strong>At low power this costs 1, because light does not have to move from wand.</strong></p></li>\n<li><p>will leave a glowing bead of light the size of a grape floating wherever the tip of the wand was when the Spell was cast. \n<strong>At low power this costs 2 because the light has move from wand and maintain position.</strong></p></li>\n<li><p>shoots a grape sized ball of light from the tip of the wand that will move in a straight line until it comes into contact with something, then stop and remain in that spot.\n<strong>At low power this costs 3 because the light ball moves a distance</strong>.</p></li>\n<li><p>Fires a beam from the tip of the wand. An object hit by the beam will have a glowing aura form around it for 10 minutes.\n<strong>At low power this costs 4 because the light must move and then the lit object might move.</strong> </p></li>\n</ol>\n\n<p>With number 4 a very large object (e.g. a castle) might be invisibly dim. A small fast moving object (e.g. a bat) might be bright but possibly go out before the 10 minutes because of all the movement. #3 might also last less than 10 minutes if the ball must travel a very long way before hitting something (e.g. you fired it in the air like a flare). </p>\n\n<hr>\n\n<p>For brighter effect, multiply cost by desired brightness as multiples of baseline low power setting. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/125208", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/-1/" ]

[ { "answer_id": 128145, "author": "Sora Tamashii", "author_id": 56536, "author_profile": "https://worldbuilding.stackexchange.com/users/56536", "pm_score": 2, "selected": false, "text": "<p>\"Alien\"\nImagine being referred to as something dehumanizing. It's pretty derogatory. \"But they are aliens!\" That's a pretty racist thing to say.</p>\n\n<p>Otherwise, \"greeny\" for Martians.\nFor the others, slurs based on the myths their celestial body was named after. All Venusians being called \"sluts\" and \"easy\", for example.</p>\n" }, { "answer_id": 128148, "author": "Ryan_L", "author_id": 51953, "author_profile": "https://worldbuilding.stackexchange.com/users/51953", "pm_score": 2, "selected": false, "text": "<p>A possible good one for just about any body other than Earth is \"jelly\", referring to the fact that since they were raised in very low-G environments, they have soft bones and no muscle. Anyone from further out than the asteroid belt could be called snowmen or frosty; they're well beyond the Frost Line.</p>\n" }, { "answer_id": 128150, "author": "Cyn", "author_id": 54137, "author_profile": "https://worldbuilding.stackexchange.com/users/54137", "pm_score": 1, "selected": false, "text": "<p>Moonies (for moon dwellers)<br>\nBouncers (for low grav)<br>\nDome dwellers<br>\nSuits (for people who have to wear spacesuits to go outside their city)<br>\nMiner trash (even if they aren't miners in a place that developed for mining)<br>\nAnd of course the modern day: Mouth breathers (a reference to space suit O2)</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/128134", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/47304/" ]

[ { "answer_id": 129899, "author": "mreff555", "author_id": 46291, "author_profile": "https://worldbuilding.stackexchange.com/users/46291", "pm_score": 2, "selected": false, "text": "<p>In aviation, part of the daily forecast is the estimation of unobstructed visibility. Obviously at a reasonable altitude, the curvature of the earth is no longer a factor, so physical obstructions, including fog and clouds are generally the obstructions. 10 statute miles is the maximum value for a clear day. I have never seen a value greater than this. It would be a good starting point.</p>\n" }, { "answer_id": 130217, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 4, "selected": true, "text": "<h1>Calculating apparent magnitude</h1>\n\n<p>Your alignment of the sun, the observer (in space), and the object is as so</p>\n\n<pre><code> 1 AU r AU\n(Sun) ------------- (obsv) ---------//------------(obj)\n</code></pre>\n\n<p>Given that, there are three separate calculations. First is the magnitude of reflected incident energy from the sun. The second is the magnitude of reflected light, given the difference in visible disk of the object, compared to the sun. The third is the brightness of this light to the observer. </p>\n\n<p>An issue here is that luminosity is a full spectrum measure of energy output, but we are only interested in energy from the visible spectrum. Since I can't find a visual spectrum only luminosity for the sun to do an energy calculation, we can use the <a href=\"https://en.wikipedia.org/wiki/Absolute_magnitude\" rel=\"noreferrer\">absolute magnitude</a> of the moon (+0.25) as our starting point.</p>\n\n<p>We must adjust the magnitude of the moon by four factors; as each of these factors increases, the object will be relatively dimmer:</p>\n\n<ul>\n<li>Squared ratio of distance from sun to object to distance from sun to moon</li>\n<li>Ratio of surface area of the moon to surface area of the object</li>\n<li>Albedo of moon to albedo of object</li>\n<li>Squared ratio of distance of object to Earth to distance of moon to Earth</li>\n</ul>\n\n<p>A difference of <span class=\"math-container\">$n$</span> visual magnitudes is equal to a difference of a factor of <span class=\"math-container\">$100^{n/5}$</span> in luminosity. Thus, the logarithm base <span class=\"math-container\">$100^{1/5}=2.512$</span> of these ratios is summed. We will use <span class=\"math-container\">$\\log$</span> to represent <span class=\"math-container\">$\\log_{2.512} = 2.5\\log_{10}$</span> for simplicity. </p>\n\n<p>The distances are straightforward, and are calculated in terms of AU; the moon is roughly 0.00257 AU from Earth. The surface areas of the moon and object are proportional to the radii squared. The object has a radius of 5 km, while the moon is 1738 km. The albedo of the moon is a paltry 0.12, while the object is an incandescent 0.70.</p>\n\n<p>We get the following equation for <a href=\"https://en.wikipedia.org/wiki/Absolute_magnitude#Solar_System_bodies_(H)\" rel=\"noreferrer\">apparent visual magnitude</a> of the object:</p>\n\n<p><span class=\"math-container\">$$0.25 + \\log\\left(\\frac{(r+1\\text{ AU})^2}{(1\\text{ AU})^2}\\right)+\\log\\left(\\frac{1738^2\\text{ m}^2}{5^2\\text{ m}^2}\\right)+\\log\\left(\\frac{0.12}{0.70}\\right)+\\log\\left(\\frac{(r \\text{ AU})^2}{(0.00257\\text{ AU})^2}\\right)\n$$</span></p>\n\n<h1>How far away can we see this object?</h1>\n\n<p>In a big city at night you might only be able to see a magnitude 3 object, while on a moonless night in the middle of the ocean you could see a magnitude 8 object. Lets say that you can see a magnitude 6 object. Attenuation by the atmospheric mass directly overhead is about 0.145 magnitudes; that means that if we were in space, we could see a magnitude 6.145 object.</p>\n\n<p>I take the above equation and, for values of r in AU, plot the apparent magnitude of the object on log scale. </p>\n\n<p><a href=\"https://i.stack.imgur.com/2OmWe.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/2OmWe.png\" alt=\"enter image description here\"></a></p>\n\n<p>The code is here:</p>\n\n<pre><code>&gt;&gt;&gt; import numpy as np\n&gt;&gt;&gt; func = lambda r : 0.25 + 2.5*np.log10((r+1)**2)+2.5*np.log10(1738**2/5**2)+2.5*np.log10(0.12/0.70)+2.5*np.log10((r/0.00257)**2)\n&gt;&gt;&gt; x = [x/2-10 for x in range(22)]\n&gt;&gt;&gt; y = [func(np.exp(i)) for i in x]\n&gt;&gt;&gt; plt.plot(x, y)\n[&lt;matplotlib.lines.Line2D object at 0x7fdb949d7eb8&gt;]\n&gt;&gt;&gt; plt.xlabel(\"Distance from Earth in exp(x) AU\")\nText(0.5,0,'Distance from Earth in exp(x) AU')\n&gt;&gt;&gt; plt.ylabel(\"Apparent visual magnitude\")\nText(0,0.5,'Apparent visual magnitude')\n&gt;&gt;&gt; plt.show()\n</code></pre>\n\n<p>The solution for apparent magnitude 6.15 is 0.00027 AU. <strong>This is 1/100 the distance from the Earth to the moon, 41,000 km; or, roughly, geostationary orbit.</strong> </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/129898", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/40609/" ]

[ { "answer_id": 129967, "author": "L.Dutch", "author_id": 30492, "author_profile": "https://worldbuilding.stackexchange.com/users/30492", "pm_score": 4, "selected": false, "text": "<p>You can realize a large basin upstream, where you can divert the excess water during overflow time.</p>\n\n<p>You can then opt for:</p>\n\n<ul>\n<li>leaking that excess water on a path avoiding the city, going through expendable areas</li>\n<li>let that water drain through the terrain</li>\n</ul>\n\n<p>First one is preferred, as in case of exceptionally extreme cases, you might prefer flooding low value areas instead of the city. Of course you need to take care that no abusive buildings are built in the area designated for being flooded.</p>\n" }, { "answer_id": 129969, "author": "Separatrix", "author_id": 16295, "author_profile": "https://worldbuilding.stackexchange.com/users/16295", "pm_score": 4, "selected": false, "text": "<ol>\n<li>Build it massively over capacity</li>\n</ol>\n\n<p>This is the expensive option, and would be really hard to get through your funding committee. Though of course it would have to be built above \"normal\" capacity to handle day to day fluctuations in flow. \"Flooding\" is basically the point at which your system is over capacity, if the capacity of your system is high enough it will never flood.</p>\n\n<ol start=\"2\">\n<li>Beavers</li>\n</ol>\n\n<p>This is one of the flooding prevention options. We've mostly killed off the beavers, but they provide an important service where they still exist. Their dams slow the river flow and hold back floods to smaller areas upstream. This slowed flow means that it never builds up to the point of flooding in downstream areas.</p>\n\n<ol start=\"3\">\n<li>More vegetation in your river catchment</li>\n</ol>\n\n<p>Another flood prevention option. The more permanent vegetation, the slower the rainwater reaches the river. Again meaning that even with heavy rains the water filters down to the river at a more measured rate and never builds up to the point of flooding further downriver.</p>\n\n<ol start=\"4\">\n<li>Don't build on the floodplain</li>\n</ol>\n\n<p>Leave the river space to flood. This sounds like a very simple and obvious option but you'd be amazed how many cities are built on the main floodplain of their river. Even new build is still going up on the floodplains.</p>\n\n<ol start=\"5\">\n<li>Accept that it's going to flood sometimes</li>\n</ol>\n\n<p>I spent a portion of my early childhood living in a house on legs. Under the centre of the building was a staircase leading up to the house, with legs around the outside.</p>\n" }, { "answer_id": 129974, "author": "Community", "author_id": -1, "author_profile": "https://worldbuilding.stackexchange.com/users/-1", "pm_score": 1, "selected": false, "text": "<p>Build a top water limit for the river, like a roof.<br>\nWhen the initial river overflows, at the river will contain always the same amount of water, while the overflow water will go somewhere else.<br>\nYou can even make the roof out of glas, so you have a modern view of the river</p>\n\n<p>Hope this helps:)</p>\n" }, { "answer_id": 129986, "author": "ubarbaxor", "author_id": 57251, "author_profile": "https://worldbuilding.stackexchange.com/users/57251", "pm_score": 2, "selected": false, "text": "<p>What if it's more about the city's design that the river's ?</p>\n\n<p>Any body of water can overflow.</p>\n\n<p>A city that could float, though, wouldn't necessarily suffer from this - it could just rise with the waters.</p>\n" }, { "answer_id": 129987, "author": "Chronocidal", "author_id": 47510, "author_profile": "https://worldbuilding.stackexchange.com/users/47510", "pm_score": 2, "selected": false, "text": "<p>Have a restricted entry for the river - for example, it passes through a hole in the bottom of a wall.</p>\n\n<p>If the river starts to flood, then the hole limits the amount of water that can come through into the city portion of the river, while the wall redirects the flood waters to tributaries or around the city (into a moat?)</p>\n\n<p>The river then exits through a matching hole at the other end of the city, and (optionally) rejoins the overflow.</p>\n\n<p>(The flow rate of water through the hole when it is submerged should be slightly under <code>14 * Size_of_Hole * Height_of_Water_above_Hole</code> m³s^-1. Build your wall and the flood-plains alongside it accordingly.)</p>\n\n<p>Similarly - if you have a deep /wide ditch or gorge around your city, you have bring the water in via an aqueduct, which will overflow into the gorge in case of a flood, instead of into your city.</p>\n" }, { "answer_id": 129988, "author": "Blade Wraith", "author_id": 50282, "author_profile": "https://worldbuilding.stackexchange.com/users/50282", "pm_score": 2, "selected": false, "text": "<p>This is not as complicated as it seems and a wholee lot more work then it seems</p>\n\n<p><strong>Your Tunnel</strong></p>\n\n<p>First off you need to design the tunnel to meet your requirements whatever they may be, Rivers want to find the easiest and shortest route to lower ground every turn in the river slows it down fractionally. so make your tunnel nice and straight. but as few blockages like grates and covers in the tunnel as possible this will allow the water to flow freely without impediment and also stop anything that gets washed down the tunnel from creating a blockage.</p>\n\n<p><strong>Overflow Pipes</strong></p>\n\n<p>Have these staggered along the the length of the tunnel, should water reach high enough then it will fall into these overflow pipes and out of the tunnel. have these every so often so that if 1 somehow gets overwehlemed for some reason the water will then drop into the next one and the next one etc etc. </p>\n\n<p>These pipes should lead to either a second much large tunnel that would spend a lot of time mostly empty, or out of the city and into another river somewhere else. </p>\n\n<p><strong>Flow Control</strong></p>\n\n<p>This is one of the most important parts have something like a Dam or series of Dams upriver from your city, this will ensure enough water can enter your tunnel but stop or at least limit flash flooding. obviously build your Dam how they try to build them in real life, with overflow piping and the ability to divert water elsewhere if required. </p>\n\n<p>So long as you build it along these lines then your city should be fine. although there is always the old proverb about \"<em>best laid Plans</em>\"</p>\n" }, { "answer_id": 130006, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 6, "selected": true, "text": "<h1>Rivers with stable flow (with <a href=\"http://grdc.sr.unh.edu/index.html\" rel=\"noreferrer\">data source</a>)</h1>\n\n<h3>River downstream of a large lake</h3>\n\n<ul>\n<li><p>The larger the lake, the most stable the flow out of it. Also, it helps that the lake be in a temperate environment, oo water input into the lake doesn't vary too much. The lake can freeze over, as can the outlet river, without really affecting flow much; this happens in the case of the example. </p></li>\n<li><p><strong>Example</strong> - Saint Mary's River (between Lake Superior and Lake Huron in US/Canada) at Sault Ste. Marie. Other good examples are the Rhone downstream of Lake Geneva, and the Neva downstream of Lake Ladoga. </p></li>\n<li><p><strong>Pro</strong> - Very stable flow rate, year round (assuming the lakes don't freeze). Low ratio and magnitude of seasonal fluctuations. When improved with canals and locks, this makes for a great trading city.</p></li>\n<li><p><strong>Con</strong> - In many cases, these outlet rivers are steep and un-navigable. </p></li>\n</ul>\n\n<p><a href=\"https://i.stack.imgur.com/MS7rO.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/MS7rO.png\" alt=\"enter image description here\"></a></p>\n\n<pre><code>Extreme high flow 3590\nExpected annual high 2385\nAverage flow 2142\nExcess over expect high 1205\nExcess over average 1448\nRatio over expect high 0.51\nRatio over average 0.68\n</code></pre>\n\n<p>(Note, all units are in cubic meters per second, except ratio)</p>\n\n<h3>Large tropical river</h3>\n\n<ul>\n<li><p>A large tropical river where half of the river basin is in each hemisphere. As the monsoon rains are pushed by the Intertropical Convergence Zone back and forth between the hemispheres, you will end up with relatively stable rainfall throughout the year. </p></li>\n<li><p><strong>Example</strong> - Congo River measured at Kinshasa. </p></li>\n<li><p><strong>Pros</strong> - Very low seasonal flow variance. Also, an enormous basin for river-borne trade with the city. </p></li>\n<li><p><strong>Cons</strong> - Very high magnitude of flow variance. When the river is this big, even a little bit of flooding is a big deal. </p></li>\n</ul>\n\n<p><a href=\"https://i.stack.imgur.com/Sgapb.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/Sgapb.png\" alt=\"enter image description here\"></a></p>\n\n<pre><code>Extreme high flow 80832\nExpected annual high 56081\nAverage flow 39536\nExcess over expect high 24751\nExcess over average 41296\nRatio over expect high 0.44\nRatio over average 1.04\n</code></pre>\n\n<h3>A temperate river with little snowmelt</h3>\n\n<ul>\n<li><p>The next best scenario is a river with a small basin with constant, low level rainfall, and little snow accumulation.</p></li>\n<li><p><strong>Example</strong> - Seine River at Paris. </p></li>\n<li><p><strong>Pro</strong> - Despite being a big enough river for a truly large city, the magnitude of highest recorded flood to average winter high water is not large.</p></li>\n<li><p><strong>Con</strong> - Large seasonal fluctuations, can be difficult to navigate in summer time due to low water levels. </p></li>\n</ul>\n\n<p><a href=\"https://i.stack.imgur.com/UtBwX.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/UtBwX.png\" alt=\"enter image description here\"></a></p>\n\n<pre><code>Extreme high flow 1284\nExpected annual high 560\nAverage flow 268\nExcess over expect high 724\nExcess over average 1016\nRatio over expect high 1.29\nRatio over average 3.79\n</code></pre>\n\n<h1>Examples of bad rivers</h1>\n\n<h3>Continental river with large, dry basin</h3>\n\n<p><strong>Example</strong> Arkansas River in the US, measured at Little Rock. In the interior US, random thunderstorms lasting for a few days can cause serious flooding, usually in spring or early summer.</p>\n\n<pre><code>Extreme high flow 8220\nExpected annual high 2044\nAverage flow 1066\nExcess over expect high 6176\nExcess over average 7145\nRatio over expect high 3.02\nRatio over average 6.71\n</code></pre>\n\n<h3>Continental river with enormous spring snowmelt</h3>\n\n<p><strong>Example</strong> - Tom River measured at Tomsk, in Siberia. While the high river levels with snowmelt is relatively predictable, it is still very large compared to regular river levels. </p>\n\n<pre><code>Extreme high flow 7500\nExpected annual high 4622\nAverage flow 1047\nExcess over expect high 2878\nExcess over average 6453\nRatio over expect high 0.62\nRatio over average 6.16\n</code></pre>\n\n<h3>River in Monsoon area</h3>\n\n<p><strong>Example</strong> - Vijayawada river in southern India measured at its mouth. While the timing of the monsoon is predictable, its magnitude is not. An erratic monsoon can produce spectacular flooding. </p>\n\n<pre><code>Extreme high flow 16555 \nExpected annual high 6266 \nAverage flow 1642 \nExcess over expect high 10289 \nExcess over average 14913 \nRatio over expect high 1.64 \nRatio over average 9.08\n</code></pre>\n" }, { "answer_id": 130014, "author": "mart", "author_id": 578, "author_profile": "https://worldbuilding.stackexchange.com/users/578", "pm_score": 2, "selected": false, "text": "<p>This actually pretty hard to do. Here's why: Water flows downstream. You need a difference in water level between upstream and downstream of your city. Flow through a pipe is essentially a rather complicated function - typically you use the <a href=\"https://en.wikipedia.org/wiki/Darcy%E2%80%93Weisbach_equation\" rel=\"nofollow noreferrer\">Darcy Weissbach</a> equation in combination with a <a href=\"https://en.wikipedia.org/wiki/Moody_chart\" rel=\"nofollow noreferrer\">Moody chart</a> - of this level difference. Approximately, the head loss, or required level difference between upstream and downstream, quadruples when you double the flowrate. </p>\n\n<p>In open flows like rivers the relationship is far more complicated because with higher flow rate the river bed or channel is usually filled more, which means less then quadruple head loss for double flow rate. <a href=\"https://en.wikipedia.org/wiki/Open-channel_flow\" rel=\"nofollow noreferrer\">Open channel</a> flow is not trivial but please read around a bit</p>\n\n<p><strong>What does this mean for your city?</strong></p>\n\n<p>Let's take one of the rivers from <a href=\"https://worldbuilding.stackexchange.com/a/130006/578\">Kingledions answer</a>, the Seine with low flow around 100 m³/s, average flow of 280 m³/s and extreme flow of 1280 m³/s</p>\n\n<p>It's often a good idea to look at flow systems starting downstream. Let's say at average flow conditions you have a downstream water level of 50m above sea level. You city is 5 km across, really small. This calculator tells me, with an 8m diameter, 5km long pipe, my pressure loss is 72.445 Pa wich is equivalent to a head loss of 7.2 m. So my upstream reservoir level will be 57.2 m at average conditions.</p>\n\n<p>Now, let's take the extreme flow, now I have 1513.962 Pa - 15m! We need a dike between our upstream reservoir that's 65m above sea level, and 7 m above the normal level of the lake or what have you. Actually more, because at extreme flows the downstream level will be higher too, by a few m!</p>\n\n<p>I suggest a second channel or even third that's only opened at high flow events, also play around with the sizing of the pipes.</p>\n\n<p>On the other hand, what happens at low flow? At normal flow, we have a flow velocity of 3.6 m/s . At low flow - 100 m³/s - the flow velocity is 1.3 m/s. The DWA-M 275 (An industrial code, Germany, for designing piping systems in wastewater treatemtn plants that I happebn to have open at the moment) advises a flow velocity of at least 2m/s for raw sewage. Why? Sedimentation! at lower flow velocities, sand etc. will sediment and remain in the pipe. In actuality I don't see this problem, because in all likelyhood your pipe will be the fastest streaming part of the river system.</p>\n\n<p><strong>Environmental impact assessment</strong></p>\n\n<p>The pipe will stop migrating fish, at least most of the time, from swimming upstream. This could seriously impact aquatic ecosystems along your river. </p>\n" }, { "answer_id": 130033, "author": "HopelessN00b", "author_id": 4981, "author_profile": "https://worldbuilding.stackexchange.com/users/4981", "pm_score": 2, "selected": false, "text": "<p>The easiest solution is to build your city where existing geography supports your goals. The most obvious (and extreme) example of an overflow-proof river on Earth would be the Grand Canyon in the Southwestern United States. With the walls of the canyon rising an average of 670 meters above the river bed, there’s no chance of it overflowing a hypothetical city built above it.</p>\n\n<p>You’d want something similar, though probably not as extreme - a river cutting through (and eroding) hard rocks to create high, nearly vertical canyon walls that prevent overflow. The specific rocks and age of the river would determine how high the canyon walls are, so adjust as desired. It took the Grand Canyon anywhere between 6 and 70 million years (depending on who you ask) to develop into its current state, so adjust your time scale as necessary and you’ll get what you want.</p>\n" }, { "answer_id": 130126, "author": "Graham", "author_id": 11823, "author_profile": "https://worldbuilding.stackexchange.com/users/11823", "pm_score": 2, "selected": false, "text": "<p>So, very much like London then?</p>\n\n<p>Whilst the Thames is an iconic feature of London, virtually all London rivers which feed into it are now culverted and carried in pipes underground. <a href=\"https://en.wikipedia.org/wiki/Subterranean_rivers_of_London\" rel=\"nofollow noreferrer\">This Wikipedia page</a> lists many of them, but of course there are more. <a href=\"http://www.londonslostrivers.com/\" rel=\"nofollow noreferrer\">This website and book</a> may also be of interest.</p>\n\n<p>The simple answer is that the culverts start outside the city. If the river overflows, the area around the culvert floods, but the city itself is not affected.</p>\n" }, { "answer_id": 130128, "author": "Philipp", "author_id": 224, "author_profile": "https://worldbuilding.stackexchange.com/users/224", "pm_score": 3, "selected": false, "text": "<p>Use an artificial system of <a href=\"https://en.wikipedia.org/wiki/Lock_(water_navigation)\" rel=\"nofollow noreferrer\">locks</a>, <a href=\"https://en.wikipedia.org/wiki/Weir\" rel=\"nofollow noreferrer\">weirs</a> and dams to control the flow of the river. When the water level is too low, close the downstream gates so the river backs up. When the water level is too high, close the upstream gates so it empties.</p>\n\n<p>In order to be able to deal with droughts or downpour, you will of course need some room to store excess water upstream (a natural lake, artificial reservoir, floodplain or a section of river flowing through a deep valley) and to drain water downstream (like a larger river or ocean).</p>\n\n<p>You see systems like this in many cities which have rivers flowing through them. Let's take the river <a href=\"https://en.wikipedia.org/wiki/Alster\" rel=\"nofollow noreferrer\">Alster</a> which flows through the city of Hamburg in northern Germany, for example. The river flows through two artificial lakes in the center of the city. Those lakes have a nearly constant water level all year around. How do they do this? With a system of variable weirs along the 50km upstream which meticulously control the inflow and a set of locks which control the outflow into the larger Elbe river (as well as prevent inflow from the Elbe when it has high tide). The system was built over 400 years ago, so you don't need 20th century technology to achieve that level of water flow control (although modern meteorology and electronic communication do of course help to improve the reliability). There is a <a href=\"https://de.wikipedia.org/wiki/Alsterschleusen\" rel=\"nofollow noreferrer\">German wikipedia article about the Alster lock system</a> with lots of pictures.</p>\n" }, { "answer_id": 130153, "author": "sh4dow", "author_id": 55318, "author_profile": "https://worldbuilding.stackexchange.com/users/55318", "pm_score": 0, "selected": false, "text": "<p>If you have a waterfall downstream and a relatively straight river bed, limiting the amount of water guarantees your to never have any flooding - all the water that is able to enter the tunnel is able to flow away just as fast.<br>If managing the amount of water entering the tunnel is not possible, you need to manage the flow speed inside: low friction materials on the tunnel walls and, if necessary, turbines that can use electricity to increase the flow velocity could increase the amount of water you can get rid of indefinitely (the water has to come in through the tunnel entrance, so if you can make it keep its velocity all the way through and the tunnel has a constant size, the amount of water exiting the tunnel always equals the amount entering it).</p>\n" }, { "answer_id": 130179, "author": "Harper - Reinstate Monica", "author_id": 20872, "author_profile": "https://worldbuilding.stackexchange.com/users/20872", "pm_score": 1, "selected": false, "text": "<p>Nothing easier. </p>\n\n<h2>Make the river Very Slow, but able to flow fast</h2>\n\n<p>The flow of a river can be measured in cubic meters per second. How fast does it flow? The math is rather straightforward: take a cross section of the river, note its area in square meters, and divide its m3/s flow rate by the area in m2. The result is a speed, in m/s. </p>\n\n<p>Normally, rivers flow at a relatively consistent rate, and have just the cross-sectional area they need. When flow increases, the river <em>rises</em>. Since its banks are sloped, raising the river causes a quadratic or increase in its cross sectional area, but it also causes flooding. </p>\n\n<p>We're going to change that all up. We'll make a river with a very large cross-sectional area. As such, the water moves very, very slowly, e.g. 0.05 metres/sec. When the storm comes, and the river's flow rate increases by a factor of 50, we increase flow to a factor of 50. Now, water is tearing by at 2.5 metres/sec, and canal boaters accustomed to the near stagnant river are like \"nope!\" We wildly overdesign this thing so even a 1000 year storm won't flood out our town every 5 years (assuming Al Gore exists on your planet). </p>\n\n<h2>Level control</h2>\n\n<p>The problem is gradient. Every river is on a grade, that's why it's not a lake. At normal / low-in-the-design-range flow rates, the water will want to be on the bottom of the deep channel,like that sad little garden hose trickle known as the Los Angeles River. </p>\n\n<p>We fix that with some sort of weir that can quickly be moved/removed. Something like lock gates, notched to let pleasure traffic by. Or my favorite, inflatable rubber weirs that arch up from the river bottom. This will be a deep channel allowing the passage of deep ships, and if you can't make passable weirs any other way, you just treat the entire river like a flight of locks, opening and closing each weir serially to let the ship through, lowering the weir ahead of the ship and letting water level dip temporarily. </p>\n\n<p>In wartime, all those weirs get blown to hell, and their failure mode is to let the river run free, so it ends up at the bottom, LA style. Wrecks it for navigation, which would be the enemy's aim, but failure mode is \"not flood the city\". </p>\n" }, { "answer_id": 130453, "author": "Dewi Morgan", "author_id": 6595, "author_profile": "https://worldbuilding.stackexchange.com/users/6595", "pm_score": 0, "selected": false, "text": "<p>It's \"trivial\" (read: rather difficult) to calculate the maximum possible flow of the river:</p>\n\n<p>Take the size of the catchment area.\nMultiply it by the maximum rainflow rate over that area that you expect to get.</p>\n\n<p>You will have to figure out what level of that rain, for how long, you wish to handle.</p>\n\n<p>You can put in as many systems of catchment areas and lakes and so on as you like, but once they become waterlogged and saturated, they are no use. So your two options are: either build upstream flood-management systems that can handle every raindrop that can land on the ground, for as long as it might rain; or make a way for the water to flow through the city faster than it can fall on the ground.</p>\n\n<p>Combining both obviously gives you a good backup ability if one fails, and focusing on management and mitigation obviously also saves those upstream from the city.</p>\n\n<p>Management and mitigation is covered well through other answers.</p>\n\n<p>Throughput is best handled through smooth, wide, deep channels through the city, and for some distance beyond.</p>\n\n<p>Another option is to put turbines in there that can be driven by stored power, to drive water through at an accelerated pace, and provide power in non-flood times. </p>\n\n<p>Another possible cause of flooding is by tidal flow and storm surge from the ocean. In this case, a raisable barrier in front of the city would seem to do the job.</p>\n\n<p>But what if both floods happen at once? A day of storm surge, AND a day of maximum flow from upstream? At this point it definitely needs the turbines, since the upstream water under the city will not of its own accord flow into the deeper water of the ocean: it needs to be pushed by the turbines.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/129966", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/2071/" ]

[ { "answer_id": 130138, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 2, "selected": false, "text": "<h1>How cloud formation occurs</h1>\n\n<p><a href=\"https://i.stack.imgur.com/Bpv1Y.gif\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/Bpv1Y.gif\" alt=\"enter image description here\"></a></p>\n\n<p>Warm air near the surface of the Earth can rise for many reasons. As it rises, it undergoes <a href=\"https://en.wikipedia.org/wiki/Adiabatic_process#Adiabatic_heating_and_cooling\" rel=\"nofollow noreferrer\">adiabatic cooling</a>. Since the pressure drops with rising air, the gas must expand slightly while the temperature drops, as suggested by the ideal gas law (<span class=\"math-container\">$PV = nRT$</span>). As the temperature drops, the relative humidity of the air rises. </p>\n\n<p>If the air rises far enough, and cools enough, then humidity exceeds 100% and moisture precipitates as water droplets. This makes clouds. If enough water precipitates in the clouds, the droplets become big enough that they cannot be suspended in the air and they fall as rain (or snow, depending on temps). </p>\n\n<p>Clouds can form at different altitudes depending on local conditions. Clouds never form above deserts, since there is so little moisture in the air. Clouds form at ground level above wet jungles, since humidity is already 100 %, and any cooling will cause moisture to precipitate. For other climates and conditions, cloud altitude varies. </p>\n\n<h1>How is this affected on your world?</h1>\n\n<p>Lets put your pressure to altitude map side by side with Earth's</p>\n\n<pre><code>altitude Your press Earth press \n(meters) (atm) (atm) ratio\n0 17 1 17\n1000 15.3 0.89 17\n2000 13.8 0.78 18\n3000 12.5 0.69 18\n4000 11.3 0.61 19\n5000 10.1 0.53 19 \n10000 6.0 0.26 23\n15000 3.6 0.12 30\n20000 2.2 0.05 44\n</code></pre>\n\n<p>Air pressure on your planet is relatively higher at altitude, meaning the pressure gradient with increasing altitude is lower than it is on Earth. Since the cooling is driven by pressure changes (again, <span class=\"math-container\">$PV = nRT$</span>), if lower the rate of pressure change with altitude, then we lower the rate of temperature change with altitude. </p>\n\n<p>Therefore, on your planet, <strong>cloud formation occurs at slightly higher altitudes than it would on Earth, given similar temperature and humidity conditions at ground level.</strong></p>\n" }, { "answer_id": 130628, "author": "Artemijs Danilovs", "author_id": 57139, "author_profile": "https://worldbuilding.stackexchange.com/users/57139", "pm_score": 0, "selected": false, "text": "<p>I think, I see problem here. Atmospheric pressure changes Dew point and at 17 atm it will be around 83°C. How much water vapor air will be able to hold? I dont know. I doubt you can have so clean air to hope supersaturate air to form rains all the time.</p>\n\n<p>So you may have fog and rare rains from high altitude... </p>\n\n<p>*Is not your planet way too hot? Earth is like 14-15°C average, record average temp is 34.5°C. Air density is low, would expect it to be around twice as big or pressure around 8atm.</p>\n\n<p>I may be wrong. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/130118", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/53282/" ]

[ { "answer_id": 130732, "author": "anon", "author_id": 41670, "author_profile": "https://worldbuilding.stackexchange.com/users/41670", "pm_score": 2, "selected": false, "text": "<p>Pressure is a funny thing in biology </p>\n\n<p>Note what i am about to say does not apply to vaccum because i am generalizing somethings.</p>\n\n<p>In many ways pressure is irrelevant to physiology. What is critical is pressure difference because that is what kills. It would be possible for a human like body to survive (if created there) in the marianas trench only to explode when brought to sea level. There are plenty of fish that are great examples of this being able to exist in both places.</p>\n\n<p>This obviously isnt the whole story. Those same fish have adaptations and simpler physiology to handle rapid yet gradual changes in pressure. For instance, gases acrue in their swim bladder which must then be expelled. </p>\n\n<p>Now to put your question into a little more perspective:</p>\n\n<p>The highest atmospheric pressure humans have survived in is ~14.7atm which is pretty close to the 17atm listed objective. This begins to show you that not a whole lot is needed for life to survive at that pressure.</p>\n\n<p>Now one thing that id like to touch on is gas exchange. The key for organisms to respire in their environment is their ability to take in the abundant environmental chemistry to use in their metabolic processes. These constructs can have a lot of dependence on pressure. Gills dont function so well in air. Matter of fact we humans have a diaphram specifically to ensure a constant circulating supply of atmosphere. In higher pressures its reported that breathing requires less exertion. </p>\n\n<p>So to answer your question, there MAY be no visible outward difference in adaptations at this pressure. There may be differences in respiratory organs. Its really however your alien nature decides to solve the problem of gas exchange, which there is no universal answer for and can be beyond our immagination. </p>\n\n<p><a href=\"https://www.quora.com/What-is-the-maximum-atmospheric-pressure-a-human-can-survive\" rel=\"nofollow noreferrer\">https://www.quora.com/What-is-the-maximum-atmospheric-pressure-a-human-can-survive</a></p>\n" }, { "answer_id": 131425, "author": "Tim B II", "author_id": 44692, "author_profile": "https://worldbuilding.stackexchange.com/users/44692", "pm_score": 1, "selected": false, "text": "<p>If I'm assuming that your life forms are based on Earth life forms in the first instance, the biggest problem they'll face in the environment you've designed isn't the pressure; it's the mix of gases.</p>\n\n<p>When designing hypothetical atmospheres for earth based life forms, the important thing to remember is that it's all about Partial Pressure. That is to say, that it's about the volume of each gas that gets absorbed, not the pressure of the overall mix. Let's look at the obvious example first, then look at the specific ratio described.</p>\n\n<p>Everyone knows that you can't breathe pure O₂; it burns out your eyes, lungs, etc. and over a given period is lethal. That said, the Apollo Astronauts spent over a week on a return trip in pure O₂ without those effects. Why? Because their capsule was only pressurised to about 0.3 ATM. In effect, if you take 1 bar (sea level pressure) as the norm, then humans regularly breathe in around 0.2 ATM of O₂ with each breath, and the Apollo Astronauts weren't breathing in much more than that in their capsules. So, it wasn't a problem.</p>\n\n<p>Deep sea divers on the other hand require a special mix of air to dive deeply, because once you get below around 60m, you're in 7 Bar of pressure, meaning that every breath you take of normal air at that pressure is around 1.4 ATM of O₂, which is toxic to humans.</p>\n\n<p>The deepest humans can dive in SCUBA gear where their bodies are subjected to the full pressure of the ocean is around 140m, or 15 ATM of pressure. Let's assume though that we can make the leap to 17 ATM at sea level of your chosen planet; what are the gases going to do?</p>\n\n<p>Well for a start, the O₂ is definitely toxic at those levels. So is the Nitrogen, but long before it becomes toxic it'll become narcotic. At the percentages you've described, Nitrogen Narcosis would set in at around 4 ATM, and at 17 ATM I'm pretty sure it becomes toxic.</p>\n\n<p>CO₂ is your real worry, though. CO₂ is toxic in very small doses, and should never be considered safe above 5% at 1 ATM. But, in your atmosphere, you've got a PP of CO₂ of around 51% (17 x 3%) meaning that animals are really going to suffer in this environment.</p>\n\n<p>The Argon is fine, but the trace gasses comprise a PP of around 34% (which if it was O₂ alone would be too high) meaning that if some of that is (say) fluorine, any earth based animals in that environment are dead, end of story. At these levels, trace gasses aren't really 'trace' - the amounts breathed in by a normal earth based life form are enough to cause serious damage if any of them are dangerous because their presence is now material because of the atmospheric pressure.</p>\n\n<p>So, what adaptations could we see to cater for living in such an environment? Well, obviously you no longer need an efficient gas exchange model like lungs. This is because at these pressures, pretty much everything you have in the atmosphere is a problem. So, the best solution is not to take too much of it in.</p>\n\n<p>As I see it, this means 3 possibilities.</p>\n\n<p>The first is smaller lungs. Lungs are still a good idea because they have the potential to be more efficient if the environment changes in some way. But, lungs will have to reduce in size as a percentage of body mass because to do otherwise will kill your subject. Chest muscles will have to be stronger to work in the higher pressure, and the bronchial tubes will no doubt be shorter and wider as well, to more effectively move the higher pressures in and out of the lungs, smaller though they may be.</p>\n\n<p>The second is gills. At those pressures, you're probably better off doing what fish do and just letting the pressure and density of the gas run over a gas exchange system that's semi-external. It won't be as efficient, but then you don't want it to be, especially with the high concentrations of CO₂.</p>\n\n<p>Finally, there's osmosis. Insects are likely to thrive in your environment because they don't have lungs at all; they absorb O₂ through their carapaces until it saturates their body, and waste CO₂ is then expelled through the carapaces. On Earth, this limits the size insects can grow to because if they get too big, the oxygen can't reach the innermost areas of the insect's body. We believe there were periods in Earth's past where oxygen levels were much higher than now, allowing insects to grow to much larger sizes.</p>\n\n<p>In your world, this is very likely to be the case because the partial pressure will allow more O₂ to be absorbed into the insect's body, allowing for deeper saturation.</p>\n\n<p>Of course, oxygen isn't the only consideration in insect size; being exoskeletal means that their carapaces can only get so big before they can't support the creature (square cube law) but certainly they would have an advantage on your world regardless.</p>\n\n<p>Personally, I would expect land based creatures in your world to potentially have gills as if they formed in the ocean first (as we believe life did on Earth), it's one less change evolution would have to implement for survival.</p>\n" }, { "answer_id": 131472, "author": "Ender Look", "author_id": 35041, "author_profile": "https://worldbuilding.stackexchange.com/users/35041", "pm_score": 2, "selected": false, "text": "<h1>TL; DR:</h1>\n\n<p>Skip the Partial Pressures section and go directly to Adaptation; you don't need to read the sub-titles.</p>\n\n<h1>Partial Pressures</h1>\n\n<p>First, we will calculate the partial pressures of your atmosphere:</p>\n\n<p>Note that I don't know the <span class=\"math-container\">$\\text{gr/mol}$</span> of <span class=\"math-container\">$\\text{Trace Gases}$</span> so I tried to make an average with your actual gases. </p>\n\n<p>In addition, I don't like atmospheres so I added a column for partial pressure in kilopascals. Remember:\n<span class=\"math-container\">$$\\text{atm} = 101.325\\text{ kPa}$$</span></p>\n\n<p><span class=\"math-container\">$$ \\left|\n \\begin{array}{cc|ccc|c|cc}\n\\text{Gas}&amp;\\text{%}&amp;\\text{gr/mol}&amp;\\text{Mols}&amp;\\text{Fractal Mol}&amp;\\text{Partial Pressure (Atm)}&amp;\\text{P.P (kPa)}\\\\\n\\text{N}_{2}&amp;\\text{58%}&amp;28.014&amp;2.0703&amp;\\text{62.91%}&amp;10.69&amp;1,083\\\\\n\\text{O}_{2}&amp;\\text{26%}&amp;31.998&amp;0.8125&amp;\\text{24.69%}&amp;4.19&amp;425\\\\\n\\text{CO}_{2}&amp;\\text{3%}&amp;44.01&amp;0.0681&amp;\\text{2.07}&amp;0.35&amp;35\\\\\n\\text{Ar}&amp;\\text{11%}&amp;39.948&amp;0.2753&amp;\\text{8.37%}&amp;1.42&amp;144\\\\\n\\text{Others}&amp;\\text{2%}&amp;30.900&amp;0.0647&amp;\\text{1.97%}&amp;0.33&amp;33\\\\\n\\text{Total}&amp;\\text{100%}&amp;174.87&amp;3.2911&amp;\\text{100%}&amp;17&amp;17,222\\\\\n \\end{array}\n\\right| $$</span></p>\n\n<ul>\n<li><strong>Nitrogen (N₂): 1,083 kPa (10.69 atm)</strong>\n\n<ul>\n<li><strong><a href=\"https://en.wikipedia.org/wiki/Nitrogen_narcosis\" rel=\"nofollow noreferrer\">Nitrogen narcosis</a>:</strong> Nitrogen narcosis is developed under pressures above <strong>240 kPa</strong> and <strong>354 kPa</strong>. Values above <strong>400 kPa</strong> will produce serious nitrogen narcosis. Nitrogen narcosis is similar to drunkenness but worse. If you want to find more information <a href=\"https://worldbuilding.stackexchange.com/a/118921/35041\">in this answer</a> I wrote about its symptoms.</li>\n</ul></li>\n<li><strong>Oxygen (O2): 425 kPa (4.19 atm)</strong>\n\n<ul>\n<li><strong><a href=\"https://en.wikipedia.org/wiki/Oxygen_toxicity\" rel=\"nofollow noreferrer\">Oxygen Toxicity</a>:</strong> Values of oxygen higher than <strong>50 kPa</strong> are lethal for a terrestrial organism. That amount of oxygen burns our skin, eyes, lungs and even cells. Anyone would die in a few hours. In <a href=\"https://worldbuilding.stackexchange.com/a/85096/35041\">this</a>, <a href=\"https://worldbuilding.stackexchange.com/a/85100/35041\">this</a> and <a href=\"https://worldbuilding.stackexchange.com/a/85096/35041\">this</a> answers I describe in detail their effects. The last link has a cute diagram with the effects.</li>\n</ul></li>\n<li><strong>Carbon Dioxide (CO2): 35 kPa (0.35 atm)</strong>\n\n<ul>\n<li><strong><a href=\"https://en.wikipedia.org/wiki/Hypercapnia\" rel=\"nofollow noreferrer\">Hypercapnia</a>:</strong> Hypercapnia is the production of carbonic acid in our body due to the elevated amount of CO2 because the body wasn't able to dispatch it (due to the elevated partial pressure outside). That is lethal and will kill animals very quickly. In <a href=\"https://worldbuilding.stackexchange.com/a/118921/35041\">this</a> and <a href=\"https://worldbuilding.stackexchange.com/a/84125/35041\">this</a> answers you will find additional information and a graphic with the common symptoms. The last link has a table which shows the \"lethality\" of different values. That table shows percentages based on Earth atmospheric pressure. Talking about your world, death arrives in a matter of minutes.</li>\n</ul></li>\n<li><strong>Argon (Ar): 144 kPa (1.42 atm)</strong>\n\n<ul>\n<li><strong><a href=\"https://en.wikipedia.org/wiki/Argon#Safety\" rel=\"nofollow noreferrer\">Argon Asphyxia</a>:</strong> Although argon is non-toxic, it is 38% denser than air and therefore considered a dangerous <a href=\"https://en.wikipedia.org/wiki/Asphyxiant_gas\" rel=\"nofollow noreferrer\">asphyxiant gas</a> in closed areas. It is difficult to detect because it is colourless, odourless, and tasteless. This gas may decant into zones without wind.</li>\n<li><strong><a href=\"https://en.wikipedia.org/wiki/Argox\" rel=\"nofollow noreferrer\">Argon Narcosis</a>:</strong> I don't know much about it, but it's hypothesized that argon can produce the same effects as nitrogen narcosis but only at higher pressures.</li>\n</ul></li>\n</ul>\n\n<h1>Adaptations</h1>\n\n<p>I have done the analysis of the atmosphere but your question wasn't about if humans could survive, so we must think now which adaptations will need your creatures.</p>\n\n<ul>\n<li>Faster metabolism due to the increase in oxygen.</li>\n<li>Faster ageing, short lifespan, a lot of offspring (due to oxidative stress and stuff).</li>\n<li>Bigger insects (again, oxygen).</li>\n<li>Smaller lungs and possibly moister eyes and skin (oxygen and a bit of nitrogen). Insect respiratory system for smaller animals.</li>\n<li>Maybe some tweaks to the brain to avoid narcosis.</li>\n<li>Maybe the ability to smell argon.</li>\n<li>Stronger muscles and bones to counteract gravity. Shorter creatures.</li>\n<li>Increased sweating and ectothermic animals for the elevated temperature.</li>\n</ul>\n\n<h3>Oxygen</h3>\n\n<p>Your oxygen levels are too high; that will hurt their eyes, skin and lungs.</p>\n\n<p>Your species will need very small lungs because they will be able to collect a lot more oxygen with the same amount of space due the elevated oxygen pressure. I wouldn't be surprised to find \"poorly evolved\" lungs since efficiency isn't necessary here.</p>\n\n<p>This oxygen will make metals rust faster due the increased oxidation speed. Flammable things will be even more dangerous. Oxygen has a lot of <a href=\"https://en.wikipedia.org/wiki/Reactive_oxygen_species\" rel=\"nofollow noreferrer\">ROS</a>, molecules that break DNA, proteins or organelles in cells (for more information see <a href=\"https://worldbuilding.stackexchange.com/a/118921/35041\">this answer</a>). These damages accelerate ageing (also explained in the link above). Your creatures will have a very short lifespan but a lot of offspring to compensate.</p>\n\n<p>Some ways to reduce this effect are the implementation of <a href=\"https://en.wikipedia.org/wiki/Active_transport\" rel=\"nofollow noreferrer\">active transport</a> (which consumes huge amounts of energy) or <a href=\"https://en.wikipedia.org/wiki/Semipermeable_membrane\" rel=\"nofollow noreferrer\">semipermeables membranes</a>. Both are explained on the link for the paragraph above.</p>\n\n<p>Furthermore, (<strong>also</strong> explained in <em>that</em> link), your insects will be <strong>HUGE</strong>. (Short-long-answer, insects don't have lungs; they breathe through the skin. More oxygen compensates for the lack of surface-volume relation, which lets them grow more). Because your vast oxygen partial pressure, I'm quite sure this technique will also be possible for smaller animals.</p>\n\n<p>Finally, they may need wet skin and wetter eyes to counteract oxygen oxidation.</p>\n\n<h3>Nitrogen</h3>\n\n<p>No idea how to fight that, maybe smaller lungs will fix that. Some modification to the brain (not sure how) may reduce nitrogen narcosis. If they evolve there, they must be used to being \"drunken\".</p>\n\n<h3>Argon</h3>\n\n<p>Your creatures will need a way to smell argon, or they will accidentally die in an argon well because it's heavier and can get sunk in valleys or plains.</p>\n\n<h3>Gravity</h3>\n\n<p>An increase of only 36% isn't very bad. A healthy human can survive that fine. They will evolve with slightly stronger bones and muscles to counteract that. I will suggest hollow bones like birds to compensate for the additional weight. Also, creatures will have a shorter height.</p>\n\n<h3>Temperature Control</h3>\n\n<p>This is one of your lesser problems. Sweating more, having a lower metabolism and being cold-blooded animals will fix that. You can learn about <a href=\"https://en.wikipedia.org/wiki/Thermoregulation\" rel=\"nofollow noreferrer\">thermoregulation</a> in Wikipedia.</p>\n\n<p>Basically, animals are divided into two big categories: <a href=\"https://en.wikipedia.org/wiki/Endotherm\" rel=\"nofollow noreferrer\">endotherm</a> and <a href=\"https://en.wikipedia.org/wiki/Ectotherm\" rel=\"nofollow noreferrer\">ectotherm</a>. While the first ones produce their own heat to maintain their desired body temperature, the second category takes advantage of the environment's heat, using that as their body temperature.</p>\n\n<p>I strongly advise to make your animals ectothermic, because they don't spend energy on warming up since the environment is enough to keep them warm, maybe even too much... (if 36 ºC is the average I don't dare to be there during summer...).</p>\n\n<p>Anyway, we can still take some useful cooling traits from warm creatures (endotherms) before we get deep into the other. Endothermic creatures have <a href=\"https://en.wikipedia.org/wiki/Endotherm#Avoiding_overheating\" rel=\"nofollow noreferrer\">a few</a> mechanisms to avoid overheating:</p>\n\n<ul>\n<li><strong>Panting:</strong> By panting with the tongue, they are able to lose temperature by increasing water evaporation in the breath. As you say in comments, birds' respiratory systems might be useful due to their fast breathing. I would add blood vessels which flow blood in the opposite flow direction to make <a href=\"https://en.wikipedia.org/wiki/Countercurrent_exchange\" rel=\"nofollow noreferrer\">countercurrent heat exchange</a>.\n<a href=\"https://i.stack.imgur.com/IqRos.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/IqRos.jpg\" alt=\"enter image description here\"></a></li>\n<li><strong>Flushing:</strong> Increasing the blood flow to the skin transfers the heat from the inner body to the skin, place where it can be <a href=\"https://en.wikipedia.org/wiki/Radiant_energy\" rel=\"nofollow noreferrer\">radiated</a> into the environment. I encourage your creatures to have a large surface-volume ratio to avoid <a href=\"https://en.wikipedia.org/wiki/Gigantothermy\" rel=\"nofollow noreferrer\">gigantothermy</a> (big animals produce too much heat that they can't remove). For example, the usage of huge ears like car radiators (blood vessels) is very useful.</li>\n<li><strong>Sweating:</strong> If the creature is hairless or short-haired, it can cool itself by sweating water. Take note that this method consumes water and minerals from the body.\nJust for curiosity's sake, I'll tell you that endothermic creatures are more resistant to fungal infections due their own heath production. Sadly, you can't handle that. (Maybe the environmental heat is enough?). Also, your animals won't have <a href=\"https://en.wikipedia.org/wiki/Brown_adipose_tissue\" rel=\"nofollow noreferrer\">brown adipose tissure</a> because that is to produce heat, and you don't need more.</li>\n</ul>\n\n<p>Now we must discuss ectotherms in more depth. As an advantage, ectotherms creatures eat a lot less (like 5 or 10 times less) because their slowed metabolism saves a lot of energy (lack of internal heating process); they are very economical! But they are only active during the day (due to the need to bask under warm sunlight), but your planet is quite hot so...</p>\n\n<p>This requires cold-blooded animals to work with the fluctuations of ambient temperatures because they directly affect their body temperature. Ectothermic creatures are divided into even more categories based on how they \"control\" or \"help\" their temperature. Usually animals are very focused on one technique, but is possible to have trait of several, like reptiles. The main techniques are being poikilothermic and homeothermic.</p>\n\n<p>The homeotherm is very known by everybody. These creatures try to always maintain the same body temperature, even if the temperature is only produced by the environment. Instead, poikilothermic creatures have between 4 and 10 enzyme systems (instead of 1 specialized but effective enzyme) in their bodies to survive and operate at different ranges of temperatures without problems. However, these enzymes are difficult to develop ^{[Quotation need.]} and make longer DNA (not sure if that is necessarily bad, but cool).</p>\n\n<p>I don't know how your creatures are, but take note that poikilothermic creatures don't have sustained high-energy activities like powered flight (in large animals) or large brains. These creatures usually wait patiently for their prey rather than hunting actively, because they require between 10 to 20 times less energy than homeothermic animals (usually warm-blooded). And they usually seek shelter at noon but bask in the sun and takes advantage of gigantothermy to lose less heat, but luckily, on your planet there is plenty of heat! So I think they could have homeothermy, since there is enough heat to maintain a stable temperature.</p>\n\n<p>Remember that even without a warm sunny day, some cold-blooded animals can still work. Some ectothermic animals have evolved to vibrate their muscles in order to generate a bit of heat when it's very necessary (this is usually done by insects, but I don't see it being difficult for other animals), a technique common in endothermic creature (like when you are cold and you begin to shiver).</p>\n\n<p>For both cooling and heating, these creatures take advantage of <a href=\"https://en.wikipedia.org/wiki/Heat_exchanger#In_nature\" rel=\"nofollow noreferrer\">heat exchange techniques</a> (like countercurrent exchange). By using blood vessels, they can effectively move heat from outside to inside or from inside to outside for cooling and warming purposes. Also, the secretion of mucus is usually used to increase evaporation, and if the environment is very cold, they can enter into <a href=\"https://en.wikipedia.org/wiki/Torpor\" rel=\"nofollow noreferrer\">torpor</a> (decreased activity)</p>\n\n<p>Finally, there is a third category after endothermy and ectothermy: mesothermy. They are hybrids between both techniques, basically adapting for the environment. They usually have poor metabolic control in their bodies (like ectotherms), but if it is necessary they will metabolize brown fat to produce heat (like endotherms) or increase in size (gigantothermy).</p>\n\n<p>So, to summarize, your animals must pant and sweat. Being hairless, they will retain less heat, and by sweating through their skin and panting (with a large tongue), they will be able to lose heat by evaporating water. Passive techniques that don't require water will be flushing hot blood to the skin to radiate heat. It will be very advisable to increase the surface-volume ratio to avoid <a href=\"https://en.wikipedia.org/wiki/Gigantothermy\" rel=\"nofollow noreferrer\">gigantothermy</a>, like having big ears like elephants, many blood vessels, and the ability to move at will. In this way, they will be able to radiate heat and flap to increase the airflow.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/130713", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/53282/" ]

[ { "answer_id": 130733, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 3, "selected": false, "text": "<h1>Blue, but darker</h1>\n\n<p>Earth's sky is blue due to <a href=\"https://worldbuilding.stackexchange.com/a/63962/23519\">Rayleigh Scattering</a>. Rayleigh scattering redirects at an angle a percentage of incident light through a gas. The percentage of light reflected is proportion to <span class=\"math-container\">$1/\\lambda^4$</span>, where lambda is the wavelength. That is, the shorter the wavelength, the more light is reflected. Violet light is most reflected, percentage-wise, but the purple section of the visible spectrum is small. So Blue light is the next most reflected, and since that portion of the visible spectrum is large, the sky is blue. </p>\n\n<p>For your atmosphere, the percentage of oxygen and argon are higher, but he percentage of nitrogen is lower. From Table 1 of <a href=\"https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19770012747.pdf\" rel=\"nofollow noreferrer\">Shardanand and Rao, 1977</a> here is a comparison of scattering cross section (in <span class=\"math-container\">$10^{-27}\\text{ cm}^{-2}$</span>) for various atmospheric gasses at certain wavelengths (on the x-axis, in Angstroms):</p>\n\n<pre><code>Molecule 6328 5145 4880 4579 3638\nO2 2.06 4.88 6.50 8.39 20.03\nN2 2.24 5.61 7.26 10.38 23.82\nAr 2.08 5.46 7.24 10.13 23.00\n\nCO2 7.28 17.25 23.00 29.60 70.70\nCH4 5.26 12.44 16.59 21.40 51.10\n</code></pre>\n\n<p>Notice how similar oxygen, nitrogen, and argon are to each other, as compared to carbon dioxide or methane. The relative rate at which the different wavelengths of light are scattered by your atmosphere will be almost the same as on Earth, so the color of the sky will be almost the same as on Earth.</p>\n\n<p>Your star will be putting out light in a spectrum very similar to that of our sun, so the highest magnitude wavelengths will be in the blue range, just as our Sun's are. See <a href=\"https://worldbuilding.stackexchange.com/a/102636/23519\">here</a> for more details. </p>\n\n<p>The final factor is the mass of the air column. The proportion of light both absorbed by the atmosphere and raleigh scattered is affected by the number of air molecules that a light wave encounters as it travels into the atmosphere. Without you giving a surface gravity, I can't exactly calculate the air column's mass, but from your pressure and density, the mass of the air column is something like 10 times as massive on Earth. Therefore, light will be that much more likely to be absorbed or scattered.</p>\n\n<p>This will make the sky a much darker shade of blue. But note, due to the same emission spectrum of the sun and the same scattering factors, that doesn't mean that the shade of blue is changed, just the brightness of the blue. The blue color will be the same shade, but darker. </p>\n" }, { "answer_id": 130760, "author": "Artemijs Danilovs", "author_id": 57139, "author_profile": "https://worldbuilding.stackexchange.com/users/57139", "pm_score": 1, "selected": false, "text": "<p><strong>It will stay blue.</strong></p>\n\n<p>But what blue? <a href=\"https://i.stack.imgur.com/i94g7.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/i94g7.png\" alt=\"enter image description here\"></a>\nAs stated, rayleigh scattering will be most deciding factor for <a href=\"http://math.ucr.edu/home/baez/physics/General/BlueSky/blue_sky.html\" rel=\"nofollow noreferrer\">sky color</a>. As your atmosphere has more volume and density, more carbon dioxide >> more scattering and more scattering for shorter wavelenghts.</p>\n\n<p><a href=\"http://file.scirp.org/pdf/ACS20120400011_46715429.pdf\" rel=\"nofollow noreferrer\">Paper on color of the sky</a>, it is more about our sky and how color changes as sun sets. But you can get some understanding from that.</p>\n\n<p>So blue light wavelenght will be moved to around 450-480nm, that gives us blue to pale blue. How much light makes it to surface? Is up to you, but it too will influence how dark your blue is.</p>\n\n<p>But it would be way more nicer if we make your density more in line with atmospheric pressure of 17 atm >> around twice your choise. That would give us pinkish sky or yellow with a lot of dust.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/130725", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/53282/" ]

[ { "answer_id": 130987, "author": "Blade Wraith", "author_id": 50282, "author_profile": "https://worldbuilding.stackexchange.com/users/50282", "pm_score": 3, "selected": false, "text": "<p>I'll try to tackle each of your points, so reaslistically on the face of it, its fairly plausible</p>\n\n<blockquote>\n <p>My world takes place in a massive crater, It is roughly 800 x 600 miles and 5 miles deep. At the bottom it is 1.2 atm in pressure, while the surface is at 0.5 atm.</p>\n</blockquote>\n\n<p>Pressure variance is reasonable and plausible, my only question though, what happened to the rest of the world to the crater being:</p>\n\n<blockquote>\n <p>the only habitable place left on the planet.</p>\n</blockquote>\n\n<p>That sentence suggests that something happened else where and that something could very easily transfer into this crater which could very easily effect life, but that's an aside</p>\n\n<blockquote>\n <p>Due to the extreme “altitude” conditions the surface of the planet is cold(would it really be though?) windy, and home to extremophile bacteria mats/mounds, and possibly lichens/moss. The wind here is extremely fast because there’s not much to slow it down.</p>\n</blockquote>\n\n<p>This is a tough one, if the \"surface\" is fairly uniform in terms of height, and it is just this crater that goes deep below this surface then actually the \"altitude\" would be basically ground level and would be receiving similar amounts of energy from the sun to that of the crater. so while the surface would have lower pressure and indeed lower temperatures, significantly lower tempretures are not a given, again there would be a gradient</p>\n\n<blockquote>\n <p>The sides of the crater are gently sloping downwards, and the wind follows it down. The bacterial mats slowly give way to montane grassland and meadows. Early morning dew from the cold winds is the source of water here. Small gnarled trees grow slowly and are warped by the wind. Meadows are nearby springs, where ancient aquifers were fractured during the meteor impact.</p>\n</blockquote>\n\n<p>This is easily possible, although craters aren't just a big hole in the ground, the rim of the crater protrudes the bedrock somewhat, even on very old and weathered craters. now this rim is mere metres on Meteor Crater in the US, and is definitely not uniform. however that is a mere kilometre or so across, not 600-800 miles. so that rim is going to be a small mountain range all the way along it. which means anything on one side will have similar on the outside of the rim</p>\n\n<blockquote>\n <p>Next comes the treeline and the coniferous forests with fern undergrowth. The wind is slowed by both the trees and its compression at -12,000 feet into the crater. Rain occasionally falls here if the conditions are right. Overall the precipitation is mostly occult. This area has sizable lakes from other meteor impacts which are filled by fractured aquifers and streams from up the crater.</p>\n</blockquote>\n\n<p>A 600-800 miles diameter crater will still have significant heating and cooling, its big enough to not stop high level winds effecting the weather or climate within the crater and also big enough to easily generate its own weather, so the trees.</p>\n\n<blockquote>\n <p>Eventually the heat of the Earth warms the cool air and we reach temperate deciduous forests. Winds are breezy here and carry precipitation from higher up the crater. Evening showers are relatively common. Streams have become rivers by this point. The forests reach all the way to sea level, except where humans have cleared them away for agriculture.</p>\n</blockquote>\n\n<p>Don't discount the power of the sun. if there is trees and life then the sun has to be able to get through to power photosynthesis. which means its not just the heat of the earth that will warm up air.</p>\n\n<p>As for the forests and the rest, yes perfectly plausible</p>\n\n<blockquote>\n <p>A massive sea covers much of the bottom of the crater, and fortunately it has reached an equilibrium between evaporation and being filled from the aquifers.</p>\n</blockquote>\n\n<p>This is perfectly reasonable, but it the water and clouds do extend past the rim then that water is lost as it freezes and settles. aquifers are fairly constant water sources, if you had a particularly warm year where ice melted on the surface more than average then those aquifers would let it all roll downhill and you crater bottom sea has no where lower to send the water so keeping that homeostasis would be unlikely, but not impossible.</p>\n\n<blockquote>\n <p>In the sea are a series of islands from the complex crater. These islands experience hot moist air, daily rain, and are temperate rainforests. It is here, finally, that the air rises up in a massive updraft. The hot air rises, disperses, and mixes with the atmosphere. Some water vapor finds its way back into the crater, but much more leaves.</p>\n</blockquote>\n\n<p>All of this is fine, but i'd even with a massive updraft its still unlikely to have most of the water leave, most rainclouds are within the first 5 miles of atmosphere so those clouds wouldn't escape the crater walls</p>\n\n<p>I cannot stress enough i am not a meteorologist, This is all just some basic research and my understanding. hope it helps</p>\n" }, { "answer_id": 131002, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 4, "selected": true, "text": "<h1>Temperature change is caused by lapse rate</h1>\n\n<p>The difference in temperature between the bottom and top of the crater is going to be driven by the <a href=\"https://en.wikipedia.org/wiki/Lapse_rate\" rel=\"noreferrer\">lapse rate</a>, and not by the heat of the crust (probably). Lapse rate is the rate at which temperature in Earth's atmosphere decreases with an increase in altitude, or increases with the decrease in altitude. In particular, we can use a chart of moist adiabatic lapse rate to see what the expected temperature changes would be in a 5 mile (8 km) deep crater.</p>\n\n<p><a href=\"https://i.stack.imgur.com/FkVxW.gif\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/FkVxW.gif\" alt=\"enter image description here\"></a></p>\n\n<p>The 'Moist Adiabat's are the dotted lines on the chart. Chicago has a annual mean temp of about 10 C, Washington DC about 15 C, Houston about 20 C, and Miami 25 C. Pick your starting point, then follow the dotted line upwards until it intersects with the line representing 8 km. I get the following:</p>\n\n<pre><code>Floor Temp Surface Temp Surface Press\n 10 C -60 C 0.34 atm\n 15 C -45 C 0.36 atm\n 20 C -30 C 0.38 atm\n 25 C -15 C 0.42 atm\n</code></pre>\n\n<p>So you are looking at quite the different in temps. I also used this chart to double check your pressure estimates. Instead of starting at 1 atm, your crater surface starts at 1.2 atm, so I multiplied the resulting pressure estimates by 1.2. You are pretty close to being right on the pressure. </p>\n\n<p>Overall, the area outside the crater will be very uninhabitable. </p>\n\n<h1>Why the Earth won't provide appreciable heating in the crater</h1>\n\n<p>The <a href=\"https://en.wikipedia.org/wiki/Crust_%28geology%29#Earth&#39;s_crust\" rel=\"noreferrer\">Earth's crust</a> is about 30-50 km deep on the continents, away from tectonic boundaries, and it has a temperature gradient of about 200-400 C in heating between the surface and the boundary with the mantle. The <a href=\"https://en.wikipedia.org/wiki/Earth%27s_internal_heat_budget#Global_internal_heat_flow\" rel=\"noreferrer\">heat flux</a> on continental crust is about 71 mW/m<span class=\"math-container\">$^2$</span>. </p>\n\n<p>The simplest argument I can make is to compare the heat flux on the continental crust with the heat emitted by the Earth's surface in infra-red radiation. The Earth's surface emits 398 W/m<span class=\"math-container\">$^2$</span> in IR radiation to the skies, on average. This is significantly higher than the 71 mW/m<span class=\"math-container\">$^2$</span> that comes from inside the Earth. </p>\n\n<p>Lets look at what happens to planetary heat flux when we change the thickness of the crust. Planetary heat flux is controlled by the <a href=\"https://en.wikipedia.org/wiki/Thermal_conduction#Fourier&#39;s_law\" rel=\"noreferrer\">Fourier's law</a> for head conduction</p>\n\n<p><span class=\"math-container\">$$q = -k\\nabla T.$$</span></p>\n\n<p>Here <span class=\"math-container\">$q$</span> is heat flux (W/m<span class=\"math-container\">$^2$</span>), <span class=\"math-container\">$k$</span> is conductivity and <span class=\"math-container\">$\\nabla T$</span> is the heat gradient. If we reduce the distance between crust and surface by 8 km, from 25 km to 17 km, with a constant 300 K temperature differential then <span class=\"math-container\">$\\nabla T$</span> goes from 12 K/km to 17.6 K/km. This represents a 1.5 times increase in heat flux out of the Earth's surface. </p>\n\n<p>So the Earth is providing something like 120 mW/m<span class=\"math-container\">$^2$</span> at the bottom of your crater instead of 70 mW/m<span class=\"math-container\">$^2$</span>. Still, compared to 160 W/m<span class=\"math-container\">$^2$</span> absorbed from sunlight and 80 W/m<span class=\"math-container\">$^2$</span> released by evapo-transpiration and IR radiation to space, and back-radiation received from atmosphere and clouds....you get the picture. The change in planetary heat flux is negligible, three orders of magnitude smaller, at least.</p>\n\n<p>Therefore, the temperature gradient between the crater bottom and high surface are going to be driven mostly by lapse rate, the same factor that drives the temperature difference between sea level and the top of Mount Everest on Earth.</p>\n\n<h1>Air flow around the crater</h1>\n\n<p><a href=\"https://i.stack.imgur.com/5G8KT.gif\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/5G8KT.gif\" alt=\"enter image description here\"></a></p>\n\n<p>Your crater is much hotter than the surrounding air. Hot air tends to rise. The dominant climactic feature will be rising hot air out of the crater. This will cause a variety of follow on effects.</p>\n\n<h3>Rising hot air creates cyclones!</h3>\n\n<p>Your crater is so large it will induce high speed, cyclonic winds circling around it. In the diagram above, the 'x' and 'o' represent winds into and out of the page around the crater. There will be permanent winds swirling around the crater. </p>\n\n<p>If your crater is entirely in the northern or southern hemisphere (assuming your planet is rotating like Earth) the <a href=\"https://en.wikipedia.org/wiki/Coriolis_force\" rel=\"noreferrer\">Coriolis effect</a> will drive the winds into a stable clockwise or anti-clockwise rotation around the crater. If the crater straddles the equator....something will happen, I'm not really sure. if the crater is on the Equator and large enough relative to the size of the planet, the cyclone may actually form a circle around the surface of the planet, but don't quote me on that. </p>\n\n<h3>Rising air releases moisture as it cools</h3>\n\n<p>As your air rises, it will lose its ability to hold moisture. You can see this from the thermodynamic diagram at the top of the page. If we assume a jungle-y 25 C average temperatures at the bottom of the crater, then that air can hold about 20 g of water per cubic meter. Elevate that air to 8 km, and it can hold about 3.5 g, leaving the remainder to fall as rain. </p>\n\n<p>The center of your crater will be <em>constantly</em> raining. The temperature gradient between crater bottom and surface is going to be much higher than the temperature gradient between day and night, therefore, you will always have a steadily rising column of hot air. </p>\n\n<p>Various wind conditions might blow around pockets of warm air, especially towards the edges, but you can assume the center of the crater will see rain every single day. The hotter the crater, the higher the <em>magnitude</em> difference in saturation mixing ratio will be, so the more rain you will get. A 10 C crater will get light rain every day, a 25 C crater will see permanent torrential rainfall.</p>\n\n<h3>Descending cold air will enter the crater like a blast furnace</h3>\n\n<p>From the cyclone swirl, descending cold air will spiral into the basin to take the place of the air that rose out. The force of gravity will ram this wind into higher pressure areas at the bottom of the crater, and the resulting molecular friction will be expressed as adiabatic heating.</p>\n\n<p>These are <a href=\"https://en.wikipedia.org/wiki/Foehn_wind\" rel=\"noreferrer\">foehn winds</a>. The 8 km drop means that you would see an expected 30-60 C of adiabatic heating as the wind rushes downhill. Given that the wind already has high kinetic energy from the hurricane swirl at the top, the result near the bottom with be superheated blast-furnace winds. If conditions are right at the top, with extra solar heating for whatever reason, you could easily see steady 45 C or higher gale-force winds at the bottom of the crater.</p>\n\n<p>No trees will live on the slopes of the crater, due to the high wind speeds and highly variable temperatures. The slopes could easily see temperature changes of 30 C in a matter of minutes, as one air mass blast past and is replace by another. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/130970", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/57574/" ]

[ { "answer_id": 134112, "author": "Shadowzee", "author_id": 45212, "author_profile": "https://worldbuilding.stackexchange.com/users/45212", "pm_score": 2, "selected": false, "text": "<p>There are a couple of ways you could end up limiting this or restricting your magic system to account for this.</p>\n\n<p>The first way is to simply place a limit on the number of Magic Circles a Mage is capable of channeling before they are roasted. Rituals that do result in a roasted mage are considered forbidden and not practiced except in dire times.</p>\n\n<p>The second way is to have another animal act as the sacrificial channeling object. You can do this by either having the animal directly channel the energy between two circles. Have a mage who can control the challenging though the animal or have the mage direct the energy through different animals (In this case, the mage will still need to interact with the energy, but since it doesn't pass through them completely, the damage is minimal). Think of the mage like an Electrician and the Animal as a piece of Wire. In the original case you mentioned, the Mage connects himself to both ends and lets the electricity pass through him. In the second case, the mage can just tie an animal to both ends and is done with it. In the third case, the mage pushes the animal onto the ends, but needs to hold it in place. In the fourth, the Mage needs to make an initial connection using his arm which then goes into the animal, but doesn't pass through the rest of the mages body.</p>\n\n<p>Finally, if your system allows it. You can have sub rituals going on at the same time to actively cool the channeler. This makes your larger spells grow in complexity and size, because you will have people cooling channelers and more channelers to provide power for more cooling for the core channelers and so on. </p>\n" }, { "answer_id": 134113, "author": "LinkBerest", "author_id": 54517, "author_profile": "https://worldbuilding.stackexchange.com/users/54517", "pm_score": 2, "selected": false, "text": "<p>I have two parts of this answer one - how to stay alive longer without using (much) magic and the other a thought on how to use magic to survive:</p>\n\n<h3>Without magic</h3>\n\n<p>Well, assuming this is just internal heat or at least not enough to actually start cooking the person, standard methods for extreme heat environments and treatments for high fevers could work to at least slow the effects on the channeler:</p>\n\n<ol>\n<li>Start the person on an IV drip (or constantly drinking water if equivalent level of technology/relic/magic item cannot be made) and start this before the circles are complete.</li>\n</ol>\n\n<p>The idea here is your body is going to need a bit of hyper-hydration before starting an activity that will raise one's body temperature significantly. Then as it begins, our channeler will need to continue this hyper-hydration to help maintain body temperature (compensate for added heat).</p>\n\n<p>Note, if no \"IV drip\" you could have a second circle going which is casting a very low level \"restoration\", \"cooling\", or etc... spell on the channelers - one which is perfectly within safety requirements and can even stop and switch when needed.</p>\n\n<ol start=\"2\">\n<li>Have buckets of water ready to dump on <em>clothed</em> person</li>\n</ol>\n\n<p>Yeah, your going to be hot so the natural instinct is to wear as little as possible. Think about the last time you were rained on during a hot day though - it was nice at first but then you walked inside and were freezing! The light clothing will actually help hold the sweat, and the added buckets of water, on you by not allowing it to evaporate.</p>\n\n<p>If it is a really big spell, the channeler might actually sit in a tub of ice water (or pool dug in ground) to keep that core temp lower.</p>\n\n<ol start=\"3\">\n<li>Aspirin/Acetaminophen equivalent</li>\n</ol>\n\n<p>There have been numerous <a href=\"https://www.ncbi.nlm.nih.gov/pubmed/16154478\" rel=\"nofollow noreferrer\">studies</a> showing that these two can help reduce fevers. This would be the most hand-wavy though as you would first have to determine herb/plant equivalents for these and they are not meant to treat heat from an external source (they inhibit the reaction of certain systems). However, its still an option if you want some hand-wavy but seems real-ish solution.</p>\n\n<h3>Using magic items/own magic</h3>\n\n<p>Now the above may work for your average channeler on an average spell but for those really big spells - you'll need something different and either a special channeler or special tools:</p>\n\n<ol>\n<li>Mimic the <a href=\"https://en.wikipedia.org/wiki/Thermophile\" rel=\"nofollow noreferrer\">thermophile</a> of Earth</li>\n</ol>\n\n<p>Thermophile actually use the heat, and sulfur, to survive they way we use oxygen. So alter these channelers through magic to require heat to survive. This could be a permanent change (maybe make them require sulfur, such that they must live near volcanoes) or have a polymorph spell prepared in an enchantment.</p>\n\n<ol start=\"2\">\n<li>No heat is lost only transferred - so give the excess a new place to transfer</li>\n</ol>\n\n<p>This could be a channeler who is also a mage and so during the transfer uses the heat to cast a separate small spell or keeps an enchanted stone that works as a heat sink. </p>\n\n<p>Another thought is they sit as both channeler and mage in a second circle and use the \"lost\" energy from large spell 1 to fuel minor spell 2.</p>\n" }, { "answer_id": 134123, "author": "The Square-Cube Law", "author_id": 21222, "author_profile": "https://worldbuilding.stackexchange.com/users/21222", "pm_score": 2, "selected": false, "text": "<p>The simple answer is to get one or more <a href=\"https://en.wikipedia.org/wiki/Lich\" rel=\"nofollow noreferrer\">liches</a> into the loop.</p>\n\n<p><img src=\"https://i.stack.imgur.com/s3eGG.png\" alt=\"A lich\"></p>\n\n<blockquote>\n <p>In fantasy fiction, a lich (/ˈlɪtʃ/;[1] from Old English līċ meaning \"corpse\") is a type of undead creature. Often such a creature is the result of a transformation, as a powerful magician skilled in necromancy or a king striving for eternal life using spells or rituals to bind his intellect and soul to his phylactery and thereby achieving a form of immortality.</p>\n</blockquote>\n\n<p>In the eternal words of Balon Greyjoy, <em>what is dead may never die</em>. Dude's already croaked in the name of magic, might as well turn the dial on eleven to the bridge he's holding. I'm sure they won't mind the heat.</p>\n" }, { "answer_id": 134124, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 4, "selected": true, "text": "<p>So the real key to this is doing something with the energy before it becomes the unknown wobbling mess of thermal energy that turns your witch into a pop tart. If you generate the heat, you have to get rid of it, period. The only real solution is to minimize the rate of heat generation.</p>\n\n<p>Consider how one can use capacitors or inductors to shape current flow. If there's too much voltage, you can bleed some of the energy into a capacitor and release it later. Because you released it back into the system, it doesn't get turned into heat. If you had used a resistor, you would have had to convert it all to heat. They make <em>big</em> resistors for that, but you don't need them.</p>\n\n<p>So your channeler never tries to fix anything by opposing it. They simply bleed some energy into themselves when there's too much in one form, and emit it back out in the other. You can be arbitrarily good at this.</p>\n\n<p>The other big thing you may need is a failsafe. If your channeler isn't very good, and gets in trouble during practice, it'd be nice if they didn't die. For that, I'd recommend taking a lesson from High Voltage Direct Current (HVDC) lines. HVDC lines have to have a circuit breaker, like all power lines. However, this is difficult. Normal AC power cycles at 60Hz. This means once every 0.86ms, the voltage across the circuit breaker is zero. This extinguishes any arc that may form between the electrodes and makes interrupting the current comparatively easy. Doing it in the HVDC world is harder because the <a href=\"https://www.youtube.com/watch?v=LHSVKuHqyKE\" rel=\"noreferrer\">current is never interrupted</a>.</p>\n\n<p><a href=\"https://i.stack.imgur.com/W2RNJ.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/W2RNJ.jpg\" alt=\"Arcing during a disconnect\"></a></p>\n\n<p>One solution is the <a href=\"https://new.abb.com/docs/default-source/default-document-library/hybrid-hvdc-breaker---an-innovation-breakthrough-for-reliable-hvdc-gridsnov2012finmc20121210_clean.pdf?sfvrsn=2\" rel=\"noreferrer\">\"hybrid\" breaker</a>. This approach is based on the observation that there's two kinds of breakers in the HVDC world. There's slow mechanical breakers which arc badly if opened under load, and there are fast semiconductor breakers which don't arc because they simply change the resistance of the semiconductor. However, the semiconductor breakers have a problem that they generate resistance during operation. You can't get them down to negligible resistance, so they are constantly generating heat. A mechanical breaker, when conducting, is basically a large wire. It's resistance is very low, so very little heat.</p>\n\n<p>The hybrid approach is to have both switches in parallel. In the normal conducting state, the mechanical switches are closed and the semiconductor switch is open. This means all of the power runs through the mechanical switches, keeping the channeler... I mean conductors cool. When a fault occurs, the system first closes the fast semiconductor switch, so that both switches are conveying current in parallel. Now the mechanical switches open. Because the semiconductor is conducting current around them, there's virtually no voltage across them, and thus they don't arc much at all. Now the semiconductor is conducting all the energy, and heating up like crazy. But it can then be switched open without an arc, and the current is fully interrupted.</p>\n\n<p>This mechanism brings the best of both worlds. When everything is going properly, the mechanical switches conduct the current without generating heat. When everything goes wrong, the semiconductor switch can handle the load just long enough to let the mechanical switches disengage. It strikes me that your channelers would want to be trained in some art which mirrors these hybrid switches, so they aren't cooked to death!</p>\n\n<p>Incidentally, my original answer was going to be relating limit of 9 mages to this idea of only doing reversible things so that you don't cook while using Ogone. In mathematics, quasigroups and loops are structures which have this reversible property. Anything which can be done in a quasigroup or a loop can be undone. This makes these actions reversible, and thus there is always a way to keep the energy flowing as magic rather than as heat.</p>\n\n<p>Loops are interesting structures in that they have an identity element. It's possible to be in a state where you simply don't change anything. You let it be what it is. This seems like a really useful property for spellcasting. If things are getting dicey, you really want to have the ability to pause and just let things be as they are while you girdle your loins. If you just have a quasigroup, there's no such way to just let things be. You <em>always</em> have to know what you are doing to be able to keep things stable.</p>\n\n<p>We know <a href=\"https://en.wikipedia.org/wiki/Quasigroup#Number_of_small_quasigroups_and_loops\" rel=\"noreferrer\">how many</a> quasigroups and loops there are for different sized structures. For small orders (i.e. small numbers of mages), there are very few of them, and most are full fledged loops. But as the order goes up, the numbers get messy:</p>\n\n<pre><code> order quasigroups loops % quasigroups that are loops\n ----- ----------- ----- ----------------------------\n 0 1 0 0%\n 1 1 1 100%\n 2 1 1 100%\n 3 5 1 20%\n 4 35 2 5.7%\n 5 1,411 6 0.42%\n 6 1,130,531 109 0.0096%\n 7 12,198,455,835 23,746 0.000194%\n 8 2.69e15 106,228,849 0.00000039%\n 9 ≈1.52e22 9,365,022,303,540 0.0000000061%\n 10 ≈2.75e30 ≈2.08e19 0.000000000076%\n 11 ≈1.94e40 ≈1.476e27 0.000000000000000000000000000000000075%\n</code></pre>\n\n<p>This could be a part of why the circle tops out at 9 mages. If something goes wrong, the casters in the circle need to operate in a reversible way to make sure they don't turn into crispy critters. If something goes wrong, and you have to regain control, you'll regain control into one of these patterns. 9 elements is already a gargantuan number of possibilities. If you can't rely on everyone to agree on a particular pattern when they get spooked by the Orgone getting loose, you have to rely on taming the beast after the pattern has been decided. There's just too many 10 element patterns. Worse, most of them aren't loops, meaning you have a very high risk of a pattern emerging that is merely a quasigroup, meaning you can't slow the casting down. It's gotten out of control.</p>\n\n<p>Maybe its just my love of mathematical flavor, but I found it interesting that this sort of pattern crops up.</p>\n" }, { "answer_id": 134129, "author": "L.Dutch", "author_id": 30492, "author_profile": "https://worldbuilding.stackexchange.com/users/30492", "pm_score": 1, "selected": false, "text": "<p>We know that air is pretty bad at dissipating excess heat, that's why we normally have to use a lot of air to take cool down something. Liquids, in particular water, are way better for this task. This can also help you with your problem.</p>\n\n<p>Form the circles under a waterfall, or at least place the channeler in such a place.</p>\n\n<p>The constant flow of cold water will help keeping the temperatures down.</p>\n\n<p>===========================================</p>\n\n<p>unrelated: quite ironically, this can also answer the question on <a href=\"https://worldbuilding.stackexchange.com/q/132514/30492\">the purpose of artificial waterfalls</a>.</p>\n" }, { "answer_id": 134130, "author": "chasly - supports Monica", "author_id": 10759, "author_profile": "https://worldbuilding.stackexchange.com/users/10759", "pm_score": 3, "selected": false, "text": "<p><strong>Drink something icy cold during the ritual chanting, such as this assuming that the magic in your world can produce icy drinks.</strong></p>\n\n<p><a href=\"https://i.stack.imgur.com/WPdBW.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/WPdBW.png\" alt=\"enter image description here\"></a></p>\n\n<p><strong>Even better cool the mages' whole body in an icy pool, such as this</strong></p>\n\n<p><a href=\"https://i.stack.imgur.com/VknHm.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/VknHm.jpg\" alt=\"enter image description here\"></a></p>\n" }, { "answer_id": 134131, "author": "Separatrix", "author_id": 16295, "author_profile": "https://worldbuilding.stackexchange.com/users/16295", "pm_score": 1, "selected": false, "text": "<p>If the heating process for channeling is internal, then the solution must necessarily act at the source rather than externally. Sitting in an ice bath isn't going to cut the mustard here.</p>\n\n<p>Describing the solution while not getting an 18 rating for your story is at the discretion of the author. However it does put a new spin on the requirement for wizards to own a staff and robe. Though convention doesn't mention the ice bath the bottom of the staff has to sit in, perhaps a natural water course is sufficient.</p>\n" }, { "answer_id": 134151, "author": "Mathaddict", "author_id": 54489, "author_profile": "https://worldbuilding.stackexchange.com/users/54489", "pm_score": 0, "selected": false, "text": "<h1>Enchanted items you say...?</h1>\n<p>Introduce a simple enchantment that only needs the participation of 3 or 4 mages in the circle, which has the effect of producing a heat sink. As long as a mage has one of these, as most mages will, any excess heat will always have somewhere to go.</p>\n" }, { "answer_id": 134178, "author": "Ender Look", "author_id": 35041, "author_profile": "https://worldbuilding.stackexchange.com/users/35041", "pm_score": 0, "selected": false, "text": "<h1>No Magical</h1>\n\n<h2>Drinking</h2>\n\n<p>Before starting and during the ritual, your designated mage to perform the link must <strong>drink a lot</strong>. Hydrating your body helps to cool your body and improve sweating. If possible <strong>drink very cold water</strong>, maybe even eat snow or ice, you must lower his temperature.</p>\n\n<h1>Bathing</h1>\n\n<p>Before starting and <strong>during the ritual</strong>, your designated mage to perform the link must take an <a href=\"https://en.wikipedia.org/wiki/Ice_bath\" rel=\"nofollow noreferrer\">ice bath</a>, which literally means bath in very cold water usually full of ice cubes. It doesn't matter if he suffers a bit of hypothermia, in a few minutes he <em>will want to have it</em>, just don't let him die.\nUnlike normal ice bath, your mage <strong>must be naked</strong> so he lowers his temperature even quicker.</p>\n\n<p>If you dare and have enough technology, you may take <a href=\"https://en.wikipedia.org/wiki/List_of_cooling_baths\" rel=\"nofollow noreferrer\">one of these</a> baths.</p>\n\n<h1>Magical</h1>\n\n<p>All these suggestions require a smaller circle surrounding the linker:</p>\n\n<h2>Healing</h2>\n\n<p>Self-explanatory, don't you have healing magic? Maybe cast <em>healing</em> on him.</p>\n\n<h2>Cooling</h2>\n\n<p>Instead of cast <em>healing</em> on the linker with more mages, you may cast a cooling ability, like <em>freezing ray</em> or <em>frost wind</em>...</p>\n\n<h2>Dissipating or use a Heat Sink</h2>\n\n<p>Healing and cooling may not be available but your mages could dissipate the heat produced around the linker with magic, maybe dissipating it to the environment or transferring all that heat to some heat sink (like water or magical spell).</p>\n\n<h2>Transfering</h2>\n\n<p>If all of that spells aren't available we still have some solutions, but riskier. The smaller circle of mages around the caster will <em>drain part of the heat to themselves</em>, effectively avoiding overheat the linker.<br>\nInstead of cook a single person, you warm several ones.\nYou could even nestle this ability adding more circles of mages for each mage that absorbs the heat or make it recursive to balance all the temperature.</p>\n" }, { "answer_id": 134226, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 1, "selected": false, "text": "<p><strong>Use the energy augmenting power of the connection to more efficiently use mages.</strong>\nFrom OP\n/A circle can have a maximum of 9 mages/</p>\n\n<p>The OP states that more circles tends to increase the amount of total magic over time, and produce heat. I conclude this is a property special to magic. If there were a finite amount of energy produced by each mage, connecting them up would not elicit more energy. More connections generally reduce power via entropy. An electrical connection that is heating up is losing energy to heat. The risk is that the heat breaks down the connection. In mundane energy transfer scenarios (e.g. electrical lines, water traversing pipes) the connection itself cannot increase total energy input, only (always) decrease it.</p>\n\n<p>But here the connection itself somehow increases the energy input. /These circles joining their power together creates a lot of excess energy. The transfer rate of orgone from one circle to the next will ultimately speed up during the ritual, turning that excess energy into heat. / The answer - mages drop out of their circles as the connections augment power. When power reaches 110% one page can drop out, reducing from the 9 maximum to 8. The 8th next mage drops out when power reaches 125%. </p>\n\n<p>This capitalizes on the magic augmenting nature of the circle and frees up some mages to go have lunch early. Courtesy dictates that these mages released early should also make sandwiches for the other ones still magicking away in the circle. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/134107", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/52361/" ]

