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682vtz | Culture | Why is prostitution illegal? | It's not illegal if you record it, then it's considered paying her for a porno and is perfectly legal. Yes that is a loop hole. Pay for a prostitute that is ok being recorded, set camera up. If cops come busting in, well they can't do shit now cause technically your making a porno. If you don't record, it's illegal. Yep laws are weird. I'm talking about in the United States btw | 4 |
c5geos | Biology | What sexual gratification do girls get from blowjobs? Like I know why males like it, but what is so good about it for females? | Just like making the person feel good I guess. Same with eating a girl out, however that seems to be less common among straight people. | 5 |
8oy2d7 | Other | How do psychiatrists decide what antidepressants to prescribe? | (Not a psychiatrist. Brand new doc, about to start my FM residency) Typically you start with the stuff that has the best evidence for the patient’s particular disorder because those will have the best risk/benefit for most patients. You take into account age, overall health in case there are metabolic problems, allergies, and comfort with certain side effects. For instance, some patients have really bad insomnia with depression, so you’d be more likely to use something a little sedating in those patients than you would be in patients who have hypersomnia (too much sleep) with their depression. You also consider things like drug cost and coverage because that might prevent the patient taking it. If first line stuff isn’t working, or there’s nothing in the first line stuff that is acceptable to the patient, you start moving down the list in the same way. | 6 |
cowbla | Biology | Whats bad about shrooms Right now I am on vacation in Amsterdam and the thought of shrooms effect on your health never crossed my mind till now. I mean there must be something negative. | They aren't a health hazard by themselves, it's that they bring you into a mental state where you can make very bad decisions. Combining them with other drugs or alcohol can make it more dangerous, both for yourself as to others. There have been some incidents of people jumping from windows, blindly running into traffic or simply getting lost on the streets and eventually getting robbed (or specifically for Amsterdam: falling into a canal). That's why it's important to use them in a safe environment, preferably at home or in a quiet outside location with a sober 'guide' or 'sitter' that can fix things before it turns into a bad situation. There's also the risk of a bad trip (basically getting stuck in intensely bad mood or even panic), so doing it by yourself or with people you don't like or trust can also be a very negative experience if there's no one who can help you out of it. Another tip: have some candy or fruit available as sugar helps to bring you down a bit when it gets too intense. And never take an extra portion because 'you feel nothing', better to just do it again some other time with a slightly higher dose. | 5 |
9w5kmu | Mathematics | What is a Mandelbrot zoom and how does it work. I was watching a video on ‘[The hardest Mandelbrot zoom]( URL_0 )’ and I can’t understand how this is generated by a calculation or what makes all the different colours. | The Mandelbrot set is a kind of interesting thing. Basically, you plug a complex number (a+bi, where i is the square root of negative one) into a fairly simple equation. That equation poops out another complex number. Then you plug that new number into the equation, rinse, and repeat. After a bunch of rinsing and repeating, one of three things happens to the real (a) part of the complex number: 1. It blows up to infinity 2. It goes to zero 3. It hones in on some value (called an "attractor") The color in a rendered Mandelbrot render corresponds to *how many times* you had to recycle the given point to find out what it does. [Here's]( URL_1 ) an instructional video (warning: has some NSFW language -- not much, but a little). [Here]( URL_0 ) is a link to Fractint, a really nifty program for displaying Mandelbrot sets on your PC. Hope this helped. | 2 |
8dcfks | Biology | why do our hearts not get tired Misnomer, i know it has something to do with special tissue, i am curious about this, furthermore, why cant all our muscles never tire, | The heart pumps blood almost directly into itself, and drains blood from its venous circulation directly into the right atrium. This is the main difference. Your other muscle tissues are far away, there is a lot of them relative to the size of the heart, and they receive blood more slowly. This means more delays in getting oxygen to these tissues, and more delay removing metabolic waste products, and just a *lot* of muscle tissue to supply. When we exercise, the expanse of our skeletal muscles is simply too much for our body to run at peak efficiency indefinitely. Our muscles run out of oxygen, glucose, and build up waste products eventually. The heart, conversely, is first in line for the good stuff from our arterial blood supply. Similarly, it's sized such that more than enough blood can get to it, and feed/remove waste from it, so tat it can run indefinitely at peak efficiency. That said, there are things that can happen which cause the heart to become less effective and have to grow in size to compensate. It isn't getting tired per se, but it's certainly strained in these situations. This is cardiomegaly, and is related to heart failure. | 2 |
7pkrsz | Other | What Hanlon’s Razor is. The textbook definition, “Never attribute to malice that which can be adequately explained by stupidity,” has been confusing me for a while. | In general, stupidity is more common than malice. People might selfish and self-centered, but rarely overtly wish ill of others. In other words, that guy who has his shopping cart turned sideways while spending five minutes trying to decide whether he is ready to step up to "spicy nacho" or should play it safe with "cool ranch", he isn't specifically trying to infuriate you, he just has his head up his ass. | 5 |
aiwhw7 | Technology | How does switching to electronic alternatives (for example E-cars) help environment? I have come across many articles lately which said that electronic cars and vehicles are future because they help reduce emissions. But I always thought, how is that possible. Most of the countries still fulfil their electricity demands by generating electricity in thermal power plants, which also releases a lot of hazardous gases into the environment. Not only this, countries which use nuclear energy as their primary source, have to deal with nuclear waste, which again, is extremely hazardous if not handled with care. Another example of this is switching to computers. Human resource development ministry of India recently announced that most of entrance exams will now be online. Many environmentalists hailed this move saying it will save a lot of paper which, in turn, will save a lot trees from being cut. But maintenance of computer itself is not a completely environment friendly task. Lets say someday, its monitor is needed to be replaced. Now, the spoilt monitor is an electronic garbage and has potential to cause a lot of damage to environment if not managed properly. And just like 70-80% countries on this planet, India is terrible when it comes to e-waste management. Also, not to forget the electricity it uses in its lifetime which is again primarily coming from a pollution-causing thermal power plant. So, basically what I mean to say is, we are trying to conserve one thing which is in front of us, but deteriorating the other which is not necessarily in front of us. | Simply put, studies have shown that so long as an EV is driven for a certain amount of time, (\~10 years IIRC) the emissions related to its manufacturing and continued use are less than that of a vehicle with an ICE even when electricity is produced by coal. When the energy is produced in a more sustainable manner, that time is much shorter. | 3 |
dufsik | Technology | What makes the TV do the clicking/crackling noise when you switch it on? | If you're referring to old tube TVs, they operate by actually firing a stream of electrons at the viewing surface to light it up. So the front actually has a bit of a static electrical charge, and you can hear that as the electricity builds up as the crackling. On both flat panel and CRT/tube TVs, they still use a lot of electricity so there's a mechanism to open/close the major flow of power to the electrical components using the most electricity and you can hear it click on/off. A lot of electrical devices do that. Probably the biggest thing you have doing the same thing is a car - can you hear clicking noises that are not the key turning as you turn it on but not started the engine yet? | 2 |
6y62iy | Other | Why are many people so ignorant of commonly accepted facts? | These obviously false beliefs are based on *conspiracy theories* that claim a group of powerful people are trying to fool us. You're not alone in asking, and kind strangers have explained: 1. [ELI5:Why are some people so susceptible to believing in conspiracy theories? ]( URL_5 ) 1. [ELI5: Why do so many people believe conspiracy theories ? ]( URL_6 ) 1. [ELI5: conspiracy theories. How do people believe them so vehemently? Where do all the big theories come from? ]( URL_2 ) 1. [ELI5: Why do so many people believe in ridiculously complicated 9/11 conspiracy theories (controlled demolitions, holographic planes, mini-nukes, etc) instead of simple ones (hijackers were government agents, other people had advanced knowledge, etc)? ]( URL_7 ) 1. [ELI5 the Illuminati and why so many people believe in them. ]( URL_0 ) 1. [ELI5: Why do people deny the moon landing? ]( URL_4 ) 1. [Why People Believe Conspiracy Theories ]( URL_3 ) 1. [Why Do Some People Believe in Conspiracy Theories? - Scientific American ]( URL_1 ) | 1 |
