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o0xpqy | 0K (Kelvin) is supposed to be the lowest temperature reachable but it's only theoretical. In definition it means there is absolute zero motion. But why is that, that some elements are still not "solid" in this temperature? | Like helium which never turns into a solid block on normal pressure? | Physics | explainlikeimfive | {
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"The protons and neutrons in atoms are made up of particles called quarks. Quarks have a very low mass and what is ultimately giving a proton/neutron most of its mass is that fact that the quarks inside of them are spinning at close to the speed of light. There are three quarks in a proton. Two of those quarks have a charge of +2/3. One of them has a charge of -1/3. The quarks themselves are arranged in a sort of triangular shape. At large distances these charges cancel out so that a proton appears to have a net charge of about 1, and for nearly all applications we can consider that charge to be 1. But its not *exactly* 1 - it varies depending on the position of the quarks relative to you. When the negatively charged quark is on the opposite side of the proton you experience a charge that is very, very slightly stronger than 1. When it is on the side of the proton facing you, the charge is very, very slightly less than 1. Neutrons work the same way, except the one of the quarks in a neutron has a charge of 2/3 while the other two have charges of -1/3. So depending on the position of the quarks in a neutron, you will experience a charge either slightly higher or lower than 0. This extremely slight net charge is sufficient for a proton or neutron with \"0\" energy to, nonetheless, cause other nearby protons and neutrons to wobble a bit, resulting in them having some very minimal amount of energy. This, in turn, causes atoms to have a constant, slight wobble (which will also result in the wobbling atoms very slightly \"bumping\" into nearby atoms). We can't stop this wobble because on a very fundamental level we don't have any mechanism to influence the quarks inside of proton/neutron, so we can't slow them down. Also, because the speed of the quarks is, itself, responsible for most of the mass of the proton/neutron, if you did somehow manage to slow those quarks down they would stop being a proton/neutron and start being something else, which doesn't necessarily solve the problem if what they turn into can't be measured, like dark matter - or if the energy in the quarks ends up getting liberated, such as through the transformation of a quark into high energy electrons or positrons.",
"0K is the theoretical minimum point of energy - not the point of *zero* energy. Pressure plays a big role too. Substances move toward a solid state as temperatures decrease **or as pressure increases**. So if there is a change in pressure at absolute zero, there could be a state change.",
"A solid is a structured configuration of molecules or atoms and forms in low temperatures because for most molecules this structured way has a lower energy then a less structured fluid or gas. This is because of the interactions between the molecules or atoms. As a simplified \"rule\" you could say: if the interactions between molecules is higher, it will form a solid at higher temperature. For helium these interactions are very weak. A second effect is quantum uncertainty. For very light particles the uncertainty on the position is relatively large compared to the distances in possible solids of those particles. For hydrogen (I forgot if it was also the case for helium, it had been a long time since my studies) the uncertainty is even bigger then the distances between particles, so it can't form a structured lattice. Helium, and some other atoms, will form an even more energetically favourable phase before they could become solid. They form a bose-einstein condensate, also called super-fluid helium. This is fundamentally different from a fluid. It is a quantum state were most of the helium atoms are in exactly the same state (have the same quantum numbers).",
"This isn't an answer to the question, but a correction. 0k isn't reachable, theoretical or not according to the 3rd law of thermodynamics.",
"It's worth noting that 0 K is theoretical (extrapolated) point where gas volumes would decrease to zero then, if they could keep cooling, become negative (negative volumes defy or 3D understanding), and happens at a temperature we can only approach. Not necessarily where particles cease motion...",
"Lots of great responses. I'll try to answer this like I would to a 5yo. With videos! (see below) When temperature reaches 0 Kelvin - all motion stops. Almost all materials we know go solid the colder you get. So we assume solids are the most \"stable\" or have the \"least jiggling of atoms\". But that's not always the case. Helium is a funky little atom and it's very very stable as a liquid. Near Zero-K it becomes a superfluid which funky properties (no measurable viscosity in most cases ... because viscosity is complicated) [ URL_1 ]( URL_1 ) Some atoms, when they get near Zero-K, they start to overlap in space ... and because of this they all become a single \"super atom\" - technically we say they share a single Quantum Mechanical wave function. At this point it's not solid, liquid, or superfluid ... it's a 5th (6th? 7th?) state of matter - Bose-Einstein Condensate. [ URL_0 ]( URL_0 )",
"It's called zero point energy. Even at the lowest temperature quantum mechanical laws say there's a tiny bit of energy. Otherwise stuff like Heisenberg's Uncertainty Principle break down. That's barely enough to melt helium."
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o0y3dx | Why does it take 1+ hours to charge something when electricity is almost instant? | Technology | explainlikeimfive | {
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"If you open your bathroom tap, water comes out immediately, because there was water in the pipes, and that water is under some pressure so it wants to come out if you give it an opening. So in that sense, the delivery of water is \"instant\". However, it still takes a good while to fill up your bathtub with it, because the pipes only allow a certain amount of water through them, and the pressure only pushes it through the pipes at a certain rate. To speed up the flow, you would need to increase the pressure, but if you increase it too much that will damage the pipes. To prevent that you would have to make the pipes stronger or wider. Electricity is very analogous to this. The water pressure is analogous to voltage. The higher the voltage, the faster electrons are getting pushed through your outlets. The pipes are analogous to the wiring, which has a certain *resistance* that puts a limit on how many electrons can pass through every second. If that flow of electrons (the current) becomes too strong, it damages the wiring. So that puts a limit to how many electrons can flow out of your power outlet every second, just as there is a limit to how much water can flow out of your faucets. And so just as it takes a while to fill up your bathtub with water, it also takes a while to \"fill up a battery with electrons\" (that's not precisely what happens but it's close enough). (The limits aren't just in your power outlets of course - they are in all the wiring that is involved, including the charger you're using, which has its own limits to how much electric current can pass through.)",
"It depends what technology is used to store the charge. Capacitors charge and discharge in a very short time (milliseconds to seconds) but hold a very small charge. All of the common battery systems in household use use chemical reactions to store energy. Those chemical reactions need time to happen. Still there are often specific quick charge routines that cut the time far shorter often at the price of a reduced battery lifetime."
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o0y6ut | When looking straight at a light, why does the shape of it stay in your vision? | Biology | explainlikeimfive | {
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"When we see light, it enters through the pupil and shines onto the retina, the light-sensitive lining at the back of our eyes. If a bright light shines on the retina long enough, the part of the retina it’s hitting becomes somewhat desensitized to light, so when we look away, the desensitized part doesn’t immediately respond to the new input it’s receiving. This causes us to perceive a negative space in our field of vision that’s in the shape of the bright thing we were just looking at until the affected part of the retina becomes sensitive to light again."
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o0ze3k | why does glass absorb infrared and ultraviolet light, but not visible light? | Physics | explainlikeimfive | {
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"It has to do with how light interacts with matter. To absorb light, you need to have things work just right. You may have heard that light is quantized, what this means is that it only gets absorbed in specific chunks, one photon at a time. And all the energy of that photon has to go somewhere. It turns out there are a few different places for that energy to go, and since each color of light has different energy, those different absorption mechanisms affect the colors differently. Ultraviolet has the highest energy, it’s absorbed into the electrons in a material, kicking them up in energy or ejecting them from the atoms entirely. Infrared light is absorbed into the vibrations of the atoms and molecules in a material. For glass, visible light isn’t high enough energy to be absorbed by the electrons and too high to be absorbed as a vibration. Remember, it’s all or nothing - you can’t absorb half a photon. It gets a bit more complicated since you also have to absorb the momentum of the photon, and not matching the quantized momentum kick will lead to the photon not getting absorbed either. Different materials have different thresholds for these absorption methods, and a huge difference is whether things are metals or not. Metals have completely different architectures for their electrons, but the basic concepts of “need to absorb a whole photon” still apply.",
"FYI: as my bleached out hardwood flooring and carpeting can attest to, glass does not block UV unless it is treated to do so.",
"Materials are made of atoms. Each different type of atom, compound or molecule interacts with light differently. This is mainly because of how their electrons are arranged around the atoms and molecules. Some compounds absorb some frequencies of light and not others. The atoms in glass used for windows don’t interact with visible light because their electrons aren’t arranged in a way to do so. But they do absorb UV. That’s why they’re good for windows! Other glasses are good at absorbing X-rays and so are good to use in X-ray machines. Things to google: electronic band structure & optical absorption",
"This isn't a full answer, more a comment. But if glass didn't allow visible light through we wouldn't use it as a window - we'd find some other material. And since we don't see in infrared or ultraviolet then we don't care if our windows absorb those frequencies. Glass is a Goldilocks material for this reason.",
"A lot of decent explanations of how electrons absorbs photons, but most comments don't answer OPs original question and many include misinformation. Glass does not absorb (much) UV or infrared light by default. However, it is common more recently (last 10-15 years) for glass to be manufactured with a \"low-e\" coating (low emittance). This coating is made of a compound that specifically reflects (like a mirror) infrared and much UV light. Since UV and infrared are invisible to our human eyes, these coatings don't look like mirrors, they look clear; but if you have infrared vision, they would look shiney. How does a compound only reflect certain types of light? Many other commenters have attempted to explain and some are correct. There is actually a lot of empty space in between atoms. Think of the size of an atom as a football field and the nucleus as a football in the center of the field with the electrons as M & Ms orbiting around the field and the stands. That's a LOT of empty space between individual atoms; plenty of room for photons to slip through! But how do most materials absorb most light and end up being opaque? Well, photons are absorbed by the electron \"orbitals\", NOT by the electron (per se) or by the nucleus. The orbital is just the area within which the electron orbits, and they have weird shapes; it's very complicated, so lets just imagine that some electrons orbit in the home team goal zone, some orbit in the away team goal zone, and some orbit in the spectator stands. If a photon passes through the orbital of an electron, the orbital may absorb that photon; the energy of that photon is then transfered into the electron in that orbital. But here's the thing: not all orbital absorb photons. Some orbitals will let photons pass right through them, others will only absorb photons of certain wavelengths (like UV or infrared). Why don't all electron orbitals absorb all photons? That has to do with complex quantum resonance and interactions between fermions (which I don't fully understand). It also has to do with how many orbitals the atom has, how close they are to being full of electrons, what types of electron bonds they have with surrounding atoms, and many other factors that I can't fully comment on. Suffice to say that \"low-e\" coatings in glass windows are made of a material that researchers discovered that has atoms with electron orbitals that like to absorb (and then reflect) UV and infrared, but which ignore visible light. How fortunate for our energy savings that they discovered this, so that we can see beautiful things through our windows but not over-heat our buildings in the process!",
"Some of the other top responses do a somewhat decent job of approaching the answers to this problem but honestly, the real answer is somewhere between \"we sort of know\" and \"you really need a PhD in physics or material science\". For example, take most of the top responses as ask this: What's the difference between frosted glass (found in shower doors or interior separation), silvered glass (also called a mirror), a lens, tinted glass (your car windows), polarized glass (your sunglasses), and low-emissivity glass (your double pane windows) and you'll very very quickly run into some terrifying quantum phenomena and run into issues involving coherence, polarization vectors, complex index of refraction, permittivity tensors, evanescent fields and plasmon-polariton interactions. It really is a very simple question with a horrendously complicated answer that is barely captured by even one textbook. So why do some varieties of glass absorb IR and UV? Because over the past millennium, we tried adding random shit to hot sand and cooling it in different ways until we found things that did that and it is in the nature of those types of glass to do that.",
"Wavelengths. Wifi is light. Bluetooth is light, radio, everything wireless is light. And to those wavelengths everything is clear like glass. For x rays your flesh is but your bones aren't. For different colored glass, the material allows only certain colors through. Just the composition of it and how it absorbs or reflects certain wavelengths of light. Which is to do with chemistry/quantum physics and how materials interact with wavelengths of light.",
"A particular matter being transparent for a certain kind of light means that it is physically unable to tap into the energy provided at that the particular frequencies of the radition (\"absorption\"). Absorption happens when electrons in the matter resonate with the frequency provided. They can only resonate and hence absorb radiation when they are bound with the \"right\" strenght, like someone sitting on a swing: If you push in opposite directions too fast, the poor person will not move. If you push every other year, they will swing, but not gain energy either. But if you push just at the right times, they will swinger higher and higher... resonance! Glass is transparent, because its electrons are either too stiffly bound (absorbing UV) or too losely bound (absorbing infrared), but non of them are able to absorb visible light.",
"I wouldn’t think infrared is absorbed. Have you been in a greenhouse? It’s hot AF. That heat got in there thanks to the radiating of heat via IR. My understanding could be way off. Please correct me if I’m wrong."
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o0zlre | how did they estimate in the first place how many calories our bodies consume with the different activities? | Biology | explainlikeimfive | {
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"Whenever you burn calories you are consuming carbohydrates and oxygen to make carbon dioxide and water. So a simple way of calculating the rough amounts of calories you burn is to monitor the air you breathe out and measure the amount of carbon dioxide. This can be calibrated with similar long term studies using things like measuring weight and food intake so we know it works right. So we know that measuring the carbondioxide in your breath is a very accurate and calibrated method. You might see olypic athletes exercize with a tube in their mouth for promotional images which shows them performing such a study."
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o100ui | What actually happens when a body rejects an organ or blood? And how can an organ/blood be rejected in the first place? | Biology | explainlikeimfive | {
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"Your immune system attacks it. Organ donations are a new thing, and we have immune systems that evolved to attack intruders. If an organ isnt recognized your immune system doesn't know its a kidney, they just see a mass of foreign cells and will attack. That's why they have to check if an organ is a match, and even then they have to take a lot of steps to try and prevent \"rejection\" of the organ",
"We do have quite a complex and intricate immune system which works on multiple layers to prevent foreign things from entering our body. There are several different ways in which this can work to reject organs. In the case of blood there is a specific part of the immune system which fills the blood with certain antibodies that will connect to any foreign blood cells and cause it to clot. It just so happens that the specific combination of antibodies is just the antibodies our cells are not subject to. The most critical antibodies is the A, B and d antibodies which is what you specify when you specify your blood type. But there are over fourty such antibodies which does the same although at a lesser extent. You do also have similar systems for the other organs. We make antibodies which trigger on things that are not our own cells, including viruses, bacteria, parasites and cancer. And these will sometimes detect that there is a foreign object there when in fact it is a transplanted organ critical for our survival."
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o10sin | Why do stocks go down when something irrelevant happens? | Economics | explainlikeimfive | {
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"The stock market is not rational or logical. It can go down because of a tweet or a picture; it can go up for equal non-reasons. Stock prices change in response to peoples' knee-jerk reactions.",
"To add on to what some others have said, a lot of this can be somewhat of a feedback loop. Some stockholders see this happen on TV, so they therefore assume that the stock will drop, so they sell while it's at a higher price to either lock in their gains, or buy back in after the price drops. So it could very well be the case that nobody is actually intrinsically valuing the Coca-Cola company lower because of this slight negative PR, they're just expecting that other people will, therefore the price drops as a bunch of people sell off.",
"Most of the portfolios with large capital to my understanding are automated and watch any news or information about the companies carefully, one of the flaws of Technology is not using common sense like in your example lol."
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o113ec | I'm not a huge drinker. People always talk about getting different kinds of drunk on different kinds of alcohol. To your body, isn't alcohol just alcohol? Sure, proof would matter, but does your body know the difference beyond that? | Biology | explainlikeimfive | {
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"Yes alcohol is alcohol but drinks often have other things in them e.g. some have a higher sugar content than others, which might impact how you feel / react physiologically. However \"mixing drinks\" leading to a worse hangover is a myth - it's just that mixing drinks is correlated to nights when people drink more alcohol in general.",
"Most alcohol that goes through your body is ethanol. However, in different beverages, you get minor components called fusel alcohols, which belong to a larger class of chemicals called congeners. These types of alcohols aren’t ethanol, but include alcohols like 2-methyl-2-butanol (2M2B, quite psychoactive, or other amyl alcohols), isopropyl alcohol, or 2-phenylethanol. These alcohols do exert some effect, and may contribute to slight variations in how you feel with different alcoholic beverages. For example, you might’ve heard that some people tend to get more aggressive on darker beverages such as dark rum or whiskey. This is one explanation. For instance, isopropyl alcohol is psychoactive in its own right. It has sedative effects of its own, is roughly twice as toxic as ethanol IIRC, and tends to only affect the GABA receptors rather than a myriad of receptors like ethanol does. In addition, its metabolite acetone is also psychoactive. Edit: [Here’s a nice source]( URL_0 ) that runs through the most common fusel alcohols.",
"While what others say about the chemical composition of drinks being slightly different is true, this isn't actually a very significant effect. Your main intuition that the body doesn't really know the difference anyway is correct. But people interpret situations differently and behave differently on different occasions - even without alcohol. For example,e when getting drunk on beer it was likely just a relaxed fun evening with some close friends, this will influence your behaviour when drunk much more than the type of alcohol. When people get drunk on tequila on the other hand, they probably set out to party hard and get drunk -leading to wildly different behaviour. It isn't so much the type of alcohol we drink but what mood we were in before getting drunk. It influences our choice of drink as well as our behavior when drunk.",
"The amount of water and sugar (and other stuff) will change how it effects you. For example I was drinking whiskey one night and realised I was getting thirsty because I wasn't getting enough water. And yeah you will feel different if you get a big dose of alcohol at once to if you drank it slower.",
"The biggest impact on what \"type\" of drunk you get is your mood, and generally speaking different types of alcohol are often consumed under different circumstances. It's also important to remember that all of the stories you've heard about \"different kinds of drunk\" are entirely anecdotal. Sure, varying concentrations will determine *how quickly* you get drunk, along with whether or not you drink on an empty stomach, drink quickly vs. more slowly, and so on, but ultimately, a BAC of 0.2 is a BAC of 0.2, regardless of the source. Shots and mixed drinks are typically consumed quickly in a more lively, more upbeat (think 'party') atmosphere, so people that get drunk in those atmospheres are typically in a mood to be wild, excitable, or spontaneous. As a result, people often describe shots as leading to a wild kind of drunk. Wine, by comparison, is more often consumed in a relaxed setting, so it's often described by people as being a more soothing, relaxed, or 'calming' drunkedness, often associated with feeling sluggish or sleepy. Beer tends to vary, since it's a broader drink that is consumed at both ends of the extremes I gave above. People that drink beer at sporting events or parties will describe getting wild and crazy when they get drunk, while people that drink it with a meal or while relaxing at TV will often describe it helping the relax or unwind. TL;DR - The \"kind of drunk\" you get from alcohol has to do with the mood and environment in which you consume it rather than the source of the alcohol itself.",
"Generally there is no difference just because it's a different drink. Now there are exceptions if you're drink contains another drug in it (like copious amounts of caffiene) but if we're just talking alchohol, it's the same. What can be different, is the correlation of when and how you drink those different drinks. As an example, when I drink beer, it's ussually slow and steady. A single \"Tall Boy\" can will ussually last me 2 hours or so and I normally just have one. The result, not much if any buzz. That said, if I've had a rough day and sit back to some nice whiskey, It's ussually a 3-4 ounce pour and will get sipped over an hour and I might have two or in some rare cases three drinks. There's a big difference there in terms of the rate of consumption, the total amount consumed and my mood when consuming it. Turn to something like Tequilla, and it's something I'm going to ussually drink once a year, at a special occasion, with friends when we are already pumped up. It's going down as shots and ussually far too many of them. Again, rate of consumption, total consumption and the mood I'm already in is different.",
"ELI5: it’s make-believe to think different booze makes you feel differently. It’s an effect of your mind’s creation. Ethanol is ethanol, end of story. If there’s other forms of alcohol in your drink, then you’d be very sick, dead, or there wouldn’t be enough to tell a difference. Man this is a bad ELI5. So many responses that completely nonsense. OP: don’t listen to any of these folks unless they have a source. Like this: URL_0 Results: **Findings suggested that individuals may expect different effects from consuming different types of alcoholic beverages.** Participants expressed more agreement that wine would have relaxation effects and rated this effect more positively. Participants expressed more disagreement that beer or shots would have effects on sexuality and rated sexuality effects more positively for wine. Participants reported less agreement that wine would have impairing effects, as well as more disagreement that wine would affect risk, aggression, and self-perception. Impairing effects of wine were also viewed less negatively than other condition beverages. Conclusions: Findings suggest that individuals may hold different beliefs about the effects of wine, compared with beer and shots of distilled spirits. Research and interventions targeting general alcohol expectancies may miss important between-beverage differences in **perceived effects and subjective evaluations regarding alcohol’s effects.**",
"There are other plant derived active substances in beer, wine and every other beverage. Alcohol is the same but theres different amount of it.",
"No. There's no difference between alcohols. Like whiskey makes you angry or tequila makes you happy. Garbage. The ratio of water to etoh makes a difference in how fast you get drunk. That's about it. If you start mixing substances like vodka and redbull, then you can get some different reactions. If you drink a 5th of tequila or a 5th of whiskey, or a 5th of vodka it's all the same assuming they're the same proof. Anything anyone says different is anecdotal and there would be different circumstances.",
"Also, your body has a set-point metabolism for breaking down alcohol, so drinking coffee, sleeping, etc... doesn't make you recover any faster (though sleeping does pass the time to get you closer).",
"In this case, people are associating certain drinks with the ease they can put them away. People getting \"fucked up\" on tequila, etc. are really just saying \"I like the taste of this mixed drink, and the social situation where I drink it, so I tend to drink more, faster\""
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o11a61 | How is the value of money determined? | Economics | explainlikeimfive | {
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"The value of pretty much anything comes down to \"what would someone give me for this\". People will give up pretty much anything for the right amount of the right kind of money and that gives it value."
