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mj2elu | How come the outside of a plastic water bottle filled with room-temp water feels colder than a empty plastic water bottle? | Physics | explainlikeimfive | {
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"Hot and cold is actually the transfer of heat. When something feels hot, it’s because you are absorbing its heat. When something feels cold, it’s because it is absorbing *your* heat. Water is very good at absorbing heat, unlike air. So room temperature water will feel colder unlike room temperature air.",
"The human sense of \"temperature\" is not actually a sense of actual temperature like a thermometer. We aren't designed that way. Instead it is more like a measure of heat energy flow. Objects feel \"hot\" when we sense heat \"entering us\" and feel \"cold\" when we sense heat \"leaving us\". This is why standing in air at 70F feels OK while standing in water at 70F feels cold. Water is a better heat conductor than air and heat leaves our body quicker through water than air. This is the same reason why a block of metal at 50F \"feels\" a lot cooler than a block of wood at 50F. The same thing applies to an empty vs a full water bottle."
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mj2pnc | I've got a box of figures for a board game that says "This is not a toy." Why would it say this when it absolutely is a toy? | Other | explainlikeimfive | {
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"\"Toy\" suggests it's for a small child so they won't have been tested or certified for child safety. They may also be more fragile so if you treat them roughly like a toy you can't complain if they break.",
"If it’s a game piece it’s considered a token or pawn for the game only. Referring to the pieces as a toy indicates that it can be played with as a stand alone pieces, which the company it trying to prevent because it wasn’t tested for safety in that way.",
"Toys are safety tested for things like small children chewing on them. Board game pieces are not, if the game is marked for a certain minimum age (12 or 14 in most countries.)",
"My bet would be tariffs. It might not seem like it, but the distinction between “toy” or “game” or “replacement parts” could have a meaningful effect on the import tariffs and they may have had to argue that fact on inspection before and are making extra sure that they don’t need to do that again. Here is a [short Planet Money episode]( URL_0 ) demonstrating some of the distinctions and considerations surrounding tariffs."
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mj2y7c | Why and how do men's belly grow bigger as they age? | Biology | explainlikeimfive | {
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"As men get older they do less exercise (generally). But they tend not to reduce the calorie consumption by an equal amount. The excess calories that are not burned are stored as fat. Men generally have the majority of their fat cells around the abdominals so this is where the fat gets stored.",
"They don‘t naturally, but aging often makes it harder to be active and your metabolism slows down. If an individual gains weight most often from a combination of eating to much and not exercising daily they put on weight and for men usually that is in their stomach, the reason why it is in their stomach is because evolution, when human males hunted it is more efficient for that weight to be in the stomach when running/fighting",
"Men first store fat around their belly, as opposed to women, who store fat at their thighs, butt and breasts. Another reason is weak abs. When you don't train your abs, and they get weak, they can't prevent your belly from sticking out: when your abs are strong enough, it'll hold your belly in even in a relaxed state.",
"There are a few reasons: Lower testosterone causes to body to store more fat, as a man ages his testosterone levels decrease. Men often eat more and as they get older they start to slow down physically but they still eat the same amount. Older people tend to exercise less or get no exercise at all, less exercise means more fat is stored. The abdominal muscles become weaker as we age, the belly slouches and sticks out more.",
"Because they stop exercising as much, their metabolism slows down, and their testosterone levels drop. You can prevent this from happening by eating healthy and excercising.",
"I'm seeing a lot of debunked information in the comments here. Be careful with the explanations that focus on calories in vs out. They're not entirely wrong, but they're not entirely correct. There is a lot of research showing that exercise has a much smaller effect than what you eat. The \"calories in vs. calories out\" school of thought would be correct if organisms were what physicists call \"closed systems,\" but we're not. Our endocrine system, for example, will change our metabolism based on what and even when we eat. Research on continuous objectors during WWI showed that when the body is deprived of calories, it simply uses fewer of them. When the calorie supply returns to old levels, the body actually remains at a lower level of usage and puts on extra fat as an emergency supply in case another famine occurs in the future. When your belly (not \"stomach,\" because that is actually an organ which is higher up in the torso) sticks out while at rest, that is due to having an excess if visceral fat. Visceral fat is fat which accumulates around, between, and possibly even inside the organs. It is the most unhealthy kind and can lead to serious health issues. (This is an oversimplification, but this is an ELI5.) The standard American diet is heavier in refined carbohydrates than we evolved to handle. Things like flour and processed sugar and white rice are actually quite unhealthy in longer term contexts even though they have huge advantages for short term survival and taste really good. People from cultures which don't eat these and other high glycemic index foods tend to not have as many issues with visceral fat and also tend to live longer. Look up longevity \"blue zones\" and URL_0 for more information. This standard American diet has gradually become very common in the world, including most \"western\" and \"industrial\" countries. That isn't to say that carbohydrates are bad for you. They're actually necessary. But the ones that have the fiber broken up (flour) and their nutritional content striped (white flour, white rice, alcohol, sugar) cause a chain reaction of your hormonal/endocrine system and results in storing visceral fats and fats inside your liver (a.k.a. nonalcohol fatty liver syndrome.) I actually have direct experience with this. I spent about 5-6 months trying to avoid these foods most of the time for medical reasons. During that time, I didn't significantly change my exercise levels. I ate larger volumes and more often, but lost over 15 pounds and my waist size went down enough that my pants fell off when I wasn't wearing a belt."
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mj3b4s | Why can time only move forward? | Physics | explainlikeimfive | {
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"The laws of physics, with *almost* no exceptions, are time-reversible, which means that a \"backwards\" flow of time would not violate any laws locally! So the question \"why this direction and not the opposite?\" is a very good one to ask. There's an answer to your question that's a bit more concretely rooted in physics and is related to how thermodynamics and entropy work, but it's actually a bit of a dry, unsatisfying answer. I think the more satisfying answer is a bit more philosophical in nature, and it's to ask: What if time *were* going backwards? What would that feel like? Would it feel like anything? In order for time to be 'going' a certain direction, would we need to carry memories from one moment into the 'previous' one instead of the next one? It seems ike whichever direction time goes in, that's the direction which we would inevitably call \"forward\", doesn't it?",
"So we aren't entirely sure. But about a decade ago I attended a lecture by a Nobel Laureate who explained a pretty interesting theory. He claimed that time was a function of the average increase in entropy of the universe (as opposed to the average entropy increasing with time.) He claimed that time may very well flow backwards briefly, but because the universal decrease in entropy would cause all life to flow backwards, when entropy resumed its normal flow we would be completely unaware that it had ever moved differently.",
"This is one of the great unanswered questions in modern physics. We simply don't know. There are a few competing theories, but this sort of thing is very hard to test. Here's a basic explanation of one of the more popular ideas: [that time flows in the direction of increasing entropy]( URL_0 )."
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mj3qt8 | Where do the male and female organisms come from? Don't we all come from unicellular organisms and isn't it beneficial for nature to not be dependent on one of two genders to reproduce? | Biology | explainlikeimfive | {
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"The evolutionary advantage of sexual reproduction is that it enables better genetic diversity and adaptations. Asexual reproduction is mpstly advantageous when resources are abundant and there is not much need for change over the different generations.",
"What is more true of the simple is not necessarily true for the complex. For unicellular or simple organisms, asexual reproduction is generally efficient. For complex organisms, it isn't necessarily efficient. There is a cost associated with growing and maintaining reproductive organs in complex organisms. Organisms have to contest and compete in their environment - the ability to obtain energy (through food), the ability to protect itself or run away, the ability to gestate and raise their young.",
"Having different genders is a benefit. Hermaphrodites still need to exchange DNA to have healthy/fit offspring after many generations. So it often ends up in a fight who over who gets to be the male, since the female has the tough job of producing eggs while the male counterpart can simply move on to the next mating. With fixed genders that isn't an issue, so the costly fighting is skipped. It originally formed as two closely related organisms specializing in different forms of reproduction, one made lots of small offspring where only the toughest survived, the other made one big and sturdy offspring with lots of ressources invested. And then somehow they mutated to be able to combine DNA wich allowed to combine the benefits of both methods. It basically started as two symbiotic \"species\""
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mj3vlb | Why does weed make music, food, and orgasms better? | Pretty simple question, really. Anyone who has experienced weed or knows much about it knows that these 3 things are amplified under the influence. I don't understand the psychological/physiological mechanisms behind these tangible effects. I guess it would be worth asking why it makes people paranoid, as well. Truth be told I don't really understand how drugs or intoxicants in general affect people as it relates to the changes their bodies/brains undergo while under the influence. | Biology | explainlikeimfive | {
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"Disclaimer: I don't know the real neurological basis behind this, and this answer could be wrong or incomplete. I'm getting this from the Pollan book \"How to change your mind\". During normal waking consciousness, your brain works in a kind of routine way. Your brain cells tend to work in networks: when one stimulus is present, it associates with responses in a habitual way. This is what Pollan calls the 'default mode network'. What psychedelics do, and the change of consciousness that comes with them, is get you out of these deep routine tracks. Where before, your brain responded to a stimulus (music, food, orgasms, ...) in a standard way, almost a conceptual way (I know this music, I know this sensation, I know this taste, ...), being outside this default mode network gets you out of the concept, and into a more direct experience of the stimulus. The layer of habitual thoughts, analysis, comparisons, labels, judgment, memory, etc... your mind makes up and has gotten used to, has diminished, and what remains now is a more direct experience which for example Buddhists practice (mindfulness), (and which I believe was the original point of spirituality and religion). It's the difference between \"looking at the menu\" and \"eating the meal\"."
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mj43ud | How do we know the weight of objects in space when we have no physical way of weighing them? | I just saw that apparently the whole of Saturn could float in a bathtub or something. How could we possibly know such a thing? Edit: sorry for the uh technical error haha, I realised too late that I put weight but I did indeed mean mass, my bad I wrote this post after just waking up. | Physics | explainlikeimfive | {
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"We can see moons of Saturn going around it, and can measure their periods. We've determined the distance to Saturn, so we can calculate the size of their orbits, and the diameter of the planet. Using Newton's law of gravity, we can calculate the mass of the planet, and thus the overall density (mass divided by volume) of the planet. It works out to be less than that of water, though of course the density varies with depth in the planet.",
"Not to get pedantic here, but rather for your education, I feel I should mention that \"weight\" refers to the amount of force acting on an object, which depends on a number of factors. What you are really asking is how we know the *mass* of an object.",
"First of all, it is not the weight of something that determines whether it floats (e.g. in water) or not, it is the *density*, i.e. the mass in relation to size. The mass can be inferred from a lot of observations, as others here have already said, including the movements of other nearby objects (like, moons). We can also observe the size of these bodies – at least for the planets, it is a bit harder for faraway stars – and with these two parameters it is possible to calculate the density. For the “gas giant” planets, the average density is indeed lower than water (i.e. it would float). But that does not mean that any bit of Neptune or Saturn brought to Earth would actually “float”. As the name says, these are giant blobs of gas, so most of it would rather fly away ... and in their cores the gas is so much compressed that it may actually be much denser than water and sink – except that in Earth’s atmosphere that pressure would be gone and it would turn to gas again... all in all, this “floats in water” thing is more a way of communicating that they have a relatively low density, not something that one could actually do."
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mj4k0m | Why are rechargeable batteries only 1.2V? | A lot of devices expect 1.5V batteries and report 1.2V rechargeables as empty sooner. Wouldn’t it be better to make rechargeables 1.5V as well? What is preventing that to happen? | Technology | explainlikeimfive | {
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"The voltage generated in a battery is due to specific chemical reactions between the electrodes and the dielectric. This is more or less predetermined by what the battery is made of. There are other features more important in a battery - safety, reliability/rechargeability, size and energy density, current carrying capacity, cost etc. Modern commercial batteries have to optimize the above. The voltage is a very very minor issue ultimately because voltages are easily and efficiently adjusted by external circuitry. There is essentially no point to making a battery $10 more expensive just to try to eliminate $1 worth of external circuitry.",
"It's because of battery chemistry. The voltage of a battery depends on the 2 reaction partners inside the battery. While the material used in non rechargeable batteries is delivering a higher voltage, it is reacting in a way that can't be reversed (you could recharge it theoretically, but you cant do it often, and it's VERY DANGEROUS so DON'T do it.). A rechargeable one is like water ice. You can melt it, and freeze it back without quality loss. A non rechargeable battery is like ice cream: you can melt it, but if you try to freeze it back in, it's becoming a hard block of frozen milk. But sometimes you just want Ice cream and not an ice cube. So you have both. Why electronics need that bit higher voltage? I honestly don't know. It may be a spacing/comfort/engineering reason. Maybe a monopoly. That's a question to another person.",
"The choosen battery materials define its voltage and through packaging batteries together you can only end up on integer multiples of this voltage. Rechargeable batteries use different materials than none-rechargeables which leads to the difference of 0.3V. So it would either be 1.2V or 2.4V for the rechargeable.",
"Voltage depends on the battery chemistry. Though alkalines run out of energy around 0.8v, and most 1.2v rechargeables provide all their usable energy by that point as well. It's possible your device has a cutoff voltage too high even for alkalines, or your rechargeable batteries just have a very low energy density. Are they NiCd?"
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mj53g6 | why worriedness can cause physical issue like lose of appetite, feeling nauseous, fast heartbeat? | Biology | explainlikeimfive | {
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"It’s just the fight or flight response. The part of the brain responsible for the response is quite primitive, it doesn’t know why you’re worried, it just assumes you’re in danger and prepares your body to fight or flee, even though it may not be necessary."
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mj5doq | What exactly causes the "pregnancy craving"? | It surprises me that it suddenly occurs for specific fruit or food, I don't think it's just for sugar. All fruits(?) have sugar but pregnant lady suddenly want a specific fruit like watermelon & plum etc, any other fruit can't replace it | Biology | explainlikeimfive | {
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"Everyone's brain makes a substance called Neuropeptide Y (NPY). NPY is known as one of the most potent appetite stimulants, and recent research has suggested that NPY production is increased in pregnancy. This growing appetite may be responsible for some pregnancy cravings.",
"When a baby is growing, it takes all vitamins and minerals it needs from the mother’s body. Cravings are often caused by shortages of something. Not all cravings will actually solve the deficiency, though. Pregnancy pica (eating inedible or non-food objects) is a real thing. A common example is for pregnant women to crave frozen water when they are iron deficient. In general, if you really crave some food, it likely contains something you desperately need. (As long as it’s not inedible, you’re good.)"
