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6d4k0w | Other | How come we never taught birds of prey to fish for us? | We do. Chinese fisherman have been using comorants to fish for thousand years. But it's highly inefficient compared to netting. | 1 |
5x4xhe | Biology | Will a more obese person burn more calories with the same daily activity as a thinner person strictly because of the amount of effort necessary to keep up? | Most exercise equipment that count your calories burned ask you to input your weight for this reason. | 12 |
dq0ost | Physics | How come sometimes when you shake a phone or other slightly dim light source in a dark room, it appears as if its springy and not moving at the same time/rate of your hand? This might sound silly, but I've noticed this with my phone screen, and the lights on a closed 3ds, when i shake it in a dark room at night, it seems like its delayed or springy, it doesn't move like a fixed object in my hand. Edit: it only seems to work in the dark, not when the light is on Edit 2: could it have something to do with brighter lights being more prominent and noticable? | Nothing to do with LED flicker, this happens with solid natural lights too. It's called the Hess effect and it's because the brain detects bright objects faster than dark ones, there's about 150 ms of delay which is easily noticable when you shake your phone or move your eyes around, makes it seem as though the bright parts are shaking compared to the darker surroundings. [Source]( URL_0 ) | 2 |
9slw6j | Mathematics | what is a theorem I saw many posts about theorems here, but they are written by adults. What i'm looking for is an example for a real 5 year old child (or six year), but to a child who doesn't have "advanced" mathematical concept, so, the example of the pithagorean theorem doesn't fit here because it implies knowing what is area and a 5 or 6 year old child doesn't know it. I can think some other example, but i don't know which one can be easiest to understand for a real child. I apologize if the question was already made but i didn't find it | A theorem is essentially a statement that we know to be true to because we have proved mathematically that it is true because of other statements that everyone agrees is true (such as "a thing is equal to itself"). | 2 |
5rdp0j | Biology | Why do we feel a lump in our throat when we hear upsetting news? | Dunno but ive got this thing called globus pharyngeas which basically means i constantly have that feeling, its theorized that its an anxiety induced disorder. First occurred two years ago during a period of severe anxiety and never went away. Its much worse when im anxious. After a while i learnt to live with it, and now i dont really notice it unless anxious. | 8 |
7odztq | Technology | If lie detectors (polygraph) are a pseudo science the why are they still used in court cases and by law enforcement? | The lie detector results themselves are generally not admissible. However, after the polygraph is administered, the questioner will review the results with the individual. “When I asked this question, your response indicated deception, why is that?” The follow on questions to the polygraph are what is useful. | 11 |
m7wvag | Biology | Why does Australia have so many weird creatures compared to everywhere else? What is it about their geography or other factors that makes them so attractive to the scariest bugs and other creatures? | Australia has been separated from the other countries for a long time so different animals had the opportunity to diversify into many niches. Like for example, placental mammals never made it to Australia, so the marsupial and monotreme mammals didn't have them to compete against, they had the opportunity to become established. Same for the surrounding islands, many had different animals filling out the niches that would usually be filled by placental mammals, such as small running birds that took the niche usually filled by rodents. The Kakapo is a heavy, flightless nocturnal parrot from New Zealand that was very successful before European humans introduced mammalian predators. The bird is well camouflaged and it's natural predators were all birds of prey that hunt by sight, so when it feels threatened, it freezes to be harder to spot. When cats, ferrets and other placental mammals were released on the island, the kakapo's defence mechanism was useless because those mammals hunt largely by smell. There are now very few kakapo left alive. This is an example to show how a completely unique ecosystem of birds filling in what we know as mammalian niches had developed on New Zealand and was very successful until invasive species were introduced. Plants are different in Australia for the same reasons animals are- there was a long period of time where Australia was isolated, so the living things there had time to evolve independently of the rest of the world. The life on Australia when it became isolated was the entirety of the Australian gene pool, and the traits that evolved in Australian nature were limited to that pool and the mutations that happened on the island (so that's why no placental mammals evolved there, they were not part of the available gene pool). Other continents had different gene pools and mutations. Over millions of years, evolution occurred differently based on these different starting conditions. "Scariest" is not a real descriptor for animals, but if you're talking about venemous animals being found on Australia- they're also found in Asia and Africa etc. That is not something unique to Australia, nor is having many invertebrates. If you're talking about the *potency* of venom found in Austalia, then it could be an evolutionary arms race situation. All the snakes in Australia are elapids, which are venemous. So the gene pool for snakes contained venom from the start. More potent venom is advantageous to a snake because it means it can bring down larger prey and ensure they don't get away before the snake can eat them. If the more potent snakes are better at survival than the less potent snakes, you will see a trend of venom becoming more potent as weaker snakes are selected against. The result is that all the remaining snakes are highly potent. This type of situation is also applicable to invertebrates, reptiles and mammals- it is common for venemous or poisonous species to become more potent over evolutionary history especially when their neighbours are using the same tricks. All in all, Australia is unique because it has been evolutionarily isolated for so long that it built up ecosystems out of completely different animals and plants as we have in the rest of the world. Traits like very potent venom evolved because they provide a fitness advantage, just like birds evolving to become ground dwelling, or plants evolving to be drought resistant etc. | 3 |
dtmbps | Biology | what causes the "aura" part of a visual migraine? | For what it's worth here.. I started with visual migraines (flashing lights, triangle shapes in an arc that increased in size until it obliterated my vision for 20 minutes), then progressed to ones followed by the massive headache part. I went from having them once every 4-6 months, to having them multiple times per week. I worked in a place where a person up near the front entrance was using those scented wax things constantly and someone in the back office was using the aromatherapy oils, and my office was sandwiched between the two. I started a new job 11 months ago with a new employer and no scented anythings, and I haven't had a migraine since. Visual or otherwise. My boss at the old job also had one of those where she couldn't understand what was written, she would read something really slowly, one word at a time, then say "does that make sense to you?" and I'd say "yes" but she couldn't understand it. She went to the hospital for it. I want to tell her to get away from those scents, but she was really into the essential oils thing. | 4 |
ca8xhd | Biology | Why do surgeons close surgical incisions with stitches instead of cauterizing them? | Because you want the skin to heal together. Cauterizing it stop the bleeding, but the skin wouldn't heal together because both sides of the wound are sealed off. | 4 |
e16drx | Engineering | Why do most commercial airliners have those little pods on the bottom of the wing? Are they for stability or extra fuel storage? | They are Flap Track Fairings which contain the necessary gear to move the flaps on the wings. They can also be Anti-Shock bodies, which reduce wave drag at transonic speeds. | 1 |
io182v | Biology | why do whales and dolphins have lungs that breathe oxygen instead of gills that allow them to stay underwater? | Whales & dolphins evolved from land animals; they adapted their existing lungs to living in the water and that was good enough to allow them to survive with out evolving back to gills. The fact that sharks & whales both exist show that neither gills nor lungs is strongly preferred for survival; lungs provide far more oxygen and allow whales & dolphins to sustain their warm-blooded metabolism and speed, gills don't provide enough for that but do allow continued submergence. | 7 |
6gllqc | Economics | Why do MLMs seem to be growing while simultaneously all other purchasing trends are focused on cutting out middlemen (Amazon Prime, Costco, etc.) Maybe its my midwestern background, but tons of my Facebook friends are always announcing their latest MLM venture (HerbalLife, LuLuRoe, etc.). But I'm also constantly reading about how online sales are decimating big box retailers and malls. So if the overall trend is towards purchasing online, how are MLMs growing? Or maybe everyone is selling and no one is buying? Thought someone here might have a more elegant explaination. | *"There's a sucker born every minute"* is the simplest answer. A slightly more complicated answer is that many of these MLM's are entangled with Evangelical Prosperity Gospel movements. "You have to plant a seed so God can prosper you!" So - see above. Squared. | 59 |
e3msfd | Economics | why can a country like the USA go into trillions of dollars into debt but other developed countries have to be careful? | Think of it like this. If you have a really well paying job, you can take out a really big loan. If you have a very bad job that doesn't pay very well, you can't take out a really big loan. You may not be able to take out a loan at all. The USA has the equivalent of a really well paying job. We make lots of money compared to other nations, so it's not that bad for us to have really big loans that we have to pay off slowly. Whereas, a smaller nation doesn't produce as much money, so any loans they get must be smaller too. | 2 |