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o129h2 | Why is the amount of water required for producing something (food, clothes, etc..) used as a measure of sustainability? | I get that if it’s produced somewhere where water is scarce it’s important not to waste it but where I live freshwater is incredibly abundant why does it still matter? | Other | explainlikeimfive | {
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"Industrial production tends to use massive amounts of ressources. If not well managed, even the most abundant of ressources can become depleted given enough time. Another reason is that industrial processes often cause pollution and if not managed (often mandated by law), polluted water could be dumped back into the environment. The water may not be reusable without (heavy) treatment, therefore not sustainable for the long term. Another reason could be that a big corporation could set up shop in an area, exploit the ressources without caring about the environment. Once the ressource is depleted or the market has dried up, the corporation leaves. The local inhabitants are now left economically deprived in a degraded environment which could have been better preserved when the moneyed corporation still had an interest in the area.",
"Two things. There's a good chance that a lot of what you buy (especially clothes) is imported from somewhere else. The place where those clothes are made might not have an abundance of water. Also, it still takes energy to move the water around the country. Or, if the water goes back into the water system, it needs to be processed to allow it to be reused, which also takes energy.",
"Only three percent of Earth’s water is drinkable, only one percent is readily available without digging wells into aquifers. It takes millions of years for an aquifer to get filled/refilled so once drained, that’s effectively it for millions of years.",
"Fresh water is the one thing that people absolutely need in order to survive. I'm glad it's not a problem where you live, but globally, water scarcity is an actual and increasing concern. In any case, can you think of a better measure? And why would it be ok to \"waste\" any resource, no matter how plentiful it appears? That's what led us to our present position.",
"There is a concept named \"tragedy of the commons\" . It is that when people have unlimited use and unlimited access to a vast but finite resource, that people will use that resource until it vanish. So it's important to clarify how much resources are been used to make something because we need to now how much of it was lost and how much need to be returned.",
"Fresh water is just one measure of sustainability. I’ve usually heard it talked about in reference to the area where things are produced. Like almond production in California. If water is abundant where you live that doesn’t make almond production in California sustainable. If production is appropriate for the local resources it is not an issue. It’s sustainable. Ultimately sustainability can be considered about every resource used to produce every product. Building houses requires lumber. Lumber forests are managed on decades long timescales. Recently some things occurred that shifted that supply and lumber prices shot up. One thing that happened was that insects were killing trees and the tree harvest shifted a little each year. What they thought was sustainable is not and the market changed dramatically seemingly overnight. The reason water often comes up is because everyone needs water. Many different industries as well as people. If water is not managed sustainably government need to start making choices between food production, industrial production, human drinking water, river ecosystems. Rivers can be very long so choices in one region can effect people/jobs/wildlife hundreds of miles away, possibly in different countries. Ultimately it is better to manage thing sustainably than to try to mitigate the damage from unsustainable practices. Also things change so what is sustainable today may not be tomorrow. So it’s very dynamic."
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o12wz3 | If having a toothbrush with harder bristles can damage your teeth, why can a dentist work on your teeth with metal without damaging anything? | Just came back from the dentist and I couldn't help but feel like she was being way to harsh, even tough she probably knew what she was doing. But how does it work? Do they use a special kind of metal or anything? | Biology | explainlikeimfive | {
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"Same reason why 115 decibels infrequently won’t make you deaf, but 115 decibels constantly will.",
"Years of training and experience, and proper use of the tools. They aren't aggressively scrubbing your teeth with the various picks and such. They are carefully and specifically targeting the hard build up on your teeth and picking it off. Think of it like a paint scraper. Used properly, by a person who knows how, it can remove paint from an object without damaging the object. Used too often or incorrectly, it can definitely damage the object",
"pretty much a case of \"The only difference between a surgeon and butcher is precision.\" a dentist's tool set is nothing unique, they have the training to minimize any collateral damage they could so.",
"If you saw the dentist twice a day every day, then their work probably would start to cause damage. Anything you do every day will always have more of an effect than something done once in a while (off topic, but that’s why with fitness, doing a little bit every day is better for you than only going to the gym once in a while but doing a lot). Plus as others have said, although it may feel jarring and uncomfortable, dentists train for years to be able to work on your teeth without damaging them. They use harsher tools, but with great skill. Meanwhile, even children can use a toothbrush - it’s less damaging, but requires less skill.",
"Harder bristles are specially damaging to your gums which is highly overlooked. Softer options are meant to be gentler on them gums. This is why Gum specialist will advise softer bristles while regular dentist don't really care. (Harder bristles is usually associated with removing more gunk and pieces of food that could later become tartar but that mindset ignores the proper use of floss).",
"The factor here is TIME. Over time, hard bristles will cause damage. A dentist uses metal for a few minutes once or twice a year.",
"We’re more concerned about your gums that the hard bristles can damage. Some people have thin gingiva (thin biotype) that are more susceptible to recession. If you use a hard toothbrush, you can drastically expedite the gingival recession. Now your saliva is normally a neutral pH. Whenever you eat, bacteria in your mouth eats too and releases acid, dropping your pH to 5 or lower depending on what you just had. Your teeth are ions being held together by an ionic bond, kind of like salt. Salt can be grainy or it can be in a cube. You teeth are bonded together super strong (enamel is the strongest material in your body!) You shouldn’t brush you teeth immediately after you eat because your pH is still acidic and will erode your teeth. If you add something abrasive like a hard bristle toothbrush, it will erode it even faster. Some toothpastes, like charcoal toothpaste, is also horrible for your teeth due to the abrasiveness. When dentists scale your teeth, we are only scaling the tartar on your teeth. Intact enamel won’t be damaged."
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o12xwb | How did the Nazis know who was a Jew and who wasn’t? | Other | explainlikeimfive | {
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"Nazis took a look at family history, and iirc, Jews until Nazism took over weren't the most shy about expressing their beliefs",
"IBM helped a lot. There were no computer databases in the 1930s, but punch cards and IBM tabulation machines were a thing already and that was a big way o keep track of people's identities. In 1933 Germany had a Census where people were people's religion was noted, the result together with other government registries was later used to help implement the holocaust. There was also simply the fact that people knew who was a Jew. People knew if their neighbors were Jewish and would tell authorities that in many cases. Since the business and properties of Jews were confiscated there were a large number of people who stood to gain from selling out the Jews in their midst. It went to the point where children were tasked with creating family trees in school to prove that they were Aryan. If you had a grandfather who was Jewish that was much easier to cover up than being an actual practicing Jew yourself. OF course in the chaos of the war some people got away with claiming to be someone else from somewhere else with no way for authorities to check up on their claims. If you looked Aryan enough and claimed to be German from a place where there was currently no way to check up on your claims you had a chance to survive. Of course for males the fact that your missing foreskin would betray you if anyone ever saw you naked was another big problem. Still a few managed to survive to the end of the war without being found, but too many were damned by paperwork, betrayed by their neighbors or found it in some other way.",
"Similarly to the red scare and the Salem Witch Trials, some people were forced to out their Jewish neighbors, friends, or family in order to avoid punishment.",
"The Germanic states were very good at record keeping in the 19th and early 20th centuries, so it was pretty easy to go through family records and find out ancestry. Anyone trying to hide were often turned in by friends or neighbors. And some people, like my friend's grandmother, weren't even Jewish, they just had \"Jewish-sounding\" names and were assumed to be.",
"Family history and informants mostly, but with males they sometimes made them drop trou to see if they were circumcised"
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o13bcv | why is pi infinite and how come we can still use it to calculate something finite (like the area of a circle)? | Edit: Thanks for all the answers. I guess this question is solved. Pi is not an infinite number, but the number we use for calculations is an infinitely close approximation. Just like 1/3=0.3 We can use less digits in calculations as we don’t need to be *that* accurate. | Mathematics | explainlikeimfive | {
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"Pi isn't infinite. It's decimal portion is infinitely precise. As for how we can calculate it, we have figured out formula for Pi. For instance, one of them is that `π/4=1-⅓+⅕-⅐+⅑...`. you can just keep calculating more terms and getting closer and closer to the actual value for Pi.",
"There are lots of infinitely precise numbers. 1/3 is infinite, 0.333333... forever. It’s still just 1/3 though, and you can do math with it. Pi is the same, Circumference/Diameter. The number you get has an infinite number of non-repeating decimal places, but how accurate do you really need to be? You didn’t measure the circle down to one quadrillionth of an inch, so you don’t need to include the 20th digit of Pi when you’re doing the math. 3.1415 is “good enough” for most purposes. Maybe add a few more digits if you’re doing actual rocket science.",
"pi is not an infinite value, we know exactly how to calculate it(one of the ways is the result of diving a circle's perimeter by its diameter), the issue is that actual value is infinitely precise so more decimals places just make it so you are using a closer approximation of the true value and there is very lil usability on that instead of treating it as a constant or using a less precise approximation.",
"Just because pi is infinitely long doesn't make it infinitely big. There are lots of infinite numbers that do the same thing. (Technically, it's all numbers, but I'll skip over how the number 2 is infinitely long.) For example, an infinite number of threes after the decimal is one third. Not \"about one third\" but exactly one third. We can't calculate with an infinite amount of data though, so we approximate the number to enough places that we get an accurate enough answer. If only use 80 digits of pi, I can work out the circumference of a circle the size of the observable universe to plus or minus the size of a proton."
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o13cep | How does toothpaste get the pattern in there? | Surely it all mixes up when inside the tube? | Technology | explainlikeimfive | {
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"Because Toothpaste is an interesting fluid. Inside the tube when you're not squeezing it, the toothpaste stays in it's solid colour blocks. When you squeeze the tube, the shear force you apply causes the fluid to flow out of the nozzle. The toothpaste has something known as 'thixotropic rheology'. This means that when you remove the pressure, (i.e. once it is on your toothbrush), the stripes regain their thickness, enabling the product to look like a three-striped cylinder."
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o13cog | If flat earthers exist, why do they think the government is hiding that information from them? | Earth Science | explainlikeimfive | {
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"Some ex-conspiracists say they had mental health problems involvoing paranoia while believing in such things. I think some of these people just believe that everyone and everything is against them and means them harm. Also conspiracies are easier to understand than real life and they tend to back each other claims up."
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o153io | What would happen if someone got multiple different flu shots? | Biology | explainlikeimfive | {
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"You actually do get multiple different flu vaccines. The normal flu vaccine you get each year actually contains the vaccines for, generally, 3 different strains of the Flu. They are the ones Virologists think are most likely to appear in your area that flu season. So to answer your question, really nothing special. The flu virus in the vaccine is not harmful to your body, and so your body has an easy time building up the necessary antibodies for each flu strain.",
"Generally speaking a second flu shot carries with it an increased risk of adverse reactions, and doesn't really do a whole lot to boost your chance of not getting the flu. So it isn't that getting a second one *will* cause something bad to happen, it's just that a second one really doesn't do anything positive for you....so generally speaking, it's more \"harm\" than good. (that \"harm\" being just a higher chance of fever-ish symptoms) So it's generally just \"recommended one dose\" rather than a warning of \"do **not** get a second dose\"."
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o15jdg | why the Mayan calendar was such a big deal? | Other | explainlikeimfive | {
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"Like many ancient cultures, the Mayans had a lot of free time at night to stare at the sky and track the motion of the stars and planets. They were quite good at this, and they developed multiple highly accurate calendars for government and religious purposes. One of these calendars - the Mayan “Long Count” Calendar - uses a complicated set of numerical systems to count from the “beginning of this creation” up to “the age of the end of the last creation” i.e. it lasts as long as the last universe did. This date it ends on is December 20th, 2012. Now the Mayans themselves made no specific predictions about this date, and had calculated out astronomical phenomena and predictions for dates beyond it. As far as we can tell, they did not expect anything of great significance to occur, beyond noting the current universe is now older than the previous one. That didn’t stop people from going nuts though, and there was a lot of idle speculation (although I doubt may truly believed it) that the Mayans had predicted the end of the world.",
"It was a bit like if you picked up a paper calendar designed to have one page per month for the next hundred years, noticed that it ended on December 31st of 2121, and decided that this meant that the calendar maker knew this was when the world was going to end. The Mayan calendar ended there for whatever reason, but the leap from \"this is when the Mayan calendar ends\" to \"the Mayans knew the world would end on this date hundreds of years in the future from when they made this calendar\" was a huge one unsupported by any actual evidence. Sure enough, when \"doomsday\" came, we just flipped to a new calendar page. Nothing more. Of course, conspiracy theorists don't need actual evidence so they kept repeating theories about how this was going to be some horrible doomsday. Like all apocalypse/doomsday conspiracy theories, though, it was proven wrong and didn't happen.",
"It wasn't. A bunch of conspiracy weirdos and doomsdayers latched onto a weird interpretation of the Mayan calendar to declare that the world was going to end in 2012. It turned into a bit of a meme, a lot of crazy people panicked, and then nothing happened.",
"It's a big deal because the Maya had excellent astronomical records and technology. Their civilization was advanced enough to make solid observations, and their writing was sophisticated enough to facilitate the continuance of their civilization for centuries. They also developed mathematics, architecture, and farming technologies that helped to keep them successful. This is why it was (is) important in the span of human civilization. The calendar, like most calendars, was also steeped in Maya notions of their own place in the universe and the structure of the universe itself. Stripped of relevant context, the bones of those notions became fodder for keyboard warriors and conspiracy nuts, and we got the 2012 nonsense."
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o15ok7 | how do flameless ration heaters work? | I was watching a few MRE videos and I always saw that there are flameless ration heaters featured for heating up some of the meals. I never understood it can heat stuff up with only water, and the fact that I’m autistic doesn’t help either. Can someone give me a simple explanation? | Chemistry | explainlikeimfive | {
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"It works by creating a chemical reaction when the metal magnesium comes in contact with water much in the way that a hand/boot warmer creates heat by having an iron isotope react with the oxygen in the air to create heat. When two chemicals interact you have a chemical reaction that can range from them repelling each other (oil and water) all the way to a rapid/quick release of energy (how things like TNT cause an explosion). One of the main byproducts of chemical reactions is lost energy in the form of heat. The MRE flameless ration heater has a chunk of magnesium (MG) in it and when you add water (H2O) you end up with MG(OH)2 + H2 + heat."
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o15xow | If my brain is able to remember thousands of faces and telling them apart with such accuracy, why is it so hard to describe a face without seeing it? | Biology | explainlikeimfive | {
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"Memory recall, vocalization, and human facial recognition all occur in 3 different areas of the brain. From an evolutionary perspective, each area developed for different reasons and at different times... The default connections between them can also be relatively weak without constant use or practice. So recall of a face and a connection to a memory of a name is a pathway that is used consistently throughout everyone's life. In internet terms, it's one of the pathways that may have started out as an 8-baud modem connection, but has been constantly upgraded through DSL, Cable, and Fiber. Alternatively, recalling a face and actually *describing* a person is something that people tend to do a small handful of times at best. The lack of use tends to ensure that connection doesn't really get upgraded past our dial-up stage. This is a connection that stays relatively undeveloped. The brain is pretty amazing and flexible and with consistent practice, most people could become much better at this (as well as many other tasks.) This is the exact reason why practice is so darn important to become a professional at nearly anything. Similarly, things that aren't practiced tend to remain very difficult.",
"Recognizing a face is about pattern recognition. When you see the letters in this sentence, you can tell the t from the g at a glance, right? How would you verbalize what you're seeing? You would need at least one or two imprecise sentences for each letter to try and convey what your eye can take in immediately, and even then, different people will conjure different images based on your wording. Language did not evolve to precisely convey pattern recognition. That's not its purpose, and when asked to do it, it is a clumsy instrument. We have created shorthands \"Roman Nose, Widow's Peak, High Cheekbones, Full Lips, Deepset Eyes, Thick Neck, etc.\" that don't really paint the picture so much as narrow it down. That's about as much work as language can do to communicate the fine details pattern recognition gives us without an actual verbal label.",
"Fun fact, some people can't even imagine the abstract images you got going. Based on the Reddit posts I come across, it's fairly common for people to reach adulthood without realizing other people can in fact visualize things and \"see\" them in their head. If you can't see things in your head, it's called aphantasia.",
"Words attempt to publicize the private (mind), among other things, but they're not very good at it. The thoughts, feelings, perceptions, memories, etc. are always richer and more vibrant and \"spicier\" than descriptive attempts to capture them. I'm not sure that this a face thing any more than it's a sunset thing, an excellent-lay thing, a powerful-trip thing, etc. Language is just severely lacking, at best.",
"I think you have answered the question yourself: \"I lack the proper words to describe it\". Picture something blue. Now, tell me what that color is. Most people will describe it by comparing it to something most people are familiar with. You might say \"It's like the sky, but a little darker.\" That doesn't really precisely tell me what color you see. Now suppose that we both have Pantone color samples close at hand. Now you can say \"It's Process Blue C\", and I will know exactly what you mean. Pantone gives us a huge vocabulary (more words) to describe colors. So it is with faces. You may not know the difference between a hook nose, a button nose, straight shape or convex, raised base or lowered, etc. But that doesn't mean that language doesn't exist. You just don't have it.",
"If you can remember it that accurately, it's probably you are lacking in the vocabulary. If you took sometime to study different face shapes, eye shapes etc and learn the terminology you would be able to better describe a face."
