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m41p1n | Is space infinite? Is there something else "outside of outer space"? | Other | explainlikeimfive | {
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"> Is space infinite? We think so. And it’s also getting bigger, which sounds silly because infinite acts silly. > Is there anything outside of space? Some people think so. String theory thinks that our universe is like a hole in cheese. And every hole in the cheese is a different separate universe. Other people think this is the only universe.",
"I heard one hypothesis that if you were to start traveling perfectly straight in one direction, you would eventually come back to where you started. It's like you circled back, but you were going in a straight line the whole time. How that works, I don't know, and I'm not sure if it's still an idea being explored, but it's certainly interesting.",
"Honest answer nobody truly knows. We can only see so far into the night sky due to the speed of light. But we don't know if there are stars or anything beyond that distance since the light has not reached us yet if the stars were beyond that distance. There could possibly be other matter beyond this distance but we have no way of actually knowing. It could even potentially be infinitely big.",
"No, there's nothing outside of reality. Nothing we could comprehend, anyways. Space is, by its definition both limitless and finite. Finite in that there's an edge of space, the outer edges of the Big Bang explosion that brought everything into existence, but we'll never be able to reach it due to spatial expansion. Space itself is expanding faster than the speed of light and that's the absolute limit of how fast anything can move without breaking the laws of physics. And even if we could go faster than light, space itself is vast beyond comprehension. We're one planet around one star in one galaxy among countless galaxies. You could literally hurt yourself trying to imagine the vastness of reality and space. There's a video out there that shows the vast scale of the universe as it starts off at Earth and then begins to scale outward to show the solar system, then the local star cluster, then the local region of the Milky Way galaxy arm, then the galaxy itself, then the galaxy cluster, and on and on and on and at some point, it stops having any meaning.",
"The short answer is: we don't really know. I don't really know enough about physics to explain our best guesses though, sorry",
"Space is infinite*. I'd like to say that there is nothing outside of outer space, but the phrase doesn't actually make sense. The universe is defined as \"all that there is\". \"Outside of the universe\" is a phrase that contains a contradiction. * Disclaimer lalala: as far as we currently know. Future refined measurement might find a positive curvature to the universe, making it finite. In that case, \"outside the universe\" would still make no sense. Travelling in a straight line at a theoretical arbitrary speed that magically ignores relativistic effects would just eventually bring us back to where we started. We still wouldn't be able to \"leave the universe\"."
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m42fsm | Why is it harder to stay asleep when you go to bed at an earlier time than your normal bed time (i.e. 7pm rather than 11pm)? | Other | explainlikeimfive | {
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"Your brain loves patterns and expects them, adjusting the whole body function around established ones. Pattern is known and safe so it slowly starts to prep for sleep way before bedtime, anticipating rest but if you go before it may simply be not ready. This is why sleep hygiene is important.",
"The ‘sentinel theory’ suggests that humans can train themselves to sleep during a certain time of day because our ancestors would have been preyed upon and only felt comfortable sleeping when others were taking watch. So individuals slept and guarded in shifts instead of collectively sleeping at a certain time."
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m42iep | Why does a beer overlow when someone hits the top of a beer with the bottom of theirs? | Other | explainlikeimfive | {
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"Because it causes the bottle to almost intantly move down, but the beer tends to stay where it was. This causes a considerable decompression between the beer and the bottom of the bottle, favoring the formation (and expansion) of bubbles, which will rise and form the foam that you see. Basically umit's the sped up version of shaking the bottle P.s. sorry for my english",
"The impact causes a series of alternating expanding and compressing waves to bounce between the bottom of the bottle and the surface of the beer. These waves have an effect on the beer that cause large air bubbles to form. The same waves then break the big bubbles into many tiny bubbles. These tiny bubbles have a higher surface to volume ratio causing them to expand rapidly and that’s where the overflow comes from"
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m4332x | Was there a time when the universe didn’t exist? And if so, how can something arise from nothingness? | Physics | explainlikeimfive | {
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"Based on the laws of physics something can’t come from nothing. So that tells us either there is something out there that made us. Or someplace has to exist with different laws of physics that allowed all of this to be created from nothing. Either way physics can’t tell ya whats on the others side, you’re better turning to religion lol."
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m43s6u | What are the Panama papers? | Economics | explainlikeimfive | {
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"It was basically proof that a lot of the richest people and biggest companies in the world are engaged in complex schemes of fraud, money laundering and tax evasion via offshore shell companies.",
"It was a ton of leaked documents from a Panamanian law firm called Mossack Fonseca that confirmed widespread tax evasion and fraud by a wide range of corporates, celebrities and politicians worldwide,",
"It was a giant leak of documents from a Panama-based financial services company that mainly dealt with wealthy people's private bank accounts in tax havens using shell companies. You know the stereotype of the 'Swiss bank account' being used to hide large sums of money in foreign countries where your home government couldn't tax it? That's basically this, but mainly in Caribbean nations nowadays. People named in the documents included heads of state, relatives of royals, government officials, businessmen, celebrities, and more. The majority of them were from Europe, the Middle East, and South America, with the highest ranking person named being King Salman of Saudi Arabia. Lots of people involved in FIFA were named, including their President. While this is generally scummy, it's not necessarily illegal in and of itself in most countries due to loopholes(hell, the fact that it's legal is why so many people went for it in the first place). However, some of the shell companies set up were involved in things like fraud, organized crime, and terrorism. One of the more notable things that resulted from the investigation was a political crisis in the Mediterranean island nation of Malta. Maltese journalist [Daphne Caruana Galizia]( URL_0 ), who was in the middle of investigating ties between shell companies the Panama Papers to both the Maltese government and organized crime, was killed by a car bomb. It's believed that she was killed by the mob with the aid of a prominent Maltese casino owner who had shell companies mentioned in the Papers. Investigations into her death not only revealed that several cabinet ministers were involved in shell companies in the Papers, but that the Prime Minister had also tried to stymie the murder investigation to protect his reputation. General outrage over both his cabinet's corruption and his stonewalling the investigation led to his resignation in 2019.",
"You know rich people? You know how they like money? Turns out that pretty much all of them were evading paying taxes on that money. Like, a lot of taxes. Billions of dollars, even.",
"Rich people tend to stay rich by avoiding paying the taxes that poor people do. One of these tricks is storing the money outside of the country where the tax should be paid. Places like Panama are \"tax havens\" where money can be hidden without tax being paid. The Panama papers was a leaked set of documents exposing specific instances of this crime by high-profile people.",
"To enable international trade, there must be taxation laws that allows money to flow from one country to another without taxation. Now, imagine that you would want to use this basic idea to entirely avoid paying taxes. What do you need then? You need a flow of money that is difficult to oversee. You need someone who helps you move money to and from countries where it's difficult - if not impossible - to ask a bank who the money belongs to. Panama is a country where it's somewhat difficult to look into where money comes from and where it goes. A law firm in Panama has specialised in tax evasion setups (entirely legal, based on the basic idea of free flow of money. Often illegal or at least immoral in your country of residence to make use of this kind of services) and they have been doing it A LOT. Someone in their staff with access to legal and financial documents (electronic documents, I assume) blew the whistle on them and gave a really large set of documents to an international corporative organisation for reporters. The reporters, from several different countries, looked into the documents FOR MONTHS. And then, on the very same day, they all released information about their rich celebrities, royalties, politicians (including some prime ministers) and some organisations that are trying to play the poverty- and/or moral-card all the time. Internationally. Globally. The result, except the bit where a lot of national tax authorities now have proof of tax evasion and sometimes tax fraud, was that a whole lot of people were publicly shamed. Some politicians resigned. Some complies have tossed out their CEO's and some celebrities are now left without their contracts. And so on. Pretty interesting few days, that was."
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m43w06 | Why is space expanding? Can we detect it? If so, what causes it to expand? If not, is there a theoretical way to detect what causes it to expand? | Physics | explainlikeimfive | {
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"> The way I understand it is that space is expanding constantly and while the expansion itself isn't faster than the speed of light, it appears that way because there is just so much space. How 'fast' the expansion is depends on how far apart two points are, so saying it's faster or slower than something doesn't *really* make sense. The distance at which it becomes faster than light is the cut-off point of what we call the *observable universe*, because obviously light will never reach us coming from a galaxy that's moving away from us at faster than the speed of light. > Is that how space is expanding? To the best of our knowledge, space is not made of discrete cells. There are some theories which try formalizing something like this (e.g. loop quantum gravity) but the only accepted theory of the universe (general relativity) treats space as an infinitely divisible continuum. Of course, we also know that general relativity is wrong, because it breaks down at quantum scales. So the true answer is \"we don't know\". > Do we know how and/or why space is expanding? No. We do know some things though: For one, space seems to have expanded *very, very* rapidly in the early universe, driven by some unknown force. We call this \"inflation\", and attempt at modeling it have sometimes attributed the cause to some currently-unknown \"inflation field\". As of today we have no evidence for or against these theories. Also, the expansion of space seems to be *accelerating*. We don't know what causes this acceleration, which is why we gave it the name *dark energy*. So in a way, it's accurate to say that \"dark energy causes the expansion\", but that doesn't really answer the question because we don't know anything about dark energy other than that it causes the expansion of the universe. The best guess we have at what dark energy could be is that it's caused by random quantum fluctuations, but the rate of expansion predicted by the latter and the rate of expansion we measure are off by 120 orders of magnitude. So the correct answer is \"we don't know\". > Can we \"zoom\" in to see it? No. Certainly not at the energy scales we've been probing. The largest microscope ever built (the LHC) hasn't been able to detect anything relevant to quantum gravity or dark matter / dark energy. Of course, particle physics remain convinced that if only we had an *even bigger* microscope, we *should* see something."
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m445uh | why do batteries charge quicker when they’re empty. | I’ve noticed that my phone will charge really quickly up to 50%ish and then the speed it charges to 100% is much slower. I’ve found this true for other devices too, why do batteries charge quicker when they’re empty and then the speed slows down to get it to 100%? | Technology | explainlikeimfive | {
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"Think of pouring water into a mug. When it's empty, you can pour quickly. But unless you want spilling boiling water all over, you have to slow down when it's getting full. Overcharging batteries, especially the lithium kind is bad. It damages the battery and can result in the battery catching on fire if you really overdo it. That's why these days we have charge controllers that take care of doing the charging right, and protection circuits that will disconnect the battery if something goes wrong.",
"This is because of how modern lithium battery charges. The battery starts with a \"constant current charge\". Where the charger gives the battery the amount of electrical current the battery is rated for. And the battery charges at it's best speed. However, as the battery fills, the voltage inside the battery goes up. And to avoid damage to the battery the charger now has to switch to \"Constant voltage charging\". Here, the charger feeds the battery only with a certain amount of voltage or \"pressure\" and the battery simply takes as much electrical current as it can handle. And it charges signifficantly slower therefore."
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m44cuu | why do we have different time zones instead of everyone being at the same current time and simply doing things at different hours of the day? | Other | explainlikeimfive | {
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"Two questions being asked here: 1. Why *are* things this way? and 2. Why might we want to *keep* things this way? I'm not sure about the historical context leading to the first answer, but I can come up with some ideas for the second answer: - Right now, statements like \"need to wake up at 5:00\" are culturally unambiguous, because everybody in the world understands how awful it is to wake up at 5:00. Changing that will make it more difficult to communicate time information relative to your day/night cycle. (Though admittedly a weak point, since \"after 5 hours of sleep\" works just as well) - In a legal context, it's possibly easier to formalize \"citizens must remain silent from 22:00 to 5:00\" rather than having to go with some awkward description like \"from -2 hours to +5 hours *relative to midnight*\", which is technically just what \"22:00\" and \"5:00\" already mean anyways. - With a fixed time zone, DST would translate to needing to adjust all your memorized times, i.e. your meeting is now always at 3:00 instead of 2:00 - having locally shifting timezones allows you to keep the same times in your head even as the mapping from time to day changes. If you want to preserve this property you'll still have weird +/-1 hour differences, which somewhat defeats the point. - In most contexts where it matters (international trade, technology, etc.), people already use UTC as this universal source of constant time. But most things that depend on the time (i.e. primarily local events) aren't really burdened by timezones existing. - Changing things now would be a massive disruption to the entire ecosystem, people's habits, etc. - look at how long it's taking to standardize units of measurement across countries, to get a sense of how difficult it would be to standardize the units of time. All in all it seems like an idea with some neat fringe benefits for frequent international travelers / collaborators, but probably relatively inconsequential to our everyday life and doubtfully worth the effort of disruption.",
"The whole idea with the time zones is that everyone should - with a small shift that isn't really noticeable - have midnight in the middle of the night and noon in the middle of the day.",
"The way we track time is relative to the position of the sun. If you said \"noon\" no matter where you are you can determine the \"noon\" that is relative to you by the sun's position in the sky.",
"It wouldn't work for many reasons. If you wanted to phone somebody far away you would still have to work out which part of their wake/sleep cycle they will be in. Just because their clock says the same as yours doesn't meant that they will be doing the same thing you are. You would still have to look up their location in a table to find out if it was a good time to call. There would be a bigger variation because without the hour slots, everybody's circadian rhythm would tend to revert to local Sun time.",
"This would just shift the problem of having to know what time is it now in US East Coast, to, say, what poeple would be doing at this time in US East Coast. Now I know it is 1PM in Hungary, my colleagues in NY are behind me 6 hours, so it is 7AM there. NOW as I know what I would do at 7AM I can put myself in their situation and know that they are probably waking up, having breakfast, drive kids to school, just as I would do at 7AM. Given the time would be 1PM there as well as here in Hungary (although \"AM\" and \"PM\" would lost their meaning) now I would have to think about \"what time it would have been there\" so I do not disrupt their lives. It is usually custom that we don't call people on phone during lunchtime. When would be lunchtime on this new system? Everytime. This problem would bring back timezone shift to the system indirectly (you would have fo calculate with that), which would make things harder.",
"If you have time zones varying with longitude, then the time is basically telling you \"where is the sun in the sky right now\" Imagine you're going on a long plane or train journey, travelling across multiple time zones. When you get off, you want to know if the shops will still be open, if it'll be dark out, when you should start thinking about finding some food, that kind of thing. With time zones, this is easy. Your pilot tells you what the local time is, or you look for a clock when you get off, or your phone tells you, and now you have a pretty good idea of all of that stuff. Without time zones, you know it's 3 PM, but you have no idea what that means. Maybe you can take a guess based on how far away it is, but still; you don't know if it's light or dark out, how many people will be out on the streets, whether anything will be open. And every time you travel you have to keep mentally adjusting to remind yourself _3 PM doesn't mean mid afternoon here, it's late evening_, which would be quite confusing, particularly if you travel a lot. Or even simple things, like reading a news story and it says \"the crime happened at 10 AM\" but it's in a distant country so you have no idea what that means. Or you're trying to schedule a meeting with people across what would currently be multiple time zones. Since the time zone is the same for everyone, you have to awkwardly ask everyone what times they'd be awake for rather than just looking at their time zone and immediately being able to work out something that makes sense for everyone."
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m44uh6 | Why does the temperature gauge on my shower have so little margin for error? | All my life. Every shower I have ever been in has the most sensitive temperature gauge. One tiny movement turns the water from freezing to boiling. Doesn't this kind of defeat the point of having a whole swinging arm when I can move it a millimeter and feel like I'm burning myself? | Physics | explainlikeimfive | {
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"There is a thing called a pressure balancing unit that sits behind that valve that can help adjust for the difference in water pressure between hot and cold. My shower at home did exactly this, either freezing or boiling, until I changed this part. Cost about 20 bucks",
"Most people set their water heater too hot. Lower the temperature on your water heater and the change will be much more gradual."
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m45ww9 | Why do some medication have to be taken in solid form? Why can't they all just be liquid for those who have trouble swallowing? | Biology | explainlikeimfive | {
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"Some can be ground up and put in, say, applesauce. But some, that are designed as extended release can’t be, because the capsule containing them is designed to dissolve at a certain rate so that the effect is spread out over a longer time",
"Some are extended release or timed release pills. This makes the delivery more reliable and convenient. (A liquid form might need someone to take a dose every 2 hours which would be very inconvenient and easy to make mistakes) Things dissolved in liquid are harder to carry around, easier to get the dosage wrong and may also have less shelf life.",
"Can be for various reasons. A solid tablet allows for accurate dosage control of the active agent over time by structuring its layers and components in a way that they dissolve in a predictable manner. *Taking* medication is also only the final step. Before that come multiple different iterations of transactions, storage and manufacturing. The specific form a medication takes is a compromise between the requirements of all those different steps.",
"Hey, a question I can help with. I am a pharmacist. In the US, most adults prefer pill dosage forms (tablets, capsules, caplets, etc) over taking a liquid formulation. Since most medications are generally for adults, there isn’t as much of an incentive to develop of liquid form (solution, suspension, or emulsion). A lot of drugs taste TERRIBLE, and you are not able to make the drug in liquid form palatable. Clindamycin liquid is a great example of this, they made the liquid version to make using in children easier. I try to dissuade providers and parents from using the liquid because the kid won’t be able to stomach it. It tastes absolutely disgusting. I’ve had multiple parents ignore my advice, then come back the following morning asking if we can get them switched to clindamycin capsules. The other discussions about extended release formulations are only part of the story, there are ways to make the medication slowly release over time in a liquid, but they are way more expensive currently. Quillivent XR and Dynavel XR are the two that come to my mind.",
"In many cases, pills act as a \"container\" for the actual ingredients to protect them from stomach acid. This way, the ingredients can actually make it into the intestines and do whatever they're supposed to do."
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m46n9y | ; Why are we designed to forget? | Biology | explainlikeimfive | {
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"Our brains have to dump excess information, otherwise we wouldn’t be able to function long term. We make thousands of decisions a day, we see and hear so much that we need to get rid of it. Important information gets stored long term but the useless stuff has to get erased."
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m46xku | Gaslighting | Other | explainlikeimfive | {
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"Gaslighting is an abuse tactic that makes the target of the abuse to start doubting their reality. The abuser denies events, attempts to convince their target that events unfolded in a different way.",
"Gaslighting is when one person makes another person think that something was their fault, when it actually wasn’t their fault.",
"Have you ever been in an argument and suddenly everything you say is incorrect and it's clear that you're in the wrong and they were completely right and it's all your fault? They're probably gaslighting you. It's a form of mental manipulation and it's very popularly used by narcissists.",
"The original meaning of *gaslight* refers to a tactic in abusive relationships where the abuser tries to make the abusee not trust their memories, senses, or impressions of things. They do so by lying about what did or didn't happen to create the sense that the abusee is misremembering or misinterpreting. For example, a simple example might be something like: > Abusee: Well, when you came home last Thursday, you were yelling and screaming and being a huge jerk to me. > Abuser: What? I was just a little stressed but I was nice all evening, remember how I made you dinner? [assume that they did not do this] > Abusee: [Thinking: am I just making something out of nothing? I don't even remember them being nice, I must be missing the good things] The goal here is that the abusee doesn't recognize or conceptualize the abuse as abuse. If the abusive member of the relationship is mad, the abusee might interpret that as \"oh well I just screwed up X like I always do, of course they're mad\" rather than \"I deserve to be treated with respect and this is wrong\". In extreme cases, they may doubt that clear cases of abuse like being beaten actually happened at all. Like most abuse tactics, it's a mix of undermining self-esteem (\"you can't trust yourself\") and creating dependence (\"so you need to trust me\"). Unfortunately, this specific use has gotten a bit diluted, and the term is sometimes (incorrectly) used to just mean \"lying\"."
