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762w7k | What prevents a penetration tester to simply not report a security weakness and then in the future uses it for his own unethical hacks? | Technology | explainlikeimfive | {
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"The short answer is morals and reputation. \"White Hat\" hackers make ridiculous amounts of money doing what they do because they have good reputations and skills. If it's ever shown that they didn't report an exploit that means they are either not good at what they do or they're dishonest. Both ideas would kill their business quick."
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763j1s | Why does the melanin in our eyes not react to sun exposure the same as the melanin in our skin (i.e. darken our eyes in the summer)? | Biology | explainlikeimfive | {
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"Alright, I have a definitive answer. There is a pretty simple difference between cutaneous melanocytes (melanin producing cells in your skin) and uveal melanocytes (melanin producing cells in the uvea or middle layer of your eye that includes the iris). The melanocytes in your skin are stimulated to begin melanogenisis (making the sweet sweet melanin) by hormones called melanotropins. The primary melanotropin that mediates your skins UV response is alpha-MSH. The melanocytes in your eye do not respond to this hormone. That's it. The pigmentation of your iris is not affected by the suns rays. Doesn't mean it won't burn them though :D",
"I'd imagine its because indirect sunlight is not enough to get a tan. You can stay in a well lit room all you want, if you're not in the actual sunshine, you're not going to get a tan. And consider that it takes several minutes or tens of minutes of being out in the sun to start tanning. Seeing how our eyes are organic lenses and direct sunlight tends to burn them out, I think you can deduce why we can't exactly tan our eyes :)",
"When you get a tan, *your skin* is manufacturing more pigment. The melanin isn't doing anything special. Your eyes don't have a reason to.",
"As far as I can tell, the explanation is that the ~~lens of the eye~~ cornea filters out UV light, so there is no UV (which triggers melanin darkening and generation) actually reaching the melanin in your iris.~~ EDIT: Initially I thought it was the lens, as it also acts as a UV protector, but people, correctly, pointed out I know jack shit about eye anatomy and the lens is behind the iris. URL_0",
"TL;DR: Your eye can get a sun-tan and a sun-burn, but this will cause permanent damage. The white of your eye does not tan because it does not have the ability to produce pigment. The iris of your eye has the ability to get a tan, but doing so would require active effort, a lot of pain, and would cause permanent damage to your vision. ----- You may recall from the last eclipse that there was a lot of whooplaah regarding eye damage from looking directly at the event. Your eye can get a sunburn, and that causes permanent damage to your eye if the inside of the eye is burned. 1) The Sclera (White of your Eye) The reason that your skin tans is because UV light causes the skin to produce pigment - the more pigment produced the darker your tan. There are cells called melanocytes and they are light sensitive, but they are burried under a couple layers of skin. UV light can pass through the upper layers of skin, and when they get to the melanocytes it causes them to produce melanin (pigment). This is why sunlight will give you a tan, but your bedroom lamp will not. It has to have concentrated UV lengths. As time passes, your outer layer of skin dies and is shed, and new layers of skin are created deep inside you, and everything shifts outward. This means that the melanin-rich cells will eventually dry up and get blown away - and your tan will fade - as your layers of skin shift. The white skin of the eye is called sclera and it is built different from your normal skin. It is mostly collagen - a strong connective tissue like what tendons are made of. There are very few melanocytes in the sclera, so there is nothing to produce the 'tanned pigment' to change color. When the sclera is burned it turns red due to increased blood flow. However, some individuals who suffer from melanoma *do* have large amounts of melanocytes in their sclera or deeper regions of their eye. When these regions of their eye start to tan from exposure to the sun, it causes pain and eventually turns into a tumor. The tumor eventually destroys the eye. 2) The Iris (Colored portion of your Eye) The iris is over 50% melanocyte, and the melanin produced plays a large part in determining eye color. The melanocytes react to UV light just like your skin, however, they receive much less UV light than the rest of your body. Remember, it isn't *sunlight* that gives you a tan, but the *UV portion* of sunlight. When sunlight hits an object, that object reflects portions of the light but most of the UV energy is absorbed. Very few objects reflect more than 10% of the UV light that hits them (that's why sunlight warms us up). So if you look a tree out in a field the sunlight is hitting the tree, the UV is absorbed, then the light bounces off and hits your eye. That's a lot less UV energy, so the melanocytes in the iris don't react very much. Additionally, the iris is not on the surface of the eye. There is a clear dome called the cornea, and between the dome and the iris is a liquid called aqueous humor (intraocular fluid). Both of these structures, but especially the fluid, have proteins that [scatter and absorb UV light]( URL_0 ) before it gets to the melanocytes in the iris. Effectively, your eye contains a sunscreen for your iris. ----- All of this is to say that if you were to look directly into a UV lamp you would be able to tan your iris, but it would do so at a slower rate than your skin, and this would cause permanent damage to your eye and ruin your vision, and you'd develop blind spots before any noticeable difference occurred in your pigmentation.",
"The melanocytes in your eye do not respond to the hormone responsible for tanning by increasing melanin production. That being said, UV still hits them. That UV still damages DNA and can still cause a melanocyte to turn cancerous. Ocular melanoma is a thing, and very frequently fatal, because people don’t think to check for it, it rarely has symptoms until too late, and it’s usually spread to inoperable areas once discovered. The only way to find it is via a optometrist exam, and unless you wear glasses/contacts and get them regularly, you probably never get checked."
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763t5d | How are the media and public figures able to publicly accuse someone of sexual (or any other) crimes without any due process of law? | OK, no, this is not a thinly veiled defence of anyone who may or not be in the public eye right now - I want to see rapists and sexual predators crash and burn. But this case seems unusual in that all the public allegations are being taken as proven, and various actions being taken (stripping of membership in various associations, etc. etc.) without anything having been proved criminally. Also, newspapers putting all the accusations in print, where I feel in the past they would have been more coy (they might have talked about "alleged misconduct by a well-known personality", blah blah). Is it just that these kinds of accusation are merely covered by libel law, and this is everyone going "Well, it's obvious this is all true, so sue us", or is it a free speech thing, or..? I'm not from the US, so maybe this is normal... I am just thinking about situations where someone turned out to be innocent, but had basically been witchhunted to oblivion, aren't there mechanisms in place to prevent that? | Other | explainlikeimfive | {
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"Due process, mostly, refers to procedural actions necessary before Govermental officials can act in certain ways. For example, before you can be placed in jail (i.e. Have you right to liberty removed) your due process rights require trials and the like. In those trials you are presumed innocent. That is where the idea of innocent until proven guilty comes from. It is a procedural posture that is required in criminal cases. Public figure, like celebrities, can say whatever they'd like. There are laws to prevent them from saying untrue things that could harm someone, these are called defamation laws. They make it so that you can't publically declare something that is untrue to specifically harm me. There is a tight balancing act between what is considered defamation and what is protected by the first amendment in the US. Generally the person defamed is the only person who can fight Suh statements, by suing. However truth is always a defense in those law suits. If the person being allegedly defamed knows he's not gonna win on the truth he's not gonna bother suing. And private (as in not governmental) can do whatever they'd like in terms of membership. There are no due process laws that govern that. They may have internal policies to deal with it but that's a corporate governance issue. And yes there is always a concern that this is just a witchhunt. However in instances like this that seems improbable.",
"The media doesn't accuse people of doing bad things, they just report that someone else has accused the person. So they don't say, \"Jimmy pushed Maria,\" they say, \"Maria says Jimmy pushed her,\" which is true. They don't say whether Maria is telling the truth or not. As for Maria, Jimmy can take her to court if she's lying, but he would have to be able to prove that he never pushed her and that she's lying on purpose to get Jimmy into trouble.",
"Good journalists don't accuse anyone, they present facts and analysis. Reporting \"several women have claimed so-and-so assaulted them\" isn't an accusation, it is what several women said. > without anything having been proved criminally A criminal conviction is the standard you need deprive someone of their freedom and property. Private citizens are allowed to make their own judgments. And freedom of association means we have the right to kick someone out of our club because we think they might be a rapist. > I am just thinking about situations where someone turned out to be innocent, but had basically been witchhunted to oblivion, aren't there mechanisms in place to prevent that? There are. Libel laws can punish journalists who say things they know, or should know, are not true. And journalists who publish non-libelous but irresponsibly wrong stories do not remain journalists at respected institutions for long. But the sad reality is sometimes the press gets it wrong and an innocent person suffers unjustly. Unfortunately, the only alternative is sometimes not allowing the press to print things they have reason to believe are true, and that is far worse. For every Richard Jewell, there are probably a hundred victims of crimes committed by powerful people who are afraid to come forward. These perpetrators only face justice when their victims come out in force, and allowing a powerful person or organization to shut the press down to avoid exposure is far more damaging. Imagine if an organization like the Catholic Church was able to suppress reporting on their sex abuse scandals."
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763wwi | How exactly does surface tension work,and,what is the maximum weight that this rule would apply to on water? | Other | explainlikeimfive | {
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"Surface tension the result of molecules in a liquid being attracted to each other (\"cohesion\"). The attraction is, in very simple terms, basically magnetism. For any given molecule, odds are very good that the electrons in the molecule (which have a negative charge) are not evenly distributed. The more uneven the distribution, the greater the difference in charge (i.e., \"polarity\") between one \"end\" of the molecule and the other. And the greater the polarity, the more strongly the positive end of one molecule will be attracted to the negative end of another, leading to increased surface tension. Here's the thing though: this is really, *really*, not a very strong force. There's a lot to be said about the relationship between cohesive forces and the states of matter (i.e., solids, liquids, gasses, etc.), but this is ELI5, so let's just say that the mere fact that we're talking about a liquid tells us that the actual amount of *force* involved in surface tension is going to be *really* low. Thus, the amount of weight that surface tension is going to be able to support is also really low. But it's not just a question of comparing weight to surface tension. Any object that is \"wettable,\" i.e., is electrically attracted to water, will break surface tension no matter how light it is. For an object to float, not by virtue of being buoyant (i.e., less *dense* than water), but purely on surface tension, it's going to have to not only be relatively light, but not wettable either. Further, it's also going to need to not be \"pointy\" in such a way that it will pierce through surface tension by sheer displacement. A metal sewing needle is a perfect example here. They're made of metal, so they're denser than water, and thus will not float based on their buoyancy. But being metal, they're not particularly wettable either. If you lay one down very, very carefully on its *side*, the surface tension of water is sufficiently strong that the needle will \"float\" in a little depression in the surface of the water. But disturb the water almost at *all*, whether by making waves, dropping the needle too quickly, or putting it down on its point, and the needle will sink immediately, being far denser than water. With all of those things combined, it should be apparent that there is no specific \"weight\" limit here, because whether an object will be supported by surface tension is a factor of several different variables and conditions. But a needle is probably about as heavy as it's going to get. Much heavier, and the weight will be too much for the surface tension to support. And though you'd think that you might be able to get more weight in if you expanded the surface area of the object, do *that* too much and it's going to break the surface tension by sheer displacement."
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76472z | Are showers better for our hygiene than baths? | How true is the fact that when we bathe we sit in water full of our filth? Is it more unhygienic because of that? Or does the dirt perhaps gets diluted in water and all those facts are really myths? Is there any scientific paper about this topic? | Biology | explainlikeimfive | {
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"Say you have one dirty spot on you. A shower washes away the dirt because of the flowing water. A bath dissolves the dirt and spreads it evenly all over you as you soak in the dirt containing water. It is obvious what is more hygienic.",
"I'm personally not a big proponent of a regular bath schedule. Time and routine make showers the better option especially since, a, you need to not smell like socks at work, and b, unless your day's all free, baths take too long. I need fifteen minutes for a full shower, five to soap up and scrub off, five to wash off, five to stand quietly under the water. Wednesdays I need ten minutes extra to wash my hair. And then I'm set for the day. But sundays are a whole different story. Sunday I can fill up a tub with bubbles and have a legit movie star soak, with music and off key singing and all that. Any time I'm a mess though, I prefer showers. A tub's more for soaking than scrubbing, especially if there's mud or dog involved."
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764hen | Your brain stops thinking rationally when you're horny | Biology | explainlikeimfive | {
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"If you're really really hungry, you might eat food that you don't normally like because your body knows it needs food. It tells your brain, \"Taste isn't important right now, you just need to eat!\" When you're horny, your body is saying, \"I really really need to make a baby,\" so it tells your brain to stop worrying about other things because they're not important. In both cases, your brain is telling your body, \"No, I don't want to do that thing because something bad might happen!\" Your brain and your body argue and sometimes your body wins and sometimes your brain wins. You should always try to help your brain win.",
"From an evolutionary standpoint, being horny and focusing on having sex over other chores is as advantageous as it gets because the point of life from a biological standpoint is to reproduce. The only reason we label it as irrational thinking is because of culture or society's idea of proper behavior. Ask this question 10,000 years ago and people would be like \"why aren't you always trying to have sex?\""
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764jql | How do cell phone cameras adjust focus without any moving parts? | Technology | explainlikeimfive | {
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"They do have moving parts. A really, *really* tiny linear electric motor moves the lens forward and backward. URL_0"
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764zli | what happens to all the 'good' bacteria in your body once you die? | So apparently our body is made up of billions of micro organisms that work to keep us alive. What happens to them the minute we die? | Biology | explainlikeimfive | {
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"They go to bacteria heaven, like all good organisms, great and small. What happens is what you'd think happens. They eat whatever's left inside you that they usually eat, then die themselves."
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7654oc | How does Gravitropism work? | Additional: How would affect plants in places with other gravity, e.g. Moon? | Biology | explainlikeimfive | {
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"Some plant cells are sensitive to gravity, and the plant uses this information to send the root down and the stalk up when the seed germinates. It would not work as well on the Moon or Mars, where there is less gravity, but some effect is still likely. Of course, both these places have a larger obstacle to plant life - no atmosphere."
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765542 | what actually happens to your body when you overdose on sleeping pills? | Biology | explainlikeimfive | {
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"It depends on the specific mode of toxicity of the drug in question. Some sleeping drugs are toxic because above a certain dose they damage one or more of the bodies organs and they could potentially damage any organ. Some cause your heart and breathing rate to slow to the point of stopping. I'm sure someone will add other ways that sleeping drugs can kill you :o).",
"In the brain there are GABA receptors, and they inhibit the neurons they are attached to. The chemical structure of sleeping agents bind to a specific subunit on the GABA receptor, and inhibit the neurons more than normal. These GABA receptors are everywhere, so they are also in the brain areas involved with maintaining your involuntary breathing, blood pressure, temperature, all that jazz. What typically happens is there is so much inhibition in the brainstem and midbrain that respiration gets so slow and blood pressure drops, so not enough oxygen gets to your organs, and you die. Normally when O2 levels get low like that the brain has reflexes to wake your ass up or increase your heart rate, but the inhibition gets to those places as well and you have no backups to wake you up to put you into manual override."
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765dtz | Why when I think of, for example, sour candy or food, does my tongue tingle and make a ton of saliva? | Biology | explainlikeimfive | {
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"The thought of lemons is enough for the brain, which will send signals to the salivary glands which will start to produce greater volumes of saliva. This is a conditioned reflex action .A conditioned reflex action is a reflex action acquired from past experience or learning. First when you had not tasted lemons, thinking of lemons caused no watering of the mouth. But when you tasted them you came to know they are sweet and sour and so you started liking lemons. Now, you like lemons so when you will see a lemon your mouth will start watering. Your mouth will also start watering even when anyone will mention the word lemons in front of you. This is true, go ahead and try it! You will have to read about Pavlov's experiments with dogs, they explain this in detail."
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765idp | What's that tingly sensation you get in your stomach from driving over bumps and during rollercoasters? | Biology | explainlikeimfive | {
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"That's weightlessness. Your stomach has weight, so as you go about your day it presses down on the flesh below it. When you go over a hill on a rollercoaster, though, you (and everything inside you) suddenly become weightless. Your stomach no longer presses downward on that flesh. That tingly feeling is the nerves in your abdomen going \"whoa, wtf, where did the stomach go? Why isn't it weighing down on us like it usually is?\""
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765mxz | Why does our sense of self seem to be focused on our heads? Do people lacking senses (sight, hearing) still feel like their head is their center of self? | Biology | explainlikeimfive | {
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"We feel like that because the brain is in the head, and we've been taught that the brain is the organ that does our thinking. In older cultures that didn't know what the brain did, they didn't have the same focus on the head. The Romans, for example, thought that thinking was done in the heart, and so they treated the chest/ribcage as the center of the \"self\". Even today you get flashes of \"self\" that aren't head-focused. People talk about having a \"gut feeling\" about something, or \"listen to your heart\"."