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o16cz1 | How did the first weight get weight to know how much it weights? | Mathematics | explainlikeimfive | {
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"It more-or-less went, \"We need to define a weight, so we take this object and say that it defines the unit and calibrate our scales to match.\" In the case of the kilogram, it was defined as \"the mass of one liter of water,\" and so no matter how massive one kilogram of water actually was, that mass set the definition.",
"Weights are defined in relation to something else. Before the modern era you’d have a set of standardized weights selected by the leadership. A pound is equal to this rock, specifically. If you want to measure pounds elsewhere, you will need to have a weight made that’s exactly the same as this rock. It’s not super accurate because you eventually have copies of copies of copies of the standard floating around and people dicking with the scales, but it’s good enough for collecting taxes at the far ends of your realm. These days the basic concept really hasn’t changed much, but we’ve now defined the standard as some fundamental measurement of the universe so that it doesn’t change slightly every time you measure it.",
"To put it more simply, you start out with something use that as a unit. Let's say you pick up a rock. This becomes the new Rock standard. Everything can be related back to how many Rocks or parts of a Rock it weighs. If you need a second Rock, you can sand down another rock until it weighs the same as the first Rock. Eventually people got better at measuring things so they kept changing how to define what a rock was.",
"It's not that we need to figure out how much the first weight weighed. It was that we defined some weight to be that unit. Until very recently, there was something called the Standard Kilogram. This was a piece that was held at the International Bureau of Weights and Measures in France, and was the source of truth for what a kilogram was. Other first-level units were created by measuring them against this, and then others were created measuring against the first level units, and so on, until finally the bathroom scale you bought for $9 was calibrated against tools that can have their calibration data charted all the way back to that standard kilogram."
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o16dlk | how is passing out different from falling asleep and vice/versa | Biology | explainlikeimfive | {
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"Passing out is due to low brain activity. When you sleep the brain is active in various ways and in some stages it's more active than when you are awake. Since you are mainly unconscious for both people think they must be similar but they are very different states of the brain."
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o16xop | how does your car radio know to send sound out of specific speakers? | I'm thinking of when songs are coming from only the left side, or right side, or maybe the drums sound like they're behind you. Not all stereos are set up for multiple speakers, but the same sounds come out of them. | Technology | explainlikeimfive | {
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"Left vs Right is encoded in the FM radio signal, or music player source. Things like the drums are also that sort of an imaging evvect, plus better bass response from larger speakers in the rear.",
"Already some good answers here. I'll add that some radios (and especially when you get into aftermarket territory or optional name-brand factory radios) use bandpass filters to target certain speakers like sending bass to woofers intended to provide some boom-boom or sending high pitches to tweeters.",
"When you tune to a radio station, such as FM 99.9, you might think that radio station is exactly at 99.9 MHz. In actuality, it's a range of frequencies around that point (which is why the next channel isn't for 0.2 MHz above or below). In that frequency range, there are multiple signals being sent. You can get a left channel sound, a right channel sound, and even quadraphonic sound.",
"* Most music we hear is in a format called \"stereo\", which means there are two channels of audio, called \"left\" and \"right\". * When a radio station broadcasts a \"stereo\" signal it's actually broadcasting two signals at the same time. * And that means the radio is receiving two signals at the same time. * So it just plays the left signal on the left speakers and the right signal on the right speakers."
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o1764j | Why do inconsistent computer glitches happen? | I understand "stable" glitches. By stable, I mean glitches that occur whenever you put in an unexpected input. For instance, a programmer may not have expected users to enter "0" into a field. So **every time** I enter 0, the program glitches. Or **every time** XYZ situation happens, a glitch occurs. But I don't understand unstable glitches. That is, glitches that appear to happen randomly even if you perfectly replicate the scenario. Why do these happen? I wrote a simple autohotkey script for example: > +Up::{Volume_Up} It seems like 90% of the time it works, and 10% of the time it doesn't. As a test, I used the function in as controlled of an environment as I could do. I am not opening new programs or doing anything new. I disconnected from the internet, closed all backgroun processes, etc. The only thing that changes is the time. I just sit on my Desktop changing the volume, and sometimes it randomly doesn't work. That wouldn't be due to inconsistency between the layers, since nothing is changing except me pushing the volume up button. To clarify, I am not looking for help troubleshooting my script. I am just curious about the general reasons for unstable glitches. I mean, code is a logical flow of instructions, so if you replicate the glitch inputs, the glitch should occur again. But some glitches occur once and can never be replicated. Why? | Technology | explainlikeimfive | {
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"Most things about computers are deterministic, meaning they're predictable (input A results in output B). However, there are two reasons we observe instability: 1. Most *observed* instability is *actually* deterministic. That is, if you perfectly recreate the conditions, the glitch will occur in exactly the same way. However, computers are very very complex and it's very difficult for a human to understand all of the variables and interactions involved, so we just throw our hands up and call it a glitch even though everything happened the way it was \"supposed\" to (at least, according to the computer). Basically, the complexity exceeded our ability to comprehend it, even though it was operating \"perfectly\". 2. Rarely, instability is due to \"random\" factors. A neutrino or ionizing radiation hitting juuust the right place inside a chip to flip a bit, or malfunctions due to overheating or a bad component (such as a capacitor drying up) causing signals to go outside their intended range. These are pretty rare, because a lot of storage and communications inside the computer are protected with error detection and error correction algorithms, so that even a wrong bit in RAM or traveling across the bus can be corrected by clever hardware and software.",
"Unpredictable software failures are often caused by one of several things: 1 - Memory use after free. The program puts important information in a block of memory, then later (because of a bug) tells the operating system \"I'm done with this memory, feel free to put something else there\". But since the program still thinks that memory is for the original purpose, finds incorrect data there. If it takes a long time before some other data it put there, things might work for quite some time. But once something else is stored there, you might have your glitch. 2 - Memory smasher. The software wants to write to memory, but the memory address it tries to use is totally wrong (because of a bug). If the random memory it's writing too is rarely used, then things will appear to work, but if it accidentally overwrites something important, there's your glitch. Sometimes, the glitch can happen minutes or hours later. 3 - Race. Computers can do multiple things at the same time. Software is **supposed** to use a *lock* to say \"Nobody touch this, I'm working here\". But, if that step is skipped, two parts of the program can. modify the same data at once and leave it in an inconsistent state. The chances of two parts of the program changing critical data at exactly the same time are sometimes small, so this glitch feels occasional and random. \\*edit to a word."
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o17e7b | How do humans come up with words to describe things? How did we get such a vast number of languages? | Biology | explainlikeimfive | {
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"At some point humans gained the ability to make noises (long before we were humans). Over time, the complexity of noise we could create increased, and became what we now call speech. It's thought that the first words we ever gained were derived from onomatopoeia - the brain has an innate sense of shape when it comes to sounds, like the word \"bone\" sounds very round and smooth because it has a long open O sound. It's likely that words originated in making these kinds of onomatopoeic sounds to describe things to each other. If i wanted you to pass me that bone, I might point at it and gesture towards myself and make a sound that sounded kinda.. boney. If I did that enough then you would start to associate the sound I made with the object of a bone, and then if I said that sound without pointing at a bone, you would still know I was talking about a bone. Over time, the complexity of social interactions and the things humans needed to interact with and talk about increased, creating a language. Although I also want to make it clear that there was no point where the first word was invented like this. In reality, language would have been a slow evolution from other communicative sounds like \"the sound we all know we make when there's a snake about that makes us avoid the snake\". Language is also a bit subjective. The way I speak is at the very least slightly different to the way you speak, but probably quite a lot different. For example, assuming you're American, you may pronounce the rhotic R in words like car, which isn't something I do because I speak one of the English dialects that doesn't do that. This means that technically, your \"car\" and my \"car\" are slightly different words that just sound similar enough that we both understand each other when we say them. This extends to hearing too - I *hear* words slightly different to the way you do. As babies, our brains are very malleable. It can't distinguish between sounds it hears, it just hears noise. One of the first things it must do is learn to identify sounds, and in language, it does this by categorising groups of sounds as all being the same sound. Take for example the case of Japanese people and the letters R and L. The sounds that correlate with Rs and Ls actually exist on a spectrum from very R at one end to very L at the other. People who grow up speaking English will sort sounds in this spectrum into two categories, R and L, by splitting the spectrum down the middle. People who grow up speaking Japanese however will sort all of these sounds into just one category, because the Japanese language doesn't possess both letters (the single sound it possesses is typically transliterated as R, but in reality it's kind of halfway between R and L on average) That means for Japanese people, R and L are the same sound, and they can't actually hear the difference between them, because the brain collects all of those sounds and just puts them all in the RL bucket. These slight differences in the ways people speak and hear language produces gradual change over time. For example, in many English dialects, the words \"your\" and \"you're\" used to be pronounced differently, but many young people hear and say them exactly the same, with no pronunciation difference, because slight differences in the way their brains process language makes them sound the same. This is why some people think that it doesn't matter which you use. To them, they're genuinely the same word. This explains why there are so many different languages today: As people spread out across the world, they began to settle down as agricultural societies. This shift to a sedentary lifestyle meant they no longer regularly met and interacted with other people. Small differences between how one group of people and another experience language are allowed to accumulate and become exaggerated over time because of this, until eventually people in France are talking a very different language to people in Italy, despite both originally being the same language (Roman Latin). Because these changes are gradual, you can trace them back through time too: Some languages share close common ancestors, like French and Italian (tracing back to Latin), others share more distant ones, like French and German (who were last the same language long before the Roman empire as some kind of pre-European thing). These relationships can be traced back to a language called proto-Indo-European, a language that is now extinct, but that is the common ancestor of all European, Iranian and Indian languages. That is, all European, Iranian and Indian languages throughout history used to be one language spoken by one group of humans, who spread out, and as they spread out their languages changed very gradually. It's also hypothesised that there is one language from which all languages are descended, but language has changed so much over the hundreds of thousands of years we've been speaking them that we have very little idea what it sounded like.",
"Humans literally just make up words. If you use it enough, it spreads, other people begin using it, it becomes accepted, and eventually finds its way into a dictionary and becomes \"official\". The vast number of languages mostly comes down to humans having relatively small social circles for most of history. You might only speak with people from your village, your province, your island, your country. Every culture figured it out on their own, which is why you see such interesting variations."
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o17gv1 | Why do drunk people, instantly sober up when put in a stressful situation? | Biology | explainlikeimfive | {
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"They don’t. Their reaction times and processing ability is still impaired. They’re just seriously trying instead of not caring.",
"It doesn’t, adrenaline in your system might “perk you up” but this isn’t much different then being sleep deprived and slamming a dozen Red Bull’s. Sure for a short time you feel more alert and focused, but you are still very much impaired.",
"Adrenaline sir. So it kinda takes a very stressful situation like a fight or an emergency to pump ur body full of it.",
"Why do I see this question on Eli5 at least once a week?"
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o18ik4 | How do CDs and DVDs work? | Technology | explainlikeimfive | {
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"A laser shoots at the shiny side of the disc and based on how it is reflected back, that part of the disk is read as a \"1\" or a \"0\". There are two main ways of encoding information on the disk. The first is to actually press little indentations onto this disk. This is permanent but reliable. The second is to have a special kind of dye. You can \"burn\" information into this dye with the laser, allowing you to write and re-write information to do the disk."
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o19crp | if I do 100 pushups in a day spread out do I benefit more or less than if I do 100 pushups in a shorter time span like about 5 minutes. | Biology | explainlikeimfive | {
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"It depends on a couple factors. 1. What is your goal? Do you want to be able to do as many pushup in a row as you can? Do you want to be stronger? Do you want to build muscle? 2. How many pushups can you do in a set?",
"Benefit is the wrong term to use. If you force you muscles to lift your bodyweight at angle (push up) 100 times in five minutes you will stress the muscles way more and thus grow more muscle in the torso and and arms (bicep, tricep, pectoral etc ). If you do 5 push ups every 20 mins throughout the day, you won't stress the muscles, but will keep a higher heart rate and thus gain a cardio improvement and gain lean muscle in the torso in the process."
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o1a8kj | -Why is it “better” to pay a mortgage than to buy a home up front? | Is there any truth to this in modern day economics? Was this something that made sense in the past? I don’t get why paying interest to carry a mortgage is better than paying in full if you can afford and not losing money to interest payments. | Economics | explainlikeimfive | {
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"Mortgage interest rates are low, especially now, they are somewhere around 2-3%. Avg yearly returns on investment portfolios is around 7-8%. So, put your extra money in investments instead of at the mortgage and you'll come out ahead.",
"The idea being that interest rates are super low and if you had, say, $300k in cash to buy a home you’d be better off putting down $30k and taking out a loan at 3% or whatever and putting the other $270k in the market where it could earn way over 3%. It should be said, though, that this doesn’t take the element of risk into account and … you have to actually put the money in the market. A lot of people take the extra money and suddenly they’ve bought a new car, and put in a pool, and bought new furniture for the entire house, etc. etc. In the past when interest rates were at 7-15% it made no sense to do this. You were better off buying a house in cash. But now with interest rates as low as they are? It’s a different story.",
"I recently faced this and decided to pay off my mortgage. If you have no debt, there's little that can hurt you. You may decide that you'd rather get more returns on investments, but that can backfire during a recession.",
"These options are not equivalent. You're pretending it's like \"turn left\" vs \"turn right\", when it's really \"turn left\" vs \"fly up\". Paying up front requires a huge amount of cash for which you have no lost opportunity cost. That's not common in reality. In reality, most people who have a house worth of money don't have it under their mattress, they have it invested in some money-making thing. A mortgage with a 3% interest rate is more desirable when you can invest your capital at a 4% interest rate in some other vehicle."
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o1auju | How do Robbins (and other birds) know where the worms are in the ground? | Biology | explainlikeimfive | {
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"They can hear the grubs and worms moving in the ground. If you ever see them hopping around you'll notice they tilt their heads back and forth trying to triangulate the exact position to strike the ground.."
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o1aw8h | When an animal can "see" more colors then humans can, is the difference just in the cones, or is there also a difference in brain structure/optic nerve to be able to conceptualize the new color? | Biology | explainlikeimfive | {
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"Good question. As it turns out, in humans there does not appear to be specific neural circuit patterns dedicated to specific colors and this leads some researchers to entertain the idea that while colors tend to evoke the same emotions in people, one person's blue might be another person's yellow. I disagree with this but that is a different topic. Anyway the interesting thing is humans can see in to the true ultraviolet range when the lens is removed and/or replaced with a synthetic one made of a material that does not block UV, and some humans are tetrachromats, meaning they have three versions of one of the color receptors that are different enough from each other to allow them to perceive more colors than normal. These people can see colors for which we have no name and for which people with normal vision have no concept of. So it appears the brain has the capacity to process wavelengths beyond that which our eyes can detect but there probably is some species to species limitation.",
"You don't really need different wiring (just more of the same to process the extra information). You just need the receptors capable of registering the different wavelenght."
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o1ax4s | How is it possible that we can control our breathing consciously and subconsciously while we leave the rest of our internal bodily functions to our...you know...our own body? | Like...how did we learn to breathe on our own when we first came out of our mother's womb (which was basically an nutrient rich aquatic pod). | Biology | explainlikeimfive | {
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"You automatically dump the fluid in your lungs and start breathing as soon as you’re born. This is a reflexive behavior hard-wired into a baby’s brain. We have active control over breathing because it’s sometimes necessary to pause the process - think swimming or walking through a cloud of smoke. We’ve also tied our breathing to our vocalizing (you must exhale to speak) so fine control over the system is necessary for any animal that’s trying to project sound using their lungs.",
"Our brains don't trust us to keep ourselves alive. Most animal's brains don't actually. That's why it's hard wired into our brains how to perform voluntary activities apart from the subconscious ones, AND why even when we do things like breathing manually, there's still an emergency switch that usually over ides your control. If you try to hold your breath for as long as you can, eventually your body will just force you to breathe."
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o1b7vm | Why do some babies not like their mother's milk? Also why do we use a cow's milk as a substitute? | Biology | explainlikeimfive | {
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"What you eat goes into breasts milk. So eat something that does not taste good to for the baby or say just lactose intolerance and baby does not like. Can also explain crying for no apparent reason. Cows milk is NOT a substitute for breasts milk. Noting is really. There are some things you only get via breasts milk. Some things are ok, like baby formula.",
"Some babies cannot tolerate their mother's milk, I don't think it's so much that they don't like it (like taste). Some have to use a soy formula to get away from regular milk, my sister had to use goat's milk because she had severe stomach issues. COWS milk is NEVER used as a substitute for babies. It doesn't provide the right nutrition."
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o1buqx | Why are anal muscles involved whenever one sneezes ? | Biology | explainlikeimfive | {
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"Hahahaha there's no delicate way to put this. It's to prevent you from forcefully shitting yourself. Humans evolved over time with certain traits that are suited for social groups. Groups that just pooped where they ate and lived died off. Somewhere along the line we developed a trait to clench up when we sneeze, that provided an advantage, that group bred more successful offspring, and eventually the trait became prominent in the species.",
"this is kinda funny as there is no way to say this otherwise: its literally to keep you from crapping yourself when you sneeze. Sneezing involves a fairly violent set of contractions in the core that if the anal muscles didn't contract with it it would push everything in the lower bowl out :V. why we do it..effed if we know, evolution is weird like that.",
"The vagus nerve. Same thing that can cause a heart attack if you poop too early in the morning."
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o1cfvp | How do people die in their sleep? Wouldn’t the pain of a heart attack or whatever it is be enough to wake them up? | Biology | explainlikeimfive | {
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"Not if it kills them. Sure, maybe it woke them up and then killed them, but it's pretty hard to distinguish those two cases after the fact."