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m47dji | If globular clusters are thousands or millions of stars together in one place, why do they look so faint through a telescope? | For example [Omega Centauri]( URL_1 ), a globular cluster with an estimate of 10 million stars, and yet, it looks like [this]( URL_0 ) through a telescope with an exposure of less than a second. It's even fainter if you look at it with the naked eye. Then how is it possible that a single star that we see in the sky or through the telescope is brighter than a globular cluster with millions of stars together in one place? | Other | explainlikeimfive | {
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"Short answer. They're really really really really far away. Like when you look at pics of NYC from space at night. You can make out the individual lights and you prolly wouldnt see just one. But all of them together, from far away they look like one light",
"Well, the Omega Cluster is the largest known Cluster of stars, 17,000 lightyears away with a diameter of 150 light years. That puts the apparent size of the cluster at about 1 degree. However, we are getting far less than 1/360th the amount of light from that Cluster, because *we* are so small, and most of the light generated by the stars within it is missing us. Earth's apparent size from the Cluster is 1/70.9billionth of a degree. 10,000,000 stars means 10,000,000 times more light, but that tiny profile of Earth is only getting... 62,344,906km^2 facing surface of Earth 3.25e35km^2 surface area of light from stars at 17000LY divide by 10,000,000 for the number of stars in the cluster and 62M for the size of Earth, and ~150M to account for the distance between the Sun and Earth, and the average star in the cluster would have to be 3,485,223,704,382 times as bright as the sun for it to shine *like* the sun in the sky. Naturally, that's absurd. The total mass of the Cluster is \"only\" about 4 million solar masses, meaning we are getting about 1/871,305th the amount of light from the Cluster as we do our Sun. Especially in areas where light pollution is heavy, the stars in the cluster, big as it appears physically, is just not bright enough to see clearly, being roughly half as dim as Saturn. Telescopes like Hubble can see it as clearly as possible, but they are nowhere as bright as they started out.",
"A car headlight is super bright when you are standing right in front of it, but if you see a headlight from miles away it is just a small point of light. The same thing applies to the stars and the globular clusters, the scale is just much much bigger!"
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m47ejn | How do trick candles work? | Chemistry | explainlikeimfive | {
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"Magnesium powder in the wick. Even after it's blown out, the residual heat is more than enough to ignite the magnesium, then that gets hot enough momentarily to re-light the wick."
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m47ki8 | Where does crypto get its value? | Technology | explainlikeimfive | {
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"Stocks don't give us products. 99% of the time you are buying the stock from someone else and no money goes to the company. The only reason why crypto had value is because people want it. Like gold, it's not really useful, but we give it value and use it as a currency. They do have some privacy and other benefits as opposed to other currencies, but I don't think that's what you're asking.",
"I mean, what we call money isn't that valuable either. It's just paper with stuff printed on it, and metal coins. That metal isn't even valuable like gold. We as a society agree to act like it has value and it can be traded as such. Crypto-currency is a concept for an alternative form of money - one entirely online, without a controlling government, and with a good deal of transparency - that took off in popularity. Mining is actually a necessary part of how the process works and needed to make bitcoin function at all, so miners are rewarded for their efforts with small bitcoin payouts periodically. I don't think anyone expected the value of a bitcoin to get so high. If you believe something has value and you want more of it, and everyone around you believe something has value and want more of it, and there's only so much of it to go around... Then that's enough for it to have value, isn't it?"
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m47ktf | Why if something can travel faster than lights, it will have backward time? | Physics | explainlikeimfive | {
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"Quick crash course in relativity: You know how, when driving along on the highway, if you look over at the car next you, it appears that they aren’t moving, or are moving very slowly compared to you, while the ground is rushing by going backwards very quickly? This is because we measure speed relative to ourselves. And, in fact, we can only measure speed relative to something else. So relative to you, that car going the same speed as you is not moving. Relative to the ground, you are both going 60mph. Well, light behaves a bit weirdly. A little over 100 years ago, some people, including Einstein, noticed that in the math we had explaining the behavior of electromagnetism, the speed of light was a constant. But if all speed is measured relative to something else, what is this constant speed of light being measured against? One of Einstein’s big breakthroughs was determining that the answer was, in fact, *everything*. So to go back to our car example. You have three people. One standing beside the road. One in a car going 50mph. Another in the next lane over going 60mph. To the person on the side of the road, the cars each look like they are going forward at 50mph and 60mph. To the first car, it looks like the person is going backwards at 50mph and the second car is going forwards at 10mph. To the second car, it looks like the person is going backwards at 60mph, and the other car is going backwards at 10mph. But all of them see light moving past them at the speed of light *relative to themselces*. Have a spaceship that can go 10% of the speed of light? Light doesn’t look like it is passing you at 90% of the speed of light. It looks like it is passing you at the speed of light. Have a space ship that can go 99% of the speed of light? Light doesn’t look like it’s passing you at 1% of the speed of light. It looks like it is passing you at the speed of light. How is this possible? Well, it turns out that as you speed up, time slows down, and distances contract in the direction of travel such that the math works out to have light always moving at the same speed relative to any given observer traveling at any given speed. As an example, let’s say you launch a spaceship from Earth traveling at 86% of the speed of light, which I happen to know is approximately the speed that gives you a time dilation factor of 2. They’re traveling to the closest star which is 4 light years away. At that speed, you calculate that it should take them 4 years and 8 months to get there, and you will see them arrive in 8 years and 8 months, once the light from the time they arrive has had 4 years to travel back to Earth. So you wait 8 years and 8 months, and sure enough, you see them arrive at the star, and you also see that on the ship, because of their high speed, only 2 years and 4 months passed, despite the trip appearing to take 4 years and 8 months to you, once you factor in the light delay from the distance. Additionally, to the people on the ship, the distances in their direction of travel became shorter, so what to you appeared to be a 4 light year trip, only seemed to be a 2 light year trip to the people on the ship, which is how they were able to travel that distance in (to them) 2 years and 4 months. But, again, we can only measure speed relative to something else. So while the spaceship is traveling at 86% of the speed of light relative to Earth, from the perspective of the spaceship, they look back at Earth and see Earth traveling at 86% of the speed of light away from *them*. And, after accounting for the light delay, they see the clocks on Earth ticking at half the rate of the clocks on the spaceship. Both the Earth and the spaceship see each other as the one whose time is moving slower. How is *that* possible? Now we get to relativity of simultaneity. It turns out that observers will only agree on the order of events if those events take place close enough together in space and far enough apart in time that there is enough time for light to travel between the two events. Note that, a beam of light doesn’t actually have to travel between the two events, just that in principle there must be enough time that one hypothetically could have. If that is not the case, then observers traveling at different speeds will disagree on what event happened first, or whether two events happened at the same time. Let’s go back to our example. On Earth, you have calculated that the spaceship should pass the target star 4 years and 8 months after leaving Earth. You won’t *see* them reach the star for another 4 years after that point, because it takes 4 years for light to reach Earth from that star, but you know the date that the spaceship should reach the star, so you hold a big party to mark the occasion. Meanwhile, on the spaceship, they pass the star after 2 years and 4 months, and looking back at Earth, they calculate that only 1 year and 2 months have passed on Earth since they left, though it will be over 2 years before the light from that time catches up to them. As they continue further along, after ~20 years, they will finally see the party you held when they determined that you passed the star, but you will calculate that this took place 9 years and 4 months after you left, that is, not when you passed the star but 7 years after you passed the star. You and Earth both disagree with what was happening at each location simultaneous with local events, *even after* accounting for the light delay. And all experimental and theoretical evidence we have say that these two different perspectives on what happened are *both equally correct*. So, now we have all of the pieces for understanding why faster than light travel would also allow for time travel. Let’s say that in the four years and 8 months since the space ship left, there has been a big technological breakthrough and we have developed teleportation technology. You can travel anywhere in the universe instantly, which is much faster than the speed of light. Now we’ll say that everyone thinks it would be a grand idea to have the first large scale test of this technology at the party by teleporting you to the distant star just as the spaceship arrives. So you do. You get sent straight there, and the spaceship picks you up. You just left Earth 4 years and 8 months, but from the perspective of the spaceship, only 1 year and 2 months have passed on Earth since you left. You’re from the future! But now to really nail it in, again, since you are on the space ship, it really only has been 1 year and 2 months on Earth from your perspective now, so if you teleport straight back to Earth, you will arrive there over three years before you initially left. Faster than light travel combined with relativity of simultaneity means that a superluminal traveler can arrive back at their destination before they even left it. Hence: backwards time travel."
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m47trn | Why is it somehow easier to apply eyeliner and mascara when one’s mouth is open? | Other | explainlikeimfive | {
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"Because opening your mouth pulls all the skin on your face down, and stretches it taut. This in turn also tightens the skin below your eyes, giving you better access."
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m4832o | Non-Fungible Tokens (NFT) Megathread | There has been an influx of questions related to Non-Fungible Tokens here on ELI5. This megathread is for all questions related to NFTs. (Other threads about NFT will be removed and directed here.) Please keep in mind that ELI5 is **not** the place for investment advice. **Do not ask for investment advice.** **Do not offer investment advice.** **Doing so will result in an immediate ban.** That includes specific questions about how or where to buy NFTs and crypto. You should be looking for or offering explanations for how they work, that's all. Please also refrain from speculating on their future market value. [Previous threads on cryptocurrency]( URL_0 [Previous threads on blockchain]( URL_1 ) | Economics | explainlikeimfive | {
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"This comes down to what is meant by *fungibility*. Basically, when we describe something as *fungible*, what we mean is that you can readily replace it with something equivalent and that's fine for everyone concerned. Take a dollar bill, for example. We say it's fungible because if someone rips up a dollar bill in your wallet, they can replace it with another dollar bill and you're no worse or better off: both of those dollar bills spend the same. Similarly, one share of Apple stock is worth the same as any other share of Apple stock. It doesn't really matter which one you have, because from the perspective of being able to get value from it, number 304 is the same as number 3,539. One 1kg lump of pure gold is functionally the same as another 1kg lump of pure gold, if you're using it as a store of value. They're designed to be equivalent and interchangeable. (Keep in mind that this isn't just about the value of the item. One share of Company A might be priced the same as one share of Company B, but you can't just swap those shares even if they're technically worth the same. To be fungible, the two items have to be functionally identical.) However, now imagine the lucky dollar bill you have that you saved from your first paycheck -- the one you believe brings you good luck, [Scrooge McDuck style]( URL_0 ). If someone rips up that bill, then replacing it with another dollar just isn't going to cut it. It's no longer a *fungible* item. So now imagine something like a book. You can have a fungible copy of a book (any mass-market paperback is pretty much interchangeable with any other, after all; if all you're buying is the text, you're fine). However, you can also have *non*-fungible copies of a book -- like, for example, a first edition with a limited cover and a signed bookplate from the author. Once those are all sold, you're out of luck if you want to get one. They're just not making any more. This has been a big selling point for physical media for decades, with collectors -- and people willing to pay a premium -- paying more to get that unique extra, even if they're not *technically* getting more out of it. (It's not like buying a special edition of a DVD with extra commentaries and special features, for example.) This is the reason why an original Picasso costs so much more than even the most skilled reproduction. You're not just paying for the look of the painting, but for its history and provenance. You're paying for the fact that it's a Picasso. But how does that work with the shift towards electronic media, such as digital art and ebooks? After all, the whole *point* of digital media is that (in theory at least) it's infinitely reproducible. My copy of an ebook is quite literally an identical copy of your copy, right down to the same ones and zeroes. You can't really have a collector's edition of an ebook, right? How do you have something *special*, given the technology that allows you to create an exact copy in the time it takes you to press Ctrl+V? This is where [blockchain]( URL_1 ) comes in. Remember how, with cryptocurrency like BitCoin and Ethereum, the whole point is that you can use what's basically a giant list to keep track of where the money is, and who owns what? You can use that same technology to ensure that you own a 'limited edition' version of a creative work that, because it's digital, would otherwise be infinitely reproducible. Just like the person with the limited-run edition of their favourite novel on their bookshelf, or an original painting by their favourite artist, you have a token that says (effectively) 'I bought one of only 200 limited edition versions of this piece, and no matter how many times the piece itself is copied, there will only ever be 200 of these tokens. As a result, it is special.' For some people, it's for bragging rights. For some people, it's to support their favourite creators by buying a 'premium' version that's unique to them (or certainly more unique). For other people, it's an investment; as with any good where only a limited number exist, they may expect it to increase in value over time, so it can be sold on. In short, it's a way of applying some of the limited edition value of physical objects to the digital marketplace by creating an artificial scarcity.",
"I drew a stick man in mspaint. Lambo when?",
"I've been trying to understand this all day and every time I think I'm getting close I get lost again and feel like an idiot. As far as I understand Nft users: 1) steal art, or the artist who has decided to do this, makes art. 2) use the blockchain to create a limited amount of a digital thing that would otherwise be infinite 3) sell big bc exclusive 4) kill the environment because of electrical consumption What I'm really struggling with is the concept of tokens and hashes. How do they add a token? Are they crypto mining for ownership and hoping a token that matches something about the arts footprint is uncovered? Are the hashes and mining just to produce of more of the digital copy of the art? (I'm not even fully sure what a hash is please help. I only learned what a blockchain was this morning)",
"So as an artist, if someone places an NFT on my work, does that mean that it is theirs now? Do they profit off my work? Is my work universally now known as theirs? Also, do I need place NFTs on my own art now to really claim it as mine?",
"Can someone explain what is means to actually \"own\" a NFT of a file/tweet/art/etc? & #x200B; for a durable good, from a collectable card to a house, the owner has control. they can hide it, destroy it, decide who gets to see it, charge rent (either by admission, viewership, or actually loaning of the good itself), etc. & #x200B; Now you take a NFT of a popular piece of art readily found on the internet. You don't get exclusive right's to its use, you don't get control over the asset, you don't have copyright over it, etc. & #x200B; So what are you \"buying\" with a NFT. What does it mean to \"own\" an NFT of Random JPEG XYZ? & #x200B; Thanks!",
"This is basically the digital asset equivalent of \"buying a star\", right?",
"Can someone explain what on earth this whole thing is about lol",
"I don't understand how NFTs affect the environment. It apparently takes a lot of computers a lot of electricity to make an NFT. But what are they doing? Why is this particular type of work more harmful to the environment than, say, SETI@home, which also made computers keep running full-time? What is the \"mining\" specifically, that causes environmental damage? Thank you.",
"Ok, I've read some articles, all the answers here and I think I pretty much understand all of this except for one thing... What exactly does link the NFT to the actual object / thing / bits that it is representing? Nothing, right? It is just an agreement between humans that this NFT is for this .JPEG? A purchase contract of a sort? But the .JPEG is by its very nature completely fungible, because that is how computers work. No set of bits ever gets really moved or is original. It is all just copy of a copy of a copy... Sot here is no possible link between the NFT and the so called \"original\". There is just the \"NFT\" and that is the thing by itself? And considering the above this means that someone can produce an infinite number of NFTs for the same .JPEG..?",
"Am I old or has the concept of property and ownership officially jumped the shark?",
"Why is this all of a sudden getting so much traction that it requires a mega thread?",
"Is the value to society created by NFT’s worth the electricity consumed? Bitcoin has helped a significant number of people who either do not have access to a bank or live in a country with hyperinflation so I get why some blockchain projects are worth the energy, but I’m not convinced that NFT’s are even necessary."
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m484dg | How come vehicle headrests are removed in movies and TV shows? | Other | explainlikeimfive | {
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"It's just a visibility thing, so that the viewer can see the back seat passengers better. The rear view mirror is frequently missing as well.",
"It depends on the shot, sometimes it makes the character driving/in front look taller, or sometimes to show passengers at the back. Sometimes it's just aesthetics."
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m48ybn | Why do some body parts "fall asleep" and others are spared from this? | Biology | explainlikeimfive | {
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"When you sit in a manner than presses on a nerve, you end up with numbness and tingling downstream where that nerve usually works. This can happen when sitting on the toilet too long and bending your legs, or when your rest your armpit on a chair for a long period of time. Any nerve can have this feeling, its just that these two are most common as its hard to compress other nerves via normal activities."