kxzhp5 | Biology | Why do we find 'things' beautiful. Not people, I get the logic behind finding a person, a 'mate' attractive. But a sunset, a pretty flower, a super car... Why? What is the logic / reasoning for finding these 'things' beautiful... | URL_0 Kurzgesagt covers it really nicely, but I don't think they give a definitive definition. It's beautifully animated. Worth watching just for that. | 3 |
iwpdz5 | Technology | Why can’t we just make blood? Or better yet why can’t we make a blood replacement that is more efficient? | It's too complicated. Blood is made of live cells: * Red cells handle the transport of oxygen and carbon dioxide, and they do this by reacting, one atom or molecule at a time, and taking the oxygen and/or carbon dioxide inside the cell, to transport it. Oxygen specifically it's very reactive, it rusts materials, it burns them, it reacts very easily, so the red cells use complicated organic chemistry to "transport it safely" and deliver it to the cells in your body. * White cells deal with intruders and infections, detecting all sorts of foreign bacteria, and eating them, and otherwise identifying the cells in your body correctly, and not hurting them. * Blood has platelets and other organic compounds that make it clot, when you get a cut the blood clots / hardens, blocking the cut and more blood from seeping out. * Blood transports hormones, nutrients from your digestive system, byproducts of digestion to be taken out by your kidneys, etc. It's just too complex; we don't have chemistry that's complex enough to handle all these functions with just chemicals, and we don't have the biology that's advanced enough to create designer blood cells to handle these functions. | 6 |
7fswz8 | Other | Why do some people think that two certain individuals look alike, while others may think they do not? | People learn to use different things to tell people apart. Some people rely a lot on hair color/style, and facial hair for men. Others look much more are facial features, especially the shape of eyes and nose. | 3 |
6xt6qi | Engineering | How are nuclear weapons tests underground without destroying the land around them or the facilities in which they are conducted? **edit** FP? ;o Thanks for the insight everyone. Makes more sense that it's just a hole more than an actual structure underground | i read somewhere, (can no longer find it, but if anyone can, please post). there was a test where the shaft was filled with water, and a massive steel door was put on the top, perhaps to just close it, or whatever. but what happened was that alot of that was was instantly turned into steam, hyperpressurizing the shaft, the subsequent blast sent the steel door into space at a rate of (if i can recall correctly) at about 6MPS or could have been much faster. it set the record for the fastest/largest/heaviest projectile sent into space, i'm pretty sure its still going because it would weigh so much and would escape earths orbit within minutes if not longer. i can't find the story anymore. the steam acted as a buffer and did not vaporize the door. | 21 |
cc77uj | Biology | what would it be like for humans to see in tetracromacy? | An extra sensation isn't something which can easily be described but we can make some extrapolations by looking at color blind people who only have two functional kinds of cones. It would mean you could distinguish between different colors which appear identical to normal people; someone might see that two jackets are the same shade of blue while your fourth cone which can see some ultraviolet can tell one is more absorbent to UV than the other. Due to how language works you may not have a word for this sensation. You might just say "It looks more ultraviolet" much like how we might tell a colorblind person that a shade has more of a color they can't distinguish. | 2 |
e2tvaq | Physics | If matter can't be created or destroy where did it come from? | Lawrence Krauss has a very good lecture on the origins of the universe, how we know and where matter comes from. It's ELI18 but that's quite the simplification from what he teaches PhD students [ URL_0 ]( URL_0 ) & #x200B; Long story short, some kinds of energy are mathematically negative. Matter is a form of energy. If you were to add up all energy (including matter) the net sum would be zero. | 12 |
g6aayg | Other | If the US government knows how much every citizen owes in taxes, why does each citizen have to figure it out on their own? | They know this for for *most* taxable stuff. But if there’s anything unusual then no, they probably don’t know what you owe for that. Regardless, taxes could be much simpler; the reason they aren’t is because tax prep companies make billions from complex taxes and lobby to prevent that from changing, and also because politicians are constantly tweaking taxes to please or placate this or that special interest. | 3 |
eckt74 | Physics | The Day the Mississippi Flowed Backward I understand the a massive earthquake in 1812 caused the Mississippi to run backward but I don't understand the physics behind it. Please explain it to me like I'm 5? [ URL_0 ]( URL_0 ) | Earthquakes can cause the ground to rise or sink. And, obviously, water generally flows downhill. What happened is that the sinking of the ground (because earthquake) formed new low spots in the riverbed. This meant that "downhill" was now the other direction, so the water had to flow that way until it filled up the new low spots (which made it effectively "uphill" again, at which point the river flowed the correct way.) | 2 |
87kw48 | Chemistry | Why is, no matter the colour of the shampoo, the foam always white? | The dye chemical tends to not want to hang around in the very thin soapy matrix that forms the bubble wall. Then, if you do have a dye that will work, it still takes a fairly high concentration of it to be visible. That's a problem because when the bubble pops it leaves a dark dye stain behind. To solve this you need a dye that will quickly degrade chemically into harmless, colorless products. Fortunately, dyes have been invented specifically for this purpose and are used in the [Zubbles]( URL_0 ) product. You might enjoy reading about the development of the dyes if you'd like a somewhat deeper look at the challenges that colored bubbles present. | 8 |
a9natf | Chemistry | How come a 1°C variabilty in global temperature makes such huge impact on the planet? | 1 degrees is the average, there are pockets which will be worse off by many degrees. It might turn grassland into desert or make a body of water unable to keep up with evaporation, or make an area more habitable for an invasive species such as pine beetles It's like the human body, a degree change in temp will make a person feel much worse and have tangible effects | 3 |
il6uxc | Other | what exactly makes online learning so much less engaging than in-person? why can't people focus as much during lectures? what about the screen makes it such a different experience? (biologically/psychologically speaking). | A classroom is dedicated to learning. There's no games, no social media, no pets, no distractions, and a "social contract" that you're all there to learn. A screen is the complete opposite. It's where you play games, watch youtube videos, browse funny cat pictures, chat with friends on social media, etc. So, instead of "I can't do all these fun things, time to focus on learning" it's "how can I get away with doing all of these fun things that are literally at my fingertips?" | 2 |
73gnsz | Economics | Why does it appear that a disproportionate number of homeless people are older men? | I asked the same question to a group of social workers at a homeless shelter. They said impoverished women have a much easier time finding someone to take them in, whether it's a family member or a kind acquaintance or a romantic/sexual partner. That can open them up to violence, coercion and exploitation, but it does keep them off the streets. I don't think there's a disproportionate number of older homeless people, though. I'm not aware of stats either way, but there are lots of homeless youth and that's a big problem. I think you just don't identify them as homeless on sight. | 6 |
79uq7g | Chemistry | How do they put the vitamins in vitamin pills? | Great responses. I will just add that in biochemistry terms, "vitamin" just means something that your body requires that it doesn't make itself, meaning you've got to get it from your diet. Edit: I am here referring to the types of dietary vitamins OP was asking about. Also note that vitamins are organic compounds, meaning they have carbon in them. | 11 |
kvg6un | Other | Protein powder?? | It is an easy way to get in calories and protein. To build muscle you have to eat more calories than what your body uses in a day, and protein is essential (eating ice cream for all your calories will not help you). If you get in these calories and protein through food, there is no need for protein powder, however it is an easy way to get some nourishment to your body right after a workout. Eating a lot of protein can be difficult, so the powder is just an easy way to bridge the gap. I mix mine with milk, yogurt, fruit, and oats, so I end up getting over 700 calories in one shake. | 3 |