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o1chjx | why can’t lions survive on a plant based diet | Why can’t a lion survive on a plant based diet | Biology | explainlikeimfive | {
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"Because their bodies lack the enzymes necessary to break down cellulose and other nutrients in plants. Their metabolism/digestive system is evolved to process meat *almost* to exclusion. There are instances where carnivores will eat plants in order to aid digestion or to alleviate digestive pain, but they can't extract enough nutrients from plants to survive on them alone.",
"there are specific nutrients (like iron) that lions, or any carnivore, can only get from meat. also meat is much more calories dense than plants, and a hunter needs lot of calories",
"Their digestive system is not built that way. They have shorter tracts that are not prepared to long digestions you would need for taking out nutrients out of a plant based diet. We don’t have a meet based digestive system either, we’re half way between a cow and a lion.",
"The real answer is that lions, like other felines, have evolved over millions of years to eat meat, and in the process have acquired several quirks of anatomy and physiology that make them unable to live off of plants. I don't know about lions specifically, but domestic cats have many specific nutritional needs. They need a source of the amino acid taurine, pre-formed vitamins A and D, pre-formed arachidonic acid, and a high protein diet rich in the amino acid arginine. In other mammals such as dogs or people all of these can be easily synthesized from similar compounds found in plants, but cats have lost these pathways. Of course, that's not really what you're asking. You're asking why we can't formulate a plant-based diet to feed to lions kept in zoos. And in fact, **we could if we really wanted to.** Taurine, arachidonic acid, arginine, and vitamins A and D are easy to synthesize. Lions probably have other specific needs, but we could figure those out and synthesize them too. It might be hard to wrap this all up in a vegan package that a lion really wanted to eat, but I think it could be done--maybe using the Impossible Burger heme technology. BUT, figuring all this out would be 1) expensive, and 2) would require feeding lions sub-optimal and potentially dangerous diets, potentially for years, while we figured out a diet that works and proved that it works. In my opinion this would be impractical and unethical. No one who works in the zoo world is particularly bothered by the idea of feeding meat to carnivores, so there's no incentive to develop this kind of diet. TL;DR - animals need nutrients, not ingredients, and that includes obligate carnivores, but that doesn't mean developing new diets is easy."
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o1cmhg | If there’s a penta X disease (a female with 3 extra chromosomes) why isn’t there a sextuple X disease / is it possible? | Other | explainlikeimfive | {
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"The meiosis pathway that produces egg cells generates a total of four X chromosomes, so it would be difficult to have more than five (4 plus one from the father). You’d need a concurrent division failure in the father to produce a sperm with multiple sex chromosomes, a rare event. The odds of two such rare events occurring at the same time are quite low. If it did manage to occur and fertilize, major chromosomal abnormalities are often catastrophic and the fetus fails to develop. It’s possible that a six-X embryo has occurred before, but did not survive."
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o1cnti | How you can get hydrated from an IV without actually drinking the water | Biology | explainlikeimfive | {
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"When you drink water, it gets absorbed into your bloodstream. That's what being hydrated *is*. IV hydration just skips the middleman.",
"It's easy to think of the way your body gets water as like a tiny factory where workers inject water into cells. That's not really how it works, though. Imagine you put a piece of rubber down the middle of an aquarium, then filled one side with water. The water stays on that side, right? That's because the particles that rubber is made of are so tightly-packed water molecules can't fit between them. Now imagine you put a screen in the aquarium and did the same thing. Both sides would fill up because a screen's holes are WAY bigger than water particles. But that also happens if you make a screen with holes that are *just* the right size for water particles to slip through. It'd be very slow, but if you filled up one side of the aquarium and let it sit long enough, you'd find both sides half full. This is a process called \"osmosis\" when water does it, and \"diffusion\" when anything else does it. Those are fancy words that just mean if you have a lot of something on one side of a screen, less something on the other side, and there's a way for the something to get through the screen, it will move from the \"a lot\" side to the \"a little\" side until they are even. This is even true if, say, one side of the screen is water and the other is salt water. The side with salt water is \"less water\" since salt is taking up some of the space on that side. So some water on the \"only water\" side will move through the barrier until there's an equal amount of water on both sides. (Also, the salt might move out, depending on if it can fit through the screen.) Your body's cells have holes in them that are *exactly* the right shape to let water in, and a little bit of an ability to close those holes if they don't think they're thirsty. Your cells have a lot of stuff that isn't water inside of them, so if they're floating in water and the holes are open, they'll take in water through osmosis. Usually that happens as blood goes through certain organs, but if there's extra water in the bloodstream it can get absorbed there, too. The cells aren't picky about where they get their water. (But we don't really inject pure water, we use \"saline solution\". That has some salt in it and other stuff that slows down how fast the cells absorb the water from the solution. Cells *can* close the holes and stop water from coming in, but it takes a little bit of time for them to do so and if water's coming in too fast, they can actually get overfilled and burst! That's bad news. Let medical professionals do the work, because they know things like this!)"
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o1cpmw | Why do spiders tend to build their webs in corners? | Biology | explainlikeimfive | {
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"Well, imagine that you lived in a giants house and you needed somewhere to hang up your hammock. You're gonna need 2 anchor points that are fairly close together and wont be moved. Walls are an obvious starting point, but 99% of points on a wall are going to be too far away from another wall to anchor to. The only points where 2 different walls are close enough together to anchor together are in the corners.",
"I would imagine the anchor points like everyone here has suggested, and perhaps more protection from a closed area in the back? Are there any spiders to weigh in?"
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o1e2ig | How is Trigonometry used in Astronomy to find distances between the Earth/Sun and other state/planets? | Mathematics | explainlikeimfive | {
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"I know this one, but maybe perhaps not that well in english. See every triangle is known shape. We know a few things about every right triangle out there, we know that a^2 + b^2 = c^2. We also know a triangle is 180 degrees. From that we can extrapolate at what angle the three points on a triangle has (trigonometry). When observing things in space, you have already made one \"line\" just looking at the thing you are looking at. That would be one side of a triangle - Earth to moon is one such example. Now to get a second side of the triangle you could draw a line between the Moon and another known object, let's take the stars. That gives us two known sides of said triangle. Me got A (Moon to Earth) and we got B (Moon to Sun). Now because we know the things we know about triangles, we can figure out the last side, at what angle it meets the other (remember, total of 180 degrees in one triangle) and with that we can figure out the unknown distance C (Sun to Earth). This works on objects on earth or even in space, all you have two know is two points and you can figure out the distance to anything based on how the angles of said triangles points. Pythagoras Theorem works with finding out distances based on the two other distances (a^2 + b^2 = c^2) - Trigonometry takes this one step further and figures out distance based on ANGLES of where two sides of a triangle meets. Look at this picture and keep this in mind: URL_0"
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o1e40c | Can you fill up your bladder faster by swallowing excessive amounts of saliva? | Biology | explainlikeimfive | {
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"If it is a bottle of someone else's saliva, yes. If you are swallowing your own saliva as you create it, no. Creating saliva would be pulling as much water from your bloodstream as you are getting from absorbing water from your saliva."
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o1h55o | What is in metadata and why would someone ask a phone company for it? | Technology | explainlikeimfive | {
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"You call someone. The words you say to them, that's the data. The originating phone number, the destination phone number, the time you called them - that's the metadata (the data about the data). It can tell people information without having to access the content of the call (which is more difficult to get). If you're calling a tow truck company at 5pm, I can infer that your car broke down on your way home from work. I can then see what other calls you've made around that time which are probably related.",
"Phone metadata is calling number/called number/number of rings before answer/ length of call/who hung up/ ... . Let's say some reporter leaks secret information. That's OK, in the US, but giving the data to the reporter is a crime. So, you get the reporters metadata to see everybody they called on the phone. Reporters like to talk on the phone, because that way \"The Man\" can't know what was said. If you text them the data includes what was said. Then you think Senator Dumbo was the source of the leak, so you get all their call metadata and see if there are any connections. Sure, you might find they both ordered something from Comet Pizza, but you might also find out that they have been using Joe Smith as a courier. It's a source of leads, not a smoking gun (most of the time)."
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o1hgpl | how do spiked selzters not contain any sugar if some of their main ingredients are cane sugar? | Other | explainlikeimfive | {
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"Are you talking about total sugar or added sugar? They're different. Before fermentation, a drink can contain, say for example 13g of sugar per serving. After fermentation, yeast will have converted most of that sugar into alcohol and CO^2 . If the amount of remaining sugar is less than 0.5g per serving, the FDA considers it \"sugar-free\". According to [this website]( URL_0 ), any sugar added *after* fermentation will need to be specifically labeled as \"added sugar\". TL;DR sugar in the drink before fermentation is gone from the final drink.",
"Short answer: The sugars have been eaten already. Alcohol is produced by fermentation. Fermentation is a fancy word to describe the process of bacteria eating sugar and pooping out alcohols. You can ferment anything with sugar and get different results. Ferment pure sugar cane and add extra carbonation to the resultant liquid, you've created a spiked seltzer. Ferment grapes, you get wine. Ferment fruit, you get fruit wine (blueberry wine, strawberry wine, peach wine, etc.). Ferment a grain like barely, wheat, or rice and you get beer. Ferment barley and hops together to get an IPA. Ferment honey and you get mead. You can also further refine the fermented product through distillation to get hard alcohol. For example, if you ferment corn and distil the results you get whiskey. Ferment something high in sugar like potatoes and distil it to get vodka. You can even ferment and distil cacti to get tequila. If instead of adding carbonation you distilled your fermented sugar cane you'd have rum. That said, the bacteria don't necessarily eat *all* the sugars. This is easily seen in wine: the difference between a dry wine and a sweet wine is how much fermentation took place. If the bacteria ate all the sugar in the grapes it will be a dry wine, but if they leave some behind it's a sweet wine. This gets into the \"no added sugar\" thing discussed in other comments, since the sugar in the drink is leftover from fermentation as opposed to added later on."
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o1itns | Why does speeding up recordings make them higher pitched? | Technology | explainlikeimfive | {
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"Sound is a frequency of waves in the air. The closer together those waves are, the higher the pitch. When you speed up a recording of someone/something then those waves are moved closer together. If you slow down a recording those waves spread out and lower the pitch"
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o1j1tp | Why is magnesium oxide inversely proportional to the dose taken? | I have IBS-C and was prescribed 250mg of magnesium oxide to help. That wrecked my gastrointestinal system, so my doctor recommended 500mg. I am tolerating 500mg well, which doesn't make sense. Edit: taking magnesium oxide for IBS-C, not IBS-D. | Biology | explainlikeimfive | {
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"One action of magnesium oxide is to relax muscles by acting on the sodium channels. If your guts are in knots from IBS, spasming and twitching to cause your intestinal distress, then more magnesium oxide to increase its effectiveness makes sense. The magnesium wasn't wrecking your guts, they were already wrecked, hence the IBS-D."
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o1j5cp | What makes the loud 'boom' when something breaks the sound barrier? | Physics | explainlikeimfive | {
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"Aircraft create pressure waves in front and behind themselves in the air. It's like the bow and stern waves a boat creates in water. As the aircraft approaches the speed of sound (which is basically the speed at which pressure waves can propagate in air), they get bunched up. The ones at the front can't get away fast enough from the new ones. At the speed of sound, they merge into a single pressure wave, which ends up in a cone shape (a Mach cone). So at the front of the plane is very high pressure, and at the tail very low pressure. The sound you hear (actually a double boom) is the high pressure wave at the nose hitting you, and then the return to normal pressure after the tail passes you."
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o1jjl1 | the difference between petroglyph and hieroglyph. | The main difference between Petroglyph and Hieroglyph is that the Petroglyph is a pictogram and logogram images carved on a rock surface and Hieroglyph is a pictographic sign. I am not smart enough for this explanation. | Other | explainlikeimfive | {
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"With Hieroglyphs, each symbol represented a word or concept and, together, formed the basis of a written language. Petroglyphs, even if they were also images on rock conveying some meaning, they weren't specific words or concepts that translated into sentences. They were more an art form rather than a language.",
"Think of a petroglyph like a carved mural or picture and a hieroglyph as symbols telling a story like writing. Technically they both tell stories, but Petroglyphs are more like art."
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o1jn0k | why do they describe tv shows as x number of camera show? | Other | explainlikeimfive | {
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"It describes a lot about the nature of the show and how it is filmed. For example, a sitcom is usually a 3 camera show. What that means is that the show probably has a soundstage with standing sets. Using 3 cameras simultaneously, each facing a different angle, allows them to film the show live, like a play. Like person #1 talks, and they have one camera on them, then person #2, who they're talking to, replies, and there's a separate camera on them that they switch to, with no need to stop and set up the lighting and scenery and placement of the actors again. A third camera might be a wide shot that encompasses both speakers. So think of Friends--most filmed in 2 apartments or the coffee shop where they hung out. Such shows tend to be cheaper to produce (not counting actor salaries) because they're in one place at one time. A one camera show tends to be more complex and take longer to shoot because each shot is separate and they have to set up the lighting and sound and scenery and placement. One person might talk and they film that person plus the back of the head of the other person. Then they re-set everything and film the face of the second person and re-act the sequence. Then they may have to shoot it a third time with a wide shot of both of the people. And then they may have to move to build a new set, or go to a different location entirely to film something. Like with a procedural cop show where every scene is on a new set rather than a standing set. This costs more, usually, plus filming can take many days to do, having to set everything up anew for each scene."
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o1jzsu | What is the purpose of the appendix in a human body? | Flairs wouldn't show for me so sorry if I chose the wrong one :( I want to know if it's actually true that the appendix does nothing and it would bs great if I could get some answers. | Biology | explainlikeimfive | {
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"h218lrf"
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"While there are a lot of theories on how it was used eons ago, the current appendix function is that of bacteria storage. It is a little skin pouch filled with probiotic goodness. If you poop too much or are I’ll and need to replenish, your appendix will dump some back into your intestines as needed."
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o1ktuo | How do taste buds work? | Biology | explainlikeimfive | {
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"text": [
"Taste buds work much like a lock and key do. The tastebud has several \"holes\" on it that act as locks, accepting a few different \"shapes\" of molecular \"keys.\" When something sweet meets a sweet tastebud, the key fits into the lock and charged particles start flowing. These charged particles signal our nerves, and thus our brain registers a flavor."
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o1m0k8 | how does a DVD have the capability to play and store continuous sounds and motions and make us be able to see a movie? | Other | explainlikeimfive | {
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"It’s one giant string of digital data (1s and zeros— a strong enough microscope can actually see dots and dashes in the surface of the dvd). In the same way there’s one loooooong groove on each side of a record, there is a huuuuge amount of data encoded on a dvd. Inside the DVD player is a setup to allow it read and store data ahead of what’s being shown, and that information is both audio and video data. Blu-ray players actually store more data by using a narrower laser beam, allowing a denser spiral of data to be stored.",
"It's all encoded in zeros and ones, mounds and valleys. Your player reads the data and then converts it into something you can use. For example a video has a frame rate. This means it shows images really fast, it's not a continuous video. It flashes these images faster then your brain can process. Your brain blurs them together and makes a video. All of this happens very very quickly."
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o1m65b | When your body burns fat, where does the fat go? | Biology | explainlikeimfive | {
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"You breath it out. When you breath in, most of the air is effectively inert (it's not doing anything for you). The important thing is the Oxygen in the air. That gets absorbed into your bloodstream in your lungs, and brought somewhere else in the body. At that somewhere else, it will undergo a chemical reaction with Glucose (sugar). This essentially takes the Carbon out of the sugar, gives it to the Oxygen to turn it into CO2, and the rest of the sugar is now just some amount of H2O (water). The reaction also releases energy that your body uses. That CO2 goes back through your bloodstream, into your lungs, and you breath it out.",
"The byproducts of fat metabolism leave your body: As water, through your skin (when you sweat) and your kidneys (when you urinate). As carbon dioxide, through your lungs (when you breathe out).",
"You breathe it out. Simplest explanation is plants use carbon dioxide (think of it like Lego bricks) from the air to make sugars (putting smaller Lego bricks together to make larger assemblies). You eat those, or you eat things that ate plant sugars, but it's the carbon that's the most important. Your body rearranges the carbon those sugars (Lego bricks again) to make new things like fat. When you burn the fat, your body is taking those Lego brick assemblies apart, and you simply breathe the carbon back out as you exhale."
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o1mbxe | How and why cancer kills people, why someone with colon or stomach cancer dies? | I do not understand how cancer in some organs not so vital in my opinion such as the colon or the stomach, leads to death in people, sorry if it sounds very ignorant, but I would understand if the cancer is in the lungs, liver or heart, because some damage in these organs, means that the people deteriorate very quickly. What damage does it cause in colon or stomach that ends up being fatal? | Biology | explainlikeimfive | {
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"Besides all the other “everything matters” comments you will get, cancer SPREADS. It starts in 1 place and typically that is what your cancer is referred as. Technically, my grandmother died of breast cancer. However, it was also in her lungs, liver, kidneys, pancreas, stomach, and even her intestines by the time she passed. Once something has cancer, even something “non-vital”, it will continue to spread throughout the entire body just taking over the things that you have decided are actually vital. That’s why people take chemo/radiation sometimes for years on end, because it will just keep growing if they don’t get ahead of it.",
"Excuse me? Stomach isn't importaint? What? How do you get nutrients? How do you digest food? And can you live without it? Our body is a connected machine. If one system \"shuts down\", it affects everything else.",
"I can answer from experience into one of the ways colon/bowel cancer is dangerous. As well as the chance to spread to lymph nodes, the cancer can cause tears and holes in the bowel. This leads to leakage into your abdomen causing infections.",
"I'm not an medical expert, but I believe many times it is because the cancer is at too advanced a stage to treat successfully when it is detected. Because places such as the pancreas or colon are not easily visible on x-rays, ultrasound, MRIs, etc, and many diseases have similar symptoms, the cancer can be overlooked (which is why you should get regular colonoscopies after 50, people).",
"A few things: there are very few parts of our bodies that aren’t important. One such place is the galblatter. It’s vestigial and unimportant. However, most places where cancer lives are important. The stomach and colon is vital. Besides, as cancer grows, it spreads to other parts of the body",
"When you have gastrointestinal cancer (stomach, colon etc.) people either die from the metastasis (the cancer spreads to an area that causes more life threatening issues) or if they're getting chemo, which can cause issues with your blood cells (oxygen transport and immune system mostly) or they die of nutrition deficit. If you have cancer in your intestines, it can cause blockages which cause build up and you can't eat food anymore. You can be put on IV \"food\" called Total Parenetral Nutrition (TPN) but it's not something you can really live the rest of your life off of and comes with a lot of potential side effects and negative effects. Cancer in these areas can also cause you to feel nauseous and not want to eat. That is why rapid and unexplained weight loss is one of the signs of gastrointestinal cancer. When you don't eat, you don't get the energy your body needs to function properly. For example, our bodies need potassium. It's vital for the cells in your body to communicate and function, particularly your heart. Humans can't make potassium, so if you don't eat it, you can have all kinds of negative effects. These cancers can also get large and compress other areas in the body causing pain and damage. Source: Am a nurse who just did a rotation on an oncology unit."
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o1mj5i | How does radiation stick to an object and can be dangerous for humans? | I've read an article about abandoned cars and other stuff from the fukushima zone getting recovered and being used again, but they are still radioactive contaminated. Same thing with chernobyl. In my understanding, a human gets radiation sickness by "being hit" from the radiation which emmits directly from the source, e.g. the exposed core of the chernobyl reactor. The radiation shoots through your body, which can destroy your DNA and stuff. But how does that work for other objects, like a brick? If a brick was directly exposed to the open reactor, how does it store the radioactivity and how is the brick itself dangerous for humans? I always imagined a open reactor as "gun" which "shoots" the radiation into humans and objects in form of waves/particles, but i don't understand how the object itself becomes dangerous for humans, once it was hit by radiation. That would mean that the brick now also is a "gun" which shoots radiation | Physics | explainlikeimfive | {
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"The big thing for Chernobyl and similar things is the release of radioactive dust and particulate that sticks to objects and gets breathed in. Particularly Chernobyl with the massive explosion and fire spewing out smoke, ash, and dust from the reactor, which got stuck to the firefighter uniforms, buildings, debris, clothing, vehicles... Breathing in radioactive dust *massively* increases the danger by bringing the source closer to vital organs and tissues. Some materials *can* be made radioactive ([induced radioactivity]( URL_0 )), but this is not terribly common outside of direct exposure to the core itself or the radiation pulse of a nuclear device, or something of similar intensity. Bombs initiated near the ground can activate and vaporize a large quantity of topsoil and debris and throw it into the atmosphere, along with mixing it with whatever core material is left over after the blast.",
"In the case of Chernobyl, the explosion ejected radioactive material from the core. So all those objects were coated/\"soaked\" in radioactive material that was still emitting radiation. That made them hazardous. Fukushima had a similar release of radioactive material."