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765op1 | During the War of the Currents, Tesla and Edison battled over superiority between alternating current (AC) and direct current (DC). Why is alternating current regarded as more superior than direct current? | I know that the main difference between alternating current and direct current is that direct current flows from one direction while alternating current goes back and forth in the same circuit. But what difference does it make? Why does this make alternating current superior than direct current? | Physics | explainlikeimfive | {
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"It is not really superior. Automobiles use direct current. The one really important difference up to now is that transformers can be used to step up and down the voltage with alternating current. At the power plant the voltage is stepped up tremendously to be carried on high overhead wires. High voltage means low current. Low current means more power transmitted over same size wires with less loss due to resistance. The voltage is stepped down before use in residential and most commercial buildings. Only alternating current can do this using transformers. There may also be advantages in industry where triple phase alternating current can be made available. Direct current is actually less dangerous if people connect across the voltage.",
"Power needs to be transmitted at high voltages to minimize losses in the system. You don't use high voltage so it needs to be \"stepped down.\" AC can be stepped down easily and efficiently with a transformer circuit. Before semiconductors, there was no efficient way to step down DC. Or at least nowhere near as efficient as a transformer with AC. Because AC has fewer losses when it was stepped down, it was cheaper for power companies to adopt AC generators and transmit that instead of DC. There were additional problems, for example it was easier to convert AC to DC for applications than convert DC to AC reliably. So that's why we use AC in our power grids. That said, things aren't the same today as they were a century ago. High voltage DC has fewer losses in the wire than AC, and modern electronics has made efficient DC/DC and DC/AC conversion possible. Over new and long distance transmission, DC is used today instead of AC.",
"The reason is because of long transmission lines. The transmission lines themselves also have resistance, i.e. some of the power that is being sent through them is lost to resistance. However, the higher the voltage is you send through, the less power you lose this way. BUT very high voltage is dangerous and you want much lower voltages to actually use the electricity. With AC it's rather easy to change the voltage through a transformer. With DC it's not so easy to adapt the voltage. And that is why the electricity grid is AC."
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765u0l | Why is it hard to implement a standard volume across various mediums like radio and television? | Differences in recording equipment and technology, conversion from analog to digital signals, processing/remastering and the disparity between mediums (radio vs. television vs. podcasts, etc.) lends itself to making a standard hard to define. Here we are, well into the 21st century and even within the same podcast I have to turn the volume down between commercials and the "show." Television commercials consistently vary in volume from the main program and don't get me started on radio. With everything going digital, is there a way to form a standard volume through a "universally accepted standard" or "universal protocol"? | Technology | explainlikeimfive | {
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"Hey there I work for 2 major broadcasting companies in Canada, and in one (where I currently am, on a 10 hour shift) I am the person who ingests, quality checks, and approves all the commercials we air across all of our 7 channels. So in Canada and the US, there are laws dictating how loud content is allowed to be. This includes both the actual show you are watching/listening too, and the commercials that are in between. Basically, the government says \"the maximum output allowed by anyone is _______\" and we all have to abide by that. My companies policy is that commercials must be withing -24 +/-2 LKFS (LKFS is a measurement of loudness). So every night I get a sheet of 40-150 commercials that need to be ingested, and I adjust their levels to be within this range. So the best way to think about this is that the commercials themselves are not what are loud. Everything else is quiet. A standard has been set for everything across the entire network, and commercials are always safely within the margins. However, since the content you are actually trying to watch is dynamic, with loud and quiet spots, you likely are listening to it slightly louder than that standard would want you to so its easier for you to hear dialogue, or quiet parts in the show/music. This is especially noticeable if you constantly ride the volume level on your stereo or television when something loud happens. Since commercials generally want to be heard easily, and typically don't have dynamics, they seem to be much louder than everything else. Side Note: There are ways that commercials can actually be slightly louder than others. Since the volume standard we use is an average over the entire spot, a quiet commercial with a loud portion at the end or a commercial of just straight dialogue vs dialogue over music can come out with different averages. Generally I adjust the volume of spots like this that seem super loud so they are more in line with the standard. Hope this helps",
"It's not that it's hard it's because it's on purpose. Commercials come in louder because the advertisers want to ingrain their product in your mind and make sure you hear loud and clear what they are selling.",
"Posted in response to someone else’s answer but for OP I’m posting again for an answer. It’s not that the commercial is louder, it’s that the commercial is set to the highest volume point of the show, so while the show changes volume to add drama by raising it for shouting scenes and lowering it for somber scenes, the commercials don’t change along with the context of the show. This is the real reason commercials seem louder than the show.",
"Our ear judges loudness as an average of loudness over time. A dramatic tv program will naturally have peaks and troughs in volume as different situations unfold (building tension with silence before a big scare in a horror movie for example). Advertisements are “compressed” ie the loudest sounds are made quieter, the quieter sounds are made louder, and the general volume of everything is increased and pushed to the max. This is because they want your attention. Generally you’ll find that radio sound levels are pretty regular as they’re made to be heard over the sound of your car, and no station wants to be quieter than the rest so they all pump it up to the max. You’ll also notice no difference in volume when the song goes from acoustic intro to anthemic Rock chorus. As for podcasts, even some very popular ones have pretty sketchy audio production but that’s generally improved over the last few years. In my opinion, unskippable ads will probably start infiltrating soon and they will become more monetised, in which case they’ll fall into line with radio standards."
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765y6m | why mammal females often are smaller than males? | Females have to carry fetus and protect themselves and babies, why are they often smaller than males? | Biology | explainlikeimfive | {
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"Mammals typically live in groups, and males typically compete for mates. Both this competition and the need to defend territory and protect the group leads to natural/sexual selection favoring typically larger males. A larger male can defend against threats better, can fight other males for mating rights better, and females who want to choose the best mates will favor them. Females don't have as much luxury in being able to grow larger/stronger/etc., because their bodies' effort goes more towards rearing children. A male only has to survive long enough to bang, basically, so his body can be large, energy-hungry, and shorter-lived. A female has to be able to devote a significant chink of her effort and nutrition and time into raising young. (Note this doesn't hold true always, or as a blanket rule. It's how it works out for many species, but the ins and outs of sexual dimorphism go way deeper than this.)",
"In general, males tend to be larger when they have to compete for access to mates. Larger animals tend to win in conflicts, so larger males tend to win in conflicts for access to females. They may also be more attractive to females. Male size gets \"inflated\" above what would otherwise be selected for. In mammals, male competition for access to females is relatively common, so large males are relatively common. Females tend to be larger when large size is important for maximizing female reproductive output. In species where the female produces large numbers of offspring, being larger means more offspring means higher fitness. For example, a larger female fish might pump out 100000 eggs while a smaller female of the species might only make 10000. This causes \"inflation\" of female size over what would otherwise be favored. Larger females are relatively common in fish, reptiles, and amphibians, but rare in mammals. Mammals use maternal care, and female fitness is limited more by the number of babies she can _care for_ than the number she can produce. Females need to be at a size where they can efficiently forage and evade predators, which means not abnormally big. So larger females in mammals are rare."
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76622j | Can someone explain why we use the 'number' infinity? And also how if you continually take 1 away from infinity how it will never reach a numerical number? | Mathematics | explainlikeimfive | {
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"Infinity is a concept, an idea. It is not a number and it follows its own rules which are not always consistent depending on the infinity type in question. You cannot remove a finite number of 1 and get infinity down to a finite number. By definition there are an never ending stream of '1' that make up your infinity. You can subtract all day long and have an infinity to go. We use the concept because it is useful. It makes it easy to calculate trends and limits and is an integral part of so many concepts in maths that cannot be dismissed. (How many points make up a sphere? Infinite)"
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76640g | What is the relationship between natural resources and economic growth? | Economics | explainlikeimfive | {
"a_id": [
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"text": [
"Complicated. At best. Having access to abundant natural resources certainly seems to *contribute* to \"economic growth\", but it's hardly the only factor. The best economic results come when a particular economy can engage in large-scale \"resource extraction\" for *domestic* use. Think coal in England during the nineteenth century, or natural gas in the US over the last decade. In both cases, access to large quantities of a particular natural resource was an economic benefit for the particular regions that contained it, but the \"real action,\" as it were, comes from the fact that those resources were being consumed by industries in the same country. The resource extraction regions benefit from vigorous demand for resources, and the more industrial regions benefit from having ready (and therefore *cheap*) access to necessary natural resources. Everybody wins! But those two things don't necessarily go together. Take Japan, for example. As far as natural resources go, Japan got a raw deal. It's an island nation (archipelago, really). It has no mining industry to speak of. Never has. It has a *tiny* (and massively protected) agricultural sector. It catches an absolute crap-ton of fish and other seafood, but its fishing fleets go all over the Pacific, and it *still* imports something like half of its seafood. And it's *still* got the second-largest economy in Asia and the third-largest in the world. Exactly why that should be is an interesting question, but clearly, having bupkis in terms of natural resources hasn't slowed it down much. By contrast, consider Africa. *Abundant* natural resources of *many* different kinds. Minerals. Agricultural land. Fossil fuels. Precious stones. And almost uniformly *crappy* economies. There are historical reasons for this, to be sure. But look at the Middle East too. Those countries tend to be pretty rich, sure. . . but they're *highly* dependent upon oil extraction, to the point that a lot of them are in increasing trouble what with oil prices hovering stubbornly around $50/bbl. If this keeps up much longer, the Saudis, Kuwaitis, Emiratis, etc., could be in real trouble if they don't find something else to do with their economies. Because right now, it's basically \"oil\" and \"tourism.\" And if it wasn't for the former, the latter wouldn't be *nearly* enough to keep things going. They might well be worse off than many African nations, many of which can at least grow *some* of their own food."
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766e6b | why are ghosts commonly portrayed as people with a sheet over their head ? | Other | explainlikeimfive | {
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"text": [
"What a fascinating question. My quick google-foo indicates that those are not bedsheets, they are Burial Shrouds. And it was decided - some time in the 19th century - that this was a good convention to use in theatres, so you could recognise that this was somebody who was supposed to be a ghost. Because how else would you let the audience know that the person was dead? And seemingly the KKK attire is meant to be \"ghostly\"."
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766zd1 | Why are erasers made of rubber, and what makes them able to erase graphite? | Is it a friction thing? When you erase little bits of rubber break off and are coated in the graphite. Why/how does the graphite appear to stick to the rubber? | Chemistry | explainlikeimfive | {
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"OH MY GOSH, some of my useless chem knowledge can come into play. What other people have said is close, but not entirely correct. You're not using friction per se to just \"rub off\" the graphite. What is happening is actually a solubility between two nonpolar solid substances, the rubber and the graphite. So the London dispersion forces (really weak intermolecular forces) between these molecules are attracted to each other and as you rub and create heat it increases the attraction and removes more graphite from the paper as it is attracted to the rubber. That's why you get dirty rubber dust. That's also why your lead sticks to paper to begin with, those same London dispersion forces are attracting the lead to the paper. Those forces are actually a little stronger than attraction between the graphite and the rubber which is why you have to put a little energy into getting it all out. ☺ Edit: I was so excited I forgot to answer your question completely. Erasers are made out of rubber because it is a nonpolar solid material which attracts other nonpolar solids, like graphite. The way it is malleable and crumbles (like others mentjoned) makes it less abrasive to the paper itself. Edit 2: Rubber being nonpolar is also why it is an insulator and does not conduct electricity. Wooooo! SCIENCE! Edit 3: Thanks for the gold!! Can someone ELI5 to me what I do with it?! (Can't wait for all the unecessarily advanced explanations 😋🙃) Edit 4: Whoa, my dudes. Did not expect my highest comment to be about sciencey wiencey erasers! This gal needs to go finish her homework and break away from the Reddit vortex, though. I need to make corrections on the rubber/conductivity (Edit 2- defo some misleading info) and will do it at some point later tonight! Thanks to all who shared their questions and knowledge! Hope you guys are all off sciencing now! ☺",
"Because graphite is very brittile and the rubber snaps the little pieces off the paper without tearing the paper. It doesn't work for pen because ink actually soaks into the page. [Here is graphite on paper under a microscope]( URL_0 ) The graphite sticks to the rubber because it is sharp and rubber is soft. Little spikes of graphite get stuck in the rubber, weakening the rubbers structure, causing the forces that bind the rubber to itself to be less than the force of friction. This is why hard erasers suck ass.",
"Just a follow-up question: why aren't they able to erase coloured pencils effectively?",
"Although erasers were originally made from rubber, it is more common today for them to be made from vinyl or plastic. Here is a video elaborating on the history of the change: (Start at 9:27) URL_0 As everyone else has said, erasers work through friction. The rubbing transfers the graphite from the paper onto the eraser, leaving the paper relatively undamaged.",
"It is a friction thing mostly. The friction from rubbing the eraser across the paper causes it to warm up slightly, this causes the rubber to become sticky. At the same time, this friction loosens the graphite from the paper fibers and allows it to stick to the rubber. This friction also weakens the surface of the rubber so that enough rubbing will cause small bits of it to roll up and tear off. Thus exposing fresh rubber for more graphite to stick to.",
"so to add to the question: were erasers invented by a chemist with an understanding of the molecular attraction or was there a happy accident that led to erasers?",
"In extremely simple terms, graphite has a stronger bond to rubber erasers than it does to most types of paper. Erasers are made of rubber because it reaches into the texture of the paper better than other materials.",
"I saw this on how its made. The rubber is actually the structural material that dissolves vulcanized vegetable oil. The oil is more responsible for the erasing than the rubber. [episode]( URL_0 )"
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7670tr | caterpillar life | How are caterpillars born. Like do butterflies get it on? Lol | Other | explainlikeimfive | {
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"dobrpv5"
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"text": [
"caterpillars hatch from eggs. And yes, butterflies do \"get it on\" to use the parlance of our times. They mate tail to tail, often for several hours, while perched. The female than goes and lays her eggs."
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767hp3 | When taking multiple medications at once, how does your body sort them out & send them off to do their individual tasks after being broken down simultaneously in your stomach? | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"That's not what happens. Your body dumps them all into your bloodstream, and they float around everywhere until they find the right shape of molecules to stick to."
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767kyu | How does a radio station send metadata like song name to my car's radio? | I was driving in my car, and for the first time noticed that the name of the current song on the radio was scrolling across the little LCD screen, and I wondered how that metadata works from the radio station's perspective. | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Modulation became more efficient, which opened up space in the guard bands to transmit digital information on a sub carrier. Edit : okay imagine that while recording the song the radio station was tapping out a special code in the background of the song that only your car radio could hear. That code is the meta data.",
"You're seeing the effects of the Radio Data System (RDS). Basically the radio stations encode simple data as a series of a high-frequency (inaudible to humans) tones which a decoder in your radio can detect and decode. RDS is used for other things too like traffic information (many dedicated GPS units can tap into this) and clock synchronization."
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767nb1 | How much control does a POTUS have over the CIA? | From what I know, officially, the CIA "doesn't operate within the United States" or something like that. How much control does a President have over the CIA? Who is the person at the top of the CIA chain of command? And how does that person get that job? (I searched, this hasn't been answered here, unless I'm searching wrong. If this has already been answered I'll just read that, Thanks all.) | Other | explainlikeimfive | {
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"The president can direct the CIA in certain areas and generally give approval for certain activities. Overall, the agency reports to congress for civilian oversight. Its headed by the Director of Central Intelligence. Generally a person would be appointed to the position by the president. URL_0"
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767sft | Why is it so hard to stick a landing when jumping out of a fast moving car? | Physics | explainlikeimfive | {
"a_id": [
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"text": [
"Because you’re moving and the road isn’t. Try to stick a landing by jumping on a treadmill on high, same concept."
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76893b | California couple survived wildfire by staying in a pool for 6hrs... How is that possible? | Chemistry | explainlikeimfive | {
"a_id": [
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"doc1t4a"
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"text": [
"Heat rises. Because the pool was underground, it wasn't heated as quickly. Heating water is actually the hardest part of cooking, because it's not an easy substance to heat compared to others. The malliard reaction that causes browning, for example, has trouble happening if meat is too wet. Which is why they advise folks to pad stuff dry before searing it. It allows the sear to happen faster, because it doesn't have to heat up the water on the surface of the food, just the food. If it was an above-ground pool, there would be more surface area exposed to the fire, and they might have cooked to death. The same thing happens with bathtubs, both because heat comes from the sides, and because a smaller amount of water is easier to heat.",
"Both water and the planet earth are absurdly good insulators. The surrounding soil is always about 60-65 degrees F. Also, it takes a very long time with a very strong heat source to heat a pool, without cycling the water, the water at the bottom of the pool (the coolest) remains a heat sink for the rest of the pool. Finally, the fire just doesn't get that close to the pool. Not only is it in ground, it's also surrounded by cement. What I think is amazing is that they did not suffocate. The contour of the hill and the pool must have provided enough of a pocket from the soot/ash to not settle around them. Then again, wind that drove the fire might have been an asset in that regard."