6e2act | Other | How do motorbike riders drive safely in the rain? Rain drops on helmet, boots wet etc | Not sure in what respect you mean, really, but... Good tires with decent tread. Some tires are better in water than others, same as your car. Riding properly for the conditions. Allowing more room for braking, more time for errors. Being a bit more methodical. Boots? yeah, improper footwear can be a hazard on slippery surfaces, but only when stopped. (foot slips out from under you, but in almost 37 years of riding, I've only ever felt a foot "slip" once. Goggles, helmets etc... good gear is ventilated well, preventing "fogging". At riding speed, the water on the lenses/shields just blows off. The biggest danger in the rain is... getting cold. Which, again... is alleviated with proper gear. | 2 |
6vu4nv | Economics | Despite the push of Affordable Education in the United States, why does it feel like it has actually become unaffordable? | College costs have risen faster than inflation and faster than incomes. So the natural consequence is that it's less affordable than it used to be. The cause of tuition increases is a combination of demand (more people than ever are going to college), non-education related expansions in many school systems (the number of administrators in the school system has grown very very fast) and a lot of those administrators are getting paid a ridiculous amount of money. URL_0 oh, also subsidies have contributed to the cost inflation. Schools can ostensibly claim they give many scholarships when really it's government grants. How do you take in as much grant money as possible to pay yourself (when you're an overpaid administrator)? Get more students... or charge them more. | 2 |
fqs21b | Biology | why does the corn acquires the shape of a popcorn when exposed to heat? Just a shower thought (question?) I can't get my mind out of. | A combination of two things: starch and water. Ordinary corn, like feed corn, has plenty of starch, but it won't pop. This is because the water content of the kernel is too low; the starch essentially burns. Insofar as being popcorn goes, that's no good. Popcorn, on the other hand, has a significant amount of water in each kernel. As the kernel is heated, the starch softens but the water vaporizes, turning into steam. Sooner or later, the amount of steam inside creates so much pressure that the hull of the kernel can't contain it any more. The hull cracks, and a foam of steam and soft starch bursts out. The starch cools quickly, becoming a firm solid again. However, because it cools so quickly, it doesn't lose that foamy texture, leaving it as that fluffy grain you know as popcorn. If the starch cooled more slowly, it would collapse and rather than a fluffy piece of popcorn, you'd have a little starch lump. Here's a video of popcorn popping shot by a high-speed camera (the actual pop starts at 1:22: [ URL_0 ]( URL_1 ) You can see the kernel shell beginning to crack, which allows the softened starch and steam foam to begin to escape. Almost as quickly, the starch cools, setting that foam into a solid shape. | 2 |
lg41tg | Technology | How do green screens work? | It doesn't *have* to be a green screen, it just has to be a color that isn't being used in the rest of the set and costuming design, which is often light green. In modern times, they use a computer to filter the color of the background out for the rest to be superimposed onto another video. In films like Hulk, where there might be a lot of green on the actors, they might switch to a blue screen or pink screen for their masking, or just make sure that the green they're using for the characters is substantially different from the green screen. Green is most commonly used because it is distinctly not similar to all shades of human flesh. The process began in the earliest methods of filmmaking, with black matte draping being used to superimpose actors into footage via double exposure. | 3 |
ew4sr6 | Technology | how do car heaters get their heat? | The water that’s pumped around the engine to keep it cool is routed to the inside of the car. That water is of course hot from taking the heat away from the engine. Under the dash board in the car is a small radiator that the hot water runs through. Add a fan behind it and you have a heated cabin. | 6 |
9b6bh8 | Biology | Why does fruit start to rot on room temperature, but can stay good for weeks in the fridge? EDIT: Thanks a bunch guys! | Fruits produce an enzyme that causes them to ripen. Refrigerating the fruit stops the production of that enzyme. At room temperature the enzyne causes the fruit to ripen quickly. Add this to the aforementioned bacteria and you have gotten fruit. | 2 |
6g03ug | Chemistry | The effect of ADHD medication (Ritalin) on those who use it, but haven't been diagnosed with it. CONTEXT: During a recent brief discussion with my doctor I asked whether there was a benefit for people who used Ritalin, but aren't diagnosed with ADHD. She responded by saying that there isn't one and that, that's one way specialists are able to tell, besides tests and what not. This comment left me somewhat confused as I'm aware that there is quite a large market around selling Ritalin/Adderall illegally, hence the heavy regulations on prescriptions. On one hand I know it's popular with university students to assist with studying, however, on the other hand I've heard that people abuse it to gain a high. QUESTION: Are the people who obtain and use it illegally for the assistance they gain with studying/working, people who have ADHD but haven't sought out a specialist to get a diagnosis. While the people who use it for the purpose of getting high do not have ADHD? If so, what difference in an individual's brain chemistry causes this drug to react to react differently for people who have it versus the people who don't. Tl;dr If someone gains the intended effects of Ritalin/Adderall does this confirm they have ADHD? And that getting a high from taking it, is indicative of not having it? If yes, chemically speaking, why? | To the original question - Anybody who takes speed/adderall (in a medically significant dose) will feel it. I worked with a lawyer who was prescribed it in his late 30's. It was a disaster. Inside of a year, he was taking cocaine which became easier for him to get, and he lost his license. I don't know if he had ADHD or not...seems like a pretty "voodoo" diagnostic, in my lay opinion. I'm largely ignorant of the medical process involved in diagnosing ADHD, but when one of our kids' pediatricians recommended that one of my kids take speed, I immediately changed pediatricians. At the time, it seemed like they were handing that shit out like Pez. This was about 10 years ago. | 39 |
gztei1 | Chemistry | Why does shampoo bubble so much more on the second wash? | Shampoo can't bubble as much when it's dirty. When you're clean, the bubbles are clean so YAY MORE BUBBLES! | 2 |
h8vx2o | Biology | How after 5000 years of humanity surviving off of bread do we have so many people within the last decade who are entirely allergic to gluten? | There are possible connections with the presence of pesticides and chemicals in commercially grown wheat, specifically glyphosate, that seems to correlate. Increasing usage of these products coincide well with increasing gluten sensitivity and allergy. I don't have any studies to link as I am working at the moment but it is something I have read in a few places and discussed with academic friends of mine. Worth a look. Edit: This is the one I have read. I am not a biologist so I can't speak to the quality of data or analysis, but it is worth a look as it seems like some pretty clear connections to me! URL_0 | 22 |
mh9ejh | Earth Science | why does the moon appear larger earlier in the night, when it’s “rising” as opposed to later in the night when it’s higher in the sky? | We think its because near the horizon you have known objects to compare its size to. Its easily testable that it is just an optical illusion and no size change is happening, hold a coin at arms length and it will cover the moon both near the horizon and at the zenith by the same amount. | 2 |
i697kw | Biology | Why do our hands sweat when we are nervous? | Your 'flight or fight' response is activated when you are nervous. This response readies your body for action (e.g. running from prey). Your heart beats harder and faster to get more blood around your body. Blood is diverted away from unhelpful organs (e.g. your digestive system). You flush and sweat to help cool down your body. | 2 |
nrq3jt | Biology | Aging: how does it work? How does the body/cells one day know to start deterioration instead of growth? Why, when I'm young, can I regenerate tissues faster than I could in 30 years? Basically just need an explanation as to how aging works, and why it works. | Think of your body’s cells like a rechargeable battery. You can recharge them over and over again but eventually they wear out. Your metabolic processes are very complex, so complex that they’re not even fully compatible with themselves. These metabolic processes damage cells through the course of your life. The damaged cells need to get killed off by the immune system and replaced. Adult stem cells divide replacing the damaged cells. You only have a certain number of adult stem cells in your body for each organ. Adult stem cells can only divide a certain number of times, limiting their regenerative capacity. The more you damage an organ, such as tanning skin in the sun, the faster youre using up your stem cell’s regenerative abilities. Your body actually starts destroying itself before you’re even born. You don’t notice this early in life cuz your stem cells are so good at repairing damage. Also, aging in this sense, & development, are 2 totally different things. Your development is controlled by timing genes. If we wanted… we are fully capable of engineering ourselves to age 30% slower. By duplicating genes we already have that neutralize free radicals and other metabolic waste, we can slow the cellular damage. We can also do things to stabilize the telomeres. We’ve had this technology for at least 20 yrs and it works the same with every animal. It’s actually surprisingly easy. | 2 |