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mj5wai | Why are we recommended to wash vegetables/fruit before we eat it? | Biology | explainlikeimfive | {
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"Farmers use pesticides and other chemicals during the farming process. These can be dangerous to consume. Additionally; bugs, slugs and the like when ingested can cause illness and also not taste very nice. It is therefore recommended that before consuming, pieces of fruit, veg and salad etc should be rinsed well so as to not cause illness. * Also contamination can occur in the place of sale such as colds, flu and I can't think of another illness which might spread easily from person we should be mindful of at the moment :)"
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mj6mgr | Why did the UK choose to devalue its currency in 1949 by 30%, taking it from $4.03 to $2.80 overnight. | Economics | explainlikeimfive | {
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"I don't know about that specific situation, but the reason to devalue a currency is typically to get the economy out of a crisis. When your currency is cheap, then your products are cheap in other countries, so your export demand increases (at the cost of more expensive imports). That helps stimulate the local industry",
"When you have fixed exchange rates, you'll sometimes have to adjust them based on economic conditions, since the market can't do that itself. In fact if you don't, sooner or later reality will force you to. Post war, Britain was heavily indebted to the USA. Despite a soft loan agreement with repayments over fifty years, the pound remained once again under intense pressure In 1949 Stafford Cripps devalued the pound by over 30%, giving a rate of $2.80.",
"Britain was on its arse after World War II. The infrastructure of the country had been depleted and hadn’t been invested in for the length of the war and Britain had had to borrow huge amounts of money from the US under the Lend-Lease programme. The only option was to put the industrial powerhouse of the nation to work and to export as much as humanly possible to generate a surplus of payments. It was necessary to devalue the currency so that British products were attractively affordable overseas."
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mj6yj9 | Why is cocaine bad for you? | So I have this friend who does cocaine socially, he's not addicted I don't think but only does it when out at a club or a house party. So I was talking to him about it and he is pretty self convinced its not bad for you and just enhances your mood when drinking and makes your night better and to be honest I couldn't have a debate as I know nothing about it so can anyone enlighten to me as to why is it bad for you? | Biology | explainlikeimfive | {
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"Basically it constricts your blood vessels and causes your heart to pump faster. Like squeezing a hose and make more water pump though it. Fine every now and again but if you’re doing that regularly the hose is going to get damaged. Particularly at the area that the water first goes in because it’s taking the brunt of the pressure. Over time it can lead to blood vessels bursting and that’s why many people who do lots of cocaine over long periods of time, end up with coke bloat. They end up all puffy and red in the face and generally overweight. Despite the initial loss in appetite that cocaine has and the weight loss people first see, long term users nearly always end up bloated. It can also cause a thing called pericarditis, which is an inflammation of the muscle that covers the outside of your heart. This can lead to hospitalisation at best, or death from a heart attack at worse. I have had three friends that have been hospitalised from pericarditis and one friend that had to go to a psych-ward for hearing people that didn’t exist because he had been out for months on end doing drugs at parties. TLDR: If you do it once every now and again you’re going to damage your body but that’s true of any drug. If you are out doing cocaine once a week or more, you’re going to do long lasting damage to your heart and central nervous system, which is going to leave you in need of either psychological or medical attention. I’ve seen it too many times.",
"“Just enhances” is how most start the journey into altered states on different drugs. For some reason, your friend is not content with how he may participate in those social settings without using cocaine. And so to cope, he is on that journey now. Cocaine is addictive. I did it for some years and gradually increased because it felt soooo good. Also, I lived in Puerto Rico at that time and it was more accessible to me: money wise and location wise. Add to that, I shared it with my then partner, and doing that kind of cements even more the attachment to an addictive substance. If someone is with us doing it, then we’re okay right? (Is the thinking mind) When I moved to Texas with my partner, we tried to find some but it was expensive and not easily accessible. In turn, this helped me to break away from it. (Down the road though, other drugs came into play and crumbled our relationship slowly but surely). *No longer with him, I thank God every day* So now, let me explain my own trips on cocaine. For some time now, after leaving that relationship, I grew to understand more of myself in different aspects. Namely, that I am a neurodivergent individual - I identify heavily with ADD (hyperactive representation) and ASD (high functioning end of spectrum - the term “high functioning” is misleading by the way). Research still ongoing, I understand much more of my life now the more I look into this. Why do I mention it? When I used cocaine back then, for this FIRST TIME in my life my thoughts didn’t race so much ahead of my ability to speak and sustain conversations without so many tangents. Focus is everything! And why so many of us keep “failing” under society’s standards (mostly built on neurotypical perspective). To have that focus while hanging with my partner and being able to delve deeper into conversation (= bonding) was gold for me. If I could do this well on a few snorts, then the rest of my life could benefit as well from this “enhanced me”. For neurotypicals who might engage in cocaine use, they might feel “speed up” or faster than normal. From my experience, I felt calmer in my mind and therefore, more alert and able to last a night hanging out and socializing and being all around confident in myself. Strangely, this same calm feeling came over me when I first tried Adderall, secondhand. I trusted back then a coworker and took it without question. (I don’t recommend this though!). After watching the documentary Take Your Pills on Netflix, I understand then the eerie similarities of the components between cocaine and Adderall. It’s a whole thing, hope you watch the doc. To conclude, I haven’t used cocaine in years and do not surround myself with others in the at world, because my priorities for my life are different. I would be able to say No if someone offered me some. But I do remember the feeling of beautifully managing my own attention and for that alone, I stay away from this drug, knowing its hook on me. I wrote all this because of my own experience. I am no doctor, psychiatrist or physician, so take what you will and leave the rest. For me, ultimately, it was important for me to tell you this NOW. I would not wish you to get entangled into cocaine, no matter what your friend might say about it. Please know there are healthier ways to manage your doubts, fears or insecurities to better nourish your self in long lasting ways, not ephemeral. Take care, stranger. Stay safe and stay inspired.",
"I'm no expert on anything however I am a recoving addict. Not everyone gets addicted to substances, I have friends who still use drugs socially (10 years on from when we started) but some people do get addicted to substances. Addiction is horrible, it takes away everything from you. Thats one bad thing that could come from coke use. Have a wonderful day 😘",
"Because it's a central nervous system stimulant. And the nose is a mucossl membrane, which means it's essentially sponge like and can secrete and absorb. So coke hits the nose and is instantly absorbed into the blood stream. Whereas things like pills take time because it needs to be digested and processed by the kidneys and livers. Of course cocaine is bad for you lol. I used to talk MDMA \"socially\" only when I partied. Turns out, there were a lot of parties lol.",
"It’s highly addictive and if you’re being dumb that night you can overdose. I’ve done coke plenty of times, just gotta be careful who you do your drugs around really. Im sure it’s probably not good for your nose either",
"It's pretty addictive and can harm your body in a number of ways. It's one of those things where if you do it a lot it's really bad for you, but if you occasionally use it like your friend does and don't get addicted you're probably going to be fine."
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mj6zx2 | what is fuzzy logic? | Mathematics | explainlikeimfive | {
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"Hi. I dont work IT so someone else can do a better job here than me, but generally its trying to vaguely match similar things. Like matching car make toyota to toyo, or matching civic coupe to civic coupe 2 door. Traditionally in joins or vlookups you need an exact match, fuzzy logic instead is looking for the most similar matches and assigns a score based on how similar the match is. There are many methods and softwares, and you assign a maximum score threshold or a maximum number of matches. They are ideally used in situations of user inputs to get through keystroke errors, or trying to match data from 2 different sources with different formatting in my experience. Resulting matches need to be monitored in lower similarity scored matches. Now I cant speak to too many types or how they are used today, but trying to match peoples inputs of name to say vehicle driving history reports could be a common use, or i think the address suggestions you get from address inputs use it too against melissa data. For example my street is a 101 crossing, and that always gets flagged for 101 xing online. I can use it to turn a week long job to a few days and cut down about 50% of manual research work consistently, while tossing the other 50% of results as unacceptable. Hope that helps."
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mj70p9 | what is chaos theory, and what is it used for? | Please no butterfly analogies. | Mathematics | explainlikeimfive | {
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"Quantum magic aside, if you have 100% knowledge about state of system, you should be able to predict its future using physics. In practice, you never have 100%, you are limited by the accuracy of measurements you can take. Usually, this is good enough. Approximate information about the system allows us to make approximate predictions. For example, we may be able to predict that a cannonball will fly somewhere between 100-110m. We would know the exact number if we knew how every single air particle it hits on its way is behaving, which we don't. But on the whole, it's a useful prediction. However, if a system is chaotic, predictions based on approximate data will not just be mildly inaccurate, they will be so wildly random they are basically useless. For example, the movement of single grain of sand in a sandstorm. It's so light and surrounded by so many particles of similar size bumping into it, a tiny variation will send it off on a completely different course. It's pointless to even try guessing where it ends up. Some systems fall somewhere in-between: in short term, we can make reasonably good prediction, but the accuracy steeply falls off with longer-term predictions, until the system becomes completely chaotic. Examples of such systems are weather and the movements of celestial objects. & #x200B; Edit: u/bluebell_sugarslay raises good points in [his comment]( URL_0 ). I maintain my example is correct, though, if my explanation is a bit lacking. If we were talking about a single grain riding an invisible predetermined roller-coaster, so to speak, the system would indeed not be chaotic despite its complexity. However, the many grains of sand and air molecules themselves in a sandstorm interact with each other constantly, which I believe does make the system chaotic.",
"URL_0 This gif probably shows it best. Three double pendulums, starting at almost exactly the same state, will have wildly different speeds and locations only a few seconds in. Chaos theory, in a nutshell, is the study of how such systems behave, including but not limited to: * When/how fast such systems diverge (for example, the pendulum example is mostly similar for the first few seconds) * When they *don't* diverge (because many chaotic systems only have regions where it is chaotic; going back to the pendulum, 3 pendulums starting close to the bottom obviously is not chaotic) * How strongly such systems diverge, with respect to differences in the starting condition",
"Chaos theory is the theory that there exist certain mathematical and indeed natural systems that are highly erratic and diverse, to the point where they may seem to be totally random, but are in fact entirely predicted by the underlying equations. A [double pendulum]( URL_0 ) is one such system, a [dripping tap]( URL_2 ) is another. The issue is when such systems exist then an absolutely tiny change to the initial conditions can have massive effects. Two almost identical double pendulums will have completely different motions for example, or the absolute tiniest difference in how tight a tap is closed will be the difference between different drip patterns and indeed whether the pattern is regular or erratic. Chaos theory has multiple uses. For example most modern cryptography is based upon mathematical processes that produce radically different and thus impossible to guess outcomes but which can be recreated if you have the exact initial conditions. In other words you need a system that looks random but isn't. Which is what Chaos is. Various systems in biology and economics also involve chaotic behaviour: it looks random and is exceptionally difficult to predict, but it is responding to underlying equations, it's just that those equations are highly chaotic. Finally chaos theory is useful at the interphase between physics and philosophy to explain how our universe can be entirely deterministic (ie the end result of various knowable physical processes) but also contain such diversity and unpredictability. Tiny changes in the initial condition of different parts of the big bang can produce all the diversity that is the universe we see. And combine chaos theory and [Heisenberg's uncertainty theory]( URL_1 ) which holds that it is impossible to perfectly measure the initial conditions, because on a quantum level you change the conditions by trying to measure them, and what you're left with is an explanation of how the universe can be completely impossible to predict, and yet fully explained by laws that we understand.",
"It is used mostly in mathematics to explain systems that are highly sensible to early conditions. Imagine throwing a marble from the exact same point 1 million times. The conditions of air resistance and other variables will change the course of the marble every time. Chaos theory is just that, scenarios that by having just slight early changes lead to completly different outcomes. Its studied because it can help us understand aerodynamics and particule movement more precisely",
"Holy hell, these answers are not what I would tell a 5 year old. In science and especially physics, we expect the same result if we do the same thing, and if I do two similar physical things, I expect similar things to happen as a result. If I put a bucket filled with water on a seesaw, the seesaw moves down; if I put a heavier bucket on a seesaw, I expect it to move down faster; if I throw a ball to my friend, it goes to them, if I throw it a little bit to the left, I expect the ball to go a little bit to the left. If something is “chaotic”, I might throw the ball a little bit to the left, and then the wind takes it and makes it sail off in some other direction. I can look at how the wind changes where the ball was going to go and say “yes, I can see why it did this very different thing”, and I could've done a better job predicting where the ball would go if I measured the wind, but we would not ordinarily expect the outcome to be so different from such a small change, even though we can account for the changes. ELI10 A chaotic system is something where tiny changes lead to very different outcomes. The classic example is this, [a double pendulum]( URL_0 ). That gif traces how the pendulum moves over time. The two start at virtually the exact same position, when I release them and let physics take over, I can calculate where they will be exactly at every second, and briefly they look the same because of how similar their initial conditions were, but that small change snowballs, and very quickly the two follow very different paths. That is chaotic. As for how is it used, there are a variety of systems to measure how chaotic a system is. A lot of natural processes we care about are chaotic, like the weather, so understanding the math of chaos helps us understand those processes.",
"Life....uh finds a way Chaos theory in ELI5 terms states that there is an order to seemingly random situations...every outcome is determined by a hell of a lot of variables",
"Consider the difference between dropping a bowling ball from the 10th floor and dropping a small feather from a the 10th floor. In the first case you should be able to predict the landing spot to a meter even if you're dropping the bowling ball by hand. You could quite easily improve the accuracy by dropping the ball with a robot arm or waiting till the wind is down. You can drop the ball from a higher place and the calculations won't be much more complicated. If you control the conditions to a reasonable precision, your result will be reasonably precise. In the second case, you'd be lucky if the feather landed at the feet of the building you're dropping the feather from. You can't even predict the landing spot with very complicated computer models. Even if you control the conditions to a really good precision - dropping the feather inside a big building to reduce wind, using a robot arm to drop the feather - your result will be wildly inaccurate. You can't control the conditions well enough to get reasonably good precision. The first system can be predicted with pretty simple models. The second one needs to be so precise that it's practically impossible to predict.",