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m4asqb | How does a game like RDR2 spend 7+ years in development and release with such advanced graphics technology | When they started writing game code ~7 years ago didn’t they need to lock themselves into an engine? And wouldn’t that game engine be outdated visually by the time they release the game? | Technology | explainlikeimfive | {
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"game devs often interact with hardware devs and have access to development kits, with features not yet available to the public [projects have tanked because of poor communication/choices between devs and the hardware folks]( URL_0 ) > Timing and industry changes turned to trouble for Prey. It was mostly developed on the 3DFX card and the Glide API (\"It was the hot shit API of the day,\" Schuytema says) but internal troubles at 3DFX hit just as the Prey team was ready to go all-in with Glide. Meanwhile, Microsoft was getting its Direct X API off the ground. The team moved away from Glide, and ended up going with Direct X instead.",
"They lock themselves into an engine API, but they don't spend 7 years working with the same version. Every few months, they baseline a better version of the game. Sometimes that version just has more \"game\" in it and sometimes it has migrated to a better version of the engine. It's not a 7-year straight line, that wouldn't have likely been funded. Rather it's an iterative process that just took 40-ish iterations to get a game that was great enough to release.",
"The great thing about using game engines in the first place to make games, is that it keeps the \"data,\" and the \"engine,\" pretty separate. This means you can have one group working on making models, textures, level scripting, etc. and another team can work on improving the engine and keeping up with modern tech. As long as the team working on the engine don't change the way the engine reads data, then it will just load in the same data the way it always has, just with better graphics or whatever. Only if there is a breaking change would things have to be re-done. This is also a big reason (not the only reason though) why we see \"fake,\" E3 trailers and such. When a game is announced really early, they are running on a PC that's light-years ahead of current tech, using models and maps that would never run on a modern system, simply because that's where the devs *think* tech will be in 7+ years. Sometimes they get this wrong and have to scale back ~~-------------------------------------------~~ **EDIT:** I'm getting the same questions a lot about the \"fake,\" E3 trailers and such, so I'll post the answers here: * It happens * Game devs aren't stupid. They know nobody looks good when the released game doesn't live up to the hype. * Devs that have a more corporate structure are more susceptible to this, as they have to pitch games to more \"business types,\" who don't understand how games are developed and it's more effective to show flashy graphics than 15 power-point pages explaining your revolutionary game-mechanic or technology. Same deal when you're making an E3 trailer. * Games that fall into the \"cross-gen,\" release window are especially susceptible to this as you are targeting still-in-development hardware which you want to push to it's limits, but those limits are frequently changing. You guess at what you think you'll be able to get running, and then you cross your fingers hoping you actually can by launch. * There *is* a level of responsibility of the devs to communicate early on that the game is changing, however game development is so incredibly turbulent that it's difficult to even know when to cut your losses. The general audience also needs to understand that features are cut because they don't work out, things change, that's development. * The situation with CDPR was the perfect storm of failures in PR and management, combined with the points above that it failed so spectacularly and ended up an outlier and an edge-case. I would really recommend everyone who is interested in game-dev to give yourself a 2-month limit and make a small game. It's extremely fun and rewarding, but it will really shatter your understanding of what actually goes into making one of these things.",
"I'm stoned right now and had to read the title five times as I couldn't understand why R2D2 was a game...",
"In short: Once everything is laid out for a game, not many things change during the development, other than the more detailed assets and lighting is added.- but that depends on hardware capabilities in order to render a number of things on the screen. More computing power- > more things can be rendered on the screen- > more detailed assets in the game- > nicer graphics. Sometimes placeholder dummy test assets are used in order to start with the development and start working on other fields such as mechanics, combat, quest, story etc. Then later on these will be changed with high def, nice 3d model. Think of the years between the start of the game development and the end of game development as the weather conditions. And think of the game assets as clothing items. Imagine as if you are going out for a job interview. You carefully plan everything before going there. You leave the pet at a friends place, you make sure that you know what to say during the interview, you go over some questions that they might ask you, you prepare your resume, you look for the company details, policy, salary, you practice speaking in front of the mirror.. then the only thing what's left is - to choose what you gonna wear for the interview. Let's say that interview was scheduled for January, during that time it rained hard for days. You prepared what you gonna wear, obviously something warm, a raincoat is a must and waterproof makeup probably if you were a girl. - for that weather at the time that was the best obvious choice of clothing. \\- then suddenly the interview was postponed for next week.. But next week the weather is totally different, its quite hot, no rain in sight...so obviously you had to change things around...(you don't need a raincoat, no need for warm clothes..etc) this time though, you didn't have to plan and prepare anything as you already finished that part beforehand, all you had to do is to change your clothes to suit that day's weather. The same goes for the games, once the foundation is laid out, things change, but they are much more straightforward to change than to plan everything from scratch. & #x200B; Each game consists of many different components. To simplify it we gonna assume there are only these for now: \\-Characters - (3D models of the character, textures/UVs, materials, their voice lines, rigs, and animations.) \\-Environment - Assets such as foliage, buildings, objects... Post-process effects and lighting - Fog, lights, clouds, ambient effects, shadows, scattering... \\-Game mechanics \\-Story \\-Cutscenes Most of the things wouldn't make any difference if they were made 7 years ago or today. \\-For example, when low poly characters are created, you can rig them, make animations for them, do the voice lines, combat system, controls. The same goes for level design, when assets are created (Buildings, props, foliage, terrain...), you can texture them and place them into an appealing composition that makes the level- well level! \\- Assuming that the programing part is finished, combat system, animation blends, controls, quests, there is really not much left to do, other than cutscenes-but those are usually done with really high poly, very detailed assets/models cause they don't have to be rendered in real-time, and you can add effects in post-production using video editing software. Once you have these laid out, you pretty much have a complete game. Most of these things don't even need to change from that point other than fixing bugs and some incompatibility issues due to the different engine version advancements. The only thing that really changes over the years is the polycount of the character/ assets that can be drow on screen, and lighting post-process calculations can change from time to time.- those dependable on the computing power. With each new generation of GPU-s they move this slider further up, so the polycount of the model increases, and thus looks more detailed. They also add new things that can trick you into thinking there is geometry where actually there isn't any. So for example let's say that in order to render some game in 2016 at 1080p with 60-fps, the max polycount used by the assets on the screen is 10 million. Fast forward to 2021, we could probably render 50 million or more..So this thing allows devs to create more detailed characters, swap them with the old ones created in 2016, while keeping their animations, voice lines, mechanics...etc.",
"It's easy to forget, but a game that released a year ago may have started development even before RDR2 did, so in a way we're seeing today the results of industry trends 5+ years ago in games releasing now. Beyond that, major game releases like this tend to communicate their needs to Nvidia and AMD, and those GPU companies take that information and will often tailor their upcoming GPU architectures to suit various industry trends, within reason, of course.",
"Follow up eli5: How was RDR2 so drastically better than cyberpunk despite less development time and developed like 3 years sooner?",
"Yes they lock themselves into an engine. But engines limits are years ahead of what consumer hardware can handle. If they could magically finish that game in 1 day it would be able to work like now, but noone would own a computer to actually play it without lags. Also the graphic optimization is a pretty late process in the developement. And the engines can be patched with new features too.",
"Most of the time, these are the games that set the new standard. That's why it take so long, because they are creating new features...new ways. Then they can fine tune it to the most advanced graphics before release.",
"The engine is not as important as some people think. Some game engines may make decisions that are difficult to change without a lot of work. But it can always be done. Many game engines used today have started from a codebase that was originally made for the first Quake games. They are being upgraded to this day, even if they have received new marketing names.",
"> And wouldn’t that game engine be outdated visually by the time they release the game? Most, All? of these answers are very off base. Game engines aren't some monolithic unchangeable black box. They're a collection of tools that render graphics, handle physics , sound, scripting, the AI, on and on. Those tools are more or less independent, and are often designed to be modular. If you want to improve the physics, you can do so without throwing out the entire engine. For that matter it's often possible to integrate someone else's tools, or ones you've built in house, with that engine. Want to add better fluid simulation at a later date cause there's some new techniques available now? You can probably just do that. Want to include higher res textures? The rendering engine doesn't really care how high res the textures are, you can change that pretty much arbitrarily. Better lighting effects? All you're doing is messing with the tools that handle lighting. The game world doesn't care *how* it's lit, and all the light sources don't care or know how they light things up. Project management is also key. If you know your going to spend half a decade developing the game, you can anticipate improvements in tech. So you can move features that rely on it till later in the devlopment cycle, while focusing on parts of the game where you expect things to be more static. Rockstar is a good example there because they use their own engine. GTA4 and RDR2 are built on the same engine. They've just updated it as they went along. for Red Dead Redemption 2 one of the big changes was pre-calculated global illumination and it's entirely possible that wasn't a finalized feature till the last year or two of the games development. Being 'locked in' to an engine is not terribly restrictive. Just like anywhere else, a toolset that limits your ability to do and change things is a bad one.",
"Lets say you tell me to draw a triangle. Specifically you say “draw a triangle”, and I draw triangle. Today, it takes me 3 seconds to draw a triangle. Now lets fast forward a couple of years. I’ve gotten really good at drawing triangles. Now, it only takes me 0.5 seconds to draw a triangle. However, the way you ask me to draw a triangle hasn’t changed. When you say “draw a triangle” I draw a triangle just as before, only faster. Now imagine you ask me to draw a thousand triangles. At 3 seconds a triangle, that would take me 3,000 seconds. But if I said to you; Give me a couple of months and I reckon I could draw a triangle in 0.5 seconds, then you could plan for a future where asking me to draw a thousand triangles takes a mere 500 seconds instead of 3,000. Also, the way you ask me to draw a triangle doesn’t have to change. You could write a letter asking me to draw a thousand triangles, and it wouldn’t matter if received that letter today, or in a years time. The only difference would be how quickly I drew those triangles. Thats how programming works. The instructions stay the same, but the way those instructions are executed can change. When you ask me to draw a triangle, you don’t care how I draw it. All you care about is wether or not you get a triangle. If I tell you that I’m sure I can figure out a faster way to draw triangles, then you can plan ahead for a future in which you can ask for more triangles in a given amount of time. Thats how game engines work. Game engines draw triangles. The faster a game engine can draw a triangle, the more triangles it can draw in a given frame, and the better the graphics are. When a game engine draws a triangle, it has to compute all kinds of things like textures and lighting for every single triangle in every single frame. The people making the game just ask the engine to draw as many triangles as possible.",
"Actually most advanced graphics techniques are based on existing algorithms, some as old as the 1970's or 80's, it's just that the math involved is extremely processor intensive to do in real-time. As processing power increases the can run more of these calculations in real-time.",
"It... didn't? Raytracing was the current 'cool new tech' when they released and they don't have it. High Dynamic Range had been around for a while but was still 'current' when it released and they couldn't get it to work correctly until a few patches later.",
"They're very familiar with the hardware they're writing the game for, and they design the game around looking as good as possible on that hardware. And because they've been working with it for so long, they know every trick in the book. Everything about the game - from the lines of sight on the map to how story missions are structured - is designed to make the graphics look as great as possible, given the limits of how quickly the console can load and process stuff. (If you were given the ability to drive around really fast in a car, or fly above everything in a plane - like in GTA5 - things probably wouldn't look as good.) They also put a ton of money into art direction - a game designed by talented people is going to look far better than one made by amateurs, regardless of resolution and shaders and what have you. RDR2 looks the way it does in large part because it was made by very skilled artists, not because of \"advanced graphics technology.\" The actual resolution RDR2 runs at on stock consoles is nothing special, but lots of smart people spent years making sure the flaws show as little as possible. (That's also why the PC ports of Rockstar games don't blow people away nearly as much, when compared to games designed from the ground up to look great on the PC - or the PC and consoles - and why they don't run very well on low or mid-level PCs, even though those are technically more powerful than the consoles.)",
"At any given point in time, the graphics we *can* create, period, are way beyond what the average consumer has in the way of hardware. The graphics you will see in games many years from now *could* be made now if everyone had the hardware to push it."
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m4df5x | Can someone please explain the tolerance paradox like I’m 5 I don’t know why I’m struggling | Other | explainlikeimfive | {
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"If a society is perfectly tolerant with no boundaries, eventually someone or some group who is intolerant will take advantage of everyone else’s tolerance and come to power/take over. So for tolerance to continue to exist in a society, that tolerant society must intolerant of intolerance to protect its tolerance for everything else. Seemingly a paradox, to stay tolerant one must be intolerant of intolerance. For some extra context, this was created by a philosopher Named Karl Popper, a man born in 1902 in Austria with Jewish ancestry. In the 1930s he was forced to flee Austria to the UK with the threat of Nazi Germany annexing Austria.",
"You cannot tolerate all positions, because some of them would destroy all tolerance. If you tolerate fascists, they will abuse that tolerance and you end up with a fascist society in which *nothing* is tolerated that doesn't follow party lines.",
"Tolerance is the principle of being willing to coexist with those who are in some way different from you. One way that someone can be different from a person who is willing to coexist with others is by being unwilling to coexist with anyone different from them. Thus a fully tolerant society would by necessity tolerate intolerance, which would inevitably undermine the overall tolerance of the society. Thus the tolerance paradox. How does a philosophy that rests on the idea of coexistence with other ideas deal with the idea that coexistence is impossible? If you reject that idea, you are being intolerant and the perfect state of tolerance fails. If you accept it as legitimate, likewise, the perfect state of tolerance fails.",
"> Less well known [than other paradoxes Popper discusses] is the paradox of tolerance: Unlimited tolerance must lead to the disappearance of tolerance. If we extend unlimited tolerance even to those who are intolerant, if we are not prepared to defend a tolerant society against the onslaught of the intolerant, then the tolerant will be destroyed, and tolerance with them.—In this formulation, **I do not imply, for instance, that we should always suppress the utterance of intolerant philosophies; as long as we can counter them by rational argument and keep them in check by public opinion, suppression would certainly be most unwise**. But we should claim the right to suppress them if necessary even by force; for it may easily turn out that they are not prepared to meet us on the level of rational argument, but begin by denouncing all argument; they may forbid their followers to listen to rational argument, because it is deceptive, and teach them to answer arguments by the use of their fists or pistols. We should therefore claim, in the name of tolerance, the right not to tolerate the intolerant. We should claim that any movement preaching intolerance places itself outside the law and we should consider incitement to intolerance and persecution as criminal, in the same way as we should consider incitement to murder, or to kidnapping, or to the revival of the slave trade, as criminal. This is Popper's quote where he talks of the paradox, the only place, in its entirety. It's often misquoted and misintepreted as blanket justification of intolerance against intolerance, but it's worth noticing the often omitted bolded part, that counter-intolerance is justified *if [the original intolerance] is not counterable by rational argument and held in check by public opinion*. Without it, anybody could claim anything as intolerant and therefore not to be tolerated. The paradox also applies as much towards far left intolerance as it does towards the far right. Popper made no distinction there.",
"Say a Neo Nazi comes into a bar you own/manage. And you say, well I guess I have to let him buy his drink. He's a paying customer. And he's not blatantly offensive. So, you let him have his drink. But then tomorrow he brings in his Nazi friend, and his friend is also more or less okay. You don't like them, and the occasionally say something casually racist, but... it's a free country. Do you really have the right to make them go away even though you don't really like them? But then the next thing you know, they've brought all of their friends. And now you're running a Neo Nazi bar. And nobody else wants to come by the bar b/c they don't want to get harassed by the Neo Nazis. Now it's too late, and you don't know how to change things because now the clientele has shifted, and the bar has a reputation all over town as a Nazi bar. So, you have to be intolerant of Nazis, because if you don't they eventually push everybody else out, and their intolerance takes over."
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m4dtna | Why does soaking dishes in water make it easier to wash? | Chemistry | explainlikeimfive | {
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"Think of when you dunk Oreos into milk. The Oreo gets softer and easier to eat. The same applies for any food particles on plates when they get soaked. They soften up and become easier to wash off."
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m4ee2w | Why are truffles not considered as plants? | Edit: ..or in general: Why are mushrooms not considered as plants? | Biology | explainlikeimfive | {
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"Because truffles are mushrooms, mycorrhizal mushrooms to be exact. This means that they form in relationship to trees. Now, to answer your question. Mushrooms aren't plants, they are fungi. Fungi have characteristics of both plants and animals, and mushrooms are incapable of photosynthesis.",
"Everyone else already answered fungi. Fun fact, fungi are closer related to animals than plants"
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m4ejgj | How does confirmation and anchoring bias affect ones thinking? | Other | explainlikeimfive | {
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"Confirmation bias is when you only tend to notice evidence that backs up what you already believe, and either disregard or forget things that don't. For example, if someone believes in horoscopes, and their horoscope tells them they are going to have a good day, they'll notice all the little things that are better than average. 3 green lights in a row on the way to work, a parking space near the door of the building, etc. On the other hand, if they were told they were going to have a bad day, they'd maybe notice that all the other lights were at red, and it was raining when they got out the car. It's the same morning, but they pick up on different aspects. The \"bad day\" conditions them to notice the rain but forget the parking space. The \"good day\" conditions them to say \"well it might be raining but at least I didn't have to walk far.\""
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m4f321 | What are the practical applications of calculus? | So this isn't a "learning calculus is pointless" post. I'm sure it's not pointless, but what is an example of how calculus is used to solve problems in the real world? I remember studying parabolas and such in high school but I didn't learn why, just memorized whatever I was supposed to. I took regular grade 12 math but didn't take calculus and have always been confused by what it actually is... | Mathematics | explainlikeimfive | {
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"There are effectively no real-world engineering problems that don't involve calculus. Everything involving structures (houses, bridges, car bodies, boats), moving fluids (plumbing, sewers, airplanes, boats, car shapes), or control systems (thermostats, cruise control, power steering, autopilot, your oven) are resting on calculus because the governing equations are differential equations (a type of calculus-based equation). Everything is subject to force = mass times acceleration, and acceleration is the second derivative (in the calculus sense) of position. So \\*anything\\* that involves solving for where or how fast or how hard something moves is calculus. Even the non-calculus-looking equations like \"distance = 1/2 times acceleration times time squared\", for distance under constant acceleration, is the solution to a specific differential equation. We just use it so often we often skip the calculus and go straight to the result.",
"Calculus is the study of \\*change* And, in short, shit changes. You want to figure out (with numbers) how something will react to a new change, you're gonna be using calculus. The 'harder' parts of calculus look at how fast something is changing, or try and figure out how much something has changed.",
"The most basic example is finding position, velocity, and acceleration of a moving object using the fundamental theorem of calculus. Velocity is equal to the integral of acceleration. Position is the integral of velocity. You can differentiate velocity to get acceleration and differentiate position to get velocity. Calculus can also be used to model population growth and decay. It can be used to see how long a chemical will persist in the environment. It is used to find the center of gravity and center of mass for objects, which helps with designing pretty much everything. I have taken calculus 1, 2, and 3 while pursuing my engineering degree. Calculus is used in most of my classes and I have other examples if you want. Any questions are welcome : )",
"There are a lot of applications to different jobs, but the best takeaway I’ve ever heard for why EVERYONE should learn it is because it’s good practice for your brain. Football players don’t lift weights during a game on the field, but they do it outside of game time because it makes them stronger. Same with math. A calculator may be accurate, but it doesn’t help you develop your problem solving abilities, nor does it help when you need to figure out what variables should be input. That last one is usually provided on a test, but in a job or on a worksite it’ll be a different story. The easier it is to do calculations in your head because you practiced this complex stuff, the easier your life will be even if you never use specifically calculus ever again",
"Long ago, the guys at the railroad yard lost the stick that you dip into the diesel fuel storage tank to read out how much diesel is in the tank (yes, idiots were involved). The tank is a simple cylinder lying on its side. Using calculus, we calculated the volume of fuel in the tank at various depths, from 'essentially empty' to 'full'. From that table of results, we made them a new measuring stick that was marked in gallons. So, there's a practical application for you.",
"Do you have an equation you're trying to use? Is one of the variables in that equation changing over time, or as a function of some other variable that is changing? Then you're probably gonna want to use calculus. ------ > I took regular grade 12 math but didn't take calculus and have always been confused by what it actually is... Calculus is the study of how changes in one thing produce changes in another thing. For example, suppose you have a square with a side length of 6 cm. Then the square's area is 36 cm^(2), right? Now, imagine the square is *growing*, with the side length increasing by 2 cm / sec. How quickly does the area change? Since real-world engineering problems almost always involve one quantity changing as another does, calculus has so many applications that it's impossible to list them all. Just a few examples: * A rocket's thrust at any one moment can be computed with basic physics. But the rocket gets lighter as it burns through its fuel, so the thrust changes over time. * Hot food cools down quickly. But as it cools, it becomes less hot, so it cools down less quickly. How does it cool down over time? What kind of curve does it follow? * You have some function and you want to fight where it reaches its maximum value. At its maximum value, it isn't changing, so you can convert this problem into a question about when the function doesn't change."
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m4fw64 | Why is 0! = 1 | Mathematics | explainlikeimfive | {
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"There are a few ways to think about it. * n! is the number of possible sequences you can form with n elements. E.g. 3! is 6 because you can do 123, 132, 213, 231, 312, and 321. There is only one sequence of no things, namely the empty sequence with no symbols. * n! obeys the law n! = n \\* (n-1). For this to work for 1!, we need to have 1! = 1 \\* 0!, i.e., 1 = 1 \\* 0!, which only works if 0! = 1. * The factorial can be seen as a special case of the [gamma function]( URL_0 ), which would give 0! = gamma(1) = 1. Ultimately, though, ! is just a symbol - we can define it to mean whatever we like, and defining 0! = 1 turns out to be convenient because it makes formulas work for 0 the same way they work for other numbers.",
"One way to think about it is the number of permutations of nothing. This is also by convention. For a more detailed explanation see the video: URL_0"
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m4gbkk | Purpose of tears while being sad | Biology | explainlikeimfive | {
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"Humans are social creatures and have adapted to pick up on no verbal cues before verbal. Empathy is an important trait in communal living. It is beneficial to have a physical trait to trigger empathy amongst others during loss. Tears show that you are sad and would elicit an empathic response from those in your tribe.",
"Why we excrete water from our eyes as an emotional response is not understood. When it comes to the human body, there's more things that we don't understand than we do. And we understand a lot about it. Source: The Human Body, an Occupant's Guide By Bill Bryson (highly recommend if you want an ELI5 for the entire human body)"
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m4gqup | ; Why is the research of long-term effects of vaping so vague? | I know that Vapes were not around long enough for easy evidence to support the title, but how come people studying this evidence have been vague with their hypothesis of long-term Vaping side effects. | Biology | explainlikeimfive | {
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"> but how come people studying this evidence have been vague with their hypothesis of long-term Vaping side effects. Because they can't say anything with certainty, entirely because the data doesn't exist yet, and there aren't really any analogues to study *except* smoking cigarettes. Medical professionals are subject to professional ethics, and part of that involves not saying anything with certainty unless you're *actually* certain. We don't have the data, ergo we're not certain.",
"Since they havnt been around long-term they are avoiding what could be a ciggarette-type debacle. Where they said ciggarettes were good(and getting paid to say so) in reality ciggarettes are really bad for your health, the same with vapes. In essence they will wait till they know for certain before saying how bad it is."
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m4hqgy | Why do Webpages on mobile devices especially still jump around frequently while loading? It goes as far as you cannot reliably trust what you about to hit will be still there when hitting it. Can't there be a load order that prevents that? | Technology | explainlikeimfive | {
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"Scripts load at various times, often triggered by other scripts and elements on the page. Also, many images are not properly coded with width/height info causing the image load to make the page fluctuate. A fun way to learn about how the web really works is to use an add-on like noscript. You will have the base page load (html) and each script in the page will need you to manually turn them on one-by-one. Well, you don't HAVE to, there is an \"allow all scripts on the page\" button. Some pages only have one or two script approvals required. Journalism/media sites will have so many you will need to approve them all, then approve the scripts those scripts loaded. Possibly multiple times. As the scripts load, you can watch the content on the page jump around as they load in. That's what is happening normally every time you load that page, just mostly all at once.",
"There's a few possible reasons. Many web sites, and especially mobile pages (which still baffles me) are built client side by scripts. So the slower CPU in phones may lag that a bit. Pictures are downloaded separately from the page itself so there is a delay while the browser figures out what it's building and adjusts as it learns more. And of course, so many pages are designed to detect the screen size and adjust their own layout. That may be delayed and cause the page to be redrawn with the new layout to accommodate the new size as the script kicks in and realize what's going on. Of course, there are other possibilities and I can only speculate without actually seeing the site in question. In my opinion, what's considered modern and \"the way to do things\" on the web today is dumb and responsible for these annoying browser behaviours. You can design a page that loads properly the first time and doesn't do this, but the web designers have to change how they make web sites and give up that automatic adaptation to the screen resolution. Geez, web pages are more complex than some actual PC and phone apps."