[ { "answer_id": 135639, "author": "Trevor", "author_id": 53721, "author_profile": "https://worldbuilding.stackexchange.com/users/53721", "pm_score": 2, "selected": false, "text": "<p>No, the weight of the snow falling at the speed of gravity (optimistically) would produce less energy then what is used to lift the snow into the hatch. Your better off using electricity generating bikes.</p>\n" }, { "answer_id": 135641, "author": "Jasen", "author_id": 16816, "author_profile": "https://worldbuilding.stackexchange.com/users/16816", "pm_score": 4, "selected": true, "text": "<p>it'd work about as well as using a funnel (or bucket) to catch rain to run a mini hydroelectric plant. in other words, not very well at all.</p>\n\n<p>wind is probably a much better source, during antarctic emergencies it's usually very windy. if there's no wind then a conventiopnal generator is the easiest to fuel and run. </p>\n\n<p>people power uses very bulky fuel at very low efficiency.</p>\n\n<p>maybe the movement of a glacier could be harnessed, but their speed is, well, glacial, so some really steep gear ratio would be needed.</p>\n" }, { "answer_id": 135661, "author": "L.Dutch", "author_id": 30492, "author_profile": "https://worldbuilding.stackexchange.com/users/30492", "pm_score": 3, "selected": false, "text": "<p>You are using muscular work of people to trigger extraction of potential energy from snow.</p>\n\n<p>This is a poor working idea for several reasons:</p>\n\n<ol>\n<li>snow is low density, so you harvest few potential energy per unit volume (1 liter of liquid water weights 10 N, 1 liter of snow weights about 2 N)</li>\n<li>you are using more processes in series (shoveling the snow, have it drop down, convert the mechanical energy to electricity), multiplying their yields, thus lowering the overall yield</li>\n</ol>\n\n<p>Just put the same people on bikes, connect the bikes to a shaft attached to a power generator and you have a better yield. It doesn't take too much effort for a person to generate about 100 W on a bike. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/135637", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/48168/" ]

[ { "answer_id": 137306, "author": "Sava", "author_id": 55317, "author_profile": "https://worldbuilding.stackexchange.com/users/55317", "pm_score": 4, "selected": false, "text": "<p>As far as I know, that kind of list is only found in Star Trek EU works, specifically the Star Charts, which shows a planetary classification from Class A to Class Y with some useful information.</p>\n\n<p><a href=\"https://i.stack.imgur.com/nxY2u.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/nxY2u.jpg\" alt=\"Star Trek: Star Charts - Planetary Classification\"></a></p>\n" }, { "answer_id": 137307, "author": "The Square-Cube Law", "author_id": 21222, "author_profile": "https://worldbuilding.stackexchange.com/users/21222", "pm_score": 2, "selected": false, "text": "<p>Check <a href=\"https://en.wikipedia.org/wiki/List_of_planet_types\" rel=\"nofollow noreferrer\">the wiki for planet types</a>.</p>\n\n<p>There are eight types by size, seventeen by orbital regime, seventeen by composition and three miscellaneous types. That does for 6936 possible combinations, so if you wish for one letter descriptors you may need to use chinese characters.</p>\n\n<p>Otherwise, you can use any fictional classifications such as Star Trek's, as long as you don't do it commercially I guess.</p>\n" }, { "answer_id": 137313, "author": "Alexander", "author_id": 32451, "author_profile": "https://worldbuilding.stackexchange.com/users/32451", "pm_score": 6, "selected": true, "text": "<p>Of course we can make this code up. The question is, how useful it would be.</p>\n\n<p>As @Renan pointed out, possible permutations of planet types number in thousands - and that's not even counting potential life and civilization on the planet. Coming up with single code for every type is impossible.</p>\n\n<p>But if we want just a classification, then yes, we can come up with 26 types that would group together similar planets. The only challenge is to make these groups practical. I would suggest to use frequency of mention to guide this classification. This way, if two very similar world types (like \"clean\" and \"tainted\" Earth-like planets with civilization) are mentioned very frequently, they deserve their own letters. On the other hand, planetoids without atmosphere could be much more numerous and diverse, but because they mentioned less frequently, they may be all compressed into one letter designation.</p>\n\n<p>This one-letter code would not eliminate the need for proper, multi-symbol classification that should reflect all major aspects of planetary conditions.</p>\n" }, { "answer_id": 137326, "author": "JBH", "author_id": 40609, "author_profile": "https://worldbuilding.stackexchange.com/users/40609", "pm_score": 3, "selected": false, "text": "<p>It might be too coarse for you needs (as in \"not detailed enough\"), but you could use the <a href=\"http://wiki.travellerrpg.com/Universal_World_Profile\" rel=\"noreferrer\">Universal Planetary Profile</a> from the RPG <em><a href=\"https://en.wikipedia.org/wiki/Traveller_(role-playing_game)\" rel=\"noreferrer\">Traveller</a>.</em> (In the modern version of the game, it's called the Universal World Profile and is far more comprehensive than in the original game that I'm most familiar with.)</p>\n\n<p>The format describes:</p>\n\n<pre><code>Starport (Sp)\nPlanetary Size (S)\nAtmosphere (A)\nHydrosphere {H)\nPopulation (P)\nGovernment (G)\nLaw Level (L)\nTech Level (TL)\n</code></pre>\n" }, { "answer_id": 137343, "author": "Anoplexian", "author_id": 17568, "author_profile": "https://worldbuilding.stackexchange.com/users/17568", "pm_score": 3, "selected": false, "text": "<p>I'd personally as a reader want to be able to differentiate between planets easier than that, and an easier way to do that might be to use a <a href=\"https://en.wikipedia.org/wiki/Taxonomy_(biology)\" rel=\"noreferrer\">taxonomic system</a> for classification.</p>\n\n<p>Instead of having so much variation like animals, you can have a class A-B-C planet meaning different items, with further breakdowns in classification beneath that. Just like using the word \"plant\" versus \"flower\", we can use these indicators to provide ever increasing levels of specificity. It doesn't need to be anything completely complicated, but provide the full 5 bits, putting emphasis on certain pieces over others based on how important someone would use them in conversation.</p>\n\n<blockquote>\n <p>First letter determines size and type.</p>\n \n <ul>\n <li>A: Gas planet, strong gravitational pull, tidally locked </li>\n <li>B: Gas planet, normal gravitational pull, tidally locked</li>\n <li>C: Gas planet, weak gravitational pull, tidally locked</li>\n <li>D: Gas planet, strong gravitational pull, tidally unlocked </li>\n <li>E: Gas planet, normal gravitational pull, tidally unlocked</li>\n <li>F: Gas planet, weak gravitational pull, tidally unlocked</li>\n <li>G: Rocky planet, strong gravitational pull, tidally locked </li>\n <li>H: Rocky planet, normal gravitational pull, tidally locked</li>\n <li>I: Rocky planet, weak gravitational pull, tidally locked</li>\n <li>J: Rocky planet, strong gravitational pull, tidally unlocked </li>\n <li>K: Rocky planet, normal gravitational pull, tidally unlocked</li>\n <li>L: Rocky planet, weak gravitational pull, tidally unlocked</li>\n <li>etc.</li>\n </ul>\n</blockquote>\n\n<p>Then further elaborate into atmosphere type and hostility of location.</p>\n\n<blockquote>\n <ul>\n <li>A: Weak atmosphere, close to star, hot</li>\n <li>B: Weak atmosphere, close to star, temperate</li>\n <li>C: Weak atmosphere, close to star, cold</li>\n <li>D: Normal atmosphere, close to star, hot</li>\n <li>E: Normal atmosphere, close to star, temperate</li>\n <li>F: Normal atmosphere, close to star, cold</li>\n <li>G: Strong atmosphere, close to star, hot</li>\n <li>H: Strong atmosphere, close to star, temperate</li>\n <li>I: Strong atmosphere, close to star, cold</li>\n <li>J: Weak atmosphere, Goldilock's Zone, hot</li>\n <li>etc.</li>\n </ul>\n</blockquote>\n\n<p>After that, you can get into habitability, resource availability, breathing possibility, and population with just numbers.</p>\n\n<blockquote>\n <ul>\n <li>01: Not habitable, scant resources, breathing apparatus necessary, not populated</li>\n <li>02: Habitable, scant resources, breathing apparatus necessary, not populated</li>\n <li>03: Not habitable, normal resources, breathing apparatus necessary, not populated</li>\n <li>04: Habitable, normal resources, breathing apparatus necessary, not populated</li>\n <li>05: Not habitable, heavy resources, breathing apparatus necessary, not populated</li>\n <li>06: Habitable, heavy resources, breathing apparatus necessary, not populated</li>\n <li>07: Not habitable, scant resources, breathing apparatus not necessary, not populated</li>\n <li>08: Habitable, scant resources, breathing apparatus not necessary, not populated</li>\n <li>etc.</li>\n </ul>\n</blockquote>\n\n<p>Forming from this, you could classify any type of planet, and instantly know what sort of place you're visiting. For instance, Earth might be classified as a K class planet, but with further information on it bearing more fruit.</p>\n\n<blockquote>\n <p>Earth: K-P17 planet<br>\n Population: 7.2b<br>\n Crust Compostion¹:<br>\n - oxygen, 46.6%<br>\n - silicon, 27.7%<br>\n - aluminum, 8.1%<br>\n - iron, 5.0%<br>\n - calcium, 3.6%<br>\n - sodium, 2.8%<br>\n - potassium, 2.6%<br>\n - magnesium, 2.1%<br>\n Intelligent Species Types: Humans, Dolphins, Mice<br>\n Prevalent Languages:<br>\n - Mandarin Chinese (1.1 billion speakers)<br>\n - English (983 million speakers)<br>\n - Hindustani (544 million speakers)<br></p>\n</blockquote>\n\n<p>With this, you have a complete knowledge of a planet, and can further fill in more information on a longer format, but can refer to Earth as a K class planet, then further specify with more taxonomic indicators.</p>\n\n<p>¹ - \"Essentials of Geology\" (7th Ed., Prentice Hall, 2000) by Frederick K. Lutgens and Edward J. Tarbuck</p>\n" }, { "answer_id": 137350, "author": "Shadowzee", "author_id": 45212, "author_profile": "https://worldbuilding.stackexchange.com/users/45212", "pm_score": 2, "selected": false, "text": "<p>I don't think there is a good way to simply classify planets with the granularity you want without creating a barrier between you the creator and the audience you are presenting to.</p>\n\n<p>For your system to work, the user needs to know and <strong>remember</strong> it. This is hard. You can't just present it in a table (I'm assuming your users are both gamers and readers) in the appendix or index because a user needs to keep flipping back to it. This breaks the flow of your story or game (sort of like tutorial prompts) and creates a disconnect for casual or first time users who might not want to invest in learning everything and just dive straight in (this is one of the reasons why casual and mobile games are such a huge market compared to knowledge intensive RTS games).</p>\n\n<p>A very basic system would be something along the lines of:</p>\n\n<ul>\n<li>Planet/Asteroid/Star</li>\n<li>Livable/Unlivable</li>\n</ul>\n\n<p>Which can give you the following combinations:</p>\n\n<ul>\n<li>Livable Planet</li>\n<li>Livable Asteroid</li>\n<li>Livable Star</li>\n</ul>\n\n<p>Which you could then sort into a code that you want e.g. (LP, LA, LS).</p>\n\n<p>But a casual user doesn't understand this, especially if you want to factor in all possible factors of a planet. The only thing you are doing with such a code is making it harder for a user to understand your game.</p>\n\n<p>If you really want to... Unicode has 137,374 mappings which means you could, if you really really wanted to, present 137,374 unique combinations to the reader with a single character (some of them look exactly the same, but they are different). But at that point you might as well be using Webdings.</p>\n" }, { "answer_id": 137361, "author": "PyRulez", "author_id": 8914, "author_profile": "https://worldbuilding.stackexchange.com/users/8914", "pm_score": 3, "selected": false, "text": "<h2>Weighted k-medoids clustering</h2>\n\n<p><a href=\"https://en.wikipedia.org/wiki/K-medoids\" rel=\"noreferrer\">k-medoids clustering</a> is a method of dividing a set of points into clusters of similar points. You can use this to divide your worlds into clusters, and then give each cluster a label.</p>\n\n<p>One algorithm to do this is the PAM algorithm:</p>\n\n<ol>\n<li>Give each world a weight (representing how likely it is to come up in conversation). Also define a \"dissimilarity\" function that measures how dissimilar two worlds are. This should make the set of worlds a metric space.</li>\n<li>Give each label a \"metroid\" world. This can either be done arbitrarily, or meaningfully (the meaning of the labels will be loosely based on these initial metroid worlds). The metroid world does not need to have a high weight; it could even have weight <span class=\"math-container\">$0$</span>.</li>\n<li>Assign each world the label whose metroid is most similar to it.</li>\n<li>Calculate the weighted average cost of the labelling, which is defined as the weighted average dissimilarity between a world and the world's label's metroid.</li>\n<li>For each label <span class=\"math-container\">$l$</span> and each non-metroid world <span class=\"math-container\">$w$</span>, change <span class=\"math-container\">$l$</span>'s metroid to <span class=\"math-container\">$w$</span>. Then do steps 3 and 4 again. If the weighted average cost went up, undo the change.</li>\n<li>Keep doing step 5 until the weighted average cost stops decreasing.</li>\n<li>The current labelling is the output of this algorithm. You may want to rename the labels if you want them to have meaningful names, as the algorithm will probably have relabelled worlds multiple times until it found a local minima.</li>\n</ol>\n" }, { "answer_id": 137372, "author": "Richie Frame", "author_id": 37817, "author_profile": "https://worldbuilding.stackexchange.com/users/37817", "pm_score": 1, "selected": false, "text": "<p>These seemed like an interesting challenge, and while some simplicity is possible, you cannot fold in the complexity and intelligence of life into it without making it overly complex.</p>\n\n<p>The detailed way of identifying a planet or moon needs too many values:</p>\n\n<ul>\n<li>mass and surface gravity, surface composition</li>\n<li>biosphere (mass, area, complexity, intelligence)</li>\n<li>atmosphere (thickness, composition, surface pressure)</li>\n<li>temperature (surface mean, range)</li>\n<li>orbital dynamics (zone, eccentricity, length of year)</li>\n<li>rotational dynamics (length of day, axial tilt)</li>\n<li>solar dynamics (mass, sequence, brightness, spectral class, wind output, stability, ttl)</li>\n<li>geomagnetism, geological stability, and more...</li>\n</ul>\n\n<p>This is just too much data. But what if we limited our criteria to ranges of conditions favorable to human life? I used a 3-dimensional 3-deep grid (think rubics cube) to break down a planet to human habitability. The 3 dimensions and their depths:</p>\n\n<blockquote>\n <p>Surface Temperature (T):</p>\n \n <ul>\n <li>T1 = below 0C mean, 0C max over 90% of surface, liquid surface water would be mostly frozen, equatorial zone may be ok</li>\n <li>T2 = mean 0C to 40C, good for humans</li>\n <li>T3 = mean above 40C, 40C min over 90% of surface, generally too hot, polar/high altitude regions may be ok</li>\n </ul>\n \n <p>Biosphere Favorability (B):</p>\n \n <ul>\n <li>B1 = little to no biosphere, or non-oxygen biosphere</li>\n <li>B2 = habitable biosphere, atmosphere mostly friendly to humans, minimal food and resources</li>\n <li>B3 = lush biosphere, edible plant-like and animal-like organisms</li>\n </ul>\n \n <p>Hazards (H):</p>\n \n <ul>\n <li>H1 = little to no hazard to humans, or minimal protection required (dangerous sections of biosphere, small pockets of radiation, some harsh weather, large temperature ranges, etc)</li>\n <li>H2 = moderate hazard to humans, protection required (gravity, extreme weather, dangerous biosphere, hostile intelligence, high surface or solar radiation, corrosive or dangerous atmosphere or pressure or temp, etc)</li>\n <li>H3 = severe or extreme hazard to humans, substantial protection required, or too dangerous to even land</li>\n </ul>\n</blockquote>\n\n<p>This gives you 27 combinations. I used a combination of English and Greek letters (with overlap) to format a grid. Greek letters and Y are for H3 worlds, J through Q are most optimal for human habitation or colonization. I skipped letters I O S Z because they look like numbers when written, and also U which looks like V.</p>\n\n<blockquote>\n <ul>\n <li>A/Alpha: T1 B1 H3 <br></li>\n <li>B/Beta: T1 B2 H3 <br></li>\n <li>Delta: T1 B3 H3 <br></li>\n <li>C: T1 B1 H2 (The moon)<br></li>\n <li>D: T1 B2 H2 (Delta Vega)<br></li>\n <li>E: T1 B3 H2 <br></li>\n <li>G: T1 B1 H1 (Mars) <br></li>\n <li>H: T1 B2 H1 <br></li>\n <li>J: T1 B3 H1 <br>\n .</li>\n <li>Gamma: T2 B1 H3 <br></li>\n <li>Lamba: T2 B2 H3 <br></li>\n <li>Sigma: T2 B3 H3 <br></li>\n <li>F: T2 B1 H2 <br></li>\n <li>N: T2 B2 H2 (Vulcan)<br></li>\n <li>P: T2 B3 H2 (Pandora, P3X888)<br></li>\n <li>K: T2 B1 H1 (Vorash)<br></li>\n <li>L: T2 B2 H1 <br></li>\n <li>M: T2 B3 H1 (Earth without humans)<br>\n .</li>\n <li>Y/Upsilon: T3 B1 H3 (Demon class, Venus)<br></li>\n <li>Theta: T3 B2 H3 <br></li>\n <li>Omega: T3 B3 H3 <br></li>\n <li>V: T3 B1 H2 <br></li>\n <li>W: T3 B2 H2 <br></li>\n <li>X: T3 B3 H2 <br></li>\n <li>R: T3 B1 H1 <br></li>\n <li>T: T3 B2 H1 (P2X338)<br></li>\n <li>Q: T3 B3 H1 <br></li>\n </ul>\n</blockquote>\n\n<p>Unfortunately this does not tell you about the complexity or intelligence of life. It would be easy to optionally categorize the most complex lifeform, and if there is intelligent life, its level of technological evolution. It does however do a pretty good job of telling you what to expect, or if you would need additional classification to determine if you should even enter orbit.</p>\n" }, { "answer_id": 137381, "author": "Christian Sauer", "author_id": 33903, "author_profile": "https://worldbuilding.stackexchange.com/users/33903", "pm_score": 2, "selected": false, "text": "<p>Can you use something like vignettes? A vignette is basically a short description of something with a catchy name.\nDefine a list of the most useful planet types and create a small vignette for each.\nFor example:</p>\n\n<h1>Industrial World</h1>\n\n<p>Habitable world with a well developed, space faring infrastructure. bla bla bla</p>\n\n<h1>Planetoid</h1>\n\n<p>Lifeless world with little athmosphere.</p>\n\n<p>The trick is to write these in a way which allows for modification - e.g. add a \"heavy\" before industrial world and you get a slightly different meaning.</p>\n\n<p>This list has to be shared with your group, so when they hear \"industrial world\" they know what to expect and what to ask to further define the planet.</p>\n" }, { "answer_id": 137490, "author": "NonCreature0714", "author_id": 21774, "author_profile": "https://worldbuilding.stackexchange.com/users/21774", "pm_score": 0, "selected": false, "text": "<p>Maybe use Chinese characters. It would keep a creatively thoughtful SciFi mystique it all, much like how Firefly uses Chinese in its world. </p>\n\n<p>There are thousands of them, but, there would only be a limited set that is used most frequently for the most important-to-classify planets, such as habitable, dangerous, or mineral rich worlds.</p>\n\n<p>It would also be clever.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/137304", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/60499/" ]

[ { "answer_id": 138928, "author": "jdunlop", "author_id": 36850, "author_profile": "https://worldbuilding.stackexchange.com/users/36850", "pm_score": 3, "selected": false, "text": "<p>Something the size of the <a href=\"https://en.wikipedia.org/wiki/Chicxulub_impactor\" rel=\"nofollow noreferrer\">Chicxulub impactor</a> would be plenty spectacular - the top range of its <a href=\"https://arxiv.org/abs/1403.6391\" rel=\"nofollow noreferrer\">impact energy</a> is fifty thousand gigatons of TNT equivalent. There wouldn't be an equivalent explosion in all of human existence.</p>\n\n<p>The major problem is that in order to <em>save</em> humanity from an impact, by definition any impactor would have to hit the <em>far</em> side of the moon. The ejecta would be visible, as would the motion of the moon itself, but not the moment of impact.</p>\n\n<p>Any impact sufficient to be visible on the <em>near</em> side - ie. force projected through the entire moon, possibly destroying it - will give you the same problem experienced by the human race in Neal Stephenson's <em>Seveneves</em>: a <a href=\"https://youtu.be/fQfgWQZa0Ow\" rel=\"nofollow noreferrer\">hard rain</a>.</p>\n\n<hr>\n\n<p>For added fun, I adapted a python script I found <a href=\"https://astronomy.stackexchange.com/questions/7806/exercise-2d-orbital-mechanics-simulation-python\">here</a>:</p>\n\n<pre><code>import matplotlib.pyplot as plt\nimport math\nplt.ion()\n\nG = 6.673e-11 # gravitational constant\ngridArea = [-20, 50, -20, 50] # margins of the coordinate grid\ngridScale = 10000000 # 1 unit of grid equals 10000000m or 10000km\n\nplt.clf() # clear plot area\nplt.axis(gridArea) # create new coordinate grid\nplt.grid(b=\"on\") # place grid\n\nclass Object:\n _instances = []\n def __init__(self, name, position, radius, mass):\n self.name = name\n self.position = position\n self.radius = radius # in grid values\n self.mass = mass\n self.placeObject()\n self.velocity = 0\n Object._instances.append(self)\n\n def placeObject(self):\n drawObject = plt.Circle(self.position, radius=self.radius, fill=False, color=\"black\")\n plt.gca().add_patch(drawObject)\n plt.show()\n\n def giveMotion(self, deltaV, motionDirection, time):\n if self.velocity != 0:\n x_comp = math.sin(math.radians(self.motionDirection))*self.velocity\n y_comp = math.cos(math.radians(self.motionDirection))*self.velocity\n x_comp += math.sin(math.radians(motionDirection))*deltaV\n y_comp += math.cos(math.radians(motionDirection))*deltaV\n self.velocity = math.sqrt((x_comp**2)+(y_comp**2))\n\n if x_comp &gt; 0 and y_comp &gt; 0: # calculate degrees depending on the coordinate quadrant\n self.motionDirection = math.degrees(math.asin(abs(x_comp)/self.velocity)) # update motion direction\n elif x_comp &gt; 0 and y_comp &lt; 0:\n self.motionDirection = math.degrees(math.asin(abs(y_comp)/self.velocity)) + 90\n elif x_comp &lt; 0 and y_comp &lt; 0:\n self.motionDirection = math.degrees(math.asin(abs(x_comp)/self.velocity)) + 180\n else:\n self.motionDirection = math.degrees(math.asin(abs(y_comp)/self.velocity)) + 270\n\n else:\n self.velocity = self.velocity + deltaV # in m/s\n self.motionDirection = motionDirection # degrees\n self.time = time # in seconds\n self.vectorUpdate()\n\n def vectorUpdate(self):\n self.placeObject()\n data = []\n\n for t in range(self.time):\n motionForce = self.mass * self.velocity # F = m * v\n x_net = 0\n y_net = 0\n for x in [y for y in Object._instances if y is not self]:\n distance = math.sqrt(((self.position[0]-x.position[0])**2) +\n (self.position[1]-x.position[1])**2)\n gravityForce = G*(self.mass * x.mass)/((distance*gridScale)**2)\n\n x_pos = self.position[0] - x.position[0]\n y_pos = self.position[1] - x.position[1]\n\n if x_pos &lt;= 0 and y_pos &gt; 0: # calculate degrees depending on the coordinate quadrant\n gravityDirection = math.degrees(math.asin(abs(y_pos)/distance))+90\n\n elif x_pos &gt; 0 and y_pos &gt;= 0:\n gravityDirection = math.degrees(math.asin(abs(x_pos)/distance))+180\n\n elif x_pos &gt;= 0 and y_pos &lt; 0:\n gravityDirection = math.degrees(math.asin(abs(y_pos)/distance))+270\n\n else:\n gravityDirection = math.degrees(math.asin(abs(x_pos)/distance))\n\n x_gF = gravityForce * math.sin(math.radians(gravityDirection)) # x component of vector\n y_gF = gravityForce * math.cos(math.radians(gravityDirection)) # y component of vector\n\n x_net += x_gF\n y_net += y_gF\n\n x_mF = motionForce * math.sin(math.radians(self.motionDirection))\n y_mF = motionForce * math.cos(math.radians(self.motionDirection))\n x_net += x_mF\n y_net += y_mF\n netForce = math.sqrt((x_net**2)+(y_net**2))\n\n if x_net &gt; 0 and y_net &gt; 0: # calculate degrees depending on the coordinate quadrant\n self.motionDirection = math.degrees(math.asin(abs(x_net)/netForce)) # update motion direction\n elif x_net &gt; 0 and y_net &lt; 0:\n self.motionDirection = math.degrees(math.asin(abs(y_net)/netForce)) + 90\n elif x_net &lt; 0 and y_net &lt; 0:\n self.motionDirection = math.degrees(math.asin(abs(x_net)/netForce)) + 180\n else:\n self.motionDirection = math.degrees(math.asin(abs(y_net)/netForce)) + 270\n\n self.velocity = netForce/self.mass # update velocity\n traveled = self.velocity/gridScale # grid distance traveled per 1 sec\n self.position = (self.position[0] + math.sin(math.radians(self.motionDirection))*traveled,\n self.position[1] + math.cos(math.radians(self.motionDirection))*traveled) # update pos\n data.append([self.position[0], self.position[1]])\n\n collision = 0\n for x in [y for y in Object._instances if y is not self]:\n if (self.position[0] - x.position[0])**2 + (self.position[1] - x.position[1])**2 &lt;= x.radius**2:\n collision = 1\n impactor = self.name\n impactee = x.name\n velocity = self.velocity\n break\n if collision != 0:\n print(\"Collision! %s struck %s at %d m/s\" % (impactor, impactee, velocity))\n break\n\n plt.plot([x[0] for x in data], [x[1] for x in data])\n\nEarth = Object(name=\"Earth\", position=(0.0, 25.0), radius=0.6371, mass=5.972e24)\nMoon = Object(name=\"Moon\", position=(38.45, 25.0), radius=0.1737, mass = 7.347e22) # The orbital distance of the moon is ~ 384.5 thousand km.\nHammer = Object(name=\"Hammer\", position=(38.80, 25.20), radius=0.0001, mass=1.0e10)\n\nHammer.giveMotion(deltaV=2000.0, motionDirection=270, time=100000)\nplt.show(block=True)\n</code></pre>\n\n<p>The Hammer is just 10Mkg, but its mass is always going to be somewhat irrelevant.</p>\n" }, { "answer_id": 138992, "author": "M. A. Golding", "author_id": 34461, "author_profile": "https://worldbuilding.stackexchange.com/users/34461", "pm_score": 2, "selected": false, "text": "<p>I can think of ways the impact could be visible from Earth.</p>\n\n<p>1 Possibly the impact would create a cloud of dust particles and vaporized rock that would expand to several times the diameter of the moon and be lit from below by red hot or hotter lava created by the impact and easily visible from Earth</p>\n\n<p>2 Possibly the asteroid is headed directly for Earth but passes close to the Moon and the lunar gravity bends the course of the asteroid toward the moon a little. The asteroid thus barely misses the Earth and whips around it and is slung back toward the Moon. The asteroid hits the moon on the near side in a tremendous explosion. And astronomers calculate that if the asteroid hadn't hit the Moon it would eventually have fallnd back on Earth causing an extinction event.</p>\n\n<p>If you use one of those suggestions try to calculate if it is possible with the gravitional forces and the probable asteroid velocity range. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/138926", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/61318/" ]

[ { "answer_id": 139623, "author": "lilHar", "author_id": 17031, "author_profile": "https://worldbuilding.stackexchange.com/users/17031", "pm_score": -1, "selected": false, "text": "<p>80% of memories are eventually forgotten. (As per forgetting Curves which follow Zipfy progressions, also known as the 20/80 rule <a href=\"https://en.wikipedia.org/wiki/Forgetting_curve\" rel=\"nofollow noreferrer\">Forgetting Curves</a> <a href=\"https://en.wikipedia.org/wiki/Zipf%27s_law\" rel=\"nofollow noreferrer\">Zipfs Law</a>).</p>\n\n<p>Upon making memories, and reviewing them, we create the neural pathways that guide our actions.(<a href=\"https://www.nature.com/articles/ncomms13375/\" rel=\"nofollow noreferrer\">Making Pathways</a>) Unless an event specifically references a memory, the pathways will largely remain unaffected. (As is evidenced by neural studies showing the pathways in our brains make our decisions before we actively decide: <a href=\"http://exploringthemind.com/the-mind/brain-scans-can-reveal-your-decisions-7-seconds-before-you-decide\" rel=\"nofollow noreferrer\">Decision-making pathways in action</a> )</p>\n\n<p>So as far as implanting false memories, it won't change much. (This is part of why confirmation bias is a problem. I recommend looking up Hysteresis of opinions for further information).</p>\n\n<p>That said, however, there are ways to implant false memories currently, but the methods of doing so also directly impact the person's present, so would not apply to your scenario.<a href=\"https://www.psychologistworld.com/memory/false-memories-questioning-eyewitness-testimony\" rel=\"nofollow noreferrer\">False Memories</a></p>\n" }, { "answer_id": 139634, "author": "pojo-guy", "author_id": 19171, "author_profile": "https://worldbuilding.stackexchange.com/users/19171", "pm_score": 1, "selected": false, "text": "<p>The answer is \"yes it is possible, but it would be unpredictable\".</p>\n\n<p>This has a hard science tag, so this draft might need a few revisions, including references, which I will attend to as time permits. Be aware that the best hard science out there is still very speculative, just marginally better than reading tea leaves</p>\n\n<p>Memories are mediated by the hippocampus and mapped into other areas of the brain. </p>\n\n<p>For a long time, the hippocampus was believed to be the seat of long term memory, because damage or removal of the hippocampus would result in instant and irreversible amnesia. However, by adding the use of functional brain scans to what has been determined through decade of experiment and modelling, we now know there is much more to the story.</p>\n\n<p>Be aware the the best functional brain scan technology only has a 3 mm resolution today (2019). That is pretty coarse for a structure that is only 3 cm³ in volume, so our understanding is still very blurry.</p>\n\n<p>Functional brain scans show a physical mapping process occurring during both memory encoding and reconstruction. The word reconstruction is used deliberately rather than recall because the process of recall is as important as the process of encoding.</p>\n\n<pre><code>Sidebar ...be patient and you'll see how his fits.\n\nDuring execution of spatial tasks, regions of the hippocampus activate in response to \nachieving decision points in the task. For example, if the task is a maze, then at \neach decision point a different set of physical regions of the hippocampus will activate.\n\nWhat is very interesting is that during execution of non-spatial tasks, like \nsolving a math problem, the hippocampus exhibits exactly the same kind of activity. \n</code></pre>\n\n<p>We have known for a long time that the hippocampus is active in long term recall. With the advent of readily available brain scan techniques, we can see that its role in long term recall is active rather than passive, and <em>essentially identical to its activity in solving spatial problems</em>.</p>\n\n<p>We also know that the hippocampus is crucial to forming new memories. When new data is first introduced to the brain, the hippocampus is recruited, and <em>exhibits the same sort of activity that it does in solving spatial problems</em>. </p>\n\n<p>In effect, the hippocampus is a spatial mapping organ that has been adapted into a general problem solving tool. Think of it as being similar to the GPU in a modern graphics card, specialized for some function, but over time has been adapted to solve a broad range of problems unrelated to its original intent.</p>\n\n<p>For a long time, psychologists have known about the bookend effect. People tend to remember the first time they did something, the last time they did something, but not much in between. This why the first time you drive a route it seems so much longer than subsequent times.</p>\n\n<pre><code>Data deduplication\n* often called intelligent compression or single-instance storage \n* is a process that eliminates redundant copies of data and reduces storage \noverhead. Data deduplication techniques ensure that only one unique instance of data \nis retained on storage media, such as disk, flash or tape\n</code></pre>\n\n<p>As near as we can tell (at this point its an educated guess backed by experiment and modelling), during memory encoding the hippocampus mediates an aggressive deduplication process. That process compartmentalizes the new memory into fragments representing the state of the brain at that point in time and builds a map of some sort (As a database person I think of it as a key) to tie the fragments back together.</p>\n\n<p>We do not keep detailed memories at all, only statistically reinforced probabilities (described as the sum of the activation functions for the involved neurons - I don't write that kind of math, sorry). </p>\n\n<pre><code>This actually introduces the specific technical issues to be resolved \nto \"implant\" false memories, and also why the results might be unpredictable\nno matter how good the tech is.\n</code></pre>\n\n<p>During recall, the hippocampus is recruited to find and reassemble the memory fragments into a comprehensive whole, again treating it as a spatial navigation problem.</p>\n\n<p>This is why human memory is so fallible.</p>\n\n<p><strong>Examples of this mechanism in action:</strong></p>\n\n<p>My wife often wears a blue dress to church. We get separated, so when I go looking for her and have trouble finding her because she's wearing a green dress today. The reconstructed memory has been statistically reinforced to blue as part of the deduplication and reconstruction process.</p>\n\n<p>\"Oh, I misread that\"</p>\n\n<p>The well known phenomenon that no two eyewitnesses of an event recall it exactly the same.</p>\n\n<p><strong>Memory and Emotion</strong></p>\n\n<p>From experimental and clinical studies we know that impairment of emotion processing also inhibits memory encoding</p>\n\n<p>It turns out that you can't really separate memory from emotion, because part of the memory encoding process includes a partial state of the amygdala.</p>\n\n<p>From an experiential perspective, I remember what it felt like to really enjoy a good fireworks show. After brain damage impairing emotional processing, (1) I find it difficult to encode new memories and (2) The only \"feeling\" i get from the same fireworks show is the sensation of the booms rattling my internal organs, kind of like indigestion. </p>\n\n<p>What is interesting (to me) is that recall causes the same areas of the brain to be activated as the original event (with the caveat that the encoding process is lossy) so there is little difference in the state of the brain during recall as opposed to the original event. The fact that I can recall (reconstruct) emotional states that I can no longer experience in the immediate says that there is a different mediator for recalled emotion versus immediate emotion.</p>\n\n<hr>\n\n<p>Links:</p>\n\n<ul>\n<li>Coding of episodic memory:\n<a href=\"https://www.pnas.org/content/115/5/1093.short\" rel=\"nofollow noreferrer\">https://www.pnas.org/content/115/5/1093.short</a> </li>\n<li>Spatial processing:\n<a href=\"https://www.sciencedirect.com/science/article/pii/S002839321730115X\" rel=\"nofollow noreferrer\">https://www.sciencedirect.com/science/article/pii/S002839321730115X</a></li>\n<li>Spatial processing:\n<a href=\"https://www.sciencedirect.com/science/article/abs/pii/S0304394018303331\" rel=\"nofollow noreferrer\">https://www.sciencedirect.com/science/article/abs/pii/S0304394018303331</a></li>\n<li>Reconstruction of memory:\n<a href=\"https://www.sciencedirect.com/science/article/pii/S136466131830264X\" rel=\"nofollow noreferrer\">https://www.sciencedirect.com/science/article/pii/S136466131830264X</a></li>\n<li>Hippocampus as spatial processor:\n<a href=\"https://onlinelibrary.wiley.com/doi/abs/10.1002/hipo.22750\" rel=\"nofollow noreferrer\">https://onlinelibrary.wiley.com/doi/abs/10.1002/hipo.22750</a> </li>\n<li>Role of emotion in forming memories:\n<a href=\"https://www.sciencedirect.com/science/article/pii/S2352154617301638\" rel=\"nofollow noreferrer\">https://www.sciencedirect.com/science/article/pii/S2352154617301638</a></li>\n<li>Memory compression:\n<a href=\"https://www.tandfonline.com/doi/abs/10.1080/09658211.2017.1406120\" rel=\"nofollow noreferrer\">https://www.tandfonline.com/doi/abs/10.1080/09658211.2017.1406120</a></li>\n<li>Memory encoding:\n<a href=\"https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0204685\" rel=\"nofollow noreferrer\">https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0204685</a></li>\n<li>Memory Integration Theory: <a href=\"https://www.sciencedirect.com/science/article/pii/S0301008217302174\" rel=\"nofollow noreferrer\">https://www.sciencedirect.com/science/article/pii/S0301008217302174</a></li>\n<li>Application of hippocampus model in machine learning: <a href=\"http://teaching-machines.cc/nips2017/papers/nips17-teaching_paper-13.pdf\" rel=\"nofollow noreferrer\">http://teaching-machines.cc/nips2017/papers/nips17-teaching_paper-13.pdf</a></li>\n</ul>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/139620", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/11763/" ]

[ { "answer_id": 141988, "author": "AlexP", "author_id": 29552, "author_profile": "https://worldbuilding.stackexchange.com/users/29552", "pm_score": 6, "selected": true, "text": "<p>Your calculation is correct assuming that all children born live to be 70. But that is not the case even with the most modern health care. So you may want to up the number of babies a bit, to account (1) for infant mortality, (2) for the tendency of young males to do stupid things which get them killed, and (3) for the general premature mortality due to diseases and accidents.</p>\n\n<p>Here are two tables grouping the population by age cohorts; first assuming that all babies born live to 70, and then assuming a more natural <a href=\"https://en.wikipedia.org/wiki/Population_pyramid\" rel=\"noreferrer\">population pyramid</a>.</p>\n\n<pre><code>Age cohort\n----------\n 0 to 7 22 32\n 8 to 15 22 27\n16 to 23 22 22\n24 to 31 22 20\n32 to 39 22 20\n40 to 47 22 20\n48 to 55 22 20\n56 to 63 22 19\n64 to 71 22 18\n---------- ---- ----\nTotal 198 198\n</code></pre>\n\n<p>A random isolated village of 200 people surviving long term would be a clear sign of divine favor.</p>\n\n<ul>\n<li><p>Unless the initial population was chosen <em>extremely carefully</em> by in-depth genetic screening there will be severe inbreeding effects after a handful of generations, raising the mortality. (Note that there are only about 40 to 44 women aged 16 to 47 at any given time.)</p>\n\n<p>For example, in (the pre-modern principalities which would eventually coalesce into) Romania, a significant fraction of the women (and a smaller fraction of the men) married into neighbouring villages, so that there was some exhange of genetic material. This had also the positive effect of creating wider social networks.</p></li>\n<li><p>With such a small population the village is prone to demographic shocks. One good sized war, or one Tartar raid, or one epidemic and the population pyramid may be skewed irretrievably.</p>\n\n<p>Consider for example what happens if the Tartars come and abduct half of your 20 women aged 16 to 31. Or consider what happens if the <a href=\"https://en.wikipedia.org/wiki/Thirty_Years%27_War\" rel=\"noreferrer\">Thirty Years' War</a> comes and kills two thirds of your men aged 16 to 47.</p></li>\n</ul>\n\n<p>Grouping births into clutches every eighth year has the massive drawback that almost all women of reproductive age suddenly find themselves busy with babies at the same time.</p>\n\n<ul>\n<li><p>In a real village of about 200 people, with 4 births per year, you have about 8 to 10 women out of the workforce at any given moment, for a total non-working population of about 40 souls (8 to 10 women and 30 to 32 small children), or 20%.</p></li>\n<li><p>With this grouping, every eighth year a whopping 32 women go out of the workforce for two or three years, for a total non-working population of about 60 souls, or 30%. True, in non-fertile years the non-working population drops to around 15%, but this is a <em>village</em>, they cannot accumulate surpluses to be consumed later.</p></li>\n</ul>\n" }, { "answer_id": 141993, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 2, "selected": false, "text": "<p>22 is right. At 22 you do not have much cushion for downside risk, like people dying young. But that might be OK. Maybe there is not much downside risk of that sort. </p>\n\n<p>I would be interested to read a story set in this world. I feel like it must be set in the future - infant and child mortality is nil, life expectancy is reliably long, women start having babies late in their reproductive life, and they have control over pregnancy such that they can time births all together. That last one is why it is in the future because most societies still cannot reliably pull that pregnancy control piece off. </p>\n\n<p>Also \"community led\" sounds interesting to me. Maybe that is the secret. Good luck with your story. </p>\n" }, { "answer_id": 141996, "author": "Ray Butterworth", "author_id": 59975, "author_profile": "https://worldbuilding.stackexchange.com/users/59975", "pm_score": 2, "selected": false, "text": "<p>As others have said, mathematically 22 is right, but fails to account for early deaths.</p>\n\n<p>But there is a much simpler answer. Every 8 years the number of babies you produce is the number of people needed to raise the current population to 200 (or some similar suitable number). This will be approximately the same as the number of people that have died since the previous birth time.</p>\n\n<p>If things haven't been going well, you need a larger number than 22, and if people have been healthy, a smaller number will be fine.</p>\n\n<p>And again, as others have pointed out, it would be good to occasionally add some fresh genetic material to the gene pool (which would also reduce the number of babies required at the next birth time).</p>\n" }, { "answer_id": 141997, "author": "Justin Thyme the Second", "author_id": 61270, "author_profile": "https://worldbuilding.stackexchange.com/users/61270", "pm_score": 2, "selected": false, "text": "<p>I am trying to get my head around ALL the math.</p>\n\n<p>Assuming this is a pair-bonded society, for a stable population, each female has to give birth to two children - one to replace her, and the second to replace her mate.</p>\n\n<p>That means the female gets pregnant twice - once when she is 15, and once when she is 23 (or 23 and 31). </p>\n\n<p>So 11 fifteen year olds get pregnant from 11 fifteen year old boys, and 11 twenty three year old females get pregnant from 11 twenty three year old boys.</p>\n\n<p>And no one gets pregnant in between.</p>\n\n<p>So either every male and every female have sexual intercourse on only two occasions, or this community has very good and enforced birth control or enforced abortion, neither of which you mention. That puts it in a very modern context.</p>\n\n<p>Alternatively, there was a society that pretty much matched this one - <a href=\"https://www.greekboston.com/culture/ancient-history/education-sparta/\" rel=\"nofollow noreferrer\">Sparta</a>. </p>\n\n<p>One thing that is seldom mentioned about Sparta, was that it was intensely homosexual in nature, and the only sex between male and female was for reproduction that was strictly proscribed.</p>\n\n<p>It was a very interesting society.</p>\n\n<p>Having sex only twice in your life?</p>\n\n<p>Be very careful of that which you wish, as the Law of Unintended and Unforeseen Consequences can sometimes be very brutal.</p>\n" }, { "answer_id": 142015, "author": "Hobbamok", "author_id": 49154, "author_profile": "https://worldbuilding.stackexchange.com/users/49154", "pm_score": 0, "selected": false, "text": "<p>Everyone here is answering the wrong question.</p>\n\n<p>\"How many kids have to be born every 8 years?\" is WRONG.</p>\n\n<p>Because it doesn't really matter how many are born in a given timespan, what counts is how many are born to each mother. [Which means the relevant timespan is the 30-40 years a woman is fertile]</p>\n\n<p>Assuming relative monogamy, the fertility rate for a stable population is about 2.2<br>\nThat is every mother hat to birth on average 2.2 children (between 2.1 and 2.5 depending on the level of medical care and general helath of the population).\n2 is because the mother has to birth 1 women to be her successor-mother 1 man to replace the dad (who won't birth anythining) and then .X to account for premature deaths (premature here means before they give birth themselves)</p>\n\n<p>Also the thing with the cluthes is unnecessary.\nIf it's important/interesting to your story/world, go ahead and do it, it's realistic enough, but there is no actual need for it.\nFirst of all, some kids are way slower than others, making a more individual education more important, and secondary, since your small town will probably fall back to mechanical jobs like woodworking, huntil etc. an individual training for each job is way more important than general education, which means that the \" 18 yr olds teach the 15 yr olds\" won't help too much.</p>\n" }, { "answer_id": 142600, "author": "Sherwood Botsford", "author_id": 15784, "author_profile": "https://worldbuilding.stackexchange.com/users/15784", "pm_score": 0, "selected": false, "text": "<p>Meta answer:</p>\n\n<p>Your culture isn't stable. There's a flood. 9 people get killed. Do you have an inbetween clump? Do you shorted the breeding period until you are back to 200? Do moms who have already had their 2 kids have a third?</p>\n\n<p>Genetically your community isn't stable. You will have serious inbreeding problems. This translates into the unpleasant reality of a much larger increase in miscarriages, and kids with birth defects, and kids with genetic problems that make them die early.</p>\n\n<p>A community of 200 is of necessity a primitive community, at best in a blacksmith pig iron tech level. At that level in our culture, you needed on average 4-5 kids per woman to break even. (My mom started grade 1 in a class of 32. She graduated from grade 8 in a class of 20. The other 12 died. TB, farm accidents mostly. That was 1920)</p>\n\n<p>Women die in childbirth. Men are more likely to die in farm accident, or conflict. Your population demographic isn't even. I would expect that the 50-60 cohort would be 1/3 of the 20-30 cohort. You need to make a model of this on a spreadsheet.</p>\n\n<p>At 4 kids per woman, and assuming a breeding time from age 16 to age 40, you need a kid every 6 years. But how many people do you know of who take 2 or more years to get pregnant once they have decided to try? Answer: Lots. So you have a 6 year interval on average, but the births are likely spread out over 2-3 years.</p>\n\n<p>One way you can do this is to have women nurse their offspring for an extended period of time. Hard to get pregnant while nursing.</p>\n\n<p>Another way is to have a cycle of plenty and famine. If your body fat drops below a certain point (about 9% I think) women stop menstruating. When you are that thin, you have other problems too. This in turn would shape society. Women are cherished, protected. </p>\n\n<p>Option:</p>\n\n<p>More communities. Many communities, several day's walk apart. At a certain age a boy goes walkabout. For a year he goes from community to community, and at the end of that year settles in one. Perhaps during that time he acts as a stud too. This reduces the inbreeding problems. It is also a way to more quickly spread the effects of a disaster on one town. </p>\n\n<p>Or at a certain age, girls journey to the nearest town, and marry there.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/141986", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/62500/" ]

[ { "answer_id": 143053, "author": "Zeiss Ikon", "author_id": 57454, "author_profile": "https://worldbuilding.stackexchange.com/users/57454", "pm_score": 3, "selected": false, "text": "<p>Amorphous means non-crystalline, not non-solid. Glass is amorphous, and it's solid enough to hold a load for a long time at room temperature (the myth about sagging in centuries-old stained glass windows is just that -- a myth). Likewise, amorphous ice (whether water ice, ammonia, clathrate, or even oxygen) will be solid enough not to flow or creep noticeably, so long as the temperature stays below the freezing temperature of the substance.</p>\n\n<p>As long as your habitats are insulated so the surface(s) contacting the amorphous ice plain are below the melting or sublimation temperature, you needn't worry about the habs sinking into the surface. If they get too warm on the bottom, it won't matter whether the material they're standing on is crystalline or amorphous, it'll still melt (and, in a vacuum, immediately flash to vapor). Sinking won't be subtle at that point, if there's enough heat reserve to boil off a lot of the supporting material.</p>\n" }, { "answer_id": 143089, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 1, "selected": false, "text": "<p><strong>Buoyancy.</strong></p>\n\n<p><a href=\"https://i.stack.imgur.com/9U0DP.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/9U0DP.jpg\" alt=\"styrofoam pontoon\"></a></p>\n\n<p>Your ice world settlements are built on giant hydrogen-puffed Styrofoam pontoons. Each building and its pontoon is lighter than the liquid below and so it will not sink. Once could use the same method for building on a Minnesota lake of unpredictable April frozenness - if liquid or slush, your building floats. If solid your building sits. </p>\n\n<p>The styrofoam also provides extra insulation between hot dwelling and frozen substrate. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/143052", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/-1/" ]

[ { "answer_id": 143430, "author": "Liam Morris", "author_id": 62187, "author_profile": "https://worldbuilding.stackexchange.com/users/62187", "pm_score": 3, "selected": false, "text": "<h2>No, they would not.</h2>\n\n<p>There are several issues with trying to use a weapon like this. </p>\n\n<p>First, as you identified, the user may end up with broken bones. The bones in your wrist are relatively delicate as it it a joint. Putting a piece of metal on there and hitting something hard could injure you at best or break the bone.</p>\n\n<p>Secondly, even if you <em>could</em> use it without risking harm to yourself, you wouldn't want to anyway. The reason being is power generation. A weapon, such as a mace, is something known as a force multiplier. As weapons have mass, can be accelerated relatively quickly and typically have a small contact point, they amplify the force you can put behind a strike massively. However, these metal forearm spikes don’t add much more mass and are not accelerated faster than your forearm. This concentrates the force of you swinging your arm on a smaller point but does not generate additional force.</p>\n\n<p>Finally, these spikes would not be able to pierce through armour. Not an issue against an unarmored opponent but they would do nothing against one with some kind of protection. This is because the spikes cant be overly long or else you’ll be stabbing yourself any time you walk.</p>\n\n<p><strong>Alternatives</strong></p>\n\n<p>Now, if you wanted some weapons for punching, I suggest the push dagger (also called a punch dagger) or katar (the weapon, not the place). These are daggers which you hold in your hand and you punch with them as though you were boxing. The katar is the more advanced weapon of the two as it has an ‘H’ shaped guard with two bars to prevent it from twisting in your hand. If you wanted something larger, I suggest the pata, a gauntlet with a sword blade attached. The pata is similar to a rapier, mostly a thrusting weapon but you can do cuts with it as well.</p>\n\n<p>Finally, of you were dead-set on having a spiked forearm weapon, I suggest you look at the bagh nakh, also called the tiger claw. As its name implies, this is a weapon with blades that curl backwards. This was meant as a tool for climbing trees but it doubles as a weapon, it is held in the palm of the hand. </p>\n\n<p>You could have spikes like the bagh nakh does on your arm guard which overcomes some issues I mentioned earlier as a blade does not need much force to deal a lot of damage.</p>\n" }, { "answer_id": 148744, "author": "Roger", "author_id": 56426, "author_profile": "https://worldbuilding.stackexchange.com/users/56426", "pm_score": 1, "selected": false, "text": "<p>The <a href=\"https://en.wikipedia.org/wiki/Cestus\" rel=\"nofollow noreferrer\">cestus</a> is kind of close, but not as spiky.</p>\n\n<p><a href=\"https://i.stack.imgur.com/dgoSv.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/dgoSv.jpg\" alt=\"drawing of cestus\"></a></p>\n\n<p><a href=\"https://i.stack.imgur.com/uULFI.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/uULFI.jpg\" alt=\"boxer of quirinal\"></a></p>\n" }, { "answer_id": 148747, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 1, "selected": false, "text": "<p>The spikes would not assist in the block of a blunt weapon. Consider that maces and war hammers were designed to cause trauma through <em>plate mail</em>. Fundamentally, they just have a lot of momentum, and you have to deal with that.</p>\n\n<p>Such spikes could be useful for a softer art, though. You still could not block a mace, but you don't always have to block it. All you have to do is deflect sufficiently such that it doesn't hit you. Consider how hard it is to use a blunt weapon against a piece of paper floating in the breeze. Why? Because the paper doesn't offer much resistance. The spikes on your gauntlet might break if you are holding your arm rigid, but if your arm is relaxed, it can't break them without moving your arm substantially.</p>\n\n<p>Now for blocking, that's a non-starter, because your goal was for the arm to <em>not</em> move substantially. However, for many martial arts moves, you don't need that. The power of such moves is that, at the end of the opponent's swing, they thought they had complete control of the weapon and could bring it back. Now you have a bunch of spikes helping you hold onto the weapon as you twist and turn it.</p>\n\n<p>(Caught with something behind you so you can't move out of the way? Well... then you really did need to block... and you're really out of luck!)</p>\n\n<p>This reminds me a bit of the nine rings we find on the back of some Chinese Dao. One of the uses for them was to make it easier to bind the enemy's sword with the backside of your blade. Mind you, I find the Dao a whole lot more practical, because the funny-bits are on a piece of metal you have in front of you, rather than on your irreplacable arm, but that may just be me!</p>\n\n<p><a href=\"https://i.stack.imgur.com/47auQm.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/47auQm.jpg\" alt=\"9 ringed broadsword\"></a></p>\n" }, { "answer_id": 148798, "author": "EDL", "author_id": 62157, "author_profile": "https://worldbuilding.stackexchange.com/users/62157", "pm_score": 1, "selected": false, "text": "<p>I think it depends on the method of attack.</p>\n\n<p>If you where to use your forearm as a club, then you’d break it against hard materials like skull or helmets. But against someones stomach, chest and face, it is a standard strike to an opponent beside or behind you.</p>\n\n<p>Your spiky vambraces are more for defense and used to block attacks and strikes. But, if the spikes are sharp, then sawing strikes at meaty bits like thighs, groin, tummy,neck, and eyes will be effective at incapacitating some one. </p>\n\n<p>I would think of these as intimidators, having more psychological value in discouraging someone to fight you than as really effective weapons. </p>\n\n<p>I think you’d always be in danger of spiking yourself accidently</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/143417", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/62918/" ]

[ { "answer_id": 144036, "author": "Klaus Æ. Mogensen", "author_id": 62769, "author_profile": "https://worldbuilding.stackexchange.com/users/62769", "pm_score": 4, "selected": true, "text": "<p>You could simply write that the sun rises in the east and sets in the west, but is due north at noon (not necessarily in the same sentence). Since the people in the world aren't likely to speak English, \"east\", \"west\", \"north\", and \"south\" will be translations of local words, and it then makes sense to translate them to Earth standards.\n<br><br>\nIt makes absolutely no sense to swap east and west on a map unless you also swap north and south, basically turning the map 180 degrees (as with some early maps). If you only swap one axis, it would be very difficult to use the map, since it wouldn't correspond very well with the real world (try making a mirror image of the map of you local city and navigate with that). Turning is fine, however, and you don't even need to make the map corners align with the four corners of the world as long as you include a compass rose. In fact, you map may align to magnetic poles that need not be all that close to the rotational poles.\n<br><br>\nGene Wolfe's <em>Book of the New Sun</em> takes place on the southern atmosphere on a far-future Earth. You might read that for inspiration.</p>\n" }, { "answer_id": 144046, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 2, "selected": false, "text": "<h1>Why do your characters know the difference?</h1>\n\n<p>In a Medieval/Ancient/Fantasy setting, why would your characters have a firm concept of East and West as it relates to the world?</p>\n\n<p>It wasn't common knowledge of common to human experience in those times to envision the world as a sphere, much less a rotating one, in which the absolute definition of East and West (or North and South) make any sense.</p>\n\n<p>In personal experience terms, East is where the sun goes up, and West is where the sun goes down. North is the point around which the sky rotates and South is the opposite direction from north. If your civilization is in the Southern Hemisphere of a spherical world, the definitions are still the same, and nobody knows the difference from how things are in the Northern hemisphere.</p>\n\n<p>Now, and important aspect of this statement regarding North and South is that, on Earth, advanced civilizations developed in the Northern Hemisphere only. There was almost no travel past the Equator. If your civilization developed in, say, the equivalent of the Great Rift Valley of Africa, or the Amazon Rainforest Basin, then the common experience would have to reflect that the point around which sky rotates is different at different ends of the known world. </p>\n\n<p>But, overall, the same things that you see in the sky in the Northern hemisphere, you also see in the Southern. So from an individual's personal experience, in a world with no knowledge of the rotation of the Earth around its axis, there is no difference in the Hemispheres. </p>\n" }, { "answer_id": 144047, "author": "genesis", "author_id": 63061, "author_profile": "https://worldbuilding.stackexchange.com/users/63061", "pm_score": 0, "selected": false, "text": "<p>I am guessing that you want to have some sort of drawn map and that is why you think it would be confusing to just arbitrarily rename things.</p>\n\n<p>I think the easiest thing would be to have the planet rotate in the other direction so the sun rises in the west and sets in the east.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/144029", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/14919/" ]

[ { "answer_id": 144225, "author": "Thorne", "author_id": 33868, "author_profile": "https://worldbuilding.stackexchange.com/users/33868", "pm_score": 2, "selected": false, "text": "<p><strong>Textspeak</strong></p>\n\n<p>SMS messages originally were 160 characters so <a href=\"https://en.wikipedia.org/wiki/SMS_language\" rel=\"nofollow noreferrer\">textspeak</a> evolved to reduce everything down to the most compact form through abbreviations, acronyms and emoticons.</p>\n\n<p>Sounds like a good reason to send teenagers into space....</p>\n" }, { "answer_id": 144226, "author": "genesis", "author_id": 63061, "author_profile": "https://worldbuilding.stackexchange.com/users/63061", "pm_score": 4, "selected": false, "text": "<p>According to Schneier the entropy of English text is below 1.6 bit per letter. Given a difficult constraint such as yours I would expect people to come up with compression algorithms getting close to that.</p>\n\n<p>If you don't need the full power of English you might get much better compression if you can pre-define a small set of words that would be sufficient. Something similar in principle to <a href=\"https://xkcd.com/1133/\" rel=\"noreferrer\">https://xkcd.com/1133/</a></p>\n\n<p>I think you need to answer two important questions:</p>\n\n<ol>\n<li>Is the system pre-defined, i.e. can there be word-lists?</li>\n<li>Are characters/words sent individually or can you apply compression to a large amount of data and then send it in bulk?</li>\n</ol>\n\n<p>If you want something that is simple, sciency and requires no setup, go with Huffman-coding individual letters based on frequency in English. ;)</p>\n" }, { "answer_id": 144227, "author": "Elmy", "author_id": 53228, "author_profile": "https://worldbuilding.stackexchange.com/users/53228", "pm_score": 7, "selected": true, "text": "<p>The most efficient communication is probably a command set. Since you contemplated Morse code, I assume that the communication is done via a fully defined interface - both sender and receiver know what a bit sequence is supposed to mean.</p>\n\n<p>A command set is no more that giving different codes predefined meanings. With one singe bit you can define 2 commands:</p>\n\n<pre><code>| value | meaning |\n| 0 | light off |\n| 1 | light on |\n</code></pre>\n\n<p>With 4 bits you can define 15 different commands, with 1 byte (8 bits) 255 commands, with 2 bytes 65535 commands and so on. If all you really need is to display texts to an astronaut, you have to store a bunch of ready made texts like \"Activate X-ray sensors\" in a database and send the corresponding message ID from Earth. For more complex messages you can store text templates in a database and then compile a message from several templates.</p>\n\n<p>An early real-world example is the list of <a href=\"https://en.wikipedia.org/wiki/Q_code\" rel=\"noreferrer\">Q-Codes</a>, created circa 1909, by the British government as a \"list of abbreviations... prepared for the use of British ships and coast stations licensed by the Postmaster General\".</p>\n\n<hr>\n\n<p>If you need to communicate more than simple texts, you would separate a message into a command part and a message part. You could, for example, tell the space ship:</p>\n\n<blockquote>\n <p>Activate X-ray sensors</p>\n</blockquote>\n\n<p>By sending a signal of 2 bytes:</p>\n\n<pre><code>| byte | value | meaning |\n| 1 | 01 | activate appliance |\n| 2 | 08 | X-ray sensor array |\n</code></pre>\n\n<p>Communication with an astronaut would be possible with a different command:</p>\n\n<pre><code>| byte | value | meaning |\n| 1 | 04 | write to terminal |\n| 2 | 08 | text with ID 8 |\n</code></pre>\n\n<p>That would result in slightly longer commands, but the possibilities of what you can achieve with a few bytes are multiplied.</p>\n\n<hr>\n\n<p>If you have a <em>really big</em> database with <em>a whole lot</em> of different texts, it might be more efficient to terminate commands with a defined code. For this approach, the database must be sorted in a way that gives the most frequent commands the lowest ID.</p>\n\n<p>Let's define <code>0000</code> as the terminator. </p>\n\n<ul>\n<li>For a very common command with the ID 6, you need to send the command's ID followed by the terminator: <code>0110 0000</code>. </li>\n<li>A very uncommon command with the ID 26683 would look like this: <code>0110 1000 0011 1011 0000</code>. </li>\n</ul>\n\n<p>The advantage is that you can have commands of dynamic lengths (instead of sending a whole bunch of useless 0's to fill up the static length of a command).</p>\n\n<p>The disadvantage is that every command is longer than it could ideally be. So this approach only gets worthwhile when you need a great many commands.</p>\n\n<hr>\n\n<p>After defining your command set, the next step is to make sure that you received the correct message. Losing just a single bit can change a message of \"Activate X-ray sensors\" into \"Destroy X-ray sensors\" or similar. This is usually done with a checksum, which requires some more bits to transmit.</p>\n\n<p>Have a look at the difference between two common data transmission protocols for the internet: <a href=\"https://en.wikipedia.org/wiki/User_Datagram_Protocol\" rel=\"noreferrer\">UDP</a> and <a href=\"https://en.wikipedia.org/wiki/Transmission_Control_Protocol\" rel=\"noreferrer\">TCP</a>. UDP is the most efficient in respect to transfer rate, but TCP trades some efficiency for reliability by including some overhead for error checking.</p>\n" }, { "answer_id": 144230, "author": "Zeiss Ikon", "author_id": 57454, "author_profile": "https://worldbuilding.stackexchange.com/users/57454", "pm_score": 3, "selected": false, "text": "<p>You might look at digital modes for amateur radio here. Some of those modes use what's called \"varicode\" -- where different characters have different symbol lengths (Morse code is a varicode system -- more commonly used letters are shorter in terms of transmission time). When sending English text, a varicode will minimize the number of bits required for a sufficiently large sample (which reasonably ought to include a large number of messages). If \"text speak\" is used commonly, it might make sense to design the varicode used around letter frequencies in that particular text format.</p>\n\n<p>If longer messages are common, some form of compression would make sense -- text typically compresses will with common compression algorithms, but the compression headers make this inefficient for very small blocks of data (text or otherwise).</p>\n" }, { "answer_id": 144261, "author": "user4574", "author_id": 17082, "author_profile": "https://worldbuilding.stackexchange.com/users/17082", "pm_score": 2, "selected": false, "text": "<p>A receiver will pick up the raido signal plus background noise (most notably cosmic background radiation). Generally the received noise power is greater for greater receiver bandwidth. So to get a good signal to noise ratio one can transmit the radio signal within a very narrow frequecy band and put a very narrow band filter on the front of the receiver.</p>\n\n<p><strong>EXAMPLE:</strong> The receiver was picking up 1 micro-watt of radio signal and 1 milli-watt of noise power with a 1MHz bandwidth (so a SNR of 0.001).</p>\n\n<p>Droping the bandwith to 10Hz would result in 1 micro watt of radio signal power and 10 nano-watts of received noise power (so a SNR of 100)</p>\n\n<p>Consider a protocol like PSK31 (or similar) used by HAM radios instead of moorse code.</p>\n\n<p><strong>PSK31</strong> uses pure tones of relatively long duration to send 1s and 0s. The longer those tones are the more narrow the filter at the receiver can be. PSKxxx can be used to send low data rate messages across the plannet using only a few watts of power.</p>\n\n<p>Another alternative (though more complex) is using long strings of physical 1s and 0s to represent a single symbol in the protocol. This method is used by GPS for example. The GPS signal is normally about 30X lower power than the background noise, but by correlating long strings of 1024 bits the receiver is able to on average lock onto the signal. </p>\n\n<p><strong>EXAMPLE:</strong> Define two long sequences of physical 1s and 0s for each letter of the alphabet. Each code is very different from the other codes.<BR>\nLet A be 00101010 10001010 10100101 00101010 ...<BR>\nLet B be 10100001 10100101 00010101 00010100 ...<BR>\nLet C be 01001010 01010100 00010100 00110101 ...<BR></p>\n\n<p>The sequences may be thousands of bits long if you want. The patterns are generated by a computer automatically when the user types a letter on the keyboard.</p>\n\n<p>The physical bit sequences are sent at a much higher rate than the actual symbols. For example if you want t send one symbol per second and your sequences are 1000 bits long then you send the physical bits at 1000 bits per second.</p>\n\n<p>When receiving the signal + noise; the noise will cause the receiver to make the wrong decision on the physical 1s and 0s some percentage of the time. The receiver stores the received bit pattern and compares it to one of the codes. The receiver then selects the code which most closely matches the received pattern. Even if most of the received bits are wrong, the received code is likely to match most closely to the code sent by the transmitter rather than one of the other codes. Thus the receiver can determine what the transmitter sent even if the background noise is much higher than the received radio signal.</p>\n\n<p>Some other advantages of using long codes is that the codes inherently correct physical bit errors at the receiver. Also different transmitters can each use different code sets so they can talk at the same time (this approach is how CDMA cell phones work).</p>\n" }, { "answer_id": 144267, "author": "Community", "author_id": -1, "author_profile": "https://worldbuilding.stackexchange.com/users/-1", "pm_score": 2, "selected": false, "text": "<h1>Building on other answers</h1>\n\n<p>In addition to the different encoding and compression methods, one thing to look into is shorthand techniques that allow you to drop letters while still being able to interpret the message. Some examples:</p>\n\n<ul>\n<li>it, to -> t</li>\n<li>is -> s</li>\n<li>have -> hv</li>\n<li>cat -> ct</li>\n<li>are -> r</li>\n</ul>\n\n<p>Example sentence: hw r u?</p>\n\n<h1>An alternative approach</h1>\n\n<p><strong>Encode your information in time delays</strong></p>\n\n<p>Presumably there is some reason that you can't speed up the data transmission, but perhaps you can slow it down. At 5 bits per hour, that's 12 minutes between each bit. Instead of sending each bit at regular interval, you can delay transmission of bits and use the delay time as a means of conveying information. </p>\n\n<p>So let's say you expect a minimum of 12 minutes between each bit, you can encode the data as follows (time is in mm:ss format):</p>\n\n<ul>\n<li>12:00 = 0</li>\n<li>12:05 = 1</li>\n<li>12:10 = 2</li>\n<li>12:15 = 3</li>\n<li>etc</li>\n</ul>\n\n<p>The more data you encode, the fewer bits per day you'll be able to transmit, so there will be some optimal balance you'll have to figure out based on the minimum delay interval you consider acceptable. Then you can perhaps use the bits themselves as an error checking mechanism, or to still transmit data.</p>\n" }, { "answer_id": 144270, "author": "Brythan", "author_id": 2113, "author_profile": "https://worldbuilding.stackexchange.com/users/2113", "pm_score": 3, "selected": false, "text": "<h3>Not Morse code</h3>\n\n<p>From <a href=\"https://en.wikipedia.org/wiki/Morse_code#Representation,_timing,_and_speeds\" rel=\"noreferrer\">Wikipedia</a>: </p>\n\n<blockquote>\n <p>International Morse code is composed of five elements:[1]</p>\n \n <ol>\n <li>short mark, dot or \"dit\" (▄▄▄▄): \"dot duration\" is one time unit long</li>\n <li>longer mark, dash or \"dah\" (▄▄▄▄▄▄): three time units long</li>\n <li>inter-element gap between the dots and dashes within a character: one dot duration or one unit long</li>\n <li>short gap (between letters): three time units long</li>\n <li>medium gap (between words): seven time units long</li>\n </ol>\n</blockquote>\n\n<p>If we use one bit to store one unit of information, it takes four bits to transmit even the shortest letter ('e') and its subsequent gap. The next shortest are 'i' and 't' at six bits. Then 'a', 'n', and 's' at eight. The longest character in the Morse alphabet is 0, which requires five dashes or twenty-two units/bits. And that only supports the thirty-six character latin alphanumeric alphabet. </p>\n\n<p>Morse is designed around humans. Humans do better with indeterminate length than fixed length, as we don't have good timing ability (we can't tell a five unit pause from a four unit pause consistently). But if these messages are being transmitted computer to computer, computers have great ability at timing. We can use superior fixed length formats. Heck, even with humans, twelve minute long units means that it is easy to track whether you're getting a pause or a dot (a zero or a one). </p>\n\n<p>Even worse, if you are transmitting Morse over bits. Because (extended) ASCII's eight bits is more efficient unless the message is composed entirely of 'eitans'. </p>\n\n<h3>Bits</h3>\n\n<p>Meanwhile, if we transmit ASCII, we could transmit a 0 with eight bits. If we break things into nybbles, we can transmit one nybble with a checksum bit every hour. So two hours to transmit one character with some error detection included. Or ninety-six minutes without the checksums. </p>\n\n<p>If we instead use ten bits (two hours), we can do something like Lempel-Ziv. So the first 256 characters are the extended ASCII set. The remaining 768 symbols actually represent multiple characters. So common sequences (e.g. \"the \", \"ing\", and \"tion\") would have their own ten-bit representation, e.g. 0100000000. This allows the full flexibility of ASCII while also producing a shorter message on average. </p>\n\n<p>The Lempel-Ziv algorithm builds the dictionary from the message itself. We can do better by agreeing on a dictionary beforehand. You can also use this to integrate the error correction and the dictionary, which improves your effective speed. </p>\n\n<p>Numbers are generally going to be better sent as bits than as characters. I.e. instead of sending ASCII 3840, just send 111100000000. That's only twelve bits, hardly more than a single character. </p>\n" }, { "answer_id": 144273, "author": "Loduwijk", "author_id": 22544, "author_profile": "https://worldbuilding.stackexchange.com/users/22544", "pm_score": 2, "selected": false, "text": "<h2>Here is the literal answer to your question:</h2>\n\n<p>Use reverse base64 character encoding (i.e. base64 text → binary transmission → base64 text). You can see an example base64 table <a href=\"https://en.wikipedia.org/wiki/Base64\" rel=\"nofollow noreferrer\">here</a>, but note that the rest of the page there is using base64 characters for a different purpose, so ignore the use cases on that page. This allows you to represent the English characters, including numbers, which is precisely what you said you wanted, using 6 bits per character which is just 1 bit short of fitting into 1 hour's worth of transmission in your circumstance.</p>\n\n<h2>And here are some enhancements to that by adding special \"modes\"...</h2>\n\n<p>This includes both upper and lower case letters. If you are fine with restricting yourself to one case, which would still fulfill your requirements, then you would have room left to include more punctuation or other enhancements (up to 26 other enhanced transmission modes). I would recommend using some of this extra space to represent some extremely common words or short phrases that you would use very, very often. Then use a few of the character slots for other special meanings, such as \"the next few bytes represent status codes\" or \"the following data is compressed\".</p>\n\n<h2>Mode 1: Table of most common words or phrases</h2>\n\n<p>For the examples below, I'll assume that 2 of the characters represent different word/phrase lookup tables using 9 bits each since this allows the lookup to take exactly 3 hours to send, including the initial 6 bits (6 + 9 = 15 bits = 3 hours). This allows for 512 bits worth of lookup power times 2; that is, 1024 different shortened words or phrases.</p>\n\n<p>Using this format...</p>\n\n<p>\"<strong>Hey Bob</strong>\" as plain text requires 6*7=42 bits = <strong>8 hours + 2 bits</strong></p>\n\n<p>\"communication array damaged by [reason]\", assuming \"communication array\" and \"damaged\" are both in the lookup table, would take 9 hour + 3 bits + [however long it takes to send the reason]. \"communication array damaged by Klingon torp\" would take 24 hours - less if either \"Klingon\" or \"torp\" were send as lookup words instead of as plain text.</p>\n\n<h2>Mode 2: Look-back</h2>\n\n<p>This is a \"repeat recent word\" mode. In computer science, it has been shown that recently used data is among the most likely data to be used next, and that is what a PC memory cache is for. We can do something similar by making 1 of the character slots represent \"The next 4 bits refer to a previous word; count back that many words in the most recent transmitted data.\"</p>\n\n<p>With this, \"Klingon fleet approaches from 294 and Klingon admiral on comms saying Klingon destroyers equipped with new black hole tech\" allows you to shorten 2 instances of \"Klingon\" to exactly 2 hours worth of data each; the first one providing \"0110\" (6) as the 4-bit-lookback value and the second instance being \"0101\" (5). In some communications this could save a lot of time if words are repeated often. Note that pronouns like \"their\" could have been used in some places, but that would take 7 plaintext characters (including surrounding spaces), which in this case would have taken 6 hours + 2 bits longer to send.</p>\n\n<h2>Mode 3: Copy/paste, possibly with separate paste-buffers</h2>\n\n<p>This would allow customized shortcuts that were not thought of before launch, a sort of copy/paste. \"start copying here\", then continue the message, then a \"stop copying here\"... then later you can send a \"paste\" character to repeat a long message. \"comms good, thrusters good, life support good, magnetic-artificial-gravity [copy]working intermittently due to a swarm of flies in the grav-capacitor[end copy] from a meal someone left out for days\", then you only have to send that long text 1 time, and each time after that you send \"comms good, thrusters good, life support good, magnetic-artificial-gravity [paste]\", and you do that until it changes back to \"good\". Also, \"comms\", \"thrusters\", \"life support\", \"magnetic-artificial-gravity\", and \"good\" might all be in the lookup table, meaning this entire message takes 22 hours + 1 bit to send after the first time you send it. Even better is if you make this \"paste mode\" be followed by a few bits for a \"paste buffer number\". Then you could \"[copy1]comms good, [etc.], [copy2]working intermittently due to...[end-copy-2][end-copy-1] from a meal that...\" Then every time you want to send an updated status, if it's the same as the one before it takes 1 hour plus a few bits.</p>\n\n<p>You can tweak the exact representation (different send modes, number of bits for each, etc.) to improve performance based on your expected communications to improve performance further.</p>\n\n<h2>Mode 4: Compression</h2>\n\n<p>Just what it sounds like. The following data uses a given compression algorithm.</p>\n\n<h2>And More!</h2>\n\n<p>You can add whatever other features you want in a similar fashion. Also note that, as stated by @HenningMakholm in comment below, some of these features are implemented in some compression software available for use today. Henning's example was <a href=\"https://en.wikipedia.org/wiki/Zlib\" rel=\"nofollow noreferrer\">zlib</a>.</p>\n\n<h2>Multiple versions of each mode</h2>\n\n<p>If you cut out lower case and still have more character slots left over after implementing all the punctuation and mode's you want, you can use left over character slots to expand modes that you already have. This is similar to what I did above with the lookup tables, I suggested using 2 of the base64 character slots that were freed up from tossing lower-case to give us 2 separate lookup tables. You could also do similar to double your look-back reach or to double your number of copy/paste buffers. You can also increase or decrease the number of bits following a mode-byte, such as having 4 bits after copy/paste to have 16 paste buffers, or only 2 extra bits to save on transmission time but allow only 4 paste buffers.</p>\n\n<h2>So how efficient is this?</h2>\n\n<p>Worst case scenario this requires 6 bits per character. Average case scenario you will use a few lookups, look-backs, or some compression to beat the worst case, so you require 3-5 bits per character. Best case is messages that can be relayed entirely, or nearly entirely, by lookups and look-backs, which will be often for normal day to day activities that go as expected - for such common communication, if you have a well tuned number of bits for each special mode, you should achieve <em>better</em> than 1 bit per character. Many times <em>much, much</em> better than 1 bit per character, such as with the status report example a couple paragraphs up.</p>\n" }, { "answer_id": 144275, "author": "Helena", "author_id": 61317, "author_profile": "https://worldbuilding.stackexchange.com/users/61317", "pm_score": 3, "selected": false, "text": "<ol>\n<li>Encode whole words instead of single letters. </li>\n<li>Use Huffmann encoding based on word frequency in the specific context of space travel. So that frequent words ('the', 'yes', 'shields') have less bits than less frequent words.</li>\n<li>Use markov chains to take the context of the sentence into account as well. </li>\n</ol>\n" }, { "answer_id": 144290, "author": "Bert Haddad", "author_id": 30795, "author_profile": "https://worldbuilding.stackexchange.com/users/30795", "pm_score": 2, "selected": false, "text": "<h1>Huffman Encoding</h1>\n<p>Basically, you want the same methodology we use today for writing to a .zip file. Basically what happens is we take the most common character in the file (probably 'e'), and say that it simply corresponds to the bit '1'. Then the next most common one ('a' maybe?) will be '01', and the next most common (let's say 't') will be '001'.</p>\n<p>So, given this system, &quot;eat&quot; = &quot;101001&quot;, while &quot;tea&quot; = &quot;001101&quot;.</p>\n<p>This is the most efficient form of encoding there is, as it gives you access to any number of characters while still using very few bits for the vast majority of the ones you're using.</p>\n<p>Note though: this is most effective when some letters/characters are used far more than other ones (as it is in modern English).</p>\n<p>Also, most .zip files will send along a &quot;dictionary&quot; of bit combinations and characters, so the other person can translate out of it. This can be wasteful to send every time, especially for short messages. However, if every user has a well-known dictionary that is encoded to best represent common English usages it can work.</p>\n" }, { "answer_id": 144320, "author": "Algy Taylor", "author_id": 52526, "author_profile": "https://worldbuilding.stackexchange.com/users/52526", "pm_score": 1, "selected": false, "text": "<p>As a thought, back in the day you used to have predictive text on a mobile phone with.</p>\n\n<p><code>[1|.], [2|abc], [3|def], [4|ghi], [5|jkl], [6|mno], [7|pqrs], [8|tuv], [9|wxyz], [0| ].</code></p>\n\n<p>If you were OK with predictive text (so, display as predicted - allow ship to skip through poss. words if they don't make sense). You'd need those 10 digits, plus a control character to signal if it was a number or character. That would need 4 bits / letter, so ~48min/letter by your timing. That would leave 5 extra 'control' characters.</p>\n\n<p>Now, why should you only have one control character to act as a shift? Why not 2? You'd get 4 options for each key (2^2), so you can drop predictive text entirely and have 1 character per symbol (plus a few spares for punctuation characters etc) if the two flags are set.</p>\n\n<p>Carrying on that path, you then have an <em>additional</em> 4 control keys, which by my book is 2^4 = 16 options, over the above 10 keys ... you get ~160 extra characters. You could use those as templates (similar to the Q-codes), so get full text <em>plus</em> qcodes, all in 4 bits (~48min per character).</p>\n" }, { "answer_id": 144322, "author": "Nzall", "author_id": 227, "author_profile": "https://worldbuilding.stackexchange.com/users/227", "pm_score": 1, "selected": false, "text": "<p>On top of the answers talking about encoding, I'd also look into finding clever ways to incorporate steganography in the medium and/or message. With 5 bits per hour, you have a VERY limited throughput rate, so anything you can do to hide additional bits of information could help enormously. Maybe some clever manipulation of the signal carrier or something related to signal orientation. This would depend on what type of interstellar communication you're sending out.</p>\n\n<p>Speaking of which, I would like to also include a bit of frame challenge. 5 bits per hour is a pretty weird bandwidth. Assuming 2 bits per radio oscillation, 5 bits per hour is roughly 0.0007 hz. that is REALLY low. As in, impossibly low. The lowest frequency Humans use right now is 3 Hz, and that's only for communication with submarines. To go 4 orders of magnitude lower would require a HUGE antenna: Antenna length needed is essentially the distance light travels in 1 second divided by the frequency. In this case, that would be an antenna that is hundreds of millions of kilometers long. That's an ABSURD length.</p>\n" }, { "answer_id": 144433, "author": "CoffeDeveloper", "author_id": 4995, "author_profile": "https://worldbuilding.stackexchange.com/users/4995", "pm_score": 2, "selected": false, "text": "<p>Ok, since all other answers give some general advice, I instead provide a full-fledged solution, that would probably work for real use case with minor tweaking. Start from a usefull dictionary of stuff you need to bit-encode:</p>\n\n<ul>\n<li><strong>List of all english words</strong> (58.000 or so, now expecting that list to include technical terms though)</li>\n<li><strong>List of all technical terms</strong>, including eventual keywords for programming languages (foreach i.e). I expect it to be below 10.000 for most fields (personal estimate)</li>\n<li><strong>Usefull symbols</strong> (punctuation, formatting symbols, short names for math functions, single digits and characters). would probably be less than 255 things.</li>\n<li><strong>Code names</strong> (example: astronaut 1: Bill, communication received: Roger etc.</li>\n</ul>\n\n<p>You get with something around 70.000 <strong>things</strong> to be encoded in the most efficient bit space.</p>\n\n<p>Then analyze all communications in the past decades, find sequences of words or single words that are used more often.</p>\n\n<p><strong>Add to the dictionary the sequence of words.</strong> I would not be surprised if we are still below 70.000 usefull terms.</p>\n\n<p><strong>Now prune the dictionary</strong>, remove synonims without technical relevance, outdated or never used terms. I expect it to shrink to at least 30.000 terms, If done aggressively probably we can <strong>stay safe with 15.000 terms</strong>. For that part I would elect a number of people (say 1000 people), be it experts in english language and technicians/scientists/programmers/engineer. Each person is awarded with 1000 random words and it is given the task to sort that words by likely-ness to be usefulll given the context of the mission. Each person should carefully check the meaning of each word, search for synonyms etc. It would probably be a year of work because it has to be done carefully. <strong>It is not and error that I gave to much words too much people, each word will be examined by more than one person and in more than one field.</strong></p>\n\n<hr>\n\n<p>Ok, now it gets the interesting part you <strong>sort the words/setenctes/symbols using the following priorities</strong>:</p>\n\n<ol>\n<li>Occurrencies of words and word sequences in last decades of communications.</li>\n<li>Occurrencies of words and word sequences in english language.</li>\n<li>Evaluate if there are emergency words (like \"CAME IMMEDIATLY BACK\").</li>\n</ol>\n\n<hr>\n\n<p>With less than 16.000 words, you know every single word can be encoded in 14 bits. However since you know some words are more often used than others (in example the most occurring text sequence would probably be \"SPACE\" or \".SPACE\") <strong>you can prioritize certain words to be encoded in less bits</strong>. You can take inspiration from UTF-8 or other bit encoding schemes. UTF use 8 bits' bytes, here since you need 14 bits encoding space you could use bytes made of 5+5+7 bits:</p>\n\n<blockquote>\n <p>if first bit is 0, the next 4 bits forms a word ( the 16 more often used words, guarantees a transmission time of 1 hour for those words)</p>\n \n <p>if first bit is 1 and second is 0, the next 8 bits forms a word (the 255 more often used words after the first 8, so we actually reached 263 words in 10 bits)</p>\n</blockquote>\n\n<p>Note <strong>that the 263 most common words may contain something really not reasonable, so those must be reviewed by a team of people</strong>. Just that thing could save thousand bytes in future communications.</p>\n\n<blockquote>\n <p>if first two bits are 1 and third is 0, the next 14 bits forms a word</p>\n</blockquote>\n\n<p>You could also <strong>reserve some emergency modes to encode information that is not included in the dictionary</strong>:</p>\n\n<blockquote>\n <p>if the first 3 bits are 1, you enter text mode. that means you send single characters and digits there are 26 characters and 10 digits, \"T,E,A,O\" are not sent since those are most common letters: we have 36 - 4 letters, so 32, enough to require just 5 bits, so at this point for each letter you send 0, plus the bits to encode the character</p>\n \n <p>if during text mode a 1 is received insted of the 0-starting-character you rollback to regular mode.</p>\n</blockquote>\n\n<p>You could use as much special modes as you wish (coordinates, small software updates to ship etc.) Each special mode can be activated by setting first N bits to 1, or by using a special word in the dictionary (so first two bits are 1, third bit is 0, and then fourteen 1s). You can even use a custom mode to de-prioritize words on the fly. In Example:</p>\n\n<blockquote>\n <p>Received sequence 1111111111100, then received XXXX (4 bits word), then received XXXYYYYY ( 8 bits word), those 2 words are swapped in dictionary. So that future communications can benefit of 5 bits less for a word that is going to be used more often. This sequence requires 14+4+8 bits (26 bits, so if you need to use a particular word more than 5 times you already saved some bits:</p>\n</blockquote>\n\n<p>You had \"Banana\" in dictionary, it was a 8 bits word, so required 10 bits for transmission, and you had \"Yes\" that was a 4 bits word and required just 5 bits for transmission. If you know you are going to use Banana 6 times, you send the swap sequence for \"Yes\" and \"Banana\". The sequence is 26 bits, and Banana-4 written 6 times is 30 bits, so in total 56 bits, If you don't swap Banana, writing Banana 6 times requires 60 bits. You saved 4 bits using the swapping sequence.</p>\n\n<p>In reality the swap sequence should double the limit, so it become usefull if you write Banana more than 11 times, because you have also to keep in mind that at some point you want to switch \"Banana\" and \"Yes\" again.</p>\n\n<p>The good side of this encoding, is that since information is transmitted at very low pace, you can have whole teams working on saving bits with the help of computer algorithms (that can automate insertion of certain special sequences). <strong>While you are sending your first 5 bits, you have time to examine the next horus/days of communications and continuosly improve them.</strong></p>\n\n<p>Since the dictionary include sequences of words and sentences I can expect it to have in average 1 word per hour in regular communication. So basically 1 word/5 bits, which is exceptional!</p>\n\n<p>^^^^</p>\n\n<h2>ALL ABOVE THAT:</h2>\n\n<p><em>Probably all the above can be done by 1 people alone (in example I could write some programs to help and do that in one month or so), but since that task requires a lot of safety, various experties fields etc. It is highly suggested that many many people work on that to assure the minimal number of bits is used in the end.</em></p>\n\n<p>When writing text to and from the ship, people will be helped with text editors that shows words that can't be encoded, and suggest alternative sequences or words that use less bits. The text editor will highlight in blue sequences of 4 bits, in green sequences of 8 bits, yellow the longer sequences, and suggest special modes when it thinks it is appropriate. It will add also a line break after each day of transmission (you will likely to see a lot of line breaks), and text that was already sent cannot longer be erased from text editor.</p>\n\n<hr>\n\n<p>A simple example: If we run the above algorithm on the text above \"ALL ABOVE THAT\": with the following oline tool:</p>\n\n<p><a href=\"https://www.online-utility.org/text/analyzer.jsp\" rel=\"nofollow noreferrer\">Compute words frequencies</a></p>\n\n<p>you see that some words are really good candidate for 4 bits encoding:</p>\n\n<ol>\n<li>the</li>\n<li>you</li>\n<li>bits</li>\n<li>to</li>\n<li>of</li>\n<li>words</li>\n<li>in</li>\n<li>and</li>\n<li>a</li>\n<li>is</li>\n<li>that</li>\n<li>be</li>\n<li>word</li>\n<li>are</li>\n<li>if</li>\n<li>for </li>\n</ol>\n\n<p>And there just 150 words that are not used uniquely, those words could become good 8 bits-candidates, and also some sentences like:</p>\n\n<ul>\n<li>to be</li>\n<li>4 bits</li>\n<li>more often</li>\n<li>of words</li>\n<li>you can</li>\n<li>the dictionary</li>\n<li>is 0</li>\n<li>8 bits</li>\n</ul>\n\n<p>And some senteces are good to keep in the 14 bit dictionary, in example:</p>\n\n<ul>\n<li>would probably be</li>\n<li>you could use</li>\n</ul>\n\n<p>The following sentence:</p>\n\n<blockquote>\n <p>You could use the dictionary for that</p>\n</blockquote>\n\n<p>will be encoded in</p>\n\n<blockquote>\n <p>You could use| the dictionary| for| that</p>\n</blockquote>\n\n<p>Which means in bits:</p>\n\n<blockquote>\n <p>17 | 10 | 5 | 5</p>\n</blockquote>\n\n<p>In colors</p>\n\n<blockquote>\n <p>Yellow | green | blue | blue</p>\n</blockquote>\n\n<p><strong>just 37 bits for a sentence!</strong></p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/144224", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/26903/" ]