7ol2tt | Biology | What determines whether gas comes out your mouth or your butt? | Eli5: is there any health benefits to eat stuff that makes you gassy? | 4 |
7xs4b6 | Biology | Why does, when getting hit in the balls, the pain get worse over time and leave you with a stomach ache? Today I (self inflicted) got hit in the sack. It started out at a mild 3/10 and kept ramping up to a solid 7.5/10 on the pain scale. The pain subsided but it was replaced with a similar level stomach ache that lasted ~30 min. I'm fine now btw | When hit in the balls try standing and jumping up and down on your heals It causes your balls to drop and relieves the pain If are man enough to stand that is I was a full contact martial artist, trust me this works | 4 |
6m075m | Biology | I just read about a tiny hormone chip which is inserted into your arm that can prevent all periods and pregnancies for a few years. How does this work, and is it trusted? If so, how is this not a very big deal? | The Implant is so common here in the UK though still not as popular as the pill. When I first got one I had it for 1 year and had no problems at all and never had to worry about either of the issues in question. The second one I got was meant to be for 3 years but I got it removed after about 18 months as my TOTM became completely unpredictable. | 11 |
7479dc | Repost | When an organ is removed, like a kidney, what happens to the space where the organs used to be? | FYI: For kidney transplants, the bad kidney is more often left inside the person... so they now have three kidneys. | 3 |
7sdk36 | Engineering | what is the advantage of the multi-rotor design used for drones over that of the conventional helicopter rotor setup? | small electric motors are extremely compact and efficient, with minimal mechanical complexity. with 4 rotors, and sufficiently intelligent control software, a drone can maneuver in any way a conventional rotorcraft can through varying the output of its 4 rotors. real helicopters are gas powered. the combustion engine and its support systems are powerful, but work better as large single units. having multiple engines would become wildly complex very quickly. electric doesn't scale well in vehicles because of batteries. | 6 |
6sf8u6 | Culture | Why are lie detectors used during a police hiring process when they cannot be used in a court of law to determine someone's guilt? | Everyone here seems to just be taking it in their stride that, oh yeah sure, potential police officers are given polygraphs, that's totally standard procedure. Wtf? They actually do this? Is this an American thing? Do they do that here in the UK too? I've never heard of it being done, not even in pop culture or TV shows. Am I the only one who's never heard of police departments doing this? | 45 |
6cfbh3 | Technology | How were movies edited, processed and beautified with effects and text before computers were common? | Movies were edited by physically cutting and arranging film with blades and adhesive tape. The amount of "processing" and effects were very limited, but might include frame by frame airbrushing or practical effects. Text would be added by painting the words on a clear overlay on the film. The composite image would then be photographed to form the final product. | 2 |
jk4r4p | Economics | Why is the accumulation of wealth in the upper class bad for society as a whole? | In general you want people buying things to make the economy go brrrrrr, poorer people spend money on things like food and consumer goods while rich people generally hoard money. If poor people stop spending money the economy stops going brrrr. | 5 |
9nthoy | Culture | China and Russia disappear people and it makes news but nothing happens. Why is it when this happens in Saudi Arabia there’s a huge international backlash? | Journalist For US newspaper At an embassy Of an "ally" of the US In a third party country & nbsp; Those factors all combine to make it a particularly egregious event. | 6 |
jpz00q | Other | Why is ‚socialist‘ an insult in the US? | Americans on the right don't understand the term and equate communism with socialism so when a right wing politician is talking about socialist things they mean communist. | 5 |
encu0g | Physics | Every article I read about ear pain during airplane's descent was saying that the reason of that is pressure change. However in modern airplanes the cabin is fully sealed and pressurized. So what is the reason of bad in ear pain? | It’s not fully sealed— you’d need to bring a supply of oxygen on board if you weren’t pumping in outside air to replace the air in the cabin... There are compressors that push air in, and only a limited amount of air can flow out, so the cabin pressure is higher than it would be if you were totally exposed at that altitude. But it’s not as much pressure as there is at ground level. | 4 |
jxa7le | Economics | Why does the price of everything keep going up? | The money in our society is what is referred to as "Fiat Money", this is money that is only valued by being backed by a central government, meaning it has no real intrinsic value. This is different than representative money, where for example a bill is worth some amount of gold/silver. Because the money is only backed by the government, its value is more or less determined by how much there is, just like the value of gold is based on how much there is, the more there is in circulation, the less it is worth. Central banks (The ones who print money) try to keep a steady, slow inflation rate, because this is what most economists consider a healthy economy. If the value of money lowers, it's called inflation If the value of money increases, it's called deflation If a country prints ridiculous amounts of money, this results in hyperinflation, where the value of money decreases at a rapid rate, and eventually, becomes essentially worthless, like $1b is worth the equivalent of a penny a few months prior, and money becomes more valuable as a heat source than money | 6 |
7iwaxj | Repost | Why are there so many types of screws? (Phillips, flathead, Allen, etc.) Why isn’t there a single, standardized type of fastener? | In short, because manufacturers and engineers are constantly improving and customizing products for their specific applications. Fasteners are the easiest thing to change when engineering a new product. It is easier to design a new fastener then scrap a good design because stock fasteners won't work. Thus, you have tons of different types of screws on the market. For a specific example, look at just machine screws. Originally, there were basically just slotted drive screws that you would drive with a Slotted or "flat head" screw drivers. The slotted driver would tend to slip out of the head so in the 1930's the Phillips screw and screw driver was invented. In both cases, they made a flat head for countersinking into the surface of a material, and a round head that stood proud of the material for use in hard materials that didn't easily countersink. Unfortunately, the Phillips drive can still slip and will tend to strip easily so at some point the Allen drive or internal hex drive was invented. That fastener was made with several head styles as well and was also made with a very strong alloy for high strength industrial applications. However, the internal hex drive can still strip in high torque applications so engineers improved on it with the development of the Torx drive (also called star drive, or six-lobe). As you can see, just the narrow application of machine threaded screws, we are already at dozens of combinations of heads and drives. Multiply that by several different materials that they can be made of (soft steel, alloy, stainless, brass), dozens platings and coatings, and dozens of different lengths for each combination and we have options in the thousands. Now there is a more recent issue of products being made with custom fasteners with obscure drives in order to make it harder for the consumer to service the items themselves. This is common in electronics and automotive applications. This has increased the number of different types of fasteners exponentially as well. Every type of bolt, wood screw, pin, and clip has gone through a similar progression and evolution. | 12 |
iq101w | Mathematics | How do doctors make predictions of how long someone will live or if they'll ever walk normally again? I was rewatching an old video on YouTube and the guy was able to walk again after 10 months of practicing yoga and losing 140 lbs. If no one on earth can exactly predict when someone will die or if they'll be able to walk again, how and why do doctors come up with these predictions? URL_0 | There's no secret, science, or trick behind it. When you do something a bunch of times, you get pretty good at predicting what'll happen. A basketball player who throws a lot of balls will get pretty good at knowing where a ball is going to land. A lawyer who handles a lot of criminal cases is going to get pretty good at knowing what sentence a specific judge is going to hand out. A doctor who treats a lot of people with a specific condition is going to get pretty good at knowing when that person's going to die. It's all just a guess, based on previous experience. | 18 |
nhbu5o | Biology | How does Decaf coffee work? Like isn’t caffeine naturally in the Coffea plant? | There is indeed caffeine in coffee beans. And when you brew coffee you extract all the caffeine with the flavors and colors in the beans. But there are some solvents which will only dissolve caffeine and not any of the flavors and colors in the beans. So if you brew using these solvents instead of ordinary boiling water then you only get the caffeine. What you are left with is coffee beans with all its flavors and colors but with only trace amounts of caffeine. | 6 |