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m4i5ie | how the ancient knew the curviture of the earth | Mathematics | explainlikeimfive | {
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"You use a specific time and date, specifically solar noon on the summer solstice One of the places happened to be pretty much on the Tropic of Cancer and story held that at noon on the summer solstice there was no shadow in the bottom of deep wells in Syene so the sun must be directly overhead then so that's a nice 0,0 point 5000 \"stadia\" north of there was Alexandria. Because they're in roughly the same North/South line (meridian) and Syene was known to be under the sun they only needed to measure the angle to the sun on the summer solstice from Alexandria No timed measurements, no long distance coordination. Just good selection of the reference point so only one measurement is needed",
"Ships on the horizon disappear from the bottom-up (with the mast disappearing last). Clever sailors could've used this fact to deduce that the earth was curved (and therefore round)",
"They measured the lentgh of two different summer solstices. It doesn't matter if you take the measurements simultaneously, you only need to take them at the same time of day and the same date."
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m4ia7z | why do we need sleep? | Biology | explainlikeimfive | {
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"It's rather complex, for an ELI5 answer. But, basically, the mind and body don't merely \"rest,\" while sleeping. A lot of other things are going on. For example, when you sleep, your brain transfers memories from short-term memory into long-term memory. That's part of why people sometimes lose recent memories if they drink too much, or use drugs, or become badly injured--the brain doesn't experience normal sleep, so the short-term memories may never be properly processed, and those people may be unable to recall what happened. The body and brain also perform certain maintenance and repair functions, during sleep, because the body and brain aren't occupied doing other things. Think of it like when you update your computer. If you try doing it while watching Netflix or playing a video game or browsing Reddit, your computer may function more slowly and the update may take longer. That's why it's often easier to install updates when you're not dong other things on your computer. So, sleep is more than \"lack of energy\"--it's another mode of operation during which the mind and body perform critical functions necessary to the proper functioning of the person or creature."
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m4igua | - If you drink some coca cola after eating a chocolate sweet, Why do the taste buds not absorb all of coca colas flavor, as it ends up tasting like fizzy water with sugar diluted into it. | If I'm ever eating different kinds of sweets I always eat them in a certain order in order to get the proper taste back. First World problems.. | Biology | explainlikeimfive | {
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"Pretty sure it has to do with acclimatization of taste buds. Think about it like getting into a hot bath; you feel hot initially but your body slowly gets used to the heat. When you get out again, the room temperature air suddenly feels like an Arctic wind. The same process happens with your tastebuds, which get used to the insane amounts of sugar in chocolate and won't be able to taste the slightly less insane amounts of sugar in your soda. There are some cuisines that actually rely on acclimatization and build the order of meals around their flavor intensity (try searching up sushi eating order)."
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m4ixxs | Why does spending a few hours out in the sun at the beach make you get so tired? | Or any amount of time out in the sun for that matter, but particularly the beach. | Biology | explainlikeimfive | {
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"Dehydration. The beach tends to have a constant breeze, so you don't notice yourself sweating as much as you actually are. There also is very little shade, so you body overheats a little. This also means furthering dehydration, but it also throws your body out of equilibrium, exactly like having a fever.",
"ELI5: Sun/Heat = Sweating More Sweating = Needing more water Not getting enough water = thirsty, tired, grouchy, headache ELI20: Most people don't realise that they are suffering heatstroke/exhaustion when it's minor, but feeling tired, sluggish, moody/short-tempered, having a headache, having chills in the evening are all indications that you got too much sun and not enough fluids. But there are other likely factors, we tend to be more active just by wanting to be outside in the warmer weather, despite physical activity being much tougher in the heat/sun, so it makes sense it's more tiring. For example, if you spend the day at the beach, you most likely have walked a fair bit on uneven terrain, possibly played in the sand, built sandcastles, buried your peers, kicked around a ball, played frisbee with your dog etc. There is also limited shade at the beach, compared to a park, woodland or the backyard, and you probably won't reapply sunscreen nearly enough throughout the day. You have likely been far away from convenient drinking water sources so have rationed yourself to whatever you brought with you (and we're lazy devils, so probably didn't carry 2L of water per person from the car to our spot on the beach), possibly indulged in sugary treats like ice cream, maybe even a few beers. All things that can contribute to dehydration. Also, you most likely took a swim in the water. The sea/ocean is powerful and even just standing still in it requires more effort than standing still in a lake or shallow stream, but most of us are splashing around in the water, chasing each other, swimming, jumping waves etc. Swimming in any condition (pool, lake, river etc) is a full-body workout that most will find tiring unless they do it regularly. Nobody asked, but here are some top tips for when you're spending time in the sun: **1. Drink more fluids.** Invest in a decent sized water bottle (I personally like a 1L, not too bulky and I know that if I fill it twice in a day, I've nailed my intake) and get in the habit of taking it with you everywhere you go. Sip regularly, when you leave a room, sip, when you sit down, sip, when you get to your car, sip, whenever you pick up your bottle to go somewhere, sip, whenever you're about to set it down again, sip. If you start feeling thirsty, you're already becoming dehydrated. Sip constantly so you are ahead of the game. If you're going to be away from water sources for most of the day, make sure you drink plenty before you set out. This is easier than it sounds, drink a glass when you first wake up, a glass with breakfast and a glass before you leave the house and you're already around 750ml down. Take any opportunity to top up your bottle and if you're driving somewhere, keep extra water in the car so even if it's a bit of a walk, you can go back to the car and top up. Carbonated drinks take up more room when we consume them, which means we drink less, plus the caffeine and sugar in them don't exactly help us with hydration. Caffeinated drinks can make us more likely to pee as they have a diuretic effect, which makes us drink less because we don't want to be peeing all the time. If you're really a water hater, try flavouring it with low sugar squash/cordial or throwing in some cucumber or fruit slices to naturally flavour the water. Personally, I like to stick to water as it means my bottle is easier to keep clean (and I'm therefore more likely to stick to using it) and I find that because I drink little and often, I don't really think about the taste a whole bunch. Yes, if you increase your fluid intake, you will, initially, pee more. But if you stick to it, you will adapt and return to a normal pee schedule. Your pee should be clear. A good guide for how much water to drink: Your weight in lbs / 2.2 X your age / **28.3** = how many ounces of water to drink. If exercising or in hot weather, add 1-3 cups (8-24 ounces) Example: A 150lb 30-year-old should drink 72 ounces (9 cups/2.2 liters) a day. Which is around 133ml per hour over 15 hours, or about a third of a standard soda/beer can, most people would have no issues sending a full soda/beer in less than 30 minutes, so it's really not a lot to aim for. **2. Sunscreen.** Forget about working on a sweet golden tan, you'll get there with enough exposure eventually anyways and it's not worth risking your health for. Most people are faking it anyways. Minimum 30 SPF broad spectrum. Apply according to the directions (typically minimum 15 minutes before exposure, then reapply every 2 hours or after any time you've been in water). How SPF works: In \\*theory\\* the SPF number indicates how much longer you will take to burn than without sunscreen. So if you typically burn after 10 minutes on a sunny day, SPF 30 would give you **up to** 5 hours of protection (10 minutes x 30). That being said, this is in laboratory conditions, where sunscreen is not being rubbed off by clothing, removed by sweat/water etc, this is why it is important to reapply as directed and not just slap on sunscreen and assume you're good for 5 hours. **Protip:** Buy a face-specific sunscreen for your face. They are lighter on the skin and are less likely to run into your eyes when you sweat. They are also designed to sit well underneath make-up, if you're that way inclined. **3. Cover up.** Either in loose and cool clothing that covers your arms and legs, or you can buy clothing that is SPF resistant, including swimwear, shorts, hiking shirts etc. Wear a hat, the broader the better, but even a baseball cap to protect your face is better than nothing. Try to avoid dark colours like black and navy as these absorb the sun instead of reflecting it away from your skin. Keep in mind that you can still burn through some fabrics. **4. Seek shade regularly.** Even on a cloudy day, the UV index can still be as high as 2. Very fair-skinned people can get sunburn after 30 minutes of exposure in these conditions (darker-skinned people can spend longer outside but may experience sunburn after 1-2 hours. Depending on the UV index that day and your natural untanned skin tone, you should seek 15 minutes of shade every 15-60 minutes. If you have sunscreen on, you can go longer, but I'd still suggest everyone regardless of skin tone, sunscreen etc, taking a 15-minute break from the sun at least every hour and a half if possible. Use this as an opportunity to drink fluids and top up sunscreen. If you can't get to decent shade, spend less time at the location. Remember to bring a shelter that actually blocks uv rays, some parasols/umbrellas do not block the harmful sun rays. Don't forget that rays can be reflected by water, pavement, glass, even grass, heck even snow. So even though you're under a shelter, you're still getting a healthy dose of UV rays to the face. Good shade should provide sun protection from the sides as well as above. **5. Try to avoid the sun during peak times.** This will vary depending on your location, but generally between 10am and 4pm are peak hours when the sun is at it's highest and most powerful. If possible plan your outdoor activities around peak hours, or plan to take a long break during midday - go somewhere cool to grab some lunch and sit inside or out of the direct sun to eat. Picnics and BBQs are awesome, but if there's no significant shade to sit in, maybe best saved for another day or location. **6. Boring I know, but avoid alcoholic beverages, or at least save them for the evening.** They not only help you to dehydrate, but they impair you, so you're more likely to fall asleep in the sun and forget to put on or top-up sunscreen, plus, being drunk covers up the symptoms of sunstroke/heat exhaustion until it's too late. I once had to fetch medics at an event for an olive-skinned looking guy who had been sat topless in front of me in the beating 34c sun for the last 3 hours, drinking nothing but beer, who just straight-up keeled over on the concrete, hitting himself on the head. I'd been observing him for a while as I noticed his behaviour changing and was getting concerned for him (I work in first aid so have a keen eye and lots of experience). None of his buddies reacted appropriately as they were all drinking too and just thought he'd passed out drunk and it was very funny. The guy was sent to the hospital in an ambulance by the event medics for severe heatstroke. Untreated heatstroke can damage your brain, heart, kidneys and muscles and like a normal stroke, the longer it's left untreated, the more dangerous it can be. Edits: formatting, mistake in math equation"
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m4j6b2 | why are plastic chocolate bar wraps so hard to tear apart when they have a smooth normal edge, but so easy to tear apart when they have a little dent on the side? | Technology | explainlikeimfive | {
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"If you pull apart two ridges of the dented area **all** the force from you pulling is concentrated in a single point, where the two edges meet, allows the material to rip. If you're pulling apart a smooth piece the force gets evently distributed between your fingers."
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m4jlxw | Why are there auto-playing videos on so many websites? | Technology | explainlikeimfive | {
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"10 seconds of content to get to 2 minutes worth of unskippable ads. They gotta pay the bills somehow, after all."
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m4kqtj | What is happening to your throat when you lose your voice from screaming too much? | Biology | explainlikeimfive | {
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"Our vocal cords that are in our throat get irritated from overuse because screaming is much harsher on them than talking, just like they can get sore from a cold or too much smoking. They get swollen. A little swollen and they don't move properly, so your voice is husky, very swollen and they stop moving altogether so your voice is gone until they recover."
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m4kvdp | why do skinny people get drunk more easily? | Biology | explainlikeimfive | {
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"Because they're smaller. Less water in their body. So the same amount of alcohol will cause a higher percentage of alcohol in the blood. Basically the alcohol isn't diluted as much as it would be in a larger person."
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m4l5d9 | If fusion doesn’t produce much radioactive waste, why does a nuclear bomb produce so much radioactive material? | Chemistry | explainlikeimfive | {
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"The initial atomic bombs used fission reactions, which create much more radioactive fallout, rather than fusion reactions for the explosion. Later fusion bombs use an initial, smaller fission bomb to trigger the larger fusion detonation. These have much less fallout for their yield, but the fission primer still creates radioactive fallout.",
"A nuclear bomb doesn't derive most of its energy from fusion. As strange as it sounds, a nuclear bomb actually derives most of its energy from its inert case. U-235 is the \"fissile\" isotope of uranium - that's what makes up the initial stage of a nuclear bomb and is the difficult isotope of uranium to get. The first U-235 stage is used to detonate a second stage consisting of what is *probably* a mixture of deuterium and tritium. That second stage releases most of its energy as neutrons, which doesn't actually cause much of an explosion. Those neutrons from the second stage then hit the bomb's casing, which is made out of Uranium-238. Uranium-238 isn't \"fissile\" in the sense that, unlike Uranium-235, it won't undergo a chain reaction on its own. But when a U-238 nucleus gets hit by a fast neutron from the fusion second stage it *does* undergo fission and that is what produces most of the energy in a nuclear explosion. The problem with U-238 it that it is a particularly dirty fuel - the products from it undergoing fission are intensely radioactive and not all of it undergoes fission. Some gets transmuted into plutonium which is, itself, long lived radioactive waste. The only bombs that have derived most of their energy from fusion are believed to be test bombs. Those bombs *probably* used lithium-deuteride as a fuel. The problem with that is that lithium-deuteride is really expensive and until recently it wasn't even possible to produce very much of it. That expense makes it justifiable to use when you're building a single bomb for testing purposes but if you need to build tens of thousands of bombs its just not an economic reality to use it. Finally, even though fusion *can* be \"clean\" fusion reactors really aren't. The fusion fuels that are economically practical to use all generate a lot of fast neutrons. Those neutrons turn most metals radioactive, so if you're building your fusion reactor out of metal then after running it for a few months it turns into a radioactive hulk. The Wendelstein 7-X is a fusion research reactor that's currently under construction. If it works (which it may not) then it will be the first fusion reactor that can run for more than a few seconds at a time. Even then, they have to limit its operation to 30 minutes per year because any more than that and the reactor itself will become radioactive before they can finish the experiments they have planned for it."
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m4lp79 | why do we look better in mirror yet ugly in selfies? | Other | explainlikeimfive | {
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"Because you only ever see yourself as a mirror image in a mirror. Selfies show you what everyone else sees. You're welcome to start self loathing as the rest of us do when we learn this.",
"The other answers are only part of it. Yes you are use to seeing your flipped image and seeing it unflipped you become aware of all the unevenness of it. Second, the camera focal length can distort your facial features to be bigger or smaller than they are. Lastly, the way cameras take in light, your features may not 'pop' as much in photos compared to in person."
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m4mb44 | why do we clench our teeth/lips when doing some strenuous physical work? | Biology | explainlikeimfive | {
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"Basically, same reason you clench up everything else. When you're doing something like, say, pulling on a rope in tug-of-war, you're basically trying to use all of your muscles as much as possible, so you're just like \"clench everything\". Your jaw and lip muscles just happen to included in that."
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m4mvxw | Is there any scientific research that proves string instruments (violins, guitars, etc. ) sound better with age? | Other | explainlikeimfive | {
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"If there was, it wouldn't be about sounding \"better\". It'd be about some more objective characteristic of sound."
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m4mznd | How do we develop internal clocks. Even without an alarm going off I will wake up between 7 and 7:05 am doesn't matter if I go to bed at 9pm or 3am. Like how does this work? | Biology | explainlikeimfive | {
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"Your body reacts to many things. For example, sunlight and increased sound will let your brain know it is morning time. Darkness and quiet will let your brain know it’s night time. Your brain likes to form habits, so if you get up at certain times often enough, you’ll find they happen automatically sometimes. Your body is “used to” ending sleep at that time. These things combine to make a “circadian rhythm”, your sense of time, when you get tired and when you get up. If you close yourself in a concrete box with no sound and no light, you would keep this rhythm for a little while. But just like trying to keep an actual rhythm when the music fades away, you will drift slowly away from the beat. You would slowly start getting tired at different times if you had no external stimulus. You could “reset” or play with this sense of rhythm. Heck, some people can just close the blinds and that is enough to make them sleep longer."
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m4n1ih | Why are people so perplexed by the purpose of the appendix? | Title basically says it all. We aren't sure what it does, but is there a reason why? | Biology | explainlikeimfive | {
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"We do know some of the functionality of the appendix, for example it's role in the immune system. But the function(s) we do know about apparently have nothing to do with its specific location and and shape, combined with the fact that it's removal didn't seem to have any adverse effects, which led people to assume it was vestigial; it used to have a role but no longer."
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m4naxz | why is drinking our own blood bad for our health? | Biology | explainlikeimfive | {
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"It is and it isn't. Fundamentally, there's nothing dangerous in healthy blood but you can't survive on blood alone. Especially not your own blood as there's some losses involved. Rather, the danger comes from unhealthy blood or things blood has picked up along the way. Germs are the biggest threat here as blood is a near perfect environment for things to grow. There's also the risk that the person giving the blood was sick but didn't know it. Also, drinking blood has cannibalistic implications and society tends to break down when we see each other as a source of food."
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m4nplf | How come humans need around 1,500-2000calories for basic survival of the Body but people suffering from severe anorexia can carry on for years eating a lot less. | Biology | explainlikeimfive | {
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"1500 to 2000 calories is what the body needs to remain healthy. Less than that and the body begins cannibalizing non essential things. It starts with fat stores, then it goes to muscles. All in the name of keeping energy supplied to the vital organs. Severe anorexics will consume just enough calories to keep their brain, heart, and lungs functioning but their body will essentially be digesting itself. That's why you'll see malnourished people looking like skeletons with skin stretched over the bones. Their muscles are barely there anymore.",
"Humans need 1500-2000 calories to maintain a healthy body weight. They can survive for a very long time on less. Your body makes up the difference by consuming itself. Your body will begin to break down your muscles for energy to keep you alive. This leads to unhealthy body weights like you see with severe anorexia",
"Your metabolism will slow down to limit the damage. You'll be tired and cold and have trouble thinking and you'll slowly loose muscle and sometimes bone mass but you'll survive for some time.",
"1500-2000 is a general guideline. I need 2500-2700. People survive on less because the body basically eats itself by consuming muscle and fat. It also reduces its metabolic rate to ensure survival. People with anorexia may also eat a healthy amount of calories but exercise intensely and use laxatives to keep their weight down. In the end the body cannot live like that forever, it eventually gives up as it can no longer maintain homeostasis.",
"You probably need a few hundred calories to stay alive. This is why prisoners get rice or bread and water . Any number of fashion models talk about their all salad eating. They also don't live active lives.",
"There is also a problem with your scale. Basic survival in your sentence refers to average life expectancy age of 80. If the anorexic individual lives only a quarter of that the have not survived because they did not meet the requirements for “basic survival”. There is a lot of damage that can be done that is irreversible as well not all effects but depending on how the organs get messed up and how they reintroduce food they could permanently affect their life expectancy."
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m4nyop | Why do drugs make you stupid/lower your inhibitions, and by extension could ANYTHING that feels good enough cause a similar effect (a really good burger, or orgasm?) | Biology | explainlikeimfive | {
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"Good judgement and awareness is a balancing act and any extreme can knock you off balance, changing how you think and perceive. Extreme pain, for example, also can make you irritable and lower your inhibitions about expressing anger. So yes, anything that is extreme enough can lower your inhibitions and it doesn't have to feel good. It just has to be big enough."
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m4o2gb | Why do (most) people stop wetting the bed as they grow older? | Biology | explainlikeimfive | {
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"text": [
"Practice and development. Younger brains are less developed so they don't register everything they should or control the body properly. Likewise, holding in your pee hasn't become habit yet so you need to be conscious to do it."
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m4o6nm | What is the difference between evaporation and vaporization? | Chemistry | explainlikeimfive | {
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"Even though someone answered you already, I'd like to elaborate. Both words indicate a phase transition from liquid to gas but under different conditions. If you fill a bucket with a layer of water and leave it outside, by the end of the day you'll see that no water remained. (Assuming that it isn't freezing ;p) Now I can bet anything that during this whole process, I can touch the water without burning my fingers. This is because the water never boiled. This phenomena is called evaporation and is a natural process. It is also possible to force a phase transition by decreasing pressure or increasing the temperature. This will make the liquid boil and in this case, the phase transition is called vaporization. So the words both refer to the same principle but under different conditions."