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o1nblv | - In regards to the food chain, are humans without weapons considered predators, gatherers or something else? | Biology | explainlikeimfive | {
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"text": [
"We evolved as herbivored that first did fruit stuff in trees, but were forced to the ground and forced to change our diets to omnivory when some dry climates started killing the trees we were living in. Our earliest ancestors were really eating whatever they could find, but since they didn’t really have the raw power or claws or teeth to hunt, most of the meat was scavenged. Only after a while of that did we find out that tools and fire could help make the most of what food we had, and then with better tools we could hunt our own food consistently. So we’d basically just turn into big raccoons, just eating whatever we can get our hands on",
"I mean, I am without a weapon now, but when the time comes I can absolutely pick up a weapon and wack my prey with it. We are definitely predator gatherers. It’s like my cat. In regards to scratching the crap out of thighs, my cat with her claws retract is still a scratcher, by nature that he can absolutely *shing!* and scratch the crap out of my thighs at any point he wants. It can be argued if I am to wack a grizzly bear with my stick, I’m absolutely going to get my ass kicked. But remember when it comes to the place in the food chain, we do not consider weak-sauce outliers like me, but the race as a whole. Humans are predators because as a race, we have pretty much hunted every species, and on top of the food chain we stand.",
"An easy way to determine predator from prey is eye placement on the head. If the eyes are forward (apes, humans, dogs, bears, big cats) - predator. Eyes on the side mean you're prey."
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o1o1x7 | How can things like sunburns and smoking still increase risk for cancer decades after their damage has been done to the body? | Biology | explainlikeimfive | {
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"text": [
"Cancer is basically a copy-error in a cell mutating into a big problem. Nearly every cell that has to split to recover from an injury can end up with thay issue (and I only use the word 'nearly' to avoid some smartass coming up with an example I didn't know about). The more the cells divide like that, the older the cells are. The older a cell is, the more likely it is to lead to cancer on mitosis (cellular division). This isn't a comprehensive explanation, but it's as simple as I can keep it, without failing to answer the question.",
"Imagine you're building a brick wall. At some point you used some faulty bricks, but then you finished up the wall with solid bricks and it's standing fine, those faulty bricks weren't a major problem. At some point in the future, some of your good bricks get damaged. Normally it wouldn't be a big issue, but it happened to be right around where those faulty bricks were and now the structure is too weak in that spot and the wall collapses. Smoking/UV radiation damages DNA, the building blocks of your cells. In much the same way, that initial damage might not cause cancer, but the damage persists throughout your life and makes any future damage more likely to cause cancer."
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o1oj7j | why animals can drink water from anywhere, but humans will get sick and die in many horrible ways? | Biology | explainlikeimfive | {
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"text": [
"For starters, animals don't just drink any water from anywhere and are 'fine.' They get parasites and diseases too. For the most part they can get by despite all of this, but it isn't like they're immune to it. Secondly, humans can build up a resistance to the bad stuff in the water over time. My bio professor told us how he had to sip a little untreated water at a time while working in Mexico due to their lax water treatment methods at the time, but eventually built up a resistance to the nasties in the water. But you're right in that animals typically are less affected than humans by all the pathogens in water. Why is that? Well being able to withstand all the things that can make you sick in water takes resources from any animal. Like an extra strong immune system or more rigorous digestion methods. That isn't free. Devoting resources to that leaves less energy for everything else. An animal that didn't need to devote those resources to purifying water would be strictly better off. Since humans have figured out how to drink from safe sources, we have evolved to devote some of those resources elsewhere, like growing a bigger brain. As a more ELI13 version. It's a lot like you're playing a strategy game like starcraft or civilization and for whatever reason you know you don't have to deal with flying units. This allows you to forgo devoting resources to anti air measures and instead use those resources to climbing the brain tech tree faster."
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o1oorp | How does stock trading work? | Economics | explainlikeimfive | {
"a_id": [
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"text": [
"Ok let's break it down! Back to basics. I have a company. I wanna sell crap to people. But before I can *make* money I *need* money. This is what we call 'funding'. I couuuuld borrow money and promise to pay you back that exact amount (with interest -- basically a reward to you for parting with your money). This is **'debt-based' financing**. But what if I'm not so sure I can pay you back that fixed sum? A-ha! I could just sell you a **share** of the company. When I make profits, you get a share (heh) of it. If I don't make profits, you suffer with me too. Yikes. This is **equity-based financing**. What do we call that share of my company? Why a share of course! (And that's why I hereby bestow on you the honorary title of **shareholder.** You hold shares. That's what you do). We also call this a **stock**. But what does all of this have to do with the stock market? Well... what if *you* don't want to hold on to that share forever? What if you need money right now, or you just don't like my company? If this is you, then you can just... sell your share to someone else! If my company is 'public' i.e. anyone is free to have a slice of it, if they're willing to pay -- you can just trade it on the **stock market**. **The stock market is a place where you get to trade the slices you own of a company with other people who want to buy it.** What price can you sell that share for? Here's the kicker: Any price. Really. As long as someone else is willing to buy your share at the price you quote, well, you got yourself a deal. That's the essence of stock market trading -- two people agreeing to make an exchange over the ownership of a company. Maybe it's driven by **fundamentals** like whether the company is making good profits. Or maybe it's driven by patterns or '**technical**' factors, influenced by human emotion or speculation. The stock market is as weird and dumb (or smart) as we are -- because we are the stock market (if you trade that is). This is why the stock market can be so volatile and sometimes lead to weird news stories... like Ronaldo saying he prefers water to coke and suddenly we're all taking about Coca Cola having it's market value wiped. [This video]( URL_0 ) explains the stock market a bit more, and draws a distinction between **book value** (which I think most people think of when it comes to 'value') and **market value** (which is what we usually talk about in the news). I hope that gives you a bit more clarity. I'm sorry I didn't touch on things like how you literally can trade using certain platforms, but I wanted to give you a conceptual understanding of the topic first and foremost. Let me know if you have further questions! Edit: Touch-ups to the response."
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o1ozva | Why there exist so many USB partitions? NTFS, FAT32, Extended Journal and some OS recognize only some of them whereas other USB peripherals never have this issue. | Technology | explainlikeimfive | {
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"text": [
"First, those are examples of *filesystems,* not partitions. A partition can have a filesystem on it, though. A lot of filesystems exist because computers have been around a long time, and some of them get phased out over time (FAT to FAT32 to NTFS), and sometimes some people want to use a different filesystem for a different operating system (Linux can use ext2/3/4, for example). Some OSes just don't know how to read certain filesystems, while others do.",
"this is not a problem with usb peripherals in general but one of storage media (such as hard drives, memory cards and usb memory sticks). this collection of different partition types has grown historically because every manufacturer wanted to develop the perfect format for their needs, but no one voluntarily makes a universal solution with an acceptable license",
"Each file system has different advantages and disadvantages, as time goes forwards, and files sizes are increasing, older file systems won't work as quickly and support large files. Each operating system has adopted it's \"own\" style of file system, and usually it's not compatible with other systems as the code each operating system runs on is different. The \"Fat16\" file system is probably the most widely supported, but as a result, it's maximum file count and maximum folders are low, it can't support files larger then 4gb, limited maximum path names, and a few other things. Usb is different as it's hardware only, and USB is just a serial connection, that's really fast and follows a robust standard that makes default or blanket drivers possible for operating systems to at least get working"
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o1p3gp | Why was it so hard to bake a cookie in space? | I just red a article talking about the first cookie being baked in the space station (that was a while ago), but I don't understand why it wasn't done before and why is such a big deal now. It looks like a company put a lot of effort just to send this cookie to be baked! And also they were not able to eat it. I would love o understand more about that! Thank you! | Technology | explainlikeimfive | {
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"text": [
"Pretty much all of the things you take for granted about cooking here on Earth are different in microgravity, and doubly so because of the safety concerns on a space station. In microgravity, there's nothing to hold a cookie to a pan. A system needed to be devised to keep the cookie stationary so it didn't float around inside the oven. Crumbs are also a big risk in space. They don't fall, so as they float around the station, they can get lodged into sensitive equipment or even accidentally get inhaled by the astronauts or get in their eyes. A system needed to be devised to minimize crumbs. Heat is a huge deal in space for 2 reasons. First, a fire would be far more catastrophic on the space station than on Earth, so an oven needed to be designed that would eliminate any risk of fire. Heat rejection is also a big deal, because the electronics in the station generate a great deal of heat, and that needs to be accounted for. You can't just open the oven and let it cool off, the station's climate is very tightly controlled. Even the chemistry of baking in space is different. On Earth, we rely on gravity to allow dough to rise. In microgravity, the gas bubbles don't rise, so everything is kind of clumped together. What would that look like? Would it be palatable? Would it hold together or just crumble? Would it heat evenly? We have to test to see. As for why they couldn't eat it, there are 2 reasons. The first is that if they eat it, they can't send it back down to Earth to be analyzed. We want to know how well the oven works, and we can't do that if there's no cookie to analyze. We also want to make sure this unusual cooking method fully cooks things. We don't want astronauts getting food poisoning in space."
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o1ppu7 | How do places like Home Depot or Lowe’s color match paint colors from a paint chip sanple? | I just got this done today and the paint is identical to the color I’m repainting from previous tenants. How does this witchcraft work??? | Chemistry | explainlikeimfive | {
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"text": [
"Basically, computers. There is a computer scanner that scans in the object you are trying to duplicate. That scanner feeds into the computer and the computer calculates the exact color recipe that has to be made. Then the tech goes and gets the colors and measures them into the right volumes and it gets mixed together, and poof. Matched colors. Not all colors can be matched exactly though. Sometimes the colors and amounts needed to match really aren't available in small batches like 1 gallon. Gotta remember, all colors are essentially made of the basic colors."
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o1q1mj | Why do particular metals (not sure which kind) found in some jewelry/sunglasses sometimes cause a rash or reaction on your skin? | Chemistry | explainlikeimfive | {
"a_id": [
"h22643w",
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"text": [
"Im thinking you may be thinking about nickel. My cousin has some skin irritation with too much nickel in their diet. A quick search shows that nickel accessories, like zippers, glasses, and jewelry, causes allergies. Just from a basic search, it seems like no one has found exactly why this happens.",
"Whatever that material is, you have an allergy to it. Often times the culprit is nickel, which is used in really cheap but fancy looking jewelry. Try some of the hypoallergenic ones, see how those work for you, but it's also entirely possible that you need a solid silver, gold, platinum, titanium, or surgical steel jewelry. On sunglasses it's harder, but you can paint clear nail polish over the metal bits to give a buffer between it and your skin."
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o1s94e | Why does stubbing one toe hurt so much more than stubbing 2 or more toes? | Biology | explainlikeimfive | {
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"text": [
"All the energy is being transferred into one single joint instead of two or more. Same energy and more surface means less energy on any point."
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o1sb7j | Why 33hz frequency is called "The frequency of the Great Pyramid" and what's so special about it? | Other | explainlikeimfive | {
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"The pseudohistory industry regularly makes up things like these. Their target audience is a community of scientifically illiterate, gullible but also selectively skeptical people who enjoy fiction that's sold to them as factual. \"Resonance\" is a big theme that ties into Numerology and Spirituality. Making up that 33hz is \"The frequency of the Great Pyramid\" sounds scientific enough for their audience, but it's really just a collection of words that doesn't mean anything.",
"There is a myth that the Great Pyramid of Giza was designed to resonate at 33 Hz although there is very little evidence of this actually being the case. Some people beleave that this frequency have some sort of supernatural significance and attribute any number of properties to it. Most people who trust the evidence we are able to collect however are far more skeptical of these claims. The only properties we have found is also present in surrounding frequencies. So while 33 Hz may be a good setting for your power massager so too is 25 Hz or 40 Hz."
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o1sz6h | How do our eyes "get used to the dark"? | Biology | explainlikeimfive | {
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"Your pupil dilates, meaning it enlarges and allows more light to enter. It can take a few minutes, but once more light is allowed to enter, you're able to see more. If you shine a bright light on someone's eye, you'll see the pupil quickly shrink. Fun fact, pirates wore an eye patch because it meant when they went from the bright deck to the dark inside, they would have one eye already adjusted to the dark so they wouldn't be blind for a few minutes while their eyes adjust. Edit: I am not entirely correct. a)The pirate thing appears to be based on zero evidence. Apologies for propagating a myth. b) pupil dilation is a seconds long process, and only part of the story when it comes to night vision.",
"The pupil opening is a minor contribution to the overall adjustment, allowing for about a factor of 10 improvement in low light visibility. The rest of the improvement in night vision is done chemically, by regeneration of photopigments, which increases the sensitivity of the retina, by between 10,000 and 1000,000 times If you are familiar with cameras, the pupil dilation is like opening up the aperture. The increased retina sensitivity is like increasing the ISO (but with a huge ISO range available) [This is the Wikipedia article ]( URL_0 ) that discusses eye adaptation",
"Your pupils (the dark circle in the middle of your eye) dilate, taking in more light, so you take in more information! Really simple as, I hope I didn’t get anything wrong",
"Light dims more and more, then eyes go \"Can't see very well, want MOAR light\" and then pupils dilate to try and take more light in so you can see better in areas with poor lighting."
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o1uyb1 | How can your feet be ice cold, meanwhile the rest of your body is burning hot? | Biology | explainlikeimfive | {
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"What makes you feel heat is the blood circulation, your body will, to prevent you from freezing, limit the circulation on your fingers, nose , and genitals(if you're male), yo avoid losing heat through the extremities and keep the blood rushing where he is most important",
"Weak circulation. Your feet are the furthest thing from your heart. When your hands/feet are colder than the rest of your body, less \"fresh\" blood is reaching them than there should be. It's like a house with poor heating and your feet are rooms at the end of a poorly ventilated hallway"
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o1vk9a | Why do the eyes of rats and mice seem to consist of only one big pupil? | The eyes other other mammals have some type of pupil that can dilate to let more light in. However, the eyes of rats and mice just seem to just have a large black pupil that doesn't dilate or contract. Why is that? | Biology | explainlikeimfive | {
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"They do actually have a pupil it’s just that usually you’ll only see it if you happen to see their eyes in the right light at just the right angle [this gives an example]( URL_0 )",
"Most Rats & Mice have Black eyes which is why they look like they don’t have irises. There are pink eyed ones which are albinos & Ones with Ruby eyes, they look black until they are in bright light then their eyes are dark red, this is caused by a similar gene mutation like the Lutino one in birds, all birds with the Lutino gene mutation have bright yellow feathers & Ruby Red Eyes regardless of breed.",
"Mostly they just have big dark irises that cover most of the visible eyeball around the pupil. Actually if you look at most mammals you will find that this is the case, it's just a bit easier to see the iris as distinct from the pupil in animals with larger eyes. Actually showing the white part of the eye is unusual in nonhuman mammals. So why do humans do it? Well, humans are very social and often cooperate on complex tasks in a way that other mammals don't. It's thought that by showing the whites of our eyes we make it easier to track each other's vison, which makes coordinating action easier since it's easier to tell what the other person is looking at."
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o1w4yt | Not being able to remember what we want exactly , but having an idea of what we're looking for | Biology | explainlikeimfive | {
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"Knowing you know the information but being unable to recall the information is a **\"Lack of Association\"** issue. Memories are tied/linked to each other by chains of ideas. If there is no link where you currently are to where you want to go -- you will be unable to recall it. Which is why we often think - where were you? what did you smell? what did you see? who were you with? when trying to recall information. Those links may lead to the missing information that you know that you know. Further Information: [ URL_1 ]( URL_1 ) Looking for something and not seeing it despite directly looking at it is a **\"Change Blindness\"** issue. If you are actively looking for your keys -- you look in all the normal places. However, your brain also discards the \"not-normal\" places automatically. Your brain says \"Why would your keys be in the fridge? Its never in the fridge\" So even when it is in the fridge.... well your brain actively discards that information, because it doesn't match what is normal. Further Information: URL_0",
"The name of this concept is on the tip of my tongue… It’s because we don’t use memory addresses like a binary computer, in human brains memory is state and association based so sometimes you know you know something but cannot direct your brain to recall it.",
"Memories are linked, such as you wouldn’t look for the fridge in a bedroom (possible, but imporbable). If you are looking for your keys, you probably go first to where they usually are or you last went."
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o1wjnx | How are game engines made and why are they necessary for games and why are there so many of those? | Technology | explainlikeimfive | {
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"A game engine is a lot of reusable code that different game studios can use to make their games. Game development teams do not want to spend a lot of time reinventing the wheel with each game. Rewriting code on how to handle physics, how to handle a hitscan bullet, how to handle a projectile weapon, etc. This code is essentially going to be the same in every game that uses them, so why spend a lot of time writing it for each project? This leaves the game developers the time to actually code the stuff that makes their game *different* from others.",
"I want to add one extra point: Most game engines are basically reusable pieces of code that every game needs, but there is one extra thing game engines usually ensure: Platform interoperability & #x200B; Kind of like how a web browser ensures you see the same webpage no matter what operating system you use, an important responsibility of a well designed bigger game engine is to ensure that the game looks, feels and acts the same on all platforms the game ships on (PC, Console, Mobile, etc.) without the game designers or the developers having to write a single line of code to achieve it.",
"Game engines haven't always been a thing. They were created to reduce the complexity of developing every game from scratch. Sometimes games will want to do some cool new feature, so a studio will make a new engine, or modify an existing one to meet that goal.",
"Suppose you want to make a game. You have a cool story, you've drawn some cool character designs, your notebook is full of great ideas! Now, write the computer code to make all that magic happen on the screen. But! You're a designer, not a coder. You don't know how to code. Or, more realistically, you're not interested in learning to code or building the HUGE team necessary write all the code. So, you license the code from someone else, who has written the program. That's the game engine. This story also works the other direction. Suppose you're a coder. You have figured out a really clever algorithm - perhaps a very, very fast way to computer the inverse square root. (John Carmack actually did this.) This super quick algorithm is now a core element in some software you're written that draws 3D objects on the screen. This software would make a really cool game! But! You're a coder, not a game designer. You don't know how to design games. It doesn't really interest you. So, you offer up your software for other people to use to design their own games."