bk3fa3 | Biology | Scientifically speaking, how do we generate the voice in our head that says all of our thoughts? | My brain for some reason decides to take it a step further than my own voice. When I spend a lot of time with a person, sometimes I end up thinking in their voice. I can switch it back if I focus on it for a second, but usually it'll stay their voice for a while. & #x200B; Also, I am studying abroad in a non-English speaking country and even though I'm not fluent, I will sometimes end up thinking in the second language. | 21 |
ij3qol | Biology | Why is heart stoppage the indicator for death? If the brain is the root of conciousness, shouldn't it be when that stops working instead? | It's not though. If your heart stops they can still provide cpr for over 20 minutes after your heart stops. After that they generally stop because there isn't enough oxygen going to your brain and that is where brain tissue starts to die off. They usually wait until you are brain-dead or you have brain tissue death before stopping resuscitation. | 15 |
b7evn3 | Biology | How do humans not regularly roll over and fall out of bed while sleeping? | We have a reflex leftover from apes who used to sleep in trees... we are aware enough of our surroundings to wake up if we feel unsafe (watched, noises, etc.), to stay balanced, to roll over and sense if we're over a precipice, and also to grab onto things if we feel ourselves falling. You can test for the reflex, and you can sometimes experience it if you roll over in the night and have a sense of falling which causes you to wake up, you'll often be gripping the sheets or pillows tightly ("a branch" or similar in your mind's eye). Otherwise literally every animal, from birds to tree-dwelling monkeys, anything that sleeps up high, wouldn't make it through one night. We've kind of lost it, and it's by no means perfect - even birds fall out of their own nest sometimes, but it's still there and it shows itself sometimes. | 6 |
cn32q0 | Biology | How did we figure out what plants and animals were edible? Did someone just take one for the team and try it and if they didn’t die we knew it was safe to eat? | Fun fact - the fly agaric toadstool/mushroom is deadly, it used to be used in a bowl of milk and honey for pest control waaaaay back in the day. Druids and shaman learned that the potency of the poison could be reduced by saliva in the mouth leaving a strong hallucinogenic mush, so in order to harness the hallucinogens other members of a tribe, mostly the women iirc, would chew and spit out the poisons leaving the triptastic mush for consumption of the shaman. How that process was ever discovered is beyond me. | 14 |
64bip7 | Culture | Why do people tape their laptop webcams when they are not using it? A good amount of my friends do it, whether they are a tech person or not, but I never really understood the point of it. | Big brother is always watching! That and if anybody else hacks your computer they can basically watch you with your own camera. | 5 |
g1h7ic | Biology | What causes the urge to toss and turn in bed when you're already comfortable? | Could be numerous reasons. There could be something there subconsciously, even though you're not directly thinking about it. It could be something completely irrelevant such as the comfort of the bed, the bedsheets or the temperature of the room. Word of advice; when you don't fall asleep within 20-30 minutes, get out of bed, go into a different room and do something that will help you nod off - listen to some music, read a calming book, meditate - don't do anything that stimulates the mind. The reason why you're going to want to leave your bed is that you don't want to associate feeling anxious and restless with the bed itself. That could lead to insomnia. | 1 |
6ba5h4 | Biology | If drugs stay in the body and are still detectable in the body weeks after use, then why do the effects of the drug only last hours? | "Drugs" don't stay in the body for weeks. The drugs are metabolized into other things that don't impact the body the same way, and *those* can stick around in the body for quite a while. Most drug tests are looking for metabolites. | 4 |
7zadkg | Culture | what's a method actor? I'm currently obsessed with Daniel Day-Lewis and his marvellous work in Phantom Thread. He's said to be a method actor, and I wanna know what concretely that means. Also, I can't get the joke from this URL_0 Which makes me even more upset. | [Method Acting]( URL_0 ) is an intense way for an actor to inhabit a character, even when they aren't on camera. Like, they only want to be called by their character name, they ARE the character at all times and the camera just happens to be filming it at some point. Christian Bale is another actor who goes full method. In the video you linked, if the person portraying Jesus was a method actor, he wouldn't be violent. He would want peace and love, so "not a method actor" is like "well duh." | 4 |
knwozv | Physics | if "blue light" negatively affects sleep, why do colour-changing night-lights include blue? Is there a difference between the "blue light" from phones, TVs, etc and actual blue light? | Your eyes have a set of blue-sensitive cone cells that go directly to a gland in your brain that produces melatonin, which is the neurotransmitter responsible for making you feel sleepy. Blue light turns the gland off, allowing other neurotransmitters to take over to make you feel more awake and alert. All light is disruptive to sleep, but yes, blue light is particularly bad. I'm not any kind of medical professional, so I can't offer any advice other than to talk to a doctor or a sleep specialist if you notice your son having difficulty sleeping. I *can* say that using a different color night light couldn't *hurt* - but only if it doesn't lead to him not *wanting* to sleep without the night light or being upset without it. Any color-changing light has to include blue because without it the light couldn't be anything other than red, orange, yellow, green, and anything between those. You'll see lights labeled as having "RGB" which means they actually have three different kinds of lights - red, green, and blue. Your eyes only detect those colors directly - everything else activates those cone cells in different amounts. Basically, some red light and some green light will activate the cells in your eyes exactly the same way that yellow light will. RGB lights change color by adjusting the brightness of red, green, and blue lights. Plus, the people marketing the night light aren't always concerned about whether their light impacts sleep negatively. Indeed, as I said *all* light disrupts sleep already. People are willing to spend money on a blue night light, so they are willing to sell them. Blue light is blue light. I mean, the exact wavelength might be different. Your eyes are *most* sensitive to light at 445 nm, so I suppose if the light coming from the device is that wavelength or close to it you'll be affected more. Other than that, though, it's all blue. All RGB color spectrum devices work the same way. Your phone just has very tiny [subpixels]( URL_0 ). Exactly *how* a device creates the blue light can be different: LEDs or blue phosphors or whatever. Some high-end devices have a forth subpixel color in violet to be able to display more colors. | 2 |
axmgpx | Biology | What happens with your body when you get chills from hearing someone sing well? | Scientists believe that this happens to about 50% of people. They have studied it in music listeners and theorize that it is linked to being "surprised" by an unexpected change in the music. Like during a really cool "part" of the music. Brain scans show that different areas of the brain light up brighter in people who feel this while it is happening. | 6 |
iscfco | Other | Why are you more likely to get a cold/flu during colder/winter months? | Because you’re in enclosed spaces with a lot of people. In the summer months, you’re spread out, social distancing. In colder months, you’re locked down. | 2 |
e21uzk | Other | How does a government knows the exact amount of physical money at any point in circulation?! Does that amount account for black and grey market transition / ownership?! | The government doesn't know the exact amount. Literally every day thousands of dollar notes are damaged and destroyed without the government knowing. The only way it guages the supply is by reading the tell-tale signs in the economy. If a bank reports that the number of $20 bills being deposited dropped by %1 each year, then the government could use that to help get a sense of how much they need to print. | 1 |