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768af7 | . Is laughter closer to involuntary or a social cue to let others know you find something funny? | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"Both! Laughter is the second language of the human species (the first being crying). It emerged from play-fighting in our ancestral primates. It means, \"this is an opportunity for learning, there is no danger.\" This kind of laugh is called a Duchenne laugh. However, there is a different kind of laughter - non-Duchenne laughter - which is strictly social. It means, \"I want you to laugh, or at the very least I want you to see me as laughing.\" This includes sympathetic laughter, nervous laughter, manipulative or appeasing laughter. All of these forms are strictly social responses. The difference? The eyes! While it is possible to fake a Duchenne Laugh (simply squint your eyes to make crows feet) people don't often do it. It is also impossible to perform a sincere Duchenne Laugh without squinting. The same is true for smiles. This often confuses young children who Duchenne laugh frequently but are expected to give a wide-eyed, static, humorless smile for photographs."
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768lq1 | Why do our muscles get sore? What actually happens in our body to cause this? | Biology | explainlikeimfive | {
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"text": [
"As you work out, you create micro-tears in your muscle fibers. These tears are very important because your body will release certain growth hormones to help in their repair, which will cause your muscles to grow stronger. These tears will cause some inflammation to occur in the muscle as more blood flow is directed towards it. This inflammation will cause muscle soreness that can last a few days. Additionally, there will absolutely be a rise in acidity in your muscle as you exercise. This is due to more CO2 being released in the area as your muscles create the energy needed (in the form of ATP) in order to contract. Again, this is actually very important! even though this acidity can cause irritation, your red blood cells will actually release oxygen much easier when acidity increases. So, your muscles are working hard and acidifying the blood around it, your red blood cells respond by giving more oxygen molecules to the hard working muscle"
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768m9h | When an animal gets freaked out by a new item they haven't seen before, why do they move back and forth and left and right, spazzing like crazy? | Example: URL_0 | Other | explainlikeimfive | {
"a_id": [
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"text": [
"Dogs are basically wolves who don't grow up. It is a process call neotony, common in domesticated species, where adults retain juvenile characteristics all of their lives. In general, juveniles are less aggressive, and in breeding that characteristic into the dogs, many other juvenile features come with. This tends to mess with their instincts a bit, as they have some of the old wolf behaviors and don't know what to do with it. When a wolf sees something new, they become excited because it is likely either food or danger, and they are getting primed for attack. When a safe and well-fed dog sees something new, they have the same reaction. Since they have likely been trained to not attack things, they just stay spazzed out for a while."
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768mxo | if birth control makes your body think you’re pregnant why don’t pregnancy tests always test positive when you’re on it? | Biology | explainlikeimfive | {
"a_id": [
"doc4fo5",
"docemnv"
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"text": [
"Birth control affects the levels of hormones like estrogen/progesterone, which are always in your body (the levels just fluctuate). Pregnancy tests test for HCG (human chorionic gonadotropin), a hormone which is produced by the placenta (and therefore only present if the person is actually pregnant).",
"Birth control pills do NOT make your body think it's pregnant. That was just an idea thought up by the inventors of the birth control pill when they first introduced it in 1960. Public knowledge about hormones and the female reproductive system wasn't great at that time, so they didn't want to go the route of a complex explanation. However, everyone knows that you can't get pregnant while you're pregnant [except in extremely rare cases, but that's beside the point], so just saying that 'it makes your body think you're pregnant' is a good explanation that makes sense enough to give users confidence that the pill would work. What it really does could more accurately be described as making your body think you've just released an egg. When the ovary releases an egg, the place on the ovary where the egg was released starts releasing progesterone, which shuts the ovary down from producing any more fertile eggs. The eggs that have been ripening there will shrivel up. Birth control pills contain progesterone, which keeps the ovaries from producing any more eggs. That's all that the \"mini-pill\" or \"progesterone-only pill\" does, as well as some other progesterone-only birth control. But to that is added estrogen in most pills. Your pituitary gland normally produces a hormone that stimulates your ovaries to start maturing an egg. As the egg matures, it releases estrogen, and the high estrogen tells the pituitary to stop stimulating it. If your birth control pill contains estrogen, then it's mimicking the signal to the pituitary that there's already been enough stimulation and there are fertile eggs ready for release. So the pituitary stops releasing a signal telling the ovaries to ripen eggs. So there's this two-pronged attack."
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768thp | Why does eating spicy food make my nose run? | Biology | explainlikeimfive | {
"a_id": [
"docg0rx"
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"text": [
"Capsaicin is a chemical in some spicy foods like peppers. Allyl isothiocyanate is an oil in some spicy foods like mustard. Both irritate the linings of your nose and lungs. Your body thinks it is being attacked, and does whatever it can to stop the attack. This is why some people sweat, produce tears, produce mucus (snot), or even gag when eating spicy foods."
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768uzt | how can you get a bruise or a cut and not notice or feel it until you either use hand sanitizer or someone notices and tells you | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"Your skin has specific types of nerve cells to signal different sensations to your nervous system. For instance, when you put pressure onto your skin, that activates pressure sensitive nerves, which send the signal to your brain, and you feel pressure there. Likewise, there are specific nerve cells that signal pain, called nociceptors. Nociceptors fire in response to a few different stimuli, including high temperatures and tissues being damaged. There are several different kinds of nociceptors as well, that respond to different stimuli (although there may be some overlap). If you're very lucky when you get cut or bruised, you may not activate the nearby nociceptors, particularly if it's not a particularly large injury. The nociceptors have an activation threshold - just like something may not be hot enough to be painful, your injury may not be bad enough to activate those nerves. Or if it's a small cut, it may just have managed to miss the nerves entirely. Once you're cut, though, your body will still activate some parts of your immune response, including those that make nearby nociceptors more sensitive. There are some nociceptors that don't even activate at all until there's already been an immune response. And because there are different kinds of nociceptors, when you use hand sanitizer, you're activating the nerves that are sensitive to harmful chemicals, even if the ones sensitive to tissue damage still haven't activated. Or if you poke a bruise, you may activate some of the pressure sensitive nociceptors that hadn't fired before. There are also a number of reasons why your nociceptors might fire, but you won't notice. Your brain does a lot of prioritizing of what signals to make you consciously aware of and deal with. If an injury is small enough, if you're busy doing other things and worrying about other things, your brain may ignore that signal. The nociceptors can't fire forever, so eventually they'll stop and it won't be until after then that you have the brain space to pay attention to the pain. Imagine, for instance, someone who is busy playing an intense sport and they get a small cut: they're too busy trying to win to notice. You can also train yourself to ignore pain and get used to it, so that eventually you just fail to notice it consciously. When you are made aware of it, when someone points it out, suddenly your brain is focusing on those signals and letting them through to your conscious awareness so it starts hurting. And again, if you poke the injury or try to wash it, you'll be activating additional nerves. The small signal coming from the cut before may not have been enough to cross the threshold of pain in your brain, but suddenly a bunch more are firing, making the signal stronger so it's enough to get through that priority filter so you consciously feel it."
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768wo2 | Why do beavers make dams? | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"1. Protection. They live in the pond they created with underwater openings to their lodge. 2. Food. It's easier for them to gather trees for bark by floating them in the pond. Source: did a 3rd grade report on beavers in 1983. I made a diorama and everything!"
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7693qj | What are the “dots” you see on windshields of a car through polarized glasses? | Further questions: Some cars have more dots, some have so many dots you can see a rainbow pattern. Why? Two identical models of a car don’t have the same pattern (although it’s never the case where one car has none. Usually one has a thick rainbow pattern, and the other has a discernible but thinner pattern). Why? | Physics | explainlikeimfive | {
"a_id": [
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"text": [
"It’s an effect called birefringence. When the glass goes through the tempering process, different stress patterns form in the glass that cause partial polarization. These patterns become much more apparent when viewed through polarized lenses. [More info]( URL_0 )"
],
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7698u9 | Is the a limit to the number of pathogens our immune system can remember? | When we get sick or get a flu shot, our immune system remembers how to fight off the disease so it can do it quicker next time. Is there a limit to the number of diseases it can remember? | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"Well, technically there is. But it's an immensely large number. What happens when you get vaccinated is that your B-cells, which have 10^18 possibilities to form a complementary antibody to the pathogen you are vaccinated against, are primed to memorize said antibody pattern. Since each B cell is specific to eyactly one antigen, you can technically remember 10^18 antigen sequences. And that is only counting the numbers of possibilities from gene rearrangement, not included spontaneous mutations, so it's likely even more than that."
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769id0 | Why do some substances say "Do Not Induce Vomiting"? | This said liquid is Cataclean, to help clean your engine, but why would you want to keep the fluid in your stomach, as opposed to expelling it? | Biology | explainlikeimfive | {
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"text": [
"In general, that warning is used on chemicals that will do more damage being expelled than being dealt with other ways like charcoal for one simple example. I can't speak to that chemical specifically.",
"It burns the esophagus going down and you don't want to make that worse by having it burn again on the way up. You could restrict the breathing to the point they suffocate.",
"Some fluids cause damage on contact rather than by being poisonous. Many caustic fluids like Drain-O for example burn your throat on the way down and then on the way back up. While leaving them in your system forever would kill you (and thus vomiting is better than zero treatment) we have the miracle of modern medicine called a stomach pump. Basically because it's less toxic in your stomach for as long as it takes to get to the hospital than it is passing through your throat twice. If you're ever in a post-apolycptic scenario with someone who drinks drain-O however, this advice may not apply. But in that situation they are going to die anyway and you might as well make it quick with a bullet to the head.",
"When you vomit you tend to cough, coughing introduces stuff in the mouth into the lungs (aspiration). Some chemicals are better off in the stomach than the lungs, lesser of 2 evils kind of thing, the stomach is better at dealing with \"bad stuff\" than the lungs."
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769x3x | If an infinitely fast car was on a finite loop, (ignoring physics laws which throw it off the track) wouldn't it just ram into itself? If not, why? | Physics | explainlikeimfive | {
"a_id": [
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"text": [
"It's a truly meaningless question. An infinitely fast thing is everywhere at once, defying any notion of \"where it is\" or of \"hitting or not hitting\" anything.",
"The length of the track minus length of the car will always be the distance the car has to travel to hit itself regardless of speed. So no.",
"Speed is distance over time. So to get back to the starting point with no time passing you would have to divide by zero, which is undefined in math. So the answer is we don't know."
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769zxm | What determines if someone has a nice singing voice? | Biology | explainlikeimfive | {
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"Ahoy, matey! Yer not alone in askin', and kind strangers have explained: 1. [ELI5: Why are some people born with a good singing voice and others aren't? ]( URL_0 ) 1. [ELI5: What determines whether or not someone is a naturally good singer? ]( URL_1 ) 1. [ELI5: Why are some people born with a better singing voice or a higher vocal range? ]( URL_4 ) 1. [ELI5: what make our voices sound different and what do \"good\" singers/voices have that \"bad\" singers/voices don't, assuming they aren't tone-deaf? ]( URL_5 ) 1. [ELI5: Is there a physical difference between someone that can sing and someone that cannot? ]( URL_2 ) 1. [ELI5: What is it that makes someone a naturally talented singer vs. someone that sounds like nails on a chalkboard? ]( URL_3 )"
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76abtp | Why does the Fed matter so much? And what sort of power do they have over the US economy? | Economics | explainlikeimfive | {
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"The Federal Reserve matters because it is the Central Bank of the United States and the lender of last resort for all of our other banks. It has a great deal of power over the economy, primarily through the buying and selling of Treasury Bonds and setting the \"ground rules\" that all other banks follow. It's worth noting that people tend to massively misunderstand what the Fed is. It is not a Private Bank, it is a weird mix of Private and Public. It's Board of Directors is appointed by the President, but the Fed does not have to seek approval for its actions from Congress or the President. So it is an independent agency that ultimately acts on its primary mission - keep the US economy ticking along nicely."
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76aoa5 | How do radio antennas work? | I bought a Tecsun 310et to play around with, I saw that it had a 3.5mm jack port on the side for an antenna, I made one with a length of powercord and a 3.5mm jack. However, it's just a single cable, one end is connected to the radio and the other is flapping in the wind, It seems to work, I pick up more signals in the automatic search, but how do the electrons move back and forth if it's not in a circuit, I was always told that for electricity to flow, it needs to be in a loop. If slight electrical oscillation are induced in this single cable then how is that working? and how are other types of antenna wired? | Physics | explainlikeimfive | {
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"Antennas are an interesting exception to the \"it has to be a closed circuit\" rule. Radio waves are oscillations in the electric field(*). The field pushes electrons back and forth inside the antenna. If electrons are being pushed toward the tip of the antenna, without a closed circuit, they can't keep going that way, but they can pile up at the tip briefly. But then the electric field reverses direction and pushes them back. And back and forth and so on. Think about it like a bathtub. You can't make water flow continuously from one end of the bathtub to the other without pipes to close the loop, like one of those \"endless swimming pools\". But you can make the water in the bathtub slosh back and forth, piling up briefly on each side. The other end of the antenna is connected to the rest of the circuit, so the \"sloshing\" electrons create an alternating current there. These currents are *tiny*, so you need an amplifier to make them strong enough to use. (*) magnetic field too, but nevermind that."
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76b3ck | Why are the bottoms of wine bottles concave? | Other | explainlikeimfive | {
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"It adds strength to the glass bottle. This is similar to soda cans too. I'm sure you heard that an arch is a very strong support system, right? The romans used it all the time and it is still used today. Well, what is a concave bottom of the bottle but a bunch of arches lines up into a circle? It makes for bottle that is much harder to break."
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76b4b9 | How do ink remover pens work? | Kind of a follow-up to the eraser question. Do ink removers suck up the ink? Is there a reaction that changes the color of ink? | Chemistry | explainlikeimfive | {
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"If by ink remover pens you mean \"erasable pens\", the way they work is actually quite simple. With those sort of pens, the ink that they use is actually heat sensitive. When you're using the eraser with them, the rubbing action on the paper creates friction which in turn creates a small amount of heat. This heat, while very minuscule is actually enough to break down the ink and make it \"disappear\". Another way to test this is the case, is to use one of these pens and draw anything you would like on a post-it note. Then you can use a heat source like a small candle flame or a lighter and hold the note over the heat (not so close to burn it of course) and what you have drawn will disappear."
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76b68a | What are they key differences between a prebiotic, probiotic and antibiotic? | Biology | explainlikeimfive | {
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"helpful gardening analogy: prebiotics(the fertilizer) help grow the probiotics (the good bacteria) while antibiotics (the poison) kill the bacteria",
"Currently the only substances known to have a prebiotic effect are inulin and galactooligosaccharide. Top dietary sources for these are chicory root, Jerusalem artichoke, dandelion, as well as more common place vegetables such as garlic, leeks, onions, and asparagus. Many other dietary fibers are suspected of being prebiotic but need further research to confirm. Following the metaphor above, you don’t want to suddenly over fertilizer the guilt flora unless you are willing to put up with the side effects of sudden rapid bacterial growth, i.e. bloating and gassiness. It won’t cause any lasting harm but also probably won’t be very comfortable either. Best advice is to slowly start integrating more pre and pro biotic foods into your diet to give your gut time to adjust. TL;DR If it’s white/green, crunchy, and grows underground it’s probably prebiotic, but too much too quickly will leave you bloated and gassy."
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76bamb | Why is it that scrambled eggs don't really have a very strong smell to them, but hard-boiled eggs give off an extremely pungent odor? | Chemistry | explainlikeimfive | {
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"The smell in scrambled eggs has had many opportunities to escape while being scrambled, but cracking the hard boiled egg allows them to hit your nose all at once.",
"Boiling often overcooks the egg, creating a chemical reaction that makes a new (smelly) sulfur compound in the yolk. Scrambled eggs are never cooked that long."