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o1wupx | Why do we sometimes hear things that never happened or were never said? | Sometimes I think someone has called my name and they never said anything. Sometimes I've even heard what seemed like someone shout right next to my face, but that mostly happens when I'm close to falling asleep! I hope that makes a bit of sense! | Other | explainlikeimfive | {
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"Your brain makes stuff up (or remixes stuff from your past memories) all the time, but usually we can easily distinquish between the \"inner voice\" of our imagination (or mental images) and reality. In some cases, for a number of different reasons, it fails and we experience hallucinations. Also, sometimes our brain thinks that it detected something in the outside noise and makes you think that you actually heard somethink. Hallucinations are not great but what you are experiencing when you are falling asleep is pretty normal and it's called hypnagogic hallucinations. They aren't a sign of any illness, it's just your brain slowly preparing to fall asleep, shutting down some systems and activating some others, so that's kinda like fragments of an incoming dream get mixed with reality.",
"First off... most of the things you perceive in life are a bit artificial. For example: You think you can see colors in the periphery besides your focus. Actually that's biologically impossible since the receptors that perceive your periphery are mostly only seeing black and white, more accurate the brightness. So your brain fills in the gaps by experience or memory. I think that is what is happening to you. You are in a situation and hear or see something. Now you expected a specific reaction because you are subconsciously used to it. For example: Maybe you know the situation where you have to ask someone several times what they said, although they clearly stated it and it should be easy to understand. But maybe your thoughts were in a completely different direction and the words spoken didn't meet your expectation. Now your brain needs time to adjust. If it's not that, you are having hallucinations but it think that's unlikely from what you said. Additionally there are interesting experiments where test subjects are conditioned to a specific sound while doing a specific task. Now the sound is gone while they do the task and can still sometimes hear the sound. Of course it differs depending on how susceptible a person is to these kinda manipulations."
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o1xpe4 | can you transfer a embryo from womb to womb? | Is it possible to transfer a embryo/baby from your womb to a surrogate mother womb and if yes up to how many months. | Biology | explainlikeimfive | {
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"No, embryos are too small, too delicate, and stuck into the lining of the uterus until they get big enough to have a circulatory system that is connected to uterus.",
"In theory you could transfer a fertilized egg from one womb to another but the egg is too small to find. And after a few hours it will have attached to the womb and can no longer be moved. What is being done sometimes is that the egg is fertilized in a tiny vial in a lab. By doing it this way we can easily locate the egg. It is then possible to transfer this fertilized egg to a womb. This is primarily used to increase the chance of fertilization but it can also be used when there is a need for a surugate mother."
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o1y75g | Why does something sound louder at the same volume at different times? | If our ears work by their ability to receive detect and interpret vibrations, why does my music sound louder in the morning or before I go out and do something but later, at the same volume levels, it sounds much quieter? And if this is a bodily response to adapting to loud sounds we encounter, why can’t we “adjust” volume manually ourselves? | Biology | explainlikeimfive | {
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"It is likely to be a brain and instinctual mechanism from our evolutionary past. In the wild, it is UNUSUAL noises that alert an animal to danger. The brain can only focus on a few things. If it tried to process every sound at \"equal\" priority, it would risk missing out on the important ones. In a super low background noise environment (google anechoic chamber) a person can even start hearing their heartbeat and blood flowing in their ears. This is your brain adapting its perceptive resources on the critical stuff. You don't want to hear the wind blowing on leaves if it means not hearing a predator coming to get you, basically. Even sight works in a similar way. Many animals detect motion much better than they can perceive still objects. Again, this is the way brains work to improve survival."
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o1ylt8 | House temperature in summer | So the ac is broken and yesterday in California at night the temperature was 91 F outside and inside in this upstairs room in the house..downstairs 82..just worked out in this same room this morning...currently the room measures at 83 F right now downstairs 78 but the outside temp is 58? The windows were open both times...why isn't it much cooler in the morning? | Earth Science | explainlikeimfive | {
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"You can not just replace the air and expect the temperature to change dramatically. The air in your house is one of the things with the least amount of thermal mass. All your walls, structure, furniture, etc. have a lot more mass and is still at the old temperature. It takes some time to cool those tens of tons of materials that your apartment is made of.",
"I haven’t had AC in about two years. From experience I think it depends on a few factors. Your house holds heat. For example, my house is brick and brick holds heat very well for an extended period of time. You mentioned that you were upstairs. Heat rises so it will be warmer upstairs. Electronics give off heat. You mentioned the windows were open but sometimes this still doesn’t create the ideal conditions to circulate the warmer air (it rises, remember). I point some of my fans towards the ceiling to help with this. Fabric stores heat. Sofa, carpets, etc. There are just a few things I have noticed as I have adapted to living without an AC."
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o1zroo | Why does HMDI need such high bandwidth compared to Ethernet? | When we stream 4k video from Netflix for example, they recommend a minimum speed of 25 mbps.But HDMI 2.0 has a bandwidth of 18.0 Gbit/s How can we recieve 4k video with a connection speed of only 25 mbps when we need 18.0 Gbit/s to send the video to our TV? I think it is to do with compressed vs raw 4k but do we really compress it to this an extreme? I would have thought this would result in so much loss that we are no where near 4k in the end. | Technology | explainlikeimfive | {
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"Netflix, Youtube etc. all compress the hell out of their videos. Video compression is a lossy system, so some of the detail in the image goes away when it's compressed--the critical thing with the compression algorithms is to try and ensure what goes missing is stuff you won't notice. Nonetheless, if you were to run the uncompressed 4K video alongside the streamed version you would almost certainly be able to tell the difference. As for the bandwidth requirements, 4K video is 3840x2160 pixels. You need 3 bytes to store each pixel, so each uncompressed video frame is nearly 24Mb of data on its own. If you're streaming that video to HDMI at 60 frames per second, then you need a minimum bandwidth of a little bit over 11Gbps. HDMI gives you a fair bit of overhead there, but certainly not so much that you could say 18Gbps is overkill.",
"You stream compressed video over the internet. But then what happens? Your computer decompresses that video and sends whole 4k frames to the screen. As smart as your screen is, it's supposed to be a relatively dumb output device, so that it can operate independent of whatever video format you're sourcing, or how much computing power is required to reconstitute the original frame data.",
"4K video is 3840 × 2160 pixels with 3 colors and 8 bit per color. So you need 3840\\*2160\\*3\\*8=199,065,600 bit for a single frame. At 60 frame per second that is 11,943,936,000 bits or 11 Gbit/s The first 4K video at 60 Hz on Youtube I founds was URL_0 it is 961.43 MB for 5:13 video The amount of data per second is 961.43*1024^2*8/((5*60+13))= 25,767,000 bits per second. This includes audio so the video size is smaller That is a compression range of 463:1 even if audio is included in one but not the other. So the answer is compression that reduces file size but factors of a couple of hundred times.",
"> How can we recieve 4k video with a connection speed of only 25 mbps when we need 18.0 Gbit/s to send the video to our TV? * Compression. * You are downloading a map and a set of instructions that tell your device how to recreate each frame of the video. * Once that frame is recreated, the data for over 8 millions pixels needs to get from your device to the display. * Also up to 8 channels of audio, plus other data, and the HDMI spec also includes room for a 100mbps ethernet link embedded inside the HDMI link",
"Compression: the information sent over a video cable is essentially completely uncompressed video: an uncompressed image is being transmitted for each frame."
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o1zu68 | How is there so much protein in cow's milk when a cow's diet consists mostly of grass which I assume is mostly fiber? | There's a significant amount of protein in milk and I've always wondered how this is possible considering cow's just eat grass? Does their stomachs convert grass into protein in a special complex way or something? I don't understand? | Biology | explainlikeimfive | {
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"The carbs in grass get rebuilt as the plant matter is digested through the cow's intestines. They become amino acids and then are built again as protein and other stuff for the cow's milk and so on.",
"When you say “so much”, what do you mean? There’s only about 3.4g of protein per 100g of milk; compared with pretty much all other animal products that’s not that much. That aside, grass also has protein, fats and sugars; all living things do. Cow digestive system is also very efficient and bacterial fermentation helps extract nutrients from within cell walls, which gives them enough amino acids to constitute proteins for muscle, milk etc.",
"Cow stomachs contain a lot of bacteria that can digest the grass and produce energy/protein for their own use. The bacteria, in turn, are digested by the cow, which then breaks down those proteins into amino acids and uses those to build their own proteins."
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o2038y | how do fingertips work? What makes them so unique and why they generate on the fingers and not other parts of the body? | Biology | explainlikeimfive | {
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"All of your body is unique. It's possible to identify people just by the shape of their hand if you use spacers to hold the fingers in place. Same with retinas, face proportions etc. Fingerprints just get more attention because they're a small area and have been historically important for identifying people as we leave them everywhere. They are also easy for us to see. But there is nothing more unique about them then any other part of your body. Technology wise there is a big move away from fingerprints as an identifying mark because people have dirty hands, and so the reader is less reliable without frequent cleaning. Your phone, CCTV surveillance, Facebook tagging your photos etc use facial recognition.",
"Every part of your body is unique. Fingerprints are just exceptionally easy to tell apart and, more importantly, to *collect* since everything gets touched by fingers."
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o20hot | How do they decaffeinate coffee and tea? | Chemistry | explainlikeimfive | {
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"Tea can be any blend of herbs and flowers, many of which are naturally decaffeinated. Coffee can be decaffeinated by using chemicals, or by washing the beans over and over again (this is called “Swiss water processing” and is the kind to buy!).",
"\"They\", as well as you and me, all function the same. We defecate coffee and tea like any other drink or food. It goes in through your mouth, in your stomach, it gets digested, water and nutritional matter travels via the bloodstream to all the organs, then dangerous or unneeded matter gets out of the body via pee or poop. When you go to poop, that is what is called \"to defecate\". You sit on the toilet, relax, poop comes out. Why would you ever think that coffee and tea would have to be defecated in any other way than all the rest of the stuff?"
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o20j6k | I’m sure this has been asked, but why can’t we cure cancer? | Biology | explainlikeimfive | {
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"1st difficulty is finding traits that all cancer cells have in common. Since you can have cancerous brain/bone/muscle/etc cells, and these don't have a lot in common, this is hard. 2nd difficulty is that those cancer cells are YOUR cells. They're...misguided, but they're still yours. This means your body doesn't typically take issue with them, so they grow and reproduce without issue. Lets say you want to kill all the criminals in the population- how do you identify them when they are *part* of the population? You *could* just kill *everyone* but that doesn't help society much. 3rd difficulty is that even if you know exactly where those cells are, what do you do about it? If I have a clump of cancer cells in my finger, surgery would be easy, and worst case I just chop off my finger. Different story if the cancer is in your brain or your bones. 4th difficulty is that cancer spreads. If you catch it early, you might be able to cut it out, or shoot it with radiation, or poison it. But if you don't catch it until it spreads throughout your body... well...cancer cells are killed by the same things as healthy cells are. How do you target only the cancer cells, while not killing the cells you need to survive? (See difficulty 1-3)",
"Because cancer isn't a singular thing. There are many types of cancer, which effect different parts of the body in different ways, and caused by different things. There's no such thing as \"generic\" cancer, so there is no generic cure for it.",
"Cancer is not a single disease, it's a group of many different diseases, each one with their unique properties that require unique different solutions. A tumor is when a cell suffers a mutation that makes it reproduce out of control, so it starts growing a mass that isn't in harmony with the rest of the organism. Cancer is what we call a malignant tumor, a type of tumor that is capable of spreading to other organs, by direct expansion, but also because some cells get into the blood stream or the lymphatic system and colonize other distant organs (this last thing is called metastasis). Now, whenever we have an infection caused by a cell from a different species (like bacteria, or a fungus), we give a medication that targets some molecules on the surface of the cell (some of these are called receptors). The medication is like a key, and those molecules on the surface of the cell are like keyholes, your immune system defends you in a similar way. But cancer cells have a problem, in most cases their receptors are very similar, or exactly the same as the ones from your own healthy cells (because cancer cells originally come from one of your own cells that went out of control), you can't give a medication that kills this cancer cell without attacking many of your own cells. That's why some chemotherapies are so aggressive for the patient. But some other cancer cells are worse, they have no receptors at all on their surface, or not useful receptors, they are like a blackbox, where you can't give nothing, no medication that can target them to kill them, because they have no keyhole for any key. That being said, we have advanced a lot on chemotherapies, many types of cancers are fairly treatable, and indeed curable if treated with enough time. So we can cure cancer, but it depends on the type of cancer, on the receptor on the surface of the cancer cells, and on the behavior of those cells. Other types of cancer, evolve very rapidly and you can't detect them until it's very late, when it has spread everywhere and it can't be cured anymore, they can only be delayed."
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o20ou2 | Where does wind come from? I thought it came from clouds but I've just had two really windy days with no clouds in sight | Earth Science | explainlikeimfive | {
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"Hot air goes up, usually heated by the sun. Some cold air comes rushing in to get the place of the previous air, and wind is created. Earth's rotation and different heating on different spots also contributes to winds, but is basically hot air going up and could air coming to take its place.",
"It comes from higher pressure cells moving into lower pressure cells. Essentially when some portion of the atmosphere or air gains heat energy it becomes excited and tends to expand and move around which can displace some colder areas of the atmosphere...it exerts force and movement. Molecules are bumping into each other and swirling and flowing and pushing each other along. The warmer the air is the more space is going to take up and the colder the air is the less space is going to take up, so warm air has higher pressure and cold air has lower pressure. The heat tends to want to transfer to the cold so higher pressure cells are drawn to lower pressure cells and that can produce molecular/atmospheric movement that we feel as wind."
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o20z4y | Why can satellite television service easily play high quality movies/shows, while satellite internet service buffers videos constantly even in low quality? | Technology | explainlikeimfive | {
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"Satellite TV is broadcast; the satellites \"blindly\" send TV just once, and everyone watches it at the same time. Easy peasy, but you have fewer choices of what to watch (\"500 channels and nothing on\"). Satellite internet is two-way. Unfortunately, the delay between transmission and reception for geostationary satellites is about an eighth of a second each way. So an eighth of a second from you to the satellite, plus an eighth of a second from the satellite to the ground station (where the satellite gets *it's* internet connection), plus however much time it takes for the normal wired internet connection to complete, plus an eighth second for that data to get uploaded to the satellite, plus another eighth of a second for that data to get back down to you. So you're at more than half a second for a full back-and-forth data exchange. This is a problem for internet traffic, because either side sending data needs a reply for confirmation that the data was properly received. The longer the transmission delay, the more difficult it is to send large amounts of data, because any lost or corrupted data will incur a large \"penalty\" delay as acknowledgements are delayed more than half a second, which means re-transmissions are delayed more than a full second. If everything was working perfectly, internet protocols allow a lot of packets \"in-flight\" with occasional receipt acknowledgements, but just a single lost or corrupted packet will make the whole thing just grind to a halt for at least a full second. Additionally, whenever a delay like this happens, internet protocols automatically slow themselves down (because there's no point in trying to stuff 100Mb/s through a 10Mb/s connection). Plus, you're sharing limited bandwidth with a bunch of other satellite users. Which, BTW, is why the new Starlink satellite internet is designed to solve this problem by using satellites in Low-Earth Orbit: so they are much closer and have much less delay. (It also uses a *lot* of satellites -- instead of just a handful of traditional satellite internet satellites -- to allow more bandwidth for more users.) Edit: fixed delays, thanks koolman2",
"Satellite TV is one-way. It beams content out, and doesn't care one bit whether anyone is receiving it. Satellite internet requires 2-way communication, which means you have to exchange a bunch of signals with a satellite 35,000km away, and that takes some time.",
"Satellite tv doesn’t care about latency between your action and a change on the tv, no matter what people do, everyone on that channel is watching the exact same part of the same show at the same time. Since the message isn’t custom, it can be made faster.",
"Most of the commons have addressed the obviously needed bidirectional aspect of satellite Internet. But that’s only part of the reason it’s so slow for video streaming. The biggest reason is that there is only a finite amount of bandwidth on a given satellite or transponder. This is not an issue when broadcasting video to whoever wants to pay for it and tune it in. But when you want to have individual access to data it must be shared amongst many users, and therefore each user only gets a small sliver of the satellite’s available bandwidth. It would be like having one, let’s say cable, internet connection to a city for all to use. Each user’s speed would be quite slow.",
"Satellite tv: there's a band playing music (broadcasting). Anyone can sit there and listen. But you're gonna be listening to the same song as everyone else. Satellite internet: you go to the music shop and pick a song to listen to on your headphones. The shop attendant (or you yourself) has to dig around and find the music you want and put it in to your listening device. There's also a bunch of other people in the shop that the attendant had to take care of as well. But you're also listening to your own choice of music that can be different to everyone else",
"To send 500 channels to 500 million people only uses \"500 bandwidth\", but 1 million people using 1 connection each uses \"1 million bandwidth.\". That's 1/500th the amount of users using 2000 times more bandwidth or 1,000,000 times more bandwidth total. That assumes that each user is only using the same amount of data as watching one stream."
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o21uhi | The “CAGED” system for the guitar | Can somebody explain to me what the reasoning or the “philosophy” behind it is? I know ( moreso accepted because I haven’t really applied it ) how it looks on the guitar with the shapes and such but It’s not connecting ( coming to me in a holistic way if that makes sense ) | Other | explainlikeimfive | {
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"I hate that people call it a \"system\". It's not a system, it's a basic observation. C, A, G, E, and D are the five movable chord shapes, meaning they can be played as barre chords anywhere on the neck. If we want to play an F chord, we could play it as an E-shape chord on the 1st fret, a D-shape chord on the 3rd, a C-shape on the 5th, an A-shape on the 8th, a G-shape on the 10th, and then repeat again with E-shape on the 13th (and so on). That's it. It's not a philosophy, it's not a method, it's not a \"system\", it's just an observation about chord shapes. It doesn't help you play the instrument, and it doesn't even really help you find ways to play a chord, since you still have to know your way around the fretboard.",
"It is a long since I saw the real explanation of it but the general idea is that shapes on guitar are movable. If you play a C major triad, move the same shape two frets up and you get a D major triad. \"In the same fret range\" you have different shapes for the same thing and these shapes are often referred as the C,A,G,E and D shape corresponding to the ground note in the lowest possible position of that shape. A good example are bar chords. The most common bar chords are the E shape, where your fingers make the pattern of an E chords but with a bar instead of playing open strings, and the A shape. But you can do the same with a C,G or D chord. This way every chord can be played in multiple different shapes but at different positions, improving the number of possibilities. The reason it are C,A,G,E and D has to do with the tuning of the guitar. In normal guitar tuning C,A,G,E and D major, minor, 7, ... can all be played as open chords (played with also playing open strings) while other (F an B) can't."
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o21wrm | How do Bone Conduction Headphones work? Are they dangerous? | Technology | explainlikeimfive | {
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"No they aren't dangerous. They use vibrations in the bone or skull to generate sound. This means you could listen to music while not having buds in and thus hear all ambient sounds aswell. Very convenient on a bike for instance. Some hearing aids will have a screw in your skull and attach the device to it. The vibrations will travel to your inner ear and make you able to hear better (as I recall, correct me if I'm wrong)",
"Head bone is connected to the ear bone. Have someone tap on your head with a spoon, then tap on their head. When they did it to you, it was loud, when you did it to them, it wasn't. You can also tap on your knees and compare the sound to someone else doing the same. The difference is bone conduction. You can experiment wearing ear plugs. Sound travels through a medium as a wave, just like ripples in water when you drop a pebble in it. Air is the most common medium, but it doesn't have to be. When you put a string between two cans, the string is the medium. In space, the medium is gone. A loud speaker a foot in in front of your would give you no sound. If you put your forehead on the speaker cabinet, your head becomes the medium, and you will hear it. Bone conduction. People who are around very loud things can only lower the sound so much by combining earplugs and earphones (about 40db max off the top of my head), because bone conduction will still make it loud. Covering the head with some types of helmets can further attenuate bone conduction (of which the skull is the primary contributor). Even then, you can only do so much."