a447xl | Mathematics | Why do many things, e.g. students grades in a class each year, follow the distribution of Bell Curve? Shouldn't they follow a random distribution each time? | Fun fact: If you want to get an ELI5 answer that is correct (for mathematical questions), try /r/learnmath. A lot of answers in ELI5 are guesses anyway, and in mathematics, that's *really not* how this works. **Edit: This was more from experience with past ELI5 threads. In this thread, there are some really good answers, e.g. from /u/OhItsPreston - great work** So, let's answer this: First of all, what do you mean by "random distribution"? That you use this term suggests, that I should really start explaining from the very beginning. A "distribution of a random variable" (random variable = grade of the student) is, to simplify, a list of probabilities: One probability for each possible outcome (these outcomes are called "events"). For example: Probability of a 1 = 50%. Probability of a 2 = 20%. Probability of a 3 = 20%. Probability of a 4 = 10%. That would be a distribution for a single grade of a student. (I used numbers instead of letters A, B, C, D for the grades here so we can do math with it. Don't get hung up on the meaning of an average of 1.7 or something). Now we can do some fun mathematics with this beast! We can compute the "Expected Value of the Student Grade", which is a fancy way of saying "average grade, if he takes this test 1 billion times, we sum all up and divide by 1 billion". The expected value is computed by multiplying each result (1, 2, 3, 4) with its respective probability of occuring (0.5, 0.2, 0.2, 0.1 ; I converted the percentages to decimal representation for this, because percentages are ugly to do math with), then adding them together. So 0.5 + 0.4 + 0.6 + 0.4 = 1.9 is the average grade. This is going to be a great student! But the average doesn't really tell you everything there is to know. There is something called the "Variance of the student grade". This is a bit more difficult to compute (you can do it by hand, but you are better served with an excel spreadsheet or something), but in simple terms it means "how far from the average are the grades this student usually gets". If we have a Variance of 0, then the student gets a 1.9 all the time (which is nonsense, since that grade doesn't exist). If the Variance is 10000, he gets a lot of negative grades and huge grades, and only few grades close to 1.9. Which is obviously also not the case. The actual variance for this example of student grades (there's a formula for it, I can explain that further if you are interested) is 1.09. Then there is something called the "standard deviation". You might have heard of it. This is just defined to be the square root of the Variance. In our example it would be about equal to 1.044, because 1.044 \* 1.044 equals about 1.09. Duh. The standard deviation is interesting, because most formulas only need the square root of the variance (for a variety of complicated reasons). So we gave this square-root-of-variance its own name: standard deviation. Now we have found out the **Expected Value** and **Standard Deviation** for our **Probability Distribution**. Are you ready for part 2? In part 2, we are going to investigate why this must always result in a Bell Curve. | 3 |
k15vsv | Chemistry | What are you seeing when you look at fire? Not the logs, but the part up high that's emitting light? | Oxygen is electro negative, and is violently stealing electrons from the fuel. Im a firefighter and have been trying to figure out what the actual flame is for forever. It's tough to understand and I don't have it all figured out. Btw the "glow" everything has isn't the flame. As people have said, the glow on logs or something is that heat that everything has entering into the visible spectrum, but the flame is different i think. Though I could be wrong. Btw, did you know the flame of a candle is hollow? | 3 |
5wo7vi | Biology | Why can humans only hold their breath for a few minutes while, say, marine iguanas, with their tiny lungs, can hold it for about 30 minutes? | Pound for pound, mammals require about 20x more energy than reptiles. That means mammals will require about 20x the food and oxygen to survive. 30 / 20 = 1.5 minutes, so the math checks out. | 5 |
6e4n21 | Economics | Why does the price of name brand foods vary at different stores but the price of electronics such as video game consoles are the same at every store? | Food is fairly cheap to produce and the markup is pretty huge depending on the food. A bag of chips that costs 50 cents to make will sell for 2 bucks. That's a sweet margin. And it gives room for discount stores to cut prices and have sales, etc. Additionally the price of food often fluctuates. The 2 dollar price is a good average that covers increases and decreases in potato costs if there's a bumper crop or famine. There is a theory for example that McDonald's times the return of the McRib with the ebb and flow of pork futures on the commodities market. Video game consoles have much thinner margins. And the margins are consistent. Aluminum, plastic, and Lithium don't have bumper crops. Microsoft actually sold the first XBox at a loss because they had a longer term strategy of getting into the console market and putting an XBox in your living room as a sort of entertainment hub. Sony is the same way. Their goal isn't for you to buy their console, their goal is to get you to buy into their system. Sony has a stake in BluRay licensing which is why the PS3 was so gung ho on introducing BR discs. Because these consoles use cutting edge tech, the process required to make them is slow and laborious and specialized. Over time it gets easier and faster and more automated which is why price drops occur later on. Nintendo is not in the same game, they want their consoles to make profit. So that's why their consoles are cheaper and that's why their tech is a generation behind, because it's easier to make older tech. In any case, the costs of making a PS4 don't fluctuate the way that potato chips do, and even then, there's not much room for sales. | 6 |
6xu07q | Technology | Why do we instinctively seem to hit machines / devices that aren't functioning properly? Where did this come from? | On top of the other answers things like jukeboxes were self contained but played records. If a needle skipped you could hit it on the side to put the needle back into it's proper position. At least that's what the Fonz taught us all. Pinball machines are another thing that would get routinely hit, balls would get stuck or you wanted to not lose you could rock the machine. Then there were NES systems that could also benefit from a good smack on the side from time to time to get a game to play right. Some games would not make contact right with the system and you would have these artifacts on the screen. Smacking it would help the system make contact with the cartridge. | 19 |
ic2lxn | Physics | how does resonant frequency cause the item to break when that frequency is played? I always find it weird that glass breaks at its resonant frequency and want to know why it causes it to break | If you're ever pushing someone on a swing, you know you want to give them a push when they're on the way forward right? It's a similar thing with materials and their resonant frequency. When something is vibrating, the structure of what it's made out of causes it to vibrate at a certain rate. Similarly, if you were singing a perfect note, that is causing the air to push in waves at a certain rate. If you line up those things perfectly, then each time the air pushes, it is in line with the object vibrating in one direction. This means the sound wave is helping to make the vibration bigger, just like pushing a swing at the right time. Eventually, if do this more and more, you can potentially ~~push them right over the top of the swingset~~ break the glass because it is vibrating itself apart. | 1 |
kp7qum | Other | Why Does Everything I Touch Try to Electrocute me? | If you put a humidifier in you house the static shocks will stop. Dry air is an insulator and allows static charges to build up. Humid air grounds you and permits the static electricity to dissipate. | 2 |
8fo175 | Biology | Do very overweight people need to take a larger than normal dose of medications to get the same effect? | When people get fat, not everything gets bigger. When organs get bigger, that is usually a problem/sign of a problem. Most often, when a person gets fat, most of the extra bulk is literally fat, adipose cells. There are some other increases, like in bone mass and skin, but not a lot of stuff inside the body gets bigger. Lots of drugs dont really target fat or skin, so it doesnt really matter too much...though you do adjust somewhat for certain things. | 8 |
6p0oa7 | Other | how you can make people hold such big secrets as Area 51 without having some leaked information? | You really can’t. The best proof that there is nothing super secret at Area 51 is the fact that nothing has leaked other than their work on stealth aircraft and related. | 56 |
5nkds8 | Technology | While being put "on hold" on the phone, why do songs played have such dreadful quality, while voices come through just fine? | It's a combination of a number of factors, but the biggest issue is that phone lines have been "optimized" to favor voice sounds over other sounds, and as a result many of the upper and lower frequencies that make up the music you're listening to get cut out by the phone's filters. In other words, it doesn't sound like voice, so it gets cut. The result is that the music you hear is messed up. Combine that with systems that play low quality music files/sources to begin with and you can see how things get really bad. | 3 |
gqfk04 | Other | When and why did a single player mode in a game become synonymous with the term "campaign"? | It's actually not. There are singleplayer modes that are not campaigns. This is especially true of genres that aren't shooters. Shooters typically have multiplayer modes and maybe a singleplayer campaigns, but there are singleplayer games with no campaign at all. A campaign is a set of adventures, levels or whatever that forms a complete experience beginning to end. Generally it indicates PvE, but I am aware of one PvP campaign, but it's rare. Some singleplayer modes are sandboxes, where there's nothing set at all and you just play. This is most common in 4x and other strategy games, where the most common playmode is a random map with other random elements in which you are tossed and told to do whatever. There's also roguelike modes, which are like a fusion of campaign and sandbox. It's kinda a random campaign, only more random that sandbox and you generally get one life and the entire game resets when you die. If it helps, the immensely popular Minecraft is a sandbox style game. Even the multiplayer mode is a sandbox. As others have said, the actual name campaign comes from RPGs, where a campaign is a series of adventures that you play through and which eventually ends. | 5 |