ldn8qd | Earth Science | What is motor oil actually made of and why is it called a “fossil fuel”? | Motor oil, like gasoline, is made from crude oil and crude oil comes from the ground. Coal, crude oil, and natural gas are all considered fossil fuels because they were formed from the fossilized, buried remains of plants and animals that lived millions of years ago. Because of their origins, fossil fuels have a high carbon content. | 2 |
8c7vbx | Engineering | How can all electrical appliances use the exact same power? So if you have a voltage X and a current intensity Y. Doesn't that mean all electrical appliances get a power that equals P=X*Y? (before stepping down voltage in their inner transformers where this P will only be decreased by the transformer efficiency). How is that possible that a 40 inch TV screen takes as much power as an electric shaver for example? is that rest of that energy wasted? | They don't use the same power. They operate at the same voltage. Voltage is electrical *potential*. The power that a device actually consumes relies on the reststance the device presents to the grid. Less resistance means more current, which means more power. A washing machine needs more power than a clock radio. The washing machine presents less resistance to the grid, which lets more current flow through it, which the washing machine's motor uses to wash your clothes. The clock radio needs only a little power to run the display and radio. So it presents a lot of resistance to the grid, thus drawing only a little current. Think of voltage like water pressure in your residental water main. The pressure is the same in all the pipes in your house. You can open the tap wide open to water your lawn or fill your bath tub. Or you can open the tap just a little to dribble water onto your toothbrush. An appliance's electrical resistance is the size of the "hole" it presents to the electrical "pressure" (voltage) in your house's mains. ###more resistance = smaller hole = less current = less power consumed | 3 |
j10o8h | Biology | What determines whether a gene is dominant or recessive? | The net outcome is pretty obvious. If one parent has it, and half their kids get it, then that's a damn good sign you only need one copy for it to get expressed. Get enough people and enough kids and the statistics become clear. The mechanism of what exactly in DNA makes something dominant or recessive is [kinda complicated]( URL_0 ). Effectively, does it need both copies of DNA to make a working protein. If it works fine on it's own, then it's dominant. If it needs both halves, it's recessive. And there's plenty of in-between. (Seriously, nothing in biology is black and white, it's a goopy fuzzy mess of "typicallys" and "most of the times".) | 2 |
5ld3ls | Biology | why does it hurt when you swallow a beverage "wrong" ? Some people will say "oh it just went down the wrong tube..." what is the real reasoning behind this sharp pain? | There are two pipes in your throat: one for food/drink and one for air. When you normally swallow, your air tube closes off and food/drink goes into your food pipe. Two things can go wrong to cause an unpleasant sesnation: 1) food/drink enters your air tube by accident, making you cough and splutter, this is the body's natural response to protect your lungs. 2) the food/drink goes into your food pipe, but something holds it up and it becomes stuck, leading to pain/discomfort. Source: Medical Speech Pathologist specialising in swallowing disorders. | 11 |
7b0z7i | Engineering | How do studfinders work? | They have an electronic oscillator circuit which changes frequency in the presence of matter. The wall has capacitance which changes with density. You put the finder against the wall, press the button, and it does a calibration based on the drywall or paneling. When you move it across the wall, it senses changes in the oscillator's frequency and converts the deviation into a few distinct levels to light some LEDs. | 1 |
9kwoc3 | Physics | why is it freezing in space if there is no matter in the vacuum to transfer body heat into? | There's still blackbody radiation. But you're not wrong, if you were exposed to space there'd be a number of problems, but being cold isn't one of them. It is true that the ambient temperature is very low, and you'd eventually radiate away all of your heat, but that would take a while. The ISS, in fact, has large cooling fins and complicated cooling systems, and not heating systems, for this reason. | 12 |
h8fubm | Technology | What is x86-64 and other than the design freedom, what is the advantage of Apple switching to ARM processors? I have a decent understanding of computers, Ive built many custom PC’s, coded arduinos, but I don’t know much about these processors and the technical things behind them. | ARM processors use a reduced instruction set— basically, they speak a “simpler” language than x86. Besides making it simpler and more efficient to actually send commands to the processor, they can skip physical parts and processing steps that would be needed to interpret/execute more complex instructions. This tends to make ARM CPUs more energy efficient, and more cost effective, than full blown x86 CPUs. And if you have a limited amount of energy or money available, this means ARM offers the best performance possible within those limits. This is why all modern phones use ARM. There are uses where x86 could be better or necessary, but in *most* everyday consumer computing, the expanded capabilities of x86 vs. ARM don’t offer much benefit. The main reason x86 is in wide use is the huge ecosystem of operating systems and software that runs on it, and the number of developers who can *make* software for it, and will continue making software for it in the future. Versions of Windows for ARM were failures because the biggest benefit of Windows is compatibility with a *ton* of software, and that version of Windows gave up that advantage. Apple’s in a good position to change this because they have tons of money to invest, or risk, on this, software compatibility isn’t their biggest advantage in the first place, and the advantages of Macs are largely based on a few professional programs including Apple’s own software (like Final Cut for video editing)... so they can make sure the most popular programs, particularly for professional users, continue to work through the transition. | 1 |
gpjl78 | Biology | How do farmers grow food that does not produce its own seeds? For instance in an apple, if you plant a seed which is in the center of the apple, you get another apple. (It’s prbly more complicated than this) But what about something like a banana? I know there are banana trees, but bananas don’t produce their own seeds, so how are you supposed to form more bananas? | There are multiple ways to propogate plants without using seeds. Tissue cultures use a small slice of tissue grown in a nutrient medium. Apple trees are propogated by grafting cuttings onto the roots of another species of apple tree. Other species of plants take branches cut off them and just put into soil or other medium where they take root. | 1 |
7vcfx2 | Physics | If the densest element a star can form is iron, then where do other denser elements come from? Uranium is the densest naturally occurring element, or so I've been told. A star can form elements in it's core through fusion, and iron is as dense as it gets. So how do we end up with elements denser than that. Where are precious metals and rare Earth metals, among other things, formed? | Things can fuse beyond iron, but it takes more energy than it releases. A star works because the reaction makes enough energy (along with gravity) to keep the process going. Once the process *consumes* energy, it won’t happen for long. Interestingly, beyond iron, breaking an atom up releases more energy than it requires. This is why nuclear reactors and atomic weapons work. So in a star, at the very end, a star does do this for a very brief amount of time. It consumes more energy than it emits, and becomes unstable. What happens next depends on how big the star is and how violently it compresses under at gravity at the end. That happened a lot a long time ago, and the stuff that was blasted away clumped up in a cloud of dusty rocky stuff that coalesced about 5-ish billion years ago and made the Earth. The elements we have past iron are just the silver lining of lots of star death-explosions. | 5 |
cr6y5g | Biology | Why are viruses like the measles so dangerous? Wouldn't the virus want to keep the host alive to help it spread? | Most people who get measles dont die from it. Measles are dangerous because it can induce lethally high fevers. But, generally, microscopic organisms like viruses are built to reproduce in a given environment (like the human body) rather than travel through different environments. Their ability to spread from host to host is often incidental, such as through a transfer of bodily fluids. Also, viruses mutate frequently, so the "successful" viruses we know about usually spread by airborne means or skin to skin contact. There have probably been thousands of lethal viruses that only killed one person then died out with them because they had very specific or no means of transmission. | 5 |
c32xt4 | Engineering | So I’m pretty sure everyone has slipped in the tub or almost slipped. Why are standard shower surfaces and tubs not made out of non slippery materials? | My understanding is that the surface itself is pretty non-slip and it’s the soaps and shampoos and conditioners that we use that can make them slippery. I use a body wash that turned it into a slip-n-slide. PainfulAF! I see the tubs that have a textured surface on the bottom and they are usually filthy cause the dirt gets in the crevices and hard to clean. Not sure I was any help of why this one thing moved me to comment when I rarely do 😂😂 | 3 |
6aewyf | Technology | Why do news websites insist on using terrible video players when it would be easier and more user friendly to embed Youtube videos? | In order to use YouTube to embed a video on their news site, they have to upload that video to YouTube. Once they upload that video to YouTube, it's available across URL_0 . Google makes the money from ads on URL_0 , sharing only a small part with the person who uploaded the video. The news organization sells the ads for their own website, keeping ALL the revenue. Therefore, the news site would like their video to appear on their own site but NOT across URL_0 Other video providers offer similar functionality as YouTube, even if you think the older is not as good, which allows the news organization to own the advertising and sometimes added features like better analytics or copy protection or regional targeting, etc. I wish YouTube would offer similar functionality and crush all these other companies, but that would be in some conflict with their primary business model, and so far they haven't chosen to go there. | 13 |