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76bi9r | Why does a speaker makes a sharp noise when a mic is near? | Physics | explainlikeimfive | {
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"Oh oh this one is mine! This is called feedback. Essentially when you make a sound into the microphone and it comes out of the speaker. Simple enough. But if the mic gets close to the speaker and “hears” something that is coming out of that speaker it tries to feed it back to the speaker and this happens over and over very quickly until it is just one sound stuck that gets louder and louder until something breaks the cycle."
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76bipe | Why do some people get sick when the weather changes? | Biology | explainlikeimfive | {
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"One reason that more people tend to get sick when it gets cold is because they start spending more time indoors, enabling whoever's sick to spread it to others more quickly and easily.",
"There is probably not a single answer. For example, my asthma plays up when it gets cold, because in the UK \"getting cold\" usually means \"getting damp\" and cold, damp conditions don't play nicely with some asthmatics. Similarly, some migraine suffers say that thunderstorms trigger attacks, although the science is not clear as to whether it is the storm - and associated atmospheric pressure changes - that are the trigger, or the humid, languor-inducing conditions (which tend to precede thunderstorms) that lead people to sit and stew. They have never bothered me. Warming weather can also set off things like pollen releases that trigger allergies and warm damp weather is a playground for infections of all kinds. And any weather than makes anyone a bit sneezey is going to play merry hell on a crowded commuter train."
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76bjg6 | How does testing nukes not trigger a nuclear winter? | ELI5 We hear it in the news all the time about how radioactive fallout from a nuke will plunge the planet into a nuclear winter, poison everyone with radiation and kill 90% of the population within 2 years and whatever other scare stories they come up with. How is it that through the years, with all the nuclear missiles that have been fired and tested, we aren't all dead yet? How does a test missile not have the same devastating consequences of a missile fired at a city? Did the world suffer a nuclear winter after Nagasaki? Please eli5 | Physics | explainlikeimfive | {
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"\"Nuclear winter\" is a term used to describe a global cooling due to particles being put into the air by fires resulting from large-scale nuclear attacks. It is a very real effect that has been observed from volcanic eruptions and large-scale biomass burning (forest fires). The main culprit is not the nuclear devices themselves, but the uncontrolled burning they cause in densely packed cities. The particles that are put in the atmosphere do not last a long time, so it is not something that builds up over time. Nuclear testing is usually done under controlled conditions in remote locations so there isn't a lot of burning associated with them. Testing these days are underground where no burning occurs and all the radioactive particles are (hopefully) contained. The actual nuclear bombing in Japan in WWII was not nearly large enough to produce noticeable cooling. The firebombing of cities both in Germany and Japan probably produced more particulates than the nuclear bombing, again, it is the burning that matters.",
"It is not a single nuke that would trigger nuclear winter, but all the nukes going off at once. A single nuke despite its destructiveness is not that much of an influence on global climate. It helps that after a certain point nukes weren't tested above ground as much but under ground. Having a full scale nuclear war would mean that everyone would launch all their nukes. These nukes would not go off in some desert in Nevada or some atoll in the pacific or in the frozen north of siberia, but actually where there was stuff worth destroying. They would kick up tons of ash and dust and debris into the atmosphere and with enough of the stuff in the atmosphere it would blot out the sun for a while. We had something similar when a big volcano exploded in 1815 and the stuff it threw up into atmosphere blocked out the sun for much of the world for so long that the next year there was no summer to speak of. Crops failed people hungered and starved and everyone was cold. Lots of atomic bombs going of at once all over the world would be similar but bigger and there is a chance that it would stay cold long enough to kick of a chain reaction. Things might take a long time to get warm again and that would be bad for humans who need food to survive."
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76bo4e | Why is oil being traded in dollars supposed to be so important to the USA? | I have heard people suggest several times that certain countries had plans to move away from trading their oil in US dollars (Libya and Iraq were the countries I heard, but the point could be relevant to any country), and that this is one of the main reasons why the USA decided to take action against them. The thing is I can't understand what difference it makes what currency oil, or any other mineral is traded in. Can someone help me out here? | Economics | explainlikeimfive | {
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"Right now the US dollar is the world reserve currency, meaning it is the standard used for trade around the world. This does two things: - Countries need to purchase US dollars for trade. This creates international demand for the US dollar and increases its value while giving money to the US. - Countries that own large quantities of US currency have an incentive to favor international policies that keep its value high so they don’t lose money This increases the strength and influence of the US in the world."
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76buzj | Why is tupperware wet coming out of the dishwasher, when plates and glasses are all dry? | Chemistry | explainlikeimfive | {
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"Ceramic plates and glasses have a higher heat capacity - they can \"hold\" more heat, which is why they are hot when you take them straight out of the washer. Because they're hotter, they cause the water on their surface to evaporate. Plastic is less dense and has a lower heat capacity, so the water that collects on them doesn't evaporate as easily.",
"There are two somewhat related properties of the plastic that affect its ability to evaporate water - its specific heat capacity and its thermal conductivity. With specific heat capacity, that is the amount of energy it takes to heat an object up to a particular temperature. Plastic has a higher heat capacity (1.67 KJ/Kg K) vs clay (0.92, or 1 for bricks ( URL_1 ). This means that if the dishwasher doesn't heat long enough, it is possible for the plastic to actually have a lower temperature than the ceramic. Second, and more importantly, is the thermal conductivity. This is the ability of an object to conduct heat through itself. This means that even though one side of an object is 100°C, the other side could be room temperature if conductivity is poor (think of home insulation). Plastics generally have really bad conductivity. URL_0 shows HDPE has a thermal conductivity of 0.42-0.51 W/mK . Ceramics are difficult to pin down...there are a lot of variations on what type of ceramic plate you have, but the value for slate is 2.01, sandstone is 1.7, and even Pyrex is 1.005 - all higher than HDPE. This means that there is more energy moving THROUGH the material and that the time it takes to heat up is less as conductivity is higher. There is less resistance to getting warm and absorbing all the energy its specific heat capacity wants. It takes energy to evaporate water, and higher thermal conductivity allows the container/plate to recover that lost energy faster. A great example of how conductivity can really matter is if you put a stainless steel pot and a vacuum insulated container in the dishwasher. They are made of the same material (same specific heat), but the container is insulated solely because of its shape, which helps prevent heat getting to the inside and reduces conductivity. The vacuum insulated container may come out wet on the inside (depending on how you placed it in there). Edit - okay, I realize I was kind of high level, sorry. The point is that some things move heat faster than others, and water evaporating takes heat away from the dish. Ceramic replaces the lost heat faster, so it can evaporate the next drop of water faster. Edit 2 - thank you /u/unclefishbits for the gold!",
"I know others are talking about heat capacity and stuff, but in my dishwasher everything that's flat gets dry; everything that's curved somehow does not. For example, I put my ceramic coffee mugs into the rack upside down, and the bottoms, which are slightly concave, are still wet when I pull them out. My ceramic plates I put it on edge and are dry. My tubberware, like my coffee mugs, aren't edge down, and the water catches in the nooks and crannies in the same way. The shape of an edge-down dish or flat surface allows the water to spread out, which gives it more surface area to evaporate or plain drip off. When there's a curve to catch water, like the lip under a tubberware edge, the water can \"pile up\" on top of itself, so it takes many times longer to evaporate. At least in my dishwasher, those are the areas where water accumulates for me, regardless of the dish's material. Edit: If we're going to talk heat capacities, water has the highest heat capacity of any of these materials by a considerable margin, so merely the surface-to-surface contact of water with a dish, whether plastic or glass or ceramic, isn't going to mean as much if the water is stacked up in a groove insulating itself. The surface area:volume should be the greatest factor, imo. The small difference in time the water's contact layer is exposed to a glass's higher temperature before plastic reaches about the same temperature will play a minimal role in comparison. But that's just my speculation. It'd be interesting to put a plastic plate into a dishwasher, with the same shape as a ceramic/glass plate, and see. My speculation is all 3 would be dry.",
"Aside from the thermodynamic properties of Tupperware vs ceramic (i.e. heat capacity), the molecules that make up Tupperware are probably more polar than those of ceramic (they’re “stickier” and are better able to hold a similarly polar molecule like water).",
"Lots of good answers already. Stainless steel tub dishwashers don't generally use a heating element to dry. The steel walls cool faster than ceramics, pots and glass and the water is naturally condensed on the walls and drained. Because it has a lower heat conductivity the plastic loses heat faster than the walls of the tub and doesn't allow for the convection drying to happen. Also don't buy a dishwasher that pops it's own door open when finished unless it's installed directly under stone. It will ruin your cabinets. Source: I sell this shit everyday",
"Tupperware’s shape has a lot of ridges and ‘pockets’ around the containers lip that collect puddles of water. (when the Tupperware is upside down) That combined with its low specific heat cause it to still be wet when the dry cycle is complete.",
"Likely there is also an issue with surface tension and wetting of the material. Ceramic and glass have similar wetting (i.e. the contacting angle is small) so they will tend to 1) have more surface area expose per unit mass so evaporate better, and 2) be more likely to bead and slip off the material due to less frictional area for the same unit mass. Plastics have a larger wetting angle which means less surface area is exposed for evaporation and water will be less mobile on the surface.",
"Specific heat isn't going to do anything noticeable about evaporating water out of the dishwasher like most people are commenting. Everything gets to be the same temp so specific heat and heat capacity won't really matter. Plastic is hydrophobic so water beads on the surface, while glass and ceramics are hydrophilic so water beads much smaller. Water evaporates faster when in smaller beads because it has more surface area. Next time you do dishes don't have the dry cycle on and look at the dishes right away. The plates and glasses are covered in a thin sheet of water while plastics are covered in large beads.",
"For water to evaporate it needs to get really hot, during the drying cycle the dishwasher makes the air inside of it hot to make the water on the dishes evaporate. During washing plates and glasses get really hot because they heat up easily from the hot water, tupperware doesn't heat up easily so it doesn't get as hot. The hotter the dishes are during the drying cycle the hotter the water on the surface of the dish, the more easily the water can evaporate with hot air inside the dishwasher.",
"Quite simple when you think about one thing - mass. Plates and glasses have more mass, so retain heat for longer, meaning the surface water has a better chance of evaporating. Tupperware, on the other hand, has less mass so doesn't retain heat as well, so ends up cooling down before the water evaporates.",
"It has to do with thermal mass. The glass and ceramic have the ability to hold onto, and release, heat slowly. Once hot, they release heat over time. This aids in the ability for them to help evaporate water in the dishwasher during the dry cycle. Plastic, on the other hand, is a poor heat conductor beacuse of its low thermal mass. Once heated by the air in the dishwasher, the plastic is fine. Once the air starts to cool, the plastic easily gives up it's stored heat. Since the plastic doesn't retain heat, any water on the surface tends to stay there because it doesn't evaporate.",
"Dishwashers dry by heating the items inside. Tupperware is an insulator (it's made of HDPE) Ceramic plates, glass and metal pots are better conductors of heat, so they heat faster to a level that evaporates water.",
"Plates get hot. The water evaporates off them. Plastic doesn't get as hot. The water doesn't evaporate as much.",
"It doesn't have enough mass to remain warm enough for long enough to evaporate the water sitting on it. Glass and metal are much more dense than plastic (density is just amount of mass in a given volume). They are able to hold enough heat for long enough.",
"Surface tension and droplet adhesion play a BIG role. Immediately after my dishwasher finishes the wash cycle, there are huge numbers of water droplets stuck to the bottoms and sides of the plastic items and not on the glass or ceramic. The rest of the explanations about heat capacity are true, too, but the plastic items start off \"wetter\" at the beginning of the drying cycle because of the larger number of stuck droplets.",
"Could it have anything to do with the building blocks (polymers) that form plastics and the way soaps (surfactants) work? If my understanding is correct, the building blocks of plastics are surprisingly close to certain fats, and said fats will actually bond (albeit on a very small scale) to some of the blocks (which is why if you want a \"perfect\" meringue, you use metal, glass, or anything but plastic. The resulting residual fat entering the bubble-matrix will make it grainy/not-so-great.) Since some fats are inherently attracted to these building blocks, when the soap comes into play, one end of the soap molecule grabs the fat, and the other grabs water, forcing it to hang around much longer? As indicated by the question marks at the ends of those, I'm no where *near* certain, just going by what I believe to be correct. If someone, anyone, can correct/verify/tear me a new one, I'd appreciate it\\^_\\^"
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76c04d | Why do humans only eat food that has an organic origin? Are there any types of non organic food with high enthalpic energy that we can eat? | Biology | explainlikeimfive | {
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"Sugar substitutes like Aspartame are synthetic, and can be metabolized to derive energy. They are typically designed to be sweeter than sugar and less energy rich then glucose. However, there is no reason why something more energetic than sugar cannot be designed. However, it is undoubtedly far more cheaper to use glucose from organic sources (because of its abundance) than to synthesize an energy rich molecule in large quantities. Basically, unless we discover a process of creating energy rich molecules that is more efficient and more scalable than photosynthesis, organic sources will remain cheaper. One candidate is [polyphosphate]( URL_0 ). This molecule is inorganic and can be used by cells to obtain energy.",
"Our metabolism is mostly driven by enzymes that are themselves organic (that’s not to say that they can’t evolve to react with inorganic substances like in some archea), and all of them function on only one substrate (thing to be broken down or made). Most commonly, our enzymes only work on organic things; that’s why we can most commonly only digest organic things Edit: as a side note, an organic molecule is one that is carbon-based (with carbon at the center of its covalent bonds), as opposed to a molecule that does not have carbon or has only ionic bonds. I thought this might clear up some confusion over the definition of “organic”"
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76c11h | Is it medically possible for animals, including humans, to switch brains and has that ever been attempted? | Biology | explainlikeimfive | {
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"It is theoretically possible and some rather macabre experiments have [provided evidence of modest and transient success.]( URL_0 ) It is relatively easier to perform a head transplant since all connections to the brain bundle up neatly as they pass through the neck. It then technically is only matter of connecting all the nerves and blood vessels, spine and muscles. Connecting nerves, blood vessels, spine and muscles is something Doctors regularly do even today with other injuries. So there is no reason why it can't be done for the head. The main question scientifically is whether the brain will be intact through the procedure - and several strategies such as artificial blood flow, cooling down etc have been suggested so that the brain doesn't die from lack of oxygen. The thing that stops us though is the 'disgust' factor. Will the experiments be socially acceptable? Is there going to be significant benefit to be gained from investing in what is currently a highly experimental and controversial procedure with poor success rate?"
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76c8t5 | If cancer is due to damages DNA, how do children, with newer DNA, get cancer so often? | Biology | explainlikeimfive | {
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"Children can be created with damaged DNA from their parents, as gametes (sperm and egg) pull their DNA from the parent, which may have mutated locally. In fact, such mutations causing the fetus to be non-viable can trigger the female's body to spontaneously abort the pretnancy, commonly known a miscarriage.",
"How new the DNA is isn't an indicator of how undamaged it is. If the DNA started damaged, it could result in cancer immediately. The process of generating DNA for offspring is not perfect and mutation and other DNA-copying mechanism errors can cause problems in new DNA.",
"1) Cancer is an accumulation of a series of random mutations, some of which can be passed down. So one child may need 5 mutations and another need 20. 2) There is no set rate at which these mutations happen - one child may get all 20 by the age of five and another child may randomly not get 5 by the time they die of old age at age 80. 3) Children don't get cancer so often. It's very rare compared to adults, and MOST 70 year olds have multiple tumors. But of course it's more heartbreaking when a kid dies so you see it in the news a lot more so you think it's more common than it is.",
"They don't, not really, you just hear about it more often. You don't see tearful news stories and fundraising campaigns for 58-year-old men with prostate cancer. The [rate of cancer]( URL_0 ) is far lower than that of adults.",
"Each time a cell divides into two cells, there is a tiny chance of an error in the DNA copying. Since children are growing rapidly, cell division is happening billions and billions of times. It usually works fine, but occasionally a terrible error occurs, leading to cancer.",
"They don't. Childhood cancer rate is 1 in 330. The population as a whole has a cancer rate of 1 in 220."
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"http://www.cancerresearchuk.org/sites/default/files/cstream-node/cases_crude_all_I14_0.png"
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|
76crqf | Why does rain fall in a constant downfall instead of one giant burst of dropping the water? | Other | explainlikeimfive | {
"a_id": [
"doczwao"
],
"text": [
"Water vapor is suspended in the air. Warm air can hold more water in it than cool air, so as the air cools it allows water to condense into small droplets of water which manifest as a thin mist or cloud. Water in vapor form is transparent and invisible to the naked eye. Obviously once those tiny droplets start to collect together they cannot stay airborne for the time it would take a huge cloud to get all the water together to form one big droplet, so once they reach a critical size they fall. Also remember that cooler air can hold *less* water in it not *no* water, and it takes time for the air to change temperature. So as the temperature falls the water gradually condenses out of the air and falls over a period of time rather than all at once. Finally you should note that similar to how evaporation will cool the surroundings, condensation is considered a warming process as that parcel of water must release heat into its surroundings to condense. It took heat to evaporate that water in the first place and that energy comes back out as it changes phases again. This means that as the water condenses it tends to slow the rate of future condensation, spreading out the rain over time."