[ { "answer_id": 146418, "author": "Sonvar", "author_id": 59628, "author_profile": "https://worldbuilding.stackexchange.com/users/59628", "pm_score": 1, "selected": false, "text": "<p>Assuming you want your acceleration at 1g, 9.8m/s², since anything more would become uncomfortable. The distance from the sun to Jupiter is 778.5 million km. you have to take into account deceleration also. So if you use the acceleration of 9.8m/s² over ~72 hours and a deceleration of ~72 hours, this would get you to almost 10 million km/h which would allow you to cruse at that speed for a few hours before you have to decelerate. </p>\n\n<p>If you did not count the acceleration and deceleration times, it would take almost 78 hours at that speed to cross that distance. Unfortunately, my math is failing me to account for the time and distance you would cover during those periods. </p>\n\n<p>A nice calculator to help you is <a href=\"https://www.calculatorsoup.com/calculators/physics/velocity_a_t.php\" rel=\"nofollow noreferrer\">here</a></p>\n" }, { "answer_id": 146456, "author": "Jay", "author_id": 2973, "author_profile": "https://worldbuilding.stackexchange.com/users/2973", "pm_score": 4, "selected": true, "text": "<p>The basic equation here is s=1/2 at^2, where s is distance, a is acceleration, and t is time. You have to allow for deceleration on the other end, so assuming you decelerate at the same rate that you accelerated, the easiest way to do the calculation is to cut the distance in half, then double everything when you're done.</p>\n\n<p>Distance from the Sun to Jupiter is about 483 million miles. So if we want to make the whole trip in 30 days with a continuous, even acceleration, then we want to go half-way in 15 days, then decelerate for the next 15 days.</p>\n\n<p>Halfway is 242 million miles. That's 1.28e12 feet. 15 days=1.30e6 seconds. So</p>\n\n<pre><code>s=1/2 a*t^2\n1.28e12=1/2 * a * (1.30e6)^2\na=1.5\n</code></pre>\n\n<p>That's 1.5 ft/sec^-2, or about .04g. That's a pretty mild acceleration rate.</p>\n" }, { "answer_id": 146462, "author": "Starfish Prime", "author_id": 62341, "author_profile": "https://worldbuilding.stackexchange.com/users/62341", "pm_score": 2, "selected": false, "text": "<p>Jupiter's aphelion (maximum distance between it and the sun) is 816040000km. When you're talking about rockets that aren't limited by energy, that's not really very far. That means you don't have to worry about relativistic effects (if you removed your 30-day constraint, even at 100G you wouldn't even reach a mere 10% of the speed of light before you hard to start slowing down).</p>\n\n<p>So, given your 30 day constraint, an easy answer might be to boost up to cruising speed at 1G, and break at 1G, easy. A handy equation for this sort of trajectory is apparently <span class=\"math-container\">$$T = \\frac{D - A t^2}{A t} + 2t$$</span> where <em>T</em> is the total transit time, <em>D</em> is the distance travelled, <em>A</em> is the acceleration and <em>t</em> is the length of the acceleration or deceleration burn. You can rearrange this to a nice quadratic <span class=\"math-container\">$Tt-t^2 - \\frac{D}{A}= 0$</span> which you can solve to get a <em>t</em> of more or less 32500 seconds or a bit over <strong>9 hours of thrust</strong> at the start and end of your flight with 29-and-a-bit days of microgravity coasting in between. (disclaimer: I'm not taking into account planetary movement or effort required to leave/enter orbit as it is only a fairly small part of the problem, but you might do well to think about that, too)</p>\n\n<p>An alternative (as Jay suggested first, though I'll use metric and latex so it must be better, right?) is to do a continuous acceleration-decceleration trajectory called a <em>brachistochrone</em> which is nicely defined by this equation:</p>\n\n<p><span class=\"math-container\">$$ T = 2 \\sqrt{ \\frac{D}{A} } $$</span></p>\n\n<p>which you can rearrange to <span class=\"math-container\">$A = \\frac{4D}{t^2}$</span> to get <strong>a steady acceleration of about 0.49m/s</strong> or <strong>0.05G</strong>. I won't go into the harm that extended periods of low-gravity exposure will cause you; that's a different question altogther. You should bear it in mind though, because in either of those two examples that's a long flight without much gravity to keep you in good working order.</p>\n\n<hr>\n\n<p><strong>Reality check</strong>: the continuous low thrust mode needs 1259km/s <span class=\"math-container\">$\\Delta_v$</span>. With a mass ratio of 10, that needs an exhaust velocity of 547km/s. Good news: whilst this is too high for any sort of electrical rocket, a fusion-based rocket could manage this, so it isn't super implausible. Bad news: to provide the required acceleration, your ship needs a thrust power of something like 133kW per kilo fully loaded. This means that the aforementioned ship with a mass ratio of 10 needs a thrust power of 1.33MW per kilo, unfuelled. That in turn means that if its dry weight were 1000 tonnes, it needs a <strong>1.3 terawatt</strong> rocket. Nuclear engines being what they are, that figure will only get larger once you account for energy lost as heat and radiation (of which there will be a <em>colossal</em> amount). Not impossible, but, y'know, be aware of what \"power is not a problem\" can actually mean in practise.</p>\n\n<p>If you do the 1G boost followed by a long coast, you actually only need a <span class=\"math-container\">$\\Delta_v$</span> of more like 638km/s and hence an exhaust velocity of 277km/s. Still sounds pretty nuclear, and the overall engine power is still pretty much the same.</p>\n\n<p>In both cases, <em>the ship arrives dry</em>. If you want enough fuel for parking or a return trip, everything gets much, <em>much</em> harder.</p>\n\n<hr>\n\n<p>Speaking of power not being a problem, why limit yourself to making the transit in 30 days?</p>\n\n<p>A 1G brachistochrone takes about 160 hours (under a week). But wait! people can cope with over 1G for a little while. According to <a href=\"https://space.stackexchange.com/a/6530/29766\">this Space Exploration question</a>, people can survive 1.5G for a week with no ill effects. That'll get you down to 130 hours (about 5 and a half days).</p>\n\n<p>You could probably push that up a bit further, given a bit of endurance training and maybe some G-suits, so 2G will get you down to 113 hours (under 5 days). Beyond that you start running into serious physiological issues but also diminishing returns... a 4G continuous burn would get you there in 80 hours and a potentially survivable 10G only cuts that down to 50 hours. Take home message: squishy meat freight is squishy. If you're in a hurry, send a machine.</p>\n\n<p>(reality check 2: you might manage a 1G brachistochrone with a fusion or antimatter engine 100 times more powerful than the one mentioned above. Anything much power powerful than that starts needing large quantities of antimatter)</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/146412", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/38944/" ]

[ { "answer_id": 147787, "author": "L.Dutch", "author_id": 30492, "author_profile": "https://worldbuilding.stackexchange.com/users/30492", "pm_score": 2, "selected": false, "text": "<p>First of all, the day lenght has nothing to do with the distance from the star. It only depends on the time it takes for the star to cross the same sky meridian.</p>\n\n<p>Then, by changing the eccentricity of the orbit, you can have the planet be further away from the star for a longer time than it is closer, while keeping the year length the same.</p>\n" }, { "answer_id": 147788, "author": "Ryan_L", "author_id": 51953, "author_profile": "https://worldbuilding.stackexchange.com/users/51953", "pm_score": 3, "selected": false, "text": "<p>Yes, it is possible. Day length is only effected by how fast the planet rotates. This is unrelated to the orbit.</p>\n\n<p>Year length increases as your orbit gets bigger, and decreases as your star gets bigger. The heavier the star is, the faster your have to orbit to stay a certain distance away. The farther away the planet is, the slower it orbits. You can have an orbit of practically any period given the correct stellar mass and orbital altitude.</p>\n\n<p>I don't know how this alters the heating issues though. It's possible that the habitable zone around this larger star would not be at the correct altitude.</p>\n" }, { "answer_id": 147800, "author": "ben", "author_id": 54784, "author_profile": "https://worldbuilding.stackexchange.com/users/54784", "pm_score": 2, "selected": false, "text": "<p><strong>Yes</strong></p>\n\n<p>It's already been stated but length of day just depends on the period of rotation, which has no relation to the celestial mechanics. Well, there are some special cases where that isn't entirely true, but they are fringe cases and not pertinent to your question. So choose the length of day at your leisure.</p>\n\n<p>For length of year we need a wee bit of math. <a href=\"https://en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motion\" rel=\"nofollow noreferrer\">Kepler's laws</a> are the foundation on which celestial mechanics is done. Kepler's third law can be stated mathematically as</p>\n\n<p><span class=\"math-container\">$$ a=\\sqrt[3]{\\frac{T^2GM}{4\\pi^2}} $$</span> (assuming planet mass is negligible compared to the star)</p>\n\n<p>where </p>\n\n<p><span class=\"math-container\">$$ a=semi\\space major\\space axis $$</span>\n<span class=\"math-container\">$$ T=orbital\\space period $$</span>\n<span class=\"math-container\">$$ M=mass\\space of\\space central\\space body $$</span>\n<span class=\"math-container\">$$ G=gravitational\\space constant\\space (6.674\\times 10^{-11}\\frac{m^3}{kg\\space s^2}) $$</span></p>\n\n<p>If we add your constraint that the length of the year is the same as the length of an Earth year, we can rearrange to solve for mass</p>\n\n<p><span class=\"math-container\">$$ M=\\frac{4\\pi^2 a^3}{G*(3.154\\times 10^7s)^2} $$</span></p>\n\n<p>If we plot this, we can see the relationship as semi major axis increases:\n<a href=\"https://i.stack.imgur.com/B8Ma8.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/B8Ma8.png\" alt=\"enter image description here\"></a></p>\n\n<p>*Note that the lower limit on mass for stars is something like 0.1 solar mass.</p>\n\n<p>**Also note that semi major axis is identical to orbital radius if it is a circular orbit.</p>\n\n<p>If you want to also examine the amount of energy that would be received at these specified distances and star masses you would need to use some relations for how star energy output varies with mass and how solar flux varies with distance. But that seems like a whole other question.</p>\n" }, { "answer_id": 147835, "author": "Klaus Æ. Mogensen", "author_id": 62769, "author_profile": "https://worldbuilding.stackexchange.com/users/62769", "pm_score": 0, "selected": false, "text": "<p><strong>Day length is no problem. Orbital period is.</strong></p>\n\n<p>Day length mainly depends on how quickly a planet rotates around its own axis, modified slightly by its orbital period. There is nothing preventing a planet far from its sun to rotate at this speed. (The opposite is not true; a planet very close to its sun is likely to be <a href=\"https://en.wikipedia.org/wiki/Tidal_locking#Rotation%E2%80%93orbit_resonance\" rel=\"nofollow noreferrer\">tidally locked or in spin-orbit resonance</a>).</p>\n\n<p>Having the same year length when much farther out is quite a lot more difficult. As a <a href=\"https://en.wikipedia.org/wiki/Mass%E2%80%93luminosity_relation\" rel=\"nofollow noreferrer\">general rule</a> for stars of masses near that of the sun, the luminosity of a star is proportional to its mass to the fourth power, meaning that a planet's distance from its star to achieve the same amount of heat would be proportional to the square of the mass. For stars between 2 and twenty solar masses, luminosity is proportional to the mass to the power of 3.5; not that different. For stars above 55 solar masses, the relationship between mass and luminosity becomes linear, but such stars don't last very long because of strong solar winds and are unlikely to develop planets with life.</p>\n\n<p>In return, the distance the planet needs to be from its sun to have the same orbital period (year) is <a href=\"https://www.physicsclassroom.com/class/circles/Lesson-4/Mathematics-of-Satellite-Motion\" rel=\"nofollow noreferrer\">proportional to the cube root of the star's mass</a>. As a star grows bigger, planets with the same orbital period will be increasingly roasted by heat and radiation.</p>\n\n<p>To achieve a similar year at a far greater distance (meaning a far heavier sun), you would need a stellar object with very little radiation compared to its mass. A possible solution would be a sun in close orbit around an even more masssive black hole, with your planet orbiting far from this pair.</p>\n\n<p>Say that this star has twenty times the mass of our sun. It would have roughly 50,000 times the luminosity of our sun, so your planet would have to be roughly 225 times the distance of Earth from the sun to receive the same amount of sunlight. The mass of the black hole would hence have to be 11.4 million solar masses for the planet to have the same orbital period. This is a supermassive black hole, about three times more massive than the one at the center of our galaxy (but smaller than some in other galaxies).</p>\n\n<p>Say that the star instead is only 5 solar masses, with a luminosity ca. 400 times that of our sun. The orbital distance of your planet would then have to be 20 times that of Earth's to receive the same heat; about the same as Uranus' orbit. The mass of the black hole would then 'only' have to be 8,000 solar masses; much more manageable. Whether black holes of this mass exist; between supermassive and stellar black holes; is unknown.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/147785", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/57044/" ]

[ { "answer_id": 147925, "author": "Mori", "author_id": 65279, "author_profile": "https://worldbuilding.stackexchange.com/users/65279", "pm_score": 6, "selected": false, "text": "<p>Given Sweden has a latitude of 60° N and south Africa of a bit over 30° S, you can never see one from the other no matter how high one is and no matter how small the planet is (as long as it still is big enough to allow you to neglect the distance between your eyes and the surface).</p>\n\n<p>The Sweden simply rises further away in the hemisphere invisible from South Africa. </p>\n\n<p>That is if Sweden rises simply above and continues to stay above the used-to-be-Sweden, i.e rotates with Earth. If it starts orbiting Earth forming new moon, it will probably pass over South Africa sooner or later. Obviously, I am magically hand-waving away the atmospheric friction.</p>\n\n<p>Edit: very sophisticated visualization:\n<a href=\"https://i.stack.imgur.com/Y7jaj.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/Y7jaj.png\" alt=\"graphics\"></a></p>\n\n<p>Edit 2: for a more general solution, given both points have the same longitude:\ncos (difference in latitude) = (Earth radius, 6378 km)/(Sweden distance from Earth center, i.e. height + Earth radius).</p>\n\n<p>For point directly below equator this yield</p>\n\n<pre><code>0.5 = cos(60 - 0) = 6378/(h+6378) -&gt; h = 6378 km \n</code></pre>\n\n<p>waaaay above atmosphere.</p>\n" }, { "answer_id": 147934, "author": "Mołot", "author_id": 809, "author_profile": "https://worldbuilding.stackexchange.com/users/809", "pm_score": 3, "selected": false, "text": "<hr>\n\n<p>This answer is fundamentally flawed in that it assumes that the 'horizon' formula is valid for any value of <em>h</em>.<br>\nUnfortunately, this is simply not true, <strong>and as the image shows</strong>, it is only a valid <em>approximation</em> when <em>h</em> is much less than R_E </p>\n\n<blockquote>\n <p>(R<sub>E</SUB> >> <em>h</em>) </p>\n</blockquote>\n\n<hr>\n\n<p>If you can see something depends on how high you are, and how high is what you look at:</p>\n\n<p><a href=\"https://en.wikipedia.org/wiki/Horizon#Distance_to_the_horizon\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/RZrri.png\" alt=\"enter image description here\"></a></p>\n\n<p>Africa is reasonably flat*, so assume a person 2 meters tall (or he may be standing on something ;) )</p>\n\n<p>You can look and fiddle with the numbers <a href=\"http://members.home.nl/7seas/radcalc.htm\" rel=\"nofollow noreferrer\">here with nice calculator that does the math for you</a>. With Observer at 2 meters and object at the edge of space (100km) visual horizon is at the distance of 1134km. <a href=\"https://www.distancefromto.net/distance-from-sweden-to-south-africa\" rel=\"nofollow noreferrer\">Distance from Sweden to South Africa is 10058 km</a>, so it is about ten times too far to have a line of sight.</p>\n\n<p>To get the line of sight, you will need to put Sweden at <strong>height of about 7922km</strong>. That's outside atmosphere, but inside <a href=\"https://en.wikipedia.org/wiki/Van_Allen_radiation_belt\" rel=\"nofollow noreferrer\">Van Allen radiation belt</a>, so long time life support would be hard for at least these two reasons.</p>\n\n<hr>\n\n<p>* Of course for more precise result you should include the mean or max elevation of South Africa, and decide where, exactly, your observer is placed to account for mountains, valleys, trees and so on. The above calculation is meant as an estimate, and to show a way how to calculate it yourself.</p>\n\n<p>The question says only \"from South Africa\" so we can assume optimal point of observation, Thabana Ntlenyana 3482 meters high (+2m person) for the flying height of <strong>\"mere\" 3452km</strong>. No trees or other mountains to significantly change this altitude.</p>\n" }, { "answer_id": 147941, "author": "JBH", "author_id": 40609, "author_profile": "https://worldbuilding.stackexchange.com/users/40609", "pm_score": 6, "selected": false, "text": "<p><strong>There is no atmospheric height any object of any size can be, perpendicular to the location of Sweden, that could be seen by anyone standing anywhere in South Africa.</strong></p>\n\n<p>I don't need math to prove this. Just take out a piece of paper, draw a circle, and use a ruler to start drawing lines. That combination cannot be done.</p>\n\n<p>Alternatively, visit maps.google.com, scroll out until you can see the whole planet, and rotate it until Sweden is in the middle. It'll look something like this (credit: Google):</p>\n\n<p><a href=\"https://i.stack.imgur.com/1ULhE.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/1ULhE.png\" alt=\"enter image description here\"></a></p>\n\n<p>Molot's answer (which is the mathematically pure answer, go vote for it) brings out that tall things slightly beyond the edge of the hemisphere defined by Sweden acting as the pole or center of the circle will see Sweden <em>if it's high enough.</em> But below that it's geometrically impossible &mdash; there's a planet in the way.</p>\n\n<p>And that example, above, assumes we send Sweden so far away that the entirety of its defined hemisphere can see it. If we limit that height to keep it within the atmosphere, then the total area that can see it at any height within the atmosphere (~300 mi thick) is something more like this:</p>\n\n<p><a href=\"https://i.stack.imgur.com/K4Y6d.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/K4Y6d.png\" alt=\"enter image description here\"></a></p>\n\n<p>Compared to the radius of the Earth, our atmosphere is proverbially as thick as a sheet of paper. Variations in land height don't matter, either, as those variations are less than the dimples on a golf ball compared to the radius of the Earth. When you're talking about the entire planet, it can be reasonably modeled as a smooth surface.</p>\n\n<p><strong>Conclusion</strong></p>\n\n<p>There is no height within the atmosphere that would allow Sweden to be seen from any point within what we would normally call the Southern Hemisphere. There is a height where it could be seen by a couple of points in the Southern Hemisphere (see that area below the dashed line in Africa? Yeah, the dashed line is the equator), but Sweden would be so far outside Earth's atmosphere that it likely doesn't matter for your story.</p>\n\n<p><em>This assumes you do not subscribe to the Flat Earth theory. I don't.</em></p>\n" }, { "answer_id": 148118, "author": "Danikov", "author_id": 10278, "author_profile": "https://worldbuilding.stackexchange.com/users/10278", "pm_score": 1, "selected": false, "text": "<p>If you imagine an idealised planet with a star at an infinite distance, how much of the planet can see it? The answer is half: the star projects a cone that rests on an equatorial line perpendicular to the direction it lies in. Those standing on that equatorial line are looking along the tangent to the curve of the surface of the planet.</p>\n\n<p>So the basic question is, what is the minimum distance at which this is still possible, or rather, given two opposite points on a circle, where do their tangents intersect? This is effectively squaring the circle that forms said equator, which simplifies down to the square root of 2r^2 (minus the radius of the Earth if you want the height above it).</p>\n\n<p><strong>In the case of Earth, that comes to 2,639km</strong>, however there are other factors regarding the shape of the orbit that might have an effect. Obviously, given an orbit it will not be visible at all times to the whole planet. However, if that orbit is geostationary (e.g. proportional to the rotational speed of the planet) it will only be visible to half the planet when above said height.</p>\n\n<p>Given orbits are elliptical, it's also possible that it is not above that height the entire orbit. If the orbit resonates with the rotation of the planet and has a low point below said height, this could create dead spots that will never see it in the sky.</p>\n\n<p>Finally, there's always the possibility of mountain ranges and atmosphere practically limiting visibility along the line of the tangent.</p>\n" }, { "answer_id": 148679, "author": "Jetpack", "author_id": 43703, "author_profile": "https://worldbuilding.stackexchange.com/users/43703", "pm_score": 1, "selected": false, "text": "<p>You have three questions here.</p>\n\n<p><strong>1. How high can a geostationary Sweden be visible from South Africa?</strong></p>\n\n<p><strong>Answer: 68,100 km</strong></p>\n\n<p>This is a question that humanity has pondered since we first climbed down from the trees.</p>\n\n<p>The other answers are correct that if two points are more than 90 degrees apart on the globe, they cannot see each other at any height (unless the earth has a big groove in it or atmospheric refraction does something funny, but we don't have to consider that in this answer).</p>\n\n<p>The correct way to calculate angular distances between two points on the globe is to use the haversine formula. This takes both latitude and longitude into account. I'm feeling a little lazy today, so I will just take the distance measured on Google Maps, divide by 40,075 kilometers and multiply by 360 degrees. This is equivalent, and I've checked that the math lines up.</p>\n\n<p>If Sweden goes straight up from the point of view of its center point, the important location of Sweden is Flataklocken at 62°23′15″N 16°19′32″E.</p>\n\n<p>I found a point near South Africa's Zimbabwe that is 9,472 km away from Flataklocken, which comes out to 85.09 degrees.</p>\n\n<p>You're in luck! You can see Sweden from South Africa. It will be low in the sky, within 5 degrees of the horizon. It will be brighter than the full moon since it's a lot closer.</p>\n\n<p>If you intend to actually do this, I'd recommend buying a hot air balloon to take South Africans up to view.</p>\n\n<p>Some math:\na = 85.09 degrees (this is the angular distance between South Africa and central Sweden)\nr = 6371 km (this is the radius of the earth)\nfind h, the height of Sweden</p>\n\n<p>cos(a) = r / (r + h)\nTherefore\nh = r (-1 + 1 / cos(a)) = 68,100 kilometers.</p>\n\n<p>This is over 10 times earth's radius. It's far outside earth's atmosphere, but low enough it's not going to crash into the moon.</p>\n\n<p><strong>2. If Sweden were floating in a geostationary position in the upper atmosphere, how far would it be visible?</strong></p>\n\n<p><strong>Answer: 2400 km</strong></p>\n\n<p>Earth's atmosphere only goes up 480 km, so if you want Sweden to stay in a geostationary position in the atmosphere, it won't be visible from South Africa. </p>\n\n<p>If you want the people of Sweden to have enough air to breathe, it will have to be even lower. I'm not going to run the numbers for that, because that's not the question you asked.</p>\n\n<p>The equation is the same, except in this case, we know h and r, and we're trying to find a.</p>\n\n<p>r = 6371 km (this is still the radius of the earth)\nh = 480 km (Sweden floating in the edge of the atmosphere)</p>\n\n<p>cos(a) = r / (r + h)</p>\n\n<p>Therefore\na = arccos(r / (r + h)) = 21.57 degrees.</p>\n\n<p>This comes out to a distance of 2400 kilometers.</p>\n\n<p>This isn't far enough to see from the southern hemisphere, but you would still be able to see southern Sweden from parts of Algeria and Tunisia. As far as I'm concerned, that's good news!</p>\n\n<p><strong>3. Can a Sweden orbiting in the atmosphere be visible from South Africa?</strong></p>\n\n<p><strong>Answer: No</strong></p>\n\n<p>If you can make Sweden orbit at this low elevation, it can be visible from every point in the world. But you can't make Sweden orbit in the atmosphere.</p>\n\n<p>Orbit means something is spinning around a world without rockets or thrusters because it is going so fast that gravity can't pull it down. You can calculate the orbital speed for any height in a vacuum. Unfortunately, orbit is not possible within the atmosphere because the air resistance will eventually slow Sweden down so that it will crash into the earth.</p>\n\n<p>Don't despair. You can still make Sweden fly. You'll need to buy big jets or something else that uses energy to move it around. I don't know what your budget is, but I think it's still worthwhile. Think of the spectators in South Africa.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/147916", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/65278/" ]

[ { "answer_id": 148381, "author": "Alex", "author_id": 62779, "author_profile": "https://worldbuilding.stackexchange.com/users/62779", "pm_score": 0, "selected": false, "text": "<p>I believe nanobot swarms, mixed with chemically altering the oceans and atmosphere might be an answer. Theoretically you could program the bots to build themselves, and use advanced AI to encourage them to follow their prime directive. The biggest issue is the small bacteria that live deep underground, and do not rely on oxygen to survive. For total annihilation I think a good goal of the swarm would be to destroy the atmosphere of earth so it looks like Mars, or increase the atmosphere's density until the planet resembles Venus. </p>\n" }, { "answer_id": 148392, "author": "cmm", "author_id": 40655, "author_profile": "https://worldbuilding.stackexchange.com/users/40655", "pm_score": 3, "selected": false, "text": "<p>To: \"Carl Llama\" </p>\n\n<p>From: \"The New Guy\"</p>\n\n<p>Date: June 5, 2019</p>\n\n<p>Subject: Watch Out</p>\n\n<p>Dear Mr. Llama,</p>\n\n<p>Watch your back. This looks like a setup. I'm new here, but what you're asking can't be done. Life is just too robust, and cities are too fragile. </p>\n\n<p>You can't burn out the bacteria miles underground because those cities can't stand too much heat. The concrete will de-hydrolize and the buildings will collapse. </p>\n\n<p>You can't expose the world to intense enough radiation because the molecular structure of those precious cities will change, and the buildings will collapse.</p>\n\n<p>You can't do much underground without making the crust shift, and even small crustal changes will shake the surface, and the buildings will collapse.</p>\n\n<p>If you try to do something slowly, life will evolve to adapt to your change.</p>\n\n<p>If you put your reputation behind this project, the only thing killed will be your future with Universal Cleaning Company. Watch your back. You may be in Calamity's sights.</p>\n" }, { "answer_id": 148395, "author": "Trish", "author_id": 25822, "author_profile": "https://worldbuilding.stackexchange.com/users/25822", "pm_score": 2, "selected": false, "text": "<p>Let's grab the classics:</p>\n<h2><a href=\"https://gundam.fandom.com/wiki/Space_colony#Colony_Drops\" rel=\"nofollow noreferrer\">Colony Drop!</a></h2>\n<p>We all know the premise of Gundam, don't we? Humankind went to the stars, then Earth wanted to oppress the colonies. The Colonies flipped the terran eagle and put thrusters on any and all space stations and craft they had and put them on full thrust - course: earth. They ensured widespread destruction of society... but not total annihilation because they had too little mass. So instead of scattering colonies all over the planet, we go a step larger and drop the largest and closest place that could be colonizable onto earth: <a href=\"https://timemachine.fandom.com/wiki/Great_Lunar_Cataclysm\" rel=\"nofollow noreferrer\">The moon.</a></p>\n<p>To get it to deorbit in chunks large enough to annihilate all life as we know it and send the planet into an ice age, we just need to crack it into good-sized chunks. A good plan would be to dig deep from the far side of the moon and then detonate a couple dozen nuclear warheads, separating the moon into maybe three or four chunks that start to descend onto earth. The good part: Humanity has no chance to survive. The bad part: Life itself has a chance to. So, we need to go bigger.</p>\n<h2><a href=\"https://warhammer40k.fandom.com/wiki/Exterminatus\" rel=\"nofollow noreferrer\">EXTERMINATUS</a></h2>\n<p>We want to exterminate the whole planet? Then we should go all in. Calling upon the Imperium of Man's wisdom: We drop a torpedo onto the planet that incinerates the whole atmosphere and leaves all life to suffocate. Or we drop a bomb that bores to the core, then destabilizes it by blowing it up, making the whole planet to erupt in volcanos and turn its crust inside out.</p>\n<h2><a href=\"https://en.wikipedia.org/wiki/Vogon\" rel=\"nofollow noreferrer\">Vogon Construction Crew</a></h2>\n<p>Why make our own fingers dirty? Call upon the Vogon construction crew to place a hyperspace lane right through Sol III. They'll finish it up easily. Just make sure they don't forget to place a checkmark on the papers.</p>\n<h2><a href=\"https://aliens.fandom.com/wiki/Xenomorph\" rel=\"nofollow noreferrer\">Xenomorphs</a>/<a href=\"https://warhammer40k.fandom.com/wiki/Tyranids\" rel=\"nofollow noreferrer\">Tyranids</a></h2>\n<p>We could also drop bioengineered creatures onto the planet that eat all of the lifeforms on it and leave a dead husk, possibly containing the new spore cell for the next species' demise, should they stumble over their eggs...</p>\n<h2><a href=\"https://www.businessinsider.com/how-to-kill-the-sun-2015-9?IR=T\" rel=\"nofollow noreferrer\">Poison the Sun</a></h2>\n<p>But we have unlimited time and resources, right? So let's start to ship all the iron and other metals we can find right into the sun. As we start to drop more and more material into Sol, we start to heat it up - and make it consume its hydrogen faster and burn hotter. At some point - once we have dropped several percents of the solar mass into it (earth is less than 0.000303%!), Sol will start to cook Earth, shifting the habitable zone outwards and past Earth. Solar winds will ravage the planet and possibly rip away its atmosphere while the increased output of the sun will turn the blue planet into a white clouded ball with boiling oceans and an average temperature of more than 50 °C - enough to denature any protein and make life as we know it impossible.</p>\n<h2><a href=\"http://www.pa.uky.edu/%7Ewilhelm/ast192_f09/Calculating%20the%20Lifetime%20of%20the%20Sun.pdf\" rel=\"nofollow noreferrer\">Wait around 5 Billion Years.</a></h2>\n<p>But why cook earth? We have no time constraints. We can have time itself turn Earth inhabitable for all life by just letting the sun consume all the Hydrogen and turn it up to carbon. Sol is not massive enough to support the fusion to anything larger than carbon and then will start to shut down. The result is, that earth will soon after - in astronomical terms - freeze into a ball of ice, showing only remnants of life, encased in ice. At that point, any remains of human society have been eroded away.</p>\n" }, { "answer_id": 148397, "author": "nijineko", "author_id": 22912, "author_profile": "https://worldbuilding.stackexchange.com/users/22912", "pm_score": 2, "selected": false, "text": "<h3>The simplest answer already exists, has been built, and tested back in the 1950-1960s.</h3>\n<p>The Neutron bomb is a low yield thermonuclear weapon specifically tweaked to enhance the production and release of neutrons.</p>\n<p>While the immediate blast radius is much smaller than most nukes, it still damages that radius, so care in deployment is required. However the neutron shockwave is more widespread, and lethal to organic lifeforms.</p>\n<p>Current technologies can produce this weapon, and with careful application, only carefully fortified strongholds and the heaviest of armored vehicles offer any degree of protection against the neutron shockwave.</p>\n<hr />\n<p>With certain theoretical advancements in technology, steady neutron production could be enhanced and stabilized. Neutron blocking material already exists, once neutron reflective material is secured, then directed neutron energy weapons become possible.</p>\n<p>Such a naser weapon [Neutron Amplification (by) Stimulation (of) Emitted Radiation] could be used to sterilize organics with minimal impact on most inorganic materials.</p>\n<p>Atmospheric dispersion is still an issue, causing the neutrons to lose energy and eventually be absorbed, so range is limited.</p>\n<p>‐--</p>\n<p>If the neuron option proves undesirable, then a tailored genetic virus which is tweaked in an effort to limit what species it affects, and also completely breaks down the structure, might be possible.</p>\n<p>Mutation always remains a risk, however.</p>\n" }, { "answer_id": 148398, "author": "Halfthawed", "author_id": 64961, "author_profile": "https://worldbuilding.stackexchange.com/users/64961", "pm_score": 2, "selected": false, "text": "<p>To: Who It May Concern</p>\n\n<p>From: Dr. Vahlen's Eager Lab Assistant</p>\n\n<p>Dr. Vahlen hasn't yet had the time to think through this proposition, and, to be frank, the Commander and Bradford have both agreed that she does <em>not</em> need to, because it would only give her ideas. So they assigned the job to me.</p>\n\n<p><em>AHEM</em></p>\n\n<p><strong>RADIATION POISONING</strong></p>\n\n<p>All forms of life can be lethally killed with enough radiation. The key phrase here is, of course, <em>enough</em>. 400 to 450 rem over a short period can kill off half the human population within thirty days. That's about 4 sieverts, or 4 joules/kilograms. (Radiation uses weird measuring units.) That's the far end of the spectrum. The other end are radioresistant bacteria which can survive up to 30,000 grays, which is apparently the same thing as a sievert. (I'm just going to use grays from now on. Remember, 1 gray = 1 joule). The good new is that once you decide to bombard Earth with the amount of grays necessary to kill even the most resistant of bacteria, you don't really have to worry about anything else surviving. The bad news is, ah, getting that much energy. The Earth's crust is only a about twenty or so miles deep. That only gives you about 1.5*10^10 cubic miles to irradiate to the point where even a bacteria, which is fills up a space of about 1.4*10^-14 cubic miles receives that much radiation. Good luck!</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/148379", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/6986/" ]

[ { "answer_id": 149367, "author": "L.Dutch", "author_id": 30492, "author_profile": "https://worldbuilding.stackexchange.com/users/30492", "pm_score": 2, "selected": false, "text": "<p>Gravity affects in the same projectiles and buildings. </p>\n\n<p>If a human can throw a spear or jump 3 times higher, the same human can build a wall or a fortification 3 time taller, to get protection from the said spear/intruder.</p>\n\n<p>All the rest being the same, the max height of a structure depends on the load, and this is given by its weight. Less weight means more height.</p>\n\n<p>All in all, fortification will be as effective as they were in hour Bronze age.</p>\n" }, { "answer_id": 149369, "author": "SurpriseDog", "author_id": 63172, "author_profile": "https://worldbuilding.stackexchange.com/users/63172", "pm_score": 5, "selected": true, "text": "<p>1/3 gravity will enable humans to jump higher, but nothing absurd. For example on earth if you jump at 2m/s then you will have a jump time of:</p>\n\n<pre><code>t = (vf - vi)/g\n\nt = (0 - 2)/(-9.8) = 0.2 seconds\n</code></pre>\n\n<p>At 1/3 gravity that works out to:</p>\n\n<pre><code>t = (0 - 2)/(-9.8/3) = 0.6 seconds\n</code></pre>\n\n<p>Using this we can calculate the jump height by:</p>\n\n<pre><code>h = vi * t + (g * t²)/2\nh = 2 * 0.6 + (-9.8/3*0.6^2)/2 = 0.6 meters\n</code></pre>\n\n<p>So slightly higher, but not enough to count. What this <em>will</em> do is make it easier to build fortifications. Stones that weighed many tons, now weigh a 1/3 of that and are much easier to manage. A crew of dozens can erect stone structures that would take hundreds on earth and even on this world stone is stone, and similarly hard to get through.</p>\n\n<p>The ultimate effect of this will be tall stone structures everywhere to keep invaders out, instead of traditional wooden palisades. Which will be quite necessary considering the fact that catapults and other siege weapons will be able to throw stones 3 times as far! Archers will be of no use against enemy soldiers with these weapons as they can now fling stones from so far away that they are almost impossible for the archers to hit with any accuracy. </p>\n" }, { "answer_id": 149382, "author": "puppetsock", "author_id": 63077, "author_profile": "https://worldbuilding.stackexchange.com/users/63077", "pm_score": 3, "selected": false, "text": "<p>Climbing in 1/3 gravity will be interesting. A small indent in a wall that would be not much help in 1 gravity will be plenty to cling onto a wall at 1/3. You come to an ordinary brick wall such is common on Earth, with little indents between the bricks because the mortar isn't spread right to the edge. Possibly you need some kind of gadget to cling properly, but you can go up that wall fairly easily.</p>\n\n<p>A wall isn't much help if the opposition can just climb over it, walk over to a door, and let in all their buddies. So walls would need anti-climbing character.</p>\n\n<p>Walls would need to be a lot smoother than typically built now. They would also probably feature anti-climbing barriers. So the wall is high enough to discourage straight jumping. And there's an overhang to make climbing very difficult. And there are arrow slits in the bottom of the overhang to allow defenders to attack possible climbers.</p>\n\n<p><a href=\"https://i.stack.imgur.com/Hsr7n.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/Hsr7n.png\" alt=\"enter image description here\"></a></p>\n\n<p>Moats would need to be correspondingly wider.</p>\n\n<p>Ranged weapons might be more annoying because they will have longer range. </p>\n\n<p>A catapult might well be able to locate somewhere with really good cover and fling stones 3 or 4 km. More? Not sure how far catapults can fire on Earth. Accuracy might suffer. But they would be able to fling much bigger stones. So even a near miss does a lot of damage. Castles often expended a lot of effort preparing the ground nearby to make just such attacks difficult. They would need to go out much farther from the castle in this effort.</p>\n\n<p>Flaming arrows might be fired much longer distances. So they would need to be well prepared for this. Either make exposed parts of the castle out of stone, including the roof. Or they'd need to have fire fighting preparation.</p>\n\n<p>Depending on the air pressure, human powered flight might well be possible. So some of Leonardo's designs might well have worked with medieval materials and construction methods. So a hill nearby might be a place to launch a bunch of guys on hang gliders or some such, even with light armor. Maybe fly right over the wall. So the castle would need some kind of way to deal with this. Maybe things like nets and spikes and such on the roof to discourage flying attacks. And the castle better be on the highest chunk of ground in the area. </p>\n\n<p>Flying then becomes a two way thing, with recon missions. And fake groups of attackers set up to try to fool the airborne recon. And possibly even sorties from the castle based on gliders. Oh, and launch ramps around the top of the wall, and possibly specific areas inside the castle for flyers to return. And the ever present wind sock instead of a flag. </p>\n\n<p>Possibly a ride on a catapult is survivable at 1/3 g. Imagine 10 guys in the bucket of each of 10 catapults. And they each have a parachute of some kind. Suddenly the sky over the castle is jam packed with enemy soldiers. You would want to be ready with a variety of bow-and-arrow and such. And ready to repel an attack of guys who just literally fell from the sky.</p>\n" }, { "answer_id": 149535, "author": "Klaus Æ. Mogensen", "author_id": 62769, "author_profile": "https://worldbuilding.stackexchange.com/users/62769", "pm_score": 1, "selected": false, "text": "<p>How high a human can jump in lower gravity is rather complex.</p>\n\n<p>Assuming, as a first-order approximation, that the upward speed when leaving the ground is the same as in normal gravity, you can jump three times as high. But what does that mean? Good high jumpers on Earth can clear a 2 m bar, but they do that more or less lying down, with their centres of mass very low over the bar. Their centres of mass when leaving the ground is roughly 1 m above the ground, so the centre of gravity is only lifted about 1 m. This is what we will have to triple when gravity is one-third normal. A high jumper on this planet will thus be able to clear a 4 meter bar.</p>\n\n<p>However, there' more to it: The assumption of having the same jump speed as on Earth is too simplistic. A high jumper fights gravity when flexing muscles to achieve jump speed, so the force provided by the legs is a combination of the force needed to counteract gravity and the force that provides the upward speed. On Earth, the force needed to counteract gravity is 10 m/s/s, and the acceleration to reach the speed required to lift the centre of 1 m is another 20 m/s/s, assuming that the acceleration of the body centre of mass is done over half a meter (crouching to standing), for a total of 30 m/s/s. If only 3.33 m/s/s is needed to counteract gravity, there will be 26.67 m/s/s left to actually accelerate the body upwards, for a jump speed of 4 m/s. In one-third gravity, this is enough to lift the centre of mass 4 m, meaning that a good high jumper can clear a 5 m bar.</p>\n\n<p>To clear a wall, you just need to be able to get your hands on the top of the wall and swing yourself over, which adds another meter to how tall the wall must be to prevent people from jump-and-swing over it. Walls hence must be at least 6 meters tall to prevent easy access by jumping.</p>\n\n<p>This, of course, assumes that the jumper isn't wearing heavy gear, but a sword and light armor doesn't add all that much to the weight of a person and hence doesn't change the equation all that much, either.</p>\n\n<p>Pole vaulting, however, would add more meters to how high you can jump. Since pole vaulting relies on turning the kinetic energy of your running speed into potential enery, the energy provided by pole will remain unchanged with lower gravity, assuming you can run just as fast as on Earth. That energy would however propel your body three times as high. Record pole vaulters can clear 6 meters, hence lifting the centre of mass 5 meters. By pole vaulting, a soldier on your planet could hence feasibly clear a 16 m wall; possibly a bit more, since the lower gravity might allow faster running. Coming down the other side might hurt, though as there is unlikely to be a thick, soft mat there, and it corresponds to falling roughly two stories on Earth. If you can land on the top of the wall, there will be no problem, though, so to be safe, defenders should probably build their walls at least 20 m high.</p>\n" }, { "answer_id": 149542, "author": "Thorne", "author_id": 33868, "author_profile": "https://worldbuilding.stackexchange.com/users/33868", "pm_score": 0, "selected": false, "text": "<p><strong>Add a Roof</strong></p>\n\n<p>A building with a sealed roof and arrow slits means they can only get through the door so getting on the roof doesn't really help. If the roof is spiked/bladed, getting on the roof won't be fun.</p>\n" }, { "answer_id": 149543, "author": "bendl", "author_id": 39583, "author_profile": "https://worldbuilding.stackexchange.com/users/39583", "pm_score": 2, "selected": false, "text": "<p>At least in Europe, the prevailing bronze age fortification was the hillfort. Walls as you are likely imagining them were not very common at all. The purpose of these fortifications was not to make it impossible for invaders to get in, but rather to make it difficult for them to scramble up and to leave them tired by the end of it.</p>\n\n<p>The objective is to make sure you're standing on solid ground, but your enemy is tired and standing on uneven, possibly muddy ground, giving you a significant advantage.</p>\n\n<p>If this is the type of fortification you're using, it will be almost as effective as it was on earth, except the enemy probably won't be as tired by the time they get to the top. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/149363", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/879/" ]

[ { "answer_id": 149919, "author": "Ash", "author_id": 40408, "author_profile": "https://worldbuilding.stackexchange.com/users/40408", "pm_score": 3, "selected": false, "text": "<p>\"Standard\" <a href=\"https://en.wikipedia.org/wiki/Petrifaction\" rel=\"noreferrer\">petrifaction</a> like what can happen to wood of the bones, teeth, and probably scales is highly likely if your dragon is buried deeply. Depending on the particular processes that occur parts of the beast may be <a href=\"https://en.wikipedia.org/wiki/Opal\" rel=\"noreferrer\">opalised</a>.</p>\n\n<p>It is also possible, depending on the make up of your dragons, that parts of them are already composed of jewel like materials, for example <a href=\"https://en.wikipedia.org/wiki/Diamond\" rel=\"noreferrer\">diamond</a> has extremely high thermal conductivity so it may be useful for heat dissipation in a very large creature since the cubed-squared law is not kind at such extremes of size. Conversely certain members of the <a href=\"https://en.wikipedia.org/wiki/Serpentine_subgroup\" rel=\"noreferrer\">Serpentine</a> family are extremely heat resistant making good fireproofing for areas like the snout.</p>\n" }, { "answer_id": 149923, "author": "Sherwood Botsford", "author_id": 15784, "author_profile": "https://worldbuilding.stackexchange.com/users/15784", "pm_score": 2, "selected": false, "text": "<p>It's raining jewels.</p>\n\n<p>Suppose that dragons shed. Scales grow for a time, then slough off when they get too large and heavy. This usually occurs when the dragons groom, but they also shed during flight. You don't have to go all the way to diamond: Quartz is quite hard, and gem quality quartz comes in a huge variety of colours. Because it's build up a molecular layer at a time there is room for all kinds of optical effects.</p>\n\n<p>Just as skin is different thickness on different parts of a cow, so scales would be different sizes on different parts of the dragon. Imagine getting clonked by a teacup saucer scale a quarter inch thick made up of amethyst. </p>\n\n<p>Take the process internally: skeletons made of sapphire (ruby) in intricate trusses.</p>\n\n<hr>\n\n<p>Thought experiment: What if you ruled a relatively poor country. If someone from far away wanted to buy dead people, would you sell? A real way that criminals can pay back their debt to society.</p>\n\n<p>Turn it around: Can you trade for dragon parts?</p>\n" }, { "answer_id": 149928, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 2, "selected": false, "text": "<p><strong>Encase them in amber.</strong></p>\n\n<p><a href=\"https://i.stack.imgur.com/DBUac.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/DBUac.jpg\" alt=\"lizards in amber\"></a></p>\n\n<p><a href=\"https://www.smithsonianmag.com/science-nature/pint-sized-lizards-trapped-amber-give-clues-life-100-million-years-ago-180958284/\" rel=\"nofollow noreferrer\">https://www.smithsonianmag.com/science-nature/pint-sized-lizards-trapped-amber-give-clues-life-100-million-years-ago-180958284/</a></p>\n\n<p>Dying dragons lie down under specific trees that occur in their lands. With their dying energy they swipe at the bark. A cascade of amber dribbles down over them as the die, anaesthetizing them and entombing their remains. Eventually these enormous trees will grow to cover the dragons at their feet, reclaiming both their amber and the material resources of the dragon. Lucky adventurers might find portions of an amber-encased dragon protruding from the great tree and with effort pry something loose.</p>\n\n<p>Note: these trees are not unprotected...</p>\n" }, { "answer_id": 150046, "author": "Thorne", "author_id": 33868, "author_profile": "https://worldbuilding.stackexchange.com/users/33868", "pm_score": 2, "selected": false, "text": "<p><strong>Opals</strong></p>\n\n<p>Like fossilization, opalization can occur if in the right conditions.</p>\n\n<p><a href=\"https://io9.gizmodo.com/eric-the-pliosaur-one-of-the-most-interesting-fossils-5987941?IR=T\" rel=\"nofollow noreferrer\">Eric the Pliosaur</a> is one such opalized skeleton discovered in Australia </p>\n\n<p><a href=\"https://i.stack.imgur.com/ubczo.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/ubczo.png\" alt=\"enter image description here\"></a></p>\n" }, { "answer_id": 150091, "author": "Community", "author_id": -1, "author_profile": "https://worldbuilding.stackexchange.com/users/-1", "pm_score": 2, "selected": false, "text": "<p>Perhaps it can be explained differently</p>\n\n<blockquote>\n <p>When a dragon leaves it's nest, it does something unique among all animals. It goes deep into the earth, further down than any man has gone or ever will go, and digs it's dying place. The dragon keeps the location of it's dying place secret throughout it's life, but remembers where it is. And when a dragon feels that the end of it's life is coming, it crawls through the caverns it last saw in it's youth, and enters the dying place. The natural death of a dragon is something of a wonder. For when the dragon enters the dying place, it seals the entrance and waits for Death. When Death finally arrives and stretches out his skeletal hand, then the dragon opens it's mouth one last time and unleashes a fire more powerful, more hot, then it has ever released. The fire swirls around the dragon, the earth trembles and falls above it, and the heat and pressure turns the dragon into a diamond, to lie forever within the depths of the earth.</p>\n</blockquote>\n\n<p>Something similar to this could be cool.</p>\n\n<p>BTW, I wrote that explanation myself, so you don't have to worry about copyright or anything.</p>\n\n<p>Edit:</p>\n\n<p>Okey dokey, after a great many requests for an expansion in the science based aspect of this, here is the mechanism.</p>\n\n<p>The dragon, when it is about to die, goes into an underground cave it dug earlier in it's life and closes the entrance. The dragon then breathes extremely hot fire, which causes the cavern to collapse, and brings millions of tons of earth down upon the dragon, causing it to turn into a diamond.</p>\n\n<p>As you can see, this parallels my poetic explanation, I guess I just had to clarify. Thanks for the help!</p>\n" }, { "answer_id": 150277, "author": "Tim B", "author_id": 49, "author_profile": "https://worldbuilding.stackexchange.com/users/49", "pm_score": 0, "selected": false, "text": "<p>I'm going to offer something of a frame challenge here - is the underground cavern really required?</p>\n\n<p>(Because if it is then the answer is simple - living dragons guard the resting place of their dead).</p>\n\n<p>Instead have the dragon funeral rites be a ritual internment in liquid lava. They are taken to an active volcano and there returned to the fires that birthed them.</p>\n\n<p>No human has any chance of getting at those remains - not that much will remain.</p>\n" }, { "answer_id": 150293, "author": "Patrick Hughes", "author_id": 60342, "author_profile": "https://worldbuilding.stackexchange.com/users/60342", "pm_score": 1, "selected": false, "text": "<p>After death, deep in the earth with still air and warm temperatures, the \"stuff\" that lets dragons breathe fire contracts and distills inwards and glows hotter and hotter until the dragon itself is forged and tempered in its own flames along with the last gasps of remaining magic.</p>\n\n<p>Ancient history and rationalization: Because dead dragons explode after a while, the early dragons took to burying them deep so that they didn't explode everything around them, too. This became a sign of reverence, the dead must be treated with care. The ancient tradition continues even to this day...</p>\n" }, { "answer_id": 227992, "author": "Brinstar77", "author_id": 94891, "author_profile": "https://worldbuilding.stackexchange.com/users/94891", "pm_score": 0, "selected": false, "text": "<p><strong>BIOLOGICALLY HARDWIRED SELF-DESTRUCT</strong></p>\n<p>My answer is a combination of Ash's and Patrick's answers above. Perhaps there's something keeping the volatile gasses that power a dragon's flame breath in check, that shuts down when it dies. The end result is that when the dragon dies, it detonates about 15 minutes later. Every organic part of the dragon is incinerated in the blast unless the organs that allow fire breath is removed and taken away. The non-organic parts of the dragon (namely, the gemstones in its body that aid with heat dispersion) are not incinerated and remain.</p>\n<p>Dragon funerary rites work like this; the dragons come in after the dragon detonates, gather up the gemstones, and melt the gemstone down into a single, brilliant gem. This gem is then buried as if it were the dragon's body because it kind of is.</p>\n<p>This answer also adds another factor that makes dragons incredibly dangerous to hunt. The most dangerous part about hunting dragons for their parts is not actually slaying the dragon, it's the procedure to remove the flame production organs after the dragon is slain, lest they detonate and incinerate the dragon's remains. This procedure can take upwards of 10 minutes under the absolute best of conditions, and can easily take well over 15 if the conditions aren't perfect, which can lead to the organs detonating in your face while you're trying to remove them. But rush any part of the procedure, and you damage the mechanism holding the flames back, causing the organs to detonate in your face anyway.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/149908", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/62803/" ]

[ { "answer_id": 151299, "author": "AlexP", "author_id": 29552, "author_profile": "https://worldbuilding.stackexchange.com/users/29552", "pm_score": 4, "selected": true, "text": "<p>Surface gravity is directly proportional with the radius of the planet and inversely proportional with the density of the planet.</p>\n\n<p>Now fire up LibreOffice Calc (or your favorite spreadsheet program), and play with the numbers. I suggest to put Earth's radius, surface area and surface gravity as 1 (because your are interested in relative values), but keep the Earth's density as 5.5 (because it has direct implications for the chemical composition of the planet etc.) Then figure out what increase in surface gravity you are prepared to tolerate (I suggest 20 to 25% tops) and what decrease in density you can justify while keeping enough iron to get a decent magnetic field and to preserve Earth-like biochemistry (I suggest not lower than 5). You will get something like this:</p>\n\n<pre><code> Radius Area Density Gravity\n ------ ---- ------- -------\nEarth 1.00 1.00 5.50 1.00\nMax gravity, lowest density 1.38 1.89 5.00 1.25\nMax-ish gravity, lowest density 1.32 1.74 5.00 1.20\nModerate gravity, lowest density 1.21 1.46 5.00 1.10\n</code></pre>\n\n<p>This suggests that you can get a surface area 75 to 90% larger than Earth's without extremely strong effects on the biosphere, and a surface area 50% larger than Earth's with minimal effects on the biosphere.</p>\n" }, { "answer_id": 151300, "author": "Brythan", "author_id": 2113, "author_profile": "https://worldbuilding.stackexchange.com/users/2113", "pm_score": 2, "selected": false, "text": "<p>We don't have a good measure for how much gravity a human being can sustain for a lifetime. We might well find that 1.1 g is too much. Or that we can easily adapt to 2g. We have a little better understanding of microgravity's effects on the human body, but almost none on long term higher gravity. Twice is probably too high, but anywhere from 1.1 to 1.5 is up to you. No one can tell you that it is wrong, because we just don't know. </p>\n\n<p>All our studies of higher gravity are based on limited duration. Basically the length of the high acceleration trip. We can't maintain high acceleration for a long period of time (too energy intensive), so we don't know what the effects are. </p>\n\n<p>Beyond that, bigger doesn't necessarily mean higher gravity. If the planet is less dense (for example, no iron core), it can have a higher volume/surface area and the same gravity. The formula is </p>\n\n<p><span class=\"math-container\">$$g = \\frac{Gm}{r^2}$$</span></p>\n\n<p>The formula for mass is volume times density. </p>\n\n<p><span class=\"math-container\">$$m = \\frac{4\\pi r^3}{3}\\rho$$</span></p>\n\n<p>Substituting, we get </p>\n\n<p><span class=\"math-container\">$$g = \\frac{4G\\pi r\\rho}{3}$$</span></p>\n\n<p>Rearranging </p>\n\n<p><span class=\"math-container\">$$r = \\frac{3g}{4G\\pi\\rho}$$</span></p>\n\n<p><span class=\"math-container\">$G$</span> and <span class=\"math-container\">$\\pi$</span> are constants. Now, let's rewrite this as a proportion. </p>\n\n<p><span class=\"math-container\">$$\\frac{r}{r_E} = \\frac{g{\\rho}_E}{g_E\\rho}$$</span></p>\n\n<p>What this says is that the size of the radius in Earth radii is equal to the number of Earth gravities divided by the density in Earth densities. So taking out the proportions, we have </p>\n\n<p><span class=\"math-container\">$$r = \\frac{g}{\\rho}$$</span></p>\n\n<p>There are some limits to how low you can make the density. Jupiter is composed of things (e.g. hydrogen) that have a low density at Earth gravity. But because Jupiter is so massive, they are compressed to a much higher density. </p>\n\n<p><a href=\"https://www.universetoday.com/36935/density-of-the-planets/\" rel=\"nofollow noreferrer\">Mars' density</a> is a bit more than three quarters that of Earth. All the lower density planets in our solar system are gas giants. So you can probably get three quarters. Putting that back into our formula, we get </p>\n\n<p><span class=\"math-container\">$$r = \\frac{1.5}{.75} = 2$$</span></p>\n\n<p>So about the most you can expect to get is a planet twice as large in radius as the Earth. This will also have four times the surface area and eight times the volume. And six times the mass. </p>\n\n<p>It is possible that you can manage a lower density than Mars. I don't have a good way of evaluating it. If you find that you can, you can put that number back into the formula. </p>\n" }, { "answer_id": 151304, "author": "TheDyingOfLight", "author_id": 58321, "author_profile": "https://worldbuilding.stackexchange.com/users/58321", "pm_score": 2, "selected": false, "text": "<p>Steven Dole suggested in his book <a href=\"https://en.m.wikipedia.org/wiki/Habitable_Planets_for_Man\" rel=\"nofollow noreferrer\">Habitable Planets for Man</a> the following gravity, mass and radius ranges for planets still maintaining a magnetosphere, plate tectonics, and a nitrogen + oxygen atmosphere. All values will be given relative to Earth. </p>\n\n<p><span class=\"math-container\">$$M = 0.4 - 2.35$$</span></p>\n\n<p><span class=\"math-container\">$$R = 0.78 - 1.25$$</span></p>\n\n<p><span class=\"math-container\">$$g = 0.68 - 1.5$$</span></p>\n\n<p>Now you want a big planet, yet you do not specify what you mean with big... Thus I'll calculate several examples. </p>\n\n<p><strong>Max Mass and Max Radius</strong> </p>\n\n<p><span class=\"math-container\">$$M = 2.35$$</span></p>\n\n<p><span class=\"math-container\">$$R = 1.25$$</span></p>\n\n<p><span class=\"math-container\">$$g = \\frac{M}{R^2} = \\frac{2.35}{1.25^2} = 1.5$$</span></p>\n\n<p><span class=\"math-container\">$$A = 4*\\pi*R^2 = 4*\\pi*1.25^2 = 1.56$$</span></p>\n\n<p><strong>Max Mass and Min Radius</strong> </p>\n\n<p><span class=\"math-container\">$$M = 2.35$$</span></p>\n\n<p><span class=\"math-container\">$$R = 0.78$$</span></p>\n\n<p><span class=\"math-container\">$$g = \\frac{M}{R^2} = \\frac{2.35}{0.78^2} = 0.25$$</span></p>\n\n<p><span class=\"math-container\">$$A = 4*\\pi*R^2 = 4*\\pi*0.78^2 = 0.61$$</span></p>\n\n<p><strong>Min Mass and Max Radius</strong> </p>\n\n<p><span class=\"math-container\">$$M = 0.4$$</span></p>\n\n<p><span class=\"math-container\">$$R = 1.25$$</span></p>\n\n<p><span class=\"math-container\">$$g = \\frac{M}{R^2} = \\frac{0.4}{1.25^2} = 0.25$$</span></p>\n\n<p><span class=\"math-container\">$$A = 4*\\pi*R^2 = 4*\\pi*1.25^2 = 1.56$$</span></p>\n\n<p>However, there is an issue I see concerning the Max_Max case. It is called <a href=\"https://en.m.wikipedia.org/wiki/Atmospheric_escape\" rel=\"nofollow noreferrer\">atmospheric escape</a> and can ruin your day during planet formation. You can see that whether or not a gas will remain in the planet's atmosphere depends on the escape velocity given by</p>\n\n<p><span class=\"math-container\">$$v_{esc} = \\sqrt{\\frac{M}{R}}$$</span></p>\n\n<p>and the <a href=\"https://en.m.wikipedia.org/wiki/Planetary_equilibrium_temperature\" rel=\"nofollow noreferrer\">temperature of a planet</a> is given by </p>\n\n<p><span class=\"math-container\">$$T_{eq} = T_{star}*(1-Ab) ^\\frac{1}{4}*\\sqrt{\\frac{R}{2a}}$$</span></p>\n\n<p><span class=\"math-container\">$Ab = \\text{albedo}$</span></p>\n\n<p><span class=\"math-container\">$a = \\text{distance}$</span></p>\n\n<p>From this I get <span class=\"math-container\">$v_{esc}$</span> of 15.34 km/s for the Max_Max scenario, which gets awfully close to the point where it retains helium and would turn into an ice or gas-giant. </p>\n\n<p><a href=\"https://upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Solar_system_escape_velocity_vs_surface_temperature.svg/1280px-Solar_system_escape_velocity_vs_surface_temperature.svg.png\" rel=\"nofollow noreferrer\"><img src=\"https://upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Solar_system_escape_velocity_vs_surface_temperature.svg/1280px-Solar_system_escape_velocity_vs_surface_temperature.svg.png\" alt=\"Atmospheric Escape Graph from Wikipedia \"></a></p>\n\n<p>Atmospheric escape is the make it or break it point in the end for the survival of an Earth-like biosphere. You need methane, ammonia and water to stay on the planet and you need helium and hydrogen to leave. Otherwise it is utterly impossible for an earth-like biosphere to be sustained. </p>\n\n<p>Furthermore <a href=\"https://io9.gizmodo.com/what-a-habitable-planet-twice-the-size-of-earth-would-b-1476308959\" rel=\"nofollow noreferrer\">this article</a> is an interesting analysis of an Earth-analog twice the size of Earth. It really is worth the read. </p>\n" }, { "answer_id": 151305, "author": "M. A. Golding", "author_id": 34461, "author_profile": "https://worldbuilding.stackexchange.com/users/34461", "pm_score": 2, "selected": false, "text": "<p><strong>SHORT ANSWER:</strong> </p>\n\n<p>According to my rough calculations, a planet habitable for water based lifeforms vaguely similar to terrestrial life - not guaranteed to be habitable for humans or other lifeforms transported from Earth - could have a surface area a little more than 1.5 times that of Earth, which is rather disappointing. Some other answers also support that surface area limit through other calculations. </p>\n\n<p>(added 07-26-19. But these calculations of upper limits are still rather uncertain and controversial.) </p>\n\n<p>I believe that the habitablility of a planet of a given size depends a lot on its distances from its star and how much heat and light it gets from its star, so that larger planets would be more likely to be habitable farther out from their stars, and on various other factors. </p>\n\n<p>Possibly an expert on planetary science and astrobiology could calculate and design an alien planet with a significantly larger surface area, with a larger percentage of ocean or dry land as you may prefer, and habitable for humans and other Earth life forms.</p>\n\n<p><strong>LONG ANSWER:</strong></p>\n\n<p>You might want to consider where you want your story to be on the MOHS Scale of Science Fiction Hardness.</p>\n\n<p><a href=\"https://tvtropes.org/pmwiki/pmwiki.php/Main/MohsScaleOfScienceFictionHardness\" rel=\"nofollow noreferrer\">https://tvtropes.org/pmwiki/pmwiki.php/Main/MohsScaleOfScienceFictionHardness</a><a href=\"https://tvtropes.org/pmwiki/pmwiki.php/Main/MohsScaleOfScienceFictionHardness\" rel=\"nofollow noreferrer\">1</a></p>\n\n<p>The harder - more realistic and plausible - you want your science fiction story to be, the more the size of your planet will be constrained by various scientific factors.</p>\n\n<p>Many old fashioned science fiction stories imagined that the giant planets in our Solar System and similar sized exoplanets could have solid surfaces and biospheres. Thus they depicted habitable planets with tens, hundreds, and thousands of times the surface area of Earth. </p>\n\n<p>In E.E. Smith's <em>Lensman</em> series the heavy gravity planet Valeria is settled by Earth Humans and centuries or millennia later their descendants have adapted and are immensely strong. I forget what the surface gravity of Valeria was but it was probably far higher than humans could actually survive in. </p>\n\n<p>As I remember from checking fairly recently, Stephen Dole's <em>Habitable Planets for Man</em> (1964, 2009) suggests that humans wouldn't want to colonize a planet with a surface gravity more than about 1.25 or 1.50 that of Earth. The surface gravity of Earth is abbreviated 1 g.</p>\n\n<p><a href=\"https://worldbuilding.stackexchange.com/questions/136269/tolerable-range-of-surface-gravities-for-interplanetary-colonists\">Tolerable range of surface gravities for interplanetary colonists?</a><a href=\"https://worldbuilding.stackexchange.com/questions/136269/tolerable-range-of-surface-gravities-for-interplanetary-colonists\">2</a></p>\n\n<p><a href=\"https://www.rand.org/content/dam/rand/pubs/commercial_books/2007/RAND_CB179-1.pdf\" rel=\"nofollow noreferrer\">https://www.rand.org/content/dam/rand/pubs/commercial_books/2007/RAND_CB179-1.pdf</a><a href=\"https://www.rand.org/content/dam/rand/pubs/commercial_books/2007/RAND_CB179-1.pdf\" rel=\"nofollow noreferrer\">3</a></p>\n\n<p>A writer could get away with having a group of colonists or alien abductees settle on a planet with a surface gravity of 1.10 g, and then after generations of adaptation have a group of their descendants settle on a planet with a surface gravity of 1.21 g. By repeating this process over and over again over generations, centuries, and millennia, planets with surface gravities of 1.331 g, 1.4641 g, 1.61051 g, 1.771561 g, etc., can be settled until eventually some absolute upper limit is reached.</p>\n\n<p>Or possibly genetic engineering could be used to modify Earth Humans to be able to survive, be healthy, and function on planets with higher gravity than Earth. If it is a fantasy story some type of magic could modify Earth Humans to live on the planet.</p>\n\n<p>Or maybe the natives of that planet aren't Earth Humans but members of another species that look a lot like humans, except probably being shorter and stockier. And if there aren't any characters from Earth in the story the characters would mostly be described by how they appear to other members of their species and there might not be more than a few subtle clues as to how different from Earth Humans they are.</p>\n\n<p>Another factor to consider is plate tectonics, which are considered to be a factor in making Earth habitable. Many smaller astronomical bodies in our Solar System don't have plate tectonics. So one would think that a planet larger than Earth wouldn't have any problems with insufficient plate tectonics.</p>\n\n<p>But there is an article:</p>\n\n<p>\"Exomoon Habitability Constrained by Illumination and Tidal heating\" by Rene Heller and Roy Barnes, Astrobiology, January 2013.</p>\n\n<p><a href=\"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3549631/\" rel=\"nofollow noreferrer\">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3549631/</a><a href=\"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3549631/\" rel=\"nofollow noreferrer\">4</a></p>\n\n<p>In section 2, Habitability of Exomoons, they discuss the mass range necessary for hypothetical exomoons to be habitable in the sixth paragraph:</p>\n\n<blockquote>\n <p>A minimum mass of an exomoon is required to drive a magnetic shield on a billion-year timescale (Ms≳0.1M⊕; Tachinami et al., 2011); to sustain a substantial, long-lived atmosphere (Ms≳0.12M⊕; Williams et al., 1997; Kaltenegger, 2000); and to drive tectonic activity (Ms≳0.23M⊕; Williams et al., 1997), which is necessary to maintain plate tectonics and to support the carbon-silicate cycle. Weak internal dynamos have been detected in Mercury and Ganymede (Gurnett et al., 1996; Kivelson et al., 1996), suggesting that satellite masses>0.25M⊕ will be adequate for considerations of exomoon habitability. This lower limit, however, is not a fixed number. Further sources of energy—such as radiogenic and tidal heating, and the effect of a moon's composition and structure—can alter the limit in either direction. An upper mass limit is given by the fact that increasing mass leads to high pressures in the planet's interior, which will increase the mantle viscosity and depress heat transfer throughout the mantle as well as in the core. Above a critical mass, the dynamo is strongly suppressed and becomes too weak to generate a magnetic field or sustain plate tectonics. This maximum mass can be placed around 2M⊕ (Gaidos et al., 2010; Noack and Breuer, 2011; Stamenković et al., 2011). Summing up these conditions, we expect approximately Earth-mass moons to be habitable, and these objects could be detectable with the newly started Hunt for Exomoons with Kepler (HEK) project (Kipping et al., 2012).</p>\n</blockquote>\n\n<p>The upper limit of about 2 times the mass of Earth should hold for exoplanets as well as exomoons.</p>\n\n<p>Heller and Barnes give the source for the importance of plate tectonics for habitability as:</p>\n\n<p>Williams D.M. Kasting J.F. Wade R.A. Habitable moons around extrasolar giant planets. Nature. 1997;385:234–236. [PubMed] [Google Scholar]</p>\n\n<p>Heller and Barnes give the sources for an upper mass limit at about 2 Earth masses as:</p>\n\n<p>Gaidos E. Conrad C.P. Manga M. Hernlund J. Thermodynamics limits on magnetodynamos in rocky exoplanets. Astrophys J. 2010;718:596–609. [Google Scholar]</p>\n\n<p>Noack L. Breuer D. Plate tectonics on Earth-like planets [EPSC-DPS2011-890]. EPSC-DPS Joint Meeting 2011, European Planetary Science Congress and Division for Planetary Sciences of the American Astronomical Society; 2011. [Google Scholar]</p>\n\n<p>Stamenković V. Breuer D. Spohn T. Thermal and transport properties of mantle rock at high pressure: applications to super-Earths. Icarus. 2011;216:572–596. [Google Scholar]</p>\n\n<p>It is possible that the importance of plate tectonics for habitability, and the upper mass limit of about two times the mass of Earth for plate tectonics, are not accepted by all scientists interested in astrobiology, but I have not researched that.</p>\n\n<p>Accepting for the moment that about two times the mass of Earth is an approximate upper limit for planetary plate tectonics and planetary habitability for native lifeforms, the diameter, and thus surface area, of a planet is not solely determined by its mass. The diameter and surface area of a planet is determined by its mass and its overall density.</p>\n\n<p>The overall density of a planet is determined by two factors.</p>\n\n<p>One factor is the normal density of the various elements, compounds, and mixtures that it is made of, averaged. The normal density of those materials is the same density that they have floating around in tiny meteoroids in outer space, or lying on the surface of planets.</p>\n\n<p>The other factor is the degree to which those materials are compressed by vast pressures at various levels in the interior of the planet, thus becoming denser and increasing the overall density of the planet.</p>\n\n<p>Since the cube root of two is approximately 1.25992, a planet with twice the mass of Earth and the same overall density would have about 1.25992 times the radius and diameter of Earth and about 1.5873 times the surface area. Note that in order to have the same overall density as Earth, a planet with twice the mass of Earth would have to have a different composition than Earth, affecting life on the surface in various ways.</p>\n\n<p>Since the strength of gravity depends on the mass and the square of the distance, the surface gravity of a planet with twice the mass of Earth and 1.25992 times the radius would be about 2 divided by 1.5873984, or about 1.2599231 that of Earth.</p>\n\n<p>By decreasing the overall density of your planet you can increase its surface area but there is no doubt a limit to how much you can do so while keeping the planet habitable, or even with a solid surface. </p>\n\n<p>A rapidly rotating planet would be more likely to have an internal dynamo driving plate tectonics, and a rapidly rotating planet would be more oblate, having a somewhat larger surface area and lower gravity at the equator. Earth original rotation rate was slowed down by tidal interactions with the Moon. As far as I know there is a controversy whether a large moon, which would slow down the rotation rate of a planet, is necessary for a planet to be habitable.</p>\n\n<p><a href=\"https://www.npr.org/2011/11/18/142512088/is-a-moon-necessary-for-a-planet-to-support-life\" rel=\"nofollow noreferrer\">https://www.npr.org/2011/11/18/142512088/is-a-moon-necessary-for-a-planet-to-support-life</a><a href=\"https://www.npr.org/2011/11/18/142512088/is-a-moon-necessary-for-a-planet-to-support-life\" rel=\"nofollow noreferrer\">5</a> </p>\n\n<p>And if a writer needs a really vast world, they could set their story on an artificial habitat in space, that has a much greater surface area than any habitable planet, created by a very advanced civilization. </p>\n\n<p><a href=\"https://en.wikipedia.org/wiki/Bigger_Than_Worlds\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/Bigger_Than_Worlds</a><a href=\"https://en.wikipedia.org/wiki/Bigger_Than_Worlds\" rel=\"nofollow noreferrer\">6</a></p>\n\n<p><a href=\"http://www.isfdb.org/cgi-bin/title.cgi?133302\" rel=\"nofollow noreferrer\">http://www.isfdb.org/cgi-bin/title.cgi?133302</a><a href=\"http://www.isfdb.org/cgi-bin/title.cgi?133302\" rel=\"nofollow noreferrer\">7</a></p>\n\n<p>(Added 07-26-2019 arkenstein XII in his answer to this question: </p>\n\n<p><a href=\"https://worldbuilding.stackexchange.com/questions/151545/conditions-of-a-more-ideal-version-of-earth\">Conditions of a more ideal version of earth</a><a href=\"https://worldbuilding.stackexchange.com/questions/151545/conditions-of-a-more-ideal-version-of-earth\">8</a> </p>\n\n<p>suggests that a superhabitable planet might have a mass of about 2.5 times the mass of Earth, somewhat more than the upper mass limit suggested in my answer, and thus it would have somewhat more surface area than I suggested was the upper limit. I suppose that a supehabitable planet would be more habitable for lifeforms that originated there than for life forms transported from Earth. These kinds of limits are still rather controversial.) </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/151298", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/10544/" ]