cceerk | Biology | Why is there no large animal with more than 2 eyes but spiders have a lot of eyes? | Arthropod eyes are way simpler than ours, so to be able to navigate their environment they need more "pieces" of ocular organs, we never needed to develop more "eyes" because we can see enough to survive with our two. | 4 |
kjfgul | Physics | Why magnet attracts lighter object faster, but earths gravity attracts all objects at same speed? If you have 2 iron spheres and a magnet, the lighter sphere will move first to the magnet. But with earths gravity fall tests we know that every object falls with the same speed when dropped no matter theirs weight. What makes it different? | Lighter objects do indeed move faster when tugged, but with gravity, the heavier object is also tugged more. In fact, gravity's tug is exactly enough to offset the fact that you have to tug a heavy object more to get it going as fast as a lighter object. Magnetism's tug isn't based on mass. You still need to tug harder to move a heavier object, but magnetisim doesn't tug heavier objects more. The result is that lighter objects move faster. | 6 |
97eb0q | Biology | What happens to things that get into your eye such as dust or if a bug flys into it? Does it disintegrate or is it trapped in there forever? | Your eyes will work to either cleanse it with tears or it can work its way into the crusty gunk in the corner of your eye | 1 |
5umnpy | Technology | What does it mean to "Optimize" a game? In response to this post: URL_0 I get the general idea of what it does, but what do developers actually "do" when they optimize something? | Generally optimizing in video games is trying to get the same result by doing less work. This is usually accomplished by smarter use of the platform on which the game runs or removing redundant/useless operations that were not obviously wasteful before | 4 |
c74tpl | Technology | How are companies able to manufacture each pixel on a screen, given how tiny they are and make them work the way they want?? | They don't manufacture each pixel individually and then combine them to make a screen. They essentially "print" the pixels directly onto the screen in a process called [photolithography]( URL_0 ), which is the same process that is used to make CPUs. In a nutshell, it involves applying a layer of a UV-sensitive coating onto the base material that makes up screen (or the CPU in the case of making a processor). An image of the electronics that make up the pixels is projected onto the coating with UV light, which causes the coating to harden in the places where the light hits is. The non-hardened coating is washed off, and then other chemicals are used to etch the base material where it's *not* protected by the hardened, UV-sensitve coating. Then the UV-sensitive coating is dissolved with a different chemical, and you're left with millions of microscopic, etched electronic components. That process is then repeated on the material to create all the needed layers of electronics. | 2 |
grgdvt | Technology | How can 4KB take us to the moon but barely run a phone? | Assuming you're talking about memory here. It's plenty enough to run a phone, but just not enough to run all the other shit on it. | 6 |
l7ckr5 | Economics | Stock Market Megathread There's a lot going on in the stock market this week and both ELI5 and Reddit in general are inundated with questions about it. This is an opportunity to ask for explanations for concepts related to the stock market. All other questions related to the stock market will be removed and users directed here. How does buying and selling stocks work? What is short selling? What is a short squeeze? What is stock manipulation? [What is a hedge fund?]( URL_0 ) What other questions about the stock market do you have? In this thread, top-level comments (direct replies to this topic) are allowed to be questions related to these topics as well as explanations. Remember to follow all other rules, and discussions unrelated to these topics will be removed. **Please refrain as much as possible from speculating on recent and current events.** By all means, talk about what has happened, but this is not the place to talk about what will happen next, speculate about whether stocks will rise or fall, whether someone broke any particular law, and what the legal ramifications will be. Explanations should be restricted to an objective look at the mechanics behind the stock market. EDIT: It should go without saying (but we'll say it anyway) that any trading you do in stocks is at your own risk. **ELI5 is not the appropriate place to ask for or provide advice on stock buy, selling, or trading.** | ELI5: Who loaned the Hedge fund the stocks in the first place? Are they going to make bank from this squeeze? | 489 |
jmayjr | Other | Why do we tend to listen to a new song that we like over and over again and then we can’t stand hearing it anymore? | I have always found this weird i don't do it, and never understood why people would ruin music for themselves like that | 13 |
jdffsy | Technology | Why is the main hard drive always called C: ? | Because back in the day, your first drive, a boot drive, was removable media (A:) and the second removable drive for making copies of drive A:, is naturally, B:; leaving C: as the first mass media location. | 3 |
d0y1qb | Technology | How you record on cassette tapes, and how there are cassette tape that are converted to be an aux cord. | Tape is an analogue technology, which means that it records information (sound in this case) by replicating the signal with different levels of magnetic charge on the tape. The tape can be written to by applying a strong magnetic field to the tape to magnetize it, and can be read by applying a weak magnetic field to the tape, and measuring the response. A tape recorder / player is essentially a device that converts a magnetic analogue signal to an electrical analogue signal, and vice versa. An aux cord is just an ordinary electrical cable that caries an electric analogue signal. Most cables can carry two signals at once, for stereo sound, but some cables can carry three signals, two for sound and one for a microphone. Nothing special needs to happen for a cassette player to send audio over an aux cable, except that the signal from the tape might need to be amplified to be audible. The aux cable just needs to be connected to the players analogue output, and the other devices analogue input. | 2 |
beylt2 | Biology | How does insects survive harsh weather like rain and heatwaves? Do they seek shelter in human homes, trees etc? Wouldn't prolonged weather such as this effectively wipe them out in the area? | Like Taylor swift, they just "shake it off". It's actually true for some insects! For example bees, if they get wet, they start to move their wings very rapidly to exert heat and warm up again. In the cold they would do the same in a hive to maintain temperatures. During a heatwave they will do something similar and thereby ventilate their hives. I imagine it's similar for other insects. | 1 |
cy4t4k | Technology | How do impact garden sprinklers work? I always seem to observe those garden sprinklers that go CHK CHK CHK CHK CHK CHK CHRRRRRRRRRRRRRRRRRRRR and I can never piece together how they actually work and rotate. Please, explain this like I am 5. | The nozzle of the sprinkler is mounted on a base that allows it to spin freely. The impact arm is longer than the nozzle and mounted on the same base so that it spins on the same axis. It is held in line with the nozzle by a fairly weak spring. When the sprinkler is running, the water shoots out of the nozzle and crashes straight into the impact arm. The water hitting the impact arm pushes this arm out of the way. The impact arm swings around it's axis until the spring stops it, reverses it and brings it swinging back towards the nozzle. When the impact arm reaches the nozzle, it crashes into the nozzle and pushes the nozzle a short distance around the circle. Then the water hitting the impact arm pushes it out of the way again for another cycle. The chk..chk..chk sound you hear is the impact arm repeatedly crashing into the nozzle. When the sprinkler needs to reverse, a small stopper pops up that prevents the impact arm from swinging as far as it normally would. Now, on each cycle the water hitting the impact arm pushes it out of the way. The impact arm swings a short distance around the axis and crashes into the stopper. This crash into the stopper pushes the nozzle back in the opposite direction. Then the spring pulls the impact arm back in line with the nozzle. Because of the restricted swing, the impact arm only pushes the nozzle a little bit when it crashes into it in reverse mode, so the overall movement of the nozzle on each cycle is in reverse. Then the impact arm gets pushed out of the way by the water again. The tick, tick, tick sound you hear when the sprinkler is reversing is the impact arm crashing into the stopper. The shorter swing distance is why the ticks are more frequent than the chk..chk..chk sound it makes in the forward direction. | 3 |