"In complex systems, a slight change in the system's input can give very different results. Take playing a game of pool as an example. The cue ball and all the other balls are ideally in the same places when you start the game. If you try to hit the triangle of balls in the same place when you start the game, you'll probably see most of the balls move very differently each time. This is an example of chaos theory in action. The subtle difference in how hard you hit the cue ball, how the balls in the triangle are slightly in different places each time you play, and a number of other things all snowball together to give you a very different pattern of how all the balls move around the table, even though your game's setup was so very similar to every other time you set up a game. Where this really builds up complexity is when the balls start bouncing off the sides of the table after the first hit sends them flying. A slight difference in speed and direction will cause balls to bounce off each other at different angles and sides, or even cause totally different balls to bounce off each other. This means that near the start, all pool games you play are very similar. Even after you hit the cue ball and it hits the triangle of balls, you'll still be mostly the same as every other game you've played. It's the complexity of all the balls bouncing around and off each other that very quickly turns small differences into bigger and bigger ones.",
"I recently had to explain this to my 10 year-old as we received a chaos engine from Kiwicrate. What I said was the idea behind chaos theory is the tiniest, unknowable variations at the start of a process can magnify until they have massive consequences at the end. Having the chaos engine I could demonstrate that even if we held the arms in what looked like exactly the same way we'd never be able to replicate the shapes it made thanks to tiny variations in weight distribution, even air currents and bearing heat etc. She loved it. URL_0",
"In general, scientists are in the business of predicting what will happen to a system based on initial conditions. This could mean predicting where a rocket will go if it's launched, or what chemical reactions will occur if things are mixed, et cetera. Some systems are Chaotic, which means the result is wildly different depending on tiny changes to the initial conditions. Imagine putting a marble in a box and shaking it up. You could start the marble in the (almost) same position every time, and you could use a robot to shake the box the (almost) exact same way each time, but the marble is going to end up literally anywhere in the box each time and it will be very hard to predict where it will land with even the smallest bit of certainty. It comes down to the fact that we lack the technology to do anything *exactly* the same two times (indeed, it might be literally impossible). Some systems (ones that aren't chaotic) won't care about tiny tiny differences and you will be able to predict them. Other systems, the ones that are chaotic, are immune to traditional methods and so a new theory was developed to try to predict them. Chaos theory is just the name for everything we know about predicting the behavior of chaotic systems. It's used because there are a lot of chaotic systems that matter in the world and we want to know what they will do. An example of a practical use of chaos theory is making weather predictions.",
"Does Dr. malcom even make any sort of sense in Jurassic Park or am I an idiot? Because that scene with the water droplet scene always seemed nonsensical to me",
"Chaos theory talk about a deterministic system highly sensitive to initial conditions. Explanation of those word below A system is pretty much anything. The weather is a system, throwing a ball is a system, a mathematical function is a system. As long as it can be seen as having inputs and outputs then it's a system. Deterministic just means not random. As long as exactly the same inputs are used, the output will always be the same. Addition is deterministic, because adding the same two numbers always gives the same result. The initial conditions are just the inputs to the system. In addition that would be the numbers you are summing, in the weather that would be the properties of every air molecule, all of the ground, some of space and other besides. The highly sensitive part is where the chaos in chaos theory comes from. It means that any change in initial conditions, however small, has a very large change in the result. If you're adding two numbers together, and increase one of them by 2, then the result will be 2 bigger. The change in the result wasn't significantly larger than the change in the initial conditions. Weather prediction is a chaotic system. You'll never see a prediction for much for than a week in advance, because predicting further than that is very inaccurate. Slightly warmer air in one garden from one bonfire can cause huge changes in the weather a week down the line. Another example is the double pendulum. If you attach a weight to a string, then that's a single pendulum. If you drop it somewhere then it will swing back and forth very predictably. If you then hang a second weight from the first weight however then it becomes very complicated. The weights will swing around seemingly randomly. If you make one weight slightly heavier then it will swing around in a completely different way. That's chaotic, so is chaos theory.",
"Please no butterfly analogies...it isn't an analogy. The butterfly effect is quite literally the common explanation. & #x200B; Chaos theory pretty much boils down to 'nothing exists in a pure vacuum free from all outside influence' while something works on paper 100% of the time in reality a spec of dust can snowball the results of an experiment to something completely 'wrong'. A slight deviation caused by wind pressure can mean you need more fuel to keep the airplane flying, which means you need to include more fuel when it is on the ground, which means you need more fuel available which . . . and so on.",
"The longer in the future you try to predict,the bigger the chance of you being wrong is. I think thats it",
"Minecraft. Generate multiple new worlds. Enter the same 10 digit seed number, but change the last digit by 1 each time. Explore each world and revel in how different they are. It’s the same computer code to build each world, but the input (seed) is slightly different. Now imagine it’s a tropical storm in the Atlantic. They are all built the same way, but some become hurricanes and some putter out. Studying why this happens can help save lives.",
"Great podcast episode here that made it easy for me to understand [ URL_0 ]( URL_0 )",
"There are MANY very bright folks on here, who also how to explain what they know to other people not as knowledgeable. And then they’re willing to do it, without being paid. That’s a wonderful thing. Pay attention to people like that.",
"Chaos science is the study of how organizes systems breakdown over time. Chaos theory states that in all seemingly chaotic events, patterns of order emerge. Think of chaos theory like a yin yang. Orderly systems are always moving towards a state of chaos, chaos always inevitably forms patterns of order.",
"Paraphrased from chaos by James gleick - and amazing book!! In complex turbulent simulations - like cold milk pouring into hot coffee it’s impossible to tell at any time what the temperature is at any point inside the liquid But step back - wait an hour and you’ll be able to tell exactly the temp at every point - it will be room temperature Apply this logic to all complex systems - stand back and take the wider view to make good long term decisions.",
"When you’re running a complex computer simulation with many different factors, small scale changes in initial conditions can lead to large scale changes in final outcomes, making prediction possible, but limited in scope and fundamentally based on probability. In chaos theory, you try to make your models better by accounting for the unaccountable. Your models are fallible, but honest. Because all models are fallible. There’s a parallel phrase in Daoism: The Dao that can be spoken is not the eternal Dao. Chaos theory is also closely related to the second law of thermodynamics and its application to information theory. All information is in flux, as is our ability to measure it.",
"I try a true ELI5: you know, when you drop a ball, it will drop on a flat floor and bounce up. If you repeat this, it does not reaaaaally depend a lot on that you do everything correct. roughly the same position and roughly the same height will give you a similar bounce. now think about a floor that has a lot of wiggles, the ball will bounce and the direction it bounces of will depend on where it drops on the wiggles. Sometimes it will bounce high up, sometimes it will jump away. If you want to repeat a bounce, you have to be quite exact that you hit the right wiggle and at the same spot. But if wiggles are still large enough, you can do this with practice. Some things are like this but with really fine wiggles and a very small ball. now it gets tricky to repeat a bounce and even if you try very hard, you might not be able to repeat a bounce. We still need to understand problems like these, and Chaos theory is a way to describe problems where we can't repeat an experiment exactly because we can't be precise enough.",
"Chaos Theory is essentially studying equations where the assumption that changing the equation a small amount will lead to a small change in the result is broken. The goal is to determine where this starts to happen. If you do some sort of experiment, you'd expect that if you repeat the experiment with the starting point altered slightly, then you'd get a slightly different result. Chaotic systems don't follow that. The first sort of step is finding things called bifurcations. Imagine there's an equation that tells you the elevation of your next step, based on the elevation of your current step, while walking on uneven ground. A bifurcation would occur if there was a cliff for you to step off of. One step back, and the difference between the elevation of your feet would be small. Step off the cliff, huge change. An actual example of a bifurcated system would be a rocket trying to escape from Earth's gravity. Below escape velocity, the rocket comes back down to earth. Above it, it goes off into space. A chaotic system has a certain point where you start getting those sudden huge changes *everywhere*. It might not be immediate, but changing one of those parameters, or where you start out, will lead to a result that you *cannot* predict just by knowing what happened when you started out close to it. Source:BScH in Mathematical Physics, MSc in Applied Math.",
"I'm seeing a lot of comments that have the basic idea, but wrong or misleading examples. Here is my go at it. But this is more line an ELI- 13 if only because I know my five year old wouldn't read all this. Chaos theory describes an area of mathematics that studies a specific kind of mathematical model. Math models are sometimes used to describe or predict events (like projectile motion -- the path of a tossed ball, or weather). Sometimes mathematicians study models just because of interesting properties. They do not always have a physical application. In the case of the models studied as a part of chaos theory (aka chaotic dynamic systems), they have a special property: small differences in the starting conditions result in large differences in the results. **Example 1)** Weather -- As others have pointed out: this is why long term predictions are mostly useless. The problem is that we can never measure the exact conditions (temperature, humidity, wind direction and speed, etc.) everywhere at any moment. As mentioned by [Tejaansh\\_sara]( URL_1 ), James Gleik's \"Chaos\" is a good one. It has a really great story at the beginning regarding this particular problem. **Non-Example 1)** Projectile motion is not a chaotic dynamic system. Differences in outcomes due to errors in initial conditions are predictable. This doesn't mean there will be no error in our calculation. This means that we can meaningfully predict the end result of the system and calculate a reasonable error margin on the prediction. However, error is not chaos. **The chaos in a chaotic dynamic systems is not due to difficulties or impossibility in measurement!** This is a really important point (if you couldn't tell by my exclamation point and bold), and what most examples I am reading here are missing. Even if we know the exact beginning state of chaotic dynamic system (and we can in the case of the next example), changing one small tiny itsy bitsy part of it results in big changes. **Example 2)** Pseudorandom number generator (PRNG). Randomness is a big deal behind the scenes in our society. It's used to encrypt everything online as an example. This makes generating random numbers a really important problem in mathematics. It's also a very hard problem because math is deterministic, meaning -- if you know the input, you can calculate the output. That bit contradicts randomness. One solution is to use a purely numeric chaotic dynamic system, which we call a pseudorandom number generator, keeping the initial conditions (called a seed value) a secret. Note that the pseudo in pseudorandom means it is \"fake\" randomness. This is precisely because it is still a deterministic system. The same seed value will result in the same series. However, in a good PRNG, even if someone is able to view a sequence of output values (but not the seed), they still would not be able to predict the next values. (This is an oversimplification, different PRNGs have different properties depending on what you need them for. More on that in my [other comment]( URL_0 ).) This example is interesting because you can see that the chaos is not a result of errors in measurement, but instead a property of the system being modeled. **Other cool resources:** [Robert L. Devaney's Chaos, Fractals and Dynamics]( URL_2 ) \\- It's long, but worth it, even if only for the (80s-90s?) graphics and his transparency slide \"iterator\". This is more like ELI - high school. Devaney shows Fractals -- striking visualizations of chaotic systems -- and gives examples of applications of these systems. He also shows a very simple equation that can be used as a PRNG. [ URL_4 ]( URL_3 ) \\- Is creating randomness really that hard? This website does provide true randomness, lets you generate some randomness of your own and explains how and why this is a real problem. Super cool website."
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mj7sju | Why are so few naturally occuring things bright blue? | Physics | explainlikeimfive | {
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"Cornflower, Iris, Geraniums, Hyacinth, Morning glory, Agapanthus, flax, Buddleia, Sweet pea and many other flowers are blue, pollinators often see in ultraviolet and flowers use those colours to guide them in."
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mj7wa3 | Why haven't we started harvesting energy from the core of our planet? | I'm an absolute dunce when it comes to this, so forgive me if this is a highly pseudoscientific question, but isn't the core of the planet a high-energy source, like a mini sun just chillin at the center of our planet? Would there be any catastrophic downsides from trying to harvest the energy the core emits? | Earth Science | explainlikeimfive | {
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"They use geothermal energy in Australia but that's more like using the heat from an underground volcano Google the worlds deepest mine and compare with the thickness of earths crust and that's why It might be easier to colonize mars than drill to the core of earth",
"There aren't any catastrophic downsides, it is simply rather infeasible. The deepest hole humans have ever made, Kola borehole is 12 km deep. The earth's radius is 6,500 km. Relative to human construction, the earth is very very large. Of course, we don't need to go anywhere near the core to extract useful energy. Geothermal plants around the world basically use the heat from the earth to generate power. Other than some places where this is easily accessed, the cost for doing this are very very high. It would be far cheaper to cover several large pieces of ground in solar panels to generate the required electricity. In total it would be large (\\~500,000 sq km) but that is a very small fraction of the surface area of earth (the size of the country of Egypt)"
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mj87f9 | how do robots in car factories get programmed to do tasks such as placing a door on a the car. Does a human record the actions first like a macro or are the actions written in code. | Technology | explainlikeimfive | {
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"Both ways are used. You can preprogram them, but there are also methods where a human operator moves the robot arm in a training phase to get it to the right spots and initiates the necessary action. I don't really know how common the latter is, but I have seen it done for spot-welding robots. The robot saves the path and action information and repeats it then.",
"A macro is also code, and code is what it comes down to. A robotic arm can perform a number of set movements simply by following programming that tells it to \"turn joint A by X degrees, extend piston B by Y cm, release gripper C\"... etc. The exact details are fine-tuned to the particular requirements at any given point of an assembly line."
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mj8u9p | Why is weather temperature different with the same amount of sunlight? | I live in England and notice days can have equal or even more sunlight in the day but the temperature will be lower. Why is this? | Earth Science | explainlikeimfive | {
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"Temperature isn't all to do with the amount of sunlight. The intensity of the rays vary by season so a winter day you could have a seemingly bright sunny day, but because the Earth is tilted away we receive fewer solar rays and are thus getting less energy. It also depends on wind direction. If the wind is from the north it can move a colder air mass over an area which was warmer the previous day. Vice-versa it can bring a warmer air mass from the south if blowing from that direction."