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m4o79g | Why are there different types of airplane designs? | (Couldn’t decide between Engineering and Physics flair) Why I’m asking. Surely with aerodynamics, there has to be one design that is better than all the rest as far as less drag, control, air speed, etc. So why are there so many designs out there? Let alone so many designs that actually work, cause to me they just don’t seem like they would. Note: Obviously I’m disregarding specialty planes here like water landing ones that have pontoons on them or are shaped like a boat, and others that have different specialty uses. | Other | explainlikeimfive | {
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"There are \\*very\\* few \"point-design\" airplanes...airplanes designed to be really good at one, and only, one property. Point-design airplanes tend to all look the same at a given technology level because, like you note, it's all the same aerodynamics. But virtually all airplanes have multiple conflicting design goals with multiple free variables and different specifications. As a result, there's a \\*huge\\* number of possible configurations that meet the specifications by trading different design goals against each other. With commercial airplanes, ultimately, you're solving for airline profit. This is the reason that commercial aviation has almost entirely converged on the \"tube-and-wings\" configuration with two engines and tricycle landing gear and all the wing aspect ratios and lofts are converging. Anytime you see a deviation from that it's almost always because there was some design requirements they couldn't overcome...like the L-1011/DC-10 trijets have three engines because nobody made an engine large enough to have just two for an airplane that size back when those airplanes were designed. Today we've got 777s and A350s with far more powerful engines and they just need two.",
"They're tools that serve different purposes. Like when you pick out a car, do you go for the sport? Luxury? A commuting car? A working truck? A minivan? They ask drive, but they each serve a different purpose."
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m4pl2j | Why do companies care about unionization when they could just fire anyone who ever went on strike and replace them immediately? | Other | explainlikeimfive | {
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"Because they can't. That's illegal. Moreover, a lot of companies can't actually train people to perform to the standard they want them to work to. Combined with paperwork issues, dealing with the press, and a whole host of other issues, it's generally not worth it."
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m4qadw | Matrix in mathematics | I am really a beginner in mathematics, I would like to know what actually is matrix is, why matrix was invented what applications It has in real world and how?. I (obviously) looked up it before and found it says something of linear mapping and representation. Are matrices just arrays of elements compacted together. | Mathematics | explainlikeimfive | {
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"There are a lot of ways to think about matrices. One of them is just as a grid of numbers - but this turns out to not really be the right way to make the most use out of them, because those grids actually carry a ton of properties that are important more often than you might think. In fact, there are a lot of cases where you can take a grid of numbers, treat it as a matrix, then do matrix operations that seem to have nothing to do with the underlying data, and get an output that turns out to be meaningful. Another approach is to think of matrices as a way of representing a linear transformation - that is, a function *f* that takes in one thing and spits out another, but with the property that it doesn't matter if you add before or after applying it (formally, f(a+b) = f(a) + f(b) no matter what a and b are). Typically, you think of the inputs and outputs as being vectors, possibly with different numbers of dimensions: for example, a function *f* that projects a point in three-dimensional space onto where its shadow would land on a flat plane turns out to be a linear transformation, and thus be representable by a matrix. Yet another way is to think about them as independent algebraic objects in their own right, in the same way that polynomials or geometric objects are \"things\" despite being related to some underlying concept. The algebra of matrices turns out to be extremely rich, to the point that in some sense most other algebra can be represented as a sub-structure of matrix algebra. All of these approaches ultimately give you the same answers, so what they \"really are\" is a matter of philosophy, not of mathematics. But some approaches are more or less convenient for certain applications - and matrices have hundreds of applications as one of the most important structures in all of mathematics."
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m4qqg6 | Why do video game graphics usually allow body parts to move through walls, capes to pass through your body, etc? | This is perhaps the most common, most visible, and most enduring "unrealistic" part of video games. For example, when your character is killed and they fall to the ground and their arm just flops through the nearby wall/barrel/person. Similarly, sheathing swords or wearing draped clothing usually results in your legs/elbows passing through the clothes when you run, etc. Obviously the devs would fix this if it were feasible. Does it just take too much processing power? | Technology | explainlikeimfive | {
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"Yeah, it's a computational limitation. Flexible shapes mean expensive collision-detection/physics, and most games would rather invest their computational power elsewhere.",
"So, generally entityes have a \"hitbox\", which is like the collision of the thing. But the graphics are much more complicated than a box, so some parts of the thing are not solid (what I mean by that is that if they touch something, it doesn't matter). This also explains why sometimes something may hit you, even though it looks to just barely miss you.",
"Doing collision detection and physics takes a lot of processing power. It's technically possible, but you'd need a really high-end machine to do it well in real time on all the objects in a game. Using canned animations and positions is a lot easier.",
"3D graphics are composed of triangles and the triangles are *ghostly* by nature. Collision detection and physics all have to be explicitly programmed in. The graphics card and engine do some degree of automatic culling but it's usually just removing offscreen triangles and triangles behind other triangles. You COULD program it so your arm moves away or turns invisible if it passes through your cape so it looks more realistic but why do that when no one does and that time would probably be better spent adding new content? There were NES era games with pixel perfect collisions instead of simple hit boxes but the players didn't care and those games didn't take off. Metal Blade and Spindash were more fun even though the collision wasn't pixel perfect.",
"Because graphics are just graphics. They don't have any \"mass\" to them. You have to explicitly tell the computer what bits can collide with what bits and how the graphics change. The more detailed your collision checking it the more processing power you have to dedicate to checking it. Generally you won't have a collision check for every triangle on screen: there can be billions of them and that would take forever. What happens is that usually the collision is just a series of boxes loosely fitted to the shape in question. for the big bits that works well, but sometimes those things aren't following the animation perfectly or it just takes too much effort for a tiny flub that most people just overlook anyhow."
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m4rjai | How do graphics cards actually work? | The title says it all. How do they work? I never fully understood how they did. I know that they help to render and display images, but how exactly? & #x200B; Edit: Thanks for all of the great replies! You guys really helped me to understand what exactly a GPU does, and why it's needed. | Technology | explainlikeimfive | {
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"Your CPU is good at doing general math calculations, and it's not really optimized for crunching anything specific at that hardware level. Your GPU is also really good at math, but it's specialized in doing math with matrixes. When you're rendering images onto the screen, they are able to calculate which pixels or which lines go where way faster than a CPU, and that's how they help.",
"I always thought there was little gremlins who drew pictures really fast so I’ll be thrilled to know if someone can write a smart answer",
"They are basically just little computers that specialise in rendering instructions into images that can be displayed on a screen.",
"CPUs are built for sequential calculations. What that means is basically that for your calculations, you have some steps you need to go through, and you cannot do one step before all the steps that came before have completed. That is why CPUs usually have a handful of cores (just one for the longest time, though currently they are usually in the 4-8 range for desktop computers, maybe 2 for the low end and 16 for the high end - though servers or workstations can go above a hundred nowadays). However, those cores are really fast at going through the steps of a calculation. However, when you look at an image, the calculations needed to create an image are not all like that. You have a large area where tons of similar calculations need to be made, for example things you need to calculate for every pixel of your monitor or every object that appears on screen. And the bottom-right corner depends no less on the top-left corner than the top-left corner depends on the bottom-right corner. So you are not limited to calculating everything in a fixed order, you can do calculations for multiple areas of the image at the same time. That is why GPUs are built to have thousands of processing cores (the fastest consumer GPU on the market, the GeForce RTX 3090, has about 10000 cores - the CPUs it would commonly be paired with, such as the Core i9 10900K or the Ryzen 9 5950X, have 10-16). Each individual core is quite a bit slower than a CPU core, but because of their sheer number, there are certain problems, especially those that can be divided up almost arbitrarily into mostly independent calculations, that it is faster at by just a ridiculous amount."
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m4s1ur | After prolonged exposure to severely low temperatures, why is it better warm up gradually instead of rapidly? | I'd also appreciate it very much if you can point me to sources to read up more about this. Thanks! | Biology | explainlikeimfive | {
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"If you're exposed to severely low temperature, your body centralizes the blood flow - that means that it almost completely stops all blood flow into the peripheries (your arms, legs, etc.) and the blood is flowing only through vital organs. That helps to minimize the heat loss. If you warm such person up, the contracted blood vessels will dilate, the flow in the peripheries will resume and all that blood that was stuck there (and is now very cold) will flow right back into the central organs. If it happens too quickly, the huge amount of cold blood may impair the function of the heart (you know, muscles don't work very well when they're cold), resulting in cardiogenic shock, and possibly death."
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m4s6yw | What was before the start of everything? | I understand the big bang, but how did that start? I can't get my head around something just "being" at the start. How did that first atom come about?! Surely there's a constant, something creates something which then goes on and on. | Physics | explainlikeimfive | {
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"The Big Bang model is extrapolated backwards from what we see currently as expansion of space. Reverse the expansion as you go back in time and you eventually arrive at a single point. But in this single point the thing that we call physics would be so different from what we see now that concepts like time (as you understand it) just don’t work. I am not a physicist so I can’t explain further. Sadly (Happily) there is no ELI5 for existence itself",
"First off, the big bang is the start of the laws of physics as we know them. A lot of things that were established in how the universe cooled down that could have been different. We don't much at all about what happened before a few nanoseconds into the big bang. It started everything as we know it. We don't know it if started everything everything. There's a good argument that it also kick-started time itself. As in the dimension was made directional. At T-1s, maybe it was bi-directional like the XYZ dimensions. And we have an example of that: Consider falling into a black hole, from the left. Past the event horizon, the x dimension effectively becomes directional. Before you could move left and right. But as you move faster the \"cone of causality\" tilts. Past the event horizong, it tilts past 90's degrees and NO MATTER what happens, anything to the right cannot cause any effect on anything to the left. Not even a photon can escape that gravity. Perhaps time did something similar. > How did that first atom come about?! OH! That's well after a few nano-seconds. We know that one quite well. So about 300,000 years after the big bang, things are still expanding and cooling down and that's the point where it's cool enough for the plasma to congeal into matter. Before that it's just too hot and too dense. Hotter than the sun. So hot that atoms would rip apart if there were any. But now that it's cool, the energy gets wrapped into a tighter compartment like how things freeze from liquid to a solid (not you H2O, gtfo with your crazy crystals). Atoms form, suck in a lot of energy and suddenly there's a gap between all that plasma and light/radiation can escape instead of endless bumping into something. If we look out we can see those photons, travelling for the entire life-span of the universe, just to hit our sensors today. That's the Cosmic Background Radiation. It's lumpy! > Surely there's a constant, something creates something which then goes on and on. Could be. I don't know. Also consider that right now, space in the traditional XYZ sense goes on for infinity. There's no end to it. There are always more galaxies out there..... but not for us here and now. The expansion of space is old enough that it's outpaced the speed of light for the size of our visible universe. Every year we're not seeing more space as it's photons eventually hit us, we're seeing galaxies fade away as the distance between us increases.",
"There was no \"before\". \"Before\" and \"After\" are concepts that only exist if time itself exists, and time didn't exist until the Big Bang happened."
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m4tf6y | How come the temperature can reach up to 142 nonillion kelvins but can only go as low as -459.67 Fahrenheit. | Physics | explainlikeimfive | {
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"It's a little confusing using two different units/scales as comparison. Stick with Kelvin which has a bottom limit of 0K (-459.67F). Very simply put; heat is really a representation of how much energy the particles are carrying. Theoretically you can always increase the temperature by adding more energy, however, you cannot always keep removing energy if there is no energy left to remove. This means that once all the energy has left the system it cannot be 'cooled' down further, past 0K. Removing the heat from a system also requires energy. The cooler the system is the more energy is required to cool it further. At temperatures approaching 0K the amount of energy needed to further cool it down would become infinite. So 0K is impossible to actually reach.",
"It's the limit where atoms complete cease to move and if there is no movement involved there can't be a temperature to be created. However, there's some whicky-whacky quantum physics involved there but I am not qualified enough to answer that.",
"Temperature is really the measure of how fast atoms vibrate. Whilst it's possible to continue to add energy so they vibrate more and more (i.e. increase in temperature), taking away energy slows then down. And once your reach zero movement you can't go any lower as there is no such thing as negative movement. That happens at absolute zero, which is about 459.67F.",
"There is no such thing as coldness. The lowest temperature just means there is no kinetic energy left in the system. You can't go below nothing, but you can keep pumping energy into a system to reach ridiculously high temperatures/energy levels.",
"> How come the temperature can reach up to 142 nonillion kelvins but can only go as low as -459.67 Fahrenheit. Temperature is, roughly, a measurement of the amount of heat energy within a system. A system cannot contain fewer than 0 Joules of heat energy.",
"A rephrasing of this question is \"why, on the range of all possible temperatures, do humans live very close to the bottom\". We don't know the answer for certain, but we do know that chemistry - which is the source of the richest structures known in the Universe and thus a great way to build living things - takes place mostly in the temperature range in which we live. Hotter temperatures tear molecules apart into plasma that can't form molecules, and colder temperatures make reaction rates so slow that living things (if they can exist at such temperatures) would have had much less time to evolve in the amount of time the Universe has existed so far. ---- As for the numbers, it's really best to work in Kelvin throughout. The possible temperatures are 0 K to (very large number) K, and we live at a few hundred K - close to the bottom. You can't go below 0 K for the same reason you can't have fewer than zero hamburgers: temperature (in K) measures the amount of something, and you can have nothing or you can have something, but you can't have the opposite of something.",
"Temperature is kinda the average speed of molecules bouncing around. If you stop them all you get absolute zero.",
"Not ELI5, but close. Think of it like a stock. A stock's value has no upper limitation, but can only go down to zero.",
"once the energy is 0 there is no more energy to extract, that is the point 0 Kelvin, or -459.67 F as you reference it.",
"The faster the molecules of something move/vibrate, the hotter it gets. The slower they move, the colder they get. They speed up, it warms up and vice versa slowing/cooling. Now if those molecules stop moving, they can't get any slower than standing still right!",
"You can also have 100 million cats but only go down to 0 cats. You can't have negative cats. Temperature in the Kelvin scale is defined using 0 as the point where the atoms are not moving at all. It just doesn't make sense to have negative Kelvin temperature",
"Heat is a word that describes the movement of atoms. If an atom, and it's fellow atoms are very jiggly, there is a higher measured temperature. Sometimes atoms can get so jiggly they become parts of gases. If an atom and it's fellow atoms are not so jiggly, or downright boring, the lower the recorded temperatures will be. Atoms can stand be so boring they can become parts of solids, and don't move much at all. They may sway a bit. When the atoms stand completely still, there is no measurable temperature, because the atoms have all stopped moving. This is known as Absolute Zero. Measured at 0 Kelvin, -273.15 Celsius, or -459.67 Fahrenheit. As to extremely high temperatures, well, some atoms, depending on how many there are, and what gravity exists, can become jiggletastic. Jiggletastic atoms can form something called plasma. It has a really high measured temperature, because the atoms are buzzing so quickly. Sometimes these jiggletastic atoms can bang into other jiggletastic atoms (like Hydrogen) and bang together to make Helium and really, really, large amounts of energy, which causes other hydrogen atoms to become jiggletastic and bang into other hydrogen atoms, continuing the reaction, like dominoes, hitting dominoes, hitting dominoes. This jiggletasticness can be measured as extreme amounts of heat, but it is also radiation and light, too. This is called Fusion. The atoms are vibrating so fast in Fusion, that they are measured as having huge amounts of heat. This is basically what happens in the Sun. In the centre of the sun, the temperatures are around 15,000,000 Celsius, or 27,000,000 Fahrenheit. Compared to other stars, our star is actually quite small and cool. There are super massive stars that are far, far hotter in the galaxy. There are probably other things that can get even hotter, like really close together stars near the centre of galaxies."
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m4tlv8 | Why does getting dizzy feel soo much worse when you're older? | Other | explainlikeimfive | {
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"Nurse here. I was taught it was because the interstitial fluid in the ear responsible for proprioception gets thicker as we age due to dehydration, therefore vertigo, dizziness, etc symptoms are worse. That was a long time ago and Im too lazy to look it up, but it sure sounds good.",
"It is your body saying \"Stop, you're not a kid anymore.\" When you are young you don't have the culmination of all the memories you have built up over the past 28 years. Your child brain thinks \"Weeeee, this is different and fun.\" You now know from experience what falling and hurting yourself is like now and your brain tells your body that it doesn't want to lose control. That exhilaration as a child becomes anxiety as an adult. At least for most people.",
"There is not a clear cut reason, since sensory perception is a complex process. But one big reason could be the growth development in the inner ear. We have what is essentially a leveling tool in our ear with some liquid and sensors inside. When we move around in space, that liquid moves around and tells our brain where we are at in space. A kids ‘leveling tool’ is not as developed and has less sensors, so they don’t get as dizzy. As adults, we are much more sensitive to those motions."
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m4u4ew | what do we use linear algebra for? | Mathematics | explainlikeimfive | {
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"Linear algebra is having a real explosion of usefulness in computer science right now. It’s the basis of much of machine learning. For example, Linear algebra is how Netflix recommends your next binge. You can set up a system of equations that represent different properties of movies and then find eigenvectors to understand which properties are independent of what other properties in people’s preferences. Then you can compare two movies by using the Pythagorean theorem to find the shortest distance between any two given movies on the map.",
"Linear algebra is amazing. In the early days of quantum mechanics when they didn’t have the whole picture, but were piecing together parts of it, Schrodinger had developed a more traditional for physicists, wave-equation type of approach. It was based on calculus, differential equations, and viewing matter as a wave. Meanwhile, Heisenberg had learned about this new and rather obscure branch of mathematics called linear algebra, and it turned out to be really useful. That approach focused on the “observables”: where is the particle? Or how fast is it going? Without worrying so much about the in-between. (Aside: this is called positivism.) Later, when Dirac (a genius among geniuses) entered the scene, he saw the truth: both the wave equation approach and the linear algebra “particle” approach were perfectly equivalent. Matter could be thought of as a wave or a particle. What mattered mathematically speaking was that in quantum mechanics, numbers don’t always commute (that is, A * B doesn’t always equal B * A). The non-commutation of elements is a central property of linear algebra. It’s familiar to us now that matrices don’t commute in general. The connection to calculus is because of derivatives: f * dy/dx in general does not equal d/dx (f * y). By proving the equivalence of the Schrodinger and Heisenberg pictures, Dirac unlocked an incredible amount of potential in math in general, because now you could start with a familiar wave/calculus approach, switch over to the abstract convenience of linear algebra, and then back to the familiar picture. And now as other commenters have said, linear algebra is incredibly useful in all sorts of fields, not just the physics of atoms. I strongly recommend the book “The Quantum Ten” by Sheila Jones for anyone interested in the story of the invention of quantum mechanics. There’s drama, intrigue, tragedy, romance, betrayal, sex, Nazis and physics, all in a very well-written history book that reads like a novel. Knowing the humans and the stories behind these named theorems and equations genuinely helped my understanding of the physics when I was studying this stuff in school.",
"Anything that revolves around multiple equations, with multiple variables (linear algebra started as a way to solve multi variable linear equations after all), or manipulation of values with more than one dimension can be approached with linear algebra. A few examples: \\- Geometry problems, mainly ones that you need to change the coordinates (for example, if you want to project some 3d object on a 2d plane, and want to rotate the object) \\-Calculation of values in a electrical circuits \\-Networks, and graphs: You can use linear algebra, to optimize the flow of data in a complex network system. \\-Systems that have many values that evolve through time, and interact with each other. \\- Computer Science related stuff: Machine learning, data analysis, computer graphics, network, image processing, signal processing, etc.",
"Linear algebra is usefull for many many many things. Data analysis, physics, engineering, ... The limit is linear here, but linear algebra is so powerful that we actually linearize nonlinear equations (assume they are linear as long we don't move too far from the point we linearized at) because nonlinear algebra has no general solutions for many problems",
"I just recast a work problem into linear algebra. How to take RGB camera output and correct for the fact that some green shows up in the red channel? Well you can set up a system of three equations and manipulate them. Or you can set up the matrix expression and tell the computer to find the inverse. The latter is easier. And in truth it was a lot easier to think about this with linear algebra “tools”. This is a simple problem (a toy problem for many) but it is relevant and affects our manufacturing process."