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o226ha | Why does our immune system suddenly react safe substances making us allergic? | So let's say you've been eating nuts your whole childhood. You have had nuts added to different types of food. Your body has been exposed to nuts for quite a while. What changes, for you to suddenly wake up one day and be allergic to nuts? | Biology | explainlikeimfive | {
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"As far as I know, it's a current field of research. The entire process of how allergies suddenly start out of nowhere in someone's life is not well understood yet. We do understand how an allergen eventually triggers an allergy, but why the body suddenly starts considering a certain molecule as an allergene, I don't think we have an answer for that. But I might be outdated in this knowledge, that was the consensus some years ago when I was still in college.",
"Nobody knows! There's some correlation between being raised \"too clean\" and developing allergies. Playing outside and being sent to kindergarten reduces the odds of developing allergies. but that doesn't really explain them appearing later in life, or some of them disappearing with puberty. So the honest answer to your question is, No idea, its being looked into."
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o23p97 | Why do we usually get mental blocked when being asked on the spot? | Other | explainlikeimfive | {
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"If by ‘on the spot’ you mean that a person asks a question abruptly, instead of in a natural flow of conversation, probably because your brain is processing possible ulterior motives.",
"A huge part of the problem is that your memories are not like computer files - it's a series of clues leading to information that your brain has to recall. The links can get weak over time, also they don't form on the spot. That's why you have to rehearse things. So if some one comes up to you and says \"Quick! What's the name of your Uncle's girlfriend?\" Your brain may 'freeze' because those links are weak and just can't cough up that information on the spot. If you have rehearsed something, you can minimize the 'freeze' - but only if it's what you've rehearsed. When I was sent to the Army promotion board - I had to drill and drill answers beforehand AND have a prepared response in case if forgot something. Just sitting there like a deer in the headlights was a NO-GO. Even then, that took work to get that down.",
"Trying to get into the right mental headspace to answer a question based on your knowledge (as opposed to a question about some past behavior) can take a second. In the first case, when your brain doesn't immediately come up with an answer and that awkward pause begins to develop, self-doubt, negative self-image, and concerns about what the other person is thinking can begin creeping in and steal focus from the thought processes needed to actually come up with an answer: > Why don't I know this? > > Oh, no! They're just staring at me; I bet they think I'm not that smart! > Why can't I remember their name/what our anniversary is (etc.)? > > They probably think I really don't care about them! And on and on. A way to short-circuit that is to break the awkward silence and admit the difficulty in immediately coming up with the information: > Oh, gosh! I know I know the answer, please just give me a second. It will come back to me, etc. If, on the other hand, it is a question about some past behavior that they are presumably not happy with and you're struggling to find a way to spin it to CYA or make yourself look better.... best of luck! Better to just own it and apologize then to obviously struggle to stammer out some unbelievable excuse, IMHO."
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o23r5b | How is it possible that gases (helium especially) can leave a balloon or even a high-pressure tank over time ? | Chemistry | explainlikeimfive | {
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"Hydrogen and helium are very very smol atoms (the smallest they can be and still be called atoms, in fact). So they kinda just... slip through the gaps between larger atoms that form the container. They have an easier time doing that through something very thin, like a stretched balloon, but slowly they can find their way out of solid metal tanks.",
"When you’re down at the atomic scale there’s no such thing as a solid object but rather atoms and molecules. The rubber in a balloon is made of long molecules which are basically chains of atoms. These are all intertwined. Think of it like a messy mass of chains. However there are gaps between these chains big enough to let very small things though for example helium molecules. The main molecules in “normal” air are nitrogen (N2) oxygen (O2) and carbon dioxide (CO2). These molecules are simply too big to get through the small gaps in the molecular chains."
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o245mj | what's the difference between a rare animal and one that's going extinct? | Biology | explainlikeimfive | {
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"There’s not a specific definition of “rare” It might be an apex predator that’s highly territorial and requires a large range, limiting their population. Even in the best of times, tigers and jaguars are widely dispersed throughout their habitats and have a low but stable population. It might be transient or migratory, and only present in the area for a few weeks out of the year. Boreal chickadees are quite rare in my area, but their population in general is fine. It might just be really good at hiding, and so rarely seen despite a healthy population. There’s a million bush crickets around here, but you’ll never find them. A species that’s critically endangered may or may not also be rare, but their population has undergone significant decline for some reason. They may still be common in certain areas, but have also lost huge swathes of habitat that endangers their long term survival.",
"Population trend. It's possible to have a very small but stable population – for example if it's a species that seems to have evolved to thrive in some very specific environmental conditions unique to its habitat. That would be, in your words, just a \"rare\" species. But if the population is in decline, then we can guess that there is some factor which is killing the organisms off or causing them to not reproduce well enough to sustain the population. So, by definition, that species would be \"at risk\" or \"endangered\" because if things don't correct themselves the species could continue to decline all the way to extinction.",
"Consider two animals. A population of 100 rare blind fish that only exist in one deep cave that hasn't changed much for millions of years, and a population of 100 rhinos being hunted by poachers. The blind fish are few in number because their habitat can not support more, but they're not really in danger because their environment is stable. They're not likely to face any threats unless something drastic happens like an earthquake breaking up their cave or humans drilling into it. Assuming things go on as they are, they'll stay around for another million years. The rhinos on the other hand used to have a much bigger population, but now they're on the decline. They're in the process of being hunted to extinction. If things continue as they are, poachers will hunt them faster than they reproduce until they're eventually all gone. The difference is that one faces a relatively new threat that has it on the decline while the other is in a stable situation."
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o24fbk | Why games made with C++ are more optimized? | C++ is the language used in almost all AAA titles. I seen youtube tests that show C++ to execute tasks faster than C# or Python for example. But i heard C is faster than C++ also, so why C++?. And what makes C or C++ faster than other languages (except assembly and machine code of course)? | Technology | explainlikeimfive | {
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"Python is interpreted, not compiled, so the interpreter is effectively turning the source code into machine code as you run the program. This slows it down a whole lot, and other interpreted languages have the same issue. With C or C++, you compile the code into machine code, so you only do that work once per platform, instead of every time you run the program. Now, you can write something in C and C++, and have them both the same speed, or one faster than the other, depending on what compilers and settings you use, because modern compilers are really good at optimizing code down to equivalent instructions that run faster. Which one ends up faster usually is a question of how clever the compiler is rather than anything inherent to the language.",
"C/C++ is a language built on the assumption that the developers will handle EVERY aspect of their program, this includes aspects as low level as managing memory and basic I/O(2 huge areas where bottlenecks in speed are common), if you ignore to handle any of these your program will not run at all or it just crashes when it encounter an unexpected situation, this increases complexity but because everything is managed closely you cna fine tune its performance to what you want it to be other languages like C# and Python implement automated systems to deal with some of this basic tasks so that the developer doesn't need to, but these systems are not specialized for all needs(or in some cases handling them is mandatory even if the program doesn't use them) so performance is not the best it can be. as a bonus both C and C++ have the ability to indent code from other languages most notably Assembly listings, this enables a savvy developer to implement code that is accessed VERY frequently(and hence could become a bottleneck) in Assembly in order to make sure this code is optimized at the lowest possible level before actual machine code.",
"Imagine you are writing a recipe for a Pie. In assembly you would write \"take 5 steps to the fridge, open fridge with your right hand, grab an egg...\" and it would depend on your exact kitchen. In C/C++ you would write \"Get an egg from the fridge.\" In Python you would write \"make a pie crust\" and you leave the interpreter to figure it out at run time, which is going to take time.",
"It is not universally true. However the closer the programing language is to the machine code which actually runs on the processor the more control the programmer have over the code which allows them to write more optimized code. It is things like not following conventions when it would hinder performance, taking minor shortcuts, understanding how different code will get executed in the processor and therefore how it will perform, etc. It does not mean that all C and C++ code will be fast. In fact it takes longer to write code in these languages so there may not be enough time in the project to do other larger performance improvements. And more modern compiler for the higher end languages like Java and C# can actually get better insight into the code then the developer and may do more performance optimization then most people will do on their own. Most AAA titles is written in a number of different languages depending on which works best for the given scenarios. The core of the game engine might be written in highly optimized C++ code that have been perfected over many years and is used for several titles. But the world interactions, animations and scripts are usually written in their own high level language specific to that game engine. Even things like the AI might be written in a completely separate language which is designed to make it quick and easy to work with the AI."
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o24gkq | how can an iPhone be so hard to hack when entire banking systems and other massive companies can be successfully targeted? | Technology | explainlikeimfive | {
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"Big companies have many separate systems, many of which have to talk to each other, which means many potential vulnerabilities (often the employees themselves) and you just need one. Compare that to a single hardware device with strong encryption that has a single owner/user.",
"Banks have a much, MUCH larger attack surface than an iPhone. And a whole lot more of the weakest point in any system: the humans who need to access it. There's an old adage in cybersecurity: What's the easiest way to get an employee's password? You ask them for it. You'd be shocked how many hacks are pulled that way. Kevin Mitnick got famous doing just that. With any large organization you're pretty much guaranteed to have someone gullible enough to just give you their password, especially if you create an employee ID for some bogus IT support company.",
"Apple is a monoculture. That means that only specific, Apple-targeting, techniques work. It's not true that \"entire banking systems\" have been hacked. Some companies have had some disclosure problems, where their transaction records leaked out, but it's not like hackers just transferred all the money out of their bank accounts. That mostly happens in movies. That said, there are many companies with many software systems. Hackers don't care if the take money from Target or Walmart, so they can attack all the companies and just see where they get lucky. Attacking Apple is harder, because there is only the one Apple."
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o25sgv | Does wearing glasses worsen your eyesight? | I just got glasses and im curious, some tips would be appreciated! | Biology | explainlikeimfive | {
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"No—actually, not wearing them can make it worse. if you’re a child, you should go outside. In head to head studies, children who were exposed to more sunshine had better eyesight, even when they spent an equivalent amount of time on homework. But also, make sure you’re looking up at things not right in front of your face every few minutes. This prevents eyestrain and stretches the iris muscles.",
"Assuming you are myopic (near-sighted) then your eyes should be completely relaxed when looking into a distance if your glasses are perfect. So this won't cause any problems. But if you spend your time looking at a nearby screen for hours (e.g. a computer) and you wear your glasses, then you will strain your eyes extra, because they will have to compensate for the glasses. So if you can look closely without glasses then it's probably better to take them off. In short: probably not, but it could strain your eyes when looking up closeby."
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o25w1g | Since we technically never truly ‘touch’ anything due to electron repulsion between atoms, how can we sense touch and have a very clear sense of texture? | Biology | explainlikeimfive | {
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"That repulsion compresses atoms under your skin which are sensitive to being compressed, and they send an electric signal to your brain so it knows that it has touched something."
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o26xdo | How do we know that some galaxies aren't made of antimatter? | My limited understanding is that the only interactions we have with other galaxies is through photons, and that photons have no anti-particle (or are their own anti-particle). I'm also under the impression that the vast majority of galaxies are very far apart from each other and moving further away, so we wouldn't be able to observe matter galaxies interacting with antimatter galaxies. How do we know that some of the galaxies we can see aren't made of anti-matter? Would it be important if some of them were? | Physics | explainlikeimfive | {
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"Space is not completely, entirely empty. At some point between a galaxy made of anti matter and a galaxy made of matter (or even at the scale of galaxy clusters) you are going to have a crossover point. Even if this crossover point is in deep space, there are going to be some number of anti-particles colliding with some number of particles, which would create possibly detectable bursts of energy on a somewhat regular basis.",
"There is more gas in between galaxies than there is matter in them. If there were a galaxy made of anti matter there would be a boundary where the anti matter gas that makes up that galaxy interacts with matter. This would create an extremely bright and obvious signal. We dont see this.",
"Were this the case, there would be a border between the 'matter' regions and 'antimatter' regions. Despite space being pretty empty, it is not nearly empty enough to prevent collisions at this border. The shear amount of energy being released at this border from the collisions would produce a 'glow' that should be visible from Earth. This glow would likely not be visible light, but rather ionizing radiation. We could still detect it."
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o275jr | How is an inch of rain measured? Same goes for snow. 5 inches of snow? What's the width, or height, or shape of this inch? | Earth Science | explainlikeimfive | {
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"In it's most basic, you can just put out a bucket and se how deep it fills up. The length and width just don't matter, as in a small open area, rain falls uniformly. Only the height makes any difference.",
"This one's real simple: they have collectors that are basically just graduated cylinders on a stick. The measurement is just the vertical measurement: one inch of snow or rain means that if you stick a container out on a flat surface, the rain will fill it 1 inch deep.",
"The rain measurement is made with a rain gauge. It just needs to be placed in an open area with no obstructions, like trees, above it. URL_1 Snow measurements are make with measuring sticks in an open area with a flat surface. URL_0"
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o27iz9 | What is an api and why is it useful? | From what I understand, it is a package of software that another company creates, so that a startup can use it and doesn’t have to code as much backend?? I’m only partially understanding this... edit: thanks everyone, this conversation has helped me understand the nuance | Technology | explainlikeimfive | {
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"ELI5 Answer: Think of an API like the controls to a car. You've got a gas pedal to go forward, a brake pedal to stop, a steering wheel to turn, etc. You've also got information about the car - how fast it's going (speedometer), how fast the engine is turning (tachometer), how much gas is in the tank, etc. You don't need to know *how* the gas pedal makes the car go forward or the details of how the fuel tank reads its level. In fact, the 'under the hood' operation varies wildly from car to car, but since the car's interface is (roughly) the same, you can get in just about any car and drive it. The set of controls and information is like the car's API. \"Turn this wheel to make the car go to the right. Look here to see how fast you're going.\" is like a website's API saying, \"Give me a string of text and the ID of a parent comment, and I'll post a reply to that comment\".",
"API stands for \"Application Programming Interface\". It isn't so much a piece of software that you create, but rather the interface that programmers can use to interact with the software you created. API's take a lot of different forms, but broadly, they tend to fit into one of two categories. A **Web API** is an interface that works through the internet, in most cases speaking the same language that your web browser uses (HTTP/S). In this case a company will have software running on their servers that provide some service and developers and users send requests to this API over the internet. For example, you could send a request to Twitter's API to get a list of tweets from a particular user. A **Library API** comes with a code package or library that someone creates. These are re-usable bits of code (usually for some programming language or other). But for developers to be able to integrate that code into their project, they need to know how to use it and that's where the API comes in. For example, say I'm writing a Python program and need to do a bunch of math on large data-sets. That will be a real pain to do myself (especially if I want it to be fast), so instead I could use download the numpy library, and use the functions it exposes as parts of its API to do all the heavy-lifting for me. EDIT: Replaced the last example with something a little easier to understand.",
"An API enables other developers to interact with your application programmatically. For example, if a developer wants to create an app showing the weather in their area, they can do have their computer ask the National Weather Service's API what the weather is, and the API responds with the answer. Why is it useful? Well, in this example, imagine every time you opened the weather app, some poor chap has to run over to the weather office, check the instruments, record the data and send it to you. Inconvenient right?",
"API = Application Programming Interface, which I feel does not help anyone who doesn't know what those words really mean. Application = for your apps Programming = intended for programmers / other software to use Interface = a specification for how you should talk to this piece of software. what endpoints are available, how you should format data going in, what it looks like on the way out, how you login or authenticate with the API, etc. This \"interface\" is what you or your application \"talk to\" to make stuff happen or retrieve information. These days, an API is often contrasted with an SDK (software development kit) in that you have to install SDKs on your own machine, whereas most modern APIs are just HTTP requests / web pages you load to \"talk\" to a piece of software or a service. This is not always the case, but it is the modern, trendy usage of the terms. **Since we're on Reddit, why not take a look at Reddit's API?** [ URL_4 ]( URL_3 ) And if you're logged in, you can even load this URL to see your current profile data: [ URL_0 ]( URL_0 ) I don't know what's safe to share from that response, but you'll notice it's a bunch of { data: { in: { curly: brackets } } } You might be wondering, why that weird curly brackets data instead of just a plain paragraph that says something like, \"You are /u/thefuckouttaherelol2 and you've been using this app for 3 months. You have the following features enabled, etc. etc.\" This is because most modern APIs follow the same protocols, which in programming, are just standards for how different pieces of software or hardware talk to each other. For example, Reddit's API appears to be a [RESTful API]( URL_2 ) that returns a [JSON]( URL_1 ) response. Since these are very well-known standards that are supported pretty much everywhere, it becomes really easy to write applications that communicate with Reddit and other APIs that use the same standards. This basically means I can write a piece of software that makes a **request** to Reddit's API in a well-known format. Reddit returns JSON as the **response**. My software understands both the HTTP/Rest structure requirements as well as the JSON Reddit responds with, and can convert the JSON into actual data in my program. This back and forth translation of internal program data (ex: data in a C++ or Java program) to a general purpose format (ex: JSON) and vice versa is known as **serialization** and **deserialization** \\- I can turn stuff into JSON and JSON into other stuff pretty easily because this is all standardized. XML is another popular serialization specification you may have heard of. Again, I have tools for all of this stuff. I never have to write any of it myself unless I'm deep in network programming or something like that. The tools to convert my data to/from JSON, make the HTTP requests to the server, etc. is almost always available in my programming language and platform of choice. Pretty much out of the box. Reddit, Shopify, Google, Amazon, Fidelity, etc. all publish documentation and usually offer tutorials on how to use their APIs. Most of the time, you need to sign up for an account, login through your program by calling the API with your username + password, save your login token (kind of like a cookie session ID in your web browser, but instead it's for your app?), and then supply that token for all future API requests until it expires and you're \"logged out\" by the API. Some (comparably far fewer) APIs, however, let you use them freely without requiring an account or any username/password credentials! Wild. I know this was beyond eli5 but I hope this helps someone. If you have any additional questions, just let me know! :)",
"An API is a way to expose tools you made to the world without a user interface. It can be over HTTP as others may mention but the word is not that limited. This means others can create UI for your product, or use it in automated ways. For instance you can go to google map to find out a location of a business, or other sites could use the google maps api to offer it from their site. Other places like universities may use the google maps api to process large data, without any user interface, and instead with scripts",
"An API is something released by software developers so that other software developers can use what they wrote, without needing to understand how it works. Take Steam matchmaking for instance. Game developers need to be able to use Steam so people can join/create viewable games from within their own game. They don't want to know literally every single line of code that makes Steam work the way it does.",
"Think of a candy store, and now imagine some of the candy is behind the counter. The store attendant is like an API, the candy behind the counter is the stuff you want to interact with, and you are the third-party program trying to gain access to the candy. You can ask the API to GET you certain types of candies and describe them for you. You can ask for a list or INDEX of the candy behind the counter. You can ask the API to order different sorts of candies that you find are not currently available. And finally, you can ask the API to give you some of that candy. You then can consume that information and more importantly, the candy, however you like. You can share that candy with your friends (other third-party applications) or analyze it on your own. Without the API, you would have no way of legally accessing that candy and all of the information about it. With the API, you gain a whole set of capabilities inside the candy store, and you can do whatever you want with that information (candy) outside of the candy store. Less ELI5: APIs are not just for startups, they are for anyone that has a need to gain functionality and access to certain systems, for which they lack direct access. They facilitate the flow of information and functionality between various systems. In most cases, startups could not code this functionality into their \"backends\" no matter how much work they put into its development, because the functionality (and more importantly the data) is proprietary to the third-party system they are connecting to through the API (payment providers, analytics data houses, CRMs, etc).",
"An API allows two pieces of software to talk to each other easily. So, if you're developing software A and would like to interact with software B (e.g. a social network), you would use an API by B.",
"I like the menu analogy at a restaurant. You want to provide a menu so that: - people know what is available at the restaurant (something you control) - you serve up the order instead of having the customer go into your kitchen and do who knows what. (Not in your control.) You want to provide an api so that: - people know what is available from the interface functionality wise (something you control) - you serve up the data/complete the request instead of having the client go into your system and do who knows what. (Not in your control.)",
"The API is a contract. It describes a series of functions/methods that are available to you, how you're supposed to call them and what you should expect back. The implementation of a contract/API is done in a library. You can have different libraries implementing the same API. The car example from /u/bendvis is spot on.",
"When you use a program, you are clicking on a Graphical User Interface, with buttons, text fields, and all kinds of controls. When a program uses another program or software library, it uses an API. Basically it's just a set of routines that other programs can call.",
"Lets say you're making a controller for a sprinkler system, you can set a timer relatively easily, but wouldn't it be nice if it could automatically check the forecast, and adjust how much it waters based on how much it's going to rain, or how much it's rained in the past few days? Well, that's where APIs come in. You can make a request, and get the desired information in a defined format. Example: URL_0 If you didn't have an API, you might have to buy a weather station to measure the rainfall, or you might have to scrape the data from a human readable web site, the format of which can change and break your program without notice.",
"APIs are not just for startups to reduce the amount of code they need to write they are for anyone trying to get data from another source. Application programming interfaces are just ways to access data from someone else",
"Armor Piercing Incendiary. The idea is you're shooting at lightly-armored vehicles or positions, and the round is able to penetrate the light armor and have a small explosion on the other end of the armor. Little bits of burning shrapnel going in different directions have a better chance of hitting something or causing mayhem than one solid armor-piercing bullet going in a straight line.",
"Think of the buttons on your microwave. They're an interface so you can heat food in your microwave without knowing anything about magnetrons or mains power or shielding -- you just gotta know how to use the buttons. An API is the same thing -- you don't have to know how this software actually works, you just need to learn how to use these buttons (the API)",
"APIs are a set of protocols (written as back-end code) that enable different software systems to connect and share data. If you have Siri or Google Assistant, for example, imagine asking it to play a song. The reason digital assistants are able to connect to your Spotify account or YouTube when they play music is because of API integrations. Tech companies use internal APIs as well to optimize software development within their own business. A non-technical example of an API would be a waiter. Waiters take orders from the customers and send them to the kitchen, and eventually give you your food. Essentially, APIs, or application programming interfaces, act as a liaison or middleman, accepting and fulfilling requests between different software.",
"Late to the party here but the way I like to explain APIs is like this. You ever go to the bank after hours, and only the ATM lobby is open? That ATM allows you to interact with the bank in various ways: you can deposit or withdraw money, move money from one account to another, etc. Importantly, your ability to interact with the bank in a way that is dangerous to the bank is severely limited through this ATM interface. The scope of your interactions with the bank through the ATM is much more limited than say, if you walked into the actual bank with a gun and started making demands, or if you had access to a back office computer. The bank is the software company. You are the third party company. The ATM is the API",
"So I think this is the simplest way I can explain it. Think of web development or any other application with 3 main \"layers\". 1. UI 2. API 3. Database I'm going to explain these out of order The bottom layer (#3 Database/backend): A database is a collection of data often stored in tables (kind of like an excel sheet) there are rows and columns that hold data. i.e. | City | population | | New york | 69 | | Los Angeles | 57 | The first layer (#1 ui): The top layer is the UI (user interface) it's literally what the user interacts with, any thing you see on the web is part of the ui (i can't think of anything that isn't but there may be someone out there to prove me wrong) i.e. buttons, text boxes, anything you can see on an application The seccond layer (#2 API): The api connects the two of them. Imagine an application that displays new yorks population everytime you click a button. The button is UI, the population number is stored in the database, and the api would be the code that listens for the button click and then pulls data from the database to display on the screen. So the api is that transaction that happens behind the screen (no one sees it happen). Hope this helps, it's the best I can explain."