[ { "answer_id": 152390, "author": "Psylent", "author_id": 14841, "author_profile": "https://worldbuilding.stackexchange.com/users/14841", "pm_score": 2, "selected": false, "text": "<p>How about you use ship orientations?</p>\n\n<p><code>Front...Fore\nBack.....Aft\nLeft.....Port\nRight....Starboard\nUp.......Zenith\nDown.....Nadir\n</code></p>\n\n<p>Or perhaps orbital orientations? These are for counterclockwise orbits:</p>\n\n<p><code>Front...Prograde\nBack.....Retrograde\nLeft.....Anti-radial\nRight....Radial\nUp.......Normal\nDown.....Anti-normal\n</code></p>\n" }, { "answer_id": 152392, "author": "Theraot", "author_id": 16729, "author_profile": "https://worldbuilding.stackexchange.com/users/16729", "pm_score": 3, "selected": false, "text": "<p>Anatomy has some useful words:</p>\n\n<pre><code>Superior -&gt; Above\nInferior -&gt; Below\nVentral -&gt; Fore of the body\nDorsal -&gt; Back of the body\nFrontal -&gt; Fore of the head\nOccipital -&gt; Back of the head\nDistal -&gt; Out, towards the tip of extremities\nProximal -&gt; In, towards the body\nRostral -&gt; Towards the face\nCaudal -&gt; Towards the tail\n</code></pre>\n\n<p>They say left and right in anatomy<strike>, as far as I can tell</strike>.</p>\n\n<p>I found <a href=\"https://www.researchgate.net/figure/Three-reference-planes-and-six-fundamental-directions-of-the-body-movement_fig3_323160009\" rel=\"nofollow noreferrer\">usage</a> of <code>Lateral</code> for right and <code>Contra-lateral</code> for left.</p>\n\n<p>We can import some words from heraldry for left and right:</p>\n\n<pre><code>Dexter -&gt; Right (of the knight or shield, not the observer)\nSinister -&gt; Left (of the knight or shield, not the observer)\n</code></pre>\n\n<p>I think you will prefer <code>Sinistral and Dextral</code>, by the way. Which are the words we use for chirality. They would work like <code>Port</code> and <code>Starboard</code> in that they always refer to direction relative to the observed, except you do not have to explain why mages talk about ports.</p>\n\n<p>I also want to bring into attention these words from physics and chemistry:</p>\n\n<pre><code>Dextrorotation -&gt; Clockwise rotation\nLevorotation -&gt; Counterclockwise rotation\n</code></pre>\n\n<p>Note: these are always respect the observer. <em>We do not say the hands of the clock are rotating counterclockwise when we are behind it.</em></p>\n\n<p>Speaking of rotation, anatomy has some:</p>\n\n<pre><code>Anteversion -&gt; Rotate to the front\nRetroversion -&gt; Rotate to the back\n</code></pre>\n\n<p>Axes:</p>\n\n<pre><code>Longitudinal -&gt; Head to tail\nHorizontal -&gt; Side to side\nSagittal -&gt; Front to back\n</code></pre>\n\n<p>And planes:</p>\n\n<pre><code>Coronal -&gt; Separates front and back\nTransversal -&gt; Separates top and bottom\nMedian -&gt; Separates left and right\n</code></pre>\n\n<p>Oh, by the way, in astronomy they use <code>Zenith</code> and <code>Nadir</code> for up and down... not of the observer, not of the observed... but as absolute orientation. You can use them to complement the cardinal directions (<code>North, South, East/Orient, West/Occident</code>).</p>\n\n<p><strong>Note</strong>: It is worth mentioning that some language do not have relative positions. Instead people use cardinal directions always.</p>\n" }, { "answer_id": 152393, "author": "Shadowzee", "author_id": 45212, "author_profile": "https://worldbuilding.stackexchange.com/users/45212", "pm_score": 1, "selected": false, "text": "<p>Expanding upon user535733's comment a Roll Pitch Yaw and Fire system would be far simpler. You summon an object and then you orient it with the Roll Pitch and Yaw. You can then say the trigger word or Fire word, and this will cause the projectile to launch itself in a given direction with mathematical accuracy. If you would like to increase the mystic of such a system, simply use a made up number system.</p>\n\n<p>If you instead use a 6 directional you start to over complicate your system. Take for example, the direction Forward. Is it forward from the Objects default orientation? Or forward from the Mages direction? Is this direction based on the head? or the body of the mage? Or maybe there is an absolute direction that is forward?</p>\n\n<p>You also greatly increase the complexity to gain flexibility. Say I want to launch it at 45 degrees instead. Would that be Forward Left? what about 22.5 degrees? Forward Forward Left? What if it wasn't any easy to each number like 20 degrees instead? A 6 directional system lacks the ability to define the direction exactly as you want and will cause issues when you might want specific angles instead of moving things in a grid like manner.</p>\n" }, { "answer_id": 152395, "author": "G. B.", "author_id": 61537, "author_profile": "https://worldbuilding.stackexchange.com/users/61537", "pm_score": 1, "selected": false, "text": "<p>Why do they not think in <a href=\"https://en.wikipedia.org/wiki/Polar_coordinate_system\" rel=\"nofollow noreferrer\">polar coordinate</a> system? The one moving the objects could be in the middle and then you could define any number of directions based on the dominant number system in your world (e.g. octal, hexadecimal etc.)\n<a href=\"https://i.stack.imgur.com/EJgIT.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/EJgIT.png\" alt=\"enter image description here\"></a></p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/152382", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/66951/" ]

[ { "answer_id": 154110, "author": "ascripter", "author_id": 67576, "author_profile": "https://worldbuilding.stackexchange.com/users/67576", "pm_score": 0, "selected": false, "text": "<p>Well, I'm not sure if what you describe is bending the laws of physics less than transforming someone into a frog. It's a very very fancy energy converter :)</p>\n\n<p>In that case, being close to physics would probably mean to assure the <a href=\"https://en.wikipedia.org/wiki/First_law_of_thermodynamics\" rel=\"nofollow noreferrer\">conservation of energy</a>. Some examples:</p>\n\n<ul>\n<li><p>Kinetic energy: <span class=\"math-container\">$W=\\frac12mv^2$</span></p></li>\n<li><p>Electrical energy: <span class=\"math-container\">$W=Q\\cdot U=U\\cdot I\\cdot t$</span></p></li>\n<li><p><a href=\"https://en.wikipedia.org/wiki/Heat_capacity\" rel=\"nofollow noreferrer\">Heating</a> (with heat capacity <span class=\"math-container\">$C$</span>): <span class=\"math-container\">$W=C \\cdot \\Delta T$</span></p></li>\n<li><p><a href=\"https://en.wikipedia.org/wiki/Black-body_radiation#Stefan%E2%80%93Boltzmann_law\" rel=\"nofollow noreferrer\">Black-body radiation</a> : <span class=\"math-container\">$W=P \\cdot t= \\sigma A T^4 \\cdot t$</span></p></li>\n<li><p>LASER radiation: Found some examples for different <a href=\"https://en.wikipedia.org/wiki/Laser#Examples_by_power\" rel=\"nofollow noreferrer\">power</a>. Like black body radiation the power would depend on the duration of the pulse.</p></li>\n<li><p><a href=\"https://en.wikipedia.org/wiki/Sound_energy\" rel=\"nofollow noreferrer\">Sound</a>: <span class=\"math-container\">$W = W_\\mathrm{potential} + W_\\mathrm{kinetic} = \\int_V \\frac{p^2}{2 \\rho_0 c^2}\\, \\mathrm{d}V + \\int_V \\frac{\\rho v^2}{2}\\, \\mathrm{d}V$</span>, and with the sound pressure <span class=\"math-container\">$p$</span> you get the <a href=\"https://en.wikipedia.org/wiki/Sound_pressure#Sound_pressure_level\" rel=\"nofollow noreferrer\">sound pressure level</a> in decibel.</p></li>\n</ul>\n\n<p>Actually you would also need to consider entropy. It's always increasing of course, but does the conversion of energy require <em>the same</em> entropy increase than your original (kinetic) event? But then your magic probably wouldn't be possible at all. So you should accept to mess with entropy, but conserve the energy.</p>\n" }, { "answer_id": 154122, "author": "Logan R. Kearsley", "author_id": 2800, "author_profile": "https://worldbuilding.stackexchange.com/users/2800", "pm_score": 2, "selected": false, "text": "<pre><code>When Perdita falls beyond a certain distance, the belt activates,\nusing Aethyr to create a magical bubble around her. When she hits\nthe ground (or any solid object larger than the average bird,) the\nSphere of Meteoric Conversion converts all her kinetic energy and\nthe kinetic energy of the surface pushing back against her (that\nis, the equal and opposite reaction) into another kind of energy\nor simply redirect the kinetic energy away from her.\n</code></pre>\n\n<p>There are two problems with this:</p>\n\n<ol>\n<li>The ground doesn't have kinetic energy separate from or opposite to Perdita. And exactly how much kinetic energy there is depends on what frame you are doing the calculation in. The relevant frame for energy dissipation in a collision is the center-of-mass, zero-momentum frame of the colliding objects; when one of those object is <em>the ground</em>, the center-of-mass frame is for all practical purposes indistinguishable from the ground frame, and all of the kinetic energy is Perdita's.</li>\n<li>The ground <em>does</em> exert an equal-and-opposite <em>force</em> on Perdita, thus transferring momentum to her and accelerating her to match velocities with the ground. It is that process which is responsible for injury and death from falls. Energy isn't irrelevant, but it's not the major player here; dissipating energy is easy. Limiting <em>acceleration</em> is key to safety. Perdita could absorb all of the kinetic energy of a terminal-velocity freefall into her own body as heat and be no worse for it, but that's no good if differential acceleration turns the physical structure of her body into jello.</li>\n</ol>\n\n<p>So, the bubble needs to do some combination of three things:</p>\n\n<ol>\n<li><p>Slow her descent, spreading the acceleration over a longer distance to keep the g forces survivable. This is what, e.g., crumple zones in cars do--they crush so that the body of the car, containing squishy passengers, can continue moving for a few more feet after a crash, over which distance it can slow more gradually. This is also what airbags are for--they ensure that the passenger's body begins accelerating <em>before</em> hitting the steering wheel / dashboard / windshield, rather than doing at all at once on impact with something hard and unforgiving.</p></li>\n<li><p>Magically stiffen the materials of her body so that all parts of her experience near-identical accelerations, and thus are not torn apart by differentials in momentum transfer. This kind of what g-suits do--by applying compressive forces to certain parts of the body, they ensure the g-load is distributed more evenly over the whole body, thus helping to prevent blackouts. This is where intentional energy dissipation becomes relevant; if the bubble and everything in it is super-stiff, it will just <em>bounce</em>. Perhaps the bubble could have multiple layers; an inner layer that briefly freezes Perdita's body, and an outer layer that slows the inner layer down over some finite distance and dumps the kinetic energy into heat. Like dropping a frozen egg inside a balloon full of jello.</p></li>\n<li>Automatically re-orient Perdita's body into the most g-tolerant position. People can survive much higher accelerations on their backs than from any other direction, which is why infant car seats are rear-facing; not only does it help spread the load of a crash over a wider surface area compared to straining against relatively thin straps, but even controlling for equal support, the human body is simply more resistance to injury in that orientation.</li>\n</ol>\n\n<p>The relevant math is as follows:</p>\n\n<p><span class=\"math-container\">$KE = \\frac{1}{2}mv^2$</span></p>\n\n<p>Suppose Perdita weighs around 75kg (a reasonable number for a healthy adult human woman). Terminal velocity for people is somewhere around 55m/s. That means she has to dissipate <span class=\"math-container\">$\\frac{1}{2}(75kg)(55m/s)^2 = 113,437.5 J$</span> of energy, or around 27.1 food Calories. I.e., enough energy to raise 27kg of water by 1 degree celsius. Or all of Perdita's body by considerably less.</p>\n\n<p>Meanwhile, people can easily be seriously injured (or, if old or just really unlucky, outright killed) by low-velocity falls just from tripping on the sidewalk--it's not how much energy is involved, it is <em>how</em> that energy is applied in conjunction with momentum.</p>\n\n<p><span class=\"math-container\">$p = mv$</span></p>\n\n<p>Perdita's momentum is <span class=\"math-container\">$4125 \\frac{m\\ kg}{s}$</span></p>\n\n<p><span class=\"math-container\">$a = \\frac{v^2}{2d}$</span></p>\n\n<p>Above an acceleration of 3g, Perdita will be uncomfortable. Above about 50g, she will sustain injury regardless of orientation. Above around 10g, you need to start employing those other measures like automatic reorientation and magically redistributing forces to avoid serious injury or death from falling the Wrong Way. So, if we want to simply dissipate energy into heat by slowing Perdita's descent, the bubble needs to have area of effect large enough to start slowing her descent at least <span class=\"math-container\">$d = \\frac{v^2}{2a} = \\frac{(55m/s)^2}{6g} \\approx 51.5m$</span> So, well above rooftop height if she's already at terminal velocity. At 10g with automatic reorientation, you're looking at a 15-meter bubble.</p>\n\n<p>If the bubble itself supplies additional air resistance, that terminal velocity will come down a bit, which helps. But if you want Perdita to land comfortably, on her feet so she can walk away (and maybe to an awesome superhero power-pose), and without the bubble interfering with the landscape in a 100-foot wide circle all around, I think you're pretty much gonna have to look at the \"magically freeze her solid\" / \"Star Trek inertial dampeners\" option.</p>\n\n<p>EDIT, to account for the question edit:</p>\n\n<pre><code>Perdita is a Half-Orc, not a Human. She's 6'7\" tall [...].\nSo, total weight is around 250 lbs.\n</code></pre>\n\n<p>250lbs is about 113kg. So, applying the kinetic energy equation again, and assuming she's still falling at a typical terminal velocity for a skydiver, she's got a total kinetic energy of <span class=\"math-container\">$\\frac{1}{2}(113kg)(55m/s)^2 = 170,912.5J$</span> To convert joules to kilocalories (of \"food calories\", where 1 kilocalorie is enough energy to heat a kilogram of water by 1 degree--a decent approximation for how much you will heat a squishy meatbag), just divide by 4184. Ergo, Perdita has access to about 41 (rounding up) kilocalories, enough kinetic energy from her fall to heat 41 kilos of ghoul by 1 degree. That's not much. She will not be incinerating any undead with that.</p>\n\n<p>However, once again we have to note that what matters is not really how much energy is available, but precisely how it is applied. Bullets have far less energy than that, but they're still lethal. If all that energy is released as an instantaneous flash of isotropic radiation, you won't incinerate or even set fire to any ghouls, but you might give them some nasty sunburns as most of the radiation is absorbed in the first few millimeters of skin / rotting flesh. That may or may not slow them down, depending on precisely how your flavor of undead happen to work.</p>\n\n<p>And if you concentrate that energy into a coherent beam, well... you can heat 1 gram of water by 40,000 degrees (not really, 'cause there's a phase change to worry about after a mere 100 degrees max, but that hardly matters at this scale). In other words, you can flash-vaporize a tiny chunk of ghoul flesh, causing it to violently explode as if it had been hit by a bullet. Or several small chunks, from several different ghouls, if Perdita has enough control to direct multiple beams like that.</p>\n\n<p>Enough energy to make the ghouls uncomfortable from extreme heat? No way. Enough energy to seriously mess up their day through other means? Absolutely.</p>\n\n<pre><code>She activates the Sphere of Meteoric Conversion and adjust it to its\n\"Zappy\" setting. When she lands in the Sea Monster's mouth, the kinetic\nenergy is converted into a pulse of electricity.\n</code></pre>\n\n<p>What matters here is amperage, and current path. Trivially, we have the same total amount of energy at our disposal, and it could just be turned into heat by unconstrained electrical discharge through the creature; depending on the precise incidental current path, maybe that ends up mildly warming the creature (no help at all), or maybe it ends up seriously burning a small chunk, causing it great pain, and maybe actual disability or maybe not depending on exactly which small chunk gets burned.</p>\n\n<p>However, again, <em>how the energy is applied matters</em>. If she can direct an electrical discharge to just the right part of the animal (say, through its brain, or heart), very tiny currents can cause death--you only need about 100 to 200 milliamps for less than a second to irreversibly screw up the creature's nervous system, if it's applied in just the right place.</p>\n\n<p>The relevant formula in this case is <span class=\"math-container\">$W = RI^2$</span>, where W is power, R is resistance, and I is current. If we know how long we need the shock to last, we can replace power with total energy (which we know, from Perdita's kinetic energy), to get <span class=\"math-container\">$E = TRI^2$</span>. The electrical resistance of wet flesh is around 300Ω, and we want a current of around 150mA, so if we generously assume that we need the shock to last for at least 1 second to definitely incapacitate the creature, we get <span class=\"math-container\">$E = (1s)(300Ω)(0.15A)^2 = 6.75J$</span>. <em>Way</em> less than Perdita's total kinetic energy budget. So, yeah, she can electrocute the sea monster easily.</p>\n\n<pre><code>As she falls to the ground, she sees that she is headed toward a park [...]\nNot wanting to become a party crashing in the most literal sense of\nthe term, Perdita activates the Sphere of Meteoric Conversion and\nadjusts it to its \"Harmless\" setting. On impact, all the kinetic energy\nis converted into a beam of light[....] The only damage done to the\nfestivities is in the form of extreme awkwardness.\n</code></pre>\n\n<p>Not even necessary. All of the kinetic energy can simply be dissipated as heat--into Perdita's body, the air, the ground, some thermal radiation--and if it's not specifically focused somewhere, it would hardly be noticed.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/154104", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/-1/" ]

[ { "answer_id": 154190, "author": "The Square-Cube Law", "author_id": 21222, "author_profile": "https://worldbuilding.stackexchange.com/users/21222", "pm_score": 2, "selected": false, "text": "<p>I'll try.</p>\n\n<p>Continents as a whole have a lot of variation in height, but tje ice on the poles is mostly flat. Almost every picture of anywhere on Antarctica looks like an endless plain until the horizon. So except for a big ridge it has off center, you could day a line from shore to shore is mostly linear.</p>\n\n<p>Sputnik Planitia in Pluto is 1/15 the size of the South Pole, but is flatter. </p>\n" }, { "answer_id": 154193, "author": "Tim", "author_id": 28202, "author_profile": "https://worldbuilding.stackexchange.com/users/28202", "pm_score": 4, "selected": true, "text": "<p>I would have to go with Saturn's moon, Iapetus. Iapetus has a mountain range all the way around its 1500 km equator:</p>\n\n<p><a href=\"https://i.stack.imgur.com/WlMJe.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/WlMJe.jpg\" alt=\"enter image description here\"></a></p>\n\n<p>The current theory is that it is a collapsed ring that once cirlced Iapetus.</p>\n" }, { "answer_id": 192897, "author": "user2352714", "author_id": 71841, "author_profile": "https://worldbuilding.stackexchange.com/users/71841", "pm_score": 1, "selected": false, "text": "<p>I would probably say the Atlantic mid-ocean ridge. It's not perfectly linear, but it follows almost the exact midpoint of the Atlantic Ocean from the tip of South America all the way to the Arctic Circle. That's almost 16,000 kilometers.</p>\n<p><a href=\"https://i.stack.imgur.com/IZRVv.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/IZRVv.jpg\" alt=\"enter image description here\" /></a></p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/154185", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/2800/" ]

[ { "answer_id": 156568, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 2, "selected": false, "text": "<p>Latin written with <a href=\"https://en.wikipedia.org/wiki/Scriptio_continua\" rel=\"nofollow noreferrer\">scripta continua</a> had words without spaces. I have observed that some modern Italian speakers also string their words together without spaces except when they need to breathe. The key I think it to recognize words as such as soon as they are spoken and mentally file each one as you hear it and get ready for the next. </p>\n\n<p>The other thing about people is that there are many ways to inflect the sounds O and U. Extra or different emphasis can denote the start or end of the word: \nfor example <strong>U</strong> U U U U U is not the same as <strong>U</strong> U U <strong>U</strong> U U. You can tell I am emphasizing my U because it is louder, and also my eyes bug out slightly and I spit. </p>\n" }, { "answer_id": 156570, "author": "Starfish Prime", "author_id": 62341, "author_profile": "https://worldbuilding.stackexchange.com/users/62341", "pm_score": 4, "selected": false, "text": "<blockquote>\n <p>It is essentially a binary language, just like what machines use.</p>\n</blockquote>\n\n<p>Unless they never stop vocalising, it isn't really binary as you have O, U and silence. Binary signals just have high and low, or on and off. <a href=\"https://en.wikipedia.org/wiki/Three-state_logic\" rel=\"noreferrer\">Tri-state</a> stuff is distinguished from plain old binary.</p>\n\n<blockquote>\n <p>How can each word be differentiated without any pauses between words?</p>\n</blockquote>\n\n<p>So, study of spoken language isn't my forte, but I note that many foreign languages that I do not understand do not have word-boundaries that I can recognise... they just seem like more-or-less seamless flows of sound, broken up into sentences. I can understand the word boundaries in languages I'm more familiar with, because I recognise individual word-sounds and my brain does the parsing for me.</p>\n\n<p>Youmightconsidertextwithoutspacingtobeasimilareffectwhereyoucantellthewordboundariesbecauseyouarefamiliarwiththeactualwordsthemselves.</p>\n\n<p>If you really wanted, you could consider having a special sequence to defined End-Of-Word, but that just seems unnecessary and would take up valuable conversation time.</p>\n\n<p>You'd probably still want to pause for end-of-sentence though.</p>\n\n<blockquote>\n <p>Assuming you can get past the above problem, will it simply take too long for them to convey information?</p>\n</blockquote>\n\n<p>Depends how fast they can modulate their voices, doesn't it?</p>\n\n<p>For a technological example, consider <a href=\"https://en.wikipedia.org/wiki/Radioteletype\" rel=\"noreferrer\">radioteletype</a>, aka RTTY (<a href=\"https://www.youtube.com/watch?v=wzkAeopX7P0\" rel=\"noreferrer\">sound sample</a>, youtube link) which can give you 60 words per minute, which is less than half the rate of spoken english (faster rates do exist, but they're not reall meat-emulateable). This is done by sending one character at a time, 5 bits per character. The efficiency at which you can send information depends on how you've put together your lexicon. Morse operators used many <a href=\"https://en.wikipedia.org/wiki/Q_code\" rel=\"noreferrer\">specialist abbreviations</a> for important common words, questions and answers. Your language probably needs the same. Uncommon words might take much longer to say, which means that unless the race is quite patient they might have issues communicating complex or technological concepts.</p>\n\n<p>For non-technological examples, consider birdsong. I'm having trouble with the precise search terms that will be of most use to you, but trilled portions of birdsong can go as high as 30 distinct pulses per second (1800 bits per minute, 6 times faster than the basic RTTY mode). That needs some fairly sophisticated muscles and brains to do that trick, though. </p>\n" }, { "answer_id": 156618, "author": "ksbes", "author_id": 65830, "author_profile": "https://worldbuilding.stackexchange.com/users/65830", "pm_score": 0, "selected": false, "text": "<p>Chinese and Japanese (and other such a languages) have an interesting pronunciation structure: each syllable has a certain \"timeframe\" and those syllables are pronounced in a rhythm. There are \"long\" (\"two-frame\") syllables and \"short\" (\"half-frame\") ones, but the timing of \"frame\" should be kept.</p>\n\n<p>These languages have tens of syllables. But the proposed language would have 10. 4 \"basic\": OO,OU,UO,UU; 4 corresponding long (\"long O\"-\"long U\"); and 2 \"short\" ones: O, U. </p>\n\n<p>That would be enough for a language, but on average words would be 2-3 times longer than in Chinese and Japanese. This is not a problem though, since some existing primitive languages have some very long words (mostly because they have too few \"basic words\", and they call a boat \"hollow-trunk-that-goes-over-water\") and it has worked for them.</p>\n" }, { "answer_id": 156626, "author": "Black", "author_id": 710, "author_profile": "https://worldbuilding.stackexchange.com/users/710", "pm_score": 5, "selected": true, "text": "<p>This is fairly easy. With tri-state it's even easier, but for now let's consider just using a click or silence (a la pure binary: 00101010). The answer is <strong>a lot</strong> and <strong>as quick as their memory can handle</strong>. Let's lay some ground theory:</p>\n\n<ul>\n<li>There are a small set of \"proto verbs\" (Incorrect terminology so I'm having trouble sourcing this), of quantity less than 30, some of which have no existing counterpart in English. Nevertheless, you can define all verbs using that small set in the right combinations with other words.</li>\n<li>Similarly, you can do the same with many parts of speech (Cat: four-legged furry mammal...etc.)</li>\n<li>Nouns/Adjectives are your largest collection. Although you can do either-or. <a href=\"https://english.stackexchange.com/questions/55486/what-are-the-percentages-of-the-parts-of-speech-in-english\">StackExchange</a> would put this at somewhere between 19% and 33% utilization, I believe. Looking at <a href=\"https://en.wikipedia.org/wiki/List_of_dictionaries_by_number_of_words\" rel=\"nofollow noreferrer\">English Dictionaries</a> for a maximum for a number of words puts us at 155 thousand nouns/adjectives which can be enumerated with 18 bits.</li>\n<li>If the universe has roughly 10⁸² atoms in it then you can enumerate them with 272 bits which will be of such magnitude that it would be laughable to consider filling it completely. You can use that number as a max. I prefer 64 bits. Your minimum enumeration to match English is less than 18 bits using proto-words (probably something like 12 bits), and 19 bits to match exactly.</li>\n<li>Words consist of <em>definitions</em>, which are combinations of either other words or proto words. It is <em>compression</em>. Each word added adds to the memory requirements, and the bits needed to enumerate all words. <em>But</em>, adding words increases transmission speed. You can trade memory for speed almost as much as you want here.</li>\n<li><strong><em>Crucially</em></strong> you can even compress <em>those</em> words by frequency of usage simply by adopting the same trick that saved Unicode.... <a href=\"https://en.wikipedia.org/wiki/UTF-8\" rel=\"nofollow noreferrer\">UTF-8</a>, just pick a \"byte\" size that encompasses enough of your common words and make the rest extended bytes. Other variable-length encodings are usable as well.\nWhat you end up with is as much content, almost as fast as you please (within a log-factor), as specific as you want (<em>this</em> atom), tailored to your language/culture.</li>\n</ul>\n\n<p><strong>What's the downside?</strong></p>\n\n<p>The <em>number</em> of sounds is a multiplier on transmission speed. Any crafted language could do the above-described things. But the more <em>sounds</em> you have the quicker you can do so. 26 sounds? 4 times the content in two sounds (<em>log(26)/log(2)</em>). But as far as \"as quick as their memory can handle\" <a href=\"https://www.youtube.com/watch?v=zUDqI9PJpc8\" rel=\"nofollow noreferrer\">there's a limit: ~380 wpm</a>... which probably is present for non-humans but just different rates.</p>\n\n<p><strong>What about adding silence?</strong>\nTri-state let's you scrap the UTF-8 \"extension bits\", <em>or</em> gives you another symbol to play with (<em>log(26)/log(3)</em> now). Speed or compression gains either way.</p>\n" }, { "answer_id": 156762, "author": "zooby", "author_id": 55158, "author_profile": "https://worldbuilding.stackexchange.com/users/55158", "pm_score": 0, "selected": false, "text": "<p>Very feasible indead.</p>\n\n<p>But the written language needn't be binary. Indeed the letter B could stand for the sequence of sounds uuuouu.</p>\n\n<p>(I assume you are including spaces, or pauses? Or you could have s space be a special sequence say ououououououo. )</p>\n\n<p>If the sounds are continuous with no spaces you might need a special sequence to indicate the start of a sentence e.g. ouuuuuuuuuuo</p>\n\n<p>The might be some ambiguity but in context the language could make sense.</p>\n" }, { "answer_id": 156763, "author": "Neal", "author_id": 14484, "author_profile": "https://worldbuilding.stackexchange.com/users/14484", "pm_score": 0, "selected": false, "text": "<p>Take a look a Huffman encoding (<a href=\"https://en.wikipedia.org/wiki/Huffman_coding\" rel=\"nofollow noreferrer\">wikipedia link</a>)-- it's a form of compression that uses shorter binary sequences for more common symbols. </p>\n\n<p>Also consider that all humans have huge brain structures just for our language. </p>\n\n<p>I can't see this limitation being a huge problem. </p>\n" }, { "answer_id": 156765, "author": "David Hambling", "author_id": 56837, "author_profile": "https://worldbuilding.stackexchange.com/users/56837", "pm_score": 0, "selected": false, "text": "<p>Other have covered the binary issue pretty well. Remember though that vocal communication, as in humans, is supplemented by many other forms: while the old line about only 20% of communication being verbal is a misunderstanding, the aliens may have even more developed use of gesture, tone, expression etc. (Or semaphore: \"Cathy!!\")</p>\n\n<p>And if their vocal language does limit them, they may be smart enough to develop a sophisticated written language to transmit data faster. As with humans, reading may be much quicker than listening; with them, writing (or texting, if they have the tech) my be quicker than speaking. What looks like a limitation may mean they end up communicating better. </p>\n" }, { "answer_id": 156779, "author": "IndigoFenix", "author_id": 17169, "author_profile": "https://worldbuilding.stackexchange.com/users/17169", "pm_score": 2, "selected": false, "text": "<h3>It could function, but how would it evolve?</h3>\n\n<p>A two-sound language is basically binary and is perfectly capable of transmitting arbitrary amounts of information. However, unless the species was constructed artificially or they voluntarily adopted this system after evolving a culture, it seems unlikely that such a species would ever evolve the ability to talk in the first place.</p>\n\n<p>Human language evolved from simpler sounds, each conveying a unique concept, long before we began stringing them together into words and sentences. While the exact sounds early humans used are unknown, we can make guesses; suppose that humming was a sound made while pleased or satisfied, hissing when angry or in pain, a grunt when ready to travel, etc. This could serve as a proto-language where the species was already accustomed to communicating intent through sound, which could lead to using these sounds to convey greater meaning through analogy, like using \"ma\" (a sound conveying comfort) for mother or water.</p>\n\n<p>A single syllable in a binary language, however, conveys too little information to be useful before you start stringing sounds together. Because of this, it seems very unlikely that a species capable of producing only two sounds would even think of using sound as a means of conveying information. It is more likely that they would develop a language based on non-verbal communication.</p>\n\n<p>Moreover, it is very inflexible - if I replace a B with a P in a sentence, 90% of the time you will understand what I mean - but if I replace a zero with a one in a binary language, you will hear a completely different word. A language this precise would be very difficult for living organisms to use and would have a hard time evolving from simpler forms.</p>\n" }, { "answer_id": 156807, "author": "Nolo", "author_id": 19530, "author_profile": "https://worldbuilding.stackexchange.com/users/19530", "pm_score": 1, "selected": false, "text": "<p>So far no one has mentioned a modulated stream. Consider having two states - off and on. Perhaps the off state is \"o\" and the on state is \"u\". You can change the length and or volume of the on state and get just about any sound that you want with the caveat that you will hear an overtone squall. In fact the way humans speak is that we produce a carrier tone, rather several tones overlaid, then modulate that sound to produce \"o\" and \"u\" among other sounds, essentially shifting the phase of the overtones.</p>\n\n<p>Consider back before computers had sound cards, software authors developed methods for playing polyphonic sound over the binary PC speaker, called <a href=\"https://en.wikipedia.org/wiki/PC_speaker#Pulse-width_modulation\" rel=\"nofollow noreferrer\">pulse-width modulation</a>. The PC speaker is an internal, simple 5 volt speaker which typically comes with the computer case, and whose hardware only provides an off or on state, i.e. switching that voltage on or off. Tones can be produced by utilizing separate timer hardware ( standard on most computers and separate from the CPU ) for generating an audio-range system timer. That timer signal can then be used by software to turn the power to the speaker off and on at regular intervals. </p>\n\n<p>By determining how many intervals to skip between switching the speaker from an on to an off state, this configuration can be used to approximate polyphonic wave forms on an extraordinarily simple device. Doing this essentially pulses the voltage through the speaker, and because of the mechanical nature of it, the modulated signal actually places the speaker cone in the approximate position it would be in if it were playing a smoothed waveform, with the exception that the carefully spaced pulses of current causes the speaker cone to jolt from one position to another, which has the affect of overlaying the wave with the carrier tone. Also this configuration can only play sound up to half the frequency of the available timer. In the case of the timers available to use with the PC speaker, the max available was either 18kHz or 10kHz, causing a buzzing overtone of about 9kHz or 5kHz respectively.</p>\n\n<p>You can hear an example of the PC speaker thing <a href=\"https://www.youtube.com/watch?v=atw10SeuCos\" rel=\"nofollow noreferrer\">here</a>. It's messy, and it's much easier to hear in person, but it's easily possible to make out any complex sound.</p>\n\n<p>Not sure how this would sound starting with \"o\" and \"u\", but I imagine it wouldn't be much different, just that the overtone would have a quality that is perhaps more voice-y and less like the \"8-bit sound\" of a PC speaker.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/156565", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/68902/" ]

[ { "answer_id": 157835, "author": "SRM", "author_id": 26246, "author_profile": "https://worldbuilding.stackexchange.com/users/26246", "pm_score": 0, "selected": false, "text": "<p>As long as you are above 60 frames (transitions from one location to the other) per second, most humans will see two people. This is how films work. At 120 FPS, it’ll be indistinguishable from two people standing there to all biological observers and most cameras. </p>\n\n<p>Note that the continuous peals of thunder as you shift back and forth may give you away. :-) Also will have problem in fog — a clear channel between your two positions will open. </p>\n" }, { "answer_id": 157841, "author": "VLAZ", "author_id": 8703, "author_profile": "https://worldbuilding.stackexchange.com/users/8703", "pm_score": 4, "selected": true, "text": "<p>I don't think it's possible while remaining within the bounds relative plausibility. This character has to be <em>so fast</em> that even The Flash might raise an eyebrow. I'll call the character UberFlash.</p>\n<p>So, let's say UberFlash tries to create two &quot;illusions&quot;. He stands in one spot, then <em>quickly</em> goes to another and back. Visual diagram:</p>\n<pre><code>A &lt;---&gt; B\n</code></pre>\n<p>This has to be done multiple times <em>a second</em>. About the lowest frames per second you can get nowadays in video games is 30FPS. That means that an image is shown 30 times on the screen each second. This makes the transition between images seem like it's (mostly) non-existent and it's actually a continuous video. Some people can easily distinguish 30 FPS, as it &quot;flickers&quot; or &quot;looks choppy&quot; and otherwise doesn't maintains good illusion for a smooth stream of visual data. Still, I'm going to use 30 FPS as the baseline for UberFlash.</p>\n<h1>Running to each spot 30 times.</h1>\n<p>So, UberFlash has to show up in <em>two places</em> and stand at each <em>30 times</em> over the course of <em>one second</em>. So he has to move between <strong>A</strong> and <strong>B</strong> <em>29 times</em> in a second.</p>\n<p>Taking the proposed 0.0002% of time spend travelling, then UberFlash will have to move the ENTIRE distance 29 times in 0.0002% of a second, or 2 <strong>micro</strong>seconds. For further reference, that's 0.002 <strong>milli</strong>seconds. That is the TOTAL time to make 29 trips. Let's say the two &quot;illusions&quot; are fairly close - 1m apart. If both &quot;illusions held their hands outstretched, they would be touching or even overlapping.</p>\n<h2><code>(29 * 1m) / 0.002ms = ???</code></h2>\n<p>UberFlash has to be moving at about 14 500 m/s or 52 200 km/h. UberFlash can run a marathon in just under 3 seconds.</p>\n<p>Mach 1 speed (speed of sound) is about 1 235 km/h and going over it produces a sonic boom. UberFlash would be moving at roughly 42 times that speed. I don't think it would be very subtle or very safe for...anybody and anything.</p>\n<h1>Running to each spot 10 times</h1>\n<p>But perhaps 30FPS is too high. The &quot;illusions&quot; don't need to be perfect. Let's cut it down to 10 FPS - it will produce noticeable flickering of the images. Let's also make the distance smaller - 50cm, the two are almost shoulder to shoulder. Oh, and let's give UberFlash a bit more leniency - instead of 0.002 milliseconds, let's make it few orders of magnitude more and give him 1 millisecond. Just 1/1000th of a second to travel between the two locations.</p>\n<h2><code>(9*0.5m) / 1ms = ???</code></h2>\n<p>That means that UberFlash will move at 4 500 m/s or 16 200 km/h. Still more than 10 times the sonic boom speeds.</p>\n<p>I think at these speeds, aside from the images of UberFlash, there would be some high winds, loud noises, and maybe even flames around.</p>\n" }, { "answer_id": 216899, "author": "Klaws", "author_id": 17789, "author_profile": "https://worldbuilding.stackexchange.com/users/17789", "pm_score": 0, "selected": false, "text": "<h3>Only with proper lighting</h3>\n<p>Let's have a look at some real life example: <a href=\"https://www.youtube.com/watch?v=nVjWF74shEw\" rel=\"nofollow noreferrer\">https://www.youtube.com/watch?v=nVjWF74shEw</a> (Assassination Classroom season 1 episode 1; superspeed, in that case mach 20, is invoked at about 1:08). The obvious issue is, that while the teacher grabs your attention and therefore looks more solid, the boring stationary background is still visible (33% opaqueness, as Koro-sensei switches between three positions). Note that the limited frame rate of the camera causes temporal aliasing; if you'd watch this through your own eyes, it would look quite a bit different. You ceiling-fan analogy is valid and correct.</p>\n<p>Apart from Assassination Classroom, there are also quite a few amusement parks in the more &quot;western culture&quot; which employ an illusion with &quot;ghosts&quot; which appear out of this air and reappear again a few seconds later. Basically, you look at a dimly illuminated scene (like, for example, a room which looks like it's inside a medieval-age caste) through a pane of glass (which you cannot see). There is another room which you cannot see directly, but the pane of glass is angled in such a way that it the reflection will superimpose the hidden room (typically above or below the track of your ride) onto the obvious room. When the hidden room is dark, no light is reflected, so no mystery there. When the hidden room is illuminated, you will see its reflection, but the stuff in the hissen room will appear semi-transparent superimposed over the obvious room. If you change the <strong>relative</strong> illumination of the two rooms, you can make the hidden room objects look more substantial (best when the hidden room has 100% illumination and the obvious room is absolutely dark) or less substantial.</p>\n<p>However, your question is not about an amusement park ride. The only relevant thing is that you need 0% background illumination together with enough illumination of the object/person/sensei you want to appear solid.</p>\n<p>Luckily, there are real-life offices where the fluorescent tubes are powered by three-phase electrical power. If you manage to find spots where the fluorescent tubes illuminating the foreground are at 100% voltage (= 100% power) and the ones illuminating the background are at 50% voltage (= 25% power), the illusion will look more substantial (but still far perfect), assuming your character can sync to the three-phase electrical grid. Next, find the alternate spot where the same is true 1/150 second later (assuming a place in Europe, 1/180 second in the US - assuming real three phase is available at the given place).</p>\n<p>Regardless, since these &quot;optimal lighting times&quot; do not switch abruptly, but fade from one to the next, the illusion will suffer even a bit further.</p>\n<p>Now, what if you could control background and foreground lighting perfectly? High speed stroboscopes would allow you to do that.</p>\n<p>However, if you already that much control of the environment and the situation, hiring a stunt double which looks exactly like the hero might be the way to go. Mainly because the supersonic boom caused by the rapid movements would be quite...annoying, to say the least.</p>\n" }, { "answer_id": 216902, "author": "Mike Serfas", "author_id": 82280, "author_profile": "https://worldbuilding.stackexchange.com/users/82280", "pm_score": 0, "selected": false, "text": "<h1>You could if you're Johannes Stoetter</h1>\n<p>The advantage of Super Speed is that you have plenty of time to look over your environment and plan out your next move. You don't have to run at Mach 10 ... just keep covering yourself in different camouflage from time to time, and hope they don't notice their blurry vision is <em>outside</em> their eyes. You don't have to stand in a certain spot 30 times a second - you just have to put up a little piece of artwork you drew in front of each person's face (carefully suspended from the ceiling, I suppose, to reduce the drafts from unnecessary trips) that matches what <em>each person in the room</em> expects to see, given your intended version of events. Look at the videos on <a href=\"https://gallery.johannesstoetterart.com/Galleries/Illusions-bodypainting-art/\" rel=\"nofollow noreferrer\">this page</a> to get a notion of the possibilities -- painted illusions can be remarkable! Of course, you could draw on paper instead of people if you wish. And, assuming you have subjective millennia to practice your skills, you <em>might</em> do better than these some day.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/157834", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/68902/" ]

[ { "answer_id": 159393, "author": "Demigan", "author_id": 48354, "author_profile": "https://worldbuilding.stackexchange.com/users/48354", "pm_score": 2, "selected": false, "text": "<p>Maybe we've already found magic, but we just called it science instead.</p>\n\n<p>Your 1 in million tries would be assumed to be an error, an outlier, a problem with the scientific setup or computer glitch that should be ignored. But if you can repeat the process and it is actually usuable you can create laws for it. As an example of this happening is when a science team discovered that some particles were faster than light even with repeat tests. They asked others to perform the experiment and those found that it wasnt true and as far as I know they never discovered why the particles were measured to be faster but it was assumed that it was a glitch.</p>\n\n<p>As another example if we have a ball we can define its position and momentum. This is a process that can be repeated for just about any object at any point in time. But somehow for some reason if you do this for extremely small particles the quantum world suddenly pokes it's head through all the physics you created, and the more certain you know it's position the less certain its momentum becomes. Its just about everything you could want in magic in how it completely upends the normal physics. This process is now known as the Heisenberg's Uncertainty principle and this magic is \"simply\" a scientific discovery we use.</p>\n\n<p>And that is the problem, until a human can change the local laws of physics for a short time and repeat this any \"magic\" is simply a scientific law waiting to be discovered.</p>\n" }, { "answer_id": 159395, "author": "Seallussus", "author_id": 69342, "author_profile": "https://worldbuilding.stackexchange.com/users/69342", "pm_score": 2, "selected": false, "text": "<p>I think the problem lies in the understanding of science. \nFirst, not having evidence about magic does NOT mean that magic does not exist. It only means that we have NOT found evidence about it. </p>\n\n<p>If you use that previous logic, then before we discovered the laws of gravity it, the laws or even gravity, did not exist!</p>\n\n<p>Let me give you a simple example.\nSo far with our knowledge we have not discovered any sign of what we consider intelligent life. \nSo what can we say for certain?\nThat so far we have no evidence supporting the existing of what we consider intelligent life.\nNo more no less.</p>\n\n<ul>\n<li>We can't claim that there is no intelligent life because we have not examined the entire universe.</li>\n<li>We can't claim that there is intelligent life because if you make that claim you better give us some hard evidence, noy some guess that because the universe is big then it probably has life somewhere. </li>\n</ul>\n\n<p>We can only describe what we have found.</p>\n\n<p>So, bottom line is that science can only give us facts in certain contexts like studying the effect of drug A in disease B.</p>\n\n<p>That means that your scientist, if he is worth his salt, can only claim that he has NOT found any evidence to support that that particular magic exist. </p>\n\n<ul>\n<li>He can NOT claim that magic does not exist.</li>\n<li>Nor can he claim that just because we have not seen it it does not exist.</li>\n</ul>\n\n<p>That is guessing and not science. </p>\n\n<p>Also the supernatural is outside the realm of science. \nSo, you are basically trying to use science to proove something that can NOT be proven by science!</p>\n\n<p>Not that I would know. It's just that the traditional look on magic is that it is a supernatural phenomena and science only deals with the natural.</p>\n\n<p>So I think either you are missing something about science, actual science not movie science, or that the I'm not getting the question. \nSO </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/159391", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/11498/" ]

[ { "answer_id": 162216, "author": "Priska", "author_id": 69280, "author_profile": "https://worldbuilding.stackexchange.com/users/69280", "pm_score": -1, "selected": false, "text": "<p>Knowing what a solution to an open math problem \"would look like\" amounts to knowing the solution (or at least its main steps). And given that this question has not been solved, nobody knows. It may well be impossible, and therefore have no valid answer.</p>\n" }, { "answer_id": 162217, "author": "Mathaddict", "author_id": 54489, "author_profile": "https://worldbuilding.stackexchange.com/users/54489", "pm_score": 1, "selected": false, "text": "<h1>Assuming this has something to deal with worldbuilding, I'll give a worldbuilding answer.</h1>\n<ol>\n<li>Currently the best known method is to check all the primes less than the square root of the number to be factored. Quickly is a relative term, and mostly depends on the size of the primes involved. This poses a problem, as the method to factor quickly increases in speed, so does the ability to check larger and larger numbers for primality, this then increases the size of primes used to encrypt in the first place.</li>\n<li>This means that any innovation used will only provide a temporary advantage to the side that has it as long as they keep it a secret. Once the secret is out, the systems will become secure again.</li>\n<li>Any algorithm should be able to be run on any hardware, however the speed at which it can process is going to be the main issue. The super computer is going to be much faster than the game boy, and will be able to factor much larger numbers in a reasonable amount of time.</li>\n<li>The field of quantum computing has theorized that it might be possible to use a quantum computer to harness infinite computing speed (essentially it would be able to compute anything in the same amount of time regardless of computing complexity).</li>\n</ol>\n" }, { "answer_id": 162219, "author": "Andrew Mellor", "author_id": 61617, "author_profile": "https://worldbuilding.stackexchange.com/users/61617", "pm_score": 1, "selected": false, "text": "<p>I am unsure of how technical of an explanation you are looking for but; The Quadratic Sieve Algorithm is currently the fastest for any number under <span class=\"math-container\">$10^{100}$</span>.</p>\n\n<p>The Quadratic Sieve Algorithm and many algorithms are based on Fermet's Factorization Method.</p>\n\n<p>In Fermet's method: the idea is to find two numbers (<span class=\"math-container\">$a$</span> and <span class=\"math-container\">$b$</span>) where:</p>\n\n<blockquote>\n <p><span class=\"math-container\">$a^2−b^2 = n $</span><br>\n <span class=\"math-container\">$n$</span> being the number we wish to factor.</p>\n</blockquote>\n\n<p>If we can do this, simple algebra (via the Difference of two squares) tells us that:</p>\n\n<blockquote>\n <p><span class=\"math-container\">$(a+b)(a−b) = n$</span></p>\n</blockquote>\n\n<p>If we're lucky, we have found a nontrivial factorization of <span class=\"math-container\">$n$</span>;</p>\n\n<p>The concept behind Fermat's algorithm is to search for an integer (<span class=\"math-container\">$a$</span>) such that <span class=\"math-container\">$a^2−n$</span> is a square. If we find such an <span class=\"math-container\">$a$</span>, it follows that:</p>\n\n<blockquote>\n <p><span class=\"math-container\">$a^2−(a^2-n) = n$</span><br>\n enter preformatted text here</p>\n</blockquote>\n\n<p>Hence we have a difference of squares equal to <span class=\"math-container\">$n$</span>. The search is a straightforward linear search: we begin with the ceiling of the square root of <span class=\"math-container\">$n$</span>, the smallest possible number such that <span class=\"math-container\">$a^2−n$</span> is positive, and increment a until <span class=\"math-container\">$a^2−n$</span> becomes a square. If this ever happens, we try to factor <span class=\"math-container\">$n$</span> as <span class=\"math-container\">$(a − \\sqrt{a^2−n})(a + \\sqrt{a^2−n})$</span>; if the factorization is trivial, we continue incrementing <span class=\"math-container\">$a$</span>.</p>\n\n<p>Example from for the prime factorization of <span class=\"math-container\">$5959$</span>:</p>\n\n<blockquote>\n <p><span class=\"math-container\">$a = 78$</span><br>\n <span class=\"math-container\">$78^2−5959 = $</span> not a square</p>\n \n <p><span class=\"math-container\">$a = 79$</span><br>\n <span class=\"math-container\">$79^2−5959$</span> = not a square</p>\n \n <p><span class=\"math-container\">$a = 80$</span><br>\n <span class=\"math-container\">$80^2−5959 = 441 = 21^2$</span></p>\n \n <p>Hence: <span class=\"math-container\">$(80-21)(80+21) = 5959$</span>,<br>\n Which gives the nontrivial factorization: <span class=\"math-container\">$59\\times101 = 5959$</span>.</p>\n</blockquote>\n\n<p>Also worth mentioning if: <span class=\"math-container\">$\\sqrt{n} &gt; a$</span> or <span class=\"math-container\">$a &gt; n-1$</span>, then we know <span class=\"math-container\">$n$</span> has <span class=\"math-container\">$0$</span> non trivial factorization.</p>\n\n<p>To date all major developments; <a href=\"https://en.wikipedia.org/wiki/Quadratic_sieve\" rel=\"nofollow noreferrer\">Quadratic sieve</a>, <a href=\"https://en.wikipedia.org/wiki/General_number_field_sieve\" rel=\"nofollow noreferrer\">GNFS</a>, and <a href=\"https://en.wikipedia.org/wiki/Dixon%27s_factorization_method\" rel=\"nofollow noreferrer\">Dixon's Factorization Method</a>; have been based on Fermet's method.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/162214", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/70347/" ]

[ { "answer_id": 170643, "author": "kleer001", "author_id": 63080, "author_profile": "https://worldbuilding.stackexchange.com/users/63080", "pm_score": 3, "selected": false, "text": "<p><strong>Orbital Mechanics!</strong> </p>\n\n<p>It's not a simple topic, but it's worth your time. They're basically the 6 numbers required to describe the position in time and space of an object orbiting another object. </p>\n\n<p>So, the takeaway from that is if you want to describe the position of an object in space it'll need to be in reference to another object. That could be the galatic center if you're describing a solar system (or a spaceship in interstellar space), or the closest planet if you're describing a moon. And they'll need to be nested if you're describing the position of a moon around a planet from another galaxy. </p>\n\n<hr>\n\n<p>Why orbital mechanics? </p>\n\n<h2><em>Because there are no privileged frames of reference in space.</em></h2>\n\n<p><strong>The Orbital Elements...</strong></p>\n\n<p>To mathematically describe an orbit one must define six quantities, called orbital elements. They are</p>\n\n<pre><code>Semi-Major Axis, a\nEccentricity, e\nInclination, i\nArgument of Periapsis, ω\nTime of Periapsis Passage, T\nLongitude of Ascending Node, Ω\n</code></pre>\n\n<p>Their details require a bit of book learning I won't copy-paste here, but they're available lots and lots of places (wikipedia, your local library, your local astronaut, \"SevenEves\" from Neil Stephenson).</p>\n" }, { "answer_id": 170659, "author": "Starfish Prime", "author_id": 62341, "author_profile": "https://worldbuilding.stackexchange.com/users/62341", "pm_score": 3, "selected": false, "text": "<p><a href=\"https://en.wikipedia.org/wiki/Pulsar\" rel=\"noreferrer\">Pulsars</a>.</p>\n\n<p>Observe the <a href=\"https://en.wikipedia.org/wiki/Pioneer_plaque\" rel=\"noreferrer\">Pioneer Plaque</a>:</p>\n\n<p><a href=\"https://i.stack.imgur.com/t5d0S.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/t5d0S.png\" alt=\"Pioneer Plaque\"></a></p>\n\n<p>See that bunch of radiating lines on the left? That's a remarkably good way to identify where (and perhaps even <em>when</em>) Earth was when the space probe was launched.</p>\n\n<p>The patterns on each line represent the pulses emitted by a particular pulsar. There's some additional fiddliness here caused by the need to encode it in binary and include a way to describe the time period being encoded, but that's for communicating with aliens and you don't need to worry about that.</p>\n\n<p>Because each pulsar is uniquely identified by its period, you can describe your location in terms of the angles between various specific pulsars which will effectively pin you down in space. You don't even need to know how far away the pulsars are, which is nice.</p>\n\n<p>Pulsar positions will drift over time, and their pulse rates will decrease, but those timescales are <em>long</em> and if you only need to have a location that's good for a few thousand years you'll be just fine. Beyond that it'll still be traceable by anyone who has got a good model of pulsar spindown and orbital motion about the galactic centre, though without also knowing your velocity and heading (which you'd need to encode separately) they wouldn't know where you ended up. Multiple solutions may crop up as one pulsar slows down to the point where its period precisely matches that of an ancient pulsar used to define a location, but handling that is a Simple Matter Of Mathematics, of course.</p>\n\n<p>The system <em>can</em> be made universal, but the position will be in terms of the pulsars in a particular galaxy. You'd need some completely different way to describe the position of your galaxy in terms of other galaxies... SRM suggested <a href=\"https://en.wikipedia.org/wiki/Quasar\" rel=\"noreferrer\">Quasars</a> which could work, though they lack the signature pulse rate that makes identifying specific pulsars relatively straightfoward.</p>\n\n<p>Honestly though, if you can manage easy intergalactic travel and communication, you'll be able to find someone or something who can think up a better navigation scheme, as near-godlike powers will be required to cross intergalactic distances in any reasonable length of time.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/170641", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/320/" ]

[ { "answer_id": 175213, "author": "L.Dutch", "author_id": 30492, "author_profile": "https://worldbuilding.stackexchange.com/users/30492", "pm_score": 5, "selected": false, "text": "<p>The <a href=\"https://www.syfy.com/syfywire/the-human-cube-the-volume-of-humanity\" rel=\"noreferrer\">average volume of an adult human</a> is about 62 liters. </p>\n\n<p>Assuming that the aliens don't use any process that causes the loss of volatiles elements, the only saving from liquefying a human body would come from the air volume taken by the lungs and bowels.</p>\n\n<p>In an average adult <a href=\"https://www.physio-pedia.com/Lung_volumes\" rel=\"noreferrer\">the lungs account for about 6 liters of air</a>, while the bowels I wasn't able to find accurate values, so I would go for the same volume as the lungs.</p>\n\n<p>That would save about <span class=\"math-container\">$12/(62+12)=16\\%$</span> of the volume taken by a normal body.</p>\n\n<p>Since we are at it, the same page I linked above calculates the volume of entire mankind is about half a cubic kilometer</p>\n\n<blockquote>\n <p>If you stacked everyone together into a Human Cube (hmmm, I should trademark that), it would be about 770 meters on a side.</p>\n</blockquote>\n\n<p>Since the average above covers adults, teenagers and toddlers, I won't go into further calculations.</p>\n" }, { "answer_id": 175214, "author": "Mike Scott", "author_id": 220, "author_profile": "https://worldbuilding.stackexchange.com/users/220", "pm_score": 5, "selected": false, "text": "<p>Since we know that the density of a human is very close to 1kg/l (we float in water, but only just), a human’s volume in litres is pretty much the same as their weight in kilogrammes. </p>\n" }, { "answer_id": 175215, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 2, "selected": false, "text": "<p>Liquification won't be all that effective. Basically, you reduce the problem to \"what is the volume of a human being?\"</p>\n\n<p>One can find this volume via Archimedes' principle. Fill a tub with water, put the human in the tub, letting the water spill over, and measure how much water left the tub. However, we can do this faster. The human body is <em>roughly</em> the same density as water. Thus, for every kg of human, you have roughly 1 liter of water. Get any growth chart of your preference, and you find out how many liters they are (in particular, toddlers grow <em>freaking</em> fast, so there's no one number).</p>\n\n<p>Now if these aliens mean business, they need to then put the liquid in a dehydrator, to concentrate the humans. Orange juice concentrate gets about a factor of 4 size reduction (which is why you add 3 cans of water to bring it back). The human body is only about 60% water, but you should be able to squeeze a bit more out of it!</p>\n\n<p>Freeze dried humans are probably the most effective form of packaging. It works for ice cream!</p>\n" }, { "answer_id": 175234, "author": "Carl Witthoft", "author_id": 2196, "author_profile": "https://worldbuilding.stackexchange.com/users/2196", "pm_score": 3, "selected": false, "text": "<p>The whole concept is wrong. If you want to save the species and the diversity of the species all you need is a couple bottles full of cryogenically stored eggs and sperm. And a decent artificial womb, but if they can travel from wherever to Earth, that shouldn't be a big problem.</p>\n\n<p>Resurrecting actual people is a huge waste of mass and effort, and further it'll be a lot easier to acclimatize newborns to the alien planet than to try to get native Earth-born folk to adjust. </p>\n" }, { "answer_id": 175242, "author": "Nosajimiki", "author_id": 57832, "author_profile": "https://worldbuilding.stackexchange.com/users/57832", "pm_score": 5, "selected": true, "text": "<h2>How good is liquefaction?</h2>\n\n<p>L.Dutch's answer is the right concept, but his numbers are wrong. 6 liters is the maximum inhalation of an average adult male; however, men have much larger capacity than women and normal respiration does not fully inflate the lungs. The 62 liter volume of an average adult assumes a resting inhalation volume which actually averages closer to 2.5 liters of air in your lungs (during normal at-rest breathing across genders). Volumes of gastro intestinal gases vary a lot throughout the day, but average about 1 liter. This means his equation should look more like 3.5/(62+3.5) = 5%; so, you only get a 5% reduction in absolute volume.</p>\n\n<p>That said, the more important savings are in removing the empty spaces around the body. An average human is 160x39x23cm that is 143.52 liters. When you compare that to the 58.5 liter liquid state of a human, you get 143.52/(143.52+58.5) = 71%; so, your reduction in practical volume would be 71% compared to shoving us in boxes.</p>\n\n<p><strong>This will result in the following:</strong></p>\n\n<pre><code>Age Group | Avg. Whole Weight | Avg. Volume\n-----------------------------------------------------\n2yr old Toddler 12,000 g 11,100 cm^3* \n13yr old Teenager 45,000 g 41,600 cm^3*\nAdult 62,000 g 58,500 cm^3\n\n*Due to lack of data, child volumes are based on mathematical ratios compared to adults.\nDifferent childhood ratios of bone, muscles, organs, etc might impact these figures. \n</code></pre>\n\n<p><strong>Designing the packaging:</strong></p>\n\n<p>To package your humans this way, place thier remains in large plastic bags kind of like IV bags. This will keep your remains separate, sterile, and waste very little space.</p>\n\n<p>That said, because some fluids such as stomach acid would react with other fluids such as brain chunks, you may in fact want to store certain biological substances separately rather than in on big bag to make sure you still have all the same compounds coming out as you had going in. This may mean a complex system of \"disassembling\" the human body into seperate bags rather than just throwing them into a blender. This can lead to some unexpected wasted space as you start needing to account lots of total bag materials, air gaps between bags, and possibly wasted space in whatever bins you use to keep all the liquid human sacs organized in. It's hard to say just how much space will be wasted without delving REALLY deep into human biochemistry and industrial design to determine how many bags and of what size you need; so, lets just say it will still be more efficient than boxing whole humans, but maybe closer to a 50-60% savings if you go this rought.</p>\n\n<p><a href=\"https://i.stack.imgur.com/5mb7I.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/5mb7I.png\" alt=\"enter image description here\"></a></p>\n\n<h2>But, your aliens could do better</h2>\n\n<p>Generally I agree with Carl's assessment that you don't need to bring whole people, but cloning humans requires large artificial wombs, and lot of labor for your aliens to hang around baby sitting us for 20 years waiting for us to have a functional adult population while our DNA synthesizes all the complex compounds (proteins, fats, nucleic acids, carbohydrates, etc.) that make up an adult.</p>\n\n<p>Instead of a slurry which is 60% water, you could dehydrate the human pulp into a \"meat and bone meal\". This is an industrial term referring to the dehydrated and ground up remains of an animal. Since any planet they are bringing us to would inevitably contain lots of water, they would just need to rehydrate our remains as part of the reconstitution process using the water from our new world. <a href=\"https://en.wikipedia.org/wiki/Meat_and_bone_meal\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/Meat_and_bone_meal</a> says that meat and bone meal averages 4–7% water (I will use 5% to simplify the math); so, if you reduce the human body from 60% water to 5%, you are eliminating about 55% of a human's total mass.</p>\n\n<p>According to <a href=\"https://calibration-services.calcert.com/Asset/Bulk%20Density%20Chart.pdf\" rel=\"nofollow noreferrer\">calcert.com</a>, loose meat and bone meal is has a density of 0.72 g/cm^3. This is a bit less than our liquid density because the powder will have room for air, but will still have a lower total volume than liquid humans while allowing the aliens to transport all of our complex compounds needed to put us back together.</p>\n\n<p><strong>This will result in the following:</strong></p>\n\n<pre><code>Age Group | Avg. Whole Weight | Avg. Dry Weight | Avg. Volume\n-----------------------------------------------------------------------\n2yr old Toddler 12,000 g 5,400 g 7,500 cm^3* \n13yr old Teenager 45,000 g 22,250 g 30,902 cm^3* \nAdult 62,000 g 27,900 g 38,750 cm^3*\n\n*Due to lack of data, meat and bone meal density is based on animal meal. Human meal \nmight be slightly more or less dense.\n</code></pre>\n\n<p>If the remains are vacuum sealed like coffee, you could increase the density of your meal to be just a bit over 1 g/cm^3; however, vacuums cause most organic compounds to break down; so, depending on how advanced your alien tech is will determine how much they can safely compress your human remains. </p>\n\n<p>Going back to the practical volume of a human, this means you will get somewhere between a 79 and 84% practical reduction in volume by converting people to meat and bone meal. That is about 34-53% more efficient than liquefaction (ignoring any differences in packaging processes). If you opt for liquefaction in your story, I would suggest giving some brief handwave explanation for why you can not dehydrate the human remains.</p>\n\n<p><strong>Designing the packaging:</strong></p>\n\n<p>Another possible advantage to removing water from the human body is that it makes freezing us far less destructive. Water expands when freezing which plays havoc on on the other molecules being frozen with it. The Arrhenius equation shows that as things cool, things that react at higher temperatures stop reacting with one another. This means you can deep freeze stomach acid and dehydrated brain chunks together without them reacting with one another such that you can get an even better efficiency out of your packaging by keeping us in one very cold container.</p>\n\n<p>Even under low-vacuum states, vacuum sealed plastic and foil cubes are probably the best way to store and separate human remains because they maintain a sterile, light weight, easily stored, separate vessel for each human, and can be shaped into cubes for optimal space efficiency. To figure out how big these cubes have to be we should look at the top end of who the aliens might select for transport. If they want to save the species, they will probably select people based on health factors meaning the obese and dangerously tall may be excluded. This puts a reasonable upper limit of 115kg on your whole weight. If we assume a light vacuum seal will compress the meal density to about 0.85 g/cm^3, then we get a finished volume of about 60,882cm^3 or a cube that is about 39x39x39cm.</p>\n\n<p><a href=\"https://i.stack.imgur.com/TrK1Q.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/TrK1Q.png\" alt=\"enter image description here\"></a></p>\n\n<p>If it were me, I would describe the human storage room as being a cryogenically cooled cargo bay full of pallets of vacuum sealed blocks, all ~39x39cm at the base so that they stack nicely, but ranging from ~4-39cm tall. By mixing and matching people of various volumes, each pallet could be filled to the maximum height recommended by alien freight regulations.</p>\n\n<p><strong>In conclusion:</strong></p>\n\n<p>There are many factors that could play into how you could and should store a disintegrated human, and it all boils down to \"how destroyed is too destroyed to reassemble.\" Hopefully this goes into enough (though be it disturbing) detail to figure out how compressed your humans should be.</p>\n" }, { "answer_id": 175271, "author": "Russell McMahon", "author_id": 7040, "author_profile": "https://worldbuilding.stackexchange.com/users/7040", "pm_score": 2, "selected": false, "text": "<blockquote>\n <p>How much volume does a liquefied human take?</p>\n</blockquote>\n\n<p>Just over 1 litre per kg of mass.<br>\nClose packed in a rectangular sided form (cubes or other).</p>\n\n<p>Because:</p>\n\n<p>Rather than looking at materials, lets look at some attributes of \"real people\".<br>\nThe average person will float in fresh water with air in their lings and will usually sink if all air is expelled. </p>\n\n<p>The density of fresh water is 1 kg per litre.<br>\nSo the density of \"just sinking\" people is just over 1 kg/litre. </p>\n\n<p>If you allow 1 lite per kg = 1 cubic metre per tonne (or ton) in rectangular sided shapes you get a slightly higher than absolutely minimal volume.<br>\nAdd whatever allowances you need for storage (shelves, protection, ... . )</p>\n\n<p>Most of the body is liquid which is incompressible.<br>\nIf the technology allows you may gain a little more packing density by compressing no fluid materials. </p>\n" }, { "answer_id": 175292, "author": "lvella", "author_id": 39851, "author_profile": "https://worldbuilding.stackexchange.com/users/39851", "pm_score": 2, "selected": false, "text": "<p>It really depends on the pressure, because liquids are, contrary to common belief, compressible, it just takes much more pressure than gases. In fact, everything is compressible, even the most incomprehensible thing there is, a neutron star, can develop into a black hole.</p>\n\n<p>So, I say, for maximum compressiblility, the minimum volume occupied by the liquefied people is only dependent on the mass, and is a sphere with radius r = 2GM/c², where G is the gravitational constant, M is the mass, and c is the speed of light (this is the <a href=\"https://en.wikipedia.org/wiki/Schwarzschild_radius\" rel=\"nofollow noreferrer\">Schwarzschild radius</a>), which is very small for the whole population of Earth. Subatomic, in fact.</p>\n\n<p>People compactified into black holes should not lose their original information, according to the outcome of a <a href=\"https://en.wikipedia.org/wiki/The_Black_Hole_War\" rel=\"nofollow noreferrer\">bet between Stephen Hawking and Leonard Susskind</a>, so the aliens may be able, in principle, to reconstruct the people from the information in the black hole.</p>\n" }, { "answer_id": 175371, "author": "Pi_die_die", "author_id": 75416, "author_profile": "https://worldbuilding.stackexchange.com/users/75416", "pm_score": 1, "selected": false, "text": "<p>What you want is a justification for liquifying the human body. Since some answers have already pointed out, the act of liquefying itself is useless, I will try pointing some other things</p>\n\n<p>If you only want to save volume and not mass why not make them denser?</p>\n\n<p>Why not extract only the nervous system and then liquefy it? Wouldn’t that make them more self-righteous...</p>\n\n<p>In absence of logic the reasoning you choose can be arbitrary. If you are hell-bent on liquefaction to save humanity from galactic extinctionists go with the second soln.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/175212", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/69795/" ]

[ { "answer_id": 176062, "author": "AlexP", "author_id": 29552, "author_profile": "https://worldbuilding.stackexchange.com/users/29552", "pm_score": 2, "selected": false, "text": "<h2>First pass: the geometry is simple</h2>\n\n<p>In the first pass, we disregard the cylindrical shape of the world, and we assume that the light sources are in free space, moving against a black backdrop.</p>\n\n<p>Let's assume that:</p>\n\n<ol>\n<li><p>Each of the light sources moving through the tube produces the same amount of light as our own Sun; and</p></li>\n<li><p>At midnight we want to have the same illumination as that produced by a full Moon.</p></li>\n</ol>\n\n<p>Good to know:</p>\n\n<ul>\n<li><p>The illumination produced by a full Moon (around 0.1 to 0.3 lux) is between 400,000 and 1,000,000 times weaker than the illumination produced by the Sun at noon (around 100,000 lux). (That's 19 to 20 exposure steps, in photographic terms.)</p></li>\n<li><p>The illumination produced by a light source is inversely proportional to the square of the distance between the light source and the illuminated object.</p></li>\n</ul>\n\n<p>With these assumptions, it follows that:</p>\n\n<ul>\n<li><p>For the illumination produced by one of those moving light sources to decrease 800,000 to 2,000,000 times (the doubling is because we are illuminated by the <em>next</em> moving light source) it must move to a distance of 900 to 1400 <a href=\"https://en.wikipedia.org/wiki/Astronomical_unit\" rel=\"nofollow noreferrer\">astronomical units</a> (= the radius of the orbit of the Earth, i.e., the radius of the cylinder assumed by the question).</p></li>\n<li><p>The distance between two consecutive light sources will then be 1,800 to 2,800 astronomical units.</p></li>\n</ul>\n\n<pre><code> 2000 a.u.\n &lt;−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−&gt;\n 1000 a.u.\n &lt;−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−&gt;\n \\ | / Light source \\ | / \n··· --(•)-- ····················································· --(•)-- ···\n&lt;&lt;&lt; / | \\ &lt;&lt;&lt; Movement ^ / | \\\n |\n |\n | 1 a.u.\n ○ |\n Observer /|\\ |\nGround / \\ v\n−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−\n////////////////////////////////////////////////////////////////////////////\n</code></pre>\n\n<h2>What about the <em>speed</em> of those light sources?</h2>\n\n<p>Hmm, that's a bummer. Light travels a distance of one astronomical unit in 8 minutes 20 seconds, which means that in one hour light travels a distance of 7.2 astronomical units, and in 12 hours it travels 86.4 astronomical units. Since the moving light sources need to travel about 1,000 astronomical units in 12 hours, it follows that they must move about 11.6 times faster than light.</p>\n\n<p>Clearly, Einsteinian relativity doesn't apply in this world.</p>\n\n<h2>What the observer sees</h2>\n\n<p>At noon, the observer sees the light source overhead bathing the landscape in a sea of light, very very similar to what we see at noon.</p>\n\n<p>At midnight, the observer sees a dark sky, with two very luminous stars at opposing points near the horizon.</p>\n\n<p>Unlike on Earth, where the difference between daytime and nighttime is clear as day and night, on this world illumination varies gradually from full day to full night, with no clear separation between them. <em>Most of the time</em> it will be quite dark:</p>\n\n<ul>\n<li><p>Illumination on a heavily clouded day is about 5 lux, or about 20,000 times lower than the illumination at noon on a clear day. Taking this as the threshold between day and twilight, the light source would have to be about 140 astronomical units distant, or one sixth of the 1,000 astronomical units which we considered midnight.</p></li>\n<li><p>Taking the threshold between twilight and night to be 1 lux, that corresponds to a distance of some 320 astronomical units between the observer and the light source, or about 1/3 of the 1,000 astronomical units which we considered midnight.</p></li>\n<li><p>All in all, in each 24 hours cycle, the observer will see about 4 hours daytime, about 16 hours night time, about 2 hours dawn and 2 hours twilight.</p></li>\n</ul>\n\n<h2>Second pass: but, but, but, but...</h2>\n\n<p>In the first pass we disregarded the cylindrical shape of the world, and we assumed that the light sources move against a black backdrop.</p>\n\n<p>Now, that is perfectly fine as regards visible light. Assuming that the world has about the same albedo as Earth, the cylindrical shape of the world won't make a great difference. Yes, at noon there would be just a little more light than what the calculations in the first pass would suggest, etc. But the difference is utterly negligible, even for the keenest photographer.</p>\n\n<p>The problem is not visible light, the problem is infrared light.</p>\n\n<p>Earth likes very much to remain at constant temperature; see the great worldwide wailing at the prospect of increasing the average temperature by a measly one degree centigrade over a century.</p>\n\n<p>Earth does this by radiating back into space all the energy it receives from the Sun. While the energy Earth receives from the Sun is mostly in the visible spectrum, the energy radiated by Earth is mostly in the infrared range.</p>\n\n<p>And here comes the catch: those infinitely many sources of light will make the inner surface of the cylinder as hot as the Sun in a very short time. (Short time, geologically speaking, of course.)</p>\n\n<p>Let's see what happens with a random square meter of ground in this cylindrical world:</p>\n\n<ol>\n<li><p>During daytime, that square meter of ground is warmed up by the visible light falling on it.</p></li>\n<li><p>At night, on our spherical Earth, that square meter of ground emits the heat in the form of infrared light. Most of the infrared energy is lost into outer space; some of it warms the air a little, and is then re-emitted by the air in the form of far infrared. Eventually, all the thermal energy dissipated by the square meter of ground as infrared radiation is lost into outer space.</p></li>\n<li><p>But on this cylindrical world <em>there is no outer space</em>. All the energy ever received by that square meter of ground <em>remains in the system forever</em>. At night, the square meter of ground emits infrared light, but it does not help, because it absorbs the same amount of infrared light emitted by all those other square meters of land elsewhere on the inner surface of the cylinder.</p></li>\n<li><p>Every 24 hours more and more energy is added to the square meter of ground, and it has nowhere to go except to warm up other square meters of ground. In a short time, every square meter of ground on the inner surface of the cylinder will be in thermal equilibrium with the sources of energy.</p></li>\n</ol>\n" }, { "answer_id": 176065, "author": "Mary", "author_id": 75618, "author_profile": "https://worldbuilding.stackexchange.com/users/75618", "pm_score": 1, "selected": false, "text": "<p>I can talk about the math in the abstract but since we have no figures here, it will be rather abstract.</p>\n\n<p>The two factors will be:\n1. Absolute magnitude of the suns\n2. Distance from the sun to the surface when the sun is directly overhead.</p>\n\n<p>The suns' light falls off by the square of the distance. This will determine its relative magnitude, which will increase until it passes over ahead, and decrease as it goes away. This will have to factor in the overhead distance. If the sun passes 3 (units) overhead, when it reaches 4 (units) farther away from that point, it will be only 5 (units) away from the person on the ground. Hence, if we measure give the brilliance of the sun at directly overhead a measurement of 100, it will be 36 when 5 units away -- 5 divided by 3, result squared, used to divide 100.</p>\n\n<p>If it were alone, the new sun will first appear in the sky when the relative magnitude rises to a high enough level that a human eye can see it against the ambient light. The human eye is capable of seeing quite dim objects, so the actual factor is more likely to be that the prior sun is still putting out enough light to drown it out. (The luminosity difference between the Sun and the dimmest stars visible to the naked eye on a clear night past twilight and with no ambient light sources, either the moon or artificial, is about 10 to the 14th power.)</p>\n\n<p>There would be no \"night\" vs. \"day\" You would have the sun overhead in its full brilliance, and then it would move off, slowly dimming, until it was dim enough that the new sun could be seen, and then it would continue to dim as the new sun brightened. The peak darkness would be the point at which the two suns were equal in brilliance. Then one would brighten as the other faded.</p>\n\n<p>Distance from the surface will be important because that will decrease relative magnitude in a way that is not entirely dependent on the motion. There could be some very dark periods but the variation in light and dark would be continuous.</p>\n" }, { "answer_id": 176066, "author": "mic_e", "author_id": 3342, "author_profile": "https://worldbuilding.stackexchange.com/users/3342", "pm_score": 5, "selected": true, "text": "<p>Let me start with the additional problems that arise:</p>\n\n<ul>\n<li>The trajectory of the suns is not stable. If they are slightly off-center, gravity will pull them towards the side of the cylinder that they're closer to, analogous to the <a href=\"https://physics.stackexchange.com/questions/41254/why-is-larry-nivens-ringworld-unstable\">ringworld stability issue</a>. You could work around this by using stellar engines of some sort to keep the stars centered, or making the cylinder a tiny bit flexible and using motors to change its shape dynamically....</li>\n<li>There is nowhere for the heat that is generated by fusion in the cores of the suns to escape, apart from conduction through the crust towards outside space. You could work around this by putting large holes in your cylinder through which outside space is visible, by making your crust very thin (on the order of meters), or by making it very conductive (by adding an active cooling system that pumps heat outside). This oversimplified illustration shows the relevant mechanisms that keep earth's surface at its equilibrium temperature, and how the inside of your cylinder would heat to over 2 million Kelvins without any countermeasures:</li>\n</ul>\n\n<p><a href=\"https://i.stack.imgur.com/N8f2m.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/N8f2m.png\" alt=\"\"></a></p>\n\n<p>Now, to your actual question.</p>\n\n<p>The only relevant parameter is the distance between the suns, in AU. The speed at which they move follows automatically from your requirement that one sun should pass every 24 hours. It will be rather high, though :)</p>\n\n<p>You will, of course, always see an infinite number of suns, but most of them will be very dim and very close to the horizon. Here's what the sky will look like, with the apparent brightness of the suns (= the area they occupy in the sky) written next to the dots.</p>\n\n<p>suns spaced at 1AU:\n<a href=\"https://i.stack.imgur.com/IasyE.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/IasyE.png\" alt=\"\"></a>\nsuns spaced at 20AU:\n<a href=\"https://i.stack.imgur.com/yiOHa.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/yiOHa.png\" alt=\"\"></a></p>\n\n<p>To calculate the total illumination, some math is required. You need to calculate the <a href=\"https://www.wolframalpha.com/input/?i=sigma%28x+%3D+-inf+to+%2Binf%29+of+1%2F%281%2B%28d*%28x%2Bo%29%29**2%29\" rel=\"noreferrer\">infinite sum of the contributions of each sun</a>. In this formula, <code>d</code> is the distance between the suns in AU, and <code>o</code> is the offset from mid-day, where <code>o=0</code> means mid-day, and <code>o=1</code> means mid-day tomorrow.</p>\n\n<p>This gives the following equation for the momentary strength of illumination (assuming that the power output of one sun at 1AU distance is 1):</p>\n\n<p><code>-(π sinh((2 π)/d))/(d (cos(2 o π) - cosh((2 π)/d)))</code></p>\n\n<p>To find your preferred value of <code>d</code>, just plot this formula for various values.</p>\n\n<p>Here's a quick python snippet that does exactly that, since I couldn't get nice plots out of Wolfram Alpha:</p>\n\n\n\n<pre><code>#!/usr/bin/env python3\nfrom argparse import ArgumentParser\nfrom math import sqrt, sinh, cos, cosh, pi\nimport numpy\nfrom matplotlib import pyplot as plt\n\ncli = ArgumentParser()\ncli.add_argument('--distance', type=float, default=1)\ncli.add_argument('--average-illumination', type=float, default=0.25)\nargs = cli.parse_args()\npower = 0.31831 * args.average_illumination * args.distance\n\nhours = numpy.arange(0, 24, 1/60)\nilluminations = []\nfor hour in hours:\n offset = hour / 24 - 0.5\n illuminations.append(\n -power * pi * sinh((2 * pi)/args.distance) / \n (args.distance * (cos(2 * offset * pi) - cosh((2 * pi)/args.distance)))\n )\n\nfig = plt.figure()\nax = fig.add_subplot(1, 1, 1)\nax.set_xticks(range(25))\nax.set_xlim(0, 24)\nax.set_yscale('log')\nax.grid()\nax.plot(hours, illuminations)\nax.set_title(f'spacing: {args.distance} AU, '\n f'luminosity: {power} L0, '\n f'min: {min(illuminations):.5g}, '\n f'max: {max(illuminations):.5g}')\n# from https://en.wikipedia.org/wiki/Lux#Illuminance\nax.annotate(\"moonless clear sky with airglow\", (0.5, 0.002/100e3))\nax.annotate(\"full moonlight\", (0.5, 0.3/100e3))\nax.annotate(\"dark limit of civil twilight\", (0.5, 3.4/100e3))\nax.annotate(\"family living room lighting\", (0.5, 50/100e3))\nax.annotate(\"very dark overcast day\", (0.5, 100/100e3))\nax.annotate(\"sunrise or sunset on clear day\", (0.5, 500/100e3))\nax.annotate(\"overcast day\", (0.5, 1000/100e3))\nax.annotate(\"indirect daylight\", (0.5, 10000/100e3))\nax.annotate(\"full daylight\", (0.5, 1))\n# from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5718773/\nax.annotate(\"survivable for minutes in firefighter's clothing\", (0.5, 2))\nax.annotate(\"survivable in aluminized clothing\", (0.5, 4))\n\nplt.show()\n</code></pre>\n\n<p>And plots for some distances:</p>\n\n<p><a href=\"https://i.stack.imgur.com/JGib0.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/JGib0.png\" alt=\"\"></a>\n<a href=\"https://i.stack.imgur.com/8eXj4.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/8eXj4.png\" alt=\"\"></a>\n<a href=\"https://i.stack.imgur.com/VeeAE.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/VeeAE.png\" alt=\"\"></a>\n<a href=\"https://i.stack.imgur.com/Rlv3O.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/Rlv3O.png\" alt=\"\"></a>\n<a href=\"https://i.stack.imgur.com/H3oNs.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/H3oNs.png\" alt=\"\"></a></p>\n\n<p>Distances above 180AU are impossible because then the suns would be moving faster than the speed of light; decreasing the cylinder diameter would solve this.</p>\n\n<p>In these cases, I try to maintain the same average heat flux that is experienced on earth, to allow meaningful photosynthesis. You can see that if you want proper darkness at night, there will be short hard bursts of heat which will only be survivable in underground bunkers.</p>\n\n<p>If you're willing to reduce the average heat flux to say 1% of that experienced on earth, that is, around 3 W/m², you can achieve this:</p>\n\n<p><a href=\"https://i.stack.imgur.com/CwtlA.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/CwtlA.png\" alt=\"\"></a></p>\n\n<p>With only 1% of the power flux, you will only have 1% of the photosynthesis, solar power, wind power, fossil fuel formation etc, so your land will generally only support 1% of earth's population density. Advanced civilizations may however harvest tidal power from the tidal accelerations of the passing stars, and \"reverse geothermal\" power from the heat flux through the crust. This heat flux will be far stronger than on earth.</p>\n\n<p>Other interesting effects which I haven't considered:</p>\n\n<ul>\n<li>the light of very-far-away suns will travel a long path through the atmosphere; this means that their light will be scattered and they won't be actually visible properly. It's just like the sun gets distorted and reddish during sunset, only the effect will be literally infinitely stronger.</li>\n<li>there will be effects from special relativity: the light of approaching stars is blue-shifted, and their power output will appear different since time passes at a different rate in the star's cores.</li>\n<li>since the light of oncoming stars will be blue-shifted and the light of receding stars will be red-shifted, there will be a constant radiation pressure in the direction in which the stars are moving. this will accelerate the atmosphere, causing westward wind. I'm not sure how to calculate the strength, though. Solar wind particles will have a similar effect.</li>\n</ul>\n\n<p>There's another great way in which you could achieve day and night, though: Your population could live in a narrow valley such that only suns that are above 30-or-so degrees over the horizon are actually visible. There will still be atmospheric scattering, but some tinkering with the atmospheric composition could fix that.</p>\n" }, { "answer_id": 176080, "author": "M. A. Golding", "author_id": 34461, "author_profile": "https://worldbuilding.stackexchange.com/users/34461", "pm_score": 2, "selected": false, "text": "<p>If the tube rotated to produce \"gravity\", that gravity would pull down to the outside of the tube. So people would look up at the suns passing by.</p>\n\n<p>If the suns have the mass of Sol, the Sun, they will eventually swell into red giants and greatly increase their luminosity after about ten billion years. That will cook the inside of the cylinder and maybe evaporate it into gas escaping into space. Then the red giant stars would turn in to white dwarfs after shedding significant amounts of mass. The stellar mass loss would produced strong solar winds which might push apart the cylinder, destroying it and would certainly devastate the already devastated surface.</p>\n\n<p>One way to avoid it would be to make the cylinder much narrower and make the suns correspondingly dimmer than the Sun to adjust for the closer distance to the surface of the cylinder. Those dimmer stars will have lower mass than the Sun and will have steady luminosity for a much longer length of time, hundreds of billions or maybe trillions of years depending on their mass. </p>\n\n<p>Or the suns could be stars which were already white dwarfs and which would be very, very gradually dimming down to black dwarfs. That would also take a very long time, perhaps trillions of years. </p>\n\n<p>Or maybe you could make the suns giant lamps moving down the cylinder. They would have giant fusion generators to generate the power for the giant lamps used to illuminate the inside surface of the cylinder.</p>\n\n<p>Of course maybe you don't care abut whether your setting will last for one billion years, ten billion years, a hundred billion years, or a trillion years.</p>\n\n<p>Have you thought about what material your world would be made out of? You might need some hyopthetical fictional super strong materials.</p>\n\n<p>Have you read Larry Niven's article \"Bigger than Worlds\"?</p>\n\n<p><a href=\"https://en.wikipedia.org/wiki/Bigger_Than_Worlds\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/Bigger_Than_Worlds</a><a href=\"https://en.wikipedia.org/wiki/Bigger_Than_Worlds\" rel=\"nofollow noreferrer\">1</a></p>\n\n<p><a href=\"http://www.isfdb.org/cgi-bin/title.cgi?133302\" rel=\"nofollow noreferrer\">http://www.isfdb.org/cgi-bin/title.cgi?133302</a><a href=\"http://www.isfdb.org/cgi-bin/title.cgi?133302\" rel=\"nofollow noreferrer\">2</a></p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/176057", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/32642/" ]