],
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9
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|
76cybb | Why, especially in older software, does software load times not decrease significantly with a faster SSD? | Upgrade computer storage that is 100 times faster than your old one, but that program barely opens or loads any faster. Why? | Technology | explainlikeimfive | {
"a_id": [
"doczpjt",
"doczqd3"
],
"text": [
"The SSD only speeds up one aspect: retrieving the code storage. Starting a program often involves other steps -- computations that are limited by the CPU, or network communications, unaffected by the SSD.",
"I would have to guess probably the efficiency of the code itself. I wrote a program that converts images to black and white in real time (shows the conversion on screen) and before I streamlined the code it didn't matter how fast the pc was it took the same length of time to process basically. once i streamlined it then you could see a difference in speed on my faster pcs. I could be wrong tho"
],
"score": [
5,
5
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76d6it | Which has more grip? A wide tire or a narrow tire? | Physics | explainlikeimfive | {
"a_id": [
"dod1izv"
],
"text": [
"Engineering answer: generally a wider tire will have more grip, but tires are notoriously load dependent so you'll have to look at a specific tire's engineering documentation to find the coefficient of friction at a specific load (weight + dynamic load). I believe that information is measured experimentally, rather than predicted mathematically. That's a crappy way of saying \"there is no easy answer without trying it\"."
],
"score": [
7
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|
76de7g | How do we know how much gold has not been mined yet? | Other | explainlikeimfive | {
"a_id": [
"dod5u6z"
],
"text": [
"Think of an orchard, we know that it is 1000 Sq ft, and we can measure how many oranges are on one square foot of the ground in several different spots, then average those numbers and find out how many oranges we have in each square foot of the whole field! The areas with no oranges balance out the areas with lots of oranges and give us a rough prediction of how many total oranges we would have in the field."
],
"score": [
19
],
"text_urls": [
[]
]
} | [
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] | [
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|
76dfj5 | Who gets to be the ant queen? | Biology | explainlikeimfive | {
"a_id": [
"dod3kfk"
],
"text": [
"Queen ants become that way because they are fed a special food when they are born. The worker ants decide which newly hatched ant gets made a queen."
],
"score": [
8
],
"text_urls": [
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|
76e3le | Why does rubbing your hands on stainless steel gets rid of the onion smell? | Chemistry | explainlikeimfive | {
"a_id": [
"dod8w0h"
],
"text": [
"The chemistry is described [here] ( URL_0 ): the sulphur compounds in smelly substances react with the steel and are neutralised."
],
"score": [
13
],
"text_urls": [
[
"https://www.thoughtco.com/how-stainless-steel-removes-odors-602190"
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} | [
"url"
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|
76eq7u | Why do retail and restaurant businesses make a weekly ever changing schedule? Wouldn't it be easier to give everyone consistent hours? | Other | explainlikeimfive | {
"a_id": [
"dode8pd",
"dodgr11"
],
"text": [
"Higher end stores and restaurants give their workers consistent hours, typically, but lower end stores are staffed by high school and college students and other people with multiple jobs or otherwise unpredictable schedules. Most stores have a few workers that typically work certain shifts, but there has to be a lot of flexibility to account for people requesting time off, rotating workers in so that everyone gets hours, accounting for specific workers that do or don't work well together (easier just to separate them), and that's all without getting into the variable demand caused by holidays and things. To answer your question bluntly: quality workers with consistent availability DO get consistent hours, but the nature of the work requires scheduling to be flexible.",
"At the very low end if you don't show up for you you no longer have a job and they can replace you that day. And computers are very efficient at scheduling people around expected peak hours/days/holidays/sales without putting you over 35 hours and having to give you health insurance. Because it's more profitable and because computers can do it, basically. It's less used now and more companies are moving to better algorithms that take into account employee needs because it's getting harder to replace them because unemployment is down and the wages for service workers aren't up."
],
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7,
4
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|
76et98 | How did humans begin to drink milk/utilize cows for dairy? | What brought on the advent of milking another species? Today, it is very accepted. However, the first person must have decided to just suck on the underside of a cow and drink what came out. Why? | Other | explainlikeimfive | {
"a_id": [
"dodf0w6",
"dodfu9j"
],
"text": [
"You can of course realise that \"sucking on the underside of a cow\" is probably the dumbest possible way it happened. After all, what do we drink when we're infants if not milk? And, of course, human curiosity will find out our milk is actually tasty. So you start trying the milk of other animals, preferably docile, and find out hey, this milk is pretty cool, and there's just loads of it. As for where to find it, you only need to look at what seems brimming with liquid, and being sucked on by baby cows. As to how we got to cows, I do imagine we would breed them or just live closeby to them for their copious amounts of meat and docile nature, leading to a very easy to procure food source. As for a more scientific answer, have a look: URL_0 . I guess since it happened such a long time ago, we don't really know what our interaction to these animals was like.",
"Humans will try anything when they are starving. At some point we discovered how to de-toxify lethal plant roots by burying them in sand and pissing on them and leaving them for 6 months. Who would have thought that would work but someone so desperate for food they were trying anything and everything to not die? And cows. Cows are magic for a starving village. They turn useless untended grass fields into meat and milk with little effort."
],
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9,
3
],
"text_urls": [
[
"https://en.wikipedia.org/wiki/Cattle#Domestication_and_husbandry"
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} | [
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76etb4 | How does sleep-talking work? | My 4yr old daughter has been talking in her sleep since she’s been able to say words. It’s only happens periodically, not a constant flow of words, only like one sentence. Early this morning she was saying my wife’s phone number. Just curious what causes it and how it’s possible. | Biology | explainlikeimfive | {
"a_id": [
"dodfgjo"
],
"text": [
"There are a few theories as to why people sleep talk. It can occur during any sleep stage, though it seems to be most common during the periods when sleep goes from one stage to another. It can occasionally connect to other sleep disorders like sleep walking or night terrors. In the case of sleep talking that occurs during the Rapid Eye Movement dreaming stage, it's possible that speech related parts of the brain are temporarily activated, causing the sleeper to speak what they might be saying within their dream. When it happens during non-dreaming states, or in the moments between sleep stages, it's likely caused by the mind popping slightly more into wakefulness than might be expected, leading the sleeper to randomly say things that may or may not make sense. It's a fairly common occurrence in people of all ages and backgrounds, and while it usually only happens in very short bursts, it **can** happen several times a night. It's generally not a bad or dangerous thing - just the brain and body having a weird moment."
],
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5
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76f16z | What does it mean when a game or movie has been "remastered"? | Technology | explainlikeimfive | {
"a_id": [
"dodh0i8"
],
"text": [
"When a movie is shot, it used to be shot on a roll of film, in high quality. That roll of film is called the Master. Maybe you'll remember cassette tapes, they used to have a box for you to tick for Master and Copy. When you copy the master onto a new medium, or simply onto a similar piece of film, it is very likely that some of that quality is lost. Furthermore, the master is super high quality, but hard to work with. So, for colour correction, editing, etc., it's common to downsample the master to what the end result will be. For example, if you're releasing the movie on DVD you'll make it 1080p, so no need to keep the 8k resolution you shot it in, or editing will be so much slower. However, there comes a time when technology advances, and people move from 1080p to 4k, for example, and your movie starts to look dated and low-quality. But your source footage is much higher quality, so you can take it again, put it through the whole process again, and create a higher quality version of the movie for the fans to enjoy. Thing is, it's not as easy as taking the film and converting it to what you want, since you need to once again edit it and so on, since only the source footage is at that high res. For games it's similar, for example they move the maps and game logic to a newer engine, and they create bigger textures and more detailed models, which might already exist, but which were simplified or shrunk in resolution in order to help the game run smoothly."
],
"score": [
19
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|
76f5z5 | When lightning strikes the ocean, is everything in the ocean shocked since water is a conductor of electricity? | Physics | explainlikeimfive | {
"a_id": [
"dodhi93",
"dodhoef"
],
"text": [
"The area around the strike will be momentarily charged. This is the same for a lightning strike on the ground - currents will flow through the surrounding area and you can be shocked by standing near to the strike. Very quickly though the energy will dissipate.",
"Not quite an answer to your question directly, but pure water is NOT a very good conductor of electricity. I don't know where this idea came from, but unless the water has minerals dissolved in it (like salt in seawater), it's not very conductive. Something like tap water won't have enough ions in it to be considered \"conductive\" (maybe unless you live somewhere with very hard water)."
],
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10,
6
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|
76f76a | How is snake venom used to make anti-venom? | How is venom that is so potent , from a black mamba for example, used to develop anti-venom that's administered after you have a snake bite? Isn't it still toxic? | Chemistry | explainlikeimfive | {
"a_id": [
"dodlckx"
],
"text": [
"You take some snake venom, and inject it into an animal, usually a sheep IIRC. The animal produces antibodies to counteract the venom. Then you draw some of its blood and extract the antibodies. Then you can inject that stuff into someone who's been envenomed and now they have the antibodies to fight it off. You can also effectively immunize yourself by introducing small doses of venom and building up your own antibody supply. This is sometimes done by people who deal with venomous animals for a living, but since it takes weeks/months/years to build up immunity a fat lot of good it does for anyone who just got bit for the first time."
],
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3
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76ff05 | Why do men briefly lose their sex drive after ejaculation? Why are they unable to get hard again? [NSFW] | Biology | explainlikeimfive | {
"a_id": [
"dodleah"
],
"text": [
"The best theory relates to the shape of the penis head, and the role it plays interacting with previously deposited sperm. Kind of the opposite of Ohm_eye_Gods post really, but AFAIK it's the best theory. Basically, if you were to have sex with a women with semen in her vagina, your penis would function in such a way as to drag some of it out - it gets displaced and then caught behind the ridge. This means in situations of multiple partners mating with a single female, you can increase your chances at the expense of the prior partner. This also means once you've come (as a guy) its to your advantage to very quickly stop thrusting, and to have some kind of enforced break between sessions. Hypersensitivity of the glans, loosing the erection for a while, and loosing the sex drive all function to help make sure that once sex has been finished, you don't mess with your own breeding chances. URL_0"
],
"score": [
26
],
"text_urls": [
[
"http://news.bbc.co.uk/1/hi/health/3128753.stm"
]
]
} | [
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|
76fo3x | How come drugs like Tylenol and Aleve don't come in tasty chewable adult pills like they have for kids? | Other | explainlikeimfive | {
"a_id": [
"dodnbo9",
"dodn73u",
"dodm1o2"
],
"text": [
"So kids won't eat them in mass quantities and die. BTW... If this is my 46 yr old friend Neil who still needs to crush up his pills with applesauce...grow the f up already you pussy",
"Tylenol is acetaminophen (paracetamol to our Euro cousins) and it is toxic to the liver in high quantities. No other over the counter drug is as likely to result in death as Tylenol and many cold medicines because people may not realize that many different drugs have acetaminophen in them. For instance they may take tylenol, a cough suppressant, and a cold and flu syrup, and all 3 contain high doses of the drug, resulting in liver toxicity and a trip to the emergency room or the morgue. Making something like that in a chewable form would only encourage children to eat them like candy if they got into the bottle, and past a certain point, there is nothing that can be done to counteract it and the child would die horribly. Update* There are chewable Tylenol for children and they are 140mg which is a safer and lower dosage than adult Tylenol which is 500mg/pill. The toxicity has a time component and so consuming higher than recommended amounts over a 24 hour period can lead to liver toxicity meaning that higher dose pills can exceed this threshold much quicker than the childrens formula.",
"Some medicines are bitter. Adding artificial flavors is like lipstick on a pig - you still won't want it because it tastes horrible. Some medicines go into the body by certain mechanisms - think shots vs inhalers, etc. Even though you swallow/chew so both go in the stomach, chewing exposes the medicine to saliva and gets stuck in your teeth. The saliva can potentially inactivate the medication, and you can \"lose\" some of the medication in your teeth. So the dose can be wrong or go to the wrong parts of the body. Finally, many medications are time release, or are meant to dissolve over a certain amount of time so that they give their effects at a low level for a long time. Chewing messes that up by making all the bits super tiny and basically releasing all the medicine at once."
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76g2h5 | If you spin an object in space would it ever come to a stop? | The answer probably is yes, but since there is no air in space, shouldn't there be no air resistance? | Physics | explainlikeimfive | {
"a_id": [
"dodqnvi"
],
"text": [
"No, an object in deep space would never stop spinning due to conservation of angular momentum. Unless you really, truly mean \"never\". In that case, then you probably have to take all sorts of advanced physics into account to know if a spinning thing will be spinning at the same rate in a googolplex years. There's momentum effects of light, and even in the deepest space the object would be interacting with starlight. There's probably interactions with quantum foam and all sorts of other nonsense, and then of course if we're in for a Big Crunch it's angular momentum will get absorbed back into the entire universe at some point. Something else will probably happen if we go the other direction and experience heat death. But to answer your question: No, it won't stop."
],
"score": [
8
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76gida | Why do digital time displays, such as a microwave or oven, seem to flash constantly on video? | Technology | explainlikeimfive | {
"a_id": [
"dodwixv",
"dodtjmu",
"dodxfxv"
],
"text": [
"Those LED displays save money by sharing the wires between segments. So you'll have a 7 segment display and it has 7 wires each connected to one segment for all digits, and then 4 wires that are connected to all segments but one digit. They might have a few extra wires for the other status bits and such. But this gets them 11 wires for a 4 digit display, if every segment was individually connected you'd need the ground plus one for every segment (29 total wires). Anyways, because it's wires that way you have to light up only one digit at a time, if you light up multiple digits at once you can't make them show different numbers. So what's done instead is it quickly cycles through digits, lighting up one digit them lighting up the next with a different number. It repeats this so fast that you can't see it. However cameras take short pictures, and it might catch only one digit lit up per frame. They do this at a set rate, and it has the effect of making them appear to flash at a rate slower than the camera (so a 4 digit display might appear to flash at a quarter the speed of the camera because only one digit is shown per frame).",
"It's just a refresh time offset. Lets say your microwave display is refreshed 1/20 second and you camera is refreshed 1/60. You're camera catch all 3X more image than your microwave can display so it catches the \"dead\" frame where nothing is displayed on you microwave. Your microwave don't need to refresh it's screen as often as any video capture device since it's made for human to see time. Even if it's 1/3 of a second too late in the refresh process, the human don't care. However, if a video on youtube is 1/3 late, you'll see because there's a lot more moving part than on your microwave screen.",
"A digital time display has lots of individual elements. A single digit needs 7 elements, and with 4 digits you would need 28. If you wanted to individually control each element, you would need 28 separate outputs. This costs money. To make things cheaper, you can use 7 outputs connected in common to all the digits, and 4 outputs to select which digit to turn on. Instead of turning them all at once, you can keep flashing individual digits one after another. If you do it fast enough the human eye won't normally notice flashing, and it will be as if they're lit continuously. Cameras can have very short exposure time, during which time they see only one or some of the digits being lit up. A video camera may record at 30 frames per second, but that doesn't mean it captures light for 1/30 of a second for one frame followed by 1/30 of a second for the next frame. It only needs to capture light long enough to capture enough light, and so it might capture for 1/200 of a second for each frame. Then you get interesting effects due to the combination of the digits flashing and the camera only capturing light for short periods."
],
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4
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76git0 | Why are cold sores also known as herpes? Are these herpes the same as the one on the genitals? | Biology | explainlikeimfive | {
"a_id": [
"dodugn5"
],
"text": [
"Everyone below has been close, but not quite. No, they are two seperate forms of the herpes virus. There's quite a few herpes virus's, from Herpes Simplex Virus 1 (HSV-1), HSV-2, to even chickenpox. They all work the same way, where they hide out in your spinal column and one day burst out and spread. Depending on what type and where it bursts out, it causes various effects in that region of the body. HSV-1, which roughly 80% of the population has, lodges itself in your neck, and when it breaks out, it causes cold sores on your mouth. HSV-2 sits in the bottom most part of your spine, and when it breaks out, causes genital sores. Shingles is more erratic, but when it breaks out it follows the neurons. If you have the stomach, it's kinda cool to check out. Cold sores though aren't known as herpes, it's just that they are most commonly associated with herpes cause near everyone has it (HSV-1). Cold sores are just a reaction to it and happen for a bunch of other diseases as well."