i3580i | Physics | How do we know what the centre of the Earth is made of? | Every time there are earthquakes, scientists can look at the way the shock waves (aka seismic waves) from these earthquakes move through the planet — both the speed of the waves and how the waves bounce off of denser parts inside the planet (the inner and outer cores). It’s essentially this way that we have determined the physical state of Earth’s separate layers: **Crust**: solid rock **Mantle**: solid rock (apart from a few melty bits near the top of the mantle which make magma and feed volcanoes). The mantle convects veeeeery slowly. **Outer core**: liquid metal (mostly iron) which convects vigorously. **Inner core**: solid metal (mostly iron) because the pressure becomes too high for the metal to be molten. We have determined where the boundaries for these layers are based on seismic ‘discontinuities’ - sudden jumps in the speed that the seismic waves travel. Check out [a scaled diagram]( URL_1 ) to illustrate how thick the different layers of the Earth are. On average, the crust is actually similar in thickness compared to the whole Earth, as the skin of an apple is compared to the whole apple. Also, Earth’s core is pretty damn big. If you were to tunnel down and reach the edge of the outer core, you’re still not halfway to the centre of the Earth. Much of the stuff we’ve learnt from seismic studies are backed up by a few other lines of thought: * The Earth has a magnetic field, so it must have a metallic core, at least some of which is liquid and circulating in order to generate the magnetic field. This is consistent with (1) the types of seismic waves which do and do not pass through the outer and inner cores respectively; and (2) the fact that some meteorites which fall to Earth are an iron-nickel alloy which we believe to represent the cores of baby planets in the early solar system - they got big enough to separate into bodies with a core and mantle, but then smashed apart to set free their innards. * Even before we knew all that, early measurements of the Earth’s total mass meant that we knew there must be much denser material somewhere inside the Earth, as the rock of the crust was not dense enough to account for all the mass of the planet. Iron is a good fit for all the extra density; astrophysics tells us it’s relatively common in the universe, and there is obviously some natural process which can concentrate iron into pretty pure lumps based on those metallic meteorites (we call that [planetary differentiation]( URL_0 )). * With regards to the mantle, we do have certain pieces of mantle rock which get picked up by magmas and eventually erupted as lavas containing these still solid chunks of mantle rock within. (Many people think of the whole mantle as lava/magma, but it’s almost entirely solid rock with localised melty bits here and there). The chunks of mantle that occasionally get brought up to the surface like this are known as mantle ‘xenoliths’ - literally ‘foreign rocks’ - google the term to see their striking green colour (mainly due to the mineral peridotite). * There are also high-pressure high-temperature experiments that some scientists run on specialist lab equipment, this tells us what sort of rock exists in the deeper mantle - when upper mantle materials are subjected (in stuff like diamond anvil cells) to the appropriate temps and pressures that exist closer to the core. | 2 |
6e9vpn | Other | There is air in a bag of chips. So why do the chips only get stale after the bag has been opened? | The bags are generally packed with nitrogen which is a very inert gas. When the pack is opened you allow free circulation into and out of the bag which gets rid of the protective gas and allows moisture to get in. | 3 |
790u7d | Physics | The NASA twin study. I know what it is. Just explain their findings. Like I'm 5. Years old. Thanks. | I'm reading Scott Kelly's book (*Endurance*) now, about his time in space. He's the twin who spent a lot of time in space at the ISS--recently spent a year, previously spent months at a time, including a 6-month stretch some years ago. Mark Kelly is the twin who has stayed on earth. While he's flown 4 space shuttle missions, they were each around a week long only. He's married to Gabby Giffords and brother Scott was in space when Giffords was shot. Anyway, in addition to /u/RhynoD 's great answer, I'll add that there hasn't been a lot of data yet. So far they've seen that Scott has lost bone mass and muscle strength. He got taller in space due to lack of gravity compressing him, but within a few days he went back to same height as Mark. He suffered a lot of issues re-adjusting to gravity when he came back, such as blood pooling in his legs, rashes kind of like bedsores, and some vision problems. Those are the acute differences, and after a period of adjustment they tend to go away. So now they're looking at long-term differences, and that will take time to assess. So those findings are pending over time. For example, being in space increases your risk of cancer. Both twins got prostate cancer at the same young age--mid-40s. But only time will tell if Scott's heart was permanently damaged, or if his bone loss is going to be serious as he gets older, etc. | 2 |
7urmbh | Technology | How does a mobile phone "try" to find a signal? Most of us have had a phone eat up a ton of battery when we were in an area with bad coverage because the device was working to find a signal. Isn't the antenna on it just passively receiving available cell signal? Could you make a stereo use more power by having it "try" to find a better signal on a radio station? | Most digital traffic relies on a handshake to create a connection. This hand shake has multiple parts but let's simplify it. Tower: I am a tower at 900mhz for Verizon Cell: I see you tower at 900mhz, I am cell123 Tower: I see you cell123 at 900mhz, can you use Band7 Cell: I can use Band7 Tower: Cell123 Use Band7 Cell: Using Band 7 now Tower: Cell123 send your phone data. Cell123: (Chunk of data) Tower: (checks with network) okay cell123 you are connected, here is your call routing information, data rate, and IP addresses. Cell: I am connected When you are searching for a signal your phone is picking up a lot of towers usually that are to far away to do a good handshake. It might get some data but most is too weak to make it. Once connected the phone has an existing relationship with the tower and only transmits as needed. When there is no connection it has to transmit constantly to build a connection. There is a lot more to Cellular connections but that is my basic understanding of it. Think of it a bit like the energy used to find an unknown person in a crowd versus just keeping an eye on a person in a crowd you already know. | 6 |
nopnbi | Engineering | - Why can’t we harness the electricity from lightning and save that for use to power our cities? | [A technology capable of harvesting lightning energy would need to be able to rapidly capture the high power involved in a lightning bolt. Several schemes have been proposed, but the ever-changing energy involved in each lightning bolt renders lightning power harvesting from ground-based rods impractical – too high, it will damage the storage, too low and it may not work.]( URL_0 ) | 4 |
h7ysb2 | Biology | What did people do with poor vision before the invention of bifocals? Did they just deal with it? | Before bifocals, people who needed multiple corrections had multiple glasses, or went without. | 3 |
7n8g1u | Culture | Can somebody explain the class divisions in England/UK? I visited there last year and class seems relatively important. How important is class? Are people from different classes expected to behave a certain way? Manners, accents, where they live, etc. UPDATE: I never expected so much thoughtful responses. Class in the UK is difficult to explain but I think I was schooled by the thoughtful responses below. I will be back in London this year so hopefully I will learn more about the UK. Happy New Year everyone! | Working class and upper class people are the same. They love a good time and are totally unselfconscious about themselves. Middle class people, on the other hand, spend their whole lives desperately tweaking their accents and manners to convince working class people that they are better than them and trying to persuade upper class people that they’re as good as them. It’s painful to behold. | 10 |
7mkyqs | Economics | In the movie The Social Network, how exactly did Eduardo get screwed out of the company when he signed the new contract after Facebook was re-incorporated | Pretty much all major companies in the US are based out of Delaware. Facebook wasn't. So they created a new Facebook in Delaware that would then purchase the existing Facebook. Eduardo signed the papers without reading them very closely or getting his own lawyers to look them over. He thought it was just a small bureaucratic headache, trusted Mark, and thought the lawyers worked for him. But really, the documents gave Mark the right to issue new shares as he saw fit (which is also necessary in a growing company). Mark gave those newly created shares to himself and all the other investors, but not to Eduardo. This diluted Eduardo's shares. It was a long time before he noticed. | 1 |
iwkxa7 | Other | Why are number two pencils the standard for school and tests as opposed to number one pencils or pen? | Because the device that scans the test to mark the answers correct or incorrect requires a dark enough mark to be able to see. In pencils, the higher number means lighter writing. So actually, a number 1 pencil should work just fine, but a number 3 or 4 or 5 would not be able to be picked up by the scanner. So they standardized on number 2 to make it easy for students to know what pencils to use. | 1 |
6cxi0f | Culture | Can you denounce your citizenship and be technically and officially a citizen of no country? URL_1 it possible to denounce your citizenship and be a citizen of no country? 2.If this were possible what would that look like on official documents and would it be impossible to get a passport? 3.Can you also renounce this citizen ship in later time? URL_0 it also possible to renounce and denounce your citizenship constantly? As in, there is no limit to how many times you can become an american and then subsequently denounce your american citizenship? 5.Finally is there a limit to how many citizenship you are allowed to have? 6.does renouncing or denouncing a citizenship have any effect on this? 7.If you were to have 2 citizenships and another country would not recognize you as a citizen unless you remove one would that mean your technically force to denounce a previous citizenship to become a citizen of that specific country? | As signatories of several international treaties, most states won't let you renounce your citizenship if it means you'll become stateless. The United States is among the minority of countries that lets its citizens do it. | 9 |
nrmjiy | Technology | why do downloads occur at faster rates along the download process? | Downloads are done over the TCP protocol, and TCP gradually ramps up the speed until it finds how fast things can go. When you're downloading something you're constantly sending confirmations of "yeah, I got this bit" to the source, and the source throttles things down if confirmations stop arriving in a timely manner. Things also start quiet and gradually ramp up, until the system finds the maximum speed that works. | 1 |
5vzc9e | Technology | Why is there so much footage of nuclear bomb tests, etc. from years ago, but no recent or modern footage now? Has the world stopped testing or is it just now made public? | Some countries have continued testing, India, Pakistan, and North Korea are the most recent that come to my mind. Their tests were done underground. You can't hide a nuclear "test shot" on Earth. The seismic effects are telltale and can be measured all over the world. | 4 |