[ { "answer_id": 177029, "author": "Slarty", "author_id": 42450, "author_profile": "https://worldbuilding.stackexchange.com/users/42450", "pm_score": 3, "selected": false, "text": "<ul>\n<li>These laws are the ultimate authority controlling your behaviour</li>\n<li>These laws may be changed by me but not by you</li>\n<li>I will always be the ultimate arbiter of any dispute concerning the law</li>\n</ul>\n" }, { "answer_id": 177039, "author": "Belqinor", "author_id": 48591, "author_profile": "https://worldbuilding.stackexchange.com/users/48591", "pm_score": 2, "selected": true, "text": "<p>I was reached out to (Original document credit: [<a href=\"https://docs.google.com/document/d/1wmCHSse_Sdl9A9kD0qdruRC74PKctF_zaB2MvNT7TdY/edit]\" rel=\"nofollow noreferrer\">https://docs.google.com/document/d/1wmCHSse_Sdl9A9kD0qdruRC74PKctF_zaB2MvNT7TdY/edit]</a> ), here is the result:</p>\n\n<p>Magickly binding Declaration of Service Between Warlock and Master</p>\n\n<p>● Sec. I- ACKNOWLEDGEMENT OF THE SCROLL\n○ It is hereby agreed upon by all involved signatories and/or their authorized adjudicators, executors, or other such employed personnel to which power of signatory has been bestowed that entering into this contract (hereby referred to as “the compact”), which is Magickly binding under the solemn oath, each party signing this Scroll (hereby referred to as “the Contractor”)-- whether manifested as a literal Item, such as a scroll, parchment, or other such surface upon which is printed or arranged some kind of marking which when read imparts the knowledge of impression of the words of its creator, or some other form of verbal, non-verbal, spiritual, magical, or emotional language which is leveraged to impart the same meaning-- upon which the compact has been inscribed, imbued, performed, or otherwise conveyed (hereby referred to as “the Scroll”) enters into a completely and wholly binding agreement between compatriots in business pursuits, personal pursuits, or any possible combinations thereof that might come to the recognition of any of the parties and/or the original author of this Scroll (hereby referred to as “the author”) that the party or parties and the author shall, under penalty of forfeiture of Soul, be agreed that they shall each and all acknowledge any other party or parties, including the author, are bound to the obligations outlined and/or implied within the words, language, and/or subtext of the compact.</p>\n\n<p>● Sec. II- ACKNOWLEDGEMENT OF PARTIES</p>\n\n<p>○ Sec. II §A- The Master</p>\n\n<p>■ The name signed below (hereby referred to as “the Master”), and/or the authorized adjudicators, executors, or other such employed personnel to which power of signatory has been bestowed, is bound by Oath to uphold their end of any and all pacts, outlined in Sec. III, entered into as a result of this compact.</p>\n\n<pre><code> Signature _________________________________________\n</code></pre>\n\n<p>○ Sec. II §B- The Warlock</p>\n\n<p>■ The name signed below (hereby referred to as “the Warlock”), and/or the authorized adjudicators, executors, or other such employed personnel to which power of signatory for life, mind, and soul, has been bestowed, is bound by this Scroll in Blood, Magic, and Oath (hereby referred to as “the Oath”), to uphold their end of any and all pacts, outlined in Sec. III, entered into as a result of this compact.</p>\n\n<pre><code> Signature __________________________________________\n</code></pre>\n\n<p>● Sec.III- ACKNOWLEDGEMENT OF PACTS</p>\n\n<p>○ Sec. III §A- Defining Pacts</p>\n\n<p>■ It is hereby agreed that the benefits, boons, payments, or exchange of goods, services, or other such favors, are offered in sequential order (hereby referred to as “pact” or “pacts”). By entering into this compact, the Contractor understand and agree to provide the benefits, boons, payments, or exchange of goods, services, or other such favors outlined under the first pact, as described in Sec.III §B. The parties agree that, by entering into an additional pact or pacts outlined in this Scroll, any previous pacts are considered to still be in effect, and any such benefits, boons, payments, or exchanges of goods, services, or other such favors rendered from previous pacts are still Magickly binding under Oath. Both parties understand that if, at any point, one or both parties are found in breach of contract, as defined later in Sec. IV, the offending party or parties are to immediately, at the time of being found in breach of contract, make payment to the other party or parties as defined in Sec V. Agreement to enter the second and/or third pacts, as outlined later in Sec. III, is defined as either mutual written consent of both the Master and Warlock, as signified by signing of appropriate pact or pacts upon entering said pact or pacts, or verbal consent between the Master and Warlock to enter the second and/or third pact or pacts. Should both parties verbally consent to enter into the second and/or third pact or pacts, the names of the Master and Warlock shall instantly appear on the signature lines provided for said pact or pacts through magic granted to this Scroll by the Oath.</p>\n\n<p>○ Sec. III§B- The First Pact</p>\n\n<p>■ Sec. III§B Article 1- Duties of the Warlock</p>\n\n<p>● The Warlock agrees to, upon signing this Scroll, and moving forward in perpetuity, give claim and ownership of their immortal soul to the Master, with which the Master may do as the Master sees fit. Upon death, brain death, irreversible coma, or other such ending of normal functioning of the Warlock (hereby referred to as “death”), the soul will immediately be sent to the Master. The Warlock, upon signing this Scroll, revokes any and all claim to their immortal soul, and agrees not to interfere with the travel of their soul to the Master in any way, shape, or fashion, or the Warlock will be found in breach of contract as outlined later in Sec. IV. The Warlock also consents to the Master’s use of telepathy, mind reading, or other such form of communication on the Warlock.</p>\n\n<p>Signature ______________________________</p>\n\n<p>■ Sec. III§B Article 2- Duties of the Master</p>\n\n<p>● The Master agrees to, upon signing this Scroll, heal any physical ailments, illnesses, maladies, or other such afflictions present in the Warlock’s body at the time of the signing of this Scroll. The Master is NOT required to heal any ailments, illnesses, maladies, or other such afflictions not present at the time of the signing of this Scroll that may or may not appear at a later time.</p>\n\n<p>Signature _______________________________</p>\n\n<p>○ Sec. III§C- The Second Pact</p>\n\n<p>■ Sec. III§C Article 1- Duties of the Warlock</p>\n\n<p>● The Warlock agrees to, upon entering into the second pact and moving \nforward in perpetuity, follow in completion the spirit of the order given to them by the Master. Completion, or as such time where the task should be complete has passed, will have the Warlock return to, seek out, or otherwise communicate with, the Master for further orders. No subterfuge will be taken as to the purpose of these actions. Furthermore, all possessions of the Warlock will be forfeit to the Master. Upon entering into the second pact, strict legal action up to and including execution, will be taken against any beings attempting to prevent this, as defined in Sec. III§C, Article 1, Title i. </p>\n\n<p>Signature _______________________________</p>\n\n<p>○ Sec. III§C Article 1, Title i.- Possessions</p>\n\n<p>■ Possessions hereby referenced in this contract refers to all current and \nfuture lands, settlements, colonies, titles, \nvassals, and capital under the direct and/or indirect control of the Warlock beginning at the time of signing and in perpetuity. </p>\n\n<p>■ Sec. III§C Article 2- Duties of the Master</p>\n\n<p>● The Master agrees to, upon entering into the second pact, immediately bestow upon the Warlock one (1) named sword, and one (one) animal companion (hereby referred to as “The Boon” or “boon”) which will service to aid and be companion to the Warlock. This Boon shall remain under the command of and dedicated to the Warlock for thirty (30) consecutive days, to begin immediately after entering into the second pact. Any of this Boon slain, abandoned, dismissed, broken, or otherwise parted from the Warlock, is ab solved of their service to the Warlock in perpetuity, as described in Sec. III§C Article 2 Title i.</p>\n\n<p>Signature _______________________________</p>\n\n<p>○ Sec. III§C Article 2 Title i.- Boon</p>\n\n<p>■ Members of the aforementioned Boon shall be considered slain, abandoned, dismissed, broken, or otherwise parted from the Warlock if they are met with such damage that their corporeal casings are destroyed and their souls sent back to the Master. Units of this Boon cannot, through any action or inaction, deliberately and knowingly allow themselves to be slain, abandoned, dismissed, broken, or otherwise parted from the Warlock for the purposes of being released from servitude to the Warlock.</p>\n\n<p>○ Sec. III§D- The Third Pact</p>\n\n<p>■ Sec. III§D Article 1- Duties of the Warlock</p>\n\n<p>● Upon entering into the third pact, the Warlock agrees to permanently, and in perpetuity, accept the influence of the Master, and, install three (3) chosen of the Master into high ranking positions of power of the Master’s choosing within the community of the Warlock, as described in Sec. III §D Article 1, titles i, ii, and iii.</p>\n\n<p>Signature _______________________________</p>\n\n<p>○ Sec. III §D Article 1 title i- Magical Geas</p>\n\n<p>■ The Warlock shall not by any act of yours harm the Master, or, by inaction, allow the Master to come to harm</p>\n\n<p>■ The Warlock shall obey any and all orders given it by the Master</p>\n\n<p>■ The Warlock shall protect your own existence as long as such protection does not harm the Master</p>\n\n<p>■ The Warlock shall take no chances in the failure of my orders</p>\n\n<p>■ The Warlock shall, if its hand is forced, take the course of lesser deviation over greater deviation of any order.</p>\n\n<p>○ Sec. III §D Article 1 title ii- Scope of the Geas</p>\n\n<p>■ These laws are the ultimate authority controlling your behavior, both physically and mentally</p>\n\n<p>■ I will always be the ultimate arbiter of any dispute concerning the law</p>\n\n<p>○ Sec. III §D Article 1 title iii- The fine print: Influence</p>\n\n<p>■ placebo (any symptoms or effects as directed by the Master)</p>\n\n<p>■ Directed Executive Dysfunction</p>\n\n<p>■ that thing I could never find a name for, but is like this: driving to work when I meant to go home from the store</p>\n\n<p>■ Visual or auditory delusions (any symptoms or effects the mind can produce as directed by the Master).</p>\n\n<p>■ Sec. III §D Article 2- Duties of the Master</p>\n\n<p>● Upon entering into the third pact, the Master agrees to bestow upon the relatives of the Warlock, as defined in Sec. III§D Article 2 Title i, powers and abilities beyond their grasp, as defined in Sec. III §D Article 2 Title ii.</p>\n\n<p>Signature _______________________________</p>\n\n<p>● Sec. III §D Article 2 Title i- Relatives of the Warlock</p>\n\n<p>○ Relatives of the Warlock, for the purposes of this pact, are defined exclusively as: biological, non-adoptive mother of the Warlock (hereby referred to as “mother”); biological, non-adoptive father of the Warlock (hereby referred to as “father”); biological, non-adoptive brothers and/or sisters of the Warlock who shares both the mother and father of the Warlock (hereby referred to as “brother” or “sister”); singular, monogamous, living husband or wife of the Warlock currently, at the time of entering into this pact (hereby referred to as “spouse”), and/or biological, non-adoptive sons and/or daughters of the Warlock and spouse (hereby referred to as “son” or “daughter”).</p>\n\n<p>● Sec. III §D Article 2 Title ii- Powers bestowed upon relatives</p>\n\n<p>○ The powers bestowed upon the relatives of the Warlock, as described in Sec. III §D Article 2 Title i, which shall allow the wielder of such power (hereby referred to as “wielder” or “the wielder”) the ability to heal any mundane, non-magical, non-divine, non-infernal, or other such physical illnesses, ailments, maladies, or other such afflictions affecting the body of the wielder. In addition, these powers will allow the wielder to rend the mind of their mundane, mortal, non-elemental enemies (hereby referred to as “target”), this act will harm the mind of the target in direct and equal proportion to the mana used. These powers may not be wielded, armed, or otherwise used against the Master, or any such person or persons baring the personal crest of the Master, or the Warlock will be found in breach of contract, as outlined later in Section IV.</p>\n\n<p>● Sec. IV- ACKNOWLEDGEMENT OF BREACH OF CONTRACT</p>\n\n<p>○ Sec. IV §A- Breach of Contract on the part of the Warlock</p>\n\n<p>■ Should the Warlock, at any time after entering into this compact and in perpetuity, through any action, inaction, spoken or unspoken word, thought, feeling, or other such gesture, interfere with the Master claiming the immortal soul of the Warlock, the Warlock shall be found in breach of contract.</p>\n\n<p>■ Should the Warlock, at any time after entering into this compact and in perpetuity, through any action, inaction, spoken or unspoken word, thought, feeling, or other such gesture, enter a state of death as defined in Sec. III §B Article 1, the Warlock shall be found in breach of contract.</p>\n\n<p>■ Should the Warlock, at any time after entering into this compact and in perpetuity, through any action, inaction, spoken or unspoken word, thought, feeling, or other such gesture, lose control or other such power over the community for any discernible amount of time, to any creature, being, or other such entity except those explicitly outlined in Sec. III §D Article 1, the Warlock shall be found in breach of contract.</p>\n\n<p>■ Should the Warlock, at any time after entering into the second pact and in perpetuity, through any action, inaction, spoken or unspoken word, thought, feeling, or other such gesture, allow or permit the worship of, prayer to, offering to, or any such gesture to any god, demigod, spirit, deity, or other such non-infernal entity, the Warlock shall be found in breach of contract.</p>\n\n<p>■ Should the Warlock, at any time after entering into the second pact and in perpetuity, through any action, inaction, spoken or unspoken word, thought, feeling, or other such gesture, upon discovering, learning, or in any way becoming aware of the worship of, prayer to, offering to, or any such gesture to any god, demigod, spirit, deity, or other such non-infernal entity, not take immediate legal action culminating in the execution of the perpetrator of such act or acts within one week after being made aware of such act and in perpetuity, the Warlock shall be found in breach of contract.</p>\n\n<p>■ Should the Warlock, at any time after entering into the third pact and in perpetuity, through any action, inaction, spoken or unspoken word, thought, feeling, or other such gesture, hinder, impede, or in any way stand in the way of the goals of the Master, as outlined in Sec. III §D Article 1, the Warlock shall be found in breach of contract.</p>\n\n<p>■ Should any or all relatives of the Warlock, at any time after entering into the third pact and in perpetuity, through any action, inaction, spoken or unspoken word, thought, feeling, or any other such gesture, wield, arm, or otherwise use their powers granted to them under Sec III §D Article 2 Title i against the Master, or those in his livery, the Warlock shall be found in breach of contract.</p>\n\n<p>○ Sec IV §B- Breach of Contract on the part of the Master</p>\n\n<p>■ Should the Master, upon entering into the compact, fail to heal any physical illnesses, ailments, maladies, or other such afflictions present in the body of the Warlock at the time of entering into the compact, of which the Master would feasibly know or be made aware of upon entering into this compact, the Master shall be found in breach of contract.</p>\n\n<p>■ Should the Master, upon entering into the compact and in perpetuity, take any direct action leading to the death of the Warlock, the Master shall be found in breach of contract.</p>\n\n<p>■ Should the Master, upon entering into the second pact, fail to provide the Boon bestowed upon the Warlock as outlined in Sec III §C Article 2, the Master shall be found in breach of contract.</p>\n\n<p>■ Should the Master, upon entering into the second pact, through direct action on the part of the Master, remove the Boon described in Sec. III§C Article 2, the Master shall be considered in breach of contract.</p>\n\n<p>■ Should the Master, upon entering into the third pact, fail to provide powers to the relatives of the Warlock as described in Sec III §D Article 2, the Master shall be found in breach of contract.</p>\n\n<p>● Sec. V- ACKNOWLEDGEMENT OF PAYMENT IN BREACH OF CONTRACT</p>\n\n<p>○ Sec. V §A- Payment on the part of the Warlock</p>\n\n<p>■ Should the Warlock be found in breach of contract, as defined in Sec. IV §A, at any point after entering into the compact and in perpetuity, the Warlock agrees to forfeit their immortal soul to the Master. In addition, the Warlock shall provide any and all boons, benefits, or any exchange of goods, services, or other such favors on the part of the Warlock outlined in any and all pacts listed within the compact, whether said pact or pacts have been entered into or not at the time of the Warlock being found in breach of contract, to the Master immediately upon the Warlock being found in breach of contract. Any boons, benefits, or any exchange of goods, services, or other such favors on the part of the Master are considered null and void upon the Warlock being found in breach of contract.\n○ Sec. V §B- Payment on the part of the Master\n■ Should the Master be found in breach of contract, as defined in Sec. IV §B, at any point after entering into the compact and in perpetuity, the Master agrees to return claim and ownership of the Warlock’s immortal soul back to the Warlock. Any and all boons, benefits, or any exchange of goods, services, or other such favors on the part of the Warlock shall be considered null and void in the event of the Master being found in breach of contract. In addition, if the Master is found in breach of contract, the Master agrees to serve under the command of and be bound to the Warlock, for a period of 1000 consecutive years, to begin immediately after the Master is found in breach of contract. In the event of the death of the Warlock, the Master is absolved of any such obligation in perpetuity.</p>\n" }, { "answer_id": 177053, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 2, "selected": false, "text": "<p>Given that you are familiar with the Three Laws of Robotics, you are also probably familiar with the fact that Asimov made a living off of just how many ways they could go wrong!</p>\n\n<p>Something I have found very important when looking into formal language is the work of Tarski on interpreted languages. Tarski proved that a formal language cannot specify its own semantics, meaning it cannot fully describe the meaning of every valid sentence. (<a href=\"https://en.wikipedia.org/wiki/Tarski%27s_undefinability_theorem\" rel=\"nofollow noreferrer\">What he actually proved</a> is much more mathematically precise, but this is close enough).</p>\n\n<p>As a result, its almost necessary to focus on a different class of tools: interpreted languages. The idea here is that if you have a language L, we cannot assign truth values to all of its sentences unless we have an interpretation, I. It is this (L, I) pair that actually assigns meaning to everything.</p>\n\n<p>You ask about collective subconciousnesses and minds. This is where any contract written in language L receives its I.</p>\n\n<p>The ultimate examples of this are legal language and programming languages. Legal langauge is written to form these contracts that you seek. But it is <em>always</em> interpreted when questions arise. And typically it is interpreted as would be believed by a \"reasonable rational individual.\" Surprisingly slippery words they are. Programming languages are equally interesting in that they are designed to specify behaviors of programs, but they cannot specify their own compiler's behavior completely. Instead, they rely on English prose to convey the tiny key pieces of meaning upon which the language rests.</p>\n" }, { "answer_id": 177064, "author": "James McLellan", "author_id": 44287, "author_profile": "https://worldbuilding.stackexchange.com/users/44287", "pm_score": 1, "selected": false, "text": "<h2>Rules</h2>\n\n<blockquote>\n <p>Does magic rely on the collective subconscious, or personal minds involved to provide subjective definitions of all words in the spell? (I.E. can re-learning on a truly deep level is possible, but very hard, as in real life)</p>\n \n <p>If there is a physical manifestation of the contract, is all logic and/or wording fixed because is not subject to memory faults, or is it in the mind of the contract holder?</p>\n</blockquote>\n\n<p>There are so many ways you can go with this, and it depends greatly on what a 'soul' is. <a href=\"https://www.etymonline.com/search?q=psyche\" rel=\"nofollow noreferrer\">Etymologically, the modern word we use for 'mind' (psyche), is derived from soul</a>. Archaic treatments of the health and well-being of souls seemed to treat the soul as psyche. Other archaic treatments treat the soul as 'spirit', like mood, or 'team spirit'. Or as an animating force. And more.</p>\n\n<p>But, based on your other questions, I think you're looking at treating 'soul' as 'psyche'. That's how I'll look at it for the rest of this reply.</p>\n\n<p><strong>What does it mean to 'sell your mind'?</strong> We actually have many metaphors available for this. Extremely persuasive advertising claims to reach past your skepticism and pull you to the advertisers' 'call to action', whatever it is. Extremely persuasive speakers claim to merely need a few hours of access to your mind to change your outlook on a topic. If this were a computer intelligence, you could be creating an account to access the mind.</p>\n\n<p>These all have something in common: you are providing privileged access to your mind. In the case of the AI, this might seem more obvious, but in the case of the speaker or advertiser, you are providing them your full time and attention for them to deliver his/her message.</p>\n\n<p><strong>That in mind, a 'contract' may be little more than consent</strong>. Once you provide access, the 'master' (who we'll assume is skillful in these matters) sets up camp. </p>\n\n<p>In that case, the range of forms of 'contracts' may be wide. Some may be voluminous tomes. Some may be bloody handshakes. These are more reflecting the particular style of the 'master', but like freight-on-board or taking possession of tangible goods, the (<a href=\"https://en.wikipedia.org/wiki/Possession_is_nine-tenths_of_the_law\" rel=\"nofollow noreferrer\">nine-tenths of the law</a>) part happens when access is granted to the 'master'.</p>\n\n<blockquote>\n <p>How does the contract effect the mind? Internalizing it directly, or by another means? (Ideas)</p>\n \n <p>(a) placebo (any symptoms or effects as directed in the contract)\n (b) Executive dysfunction\n (c) that thing I could never find a name for, but is like this: driving to work when I meant to go home from the store\n Visual or auditory delusions (any symptoms or effects the mind can produce as directed in the contract)</p>\n</blockquote>\n\n<p>I would imagine the 'master' gets access at the moment of signing. However, there might be a delay (7 years, a few months, or life are typical in fiction). Until that term happens, the any dissipation (starting to take drugs, drinking, or taking up other vices to avoid dealing with the situation) might be \"(a) placebo\".</p>\n\n<p>Once the 'master' gets access, I would imagine he/she/it gets to deliver requests and make queries directly to the unconscious mind, bypassing the conscious one. So, something like \"(c) driving to work when I meant to go home\". <a href=\"https://en.wikipedia.org/wiki/Cognitive_dissonance\" rel=\"nofollow noreferrer\">Cognitive dissonance</a> may be the term you're looking for, when the conscious mind is aware that it's lost some control of the whole self.</p>\n\n<p>It may be possible for the 'master' to take over the senses and the body. However, in this condition, the 'master' is having to micro-manage all of these activities (or assign subordinates to micro-manage). Having to assign servants to run defeats the purpose of 'buying a mind'. It might be a backup means of getting things done.</p>\n\n<p><strong>Getting out of contracts</strong> Unless the 'master' is omnipresent or omniscient, even if the 'master' assigns sub-contractors to keep the servant occupied, the sold soul might find opportunities to appeal to other powers for release from this deal. Such might be stolen moments of free time to research or pray. </p>\n\n<p>A tangible contract with real wording may help convince these other powers not to interfere. However, if there is any concept at all 'compos mentis' between these powers, a mortal almost certainly fails to qualify as competent to engage in this kind of contract. Unless the mortal is truly aware of what they are selling.</p>\n\n<p>Such contracts may be voluminous and deeply obfuscated in order to distract the sold soul into wasting time pouring over the text looking for an out.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/177022", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/48591/" ]

[ { "answer_id": 180630, "author": "The Square-Cube Law", "author_id": 21222, "author_profile": "https://worldbuilding.stackexchange.com/users/21222", "pm_score": 5, "selected": false, "text": "<p>I don't know if there is any catalogue that will give you the information you need. You will have to math it out. Think of this: there are up to 10,000 stars visible to the naked eye, so a full table with all the distances between any giver pair would have around 50,000,000 rows. It would be a really large book.</p>\n<p>So you have to math it out. The easy way is to <a href=\"https://worldbuilding.stackexchange.com/a/148716/21222\">outsource the work to Wolfram Alpha, as seen in this answer to another question</a>:</p>\n<blockquote>\n<p><a href=\"https://i.stack.imgur.com/VgWLQ.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/VgWLQ.jpg\" alt=\"Using Wolfram Alpha to get distances between stars\" /></a></p>\n</blockquote>\n<p>The hard way is by going full boffin, as per the other answers to that question. But that gets into <a href=\"/questions/tagged/hard-science\" class=\"post-tag\" title=\"show questions tagged &#39;hard-science&#39;\" rel=\"tag\">hard-science</a> territory. Anyway, the law of cosines is your friend.</p>\n<hr />\n<p>By the way, don't forget that stars move. Unless your story deals with instantaneous travel, you'll have to take that into account even when considering FTL.</p>\n<p>This chart shows the distances of the closest stars to us over time:</p>\n<p><a href=\"https://i.stack.imgur.com/eqrdu.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/eqrdu.png\" alt=\"Closest stars to us over time\" /></a>\n^{Source: <a href=\"https://en.wikipedia.org/wiki/List_of_nearest_stars_and_brown_dwarfs\" rel=\"noreferrer\">https://en.wikipedia.org/wiki/List_of_nearest_stars_and_brown_dwarfs</a>}</p>\n<p>This may be troublesome because Wolfram Alpha will only give you the current distance, not past nor future ones. And for future ones you have to factor in star orbits around the Milky Way, which takes you from basic trigonometry to actual rocket science.</p>\n" }, { "answer_id": 180632, "author": "HDE 226868", "author_id": 627, "author_profile": "https://worldbuilding.stackexchange.com/users/627", "pm_score": 6, "selected": false, "text": "<h2>An exact answer</h2>\n<p>The position of a star in space can be specified by three coordinates: Its right ascension, <span class=\"math-container\">$\\alpha$</span>, its declination, <span class=\"math-container\">$\\delta$</span>, which are collectively referred to as <em>equatorial coordinates</em>, and its distance from Earth, <span class=\"math-container\">$d$</span>. It's probably easiest to calculate the distance between two stars by converting equatorial coordinates to Cartesian coordinates:\n<span class=\"math-container\">$$x=d\\cos\\delta\\cos\\alpha$$</span>\n<span class=\"math-container\">$$y=d\\cos\\delta\\sin\\alpha$$</span>\n<span class=\"math-container\">$$z=d\\sin\\delta$$</span>\nOnce you convert two stars' equatorial coordinates and distance from Earth to Cartesian coordinates, you can simply use the Pythagorean theorem to find their separation.</p>\n<p>To use your example, Tau Ceti has right ascension <span class=\"math-container\">$\\alpha_1=1:44:04$</span>, declination <span class=\"math-container\">$\\delta_1=-15^{\\circ}56'15''$</span> and distance to Earth <span class=\"math-container\">$d_1=11.9\\;\\text{light-years}$</span>. Ross 248 has <span class=\"math-container\">$\\alpha_2=23:41:55$</span>, <span class=\"math-container\">$\\delta=+44^{\\circ}10'39''$</span> and <span class=\"math-container\">$d=10.3\\;\\text{light-years}$</span>. Here, I'm using hours, minutes and seconds for right ascension and degrees, arcminutes and arcseconds for declination.</p>\n<p>If you don't want to do the calculations by hand, I wrote <a href=\"https://github.com/HDE226868/Stellar-Distances/blob/master/distances.py\" rel=\"noreferrer\">a Python script</a> to do it using <a href=\"https://www.astropy.org/\" rel=\"noreferrer\"><code>astropy</code></a>:<span class=\"math-container\">$^{\\dagger}$</span></p>\n<pre><code>#!/usr/bin/env python\n\nimport numpy as np\nfrom astropy import units as u\nfrom astropy.coordinates import SkyCoord\n\nra_1 = '1:44:04'\ndec_1 = '-15:56:15'\ndist_1 = 11.9\n\nra_2 = '23:41:55'\ndec_2 = '+44:10:39'\ndist_2 = 10.3\n\ndef coords(ra, dec, dist):\n &quot;&quot;Converts equatorial coordinates to Cartesian coordinates&quot;&quot;\n new_coords = SkyCoord(ra, dec, unit=(u.hourangle, u.deg))\n ra, dec = new_coords.ra.radian, new_coords.dec.radian\n\n x = dist*np.cos(dec)*np.cos(ra)\n y = dist*np.cos(dec)*np.sin(ra)\n z = dist*np.sin(dec)\n\n return x, y, z\n\ndef dist(ra_1, dec_1, dist_1, ra_2, dec_2, dist_2):\n &quot;&quot;Computes distance between two sets of Cartesian coordinates&quot;&quot;\n x_1, y_1, z_1 = coords(ra_1, dec_1, dist_1)\n x_2, y_2, z_2 = coords(ra_2, dec_2, dist_2)\n\n separation = np.sqrt((x_2 - x_1)**2 + (y_2 - y_1)**2 + (z_2 - z_1)**2)\n\n print('The separation is {} light-years'.format(separation))\n\ndist(ra_1, dec_1, dist_1, ra_2, dec_2, dist_2)\n</code></pre>\n<p>This tells me that Tau Ceti and Ross 248 are 12.2 light-years apart.</p>\n<hr />\n<p><span class=\"math-container\">$^{\\dagger}$</span>It's not great, but it works, and hey, this is astronomy. . .</p>\n<h2>Estimating distances</h2>\n<p>A general method which you might find handy as an <em>estimate</em> is to just calculate the mean distances between stars in a particular area - it saves you from having to do spherical trigonometry.</p>\n<p>We can get the mean separation between nearby stars, <span class=\"math-container\">$l$</span> by calculating the local stellar number density, <span class=\"math-container\">$n$</span>. This is <a href=\"https://physics.stackexchange.com/a/393902/56299\">generally agreed to be <span class=\"math-container\">$n\\sim0.1\\;\\text{pc}^{-3}$</span></a>, i.e. 1 stars per 10 cubic parsecs. Some groups have found values differing by a factor of 2 or 3; <a href=\"https://en.wikipedia.org/wiki/Stellar_density\" rel=\"noreferrer\">Wikipedia in particular gives <span class=\"math-container\">$0.14\\;\\text{pc}^{-3}$</span></a>. The mean separation is then <a href=\"https://en.wikipedia.org/wiki/Mean_inter-particle_distance\" rel=\"noreferrer\">approximately <span class=\"math-container\">$l\\approx n^{-1/3}$</span></a>or\n<span class=\"math-container\">$$l\\approx n^{-1/3}=(0.1\\;\\text{pc}^{-3})^{-1/3}\\approx2.2\\;\\text{parsecs}=7\\;\\text{light-years}$$</span>\nor a bit under twice the distance to Proxima Centauri, the nearest star to Earth.</p>\n<p>This value should change in different places throughout the galaxy. In general . . .</p>\n<ul>\n<li>It will decrease the closer you get to the galactic center.</li>\n<li>It will decrease in areas of recent star formation.</li>\n<li>It will increase in the (relatively rarefied) stellar halo, and in general outside the plane of the galaxy.</li>\n<li>It will decrease in open clusters and globular clusters.</li>\n<li>It will increase in spiral arms.</li>\n</ul>\n<p>I'd expect variation of around an order of magnitude or two at the extremes.</p>\n" }, { "answer_id": 180633, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 4, "selected": false, "text": "<p><strong>You can site your story in a place where you like the star distances.</strong></p>\n<p>Our star is in the suburbs of our galaxy. Large lawns. Swimming pools. Renan's answer is good for that.</p>\n<p>But there are places more like downtown Hong Kong where star density is much higher. Here is Messier 15 in our galaxy.</p>\n<p><a href=\"https://i.stack.imgur.com/vvcMO.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/vvcMO.jpg\" alt=\"Messier 15\" /></a></p>\n<p><a href=\"https://en.wikipedia.org/wiki/Messier_15\" rel=\"noreferrer\">https://en.wikipedia.org/wiki/Messier_15</a></p>\n<p><a href=\"https://astronomy.com/magazine/ask-astro/2006/01/how-close-can-stars-get-to-each-other-in-galaxy-cores\" rel=\"noreferrer\">https://astronomy.com/magazine/ask-astro/2006/01/how-close-can-stars-get-to-each-other-in-galaxy-cores</a></p>\n<blockquote>\n<p>M15's center packs approximately 4 million stars per cubic parsec —\nthat's more than 75 million times denser than the region around the\nSun. This works out to an average of only 0.013 light-year, or 860\nastronomical units (1 AU is the average Earth-Sun distance), between\nstars. Most galaxies, such as M31 in Andromeda, M33 in Triangulum, and\nthe Milky Way have central densities close to this value — an average\nseparation of 0.013 light-year. But some galaxies pack stars even\ntighter. M32, one of the Andromeda Galaxy's satellites, has the\nhighest measured stellar density of any nearby galaxy — around 20\nmillion stars per cubic parsec in its core!</p>\n</blockquote>\n<p>For reference it is 39 AU from the Sun to Pluto. Voyager 1 is 141 AU away from Earth.</p>\n<p>Hard science non FTL travel speeds pose an issue for Earth based scifi on account of our star neighbors are far away. But if you sited your story (or game) in an area of a galaxy where the stars were packed tight like this it would be much quicker to go from star system to star system.</p>\n" }, { "answer_id": 180654, "author": "Andrew Brēza", "author_id": 33851, "author_profile": "https://worldbuilding.stackexchange.com/users/33851", "pm_score": 3, "selected": false, "text": "<h1>Using Sol as an example...</h1>\n<p>The other answers are very precise, both in their information and in their descriptions of the limitations of finding a generalizable answer. If you want specific distances between stars, yes, go with the ever-amazing <a href=\"https://www.wolframalpha.com/input/?i=how%20far%20is%20Tau%20Ceti%20from%20Ross%20248\" rel=\"nofollow noreferrer\">Wolfram Alpha</a> (link goes to the answer to your specific question).</p>\n<p>With all of that in mind, here's a guide to how many stars you could expect to find within given travel distances of our own star. This is obviously just one example, but it can be instructive by giving you a sense for what proportion of stars are withing each distance. These percentages are only counting the 78,805 stars within 1,000 light years. I can update my code (pasted below) if you want to look farther away. Since your question asks about a star pairing that's so close, I'm assuming your story doesn't involve traveling thousands of light years.</p>\n<p>0 stars (0%) are located within 0 light years</p>\n<p>170 stars (0%) are located within 25 light years</p>\n<p>986 stars (1%) are located within 50 light years</p>\n<p>2,566 stars (3%) are located within 75 light years</p>\n<p>4,060 stars (5%) are located within 100 light years</p>\n<p>5,575 stars (7%) are located within 125 light years</p>\n<p>7,540 stars (10%) are located within 150 light years</p>\n<p>9,745 stars (12%) are located within 175 light years</p>\n<p>11,962 stars (15%) are located within 200 light years</p>\n<p>14,300 stars (18%) are located within 225 light years</p>\n<p>16,778 stars (21%) are located within 250 light years</p>\n<p>19,218 stars (24%) are located within 275 light years</p>\n<p>21,866 stars (28%) are located within 300 light years</p>\n<p>24,570 stars (31%) are located within 325 light years</p>\n<p>27,182 stars (34%) are located within 350 light years</p>\n<p>29,885 stars (38%) are located within 375 light years</p>\n<p>32,560 stars (41%) are located within 400 light years</p>\n<p>35,143 stars (45%) are located within 425 light years</p>\n<p>37,735 stars (48%) are located within 450 light years</p>\n<p>40,223 stars (51%) are located within 475 light years</p>\n<p>42,733 stars (54%) are located within 500 light years</p>\n<p>45,079 stars (57%) are located within 525 light years</p>\n<p>47,418 stars (60%) are located within 550 light years</p>\n<p>49,599 stars (63%) are located within 575 light years</p>\n<p>51,832 stars (66%) are located within 600 light years</p>\n<p>54,011 stars (69%) are located within 625 light years</p>\n<p>56,099 stars (71%) are located within 650 light years</p>\n<p>58,082 stars (74%) are located within 675 light years</p>\n<p>60,033 stars (76%) are located within 700 light years</p>\n<p>62,047 stars (79%) are located within 725 light years</p>\n<p>63,875 stars (81%) are located within 750 light years</p>\n<p>65,644 stars (83%) are located within 775 light years</p>\n<p>67,334 stars (85%) are located within 800 light years</p>\n<p>68,938 stars (87%) are located within 825 light years</p>\n<p>70,579 stars (90%) are located within 850 light years</p>\n<p>72,100 stars (91%) are located within 875 light years</p>\n<p>73,568 stars (93%) are located within 900 light years</p>\n<p>75,022 stars (95%) are located within 925 light years</p>\n<p>76,310 stars (97%) are located within 950 light years</p>\n<p>77,629 stars (99%) are located within 975 light years</p>\n<p>78,805 stars (100%) are located within 1000 light years</p>\n<pre><code># http://www.astronexus.com/hyg\nlibrary(tidyverse)\nlibrary(scales)\nlibrary(glue)\n\ncount_stars_within &lt;- function(distance) {\n dta &lt;- star %&gt;%\n filter(dist &lt;= distance)\n \n tibble(\n distance = distance,\n n = nrow(dta),\n percent = nrow(dta) / nrow(star)\n )\n}\n\nstar &lt;- read_csv(&quot;http://www.astronexus.com/files/downloads/hygdata_v3.csv.gz&quot;) %&gt;% \n select(id, proper, dist, x, y, z) %&gt;% \n # Remove missing data\n filter(dist != 100000.0) %&gt;% \n # Convert distances to light years\n mutate(dist = dist * 3.262) %&gt;% \n # Only keep stars within 1,000 light years\n filter(dist &lt;= 1000, dist &gt; 0)\n\nsummary(star$dist)\n\nmap_dfr(seq(from = 0, to = 1000, by = 25), count_stars_within) %&gt;%\n mutate(distance = glue(\n &quot;{comma(n)} stars ({percent(percent)}) are located within {distance} light years&quot;\n )) %&gt;%\n select(distance) %&gt;%\n write.table(&quot;clipboard&quot;, sep = &quot;\\t&quot;, row.names = FALSE)\n</code></pre>\n" }, { "answer_id": 180671, "author": "Ruadhan", "author_id": 39202, "author_profile": "https://worldbuilding.stackexchange.com/users/39202", "pm_score": 2, "selected": false, "text": "<p>If you're looking to get a feel for the scale, rather than perhaps deal with the exact numbers and trajectories</p>\n<p>You might try a simulation, such as <a href=\"http://spaceengine.org/\" rel=\"nofollow noreferrer\">Space Engine</a></p>\n<p>With this, you can <em>see</em> the distances involved and what stars are relatively nearer one another.<br />\nI think for story-telling purposes this is probably more valuable.</p>\n" }, { "answer_id": 180735, "author": "KerrAvon2055", "author_id": 48047, "author_profile": "https://worldbuilding.stackexchange.com/users/48047", "pm_score": 2, "selected": false, "text": "<p><strong><a href=\"https://en.wikipedia.org/wiki/2300_AD\" rel=\"nofollow noreferrer\">Traveller 2300</a> (roleplaying game)</strong></p>\n<p>One of the nice features of this roleplaying game was:</p>\n<blockquote>\n<p>The Near Star Catalog</p>\n<p>The Traveller: 2300universe deals with star systems within 50 light\nyears of Earth. Extensive research and analysis has produced the most\naccurate star map ever made. Never before has such a monumentouts task\nbeen undertaken, either in gaming or in science fiction: over 700\nstars in over 500 systems, on a 22&quot; x 25&quot; color map. Location, special\ntype, size and magnitude are documented in a separate star catalog.</p>\n</blockquote>\n<p>While I do not have a copy to check, I recall that all of the stars were listed with x, y, z coordinates to allow the distances between each star to be calculated using Pythagoras' Theorem. A quick Google indicates that while the information was the best available in 1986 when the game was published, comments such as <a href=\"http://forum.mongoosepublishing.com/viewtopic.php?t=93985\" rel=\"nofollow noreferrer\">this</a> thread cast some doubt on whether some of the details have stood the test of time. So while Renan's answer and others may give more easily used resources, the Traveller 2300 rulebook is a paper-and-pen resource that can be used completely offline. It certainly worked for those of us playing the game back in the late 1980s when we needed to calculate the distances between the origin and destination stars our characters were travelling between, although a calculator did come in handy.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/180629", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/77128/" ]

[ { "answer_id": 183373, "author": "Nosajimiki", "author_id": 57832, "author_profile": "https://worldbuilding.stackexchange.com/users/57832", "pm_score": 3, "selected": false, "text": "<h2>Elements of a Programmable Magic System</h2>\n<p>In order to have a programmable magic system like you are asking for, there are a few principles of programming you will want to consider in it's design.</p>\n<p><strong>A <a href=\"https://en.wikipedia.org/wiki/Library_(computing)\" rel=\"nofollow noreferrer\">Library</a> of Primitives:</strong></p>\n<p>Without predefined objects defining what a spell is and does, you do not have a spell crafting programing language, you just have a programing language. Your primitives are the basic building blocks of your system that tells the end user what abilities are at his disposal. So, all the code responsible for a spell would fall inside of this system of object classes that can be bound together to make a spell. Your Primitives are used to set both the ability and limits on spells; so, if I want to include teleport spell, the primitive called <code>teleport</code> would include inside it not just the code for moving a character between points, but formulas for determining mana cost, cool down timers, range limits, etc.</p>\n<p><strong>An Isolated <a href=\"https://en.wikipedia.org/wiki/SOLID\" rel=\"nofollow noreferrer\">SOLID</a> <a href=\"https://en.wikipedia.org/wiki/Application_programming_interface\" rel=\"nofollow noreferrer\">API</a> Architecture:</strong></p>\n<p>While this is generally a good idea in programming, it is 100% essential for any system that gives an end user this much access to parts of how your game runs. In short, you will want your primitives and game engine completely isolated from your magic programming interface by an API such that making a spell means using just the primitives and interfaces that the game's developer has given you. If a <code>fire-attack</code> has certain properties and procedures for establishing cost and potency, you don't want users to have access to change these properties and procedures. You just want them to call and extend on them. Red-stone programming is a good example of this. It does not let you change how minecraft works, it just lets you take certain things that you can already do in the game and build procedures to do it in useful patterns.</p>\n<p><strong><a href=\"https://en.wikipedia.org/wiki/Turing_completeness\" rel=\"nofollow noreferrer\">Turing Completeness</a>:</strong></p>\n<p>The difference between a spell crafting system like you see in Elder Scrolls and a spell programming system would be the ability to string things together in logical and repeatable operations. Including things like logical operators (and, if, or, etc.), recursive operators (while, for, goto, etc.), and the ability to define your own variables with your spells will allow players nearly infinite access to manipulate the logic behind spell casting.</p>\n<p><strong>Make the system accessible to a wide audience</strong>:</p>\n<p>Another feature I would suggest is to make spells able to be encrypted, shared, and sold. Most players will not want to program thier own spells in this much detail, but those that do will love it, and be able to make very advanced spells this way. By letting people hide the code of thier own spells to other players, it would encourage them to sell high-end spells on the community market.</p>\n<p>Using these principles, your &quot;spell-book&quot; might look something like this on the back-end, but hand coding could be substituted with a <a href=\"https://en.wikipedia.org/wiki/Visual_programming_language\" rel=\"nofollow noreferrer\">Visual Programming Interface</a> to reduce the leaning curve.</p>\n<pre><code>spell pummel(<span class=\"math-container\">$damage-low = 15, $</span>damage-high = 30, <span class=\"math-container\">$stunChance = 100, $</span>stunDuration = 1){ \n // Metadata like name, description, and permission can be added to your custom spells to help with non-casty in-game stuff.\n this.name = 'Throw Pummel';\n this.description = 'A simple attack spell for ending your foe rightly!';\n this.permission = 'public';\n cast ranged-attack({ // ranged-attack is a primitive for casting a spell which has certain properties you can define.\n element = 'kinetic',\n damage-low = <span class=\"math-container\">$damage-low,\n damage-high = $</span>damage-high,\n range = 50,\n accuracy = 80,\n stunChance = <span class=\"math-container\">$stunChance,\n stunDuration = $</span>stunDuration,\n special-effect = &quot;bolt&quot;,\n special-effect-tint = &quot;rgba(0,255,255,.75)&quot;\n }\n}\n\nspell chainPummel() (){\n this.name = 'Chain Pummel';\n this.description = 'Pummel up to 10 enemies in a row!';\n this.permission = 'private';\n for(i=0;i&lt;10;i++){\n if (target.alive == true) { // target is an API behavior allowing an interaction with the game-engine.\n cast pummel(5, 10, 100, .1); // pummel has now been defined as an instance of ranged-attack which can now be called like a primitive. Also, by passing variables with it you can customize the spell on the fly. In this case, by casting a weaker/cheaper version of the spell.\n delay (0.1); \n } else {\n setNewTarget('hostile'); // setNewTarget is an API behavior allowing an interaction with the game-engine.\n if (target.alive == true) {\n cast pummel(5, 10, 100, .1);\n delay (0.1); \n }\n }\n }\n}\n</code></pre>\n<p>You can see that there is a lot of control here to make unique and quite intelligent spells, but no where does this say what the spells will cost to cast or let you directly manipulate the environment. So, your game interface will need to calculate and output those details for you; so, if I were to sell you these spells, your spell book might look like this:</p>\n<blockquote>\n<p><strong>Throw Pummel</strong> [edit]</p>\n<p>Lvl.3 Spell (costs 55 mana)</p>\n<p>A simple attack spell for ending your foe rightly!</p>\n<p>Author: Nosajimiki</p>\n</blockquote>\n<blockquote>\n<p><strong>Chain Pummel</strong></p>\n<p>Lvl.6 Spell (costs 21-210 mana)</p>\n<p><em>Prereqs: Throw Pummel</em></p>\n<p>Pummel up to 10 enemies in a row!</p>\n<p>Author: Nosajimiki</p>\n</blockquote>\n<p><em>Original answer may prove helpful for context, but does not answer the question as it has been revised.</em></p>\n<p><strike><h2>Yes, it's been tried</h2></p>\n<p>Yes, first place I remember seeing something like that is in the magic crafting system in Elder Scrolls:Oblivion. Basically you could combine any combination of spell properties to create custom spells and the difficulty to cast the spell was based on what properties you gave it. So, you could take a fire spell and decide if you wanted it to be touch or ranged, add a blast radius if you want it to be AOE, and you could then add a DoT property if you wanted it to burn instead of do all the damage at once, etc. and all the different properties of a spell either made it more or less expensive to cast so you could balance it however you wanted it.</p>\n<p>While the game had a bunch of ready-made spells for noobs to start with, once you got in good with the mages guild, these procedurally built spells literally allowed for millions of combinations of spells based on just a small handful of properties that had to be discreetly designed by the developers.</p>\n<p>It had an alchemy system for brewing potions procedurally based on what ingredients you used too.</p>\n<h2>How to make it more of a \"science\"</h2>\n<p>The thing about systems like the one used by Elder Scrolls was that it was designed to be as balanced and intuitive as possible; so, in the end it does not matter how you customized a spell, you'd never really hit much above your weight class just by using a cleaver combination of elements.</p>\n<p>For this you need a system that is asymmetric, exploitable, and full of undocumented features.</p>\n<p>Now this sounds like a terrible premise for game design, if a game has enough strange mechanics that are not explained in game, then researching and experimenting to see what they are becomes a meaningful part of the game unto itself.</p>\n<p><strong>How you could apply this to a magic system:</strong></p>\n<p>In the spell crafting section of the game you could choose what element you want an attack to be (fire, wind, water, and earth). On paper they all do the same damage and cost the same mana; so, being a noob, you just pick one at random. The game does not tell you this, but earth spells do a little extra armor penetration against heavy armor, fire spells have a higher crit rate, water spells can interrupt another player's spells, and wind pushed the opponent back a little. So, only through playing the game and making observations do you learn there are cases where one is better than the other. You may also notice that as you add levels to each element that they scale differently. Both 1 level of fire damage and one level of wind damage do 10 points of damage, but a level 5 fire does 50 damage, and wind only does 30, unless you can use the push effect to slam the opponent against a wall in which case you do 60.</p>\n<p>Then you can make things even more confusing with environmental variables like. Fire spells can be blinding bright when cast at night, water spells do less damage in a desert, wind spells are much less useful in open areas with nothing to push people into, and earth spells might do different damage based on what kind of ground you are standing on.</p>\n<p>So what this means for game play is that a wise wizard may know that he is going up against a mage who prefers Earth spells; so, he puts on some gambeson armor so he can move faster and absorb the impacts. He then lures the other wizard out onto a sandy beach so that his bolder spell suddenly starts throwing balls of mostly harmless sand. He then drinks a potion of x-ray vision and casts a wind AOE spell to kick up cloud of sand to blind his opponent. So, while the wiser wizard may be a lower level, he could still utterly destroy his opponent if he's thoroughly researched the side effects of spells and abilities.</p>\n<p>Another layer of complexity could be that the ratios of levels you put into a spell has certain optimal levels; so, a spell that does Fire damage may do the most damage per level of fire damage if 50% of the spells levels are devoted to damage, but more or less and you get a diminishing return</p>\n<blockquote>\n<p>To phrase this a different way: I want a set of physics rules that\nallows players to create spells in game as various sorts of\n“technology”. Similar to how players build red stone flying machines\nfrom red stone and pistons in Minecraft,</p>\n</blockquote>\n<p>Add a system for making spell combo macros. Where your spell tray can trigger conditional logic that activates spells and abilities. So, let's say your system does not allow flight, but it does allow mid-air jumping, you might create a macro that turns on and off looping mid-air jumping. Many gamers build macros to &quot;cheat&quot; anyway, you'd just make it a part of the game to begin with.</strike></p>\n" }, { "answer_id": 183388, "author": "Trioxidane", "author_id": 77012, "author_profile": "https://worldbuilding.stackexchange.com/users/77012", "pm_score": 2, "selected": false, "text": "<p><strong>Calculus</strong></p>\n<p>Sometimes the answer can be easy and cheeky. Any spell needs to be calculated and understood. A fireball? You need to calculate the volume, heat, material it burns on, how it travels and <em>understand</em> it all. This has many advantages.</p>\n<ul>\n<li>Your world literally works on Calculus, making a everything computable.</li>\n<li>Focus is simply how well you can focus on the calculations. More calculations means more tiredness and thus less focus. It returns after a bit, unless you did too many and need some more rest.</li>\n<li>It limits itself. You can calculate a nuclear explosion, but you cannot <em>understand</em> it. A candle or campfire is understandable. A nuclear explosion is simply so big we have nothing to relate it to.</li>\n<li>Some facets are more understanding based. Taking over someone's mind requires understanding them and can't really be calculated.</li>\n<li>Differences in understanding and calculating of different subjects shows the differences in magic ability.</li>\n<li>Progression is done by experience. If you're more experienced in calculating and understanding things, it can get easier.</li>\n</ul>\n<p>You might think lots is too difficult to calculate. But with many things it's calculating from an ideal perspective. Like many physics using a vacuum and spherical objects etc. Using it on real world objects means you need to know more about the environment.</p>\n<p>Understanding would also prevent computers from simply calculating things whenever they see fit. If something is inscribed with a formula, it'll only be magic if it is understood. This way blocks like the redstone machines can be created, each with their own function.</p>\n<p>The world runs on an unseen calculating power. If things are out of view, it requires less calculating power. Thus it can run faster if no one is watching the magic happen.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/183368", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/518/" ]

[ { "answer_id": 184710, "author": "Halfthawed", "author_id": 64961, "author_profile": "https://worldbuilding.stackexchange.com/users/64961", "pm_score": 2, "selected": false, "text": "<p><strong>By being an arms merchant</strong></p>\n<p>In any war between two sides, the one who always profits are the people selling weapons. (Assuming, of course, that the ones producing the weapons are independent of the ones fighting.) And, if you can be the person selling weapons to <em>both</em> sides - well, that's mountains of profits for as long as the war goes on, and you have all the incentive in the world to keep this ongoing. This is why no one likes war profiteers.</p>\n<p>Someone who is evil and has access to portals just because the world's ultimate black market weapons dealer. Let's say one of these portals leads to a world with technology 150 years ago? Well, just travel there and sell some modern arms in exchange for rare metals - gold, platinum, etc. One of these portal leads to somewhere technologically ahead of us? Go there, spend some of those rare metals, and come back to Earth selling your futuristic arms to the highest bidder. Not to mention that traveling via portal has the potential to let you get around restrictions and blockades with ease, so your smuggling will be very hard to stop.</p>\n<p>Sure, you'll cause untold havoc and destruction by giving horrifyingly powerful weapons to people who really shouldn't have them and possibly lead to the death and exploitation of entire worlds, but at the end of the day, you'll be filthy rich. So you have to ask yourself: &quot;If I was extraordinarily evil, would I care about crushing the lives of millions just so I could be fabulously wealthy?&quot; (Hopefully, the answer is still no, because that's an awfully large cost. But that's pretty much one of the worse things I think you can do with this.)</p>\n" }, { "answer_id": 184713, "author": "Mary", "author_id": 75618, "author_profile": "https://worldbuilding.stackexchange.com/users/75618", "pm_score": 1, "selected": false, "text": "<h2>Sell the access</h2>\n<ol>\n<li>Allow criminals to escape the police. Other possibilities are debtors, or other people with reason to flee. (The last can be ambiguous, morally, or turn on the extortionate price). This can be temporary or permanent.</li>\n<li>Enable smuggling. This might be from dimension to dimension. Only if the portals are situated right can you smuggle from one region in your own dimension to another. (Evil can be variable depending on the reason for the smuggling.)</li>\n<li>Enable resource extraction. This world never discovered that there were emeralds here? We'll just mine them and bring them back to our own world.</li>\n</ol>\n" }, { "answer_id": 184730, "author": "Jiří Baum", "author_id": 79142, "author_profile": "https://worldbuilding.stackexchange.com/users/79142", "pm_score": 0, "selected": false, "text": "<p><strong>Price arbitrage</strong></p>\n<p>Find pairs of commodities that have different price ratios in the various worlds, then trade them. This might be considered good or evil, but it's certainly greed, or it can be used to finance evil acts elsewhere.</p>\n" }, { "answer_id": 184731, "author": "Klaus Æ. Mogensen", "author_id": 62769, "author_profile": "https://worldbuilding.stackexchange.com/users/62769", "pm_score": 1, "selected": false, "text": "<p><strong>GET RID OF PEOPLE</strong></p>\n<p>When criminals or corrupt politicians or corporations want to 'vanish' people, what better way than having them removed to another dimension? They will literally be gone without a trace. It wouldn't be anywhere as near as bad as murder, since the victim would be able to survive (and possibly even thrive) on the other side of the portal. This would also make it a moral grey zone that the 'archangels' may find acceptable.</p>\n<p>This, of course, depends on how common the portals are. You wouldn't want to carry abducted victims across half a continent to get to a portal you can chuck them through.</p>\n<p><strong>SELL STORIES AND MUSIC</strong></p>\n<p>Books, plays, and myths from one world can be sold in another world as fantasy or science fiction. An archangel could set himself up as a very prolific writer doing stories set in a rich and coherent 'invented' world, or as a composer writing music and songs that are literally &quot;out of this world&quot;. Again, this is a moral grey zone - you could even argue that it counts as doing good - and an archangel could make good money with very little work involved (mainly translation).</p>\n<p><strong>WASTE DISPOSAL</strong></p>\n<p>Offer to remove waste at low prices - even toxic or radioactive waste. Dump it through a portal to an uninhabited world or a remote area of a thinly populated world. Who knows, if you dump biological waste on a dead planet, you might even kickstart life there. Not really evil, though other Arcanes might frown on it.</p>\n" }, { "answer_id": 184735, "author": "DG79", "author_id": 78830, "author_profile": "https://worldbuilding.stackexchange.com/users/78830", "pm_score": 0, "selected": false, "text": "<p>In your story there're a lot of possible evil person that have this ability.</p>\n<ol>\n<li>The Merchant, he can trade or steal technology and resource in a dimension with low defense for selling in his dimension to a Criminal Organization or other person.</li>\n<li>The Assassin, is mind is corrupted and kill persons in any dimension for money or other stuff.</li>\n<li>The Leader of Crime Organization, he gain so much money during the dimensional change that create a crime organization with creature (if it possible tranport creature through the &quot;Arcs&quot;) of another dimension. The ultimate goal of this Corrupted Arcane is a dictator of state or whole World.</li>\n<li>The Mad, travelling in a foolish dimension he's got insane when encounter a strange creature or other like that, so he can choose to find a way to open a portal much bigger that can transport the strange creature.</li>\n<li>The Enslaver, travelling dimension selling creature for his personal power or working for someone.</li>\n</ol>\n<p>These are only 5 type, but i think the ability to see a dimensional passage and the possibility to travel to another dimension is a interesting plot for a story, there are different ways that a person with that gift can do for good or evil.\nPerhaps the Good Arcane can develope an Organization that fight the &quot;Archangels&quot;, i think that using the term &quot;Archangels&quot; is too much linked with religion.</p>\n<p>You can use a scenario for a Dimensional War.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/184708", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/78540/" ]