],
"score": [
12
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|
76gsy9 | US Federal budget non-discretionary spending. | Economics | explainlikeimfive | {
"a_id": [
"dodw6cy",
"dodxzcn"
],
"text": [
"\"Discretionary\" spending is the spending that Congress can freely decide upon when it passes the budget. Although Congress has the power to decide spending, usually it pays attention to the budget requested by the president. Of course, Congress can also decide *not* to spend certain funds. Non-discretionary spending is just the opposite; Congress has already provided by law that the government must do this spending. One example is \"entitlements\" like Social Security: someone who is eligible for Social Security and applies for it must be paid the benefits they are entitled to; Congress doesn't decide on benefit amounts from year to year, but has established a formula. Non-discretionary spending often consists of taxes earmarked for a specific purpose. E.g., revenue from the federal tax on gasoline must be spent on highways or mass transit. While the distinction is important for the politics of passing the budget, note that it's an artificial one. Congress can always amend the law to make some spending non-discretionary, or make non-discretionary spending subject to its discretion. But politically, it's more difficult to pass such legislation than to change the discretionary budget.",
"With your household budget, you *have* to pay certain expenses each month, at least if you want to avoid serious consequences. You have to pay your rent, your car loan, your utilities, your groceries, etc. This is non-discretionary spending. Other expenses, like going to the movie or eating out, those are discretionary. If you are short on cash one month, you can simply decide not to do them. On the government level, non-discretionary spending is what you are legally obligated to spend. That includes repaying bonds, paying out pensions, and honoring contracts, like buying airplanes your ordered or a paying long-term lease. It also includes what some law requires them to pay, like social security and medicare. Discretionary spending is optional, but that doesn't mean is itself very import. Disaster relief, for example, is discretionary spending. FEMA got about $14 billion this year, and they get to decide how to spend most of it as they go. If they run out, they have to go to Congress and ask for more. It is important to understand the difference. You might ask what is so hard about cutting, say, 10% out of the budget. The problem is the about 2/3rds of the budget is non-discretionary, and can't be touched without passing a new law. 10% is a pretty significant chunk of the 1/3rd that is left. Also, if an agency's discretionary budget is too low, it can wind up costing more in the long run. A mess that could have been handled with a $10 billion budget will become a bigger mess with a $5 billion budget, running out of money, then waiting a month before congress comes up with the rest."
],
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|
76guhq | that unique smell from sneezing? | A smell one smells when they sneeze and sometimes they smell it when other people sneeze. | Biology | explainlikeimfive | {
"a_id": [
"doe12z6"
],
"text": [
"Saliva and mucus rushing out from your mouth and getting pushed to the back of your nose because your lungs are ejecting air out due to stimulation of your sinuses. It's kind of like when u puke and u get that gnarly taste from the puke but in nose form."
],
"score": [
8
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76gw2r | How do animals know the concept of winning and losing? | I was watching Planet Earth II and watched Komodo Dragons fight in order to mate with the female Komodo Dragon. They fought and stopped as soon as one topples the other. How do they know the concept of defeat and not continue on with the fight until death? How did these mating rules even develop? Thanks! | Other | explainlikeimfive | {
"a_id": [
"dodx3ss"
],
"text": [
"They don't \"know\" in a conscious sense, it just follows its instincts. The whole point of these competitions is to see who gets to pass the genes down to the next generation. In general, the strongest animal wins, but there is more to it than that. If an animal tries too hard, it might lose and die, and clearly not pass its genes on. Even if it wins, it might suffer serious injury, and be unable to win the next time. Whereas an animal that backs off before it gets hurt will survive to try again another day. The animal that is both strong and best able to balance trying too hard and not trying hard enough it the one who is the most likely to pass is genes on. After several generations, this behavior gets more and more refined until it is more of a ritual competition than a battle."
],
"score": [
8
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} | [
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76gx9l | Why does lava leave behind preserved casts of humans instead of totally melting them? | Physics | explainlikeimfive | {
"a_id": [
"dodwyqz"
],
"text": [
"You’re probably thinking of the casts made from victims of the Vesuvius eruption about 2000 years ago? That was ash, not lava. So the people died and fell (mostly from breathing in hot gas), and were covered by ash. The ash solidified and their bodies rotted away, leaving the empty space. (The ash was hot, but not hot enough to destroy the bodies). But you’re right, if it had been lava, their bodies would have been burned up right away (not melted though - when flesh and bones get too hot they don’t melt, they just burn up)."
],
"score": [
21
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|
76h34g | What exactly is happening when we blur our eyes on command? | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"It's the muscles around the lens, of your eye which is flexible, relaxing and letting it take it's natural shape. This is also the reason that it hurts to try and focus on something that's too close to your eyes, it squishes your lens too much. Edit: crystalline = > lens",
"Are you talking about a voluntary nystagmus? Where your eyes kinda vibrate? Or simply willfully make something go out of focus?",
"Our eyes can’t focus on really near things and really far things at the same time. But we can actively switch between focusing on near things (making far things look blurry) or focusing on far things (making near things look blurry). This is the process called “accommodation”. There is a biological lens inside each of our eyes, and when the tiny muscles connected to the lens pulls on it or relaxes, it changes its shape, which changes the way light is focused in the eye. When you “blur your eyes on command”, you’re actually controlling those tiny muscles connected to the lens. You aren’t make everything blurry. You’re just making things at a certain distance blurry.",
"It almost certainly does involve the ciliary muscle. Most people, when they are asleep or are placed in a dark room, or are under general anesthesia, put their ciliary muscle at rest. In physiological terms, this means they are slightly contracted vs. the most relaxed state possible, such that about 1.5 diopters of accommodation is induced. Some people, when they “zone out”, are able to manipulate this balance while awake, although their sensorium is slightly altered. Why some folks do this “better” than others is unknown, but that applies to many physical abilities. What makes a great athlete, as opposed to a good, mediocre, or non-athlete? It is not just hours in the gym drive or desire to win, although they all play a part. There are innate differences, between people, and I imagine it is the same for this peculiar talent, involving neurosensory and neuromuscular pathways and controls.",
"You are basically taking your eyes out of focus. It's a lot like how it works on a camera. Take a look at URL_0",
"You are willfully exercising the ciliary body within your eye. It is comprised of the muscle and processes that are responsible for controlling the shape of the lens of your eye. This process is known as accommodation and is primarily reflexive but can be controllable.",
"Can actively blurring eyes on command actually strengthen eye muscles in terms of better sight?"
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76h613 | Why are volcanoes so explosive? | You have a non-compressible fluid pushing up against a solid. Theoretically the only pressure difference should be from the difference in height between the solid earth and the magma below. But eruptions have so much more energy than that. Where does it all come from? How can it shoot clouds of ash and debris so far into the atmosphere? And for that matter, where does the ash and soot come from? Nothing is "burning" to create ash except for any plant life and organic soil. But yet volcano ash is so different from that of say.. A forest fire | Other | explainlikeimfive | {
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"You know when you have a big explosive burp from your tummy after you drink some fizzy drink? Thats the same sort of thing that happens when a volcano goes pop. Your tummy is so full of fizzy drink 'air' and more is being produced so that your tummy is forced to burp. Just like how a volcano goes pop because its full of 'lava air'.",
"There are gases dissolved in the molten rock under tremendous pressure. Its like opening a bottle of soda that has been shaken.",
"The main driver for explosive eruptions is dissolved gas. This comes from chemical evolution of the magma as it cools down or simply reacts with the host rock around the plumbing system. When the reservoir over pressures and ruptures the gas starts coming out of solution and expanding to escape, carrying fragments of the melt with it. As the pressure in the reservoir gradually comes down more and more gas comes out of solution. If there isn't much or any gas you get more effusive eruptions creating things like lava domes."
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76h9jp | How do doctors know when to stop cutting your skull so they don't damage the brain? | Biology | explainlikeimfive | {
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"med student here- they use a pneumatic drill. Designed to cut-off when there is a sudden change in pressure. You'd have to really not know what you're doing, or be intent on killing someone to screw up."
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76hbhs | This whole Ezekiel Elliot Fiasco | So I have read a ton about this and understand none | Other | explainlikeimfive | {
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"He has been accused of multiple instances of violence towards women. None of them led to a trial, because in most cases the police and DAs decided there was insufficient evidence to file charges. The NFL conducted its own investigation and concluded there was \"substantial and pervasive\" evidence he had violated the conduct policy. Note that the standard to convict someone of a crime is quite high, and private organizations are free to set their own, lower thresholds for punishment. Also note the NFL quite possibly has greater resources and placed a greater priority on the investigation than the various police departments did. The NFL decided to suspend Elliot for 6 games. Elliot appealed, and the NFL upheld the full suspension. So he sued and got an injunction to prevent the suspension until he case is heard. The NFL recently go the injunction reversed. It is likely Elliot will file for another injunction, which is likely to be granted."
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76hevo | With all the efforts to send humans to mars, how's living on that planet better than living on Earth, considering it has no resources (animals, food, water, etc.) to live in? | Other | explainlikeimfive | {
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"Among other many reasons to have a colony on Mars, perhaps the major reason is right now all Humans (and for we know, all life) in the universe is on (or orbiting) Earth. There is a chance (although very small) that all life on our planet will die due to a meteor, supervolcano, nuclear war, etc. within our lifetime. By spreading to other planets we raise the chances of humanity's survival.",
"The idea isn't that it's a better place to live, it's that we could build a place to live outside our planet. Overpopulation is beginning to become a thing in more countries and the environment is in a massive downward spiral as our carbon emissions continue to increase the levels of greenhouse gases among other forms of pollution and waste.",
"It isn't better. If: - we create a Mars colony, and - that colony becomes self-sustaining with air, food, manufacturing and *everything* else people need to survive *indefinitely*, and - that colony has a big enough population to actually carry on the human species (which would likely mean 10,000+ individuals) *then* humanity would survive if a large meteor like the one that killed the dinosaurs hit Earth. The problem is that those preconditions are so far out of the realm of the possible that it's kind of silly. If such a meteor hit Earth, and we had a colony on Mars, then that colony would die, as supplies stopped coming from Earth. And *if* this colony by some sheer miracle was able to produce its own resources, then there would still be too few people there for the species to survive. So from a species survivability point of view, a Mars colony makes no sense whatsoever, and our resources would be *much* better spent trying to preserve the Earth. But from a point of view of science and exploration, it is natural to *want* to see our species spread to other planets. It's a cool idea, it appeals to the imagination. But it has nothing to do with Mars being a better place to live, and it has nothing to do with the survival of our species.",
"Mars is an incredible opportunity to learn how to live outside of the Earth, and on a planet completely alien to us without a strong atmosphere. If we can make it on Mars, we can make it anywhere. It's close enough to Earth that we aren't in a great deal of danger if it becomes clear that it is permanently uninhabitable, and we can regularly ship necessary items between Earth and Mars, and we can even extricate Martians (people who live on Mars, not aliens) to Earth for medical or other semi-emergencies.",
"It is not that living on Mars is better than living on Earth, but that living on Earth ***and*** Mars is better than living just on Earth alone. Two planets are better than just one planet! In case something happens to one planet full of humans we still have a second planet with some humans on it. This is redundancy. The more planets with self-sustaining human colonies we have the bigger humanities chances of survival. The sci-fi Author Robert A. Heinlein had a good quote on that topic: > *The Earth is just too small and fragile a basket for the human race to keep all its eggs in it.* And Randall Munroe author of the web comic XKCD has observed: > *\"The universe is probably littered with the one-planet graves of cultures which made the sensible economic decision that there's no good reason to go into space--each discovered, studied, and remembered by the ones who made the irrational decision.\"* Going to Mars won't improve things for many singular humans, many of which live in poverty and hunger, but going to Mars and staying there will improve things for humanity in the long term. Sometimes it is hard to see the big picture when the small picture is full of human misery, but we have to invest in the future if we want to make sure that there is one."
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76hhde | Why is the consistency of my ice cream different when it melts and I refreeze it? | My ice cream is so frosty :( | Other | explainlikeimfive | {
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"Ice cream isn't just frozen. It's frozen while being churned. This gives it a fluffier consistency, filed with air pockets. You'd have to refreeze the ice cream while keeping it moving. While at rest, it freezes solid.",
"Ice cream is frozen while churned which adds air to the mixture. This is called overrun. Premium ice creams - those little containers that cost as much as the big containers - have less than 50% overrun, as little as 30%. Those big cheap containers have lots and lots of air added, 90% sometimes. If you take a cup of each and let them melt and air escape you can see a rough idea of how much product they started with before churning. It’s a fun experiment and you’ll be surprised. But this is a huge factor in your refrozen consistency.",
"It’s because of the size of the ice crystals. When ice cream is first made it is stirred while being chilled, creating many small crystals. When it melts and refreezes, the melted portion freezes back into larger crystals.",
"Ice cream has air in it that makes it fluffy. When it melts the water in it clumps up becoming ice. It's like bread that got squished. No one likes squished bread :(",
"Everyone is correct so far: it's both the air and the crystal size. There is no air churned into your ice cream when it remelts, so it doesn't have that nice mouthfeel, and it melts in your mouth much more quickly. Additionally, the ice cream was originally churned in such a way that it froze very quickly, creating lots of small crystals rather than a few large ones. Your ice cream probably refroze much slower, creating just a few larger ice crystals. This affects the texture by making it much more icy instead of that smooth creamy texture it originally had."
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76ht8f | Why does there seem to be a global rise in Xenophobia? | Or has it been there all along and people are just more vocal now/have more visibility due to the internet. | Other | explainlikeimfive | {
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"Many people displaced from Middle East wars. Eu forcing countries to accept immigrants. Taxing already broke social support systems",
"We're probably at nearly the lowest rate of xenophobia in millennia. In fact in the past, hating on foreigners would probably be considered a virtue akin to patriotism, and peoples would have derogatory labels like \"barbarian\" for foreigners. Nowdays we have the internet to connect everyone to everyone, and similarly with globalization and trade -- never have people been more connected to more foreigners. And with the internet, everyone is just people. In addition, we have journalists who exaggerate stuff for a living, a recent increase in refugees from unpopular countries, jobs being lost to foreigners. People who normally wouldn't give a crap can get scared, and people who think they lost a job or are paying to support foreigners can get grouchy about it real quick. Plus the most controversial people get the most press.",
"If you mean the rise of identity politics and nationalist ideology, my thought is that there's a perception that there's just not enough to go around. Take the women in STEM thing. If you believe that there are a finite number of STEM jobs, then every woman who gets one means a man doesn't, and the same is true of immigrants. The civil rights movement reached the highest point in 1968, which not coincidentally was *also* a point of high prosperity in the US. Things like affirmative action were accepted back then because it was not going to hurt anyone to do that. There were plenty of well-paying jobs available, even with just a high school diploma. This is no longer true. In 2017, if you want a livable wage, you need a skilled position, you need post high school education, most likely college, and you probably need at least a 3.0 and a few internships. Even then, you might not make it. So when a white man hears about women/minorities being recruited to STEM (one of the few good jobs left) he might not admit it, but it scares him. He knows there aren't enough good jobs, and if Judy gets one he might not. And it's not like he can simply go do something else, everything else either pays little or requires more (expensive) schooling. The same thing happens in the immigration debate. If there aren't enough jobs period, then it's hard to convince a poor guy that immigrants are a good thing -- they might mean he or his kids can't find jobs."