a2mucl | Biology | How does live fish sometimes manage to freeze in place in lakes, seemingly in the middle of daily fishy business? This thought came to mind when I saw a video of a fish frozen in place just as it ate another fish. | Might be to do with supercooled water. Normally water freezes at 0 Celsius, or just a bit below. But if the weather is really quiet, there's no wind or waves, and you've got a lake with very still water, it's possible for water to actually cool past that point without ice crystals forming. Then, when the water gets disturbed enough, the process of ice crystal formation begins, and it can be really rapid. You'll see this sometimes as a fun science demonstration. Someone will have a plastic jug of water that's been sitting in a freezer but is still liquid; they tap it, and the insides turn to ice pretty much immediately. | 2 |
bwx0jo | Biology | How do antidepressants cause weight gain? Title says it all. Some antidepressants are more well known for weight gain, some aren’t. What is it about certain formulas and what happens in the body? Do you just get in a happy bubble and stop caring? Or is it more scientific? | A side effect is increased appetite. It won't make you gain weight, but you will find yourself eating more if you don't pay attention. It's different for everyone. I think it's a possible side effect for many, many medications, but that doesn't mean it WILL happen for you. In fact if you eat to self-sooth, you may find that when you feel less awful, and are able to go out and do more, you end up eating less. I know plenty of people who avoid anti-depressants or birth control, or whatever important drug, because they are scared of weight gain. It's different for everyone. And antidepressants work differently on everyone. So if anyone is considering taking one, but worried about side effects. The only way to found out is to take one with the supervision of a good doctor, and let them know if any side effect is really too much. Fatigue in the beginning is common, but if it's been months and you can't get out of bed, then you need to switch to another drug. There are lots to try, and you have to find the one for you. | 4 |
696mak | Other | Why does water taste differently depending on which city you are in? | Hey! [I made a quick video to answer your question]( URL_0 ) If you don't want to read it, here are the reasons I cover: - Water is collected from different sources, ground sources and surface sources. Ground are places like wells, and surface are places like lakes and rivers. - Each place in the world collects water from different places, and uses different means of transport. Be it pipes, or bottles. This effects the taste and smell of the water. - Also, we get used to the water! It starts to taste normal, so the place you grew up would always be thought of as "normal" water, however it's different to other cities or countries. If you were to move, you'd notice a difference in taste and smell straight away. However, you'll get used to this as you start drinking it more as it becomes the norm. - Different sources have different minerals floating around too, for example a lake might have a different % of minerals, which can effect smell and taste too. Hope you enjoyed the **joke** at the end of the video. Have a great day! Sidenote: I make a lot of these videos, but they are always specific to the question asked, I loved this quetsion and decided to make a video. Sorry if anyone feels this to be self promotion. | 3 |
jjlt5f | Other | Why do companies keep incriminating documents? In movies there's always a crooked company whose employees are shredding documents when shit hits the fan. What could be in these documents (for the average company), and why do companies keep them in the first place, if they could lead them to jail? | In addition to it being movie stuff, documents are kept around for audit purposes. Having a gap is incriminating in itself. Secondly, the documents may only be incriminating once people know what to look for. Say your shady company makes a transfer to a criminal's bank account, not having the records to hand means you fail the audit straight away as money has gone 'missing'. People are going to start asking questions immediately. However, if the auditors don't know that the bank account belongs to criminals, then showing that money has been transferred doesn't raise any questions itself. Money changes hand all the time and they just need the books to balance. The criminals are using a freight company as a front. Your company ships stuff. It isn't suspicious. It's only later when Batman is tracking the money trail and pays a visit to your office that you need to shred those papers. | 3 |
kxhtld | Engineering | How is a car "able to put 70% its power to one wheel" in modern 4WD systems? Watching motoring shows in recent years they often say things like "this four wheel drive system is able to adjust the power between 50:50 to 80:20 front to back, and can then put up to 70% of that to a single wheel if needed". I understand how slip difs work, and I get limited slip difs. What I don't understand is how a purely mechanical system can move that much power around from wheel to wheel. Gearing changes would adjust speed not power, and fixed bars just can't do that. So what's happening? I'm fairly mechanically minded, but I just can't work this out. Maybe I need an Explain Like I Love Technic Lego. :) | It's adjusting torque. If I turn one wheel at 100 RPM with 10 ft-lbs and one at 100 RPM with 90 ft-lbs, I'm sending 90% of the power to the second wheel. Modern systems that can dynamically split torque around are usually AWD (4WD usually refers to systems that either send equal torque to all wheels, locked diffs, or conventional un-controlled diffs). By applying brakes to individual wheels (or sometimes adjusting the diffs on the fly) they can alter the torque split that's getting to the wheels, which splits the power. When the brakes come on unevenly, the RPM \*isn't\* the same (that's the whole point of the diff) but big power shift is the torque. | 1 |
af4e6v | Culture | Hieroglyphs...how does ancient subjective image become a modern language? | As /u/deadantelope said, hieroglyphs are not "subjective images". On top of that, hierogylphs are not a "language" they're a system of writing a language. So, to take Egypt as an example, the Ancient Egyptian language existed, and hieroglyphs were invented to write it down. How the language developed over the millennia is probably mostly independent of how it was written. Egyptian hieroglyphs, however, were simplified (which we might consider "modernisation"), but, as I understand it, were ultimately replaced by the Greek alphabet. | 3 |
gbfixl | Chemistry | Why is wet hair easier to comb? | So hair is a complex of proteins that act as a polymer or plastic. Plastics have this property called “glass temperature”. When they are below this temperature, they act more as a glass (brittle, inflexible, rigid). Above this temperature they act more “plastic” (shapable, yielding) etc. there are compounds called “plasticizers” that are able to make a polymer act more plastic without altering temperature. Water is a plasticizer. Also, this is the same reason spraying a mist of water on shirts gets rid of wrinkles. Once the water dries, the hair falls back into the glass regime and maintains its style. The water also lubricates the comb and allows it to pass more freely through your hair. | 1 |
cyaiw6 | Technology | Rather than use air conditioners that just move the heat around and use energy, why can't we extract the ambient heat energy of a hot room and convert that heat into usable energy ? | There has to be a temperature differential to collect usable energy. Since naturally the heat wants to be spread equally you can collect energy in facilitating that spread. If it's already spread equally then it takes energy to make the difference greater. | 10 |
lgmjuv | Biology | Why is the air from your mouth warm when your lips are wide open, but cool when your lips are puckered? | You are probably testing it by blowing on your skin, that gives a false impression due to evaporation of the moisture differing in a fast narrow air stream and a broad, wide one. Try it with a thermometer and see if the effect is real. | 4 |
iszzh3 | Other | What are liberals and conservatives? | That's the million dollar question, isn't it? A *lot* of political discourse/bickering boils down to who counts as a liberal or who counts as a conservative. The definition of both liberals and conservatives varies by country so there's no single overarching definition that works for all of them. You would have to specify the country first to even start getting a workable answer. That, and both camps have a lot of different subsets who aren't necessarily concerned about the same issues, or even have completely antithetical views on the same issue. Since I'm a conservative and am more familiar with the subsets of conservatism, the best example I can think of is paleoconservatism vs. neoconservatism, which is a *very* heated yelling match that centers on foreign policy, and in particular using war and the military as a foreign policy tool. It's not even really all that easy to describe the different subsets of conservatism or liberalism without the descriptions being tainted by the bias of the describer. So rather than thinking of liberals and conservatives as single "thing", it may be more accurate to think of both as large, informal coalitions of different ideologies that are held together, if not by their similarity to each other, at least by disliking the ideologies in the other coalition more than they dislike each other. | 3 |
9tl8i7 | Other | how does sword swallowing work? | It's one part illusion and one part a lot of practice. First of all, they don't use battle-ready swords. They're not at all as sharp as a weapon should be. Half of of the trick is making them *look* like swords. Second, your neck needs to be straight as an arrow and, after a lot of practice, you can just kind of slide it down and hold it down. | 3 |
ab0xq2 | Culture | Why is it illegal to walk around in public with an alcoholic drink in the US? | It is to give grounds for the police to quickly and easily deal with someone who is making a public disturbance while drunk without having to wait for them to hurt someone or destroy property. Most of the time you will not even be given a warning walking around with an alcoholic drink, but if you start being obnoxious they will arrest you prior to you doing something harmful. | 10 |