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mj9rl5 | What’s with all the fancy attachments and whatnot on the bows of professional archers? | Whenever I see an Olympic archer or really anyone who does archery professionally, their bows have a bunch of stuff sticking out from then and I’ve no clue what any of them are called or do | Other | explainlikeimfive | {
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"From looking at pictures if it’s a very long tripod looking thing that’s called the stabiliser. It helps steady the bow just like holding your arms out helps balance yourself. Other than that I see there’s a mount for a sight, it’s mounted on a pole away from the bow so you can adjust it better"
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mjar18 | Where is the bottleneck for the max speeds ISPs can provide? | Why is gigabit internet feasible in some areas/countries while 100Mb/s is premium in others? | Technology | explainlikeimfive | {
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"Some areas just don't have the infrastructure. Every single line of fiber or copper has a maximum thruput that has to satisfy every person using that line: Maximum thruput / number of customers = average max speed for each customer. To increase that, you either have to lay new lines (which is expensive - laying fiber costs between $8,500-10,000 per mile) or have bottlenecking issues when you have a ton of customers on line at once. Now, that said, much of the time the bottlenecking is artificial. ISPs without competition can reduce speeds well below their max thruput because consumers don't have a choice but to accept that due to lack of competition.",
"Their ability, or willingness due to profit margins or competition, to invest in infrastructure. Faster speeds require each customer to have a more expensive modem, they require infrastructure to reasonably be able to maintain those speeds for thousands of customers at once. 1gig is usually the highest you see because most consumer hardware can't handle more. Commercial customers can get terabit in many locations. I have an old picture of a 900GB/s internet speed test from a place I worked."
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mjawmw | How do different strands of marijuana get you different kinds of high? | Biology | explainlikeimfive | {
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"I think you meant strains. For a more accurate indicator, look at the terpenes. These are what determines the taste and effects of the particular strain. The term Indica, Sativa is getting moot by the increasing cross-breeding."
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mjb7h1 | Salvador Dali's controversial 'Paranoiac-Critical Method' of creating his paintings | Other | explainlikeimfive | {
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"Dali wrote a book called 50 Secrets of Magic Craftsmanship. I bought it on a whim when I visited the Dali Museum in St. Petersburg. The book is indescribable, but I'm gonna try, OMG. He treats art very seriously, but he is unable/unwilling to describe in a concrete way how to make art. The large majority of his advice is extremely personal to him. For example, he says if you're unsure what to paint, eat some fried eggs and take a nap in a specific kind of chair (probably Galacean, as I recall) while sitting in front of sea anemones, holding a key in between your thumb and forefinger. When you fall truly asleep, the key will fall and the ding it makes on the floor will wake you up from a dream and that's what you should paint. It's simultaneously hilarious and impressive. The most fascinating thing about Dali is no one could ever tell if he was playing a part, like full-time performance art or he was just an extremely talented loon. Around WWII Dali's paintings reflected a lot of his anxieties, in real life and in dreams. The fact that he was named after his deceased older brother which made him feel like the second version of a person. His anxieties around ants and bugs, time, perception, homosexuality, feces, dictators, war, and on and on. He considered himself paranoid or anxiety-ridden and his artwork showed the things that freaked him out the most. They are panoplies of his fears, placed in ways that had personal meaning to him. His later paintings, done in the 1960s and such, reflected a more reverent beauty and majesty as he became reacquainted with the Catholic church. His paintings seem more peaceful, they show a lot of symmetry and optical illusions, clouds, more coherent images that convey serenity."
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mjcljg | why can’t people map the catacombs with sonar, radar or what ever you would use to map underground | I know sonar is water and radar is air but something like that. Idk | Earth Science | explainlikeimfive | {
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"You can use ground penetrating radar to check for voids in an underground setting, but the results from GPR are going to be rudimentary, not very good for mapping. The better way to map the area would be with 3D mapping software from inside. You take a drone with a lighting rig and a 360 camera connected to a mapping software, and you'll be able to map out the rooms as far as the drone can travel safely, preventing danger for the human operators.",
"Photogrammetry and similar methods (laser scanning, 3D cameras, etc) are sometimes used for mapping out stuff like caves or catacombs. But it's very difficult - [caves are often narrow, dark, muddy, cold and wet]( URL_0 ). Huge, walkable and dry caves from movies and games are pretty rare. More often, an explorer is waddling in chest-deep ice cold water. And equipment for scanning is usually fragile and sensitive. There's much simpler solutions that are used - for example, a common way to discover and measure a cave is to paint water. Most common types of caves are result of water tunneling in the underground, so (rain)water goes into ground somewhere and often also exits somewhere. Speleologists (cave scientists) dump a bunch of dye in a lake or river, go to the assumed exit point (usually a spring of some kind) and wait. Once colored water turns out in the exit, you can make all sorts of predictions - if it takes many days for color to arrive, there has to be a long cave. If the color is weak, there's probably a giant underground lake that diluted the dye a lot (sign of a big cave). Sometimes colored water reappears in totally different body of water, so you can imagine which way the cave goes, or perhaps it splits into two at some point. And so forth."
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mjd1ps | Are horses born on farms naturally more docile than horses born in the wild? | I grew up watching a lot of westerns and some of the classic scenes are cowboys "breaking" wild horses so that they can be saddled and ridden. I'm wondering if horses born on a farm are generally more docile than wild horses because previous generations have been tamed. Or do horses all need to be broken if they are to be ridden? | Biology | explainlikeimfive | {
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"\"Break\" is a terrible term. It just means \"teach to accept a person on their back\". Even horses born on farms need to be taught this. But some of them do learn it easier than others. And some trainers teach it better than others. The \"brute force\" method that cowboy movies favor is actually a terrible idea. Even a farm-born horse would object to that nonsense. But the reverse is also true. You can use more rational training methods, and teach a mustang to accept a rider (so, \"break\" it) without it ever bucking or objecting. In the USA we don't have any \"wild\" horses per se. Our mustangs were all descended from domesticated horses. So they're more like \"feral\" than truly \"wild\" and they actually train into some really good, alert, intelligent partner horses. (They're like comparing street-born stray dogs to house dogs. Same genetics, different life experiences.) Truly \"wild\" horses like from the plains of central Asia are not descended from domesticated horses though. Their instincts are not the instincts of domesticated animals. They can be \"tamed\" but their behavior is a lot more oriented to wild than captive living. (Like comparing wolves to dogs.)"
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mje1vp | how did scientists determine the real flow of Electrons in a circuit? | I understand there use to be a different theory on the flow. But how did scientists determine the correct flow of electrons in a circuit? Do they have powerful microscope 🔬 that can see the electrons moving at the speed of light? What? | Physics | explainlikeimfive | {
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"Lol, so you've stumbled across a weird quirk of electronics. Electrons *do not* move at the speed of light. In fact, the electrons in a live circuit move at ~1 cm/s. It's just that they all start moving at around the same time, so it seems like they're that fast. As for the history, the answer is that James Clark Maxwell, and many others were very smart, and Maxwell made his theory for electrodynamics using a bunch of complex differential equations, which showed that the drift velocity of electrons under the E field created in a circuit is fairly low."
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mje2l0 | What makes the difference between sharp and dull pain? | Obviously, anyone can only speak of personal experience on the topic of pain, but I have had near-debilitating pain that I still considered dull, and negligible ones that were definitely harp, so it is not the degree. I have also had metaphorical lightning bolts shoot through my skull from a bad tooth that was still definitely sharp, and small pricks that were dull, so I'm not sure it is the area of effect either. | Biology | explainlikeimfive | {
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"So I explained this in a recent post. Basically, the body has 2 distinct pain pathways. Path 1 comprises thick nerve fibres which allow nerve impulses to travel directly to an area of the brain called the somatosensory cortex. The pain is immediate, sharp, and the body reacts quickly to protect itself. Path 2 has thinner fibres which transmit slowly, and terminate in many different parts of the brain. The pain experienced from this path is dull, burning and long lasting. Think about when you last stubbed your toe - there was a sudden shock, then a few seconds whilst you prepared yourself for the agony waves to come. Same difference here - sharp pain is type A fast fibres firing, dull is type C slow fibres.",
"A sharp pain is sudden, short and intense — like a lightening bolt. Usually, they’re quite painful, but they don’t have to be. A dull pain is (usually) longer lasting, perhaps chronic. You may have a “dull” pain with bursts of “sharp” pain throughout. Edit to add: Intense doesn’t need to mean painful. You can have an intense ache, for example. Dull pain can be an example of that, too."
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mjeock | Why do materials such as silk disintegrate so quickly when sealed ancient tombs are opened? | Other | explainlikeimfive | {
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"The materials in the tomb have gradually decayed such that they are *extremely* delicate. However with the tomb sealed there isn't anything to cause them to fall apart other than their own weight, so they can still be seemingly intact while even a tiny disturbance would cause them to disintegrate. When the tomb is opened it allows a lot of disturbances inside. There is air movement that didn't happen before, there is moisture, there is even just *light* that can cause chemical reactions in the materials. A very delicate material right on the edge of falling apart on its own can easily be pushed over the edge."
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mjf60j | How do big corporations (Nike, Amazon, etc) avoid paying federal taxes after reporting billions in profits? | Economics | explainlikeimfive | {
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"Okay you are JHC03 and you design, make and sell shoes. You have a design office in europe, a factory in china and a chain of stores in america. The first thing you do is make these all seperate companies. Your factories buys design's from your design office and your stores from your factory. Because you control the price of the design and the shoes you make because you both sell and buy them from your own companies, those prices can be whatever you want. If america has the lowest tax rate then you only pay your factory in china and your design office in europe just enough to break even so you don't have to pay taxes because you didn't make profit there. This means you get away with the lowest tax rate of the countries you operate in. Now you can register a company in the bahamas and register your brand there. In the bahamas you don't have to pay tax. Now you sell the right to design shoes with your logo to your europeans design office, the right to manufacture shoes with your logo to your chinese factory and the right to sell your shoes to your american stores for the next year. You can do that on every year on december 31st for exactly how much profit you made that year. Now you have no profit in countries where you have to pay tax and all your money free of tax in the bahamas. Its slightly more complicated in reality but with some accounting magic it comes down to this."
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mjfdka | What is Pascals triangle and why/when is it used? | Mathematics | explainlikeimfive | {
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"Pascal's triangle is just a certain \"adding pattern.\" You can construct it by starting with a single number 1, and then adding more rows of numbers below it, where each number is the sum of the numbers above it to the left, and above to the right. How is it used? Well, *that's* tricky. It's such an abstract idea - just a way of adding things to things - that it isn't really tied to one specific application or problem. Kind of like pi or the golden ratio, it's something that 'just pops up' in all kinds of unrelated fields. One very common one is used by schoolkids studying algebra: the rows in pascal's triangle correspond to the coefficients in the expansion of a binomial expression. For instance, (a+b)^2 = 1a^2 + 2ab + 1b^2. And \"1 2 1\" is the third row of Pascal's triangle. (Try expanding (a+b)^3 and see what you get!) Another fun one: If you colour the numbers in Pascal's triangle according to whether they're odd or even, you will start to see a famous fractal pattern emerge called Sierpinski's Sieve.",
"Pascals triangle is one of those quirky ideas that ended up having a lot of applications. Combinatorics and binomial expansion is probably the most prominent. Combinatorics is essentially counting; e.g. I have 12 marbles how many ways can I choose a set of 5. Binomial expansion is multiplication in hyperspeed; we can take advantage of its properties and do cool things, like evaluate square roots eg sqrt(2+1)=(2+1)^.5 etc"
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mjg482 | why when bugs bite do they tend to target a particular part of the body? (such as ankles) | Biology | explainlikeimfive | {
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"text": [
"Generally because that's where they are in the grass you're walking through and the space between your pant leg and sock/shoe is easiest access to skin"
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mjh68u | How does an ANOVA test determine the statistical difference between means of datasets? | I've looked into the formulas for this test myself and I really don't understand how taking the mean of a dataset can distinguish whether it is significantly different to another mean (ideally from another test group). I know this is probably wrong, but could you not just eye-ball it? | Mathematics | explainlikeimfive | {
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"I didn't know what ANOVA was but I looked it up, but I have a fair knowledge of statistics and can explain the idea behind the formula. First, the mean is the average of measured values of a certain variable on a sample. let's say the variable is height, and the sample is a group of 100 men, women, children, babies. The variance measures how different the values in a certain set are. Let's say we want to prove that the country is a factor that affects height. (this is our hypothesis) And we do our test on France, Germany and Italy which have very similar heights. Since the heights are similar on these 3 countries, the variance of means will be small. The sample will have a high variance because we measured people regardless of their age or sex. The F value will be small and the test unconclusive. If we now take Netherlands, China, France which have different means and thus a high \"between variance\" , and we only do measures on grown men only which means the \"within variance\" will be small, we will have a higher value of F and we can conclude that the country is a factor that affects height."
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mjh7r0 | What is the tiny *crack* that happens when you touch/move just a tiny bit things like TVs, monitors, furniture, doors after they've been untouched for a while? | Other | explainlikeimfive | {
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"If its been there for a while the dust will accumulate right around the edge of contact with the surface its stood on. The dust gets right into the tiniest gaps as all dust does and over time it gets a little sticky as a result of the temperature and humidity levels changing throughout the day. This can ve observed by just not dusting some finished countertops for a really long time. They will eventually become sticky to the touch. The crack you are hearing is the sticky dust seal breaking.",
"My computer monitors do this late at night and it’s really annoying. The temperature changes probably make the plastic shift a tiny bit. And the dust on the cracks."
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mjhjq3 | Why can't we isolate a group of chickens who have never been exposed to salmonella? | Couldn't we raise some in individual sterile environments, wash them, clean up after them, and only let them interact to breed? Then use them to breed a larger group of unexposed poultry? | Biology | explainlikeimfive | {
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"Salmonella, like most other bacteria, lives in the soil, on organisms, inside organisms, in grain, chicken, wild animals, humans, mice and everything else...",
"Bacteria grow in the gut and chickens, like all animals, eat and defecate. Can't really avoid that. There is no practical way to raise chickens in a completely sterile environment.",
"No creature can survive in a completely sterile environment without serious support. Chickens, like humans, need bacteria in their gut and skin and environment in order for them to be healthy. But removing salmonella is effectively what a lot of countries do. The moment it is found, the infected chickens are destroyed. In this way, populations of salmonella-free chickens are maintained. This doesn’t happen in America because salmonella is not legally considered a food contaminant like ecoli is."