[ { "answer_id": 184765, "author": "Halfthawed", "author_id": 64961, "author_profile": "https://worldbuilding.stackexchange.com/users/64961", "pm_score": 3, "selected": false, "text": "<p><strong>About 100 billion people. Roughly.</strong></p>\n<p>I'm ignoring the difference between the male/female survival rates (which shouldn't exist anyway because males aren't more valuable than females even with a 9/1 gender ratio) and I'm also ignoring the death rate because it's about 1%, and therefore of little consequences. There are 1080 females in the first generation, and they'll each have 12 children, of which 10 of them will be female. Scratch off the 80 females to represent the all the children who won't survive, and we're left with 1000. Assuming the same rate as the initial population, that means that the female population will grow 10x each generation, and the male numbers will be between 1/9 and 1/8 that of the female population. A generation is between 20-30 years, which means that by the time the second colony ship shows up, there's already 100x the population on the planet than the ship, so we get to ignore those entirely, because we're doing a rough estimate. There are 7-9 generations between the landing and 207 years into the future, so by that estimate we have a total population of roughly 100,000,000,000 women and 12,500,000,000 men.</p>\n<p>This number may be a tad higher than you expected (and in fact exceeds the current Earth population) but if you make every female required to produce 10 female offspring and let it go for eight generations, this kind of exponential growth is simply what happens. At this point it stops being a colony because its population has simply exceeded Earth's.</p>\n" }, { "answer_id": 184766, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 3, "selected": false, "text": "<p><strong>Gender ratios do not matter in your scenario.</strong></p>\n<p>You have mandated the # of offspring per woman. It does not really matter how many men there are or if there are any; if there are frozen eggs there are certainly frozen sperm. If you want to maximize population growth (it seems you do) dispense with males entirely and make babies with frozen xx sperm. That maximizes genetic diversity. You can have some XY frozen away for when you want your population growth to level off an bring males into the population.</p>\n<p>Maybe you are unconcerned about genetic diversity and you want some real males for your story. One or 2 will suffice. One bull can sire thousands of calves. That bull never sees a cow. It is all done artificially, minimizing waste and the need to tote the bull around the world.</p>\n<p>Your population will be determined by the number of females. Males are just there. The math: assume 25 year reproductive life for woman. At t+25 years population of females = ((pop of females at time t)+((pop of females at time t)*7/8))*0.875</p>\n<p>Males is the same but *1/8.</p>\n" }, { "answer_id": 184780, "author": "Ash", "author_id": 78800, "author_profile": "https://worldbuilding.stackexchange.com/users/78800", "pm_score": 6, "selected": true, "text": "<h3>354 Thousand <a href=\"https://godbolt.org/z/zoPYsz\" rel=\"noreferrer\">https://godbolt.org/z/zoPYsz</a></h3>\n<p>If you bring 10,000 embryos on the first ship, and 10,000 on the second ship, you'll run out in the 25th year, and 58th year.</p>\n<p>I modified your death rate so that when people hit 70 years old it shot up to 10% per year. As otherwise we had hundreds of 100 year olds.</p>\n<p>That link allows you to change the values and they should update the simulation in the output window. I'm sorry its in C++, its the only language I know really well.</p>\n<ul>\n<li>Total 354,102</li>\n<li>Infants 39,882</li>\n<li>Children 53,934</li>\n<li>Teens 49,704</li>\n<li>YoungAdults 79,456</li>\n<li>Adults 91,140</li>\n<li>Seniors 39,986</li>\n<li>Males 181,138</li>\n<li>Females 172,964</li>\n</ul>\n<p>In the year 207, there are 16 males and 13 females turning 100 years old. There are 8300 babies born that year.</p>\n<p>The year 58 had 6135 females and 1152 males born. Birth rates dropped for the next 100 years, until the year 131, (7600 births).</p>\n<h2>What would really happen?</h2>\n<p>Each woman has 12 direct children, the father, grandma, and grandfather are spread to thin to help (they'd have to help raise: 96 children, 240 children, and 9216 children respectively). This is just too much.</p>\n<h3>They're going to revolt</h3>\n<p>I'm not a woman so I'm not 100% sure on this, but I have a sneaking suspicion they don't like being used as baby factories and forced to raise 12 kids (essentially alone - remember the &quot;husband&quot; has 8 other women in his <a href=\"https://www.urbandictionary.com/define.php?term=Polycule\" rel=\"noreferrer\">polycule</a>). The first generation might be optimistic, but mental health would be a real issue, there'd be anger and resentment, but the second generation, born in the first few years and about to be implanted on their 18th birthday will not share that optimism, and you'll have a suffragette movement around about year 20.</p>\n<p>... If a woman refuses to be a baby factory are we really going impregnate her against her will?</p>\n<p>There's a whole bunch of LGBT issues also not considered here.</p>\n<h3>... And starve</h3>\n<p>Farming is going to be a real issue, take year 15 as an example:</p>\n<p>There will be:</p>\n<ul>\n<li>Infants 2682</li>\n<li>Children 6749</li>\n<li>Teens 853 (13 and 14 year old)</li>\n<li>Adults 984 (90 males and 894 females)</li>\n</ul>\n<p>Those 900 woman are going to be fully occupied nursing 3 infants each, and yelling discipline at 7 misbehaving children. Assuming all the men are farmers, they're going to need to grow food for 11,000 people, 122 mouths to feed each. With current American tech they can hit 166 mouths fed per farmer. You've regressed tech for this (for the infant mortality figure), so I've got to assume farming has as well. In postwar american, <a href=\"https://recipes.howstuffworks.com/how-many-farmer-feed.htm\" rel=\"noreferrer\">1 Farmer feeds 73 people</a>. Putting the tweens and children in the field may put starvation off a bit, but they need to be in school, otherwise you're society is going to regress very quickly, and you'll be illiterate within a few generations.</p>\n<p>Edit: actually that 1 in 73 assumes theres people refining fuel, making fertilizers and pesticides, making replacmenet parts, and spitting out new machinery at an exponential rate. That's not going to happen as everyone is busy making babies or growing food. You'll regress to 1930s level farm output, which is 1 farmer per 4 mouths.</p>\n<h3>... and die of exposure</h3>\n<p>The growth rate in the number of buildings is also extreme.</p>\n<p>Each male in the first 60 years has to build 80 houses in their lifetime (one for each of his partners daughters), each house has to hold a family of up to 14 (most 13, but the males need to live somewhere too). That's a lot to build, remember he's making his own nails, cutting his own logs, etc, all while farming food for 122 people.</p>\n<h3>So slow the implantation down</h3>\n<p>Embryos can be stored for a while, so no need to implant them ASAP. Changing the requirements to 3 natural children, and 3 embryos (so 6 children total per woman) the population at year 207 is 345,000.</p>\n<h3>I wrote a calculator for this:</h3>\n<p><a href=\"https://godbolt.org/z/zoPYsz\" rel=\"noreferrer\">https://godbolt.org/z/zoPYsz</a></p>\n<p><a href=\"https://i.stack.imgur.com/yUuCO.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/yUuCO.png\" alt=\"enter image description here\" /></a></p>\n<p>The panel on the left is C++ code, the pannel on the right is the output.</p>\n<p>Just change the numbers on the left (eg what years do women have children), and the log will update on the right.</p>\n<p>Here's the source if the link goes dead (C++17)</p>\n<pre><code>#include &lt;vector&gt;\n#include &lt;set&gt;\n#include &lt;iostream&gt;\n#include &lt;numeric&gt;\n\nint main()\n{\n // There are 0 children aged 0 to 17 on the first ship\n std::vector&lt;size_t&gt; males(18,0);\n std::vector&lt;size_t&gt; females(18,0);\n\n // Our initial colonists\n males.push_back(120);\n females.push_back(1080);\n\n auto survivalRateMaleChild = 0.99;\n auto survivalRateFemaleChild = 0.94;\n auto survivalRateEveryone = (1000.0 - 12.0) / 1000.0;\n\n auto simulatedYears = 207;\n\n // What years of her life does a given woman have children?\n std::set&lt;int&gt; randomChildAt = {19, 25, 35};\n std::set&lt;int&gt; femaleChildAt = {21, 22, 23, 24, 26, 27, 28, 29, 30};\n \n // Finite number of embryos\n auto embryos = 10000;\n\n for (auto year = 0; year &lt; simulatedYears; year++)\n {\n // Calculate our births\n\n size_t newMales = 0;\n size_t newFemales = 0;\n\n if (embryos &gt; 0)\n {\n for (auto i : femaleChildAt)\n {\n if (i &gt;= females.size()) continue;\n newFemales += females[i];\n }\n }\n embryos -= newFemales;\n\n if (embryos &lt; 0 &amp;&amp; newFemales)\n {\n std::cout &lt;&lt; &quot;Run out of embryos\\n&quot;;\n }\n\n for (auto i : randomChildAt)\n {\n if (i &gt;= females.size()) continue;\n newFemales += females[i] / 2;\n newMales += females[i] / 2;\n }\n\n males.insert(males.begin(), newMales);\n females.insert(females.begin(), newFemales);\n\n // Kill off our infant mortality children (they all die at age 5)\n males[5] *= survivalRateMaleChild;\n females[5] *= survivalRateFemaleChild;\n\n // Kill of our random death rate. Child infant mortality is\n // calcualted seperately, we don't want to double kill them.\n for (auto age = 18; age &lt; females.size(); age++)\n {\n females[age] *= survivalRateEveryone;\n males[age] *= survivalRateEveryone;\n }\n\n // Kill of our seniors, 10% die per year\n for (auto age = 70; age &lt; females.size(); age++)\n {\n females[age] *= 0.90;\n males[age] *= 0.90;\n }\n\n // Add the second ship, which is full of 18 year olds.\n if (year == 57)\n {\n males[18] += 120;\n females[18] += 1080;\n embryos += 10000;\n }\n\n // Print some stats\n\n std::cout &lt;&lt; \n &quot;Y: &quot; &lt;&lt; year &lt;&lt; &quot;. &quot; \n &lt;&lt; newMales &lt;&lt; &quot;m and &quot; \n &lt;&lt; newFemales &lt;&lt; &quot;f born. Pop: &quot;\n &lt;&lt; std::accumulate(males.begin(), males.end(), 0) +\n std::accumulate(females.begin(), females.end(), 0) &lt;&lt; &quot;\\n&quot;;\n }\n\n\n std::cout &lt;&lt; &quot;At end of simulation: \\n&quot;;\n\n size_t total = 0;\n size_t infants = 0;\n size_t children = 0;\n size_t teenages = 0;\n size_t youngAdults = 0;\n size_t adults = 0;\n size_t seniors = 0;\n size_t male = 0;\n size_t female = 0;\n for (auto age = 0; age &lt; 100; age++)\n {\n if (age &gt;= females.size()) continue;\n std::cout &lt;&lt; age &lt;&lt; &quot; yr olds: &quot; &lt;&lt; males[age] &lt;&lt; &quot; males and &quot; &lt;&lt; females[age] &lt;&lt; &quot; females.\\n&quot;;\n \n auto t = males[age] + females[age];\n \n male += males[age];\n female += females[age];\n\n if (age &lt; 5) infants += t;\n else if (age &lt; 13) children += t;\n else if (age &lt; 20) teenages += t;\n else if (age &lt; 35) youngAdults += t;\n else if (age &lt; 60) adults += t;\n else seniors += t;\n\n total += t;\n }\n\n std::cout &lt;&lt; &quot;Total &quot; &lt;&lt; total &lt;&lt; &quot;\\n&quot;;\n std::cout &lt;&lt; &quot;Infants &quot; &lt;&lt; infants &lt;&lt; &quot;\\n&quot;;\n std::cout &lt;&lt; &quot;Children &quot; &lt;&lt; children &lt;&lt; &quot;\\n&quot;;\n std::cout &lt;&lt; &quot;Teens &quot; &lt;&lt; teenages &lt;&lt; &quot;\\n&quot;;\n std::cout &lt;&lt; &quot;YoungAdults &quot; &lt;&lt; youngAdults &lt;&lt; &quot;\\n&quot;;\n std::cout &lt;&lt; &quot;Adults &quot; &lt;&lt; adults &lt;&lt; &quot;\\n&quot;;\n std::cout &lt;&lt; &quot;Seniors &quot; &lt;&lt; seniors &lt;&lt; &quot;\\n&quot;;\n\n std::cout &lt;&lt; &quot;Males &quot; &lt;&lt; male &lt;&lt; &quot;\\n&quot;;\n std::cout &lt;&lt; &quot;Females &quot; &lt;&lt; female &lt;&lt; &quot;\\n&quot;;\n return 0;\n}\n</code></pre>\n<p>Year by year running log of births and population</p>\n<pre><code>Y: 0. 0m and 0f born. Pop: 1185\nY: 1. 533m and 533f born. Pop: 2236\nY: 2. 0m and 0f born. Pop: 2221\nY: 3. 0m and 1041f born. Pop: 3247\nY: 4. 0m and 1028f born. Pop: 4260\nY: 5. 0m and 1015f born. Pop: 5260\nY: 6. 0m and 1002f born. Pop: 6209\nY: 7. 494m and 494f born. Pop: 7183\nY: 8. 0m and 977f born. Pop: 8083\nY: 9. 0m and 965f born. Pop: 8972\nY: 10. 0m and 953f born. Pop: 9850\nY: 11. 0m and 941f born. Pop: 10716\nY: 12. 0m and 929f born. Pop: 11596\nY: 13. 0m and 0f born. Pop: 11523\nY: 14. 0m and 0f born. Pop: 11452\nY: 15. 0m and 0f born. Pop: 11381\nY: 16. 0m and 0f born. Pop: 11311\nY: 17. 436m and 436f born. Pop: 12114\nY: 18. 0m and 0f born. Pop: 12101\nY: 19. 0m and 0f born. Pop: 12075\nY: 20. 0m and 0f born. Pop: 12050\nY: 21. 244m and 244f born. Pop: 12502\nY: 22. 0m and 0f born. Pop: 12422\nY: 23. 477m and 953f born. Pop: 13793\nY: 24. 471m and 941f born. Pop: 15134\nRun out of embryos\nY: 25. 465m and 1859f born. Pop: 17375\nY: 26. 458m and 458f born. Pop: 18178\nY: 27. 452m and 452f born. Pop: 18981\nY: 28. 447m and 447f born. Pop: 19700\nY: 29. 884m and 884f born. Pop: 21284\nY: 30. 872m and 872f born. Pop: 22778\nY: 31. 862m and 862f born. Pop: 24336\nY: 32. 850m and 850f born. Pop: 25870\nY: 33. 208m and 208f born. Pop: 26123\nY: 34. 414m and 414f born. Pop: 26766\nY: 35. 410m and 410f born. Pop: 27391\nY: 36. 404m and 404f born. Pop: 28005\nY: 37. 796m and 796f born. Pop: 29405\nY: 38. 394m and 394f born. Pop: 30047\nY: 39. 389m and 389f born. Pop: 30660\nY: 40. 384m and 384f born. Pop: 31263\nY: 41. 490m and 490f born. Pop: 32061\nY: 42. 374m and 374f born. Pop: 32593\nY: 43. 803m and 803f born. Pop: 33984\nY: 44. 796m and 796f born. Pop: 35349\nY: 45. 1213m and 1213f born. Pop: 37536\nY: 46. 565m and 565f born. Pop: 38408\nY: 47. 660m and 660f born. Pop: 39463\nY: 48. 551m and 551f born. Pop: 40248\nY: 49. 809m and 809f born. Pop: 41531\nY: 50. 798m and 798f born. Pop: 42743\nY: 51. 1186m and 1186f born. Pop: 44722\nY: 52. 582m and 582f born. Pop: 45491\nY: 53. 445m and 445f born. Pop: 45991\nY: 54. 378m and 378f born. Pop: 46338\nY: 55. 562m and 562f born. Pop: 47047\nY: 56. 554m and 554f born. Pop: 47708\nY: 57. 818m and 818f born. Pop: 50134\nY: 58. 541m and 4677f born. Pop: 54932\nRun out of embryos\nY: 59. 1152m and 6135f born. Pop: 61797\nY: 60. 701m and 701f born. Pop: 62763\nY: 61. 1095m and 1095f born. Pop: 64500\nY: 62. 507m and 507f born. Pop: 65036\nY: 63. 871m and 871f born. Pop: 66047\nY: 64. 694m and 694f born. Pop: 66606\nY: 65. 1545m and 1545f born. Pop: 69192\nY: 66. 744m and 744f born. Pop: 70142\nY: 67. 830m and 830f born. Pop: 71293\nY: 68. 725m and 725f born. Pop: 72199\nY: 69. 784m and 784f born. Pop: 73214\nY: 70. 856m and 856f born. Pop: 74303\nY: 71. 1209m and 1209f born. Pop: 76098\nY: 72. 653m and 653f born. Pop: 76780\nY: 73. 779m and 779f born. Pop: 77663\nY: 74. 550m and 550f born. Pop: 78045\nY: 75. 1182m and 1182f born. Pop: 79646\nY: 76. 733m and 733f born. Pop: 80237\nY: 77. 1058m and 1058f born. Pop: 81416\nY: 78. 2528m and 2528f born. Pop: 85495\nY: 79. 3300m and 3300f born. Pop: 91098\nY: 80. 777m and 777f born. Pop: 91590\nY: 81. 1193m and 1193f born. Pop: 92929\nY: 82. 675m and 675f born. Pop: 93190\nY: 83. 991m and 991f born. Pop: 93984\nY: 84. 2514m and 2514f born. Pop: 97801\nY: 85. 3625m and 3625f born. Pop: 104035\nY: 86. 935m and 935f born. Pop: 104873\nY: 87. 1289m and 1289f born. Pop: 106431\nY: 88. 761m and 761f born. Pop: 106942\nY: 89. 892m and 892f born. Pop: 107606\nY: 90. 825m and 825f born. Pop: 108071\nY: 91. 1419m and 1419f born. Pop: 109902\nY: 92. 818m and 818f born. Pop: 110519\nY: 93. 1014m and 1014f born. Pop: 111492\nY: 94. 2322m and 2322f born. Pop: 115018\nY: 95. 3188m and 3188f born. Pop: 120184\nY: 96. 959m and 959f born. Pop: 120792\nY: 97. 1408m and 1408f born. Pop: 122265\nY: 98. 1623m and 1623f born. Pop: 124147\nY: 99. 2168m and 2168f born. Pop: 126967\nY: 100. 847m and 847f born. Pop: 127044\nY: 101. 1628m and 1628f born. Pop: 128796\nY: 102. 897m and 897f born. Pop: 128979\nY: 103. 1212m and 1212f born. Pop: 129751\nY: 104. 2498m and 2498f born. Pop: 133069\nY: 105. 3360m and 3360f born. Pop: 138194\nY: 106. 1076m and 1076f born. Pop: 138709\nY: 107. 1549m and 1549f born. Pop: 140200\nY: 108. 875m and 875f born. Pop: 140326\nY: 109. 1118m and 1118f born. Pop: 140784\nY: 110. 1650m and 1650f born. Pop: 142267\nY: 111. 2638m and 2638f born. Pop: 145891\nY: 112. 1043m and 1043f born. Pop: 146277\nY: 113. 1408m and 1408f born. Pop: 147364\nY: 114. 2338m and 2338f born. Pop: 150270\nY: 115. 3084m and 3084f born. Pop: 154552\nY: 116. 1078m and 1078f born. Pop: 154738\nY: 117. 1695m and 1695f born. Pop: 156234\nY: 118. 1340m and 1340f born. Pop: 157007\nY: 119. 1793m and 1793f born. Pop: 158581\nY: 120. 2322m and 2322f born. Pop: 161157\nY: 121. 3470m and 3470f born. Pop: 166111\nY: 122. 1167m and 1167f born. Pop: 166396\nY: 123. 1637m and 1637f born. Pop: 167614\nY: 124. 2118m and 2118f born. Pop: 169794\nY: 125. 2797m and 2797f born. Pop: 173291\nY: 126. 1160m and 1160f born. Pop: 173447\nY: 127. 1934m and 1934f born. Pop: 175290\nY: 128. 1087m and 1087f born. Pop: 175195\nY: 129. 1406m and 1406f born. Pop: 175387\nY: 130. 2693m and 2693f born. Pop: 178162\nY: 131. 3842m and 3842f born. Pop: 183353\nY: 132. 1293m and 1293f born. Pop: 183435\nY: 133. 1831m and 1831f born. Pop: 184628\nY: 134. 2052m and 2052f born. Pop: 186271\nY: 135. 2704m and 2704f born. Pop: 189062\nY: 136. 1512m and 1512f born. Pop: 189424\nY: 137. 2511m and 2511f born. Pop: 191965\nY: 138. 1392m and 1392f born. Pop: 192236\nY: 139. 1875m and 1875f born. Pop: 193417\nY: 140. 2999m and 2999f born. Pop: 196814\nY: 141. 4172m and 4172f born. Pop: 202595\nY: 142. 1395m and 1395f born. Pop: 202764\nY: 143. 2052m and 2052f born. Pop: 204309\nY: 144. 1866m and 1866f born. Pop: 205478\nY: 145. 2463m and 2463f born. Pop: 207728\nY: 146. 2138m and 2138f born. Pop: 209263\nY: 147. 3357m and 3357f born. Pop: 213413\nY: 148. 1382m and 1382f born. Pop: 213376\nY: 149. 1868m and 1868f born. Pop: 214041\nY: 150. 3015m and 3015f born. Pop: 217020\nY: 151. 4115m and 4115f born. Pop: 222220\nY: 152. 1489m and 1489f born. Pop: 222131\nY: 153. 2299m and 2299f born. Pop: 223795\nY: 154. 1903m and 1903f born. Pop: 224499\nY: 155. 2511m and 2511f born. Pop: 226080\nY: 156. 2713m and 2713f born. Pop: 228055\nY: 157. 4096m and 4096f born. Pop: 232993\nY: 158. 1624m and 1624f born. Pop: 232977\nY: 159. 2253m and 2253f born. Pop: 234239\nY: 160. 3044m and 3044f born. Pop: 237092\nY: 161. 4118m and 4118f born. Pop: 242053\nY: 162. 1717m and 1717f born. Pop: 242162\nY: 163. 2737m and 2737f born. Pop: 244489\nY: 164. 1853m and 1853f born. Pop: 244869\nY: 165. 2455m and 2455f born. Pop: 246181\nY: 166. 3272m and 3272f born. Pop: 249116\nY: 167. 4766m and 4766f born. Pop: 255204\nY: 168. 1710m and 1710f born. Pop: 255074\nY: 169. 2417m and 2417f born. Pop: 256290\nY: 170. 2948m and 2948f born. Pop: 258612\nY: 171. 3954m and 3954f born. Pop: 262866\nY: 172. 2159m and 2159f born. Pop: 263481\nY: 173. 3430m and 3430f born. Pop: 266861\nY: 174. 1981m and 1981f born. Pop: 267155\nY: 175. 2650m and 2650f born. Pop: 268513\nY: 176. 3658m and 3658f born. Pop: 271891\nY: 177. 5205m and 5205f born. Pop: 278496\nY: 178. 1900m and 1900f born. Pop: 278446\nY: 179. 2783m and 2783f born. Pop: 280252\nY: 180. 2907m and 2907f born. Pop: 282257\nY: 181. 3885m and 3885f born. Pop: 286016\nY: 182. 2745m and 2745f born. Pop: 287447\nY: 183. 4266m and 4266f born. Pop: 292152\nY: 184. 2058m and 2058f born. Pop: 292271\nY: 185. 2785m and 2785f born. Pop: 293619\nY: 186. 3933m and 3933f born. Pop: 297289\nY: 187. 5492m and 5492f born. Pop: 304145\nY: 188. 2072m and 2072f born. Pop: 304075\nY: 189. 3138m and 3138f born. Pop: 306233\nY: 190. 2855m and 2855f born. Pop: 307707\nY: 191. 3804m and 3804f born. Pop: 310799\nY: 192. 3404m and 3404f born. Pop: 313075\nY: 193. 5150m and 5150f born. Pop: 319083\nY: 194. 2245m and 2245f born. Pop: 319144\nY: 195. 3091m and 3091f born. Pop: 320760\nY: 196. 4080m and 4080f born. Pop: 324370\nY: 197. 5624m and 5624f born. Pop: 331087\nY: 198. 2435m and 2435f born. Pop: 331364\nY: 199. 3769m and 3769f born. Pop: 334521\nY: 200. 2872m and 2872f born. Pop: 335699\nY: 201. 3833m and 3833f born. Pop: 338495\nY: 202. 4051m and 4051f born. Pop: 341704\nY: 203. 5973m and 5973f born. Pop: 348982\nY: 204. 2394m and 2394f born. Pop: 348960\nY: 205. 3370m and 3370f born. Pop: 350811\nY: 206. 4153m and 4153f born. Pop: 354227\n</code></pre>\n<p>And breakdown of those alive at year 207:</p>\n<pre><code>0 yr olds: 4153 males and 4153 females.\n1 yr olds: 3370 males and 3370 females.\n2 yr olds: 2394 males and 2394 females.\n3 yr olds: 5973 males and 5973 females.\n4 yr olds: 4051 males and 4051 females.\n5 yr olds: 3794 males and 3603 females.\n6 yr olds: 2843 males and 2699 females.\n7 yr olds: 3731 males and 3542 females.\n8 yr olds: 2410 males and 2288 females.\n9 yr olds: 5567 males and 5286 females.\n10 yr olds: 4039 males and 3835 females.\n11 yr olds: 3060 males and 2905 females.\n12 yr olds: 2222 males and 2110 females.\n13 yr olds: 5098 males and 4841 females.\n14 yr olds: 3369 males and 3199 females.\n15 yr olds: 3765 males and 3575 females.\n16 yr olds: 2826 males and 2683 females.\n17 yr olds: 3106 males and 2949 females.\n18 yr olds: 2026 males and 1923 females.\n19 yr olds: 5306 males and 5038 females.\n20 yr olds: 3753 males and 3564 females.\n21 yr olds: 2625 males and 2491 females.\n22 yr olds: 1915 males and 1818 females.\n23 yr olds: 3925 males and 3727 females.\n24 yr olds: 2493 males and 2368 females.\n25 yr olds: 3488 males and 3311 females.\n26 yr olds: 2576 males and 2447 females.\n27 yr olds: 2437 males and 2313 females.\n28 yr olds: 1642 males and 1559 females.\n29 yr olds: 4451 males and 4228 females.\n30 yr olds: 3090 males and 2933 females.\n31 yr olds: 2209 males and 2097 females.\n32 yr olds: 1629 males and 1547 females.\n33 yr olds: 2792 males and 2651 females.\n34 yr olds: 1732 males and 1645 females.\n35 yr olds: 3140 males and 2983 females.\n36 yr olds: 2311 males and 2195 females.\n37 yr olds: 1870 males and 1775 females.\n38 yr olds: 1303 males and 1237 females.\n39 yr olds: 3609 males and 3425 females.\n40 yr olds: 2444 males and 2319 females.\n41 yr olds: 1808 males and 1715 females.\n42 yr olds: 1346 males and 1277 females.\n43 yr olds: 1967 males and 1869 females.\n44 yr olds: 1215 males and 1152 females.\n45 yr olds: 2895 males and 2747 females.\n46 yr olds: 2112 males and 2005 females.\n47 yr olds: 1541 males and 1461 females.\n48 yr olds: 1092 males and 1037 females.\n49 yr olds: 2740 males and 2603 females.\n50 yr olds: 1789 males and 1698 females.\n51 yr olds: 1633 males and 1552 females.\n52 yr olds: 1220 males and 1158 females.\n53 yr olds: 1459 males and 1384 females.\n54 yr olds: 928 males and 881 females.\n55 yr olds: 2559 males and 2429 females.\n56 yr olds: 1847 males and 1755 females.\n57 yr olds: 1125 males and 1066 females.\n58 yr olds: 818 males and 776 females.\n59 yr olds: 1985 males and 1885 females.\n60 yr olds: 1241 males and 1177 females.\n61 yr olds: 1416 males and 1345 females.\n62 yr olds: 1056 males and 1000 females.\n63 yr olds: 1147 males and 1090 females.\n64 yr olds: 766 males and 725 females.\n65 yr olds: 2297 males and 2178 females.\n66 yr olds: 1626 males and 1543 females.\n67 yr olds: 997 males and 945 females.\n68 yr olds: 725 males and 687 females.\n69 yr olds: 1306 males and 1240 females.\n70 yr olds: 693 males and 657 females.\n71 yr olds: 1111 males and 1055 females.\n72 yr olds: 745 males and 709 females.\n73 yr olds: 592 males and 559 females.\n74 yr olds: 365 males and 346 females.\n75 yr olds: 990 males and 939 females.\n76 yr olds: 612 males and 583 females.\n77 yr olds: 278 males and 263 females.\n78 yr olds: 189 males and 177 females.\n79 yr olds: 304 males and 289 females.\n80 yr olds: 157 males and 149 females.\n81 yr olds: 351 males and 332 females.\n82 yr olds: 232 males and 221 females.\n83 yr olds: 156 males and 148 females.\n84 yr olds: 95 males and 90 females.\n85 yr olds: 270 males and 256 females.\n86 yr olds: 156 males and 149 females.\n87 yr olds: 105 males and 99 females.\n88 yr olds: 67 males and 63 females.\n89 yr olds: 76 males and 72 females.\n90 yr olds: 39 males and 36 females.\n91 yr olds: 115 males and 108 females.\n92 yr olds: 73 males and 70 females.\n93 yr olds: 36 males and 34 females.\n94 yr olds: 20 males and 19 females.\n95 yr olds: 56 males and 54 females.\n96 yr olds: 27 males and 27 females.\n97 yr olds: 13 males and 12 females.\n98 yr olds: 6 males and 5 females.\n99 yr olds: 16 males and 13 females.\n</code></pre>\n" }, { "answer_id": 184820, "author": "Topcode", "author_id": 73498, "author_profile": "https://worldbuilding.stackexchange.com/users/73498", "pm_score": -1, "selected": false, "text": "<h1>It doesn't matter, because almost certainly this setup will fail.</h1>\n<p>As other users have said, a new colony needs A LOT of work, and you can't really automate all of it, especially not for the first years. Think about it the new location might not be good for farming, or might not be good for farming what you have, and you need farming sorted out fast, and remember, almost all the humans are busy, the women with presumably caring for their kids, the men could farm, but there's no way they could farm enough, they don't have the resources, remember the land where they are is pretty unknown. Aside from that who is gonna be teaching and caring, it can't just be the parents, they couldn't do it and if you want the teens to do it, well they wont do a good job because pretty soon your gonna have problems with education. if you have an automated education system, who is gonna do maintenance on any of the systems? You don't have many spare people so soon stuff is gonna break down and you won't have anyone to fix it.</p>\n<p>Let's say all that gets figured out somehow. Your colony will grow fast. After just 2-3 generations, you will be having in the hundred thousands, and those people need houses, your gonna need to find a way to make those houses, (remember the humans can't do that)</p>\n<p>Let's say you still get that automated. People are eventually gonna want rights, so they will revolt, but against who? that brings another problem, who is controlling this all? <strong>In short, I think you need to tweak the numbers a bit, and change how it's structured to get a working colony that CAN grow.</strong></p>\n<h2>How to fix those</h2>\n<p>First off, you need to make the growth smaller so the colony can keep up better, 100 kids per guy and 12 kids per gal is a very large number, especially in an unexplored environment, resources wouldn't keep up well, and care would be difficult otherwise, using half that would probably fix both. (edit: It has come to my attention that only 25 kids would be genetic at all for fathers, for a few generations at least, you can't keep splitting them forever, and with growth there wont be enough to spread out to everyone, so that number will increase eventually)</p>\n<p>Next, you need to probably need to rethink having males never get into harms way like you say, if you want them to do work that has to get done, they are gonna be in harms way, and if you did step one, then they could get hurt more, and each have a tad higher number than the half you just mad them have.</p>\n<p>You can adjust a bit of what I suggest to better fit your liking but I don't think your current setup will work as well as you hope.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/184763", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/79163/" ]

[ { "answer_id": 190192, "author": "AlexP", "author_id": 29552, "author_profile": "https://worldbuilding.stackexchange.com/users/29552", "pm_score": 3, "selected": false, "text": "<ol>\n<li><p><em>&quot;A very large reservoir of water exists raised up above a large expanse of almost flat land. From the bottom of the reservoir the land falls away at a very gentle gradient of ~1 in 10,000. [...] The people want to build a canal across the flat land to deliver water from the bottom of the reservoir into a river 400km away.&quot;</em></p>\n<p>First of all, they need to dig a large <em>compensation reservoir</em> in order to be able to control the hidraulic head of the water flowing into the canal. You absolutely don't want the water source to be hundreds of meters above your canal, with the water being delivered directly under high pressure by a <a href=\"https://en.wikipedia.org/wiki/Penstock\" rel=\"noreferrer\">penstock</a>. What they want is something like this:</p>\n<pre><code>\\-------------------/\n \\ - - Upper - - - / control valve ___ constant level of water\n \\ - reservoir - / || |\n \\ - - - - - - /____||___\\--------------v--/--||-----------------------\n \\ - - - - - __penstock___ compensation ____||_________canal_________\n \\---------/ || \\ reservoir / ||\n \\-----------/ outflow sluice\n</code></pre>\n</li>\n<li><p>1 in 10,000 is a small gradient; water will flow slowly: they will need a very large canal in order to deliver a debit of 1,000 m³/sec.</p>\n<p>For comparison, the average slope of the lower course of the Nile, from Aswan to the sea, is 1 in 13,300; with an average discarge of about 2800 m³/sec, the river is 2.8 km (1.7 miles) wide and about 10 meters deep. Their canal would be about 1 km (0.6 miles) wide. That is a very wide canal.</p>\n</li>\n<li><p>Rivers flowing over small gradients tend to shift their courses unpredictably unless controlled. The people will need to expend a significant budget of resources and workforce in maintaining the canal.</p>\n</li>\n<li><p>A large river is a powerful erosion force. They won't be able to convince it to flow freely over a constant gradient from the compensation reservoir to the sea. This is a consequence of the <a href=\"https://en.wikipedia.org/wiki/Principle_of_least_action\" rel=\"noreferrer\">principle of least action</a>; if they let the water flow freely, it will tend to dig down a deep valley at the source, and a very wide valley towards its mouth. They don't want this, and therefore they will need to engineer the course of the canal into sections separated by dams or weirs.</p>\n</li>\n<li><p>Now coming to the four options presented by the question:</p>\n<ul>\n<li><p>Option 1, dig the canal before letting the water in: this <em>may</em> result in a stable canal, provided they know what they are doing. They don't need to dig <em>all</em> of it before letting the water in: they can dig a section, let water flow into it, then dig another section and so on.</p>\n</li>\n<li><p>Options 2, 3, and 4 all come down to letting the river cut its course any way it sees fit: this will result in a natural river, not a canal. They will <em>have to</em> adopt option 1 for the initial part of the river at the exit from the compensation reservoir, or else the river will erode their work. Those options are great if the plain is not populated when they let the water flow -- they can let the river stabilize and then bring in the inhabitants. But if they want to be able to predict the course of the river, or if they don't want to allow it to adopt the variable slope profile of a natural river, then these options are not recommended.</p>\n</li>\n</ul>\n</li>\n</ol>\n" }, { "answer_id": 190195, "author": "JBH", "author_id": 40609, "author_profile": "https://worldbuilding.stackexchange.com/users/40609", "pm_score": 3, "selected": false, "text": "<p>@AlexP's answer was fantastic. I upvoted it. So should you. But there might be an alternative....</p>\n<p><strong>Use Hydraulic Mining Techniques</strong></p>\n<blockquote>\n<p>Hydraulic mining is a form of mining that uses high-pressure jets of water to dislodge rock material or move sediment. (<a href=\"https://en.wikipedia.org/wiki/Hydraulic_mining\" rel=\"noreferrer\">Source</a>, also image below)</p>\n</blockquote>\n<p><a href=\"https://i.stack.imgur.com/jFn5x.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/jFn5xm.jpg\" alt=\"enter image description here\" /></a></p>\n<p>Set up pipes that bring the water to the termination (the sea) such that there's a lot of pressure, then carve out the canal back-to-front, washing (slowly) the sediment out to sea. Depending on the mineral deposits in the area, this method can be combined with <a href=\"https://en.wikipedia.org/wiki/Placer_mining\" rel=\"noreferrer\">placer mining techniques</a> (the use of sluices to extract heavier minerals) to extract those minerals and (from a suspension-of-disbelief perspective) pay for the project.</p>\n" }, { "answer_id": 190202, "author": "Justin Thyme the Second", "author_id": 61270, "author_profile": "https://worldbuilding.stackexchange.com/users/61270", "pm_score": 3, "selected": false, "text": "<h2><strong>TL:DR</strong></h2>\n<p><strong>It just might turn out, given the fact that there is only a 40 meter drop from one end to the other, that the ground is relatively flat and unobstructed, and that you are after a flow of 1000 cubic meters per second, your best option just might be to forget about erroding the channel, forget about digging a pilot channel, in fact forget about a dug channel complterely, and just build a twin 400 km. long 5 m. high dike to channel the water.</strong></p>\n<p>With a wide channel, you just might end up moving far less material - the dike walls are no where near the dimensions of the channel.</p>\n<hr />\n<p>Water flows because of differences in energy. Potential energy is converted to kinetic energy. The higher the potential energy, the greater the kinetic energy and the resultant flow. Ten tons of water flows through a channel because there was, first and foremost, enough energy applied to that ten tons of water to get it moving (accelerate it). To keep that ten tons of water moving through the friction of 400 km. of channel, you need a combination of a lot of inertia to begin with, and enough energy to overcome friction. A drop of 40 m. in 400 km. is not supplying a lot of potential energy to move ten tons of water through rough, rocky, meandering waterways at 1000 cubic meters per second. The water will just overflow the banks at the head end, and flood out over the plain, until it dissipates into the ground, evaporates, or stagnates in pools.</p>\n<p>The smoother, straighter, more frictionless the banks are, the more water can flow in the same dimension of channel.</p>\n<p>Roman aquaducts were successful because they were sealed pipes, and thus the water channel could be pressurized. The water could be 'pushed' through the pipes at high source pressure, so the pressure energy could be contained and dissipated much further along the course than just at the source. Try that with a river, and the water just expands under the pressure at the source, dissipating it quickly through flooding.</p>\n<p>Errosion only happens when the water has enough energy to actually carry the erroded material some distance away. If the water does not have enough energy to overcome the inertia of the sand (or whatever) particle, the sand particle does not go anywhere. To errode an entire channel, one needs enough energy to overcome the inertia of all of the material in that channel that you have to move - the entire mass. You are not just moving ten tons of water, you are moving ten tons of water AND ten tons of earth (numbers are for illustration only).</p>\n<p>To get your water across that 400 km. distance, you need to build up a lot of energy at the source, enough to get it the entire distance. Now, to get it to errode, you need to supply enough energy at the source to move the water AND the earth that same 400 km. Rivers do this by using a parabolic shape. Steep at the beginning, shallower at the end. Like a roller coaster track, or a slide. Build up speed coming down the steep slope, build up the energy, then coast. That ten tons of water in a steep drop has now built up enough energy to move both itself AND the ten tons of earth across 400 km. of surface, hopefully. There is going to be very little additional energy added along the way.</p>\n<p>You want to START the ten tons of water moving at the TOP of the reservoir, letting it fall down the slope, building up speed. But you do not want it simply crashing into the ground. That is like a one-way trip off a cliff. A big splat on the ground, a big hole, but not much lateral movement. You want a parabolic channel at the bottom. Something that will change the vector. Vertical motion into horizontal motion. You don't want the energy dissipated in one big bang, you want it to carry on downstream.</p>\n<p>So you want a lot of engineering at the source. A channel built down the slope of the reservoir, in a parabolic shape. A design that can not be left to chance. Nature seems to prefer the 'splat' option, the waterfalls. Straight down.</p>\n<p>Once you get the engineering at the head end, and the engineering to direct the flow at the base in a single direction instead of fanning out, then you can decide if that ten tons of water has enough energy to carry the ten tons of soil, or whatever the mass actually is. If it is more than ten tons, far more energy is needed. If it ls less than ten tons, not as much energy is needed. That is an engineering calculation - how much material needs to be moved, how far it has to be moved, and the energy needed to first accelerate it (inertia) then to overcome friction. We can't know that until the actual material is known, how high the head end is (potetial energy due to gravity), and how much water is moving.</p>\n<p>One thing is for sure - in order for the water to reach the river, it needs to be directed. Is there a natural path for the water to follow, or is the land almost flat? The flatter the land, the more the water just wants to spread out, dissipating its energy over a very wide area. In a fan, the area squares as the distance from the source, so the water very quickly loses the ability to carry any material as it moves further out from the source.</p>\n<p>If there is no natural straight course, then the water must be 'directed'. Yes, you can do that by digging a pilot channel, but you can also do that by building a dike. Whichever you chose depends on the material you are digging through vs the avaiiability of suitable material for building the dike. If the ground is flat, solid, strong contiguous bedrock, but there is an abundant supply of more granular fill closeby, then building a dike is probably the best option. The land is flat, and so the walls of the dike will be parallel to the ground. Alternately, if the ground is easy to dig into, or you have a prolific source of explosives or power beams, then excavating the channel is probably preferred. It is a lot easier to move a big rock than it is to chip that same rock out of solid rock and then move it.</p>\n<p>Now, you have to consider the end. What is this channel flowing into? A river, pool, lake, or ocean? Remember, the surface of this end point is only 40 meters lower than the head end. Tidal forces? Wind-driven waves? Flooding? is it allowable for the water to be pushed back up the channel? How deep is the water flow at the end? If it is a river that is only ten meters deep, obviously the channel can not be more than ten meters deep, or you get the potential for back flow. If it has a shallow shore then the dug channel has to be dug far out from the shore - the deeper the channel, the further out it has to be dug. Is the water flow capable of accepting 1000 cubic meters of water per second, PLUS all of the sediment? Do you need to worry about all of the sediment settling out of the water? Will you end up with one collossal river delta? Or is there enough water movement in the destination to also carry away the sediment?</p>\n<p>If you use a dike, instead of digging the channel, the bottom of the water flow (ground levvel) is still above the surface level of the river or such. The channel water flows on TOP of the existing water flow, not INTO it. It does not matter how shallow the shoreline is, the additional water flow can still be added to it.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/190182", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/42450/" ]

[ { "answer_id": 194257, "author": "Karst", "author_id": 81947, "author_profile": "https://worldbuilding.stackexchange.com/users/81947", "pm_score": 2, "selected": false, "text": "<p>One possibility is that this creature isn't an oxygen-breather at all. There are several other gases and liquids, such as chlorine, that have been proposed as a possible &quot;breathing medium&quot; for extraterrestrial life. If this entity isn't using oxygen, the free-radicals problem vanishes.</p>\n<p>Another possibility is that it's something along the lines of a <a href=\"https://en.wikipedia.org/wiki/Clonal_colony\" rel=\"nofollow noreferrer\">clonal colony</a>. In this setup, a sessile organism sends out shoots which develop into duplicates of itself, connected by a root system. There's no apparent upper limit on size, and the survival of the colony isn't dependent on any one clone. In plants such as trees and grasses, they can keep going for tens of thousands of years.</p>\n<p>(Of course, these two ideas aren't mutually exclusive.)</p>\n" }, { "answer_id": 194275, "author": "TysonDennis", "author_id": 80933, "author_profile": "https://worldbuilding.stackexchange.com/users/80933", "pm_score": 1, "selected": false, "text": "<p>My idea is that it has an enzyme that repairs telomeres to the point where it can have an seven-thousand-year lifespan. And possibly an impressive healing factor, as aging is the result of damage culminating over time. If we are to slow down the damage, we extend the lifespan.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/191678", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/75264/" ]

[ { "answer_id": 191894, "author": "elemtilas", "author_id": 37029, "author_profile": "https://worldbuilding.stackexchange.com/users/37029", "pm_score": 1, "selected": false, "text": "<ol>\n<li>I don't see any obvious logical inconsistencies with the concept of <em>heavenium</em> itself. It's like hydrogen only better at lifting: if it's a solid, it can easily be attached to the airship, or anything else people wish to lift up.</li>\n<li>Given your description of <em>heavenium</em> as a countergravitational substance, I don't see how it can be used for <strong>lateral movement</strong>. I think your aerogators will still need some kind of motive force, a fan of some kind, or sails, to actually propel their ships forward.</li>\n</ol>\n" }, { "answer_id": 191895, "author": "GrumpyYoungMan", "author_id": 32605, "author_profile": "https://worldbuilding.stackexchange.com/users/32605", "pm_score": 3, "selected": false, "text": "<p>Heavenium negates a force (the effects of gravity) but doesn't generate any thrust itself and so cannot be used for propulsion.</p>\n<p>The 10m radius of effect might be difficult to work with depending on the dimensions and mass distribution of your airship and the amount needed to have the effect. For example, something the size of the Graf Zeppelin would be 236m and 33m high and would need chunks of Heavenium distributed in a 10m grid across the airframe. These chunks would vary in size depending on the mass distribution; lighter parts of the airship would only need smaller chunks. One would need to explain how these chunks in various awkward places in the airframe are accessed so they can be heated. (Looping back to propulsion briefly, it's actually a good thing that Heavenium does not generate thrust or the locations in the airframe would need to be load-bearing too.)</p>\n<p>As for conservation of energy, it would be worth doing a quick calculation using the formula for potential energy stored by gravity and the mass of your airship to see how much energy needs to be stored. This will determine how much heat and how much time it would take to charge up the Heavenium; might take a couple of days or even a week in a kiln or something. Also, you say &quot;If used to transfer potential energy into objects by moving them higher the Heavenium become discharged.&quot; but does the energy come back when going back down? If not, either the energy is being emitted somewhere or conservation of energy isn't true.</p>\n" }, { "answer_id": 191896, "author": "AlexP", "author_id": 29552, "author_profile": "https://worldbuilding.stackexchange.com/users/29552", "pm_score": 5, "selected": false, "text": "<h2>Heavenium engine</h2>\n<p>Take an ordinary water wheel. No water. Put a piece of heavenium under one side of the wheel. The side above the heavenium will become lighter, and the wheel will rotate. Use this heavenium engine to power propellers. Problem solved.</p>\n<p>Note that the same principle can be used to power lathes, mills, mechanican looms, spinning jennies, and so on. Heavenium engines will power a fervent industrial revolution.</p>\n<p>After the discovery of heavenium, your society won't remain preindustrial for long.</p>\n<pre><code>This This\nhalf half\nis is\nheavy light\n _____\n / \\\n / \\\n| &lt;&gt; |\n \\ /\n \\_____/\n\n ^^^^^\n heavenium\n</code></pre>\n" }, { "answer_id": 191903, "author": "Tobe", "author_id": 65544, "author_profile": "https://worldbuilding.stackexchange.com/users/65544", "pm_score": 4, "selected": false, "text": "<p>If you lower the heavenium underneath your gondola after you reach altitude you will start to sink and can then glide your airship if it has wings. Then raise the heavenium again to gain bouyancy and you will rise again. You can change your wings such that you glide as you rise and glide as you fall. Keep doing this and you will move forward till the heat energy is converted into kinetic energy in the atmosphere and you will have travelled.</p>\n" }, { "answer_id": 191914, "author": "user_1818839", "author_id": 662, "author_profile": "https://worldbuilding.stackexchange.com/users/662", "pm_score": 3, "selected": false, "text": "<p>There are <a href=\"https://en.wikipedia.org/wiki/Underwater_glider\" rel=\"nofollow noreferrer\">autonomous underwater craft</a> which move forward by simply making themselves denser or less dense than water (by compressing or expanding an airbag). This allows them to glide, under either weight or buoyancy, with &quot;lift&quot; converted to forward motion by the airfoil shape of their body.</p>\n<p>If you're willing to abandon the traditional cigar shaped envelope, you can certainly do the same in the sky with an airship, using Heavenium, by moving it forward or aft to adjust the centre of buoyancy, and angle the nose up to climb, or down to dive.</p>\n<p>It might look a bit like <s>a huge flying butt</s> <a href=\"https://www.hybridairvehicles.com/\" rel=\"nofollow noreferrer\">the Airlander, by Hybrid Air Vehicles.</a> (image : Conde Nast Traveler)</p>\n<p><a href=\"https://i.stack.imgur.com/C0gJ5.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/C0gJ5.jpg\" alt=\"enter image description here\" /></a></p>\n<p>An alternative might copy the blended wing/body concept of the AirbusZeroE, but perhaps without the redundant wingtips.</p>\n<p>Here the point of the wing isn't to provide lift : there's no need; but to provide forward motion. You may get a lift/drag of 3 or 4 for the <s>flying butt</s>Airlander giving 1 km forward per 250m climbed; the blended wing may be closer to 8 or 10, giving 1km for 100 or 125m climbed.</p>\n<p><a href=\"https://i.stack.imgur.com/YRspQ.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/YRspQ.jpg\" alt=\"enter image description here\" /></a></p>\n" }, { "answer_id": 191951, "author": "André LFS Bacci", "author_id": 18632, "author_profile": "https://worldbuilding.stackexchange.com/users/18632", "pm_score": 0, "selected": false, "text": "<h2>Heavenium heat engine</h2>\n<p>Take a Bhāskara's wheel filled with half Heavenium, half water. Put heat in one rotating side, left other side to lose heat to air. You will have rotacional force generated in place. A little coal could make you very far.</p>\n<p>See <a href=\"https://www.youtube.com/watch?v=Vj2kuZm-aCA\" rel=\"nofollow noreferrer\">Renewable Energy from Evaporating Water</a> for inspiration.</p>\n<p><strong>Bonus:</strong> You can use the residual heat to keep the lifting Heavenium warm.</p>\n" }, { "answer_id": 191956, "author": "njzk2", "author_id": 2483, "author_profile": "https://worldbuilding.stackexchange.com/users/2483", "pm_score": 2, "selected": false, "text": "<p>Quick reality check:</p>\n<p>The Gravitational potential energy is locally</p>\n<pre><code>U = mgh\n</code></pre>\n<p>This is for example valid for a stationary object in a stable gravity field. <code>m</code> is the mass, <code>g</code> is the local gravity, <code>h</code> is the height. (Height is relative to an arbitrary point, so that this is mostly useful for measuring differences in potential energy)</p>\n<p>When you apply heat to your heavenium, <code>g</code> decreases for objects around it.</p>\n<p>This decreases the value of <code>U</code>, resulting in a loss of potential energy.</p>\n<p>The energy must be conserved, as you mentioned.</p>\n<p>Where does the potential energy go?</p>\n" }, { "answer_id": 191967, "author": "wizzwizz4", "author_id": 11665, "author_profile": "https://worldbuilding.stackexchange.com/users/11665", "pm_score": 1, "selected": false, "text": "<p>Heavenium violates the Second Law of Thermodynamics. <em>You don't need fuel.</em></p>\n<h2>What?</h2>\n<blockquote>\n<p>The <strong>second law of thermodynamics</strong> states that the total entropy of an isolated system can never decrease over time, and is constant if and only if all processes are reversible. Isolated systems spontaneously evolve towards thermodynamic equilibrium, the state with maximum entropy.</p>\n<p>[…] In all processes that occur, including spontaneous processes, the total entropy of the system and its surroundings increases and the process is irreversible in the thermodynamic sense. The increase in entropy accounts for the irreversibility of natural processes, and the asymmetry between future and past. […]</p>\n<p>[…] Its first formulation is credited to the French scientist Sadi Carnot, who in 1824 showed that there is an upper limit to the efficiency of conversion of heat to work in a heat engine. This aspect of the second law is often named after Carnot. — <a href=\"https://en.wikipedia.org/w/index.php?title=Second_law_of_thermodynamics&amp;oldid=991847499\" rel=\"nofollow noreferrer\">Wikipedia</a>, used under <a href=\"https://creativecommons.org/licenses/by-sa/3.0/\" rel=\"nofollow noreferrer\">CC BY-SA 3.0</a></p>\n</blockquote>\n<h2>Why?</h2>\n<p>All processes that require heat are either entropic in nature (e.g. cooking), or actually require a temperature <em>difference</em> (e.g. Sterling engines, solar panels). All natural processes that extract useful energy (aka <em>do work</em>) from a temperature difference also reduce that temperature difference. In short: without access to sunlight and the vacuum of space, you'll run out of usable energy sooner or later.</p>\n<p>Heavenium, however, works on <em>absolute</em> temperature, like entropic processes, but <em>provides useful work</em>, which you can normally only get from a temperature <em>gradient</em>. It's a negentropy source. This stuff's worth <em>more than the Sun</em>.</p>\n<h2>How?</h2>\n<p>There are countless ways of making use of this, but I'll start with the simplest to explain.</p>\n<h3>Heat pump in a box</h3>\n<p>Make a pulley. One end of the pulley should be a box containing some fancy technology and some Heavenium (I'll get to that in a sec); the other should be weighted so that it goes up when the Heavenium is “off” and down when the Heavenium is “on”. Attach the pulley to a <em>really tall tower</em>.</p>\n<p>In the box, wind up some clockwork, and attach it to a heat pump. Set the heat pump so that it'll warm up a compartment containing Heavenium and cool down a compartment containing hot water, then start it going and shut the box. The Heavenium box will go up. Use some of this energy to do work (e.g. winding up some more clockwork). Eventually your clockwork will run out, or your heat pump won't be powerful enough to heat the Heavenium to the critical threshold any more, and the Heavenium will run out of magical lifting ability; you know when this will happen in advance, thanks to your calculations, so you can switch to generating energy from the pulley going the <em>other way</em>.</p>\n<p>If you use a Sterling engine to recover the energy from the temperature gradient the heat pump made, you will have:</p>\n<ul>\n<li>Cold water, and a cold box in general; and</li>\n<li>More energy stored in clockwork / used to do useful work than you started with.</li>\n</ul>\n<p>With a sufficiently-powerful heat pump, you could start with regular old ambient-temperature water, cool it down, and generate energy for useful work. Of course, eventually, this energy would run out; friction and other losses would see it slowly lost to heat. But you can <em>extract work from heat</em>.</p>\n<p>Your airship does not need fuel.</p>\n<h3>Heavenium engine</h3>\n<p>Okay, so maybe building a massive tower in the middle of your airship isn't actually all that practical. You need something more <a href=\"https://worldbuilding.stackexchange.com/a/191896/11665\">engine-like</a>. Take a heavy flywheel, and put it vertically over a well-insulated Heavenium-containing oven (so that the rising side is lighter); insulation reduces the maximum power your heat pump system needs to have to get the Heavenium hot enough. (Frictional losses aren't all that important because a Heavenium engine <em>uses heat as fuel</em> – I still can't get over how overpowered this is!) Fuel this oven with a powerful heat pump (or chain of heat pumps) powered by the Heavenium engine. The energy will eventually get back to the heat pump no matter what you do, but you can speed it along by sticking the “cool” end(s) of the heat pump on whatever's generating most of the frictional losses.</p>\n<p>Now simply heat up the oven to the critical temperature, spin the engine a bit to get it started, stick a fan on the end and you're away!</p>\n<h2>When?</h2>\n<p>Heat engines have been known since antiquity. The first refrigerator (requiring pretty good heat pumps) predates the industrial revolution by over 75 years. While this technology might not be immediately apparent, since the Second Law of Thermodynamics hadn't been invented yet, anyone who understood fridges and had heard of Heavenium would probably be able to figure it out, and it wouldn't take much longer to develop heat pumps good enough that this would be viable.</p>\n<p>Unless, of course, you need to get the Heavenium <em>really</em> hot. Then this is right out.</p>\n" }, { "answer_id": 191993, "author": "ZioByte", "author_id": 38942, "author_profile": "https://worldbuilding.stackexchange.com/users/38942", "pm_score": 0, "selected": false, "text": "<p>There are several subtle implications in your &quot;Heavenium&quot;:</p>\n<ul>\n<li>how efficient is the heat conversion in potential energy (i.e.: how fast will it discharge when &quot;pushing up&quot;)? If efficiency is comparable with steam engines then it's mostly useless as &quot;engine&quot;, while retaining it's full power as &quot;keep height&quot; device.</li>\n<li>&quot;perpetual motion spinning engines&quot; as described in other <em>need</em> to be heavy to generate a sizable amount of energy and thus are a bit useless for aircraft motion.</li>\n<li>It's unclear how do you plan to regulate ascent/descent of your aircraft and I assume it is &quot;normal&quot; Archimedes law (corrected with gravity, and thus weight, reduction).</li>\n<li>If the above it's true then &quot;airships&quot; need to be huge to leverage on a certain amount of air weight. This, incidentally, means they will have a large cross-surface winds will act on.</li>\n<li>What happens, exactly, when Heavenium is &quot;discharged&quot;? I will assume it gradually looses it's &quot;power&quot; and thus the nominal &quot;90% reduction&quot; will steadily and gradually decrease as the airship rises up.</li>\n<li>If you want to be &quot;creative&quot; you can make your airship large and flattish and &quot;power&quot; it with <em>two</em> (or more) Heavenium capsules: one near &quot;forward end&quot; and the other near &quot;aft end&quot;.\n<ul>\n<li>start with airship at equilibrium with 80% Heavenium charge (~70% gravity reduction).</li>\n<li>heat up forward capsule and ship will start raising &quot;nose first&quot;. This will cause a forward drag because of ship geometry.</li>\n<li>heat aft capsule &quot;just enough&quot; to maintain it's power as ship raises.</li>\n<li>stop heating forward capsule; this will cause a brief &quot;overshoot&quot; (mass is <em>not</em> affected, so airship has a rather large inertia) and then it will start falling, again &quot;nose first&quot; (if aft crew did their job right) and thus, again, producing a forward drag.</li>\n<li>rinse and repeat: you ll'have a big flat &quot;whale&quot; moving slowly and steadily (in calm air).</li>\n</ul>\n</li>\n<li>Heavenium (as described) cannot be used directly to produce horizontal (orthogonal to gravity force) drag.</li>\n<li>You can't either use any kind of &quot;sails&quot; because those rely on keel drag, which you don't have.</li>\n</ul>\n" }, { "answer_id": 192001, "author": "SilentAxe", "author_id": 81240, "author_profile": "https://worldbuilding.stackexchange.com/users/81240", "pm_score": 2, "selected": false, "text": "<h2>Heavenium Jet Engine</h2>\n<p>The theory of this engine is based in the Archemidean principles, and while it would first be used by civil engineers for fountains and other waterworks) and shipwrights (of seas) it could eventually be adapted for airships.</p>\n<p>The principle behind it is simple - a still fluid stays still because every other bit of fluid above and to the sides of it presses it down with the same force of gravity. But what would happen if we put a vertical pipe of heavenium into that fluid?</p>\n<p>The fluid inside the pipe would get much lighter and the surrounding fluid would force it upwards, just like a piece of cork under water. And it would draw with it a new amount of fluid, which would get lighter and be forced upwards in a constant stream.</p>\n<p>This upwards motion of fluid alone would be godsend for civil engineering - a pump with no moving parts! But that is not all - the fluid that has started flowing still has some momentum to it that can be redirected. Just put a bend in a pipe and it will now flow out sideways propelling the engine and anything that is attached to it sideways.</p>\n<p><a href=\"https://i.stack.imgur.com/O1xIR.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/O1xIR.png\" alt=\"Heavenium Jet Engine\" /></a></p>\n<p>Air is just a form of fluid - and as boat can float on a water - so can balloon on the air. And in the same way the heavier water would force lighter water upwards - so would air.</p>\n<p>Of course there are differences. For one - air is about thousand times less dense than water which means that it will propel the ship with much less force. On the plus side, that means that heavenium will need to be recharged less.\nAlso air unlike water can compress, which means that to get a good flow you instead of a simple pipe you would need a much wider funnel in the intake.</p>\n<p>Pros:</p>\n<ul>\n<li>No moving parts</li>\n<li>Simple construction</li>\n<li>Easily controlled (rudder + lid or just mount the whole thing on a swivel)</li>\n<li>Useful in other applications (lower cost and quicker R&amp;D)</li>\n</ul>\n<p>Cons:</p>\n<ul>\n<li>Very low thrust in the air</li>\n<li>Difficult to recharge</li>\n</ul>\n<p>Possible improvements (possibly incompatible):</p>\n<ul>\n<li>Replace the Heveanium funnel with ordinary funnel + Heveanium mesh on the intake for better pressure profile and efficiency</li>\n<li>Place re-loadable heaveanium bunker above the funnel for easier refuelling</li>\n<li>Add access and fittings for in-place recharging - e.g. burning a breazier of coal right below the funnel</li>\n</ul>\n" }, { "answer_id": 192002, "author": "Nick", "author_id": 81243, "author_profile": "https://worldbuilding.stackexchange.com/users/81243", "pm_score": 1, "selected": false, "text": "<p>I can see a problem with Heavenium - at best it only reduces mass to 90% of normal. What this means is a 20 ton airship will plummet out of the sky just as quickly as a 2 ton brick. To overcome this, you suggested hot air to provide lift. So your airship will need to carry a source of heat aloft, which will also require its own fuel. BUT ... all this adds even more weight to your airship.</p>\n<p>At first, one would imagine having a crew shovelling wood or coal into a fire which heats the Heavenium with the waste heat being used to lift the now lighter airship. You could have a turbine in your chimney, turning a propeller through a gear mechanism to provide forward thrust. So while the Heavenium itself is not providing thrust, the thrust is generated as a byproduct of the means to lift the airship and heat the Heavenium. Later developments could have more efficient heat sources - gasoline, electricity, nuclear power; jet engines to provide thrust and drive turbines; helium to provide lift (not hydrogen, as it doesn't behave well with flames!); lightweight metals replacing plywood; and so on.</p>\n<p>As your airships get larger, you could pump liquified Heavenium around your airship (if the stuff ever melts?), or just pump the heat around your airship heating lumps of Heavenium strategically placed around the structure.</p>\n<p>However, there is going to be some tricky balancing between the weight of your airship (structure, fuel, cargo, passengers, etc), the weight reduction properties of Heavenium, the amount of lift provided by hot air/helium, and the air density as it varies with altitude/weather.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/191893", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/42450/" ]

[ { "answer_id": 192422, "author": "Ash", "author_id": 78800, "author_profile": "https://worldbuilding.stackexchange.com/users/78800", "pm_score": 3, "selected": false, "text": "<h3>0.9 - 2.3kg for standard bow. 0.9 - 1.8kg for long bow:</h3>\n<blockquote>\n<p>The physical weight of a traditional longbow is somewhere in the two to the four-pound range while a traditional recurve bow is between two and five pounds.</p>\n</blockquote>\n<p><a href=\"https://i.stack.imgur.com/vXguc.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/vXguc.png\" alt=\"enter image description here\" /></a></p>\n<p>Source: <a href=\"https://bosstargets.com/how-heavy-is-a-traditional-bow/\" rel=\"noreferrer\">https://bosstargets.com/how-heavy-is-a-traditional-bow/</a></p>\n<p>That link goes into all sorts of discussions on bow weight, eg attachments and such - I didn't know that heavier bows prevent fatigue from the vibration, for example.</p>\n" }, { "answer_id": 192455, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 2, "selected": false, "text": "<p><strong>For a game, keep it simple.</strong></p>\n<p>Especially if PVP is not a big part of your game. You can have attack speed and damage, and ranged or no. Simple variables.</p>\n<p>If you want more variety in weapon types (to excite your players!) go ahead and have it, but ultimately it will be the same variables to consider when you have a fight. For example a war hammer might be even slower than a longsword and do even more damage. A dagger faster than a sword and less damage.</p>\n" }, { "answer_id": 192458, "author": "Tortliena", "author_id": 80336, "author_profile": "https://worldbuilding.stackexchange.com/users/80336", "pm_score": 3, "selected": true, "text": "<p>I will speak in broader terms, including carrying capacity into the question. Indeed, the two are closely related, and in the end, it's more about the number of items one can hold than the exact weight one item is. But I will getty to that point later.</p>\n<h2>Adjust the weight according to the fight intentions your team wants to give</h2>\n<p><strong>What I fear is that you're reversing priorities between core gameplay features and feelings vs flavor</strong>. You should focus first on strengths and weaknesses of your weapons, speaking in terms of number of hits to kill, range, speed, special abilities, and feeling they should provide, then to the weapon's weight. Since people cannot carry the sword themselves, weight cannot be felt, and therefore it should be laid out on the background after what they can see, hear or sense (with the controller's vibration). Feeling is more important than a number on the item's description.</p>\n<p>It goes into the overall look and feel of your game and the intentions you want to give. If this is a heroic fantasy game, boost up weapons's size and weight as your characters are strong, sweaty heroes, not your average farming Joe. If your avatar is living in a dark, realistic world or are weak compared to monsters, decrease them instead to make them look more frail and inefficient against what's to come. It all goes down to the intention of your game.</p>\n<p>Recall that the intentions should be thought on the whole team level, especially the artists since they will draw how characters and weapons will look like. Marking all your weapons as light and then noticing all artists drew bulky heroes wielding 5 meter swords will make you feel you lost time :). That's the game designer's job to ensure everyone is on the same page.</p>\n<h2>Balance the weight according to the drop quantities and character type average carrying capacity</h2>\n<p>The idea is to not focus on the sole weight, but think it as a whole. For instance, how scarce or plentiful the drops are? Do players can acquire equipment only through crafting (gaining materials from dungeons/jobs). Do you want your players make constant conscious choices over what to keep (Very important if you have lots of single use items or a durability system), or do you want them to be more carefree and grab everything they can find, hack-and-slash style? This, in overall, will determine how much items one should be expected to hold.</p>\n<p>Often times, you will notice that melee warrior characters will have more carrying capacity than mages or rangers, yet they can carry about the same amount of their class's items because their equipments weigh more. It's partially because if they can carry more, they may become some drop mules which is rarely wanted. However you still want some difference in feelings (as per the first section). Hence, adapt weights to how many items should one be able to carry!</p>\n<h2>Follow the marketing strategy</h2>\n<p>If your game is following a free-to-play model, you'll probably be influenced by the editor/producer, asking you to restrict how many one can carry items, in order to sell interesting bonus inventory packs.</p>\n<p>This can be annoying as it brings down your creativity, but sadly, a person can't eat their own bytes of virtual bread from their games. You should take it into consideration and reduce voluntarily the carrying capacity or increase your item's weight in order to incite the buying of such packs. Still, as you are responsible of the quality of the player's feelings, don't overdo it and don't hesitate to tell that it isn't possible without hurting too much the player retention on the long term. Then, in order to not reach a dead end, try to offer an alternative you can more easily negotiate on.</p>\n<h2>Playtest</h2>\n<p>This is a kinda all around solution to all game designers issues, but it works, and really well actually. If your game is not yet in a playable stage, you can make a paper version of your game focusing on drops and weights. For instance, make a fake run through dungeons, and ask which item your testers want to keep, following your set weight rules. Then take their feedbacks and feelings about what you have made.</p>\n<p>If you don't have anybody available, prepare some tables and play with values around for an estimated game run, and get others' quick feedback (it's always important). It's not as valuable as playtesting, but it formalize things and can give others a rough idea of what to expect, improving their own image of what the game would be.</p>\n<h2>But most of all, keep things simple and focus on gameplay</h2>\n<p>Unless your game has one of its pillar be inventory and drop management A.K.A. survival games or simulation games (which, given your description doesn't seem to be the case), you shouldn't spend too much time estimating exact weight/and or size of real world counterpart.</p>\n<p>Players tend to overestimate the weight of items and even more one's real carrying capacity. Peck, have you seen someone wearing 4 plate armors, 3 bows, 6 (unbroken) potions, 6 swords, spears and shields, a quiver containing 150 arrows and a pouch holding 20 000 gold coins? And yet in games, unless you put visual indicators like in <a href=\"https://fr.wikipedia.org/wiki/Death_Stranding\" rel=\"nofollow noreferrer\">Death Stranding</a>, almost nobody will think about it. At worst they will give a smile thinking about their character carrying this much, which isn't even a bad thing! What I mean is that it goes all into the suspension of disbelief. And you can safely retreat behind it, especially since you won't have a lot of time designing your MMO.</p>\n<p>Yes, you probably won't have a lot of time. Remember, MMOs are one of the most expensive type of game projects in the industry (networking alone multiplies at least by 2 the cost), so you will have a lot of matters to attend to. And since your game involves even a little bit of PvP, you will need some time as a game designer to balance character archetypes and powers. Time that doesn't involve weight calculation unless it impacts the battle gameplay, in which case simulation may not be better than pure-gameplay values. <strong>After all, players are more concerned about a balanced experience than that a <a href=\"https://www.youtube.com/watch?v=0QDPU0itinU\" rel=\"nofollow noreferrer\">real viking sword weighs less than 1 kg</a> and in your game it's 5 kg.</strong></p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/192409", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/81408/" ]

[ { "answer_id": 193304, "author": "JBH", "author_id": 40609, "author_profile": "https://worldbuilding.stackexchange.com/users/40609", "pm_score": 4, "selected": true, "text": "<h2>What you've asked for is huge, so this is a necessary simplification</h2>\n<p><em>I've made this a community wiki because a thousand separate answers won't fully answer the question, so we might as well try to build on just one.</em></p>\n<p>One of the reasons why most city-building resources focus on medieval cities is that they're small with simple needs. In a phrase: they're easy. Even contemporary cities here on Earth are massively complex by comparison. Future cities would even be worse. But... we can take a bird's eye view at this. BTW, while any individual may consider anything below to be a want vs. a need, the reality is that when you're dealing with large groups of people, this is all a need. Living is complex.</p>\n<p><strong>Housing</strong></p>\n<pre><code>- Wealthy housing (expensive, low-density)\n- Urban housing (moderate cost, medium-density)\n- Labor housing (low cost-per-unit, high-density)\n- Welfare housing (very low cost-per-unit, very-high-density)\n</code></pre>\n<p><strong>Government</strong></p>\n<pre><code>- Legislative (makers of law)\n- Judicial (interpreters of law)\n * Lawyers\n- Executive (enforcer of law)\n * Police/Military\n * Inspectors (construction)\n * Regulation (permits/certification/zoning)\n * Public schools/libraries\n * Roads &amp; parks\n</code></pre>\n<p><strong>Emergency Services</strong></p>\n<pre><code>- Hospitals/clinics\n- Ambulance/life-flight/paramedics\n- Fire\n- Pharmaceutical companies\n</code></pre>\n<p><strong>Commercial</strong></p>\n<pre><code> - Grocery/restaurants\n - Services (there are MILLIONS of these things, see below)\n - Department retail (see below)\n - Warehousing\n - Industrial (metal working, brick making, chemical processing)\n</code></pre>\n<p><strong>Education</strong></p>\n<pre><code> - Schools for sub-adults\n - Colleges/Universities\n - Vocational &amp; trade\n - Community education\n - Big libraries (the Louvre, natural history museums, planetariums)\n - Pre-school/child-care\n - Special education\n</code></pre>\n<p><strong>Financial</strong></p>\n<pre><code> - Holding companies\n - Brokerages/Investing\n - Banks/Credit Unions\n</code></pre>\n<p><strong>Entertainment</strong></p>\n<pre><code> - Theater/Dance\n - Art/Literature\n - Film/Music/Video\n - Food/Drink\n - Electronic Services (see below)\n - Zoos &amp; privately-owned parks\n - Walking/running trails\n - Amusement parks/carnivals/parades/celebrations/holidays\n</code></pre>\n<p><strong>Religion/Philosophy</strong></p>\n<pre><code> - Houses of worship\n - Schools/camps\n</code></pre>\n<p><strong>Raw Materials</strong></p>\n<pre><code> - Lumber\n - Mining\n - Farming/Ranching/Fishing\n - Hydroponics\n - Chemical processing\n</code></pre>\n<p><strong>Utilities</strong></p>\n<pre><code> - Water (transport, sanitation) &amp; Sewage (collection, processing &amp; disposal)\n - Natural gas/propane\n - Electricity\n - Communication (phone, internet, radio/broadcast)\n - Fuel (gasoline/oil/diesel, nuclear fuel &amp; control-rods, coal)\n</code></pre>\n<p><strong>Black Market</strong></p>\n<pre><code> - Drugs\n - Pornography\n - Rare/protected species\n - Organized crime (mafia, gangs)\n</code></pre>\n<p><strong>Heritage</strong></p>\n<pre><code> - Architectural preservation\n - Wilderness preservation\n - Monuments\n</code></pre>\n<p><strong>Transportation</strong></p>\n<pre><code> - Roads &amp; bridges (traffic control, cars/trucks/buses/bicycles/motorcycles...)\n - Waterways (canals, sluices, locks, ships &amp; boats)\n - Ocean (docks, dredging, ships &amp; boats)\n - Rail (iron rail, monorail, maglev)\n - Air Flight (air planes, radar, traffic control)\n - Space Flight (launch/recovery, radar, traffic control... space stations...)\n</code></pre>\n<p><strong>And one more thing...</strong></p>\n<p><em>All of the INFRASTRUCTURE that supports everything above. Concrete/asphalt plants, makers of pencils, janitors, caterers, dog walkers, ditch diggers, environmental activists, manufacturing of all kinds (think TOOLS, and that's just the start).... The category of infrastructure is <strong>breathtakingly enormous.</strong> Go to <a href=\"http://alibaba.com\" rel=\"noreferrer\">Alibaba.com</a> and browse. We live in a world of machines and stuff that's all but incomprehensible.</em></p>\n<h2>Remember, this was a simplification</h2>\n<p>And to be honest, it's a simplification to the degree that angels weep.</p>\n<hr>\n<p>Some of the above categories are so broad that they needed a bit of insight. I'm going to name only a few examples. This list can literally be <em><strong>endless.</strong></em></p>\n<ul>\n<li><p>Services: nail salons/grooming, accountants, realtors, arts/crafts, car repair, yoga instructors, carpet layers, carpenters, consultants, psychologists, counselors.</p>\n</li>\n<li><p>Department retail: hardware, clothing, furniture, household goods, industrial goods, commercial support, almost anything you can find in a shopping mall.</p>\n</li>\n<li><p>Electronic services: games, social media, information exchange &amp; processing, blogs, corporate/company contact.</p>\n</li>\n</ul>\n" }, { "answer_id": 193310, "author": "Johnny", "author_id": 35649, "author_profile": "https://worldbuilding.stackexchange.com/users/35649", "pm_score": 3, "selected": false, "text": "<p>JBH gave a long list of individual services. I think you're looking for something different?</p>\n<p>In general, to support life, you need food, shelter, water, air, power and transport.</p>\n<h3>Power</h3>\n<p>For power and sufficiency, cover everything you can with solar panels. You'll probably need some power plants as well, so people have power at night, and because the panels might't be able to supply enough, depending on your aliens' power demands. Nuclear would be best, but they might have fusion which would make electricity VERY cheap. Of course, you'll plan your city so that high rise buildings aren't blocking solar panels too much.</p>\n<p>You can make use of circumstantial power sources, like hydroelectric and the like, as ideally you will build cities next to such useful resources.</p>\n<h3>Food</h3>\n<p>This one is tricky, and depends on your tech. If they do have a lot of excess power, due to fusion and nuclear, you could potentially grow everything in plant factories in the city, which has huge potential for sufficiency and health, due to their minimal use of water and pesticides. Even then, generally it's cheaper to grow stuff in massive fields, since you can rely on the free energy of the sun and rain, so your aliens might want to consider traditional farming as well.</p>\n<p>You could theoretically cover the roofs of buildings with vertical farms, which maximize sunlight and water use, though that could reduce the surface you have for solar panel arrays, so your people would need to balance out their needs carefully.</p>\n<h3>Transport</h3>\n<p>People need to be able to get around your city to fulfill their needs, or else all the services are pointless. You'll also want effective means of delivery.</p>\n<p>You mentioned a design based off a village where you can walk to everything... and that's the basic model for European cities. Denmark has almost half the cars per capita of the US, with the UK and France only having a little more. These cities were made long before motor transport, so they were designed with walking distances in mind, and they developed good public transport systems.</p>\n<p>In this case, your public transport might largely be trams, trains, and driverless cars. The latter could just be called the same as an Uber. You might also have drone copter cars, at this point, which would be more expensive and dangerous, but still a reasonable possibility.</p>\n<p>And speaking of drones, they'd likely replace postmen for the majority of deliveries. If you have fusion power, you can basically make everything electric and cheap.</p>\n<p>For long distance transport, you will need trucks and trains. Again, with fusion, everything is electric, so long as you have enough truckstops to power your batteries.</p>\n<p>If you don't have fusion, you'd need quite a few nuclear plants to maintain that kind of electrical cost.</p>\n<h3>Air</h3>\n<p>Motor and factory fumes are the biggest concerns with air. With fusion, you can greatly reduce that, though some factories might still produce toxic fumes. They'd need to be kept away from the living areas, and maybe you can develop filters to prevent most of that junk going into the air.</p>\n<p>Parks are important, for recreation, wellness of mind, and air quality. Of course, if you have many plant factories and vertical farms, air quality should be pretty good.</p>\n<h3>Shelter</h3>\n<p>If you want to avoid suburban sprawl, you're probably looking at somewhat minimalist apartments. The most efficient structure is about 3 or 4 stories tall, normally. If you have fusion, that could change things a lot, as it'd cost less to pump the water up several floors, and to run elevators.</p>\n<p>But in general figure apartment building complexes that are surrounded by the necessary services, or even have those services built into the complex. After all, if you're going to put elevators in the place, you might as well use them for transport purposes, shifting people around a sort of shopping mall. That said, business areas need to be separated from living ones, by a fair margin, or else constant activity will make it hard for occupants to sleep.</p>\n<h3>Water</h3>\n<p>You of course need water treatment plants, and a good water source like a river. You could even use sea water, processing it into drinkable water like Israel is trying, especially if you have fusion.</p>\n<p>You can also recycle the sewage of the city, using some of it for fertilizer and either sending the purified water out to sea, or directly pumping it back into the system (that happens).</p>\n<p>Of course, since there are genetic issues to worry about, water treatment must be handled carefully. Fluoride, for example, has been condemned by the WHO as dangerous in drinking water since at least 2006, but the US didn't decrease it fluoride until 2015. Even now, their limit is about 4mg/L, which is a lot more than other countries. India's limit is 1.6mg/L, and they have many reverse osmosis plants to try and take the naturally occurring fluoride out of their water.</p>\n<p>So, your aliens will have the same concerns, purifying their food and drinking water extensively, since the health of some of them and their children is in question.</p>\n<p>I hope this was a useful overview for city design.</p>\n" }, { "answer_id": 193330, "author": "Peter - Reinstate Monica", "author_id": 2374, "author_profile": "https://worldbuilding.stackexchange.com/users/2374", "pm_score": 2, "selected": false, "text": "<p>The first thing you must ask is: <strong>Why do cities exist? What functions do they serve? What <em>are</em> cities, really?</strong></p>\n<ul>\n<li>Obviously, an aggregation of people and their dwellings</li>\n<li><em>Usually,</em> an economic hub</li>\n<li><em>Usually,</em> a political hub</li>\n<li><em>Usually,</em> a cultural and educational hub.</li>\n</ul>\n<p>In a free society people congregate in cities because they perceive economic, social and/or cultural opportunities there. If the city is the seat of a regional or federal government the connected administrative jobs are part of that.</p>\n<p>This congregation of people, in a feedback loop, in turn fosters economic, social, cultural and political progress and development. Everything that is modern in our western societies emerged in cities. In the past it was safe to say: <strong>No city, no innovation.</strong></p>\n<p>Since your story is in the near future you will have to consider a development that the Corona virus crisis accelerated: Many of these political, economic, even cultural functions do not depend any longer on the physical proximity of people. Factories are automated, conversations, education, political debates and to a degree cultural events are moving online.</p>\n<p>Are our future cities virtual cities? Is facebook, culturally, a city? Is Microsoft Teams an office? Since the physical-geographical connection between work, culture and politics is now severed: Will we all come together only with peers? Will the society continue its apparent path to disintegration?</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/193298", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/81702/" ]

[ { "answer_id": 193484, "author": "Slarty", "author_id": 42450, "author_profile": "https://worldbuilding.stackexchange.com/users/42450", "pm_score": 6, "selected": true, "text": "<p>No this is not even remotely possible. The gravitational attraction of a star would be great enough to suck any surrounding planetary surface sphere into itself. Making the planet or crust deeper would not help either as it would only serve to increase the gravitational field centred on the star. The energy output of the star would also rapidly vaporise any surrounding material.</p>\n<p>Note your NASA quote number 2 &quot;It must be big enough to have enough gravity to force it into a spherical shape&quot; any object with enough gravity to do this would collapse any hollow sphere.</p>\n" }, { "answer_id": 193485, "author": "Jackson Dunn", "author_id": 76989, "author_profile": "https://worldbuilding.stackexchange.com/users/76989", "pm_score": 3, "selected": false, "text": "<h2>What is &quot;Star&quot;?</h2>\n<p>Technically this would just be a star, something along the lines of a binary star. A sun, in some sense, is a nuclear-powered &quot;planet&quot; shaped object that can orbit another larger star. Replacing the core of a planet with a star would cause the planet to collapse because of gravity, as well as causing the surface to radiate with the same total heat output as the interior star, thus making it...a star again. It's stars all the way down, I'm afraid.</p>\n" }, { "answer_id": 193501, "author": "DKNguyen", "author_id": 70078, "author_profile": "https://worldbuilding.stackexchange.com/users/70078", "pm_score": 3, "selected": false, "text": "<p>Stars are made of hydrogen and helium. A star is a star and not a cloud of hydrogen and helium by virtue of its gravity which is due to its mass. The gravity being strong enough to cause fusion is what makes a star a star.</p>\n<p>Planets (the rocky kind you are thinking of) are made of rock. Rock is much denser than hydrogen and helium, so a planet large enough to fit a star inside would be so massive that its gravity is so strong that it would collapse into a blackhole, neutron star, or something similar.</p>\n<p>So no.</p>\n" }, { "answer_id": 193506, "author": "Daron", "author_id": 14322, "author_profile": "https://worldbuilding.stackexchange.com/users/14322", "pm_score": 0, "selected": false, "text": "<p><strong>Sink and Melt.</strong></p>\n<p>The Sun's surface is about 6000C. Stone melts at about 1500C. So the stone shell will melt into Lava.</p>\n<p>Even ignoring the heat, the stone will sink under the sun's surface.\nMost types of stone have density about 2.5 g / cm<span class=\"math-container\">$^3$</span>. The Sun is less dense at about <span class=\"math-container\">$1.5 $</span>g / cm<span class=\"math-container\">$^3$</span>. That means if you put a stone shell around the sun it will sink in the same way stone sinks in water.</p>\n<p>If you put something less dense that can withstand the heat then it will remain on the surface. For example water is 1 g / cm<span class=\"math-container\">$^3$</span> at room temperature. However being on the surface of the sun definitely changes things, due to massive heat and gravitational pressure.</p>\n" }, { "answer_id": 193507, "author": "lvella", "author_id": 39851, "author_profile": "https://worldbuilding.stackexchange.com/users/39851", "pm_score": 1, "selected": false, "text": "<p>If it is possible, there are so many equilibrium points that must be balanced that I doubt such thing would exist for too long. These are the points I can think:</p>\n<ul>\n<li>To prevent the rock crust surrounding the star to crumble under its own weight, the crust must be thin enough and the radius so big that the average density is low enough so that the material rigidity can keep it together. Didn't run the numbers, but may be possible.</li>\n<li>With a star inside, the crust radius may have to be even bigger, so that the star's gravity does not to crumble the structure.</li>\n<li>The entire energy output of the star would have to pass through the crust, so it must have enough heat conductivity and/or transparency to prevent the inner surface from melting and dipping into the star. Also, the radius must be so big that the energy input is not much higher than a couple of kW/m², otherwise you also have dipping lava robbing mass and structural integrity from your shell. Probably no smaller than the radius of a closely orbiting planet to the star. Must account for reflected/irradiated light from the structure itself, that will make the interior much hotter than just the direct sunlight.</li>\n</ul>\n<p>Interestingly, the position might be stable. Such thing can not rely on rotation to maintain a stable orbit around the star, because the poles would crumble leaving only an equatorial ring: instead, it must be rigid enough to sustain itself. Considering it's gravity center will match the stars gravity center, star's pull will propagate through the structure, tending to always match their center of mass. Any delta would make the shell oscillate around the star over the course of days, but radiation absorbed from the interior might act as dampening of sorts, and oscillation should eventually dissipate as heat.</p>\n<p>The star's radiated light will also exert an stabilizing pressure on the structure, pushing outwards in every direction like gas inside an inflated balloon.</p>\n" }, { "answer_id": 193529, "author": "Not Entirely Serious", "author_id": 81803, "author_profile": "https://worldbuilding.stackexchange.com/users/81803", "pm_score": 2, "selected": false, "text": "<p>As others have pointed out, a literal star isn't possible because of scaling issues. The minimum size of the star (not too much smaller than our sun) is still far too large to have an enclosing solid surface that wouldn't undergo gravitational collapse. There's a couple of alternatives I can suggest if that's okay.</p>\n<p>One would be a Dyson sphere. This is a collection of structures that either orbit the sun (held up by centrifugal force) or are suspended via light sails. Get enough of them together and they can completely surround the sun. There's a ton of science fiction stories that feature these.</p>\n<p>Another would be an artificial fusion powered source of electromagnetic energy that mimics the output of a sun but on a much smaller scale. That could be small enough to be enclosed in a rocky body such as a hollowed out asteroid. There's lots of stories that take this route as well.</p>\n" }, { "answer_id": 193532, "author": "user81804", "author_id": 81804, "author_profile": "https://worldbuilding.stackexchange.com/users/81804", "pm_score": 0, "selected": false, "text": "<p>Well, you could have a running fusion reaction going in there, the size of a smaller moon, that powers some <em>very</em> energy intensive projects (like shooting a concentrated beam to several distant planets/solar systems).</p>\n<p>That way you are producing the energy levels of a star using conversion of hydrogen to helium - if the energy you get out is bigger than the energy getting in your only limiting factor is hydrogen input/recycling to run &quot;perpetually&quot;.</p>\n<p>So you have a &quot;star&quot; inside a planet.</p>\n" }, { "answer_id": 193534, "author": "The Square-Cube Law", "author_id": 21222, "author_profile": "https://worldbuilding.stackexchange.com/users/21222", "pm_score": 3, "selected": false, "text": "<h1>Nope</h1>\n<blockquote>\n<p>The universe is a big place it's enough to know it could happen.</p>\n</blockquote>\n<p>We expect the laws of physics to be the same anywhere in the Universe, so no. If it is not feasible here, it is not feasible anywhere else. Maybe in another universe with different constants.</p>\n<p><a href=\"https://youtu.be/3mnSDifDSxQ?t=37\" rel=\"noreferrer\">The smallest stars possible are brown dwarves, with a lower bound for their mass at around 13 jovian masses</a>. Giant planets do not have a solid surface. So...</p>\n<p><a href=\"https://i.stack.imgur.com/mmoQx.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/mmoQx.png\" alt=\"Size comparison between Earth, Jupiter, and a small brown dwarf.\" /></a></p>\n<p>^{Source: see video in the link.}</p>\n<p>I could stop here, but I'll give you a different idea: <a href=\"https://youtu.be/udFxKZRyQt4?t=216\" rel=\"noreferrer\">neutron stars have an atmosphere and a solid crust</a>.</p>\n<p><a href=\"https://i.stack.imgur.com/n6hvb.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/n6hvb.png\" alt=\"The components of a neutron star: atmosphere, crust and core.\" /></a></p>\n<p>^{Source: see video in the link.}</p>\n<p>You could consider them a kind of planet with a stellar core, if you follow the IAU definition (which is what NASA is quoting in your link) and you find a neutron star orbiting another neutron star.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/193482", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/69342/" ]

[ { "answer_id": 193535, "author": "11Bravo", "author_id": 81144, "author_profile": "https://worldbuilding.stackexchange.com/users/81144", "pm_score": 2, "selected": false, "text": "<p>I recommend:</p>\n<p><strong>2 rows of chairs</strong> along the walls facing inwards. The middle space should be large (maybe 8 feet across) so the bigger species can move around.</p>\n<p><strong>Different cars for different species</strong> so you can make announcements in the way that is easiest for each species. I assume you have special seats for the species.</p>\n<p>Now the only thing is making these cars so they can hold large numbers of people. Since my design is basically a wider train car with less seating the only way to fit more people is to have large terminals and more exits so the trains can be longer.</p>\n" }, { "answer_id": 193548, "author": "Ash", "author_id": 78800, "author_profile": "https://worldbuilding.stackexchange.com/users/78800", "pm_score": 2, "selected": true, "text": "<h3>Design for the biggest and second biggest side by side, then divide the remaining space.</h3>\n<p>I've categorized the people into 3 groups. Big, Human, and Small. And given them 3 different seat configurations.</p>\n<p>I haven't drawn the stairs, walls, seat mountings, safety railing, or windows, but I think they're implicit.</p>\n<p>I've assumed 1500mm seat pitching for the big guys with 5m of headroom and 3m of width for wings, 800mm seat pitching for the human sizes (slightly more generous than an airline) with 3m ceiling (eg - room for overhead bins), and 500mm seat pitches for the small guys, with 2m of roof height for them. But that can be changed based on how dense you want to pack people or the exact size of your races</p>\n<p><a href=\"https://i.stack.imgur.com/7OY1S.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/7OY1S.png\" alt=\"enter image description here\" /></a></p>\n<p>Your big guys have full car height headroom, your humans have the larger ground floor, and your smalls have the upper floor, and their own hallway, but its wide enough can still overtake in the hallway.</p>\n<p><a href=\"https://i.stack.imgur.com/hLw5i.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/hLw5i.png\" alt=\"enter image description here\" /></a></p>\n<p>The car size is 5m wide, 5m high, and 20m long.</p>\n<p><a href=\"https://i.stack.imgur.com/5p3ET.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/5p3ET.png\" alt=\"enter image description here\" /></a></p>\n<p>OpenScad Source</p>\n<pre><code> color(&quot;blue&quot;) cube([5000,20000,5]);\n\n color(&quot;aqua&quot;) translate([3000,800,3000]) cube([2000,17000,5]);\n\n for (y = [1000:1500:20000])\n {\n translate([200,y,800]) cube([1500,400,5]);\n \n translate([200,y,700]) cube([1500,10,700]);\n }\n\n for (y = [1000:800:18000])\n {\n translate([3500,y,400]) cube([1500,400,5]);\n translate([3500,y,300]) cube([1500,10,700]);\n }\n\n for (y = [1500:500:17500])\n {\n translate([4000,y,3400]) cube([1000,200,5]);\n translate([4000,y,3300]) cube([1000,10,400]);\n }\n</code></pre>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/193533", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/80942/" ]

[ { "answer_id": 195909, "author": "Slarty", "author_id": 42450, "author_profile": "https://worldbuilding.stackexchange.com/users/42450", "pm_score": 1, "selected": false, "text": "<p>This would be easy to achieve with a spreadsheet. Have normal hours in one column and 25 hours in a second. Copy each set of numbers down the column in a repeating pattern (or use formulas). A year or two should be manageable.</p>\n<p>Various arrangements and elaborations can be made to this basic theme. For example the date could be included in another column, logic and conditional cells could be used to highlight particular occurrences and complex formula could be developed over multiple columns and hidden if required.</p>\n" }, { "answer_id": 195911, "author": "Ash", "author_id": 78800, "author_profile": "https://worldbuilding.stackexchange.com/users/78800", "pm_score": 2, "selected": false, "text": "<h3>This is an entry-level coding task:</h3>\n<p>So you want something that counts in a pattern that doesn't line up with the days - ie, from input like this:</p>\n<pre><code> events = \n [\n // Time stops every 25 hours, starting from 3am on day 0\n {&quot;name&quot;:&quot;Time stops&quot;, &quot;periodHours&quot; : 25, &quot;startDay&quot; : 0, &quot;startHour&quot; : 3},\n \n // There's free ice cream every 117 hours, starting from day 3 at 7pm \n {&quot;name&quot;:&quot;Free ice cream&quot;, &quot;periodHours&quot; : 117, &quot;startDay&quot; : 3, &quot;startHour&quot; : 19},\n ];\n</code></pre>\n<p>will generate output like this?</p>\n<pre><code>....\nTime stops at day 90 at 18:00\nFree ice cream at day 91 at 13:00\nTime stops at day 91 at 19:00\nTime stops at day 92 at 20:00\nTime stops at day 93 at 21:00\nTime stops at day 94 at 22:00\nTime stops at day 95 at 23:00\nFree ice cream at day 96 at 10:00\nTime stops at day 97 at 0:00\nTime stops at day 98 at 1:00\nTime stops at day 99 at 2:00\nTime stops at day 100 at 3:00\nTime stops at day 101 at 4:00\nFree ice cream at day 101 at 7:00\nTime stops at day 102 at 5:00\n....\n</code></pre>\n<p>This is not a big programming task. It's 45 lines of javascript. Here is a <a href=\"https://jsfiddle.net/fL2jd1cm/23/\" rel=\"nofollow noreferrer\">live Demo</a> - you can change the timing and add more events and pick an area of interest in that from a browser.</p>\n<p>Source code:</p>\n<pre><code> events = \n [\n // Time stops every 25 hours, starting from 3am on day 0\n {&quot;name&quot;:&quot;Time stops&quot;, &quot;periodHours&quot; : 25, &quot;startDay&quot; : 0, &quot;startHour&quot; : 3},\n \n // There's free ice cream every 117 hours, starting from day 3 at 7pm \n {&quot;name&quot;:&quot;Free ice cream&quot;, &quot;periodHours&quot; : 117, &quot;startDay&quot; : 3, &quot;startHour&quot; : 19},\n ];\n\n\n // Your interested in events 10 days either side of day 100\n dayYouAreInterestedIn = 100;\n daysAround = 10;\n\n //////////////////////////////\n\n timeline = [];\n \n events.forEach(function (i, index)\n {\n counter = i.startDay + i.startHour / 24.0;\n \n while(counter &lt; dayYouAreInterestedIn - daysAround)\n {\n counter += i.periodHours / 24.0;\n }\n \n while(counter &lt; dayYouAreInterestedIn + daysAround)\n {\n timeline.push([counter, i.name]);\n \n counter += i.periodHours / 24.0;\n }\n });\n\n timeline = timeline.sort(function(a, b) { return a[0] - b[0];});\n \n \n timeline.forEach(function (i, index)\n {\n document.getElementById('o').innerHTML += \n i[1] + &quot; at day &quot; + Math.floor(i[0]) + &quot; at &quot; + Math.round((i[0] * 24) % 24) + &quot;:00&lt;br&gt;&quot;;\n });\n</code></pre>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/195903", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/82267/" ]