b2dvbr | Engineering | Why do some fishermen have poles with the holes (that the fishing line runs through) top versus bottom? I could’ve googled this but since reddit seems to encourage these types of easily findable questions I figured I’d ask here instead. It’s an honest question | The guides are on the same side as the reel. Some reels go on top (bait casting) some go on the bottom (spinning and fly reels) | 3 |
bqoiqx | Biology | Why is it okay to eat blue cheese, but not other things that are moldy? | It's yummy mold. Just like how there's yummy fish and poisonous fish. There's yummy mold. | 11 |
5s84qy | Economics | what happens when someone rich dies with nobody to pass it on to? Where does the money go? | A person who dies intestate, or without a will or beneficiary, will have their assets distributed "by law". There are laws everywhere to govern this sort of thing and vary by location. For example, the laws in England are different than those in the United States. In fact, in the US, the laws are by state. For the most part, the assets are placed into an account, an administrator is hired and assigned to locate the nearest living relative/s. Failing that, the assets will eventually go to the State Treasury. Generally speaking. | 1 |
649xhh | Other | Why is it okay to eat/drink stuff in a US supermarket before paying for it? This doesn't really happen in my home country (Finland) | In the Netherlands you often see parents giving their child a croissant or some form of oven baked bread. It's accepted and It's based on trust that people pay for it. Also most supermarkets have a basket of free fruit for children (must say I have had a few times I thought about getting one and telling people; my parents see me as a child...) | 20 |
b3g9bu | Economics | Why is Switzerland so rich compared to other European nations? I've read that it used to be an extremely poor country. What changed? | Switzerland was never poor. You might argue that in mideval times, all countries were poor, but Switzerland was no poorer than others. In modern times (since about 1600 A.D.) Switzerland has been prosperous. | 3 |
hq8azq | Biology | How does stretching affect the body? Animals and humans alike seem to enjoy a good stretch when first waking up or after being still for a long time. What affect does stretching have on the body that makes it so instinctual? | Because if you don't use several muscles for example in your legs or something if you sit for extended periods of time then the muscles tighten, when you stretch you loosen up those muscles and help you keep your muscles strong and flexible. Also to add onto this the reason why stretches feel so good is because the nerves in your body send messages to your brain saying, "bruh this shit **GOOD**" Also I may be wrong but I'm almost certain this is right | 3 |
hxdkrx | Biology | How can something make sense to me in half asleep state and when I'm awake and remember what I said it makes no sense at all | My husband does this. Talks kind of half awake half asleep. They’re real words but nonsense sentences. If I engage with him he’ll continue. And sometimes I’ll ask him if he’s awake and he says yes. If I keep talking to him enough, he’ll wake up more and realize what he’s saying doesn’t make sense. It’s pretty funny. | 4 |
6wit1y | Other | How can stuff be "rediscovered" in museum collections? Don't museums keep a detailed list of everything they have? | In the early days of museum collections, they would often receive hundreds of items at a time and would hastily sort them or display them. In their haste, they often didn't take detailed reports of what they had or may have overlooked an item. Then 50-70-100 years later, some new guy is going through the inventory while changing out items and come across a tag or unmarked item. Or it has been sitting in storage because when it originally arrived in say 1877; no one wanted to deal with it, didn't have time, or it simply didn't get properly inspected. So someone finally takes a look at that old piece of pottery and discovers a pre-Minoan art work depicting the Maze and the Bull, but the bull is a man in a helmet. And sometimes, it takes years to go through all the boxes and items a museum receives. Some curators and researchers could spend a lifetime on a dozen artifacts and their meaning and origins. A collection could also be passed from one location to another without ever fully being looked into, so when someone finally comes across something it is rediscovered. | 6 |
6qm9nk | Chemistry | Why does tap water from the kitchen sink taste slightly different than tap water from the bathroom sink, despite having the same source? Is it my well water??? Is it the pipes??? Placebo??? I must know. | Yer not alone in askin', and kind strangers have explained: 1. [ELI5: Why does water from the kitchen sink taste better than water from the bathroom sink ]( URL_1 ) 1. [ELI5 Why does bathroom tap water taste "different"? ]( URL_2 ) 1. [Why does kitchen sink water taste better than bathroom water? ]( URL_0 ) 1. [ELI5: Why does kitchen faucet water taste different than bathroom faucet water? ]( URL_5 ) 1. [ELI5:why does water from the bathroom tap taste different to water from the kitchen tap? ]( URL_3 ) 1. [ELI5:Why does bathroom tap water taste so much better than kitchen tap water? ]( URL_4 ) | 4 |
e7acv9 | Biology | How does the measles virus wipe out your body's "memory" of immunity to other viruses and why is this not common in other viruses? | The virus has a proclivity for immune memory cells as targets for infection. This causes the death of the immune memory cells from the action of the virus itself and from elimination by the healthy aspects of the immune system in fighting the infection. This widespread destruction of the immune memory cells, which are responsible for an individual's immune memory, therefore leads to a loss of said immune memory. The loss of immune memory is then compounded by damage to the skin, respiratory and gastrointestinal tract tissues, which are components of the passive immune system. This combined damage to both the adaptive and passive immune systems results in a higher vunerabiltiy to other pathogens. | 1 |
91dqf5 | Physics | Are there instruments that can detect every wavelength of electromagnetic radiation? If not, why are there wavelengths that can't be detected? | Depends what how pedantic you want to be, but the answer is no. Different materials respond to different wavelengths (due to their electron configuration/sterics), and unless your device is made of all of them then it wont work, and none are, mostly cause it is way cheaper to do it separately. To be super pedantic there is a limitation of what wavelengths can physically exist. The longest wavelength coming from the big bang, so unless you can recreate the big bang you can’t recreate all the frequencies, thus you can’t detect them. | 2 |
5xdhdn | Other | Why are we using a loud, obnoxious *BEEP* to censor curse words? | If we go back in time to when audio was recorded on tapes, the way to censor something is to record over it. If you just record silence over it, you'd still hear the censored content, albeit likely quieter. If you put a nice solid tone over it, it'll for sure eliminate the ability to hear what's underneath. | 3 |
j4odl6 | Engineering | Why most disposable things are made of looong lasting materials like plastic? | All in all 99% of the time it comes down to cheap and trying to spend as little money as possible | 6 |
5y7pqs | Other | Why does the US struggles to have a proper health care system, even though the premiums paid by the patients are much higher than most of the countries, where there is a working health care system (e.g. most of the European countries)? | Health insurance is the single ELI5 answer to this question. We have a multi-billion dollar industry standing between ourselves and our health care. The insurance industry making more money for everyone except the person who is sick and the millions that will never get sick. With insurance, there became a financial disconnect between the doctor and the patient. Health care providers were able to charge the insurance companies a higher rate then the individual patient could afford. And of course, the patient seeing nothing but the benefit of not having to pay that high bill basically became a product to be bought and sold by these two entities. The absolute best thing we could do as a country is dismantle the health insurance industry and return to patient/doctor relationships. The next best thing we could do is close down the VA and expand Medicaid to every single American by default funded by a large increase in the SS tax and allow those with the money to augment their coverage with those golden plans everyone wants. Thanks for the gold stranger. I'm going to trade it for some health care. | 59 |
6lm50n | Other | Why can brushing your teeth too hard damage them, but the sharp metal points dentists use to scrape enamel off don't? | URL_0 Tooth enamel is harder than steel. Tooth enamel has a hardness of 5, but steel is 4-4.5 Tooth enamel is softer than the silica found in many toothpastes Silica is quartz, which has a hardness of 7. | 21 |
62vttd | Other | What is the point of underwear? | It adds an extra layer of clothing protection from sweat and assorted bodily fluids. It makes the outer clothing last a bit longer. Notice how you buy more underwater than pants every year? | 5 |
68k80o | Repost | How do music makers know if a melody has been taken or not? If say a song you thought up just happens to have the same melody as another song you've never heard of that's already been published and copyrighted how would you know before you make a mistake of using that song? | They don't have to really, melodies and tunes are the same a lot of the time, you just don't notice it until it is pointed out. If you want a fun example of this check out "The Axis of Awesome 4 Chords". Shows the crossover of songs using the lowest common denominator. URL_0 | 48 |
bvet5l | Biology | How/why do speech impediments happen? | The Palate is the upper roof of your mouth. As it develops if it fails to close you develop a cleft palate. I underwent surgery to close the cleft and had speech therapy during elementary school. Still I had a nasally speech and had problems in socializing. Why speech impediments happen is above my pay grade. I have a speech impediment, recently a stroke, I’m disabled on my right side, I can only use one hand, I can only walk a short distance, so a speech impediment is the least of my worries. | 4 |