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mjhrky | Did the aztec's ever find out the sun rose on it's own? | Other | explainlikeimfive | {
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"The Aztec people knew that the sun rose on its own. They believed that their gods demanded blood or they would rain down vengeance upon them and blot out the sun. There is a whole legend about the origin of their nation where the god flayed a princess, beginning the awful tradition of human sacrifice. The point of human sacrifice was not to make the sun rise. It was to stop the gods from preventing the sun from rising. And - no, they never found out that this wasn’t necessary."
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mjhyzb | When trading options on stocks, how is buying “deep, in the money” calls similar to shorting a stock? | Economics | explainlikeimfive | {
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"text": [
"It isn't? Purchasing far in the money calls gives you an asset that behaves very similarly to the underlying stock itself"
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mji3dj | . How do we know everything is made up of atoms if we can’t see them? How did someone get the idea that atoms make up everything? | Chemistry | explainlikeimfive | {
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"The original idea is actually really old.. Democritus came up with the concept that if you had a rock and broke it into small pieces, they could be broken into even smaller bits.. but at some point you will reach particles that can not be broken down any further. He named those particles indivisible- in Ancient Greek that’s ‘atomos’ which is where the word atom came from. Edit: Democritus not Aristotle.",
"Other people pointed out that the idea of the atom appeared a long time ago, among greek philosophers (but not exclusively). Trying to understand the world, people conjectured that reality is concrete and could be divided up to a point, the last point being the atom. So far so good, but despite the accuracy, this idea doesn't let us \"know\" that the world is made of atoms - it is just an idea. It wasn't until the 1800s that scientific evidence for the existence of the atom came about. Jonh Dalton noticed that a certain chemical element always existed in different compounds in certain whole number rations. This suggested that there is something basic and unitary behind substances. Also around the same time scientis began to realize that gasses could be modeled reasonably well if you assume that they are made of tiny particles. Brownian motion, a similar concept, was conjectured a few decades later (Einstein was responsible for proving this idea right, in 1905). By now the idea that the world was made up of very tiny individual particules was mainstream. You really don't need to see the atoms themselves to perceive some phenomenon that can be explained through their existance. Then came the discovery of the electron, late in the 19th century, by analising cathode rays (rays that come out of a highly negative part in an electrical circuit) and figuring out that they are not waves, like light, but discrete particules. Later, scientists figured out that if there is something negative in the atom, there must be something positive too, so, in comes the proton. By later measuring the mass of atoms, which didn't quite added up to simply the sum of protons and electrons, the neutron was discovery. Today, we have certain technologies that can actually produce a \"photo\" of an atom, though not quite because what we see isn't really a photo and more like a graph of the intensity of the deflection of electrons bombarded toward an atom (not a specialist in electron microscopy, there may be other types and I may be completly wrong. Even so, the way scientists used to study the atom back in the days wasn't really by taking pictures of it, but by seeing how other things interacted with it.",
"Historians of science divide atomic theory into the \"philosophical atom,\" the \"chemical atom,\" and the \"physical atom.\" The \"philosophical atom\" is the idea from Ancient Greece, attributed to Democritus. It's one answer to the question of: if you start cutting something in half, and then cut it in half again, and then in half again, and then in half again... can you cut it _infinitely_ smaller, or at some point is there some sort of \"uncuttable\" thing that defines what a substance is? Democritus said that at some level everything must be made up of some tiny uncuttable/indivisible (\"atomos\") unit. This was by and large not the most popular theory in his day; Aristotle believed that matter was infinitely divisible, and what determined one can kind matter from another was its \"essence\" and its \"qualities,\" and that there were only four elements that matter could be (air, wind, fire, earth). Fast forward to the late 18th and early 19th century, where the Chemical Revolution was taking place, and learned scientists were realizing that you could, through careful technique, isolate the individual constituents of chemicals, and find that they were quite different from what Aristotle thought. They figured out that there were dozens, if not hundreds, of specific chemically-distinct \"elements.\" John Dalton, a British chemist, then proposed a modified version of Democritus atomic idea which said that each \"element\" was a distinct atom, and that most substances were combinations of these atoms, and that would explain why you could separate, say, water (H2O) into individual gases of hydrogen and oxygen. Dalton didn't know what an atom was made of, and it wasn't clear that atoms were truly _real_ entities — as opposed to heuristics, which to say useful ideas that might not actually be true, but gave good results. This is called the \"chemical atom\" because it was a concept in chemistry, but most chemists were somewhat ambivalent as to what atoms really \"were\" and even whether they really existed in the way Dalton thought they did. Finally, in the late 19th century and early 20th century, physicists began really probing into the nature of the atom with experiments. This is the development of the \"physical atom,\" the idea of atoms as real physical objects with a structure. The physicists discovered that atoms were not in fact \"indivisible,\" but made up of smaller bits. First J.J. Thomson found that you could remove small, electrically-charged particles from atoms — these he dubbed \"corpuscles\" but everyone hated that name and instead called them \"electrons.\" Thomson believed that atoms were nothing _but_ electrons, whirling around in a vortex, and the number of electrons told you which element it was. Ernest Rutherford and his collaborators were able to show, through other experiments, that this couldn't be quite right. Rather, they found compelling data to suggest that there was a small, hard, positively-charged bit at the center of the atom that contained most of its mass, which they called its \"nucleus.\" The electrons, they believed, spun around this nucleus like moons around a planet. Rutherford further conjectured that the nucleus was made of positively-charged particles called \"protons,\" and that the number of protons told you what element you had. There were several issues with Rutherford's model, including the fact that electrons don't quite work that way. Understanding them required the development of quantum theory and quantum mechanics. By the 1930s, James Chadwick had also be able to show that their experiments made no sense unless you assumed that the nucleus also contained neutral particles he called neutrons. And thus we had a pretty good idea of the basics of atomic structure. I could continue this story — the nuclear shell model of the atom, the nature of the chemical bond, the probing into protons and neutrons to find quarks — but I think you get the point. The development of the idea of the \"physical atom\" that we consider \"the atom\" today was not a simple thing, nor was it anything to do with \"seeing\" atoms. It was about a scaffolding of different types of understanding (philosophy, chemistry, physics) and the use of both new theories and experiments that hinted at which theories were better than others to narrow down the range of possibilities. For example, Rutherford's famous \"gold foil\" experiment involved shooting radioactive particles (alpha particles) at an extremely thin foil of gold. In the Thomson model, they would just go straight through the clouds of electrons. But Rutherford found that while some of them went straight through, some of them were reflected backward at sharp angles, suggesting they were running into something hard. By doing the math as to how many were reflected back, and what angles, he was able to show that they were bouncing off something very small but very hard (the nucleus). That's a form of \"seeing\" that does not involve visible light: it is about experimental and logical inference. And as we've seen, it wasn't 100% right — it was more complicated than Rutherford's model — but it was a definite step in the right direction. Science is what you get when you pile up centuries of good steps in the right direction; the final version might not be perfect, but it's closer to the truth than any of the alternatives. I'd also note that other than Democritus, it isn't one person coming up with these ideas. It's lots of people, working in conversation with one another, working on different sorts of problems, to which different models of the atom seem to be the answer. (Even Democritus was probably not working in a vacuum; he was responding to other problems that other people had suggested.) Science is rarely actually about one guy or gal getting the idea and it being right — it's almost always about communities working on things over long periods of time, in communication with one another. We often _tell_ the story as that of a \"lone genius\" figuring everything out, but that's because it makes for a better story, not because it's true. Even the version I've given you, which reduces the whole thing down to four people or so, is missing a _lot_ of activity and a lot of research (e.g., Thomson's idea to look for the electron as a fundamental particle and declare it the _only_ subatomic particle was influenced by a previous chemist named Prout — we rarely talk about Prout, because he just put out an idea and didn't discover if it was true or not, but he had a huge influence on Thomson, and there were people who had influence on Prout, and so on)."
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mjin50 | when ice forms, why is there a whiter inner part of it? is the whole thing the same temperature? | not sure what to flair this question, sorry. | Other | explainlikeimfive | {
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"It has to do with dissolved gases, and which parts of the water froze first. A standard ice cube tray will generally freeze 'from the outside in'. A skin of solid ice forms around the outside of the cube, and the liquid water in the middle is the last to freeze. As the ice cools to freezing, its capacity for dissolved gases goes away, and these appear as little tiny bubbles in the ice. But since they're already surrounded by ice, there's nowhere for them to escape to. So: foggy ice. If ice instead freezes from the bottom upwards, as it does in many commercial ice-making machines, then there's always somewhere for those escaping gases to bubble away to, and that's how you get that nice perfectly clear restaurant ice."
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mjiouh | ... How does a helicopter flying well above my house vibrate my windows enough to make noises but nothing else does? | Other | explainlikeimfive | {
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"Every structure has a resonating frequency. If you vibrate the air at a certain rate, some things will resonate at that rate and move more than others. This is more pronounced on something flat and crystalline, like a window, and it will vibrate to a wider range of frequencies. The helicopter blade rotation is close enough to the resonating frequency to actually make the windows rattle. Or it's really close and it's literally the downdraft causing them to rattle from the pressure difference. Not sure where our hypothetical helicopter is",
"The chop-chop-chop sound that gives helicopters the name \"choppers\" is due to the airflow round each blade in turn passing the spine of the fuselage leading to the tail. So the downdraft carries a pulsating pressure wave that causes the vibration. That's why the Chinook type with its twin rotors makes that characteristic noise as the air from the two sets interact with each other and with the fuselage. Propeller aircraft have smaller blades which rotate much faster than helicopter ones, so the sound merges into a continuous one."
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mjiyz1 | Why is oil found abundantly in some areas of the Earth but not in other areas? What caused it to form where it did? | Earth Science | explainlikeimfive | {
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"It's largely because only certain areas have the right type of geology to trap oil and gas when it forms and rises towards the surface. You need a dome-shaped layer of impermeable rock where it can collect."
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mjj8vd | Why must we imagine Sisyphus happy? | This concept is explained in The Myth of Sisyphus by Albert Camus but the essay is filled with jargon. How would you explain the concept to a layperson? | Other | explainlikeimfive | {
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"There’s no reason to, which is the whole point of the thought experiment. If you could imagine him happy with an endlessly repetitive life, that would suggest that you could also be happy with a ceaseless task and endless repetition. However, if that thought drains you, then there must be something wrong with the thought experiment. The only reason to imagine Sisyphus as happy is to examine the implications of it Edit: I answered before I saw your context. Camus’ book was about Absurdism, or the struggle between searching for a meaningful life and never finding one. The only options besides meaninglessness would be a higher power or death, neither of which Camus believed in. Sisyphus got his punishment because he refused to accept death as the final end and so even in the meaningless toil, he must have been happy, because any other option would be worse in the eyes of Camus"
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mjjbpb | What is a dust devil? Can they be dangerous? How do they form? | Earth Science | explainlikeimfive | {
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"A dust devil is a mass of swirling air kinda like a small tornado. It gets its name from picking up dirt as it travels. Tornadoes form from hot and cold air masses spinning from the sky downward. Dust devils form from spinning air from the ground up. Sometimes they can cause damage; however, it is not common. Most will just mess up your hair and pelt you with dirt."
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mjjud7 | what is the big deal with voter ID and why do people don’t want it? | Other | explainlikeimfive | {
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"The issue at hand is that there are at least some individuals in such a dire financial situation that any previous identification documents they have are either lost or expired, and taking a day off to reissue them could be really difficult, and that given alternative ways of identifying oneself at a polling place they aren't exactly necessary.",
"Voter ID laws are popularly seen as unfairly targeting poor people or minorities, due to the hassle sometimes involved in procuring ID (issuance facilities may not be open at favorable times, people would have to take off of work and possibly navigate public transportation facilities), which would disenfranchise them more than it would the middle and upper classes. This is usually seen as an attempt by Republicans to stop those people from voting, with the supposed reason being that poor people and minorities vote Democrat. However, there are so many other things in life one needs ID for that requiring ID to vote isn't necessarily as burdensome as is claimed; additionally, voter ID can help maintain election integrity.",
"Very simplified version: * Voting ID laws mean, to vote, you need to show a govt ID. For most voters, this is a complete non-issue. * The goal of requiring voter IDs is to help prevent in-person voter fraud. However, in person voter fraud isn't actually an issue and there is basically ZERO in person voter fraud, with or without voter ID laws. * So, since there is no issue with what a voter ID law is supposed to do (that is prevent vote fraud, which is non existent), why have these laws at all? * For a small, but significant segment of voters, which are overwhelmingly poor and/or minorities, they do not have official govt IDs. These voters also overwhelming vote for a single party: the democrats. Like nearly all of them vote democrats. * If for any reason you wanted to make it harder for those segments to vote, there's a simple solution: enact voter ID laws. No IDs, no votes, and it will almost completely only affect one party. * Democrats tend to be against voter ID laws, as it makes it harder for their voters to vote. Republicans are generally in favor of them, as it makes it harder for people to vote for their opponents (meaning they have a better chance to win). This is not subjective or political, both sides have said straight up what their intent is with voter ID laws. Yes, if you're asking Republicans have actually said its a political issue, not to prevent fraud."
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mjkcup | Physics question | Physics | explainlikeimfive | {
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"In what context? There's a bunch of situations where electrons interact, and not all of them does the same thing happens. [For an overly simple answer where you have 2 fermion particles in an impenetrable box]( URL_0 ) you get the situation where you have an entangled wave function that's a linear combination of the original 2 wave functions. This does not take into account wave function collapse, or any other particle interactions, and is the simplest case."