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m4u8jh | Bayes Theorem | I really don't understand Bayes Theorem. Mainly about how the probability side of it works and what each probability in the formula actually means. I've been trying to wrap my head around it for ages but whenever I try I can't. For example, here's a question I failed to understand. There was a table of skiers and snowboarders and the probability of being one and the probability of falling down for being one. The example question was the probability of falling given you're a skier and the top is P(A and B) which I think are both treated as independent but it doesn't make sense to me because P(A and B) looks equivalent to the question itself. And then the denominator is P(B) but isn't that just being a skier? I'm really confused as to how to understand bayes thereom in general and I'd love for someone to explain :') | Mathematics | explainlikeimfive | {
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"It seems to me you might be confusing Bayes' theorem with the definition and meaning of conditiontal probability so I'll try to focus on that, i.e the difference between P(A | B) compared to P(A and B). Let's say you have a small portion of the total population that's a skier (defined as someone who skies every day for exanple) , so the probability that a random person skies is quite low, also people usually don't just fall down in their day to day lives so the probability of a random person falling down on a given day is also low. Now you can imagine a scenario where skiers are more at risk on falling down by nature of their hobby, so let's just say that everyone who skies is definitely going to fall down each day they ski. So in this scenario, A is the event \"falling down on a given day\", and B is \"being someone who skies everyday\". And thus P(A | B) is the probability someone will fall down on a given day, if it's known they skied that day - we have said that all skiers fall so this is just equal to 1. Now think of P(A and B) - being both a skier and also falling down, the probability of this must be smaller or equal to the probability of someone being a skier - P(B) since you have an extra condition on the person, so it doesn't make sense for it to be bigger. Now it should be quite obvious that P(B) is less than 1 since only a small part of the population skies, which means that P(A and B) is also less than 1 - so it can't be the same as P(A | B). This example is exaggerated to try to make it easier to understand but the main point is that conditional probability is the chance of something happening given we know that something else already happened. And this isn't the same as the chance both things happen, even though at first glance it makes sense to assume they're the same."
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m4udqm | How come bees don't sting bee farmers? I have seen videos of bee farmers just scooping up bees with their bare hands. | Biology | explainlikeimfive | {
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"Bees do sting us, all the time. I get stung through my suit, visor and jeans a lot. When you see people scooping up bees or wearing clumps of bees on their face etc this is because the are handling the bees when they are swarming. When bees are swarming they are less aggressive due to the fact they have no hive or honey to defend.",
"They do sting the keeper, occasionally. In general, the keeper knows how to handle them, how to not trigger their defenses. For instance, they can use smoke to calm them down. The smoke doesn´t anaesthesize the bees, it makes them instinctively fill their bellies with food because they associate smoke with wildfires, which means hard times and chances of starvation. They become full and dull. The smoke also masks smells, or pheromones they normally use to navigate the environment. When inhibited, they go passive.",
"I know the video you saw. At the beginning she was using a smoker. That tells the bees there is fire. In a fire emergency bees swallow as much honey as they can carry for the escape which has the same effect as you post-big-stuffed-dinner. That said, I guarantee she got stung during that whole process. Bee keepers are just so used to it they don't jerk, jostle or anything. For them it's as everyday as bumping your elbow on a table. Think Steve Irwin whenever he got bit or stung. He kept a smile and a happy tone of voice that never faltered as he continued narrating. Also it was for a commercial/promo video, so they cut to clips where she is smiling and had perfect hair and makeup instead of showing the whole process.",
"Both commentors are absolutely right. I'd just like to add my two cents as someone with two colonies. As a bee keeper you know when the bees are going to be angry or not. If the weather is somewhat cold and damp (shouldn't be entering the hive) if you're in the hive for an emergency they're going to be pissed off. Similarly if it's extremely hot or windy. Bees gst wound up just like human do even with smoke. Also, I wear my suit every time and I've still been stung through it. Just comes with the territory. It's kind of a right if passage.",
"I know this is a bit of a segue from the original question, but I think it’s relevant enough to make the mention here... (This is especially important to know if you happen to be allergic to bee venom. Like I am.) When a honeybee stings you it leaves a small and still-pulsating venom sac that is attached to the back (non-pointy) end of the stinger. That sac is still mostly full, initially, and will continue to deliver venom into you through the stinger unless & until both can be removed. Without knowing any better, most of us would simply pull out the stinger & sac between our thumb & index finger. This is NOT a good approach because by doing so you are literally injecting the rest of the sac’s venom into yourself. A much better way to remove a stinger from the skin is to scrape it upward from the side, as opposed to grabbing it from the top. Using a knife blade (or even a fingernail if you have one that is long enough) catch the stinger from BENEATH the sac and lift it all upward. This way you won’t receive nearly as much of the sac’s still available venom. Hope this is helpful. Apologies for the segue.",
"For reference I had 2 hives for 3 years before local bears decided I wasnt allowed to anymore. One of them was a swarm i collected an hour away and drove home with in my back seat. We get stung but also know how to handle it. If you dont freak out the the hive generally wont get collectively aggressive. Its an exercise in zen mindset. Sometimes they get caught in hair or pressure is put on them so the reflexively sting without telling the hive there is a threat. I have also had bees crawl up my pant leg, dropped trow, and shook them out without getting stung. If you keep your cool and know their habbits you can find great success There is also a proper way to deal with a sting. After you are stung, the poison sack is stick stuck to the sticker in your skin. If you try to tweeze it out with your fingers, you are basically pushing the plunger on a venom needle. I used my knife or beekeepers tool to scrape the sticker from my skin without injecting more venoms. If anyone is interested there is a great reference book. The abc and xyz of bee culture. Its on its 30 some odd edition and was always considered my bee bible.",
"Oh they will. Traditionaly honeybees are more docile though. But like any animal if you threaten them they will attack. I worked for a beekeeper for around 7 yrs and we would tell people when asked \"We new it was a good day when you could count the number of stings you had.\"",
"They occasionally do, but honeybees are docile, and there are things that a beekeeper can do to prevent them from attacking. The main thing they can use is smoke (someone already explained the mechanism on another comment, but the end result is that the bees become \"lazy\"). There are other stuff, like not doing fast movements, using fragrances, color of clother, and where you stand (If you check videos, beekeepers access the hive from behind, they never block the entrance for the bees). Also, with time, a person can know how that particular hive behaves. So, more often than not a beekeeper doesn't get stung at all. Also, you get used to the pain. Although some people may develop stronger reactions over time, to the point where one sting can be life threatening, others get desensitized, so they aren't afraid of a few stings",
"It's a zen thing. Like a dog or horse, they can sense fear. Also, most beekeepers know when and when not to work the hives. Super hot days, or rainy days agitate bees. Also bees communicate in part via pheromones. Every bee keeper knows if you can smell the scent of bananas, you need to back off. The pheromone released that tells the hive to go into defense mode smells like bananas. Also, when bees are swarming, they are not agressive and rarely sting. They're putting thier energy in finding a new home, not defending a hive. When you see these images of people covered in thousands of bees, they've been sprayed with an isolation of the pheromone that says \"swarm\".",
"Not a beekeeper, but read that a lot of honeybee species are very docile. BUT the African killer honeybees have practically ruined that reputation. Those particular bees are very aggressive. If I remember correctly, it's an invasive species that was brought over for some reason. Edit: grammar",
"There are definitely ways to move that are far less aggravating to the bees, and getting good at smoking them just the right amount helps keep them more sedated. Also, some kinds of bees are less defensive than others, and things like the weather can affect them. But we totally get stung regularly.",
"The keepers still get stung. They just don't tell us about that part because then bee keeping wouldnt seem as fun.",
"When bees mature, they start by working in the hive. Those workers are fairly gentle. Then they go out to forage and become much more aggressive. So the hive bees aren't as likely to sting. Beekeepers use smoke to pacify them, and sometimes even feed them sugar water, which also pacifies them and may even make it harder for them to sting because they can't bend their abdomens. And beekeepers work slowly and carefully so as not to disturb the bees. But beekeepers working in a hive don't normally scoop bees with their hands. That's either handling a swarm or just someone doing a stunt.",
"My Opa was a Bee keeper and he would go out and work with his bees without wearing a suit or a hood and didn't smoke them either. He'd get stung occasionally but not very often. He told me one time that if it was going to rain that the bees would be ornery and that's when he would usually get stung. The other time people would get stung was if they were afraid of bees. When you are afraid your body releases a scent that the bees can pick up and they are more likely to sting you. Which makes sense as you'd have no reason to fear a honey bee unless you've been stung before. My Opa was the kind of guy that would get rid of a hornets nest by clapping his hands on the hive, he'd start at the bottom/entrance and work his way to the top. He'd do it bare handed as well.",
"I used to work with bees and never got stung. On my first day the head beekeeper said “they can tell if you’re anxious and they’ll react to it. Believe they’re not going to sting you, and they won’t.” No clue if he was just trying to be reassuring, or if it was true... either way it worked lol",
"My bees used to sting me occasionally. Before you do anything with your hive, you smoke them using a smoker. This seems to calm the bees. It only lasts for a little while. When they start to get active again, you use the smoker again. You also get pretty good at doing your maintenance reasonably quickly. I did love my bees",
"I'm a bee keeper, I would get stung 9 out of 10 times I work my hives at least once or twice if I wasn't suited up. Try to work a strong hive without pacifying them (smoke/sugar-water spray) and they will very likely light you up depending on the time of year. However, swarms are often very docile because they have nothing to defend and are full of honey (they load up before they leave the hive to swarm).",
"Sometimes they do sting us, but usually they prefer not to. Bees don’t like to sting because it kills them, so they only really try to sting as a last resort. Also, beekeepers know some tricks that help them avoid the stingy bees. Those tricks are: - White and light colors. Bees tend to aim for dark things when they sting because most things that hurt bees are dark-colored, so if we dress up like a big white marshmallows we are much less scary. - Smokers. These have been mentioned a lot, but basically the bees think outside is on fire so they’ll just hide inside thank you very much. - Sugar spray. Instead of smoke, you can spray bees with sugar water and they become much more concerned with licking it off of themselves than stinging. - Sunny days. Bees don’t get stingers until they grow up, and most of the grown-up bees do the work of getting food. So if it’s a nice day and the flowers are out, most of the stinger bees aren’t even home. - Smooth moves. Being slow and careful not to hurt the bees or bother them too much keeps tensions from getting high. - Good moods. A happy hive is a nice hive. Making sure your bee friends have food to eat and enough space to be comfortable makes them far less grumpy. As does preventing things like critters messing with their house or pestering them during weather they don’t like. That’s really all there is to it! Do remember that bees are a domesticated species. Just like dogs, we bred a lot of the mean out of them over a long time.",
"Some get rid of queens that create aggressive hives. Over time, the majority of their colonies will be quite gentle. It also helps to go in to the hive when it isn't rainy, windy, cold, or night time. They don't like being bothered during any of those times, regardless of how docile they usually are. I will support what others have said, that yes, if the colony is in swarm mode the last thing they are thinking about is protecting the colony from attacks. Their priority is finding a home before night falls (hopefully), so handling a swarming colony is usually quite safe. Although you should still wear some sort of protection, especially if you don't know if you are allergic. My last note (but long), beekeepers who are a bit more gentle in the handling of their colonies usually have more docile colonies as well . That is NOT to say that they don't get stung, just far less likely/often. Usually they get stung where your body hinges (armpits, inside of elbows & knees, etc) or if they bee gets inside their clothing and gets pressed or rolled. Typically the less gear you wear, the more gentle you handle the colony. You're more sensitive to where the bees are in relation to where your hand is. If you're wearing gloves and a full suit, then you are less likely to feel that bee (or few) that you are about to roll around with the back of your hand. They are more likely to sting when they are getting rolled around. The most gentle beekeepers tend to only wear a veil, and utilize their smoke to help break up the pheromonal communication. Commercial beekeepers don't have the luxury of taking their time and being gentle. They have an absurd amount of colonies to look after, so speed is paramount for them. That's why they really do need to bee wearing the full suit. A hobbyist can learn better handling techniques since they only have a few hives and can afford to take their time. (My partner is an entomologist that studies honey bees which involves a boat load of colony handling)"
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m4usfa | Why does medicines taste bitter and why can't they just add sugar to make them taste better? | Chemistry | explainlikeimfive | {
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"Pharmacist here. A lot of drugs are alkaline, and alkaline compounds taste bitter. And believe me, we *do* add sugar, but there's only so much sugar can dissolve. Metronidazole is going to be bitter as hell no matter what you do, for example. And for things in tablet form, we don't care- you're not expected to taste them much.",
"Lots of medicines are made to taste bitter to discourage accidentally overdose, especially in children and pets. Most medicines don't have to be bitter (with some exceptions, such as anti-malaria drugs) but manufacturers make them taste like that on purpose",
"I'm assuming they make them taste bitter so little kids don't think the medicine is candy 🤔"
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m4vmqg | How does a viagra pill affect the genitals only, and not all muscles around the body? | Biology | explainlikeimfive | {
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"It doesn't actually. It's a powerful Vasodilator that opens up blood vessels throughout the entire body but it works as a PDE5 inhibitor which if I remember correctly is the enzyme that tells the cells in your penis to make the erection go down. It's something like that but basically because the drug does increase blood flow in the body it can cause drops in blood pressure and if you are on medication for high blood pressure that's why they have warnings when using Viagra. In actuality Viagra was supposed to be a medicine for high blood pressure but the side effect of it increasing blood flow to the penis was such a revolutionary thing that they pretty much rebranded it as an ED medicine rather than a high blood pressure medication.",
"The genitals are not muscles. The penis is made firm by the action of inflating with blood and this expansion of blood vessels does happen all over the body. In fact the drug was invented with the intent of being used to aid in those with heart problems. So yes, it does work all over the body but not on muscles.",
"Viagra does affect a lot of different systems in your body. It does not just change the blood flow in your genitals to make you erect but also lowers the blood pressure by affecting the other blood sphincters in similar ways. In addition to this it affects your retina and some people report that their vision turns blue when taking viagra. Due to these effects viagra is commonly prescribed for other things then erectile dysfunction. It is also a common drug for self medication of high blood pressure because it is easier available then other such drugs."
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m4vpgh | Blowing out a fire and blowing to start a fire? | You blow out a candle but you can start a fire if you blow onto a small glimming piece of wood. How does that work? Can you also blow out a bigger fire if you blow hard enough and increase a candle flame if you blow a little? | Physics | explainlikeimfive | {
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"Fire wants three things to keep burning: fuel, heat and oxygen. Fuel is already there and will not be affected by your blowing (assuming you're not blowing so hard to blow away the entire candle or the smoldering piece of wood). The rest depends on how hard you are blowing. If you are blowing hard enough, your breath (which is considerably colder than the flame) will take away much of the heat of the burning flame (think blowing on a spoonful of hot soup to cool it down). If the flame does not have enough heat left, it will go out. A smoldering fire is smoldering because it cannot get enough oxygen from surrounding air to burn properly. But if you are blowing into it carefully and softly, your breath brings more oxygen in and this allows the fire to burn more intensely. (People are often confused about how the air you're blowing can have oxygen - after all you're supposed to be breathing _in_ oxygen and _out_ carbon dioxide. But in reality your lungs cannot extract all of the oxygen you breathe in, so there's plenty of oxygen left in the air you breathe out. And the air you're exhaling also moves more air along with itself as well.)",
"The other answers are correct, but in the somewhat special case of blowing out a candle it has more to do with windspeed vs flame propagation speed. When a candle burns, what's actually on fire is vapours from hot wax. The candle wax in its solid state cannot burn, it needs to be vaporised and mixed with oxygen first. You can see this vapour as the smoke wafting up after you extinguish a candle. Now, to make that vapour continue to burn and also keep vaporising more wax to feed the fire it needs heat in the shape of a flame. If we can remove the flame (which consists of gaseous matter and is easily moved by wind) from its source of fuel, then the fire goes out. Try the following experiment: light a candle, then while you hold an already burning match or lighter blow the candle out. There should be a stream of white or gray smoke rising from the wick, try to ignite that smoke an inch or two above the wick using your prepared match. You only have a couple of seconds before it gets too cold, but if you get the timing right you'll see the flame \"jumping\" down the smoke and relighting the candle. The speed at which the flame \"jumped\" is the flame propagation speed in that wax vapour. Fast, but not crazy fast. If you can blow hard enough to move the flame away faster than it can burn back upwind, you remove the heat from its fuel source and the candle is extinguished. This same trick has been used to extinguish burning oil wells, using a jet engine mounted on a tank chassis to blow very very high velocity winds at the flames. Now, attempting to blow out most other fires wouldn't work because burning wood and other solids retain enough heat in the glowing embers that the flame simply relights itself again. There's combustion going on inside hot coals in addition to in the gaseous flames, so even if you blow the flame away the fire keeps going.",
"Fire needs heat, spark, fuel, and oxygen to burn. When you gently blow on embers, they get more oxygen and burn more, starting a fire. When you blow a big puff of air on a candle, you are pushing all the sparks (flame) out of the candle, and the fire stops."
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m4wscx | How do electronics always finds themselves in situations where they need to be rebooted to work properly? | Technology | explainlikeimfive | {
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"Imagine you have directions on how to drive somewhere. You just have all the turns you're supposed to make. Then let's say you get to an intersection and there's an accident blocking the way. You end up missing a turn. Maybe the directions you have still work, but unlikely. It might be really hard to get back on track depending on exactly what turn you missed. If you could teleport back to the start and resume, you know that the instructions are supposed to work. Something similar happens with electronics. A bug can happen because of some random circumstances that creates an unexpected situation. The program then keeps carrying the error forward, so it causes bigger and bigger problems. If you restart, you get a clean state to work from. If you don't get that one little error, then it doesn't compound into a big one.",
"In addition to these other answers, sometimes software is written in a way that causes something called a memory leak. Sometimes a program is written in a way that an error tells the software to write to short term memory (RAM) without clearing old data out and eventually you're essentially putting 10 gallons of information in a 5 gallon hat and that causes issues too.",
"When a program runs, it tends to do all of the necessary setup at the beginning. If any of those things that were set up in the beginning develop an issue, restarting and repeating that setup is the fastest way to return to a good state. This is because while computers are good at detecting errors, they aren't perfect. If an error slips through, the computer, assuming it's caught all the errors, will treat this erroneous data as correct, which can have strange consequences. Errors like this are rare, however, so fixing them without restarting requires a lot more work than just restarting. Let's say you're adding 100 numbers by hand. You're 3/4 of the way through when your friend tells you you've made a mistake. You don't know where you made the mistake so you have two options. You can go back through your numbers and carefully check each addition or just start over and assume you won't make the same mistake twice. In computers there's a bit more to it but the idea is the same. Sometimes, your software uses other software you don't own. You don't know how it works or how to fix it, it's just a black box. In the analogy, this is like some of your 100 numbers being told to you by someone else based on their own math. It's hard to know if they gave you the wrong number, but you know it's unlikely, so restarting will normally fix the issue.",
"The best analogy I can think of is a whiteboard or a chalkboard. You can write on them all day, and usually you can clean them off with a dry eraser. Eventually, there's enough residue on the board that you have to use a wet spray for a true reset. Electronics can gather residue as well, whether it's static electricity or bits/bytes in the wrong positions. In the same way that you deep clean a board with a spray, you deep clean your electronics by turning them off and letting them rest for a bit."
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m4xjzd | What makes Lead as a commonly touted shield against radiation? It's commonly a point of comparison when talking about penetrative powers of different types of radiations | Is it its density? Or other absorptive properties? In the same vein, concrete too? | Physics | explainlikeimfive | {
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"It's mostly because lead is pretty much the cheapest of the dense materials. Every other elements close to it on the periodic table is a few orders of magnitudes more expensive. Being dense, lead is relatively good at blocking ionizing radiations. Being cheap, it is also readily available.",
"Atomic cross section and density. These two things determine how \"good\" a radiation shield something is. By good I mean it can be thinner for a given level of protection. Lead is the best shielding material that is easy to use. For example depleted uranium is almost twice as good but much more impractical. Depending on the radiation source concrete would need to be somewhere between 5 to 10 times thicker than lead to provide the same protection.",
"It is cheap, readily available, flexible and dense, so you can make any shape you want of any thickness relatively easily."
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m4ymid | How does the body produce what seems to be gallons of snot | Biology | explainlikeimfive | {
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"The snot (aka) mucus, is mostly water. It does contain some proteins and salts. The mucus is produced to trap particles (like dirt, pollen, or bacteria/viruses, and help flush them out. It is easy to produce because your body is mostly made up of water. When you have an allergy attack or cold, you'll notice it is much more watery. This is partly because it is easier for the cells making the snot to push out more water than proteins quickly"
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m4yv9u | What’s happening when someone faints simply by witnessing something traumatic? | Biology | explainlikeimfive | {
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"The emotional reaction makes the vagus nerve reduce heart rate and blood pressure to a point where you faint."