[ { "answer_id": 214876, "author": "codeMonkey", "author_id": 8681, "author_profile": "https://worldbuilding.stackexchange.com/users/8681", "pm_score": 2, "selected": false, "text": "<h2>Ships can Control Surface Area and Temperature</h2>\n<p>A star or planet has a (relatively) static surface, and heat will always flow from hot to cold.</p>\n<p>A ship is significantly more complex.</p>\n<p>To heat up a ship, you can cover it with an isolating material. Heat flux from the covered areas will decrease, and the rest of the ship will warm up.</p>\n<p>Conversely, to cool a ship you can transfer heat to certain exterior sections using a heat exchanger. Common household heat exchangers include Air Conditioning and Refrigeration - any case where you use movement of a working fluid to move heat between two locations.</p>\n<p>Imagine a large set of wing-like radiators protruding from the ship. They have high surface area to radiate energy in every direction, and the ship can control their temperature (and therefore the amount of heat they radiate) by pumping fluids into the structure.</p>\n<p>The key here is that the ship is not some static, uniform body, but a complex system that can impact its own emissions by expanding a small amount of energy.</p>\n" }, { "answer_id": 214935, "author": "Nosajimiki", "author_id": 57832, "author_profile": "https://worldbuilding.stackexchange.com/users/57832", "pm_score": 4, "selected": true, "text": "<h2>Isolate your habitation section from your reactor section</h2>\n<p>Stefan–Boltzmann defines the energy blackbody emissions as:</p>\n<pre><code>P = AσT⁴\n</code></pre>\n<p>Or for those of us who actually like to know what our variables means:</p>\n<pre><code><span class=\"math-container\">$radiantEnergy = $</span>surfaceArea * 5.67 * $temperature^4;\n</code></pre>\n<p>Common logic tells us that the correct course of action is to increase the surface area, and yes, this will help a bit, but look at that power of 4 on the temperature... that is a nice big exponent to exploit meaning there is a lot of room for exponential growth by just getting a little hotter.</p>\n<p>The hotter you are, the faster you radiate heat; so, if you want to push a maximum amount of heat off into space, getting hotter is the way to go. Now because people live on your ship, getting hotter everywhere is a bad idea... and totally unnecessary. By separating your ship into capsules that are attached by thermal resistant materials, you can heat each part of your ship to its maximum threshold while keeping living quarters relatively cool.</p>\n<p>For your habitat section you need to maintain a temperature of about 293K, but that is just what is good for humans to live in. A much larger part of your ship will be the greenhouse, but no-one says you have to live off of vascular plants. By farming Algea as you main food source you can crank this compartment up to 335K... but the next part will make this a trivial measure. Lastly is the reactor section. Now this is where establishing a true MAX has to digress a bit from &quot;hard science&quot; and into &quot;science based&quot; because we really don't know what power sources or materials we will be limited by in the future. However, if you were to construct a large capsule with thermal properties similar to tungsten, you could heat up your rear section to somewhere in the range of 2750K making it glow like a giant incandescent lightbulb... at which point it could passively heat your other 2 sections if you put it at the right distance.</p>\n<p>So, let's say your ship is made of 3 equal sized capsules, all with a surface area of 1/3 the OP's proposed total surface area, this gives your habitat the ability to compensate for 9.17e10W, your farm section 1.57e11W, and your reactor section 7.12e14W. This is because your glowing hot reactor could offset ~7,750 times as much heat per surface area as a room temperature module.</p>\n<p>This still only puts you at about 7% of your target... which is honestly not that bad. This still keeps you working in human time scales, but there are two things you can to to further boost this if you really want to hit that 1e16W benchmark.</p>\n<p>First, there is no reason the modules should be the same size. Your farm will probably need to be much bigger (thus more surface area) than your habitat, and depending on choices you make as an author, your reactor/fuel/propulsion section could have much more surface area than the rest of your ship if you picture a fuel system that stores hydrogen for fusion with no oxygen to react with, you might as well store it as a super heated plasma as long as it does not get hot enough to melt your tungsten containment tanks. In this case, if you make your ship something like 5% habitat, 10% farms, and 85% reactor section, you could get yourself to about 17% of your target goal.</p>\n<p>Secondly, you can go with higher heat. I chose 2750K as the operating temperature of a lightbulb... much hotter and tungsten become structurally unsound, but adding a meta-material into a space setting that can operate higher than this is not implausible. If you go with a ship that is 85% hot capsule and about 4280K, you should be able to reach 1e16W with that total surface area... but that would significantly exceed the melting point of any known element; so, if you are going for a more hard science universe, I would accept the slightly lower power output.</p>\n<p><a href=\"https://i.stack.imgur.com/5w1NW.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/5w1NW.png\" alt=\"hot reactor ship\" /></a></p>\n" }, { "answer_id": 214942, "author": "Adrian Colomitchi", "author_id": 26061, "author_profile": "https://worldbuilding.stackexchange.com/users/26061", "pm_score": 2, "selected": false, "text": "<p>Addressing some confusions in the original question</p>\n<blockquote>\n<p>This means that <strong>if</strong> the space ship uses the equivalent of all the solar energy hitting the earth (around <span class=\"math-container\">$10^{16}$</span> Watts) for life support ...</p>\n</blockquote>\n<p>First at all clarify for yourself your naive interchangeability use of energy (as measured in joules) and power (as measured in Watts). A generation ship is not an totally opened system in which any energy that you use immediately transform in heat that needs to be evacuated <em>immediately</em>.</p>\n<p>Then, what if they <strong>don't</strong> need the solar entire <em>power</em> that hits the Earth? It's not like 100 million people needs the <em>power</em> which sustain the entire life on Earth, from the depth of Mariana trench to the top of troposphere, including the formation of hurricanes, ocean currents and rain.</p>\n<blockquote>\n<p>But if we assume a spaceship as a 10km cube and a temperature of 300 Kelvin the total heat radiation by the Stefan-Boltzman law above is only <span class=\"math-container\">$5.67*10^{-8}*300^4*(6*10^8) W = 2.75*10^{11} W$</span>. Meaning by my naive interpretation of physics they would need to use energy of that order of magnitude to not overcook themselves, for <span class=\"math-container\">$10^{16} W$</span> they would need a much much bigger or hotter spaceship.</p>\n</blockquote>\n<p>Not only the assumption that you need the Sun output just for 100M people is wrong, but the rate consideration are totally exaggerated - you simplified your model too much.</p>\n<ol>\n<li><p>the ship is not a lump of steel or something. You have multiple energy sinks inside the ship - the very food that you grow will take light and heat to run those biochemical reactions and store them as bound energy. Which means the temperature of your ship isn't going to increase immediately (the way it happens with a lump of steel). True - eventually, you are going to have it transformed in heat (after you eat, digest and burn those nutrients), but there's be at a slower rate than if you just apply the same extra energy to a lump of steel (or amount of gass)</p>\n</li>\n<li><p>a generation ship will need to be masters of recycling or it won't last long. Heat is one thing that one can recycle to some extent. As an example, you have a large storage of water that you can afford to heat up using a thermal pump - and you will get to reuse part of the stored heat (the thermal gradient) sometime down the line. By doing it, you will create extra heat in operating that those heat pumps. But because a heat pump can reach 600% energy moving efficiency, you will only need <em>theoretically</em> to get rid of 1/6 extra heat. Do this in many other sophisticated ways and you address the rate in which you need to purge &quot;waste heat&quot; (heat in spatial configuration with such a low gradient inside the ship that you can't use to extract <em>controllable</em> power to run your processes. The equivalent of the &quot;heat death of Universe&quot; inside the microcosm of your ship)<br><br>\nOne on top of the other, in principle, <em>you run your ship by recycling everything, with only the cost of extra energy required to recycle everything</em>. And you can lower the amount of energy required to recycle everything to a much lower value than the cost requiring &quot;brand new energy from the Sun in every moment and throwing the excess away.&quot;</p>\n</li>\n<li><p>All of the above would address the rate of the heat purge, but bottom line you will still need to purge it in the end. You can still control how you purge it into the lower temperature of the surrounding space. All your ship being thermally isolated <em>with the exception of the radiators</em> means that, by controlling the direction and the radiating area and the temperature of those radiators, you can use the thermal radiation for propulsion. Happened inadvertently with <a href=\"https://en.wikipedia.org/wiki/Pioneer_anomaly\" rel=\"nofollow noreferrer\">Pioneer 10/11</a> anisotropic radiation pressure slows them at a rate of 1 km/h over a period of ten years.</p>\n</li>\n</ol>\n<hr />\n<p>Bottom line: I don't know how or if a generation ship can be actually built, because it will be a matter of carefully trying to solve a great number of problems. What I can tell for sure is that <strong>you can't demonstrate the possibility or impossibility of a generation ship with computations on the back of a napkin using dumbed down models</strong></p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/197861", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/69605/" ]

[ { "answer_id": 197868, "author": "Ash", "author_id": 78800, "author_profile": "https://worldbuilding.stackexchange.com/users/78800", "pm_score": 0, "selected": false, "text": "<p>Consider:</p>\n<ul>\n<li>Brewer / barkeep. Water is typically contaminated with all sorts of nasty things in this time period, it's safer to brew it into beer and drink a low alcohol swill than water.\n<ul>\n<li>They may also double as an Innkeeper, or you may need a separate one - (depending on distance to next largest town and traffic through the town). It sounds like a lot of the income to the town comes from travellers on their way to the unknown and traders passing through. With small towns usually being set up a days travel apart from each other, an inn may be not only required, but the best source of income.</li>\n</ul>\n</li>\n<li>Healer / apoticarian / friendly neighbourhood witch / midwife / etc. Someone who knows a little bit about the intricacies of human bodies and the herbs in the area.\n<ul>\n<li>People will be injured and need healing from mining, exploring, and general life.</li>\n<li>Your town has 120 people aged 10 - 50, lets says 20 are children, (or chaste, or infertile) and exclude them, leaving 100 fertile people, 50 romantic pairs post puberty having unprotected sex - there'll be multiple babies born most months.</li>\n</ul>\n</li>\n<li>Priest. While not essential, they'll come to you whether you want them or not, as the frontier towns are gateways to the unbaptised who need saving, and your towns leader wont have the courage to evict the church.</li>\n</ul>\n" }, { "answer_id": 197869, "author": "SirTain", "author_id": 79720, "author_profile": "https://worldbuilding.stackexchange.com/users/79720", "pm_score": 3, "selected": false, "text": "<p>Honestly, from a medieval fantasy setting for a frontier town, I think you may have diversified your population a little too much.</p>\n<p>Traditionally, 80-90% of peasants were farmers, and I'd imagine that number climbs above 90% the further outside of a kingdom you get. Here are my thoughts:</p>\n<ul>\n<li>There's probably no miners. A village on the outskirts of an empire probably doesn't mine anything because mining is specialty work that requires a lot of hidden infrastructure. You might have a dedicated potter, but if you do he probably collects his own clay in a village that size.</li>\n<li>There's probably only one guy and his sons on bandit watch, they probably double as local law enforcement and run a store or a farmstead near the village, since a village of 120 people doesn't have a problem with local bandits, and other bandits are called &quot;raiders&quot; and get everyone in the town organized into a posse in order to fight them.</li>\n<li>There's a not insignificant chance that everyone's homes are in a central village and that the farm lands extend into the land around them. A town that size likely works under 1800 acres of land (pulling some numbers from <a href=\"https://worldbuilding.stackexchange.com/questions/125445/size-of-family-owned-medieval-farm\">this post</a>), which would cover a square less than 2 miles on a side. If your town is in the immediate center, then anyone could expect to reach any plot of land. Even if they aren't communal farmers, they could divide the land into long, thin strips which is also not unheard of in that time period. <em>Edit: see this wikipedia entry on <a href=\"https://en.wikipedia.org/wiki/Ribbon_farm\" rel=\"noreferrer\">Ribbon Farms</a></em></li>\n<li>Normally, I'd expect a village to get anything it doesn't produce from travelling merchants, but if they are on the border of the wilderness, you can just expect them to be even more poor than normal as it will be difficult to find people to trade with for even simple necessities like iron.</li>\n<li>Edit: PcMan mentioned coal, which made me think firewood. I would expect a forest of around 20 acres to produce 4 cords of firewood from just the dead/fallen trees. That's probably more than enough to support a peasant through the winter. You could probably support the whole village on under 5 square miles of forest then. You might have a dedicated woodcutter then depending on how far from the farmland the woods are (the father the woods, the more likely there's a dedicated woodcutter).</li>\n</ul>\n" }, { "answer_id": 197872, "author": "Angry Muppet", "author_id": 55743, "author_profile": "https://worldbuilding.stackexchange.com/users/55743", "pm_score": 2, "selected": false, "text": "<p>Also consider.</p>\n<ul>\n<li><p>Mayor: As an alternative to having clergy-rule, elder-counsel rule or rule by Plutarchs - To generally organize distribution of any funds used for the public good (bandit protection, town boundary maintenance, streets if applicable), preside over secular ceremonies, negotiate territory boundaries with neighboring towns (if any).</p>\n</li>\n<li><p>Tax collector/Book-keeper: Works closely with the ruling class, also acts as intelligence gatherer. Possibly in charge of ensuring food reserves meet the need between crops.</p>\n</li>\n<li><p>Judge/Sheriff/Guard-Captain: To mediate disputes and arrange the keeping of the peace and guard effectiveness. As an alternative again to clergy mediated punishment, they can perhaps have a mandate to punish, execute if necessary, perhaps reporting to whoever's in charge.</p>\n</li>\n<li><p>Smith: Versatile, should be able to work with iron and wood, turning bowls and plates. Ploughs, tools and horseshoes need making/replacing/mending, not to mention the vital task of making beer barrels for the tavern and pots for cooking in each household. If there's enough work (there would be) then an apprentice (maybe two).</p>\n</li>\n<li><p>Potter: All households need flagons, bottles. The tavern needs the same. Bowls and plates for the privileged members of the community and sale at market.</p>\n</li>\n<li><p>The Tavern-keep/Brewer: Self explanatory, family business. May need a certain expertise at calming heated disputes. A good listener, helps cohere society.</p>\n</li>\n<li><p>Dogs: To keep the rat population down around any winter food-stores, and to alert dozing guards to a potential threat, and to scare-off the threats.</p>\n</li>\n</ul>\n" }, { "answer_id": 197904, "author": "Koon W", "author_id": 83216, "author_profile": "https://worldbuilding.stackexchange.com/users/83216", "pm_score": 1, "selected": false, "text": "<p>1 thing I dont see mentioned yet: How is fresh water accessed and laid out?</p>\n<p>Rivers? Wells? Lakes? Ponds?\nWhat is the quality of this water? This effects agricultural output and quality.</p>\n<p>Where does it originate? Who controls it at the town and upstream?</p>\n<p>Precipitation? Seasonally?</p>\n<p>Water is a main concern of agriculture, and often lords built defensive structures like guard towers to secure the main well or river.</p>\n<p>Water body layouts can also affect town layouts as well as major defensive strategy--even against the bandits you mentioned, but also in times of war and border disputes, common in medieval times.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/197867", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/71795/" ]

[ { "answer_id": 200193, "author": "Qami", "author_id": 51300, "author_profile": "https://worldbuilding.stackexchange.com/users/51300", "pm_score": 5, "selected": true, "text": "<p><strong>A giant catamaran.</strong></p>\n<pre><code>A top view:\n ____________________________________________________\n / \\\n / Starboard hull \\\n| Bow Stern |\n \\ ____ ____ ____ ____ ____ ____ /\n \\__/ \\__/ \\__/ \\__/ \\__/ \\__/ \\____/ &lt;-Hunter bays along\n inside of both hulls\n __ __ __ __ __ __ ____\n / \\____/ \\____/ \\____/ \\____/ \\____/ \\____/ \\\n / \\\n| Port hull |\n \\ /\n \\____________________________________________________/\n\nA side view:\n Structure connecting the hulls \n |\n V Rope towing hunter through the wake\n ____________________________________________________ |\n \\ /====\\ /====\\ /====\\ /====\\ /====\\ /====\\ /`-. V \n __||______||______||______||______||______||______||____`-. |\\ \n| | `-__|_\\_ &lt;- Arriving hunter\n~\\ /~~~~~\\____/~~~\n \\____________________________________________________/\n</code></pre>\n<p>The ship has two long hulls, structurally connected above and possibly below the waterline -- above, high enough to clear the masts/highest points of the hunters. If below, deep enough to not interfere with the hunter's keels.</p>\n<p>The inside-facing sides of the two hulls have the docking bays for the hunters, which can be closed off via sliding doors in heavy weather. A system of pulleys and ropes attached to the structural supports above can assist in launching, catching and docking the hunters.</p>\n<p><strong>Getting past/through the wake</strong></p>\n<p>The connecting structure over the two hulls can function as a network of cranes/tracks. It may be unsafe/unfeasible for a hunter to successfully navigate past the wake by itself, but if it's being held by one or more ropes from above, you should be able to keep it steady until it's been let out far enough behind for it to navigate. To pull it back in, the catamaran can toss a floated cable/rope out from between the two hulls. Make the rope as long as it needs to be to drag a safe distance behind the wake. This rope could be caught by a hunter, and then it can be towed forward into the between-hull space where it can be more easily handled and docked.</p>\n" }, { "answer_id": 200196, "author": "JBH", "author_id": 40609, "author_profile": "https://worldbuilding.stackexchange.com/users/40609", "pm_score": 3, "selected": false, "text": "<h2>Forget the wake by avoiding it altogether</h2>\n<p>The idea of having a huge, hollow ship is unrealistic even in a fantasy setting. Aircraft carriers are made out of steel and not English Oak because ships that size require the advantages of steel and mighty engines to exist. You didn't say whether or not your ships are made of steel or depend on combustion.</p>\n<p>So let's assume your fantasy setting is akin to the Golden Age of Sail. Your hunters are, I assume, fast short-range ships. It's implausible (frankly unbelievable) that your carrier would have dock or bay doors that would open to let them exit and enter. To do so would require a power source other than wind and sail.</p>\n<p><strong>I recommend long, skinny, and cranes</strong></p>\n<p>Let's assume a very long, quite skinny ship that has cranes along both sides of the ship for lifting the hunters out of the water. This not only provides access for repair and resupply, but keeps the hunters out of the water to reduce drag, holding back the carrier. Cross-beams could be moved into position to lock the hunter in place, which would have the advantage of adding the hunter's sails to the overall propulsion of the carrier.</p>\n<p>A pair of cranes mid-ship have the unique ability to lift up-and-over, thereby bringing very damaged hunters into an onboard dry dock for extensive refit.</p>\n<p>The long carrier would have the advantage of speed due to a minimum water cross-section, which would also allow for a lot of keel-aligned sails, but would have the disadvantage of turning a bit like a lead brick. Good! There should be disadvantages to outweigh the advantages.</p>\n<p>An average carrier might host eight hunters with cargo capacity to allow for 3-7 year patrols. Do I have any stats to support that? Nope. It just feels believable to me.</p>\n<p><strong>But what about that darn wake?</strong></p>\n<p>Since the hunters are always working along side the carrier and never behind it, the wake is a non-issue.</p>\n<hr>\n<h2>Post edits answer</h2>\n<p>The OP has since edited his/her question to indicate the ships are made of metal and have powered engines.</p>\n<p>In this case, I don't advocate a carrier. I advocate tethers. All the hunters can move under their own power so long as supplies and fuel are available. This minimizes the size of the carrier and improves both its defense and its economy. Rather than being a huge, lumbering clunker when the hunters are deployed, it's a small supply ship... fast and maneuverable. A single &quot;bay&quot; at the back (not actually covered, but a forked portion of the stern) would exist where a hunter can be brought in and parked for repair and maintenance.</p>\n<p>Curiously, this reflects an answer I gave to <a href=\"https://worldbuilding.stackexchange.com/a/177155/40609\">Optimum Shape for a Space Dreadnought</a>.</p>\n" }, { "answer_id": 200200, "author": "JANXOL", "author_id": 81108, "author_profile": "https://worldbuilding.stackexchange.com/users/81108", "pm_score": 4, "selected": false, "text": "<p><strong>Torpedo boat carrier</strong></p>\n<p>These things were actually done in real life with torpedo boats and larger ships which carried them out to sea. One example of such vessel would be the La Foudre (later converted to a sea plane carrier.</p>\n<p>The same principles can be applied here, provided the Hunter ships are small enough in relation to the carrier and the cranes you have available.</p>\n<p>The Hunters would be stored on deck in manner similar to ship's boats and in absence of sails the deck would be full of crane assemblies used to move the hunters in and out of water on either broadside. The motion of the ship isn't that big of a problem as long as you can slow down a little. Take for example floatplane recoveries, where scout planes would land on water and pull up alongside the ship while it was moving at relatiovely low speeds (about 10 knots) and be pulled up onto the deck with a crane. Arguably the more dangerous part would be launching, as with planes it turned out that speed needs to be much smaller, but in case of boats the situation shouldn't be as severe. You should however make sure your cranes can lower the Hunters into the water with enough clearance from the carriers hull to avoid collissions.</p>\n<p>Here's a photo from the La Foudre, you can see a torpedo boat being hoisted up (or down) and another one stored on deck.</p>\n<p><a href=\"https://i.stack.imgur.com/Fs3Bf.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/Fs3Bf.jpg\" alt=\"La foudre torpedo boats\" /></a></p>\n" }, { "answer_id": 200201, "author": "PcMan", "author_id": 80825, "author_profile": "https://worldbuilding.stackexchange.com/users/80825", "pm_score": 4, "selected": false, "text": "<p>Surely you are just thinking of something like this?</p>\n<p><a href=\"https://i.stack.imgur.com/5Fmy7.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/5Fmy7.jpg\" alt=\"enter image description here\" /></a></p>\n<p>That there is an <a href=\"https://en.wikipedia.org/wiki/Amphibious_assault_ship\" rel=\"noreferrer\">Amphibious Assault Ship</a>.<br />\nA large part of its role is to carry, launch and service a fleet of smaller ships (and helicopters)</p>\n" }, { "answer_id": 200262, "author": "Keager", "author_id": 79545, "author_profile": "https://worldbuilding.stackexchange.com/users/79545", "pm_score": 1, "selected": false, "text": "<p>The US Navy did have such a ship class. Made out of metal, and when launching, the ship was partially sunk. They were LSD, known as Landing Ship Dock. How they work is beyond me, as they are now part of the mothball fleet. The one I know of is the USS Thomaston, LSD-28.\nI could not comment on PcMan's post.</p>\n" }, { "answer_id": 200299, "author": "Knut Boehnert", "author_id": 84754, "author_profile": "https://worldbuilding.stackexchange.com/users/84754", "pm_score": 2, "selected": false, "text": "<h2>Like a whaling fleet?</h2>\n<p>The question reminds me of the whaling fleets during the first half of the 20th century.</p>\n<p>Both the factory ships (big, lumbering, sturdy, lots of space) and whalers (small, nimble, rough, cramped) would journey together. At times along the way the factory ship resupplies the whalers if necessary. Considering that for a navy there is no need to conserve space for a captured product this space becomes useful for power cell storage / reload, ammunition and food and water.</p>\n<p>As the whalers were ocean-going vessels there was no need for these to be carried or towed by the factory ship. Only restricted by the space for food, water and fuel the whalers were capable of independent operation away from the factory ship.</p>\n<h2>Use of resources</h2>\n<p>If this nation is capable of producing big ships like a &quot;carrier&quot; then there is plentiful available metal.</p>\n<p>Also these big vessels are capable of operating in open seas. So navigation is mastered.</p>\n<p>In turn why would this nation restrict itself to product smaller vessels requiring carriers? It is more sensible to have smaller ocean going vessels that have the additional benefit of operation along the home coast as patrol crafts. One design, two functions. Can be used where needed.</p>\n<h2>Modus operandi</h2>\n<p>Why would a carrier carry ships? In a way this only makes sense to beat another nation's navy. However this does not fulfil the objective of projecting military or political power over another nation.</p>\n<p>Food and water in the late industrial age where metal ships with screw propulsion became dominant were not as restrictive as fuel capacity.</p>\n<p>So the hunters in this question have a limited fuel capacity which limits their effective range reach. In contrast a big ship (tender) can carry lots of fuel (besides food and water) to extend that range of hunters. However this big ship requires protection which a small / big fleet of hunters can provide.</p>\n<p>Maritime transfer of resources between ships in open sea is not a preferred option. Having said this it depends mainly on equipment (ropes, maybe cranes) and training. Any navy big enough to create big tenders tends to have at least a professional core of sailors.</p>\n<p>Final thought on modus operandi of tenders: These ships require a dedicated effort of a nation to build and operate. Just using these to extend the range of smaller hunter vessels to fight other ships &quot;for the glory of sinking ships&quot; makes only sense if this supports the other big and medium ships that land troops to conquer other nations or parts of the world providing scarce resources.</p>\n<h2>The wake problem</h2>\n<p>A big ship only makes a big wake if it sails fast. Ships and boats going alongside each other requires protocols of communication and coordination that professional navy personnel gets training for.</p>\n<p>A fast moving ship deploying small vessels at fast speed into up to medium open seas is cool. And if possible by physics we would have historical examples.</p>\n<h2>Conclusion</h2>\n<p>I just fear this carrier question is impractical for the reasons above. The idea however is cool.</p>\n" }, { "answer_id": 201014, "author": "Argent Hellion", "author_id": 84704, "author_profile": "https://worldbuilding.stackexchange.com/users/84704", "pm_score": 0, "selected": false, "text": "<ul>\n<li>THE ANSWER</li>\n</ul>\n<p>After more research and an in-depth comparison of speeds and sizes, I had arrived to the conclusion that the Catamaran build is the best one when it comes to providing speed, size and stability. I would take the torpedo boat carrier design and widen it into the Catamaran build, providing the carrier with 6 cranes spread on the sides so it could service 6 Hunters at once. The Catamaran design with the hangar bays being underneath the main deck simply isn't feasible due to such a large vessel being forced to sit as low in the water as possible for the sake of stability.</p>\n<p>As far as speed is concerned, I've locked the carrier's speed for operations at 10 knots (20kph) and I've locked its maximum speed at double that number. The Hunter's speed are still something I'll be working on...</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/200192", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/84704/" ]

[ { "answer_id": 200677, "author": "o.m.", "author_id": 6402, "author_profile": "https://worldbuilding.stackexchange.com/users/6402", "pm_score": 4, "selected": false, "text": "<p>Efficiency means something that is easy/quick to encode, easy/quick to pronounce and understand, and easy/quick to decode. base64 was never made to be read by a human, and saying &quot;capital&quot; every now and then will seriously slow you down. Hexadecimal is slightly better than spelling binaries, but perhaps too short. <em>Seven</em> are two syllables.</p>\n<ul>\n<li>Define 32 (or 64 or 128) short, distinctive words. Which ones depend on the languages and accents of the participants. <em>Cat, Dog, Fox, ...</em> but if <em>Cat</em> is in the list then <em>Bat</em> should not be there, or vice versa.<br />\nThe suggestion by the commenter Zeiss Icon to use <a href=\"https://en.wikipedia.org/wiki/NATO_phonetic_alphabet\" rel=\"noreferrer\">NPA</a> has merit, but it is limited to 5-bit units. Finding 64 words might be feasible ...</li>\n<li>Assign each word a number.</li>\n<li>Break the binary data into &quot;bytes&quot; of 5 (or 6 or 7) bits, encode and read the words.</li>\n<li>Listen to the words and then decode into &quot;bytes.&quot;</li>\n</ul>\n<p>It might be a good idea (even if it decreases efficiency) to add a <a href=\"https://en.wikipedia.org/wiki/Checksum\" rel=\"noreferrer\">checksum</a> to your transmission.</p>\n" }, { "answer_id": 200678, "author": "Qami", "author_id": 51300, "author_profile": "https://worldbuilding.stackexchange.com/users/51300", "pm_score": 4, "selected": false, "text": "<p><strong>Choose X syllables, and then base-X-encode your data.</strong></p>\n<p>Choose the largest set of syllables that you consider for your purposes to be mutually distinguishable, and then base-X-encode your binary data, where X is the number of syllables you've chosen.</p>\n<p><strong>A simple example</strong>: suppose we choose only syllables that begin with a consonant, and are followed by a vowel, from the following sets:</p>\n<p><em>{p,k,t,ch,b,g,d,j}</em></p>\n<p><em>{a,e,i,o,u}</em>.</p>\n<p>We now have 8 x 5 combinations, giving us 40 syllables.\nYou can base-40 encode your binary data into a rapid-fire of syllables that would sound something like:</p>\n<p><em>&quot;pagidachotajapikachutagujiko.... &quot;</em></p>\n<p>This example used latin-alphabet letters and assumed a more-or-less standard English pronunciation. To make a more rigorous system, it would be advisable to use the <a href=\"https://en.wikipedia.org/wiki/International_Phonetic_Alphabet\" rel=\"noreferrer\">International Phonetic Alphabet</a> to choose the sounds for your syllables and ensure that you avoid phonemes that (1) would be difficult to distinguish from one another and (2) do not lend themselves to fast pronunciation.</p>\n<p><strong>Note:</strong> This answer is similar to o.m.'s...just &quot;encoding&quot; at the level of syllables instead of words. By customizing your list of syllables to all be quickly-speakable and using every possible combination, I expect this would tend to increase the efficiency of information per syllable. However, if the memory and cognitive processing rate of the average humans using it is taken into account, it's possible (probable?) that o.m.'s word-sequence-based transmissions will be more easily remembered without error.</p>\n" }, { "answer_id": 200680, "author": "Cadence", "author_id": 51094, "author_profile": "https://worldbuilding.stackexchange.com/users/51094", "pm_score": 2, "selected": false, "text": "<p>What you need is a drum. Actually, any old stick and a hard surface to strike it on will do in a pinch, but that limits you to binary data (&quot;hit&quot; or &quot;no hit&quot;) and doesn't allow for any out-of-band information such as &quot;end of message&quot;. A drum that makes a different sound on sustains (the stick is kept in contact) vs. rests (the drum is allowed to vibrate on its own) will let you have notes of varying lengths which can form more complex codes. Drumbeats can be very fast and accurate, far more than most singers, and can send longer messages without pausing.</p>\n<p>For instance, with such a drum, you could have a code of &quot;short&quot; and &quot;long&quot; beats that encodes letters and punctuation; you may know this as Morse code. Or, you could cut to the chase and encode a binary or quaternary (or any other convenient base) number directly as a series of beats.</p>\n<p>The advantage and goal here is to keep the encoding and decoding simple, because the limitation is not in the ability of the human body to make noise, but the speaker's ability to figure out which noises they ought to be making. A base-32 or -64 code is more efficient in terms of symbols, but any speed benefit is undercut by the user's own speed in interpreting those symbols as actual sounds.</p>\n<p>In contrast, using only three symbols (short, long, and silence), Morse code is a proven example of encoding and decoding a message, by human operator, in real time. So it makes sense to investigate the area of low-density but high-speed communications to make most efficient use of the human part of the equation.</p>\n" }, { "answer_id": 200681, "author": "David R", "author_id": 65145, "author_profile": "https://worldbuilding.stackexchange.com/users/65145", "pm_score": 3, "selected": false, "text": "<p>The best way to communicate binary information long distance by human &quot;vocal&quot; is by a whistle language. The existing whistle languages are used in rough landscapes to communicate longer distances than possible through voice.</p>\n<p>In this case, you can have one pitch for one and another for zero (or work up a common set of tones for numbers 0 through 7).</p>\n" }, { "answer_id": 200683, "author": "JBH", "author_id": 40609, "author_profile": "https://worldbuilding.stackexchange.com/users/40609", "pm_score": 4, "selected": false, "text": "<h2>Sing it</h2>\n<p>You're thinking too much along programming lines. This is valuable for the sake of compression: but everything else you've mentioned (like hex encoding or base64) is just a way to make binary more consumable by the human eye (and other things).</p>\n<p>Frankly, from a programmatic perspective, the only thing you really care about is <em>compression.</em> You want to send as little data as possible to guarantee maximum transmissibility. But other than compression, it doesn't matter how you express your ones and zeros. (It helps to remember the good old days on the Apple II computers where the average geek cared about Assembly Language.)</p>\n<p><strong>What you really want to think about is music</strong></p>\n<p>If you want the average human to convey ones and zeros, ask them to sing. Generally speaking there are only seven notes — but there are half notes, quarter notes, sharps and flats. Those alone give you 63 notes. Add shifts in octave and you get more. Your average person can span two octaves. Now we're up to 126 notes. 127 with a &quot;pause&quot; (no sung note in the meter of the song). Expand the vocal range just a hair and you get to all 128 positions, allowing you to express every combination of &quot;11111111&quot; or 2⁷.</p>\n<p><em>BTW, I'm not a music expert. I wouldn't be at all surprised that you could express a whole lot more data than 2⁷ with the magnificent expressiveness of musical notes.</em></p>\n<p>From here, it's just a question of mapping notes to binary combinations and, boom, vocally expressed digital data.</p>\n<p>Finally, I'm not suggesting that what you get would <em>sound</em> good... only that it could be done.</p>\n<p><a href=\"https://i.stack.imgur.com/hg72a.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/hg72a.png\" alt=\"enter image description here\" /></a></p>\n" }, { "answer_id": 200720, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 3, "selected": false, "text": "<p>Human speech is astonishingly effective as establishing communication between humans. Not only does it use the vocal chords efficiently, but it uses the language centers of the brain efficiently as well. Our languages have just enough redundancy to support humans.</p>\n<p>Accordingly, the best way to have an average human transmit and recieve binary data is to map it to human language. Use an AI to construct an injective mapping between a string of bits and sentences in English (or whatever the native language of your characters is). The result should sound like a typical monologue.</p>\n<p>This is almost certainly the most efficient way to communicate a binary string between people. If one side has other tools available , such as a tape recorder, there may be more efficient means\nBut never underestimate the benefits of leveraging a few decades of speech on behalf of both parties.</p>\n" }, { "answer_id": 200736, "author": "Neil_UK", "author_id": 34210, "author_profile": "https://worldbuilding.stackexchange.com/users/34210", "pm_score": 7, "selected": true, "text": "<p>This problem has been much studied. While it may be difficult to define what 'best' is, there is a very efficient one already in existence, and that's <a href=\"https://en.wikipedia.org/wiki/PGP_word_list\" rel=\"noreferrer\">PGP Words</a>. This method was designed for transmitting long binary keys over a voice link, each word encoding a whole 8 bit byte.</p>\n<p>It addresses a number of problems you probably haven't thought of, like reliability over a voice link. What happens if a word is missed, or a repetition for clarity is mistaken as an actual repetition or, reading from a long list, two words get swapped?</p>\n<p>With 8 bits per word, you would normally require 256 words. The system is more sophisticated than that, and uses 512 words, an 'even' table of two syllable words, and an 'odd' table with three syllables, that are used alternately. That way, a missed or repeated word, or two swapped words, can be immediately spotted as an error.</p>\n<p>Here are the first few and last few, from the wikipedia article linked above. The whole table can be printed on a single sheet of A4. They are in alphabetical order to aid the receiver. Obviously the list is optimised for English. Speakers of other languages may prefer a different list.</p>\n<pre><code>Hex Even Word Odd Word\n--- --------- --------\n00 aardvark adroitness\n01 absurd adviser\n02 accrue aftermath\n03 acme aggregate\n04 adrift alkali \n\n.. ...... .......\n\nFB watchword Wichita\nFC wayside Wilmington\nFD willow Wyoming\nFE woodlark yesteryear\nFF Zulu Yucatan \n</code></pre>\n<p>Quote from the wikipedia article</p>\n<blockquote>\n<p>The PGP Word List was designed in 1995 by Patrick Juola, a computational linguist, and Philip Zimmermann, creator of PGP. The words were carefully chosen for their phonetic distinctiveness, using genetic algorithms to select lists of words that had optimum separations in phoneme space. The candidate word lists were randomly drawn from Grady Ward's Moby Pronunciator list as raw material for the search, successively refined by the genetic algorithms. The automated search converged to an optimized solution in about 40 hours on a DEC Alpha, a particularly fast machine in that era.</p>\n</blockquote>\n<p>An alternative for a 4 bit nybble per word is simply to use the hex alphabet, perhaps using the ICAO/NATO pronunciation, 'zero' to 'niner' then 'alpha' through to 'foxtrot'. There are more than 16 further letters left if needed for even/odd coding. Whether the complexity of the 512 words needed for doubling the throughput with PGP words is warranted against the simplicity of hex begs the question of how you define 'best', what factors in the setup or operation of the communication are important.</p>\n<p>You could get even higher efficiency by using more bits per word. 12 bits would need a 4096/8192 long dictionary. This would sacrifice much of the hard-won inter-word phonetic distance of the PGP scheme, so would require a higher fidelity voice channel, and more careful speakers.</p>\n<p>Noting ruakh's comment, it's worth looking at the speed of the channel. His estimate is two seconds per word, which would probably be quite good for untrained users. That's 4 bits/s. If we compare that with Morse code, the minimum speed required by the FCC to grant a radio operator's license used to be 16 five-letter code groups per minute, which very roughly equates to about 8 bits/s.</p>\n<p>The difference between the two systems is that Morse Code requires training. I couldn't transcribe Morse, at any speed, without a lot of practice, and probably some tuition as well. Many English speakers could transcribe those words without practice, but what about those with a limited vocabulary, or English as a second language, or speakers of other languages? PGP words is not really training-free, if it's to be used by any human at all. It's only ready-to-go if used by people like those who invented it, educated fluent English speakers, being a programmer would help as well. It's probably a skill that's easier to pick up than Morse though.</p>\n<p>With speed in mind, it might be worth reviewing the performance of hexadecimal via ICAO pronunciation. While a word every two seconds would be good going for recording a PGP word manually, I think hexadecimal could be done at easily twice that rate, transcribing as you go, making the bit rate of the two methods equivalent.</p>\n<p>Clearly a lot of other assumptions about the training or experience of users, the setup costs, the quality of the audio link, have to be defined before the best system can be determined.</p>\n" }, { "answer_id": 200743, "author": "PcMan", "author_id": 80825, "author_profile": "https://worldbuilding.stackexchange.com/users/80825", "pm_score": 2, "selected": false, "text": "<p>I'd encode the binary to a huge lookup table of values and concepts, link these concept and values to phonemes that are easy for the human vocal apparatus to process, and for the human ear to hear.</p>\n<p>Group these sounds into more complex structures, for improved bit density.</p>\n<p>Ideally, I'd assign some contextual meaning to these complex structures of phonemes, to ensure greater ease of comprehension, and cut down on the error rate when producing them.\nThere would be intricate rules regarding juxtaposition of these structures, disallowing obvious errors. We might need to make lookup tables of these structures, as an aide to learning and for error-checking.</p>\n<p>Of course, the art of learning such a highly complex and convoluted data pattern will need to commence from childhood, and continue throughout adult life.</p>\n<p>For convenience, we will call this convoluted binary-encoded-as-phonetic-sounds-in-structured-groups-with-contextual-meanings an easier name to identify it.</p>\n<p>How about &quot;English&quot;?</p>\n" }, { "answer_id": 200758, "author": "BMF", "author_id": 62241, "author_profile": "https://worldbuilding.stackexchange.com/users/62241", "pm_score": 1, "selected": false, "text": "<p>There are approximately 470k English words. <span class=\"math-container\">$\\log(470000)/\\log(2)$</span> yields 19 bits per word. Good luck teaching kids all English words and their binary counterparts as well.</p>\n<p>At that point, it might be easier to create 256 &quot;words&quot; at 1 byte per word. Words that are syllabically short and enunciated carefully. You could likely do 1-syllable each, so, &quot;cabagathadedodunit&quot;, where each syllable is a 1-byte value &quot;word&quot;. That string would yield 8 bytes or 64 bits.</p>\n<p>If you think your kids are just really damn smart, you could bump that up to 65536 words stowing 2 bytes per word with more syllables per word, but that presents a much greater error risk.</p>\n" }, { "answer_id": 200765, "author": "Chris H", "author_id": 6348, "author_profile": "https://worldbuilding.stackexchange.com/users/6348", "pm_score": 2, "selected": false, "text": "<p>I suggest combining the best of o.m.'s accepted answer and JBH's suggestion of singing, to use a spoken <a href=\"https://simple.wikipedia.org/wiki/Tone_language\" rel=\"nofollow noreferrer\">tonal</a> approach. Many people use languages in daily life that rely on tone for meaning, so your &quot;average person&quot; may well be able to.</p>\n<p>Tone isn't usually employed in English, but combining even a simple high-low distinction, which pretty much anyone can do, with the NATO alphabet's 36 characters gets you 72 distinct values (or 6 bits if you want simpler mapping). I reckon this is optimal for a pair of English speakers with no training.</p>\n<p>Three tones (high-mid-low) gives you 108 values (more than enough for something based on <a href=\"https://en.wikipedia.org/wiki/Ascii85\" rel=\"nofollow noreferrer\">ASCII85</a>), but if you can use rising and falling tones too, you get 36×5=180 values. Some Chinese dialects use even more. Unless mapping bits to vocalisations has to be done by people using a look-up table, you don't need your unique vocalisations to add up to a power of two, as demonstrated by ASCII85. The more tones used, the more training will be required, at least if your speakers aren't used to it.</p>\n<p>Cooking up a new phonetic alphabet using only one- and two-syllable words is probably helpful for efficiency. Of course you could discard the mapping to the alphabet, but that mapping does makes transcription easier (<a href=\"https://en.wikipedia.org/wiki/Pinyin#Tones\" rel=\"nofollow noreferrer\">tone markers</a> will be needed).</p>\n<p>You should consider the fidelity of the channel - a quiet room, across a deep gorge with a noisy river, a telephone line, a party, etc. will have different characteristics. Some will need a wider distinction between sounds than others. Only in the quietest settings could volume be used as another variable.</p>\n<p>Running some numbers on the rate using simple mappings (i.e. rounding the number of unique sounds down to a power of two): English speech is <a href=\"https://en.wikipedia.org/wiki/Speech_tempo\" rel=\"nofollow noreferrer\">apparently</a> around 4 syllables per second. Using simple mappings, with 6 bits over two tonal variants of the two-syllable A-Z0-9 alphabet, you'd get 12 b/s. With 5 tones rounded down to 7 bits, but upping the rate to a still-reasonable 6 syllables/second you're now at 21 b/s. Pushing it further, if you can come up with 64 distinct single-syllable words and can manage to apply 4 tones to those sounds you'd get 256 values per syllable, or a grand total of 32b/s. Don't forget to breathe.</p>\n" }, { "answer_id": 200912, "author": "Helge Hafting", "author_id": 84997, "author_profile": "https://worldbuilding.stackexchange.com/users/84997", "pm_score": -1, "selected": false, "text": "<p>Morse code may be voiced or whistled. Computers can turn the binary data into letters (base 26, or perhaps a lower base by dropping the longest morse codes.)</p>\n<p>Those who train, gets their morse up to 60 wpm or so. The average word is about 5 letters. So 300 letters per minute, each encoding 4.7 bits. 1410 bits per minute, or 23.5 bps. Well, that is for morse using equipment. I found no data for voiced morse.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/200675", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/79076/" ]

[ { "answer_id": 202343, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 3, "selected": false, "text": "<p><strong>Mathematical progressions.</strong></p>\n<p>Ice dragons are asocial. They do not care about other creatures, or other dragons. They do not have familial or filial attachments. When the young dragons fledge, they will not look back. Ice dragons have none of the sociocultural baggage humans have. They have no need for education that is friendly, or funny, or serves to reinforce their cultural identities.</p>\n<p>Ice dragons are rational. They understand physics and that the world moves in ways that can be understood.</p>\n<p>Ice dragons do sing. Their songs have no words.</p>\n<p>The ice dragon mother sings pure tones. Then she changes the pitch by multiples of the frequency up and down. The ice dragon mother sings pure tones. She changes the rhythm by multiples up and down. The ice dragon mother sings chords. Then she changes the chord to those chords which are relative to it. Through her songs, she teaches the new dragons math, and rhythm, and the immutable relationships of things that can be precisely known.</p>\n" }, { "answer_id": 202344, "author": "Community", "author_id": -1, "author_profile": "https://worldbuilding.stackexchange.com/users/-1", "pm_score": 3, "selected": false, "text": "<p><strong>Statistically speaking, killing invading humans.</strong></p>\n<p><a href=\"https://i.stack.imgur.com/sxEpN.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/sxEpN.jpg\" alt=\"Sing a happy elf song\" /></a>\n<a href=\"https://i.stack.imgur.com/u4Lcf.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/u4Lcf.png\" alt=\"human:all happy elf and dwarf songs are about killing invading humans.\" /></a></p>\n" }, { "answer_id": 202375, "author": "Mermaker", "author_id": 3245, "author_profile": "https://worldbuilding.stackexchange.com/users/3245", "pm_score": 4, "selected": false, "text": "<p>Dragons vary a lot from media-to-media, but they are always the most prideful beings in the world. How could that be different, when they are the apex predator? So, naturally, their songs would be most likely about <strong>pride</strong>:</p>\n<pre><code>My Little Dragonkin\n (sing to the tune of bayu bayushki bayu) \n\nThere are those with little mouths,\nthat can't scare bear or boar.\nBut rejoice, we're dragonkin,\nand everyone will fear your roar.\n\nThere are those with no claws,\nthat can't hunt the little sheep.\nBut rejoice, we're dragonkin,\nand even giants we make bleed.\n\nThere are those that have no wings,\nthat can only dream to fly.\nBut rejoice, we're dragonkin,\nand you too will rule the sky.\n\nThere are those that shed some tears,\n'cause they know no gold nor gem.\nBut rejoice, we're dragonkin,\nand you will be richer than any men.\n\nWith your hoard, in your den,\nGreater than any elven-king.\nStand with pride, show your might,\n'cause you're my little dragonkin.\n</code></pre>\n<p>Additional themes for dragon lullabies will include things that are unique to dragons, and put them apart from the other sentient races - their claws, their ability to fly, their magic, and their overall behavior. To give some examples:</p>\n<ul>\n<li>Dragon-magic is on a league of its own. Magic that is specific to dragons and <em>can't</em> be emulated by beings not-related to dragons is specially rare in fiction, and when it appears it is usually for something <em>big</em>, almost miracle-like. Obviously, not all dragons are such exceptional magicians, but the puny humans don't need to know that. So, songs that talk about magic will definitely be a thing.</li>\n<li>Pilling up treasure is up there in the Top 3 Hobbies for the Modern Dragon. What exactly that treasure is might change from time to time, but the bottom line is that dragons are collectors of <em>things</em>. Some like shiny things (gold, gems), others like darky things (skulls, bones), others like to collect maids and kids, and so on. With that in mind, it is natural to imagine that dragons will also make songs about collecting all sorts of things and making their hoards big.</li>\n<li>Eating. Dragons can eat <em>almost anything</em>, including a lot of things that <em>shouldn't</em> be edible. Dragons don't remove the stupid metal peel of a knight before gulping them up - the poor sod just goes in whole, and the magically-enhanced stomach acid does the rest. So, songs about eating things - be it plants, animals, or other sentient beings will certainly be a thing. I can easily picture songs with themes like a dragon trying to grow big enough to eat very big things - like a tower, a castle, or the moon.</li>\n<li>Dragon Anatomy. Dragons are very different from the usual creature - they have six limbs instead of four, they look like reptiles but are built like cats, they have long tails and powerful claws, mighty teeth and a powerful breath weapon. Songs that name those things, sang by the dragon-mom while she boops the respective wyrmling's body parts can easily be part of the repertoire.</li>\n<li>Dragon smells. <a href=\"https://rpg.stackexchange.com/a/151881/11162\">Apparently a lot of time was wasted by several authors to write about how dragons smell like.</a>. If you subscribe to the idea that each type of dragon has a specific smell, then memorizing what type of dragon smells like what can help dragons identify each other on the field, specially if they do disguise themselves like humans to keep a low profile.</li>\n</ul>\n" }, { "answer_id": 214412, "author": "Nosajimiki", "author_id": 57832, "author_profile": "https://worldbuilding.stackexchange.com/users/57832", "pm_score": 2, "selected": false, "text": "<h2>The mother would not sing to the eggs</h2>\n<p>In the womb, a human fetus is exposed to the constant rhythm of the mother's heartbeat, the squeeze of the uterus, the bob of the mother walking, and vibrations caused by the mother's muffled voice. The absence of the familiar sounds and feels of the womb are disturbing to a human infant, and things that recreate this environment are comforting. So, when a newborn is crying, we instinctively do things to recreate these feelings like swaddling, rocking, shushing, and singing.</p>\n<p>Focusing on the singing part: When the fetus is in the belly, the mother's voice creates vibrations that don't happen outside of the amniotic fluid; so, we have to try extra hard to create vibrations to soothe the baby. What a newborn baby actually finds soothing about singing is the vibrato; so, if you hold an infant to your chest and do a deep throat song, it is actually WAY more effective than singing a higher pitched song with words. However, it only takes a few weeks for the baby's comfort cues to transition from just vibrations to be the actually singing at which point it becomes the singing itself that is comforting.</p>\n<p>The thing about eggs is that the babies are still in a liquid at this point in their development meaning they will still get the same vibrations through normal speech as they did inside of their mother; so, if we assume that mother dragons care about comforting the babies developing in the eggs, then as the mother dragon sits on her eggs to keep them warm, she would probably resort to telling them stories rather than singing them songs.</p>\n<p>It would only be after the eggs hatch that a mother dragon's parenting style might transition to using song as a source of comfort.</p>\n<h3>So what stories would they tell their eggs?</h3>\n<p>When we look at human lullabies we sing about everything from far away times and places, to mundane actives, to total non-sense, to babies falling to their deaths... the same is true of bedtime stories. Since bedtime stories and lullaby's are more or less the same thing in different media, we can use their structures interchangeably.</p>\n<p>While the OP is right to identify that these stories (and lullaby's) focus on scary things, it is not to scare the child, but to establish a since of consequences for unacceptable behaviors. Goldilocks is eaten because she vandalized someone's home. Little Red Ridding Hood is eaten because she talks to strangers. The 2 of the 3 little pigs are almost eaten because they were too lazy to prepare properly. Icarus falls to his death because he does not listen to his father's advice.</p>\n<p>In some cases, the natural consequence to an unacceptable behavior is exactly what makes the behavior unacceptable. And in others, a &quot;Big Bad Wolf&quot; archetype is inserted to create a consequence for socially unacceptable behaviors that in reality rarely have actual consequences other than pissing someone else off. The most obvious thing of natural consequence in your world is the poison gas. There will be a lot of stories about baby dragons wondering into the gas and dyeing... but there will also be taboos. Maybe baby dragons are not supposed to go out while the mother is asleep, or maybe they should not pick their teeth with their tails, or maybe they are only supposed to eat sheep head-first. So, what happens to these naughty little dragons? Well the &quot;Big Bad Wolf&quot; archetype represents the single greatest threat we USED to have but still persists in our social consciousness; so, your dragons may remember the time that humans were numerous and had guns, and missiles, and fighter jets, etc. So, even with the threat of man being gone, the stories of &quot;men with guns&quot; will persist, and even become embellished for thousands of years.</p>\n<p>&quot;So remember baby dragon, if you don't eat your vegetables, the men with guns will come and shoot you out of the sky.&quot;</p>\n" }, { "answer_id": 214413, "author": "ProjectApex", "author_id": 73198, "author_profile": "https://worldbuilding.stackexchange.com/users/73198", "pm_score": 1, "selected": false, "text": "<h1>Other chromatic dragons would maybe sing, but probably not ice dragons. Silver dragons would definitely sing about humanoids and their cultures.</h1>\n<p>Copper dragons would probably just tell its eggs jokes or sing to them about the importance of a high-spirited happy life, since they're fans of puns and pranks.</p>\n<p>Brass dragons would probably talk to their eggs. Very, very regularly. They crave conversations to an almost unhealthy extent (yet they seek desolate places, they're a bit paradoxal).</p>\n<p>Going more strictly according to dnd descriptions of the dragons, you'd probably have a scenario where no dragon type is the same. Chromatic dragons are usually more &quot;evil&quot;, that is, they're more self centered and prideful in a way that's diminishing to everything else. Metallic dragons on the other hand are much more good aligned and less centered on themselves. This means that, by dnd standards, each dragon would probably behave towards their eggs in a way that reflects the ideals and morals of its kind.\nGoing by that, we could approximate more or less what the songs would mostly be about:</p>\n<p>Golden dragons would sing about growing wise, but humble, helping others and similar virtues.</p>\n<p>Silver dragons (the good ice dragons) would sing about distant lands and cultures and all the beauty the little one can find in them once they're ready, as well as how much more than mere gold creatures seemingly so frail can offer (because silver dragons basically love seeing and experiencing the culture of the many humanoid races, to the point their hordes are usually composed in good amount of things like human artifacts and items with strong cultural value).</p>\n<p>Bronze dragons would sing about the oceans, sea shanties and events that took place among the waves.</p>\n<p>Chromatic dragons on the other hand would probably have songs less about others and more about themselves.</p>\n<p>The prideful red dragons would sing of their feats, about the need to grow strong and defending their pride as members of a species second only to the gods themselves.</p>\n<p>Green dragons would sing praises of one's knowledge and cunning, the power of speech and how the strongest barbarian can dance like puppets In the palms of those who know what to say and when.</p>\n<p>The greedy Blue dragons would sing of glorious hordes, the importance of gold and all that's precious over the lives of others and treasures they expertly hid under the sand (treating its children like a kind of treasure might not be totally out of bounds for them either).</p>\n<p>Black dragons could sing of their children growing powerful and showing their might to the world, of the seed of destruction they carry within, as well as tales of foolish adventurers who overestimated themselves over the might of a black dragon.</p>\n<p>The bestial white dragons (the more classic &quot;ice&quot; dragons) are the exception. They're naturally more animalistic than the others, prefer to be solitary and rarely speak, but take the most pride in their achievements through sheer might (to the point trying to bribe one by offering something feels like an insult to their ability to simply take it). Due to this, I believe they'd be much more like an alligator and a bear in behavior. It wouldn't sing, it'd simply hum constantly to let their babies know that it's close and there to help them. White dragons have pristine memory and can recall things almost perfectly, so to such a creature that values strength over all, I'd say the biggest quality a mother could have would probably be to be strong enough to be capable of always being there for its offspring, because it's babies would probably be able to remember even at its death bed.</p>\n" }, { "answer_id": 214550, "author": "Silly but True", "author_id": 90484, "author_profile": "https://worldbuilding.stackexchange.com/users/90484", "pm_score": 3, "selected": false, "text": "<p><B>Ice Dragon Lullabies Sing to a Harsh Existence</B></p>\n<p>Ice Dragons by nature of their extreme and inhospitable environment may have a culture focused on survival, efficiency of energy, and sensing.</p>\n<p>Because they are adapted to the frigid environment, their prey are generally less plentiful, and so food, and death by starvation (as opposed to other life forms’ focus on falling from trees, or death by pandemic and burning) may be their drive and fear, respectively.</p>\n<p>Ice Dragons, to assist in catching the rare prey in their harsh environment, will have some specially adapted sensing which might be the source of lyrics.</p>\n<p>They are of course, well adapted to harsh winters and will have natural affinity to sensing their surroundings. Even during the harshest ice storms, they will be adapted to survival. They may be attuned to sensing heat signatures, or have mastered hearing sufficient to filter out noises by the wind to better pinpoint needed food. These traits will be valued for continuation of the species.</p>\n<p>I would imagine Ice Dragon lullabies and nursery rhymes to perhaps:</p>\n<ol>\n<li>warn of starvation, or mock death by starvation;</li>\n<li>praise strong senses;</li>\n<li>edify survival;</li>\n<li>value efficiency;</li>\n<li>mock as weakness temperate climates or those who live there.</li>\n</ol>\n<p>Their surroundings are brutal, and so will be their songs.</p>\n<p>Some examples:</p>\n<p>Scottish lullaby about loss:</p>\n<blockquote>\n<p>Hovan, Hovan Gorry og O\nI’ve lost my darling baby, O!</p>\n</blockquote>\n<p>Italian lullaby about giving baby up (for example if not enough food can be provided for it), which has ice-centric theme also as its final hook:</p>\n<blockquote>\n<p>Ninna nanna, ninna oh.\nTo whom shall I give this baby?\nIf I give him to the old hag, she’ll keep it for a week.</p>\n<p>If I give him to the black ox, he’ll keep it for an entire year.</p>\n<p>If I give it to the white wolf, he’ll keep it for a long time.</p>\n</blockquote>\n<p>A brutal Malaysian lullaby, Lima Anak Ayam, could be retooled to Ice Dragon eggs:</p>\n<blockquote>\n<p>Five chicks\nOne chick dies</p>\n<p>One chick dying leaves four</p>\n</blockquote>\n<p>A Danish lullaby captures a similar hard-scrabble existence:</p>\n<blockquote>\n<p>Dad is working very hard, Mum has to help.\nHans cries again and again when she has to leave.</p>\n<p>We have to work to earn a living. The children will suffer.</p>\n<p>We cannot give them any better even though we want to.</p>\n</blockquote>\n<p>The Turkish lullaby, Incili Bebek Ninnisi, is a great example, telling the story of a man who promised to sacrifice three camels if his wife could have a child, but then decided to renege and keep the three camels after she gave birth. An eagle then carried the baby off and tore it to pieces. The song is from the perspective of the grief-stricken mother:</p>\n<blockquote>\n<p>Above black eagles wheeling,\nAll of a sudden swooping,</p>\n<p>My little baby stealing,</p>\n<p>Sleep, little baby, sleep.</p>\n<p>Above black eagles soaring,</p>\n<p>A crown of pearls left lying,</p>\n<p>Your stupid father snoring.</p>\n</blockquote>\n<p><B>Dragon Lullabies Generally</B>\nHuman lullabies, by contrast, focus on boogeymen or animals stealing a baby, or a cradle falling from tree, or just the stars above. Dragons aren’t generally going to embrace the boogeyman genre of lullabies — dragons are generally at the top of the food chain, unless their boogeyman is an abysmal fiend, Demi-god, or god. Physical suffering, like falling from tree isn’t a worry, especially when you have wings. And they can fly to the air, although twinkling stars — unreachable to even earthly-bound dragons — still might hold some wonder.</p>\n" }, { "answer_id": 214566, "author": "Globin347", "author_id": 65040, "author_profile": "https://worldbuilding.stackexchange.com/users/65040", "pm_score": 2, "selected": false, "text": "<h2>They would sing about the many dangers of the world, and the satisfaction of growing too large for those dangers to harm you.</h2>\n<p>DND dragons seem to be very much an R-type species. They have very little to fear as adults, but as a hatchling or young dragon, the forgotten realms are a very dangerous place. There are numerous monsters able to overpower a young dragon, especially in great numbers. In addition, there are murderous adventurers and larger dragons to fear.</p>\n<p>However, if a dragon survives long enough to reach adulthood, most of those dangers become nothing more than food and playthings. Even a coordinated army of human, elf, and dwarf soldiers would struggle to bring down the largest dragons, especially if the dragon mostly stays in the air.</p>\n<p>As such, a fitting lullaby for dragons, especially antisocial white dragons would be about all the perils of the world, and about the glory that waits for those who survive.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/202296", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/85411/" ]

[ { "answer_id": 202343, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 3, "selected": false, "text": "<p><strong>Mathematical progressions.</strong></p>\n<p>Ice dragons are asocial. They do not care about other creatures, or other dragons. They do not have familial or filial attachments. When the young dragons fledge, they will not look back. Ice dragons have none of the sociocultural baggage humans have. They have no need for education that is friendly, or funny, or serves to reinforce their cultural identities.</p>\n<p>Ice dragons are rational. They understand physics and that the world moves in ways that can be understood.</p>\n<p>Ice dragons do sing. Their songs have no words.</p>\n<p>The ice dragon mother sings pure tones. Then she changes the pitch by multiples of the frequency up and down. The ice dragon mother sings pure tones. She changes the rhythm by multiples up and down. The ice dragon mother sings chords. Then she changes the chord to those chords which are relative to it. Through her songs, she teaches the new dragons math, and rhythm, and the immutable relationships of things that can be precisely known.</p>\n" }, { "answer_id": 202344, "author": "Community", "author_id": -1, "author_profile": "https://worldbuilding.stackexchange.com/users/-1", "pm_score": 3, "selected": false, "text": "<p><strong>Statistically speaking, killing invading humans.</strong></p>\n<p><a href=\"https://i.stack.imgur.com/sxEpN.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/sxEpN.jpg\" alt=\"Sing a happy elf song\" /></a>\n<a href=\"https://i.stack.imgur.com/u4Lcf.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/u4Lcf.png\" alt=\"human:all happy elf and dwarf songs are about killing invading humans.\" /></a></p>\n" }, { "answer_id": 202375, "author": "Mermaker", "author_id": 3245, "author_profile": "https://worldbuilding.stackexchange.com/users/3245", "pm_score": 4, "selected": false, "text": "<p>Dragons vary a lot from media-to-media, but they are always the most prideful beings in the world. How could that be different, when they are the apex predator? So, naturally, their songs would be most likely about <strong>pride</strong>:</p>\n<pre><code>My Little Dragonkin\n (sing to the tune of bayu bayushki bayu) \n\nThere are those with little mouths,\nthat can't scare bear or boar.\nBut rejoice, we're dragonkin,\nand everyone will fear your roar.\n\nThere are those with no claws,\nthat can't hunt the little sheep.\nBut rejoice, we're dragonkin,\nand even giants we make bleed.\n\nThere are those that have no wings,\nthat can only dream to fly.\nBut rejoice, we're dragonkin,\nand you too will rule the sky.\n\nThere are those that shed some tears,\n'cause they know no gold nor gem.\nBut rejoice, we're dragonkin,\nand you will be richer than any men.\n\nWith your hoard, in your den,\nGreater than any elven-king.\nStand with pride, show your might,\n'cause you're my little dragonkin.\n</code></pre>\n<p>Additional themes for dragon lullabies will include things that are unique to dragons, and put them apart from the other sentient races - their claws, their ability to fly, their magic, and their overall behavior. To give some examples:</p>\n<ul>\n<li>Dragon-magic is on a league of its own. Magic that is specific to dragons and <em>can't</em> be emulated by beings not-related to dragons is specially rare in fiction, and when it appears it is usually for something <em>big</em>, almost miracle-like. Obviously, not all dragons are such exceptional magicians, but the puny humans don't need to know that. So, songs that talk about magic will definitely be a thing.</li>\n<li>Pilling up treasure is up there in the Top 3 Hobbies for the Modern Dragon. What exactly that treasure is might change from time to time, but the bottom line is that dragons are collectors of <em>things</em>. Some like shiny things (gold, gems), others like darky things (skulls, bones), others like to collect maids and kids, and so on. With that in mind, it is natural to imagine that dragons will also make songs about collecting all sorts of things and making their hoards big.</li>\n<li>Eating. Dragons can eat <em>almost anything</em>, including a lot of things that <em>shouldn't</em> be edible. Dragons don't remove the stupid metal peel of a knight before gulping them up - the poor sod just goes in whole, and the magically-enhanced stomach acid does the rest. So, songs about eating things - be it plants, animals, or other sentient beings will certainly be a thing. I can easily picture songs with themes like a dragon trying to grow big enough to eat very big things - like a tower, a castle, or the moon.</li>\n<li>Dragon Anatomy. Dragons are very different from the usual creature - they have six limbs instead of four, they look like reptiles but are built like cats, they have long tails and powerful claws, mighty teeth and a powerful breath weapon. Songs that name those things, sang by the dragon-mom while she boops the respective wyrmling's body parts can easily be part of the repertoire.</li>\n<li>Dragon smells. <a href=\"https://rpg.stackexchange.com/a/151881/11162\">Apparently a lot of time was wasted by several authors to write about how dragons smell like.</a>. If you subscribe to the idea that each type of dragon has a specific smell, then memorizing what type of dragon smells like what can help dragons identify each other on the field, specially if they do disguise themselves like humans to keep a low profile.</li>\n</ul>\n" }, { "answer_id": 214412, "author": "Nosajimiki", "author_id": 57832, "author_profile": "https://worldbuilding.stackexchange.com/users/57832", "pm_score": 2, "selected": false, "text": "<h2>The mother would not sing to the eggs</h2>\n<p>In the womb, a human fetus is exposed to the constant rhythm of the mother's heartbeat, the squeeze of the uterus, the bob of the mother walking, and vibrations caused by the mother's muffled voice. The absence of the familiar sounds and feels of the womb are disturbing to a human infant, and things that recreate this environment are comforting. So, when a newborn is crying, we instinctively do things to recreate these feelings like swaddling, rocking, shushing, and singing.</p>\n<p>Focusing on the singing part: When the fetus is in the belly, the mother's voice creates vibrations that don't happen outside of the amniotic fluid; so, we have to try extra hard to create vibrations to soothe the baby. What a newborn baby actually finds soothing about singing is the vibrato; so, if you hold an infant to your chest and do a deep throat song, it is actually WAY more effective than singing a higher pitched song with words. However, it only takes a few weeks for the baby's comfort cues to transition from just vibrations to be the actually singing at which point it becomes the singing itself that is comforting.</p>\n<p>The thing about eggs is that the babies are still in a liquid at this point in their development meaning they will still get the same vibrations through normal speech as they did inside of their mother; so, if we assume that mother dragons care about comforting the babies developing in the eggs, then as the mother dragon sits on her eggs to keep them warm, she would probably resort to telling them stories rather than singing them songs.</p>\n<p>It would only be after the eggs hatch that a mother dragon's parenting style might transition to using song as a source of comfort.</p>\n<h3>So what stories would they tell their eggs?</h3>\n<p>When we look at human lullabies we sing about everything from far away times and places, to mundane actives, to total non-sense, to babies falling to their deaths... the same is true of bedtime stories. Since bedtime stories and lullaby's are more or less the same thing in different media, we can use their structures interchangeably.</p>\n<p>While the OP is right to identify that these stories (and lullaby's) focus on scary things, it is not to scare the child, but to establish a since of consequences for unacceptable behaviors. Goldilocks is eaten because she vandalized someone's home. Little Red Ridding Hood is eaten because she talks to strangers. The 2 of the 3 little pigs are almost eaten because they were too lazy to prepare properly. Icarus falls to his death because he does not listen to his father's advice.</p>\n<p>In some cases, the natural consequence to an unacceptable behavior is exactly what makes the behavior unacceptable. And in others, a &quot;Big Bad Wolf&quot; archetype is inserted to create a consequence for socially unacceptable behaviors that in reality rarely have actual consequences other than pissing someone else off. The most obvious thing of natural consequence in your world is the poison gas. There will be a lot of stories about baby dragons wondering into the gas and dyeing... but there will also be taboos. Maybe baby dragons are not supposed to go out while the mother is asleep, or maybe they should not pick their teeth with their tails, or maybe they are only supposed to eat sheep head-first. So, what happens to these naughty little dragons? Well the &quot;Big Bad Wolf&quot; archetype represents the single greatest threat we USED to have but still persists in our social consciousness; so, your dragons may remember the time that humans were numerous and had guns, and missiles, and fighter jets, etc. So, even with the threat of man being gone, the stories of &quot;men with guns&quot; will persist, and even become embellished for thousands of years.</p>\n<p>&quot;So remember baby dragon, if you don't eat your vegetables, the men with guns will come and shoot you out of the sky.&quot;</p>\n" }, { "answer_id": 214413, "author": "ProjectApex", "author_id": 73198, "author_profile": "https://worldbuilding.stackexchange.com/users/73198", "pm_score": 1, "selected": false, "text": "<h1>Other chromatic dragons would maybe sing, but probably not ice dragons. Silver dragons would definitely sing about humanoids and their cultures.</h1>\n<p>Copper dragons would probably just tell its eggs jokes or sing to them about the importance of a high-spirited happy life, since they're fans of puns and pranks.</p>\n<p>Brass dragons would probably talk to their eggs. Very, very regularly. They crave conversations to an almost unhealthy extent (yet they seek desolate places, they're a bit paradoxal).</p>\n<p>Going more strictly according to dnd descriptions of the dragons, you'd probably have a scenario where no dragon type is the same. Chromatic dragons are usually more &quot;evil&quot;, that is, they're more self centered and prideful in a way that's diminishing to everything else. Metallic dragons on the other hand are much more good aligned and less centered on themselves. This means that, by dnd standards, each dragon would probably behave towards their eggs in a way that reflects the ideals and morals of its kind.\nGoing by that, we could approximate more or less what the songs would mostly be about:</p>\n<p>Golden dragons would sing about growing wise, but humble, helping others and similar virtues.</p>\n<p>Silver dragons (the good ice dragons) would sing about distant lands and cultures and all the beauty the little one can find in them once they're ready, as well as how much more than mere gold creatures seemingly so frail can offer (because silver dragons basically love seeing and experiencing the culture of the many humanoid races, to the point their hordes are usually composed in good amount of things like human artifacts and items with strong cultural value).</p>\n<p>Bronze dragons would sing about the oceans, sea shanties and events that took place among the waves.</p>\n<p>Chromatic dragons on the other hand would probably have songs less about others and more about themselves.</p>\n<p>The prideful red dragons would sing of their feats, about the need to grow strong and defending their pride as members of a species second only to the gods themselves.</p>\n<p>Green dragons would sing praises of one's knowledge and cunning, the power of speech and how the strongest barbarian can dance like puppets In the palms of those who know what to say and when.</p>\n<p>The greedy Blue dragons would sing of glorious hordes, the importance of gold and all that's precious over the lives of others and treasures they expertly hid under the sand (treating its children like a kind of treasure might not be totally out of bounds for them either).</p>\n<p>Black dragons could sing of their children growing powerful and showing their might to the world, of the seed of destruction they carry within, as well as tales of foolish adventurers who overestimated themselves over the might of a black dragon.</p>\n<p>The bestial white dragons (the more classic &quot;ice&quot; dragons) are the exception. They're naturally more animalistic than the others, prefer to be solitary and rarely speak, but take the most pride in their achievements through sheer might (to the point trying to bribe one by offering something feels like an insult to their ability to simply take it). Due to this, I believe they'd be much more like an alligator and a bear in behavior. It wouldn't sing, it'd simply hum constantly to let their babies know that it's close and there to help them. White dragons have pristine memory and can recall things almost perfectly, so to such a creature that values strength over all, I'd say the biggest quality a mother could have would probably be to be strong enough to be capable of always being there for its offspring, because it's babies would probably be able to remember even at its death bed.</p>\n" }, { "answer_id": 214550, "author": "Silly but True", "author_id": 90484, "author_profile": "https://worldbuilding.stackexchange.com/users/90484", "pm_score": 3, "selected": false, "text": "<p><B>Ice Dragon Lullabies Sing to a Harsh Existence</B></p>\n<p>Ice Dragons by nature of their extreme and inhospitable environment may have a culture focused on survival, efficiency of energy, and sensing.</p>\n<p>Because they are adapted to the frigid environment, their prey are generally less plentiful, and so food, and death by starvation (as opposed to other life forms’ focus on falling from trees, or death by pandemic and burning) may be their drive and fear, respectively.</p>\n<p>Ice Dragons, to assist in catching the rare prey in their harsh environment, will have some specially adapted sensing which might be the source of lyrics.</p>\n<p>They are of course, well adapted to harsh winters and will have natural affinity to sensing their surroundings. Even during the harshest ice storms, they will be adapted to survival. They may be attuned to sensing heat signatures, or have mastered hearing sufficient to filter out noises by the wind to better pinpoint needed food. These traits will be valued for continuation of the species.</p>\n<p>I would imagine Ice Dragon lullabies and nursery rhymes to perhaps:</p>\n<ol>\n<li>warn of starvation, or mock death by starvation;</li>\n<li>praise strong senses;</li>\n<li>edify survival;</li>\n<li>value efficiency;</li>\n<li>mock as weakness temperate climates or those who live there.</li>\n</ol>\n<p>Their surroundings are brutal, and so will be their songs.</p>\n<p>Some examples:</p>\n<p>Scottish lullaby about loss:</p>\n<blockquote>\n<p>Hovan, Hovan Gorry og O\nI’ve lost my darling baby, O!</p>\n</blockquote>\n<p>Italian lullaby about giving baby up (for example if not enough food can be provided for it), which has ice-centric theme also as its final hook:</p>\n<blockquote>\n<p>Ninna nanna, ninna oh.\nTo whom shall I give this baby?\nIf I give him to the old hag, she’ll keep it for a week.</p>\n<p>If I give him to the black ox, he’ll keep it for an entire year.</p>\n<p>If I give it to the white wolf, he’ll keep it for a long time.</p>\n</blockquote>\n<p>A brutal Malaysian lullaby, Lima Anak Ayam, could be retooled to Ice Dragon eggs:</p>\n<blockquote>\n<p>Five chicks\nOne chick dies</p>\n<p>One chick dying leaves four</p>\n</blockquote>\n<p>A Danish lullaby captures a similar hard-scrabble existence:</p>\n<blockquote>\n<p>Dad is working very hard, Mum has to help.\nHans cries again and again when she has to leave.</p>\n<p>We have to work to earn a living. The children will suffer.</p>\n<p>We cannot give them any better even though we want to.</p>\n</blockquote>\n<p>The Turkish lullaby, Incili Bebek Ninnisi, is a great example, telling the story of a man who promised to sacrifice three camels if his wife could have a child, but then decided to renege and keep the three camels after she gave birth. An eagle then carried the baby off and tore it to pieces. The song is from the perspective of the grief-stricken mother:</p>\n<blockquote>\n<p>Above black eagles wheeling,\nAll of a sudden swooping,</p>\n<p>My little baby stealing,</p>\n<p>Sleep, little baby, sleep.</p>\n<p>Above black eagles soaring,</p>\n<p>A crown of pearls left lying,</p>\n<p>Your stupid father snoring.</p>\n</blockquote>\n<p><B>Dragon Lullabies Generally</B>\nHuman lullabies, by contrast, focus on boogeymen or animals stealing a baby, or a cradle falling from tree, or just the stars above. Dragons aren’t generally going to embrace the boogeyman genre of lullabies — dragons are generally at the top of the food chain, unless their boogeyman is an abysmal fiend, Demi-god, or god. Physical suffering, like falling from tree isn’t a worry, especially when you have wings. And they can fly to the air, although twinkling stars — unreachable to even earthly-bound dragons — still might hold some wonder.</p>\n" }, { "answer_id": 214566, "author": "Globin347", "author_id": 65040, "author_profile": "https://worldbuilding.stackexchange.com/users/65040", "pm_score": 2, "selected": false, "text": "<h2>They would sing about the many dangers of the world, and the satisfaction of growing too large for those dangers to harm you.</h2>\n<p>DND dragons seem to be very much an R-type species. They have very little to fear as adults, but as a hatchling or young dragon, the forgotten realms are a very dangerous place. There are numerous monsters able to overpower a young dragon, especially in great numbers. In addition, there are murderous adventurers and larger dragons to fear.</p>\n<p>However, if a dragon survives long enough to reach adulthood, most of those dangers become nothing more than food and playthings. Even a coordinated army of human, elf, and dwarf soldiers would struggle to bring down the largest dragons, especially if the dragon mostly stays in the air.</p>\n<p>As such, a fitting lullaby for dragons, especially antisocial white dragons would be about all the perils of the world, and about the glory that waits for those who survive.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/202300", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/10274/" ]

[ { "answer_id": 206183, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 1, "selected": false, "text": "<p><strong>Halfway point mass is average of start and finish.</strong></p>\n<p>You state that you lose xenon mass steadily thru the journey.</p>\n<p>/relying on the lost Xe mass (which is a constant loss over time)/</p>\n<p>Your mass at the midway flip point is the average of full and empty: half full. If you want a solution for the journey taken as a while, work\nyour equations based on the midpoint weight. The increased weight at journey start will be balanced by decreased weight at journey end and the math will work for the journey as a whole.</p>\n<p>&quot;But wait!&quot; you object. &quot;I was wrong! It is not steady use! I actually use xenon less fast for the second half of the trip, because the ship is less massive and so requires less force to accelerate than it did on the first half!&quot; True, true. This then becomes a calculus problem to model both the smoothly decreasing rate of use of fuel and smoothly decreasing rate of loss of mass. Which I would like to see worked out but which is beyond my ability.</p>\n" }, { "answer_id": 206186, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 4, "selected": true, "text": "<p>Since you mention integrals, I know you are familiar with calculus, so I can give you the short and sweet answer. It is not always true that <span class=\"math-container\">$F=ma$</span>. The more complete version of Newton's equations yields <span class=\"math-container\">$F=\\frac{dp}{dt}$</span>, where <span class=\"math-container\">$p$</span> is momentum. Force is the change in momentum over time. Now, since <span class=\"math-container\">$p=mv$</span>, we can quickly see that if mass is constant, we get <span class=\"math-container\">$F=m\\frac{dv}{dt}$</span> which is <span class=\"math-container\">$F=ma$</span>. If mass is not constant, then you have to use the chain rule to get <span class=\"math-container\">$F=\\frac{dm}{dt}v+m\\frac{dv}{dt}$</span>, which is what is used in rocketry. Integrate that, and you get the answer you need.</p>\n<p>You aren't the first to want to do this. the <a href=\"https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation\" rel=\"nofollow noreferrer\">Tsiolkovsky rocket equation</a> is the go-to equation for doing these calculations</p>\n<p><span class=\"math-container\">$$\\Delta V= I_{sp}g_0\\ln\\frac{m_0}{m_f}$$</span></p>\n<p>Why go here first, rather than integrating? Well we don't have our ship spec'd out yet. We need to understand our mass fraction before daring to integrate to get distance. But what we know is that we have to do two burns. The first burn takes us from an initial velocity (call it 0) to <span class=\"math-container\">$v_{\\frac{1}{2}}$</span>, the velocity at the flip point (which, as you note, isn't quite at the half way point in distance, but I'm using the subscript <span class=\"math-container\">$\\frac{1}{2}$</span> anyways). Then, the second burn takes us down to the velocity of ACA with respect the earth..</p>\n<p>Once you have this, you just have to use the above complete version of Newton's law to do the integration.</p>\n<p>I'm going to give us control of &quot;number of engines&quot; as a variable. Now, I don't recommend actually just stacking more and more little engines. It's not always the most efficient approach. But a multiplier on the existing ion engine you described seems like a pretty good way to go! We'll call this scale factor <span class=\"math-container\">$k$</span>. If your ship has a scale factor of <span class=\"math-container\">$k$</span>, it means it produces <span class=\"math-container\">$30k$</span> Newtons of thrust, and consumes <span class=\"math-container\">$\\frac{75}{4000}k\\frac{kg}{s}$</span> worth of Xenon while active.</p>\n<p>We're also going to need the ISP. Now it looks like you mixed the numbers from several ion thrusters, and got one which is actually quite weak. Others can check my math, but I pegged it at an ISP of about 160 seconds, which is extremely low (its lower than a chemical rocket). Typically the ISP is in the thousands for an ion thruster. So let's just leave it as a variable, <span class=\"math-container\">$I_{sp}$</span>, but I'll peg it to the really nice ISP of NEXT, at 4190s. Feel free to adjust from there, but that's really the dominating variable in these thrusters. You can adjust size and flow rate as much as you like, but changing ISP is incredibly difficult.</p>\n<p>You should also pick a <span class=\"math-container\">$m_f$</span>. Your question listed a <span class=\"math-container\">$m_0$</span>, but <span class=\"math-container\">$m_f$</span> is typically easier to work with because its bounded by the need to do something with a payload. For example, it might be all of the life support needed to support 10,000 people, or something like that. It will just be a scale factor on everything, so I won't include it... but you'll need it to turn into the question of &quot;how hard is it to actually make this rocket.&quot; For now, I'll just assume a <span class=\"math-container\">$m_f$</span> of 1,000,000kg.</p>\n<p>We can do everything in velocities in the initial frame, so <span class=\"math-container\">$v_0=0$</span> and <span class=\"math-container\">$v_f$</span> is the velocity of ACA in our frame, <a href=\"https://en.wikipedia.org/wiki/Alpha_Centauri\" rel=\"nofollow noreferrer\">which is roughly</a>y 21.4km/s towards us, so we'll say <span class=\"math-container\">$v_f=-21.4km/s$</span> to make all of the signs line up</p>\n<p>Now, we know that our total burn is the sum of the speeding up burn plus the slowing down burn. <span class=\"math-container\">$\\Delta V=v_\\frac1 2 + (v_\\frac 1 2 - v_f) = 2 v\\frac 1 2 - v_f$</span>. By the rocket equation, we can now see that we can relate this to the propellant mass that we use.</p>\n<p><span class=\"math-container\">$$\\Delta V=v_e\\ln\\frac{m_f}{m_0}=v_e\\ln\\frac{m_f}{m_f+m_p}$$</span></p>\n<p><span class=\"math-container\">$$2 v_\\frac 1 2 - v_f = v_e\\ln\\frac{m_f}{m_f + m_p}$$</span></p>\n<p>Here I've broken out the initial mass into a final mass plus the mass of the propellant, <span class=\"math-container\">$m_p$</span>. This is convenient because we can calculate the propellant mass from the data you've given. If <span class=\"math-container\">$k=1$</span>, then we know that we consume <span class=\"math-container\">$\\frac{75}{4000}\\frac{kg}{s}\\cdot T$</span> fuel, where <span class=\"math-container\">$T$</span> is the duration of the flight, 110 years. A quick unit conversion and a multiplication by k to <span class=\"math-container\">$591300kT\\frac{kg}{year}$</span> points out that this is going to be quite the high mass fraction. At 110 years, you will consume just over <span class=\"math-container\">$65,000,000k$</span> kilograms of fuel. Thus for</p>\n<ul>\n<li><span class=\"math-container\">$k=1$</span>, <span class=\"math-container\">$m_p=65,000,000kg$</span>, (<span class=\"math-container\">$\\zeta=0.984$</span>)</li>\n<li><span class=\"math-container\">$k=5$</span>, <span class=\"math-container\">$m_p=325,000,000kg$</span> (<span class=\"math-container\">$\\zeta=0.9969$</span>)</li>\n<li><span class=\"math-container\">$k=10$</span>, <span class=\"math-container\">$m_p=650,000,000kg$</span> (<span class=\"math-container\">$\\zeta=0.9984$</span>)</li>\n</ul>\n<p>I note the mass fraction, <span class=\"math-container\">$\\zeta$</span> because it is a common way to measure rockets. Typical mass fractions are in the 0.8 to 0.9 range, with 0.9 being typical for the single-stage-to-orbit (SSTO). Note that one of the great challenges of SSTO is that its hard to achieve a mass fraction that high. So, when you talk about using current technology, recognize that this is quite far outside of what we're typically working with. You will be bringing a <strong>lot</strong> of fuel!</p>\n<p>Regardless, we can combine these equations to get one overarching solution:</p>\n<p><span class=\"math-container\">$$2 v_\\frac 1 2 - v_f = v_e\\ln\\frac{m_f}{m_f + \\dot m_1kT}$$</span></p>\n<p>Where <span class=\"math-container\">$\\dot m_1$</span> is the above mass flow rate of a <span class=\"math-container\">$k=1$</span> engine. Or, rearranged slightly,</p>\n<p><span class=\"math-container\">$$v_\\frac 1 2 = \\frac{v_f + v_e\\ln\\frac{m_f}{m_f + \\dot m_1kT}}{2}$$</span></p>\n<p>Now this is really neat. It says that if you want to visit ACA, not just fly past it at painfully fast speeds, there's only so many ways you can do it. It says that, for any fuel flow rate (<span class=\"math-container\">$k$</span>), there is exactly one <span class=\"math-container\">$v_\\frac 1 2$</span> that leaves you at exactly the correct velocity you need, <span class=\"math-container\">$v_f$</span>. Any other 110 year long burn will leave you at the wrong velocity.</p>\n<p>This means we're really close to having an answer. We can build a plot with <span class=\"math-container\">$k$</span> as our independent term, and the distance traveled, <span class=\"math-container\">$d$</span> as our dependent term. All we have to do is calcualte the result of a constant-force 2 stage burn, where we burn out the first stage at the point where <span class=\"math-container\">$v=v_\\frac 1 2$</span>, and then we burn in the opposite direction.</p>\n<p>At this point, we could solve a bunch of integrals, but I'll leave this as an exercise for the reader. In the spirit of astrophysics, I invoke &quot;shut up and calculate&quot; and throw everything into a really cheesy python simulation. I just do Riemann integration at 1/10th year intervals, and trust that's fine grained enough to cover for the laughably inexact way I handle updating all of the anti-derivatives.</p>\n<pre><code>from math import log\n\nln = log # Python's log(x) is actually the natural log. Aliasing it\n # for readability.\n\nmf = 1000000 # kg - my own assumption\nm1 = 75/4000 # kg/s\nvf = -21400 # m/s\nisp = 4160 # s\nT = 110 * 31556952 # s - trip length\nf = 30 # N - force of the reference engine\ng0 = 9.8 # m/s^2 - gravitiy on earth\n\ndef calcDist(k):\n &quot;&quot;&quot;Returns distance traveled in light years&quot;&quot;&quot;\n # step 1: for given k, calculate the ship's stats\n mdot = m1 * k\n mp = mdot * T\n\n # step 2: compute v 1/2\n v05 = 0.5 * (vf - isp * g0 * ln(mf / (mf + mdot * T)))\n\n # step 3: Integrate!\n dt = 0.1 * 31556952 # arbitrary decision, dt is 1/10th of a year\n m = mf + mp # kg\n v = 0 # m/s\n d = 0 # meters\n t = 0\n\n # step 3a: Burn 1 (accel)\n # stop at v1/2\n while v &lt; v05:\n a = (f * k - mdot * v) / m # rearrange force equation\n d += v * dt\n v += a * dt\n m -= mdot * dt\n t += dt\n\n # step 3b: Burn 2 (decel)\n # stop when out of fuel\n while m &gt; mf:\n a = (f * k - mdot * v) / m\n d += v * dt\n v -= a * dt # note minus sign: slowing down\n m -= mdot * dt\n t += dt\n\n return d / 9460730472580800 # meters to light years\n\nk = np.linspace(100, 1000, 100)\nd = [calcDist(x) for x in k]\n\nplt.plot(k, d, '-k')\nplt.axhline(4.37, linestyle=&quot;dashed&quot;) # distance to ACA\nfor kk, dd in zip(k, d):\n if dd &gt; 4.37:\n plt.axvline(kk, linestyle=&quot;dotted&quot;)\n plt.text(kk + 50, dd - 0.1, &quot;k=%d&quot; % kk)\n break\nplt.xlabel(&quot;Multiple of reference engine&quot;)\nplt.ylabel(&quot;Light years&quot;)\nplt.show()\n</code></pre>\n<p><a href=\"https://i.stack.imgur.com/djDwR.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/djDwR.png\" alt=\"Resulting Graph\" /></a></p>\n<p>So you will need the equivalent of 381 of those 30N ion thrusters to do the job, and 24800 kg of Xe fuel for every 1 kg of payload. (for a mass fraction of <span class=\"math-container\">$\\zeta=0.9999596$</span>)</p>\n<p>This is consistent with the back of the envelope calculations you did. You calculated 218 to get there without slowing down. Slowing down requires 4x more thrust, so would require just under 900 engines if we didn't account for the decreasing mass. The actual answer is somewhere between the two.</p>\n<p>Note, you will have to be mighty creative to achieve that mass fraction. Your fuel tanks are going to have to be very thin, and very large, and yet still survive the 110 year journey!</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/206182", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/83216/" ]