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mjknzx | Why do cell towers need to be so high and large but our cell phones can reach them at ground level with a tiny antenna? | Was just driving and had this though whole seeing some cell towers. We create these giant towers in order to broadcast over a large area which makes sense. But I started to come up short when thinking about the process in reverse. When we send a command from our phone to retrieve data or even make a call, how is it that our tiny phone can reach these towers over such a long distance with much more meager equipment? | Technology | explainlikeimfive | {
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"The cell tower isn't necessarily broadcasting stronger signal (it's usually stronger, but not by much). It's high because that's how you get a direct line of sight to the most of the phones on the street. The signal can also reflect off walls or penetrate walls, depending on frequency, but the more it reflects, the worse it gets. The other reason is that the cell tower needs to serve many phones at once. The cell tower can do it over wide range of frequencies, but the phone usually sends data back over few narrow frequencies. So the cell tower needs more power, because it sends many signals to different phones at once. But the signal levels that each individual phone is receiving and sending are not different by much. The difference is mainly because the cell tower has bigger antennas, and bigger antennas can catch more signal, so they can receive weaker signal and still process it correctly. And you will absolutely get a better signal if you raise your phone up high, so that no walls or trees obstruct the cell tower. But it's impractical to carry 3 meter long antenna on your back, so they make cell towers higher to compensate.",
"The logic goes both ways. Just as it is easier for something high up to send out signals to greater distances on the ground, it is also easier for something high up to receive signals from a larger area on the ground.",
"Your phone can talk to the cell tower BECAUSE it's so high up and easy for your cell phone to send/receive signals to. The tower is high up because it needs to talk to phones that are spread out all over the city. Your cell phone doesn't need to have a tall antenna because it ONLY needs to talk to the very tall cell tower which is easy to send signals to."
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mjkppc | do people with ADHD react differently to depressants then other people? | hello, i recently stumbled across this article explaining how people with ADHD react differently to stimulants than other people, making them more calm instead of more active: " For many **people with ADHD**, **stimulant** medications boost concentration and focus while reducing hyperactive and impulsive behaviors. " after reading about this, i got curious: Since people who have ADHD react differently to **stimulants** than other people, do people with ADHD react differently to **downers/depressants** then other people? | Other | explainlikeimfive | {
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"Let me preface by saying everyones adhd/add is different but in general no. The reason stimulants relax them is because there is an imbalance of dopamine/norepinephrine/serotonin in their brain stimulants like amphetamine methylphenidate and bupropion increase these neurotransmitters thus causing a more stable state within their brain this leads to relaxation. If an adhd person were to take a recreational dose of these drugs they will get stimulated just like us regulars. Cns depressants dont act on these 3 neurotransmitters (for the most part) they tend to act on the opioid system or the gabaergic system. Adhd does not effect these system as such their reaction to cns depressants would be the same as people without adhd.",
"We don't have all the data on this, but there are many reasons to think the answer is yes. Alcoholism and other CNS depressant addiction is strongly correlated to ADHD, so there's good reason to theorize this is the case."
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mjkqm3 | How does traffic work in movies ? | Like I know on residential they can shut down the block to film what they want. Generally speaking do they pay extras to drive around the scene to create traffic flow ? And scenes on the express way are they extras driving those cars. | Other | explainlikeimfive | {
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"Sometimes the vehicles are actually going down a street and following the traffic. A stunt driver could be placed on top of the car, driving for them but out of camera view to the actors “driving”. And sometimes the entire car is on a trailer pulled behind a truck with camera crews at all angles filming as they drive down the street. You’ll occasionally see them with police escorts in LA.",
"My brother did background acting for a while, and the answer is yes. They told him if he could bring a Prius to the set they’d give him more for the day, and since they used it in a scene they gave him more. Just like any other acting it’s all rehearsed and done slowly. Any time cars are moving quickly, near the actors, on a highway, it’s stunt drivers. Also usually high speed scenes are heavily CGI. The matrix for instance built a section of highway in the desert and just kept looping it. They added background cars and scenery later. Oh and sometimes it’s all on a green screen, and nobody is moving. ...movie magic!",
"Fun fact: when filming Forrest Gump, in all of the scenes where he is waiting for the bus (box of chocolates, where the movies starts, etc) the traffic is going the opposite direction than it does in real life. This was done so the bus door would open towards Forrest and the bus bench."
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mjlmc2 | How do phones know to turn back on when yoi restart them? | like when you turn it off, it'll stay off until you manually turn it back on but if you hit restart instead of power off how does it just know to turn back on? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"There is what is known as a BIOS ... a \"Basic Input/Output System\" which runs alongside the operating system (Android, iOS, etc...) When you tell the phone to restart, you are actually telling the operating system to restart. The last thing it does before shutting down is say to the BIOS \"Hey ... start me back up in a sec, k?\""
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mjm1wl | how do one way mirrors work | Physics | explainlikeimfive | {
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"text": [
"They don't. It's actually just glass where the glare is enhanced with a partial coating of reflective metal. This makes it difficult to see through the glass if you're in a bright room and the far side is dark because the glare from your room is too bright."
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mjmqtb | How do antibodies in breast milk work? Are they there forever or only as long as baby gets breast milk? | Biology | explainlikeimfive | {
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"Children have very weak immune system and they have to get their antibodies from their mother through breast milk. These types of antibodies exist in every adult, they called immunogloblin type A (IgA) they works like a keyhole on the surface of the baby's cell to prevent the bacteria and the virus from entering the cells, they exist in saliva and tears and breask milk. In other words they are always there. Sorry for my bad English"
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mjn1ta | How do astronomers know the age, mass, and size of distant objects like stars and galaxies? | Is there a formula they use? | Physics | explainlikeimfive | {
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"This is only a part of the answer, but it shows how deep our knowledge runs. Materials absorb light at different frequencies. If a flower is “red” it’s actually absorbing white light *except for red*, which is reflecting back into your eyes. This is true down to an atomic level. A cloud of gas absorbs light, even if it is only a tiny bit. Hydrogen would absorb and reflect different colors than other gasses, even if only slightly from our eyes. If you were to take white light and shine it through a material, and use a prism to split it into a rainbow, it would be missing parts of the rainbow. There would be lines highlighted or missing in the spectrum. These are called spectral lines. Where on the spectrum the lines are depends on the material, and you can use this to see what something is made of to some degree. Each material has its own fingerprint on the spectrum once light passes through it. So if we point a telescope very precisely at a planet, we can take all that light from that patch of sky and isolate it. If we split it through a prism we can see where the spectral lines are, and determine what it’s “made of”. Long ago, someone pointed a telescope at the sun and did just this. They noticed certain lines missing that they had never seen before. They assumed a new unknown material was present in the sun. They named it after the Greek work for sun, “Helios”. The material was named helium. Helium is odorless and colorless, and was unknown to science. Later we detected it here on earth. There are similarly long and dramatic scientific tales for how we know the planets are their size, mass, etc. Nature leaves many clues that allow us to know nearly everything around us."
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mjn6uj | How do popular words spread? | There are words that spread and are used by so many people today, despite not all of us sitting down on a table and agreeing to do so. Words like “ok,” “lit,” or “boomer.” And someone made these words up first and convinced others to start using them. How do these spreads happen? | Other | explainlikeimfive | {
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"New terms are usually spread through things like movies, tv shows and song lyrics. Occasionally the news contributes with things like “fake news” or “woke”. We just hear it so often that it becomes part of our daily lexicon.",
"Organically. There’s not exactly a rhyme or reason to what will become the next big thing as far as I can tell. Once something is big enough people will jump on the bandwagon just to not be the odd one out."
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mjna3s | Why does rolling down the back window in a car while driving create odd sounds? | It never does it with the front windows, only the back. It sounds like there is a helicopter trailing you and it actually puts some slightly uncomfortable pulsing pressure on your ears. | Physics | explainlikeimfive | {
"a_id": [
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"text": [
"So you're allowing air into the car without allowing it to escape. It causes drastic pressure changes. Rolling down another window will usually stop the helicopter sound."
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mjo6ja | Why do stars flash blue green and red? | When I look at the stars on a clear night and really focus on their twinkling, they flash red, blue, green; not at the same time but one at a time. Why is that? | Other | explainlikeimfive | {
"a_id": [
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"That's because the earth's atmosphere is thick and refracts light as it passes. There's small pockets of air, heat and particulates which diffuse, discolor and even distort objects that appear in the sky. This is a big reason for why our advanced telescopes are actually in space - where there's no atmosphere to interfere with observation!",
"Several things the earth's atmosphere which is already mentioned. Fun fact if it's not flickering than it's a planet! Also we have rods and cones in our eyes. Cones see color and fine detail rods detect light. There are more cones in center of retina and more rods in peripheral. Since stars are dim and far away it is better to look at them with rods/peripheral. If you directly look at dim stars the stars seem to disappear from view. So that could be causing the flashing. Also the light from stars is different colors. This is linked to surface temperature of stars. The hotter the star the more blue the cooler they will be more red. But you shouldn't see any stars that are green colored. Because green is the color in the middle of the spectrum of visible light so that means the star is emitting light from all possible colors so we will see the light as white."
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mjpfmp | Why do people duck when getting on and off a helicopter? | Technology | explainlikeimfive | {
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"To prevent their heads or other parts of their bodies from being caught in the rotors, which are spinning very fast and could cause death or dismemberment. It may not seem like it, but those blades have a bit of vertical flex to them and I'm sure people will take all the clearance they can get.",
"The blades have a surprising amount of flex in them, and can be very springy when not at full speed. Depending on the conditions, the blades can move more with gusts of wind, and in nasty conditions the pilot can adjust the pitch and actually use the blades to keep the helicopter secured on the ground, which in that direction of flex moves closer to the ground.",
"Former airman from a blackhawk squadron here. This is more of a requirement specific to the model of the helicopter. Not all require you to duck. But it is due to the spinning rotor blades. They're very flexible and are more dangerous at the ends than the base. I've seen people hit in the face with them, they're spinning so fast you can't see it. If you're not paying attention you can walk right into them. In one instance just the flesh of the guys face was laying on the ground like a mask. Mustache and all."
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mjpn6x | How does country debt work? Like how would the US pay the money back? | Economics | explainlikeimfive | {
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"text": [
"Modern monetary theory is basically predicated on the fact debt on national levels will never be repaid. In fact, debt must be continuously created just to sustain the current economic system in its entirety. To make this work, central bankers balance interest rates (the cost to borrow money) against inflation (the loss in purchasing power) to basically \"eat away\" the debt over time; making it \"less valuable\" as time decays. The unfortunate side-effect is that our buying power is also diminished as a result, which increases wealth inequality, because poor people have fewer capital assets."
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mjqkf7 | how does carbon dating work on old things | Technology | explainlikeimfive | {
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"text": [
"Living things have carbon atoms. There are 2 specific types to consider C12 and C14. C12 is very stable so it'll remain the same with time. C14 is not stable so it'll go away with time. By measuring this two we can tell the age of the animals. This works on animals less than 60,000 years old"
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mjrk5f | How do kids not tear their ACL the way they run around, but grown men easily do? | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"Square cube law - the stresses on a person's bones and joints grow with their mass, which grows with their volume - which is their size, cubed. The strength of those bones and joints grows with their area, which is their length times their breadth - the size squared. So as a person grows bigger, they get, proportionally, weaker. This puts things like joints under greater stress."
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mjrna3 | if atoms never touch that means we never touched anything basically, so how do feel the texture of something? | Physics | explainlikeimfive | {
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"\"Atoms never touch\" is kind of a simplified explanation. The physical model of an atom is a lot messier than you or I learned in school. We learned the Bohr model; the atom represented as a solar system, with electrons orbiting in nice circles around the nucleus. That's a useful teaching aid, but it's absolutely not how an atom really behaves. In reality, electrons behave more like diffuse clouds of fog that occupy space in and around the atom, defining its boundaries. Every atom in the universe acts this way, including the ones that make up your fingers and your phone, or your keyboard, or however you're typing here. When our fingers' electron fog presses up against something else's, the fogs distort and change shape because they don't want to overlap. That distortion is what we perceive as \"touching.\"",
"With the same poles facing each other, try to get two magnets to touch. They will repeal each other. So even without touching, you can \"feel\" the other magnet by the way it repeals. Same kind of thing happens when you \"touch\" anything. You are feeling the repulsively forces.",
"URL_0 ... This exact question has been asked and answered alot."
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mjruvc | Imaginary Numbers | Hello all, there is one thing I could never wrap my head around in high school algebra. If there are any algebrincels out there that can explain what imaginary numbers are please help me out 🙏🏼 | Mathematics | explainlikeimfive | {
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"If you know real numbers, then they can be represented as the square roots of another positive number. For example 2 = sqrt(4), 3 = sqrt(9), 1.5 = sqrt(2.25) etc etc For an ELI5, imaginary numbers are counterparts where they are the square roots of a NEGATIVE number. This number doesn't \"exist\" in a sense because no real number squared gives a negative number which is why they're called imaginary numbers. However in another sense, they are completely a valid \"value\" as real numbers and are useful for solving many mathematical problems. Example of an imaginary number is sqrt(-1) which we designate the symbol i. (more correctly, i\\^2 = -1) By defining i, any imaginary number can be represented as a \"real number\" multiplied by i. Instead of saying sqrt(-9), we can write 3i because sqrt(-9) = sqrt(9) \\* sqrt(-1) = 3 \\* i = 3i",
"Ok, I'm intrigued. Since the smart people have already chimed in, I'll swerve and ask is \"algebraincels\" pronounced \"algebra incels\" or is it a three-way portmanteau of algebra, brain, and cells (brain cells)?",
"An imaginary number is like Forky from Toy Story 4. It's not a \"real toy\" in the way we usually think since it's not bought in a store. Instead the girl just made it up one day because she needed it. Now that it's here it can be played with in all the same ways as a regular toy; we can even play with real and imaginary toys together. If you have an equation like x^2 -9=0 it has two real solutions, but a very similar equation like x^2 +9=0 has no solutions. That's not fair, so someone came up with imaginary numbers so that all equations could have solutions.",
"The simplest explanation I know is that instead of a number line, there is a number plane. The x-axis is the real numbers, the y-axis is the imaginary numbers, and everything else is complex; it has both a real and an imaginary part. The unit on the y-axis is ‘i’. As you go up, you pass i, 2i, 3i and so on. You can represent each number as a vector - an arrow - going from 0,0 to the coordinates of the number. When you multiply two numbers on the complex plane, you multiply the length of the two arrows, and add the angles together. As an example, start with 1 on the number line and multiply by i. The size of the result is 1, but it’s rotated 90°. The answer is i, obviously. When you multiply i by i, the size of the result is 1. But it’s rotated another 90°. The answer is -1. The square root of -1 is i."