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76htp8 | What are the main reasons for the lack of state-on-state warfare today? | With few exceptions (e.g. Iraq and Georgia), there has been very limited direct state-on-state fighting in the last couple of decades. What are the big reasons for this? Is it the sheer power of militaries like the USA's that makes fighting against their allies (who make up a big chunk of nations) unthinkable, or is it more to do with things like dependence on the global market and threat of isolation? A kind of extra point: when I read about modern armies, it seems a lot of equipment we spend lots on would only be used in a conflict of two advanced states, like anti-ship missiles. Why is so much spent on this, given I can't imagine it's been used since something like the Falklands? I'm assuming people will say it's because of this investment that these wars don't happen (deterrence), but even without the very latest torpedoes, aren't the massive sanctions, etc, enough of a deterrent to stop a state-on-state war? | Other | explainlikeimfive | {
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"South western Africa has been in a brutal war for decades. You don't hear all about it except through documentaries. Its mostly warlords fighting over diamonds, gold, silver, and other precious metals.",
"According to Dan Carlin (who isn't a historian, so this may get deleted) in show #59 'The Destroyer of Worlds', an exchange between the great powers today would likely have tens of millions of casualties within the first few hours. This is due to the greatly increased power of weaponry in the 20th century.",
"You've pretty much already hit the nail on the head. It's global trade. Other people are more valuable alive than dead. It's no longer quite so profitable to kill someone and steal their resources when there's not much you can do with those resources yourself and there's no-one left to sell the resources to. But we've been doing trade for millennia!, I hear you interject, and yet most of history is riddled with interstate war! Well, this argument only scratches the surface. Why there seems to be a tipping point happening _right now_ that seems to be putting an end to interstate wars, is not understood. We don't know what exactly has to happen for us to return to interstate war, nor do we know what we have to maintain to keep interstate war from happening again. It may also have something to do with an increased awareness of other people's lives, struggles and suffering. Through media and the internet, we can hear/read from people all over the world and realize we're all not that different, we all have similar desires and aversions, and anyone from anywhere could potentially be our next best friend. This makes it much harder to dehumanize groups (races, nationalities, religions, what-have-you) and makes us more receptive to the idea that helping each other (rather than fighting each other) is a win-win (rather than a zero-sum). Of course the same increased access to media also makes the populace more aware of history, e.g. how wars in the past started. I'm not convinced this is a significant factor however, especially given the dire state of most education systems around the developed world. Finally, it has to be said that democracy plays a role as well. You no longer have a king who can start a war just because he feels like it. However, once again this factor shouldn't be overstated: in 2003, less than two decades ago, Bush started a war in Iraq by misleading the populace. It makes it only a _little_ harder to start wars, it's not a panacea. I hope some research into this will be able to find out what it is we're doing right so that we can do more of it and end all wars. For the moment, unfortunately, we don't know the whole answer.",
"Several reasons really: Communication is much easier. Instead of having to have a phone call with one leader at a time, leaders can now talk via video conferences with dozens of leaders at a time to talk down issues before they escalate. Warfare is much more deadly now. Aside from nuclear arsenals, artillery and bombers have advanced to be able to easily devastate population centres leaving war a very undesirable option. Also, we've just become more \"civilised\" and don't see war as a preferred option, even if it's seen as an easy one."
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76htpp | What is the difference between a GPU and a CPU? Which would yield higher gaming performance? | I'm trying to upgrade my computer for the first time ever. It was a prebuilt one that is seven years old now. I'd like to think I am knowledgeable in the subject but I'm really not. I don't have a lot of money so if I were to buy one thing that would help me catch up to play better looking games I need to understand the difference between a CPU and GPU. I thought a graphics card was all I needed but I see talk of CPU increasing FPS. | Technology | explainlikeimfive | {
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"Both the CPU and GPU are used to process a \"frame\" of a game. Broadly speaking, the CPU works out where all the objects in the game are by taking your input, simulating physics, running game logic and so on. It then passes that information onto the GPU so it can do all the graphics processing required to actually draw all the 3d models onto the screen, with the right textures, with the right lighting and so on. These two things happen in parallel. Once the GPU is doing its thing, the CPU can start work on getting the data for the next frame ready. Then it has to wait until the GPU has finished the current frame before giving it the data for the next one. This means each frame is only as slow as the slowest component. If the GPU is slow, the CPU will have to wait around doing nothing useful until the GPU is ready. If the CPU is slow, the GPU will be waiting around for the CPU to give it the next frame's data. So both the CPU and GPU are important to getting good performance. But if you have a rubbish CPU, getting a faster GPU isn't going to give you better FPS. However, these days the bottleneck is usually the GPU. Games usually have more work for the GPU to do than the CPU (especially if you run at a high resolution), so usually upgrading the GPU will improve performance, but upgrading the CPU might not give much of a performance boost because your system is still limited by the GPU. It depends on the game though. But if your CPU is quite slow, and it is the bottleneck, then yes upgrading your CPU will improve performance.",
"GPU is what makes your graphics pretty. CPU is what makes your computer think better and faster. CPUs don’t really need to be upgraded that often. I have a gaming desktop from 2012 and my CPU works fine on max ultra settings for most games. However, it is the GPU which I had to upgrade since then. CPU is mostly notable for games which require a lot of computation but most games just make the GPU do all the work. Get a decently priced i7 (no need to go crazy) and get a 1080 and you’ll be set for another 5 years."
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76hu37 | How are IQ tests scored and what evidence is there for their accuracy engaging a persons intelligence in every day life? | I suppose one of the things I find hard to believe about the accuracy of IQ tests is there are various types of intelligence, so what is being measured and can we assume a persons overall intellect without accounting for countless variables? It just seems like a very simplistic model that trivializes a very complicated subject. | Other | explainlikeimfive | {
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"URL_0 IQ scores are a proxy for a percentile. They find out what percentage of people can achieve what level of success on the test, and scale the results to the scores. There is no reason to think there are multiple types of intelligence. It can be somewhat split into smaller pieces, but they overlap quite a bit. Insofar as you can actually measure intelligence and use the measurement to make meaningful predictions, there is only one type. You need to explain what 'in every day life' means, as it sounds like you could be defining intelligence as the ability to make good decisions, or something like that. The evidence for the accuracy of IQ tests is that they have high reliability (people will get similar scores taking the tests multiple times) and that they have a strong ability to predict how well a person can perform complex tasks. For example, IQ correlates strongly with grades achieved in school. Also, if you go to environments that require high intelligence, you will find high average IQ's. Students at elite universities will frequently be two standard deviations or more above the average IQ of the general population. IQ is a data-driven subject, it isn't guys sitting around in a circle who just decide that intelligence has one dimension. Models that say there is more than one intelligence have been suggested, but they failed to actually produce useful measurements that could predict performance. It does seem simple, but that is what the results led too, sometimes scientists find something simple."
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76hvq8 | Why is it that the alcoholic beverages with higher alcohol contents don't freeze? | Chemistry | explainlikeimfive | {
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"You can't freeze alcohol at home. Its freezing point is -97C to -170C, depending on the type of alcohol. It's the water part of the drink that can freeze: more water = less alcohol and vice versa.",
"Ethanol (ethyl alcohol, EtOH) is the type of alcohol that we find in beer, wine, and liquor. When you see the ABV percentage on a bottle, it means in any given volume of the beer/wine/liquor has that percent of ethanol in it. Pure ethanol freezes around -114 degrees Celsius which is too low for a typical refrigerator to reach. The solvent (ethanol being the solute) is water, which freezes at 0 degrees Celsius. When you have an impurity in a compound (ethanol is the impurity, as there is more water in the beverage than ethanol), it alters some of the properties. When you have little amounts of alcohol (beer) in a beverage, the freezing point doesn’t change drastically (the freezing point is about -5 degrees Celsius). However, when you have a lot more alcohol in a beverage (hard liquor), the freezing point changes noticeably (I think it’s at -27 degrees celsius), which is lower than what household refrigerators are kept at. When you have a higher content of an impurity in a compound, you will see more of the properties of said impurity begin to appear. Some of these properties are the freezing/melting/boiling point. Because there is a stronger presence of alcohol in a beverage, the freezing point will be lower than a compound with less alcohol in it. All it really comes down to is the concentration of various compounds in a solution. For example, if you have a solution that has water and any compound that has a lower boiling point, the solution will boil at lower temperatures than pure water. If you have the same volume of said solution but with more of the other compound compared to water, the boiling point will continue to be decreased towards what the boiling point of the second compound is. Edit: a few words"
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76hztw | What does the big machine for (i believe) asthma do? | So just to clarify, its this big machine thing where you have the little like drips of liquid that you put into the machine and then have this mask thing hooked up to your mouth. (details may differ from actual machine as i havn’t touched my machine in years and technology is advancing quite quickly) | Technology | explainlikeimfive | {
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"If you're talking about a Nebulizer, they vaporize medication into a mist that can be easily breathed into the lungs. Yes, the machines used to be large unwieldy things. But you are correct in that technology has improved quite a bit. My sister uses one that is only a bit larger than an inhaler."
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76i1dt | Half of infinity is still infinity... 1% of infinity is still infinity. I get why and how, but how is it interpreted using math? | Mathematics | explainlikeimfive | {
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"Infinity isn't a number, it's an abstract concept which represents something that has no end or limit. Therefore, technically speaking, there's no such thing as \"half of infinity\" - it depends on the context of the infinity. For example when talking about infinite sets (such as the integers), then if you were to create a new set using only \"half\" the elements (such as the odd integers) then this set will still be an infinite set. If you take a function such as f(x) = 1/x then the function approaches infinity as x approaches 0, so if you take \"half\" of this function f(x) = 1/2x then it will still approach infinity when x approaches 0, it will just do so \"half as fast\".",
"What do you mean by \"interpreted\"? Infinity is infinity. Even in math. It isn't a number, so you can't say something like \"Infinity plus one\", although there is something called \"infinite ordinals\" that can be used for some calculations involving whether something could be done in some finite (but potentially arbitrarily large) number of steps, where each step potentially adds multiple other necessary steps. See [this video]( URL_0 ) for more details on that kind of thing. The whole channel - PBS Infinite Series - might be useful for you to watch in general since they talk a lot about infinities in mathematics.",
"In the sense you're talking about it infinity is a property of a set. You can start out defining a statement like \"set S is infinite\" to mean S has the same size as a proper subset (here \"proper subset\" of S means a subset that doesn't include all members of S, so at least one thing is left out). That's one way it's interpreted -- you can divorce \"infinity\" from the loose idea that it has a place among ordinary numbers at all. Then from there, for convenience's sake, make several notes about, as a conceptual handle, we can organize what we know about sets a bit better by thinking of infinity as being a number. This doesn't mean infinity *is* a number, any more than giving a dog a human name makes the dog a human. For instance, if m and n are integers with m < n, then it's possible to define a one-to-one function from a set with m elements to a set with n elements, but it's impossible to do the reverse. So if we start with sets S and T with sizes m and n respectively, with m and n unknown, observing the existence of a one-to-one function from S to T lets us infer m < = n. Meanwhile, we might prove for any positive integer m, if a set S has size m, then there's always a one-to-one function from S to an infinite set. So, pretending infinity is a number that's larger than any other number unifies what we know about sets in a nice way. So we can say quite cleanly that \"if there's a one-to-one function from set S to set T, then the size of S is smaller than the size of T\", because we're letting infinity swim among ordinary numbers as sizes of sets. Compare to an alternative formulation where we have to specify rules in a more convoluted way, like \"if S and T are not infinite, then ... [repeat the same rule]\". There's a great temptation to notice this casual conflation of infinity with other numbers and leap forward with \"oh, so that means infinity *is* a number, so let's shove it into all these other places where numbers go\" and that doesn't work. It can sort of work some of the time and doesn't work other times. In particular, trying to do arithmetic with infinity just turns into a mess of contradictions or drawing endless exceptions to ordinary rules (\"you can subtract a number from both sides of the equation and still have a true equation, unless that number is infinity\"). It's best to just avoid that avenue altogether, it's useless and boring.",
"Well, one way to think of it is consider so called *cardinals*. Those are basically more generalized version of numbers as they are used to signify size. So if a peanut bag has 5 peanuts in it, then the 5 there signifies cardinality. On regular numbers, this meaning ties completely with another meaning numbers have, that is, signify position. You could arrange the peanuts somehow, so one peanut was the first, another was second, and some peanut was fifth. Once you get to infinity, these meanings aren't as closely connected, but it's handy to realize that we're specifically talking about sizes here. If you have infinitely many something, then and then you take only 1/100 of the items you have there, how many items you actually have? With cardinal numbers, we can answer this. So, cardinals are defined as if by a children who doesn't actually know numbers. You know there are as many guests as there are chocolate cake slices if you can give every guest one slice without any slices remaining and no guest being left without a slice. With infinite cardinals, this is our definition of two sets sharing the same size: if you can somehow pair every item in one set to another set, so that no item is left over in either set and no item gets paired twice, then the two are the same size. And with infinite sets, if you take only one item out of every hundred, then you can form this pairing between original set and the 1% set. Say, to use natural numbers as an example, if we pair 1 with 100, 2 with 200, 3 with 300 etc, then you have every hundreth item in natural numbers paired with natural numbers so that no natural number is left unpaired, nor is any hundredth left unpaired, and no number is paired twice. This is sort of different from how you use infinity symbol in arithmetic though. I'm honestly a bit unsure what limitations one has in assigning meaning to that symbol. My impression is that one typically just views it as this (first) infinite cardinal number and then constructs arithmetic rules to suit this intuition, but I've never seen this done formally. Every time I've seen infinity used as number it's simply been defined to work like that, and the only justification is that it's useful to do it like that."
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76i6mk | How so subreddits likeand Advice get people to respond to posts? | Other | explainlikeimfive | {
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"Well they get fuelled by questions like these and then people that are knowledgeable in the topic give an answer.",
"Karma for one, but also a desire to feel useful and share what we know. You could suggest altruism and a desire to grow people's knowledge for a better world",
"Easy one: karma. Thread goes big, some smart guy writes the easiest to understand and not too long answer and gets the karma. OPs question is answered. All is good"
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76ij08 | If our body focused on preventing telomere reduction, what changes might our bodies experience? | Biology | explainlikeimfive | {
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"Cancer. Cells continuing to divide with no limit is called cancer. If you mean instead \"what would happen to us if our bodies focused on sustaining cells /efficiency as long as possible before natural cell death what would happen?\" Is a much more interesting question.",
"To prevent telomere reduction, your cells have to stop dividing. If you meant regenerating telomeres, I don't have the answer for that"
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76ijzr | Is pollen diversity important to bee health? | Biology | explainlikeimfive | {
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"That is an interesting question, as is your nom de pleure. Here is the problem with getting the answer, to this and to a similar question. The similar question is, \"Does ingesting local honey decrease allergic responses?\" That is an unproven myth. To be able to answer either one of the questions we would have to do research. To answer your question we would have to find bees with pollen diversity, define it, locate hives with it, locate hives without it, compare some how. We could declare hives used to pollinate crops as the ones without pollen diversity. These hives are moved to places with crops needing bee pollination. Then we would have to compare them to another group of hives in a more diverse environment. Immediately it can be seen that the hives which are moved are more stressed. They are also in an environment with more insecticides. Would lack of honey production, or death of bee colonies, or some other measure be due to the lack of pollen diversity or to one or more of the other factors? Bee pollination for crop production has gone on for decades. It has been proven to work for the crop empirically. Hive owners have been willing to do the transportation for decades without too much complaint. Colony collapse was not that prevalent. Now bee keepers are having problems and are searching for answers. There are many possible reasons for their problems. Pollen diversity has not been studied but is was not a problem in the past. To answer the second question would also involve a controlled study. Using a national brand of honey would not be suitable. The contention is that it is local honey. I tried it myself and decided it was foolish to ask the question, the honey was too good."