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m50xe8 | How did vacuum tubes work? What were the differences between them and some of the earliest transistors from Bell Labs? | Technology | explainlikeimfive | {
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"In a nutshell the 'filament', sometimes known as the cathode, the part that heats up and glows, generates a potential stream of free electrons. The Anode, of the main output of the tube, collects these electrons. In between are typically one of more 'control grids'. Their purpose is to control the flow the passage of the electrons from the cathode to the anode. By varying the amount of voltage on these control grids you vary the amount of electron flow. In the simplest semiconductor there will be three layers of semiconductor material. Electrons will flow from one end to the other, with that flow regulated by the middle one. A voltage applied to that middle one will vary the output, just like in a tube. The basic function is the same, but tubes were invented in a time when semiconductors didn't exist. This is exceptionally simplified, but I hope it gives you the idea."
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m52t8e | How do liquids make it through the stomach to the rest of the body, but gastric juice doesn’t? | Biology | explainlikeimfive | {
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"Gastric juice *does* flow into the intestines. Its acidity is neutralized by pancreatic juice (which is alkaline) in the upper small intestine, and most of its components get reabsorbed by the intestines and recycled."
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m52v87 | Why does it appear that packages of flour are "leaking" in the grocery store? There's always flour everywhere, why? | Other | explainlikeimfive | {
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"You can't put flour in air-tight bags, it will mold more quickly. So, it's put in paper bags with glued seams. Glue costs money, more than flour, so the flour baggers seek to use the absolute minimum amount of glue. This heads to tiny leaks, which can accumulate over enough shoppers handling enough bags of flour to make the mess you see.",
"Powders like flour or sugar are sold in paper bags because paper is slightly breathable and wicks moisture away from the powders inside, keeping them dry. Another consideration for flour is that it's a very fine powder and static electricity in factories causes problems when the flour sticks to machinery. Paper packaging causes less static charge than, for instance, plastic."
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m5306s | why wouldn't the govt allow student debt to be discharged by bankruptcy? | Economics | explainlikeimfive | {
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"Because nobody would loan students money. If they did, students would simply file for bankruptcy after graduation, before taking their first job. Then they'd start their new jobs with no student loan debt and the lenders would go broke. If I loan you money for a car, and you don't pay, I can repossess the car and sell it. If I loan you money for college, and you don't pay, I can't cut the knowledge out of your brain and sell it someone else to recoup my investment.",
"Because many, many people would finish school entirely on loans with no intention to pay them back. People can't afford houses and new cars fresh out of school anyway, so the standard game plan would be to coordinate some extra time living with parents or roommates after graduating. Young people with no savings and fewer responsibilities don't have much to lose by just taking the bankruptcy in stride. Get degree-- > declare bankruptcy-- > move back home, or live cheap with friends while advancing their career-- > once the bankruptcy is off their credit score, they can start working toward getting those mortgages and loans"
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m5364v | We see all those layers from millions of years ago... but how is new dirt constantly and consistently added to the surface? Where does it come from? | Earth Science | explainlikeimfive | {
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"Dirt is mainly decomposed organic matter and eroded sediment from rocks. So, it kinda comes from everywhere. In an environment that only has eroded material and no organic material, you get a sandy desert. In an environment lush with life and with few exposed rock areas, you get rich dark soil.",
"Worms eat dirt and absorb all the nutrients they like, then poop out the remaining soil. They poop out so much soil it can even raise the level of the land. Charles Darwin studied worms in an area his children called 'the stone field'. By the time the children had become adults, the stones had been completely covered by soil from worms."
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m541n2 | Why does a C note sound the same as another C note an octave higher? | Same just higher | Physics | explainlikeimfive | {
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"Because something that vibrates at one frequency also vibrates at multiples of that frequency. For example, a 400 Hz tone typically has vibrations at 800 Hz, 1200 Hz, 1600 Hz, and so on. In a sense, playing a middle C also plays a high C at the same time. These extra notes are called *overtones*, and they're responsible for a lot of the way that musical notes interact. An octave up means double the frequency. So from, say, 400 Hz, you go to 800 Hz. But every overtone of 800 Hz (1600 Hz, 2400 Hz, and so on) is also an overtone of 400 Hz, so the two have a lot in common - and of course, 800 Hz is itself an overtone of 400 Hz. This is also why notes a major third apart (one note is 4/3 the frequency of the other) or a perfect fifth apart (one note is 3/2 the frequency of the other) sound good together: their overtones line up to some extent. More dissonant pairings, like a note and another note a single semitone above it (16/15ths its frequency) line up less well and produce conflicting overtones that sound dissonant to the ear.",
"The octave-higher note is exactly double the frequency of the original, lower note. If you were to draw out the wave forms, you'd see that the higher note completes two full cycles in the same time that the lower note completes one cycle. We hear this as higher and lower versions of the same note. If you were to double the frequency of the higher note, you'd get the same note, two octaves higher. As near as I've been able to find out, the perception of octaves is universal. When a similar question was asked a few months ago, I was unable to find a scholarly mention of any human culture that does not hear octaves this way - as different versions of the same note. Including cultures that employ different tuning systems for the notes within the octave.",
"The way your hearing works is that you have one nerve for each frequency you hear. When the sound resonates with this nerve it will send out a signal to your brain. But the thing is that it is not just a single nerve which resonates but also the one for double the frequency and quadruple the frequency and so on. But this means that when you go an octave up it is mostly the same nerves that trigger on this new note as triggered on the old note. There are some that does not trigger on it so you can still hear the difference but it is not a big difference. A chord actually exploits this and is composed of three or more notes that all trigger the same nerves. If you play a chord there is even less difference between the original note and the one that is an octave higher so it is even harder to hear if not impossible."
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m54j9s | If our stomach uses its muscles to help digest food, why do we rarely feel or even notice it? | Biology | explainlikeimfive | {
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"We feel very little of what is going on inside our skin, as there are few sensory nerves there. Most of the time, we \"feel\" that something is happening in our bodies when it has symptoms that affect our body surface/skin/sensory nerves. It can be difficult to determine the source of these symptoms because they might not be directly connected to the \"inside\" source."
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m55yo5 | When it comes to taxable income from the government, why do we have to pay taxes on them after receiving them? Wouldn't it make more sense to deduct the taxes from them in the first place? | Economics | explainlikeimfive | {
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"One issue is that the government entity paying their workers won't know exactly how much of each employee's paycheck will be going to federal/state local taxes, so those employees would still have to reconcile the difference anyway",
"Taxes aren't a flat percentage rate, and are not due immediately on receipt on income. When taxes are withheld at the time of receipt of income, it's only an estimate of the taxes due.",
"We try to do this. taxes have to be deducted from your paychecks. The problem is that we do not know how much everyone have to pay in taxes until the year is over and all the ledgers are closed and tallied up. Say for example that you get laid off in December, in that case you have probably been paying too much taxes all year but there was no way of knowing this. Or if your spouse made the Christmas bonus you have probably been paying too little taxes all year and again there is no way of knowing or correcting for it. And this is just simple examples. So in addition to the tax deductions on your paychecks there is a yearly review. It is done as soon as possible after the end of the tax year but this still usually means a few months as it takes time to collect all the documentation. What is being done is that your actual taxes are being calculated. And then it in checked up with what you have already paid through you paychecks. You will get money back if you paid too much taxes or you have to pay additional taxes if you have paid too little. If you constantly end up having to pay additional taxes then it is probably something wrong with your initial tax estimates that is used by your employer to deduct taxes from your paycheck. So you should double check these and update them to make them more accurate. If you end up with major financial changes which would alter your taxes then you should update the forms as well so that you are not surprised come tax day."
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m56jus | Why is usb a serial port and not a parallel port? | Technology | explainlikeimfive | {
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"It is serial because the transfer speed that was required could be managed with just two data lines with differential signaling. It also has two wires for power so a total of 4 wires. If you can have fewer wires you can make cheaper connectors and cables. USB is designed to be a way to connect stuff. This is the main reason that USB is series because it will be cheaper. Later USB standard add extra wires for dor signaling so USB 3.0 have2 additional differential pairs and a signal round for a total of 9 wires. The extra wires allowed higher transfer speed. USB-C has 23 pins connectors but only 16 wires and a shield in the cable. The difference is because some pins are duplicated do the connector can be flipped. It uses 6 wire pairs for singaling. & #x200B; Even if USB 3.0 and the USB C has multiple pairs of wire for signaling they still operate as serial connection side by side. A parallel connection would require the same timing on all wires and you would need an extra clock wire. It also requires tighter tolerances for the wire and connectors. Using them as a separate serial connection that is self-clocking is a simple way to obtain high speed. Parallel connection is simple to use if the speed you operate at is not limited by the performance of the wire but of the electronic, that drive it but it get harder and harder to do when you start to be harder and harder to do if you include signaling speed so you are closer to what is possible with the wire.",
"A single well-insulated wire is less thick than several poorly-insulated wires, so serial connections are inherently more space-economic than parallel connections. This allows USB to have thinner wires and smaller ports, which is desirable for a ubiquitous connector. This advantage magnifies with the length of the cable, which is why parallel connectors are usually only used internally or for short distances.",
"A parallel port use multiple signals and send one bit per signal in parallel to send the complete bit. A serial port use only one signal and send one bit after the other in serial. You would think that a parallel port would be faster and that is true in some cases. For example memory buses are still parallel. The problem is that in a parallel bus you need all the wires to be of the same length and quality in order for the signals to stay synchronized. This becomes a problem at higher speeds. Especially as you need so many wires it is hard to make them all the same. So a serial bus can be made much more robust, both because there are fewer wires but also because the wires does not need to be synchronized with each other. This means that even though you only have one signal you can easily increase the speed of that signal to regain any lost bandwidth. It is also much easier for the consumer as the cables and connectors are much smaller and easier to work with.",
"Because it’s way smaller than a parallel port, only having 4 wires instead of the 10 or more you would otherwise need, And it can be as fast or even sometimes faster because you can send information quicker over serial, as parallel at higher speeds can have issues with different bits arriving out of sync, even wire length can cause problems, and cross-talk between the wires",
"Serial communication sends one bit at a time over one wire. Parallel communication sends many bits over many wires at the same time. That makes parallel sound better and faster right? Well it used to be, however at high data frequency in a parallel connection it becomes difficult to keep your signals in sync. It's important for parallel communication that the signals on each wire are perfectly in sync or else you might start receiving mismatched bits from earlier/later transmissons. That little bit of extra solder on one wire, or the bit of dirt on one pin can really start to make a difference. This requires expensive electronics and high quality, bulky cables with bulky connectors. The original USB 1 & 2 only needed 4 wires, this meant it could be incorporated into low cost devices no problem. It also meant the cables themselves were cheap, it meant the connectors could be small so you could fit many of them onto a laptop, and not having to manage the parallel woes made the electronics cheap."
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m57o8l | Why we could go to the moon in 1969 but can't / won't in 2021 | Other | explainlikeimfive | {
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"There was a lot of money thrown at it as there was a need to beat the Russians to the Moon, we could have gone back before but there wasn't the pressing need or budget to make it happen.",
"We went to the Moon and found little of value. We placed some instruments that allow us to know exactly where the Moon is. It's not going anywhere. The 2022 trips are more about testing rockets than anything weneed to get from the Moon. It's just a big rock, and we have chevper rocks here."
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m58e7v | If our cells constantly renew themselves why do we die? | Biology | explainlikeimfive | {
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"Cells do in fact die, they renew and replicate but this process slows down overtime. Usually by the mid 20's cells tend to die faster than they replicate. So by the time you turn 30, you're slowly dying.",
"Answer: we're not sure yet. Recent studies have found that the little structure on the end of a chromosome, called a telomere, shortens with age and also during cell replication/repair, disease, or cancer. Scientists are pretty sure that's related to aging somehow but haven't been able to determine it definitively yet. When your body loses its ability to rebuild cells, game over",
"Part of the process are these little things called Telomeres. Each time a cell replicates or is replaced, the Telomeres are just a shade bit shorter than before. Eventually, once the telomeres are short enough, you start getting cells that don't function properly. They break down quicker, easier and then they have to be replaced again, which makes the problem worse. There's a lot of work being done now to try and do something about the shortening of telomeres, but it's a work in progress.",
"We’re not exactly sure _why_ we die, but one of the main things that’s thought to be related to aging is that our cells can’t keep renewing themselves forever. Each time a cell divides, it loses a bit of information at the ends of the DNA. We’re naturally born with basically buffers at the ends of our DNA so you don’t lose important information when the tips get lost. But over time, the ends get shorter and shorter and it can eat away at the important DNA that encodes for different aspects of life."
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m58uln | How do we know what Dinosaurs sounded like even though we’ve never heard one before? | Earth Science | explainlikeimfive | {
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"we dont know what dinosaurs sounded like. All we have are some best guesses, or, alternatively some guesses that aren't as founded in science but more artistic/cool (like the T-rex's roar from Jurassic park, where they combined the sound of a bunch of different animals, including the squeal of a baby elephant, into a roar that sounded cool/satisfying.) But for actual scientific analysis, scientists will look at things like skull/bone structures that are preserved to try to make a guess of what kind of sounds the animal might have made, sometimes comparing them to living descendants (ie birds). But again, those are just best guesses, we will likely never know for sure.",
"This video explains it. Basically they could use the skull and bones to recreate the sound. [ URL_0 ]( URL_0 )",
"We don't. It's an educated guess based on their bones and resulting tissue structure, and comparing that to what various animals today sound like given *their* bones. It is likely that we are wrong, and possibly by a lot. This is very similar to how we were also guessing at what dinosaurs *looked* like too! Early drawings based on skeletons were often spectacularly wrong. Seriously, search \"bad early drawings of dinosaurs\". This is [what some modern animals would look like]( URL_0 ) if drawn from their bones only using the actual principles first used to draw dinosaurs from their skeletons. Since then, 1. More-complete and better-preserved dinosaurs have been found. 2. The field of anatomy has learned a lot about how to predict muscle shapes based only on bones. Not even 20 years ago, we didn't know that [almost all dinosaurs had feathers]( URL_1 ). They were all drawn with scales in my kids books, because \"hey, they're lizards right?\" But that was a bad guess and now we know better. Even T-rex likely had a thin downy coat. Our knowledge of their sounds is also just a prediction. It's even less likely to be correct btw, because throats and vocal cords are soft tissue that doesn't get fossilized like bones. So we're guessing throat structure from bones, then guessing actual sounds *from that*. It's not precise at all."
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m598b8 | Why is it that when new video game consoles/devices launch they always run out of supply? | Ever since I can remember new consoles run out of stock. Xbox, Playstation, Switch...I want to believe that these companies use forecasting like every other type of business but why does the supply chain always fail? | Other | explainlikeimfive | {
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"First: They underestimate the demand. Second: A perceived or reported shortage spurs more buyers. Third: They are ramping up production. Fourth: Sheer cussedness.",
"Simple economics. If theres enough to go around, nobody will pay an exorbitant amount for it. Keep supply low, demand high, price is not an issue.",
"Creating millions of a new complex product takes time. There is also no reason to push back a release date for when you have enough for everyone. If your factories can make 250k units a months, you sell 250k a month until demand slow down. Unlike the games themselves which are very easy to make and distribute. The cost in a game is the development, which is why they push so hard for pre-orders so they don't make too many."
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m5aiwm | What is actually a "military grade cryptography" we often see in action movies? What makes it different from regular cryptography? | Technology | explainlikeimfive | {
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"It's Hollywood buzzword jargon, basically. \"Military-grade crypto\" means a cryptographic standard that the military has adopted to protect its information. In 2021, that standard is AES-256 (for top secret data). But...your wifi is protected by the same encryption standard (as long as you're using a recent standard, that is). Calling it \"military-grade\" doesn't mean anything super high-tech and fancy, in this case.",
"In the 90s, the United States actually did have export controls on encryption. If you wrote software that encrypted things, and you sent that software to another country, you could go to prison. (A well known cryptographer got around this restriction by printing a \"book\" of computer code to do strong encryption!) By around the year 2000, two things became clear and had been for a while: (1) the cat was out of the bag and the whole world had access to strong encryption, (2) online fraud was a big problem. Because of that, most export controls were eased. Before those export controls were eased, saying your encryption was \"military grade\" *did mean* something. It still does. The Advanced Encryption Standard *is developed by* the US government and presumably is used by at least some of the US military. But it's nothing special anymore, if it ever was.",
"They just want it to sound fancy on screen. The military isn't using anything better than the current consumer stuff.",
"The NSA defines 4 \"[types]( URL_0 )\" of crypto devices. \"Type 1\" is military grade crypto for classified applications. It's much more secure than the stuff used on the Internet."
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m5bkoy | How was early CGI transferred to film? | I fell down a rabbit hole of early examples of CGI from the late 50's through the 70's, and the vast majority of the videos I've found are film transfers, not video tape transfers (now that I think of it, would there be a difference in how it's transferred?). How on Earth did they transfer it from computer to film? My best guess is they would point a film camera at a CRT, or something along those lines, and I get that idea from seeing a video of one early CGI animation being transferred that way. But I can't find a lot of info on it aside from that, even after Googling, asking my dad who's an engineer, and even asking my friend who actually does CGI. I did see another thread on here explaining how digital video is transferred to film with laser scanning, so maybe even something like that? I really don't know a lot about this sort of thing, it's not a passion of mine, I'm just down a random ADHD rabbit hole and now I'm very curious. Thanks in advance for the help! EDIT: Thanks for all the answers! I've had a lot of trouble finding the right search terms, so this is great! < 3 EDIT 2: I should have specified one of the examples I was talking about. Here is a 1972 example showing the first polygonal 3D CGI URL_0 It was made by the guys who would later go on to form Pixar. Just thought I'd share this to show exactly which rabbit hole I'm down. Though special effects, both practical and CGI, fascinate me and am glad to have learned a new extra things! | Technology | explainlikeimfive | {
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"The earliest examples of CGI were indeed recorded by taking photographs of the CRT screen, one frame at a time, on 35mm film. Once you have the animation on film, it's relatively easy to composite into live-action footage. People had been combining live-action with hand-drawn animation by drawing onto individual frames of film for a long time now. Gertie the dinosaur was made in 1914 for instance. Disney, in particular, pioneered a multi-plane camera system that allowed animators to stack plates of animation frames on transparent backgrounds to create a final composition for photography to create a single frame of animation. A stack might contain for instance background, elemental animations like candle flames or water drops, plates for each of the characters and so on until a complete frame was created and photographed.",
"With something like a [Dicomed]( URL_0 ) camera designed to transfer pixels to film. I actually wrote a printer driver to send a series of TIFF files to “print” to film back in the early 90s. That was a lot of fun.",
"Artificial effects varied greatly in techniques through the early years. Once computer generated graphics were feasible, special optical printers were used to introduce them to film (Westworld, 1970), but these were pretty quickly replaced once digital compositing was achievable in the 80s - the film was digitally scanned and edited."
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m5c7l3 | What does this mean? How does this work? | “When I multiply numbers together, I see two shapes. The image starts to change, and a third shape emerges. That's the answer. It's mental imagery. It's like maths without having to think.” —Daniel Tammet | Other | explainlikeimfive | {
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"Some people, including my father and brother, can see , understand and manipulate numbers . My father hustled pool because it's all trigonometry. My brother is autistic and he sees multiplication as a grid - like the game battleship. Not smart enough to comment on a quote, but hopeful enough to maybe help?",
"I think the term is synesthesia. Some people have an ability to have a sensory perception of stimulus not common in general population. Like taste colours or sounds."
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m5cbpt | Sonar and Radar | Why are sonar and radar displayed as a line rotating around like a clock hand instead of a circle radiating out from the center? | Technology | explainlikeimfive | {
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"Because generally both devices work by having a directional antenna that sends out a pulse of radiation (or sound) and then detects the return pulses. In order to cover the entire airspace this antenna has to rotate, so you get the sweep effect on old radar screens. (Newer ones, although they work the same way, don't have the sweep visible because it just confuses the view)."