8vgnc3 | Technology | how are we set to release 5G soon if we haven't acheived true 4G? | Welcome to Mobile Network marketing where the speed classifications are made up and real world results don't matter. | 9 |
d98wjc | Biology | What is the autism spectrum? How can there be a spectrum, and if that's the case, is everyone on this spectrum? | Picture a gradient from white to black. At the left side, the image is completely black; at the right, completely white. In between those extremes are progressively lighter and lighter shades of grey. We would probably say that just next to the white is so close we can just call it white; and, the same for black. At some point on the gradient we will say that the color is more black than white. Autism is like that. It's not a binary condition, but something with varying levels of severity. Some people are autistic, but only show a few symptoms, or only show them mildly, and can function in society. They're way on the left side, deep in the black. Some people are autistic, but show many symptoms and can only barely deal with life's various challenges. We used to say such people had Asperger, but I gather that's frowned upon now. They're in the grey somewhere. Some people are autistic, and have all the symptoms cranked up to 11 and will always need help to survive: they can't talk, rarely respond to the world around them, etc. They're all the way in the white. | 2 |
5orn0d | Physics | How does electricity find the path of least resistance, and can this be used to solve the Traveling Salesperson problem? For those who don't know, the Traveling Salesperson problem is a pathfinding problem: given a set of points as inputs, find the shortest path that hits all points and returns to the start. Seems to me like electricity already does this | Electricity doesn't just follow the path of least resistance; it follows *all* possible paths—but the amount of current following each path is proportional to how well that path allows it to flow. | 3 |
6sv2vw | Chemistry | Why do we as humans like carbonation in our drinks? | Carbon dioxide reacts with water within the drink to form carbonic acid which alters the taste of the drink a bit. The bubbles also tingle your tongue altering the perceived flavor. | 1 |
7zk129 | Repost | Why do gas prices almost always include “9/10” of a cent, and how could we be expected to pay in portions of a penny anyway? | Basically when the tenth of a cent thing was introduced gas prices and wages were cheap enough that it gave gas stations a better degree of price control. If your price is $.10 going up to $.11 is a huge 10% increase in cost, so allowing them to make smaller adjustments let them price gas better. Since then prices have climbed but the tenth of a cent spot in the price has stuck around. As for how it actually works it relies on the fact that generally you buy multiple gallons of gas at once. So they just track the price like normal, and then when you finish filling up they just round up to the nearest cent and that's what you pay (the consumer always takes the loss in cases where you might have fractional cents like buying gas or sales tax). | 1 |
5xok9g | Engineering | What's to stop someone from broadcasting a radio frequency that is already taken by a local station? For example: if a local top hits station uses 92.5 FM, what's to stop Joe-Shmo from broadcasting on the same frequency and disrupting the local stations radio? | I assume that's why at night when your station turns into Mexican radio it's because they don't comply with FCC. I don't know why it seems to happen only at night either. Someone needs to ELI5. | 14 |
6azeb5 | Other | How do fish never sleep? | Fish do sleep. Fish sleep in a few different ways. Some fish sleep with half their brain at a time so that the other half is alert enough to keep them away from predators. Parrotfish [build a cocoon of mucus]( URL_0 ) to sleep in that protects them from predators. They sleep so soundly in their cocoons that divers have been known to play catch with them without the fish waking up. But yes, fish totally sleep. | 2 |
9xk8dq | Physics | How can you pull on a rope in a pulley system and only make the load move a fraction of the distance you pulled? I understand that a 2-pulley system cuts the load's weight in half and reduces work but nobody seems to be able to explain to me (at least in a way I can understand) how I can pull down 10 feet of rope from the top pulley and the weight only moves 5 feet off the ground. It literally seems to me that you're pulling 5 feet of rope out of thin air, because there's no way the rope gets longer as you pull it but the load doesn't move the distance you pulled. I don't care about things like work or energy or anything; I just want to know why you pull one distance and the load moves half that. This problem has caused me a great deal of stress over the past 3 years and was one of the biggest reasons I changed majors and I'd like to finally get it so I can move on to the next problem I'll never understand. EDIT: I'm very much a visual learner so a diagram would be helpful, but so far all the people who have tried to explain it to me either get caught up in talking about how it halves the weight of the load or can't make a diagram that I can understand. | With a two pulley system. The rope goes from your hand, over the top pulley, down around the bottom pulley, then connects to the top pulley. Then the load hangs from the bottom pulley. The length of rope from the top pulley to the bottom pulley is the same on each side of the bottom pulley. So if you pulley 10 ft of rope 5 ft comes from one side and 5 ft from the other. That means the bottom pulley only goes up 5ft. URL_0 | 4 |
k2q676 | Biology | Why is hard to move your fingers when they’re very cold? | When your body gets cold it pulls blood out of any non life sustaining areas/systems to better insulate the vital organs. So what's happening is the muscles and nerves that innervate your hand and fingers are literally operating on minimum blood flow. Think of it like they're being in power save mode | 2 |
n0tq9r | Other | why do we sometimes hold an arm up in the air for no reason while we’re watching tv or just laying on our sides? | No clue! I do this too and my husband thinks I’m a weirdo. He’s right, but that’s a different story. | 6 |
7m6z1g | Chemistry | How do we know that two identical snowflakes have never existed and never will? | The statement is trivial if you think about it. No two objects of that size are ever going to be ‘identical’ without some qualifiers, at what size-scale do you stop comparing them...atom by atom? | 3 |
kevt8q | Earth Science | Won’t the battery materials for electric cars run out? Doesn’t it take a tremendous amount of metals and rare earths to make these giant batteries, and isn’t there a finite amount? If the world truly switches over to electric, do we have any sense on how long we’ll be able to keep producing these batteries or is the assumption that we’ll develop different battery tech that won’t require as much mining and materials? | [This video]( URL_0 ) by Real Engineering does a pretty great job of explaining the current state of battery making materials. | 6 |
nv3bf4 | Physics | Time Is Relative | It might help to think of it from a different perspective: instead of asking why is time relative, ask instead whether time is absolute. Intuitively, we think that space and time is absolute. In other words, we would imagine that 1 meter would always be measured as 1 meter *no matter who measures it*, whether this observer is not moving or moving extremely fast. Likewise, intuitively, we feel that time passes by constantly for everyone, at a rate of 1 second per second universally. This means that when I experience 1 second pass by, I expect to observe 1 second pass by for all observers, including those that are moving or stationary. Now, lets ask whether or not this is actually true. It turns out (and there are historical bits of evidence leading up to it) that, when we tried to find out what this absolute space was, the experiment failed! And it lead us to ask what *is* exactly constant for all observers, and it turns out that it is the speed of light itself. Just as a quick refresher, speed is the space traversed in a given time. And so if the speed of light IS constant, but absolute space is not, then time itself but stretch and squish if the speed of light is indeed constant (and, as far as we know, it is!). What does this look like? The an example is to imagine sitting at a train station watching someone on a train moving at 99% the speed of light. You then turn on the lights at the station and you watch the light zoom off at 100% the speed of light and overtake the train, but from your perspective, it looks slow, since the light is only 1% faster than the train. Now what does the person on the train see? Well, they instead see the light zoom of at 100% the speed of light ahead of them. So what gives? You on the train station watching the train sees the light overtaking slowly, but the person on the train itself sees it rushing off into the distance. The answer is that when you look at the watch of the person on the train, you would see that his watch is ticking *a lot* slower than yours, and by the time that person's watch ticks of 1 second, the light has travelled ~~300~~ 300,000 km ahead of the train (the distance light travels in 1 second). And so the better way to think about time dilation (and space contraction), in my opinion, is to look at it via the speed of light being constant. Once you fully accept that it is the *speed* of light that the universe cares about, then it naturally follows that space and time have to warp to keep it constant. There is a lot more nuance in the theory but this should suffice for an introductory level. | 13 |