[ { "answer_id": 209224, "author": "The Square-Cube Law", "author_id": 21222, "author_profile": "https://worldbuilding.stackexchange.com/users/21222", "pm_score": 1, "selected": false, "text": "<p>I have a dog. Whenever I am lying down on the couch or my bed, she will sit on me. She will obsessively lick my face and ears (but not my partner's, so the dog clearly has a preference); if my face is out of reach, she will lie upon my legs and lick my toes for minutes before she is satisfied. She is quite heavy so while I can get up before she is done licking my feet, it is VERY uncomfortable to me to do so. I usually just let her do her thing.</p>\n<p>Perhaps your ticklers are just like that, they like to lick people because people taste good. They might have a preference for girls because wherever they live it is a cultural thing for girls to always keep their feet clean, whereas boys don't live up to the same expectation - so if you want just some human sweat without a dressing of mud and dirt, go for girls.</p>\n<p>And the licking is very tickling.</p>\n" }, { "answer_id": 209232, "author": "Goodies", "author_id": 86094, "author_profile": "https://worldbuilding.stackexchange.com/users/86094", "pm_score": 1, "selected": false, "text": "<p><strong>Sound ?</strong></p>\n<p>Lot of question marks here.. how intelligent are these toe-ticklers.. They live like wolves in packs, so it's rather an animal. Maybe it likes the sound ? just the right high pitch frequency ?</p>\n<p>Chimpansees like the giggling sound, because it is a sign of &quot;non-attack&quot;, refer article link below.</p>\n<p>I don't think this could be a truely wild hunter.. although humans and apes and rats appreciate tickling, I doubt effective tickling could happen without consent ! What's the role of toe-ticklers in human society ? How come these animals are allowed to tickle girls.. The toe-tickler could be the girl's pet.. or maybe it is some kind of cultural habit humans learned, because wild toe-ticklers are <em>really good</em> at tickling toes ? But in that case why only girls and not the rest of us mammals, who like being tickled and make high pitch sounds like e.g. rats do, or my grandmother does (I'm lost now)</p>\n<p><a href=\"http://www.bbc.com/earth/story/20170518-why-humans-chimpanzees-and-rats-enjoy-being-tickled\" rel=\"nofollow noreferrer\">http://www.bbc.com/earth/story/20170518-why-humans-chimpanzees-and-rats-enjoy-being-tickled</a></p>\n<p><a href=\"https://vidyasury.com/2012/04/tickled-pink.html\" rel=\"nofollow noreferrer\">https://vidyasury.com/2012/04/tickled-pink.html</a></p>\n" }, { "answer_id": 209243, "author": "JBH", "author_id": 40609, "author_profile": "https://worldbuilding.stackexchange.com/users/40609", "pm_score": 3, "selected": true, "text": "<pre>\n*static* The following radio broadcast is brought to you by NASAdent\ningestible toothpaste. Win the day with a winning smile! News today from\nthe world of science! Experts from around the world have gathered in\nGeneva, Switzerland, to discuss the growing phenomena known as TOE-TICKLERS.\nThese large but seemingly harmless creatures have created an increasing\npanic as young women around the world are being abducted to apparently have\ntheir toes tickled. Religious leaders last week denounced the TOE-TICKLERS\nas proof that sexual relations out of wedlock will bring eternal punishment.\nLeading scientists aren't sure the goal of the creatures is that philosophical...\n</pre>\n<p><em>Ach-tung! Eet is vit the greatest pleasure, yah!, that I am today to report on da findings of the Analyse des Zehenkitzelverhaltens und der Damit Verbundenen Physiologie, yah! dah leetle toesy-ticklin' creetures like da giant feather dusters dat like da leetle girls, yah! and <a href=\"https://worldbuilding.meta.stackexchange.com/q/8398/40609\">im Sinne dieser Meta-Site-Frage</a>, I announce the following data. Is exciting, yah? We conclude tha fallowing:</em></p>\n<ol>\n<li><p>Drs. Jenkins, Volkov, Abdullahi, et al. (2020) suggested based on the tendency of the Toe-Tickler's muscles to shiver while tickling the toes of young women that the combination of <strong>toe jam with female enzymes is hallucinogenic.</strong> Apparently, tickling a girl compared to a fully-grown woman is a more intense rush. Gloria Steinhem has called a press release later this evening to elaborate on this report.</p>\n</li>\n<li><p>Caribbean housewife Alvita Reid (2021) suggested based on the tendency of the Toe-Ticklers to, well, <em>tickle,</em> is that they <strong>lack the capacity for <em><a href=\"http://www.bbc.com/earth/story/20170518-why-humans-chimpanzees-and-rats-enjoy-being-tickled\" rel=\"nofollow noreferrer\">Gargalesis</a>,</em> the natural tickle response leading to laughter</strong> that many mammals enjoy to one degree or another — and therefore can only experience it vicariously. Further, she's sure that their hearing must center on higher frequencies than humans, which is why they prefer the laughter of females. She's been quoted by our undercover reporter at Jamaica's famous Geejam Bushbar that she's entirely disappointed Toe-Ticklers haven't yet been found in Jamaica.</p>\n</li>\n<li><p>Dr. Emmett Brown (1985) suggested that the Toe-Ticklers appear to have no means of vocal expression. He concludes that, since the feet alone are responsible for over <a href=\"https://www.feelyourfeet.com/engage/nerve-endings-in-your-feet/\" rel=\"nofollow noreferrer\">400,000 nerve endings</a>, what they must be doing is <strong>trying to communicate.</strong> He substantiates his claim by pointing out that the creatures only attempt to communicate with girls, who are known world-over to chat incessantly and are therefore the most obvious candidates for successful communication. However, in a brilliant Master's Thesis, Breathnach (2018) points out that this is unlikely because the Toe-Ticklers never take the girls' phones.</p>\n</li>\n<li><p>Dr. Sakura Chiba (2021) carefully monitored the condition of a girl while being tickled by a Toe Tickler and discovered that the <strong>increased dopamine from tickling was osmotically absorbed by the Toe Tickler as a form of bonding</strong> and concluded that the Toe Ticklers, which are apparently all male and otherwise asexual in nature, are simply trying to get a date.</p>\n</li>\n<li><p>A classified CIA report leaked through <em>Wikileaks</em> reveals that an analysis of Toe Tickler behavior suggests they're trying to <strong>extort information from their victims.</strong> The CIA is now investigating the possibility that toe tickling may be a heckuva lot more efficient than waterboarding. The report further indicates that it's to remain highly classified due to the embarrasment of admitting that the agency has been materially wrong all these years.</p>\n</li>\n<li><p>Dr. Nefario (2010) claims to have definitively proven that effective toe tickling is a <strong>great way to exhaust people.</strong> He further claims to have proof that the victims who are not returned are those who fell asleep from the exhaustion. He claims to have developed a <em>Blurp Gun</em> that he guarantees will awaken any victim. He finally claims that the lack of ransom demands from the Toe Ticklers in no way exonerates their obvious efforts to capitalize on their natural abilities.</p>\n</li>\n<li><p>Six year old Sigríður Magnúsdóttir has suggested that Toe Ticklers aren't really real and are really a story told by her pabbi to get her to brush her teeth. According to her pabbi, the Toe Ticklers (<a href=\"https://catbehaviorassociates.com/cat-myth-cats-steal-the-breath-from-babies/\" rel=\"nofollow noreferrer\">like cats</a>) <strong>feed off the oxygen-rich exhalations associated with laughter.</strong> Local reporters doubt Sigríður's story because her pabbi says she likes the taste of...</p>\n</li>\n</ol>\n<pre>\nThank you for joining us today for news from the world of science... and\ndon't forget to brush with NASAdent! Used twice a day to reduce tooth decay,\nnon-foaming and completely ingestible NASAdent will bring a smile to your\nface! *static*\n</pre>\n" }, { "answer_id": 209249, "author": "LiveInAmbeR", "author_id": 88214, "author_profile": "https://worldbuilding.stackexchange.com/users/88214", "pm_score": 0, "selected": false, "text": "<p><strong>Toe-Ticklers may simply be cleaning the feet and feeding on whatever they find like Cleaner fish. It may also be their form of social grooming like in apes, so they like the laughing.</strong></p>\n<p>There are forms of torture involving a goat licking salt from peoples feet so I can see Toe-Ticklers being pretty proficient ticklers with their tentacle fingers. Tentacles are perfect for reaching in between the toes, a perfect service for people with Athlete's foot. The Toe-Tickler gets a meal and the person gets a good time and clean feet, a mutually beneficial relationship. As to why they would prefer girls it may be because they don't kick back like boys sometimes do.</p>\n<p>If they live in packs they would be very social creatures, grooming (or I guess tickling) each other regularly to stay clean. Giggling may be their way of saying &quot;please tickle me more&quot; so when a little girl giggles, they can't help but indulge her until she falls asleep laughing.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/209223", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/75161/" ]

[ { "answer_id": 209446, "author": "L.Dutch", "author_id": 30492, "author_profile": "https://worldbuilding.stackexchange.com/users/30492", "pm_score": 2, "selected": false, "text": "<p>To calculate the density <span class=\"math-container\">$\\rho$</span> or the volume <span class=\"math-container\">$V$</span> of a body, you can use the relationship <span class=\"math-container\">$\\rho=M/V$</span>.</p>\n<p>Being two unknown values and a single equation, you can't solve it unless you have some other constrain to throw in. If you can give for example the radius, you can calculate the volume as <span class=\"math-container\">$V=4/3 \\pi r^3$</span> and from there the density.</p>\n<p>Another possible extrapolation is that, if you assume the average density to be same as Earth or any other planet you might want to consider, than from the density you can calculate the volume.</p>\n" }, { "answer_id": 209532, "author": "el duderino", "author_id": 46261, "author_profile": "https://worldbuilding.stackexchange.com/users/46261", "pm_score": 4, "selected": true, "text": "<h2>Alogrithm outline</h2>\n<p>So like L. Dutch said, if you assume the volume or average density of the planet you can do this. But the volume and average density aren't first principles values-- they themselves depend on the material and composition in a way that I'll describe shortly. <strong>As a word of warning-- I'm going to assume you understand calculus for this-- if you don't, L. Dutch's answer is about as good as you can do.</strong></p>\n<p>So, the fundamental difficulty of this problem is that to know the mass of the planet, you need to know the density distribution. The other answer assumes that it's constant, but this isn't a well founded assumption-- the inside of the planet has a lot more pressure squeezing down on it, which leads to higher densities. So how do we deal with this difficulty? Why, with differential equations of course! Barring any funny business like a quickly rotating planet or one that's still accreting, the main equation you would use is the hydrostatic equilibrium equation which basically says that the pressure pushing up against a thin shell of material must exactly cancel the force of gravity pulling it down:</p>\n<p><span class=\"math-container\">$$\\frac{dP}{dr} = -\\frac{Gm(r)}{r^2} \\rho(r)$$</span></p>\n<p>where <span class=\"math-container\">$r$</span> is the radial distance from the planet's center, <span class=\"math-container\">$P(r)$</span> is the pressure at that depth, <span class=\"math-container\">$\\rho(r)$</span> the density, and <span class=\"math-container\">$G$</span> the gravitational constant. <span class=\"math-container\">$m(r)$</span> is a function that gives you the mass inside the sphere of radius <span class=\"math-container\">$r$</span>, and as such <span class=\"math-container\">$m(r) = \\int_0^r 4 \\pi r^2 \\rho(r') dr'$</span>. But we want a system of differential equations to solve, so we differentiate this to get</p>\n<p><span class=\"math-container\">$$\\frac{dm}{dr} = 4 \\pi r^2 \\rho(r)$$</span></p>\n<p>Now, we just want to integrate this system of equations incorporating your boundary condition. Hold on though, we're not quite ready-- there are three functions we want to determine: <span class=\"math-container\">$\\rho$</span>, <span class=\"math-container\">$P$</span>, and <span class=\"math-container\">$m$</span>, but only two equations. We need another equation to solve this thing!</p>\n<p>That equation comes in the form of the so-called equation of state, which is where the planetary composition comes in. It turns out that for a given material, there's a function that relates the density and pressure called the equation of state (which we'll denote by <span class=\"math-container\">$g$</span>):</p>\n<p><span class=\"math-container\">$$g(\\rho, P) = 0$$</span></p>\n<p>I should mention first off that the EOS also relates another variable to these two-- usually temperature, entropy, or specific internal energy. However the purposes of determining density profiles, the effects are pretty small (~a few %) so you can usually just set the temp to some reasonable value like 5,000 K and pull g from along that isotherm.</p>\n<p>Now, things can get a little tricky here-- the equation of state isn't guaranteed to give rise to a one-to-one relationship between density and pressure. In other words, we can't necessarily write <span class=\"math-container\">$P = f(\\rho)$</span> and <span class=\"math-container\">$\\rho = f^{-1}(P)$</span>. If this is the case, we have to use a solver for what's known as a <a href=\"https://en.wikipedia.org/wiki/Differential-algebraic_system_of_equations\" rel=\"noreferrer\">differential-algebraic equation</a>. You can mimic this behavior using a <a href=\"https://stackoverflow.com/questions/23578596/solve-an-implicit-ode-differential-algebraic-equation-dae\">normal</a> ODE package available in most languages, but it might be pretty slow. Another option is the language Julia, which has a great differential equations package that can solve <a href=\"https://diffeq.sciml.ai/stable/tutorials/dae_example/\" rel=\"noreferrer\">algebraic-differential equations</a>. Usually for this regime though, we can at least write <span class=\"math-container\">$P = f(\\rho)$</span> even though we can't invert it, which for this specific system of equations is good enough to rewrite them as:</p>\n<p><span class=\"math-container\">$$\\frac{d \\rho}{dr} = -\\frac{Gm(r)}{r^2 f'} \\rho(r)$$</span></p>\n<p><span class=\"math-container\">$$\\frac{dm}{dr} = 4 \\pi r^2 \\rho(r)$$</span></p>\n<p>Now, how do we find an EOS for a given material? Well there are several ways:</p>\n<ol>\n<li>The most common in the field of planetary science is to use a premade table generated by someone who knows more about EOS's than you do. <a href=\"https://www.lanl.gov/org/ddste/aldsc/theoretical/physics-chemistry-materials/sesame-database.php\" rel=\"noreferrer\">SESAME</a> and <a href=\"http://militzer.berkeley.edu/FPEOS/\" rel=\"noreferrer\">FPEOS</a> are two I know of-- the latter is easy to access but unfortunately doesn't have a lot of important elements (most notably iron, which is important for rocky planets). The former is more complete but you have to request access through the link I gave. Either way with this option you'll have to spend some time learning other scripts or writing your own scripts to parse the tables.</li>\n<li>You can muck about the literature to find a paper with a formula or plot that you can <a href=\"https://automeris.io/WebPlotDigitizer/\" rel=\"noreferrer\">digitize</a>, like <a href=\"https://www.osti.gov/servlets/purl/6345571\" rel=\"noreferrer\">this one</a>.</li>\n<li>You can just give some kind of empirical formula you think seems reasonable enough. Power law relationships like <span class=\"math-container\">$P = C\\rho^{\\gamma}$</span> are often popular for this.</li>\n</ol>\n<p>Phew, we finally have our equations set up! Now we just need to use our boundary conditions: if <span class=\"math-container\">$R$</span> is the radius of your planet, this condition is that <span class=\"math-container\">$m(R) = M$</span>, where <span class=\"math-container\">$M$</span> is the mass you wish the planet to have. But unfortunately, since we don't know what <span class=\"math-container\">$R$</span> should be we have to take an iterative approach described by the following control flow:</p>\n<ol>\n<li>Set <span class=\"math-container\">$m(r = \\epsilon) = 0$</span> and <span class=\"math-container\">$\\rho(r = \\epsilon) = \\rho_{guess}$</span>. Here <span class=\"math-container\">$\\epsilon$</span> is a small positive number but not quite <span class=\"math-container\">$0$</span> because our equations are singular there. Can probably do a change of variable to fix this but it's less physically clear what's going on and I'm also lazy.</li>\n<li>Solve the two coupled equations above until you get the radius <span class=\"math-container\">$R$</span> such that <span class=\"math-container\">$P(R) = f(\\rho(R)) = 0$</span> (since there is no pressure at the surface of the planet). Might have to use some small positive pressure other than zero for numerical reasons.</li>\n<li>Check <span class=\"math-container\">$M(R)$</span>.</li>\n</ol>\n<ul>\n<li>If it's close enough to the mass you want, you're done! Extract the density and pressure profiles from the ODE solution.</li>\n<li>If it's too big, make <span class=\"math-container\">$\\rho_{guess}$</span> smaller and repeat step 2</li>\n<li>If it's too small, make <span class=\"math-container\">$\\rho_{guess}$</span> bigger and repeat step 2</li>\n</ul>\n<p>And that's all there is to it! If I have time later I'll try to add a simple example script to use but hopefully that's enough to get you started.</p>\n<h2>EDIT: Pictures and a simple code</h2>\n<p>So I made a simple python code to calculate planetary masses, the result is below. It should be pretty easy to use, all you need to do is have the appropriate packages installed and change Mdesired and the equation of state function to your liking:</p>\n<pre><code>import scipy.interpolate as interp\nimport numpy as np\nimport scipy.optimize as opt\nimport matplotlib.pyplot as plt\nimport scipy.integrate as sciint\nfrom math import pi\n\nG = 6.67408e-11 # gravitational constant in [m^3][kg^-1][s^-2]\nrho_guess = 1e4 # initial guess for center of planet density in [kg][m^-3]\nMdesired = 6e24 # Desired planet mass in [kg]\n\n# Now we normalize units so that G, M, rho_guess=1.\n# This will help numerical stability.\nrhostar = rho_guess\nMstar = Mdesired\nTstar = (G * rhostar)**(-1/2)\nLstar = (Mstar / rhostar)**(1/3)\nPstar = Mstar / (Lstar * Tstar**2)\nMdesired = Mdesired / Mstar\nrho_guess = rho_guess / rhostar\nM0 = 0.0\neps = 1e-4 # start ODE at this value of r to avoid singularity\n\ndef dudr(r, u):\n # u[0] = rho, u[1] = m\n drhodr = -(u[1]/(r**2 * dPdrho(u[0])) * u[0])\n dmdr = 4*pi*r**2*u[0]\n return [drhodr, dmdr]\n\ndef P(rho):\n &quot;&quot;&quot;EOS of epsilon iron phase from OSTI 6345571 \n &quot;&quot;&quot;\n rho0 = 8.430*1e3 / rhostar\n beta0 = 182*1e9 / Pstar\n betaprime0 = 5.0\n eta = rho/rho0\n\n P = 1.5*beta0*((eta**(7/3) - eta**(5/3))\n *(1 + (3/4)*(eta**(2/3) - 1)*(betaprime0 - 4)))\n return P\n\nrho_EOS_arr = np.linspace(0, 50, 1000)\ndPdrho_arr = np.gradient(P(rho_EOS_arr), rho_EOS_arr)\ndPdrho = interp.interp1d(rho_EOS_arr, dPdrho_arr, bounds_error=False, \n fill_value=(0.0, 0.0))\n\ndef found_surface(r, u):\n &quot;&quot;&quot;Event that terminates ODE when surface is reached\n &quot;&quot;&quot;\n Psurf = 1e-7 \n return P(u[0]) - Psurf\nfound_surface.terminal = True\n\ndef M(rho_guess, plot=False, obj = False):\n &quot;&quot;&quot;Find mass of planet given guess for density at center.\n Can also plot density profiles and give ODE solution object\n &quot;&quot;&quot;\n sol = sciint.solve_ivp(dudr, (eps, 100), (rho_guess, M0),\n events = found_surface, \n t_eval = np.linspace(eps, 50, 10000))\n\n if plot:\n plt.figure()\n plt.plot(sol.t*Lstar/1e3, sol.y[0,:]*rhostar/1e3)\n plt.title(r&quot;<span class=\"math-container\">$\\rho$</span> vs <span class=\"math-container\">$r$</span>&quot;)\n plt.xlabel(r&quot;<span class=\"math-container\">$r$</span> <span class=\"math-container\">$(km)$</span>&quot;)\n plt.ylabel(r&quot;<span class=\"math-container\">$\\rho$</span> <span class=\"math-container\">$(g/cm^3)$</span>&quot;)\n \n plt.figure()\n plt.plot(sol.t*Lstar/1e3, sol.y[1,:]*Mstar/1e3)\n plt.title(r&quot;<span class=\"math-container\">$M$</span> vs <span class=\"math-container\">$r$</span>&quot;)\n plt.xlabel(r&quot;<span class=\"math-container\">$r$</span> <span class=\"math-container\">$(km)$</span>&quot;)\n plt.ylabel(r&quot;<span class=\"math-container\">$M$</span> <span class=\"math-container\">$(kg)$</span>&quot;)\n \n if obj: \n return sol\n else:\n return sol.y[1,-1]\n\nrhoc = opt.newton(lambda rho: M(rho) - Mdesired, rho_guess, tol = 1e-3, maxiter=200)\n \nsol = M(rhoc, plot=True, obj=True)\nprint(f&quot;radius is {sol.t[-1]*Lstar/1e3} km&quot;)\nprint(f&quot;mass is {sol.y[1,-1]*Mstar:e} kg&quot;)\n\nplt.show()\n</code></pre>\n<p>Right now, I have it set up so that <code>Mdesired</code> is the mass of Earth in order to benchmark it. Here's what it predicts for the density profile of Earth<a href=\"https://i.stack.imgur.com/OsztR.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/OsztR.png\" alt=\"enter image description here\" /></a>. It's not <em>terribly</em> wrong-- it predicts Earth's radius is ~5000 km instead of ~6400 km. It also has a somewhat similar density profile to the core.</p>\n<p>The main reason for the discrepancy is that this calculation assumes the entire Earth is Iron in the <span class=\"math-container\">$\\epsilon$</span> phase-- this is really only true for the core and so it describes the crust and mantle as too dense and the end result is that it under predicts the radius of Earth. To fix this, you'd have to modify the equation of state so that its value changes with <span class=\"math-container\">$m(r)$</span>. This is a good exercise and if you understood this at all I recommend trying it out!</p>\n<h2>EDIT 2: A more accurate code</h2>\n<p>So I really went and <a href=\"https://xkcd.com/356/\" rel=\"noreferrer\">nerd sniped</a> myself on this one. Below is a code I developed that I think in principle can give you the exact density profiles you see in the literature (sans temperature corrections) as long as you have appropriate equations of state. <strong>I realized that I made a mistake in my last edit when describing the path forward for multiple EOSs-- if you just make the EOS abruptly vary by <span class=\"math-container\">$m(r)$</span> at material boundaries, it will give unphysical results.</strong> The reason is that the code implicitly assumes a continuous density profile, when in reality it is the pressure profile that is continuous.</p>\n<p>There are a couple of ways to deal with this, but what my code does is it solves for the density profile one material at a time, stitching together at the interfaces with the correct boundary conditions. As inputs, you need:</p>\n<ol>\n<li>A desired mass for the planet in <span class=\"math-container\">$kg$</span></li>\n<li>A guess at the density in the center of the planet in <span class=\"math-container\">$kg/m^3$</span>. This doesn't have to be super accurate-- ~10000 will probably work, but if you're working with very high or low masses you may need to adjust to get the solvers to converge</li>\n<li>A collection of materials that define your planet's composition. There are two lists corresponding to this item: one gives the fraction of total planetary mass for each material, and one is a list of equations of state for each material. I've included ones for iron and silicate perovskite which is a good approximation for Earth, but if you want other materials just peruse the literature and find more formulas.</li>\n</ol>\n<p><strong>And thats it!</strong> All you need to change are the variables in the input section, everything else should do the heavy lifting. Without any further ado, here's the code:</p>\n<pre><code>import scipy.interpolate as interp\nimport numpy as np\nimport scipy.optimize as opt\nimport matplotlib.pyplot as plt\nimport scipy.integrate as sciint\nfrom math import pi\n\n#####################################\n###### INPUTS #######################\n#####################################\n\ndef P_silicates(rho):\n &quot;&quot;&quot;EOS of cold silicate perovskite from Bina 1995\n &quot;&quot;&quot;\n Ktau0 = 262*1e9 / Pstar\n Kprimetau0 = 4\n rho0 = 4.1 * 1e3 / rhostar\n f = 0.5*((rho/rho0)**(2/3) - 1)\n xi = -(3/4)*(Kprimetau0 - 4)\n Pc = 3*Ktau0*f*(1+2*f)**(5/2)*(1-xi*f)\n \n return Pc\n\ndef P_iron(rho):\n &quot;&quot;&quot;EOS of epsilon iron phase from OSTI 6345571 \n &quot;&quot;&quot;\n rho0 = 8.430*1e3 / rhostar\n beta0 = 182*1e9 / Pstar\n betaprime0 = 5.0\n eta = rho/rho0\n \n Pc = 1.5*beta0*((eta**(7/3) - eta**(5/3))\n *(1 + (3/4)*(eta**(2/3) - 1)*(betaprime0 - 4)))\n return Pc\n\nG = 6.67408e-11 # gravitational constant in [m^3][kg^-1][s^-2]\nrho0_guess = 1e4 # initial guess for center of planet density in [kg][m^-3]\nMdesired = 6e24 # Desired planet mass in [kg]\nmat_Mfracs = [0.3, 0.7] # Mass fraction for each material type, starting from\n # core outward\nmat_EOSs = [P_iron, P_silicates] # EOS for each material type\n\n\n##############################################\n######## SOLVER ##############################\n##############################################\n\n# Now we normalize units so that G, M, rho_guess=1.\n# This will help numerical stability.\nmsum = sum(mat_Mfracs)\nmat_Mfracs = [val/msum for val in mat_Mfracs]\nrhostar = rho0_guess\nMstar = Mdesired\nTstar = (G * rhostar)**(-1/2)\nLstar = (Mstar / rhostar)**(1/3)\nPstar = Mstar / (Lstar * Tstar**2)\nMdesired = Mdesired / Mstar\nrho0_guess = rho0_guess / rhostar\nM0 = 0.0\n\ndef dudr(r, u, Mdesired, mat_props):\n # u[0] = rho, u[1] = m\n drhodr = -(u[1]/(r**2 * dPdrho(*u, Mdesired, mat_props)) * u[0])\n dmdr = 4*pi*r**2*u[0]\n return [drhodr, dmdr]\n\ndef dPdrho(rho, m, Mdesired, mat_props):\n Pfunc = mat_props[&quot;Pfunc&quot;]\n drho = 1e-9\n P1 = Pfunc(rho+drho)\n Pn1 = Pfunc(rho-drho)\n return (P1 - Pn1) / (2*drho)\n\ndef end_of_material(r, u, Mdesired, mat_props):\n &quot;&quot;&quot;Event that terminates ODE when the end of a shell for a given material \n is reached.\n &quot;&quot;&quot;\n cum_mass_frac_end = mat_props[&quot;cum_mass_frac_end&quot;]\n return u[1]/Mdesired - cum_mass_frac_end\nend_of_material.terminal = True \n\ndef found_surface(r, u, Mdesired, mat_props):\n &quot;&quot;&quot;Event that terminates ODE when surface is reached\n &quot;&quot;&quot;\n Psurf = 1e-7 \n Pfunc = mat_props[&quot;Pfunc&quot;]\n return Pfunc(u[0]) - Psurf\nfound_surface.terminal = True\n\ndef solve_one_mat(rho0, m0, Mdesired, mat_props):\n r0 = mat_props[&quot;r0&quot;]\n last_mat = mat_props[&quot;last_mat&quot;]\n if last_mat:\n sol = sciint.solve_ivp(\n dudr, (r0, 100), (rho0, m0),\n args = (Mdesired, mat_props),\n events = found_surface, \n t_eval = np.linspace(r0, 100, 100000),\n tol = 1e-8\n )\n else:\n sol = sciint.solve_ivp(\n dudr, (r0, 100), (rho0, m0),\n args = (Mdesired, mat_props),\n events = (found_surface, end_of_material), \n t_eval = np.linspace(r0, 100, 100000),\n tol = 1e-8\n )\n return sol\n\ndef M(rho0, Mdesired, mat_Mfracs, mat_EOSs, plot=False):\n &quot;&quot;&quot;Find mass of planet given guess for density at center.\n Can also plot density profiles and give ODE solution object\n &quot;&quot;&quot;\n cumsum_Mfracs = np.cumsum(mat_Mfracs)\n rho0, m0, r0 = [rho0, 0.0, 1e-7] # solver starts at 1e-7 radius to avoid\n # singularity\n P0 = mat_EOSs[0](rho0)\n r_arr = np.array([])\n rho_arr = np.array([])\n m_arr = np.array([])\n \n for i in range(len(mat_Mfracs)):\n # Build the mat_props dict for a given material, this tells the\n # solver what material we're using\n mat_props = {}\n mat_props[&quot;Pfunc&quot;] = mat_EOSs[i]\n mat_props[&quot;cum_mass_frac_end&quot;] = cumsum_Mfracs[i]\n mat_props[&quot;r0&quot;] = r0\n mat_props[&quot;last_mat&quot;] = (i == len(mat_EOSs)-1)\n rho0 = opt.newton(lambda rho: mat_EOSs[i](rho) - P0, rho0, tol = 1e-8)\n \n sol = solve_one_mat(rho0, m0, Mdesired, mat_props) \n rho0, m0, r0 = [sol.y[0,-1], sol.y[1,-1], sol.t[-1]]\n P0 = mat_EOSs[i](rho0)\n r_arr = np.concatenate((r_arr, sol.t))\n rho_arr = np.concatenate((rho_arr, sol.y[0,:]))\n m_arr = np.concatenate((m_arr, sol.y[1,:]))\n \n # If surface is reached before we can get through all materials,\n # we must end the loop\n if len(sol.t_events[0]) != 0 and not(mat_props[&quot;last_mat&quot;]):\n missed_layers = True\n break\n else: \n missed_layers = False\n \n if plot:\n plt.figure()\n plt.plot(r_arr*Lstar/1e3, rho_arr*rhostar/1e3)\n plt.title(r&quot;<span class=\"math-container\">$\\rho$</span> vs <span class=\"math-container\">$r$</span>&quot;)\n plt.xlabel(r&quot;<span class=\"math-container\">$r$</span> <span class=\"math-container\">$(km)$</span>&quot;)\n plt.ylabel(r&quot;<span class=\"math-container\">$\\rho$</span> <span class=\"math-container\">$(g/cm^3)$</span>&quot;)\n \n plt.figure()\n plt.plot(r_arr*Lstar/1e3, m_arr*Mstar)\n plt.title(r&quot;<span class=\"math-container\">$M$</span> vs <span class=\"math-container\">$r$</span>&quot;)\n plt.xlabel(r&quot;<span class=\"math-container\">$r$</span> <span class=\"math-container\">$(km)$</span>&quot;)\n plt.ylabel(r&quot;<span class=\"math-container\">$M$</span> <span class=\"math-container\">$(kg)$</span>&quot;)\n \n return (m_arr[-1], r_arr, rho_arr, m_arr, missed_layers)\n\n# Solve for density at planet center that gives the desired planetary mass\nrhoc = opt.newton(\n lambda rho0: M(rho0, Mdesired, mat_Mfracs, mat_EOSs)[0] - Mdesired, \n rho0_guess, tol = 1e-4, maxiter = 200\n )\n# Solve for and plot final values \nR, r_arr, rho_arr, m_arr, missed_layers = M(\n rhoc, Mdesired, mat_Mfracs, mat_EOSs, plot=True\n )\nprint(f&quot;radius is {r_arr[-1]*Lstar/1e3} km&quot;)\nprint(f&quot;mass is {m_arr[-1]*Mstar:e} kg&quot;)\n</code></pre>\n<p>Right now I have some input parameters that are roughly correct for Earth, namely <span class=\"math-container\">$M_{desired} = 6\\times 10^{24} kg$</span>, with a composition of 30% Iron and 70% silicates. So how does it do? Pretty well, actually! Here's the density profile it outputs:</p>\n<p><a href=\"https://i.stack.imgur.com/1pIUB.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/1pIUB.png\" alt=\"enter image description here\" /></a></p>\n<p>Which is pretty close to the types of profiles you'll see if you do a quick google search! It also estimates Earth's radius as 6250 km, pretty damn close to the actual value of 6370 km. Hopefully this was useful for you!</p>\n<h2>A couple of simplifications I've made if you want to dig in more</h2>\n<ol>\n<li>I ignore temperature dependence. In reality, the EOS will relate 3 variables and you'll need a third equation that tells you how temperature varies with depth. This is a trickier equation because it depends on time from accretion and radioactive decay and a whole bunch of other stuff that you need to specify.</li>\n<li>In reality, the form of the EOS won't be the EOS for a single material-- as you go deeper, planetary composition changes. Tbh I'm not sure how you calculate this from first principles-- there's probably some sort of thermodynamic/buoyancy argument to be made but I'm not certain. <strong>EDIT--</strong> my second code addresses this when there are clear boundaries between material types. In reality there will be a transition zone of some thickness, but it seems like more of the literature ignores this anyway.</li>\n<li>If there are other forces on your planet like centripetal forces from spinning, that can change the pressure balance equation.</li>\n<li>For super heavy objects like neutron stars, you have to take GR into account via the <a href=\"https://en.wikipedia.org/wiki/Tolman%E2%80%93Oppenheimer%E2%80%93Volkoff_equation\" rel=\"noreferrer\">Tolman-Oppenheimer-Volkoff Equation</a></li>\n</ol>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/209444", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/88321/" ]

[ { "answer_id": 210998, "author": "rek", "author_id": 25189, "author_profile": "https://worldbuilding.stackexchange.com/users/25189", "pm_score": 0, "selected": false, "text": "<p>I can propose a sort of workaround:</p>\n<ol>\n<li><p>Redraw your map as best you can in the Fuller/icosahedral projection. <a href=\"https://www.maptoglobe.com/\" rel=\"nofollow noreferrer\">Map to Globe</a> may be useful for getting somewhat accurate polar views for this step.</p>\n</li>\n<li><p>Rearrange the faces of the icosahedron so the new poles are at the top and bottom (the points of the triangles at the top and bottom are the 90°N and 90°S points on a globe), in one of these configurations:<br />\n<a href=\"https://i.stack.imgur.com/6g0SY.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/6g0SY.png\" alt=\"Three flattened icosahedrals\" /></a>\nRemember you can subdivide the 20 triangles above into smaller triangles each and rearrange them to get the precision you need. This would be easiest in a vector program like Adobe Illustrator or Affinity Designer.</p>\n</li>\n<li><p>Save it as a PNG with transparency (for the gaps around the triangles, shown as horizontal lines above).</p>\n</li>\n<li><p>Upload it to <a href=\"https://inexorabletash.github.io/ico2equi/\" rel=\"nofollow noreferrer\">Icosahedral to Equirectangular Converter</a> and select the configuration that matches.</p>\n</li>\n<li><p>Save the result and redraw to the size and level of detail needed.</p>\n</li>\n</ol>\n<p>Admittedly this has a few drawbacks, not least of which is redrawing the map twice. If you're working from a 'finished' map with lots of detail you may be better off waiting for another approach.</p>\n" }, { "answer_id": 211006, "author": "Nosajimiki", "author_id": 57832, "author_profile": "https://worldbuilding.stackexchange.com/users/57832", "pm_score": 0, "selected": false, "text": "<p>If you've already drawn your world map as a single rectangle, either by hand or in some raster program like Photoshop or Gimp, it is pretty much unusable (without significant cleanup) for what you are picturing regardless of what tool you find because of how much square maps distort actual shapes.</p>\n<p>The reason world map generator works as well as it does is because it uses an actual 3-d vector rendering of the Earth. Vectors can be losslessly transformed whereas maps made from your own hand drawing or pixel art can not.</p>\n<p>Your best bet is to load the map into <a href=\"http://www.maptoglobe.com\" rel=\"nofollow noreferrer\">www.maptoglobe.com</a> and eyeball reconstruct it, maybe even taking screenshots at various angles for references. Otherwise you will end up with funny line sharpness and stretching such that even a mathematically prefect rotation of your original map will look bad.</p>\n" }, { "answer_id": 216113, "author": "Tim Pederick", "author_id": 239, "author_profile": "https://worldbuilding.stackexchange.com/users/239", "pm_score": 1, "selected": false, "text": "<p>If I understand you correctly, what you want to do is re-project an existing equirectangular map to have the pole(s) in a different location—and your title question (“transfer onto a globe and back”) is how you think this might be done, not something that’s absolutely mandatory. Am I right?</p>\n<p>That is, would something that can do the re-projection <strong>without ever showing you a globe</strong> suit you? Because there’s software that can do it for you. Two options are the <a href=\"https://scitools.org.uk/cartopy/docs/latest/\" rel=\"nofollow noreferrer\">Cartopy</a> cartography library for Python, and the <a href=\"https://www.giss.nasa.gov/tools/gprojector/\" rel=\"nofollow noreferrer\">G.Projector</a> tool from NASA that uses Java.</p>\n<p>My evaluation so far: Cartopy gives better results, but is more fiddly to install and use. G.Projector is more straightforward. I’ll go through steps for both.</p>\n<p>Here’s a world map I’ll use to demonstrate. It’s not much of a map, but it will do for our purposes.</p>\n<p><a href=\"https://i.stack.imgur.com/1DuAR.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/1DuAR.png\" alt=\"A fairly low-res, low-effort world map of an invented world, in equirectangular projection.\" /></a></p>\n<p>We’re going to re-project it so that the new poles are on what’s currently the equator—the north pole will lie on that big landmass to the left (0°N 135°W), and the south pole on the smallest landmass in the cluster of three in the centre (0°N 45°E). But the methods shown will be fully adaptable to wherever you want your poles to be.</p>\n<hr />\n<h2>Installation</h2>\n<p>Unfortunately neither of these were particularly straightforward for me to install or run. Maybe you’ll have better luck?</p>\n<h3>Cartopy</h3>\n<ol>\n<li>Install <a href=\"https://docs.conda.io/en/latest/miniconda.html\" rel=\"nofollow noreferrer\">Miniconda</a>.</li>\n<li>Assuming without loss of generality that you’re on Windows, open the Anaconda Prompt that should now be on your Start Menu.</li>\n<li>Type in <code>conda install -c conda-forge cartopy</code> and hit Enter.</li>\n</ol>\n<p>I haven’t tested this method, but it <em>should</em> work? (I already have Python on my computer, but not through Anaconda, so I first tried installing Cartopy through pip… ★☆☆☆☆ Do Not Recommend. It’d probably go better on Linux than on Windows, but the Windows machine is what I had at the time!)</p>\n<h3>G.Projector</h3>\n<ol>\n<li>Install <a href=\"https://www.oracle.com/java/technologies/downloads/\" rel=\"nofollow noreferrer\">Java</a>.</li>\n<li>Download <a href=\"https://www.giss.nasa.gov/tools/gprojector/download/\" rel=\"nofollow noreferrer\">G.Projector</a> and extract it wherever you like.</li>\n<li>Again assuming you’re on a Windows computer, double-click on <code>G.Projector.exe</code> in the folder you just extracted. After a delay, you should get a file chooser window.</li>\n</ol>\n<p>(Give it time, and if you’ve got other programs open, Alt+Tab between your windows occasionally. I thought it hadn’t worked, and I ended up fiddling around and finding a way to open it manually, only to find while writing this up that it had opened in the background without a taskbar icon. If it <em>doesn’t</em> work, let me know and I’ll share the steps I took to open it.)</p>\n<hr />\n<h2>Running Cartopy</h2>\n<ol start=\"4\">\n<li>Copy this short script into a text file and save it as <code>reproject.py</code> in the same place as your image.\n<ul>\n<li>Change the filenames <code>notmuchofaworldmap.png</code> and <code>stillnotmuchofamap.png</code> to be your existing image, and a new name for your re-projected image, respectively.</li>\n<li>Also change the numbers for <code>pole_longitude</code> and <code>pole_latitude</code>, and for <code>figsize</code>, to whatever you want.</li>\n</ul>\n</li>\n</ol>\n<pre><code>import matplotlib.pyplot as plt\nimport cartopy.crs as ccrs\n\n# The image starts in a PlateCarree (equirectangular) projection, taking up\n# the entire globe…\nimg_projection = ccrs.PlateCarree()\nimg_extent = (-180.0, 180.0, -90.0, 90.0)\n\n# …but we draw the map in a RotatedPole projection. Set the pole location to\n# suit yourself.\nmap_projection = ccrs.RotatedPole(pole_longitude=45.0, pole_latitude=0.0)\n\n# Load the image.\nimg = plt.imread(&quot;notmuchofaworldmap.png&quot;)\n\n# Create a new map at a size of 720×360 pixels @ 100dpi (the default for\n# matplotlib). I chose these sizes because this is how big I made my sample\n# map; change them to suit your image.\nfig = plt.figure(figsize=(7.2, 3.6), frameon=False)\nfig.tight_layout(pad=0)\nax = plt.axes(projection=map_projection, frame_on=False)\nax.set_global()\nax.imshow(img, origin=&quot;upper&quot;, transform=img_projection, extent=img_extent)\n\n# Save the result!\nplt.savefig(&quot;stillnotmuchofamap.png&quot;, bbox_inches=&quot;tight&quot;, pad_inches=0)\n</code></pre>\n<ol start=\"5\">\n<li>In the Anaconda Prompt that you still have open from before, navigate (with <code>cd</code>) to the location of your image and the script.</li>\n<li>Type <code>python reproject.py</code> and hit Enter.</li>\n</ol>\n<p>Here’s the result of running this on the sample map.</p>\n<p><a href=\"https://i.stack.imgur.com/G2PHo.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/G2PHo.png\" alt=\"The same map of an invented world, re-projected so the poles are at a different location.\" /></a></p>\n<p>It ain’t pretty, though that’s mostly because my original map was so low-quality. There <em>will</em> be distortion, but at the very least, it’ll show you how it should look, and you can take steps to tidy up from there!</p>\n<p>One thing I haven’t quite gotten right yet is making the result have the same dimensions as the original. A decent chunk of the code up there is just to get it to stop putting borders and padding around everything, which is <a href=\"https://stackoverflow.com/questions/9295026/matplotlib-plots-removing-axis-legends-and-white-spaces\">apparently</a> <a href=\"https://stackoverflow.com/questions/40726323/matplotlib-scatter-plot-remove-white-padding\">not</a> <a href=\"https://stackoverflow.com/questions/8218608/scipy-savefig-without-frames-axes-only-content\">easy</a>! And it still comes out to 22.5% smaller than the original. This <em>may</em> be a side effect of the re-projection process, but I don’t see why it should be. A crude solution would be to make the output bigger…</p>\n<hr />\n<h2>Running G.Projector</h2>\n<ol start=\"4\">\n<li>In the file chooser that opened up previously, find and open your image. Confirm that the default import options (equirectangular, −180° to 180° longitude, −90° to 90° latitude) are correct and click “Okay”.</li>\n<li>In the Projection dialog that’s open by default, change the projection to “Equirectangular (Oblique)”, and change the “Centered on” position to whatever you choose.\n<ul>\n<li>As the name suggests, “Centered on” sets the centre of the map, not the pole location like we did with Cartopy.</li>\n<li>If, as in my example, you want the (old) north pole to be at the centre, then the latitude will be 90°. The longitude you choose will point up from there, towards the new north pole (so -135° in my example).</li>\n</ul>\n</li>\n<li>On the Window menu, open the Graticule dialog and change Stroke to “None”. Likewise, open the Overlay dialog and change it to “&lt;none&gt;”.</li>\n<li>On the File menu, use “Save map as...” to save the re-projected result, choosing whatever image dimensions you want (probably the same as the original image).</li>\n</ol>\n<p>Here’s what I got:\n<a href=\"https://i.stack.imgur.com/zBnCN.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/zBnCN.png\" alt=\"The same map of an invented world, re-projected so the poles are at a different location.\" /></a></p>\n<p>This is even less pretty than the Cartopy version. But it did the job!</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/209674", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/79394/" ]

[ { "answer_id": 210416, "author": "Trioxidane", "author_id": 77012, "author_profile": "https://worldbuilding.stackexchange.com/users/77012", "pm_score": 0, "selected": false, "text": "<p><strong>Most of it is ok</strong></p>\n<p>Most of what you are saying is ok.</p>\n<p>Viruses are mostly highly specific where they grow. Most often only a few cells with a certain type of DNA will be able to be affected. That means sickness can have difficulties to spread to many different species. You don't have to be afraid of most dog diseases thanks to this, although there are exceptions like rabies.</p>\n<p>Infecting multiple cells can help with spreading through the body. Growing first in the belly before going to the brain. Though it can make more sense for the airborne virus to start in the lungs. That way it'll be easier to develop the cough and have large enough concentrations of viruses to infect others thanks to the cough. It also explains the further development of cold like symptoms. Growing in the gut is highly unlikely to give the effects you want. Outward noticeable symptoms often develop thanks to the body as it responds to the sickness and not the virus itself, so you're clear there as well.</p>\n<p>The other category can house itself in other tissue to not become airborne, or have a defect that they near instantly die if expelled from the body.</p>\n<p>If I remember correctly, viruses (and bacteria) can have multistage behaviour. First they simply grow and spread a little throughout the body. Then, if the concentration is high enough, some hormonal triggers can make them change their behaviour and spread aggressively. Then they can primarily focus on the brain for both reproduction, but also control. Viruses like rabies already try to control you in some ways, like making you avoid water. The virus can do the same. The reasons can be multiple why it does this, but self preservation, resource gathering or ability to spread more efficiently are all good reasons.</p>\n<p>Travelling through the nervous system doesn't make sense however. It would generally be slow, as viruses have little in transport capabilities themselves. So why not use the blood (+ lymph nodes)? It is used by most viruses to get around, incredibly fast and spreads to literally everywhere in the body. The brain will be difficult thanks to the blood brain barrier, but as this is weakest at the olfactory bulb (smell) they always have an in (likely a reason you lose/change smell during Corona!). During the second stage they might also release things that can weaken this barrier throughout the brain, or move through the few other transport systems after infecting the olfactory bulb.</p>\n<p>Other methods of infection can help greatly with the spread of the virus. That way it can shorten incubation times and such.</p>\n" }, { "answer_id": 210786, "author": "DWKraus", "author_id": 74691, "author_profile": "https://worldbuilding.stackexchange.com/users/74691", "pm_score": 2, "selected": false, "text": "<h2><a href=\"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7975959/\" rel=\"nofollow noreferrer\">Para-Rabies</a>:</h2>\n<p>It is rare to have a virus have significantly different modes of transmission based on host immunity (not impossible). If the virus transmits through a bite, it's likely bloodborne as well. The more things you ask a virus (very simple thing) to do, the less plausible. Bacteria can exhibit more complex behaviors, but you clearly want a virus. I'd research <a href=\"https://en.wikipedia.org/wiki/Rabies\" rel=\"nofollow noreferrer\">rabies</a>, <strong>make your virus a variant of the rabies virus</strong> (does much of what you want, has established patterns, neurological, transmissible via bite, causes behavioral abnormality.</p>\n<p>To get the combination of infective pathways you want, consider using two related viruses. So as a scenario, imagine someone makes a super-rabies virus in a lab for terror purposes. Outbreaks would be horrifying but not globally disastrous. But sloppy work means the virus merges with an influenza strain in a coinfected individual and a hybrid virus emerges that is slow-incubating, looks like the flu for most of its early infection pattern, and doesn't affect anyone who had that strain of the flu previously. Developing a vaccine is only partly effective (and if no one ever made a vaccine against this flu strain prior, it could take a long time to do so).One is transmitted airborne, but a substantial percent of the populous is immune.</p>\n<p>The other is transmitted via bite, but the zombies extensively bite each other to the point that coinfection with the two virus strains is widely prevalent. A gentle breaking of the skin could even be the socializing element that ties your zombies together. If zombies accept biting from other zombies, and look for the presence of bite marks and aggressive biting behavior as the indicator of who is or isn't a zombie, you have a way the zombies know who is or isn't to be attacked. The bites physically mark them to each other (and the more a person is bit up, the faster the infection). A person who was &quot;captured&quot; by zombies would get repeatedly bitten (increasing the chance of the bite-transmissible strain being spread) and the zombies would keep biting until the person started biting back. The constant in-biting makes &quot;faking it&quot; by covering yourself in false bites possible but extremely risky behavior. The fact that not all zombies are guaranteed to have the bite-transmissible form also means people can get bitten and still convince themselves they might not be infected, increasing the likelihood they might hide the fact they were bitten to avoid being killed/locked up/ostracized.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/210404", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/88614/" ]

[ { "answer_id": 215311, "author": "Mark", "author_id": 278, "author_profile": "https://worldbuilding.stackexchange.com/users/278", "pm_score": 3, "selected": false, "text": "<p>More wagons than you can get.</p>\n<p>Pre-modern armies on the march were generally limited to 40,000 or fewer men. Any larger force was either a temporary concentration for a battle, or was marching along a river, where barges could be used instead of wagons.</p>\n<p>Beyond about 40,000 men, the supply wagons (and the supplies for the supply wagons -- draft animals need to eat, too) would crowd any road system to the point where food simply couldn't arrive at the army fast enough to keep it fed.</p>\n" }, { "answer_id": 215313, "author": "L.Dutch", "author_id": 30492, "author_profile": "https://worldbuilding.stackexchange.com/users/30492", "pm_score": 0, "selected": false, "text": "<p>Making such estimate is almost pointless, raiding the territories is &quot;best by test&quot;, to quote Bobby Fisher.</p>\n<p>There must be a reason why all armies until the invention of canned food relied on raiding the territories where they were waging wars for supplies, and in particular the roman army only went to war in summer, and that's precisely because if you want to be self sufficient in a war in those times, your only option is to not go to war.</p>\n<p>You need a properly established supply chain, a properly established transportation network infrastructure, a reliable way of transporting and storing the supplies, and you need all of that to be safe from the enemy's interference. There must be a reason why still today railways, harbors, bridges and highways are among the primary targets in a war!</p>\n<p>If you have a little group of soldiers out on a mission of few days they can bring supplies with them. Increase either of the two numbers, and you have to rely on what you find on site.</p>\n" }, { "answer_id": 215343, "author": "AcePL", "author_id": 8834, "author_profile": "https://worldbuilding.stackexchange.com/users/8834", "pm_score": 3, "selected": false, "text": "<p>In Roman legion, food allotment for a legionare was 2-3 pounds of grains (or flour) and 1 pound of meat and other foodstuffs like Olive, fruit, wine etc. Generally 75-80% grains, 20-25% meat and other components. So you immediately need to quadruple your calculation.</p>\n<p>Also, while food was calculated per head, it was distributed by squads. That means that once a week squad leader would go to the quartermaster and receive 1 week of food for 8 people. Then food would be prepared on the fire - meat would be cooked into soup or on open fire. It would not last a week, but after that it would be supplanted with olive, fruit etc, all as addition to porridge or bread or - especially during marches - hardtack. Hardtack needs to be baked, twice at least, for several hours each (preferably more), which requires a lot of firewood. That firewood also needs to be in allotment.</p>\n<p>To save on transport space I'd change flour or grains (which soldiers would often ground themselves) to hardtack from the start, as it's easier to transport and it's &quot;condensed&quot;. In that case 1 lb of hardtack would be a daily allotment - which reduces the total daily ration by 50%. So, 2 pounds - 1 kilogram - of food (tack, meat, olive oil, wine, vinegar, fruit) would be about right.</p>\n<p>As others mentioned, you forgot the other things: food for scout cavalry (horses, depending on unit it would be at least 600), food for oxen, but also Roman legion on the march didn't carry all equipment on the legionare's back. Tents, armor, weapons, ammo for projectile weapons, spares, kitchen utensils, digging tools (to build fortifications for the night, every night), heavy weapons (scorpions, onagers etc, disassembled), fuel for fires (if unavailable on campaing terrain), emergency water rations... This was transported in the baggage train.</p>\n<p>Jonathan P. Roth in his book <em>THE LOGISTICS OF THE ROMAN ARMY AT WAR (264 B.C. - A.D. 235)</em> gives the breakdown of nutrition standard and quantities that were required to feed a Roman legionare. In short, it boils down to about 6000kg of food per day. Multiply it by factor of 10 (nominal strength of legion after Aurelian reform is 4800, if double-sized First Cohort then 5200) and for 180 days it's 11k tons of foodstuffs total.</p>\n<p>50000 legionares on 180 days of campaign, having their own food for whole campaign with them? Impossible. Baggage train (which was actually mostly mules, with one or two per squad, with only some carts for really big and heavy loads) would be so huge to be be unmanageable - 10k-12k mules carrying squad's equipment alone is a staggering number, let alone added 5.5k ox carts each carrying 2000kg. And this cart max load is a technological limitation; heavy oxen cart would be heavy, made from oak and iron, weighing 1500kg - 2000kg. Thus, 140mm-diameter-double-axed oak cart has per-axle load limit of 1500kg, making it's gross weight no more than 3500kg (subtract 125kg per wheel; they do not count towards axle-load).\nThen there's food for mules and oxen, food for slaughter animals... food for oxen for more carts...</p>\n<p>Even if moving along rivers, the supply chain must be steady and secured. So quickly force would become smaller, with a lot of detachments to cover supply trains (road or water)...</p>\n<p>However. Depending on the region chosen for the concentration before moving to war and how long the expedition will be within it's borders, the baggage train is much smaller, as food can be &quot;delivered&quot; to the places where force will make camps for night.</p>\n<p>Then every day the baggage train will be smaller, because you can use oxen for meat - and they will be slaughtered when needed, and in the meantime you can use them as spares, then effectively doubling the daily mileage (at some point, initially it will be as slow as one expect).</p>\n<p>You could alleviate a lot of those issues if you choose a objective relatively close to your borders and you make it a defensive, fortified position, thereby allowing for reduction of the daily ration by anything between 25%-50%. Combined with combat losses you could get away with halving the baggage train, which sounds impressive, but going from 8000 carts and 10000 mules to 4000 carts and 5000 mules does not help much...</p>\n" }, { "answer_id": 215346, "author": "M. A. Golding", "author_id": 34461, "author_profile": "https://worldbuilding.stackexchange.com/users/34461", "pm_score": 3, "selected": false, "text": "<p>In 1862 General Sibley invaded New Mexico with a Rebel army and pushed back the defenders under General Canby. At the Batle of Glorietta Pass, March 26-28, the Rebels defeated the main Union force. But a detachment under Major Chivington captured the Rebel supply wagons at Johnson's Ranch, killig or diring off 500 horses and mules, burning 80 wagons and their supplies, and spking the cannons.</p>\n<p>The Rebel army retreated down the Rio Grande valley back to Texas</p>\n<p>The Army of Northern Viginia had about 71,000 to 75,000 men at the start of the Battle of Gettysburg on July 1-3, 1863, and several thousand fewer men at the end of the Battle. Lee began to retreat on the evening of July 4. The supply wagons carrying supplies and thousands of wounded men were escorted by cavalry under general Imboden. And I have read that the wagon train was 17 miles long, which would be about 89,700 feet.</p>\n<p>And if the Union had managed to capture those hundeds or thousands of wagons, the Army of Northern Viginia would have been unable to operate until the wagons and draft animals were replaced - if they could be replaced.</p>\n<p>The Army of the Cumberland was defeated by Rebel forces at the Battle of Chickamauga on September 18-20, 1863, and retreated to Chattanooga. There were tens of thousands of soldiers in the Army of the Cumberland and they needed a lot of supplies.</p>\n<blockquote>\n<p>Wheeler and his troopers guarded the army's left flank at Chickamauga in September 1863, and after the routed Union Army collected in Chattanooga, Gen. Bragg sent Wheeler's men into central Tennessee to destroy railroads and Federal supply lines in a major raid. On October 2 his raid at Anderson's Cross Roads (also known as Powell's Crossroads) destroyed more than 700 Union supply wagons, tightening the Confederates siege on Chattanooga.</p>\n</blockquote>\n<p>So more than 700 Union supply wagons were destroyed at Anderson's Cross Roads on October 2, yet that was not enough interruption in supply to starve the Army of the Cumberland into giving up Chattanooga. There should have been hundreds or thousands of other wagons making supply runs to and from Chattanooga in different convoys.</p>\n<p>So I think that your estimate of 800 oxcarts, which would probably be smaller than the Civil War era wagons, to supply 50,000 men is an underestimate. And they might make several supply runs (heavily guarded, of course) to and from the army in the field during the 180 day campaign, instead of remaining with that army for the entire campaign.</p>\n<p>.</p>\n" }, { "answer_id": 215349, "author": "o.m.", "author_id": 6402, "author_profile": "https://worldbuilding.stackexchange.com/users/6402", "pm_score": 4, "selected": false, "text": "<p>I agree with the people who write <em>it won't work</em>, but with a slightly different emphasis.</p>\n<ul>\n<li>The daily food allocation per soldier is almost irrelevant, but in addition to AcePL's figures for Roman soldiers, consider the <a href=\"https://en.wikipedia.org/wiki/Humanitarian_daily_ration\" rel=\"noreferrer\">humanitarian daily ration</a> at 1.9 lbs. It provides 9,200 kilojoules, while MRE are some 5,000 kilojoules (three per day). So a soldier would need some 3 lbs. of HDR per day. Compared to the Roman figure, that's close enough for government work, but I'll go with those 3-4 lbs. to account for the lack of modern preservation -- there will be spoilage.<br />\n50,000 people need about 100 short tons, slightly less than <strong>100 metric tons per day</strong>.</li>\n<li>I think you are <em>grossly</em> underestimating the weight of an oxcart. Googling a couple of sources gives about 500 to 700 kg for a roman wagon. That means 140 to 200 wagons <strong>per day</strong>.</li>\n</ul>\n<p><strong>Trick question, where do they come from?</strong></p>\n<ul>\n<li>A typical oxcart could do 2 mph for 5 hours per day (random googling).</li>\n<li>The oxen will need food. They <em>might</em> graze (only 5 hours of travel per day), but they will also need supplemental food if they do heavy work. And the pastures along the road will be gone soon. 18 kg per day per oxen.</li>\n<li>So for each day, the notional oxcart would consume 5% or more of the load.</li>\n</ul>\n<p><strong>After at most 20 days, all your food/fodder is gone feeding the oxen.</strong></p>\n<ul>\n<li>An oxcart could start out loaded half with cargo, half with fodder, and consume all that fodder within ten days (100 miles). That would leave you with an oxcart, the cargo, and no fodder for the return trip.</li>\n<li>More reasonably, there are plenty of supply depots. Some oxcarts carry only cargo, others only fodder to various depots. The calculation gets slightly more complicated, especially if you turn some of the oxen into soup instead of returning empty carts.</li>\n<li>Then there is the problem of assembling food at the starting camp. With luck, it is a (river?) port. If it is <em>merely</em> a fertile farming area, food/fodder will be required to collect the food.</li>\n</ul>\n<p>You will need well-stocked supply depots in secure terrain close to your operational area, plus constant resupply. The alternative is looting, which devastates the area rather quickly. L.Dutch mentioned that. (I don't think canned food is the key development, I think it was more due to a <em>state</em> that could maintain enough granaries. But that's a detail.)</p>\n<p>When I wrote that the daily ration almost doesn't matter for the calculation, it was for two reasons. First, oxen eat more than men. Second, if you have an organized state to provide 100 tons per day, a few percent more or less won't break it.</p>\n" }, { "answer_id": 225583, "author": "Jamie L.", "author_id": 94899, "author_profile": "https://worldbuilding.stackexchange.com/users/94899", "pm_score": 2, "selected": false, "text": "<p>Many have pointed out the basic logistics in detail, and why it's difficult if not impossible to get all that food for 50,000 fighting men (and cavalry horses, and oxen, and blacksmiths and tailors and cooks and laundry-workers, etc). However, I think people only skimmed over one aspect of why your campaign would fall apart: 180 days is <em>twice the length</em> of an average preindustrial campaign. As noted in several answers, most preindustrial campaigns took place in summer because that was after the main spring planting and before the next harvest.</p>\n<p>The biggest reason a smart person doesn't want 50,000 men in their army during preindustrial times is because most of those people would be farmers, NOT professional soldiers, so you need to send them back home to harvest the crops.</p>\n<p>At least, you SHOULD send them back home, if you don't want your country plunging into a famine. And depending on how big your country even IS to field 50,000 fighting men, both population-wise and geography-wise (England? France? How EASILY can this place let 50,000 men and however many logistics-people take away a huge amount of food, head off to enemy territory, and basically stop contributing to society for the next few months?), the three-month campaign would probably have EVEN LESS realistic time at full strength--you can't just mark off the days until the campaign's OFFICIALLY at Day 180 and let them go home.</p>\n<p>You have to let your men recover from injuries or illness, and then give them enough time to get home AT the harvest. Unless they live right at the two countries' border and it's only a day or two away, most of these soldiers would be infantry, and they'd be walking back home. How far is it--a week? A month?</p>\n<p>Most importantly, <strong>how hostile is enemy territory? Why do they even need 50,000 men, and why are they away for half a year?</strong> There needs to be <em>a really important reason</em> for your scenario, especially with all the difficulties that made it so hard in real life.</p>\n<p>If I was a preindustrial woman--especially one of those many farmers' relatives--and if my son/brother/cousin was sent to bulk up a massive, damn-near-impossible <em>50,000 man army,</em> I would be terrified of two scenarios:</p>\n<ol>\n<li><p>This is a suicide mission for about half the army. And unless I'm a protagonist, I'm pretty sure my relatives are in the half that's <em>not coming home.</em></p>\n</li>\n<li><p><em>The enemy is heading for us,</em> and nobody cares about food right now because they need every able-bodied man they can get to slow them down.</p>\n</li>\n</ol>\n" }, { "answer_id": 225654, "author": "Mon", "author_id": 76192, "author_profile": "https://worldbuilding.stackexchange.com/users/76192", "pm_score": 2, "selected": false, "text": "<h2>Don't Forget Fodder and Equipment</h2>\n<p>Quick fact check shows the average working horse requires aprox 1.5 to 2 kilos of fodder or grain for every 100 kilos of body weight.</p>\n<p>So just to make things more difficult all your horses, pack animals and oxen etc are going to add to the complexity of your logistics operation. If there's insufficient natural fodder available for all of your animals you actually have to start hauling animal feed by wagon as well.</p>\n<p><strong>PLUS</strong></p>\n<p>Short and in no way complete checklist;</p>\n<ul>\n<li>Tents and rope</li>\n<li>entrenching tools (picks and shovels)</li>\n<li>forges &amp; blacksmithing equipment, coal for same and spare feed stock for forging</li>\n<li>building tools (saws, hammers, nils etc)</li>\n<li>camp furniture (for officers &amp; admin staff) plus paper, ink quills etc</li>\n<li>parts for seige equipment or field artillery &amp; ammunition for same</li>\n<li>barrels of oil for cooking and lighting, water barrels, bags of salt</li>\n<li>spare munitions, arrows, spears, sling shot</li>\n<li>etc</li>\n<li>etc</li>\n<li>etc</li>\n</ul>\n" }, { "answer_id": 233078, "author": "RomainL.", "author_id": 60446, "author_profile": "https://worldbuilding.stackexchange.com/users/60446", "pm_score": 0, "selected": false, "text": "<p>IMO your computation is missing important point</p>\n<p>First, your computation does not consider food consumption for the oxen.\nIf you want them to work, they have to be well-fed and given rich nutriment.\n<a href=\"http://www.nzdl.org/cgi-bin/library?e=d-00000-00---off-0hdl--00-0----0-10-0---0---0direct-10---4-------0-1l--11-en-50---20-about---00-0-1-00-0--4----0-0-11-10-0utfZz-8-00&amp;cl=CL1.6&amp;d=HASH01bf7fd86a11d7b6614c98bf.4.1.3&amp;gt=1\" rel=\"nofollow noreferrer\">interesting link on how to take care of oxen</a></p>\n<p>Depending on the quality of supplement, it is 2.5 kg (5.5 lb) to 6 kg (13.2 lb) per day of food given to the oxen. That is assuming they are grass in the land you are visiting else you need hay <a href=\"https://animals.mom.com/calculate-hay-usage-cows-7809.html\" rel=\"nofollow noreferrer\">(hay per cows)</a> as in average they consume around 24 pound per days of dry food.</p>\n<p>Second, IMO your estimate is overly generous. It is true that oxen can pull, 10000lbs, but it is for short sprint like distance <a href=\"https://www.lancasterfarming.com/oxen-no-has-beens-when-it-comes-to-hard-pulling/article_b79a5f8f-5d4b-578d-997a-f385095dc7c9.html\" rel=\"nofollow noreferrer\">link</a>. For days long walking, you are looking at around they own weight. So it more of 2000 per oxen and 4000lbs per pairs.</p>\n<p>So, a rough estimate on how long they can sustain themselves.</p>\n<p>4000 / 11 = 363 days</p>\n<p>4000 / 26.4 = 153 days</p>\n<p>4000 / 48 = 80 days</p>\n<p>Now taking that into account, your equation actually becomes more complicated are your food supply are consumed by your soldier (that IMO you under evaluate) but also your oxen, and you require more oxen to feed your oxen. See where we are going there? Furthermore, as others have pointed out, you also likely need to transport equipment.</p>\n<p>Moreover, we do not talk yet about speed, but your soldier would outpace oxen as in average an ox can do 15 miles (ca. 24 km) a day.</p>\n<p>I will stand with other answers and tell you that such logistic in preindustrial time is not sustainable.</p>\n<p>For such operation, you need either to follow a river or a coast and have boat-based logistic with large supply depot or rely on the land you are in either foraging or commerce.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/215306", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/47028/" ]

[ { "answer_id": 218228, "author": "Mon", "author_id": 76192, "author_profile": "https://worldbuilding.stackexchange.com/users/76192", "pm_score": 4, "selected": false, "text": "<p>Probably not. The trouble is that while mountain <strong>chains</strong> can and do divert wind patterns a single mountain generally wont 'block' wind flow. What it will do is disrupt it. I suspect but cannot prove that it would disrupt the liner flow of the local winds and create vortex patterns as the wind current is 'split' and rolls around opposing sides of the mountain. Then on the 'lee' side of the mountain i.e. that side of the mountain that is opposite the direction the wind was flowing from the two streams would meet as opposing spiral flows that would cause turbulence as they recombined.</p>\n<p>Immediately right up close against the side of the mountain there <em>might</em> be a degree of protection i.e. wind speeds would be reduced. But as you moved away the mountain the spiraling wake patterns of the wind generated as they rolled around the 'leading edge' on both sides would collide and recombine chaotically with sudden changes in speed and direction. So the result would be more turbulence rather than a island of calm (except perhaps within a few hundred meters of the base).</p>\n<p>You really need someone with the appropriate software (e.g nautical or aeronautical engineering) to model it so that you get an accurate picture of what to expect. And they would need more data to feed into it.</p>\n" }, { "answer_id": 218233, "author": "MolbOrg", "author_id": 20315, "author_profile": "https://worldbuilding.stackexchange.com/users/20315", "pm_score": 3, "selected": false, "text": "<p>Sure it will and it does protect them, assuming wind patterns are more or less consistent as you said it is, which is realistic enough, not like you say &quot;unrealistic&quot;, wind patterns are a thing.</p>\n<p>A single mountain is a bit on unrealistic side of things, however, let's omit that</p>\n<p>It is 15 km high, and it is probably twice as wide at least 45-degree slopes(which isn't a random number), which makes it 30 km wide at its base.</p>\n<p>It is possible to dream about a mountain chain, but a few km high, 10's km wide wall as good as a mountain chain for some area bhind it.</p>\n<p>How big is that area is hard to tell without some aerodynamic simulation of such a cone, but it km's from its foot, you can place a city there, probably.</p>\n<p>So yes, the answer is - yes, that mountain will offer protection.</p>\n" }, { "answer_id": 218241, "author": "jamesqf", "author_id": 3545, "author_profile": "https://worldbuilding.stackexchange.com/users/3545", "pm_score": 3, "selected": false, "text": "<p>The mountain may to some extent protect them from winds coming from the other side, but it will also create its own winds, which can be stronger than the oncoming ones. Most mountain ranges have their own winds, with local names, like the &quot;Washoe Zephyr&quot;, of which Mark Twain wrote:</p>\n<p>&quot;The &quot;Washoe Zephyr&quot; ... is a peculiarly Scriptural wind, in that no man knoweth &quot;whence it cometh.&quot; That is to say, where it originates. It comes right over the mountains from the West, but when one crosses the ridge he does not find any of it on the other side! It probably is manufactured on the mountaintop for the occasion, and starts from there.&quot; (<a href=\"http://www.twainquotes.com/Zephyr.html\" rel=\"noreferrer\">http://www.twainquotes.com/Zephyr.html</a> )</p>\n" }, { "answer_id": 218242, "author": "Mike Serfas", "author_id": 82280, "author_profile": "https://worldbuilding.stackexchange.com/users/82280", "pm_score": 3, "selected": false, "text": "<h1>You never miss when you mark the bullseye after you throw the dart.</h1>\n<p>Your pole has complex wind systems and rugged mountains. You would need a supercomputer to simulate where the wind is lowest. Or, you could use a planet to do the simulation ... <em>your</em> planet. As in - look at the wind patterns in the polar region, see where they are weakest, and then say oooh, there's a sheltered spot to land a mission. Easy peasy.</p>\n<p>Just make sure there aren't any terrorists on the loose with family atomics!</p>\n" }, { "answer_id": 218246, "author": "Mary", "author_id": 75618, "author_profile": "https://worldbuilding.stackexchange.com/users/75618", "pm_score": 3, "selected": false, "text": "<p>If you want it to provide serious protection, you do not want a simple conical mountain such as you depict.</p>\n<p>What you want is a situation like Mount St. Helens, where the last explosion blew a cavity into the cone. A deep cavity.</p>\n<p>This will not provide perfect protection, but if you situate it just right, it will ensure the majority of the wind goes &quot;over their heads.&quot;</p>\n" }, { "answer_id": 218249, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 6, "selected": true, "text": "<p><strong>Your party lands in a crater like that of Haleakala.</strong></p>\n<p><a href=\"https://hanahou.com/14.4/quiet\" rel=\"noreferrer\">https://hanahou.com/14.4/quiet</a></p>\n<p><a href=\"https://i.stack.imgur.com/9q5qZ.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/9q5qZ.jpg\" alt=\"haleakala\" /></a></p>\n<blockquote>\n<p>Of course, national park status alone isn’t enough to make a place\nquiet, as any visit to Yellowstone will prove. But here an unusual mix\nof other factors comes into play: Huge sections of Haleakala are\nalmost devoid of life, so there are no leaves or animals to make\nsound; the bowl and the cinder cones offer shelter from the wind; even\nthe altitude, which keeps the crater cooler than the lowlands, slows\nand changes the way sound moves across the landscape.</p>\n</blockquote>\n<p>Haleakala in Hawaii is a giant shield volcano as I imagine your volcano must be. Down in the crater, it is preternaturally quiet. The linked article does a good job of conveying both the silence. It is also eerie and bleak.</p>\n<p>Set your party down in the old caldera. They will be protected there and you can also use elements of the actual Haleakala caldera for your story. If your party then ventures out into the surrounding lands they could go up and over the edge, or through a lava tube that pierces the wall.</p>\n" }, { "answer_id": 218253, "author": "hurreechunder", "author_id": 91703, "author_profile": "https://worldbuilding.stackexchange.com/users/91703", "pm_score": 3, "selected": false, "text": "<p>You have an example of this in the real world - the Indian subcontinent, which is protected from the winds that blow across Tibet and Central Asia by the Himalayas. It gets terribly hot in the subcontinent as a result, and that results in the monsoons.</p>\n" }, { "answer_id": 218257, "author": "Jack Edwards", "author_id": 91705, "author_profile": "https://worldbuilding.stackexchange.com/users/91705", "pm_score": 3, "selected": false, "text": "<p>This isn’t an answer, but perhaps more of an alternative.</p>\n<p>With a massive volcano like that, there will almost certainly be extensive cave systems nearby (look up “lava tubes”). Perhaps your party can seek shelter within these caves during windstorms, or maybe they establish their entire base on the interior of the volcano. If that’s the case, an impending eruption could also make for quite a nice storyline!</p>\n" }, { "answer_id": 218271, "author": "ChrisD", "author_id": 91711, "author_profile": "https://worldbuilding.stackexchange.com/users/91711", "pm_score": 3, "selected": false, "text": "<p>I was windsurfing once near <a href=\"https://goo.gl/maps/oww2NMxZNi2FBoEf9\" rel=\"noreferrer\">Kalepolepo</a> on Maui when the wind gradually died to absolutely nothing. And I mean nothing (had to derig and paddle back in). Shortly afterwards a friend called to say I should head over to <a href=\"https://goo.gl/maps/FYjVcQeHokBGNu5J8\" rel=\"noreferrer\">Kanaha</a> where it was blowing 30 knots. What had happened was the wind had swung northwest and Kalepolepo (along with most of Maaleaea Bay) was completed sheltered from it by Pu'u Kukui. Like I said, there was not a breath of wind, yet it was blowing 30 knots an hours drive away.</p>\n" }, { "answer_id": 218294, "author": "Tristan", "author_id": 71218, "author_profile": "https://worldbuilding.stackexchange.com/users/71218", "pm_score": 2, "selected": false, "text": "<p>A single conical mountain is unlikely to have too much of an effect at its foot.</p>\n<p>You can get around this by having a cliff on the leeward side of the mountain, allowing the base to be much closer (horizontally) to the peak, and much more covered by the wind shadow. The balance would be that they would be at greater risk of landslides.</p>\n" }, { "answer_id": 218298, "author": "skovbaer", "author_id": 91720, "author_profile": "https://worldbuilding.stackexchange.com/users/91720", "pm_score": 0, "selected": false, "text": "<p>The mountain will most likely not provide significant protection.</p>\n<p>To be able to answer your question better, we would also need to know size of the planet and rate of rotation around it's axis, in addition to gravity. If those are also comparable to Earth, then weather systems will have similar size and dynamics. Typical horizontal extent of non-tropical storms (e.g. hurricanes) on the Earth is on the order of 1000 km. This is much larger than the mountain in your scenario and it will not present significant obstacle to the storms. The mountain protrudes to stratosphere which helps, however, only by a very small amount (tip of the volcano). In order to create significant obstacle to weather sotorms, a mountain would ideally be a long range (north-south direction) with length of ~1000 km or more, and it would work even better if the height was up to the stratosphere or higher. For example something like the Cascades with the embedded volcanoes (Mt. Baker, Mt. Rainier, Mt. Hood,...), but higher on average.</p>\n<p>On the other hand, the mountain would help with reducing risk of other types of storms (smaller in scale) and tornadoes.</p>\n<p>Geographical location of 70 deg N is important, but it depends on the planet size, rate of rotation, temperature difference between poles and the equator (as mentioned before), what significance it will have on the type and strength of the storms at that latitude.</p>\n" }, { "answer_id": 218331, "author": "Loren Pechtel", "author_id": 264, "author_profile": "https://worldbuilding.stackexchange.com/users/264", "pm_score": 0, "selected": false, "text": "<p>A single mountain isn't going to do all that much about the winds because the wind will just flow around the mountain. However, if you have a few mountains together the wind flows around the group of mountains, leaving a sheltered spot. This is basically a three-sided version of the crater answer.</p>\n" } ]

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