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m5cjjx | What is the difference between song “featuring” someone and songs with both artists in the artist column? Especially if they both feature the same length segments for each artist. | Other | explainlikeimfive | {
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"text": [
"Featuring is usually a marketing strategy for one or both parties and most likely the song was mostly conceptualized before collaborating with the featuring artist. Otherwise the artists probably agreed to make the song together from scratch even if their voices don’t have the same air time"
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m5ckun | Why are people Nazi-sympathisers. | Other | explainlikeimfive | {
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"Answer: hatred towards a group can start with something insignificant (comments from a passerby) or maybe something serious (death of a relative by someone that's not your own). It's much easier to just hate people rather than understand that the actions of a few aren't the intentions of them all. Hitler is someone who gained an unbelievable amount of power under an ideology that can be easy to fall under and to people who resonate with hatred towards certain groups. He was part of the movement of bringing pride back into a country that had just suffered a humiliating loss, and he was an underdog who rose beyond what people imagined. You could think of him as the Tom Brady of white nationalists. Edit: sorry if you're not from the US you probably didn't understand the Tom Brady reference.",
"The Nazi mindset offers simple answers to complex problems in a way that frames the believer/follower as a hero. Nazis offer answers that are often false, inconsistent, and illogical, but never the less appealing to weak or lazy brains. Ex: Mom -- \"Tell your brother that you're sorry for pushing him!\" Nazi -- \"That's not your fault. Your brother had it coming! He gets what he wants _all the time_. Remember the good ol days before you had a little brother? Wouldn't it be nice if we could go back to that?\" Edit: formatting",
"> Still adore Hitler, *Despite* the horrible acts committed during WW2 There's your misunderstanding. Don't assume Nazi-sympathizers' brains are like yours. The (unsettling) truth is that they don't like Hitler *in spite of* his atrocities, they like him because they *agree* with those acts and think that's how things should be. If you violently hate Jews and really truly believe that they are evil monsters destroying what would be a glorious world for you and your friends, then to you Hitler's acts in WW2 *weren't horrible*. Very ELI5: They aren't being illogical (idolizing someone in spite of them doing bad), they are just also bad themselves, or at least OK with it. NOTE: AzureIronAlloy is very right about how people get into it. They're not all monstrous psychopaths. The Nazi trait of blaming others is very reassuring and thrives in hard times with a lot of poverty and feelings of powerlessness. People like believing it's not their fault, and hearing that they can rise up and make things better. Germany was very poor leading up to WW2 and people's lives sucked. A seductive whisper \"it's not your fault it's the Jews - AND if you get rid of them things will be great again!\" starts tempting even normally-decent people as they struggle to feed their families. Well guess what, present-day America has some similarities to pre-WW2 Germany. Rising poverty, deaths and unemployment from a mismanaged pandemic, unaffordable healthcare, strong racial divides in some areas. All of a sudden replace \"the Gypsies\" with \"blacks\" and \"New Aryan Nation\" with \"America Great Again\" and those old Nazi ideas start sounding good to those without strong morals and/or sufficiently desperate."
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m5cug4 | Really confuse about ddns | Technology | explainlikeimfive | {
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"Ok so the internet is all numbers that are addresses like for houses. But numbers are hard to remember so people made domain names to hide the numbers that's dns. So unless you buy a static address your address constantly changes making it hard to attach a dns to that address. You would have to keep updating your dns with the new address each time it changed. This is where dynamic dns or ddns comes into play. Instead of you updating the address each time a service updates the address each time it changes keeping your dns pointed to the correct address."
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m5d1gg | why does mining bitcoins produce co2? | All I can find on google is how much it produces, but I don't understand how a virtual currency produces co2 | Other | explainlikeimfive | {
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"The process of mining requires very heavy computation. It's a bit like brute-force cracking a code by trying every possible combimation. This is usually done on GPUs because of their massive computational power and ability to process things in parallel. Some even use custom made devices called ASIC or FPGA to squeeze the last bit of parallel processing possible. Either way, all this processing consumes a lot of electricity. To put things in perspective, a single NVidia RTX2080Ti at full power consumes around 250 watts. That's enough to run an electric bike at a speed of around 30km/h. And that's not all, those devices produce a lot of heat too. So mining rigs will require industrial-scale cooling systems to keep the processing units from overheating and catching fire. This adds considerable energy expenditure. All this energy being consumed is redundant. And most of the planet's electrical grid today still relies on coal/gas/oil/fuel, and all of these produce CO2.",
"The process of mining requires running computer hardware or specially designed chips at full utilization for long periods of time, consuming a lot of electricity",
"You gain crypto currency in exchange for \"proof of work\". Imagine a fall day and you're raking together fallen leaves for a little pocket money from your parents. The pile of leaves is your proof of work. But now that you're finished your parents blow over that pile of leaves, so your work didn't really change the state of your garden. Now your parents ask you to repeat the process, but make the same offer to your brother - but only the one with the larger pile of leaves gets the pocket money. This happens all day. At the end of the day you got pocket money a few times and so did your brother - but ultimately there's still leaves lying around everywhere as intended, so you can repeat the process for the system to continue working. You didn't produce anything constructive, you just worked for the sake of working. And that work is exhausting! So you have to eat, even if you yourself haven't produced anything of value. That's exactly what crypto currency is: Computers compete trying to guess certain numerical values again and again and again, but only the first one that gets it right is rewarded. Now all computers that work on the issue need electricity, just like you need food. As electricity production still has a large C02 footprint, so does generating crypto currency.",
"Turn on every appliance in your home. For no reason other than to waste power. You're generating CO2 because that power requires fuel to be burnt in a power plant in order for it to have been produced. Same thing, except all the appliances are mining rigs. They use up a fuckton of electricity."
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m5d75j | What were those bank tubes in the 80s, and how did they work? | You would drive through and deposit your money into the tube. Then it would get sucked up and go in to the bank itself. Why did they use them and when did they stop? | Technology | explainlikeimfive | {
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"text": [
"They are pneumatic tubes and are still in use at many banks. They use air to move the tube from the car to the window. It’s an easy way to have multiple lanes when there is only one drive up window",
"Where are you from? Those are still very much in use in America"
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m5djco | Why can’t scientists or zookeepers just make pandas pregnant via artificial means to keep the numbers up? | Biology | explainlikeimfive | {
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"text": [
"[They do]( URL_0 ). But their ovulation cycles are irregular and difficult to predict and it then takes time to see if it was effective and if not then the whole process starts over. It's not a very fast process, especially when the viable population isn't very big to begin with"
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m5eg59 | how does the whole anti noise thing work in headphones to create noise cancellation? | Technology | explainlikeimfive | {
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"A sound wave is a pressure wave. When we hear a sound, what our hearing system detects are rapid changes in how compressed or spread-out the air is (i.e. how closely the air molecules are packed together). What we perceive as a particular sound is determined by the specific patterns in these rapid changes in air pressure. Active noise-cancelling headphones include microphones to detect the \"ambient\" sound i.e. the sound that's there in the space around you (in the room, car etc.). When, in a particular moment, the ambient sound has a region of compressed air, the headphones generates a compensating region of spread-out (“rarefied”) air, and where the ambient sound has a region of spread-out air, the headphones generate a compensating region of compressed air. All this is happening incredibly fast, with potentially thousands of such changes every second. In this way, the headphones generate a sound that's in a certain sense the \"opposite\" of the ambient sound. When this generated \"opposite\" sound is added to the ambient sound, the compressions match up with the rarefactions and vice versa; the result is that the pressure changes that make up the ambient sound disappear, leaving only the sound of the music/whatever from the device the headphones are plugged into. Edited for clarity, and to add... A sound wave is a different kind of wave to a water wave, but they can both be described in the common terminology of waves (e.g. frequency, wavelength, amplitude and interference). What noise-cancelling headphones do is an example of “destructive interference”."
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m5fuiw | How do devs change the version number thing? (version 0.2.3, version 1.9.0) | Technology | explainlikeimfive | {
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"General rules of thumb: * 0.0.x - Prototype builds * 0.y.x - Something resembling the intended product, getting better as y and x increase * 1.0.0 - First release, product as intended function wise * 1.0.1 - Bug fix/very small change over 1.0.0 * 1.1.0 - Minor change like a new feature. Doesn't fundamentally change the existing software. * 2.0.0 - Major change, significant fundamental changes to form and function. Generally not back-compatible especially with save files. API changes breaking other people's software that interacts with this one (API - application programming interface, is how you can use & interact with other people's code from your code).",
"They're made up. There are various standards, which other commenters have mentioned. But at the end of they day, each company does slightly different versions of a \"standard\", or just wing it. Personally, for a library that is consumed by other developers, I would use semantic versioning. However for work we just use an incremental version for releases, since no client cares about the version they're running, only we do.",
"Each number in the version number means something. At one of my previous jobs it went: ReleaseVersion.ClientReviewVersion.InternalQAVersion.DailyBuild We generally didn't inform the client about the Daily Build version because they tended to panic (why are there so many Daily Builds? [Which weren't literally \"daily\"]). I'm sure there are many different ways to number versions, and I'm sure that are some accepted Best Practices, but we went our own way"
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m5fvfe | Why teeth do not grow for a third time when they fall out? | Biology | explainlikeimfive | {
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"In humans, you are born with all the teeth you will ever have. Even as a newborn infant you already have your adult teeth waiting in reserve in your jaw. You have one row of child teeth and another row of adult teeth beyond that. There isn't really enough room for more teeth in that arrangement. Other animals like sharks do things differently, but our rather complicated patterns of teeth that are different shapes, size and functions and precisely located in such a way as to allow you to chew and bite right, would not be possible for a shark. For most of our evolutionary history, what we have, has been good enough, and the minor drawback of now third set of teeth was made up for with how good our teeth worked. It has only been recently when people's diets have change so much and life expectancy has risen so much that the fact that many eventually run out of teeth has become a bigger problem.",
"They don't grow, they're \"reloaded\" like cartridges from a magazine. And that magazine holds exactly 1 set."
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m5gus0 | What’s happening in Beruit these days after the massive explosion on the docks a while ago? | Other | explainlikeimfive | {
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"I have family who lives there. Things are really really bad, inflation is really high, there is a set amount of money you can withdraw and a very small limit on currency conversion. Very little has been done in terms of figuring out who is responsible, because in my opinion (as backed up by the lack of investigation) the government is responsible. Relatively speaking, nothing is being done to rebuild that part of the city that has been destroyed by the explosion. People are more or less left to fend for themselves with very minimal assistance from the government. Here Sara Yafi (a cunsiltant and political activist) sums up the situation in this 4 minute clip. URL_0"
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m5kpzr | What happens when someone tickles us? | Biology | explainlikeimfive | {
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"The Tickle Response is a biological, subconscious reaction to external stimulation that induces panic and recoil. Why does our body react this way? Because if it recognizes an unusual touch to the body, like the tiny legs of a poisonous insect on your belly, then it needs to get the thing off your body, without waiting for you to think about it. You can not tickle yourself, usually, because your body can always prepare for your own touches. You can close your eyes and touch various parts of your body without looking, so it is hard to surprise your body with a touch. Same goes for clothes that you're wearing, which move along with your body in a predictable manner. The body knows there is no threat. But when your significant other sneaks up behind you and starts to push their fingers into your sides, your body reacts with a sharp jump away from the \"threat\". Even if you consciously decide not to really fight back, your body still will attempt to get away, squirming on the ground. It will call out to others, resulting in a laugh or yelp. In extreme circumstances, it will even release bodily waste to allow for easier escape. (You pee your pants)",
"Let me see if can swing an explanation fit for a five year old: “Tickles are a playful way your body uses to teach you how to defend yourself. It lets you know what parts of your body are soft and vulnerable to bites from big predator animals. It’s a memory every human has from thousands of years ago when bears and tigers would try to eat us!”",
"I am so sensitive to tickles, I can easily tickle myself I many areas. I am super sensitive to certain touches. Tickles feels like pain if somebody actively tickles me. Am I just a wuss?",
"One theory I've also heard of is that \"ticklish\" areas of the body are usually vulnerable and need to be protected. Your neck, your sides and under your armpits, ect. When someone is tickling you you instictively curl up and cover these areas. It's kind of practice for protecting these areas from something more threatening."
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m5myz3 | Why are there no "perfect drugs" that work well without side effects? | It seems like the more potent a drug/medication is, the more risks are involved with it, where as drugs with very little risk don't help nearly as much. | Biology | explainlikeimfive | {
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"I think the answer is there's not really such a thing as \"side effects.\" There's just \"effects.\" A decongestant \"may cause drowsiness\" as a side effect and the very same drug as a sleep aid \"may cause dry mouth\" as a side effect. The drug is the same, it's just whether the effects of the drug are advertised on the front of the box or not.",
"If you want the drug to make a \"change\", then you run the risk of side effects, and you are right that the magnitude of the side effects can be related to the size of the change. Organisms are highly optimized, if it takes work to make a molecule then using the same molecule for many tasks is more efficient than making a different molecule for every task. When a drug changes the rate or production for the molecule, all the tasks that use it are impacted. Maybe you want to drug to change one task so you feel better, but the molecules are all impacted and there will be side effects. Much of drug research is trying to make very exotic changes so that the net effect is more like what you want. Unfortunately, every person is different, and a different balance of tasks leads to a different amount of side effect.",
"You've mostly answered your own question: the downside to drugs that do a lot is that they do a lot, and the downside to drugs that don't do much is that they don't do much.",
"The body has a limited set of tools to interact with. Some tissues and organs use the same tool in different ways. While one organ may take a screwdriver to tighten screws, another may use it to pry things, while one more may use it to poke holes. When a doctor diagnoses someone with a few screws loose, the doctor could have the patient take a medicine that gives more screwdrivers. Sure that helps the one organ manage to tighten screws but the other organs, now with more screwdrivers, will start to pry more things and poke more holes. These unintended effects are side effects. A real life example is the body's response to opoids. Opoids are used as powerful painkillers because they imitate other chemicals in the body that block receptors that transfer the pain response to the brain. The same chemicals also trigger your gut to push your digested food down and out! One side effect of opoids is constipation. The drug brand Imodium, an anti diarrhea medicine, is actually an oral opoid that helps stop your gut from pushing too much. It's dose is not high enough to cause the pain relief for the brain but people have tried abusing it this way.",
"There are some drugs that are great and have almost no risk, but the fact that they exist means that other drugs for the same treatment don't get used anymore. So the only time you see multiple drugs for the same issue is when there's a tradeoff involved.",
"I'd say caffeine is pretty close to a perfect drug (when used in moderation). The primary routes of adminstration, coffee and tea, both show life extending properties. The only problems come from overdose or withdrawal, and even a perfect drug would have withdrawal.",
"On the molecular level drugs are generally telling your body to do something different. That signal change usually tells a bunch of other processes to behave differently, which in turn tell a bunch of other processes to behave differently, and so on. You can have a drug that only changes \"one\" thing and a zillion functions behave differently.",
"It depends on what you consider a side effect. For a young, healthy person, there are many drugs which won't cause any negative effects at all. For instance, most people who take acetaminophen (paracetamol) at appropriate doses for a headache will not experience any negative effects. Same goes for calcium carbonate tabs for heartburn, non-sedating antihistamines for allergies, etc. & #x200B; There are about a bazillion listed side effects for almost any drug, but this is from large studies - if you take thousands of people with different genetics, ages, and health conditions, someone is bound to get negative effects from almost any medication. Likewise, taking any substance at much higher than the recommended dose (e.g. overdosing) will almost always result in negative effects - this is even true of something like water or food! & #x200B; That said, if something is said to have absolutely no effects other than the intended one, there's a good chance that it's utter BS and doesn't even do that (e.g. homeopathy).",
"Many systems in the body are regulated with various neurotransmitters, proteins, ions, and the like. They work like glorified keys in locks, where some are master keys that work in many locks, others with very unique keys that only work in one place. The goal of any pharmaceutical therapy is to find a drug that acts on only the locks that are problematic, while affecting the fewest other systems. Unfortunately as before, there is a tonne of interplay between the systems. Aspirin (ASA) thins the blood (because [reasons]( URL_0 )). Have a headache or a heart attack? Take Aspirin, ASA thins the blood, allowing it to flow into constricted areas to reduce the pain or help deliver more oxygen. Have a bleeding stroke or bleeding disorder? Take aspirin and the thinner blood will...bleed even more easily. It's not so much that aspirin is a 'cure headache key', it's a 'thin the blood' key (among other effects). To the original question - why isn't there a perfect drug for a specific ailment? Because many body systems have overlap between their systems. The same thing regulating your blood pH balance can be responsible for digestive acid production and some other liver function. Affecting any one stage will carry on further down the line. Frankly, the fact that our bodies work at all is nothing short of astounding. Tens of thousands of chemical processes in delicate balance with slight perturbations causing disease and death."
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m5mzq7 | What is the difference between Newton’s method, Euler’s Method and linear approximation? | Mathematics | explainlikeimfive | {
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"Newton's method and Euler's method both use a linear approximation to solve different problems. Euler's method is for solving initial value problems--where you have some quantity and you know where it starts and how it changes, then you want to figure out what it changes to. It is essentially a method of numerically integrating a function, similar to Riemann Sums. That is to say, it would be like if you were trying to figure out how far a car travels by noting that it starts at 0, then you can check the speedometer periodically. By assuming a constant speed between checks you can extrapolate the distance the car travels during that window. That assumption of a constant speed is what makes this a linear approximation. If you additionally had an accelerometer and assumed a constant acceleration during between checks then you'd get into a higher order approximation--it would be more accurate at the expense of having to do more computation. As you consider higher and higher derivatives like these (first velocity, then acceleration, then jerk--the rate of change of acceleration over time, and so on) you move into what's known as Runge-Kutta, where the lowest order version of Runge-Kutta is Euler's Method. Newton's method is for finding the roots of an equation. This is where you have some graph and you want to know when it equals zero (which is a powerful way to solve many kinds of practical problems in engineering). You look at the value of the function at some point and you consider what its derivative is (i.e. you look to find a line that is tangent to the graph at that point), then it's quick and easy to find where that line crosses the horizontal axis. That forms the basis for the next guess--you draw a tangent line from there and follow it to its zero. This continues until you're satisfied that you've nearly enough found the zero you were looking for. *Aside: I've assumed the reader has at least a general understanding of some calculus vocabulary to keep this answer from growing too large and unwieldy. I'm happy to go into more detail about tangents and derivatives and whatnot if there's confusion there.*",
"Newton's method - I know what I have and what I want to do with it (equation known, finding target solution). Euler's method - I know what I want, but not what I have (equation unknown, trying to approximate what it is doing). Linear approximation - I don't care about any data point except for this specific one"
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m5n23u | I dont understand something about capillaries and their surface area, and am very confused as to why one is very very large, and one is small compared to that. | ELI5, Today i learned that capillaries can wrap around the earth twice, but only have a surface area of 1000 square meters. does it have to do with capillaries being very thin? Im just plain confused. | Mathematics | explainlikeimfive | {
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"Yes, it is because they are very thin, so if they were laid out end to end the line they would make would be very, very long. You probably wouldn't be able to see that line, though, because of how thin capillaries are. As to how that compares to their surface area, area is determined by multiplying length by width. So an area that is 10 meters by 100 meters would have an area of 1000 meters squared. However, the same would also be true if it was 1 meter by 1000 meters, or 0.01 meters (1 centimeter) by 100,000 meters."
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m5q9c9 | What the fuck causes the wind to keep changing direction every 30 seconds? | Earth Science | explainlikeimfive | {
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"text": [
"You appear to be describing turbulence. That is, the chaotic nature of a fluid (the wind in this case) passing through and around obstructions. My guess is that you're in an area with buildings or natural obstructions that will cause the smooth flow of the wind to be broken up into turbulent flows. On a flat plain or the ocean there is a lot less turbulence because there are less obstructions to deflect the wind.",
"It's a hideously complicated chaotic system that really doesn't like ELI5'ing. Think of a river: It flows in one clear direction from the mountains to the sea, but when you get up close the water is often seen to be swirling rather than moving linearly in the direction of the river's flow. Our atmosphere is very similar: The *prevailing winds* are reasonably consistent, but the system is absolutely massive and on the scale humans operate, the \"wind\" is often just one of those tiny little swirls you saw in the water. Sailors couldn't avoid this phenomenon, and in fact frequently would find themselves fighting against the wind, or being becalmed - stuck in a pocket where little to no gas was moving around. The \"solution\" was typically to cut sail (so you don't get blown the wrong way) and wait it out."
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