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76iqv8 | How come when you are hungry your stomach feels nauseous? It seems like a design flaw that when you're hungry, you don't feel like eating anything. | Biology | explainlikeimfive | {
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"When you start to get hungry your body starts preparing for food by producing stomach acid and other fluids that will help with digestion. If you don't eat, those fluids are still there in your stomach and for some people that can create a sensation of nausea. It will fade if you keep not eating as those fluids will be reabsorbed by your body. Or you can eat something ~~blad~~ bland, like bread or crackers, to put the fluids to use and that should help as well. Edit: Thanks for the gold!!",
"My doctor explained that it was due to low blood sugar, so your body activates the sympathetic nervous system causing a symptom like nausea. Term being \"hypoglycemia\" Growing up it was really hard for me to eat breakfast in the morning because I would feel nauseous because my stomach was so empty. I thought something was wrong until he explained it was due to my glucose levels and low blood sugar. So now i usually eat a little before bed and I don't get that feeling anymore.",
"“Hunger” is actually, loosely, a few different things. Your body has structures that can track and maintain a natural circadian rhythm, not only involving when you sleep or wake up, but also when your brain is active, when to raise or lower your body temperature, and when you are eating or resting. Your body learns to estimate the time and amount of certain food that comes into your body, and appropriately releases hormones like insulin to deal with this intake of food. When you tend to shock your body with energy-dense food every lunchtime, your body will release large amounts of insulin around that time every day. This large amount of insulin causes your blood sugar to quickly leave the bloodstream, as well as trigger other food-digestion-preparation things in the digestive system. The experience of “hunger” you describe is when your body starts doing this food-anticipation thing, but the food is nowhere to be found. In this situation, you can experience hypoglycemia (really low levels of blood sugar, or low levels of absorbable blood sugar) which can cause the nausea. Arguably, hypoglycemia to the point of nausea isn’t “normal”. If you eat a more balanced diet and significantly less sugary stuff on a regular basis, you body will learn to not overdo the insulin. And you should experience a normal craving for food, rather than weakness and nausea. That’s ideally speaking, anyway. Different people’s bodies can have different quirks.",
"A different perspective: you have two brains. One is in your head. The other is mixed in with your gut, end-to-end. Both are connected to each other. Eating is critical enough to your survival that when you don't have enough food, it's critical that eating be a priority above all other thing. So it's like having both flashing lights and a loud alarm. The criticality is linked to the reason you have two brains - **the gut brain actually came first, evolution-wise, because simple animals could do without a \"head brain\" but not without a \"gut brain\"**. So nausea is the gut-brain equivalent of pain associated with hunger. The head-brain version you are conscious of, as a human, is the tacked-on after-thought version that evolved from having a gut-brain first. This dichotomy probably has something to do with eating disorders. It's also related to other head-gut experiences as well. \"Gut-feelings\" are when a deep, emotional reptilian brain sense kicks in, and that's the part most directly connected to your gut-brain so you get queazy. \"Getting Butterflies\" when you fall in love is something you feel in your stomach and gut. Again, the part of your head-brain involved in emotions is most directly connected to your gut-brain, so you feel it there as well. This also has medical implications - you have the same neurotransmitter receptors in your head-brain and gut-brain, so often when you take a medicine for your head, you have side-effects in your gut. And vice versa. There is also evidence now that your bacterial friends in your gut can affect your health rather profoundly. It's also very likely that includes mental health indirectly.",
"The nausea is being caused by low blood sugar. Apparently, when your sugar drops too low (or too high), your body alters your stomach contractions in order to change the rate that food moves through your system. Source: URL_0",
"I get this occasionally and I used to be pretty sure it was caused by low blood sugar, but recently I was diagnosed with acid reflux and was reading up on it and it seems way more likely that what happens is your stomach is filling up with acid thinking you're going to eat but when you dont eat the acid just sits there and can make you feel nauseous, but if you can force yourself to eat a little something eventually the acid will subside (or try taking a tums or a zantac)",
"It shouldn't make your stomach nauseated when hungry, that screams H. Pylori Bacteria, Ulcers, or IBS.",
"Wait.... You should definitely NOT feel nauseous when you are hungry. You might want to see a doctor. That is definitely not normal.",
"I feel pain if im hungry, and i really want to eat when i feel that way. I never feel nausea. Is this just as common?",
"As I have been practicing interval fasting, I've noticed the nausea goes away. Almost as if you're body is producing too much of it because you're used to always digesting something and not letting your body heal.",
"When you haven't eaten for a while the liver starts to produce glucagon, this breaks signals the body to break down muscle tissue to turn into glucose so it can continue to initiate the Kreb's cycle to process fat into energy as well. So if you're so hungry you're feeling nauseous, then you're destroying muscle! Go eat!"
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76ir47 | Why is India's garbage/river pollution situation so bad? | India has a GDP growth rate of 7% and has enough economic power to have a blossoming space program, but why do they still have such a horrible situation in regards to all of the trash in and around their rivers? Is it because of the population density? Is it a culture thing? | Economics | explainlikeimfive | {
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"Actual indian here... Our pollution is so bad, because the people in power don't care, and the people who do care can't ever get to power. The indian government is a carefully balanced pile of bribery and corruption built over a foundation of pure apathy and greed. While sure, there are some diligent workers at the grassroots lever, and some naive men and women higher up, noone with both the power and the means to actually do any good cares enough. Politicians here just aim to stuff as much of the tax rupees into their own private coffers before the are elected out of office. Further, the common man isn't much better. We just vote for the same greedy pigs over and over again because we cant be arsed to make an educated decision for the good of our own country. The garbage and pollution are just the tips of the massive trash iceberg just out of sight in the sewage clogged depths. Corruption, money laundering, and just plain ineptitude are so ingrained into the Indian life, that we've begun just taking it as par for the course. If you want anything done from an official stand point at all, you better be prepared to bribe liberally. And if you think it could get better with a hard reset, think again. Leave alone following meta rules about accepting bribes and ruling fairly, indians won't even follow the basic rule of \"don't overtake a vehicle from the passenger's side\". Though I suppose I ought to be praising my country, pride in ones own and all that, fuck it. My country sucks, and if trashing it online is the best I can do, well Imma trash as best I can."
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76ivhu | What is actually happening when you "lose your voice"? | Biology | explainlikeimfive | {
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"When you make sound using your vocal chords, or vocal folds, your body is passing air through it in such a way that they vibrate. If you watch a slowed-down video on YouTube of vocal folds working, you'll see two flaps of tissue basically slapping against each other at high frequencies. In healthy vocal tissue, these two flaps line up and come into contact with one another along their entire length. If you yell, cough, or sing until your voice is tired, you're passing lots of dry air past your vocal folds, which is abrasive and causes them to become inflamed and swollen. This swelling can get in the way of the folds coming into full contact, so that they never close completely when they are vibrating. This is why people with sore throats sometimes sound \"breathy\" when they speak - lots of air is escaping without vibrating the vocal chords. For an example of what this looks like, find a video of vocal chords with nodules. I'd post one but I am on mobile. Source: am a professional singer."
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76iwcb | does dna change in adolescence and will affect our children if ever | e.g -physical features changing drastically, face shape -emotional disorders, depression and such things | Biology | explainlikeimfive | {
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"Only by mutations as far as i know. It can be changed. But it might affect your children only if the mutation affects your sperm or oocyte. Not the ones that you've already produced but the ones you are going to produce. (germinal mutation) And because they are mutated, the zigote will be affected and the offsprings will be affected aswell. p.s. Correct me if i am wrong please.",
"DNA does change to some degree-mutations and the like. This is what leads to cancer and other non-pathogenic diseases developing later in life. It's probably not going to drastically change your physical appearance because the bone structure that makes your face look the way it does is already built. The body doesn't need to use DNA as a blueprint for the shape because it only has to do minor repairs. (exception being if you have a bony cancer that causes growths. Somatic DNA mutations (i.e. those that aren't with you at birth) are incredibly unlikely to affect your children, because the cells that form gametes (sperm and egg cells) are separated from the cells that form the rest of your body fairly early in embryonic development"
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76izjy | Why is any (even bad) publicity considered good? | I understand that having your brand, product or name in the media is beneficial and obviously good publicity helps a lot. But I’ve heard a few people saying “any publicity is good publicity”. With that logic, the publicity could be bad and appear detrimental to a company or person and yet some people still consider that as a good thing as the company/person is staying present in the media. Sorry if this sounds a bit convoluted, just trying to get my head around it. Thanks for any clarification on the subject. | Other | explainlikeimfive | {
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"Going off what /u/seeasea has already stated, people are dumb. [We have a tendency to be able to recall a name]( URL_1 ) but not, necessarily, contextualize it. However, it's been proven that this only works when [the object/person/ect being publicized]( URL_0 ) was not previously known. In other words, if a company like petco or another major pet food retailer had a huge issue with poisonous dog food, their market share would go way down. However, if some mom and pop store did, then their market share - or sales- would go up because although people could recall the name, they wouldn't be able to associate it, necessarily, with the poisonous dog food. (My apologies to petco! I'm just staring at my animals while I typed this so it was the first thing that came to my mind!) Basically, if you aren't a household name already, then yes, any publicity is good publicity. However, if you are a household name already, then an opinion of you has probably already been formed and any publicity will affect that opinion.",
"If someone doesn't know you exist, they will never be a customer. If someone learns of your existence via bad publicity and they decide to dislike you, nothing changes, they were never a customer to begin with. If a customer decides to no longer be a customer because of bad publicity, that is a negative. If someone doesn't care for whatever the publicity is, and becomes a customer after learning about you, that is a positive. Depending on the nature of the publicity, and the amount of people who didn't know you existed, the increased knowledge of your existence can get you significantly more positives than negatives.",
"Best real world application I can think of is youtube drama. See how they lose subs for a while but in the end, end up with more total subs than before? They've gotten more exposure. More people know of them now. It's the same as those deals that operate at a loss in stores/fast food joints."
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76j1oi | Why do groups choose to boycott elections and has this ever been effective? | Other | explainlikeimfive | {
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"Voter turnout says a lot about the legitimacy of a process. If turnout for a vote is quite low, then nobody can really be sure of what the people actually want. If one side believes the system is rigged against them, then they should boycott a vote instead of going to vote \"no\". Heck, let's take the Catalan independence referendum. Sure, 90% of ballots read \"yes\". But there was only 40% turnout, and there was widespread accusation of ballot stuffing and people voting at multiple places. Had the opposition showed up to vote, what would happen if the results instead showed 65% or 70% saying \"yes\", but with 70% turnout? It's hard to say that ballot stuffing, voter intimidation and all that jazz could influence that many people, after all - we certainly don't want to think that so many people could be influenced by that. That looks like a much clearer \"yes\" victory despite \"yes\" taking up a lesser % of votes. If you don't trust the process, but obey the rules of that process regardless, then you will be screwed over by that process. You win by not playing that game."
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76j3qt | Why is the shape of the cosmic microwave background oval ? | Physics | explainlikeimfive | {
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"For the same reason that [this map of the world]( URL_0 ) is an oval. Ideally you'd represent it as a sphere. To represent it in 2D you have to choose a projection, in the same way as you have to choose a projection to make a 2D map of the world. The usual image of the CMB uses the Mollweide projection, which produces an oval like that world map."
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76j9wq | How we know how far stars and planets are, what they're made of and how did anyone work this all out?? | I've been watching Brian Cox's Human Universe and he talked about stellar parallax and how you can use it to work out how far nearish stars are. He then spoke about Henrietta Leavitt and variable stars, to find the distance of more distant stars, and I just don't get it. How can anyone possibly know how far stars are? He also spoke about red dwarf stars (I think) that are turning hydrogen into helium or possibly vice versa. HOW?? How is it possible to know what a star is made of, or what it does? On a side note, he spoke about Einstein's general relativity theory and that gravity doesn't pull anything down, but instead the earth is pushing up against everything. Does this mean that gravity doesn't exist and that Isaac Newton was wrong? Apologies if this has been answered here before, I searched 'stellar parallax' before asking this here. If it has been answered already, perhaps someone could link the other post. Thank you. | Physics | explainlikeimfive | {
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"Hold a finger out about a foot away from your face, and alternate winking eyes. See how the image of the finger \"moves\" a bit depending on which eye is winking? Try moving your finger much closer and then at full arm's length and winking again. Notice that it \"moves\" more when it's closer to your face/eyes? That's how parallax works. You can calculate how far away your finger is using how much it \"moves\", plus the distance between your eyes. How we know what stars are made of is from their light. If you break up that light in a (very precise) prism, you'll see bright and dark bands in the spectrum. These correspond to the elements that emit/absorbed that light as it travelled to us. From that we can tell what was making that light, and what was in the way of that light. As far as knowing what stars do on the inside, we've learned a fair amount about nuclear physics here on earth as well, tinkering with bombs n' stuff, so we think we've got a good handle on what is happening inside stars."
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76jgud | - An anechoic chamber at Orfield Laboratories in Minnesota has negative decibel levels (lower than -9db). How is this possible? | Physics | explainlikeimfive | {
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"Because 0 decibels is not the same as 0 sound. Decibels are a logarithmic scale. Every time you increase the decibel value by 6, you double the sound pressure level. This means that 0 db cannot represent absolute silence. If you double 0, you still get zero. Negative infinity would be no sound at all, whereas zero is a sound that is incredibly quiet. The zero point was chosen to be something quiet enough that humans cannot differentiate it from silence. But cannot actually represent zero sound, as zero because logarithms can't do that.",
"Decibels are a logarithmic unit. This means they are defined as the logarithm of something positive (in this case the power I believe), and thus can be any value, positive or negative. -10dB corresponds to a tenth of the power of 0db. It's the same reason as why we can have negative pH acids, as pH is a logarithmic unit too. (edit) actually now I think of it, pH is the **negative** logarithm of a quantity, but the analogy still holds as pH can be negative or positive because logarithms can be positive or negative (respectively)",
"They're dB SPL (decibel sound pressure level) and they're referenced/scaled by the lowest pressure wave a human can detect. Negative dB simply means that the sound levels in the room are below the reference level",
"Think about an earthquake, the ground is always moving a tiny tiny bit; so close to stable but not quite. Granted, we can't detect the usual movement, but with the machines used when the Richter scale was created, we could get so low that it was ok to set the lowest point measurable as zero. Nowadays, we can detect even lower: we can detect a -2, which is a few dozen matches going off. The same applies to audio. When we created the decibel scale we couldn't distinguish any difference below 0. Now we have technology that can. Sidenote: I once tried going into an anechoic chamber: I have tinnitus, it made me want to cry after mere moments. I do not like the quiet.",
"Very good answers so far. Let me attempt to add a couple of things. Let’s break out a couple of items. First it isn’t super relevant that the chamber is anechoic. But to explain all of this, anechoic means without echo. In ELI5, the walls absorb sound. This is to take better acoustic measurements. For example if you are using a microphone to measure a speaker, to get the purest measurement of the speaker, you don’t want sound waves bouncing off the walls. Quiet and anechoic often but not always go together. The rating for the room is -9dB(a). To understand this we need to understand the -9, the dB, and the (a) First the dB. This is a logarithmic ratio between two values. Fun fact. The B is a Bell named after Alexander Graham Bell of the telephone fame. The d is for Deci, 1/10th A missing item is dBSPL. Here the SPL is sound pressure level, this defines one of the two ratios, in this case 20 micro Pascals. So you can just say, for example 94 dBSPL and understand what the value is (you don’t need the second number from the dB ratio). Now here is where we get back to the (a). humans can hear a range of frequencies, from bass (kick drum) to treble (very shrill sounds). To talk about the total sound pressure over the range of human hearing, a specification tells us how much each bin of the frequency spectrum “counts for” towards a single number. There are several different methods, but know that the (a) is called A weighting. [helpful Wikipedia ]( URL_0 ) this Wikipedia image shows the most popular ratings. tl;dr a long time ago folks picked some sound level as a reference point. Sound measurements are expressed in ratios via logarithm. If something is quieter (lower) than this chosen reference level, the number is negative. Only in a perfect vacuum would there be “zero sound” as sound needs something to propitiate through.",
"0 is just a reference point, like 0 degrees Fahrenheit or 0 degrees Celsius. Analog sound is referenced to 0dBV - 0dB is one volt, and signals can be lower or higher. Digital sound is referenced to 0dBFS - 0dB is the maximum the digital-to-analog converter can produce and everything is negative dB compared to that. Acoustic sound is compared to 0 dB SPL, which is a very very quiet level but not absolutely no sound. Most sounds are louder than that (positive) but some can be quieter (negative). In order for there to be absolutely no sound at all, the air molecules would have to be still - so, absolute 0 in temperature."
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} | [
"url"
] | [
"url"
] |
|
76joa1 | Why does the sun shine ? | Physics | explainlikeimfive | {
"a_id": [
"doegpeb",
"doegkzu"
],
"text": [
"The sun is so massive that the force of gravity on the inside is strong enough to start nuclear fusion. It's shining from the energy released by literally pressing hydrogen atoms together until they're helium.",
"Light, heat, and other forms of radiation are by-products of the nuclear reaction occurring inside the sun."
],
"score": [
15,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
76jpjl | How megaphones work. | Physics | explainlikeimfive | {
"a_id": [
"doehk59",
"doehpru"
],
"text": [
"**When one shouts , the sound waves disperse in a semicircle , the power of the voice cords distributed to 180 degrees. A simple megaphone channels the sound in a small angle and thus is directional and stronger. Electric megaphones amplify the sound and still send it in a narrow cone**",
"The modern electric megaphone are a microphone a, battery pack and a speaker conned to a cone-shaped acoustic horn The acoustic horn direct the sound in one direction so it is louder in that direction. A old acoustic megaphone is only a acoustic horn that direct the sound of you voice voice in one direction. The acoustic megaphone might have been used in ancient Greece but have for sure been used from the 15th century. The electric megaphone have existed since the 1920s but was heavy and the modern light design have been available cone 1954"
],
"score": [
40,
4
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
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