8xr4jd | Culture | What is the difference between a pun and a play on words? | A pun is a narrower category, a specific kind of wordplay, typically referring to words that sound alike. | 2 |
6qdq1e | Culture | why we associate radiation and radioactive materials with the colour green? In movies and games, especially fallout franchise I see nuclear waste as the colour green, are they actually green in real life? | Many uranium containing chemicals are either pale green or glow green when exposed to UV light. For example in the early 20th century, uranium was sometimes added to glass to make it a nice pale green colour. This type of glass would glow a strong green if exposed to blue or UV light. Similarly, radioactive materials such as radium or tritium were used as an energy source to charge glow in the dark materials, such as zinc sulfide. Zinc sulfide would glow green in the dark after being charged by light, or if it was mixed with a radioactive material like radium. Paint made from a mixture of zinc sulfide and radium was often used for clocks and watches, so that you could read the clocks in the dark. Radioactive materials tend not to glow in air - they have to be extremely radioactive to glow in air, but if they did, they would usually glow blue. When highly radioactive materials are placed in water, they may glow due to "Cherenkov radiation" which is a pale blue. You can see an example in this video: URL_0 A used, and highly radioactive, fuel assembly (high level waste) is being removed from a reactor and placed into temporary storage. The process is performed under water, and you can see the Cherenkov radiation from the fuel. | 2 |
6f40r7 | Other | Why Islam if often linked with acts of terrorism? | Their "perfect words of God" beliefs are incompatible with an evolving society. the Quran orders muslims to spread and transform the world into a Caliphate. Because most muslims are not terrorists, but most terrorists are muslims. | 1 |
7zi9yb | Other | How Have the Sentinelese People Remained So Far Behind When It Comes to Technology and Basic Life? | I think most importantly, the British (originally) and Indian governments have been very strict about not officially allowing outsiders to contact them (as much as they can stop it). So that avoids the situation we see in Brazil, etc., where landowners and poachers can use superior weaponry to subdue and destroy their native Amazon tribes. (Edit: other islands in that chain were also populated with native tribes, but the British had no qualms in claiming the biggest islands for themselves and putting the natives to work for them, and setting up a Devil's Island-type prison there for their Most Important Prisoners. I guess they kept Sentinel Island as a sort of anthropological museum.) (And as others have said, the island residents are also very aggressive in defending themselves from any intruders, so that discourages the stray poachers, etc., who might attempt to land there..) | 3 |
jlomh8 | Chemistry | Why do wet foods (e.g. mashed potatoes) stay hot for so much longer than dry foods (e.g. steak)? | Every substance has a property called its "specific heat capacity". This represents how much heat energy a certain mass of that substance must gain in order to become one degree hotter, or lose in order to be one degree cooler. The specific heat capacity of water happens to be quite high compared to other substances. URL_1 URL_0 | 1 |
85yrbc | Other | What is the difference between absurdism and existentialism? I know that they both have something to do with meaning, but that's pretty much it | Some might say absurdism developed out of existentialism. Existentialism basically says the foundation of our analysis of the world has to begin with our subjective human experiences. It stresses authentic and personal meaning in an otherwise meaningless world, where other philosophical approaches might suggest meaning stems from an objective de-personalized system. Absurdism takes some of these ideas and moves them a step farther, saying not only is existence inherently free of intrinsic meaning, it is humanly impossible to find meaning in existence. The absurd part of this is the human nature to relentlessly seek the meaning in existence despite our inability to do so. I think *The Myth of Sisyphus* by Albert Camus does a really good job of addressing the Absurd and how to deal with it. Essentially, existentialism says “life is meaningless, so create your own meaning” where absurdism says “life is meaningless, so experience it as meaningless.” At least that’s how I understand it. | 2 |
iz5aji | Biology | What is the purpose of putting Hydrogen Peroxide on scrapes and cuts? | The idea is that hydrogen peroxide kills any bacteria that may have entered the scrape or cut to prevent infection. You’re trying to “clean” the wound. Another idea is that the bubbling effect the hydrogen peroxide has on your skin can remove any small pieces of debris that got into the cut. However, the use of hydrogen peroxide to clean wounds has become something of a controversy in the medical community. A lot of medical professionals say that hydrogen peroxide is *too* good at its job of killing things - it even goes so far as to kill the healthy cells, including ones your body has sent to the wound to repair it. | 2 |
66q4kz | Other | What is OCD? | OCD is short for Obsessive Compulsive disorder. It is a mental illness that is usually associated with people who do very specific things in order to handle extreme levels of anxiety. A generic example would be like in the show It's Always Sunny in Philadelphia, when Charlie's mother needs to switch every light in the house on and off three times, and she believes that doing so will actively prevent her son from dying. It can manifest in many different ways, so I'm sure there is someone out there who can better explain it, but that's the gist of it, I think. | 3 |
c99jrs | Economics | How are sport sponsors able to justify the money spent on a club/player? | It does (sadly). The number of sales of an unbranded product (generic shoes) v Jordans justifies those deals. Also brands hedge and lock athletes in before their prime (some need the $$$ and agree to below market terms). | 2 |
a1on5d | Biology | If our body keeps making new cells, how do we retain most of our memories? I've read from multiple sources in takes 7-10 years for our body to replace every cell it houses. Since that is the case, my guess is when the old long term memory cells are about to die, they must do some type of memory hand off to the newly created long term memory cells that will replace them? | You are born with all of the neurons you will ever have. Connections between them can rearrange (neuroplasticity) but the neurons don’t replicate (though they do die). | 3 |
7abey2 | Economics | Since US coins were originally made of valuable metals, why are nickels worth less than dimes despite being larger? | Contrary to other answers here, it's *not* to make the value of the metal in the nickel equal to five cents! The real answer is apparently government pork. The first nickels were minted at the end of the Civil War, when gold and silver were being hoarded. The US government introduced copper+nickel coins whose value as metal was much less than the value printed on them. The first was a 3-cent piece, and the 5-cent nickel came soon after. The director of the US Mint at the time wanted to make a nickel weighing less than 3.9 grams, but a congressional committee upped that to 5 grams. The congressmen said this was to make it a nice round number in the metric system, but it just so happens they were good friends with wealthy industrialist Joseph Wharton, who had a near-monopoly on nickel mining in the US. Wharton's congressmen were also the folks who suggested the 3-cent nickel piece in the first place. So it seems that the nickel is big because congress was in the pocket of a guy who wanted to sell more nickel. URL_0 | 1 |
j5sxv4 | Other | What is wrong with using “whataboutism” in a discussion? | Why are you limiting this to just whataboutism? What about strawman? What's about ad hominem attacks? What about other logical fallacies? See how easy it is to derail a conversation this way? Fundamentally the problem is that while it might sound a little like it is relevant to the conversation at hand, it almost never is. There are a few limited situations where it could be a valid thing to bring up, which just makes it harder to deal with. | 5 |
e7idjb | Engineering | If there are pipelines that can move oil thousands of miles, why can’t the same be done to move water thousands of miles to areas that experience frequent drought? | Um, there *are*. For example, Los Angeles and Las Vegas rely heavily on water pipeline use. A key problem with water pipelines is when you deliver water via a pipeline, you're effectively taking away water from somewhere else, and when that "somewhere else" is also staring down the barrel of a drought, they're not too happy about having to give up their water to people who decided to make a home where they knew there wasn't any water in the first place. | 7 |