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mjsah6 | What are phantom pains? | Where do they come from? What’s their purpose? And how does the body create and interpret this pain? | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"Let's assume someone lost a limb, like a finger. There was an area in the brain, that was responsible for that limb, moving it and feeling its input. Because the limb is gone it does not get any more data from the former limb and it doesn't send out commands to move it. But! The brain does not like to waste space. Since this area is now unused other functions of the brain - like inputs from the finger next to the lost finger - will move into this area. They send signals there - **but the brain still thinks, they come from the old limb and interprets them as pain.** To remedy this, people with lost limbs are encouraged to mentally still train and use there lost body parts, so that the area in the brain dedicated to them does not get rented out to other parts."
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mjso8u | What do Leeches live on when no humans are around and do they kill their prey? | Biology | explainlikeimfive | {
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"text": [
"Fish, birds, and other larger invertebrates that spend time in water - anything really that they have access to, that they can attach themselves to in order to feed on their blood. Some species are carnivorous, feeding on insect larvae, worms, and molluscs that are small enough to be consumed without chewing, since they can’t."
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mjtmwr | A practical example of all sound properties | ELI5: All sound properties are: wavelength, amplitude, frequency, speed, wave period. How can I spot and see all of these in a sound I hear? | Physics | explainlikeimfive | {
"a_id": [
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"text": [
"Firstly, 4 of those 5 things aren't as separate as you make them sound in your list. Amplitude is the only one that doesn't depend on at least one of the others in some way. Wave speed is frequency multiplied by wavelength; frequency is 1/period. To answer your question though, higher frequency (longer wavelength) means higher pitch and greater amplitude means greater volume. The speed of sound in a given material is constant.",
"Wavelength and frequency are inversely proportional and are both properties of the velocity which is constant in a given medium (as the speed of sound). So they represent the pitch of the sound; higher pitched is higher frequency and lower wavelength as the wave completes more cycles in a given time, over a given distance. Wave period is equal to the wavelength, they mean the same thing. Amplitude is basically the volume of the sound."
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mjtq3j | How does oceanarium function? How come shark don't attack other fish? | Biology | explainlikeimfive | {
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"Because sharks are not the ruthless killers they are made out to be. If they are kept well fed, they don’t need to eat the smaller fish. Also, they put some thought into composing the tanks and avoid putting species together that are prime food sources for a shark species in the wild. Most decent size sharks, like bull sharks, like to eat larger fish like tuna, which you don’t normally see much together in a tank for that very reason",
"The real reason is that the sharks get provided plenty of food so can't normally be bothered to chase down other fish to eat. However any that bump into them are fair game.",
"Most sharks kept in large aquariums have no need to chase fish, its not worth it for them to spend the energy required to catch the fish, as the aquarium provides a much easier prey, also lots of sharks prefer other prey animals instead of fish. Meaning they don't see the fish as prey."
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mjtt2h | Why, while feeling sick, the pain/agony is less intense while laying down than while sitting or standing? | Biology | explainlikeimfive | {
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"Depends a bit on your symptoms. While laying down, your body is spending less energy than when youre standing up. Your body has to make a bigger effort to make sure youre standing up or even sitting. So if youre laying down your body doing less of an effort and there for you feel more relieved. But this highly depends on your symptoms"
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mjtvo3 | Why does black absorb light? | Physics | explainlikeimfive | {
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"Black doesn't absorb light, something looks black _because_ it absorbs light. Light is white. The colour you perceive something as is the colour of the light bouncing off it. If something looks red, its because it doesn't absorb the red part of the spectrum as much as the rest. If something looks white, it's because it reflects all colours more or less equally. If it looks black, it's because it absorbs all colours equally.",
"In my understanding, it is black because it absorbs all the visible light and not the other way around."
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mju2wi | Why do electronic devices take so long to start? Why can't it just turn on the computer instantly? | Technology | explainlikeimfive | {
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"Your computer when it’s off is like an empty kitchen. To actually start cooking you have to get all your dishes out and your ingredients and do any prep work on the ingredients before you can actually start making anything. The computer needs to load lots of stuff from the hard drive into its working memory and get everything in order.",
"Imagine yourself having massive amnesia, and you only know two things: - how to read - that everything you need to do to get ready for work is written, step-by-step, in a book So you read the instructions to get up, to go to the bathroom, how to prepare (initalize) other hardware like the coffee machine or your car, … How fast you can do this depends on your reading speed, on how many machines (peripherials) you need to use, and how many different are described in your book. Edith says I should say \"Thank you\" for the award.",
"They need to go through a boot cycle, which is a series of instructions a computer has to perform basically to make sure everything loads up correctly. Phones can boot up faster than some computers, it depends on how well the device can process instructions and load all the correct data ready to access, for the system to function as intended.",
"Most simple version: In order for your computer to run (I'm assuming Windows 10, but Linux/Mac are the same) it needs to load Windows from your hard drive into RAM. Of course, there's a bit more to it than that. Let's say your computer has a graphics card- well, it also needs to load the driver (a program that tells Windows how to use the graphics card) for that graphics card into RAM. But it needs to know what the correct driver to load is first (you could have changed it since you installed windows), so it has to check and have a chat with your graphics card to see what driver to load. It has to do this with all of your hardware, including a lot of little things (Like your wifi card) that are built into your motherboard. And, of course, loading things into RAM isn't quite as simple as just copying a big chunk from the hard drive. A program needs to know where in RAM all of its data is in order to run, and since it can't know where in RAM its going to wind up ahead of time, loading a program into RAM means giving the program a chunk of memory and letting it load its data into that memory and set up all of the links so that it knows where everything is. Windows is a program just like anything else, so it needs to work that way as well."
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mjuas1 | Does the speed of Earth through space (2222 ±30 km/s affect particles in a particle accelerator, as they move with the Earth but also have to quickly change directions? | Physics | explainlikeimfive | {
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"Nope. Because there's no such thing as \"moving through space at speed *x*\" there's only moving through space at speed *x* **with respect to something else**. Admittedly, we don't intuitively think about speeds in that way because in our everyday lives we have the surface of the Earth as a convenient reference for everyone. Once we start talking about the Earth itself moving, we have to do that to keep things straight. If the particles were already moving with the Earth, they'll happily keep doing that until something changes their motion. All the particle accelerator does is add additional motion. Here's a thought experiment to illustrate the point (assuming you've been on a airliner and a bus). Imagine walking up and down the center aisle of a parked bus. Now do the same for the airliner at 30,000 ft going 80% the speed of sound. The plane one isn't harder than the bus because the speed of what you're in or on doesn't matter.",
"No because the accelerator is also moving with the earth and their direction is determined by the magnetic field inside of it.",
"The [Michelson–Morley experiment]( URL_0 ) of 1887 answers your question: no. They used light instead of subatomic particles but the same principle applies. It doesn't matter how fast the earth is moving relative to, say, the centre of the galaxy, the speed of light is still exactly the same for us in all directions."
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mjvkd4 | Convolutional neural networks | Technology | explainlikeimfive | {
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"Neural networks are computer programs that can learn complex patterns from data. You feed a neural network a bunch of pictures of cats and dogs and it “learns” what cats and dogs look like, and can figure out whether a new picture is a cat or a dog. A *convolutional* neural network has a special addition that basically tells the neural network that it doesn’t matter *where in the image* a cat is, it’s still a cat. So if the some of the pictures have a cat on the left side and other pictures have a cat on the right side, the neural network will be able to figure out what makes it a cat either way."
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mjw0y0 | How / why does the human body rapidly heal during sleep ? | I’ve always been curious as to how the body seems to heal different issues primarily during sleep, for example I’ve had a few sebaceous cysts in my life and they’re always noticeably smaller when I wake up whereas while I’m awake I can’t generally tell if anything has happened at all. Or even say the dentist, had a few wisdom teeth pulled one tike and each consecutive day after sleep the pain / swelling has been reduced drastically. I also have RA and most of the pain / swelling is always gone or reduced in the morning compared to the previous day / night ? In some sense it’s almost like my disease has been ‘reset’. | Biology | explainlikeimfive | {
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"In addition to less time and energy being spent moving around and being awake, you also do not notice things while you are asleep. During the day, changes happen over a few hours are small enough that you might not notice, but being asleep for eight hours (plus however long before you fell asleep) allows those changes to add up. It is similar to how you might not notice how much a younger sibling grows when you see them every day, but if you are gone for a summer, you will notice the change. RA is a completely different story, but it may just be that laying down and relaxing completely allows your body to reset. Then, as you go through your day, mental and physical stress, as well as the movement of the affected joints, adds up to cause discomfort. It is a little puzzling, since RA is an autoimmune disorder, and I would think it would be worse while you are asleep, since your immune system can be more active, but it might be that with RA, it is joint movement that causes the immune system to attack. (Now that I think about it, someone I know with Crohn's disease, which is similar to RA in many ways, also seems to be in more pain later in the day, and seems to be in better shape first thing in the mornings.) Hopefully, someone who knows more about RA/autoimmune disorders and the effects of sleep on the immune system can help us understand.",
"In short, the sleep cycle and circadian rhythm partly regulates the immune system. During the day, immune cells are searching the body for pathogenic invaders. At night, more energy is put into processes like healing and antibody production. It's controlled by brain-body communication, hormone and cytokine signalling, and gene expression.",
"There was a great book on this a few years ago, Why We Sleep by Matthew Walker. I haven't read it yet, but it was hugely popular and influential, and as you might guess from the fact it's a book and not an article: a LOT happens when we sleep. I know less about the physiology, so maybe someone else can speak to that, but neurologically, it's when your brain does its housekeeping and bookkeeping, basically. If when you went to bed, the day's events were a big messy pile of papers on the table, during sleep is when your brain sorts through them all, throws out the junk mail, files away the important stuff (memory formation), even noodles on some of the unsolved items (REM sleep). FYI insomniacs, meditation replicates many of the beneficial wave states and activities of sleep, so if you're not sleeping well, try a few minutes of simple meditation if you can. Bonus: It'll also potentially help you sleep better later.",
"James Herriot (British vet) wrote about a seriously ill sheep that a farmer wanted put out of his misery. Dr. Herriot administered the euthanasia drug to the sheep in a remote shed and left the farm. Dr. Herriot returned to the farm a few weeks later for something and the farmer pointed to a sheep peacefully grazing in the field and said “remember her?” Apparently the sheep was out for a few days and for whatever reason not buried. When the farmer finally went to do that, he found her alive and well... Dr. Herriot’s theory was that the sheep just needed a break from the pain so that her sleeping body could work on healing itself.",
"When the body is not occupied with other activities—such as thinking, moving or digesting, other processes will get prioritized. Immune and healing functions are particularly enhanced if you make a point of going to bed on an empty stomach.",
"If you know of the author/veterinarian James Herriot you might know he once tried to euthanize a suffering sheep. She slept for three days and woke up well. This was in the late 1930s and considered quite a discovery.",
"[ URL_1 ]( URL_1 ) Pull Quote (more info at the link): > **Promotes healing** When you close your eyes and fall asleep, your brain can attend to other issues within the body. If there are areas that need to heal, the brain can trigger the release of hormones that encourage tissue growth to repair blood vessels. This helps wounds to heal faster but also restores sore or damaged muscles. While you sleep, your body can make more white blood cells that can attack viruses and bacteria that can hinder the healing process. Your immune system relies on sleep to be able to fight harmful substances. When you don't get enough sleep, your immune system is not able to properly protect the body from infection. > > > > **Gives the body a break** When you sleep, there are less demands made on your heart. Your blood pressure will drop and your heart will be able to take a break. Sleep also causes the body to release hormones that can slow breathing, and relax other muscles in the body. This process can reduce inflammation and assist with healing. & #x200B; [ URL_2 ]( URL_2 ) Pull Quote (more info at the link above): > Your immune system releases inflammation fighting cytokines > > While you’re sleeping, your immune system releases a type of small proteins called cytokines. If you’re sick or injured, these cytokines help your body fight inflammation, infection and trauma. Without enough sleep, your immune system might not be able to function at its best. & #x200B; [ URL_0 ]( URL_0 ) Pull Quote (more info at the link above): > Sleep is vital to the rest of the body too. When people don’t get enough sleep, their health risks rise. Symptoms of depression, seizures, high blood pressure and migraines worsen. Immunity is compromised, increasing the likelihood of illness and infection. Sleep also plays a role in metabolism: Even one night of missed sleep can create a prediabetic state in an otherwise healthy person. “There are many important connections between health and sleep,” says Wu. Hope this helps!",
"Nutrition is a minefield of conflicting advice. I would say you look into lowering inflammation as much as possible. Have that as your guiding principle and you will find it much easier to navigate this minefield! The reason you may be feeling better in the morning may well be cos you are fasted. Fasting is great for fighting inflammatory processes, as you already know. Check out [Alan Goldhammer PhD]( URL_0 ) - you may have already heard of him but he has had a lot of success treating people with water fasting. He's published papers on correcting blood pressure with prolonged water fasting and I think you'll find his work interesting. I find it odd that your doctor would advice you limit fruit, but not talk about actual sugar. That stuff is everywhere and is very pro-inflammatory. It's in sauces, all manner of processed foods, even sliced bread. The reason is so that it lures you in and keeps you buying. It's addictive. All these food products are made to create profit, not to create health. With sugar being so prevalent everywhere, we need to be extra cautious of what we are putting into our bodies. Bottom line: our bodies can and do heal themselves, we just have to set them up with the right conditions to do so."