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o27xhz | Why are plastics straws so bad for turtles and not all plastic in general? What's special about straws? | I don't get the whole "don't use plastic straws" but at the same time we use tons of other plastic products. Is there a difference? | Earth Science | explainlikeimfive | {
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"The controversy of plastic straws and turtles arose from [this]( URL_0 ) video uploaded to YouTube in 2015. In it a turtle has what appears to be a plastic straw lodged rather deep up one of its nostrils. The individual in the video (a researcher named Christine Figgener) posted a write up about the incident in a [Nature journal article]( URL_1 ). There really isn't anything specifically about plastic straws that make them bad compared to other plastic items, other than: * We use and dispose of a large number of them each year * They are small and long enough to trap or get trapped in various wildlife and their orifices (holes) Though these attributes are true of many plastic items, particularly those that are small and brightly coloured - which can be mistaken for food then ingested, or just get stuck by accident. Really there is no difference, it was just the video that caused a large emotional reaction for viewers. We need to halt leakage of our waste into the environment, not just plastics but all materials, chemicals, and pollutants.",
"All single-use plastics are a problem, but a lot of them serve important purposes that we don't necessarily have great alternatives for. Inexpensive packaging to keep things fresh and sterile, for instance. But straws...we don't really need straws. So it's an easy target. There are also many alternatives in cases where straws are still kinda useful. We say \"don't use plastic straws\" because there's actually a good chance people will listen. Saying \"don't use ziploc bags\" won't work very well, because those are actually pretty functional and we can't just replace them with bits of bamboo on a whim.",
"u/OsamaBinLadenDoes explained it well. Plastic straws caused a large emotional response because of the turtle video. It got popular/viral enough that politicians latched on to it to ride that popularity wave in search of power and personal gain. Enough of them campaigned on it that some changes were made (by politicians that were otherwise fine using plastic straws and voters that need to feel they're helping). It's political theater to gain power and make people feel productive. If you really wanted to have an impact on plastic waste in the world's oceans you wouldn't start, and certainly wouldn't have stopped, with plastic straws.",
"All single use plastics are bad for the environment. Straws are just one of the biggest examples of single use plastics, and feel like they should be reasonably easy to replace.",
"basically banning plastic straws makes people think that something is being done about the plastic pollution in the oceans, when in fact, it will make no difference at all, it's like trying to tackle deforestation by banning toothpicks. a picture/video of a sea turtle with a straw up it's nose went viral and drew the sympathy of millions and politicians capitalized on it. the main offender of ocean pollution is commercial fishing vessels, but there's too much money involved for anything to actually be done about it. even things like \"sustainable seafood\" \"dolphin safe tuna\" are all basically scams."
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o29kla | why is it beneficial to raise your heartbeat count with exercise? | meant heart rate. sorry. | Biology | explainlikeimfive | {
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"The human body is either efficient or lazy, depending on your point of view - it only does what it has to do. Muscles, blood vessels etc. all take energy to maintain, so your body will save energy by not wasting maintenance on things that aren't used. Raising your heart rate shows that your body is having to work harder to keep up with oxygen demand. Do it repeatedly and over a period of time your body will get better at it by maintaining and improving your cardiovascular system."
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o2bpje | Why do babies laugh? Are they capable of finding things funny at such an early stage? | Other | explainlikeimfive | {
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"With laughter it's important to understand it's a very deeply seated evolutionary mechanism to form social relationships. You can't force true laughter, and you laugh alone much less than in groups (approximately 97% less likely). Adults usually laugh at things that are amusing. However, babies primarily laugh during social interaction or when experiencing new things. Thus, it is likely to be an evolutionary benefits. The adult is flattered because they think the baby thinks they are funny. The baby laughs in order to illicit attention and learning from adults. Essentially from an evolutionary perspective they are mimicking adults to increase their own chance of survival.",
"One of the reasons people laugh is when our expectations have been violated (usually in a benign way). I imagine a baby's expectations are violated near constantly. \"Yay, mom's here. Oh shit, mom's gone forever and all that remains are hands. Mom exists again!\"",
"I had no idea that babies got erections until I was dating a girl with a baby in my mid thirties.... I have daughters so when I walked in on a diaper change, kid was like 9 months I guess, and she was having a difficult time putting the diaper on because the kid was hard as a rock with his little baby boner and I was shocked. He was laughing and giggling and just happy as I'd ever seen him. I didn't know they worked like that when we're that young.... Wow... Didn't think when I woke up this morning that a reason would present itself to post something about a baby boner on the internets but here we are....",
"Yes. Their understanding is simple, but they have a sense of humor. My little one was really into when I stuck out my tongue and made faces for about the first 10-months. After that, I had to start falling down or dropping things. Being a dad is 85% literally clowning around.",
"Laughter is an innate response to finding something funny. Finding something funny is frequently caused by subversion of expectations. You expect one thing to happen, and then something different does. With babies, their expectations are in such flux due to lack of any experience at this whole… life… thang… that it's quite easy to subvert their expectations. They literally find everything funny. (To an extent.) So, of course they laugh a lot.",
"I remember something about laughter being an interrupted fear response. That would explain why peekaboo is funny.",
"Also, dancing. My daughter was just starting to pull herself up on furniture to stand when a song came on the radio. She instantly started dancing. She couldn't walk yet and she is bopping up and down to the music.",
"One explanation I read is that humour is when the mind makes new neuro links. When you take two previously unconnected memory or thought patterns and link them, it can trigger either a laugjter/humour response or a hate/disgust response. (This is why dead baby joke can be both funny and horrible) Babies have very few memory patterns and everything is a new connection, so if they are not uncomfortable (cold, wet, insecure hungry etc) then they are learning and making ne connections.",
"At that age they can only find dane cook,joe rogan, and carlos mencia funny. Thankfully they evolve a more sophisticated sense of humor by age 2"
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o2cjyn | what’s the actual difference between different atoms besides just some protons, neutrons and electrions? | What is it about, let’s say arsenic atoms, that makes it so much more deadly than gold for example. And please expand this to molecules too. | Chemistry | explainlikeimfive | {
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"Most of the effects you are talking about are just the chemistry of the atoms. The chemistry is a result of how many electrons they have and \"want,\" which is a result of the number of protons they have. So the difference between arsenic and gold, in the end, is that arsenic has 33 protons and gold has 79. That changes how they work chemically, and how a body will process them (it'll just excrete the gold, but the arsenic will be bioactive in nasty ways). If you had an arsenic atom and could add 46 protons to it, it'd be gold. This is what we mean by a \"chemical element,\" so if it seems tautological, it sort of is — gold is any atom with 79 protons, arsenic is any atom with 33. The number of neutrons influences the physical properties of the atom — notably it can determine whether it is radioactive or not, and how radioactive it is. So any atom with 79 protons is gold, but depending on the number of neutrons it might be normal gold, or it might be radioactive gold. These different types of atoms, with different neutron counts, are called \"isotopes.\" Lastly, molecules are just groups of atoms that are joined together by shared electrons. Again, how this works is going to be determined by the chemistry, which means by the electrons, and so ultimately the protons.",
"Interestingly enough, nothing. In most cases it's all about how the electrons exist around the nucleolus. Different numbers of electors create different \"shapes\" to the atom. What happens is that the electrons attract to the protons but repel from each other. Because of this every different number of electrons create a different atomic shape. I recommend looking up some pictures online. These shapes of electron clouds allow atoms to share and borrow elections. These exchanges create chemical bonds, and pretty much define our world.",
"The moment you start asking about \"why is X deadly\", the answer necessarily stops being about the physical properties of X itself (the number of protons and neutrons, electron configuration, etc.) and more about \"what thing in the body does it fuck with that really, *really* needs to be working properly to keep me not dead\". Typically it involves bricking a specific protein, and often it does that by accidentally getting attached to a very important part of the protein - the part where an actual reaction is supposed to be taking place - and not letting go. Rendering it as useless in sort of the same way as if you put Flex Glue instead of motor oil in your car's engine. In the example of arsenic, it bricks a protein called pyruvate dehydrogenase by sticking to the sulfur atoms in it. Pyruvate dehydrogenase is very important for the process of the cell producing energy. Without it working properly, the whole cell sort of grounds to a halt and shuts down because it runs out of energy to do anything. Gold doesn't do this. Gold doesn't really want to stick to any important proteins in your body."
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o2eou5 | Why are planes grounded when there is fog but they can fly through fog and clouds. | I dont understand when they have control towers and such advanced technology why fog can ground planes. Not much is done by eyesight now surely? | Technology | explainlikeimfive | {
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"Flying and landing are not the same thing. Flying involves working hard to stay far away anything. In that system, a cloud or fog isn't a problem. Alas landing can't work without touching the ground, gently. That gentile touching is hard to do when you can't see the ground.",
"Pilots need visibility to maneuver the airport. They need to be able to see beacons, runway marking, airport support vehicles etc. The tower needs to be able to see plane activity on the runways.",
"Instrument rated pilot here. It is possible to land a plane in “zero zero” conditions, meaning clouds are to the ground and you can’t see anything ahead of you. Doing so requires the aircraft and runway to have special equipment and the aircrew to have special training. Check out Cat III Autoland, there are plenty of videos on YouTube. Any instrument approach will have “minimums”, a required vertical visibility to land. This is typically 200 feet, or 100 feet with certain lighting systems. Approaches are flown with GPS, ground based radio beacons (instrument landing system), or a combination of the two (GLS). Visual approaches are quite common in good weather. Planes can land closer together in visual conditions.",
"It depends on who is flying. Most commercial airliners/pilots are rated for instrument-flight, meaning they can fly in adverse weather conditions like fog or night-time. But for private or charter planes/pilots, they may not be rated for that, so they can only fly when it's clear skies. Additionally, there is increased risk. Take off and landing are the most dangerous times in a flight. A plane in flight can't really do that much to get out of clouds/fog; additionally, there's not much else to run into at 30,000 ft above sea level. But, near the ground, there are a lot more hazards, so it's a lot safer to wait for clear(er) weather before taking off to minimize the risks during the already-riskiest part of the flight."
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o2gc8x | How does an EpiPen work? | Biology | explainlikeimfive | {
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"The pen itself is basically a syringe on mousetrap. Once you push the activator hard enough, a spring shoots the needle into you and the plunger on the syringe is pushed, injecting you with epinephrine.",
"Epipens contain Epinephrine (hence the name) a medicine that causes the muscles in your airways (neck and throat) to relax, which makes breathing easier. (Since most allergic reactions are dangerous because they cause your airways to tighten up/close up, suffocating you.",
"\"Epi\" = epinephrine = adrenaline. Other commenters have already elaborated a bit on what it does (relax the airways), so I'll just clarify the name because many people don't realize they're the same thing. Latin: *ad-* for \"on\"; *renis* for \"kidney\" Greek: *epi-* \"on\"; *nephro* for \"kidney\" In the body, adrenaline is made by the adrenal glands, which are indeed located above the kidneys."
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o2h1ck | Why do trailers come before the feature? | Because word suggests that they would come after the feature. | Other | explainlikeimfive | {
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"A long time ago, you would just buy a ticket to enter the theater and watch whatever was playing. There weren’t set showtimes so you could just walk in, possibly halfway through a film. After the film, they would feature newsreels, cartoons, and previews for other films (trailers!) before the feature would start over (and you could watch the part you missed) or until the next film started. Later on, tickets started being sold for specific movies beginning at specific times. More like a play. Since that created a captive audience waiting for the show to begin, it made more sense for theaters to show the ‘trailers’ before the feature, while everyone was stuck waiting to see the thing they paid to see. Hopefully giving them a reason to come back and see something new later on. The term ‘trailers’ had already stuck at this point, they just played before instead of after the film."
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o2hc70 | How did humans first find the gasses on the periodic table we use today, and how did they go about collecting it? | Like, did someone just come across helium one day, not knowing what it was, and decided to start collecting it in containers? What about neon, hydrogen, and all the others? How did they know where to look, and even when found, how did they collect it without all the gas escaping into the air around them? | Earth Science | explainlikeimfive | {
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"Helium was first discovered by analyzing the spectrum of sunlight. That's why it's named after Helios the sun. It was thought that it only existed on the sun until they were doing checks on the spectrum going through different gases that came up from the earth and they discovered that the same lines appeared as what appeared in the sun.",
"The gases on the period table where discovered gradually. After we started to make the period table logic predicted that if there is an element with 4 electrons there is probably one with 1, 7, 8 and so on. It was just a matter than of discovering a pure form and naming it. Oxygen was unknown for a long time the only hint people had was that- apparently. A rat under a dome died when closed for to long but a rat under a dome with a plant inside lived longer. About collecting it. Most non-royal gases (so everything that isn’t helium, neon, argon, xenon) etc. are in other stuff like water is just Hydrogen and Oxygen. You can do something called an „electrolyzing“ process where you use metal and electricty to split up the water and the oxygen goes to one and Hydrogen to the other pole. That dosn’t only work with water it works with lots of fluid. Royal Gases are a bit tricky. Idk how people did it in the past but nowadays we literally cool down normal breathable air until its liquid. In our air are alot more things than Oxygen. Actually only ~20% of our air is. Its mostly Nitrogen and oh- Royal gases, would you look at that. Anyway you cool it down till its a liquid, however the different gases have different temperatures where they start to become liquids. So by emptying to tank in between you can, over time, split up the different gases. Imagine if you had a sludge of molten metal with- lets just say. Gold and Iron. Golds melting point is way lower than Irons so the Iron will become solid first, you can than take the iron away and only the gold remains. It works the same with the gases just that you have to manually cool it down.",
"Helium was discovered by analysing spectral lines from the Sun, and realising that there was an element that that did not exist (or had not been found) on Earth, so they named it after the Sun, (Helios) Hydrogen was discovered by reacting iron with water. Under anaerobic conditions, this reaction only gives off hydrogen as a gas, so it was pretty easy to produce and contain. They realised that setting fire to hydrogen (reacting it with oxygen) produced water, hence the name *hydro*gen Argon, krypton, xenon and neon were discovered by liquifying some air, then gradually boiling it. This way, elements and compounds with different boiling points could be separated.",
"They found out things by doing \"stuff\" and recording the results. So they would add X to Y and see what happened, then they would put a flame above it, then do something different. All the time while logging everything that happened so they could replicate it."
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