5qrxdx | Technology | Can someone please explain how Jurassic Park (1993) was visually so ahead of its time, it seems almost comparable todays visual effects? | Despite all the "this is the answer" posts, nobody's given the actual answer yet. The big difference between Jurassic Park's CGI and the CGI of modern movies is Jurassic Park's lack of an established workflow. They were inventing the methods and the tools to create exactly the visuals they needed, step by step, because it had never been done before. So it wasn't just a CGI studio adding a bunch of dinosaurs in post, but the entire crew working to pull it off together. Now that workflow already exists, the tools to create CGI imagery already exist, and it isn't designed for specific images but for everything. But now there's an expectation that it costs a certain amount of time and money to produce a certain amount of shots, and the workflow has to be bent to that task. Think of it like a master carpenter inventing an intricate piece of furniture, and then a factory mass producing it. Edit: I knew I'd read a great comment about this very subject once and I've tracked it down. This redditor describes the reason a lot better than I did and is well worth reading if you want the actual answer to this question: URL_0 | 31 |
8jkmd5 | Other | How can tv shows like South Park and Family Guy still use the “all persons fictitious” disclaimer when they are clearly making fun of an actual person/celebrity? | Trey Parker and Matt stone, creators of South Park, have been sued over 100 times. They just don’t care haha | 12 |
lhqyw9 | Biology | Why can plants grow hydroponically just fine but if they’re in soil you need to worry about overwatering? Tomatoes are the first plant to come to mind but many others are susceptible to root rot or just “drowning” of overwatered in soil but can thrive when spending their whole lives submerged in water. -Thank you | I'm not a pro or well versed in the science, but I run a hydroponics machine for my job. I do have a BS in Ecology and took many plant and soil science classes, and then worked in the corporate environmental world for 6 years (although I could argue that was a fucking waste of time). I grow lettuce and herbs (with the very rare kale or spinach) only in there. The way my system works, is that I fill my tanks with the city water connection. I have sensors that constantly measure water pH, nutrient levels (measured in mS/cm), and temperature. The computer system sets the limits for each of these, and through chemicals injected automatically, the parameters are consistent. So I can set the limits that I know the crop will thrive on, and then that water is automatically dosed through the system at a set interval (for my system, it's every 7 minutes). There are also air temperature monitors and I have a cold A/C running consistently at set temperatures night and day. Additionally, there are grow lights every where that also are automated. So you don't need to worry about overwatering in a hydroponics system because it's meticulously calculated, down to the amount of light the plants get which can also influence evaporation, whereas in field production I have so many other variables I need to consider while watering that just don't exist in a hydroponic system. I won't go into that too much unless people want to know. But my key takeaway I want to be that hydroponic systems are consistent, whereas in ground production has many many factors influencing water levels in the soils. | 5 |
idv46j | Other | How can black and white footage be colourised? I’m probably a brainless jacket potato asking this question but it has always intrigued me. Recently there was some footage posted with an old lady making thread or something and I’ve seen the footage get upscaled and colourised etc and I’m wondering how, if the footage is black and white, it can be transformed. Side note: Thank you all so much for your answers and comments! Also a massive thank you for my first ever award! Very much appreciated honestly 🙂 This really lends perspective on how much work people put in to colourising old videos! Side note 2.0: Thank you for the second award! Never thought that my curiosity would net me all this information or awards! You guys are all champs 💪🏻 | If you're assuming its computerized you should know its main done by human artists. The artist makes reasonable assumptions about what color a particular object is and then uses the brightness information that the photo has. In some cases you might find works where a machine learning models was been trained to make a best effort. | 10 |
bjxhtq | Biology | what is happening when doing nothing out of the ordinary and a ringing just starts in one ear and eventually fades? | Mine is preceded by a sudden deafness in one ear that can almost put me off balance. Like a giant void has suddenly opened up on one side, (no reflected sound). To be quickly replaced by ringing that slowly subsides to normal in a few minutes. | 6 |
i2cblw | Physics | why does rain come down as “drops” instead of as a larger mass of water? It’s raining right now and the thought just popped in my head lol EDIT: uhh am I allowed to say rip inbox now | Long version short, gravity. Longer version. When in a cloud, water is a gas. Normally, it just kinda floats there, but it really doesn't want to. It's far too cold to want to remain a gas, but it has no real way to condense. The trigger is running into something in the air that lets it condense. What that something is doesn't matter, which is the idea behind cloud seeding btw, but that something, once the process starts, can be other drops of water if the core particle falls out. In the cloud, there are strong air currents caused by the temperature difference in the cloud, much like the convection currents in boiling water or your oven. Also like those currents, these currents have a slower velocity at the cold area, in this case higher up. These currents toss the micro drops up until they reach wherever the top of the current is or the drop is too heavy for the current to lift. The drop then falls back to the lower part of the cloud to repeat the process. This entire time, any water that is both in contact with that micro drop and cold enough to condense can join the drop, making it larger. Eventually, statistics wins and the water drop and the inertia from the gravity drop become too much for the current to lift back up, and the drop falls to earth. The drop can't become the entirety of the cloud, as that would require the cloud to spontaneously condense, which it can't do because that would require A) the entire cloud mass to have a low enough energy (be cold enough) to condense, which itself would require all the water to be within a few inches of height, and B)a single particle touching all of the water, which by the way is a surprising amount, easily enough to flood most cities and perhaps enough to flood a metropolitan area if the cloud is big enough. | 6 |
6if67f | Culture | what did families do with there spare time before the introduction of tvs? | There was radio, phonographs, toys, puzzles, games, crafts, musical instruments, and believe it or not, books and conversation. | 4 |
99bprm | Other | Why do some letters have a completely different character when written in uppercase (A/a, R/r, E/e, etc), whereas others simply have a larger version of themselves (S/s, P/p, W/w, etc)? | The German sharp s officially has majuscle form since 2017, after repeated calls for over 100 years. ẞ --uppercase ß --lowercase Useful for surnames printed in all capital letters (e.g. in passports) to disambiguate between variations, where a substitution with SS doesn't help. E.g. Rössler vs. Rößler And also where the substitution with SS has a wrong pronunciation (e.g. Straße =street), or leads to utter confusion. E.g. Masse =mass, weight, bulk Maße =measures, metrics, dimensions I wonder how this is done in Switzerland, where the ß has been rigorously replaced by SS decades ago. Did that affect surnames or location names as well? | 10 |
gtsq0o | Biology | Why do most people look up and to the right/left when they try to remember something? How can moving your eyeballs help you remember it better? | I think it's as much about social signaling as anything. Moving your eyes says "hang on a second, I'm checking out to focus on something". You're not in the conversation. | 8 |
lvyizf | Mathematics | The golden ratio. Just, in general. What is it? Why is it so important? What’s special about it? | The golden ratio, commonly represented as φ (or Phi), is a special ratio (similar to the much more famous Pi). Specifically, the golden ratio refers to a special case where the ratio a/b is equal to (a+b)/a, and is related to the Fibonacci sequence (which is a special sequence of numbers that, gradually, ends up forming a method to approximate the Golden Ratio). It has some interesting applications in geometry and logarithmic mathematics. ***However***, the Golden Ratio is also horrifyingly overhyped by popular science, new age cults, and modern artists. For example, it is commonly claimed that the Golden Ratio carries "aesthetically pleasing qualities" in architecture and art, with the Parthenon being offered up as proof, despite the fact that architects and archaeologists have never found any evidence of Phi being used in the proportions of the Parthenon. Similarly, many will point to [Nautilus Shells]( URL_0 ) as an natural appearance of the Golden Ratio...when usually the Golden Ratio never shows up (there are a huge range of ratios that end up creating logarithmic spirals that look like a nautilus shell). Ultimately, Phi is just an interesting phenomena that got overhyped by people who want to find some sort of objective measure of "beauty" in nature, even if such a measure has no real basis in reality. tl;dr Phi is to actual artists as the idea of Ancient Aliens is to actual historians. | 3 |
apblu9 | Economics | why can’t we put mussels and clams in rivers and lakes to clean them? And oysters in oceans? | The Great Lakes are actually being filtered by invasive mussels to the point where there isn't enough microalgae to go around for native species. I read an article the other day about how Lake Michigan was actually getting too clear! Go figure; awesome when at the beach but apparently terrible for native fish/inverts. | 1 |
acqdix | Economics | what is the difference between Sales taxes vs Vat? | A sales tax is only collected at final sale to a consumer. Vat is applied every time something exchanges hands. So for example lets look at a bottle of wine. In the sales tax system only the bottles final sale is taxed but in a VAT system the sand that goes to the glass maker is taxed, the empty bottle is taxed when it goes to the vinyard, the wine is taxed when it goes to the store, and then it is taxed one final time when you buy it. If the VAT system rates are low enough there will not be much difference in the final price, but there is potential for massive price inflation very quickly because you keep charging tax as you go. | 1 |
7rplek | Technology | How will the many tiny amounts of cryptocurrencies left in users wallets after transactions affect the respective currencies over time? I'm guessing there are thousands/millions of other tiny amounts of BTC/ETH etc left in user's wallets that are simply too low in value to recover. Over time will this further reduce the amount of each crypto currency? Has this been factored into the cryptocurrency technology or are we generally still in uncharted territory when it comes to crypto? | This is a problem, because each wallet with funds in (even 1 satoshi or similar minimum multiple) has to be indexed. In general, this index has to be held in RAM on every computer running the cryptocurrency software. For bitcoin, this is a big problem, as the list of wallets with funds (the UTXO set) needs hundreds of MB of RAM. In the case of bitcoin, many of these funds are "trapped" due to high transaction fees, and there is no way to spend them or merge them into more compact wallets. The result has been that the size of this UTXO set has been growing rapidly. In contrast, for cryptocurrencies with much lower fees like bitcoin cash, the UTXO set is much smaller and hasn't been growing, because it is cost effective to use these small wallets. We are still in early days, but one of the ways that this is being dealt with in bitcoin is to charge users a "small payment fee", to make sure that a newly received payment is always big enough to spend. For example, if a shop wants to sell a $20 item with bitcoin, they would add a $10 "small payment fee" to take the value up to $30. That extra $10 would cover the bitcoin transaction fees needed to merge that payment into a more compact wallet. Effectively, it is a way of getting the buyer to pay 2 transaction fees - 1 fee to pay the seller, and 1 fee to allow the seller to spend the payment. | 2 |
fyh9qr | Mathematics | How does the poor man's log₁₀ calculator trick work? So... This is an interesting one. During my high-school days, most of us here in India couldn't afford a decent calculator. We all had one of those cheap ones that can do basic BODMAS and additionally, square roots. Log books were also rare and used to go out of stock pretty fast. There is this brilliant trick that used to work perfectly to find the log₁₀ of any number upto 3 digits on this regular calculator: 1. Type the number. 2. Recursively take its square root 19 times. 3. Subtract one. 4. Multiply the result by 227697. And miraculously, it gave the log₁₀(x) accurate upto 4/5 decimal places. Sometimes even more. How does this work? | Here's how I reverse engineered it (and then reverse these steps back to see how it was first made). I'll use ~ to denote "approximately" The trick basically says: 227697( x^(1/2^19) -1) ~ log_10 x Natural logs are what you always want to work with, so I multiply both sides by ln 10, we get: 524292 ( x^(1/2^19) -1) ~ ln x Now that constant in the front is very close to 2^19 = 524288, so we get to: 2^19 ( x^(1/2^19) -1) ~ ln x Divide both sides by 2^19, and let u = x^(1/2^19): u - 1 ~ ln u which is true near u=1 (which can be seen by taking the tangent of ln u at u=1, or by Taylor series). For x < 1000, x^(1/2^19) is very close to 1, which is why this approximation is so good. If you didn't need quite as many digits, you could similarly find appropriate constants to only have to recursively square root fewer than 19 times. For example, 444.72 (x^(1/2^10) - 1) ~ log_10 x should be a decent approximation as well. Written in terms of the steps in a hand calculator, it would be: 1) Recursively square root 10 times 2) Subtract 1 3) Multiply by 444.72 This gives you 2 dp accuracy for x < 10, which is all you need for the approximation anyway because we can apply the identity: log_10 (a * 10^n ) = n + log_10 a So e.g. log_10 (724) = 2 + log_10 (7.24). The approximation with 10 recursively square roots gives the correct result to 2dp. EDIT: Thanks for the awards pals, appreciate them all :) Another note - by tweaking OPs constant of 227697 to 227695, we can go from 4dp accuracy to 6dp accuracy! See my [reply]( URL_0 ) to /u/JJ_The_Jet for details. | 8 |
5thkw0 | Other | Why can receipt printers only use thermal paper? What's the difference between receipt printers and regular printers? | Thermal paper is fast and cheap to print on, but you're not going to get any kind of high quality images on it. Since receipts don't usually need images and only basic text, it makes the most sense to use it instead of a regular printer. Regular printers use ink or toner and these cost more and take longer to produce. | 3 |
n66orf | Biology | Can insects, crabs, spiders, and other animals with an exoskeleton become overweight or obese? If so, how does it work? Do they just molt into larger skeletons? | Hey I posted about this on r/askscience a while ago. I have a PhD in insect physiology specializing in insect metabolism. Insects can develop obesity like symptoms and what looks like type 2 diabetes. The extra fat doesn't make them bigger in their exoskeleton, but does get packed in there. Here's a paper on dragonflies that get obese! & #x200B; [ URL_0 ]( URL_0 ) | 7 |
cnk6ee | Culture | Why Is Losing Your Job Called Being "fired"? | In sSpanish you say Despedir, which means to give someone their fairwells, but that literally translates as to “unask” someone. | 6 |
cufjeh | Other | How do bars and cafés keep flies away ? I'm currently enjoying a beer in a downtown bar, and it made me thinking. At home, as soon as I leave a piece of bread or beer on the table, 5 minutes later about 10 flies are spawned. Yet in a bar, there are beers lying around all the time, and I'm not seeing a single fly, nor any fly traps. What gives ? | I know this isn't the same as a bar or restaurant, but our office has regular visits from a pest control company, and they handle everything from rodents to spiders and flies. Also, I remember Gordon Ramsey mentioning the Mark of a bad restaurant is when you ask the question "What do you do about pest control?" and they answer "We don't have pests", they are delusional and most likely DO have pests. They should be saying they have regular visits from a pest control company. | 4 |
873p18 | Biology | why does alcohol affect people differently? Last night I was at a party and a friend brought a breathalyzer, so we could try to guess where we were at all night. After all of us consuming roughly the same amount of alcohol we were testing to see what our BAC was at and everyone blew 0.14%+ and I blew a .06%. Why did I get such a low number after consuming about the same amount as everyone else? | The 3 biggest factors that come to mind for me are 1 body size, the larger you are the more blood you have so same drinks = lower bac. In comparison to smaller size 2 rate of absorption, if you ate before hand your bac will rise slower than if you didnt eat. 3 metabolism/genetics, some people metabolize alcohol faster and easier than others due to genetics that determine production of alcohol dehydrogenase and other enzymes | 2 |
mgje3a | Other | Why is cancer so prevalent and has such a high rate of reoccurrence among individuals who’ve gotten treatment? | cancer is basically a series of stacking failures in a cell's genetic code that alter its normal behavior. self-destruct functions to prevent abnormalities from reproducing, differentiation that distinguishes e.g. skin cells from liver cells from muscle tissue, functions to stop cells from growing where they're not supposed to, all these things are coded in a cell's DNA and those things can break and stop working. people can be genetically predisposed to cancer, and there are environmental factors as well, but every time your cells reproduce there are copying errors. if you live long enough, eventually somewhere in your body those errors will stack up in the right ways to cause cells to become cancerous. that's part of why it's so prevalent. something like 80% of men develop mild prostate cancer in their lives. as for why people tend to get it again, there's multiple reasons. if there are environmental, genetic, dietary, etc. factors that increase a person's risk of cancer, they still apply and are still increasing their risk after they recover once. they're more likely to do regular cancer screenings and catch cancers that might've gone undiagnosed in other people. some treatments like radiation therapy increase your risk of future cancer, etc. ultimately it's just statistics. if you live long enough, eventually your number's gonna come up. | 2 |
5sbhux | Culture | Abstract art. Why is Picasso's Cubism more impactful than his Blue Period? How do people judge, let's say, a Jackson Pollock painting a masterpiece when to me it looks like chicken scratch? Why is the Malevich square such a big deal? | Oh boy, I am not sure if I can come up with a simplistic way to explain this, but I have a degree in Graphic Design, and I had to take four "History of World Art" classes, where similar questions would came up and be discussed pretty regularly, so let me just tell you how I feel about this: Art embodies more than just what you see, but a lot of times it is a connection to the artists, their stories, struggles, the struggles of that time period, or specific concept or idea from that artist about something important to them (love, death, faith etc), or even the process of creating certain piece, if it is specifically difficult or unique. Most of the times all those combined make certain pieces more valuable than others. And while art is usually visually engaging, all those things mentioned above combined can bring out variety of emotions in people who know the history of the time period and story behind the art work or the author, and that's where the real value for them lies. It can't be manufactured, or replicated, it's just tied to a piece through an artist who embedded his feelings, emotions and ideas into his/her work at specific point in time, so that piece than serves as a unique time capsule that keeps moving forward stimulating future generations for as long as it exists and as long as people keep remembering and understating what it stands for. | 4 |