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mjw35c | How do bugs just immediately appear when the weather gets warm? | Do they freeze in the winter and reanimate the second it gets warm? Like it will be freezing one day, no bugs. The next day 50^(o) F and bugs everywhere, then freezing again, they're gone. Are larvae frozen in the ground and the bugs just have an extremely fast life cycle? (Bugs meaning, mosquitos, flies, gnats, etc.) | Biology | explainlikeimfive | {
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"Pretty much yes. Most of the critters you're familiar with become less active during the colder months, ranging from full hibernation in the earth to simply laying around somewhere warm like an abandoned building. Changes in temperature trigger changes in the bugs which allow them to economize on energy and heat while they wait for food to be available again. If you know where to look you can sometimes find insects waiting it out over the winter: eggs/pupae can be in mud, bees will blob together and remain pretty docile and there's even some crickets which freeze solid! Occasionally there will be a freak weather event (an early spring followed by a last minute flash freeze for instance) and many types of life will be caught unprepared and die. I've seen flowers, bugs and even some larger animals kick the bucket this way. Obviously even this isn't enough to kill the mosquitoes, honeybees and trees off for good tho, nature be cool like that."
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mjw663 | why do most people find their voice on a video unbearable? | Biology | explainlikeimfive | {
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"You think your voice has a different timbre to it when you hear it while you talk since part of the sound you perceive originates from the vibrations in your skull set off by your vocal chords - this causes your voice to sound more rich and deep to yourself. That timbre is missing when you hear a recording of your voice and this makes it sound unnatural to you. Most people who use their voice a lot (singers, speakers, actors) usually get over this difference and won't notice it anymore as they grow as accustomed to hearing themselves from recordings.",
"I believe this is best described by pointing out then when we typically speak, we hear our own voices from a unique perspective. It's the only voice which originates from within our own skull and so this has some effect on how we perceive our own voice to sound. When we listen to a recording of ourselves, we sound *different*, as the recording device hears what everyone else hears. When we sound different, this leads to cognitive dissonance which is frankly unpleasant."
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mjwdar | () Why do some of the world’s largest Oil producers (Exxon, Shell, BP) have such a low stock price compared to Big Tech (Amazon, Google, Apple) despite having similar or better revenue? | Pretty much just this question. Why does Shell have a low stock price compared to Apple despite having more revenue? | Economics | explainlikeimfive | {
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"Stock price isn't an indication of a company's worth. Market cap is. Market cap is Outstanding Shares multiplied by stock price. A company that has 100 outstanding shares valued at $1 each, has a market cap of $100. A company who has a stock price of $100 per share, but only has 1 share outstanding has a market cap of $100. In this scenario, both companies are valued the same, despite the disparity in stock price.",
"Stock price depends on number of shares issued to determine the value of the company. A company with few shares will likely have a high stock price, but may still be of lower value.",
"Stockprices are supposes to include a reflection of potential future earnings. The prospects of oil vs tech are quite different.",
"First off share, price is a matter of market cap (total value of company) divided by number of shares. So two companies with identical market cap can have vastly different share prices based on how many shares they have outstanding. There is no set number companies issue at their IPO, and then they can do stock splits, buy back shares, have secondary offerings, etc. that all change the number of shares they have over time. Amazon could do a 100:1 split tomorrow and have a share price of $32 but it would change nothing of the operations or value of the company. And share price valuations are typically based on profitability/expected future profitability. Oil companies may have higher revenue, but they also have much greater expenses. As a result, extracting and selling oil has lower profit margins most of the time (that changes when oil prices skyrocket, as the costs to locate, extract, ship, refine, etc. don't vary much compared to the volatility of oil prices). And the writing is on the the wall for oil producers, as renewable energy sources take off, the rise of electric cars, etc. suggest that oil companies are not in a high growth industry. Tech companies typically have much higher profit margins because it's easier to scale software or web services than oil production. And tech companies are still innovating, growing new product segments, seeing continued high growth in existing markets, that suggest growth in profitability in the future."
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mjwnir | In a DC battery, if electricity flows from the negative to the positive terminal, why does the negative terminal measure 0V? | I'm thinking of AC systems where the current flows from hot to neutral and the neutral is at 0V. Why isn't this the case with DC/batteries? And is the negative terminal technically safe to touch even if the battery is 50V+? (assuming there aren't any faults with the circuit) | Physics | explainlikeimfive | {
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"What’s considered ground (0 V) is always a matter of choice. There’s no such thing as 0 V in absolute terms. For battery power, we usually call the negative terminal ground, so for example for a 12 V battery, the positive terminal is then at 12 V. But in principle, there’s nothing stopping us from considering the positive terminal being 0 V, then the negative terminal would be at -12 V. Whethet any terminal of a battery or any other voltage source is safe to touch will depend on whether you complete a circuit to a different potential than the terminal you are touching. If there is a potential difference, then there will be a current through your body."
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mjwsai | How do duracell ultra batteries have 100% extra, shouldn't batteries be full allready? | Technology | explainlikeimfive | {
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"In addition to what u/disappointingHero stated, not all batteries from the same chemistry are created equal. Sometimes the \"parts\" inside the battery are lower quality (impurities, manufacturing defects, etc), meaning that the batteries produced by one company may have varying energy levels. It is a regular practice to sell the higher quality ones for more than lower quality, even if they come off the same line. This is why you can go to Target and find the same brands selling for multiple times for what you can find them at the dollar store.",
"It's not that they're overcharging them, it's a difference in total capacity due to using different components inside.",
"Hang a bucket of hot water over your head and poke tiny holes in the bottom. That lets you shower under the bucket for 5 minutes. Now take a bucket that's wider but not taller with twice the volume of the first bucket and poke the same sized holes under it. You can now shower for 10 minutes. In this case, the charge or volume of water has doubled but the voltage or water pressure set by the water's height in the bucket has not. This doubles the run time of the shower (device)."
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mjx16m | How do whales dive nearly 3 km deep with air in their lungs | I assume that the air in their massive lungs produce a lot of buoyancy so how are they able to accurately control their depth in water? Thank you! | Biology | explainlikeimfive | {
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"They're built a little more sturdy, with reinforced airways and such. Additionally, they don't simply hold their breath the way humans do (with full lungs and all). As they dive, their lungs collapse which forces air away from the gas exchange (between blood and lungs) organs. So how can they stay underwater for so long if they don't store oxygen in their lungs during a dive? They have massive specific blood volumes....about 3-4 times what terrestrial mammals do (so per kilogram of weight, they have 3-4 times as much blood as humans). In addition, they have about twice the concentration of hemoglobin (the oxygen-transport protein in blood) as humans do. Lastly, they have an absurd concentration of myoglobin (oxygen storage protein in muscle), about 10 times more than humans. Add that all together and you have a creature whose body has a significantly higher ability to store oxygen per pound of mass *even if not stored in the lungs*, than terrestrial mammals are capable of. They can effectively push all the oxygen out of their lungs, but still have a much higher capacity for holding their breath than humans attempting to do the same thing. [(source)]( URL_0 )",
"Air compresses with depth. At 33 feet below sea level, the air in their lungs is like half the volume of sea level. So buoyancy goes down a lot with changes in depth. Once they’ve gone down a short amount, the buoyancy of the air in their lungs becomes negligible.",
"Great answers I have a secondary question, why don’t Whales or dolphins get the bends? What about the nitrogen?"
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mjx6au | Unlike us repelling our hands, (or any other body part) away from an unbearably hot surface, why do most of us try to quickly swallow away an edible when we realize that it is hotter than we anticipated? | Biology | explainlikeimfive | {
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"Would you still eat i.e. a meatball that you violently spit on your plate cause its too hot while people around you are watching? That would be my guess"
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mjxc51 | what did sheep do before us? | Biology | explainlikeimfive | {
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"> You see these videos of sheep with debilitating wool growth, to the point of immobility and blindness. How did sheep survive before we came along to shear them? Sheep in their current form did not exist before humans. Every plant or animal in your life that has in some way been cultivated or domesticated, from strawberries to bulldogs, is a **human creation**, made possible by genetic modification via selective breeding over hundreds and thousands of years. The predecessors of modern sheep did not have the almost pathologically extensive growth rate of wool for which their modern cousins have been selectively bred."
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mjxlhq | Where does mold come from? Do you risk "taking it with you" when moving from a moldy apartment to a not moldy one? | Biology | explainlikeimfive | {
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"Mold spores come from outside. Simply, yes you can transfer it from one place to another. However, mold spores are everywhere and you shouldn't be panicking about it. When air testing for mold spores, it is not a simple yes or no whether or not you have mold. It is a comparison of the outside air and the inside area. If your inside is higher than outside, you have a mold problem. Certain molds are worse than others and immediately raise concern while others are ignored. If you have visible growth it is a concern for sure. Best practice is to fix leaking appliances/water supply lines and keep air flowing in your house. **Not official advice, though I am a water/fire/mold remediation professional.",
"Yes. Spores are in the air, on surfaces, on your skin. By creating environment that prevents them from developing (low humidity, low temperature) and removing potential food sources (basically anything organic), you can control whether they develop into a problem or not.",
"Yes, the spores are naturally present in the air however, so though you might not bring that particular mould, another will be floating around pretty much anywhere you go. The way to stop it is to make the conditions inhospitable - dry being the main point. Don't allow steam, condensation or water built up in or around your home. Keep air moving through the house - you don't need huge winds and draughts, though... just a small slot open on your double-glazing, which is why they put the slots in double-glazed windows, or a gentle movement of air. In my old house (1930's brick) there was a big condensation problem, leaving mould on all the windowsills, and we cured it overnight with what is basically a fan designed to pull air from the attic and lightly waft it down into the main house. A 3-bedroom house was ventilated well enough by a fan you could barely hear pulling enough air through the house that you could barely feel it (we installed it on the loft hatch, so it didn't even need any building work). If you keep air moving, which helps dry, and keep the house itself dry - ventilate the bathroom, use a cooker hood, make sure there are no water leaks, etc. - then mould will settle as it always does but it won't be able to take hold and grow. Mould is present in the air. It actually spores into the air all the time and it's present in every soil, the outside world and in your house. Those spores are therefore everywhere and you can't get rid of them (no matter how much you clean, etc.). All you can do is ensure they can't grow into a full mould, by keeping things clean, dry and ventilated.",
"In a technical sense, yes, you can 'bring it with you' by transporting some mold bodies or spores from one place to another. In a practical sense, no, this doesn't have a very meaningful impact on whether your new place will be moldy or not. Mold spores are *everywhere*, they get on *everything*. The cleanest and most mold-free apartment in town, still has a light dusting of mold spores on every surface. The difference between a moldy apartment and a not-moldy one, is whether there's anywhere for those spores to land and grow into a fungal colony. In order to do that, mold needs to land somewhere that: \\- stays humid most/all the time \\- isn't too hot or cold \\- doesn't get much sunlight \\- doesn't get frequent cleaning. And the most important one is humidity. If your new place is kept dry, then all the mold spores in the world won't be able to colonize it. And if your new place is damp and dark, then mold will take hold no matter *how* carefully you cleaned your things before moving.",
"Mold is a type of fungus. It reproduces by spreading spores into the air. These spores generally only go a short distance, so they’re not really something to worry about most of the time. If the type of mold is particularly resilient or particularly harmful, then tracking from one place to another may be a concern, but often times washing your fabrics before moving them is enough to keep the spread down and kill any spores that may be hangers-on.",
"I’m a lawyer and specialize in real estate law. I get a lot of phone calls about “mold”. End of the day, any time you have moisture, you will have mold. Period. It’s everywhere and there’s only one thing you can do about it: creat a dry environment. Nothing else short of massive laboratory grade technology will stop it. Most molds are harmless. Some people have allergies that don’t get along with mold. Only in the rarest cases will you find a “toxic” mold, and that’s usually only found in hot, humid environments like the coast along the Gulf of Mexico.",
"From personal experience: Get rid of carpet in your bedroom. Carpet, if it gets wet frequently from spills, wet shoes, etc, is a great place for mold to grow, and yes you can track the spores on your shoe soles from one place to another. If you find mold, WEAR A RESPIRATOR when you clean it. I didn't and scraped it off like an idiot and wound up in the ER, it felt like I had been dosed with a drug (racing heart, confused thinking). I keep a spray bottle of vinegar in every room now and once a month I spray down window sills (mold loves those too), under sinks, and everywhere in the bathroom. Vinegar is a miracle cleaner, totally non-toxic to you, but it dissolves mold instantly and helps prevent the spores from dispersing as you clean it.",
"Mold. (Mycelial fungus) If you're on (in, under, over) planet Earth it's part of your environment. So are the spores by which it propagates. No escape... The good news is that they're integral to all the other biological phenomena here in our Homeworld...including our species. As to the issue of \"too damn much mold where I don't want it\" it comes down to denying it the stuff it needs to grow...substrate (what it eats), moisture (which it needs just like us).",
"Sir, I’m sure you are a terrific lawyer, but you are not a terrific microbiologist or even a very good mold remediator. Your statement, “some People have allergies, that don’t get along with mold, is nonsense. That’s like saying, some people have high blood pressure, that doesn’t get along with radon. It is a ridiculous statement. Molds can be allergenic, whether or not you have allergic reactions to other things. Molds also deliver mycotoxins that can make some very very sick. It’s not something to be taken lightly or dismissed. Also, your geographical description of where mold is, is nonsense. Mold is everywhere. Some of the most serious cases of mold are in the high desert, the Northwest , or Eastern seaboard. For heavens sakes, they are shutting down a hospital in Seattle for mold. Folks, mold is serious.",
"As others have said, mold is everywhere. The key to avoiding it is to reduce the environments where it flourishes. Mold likes damp dark places with little ventilation. Identify and remove these and all will be well. The ramifications of this are almost endless. I will leave the list to your imagination (and skill). To remove it, high-concentration hydrogen peroxide is your least-toxic option. Works a treat.",
"I moved from a nasty mold situation, allergy-triggering for me, in an apartment to a house. Of course it poured the day we moved and a few things got wet. But I never noticed anything once we got to the house. I was really stressed about it but it wasn't bad. The moisture in the air was way more important than the presence of whatever mold was living on things when we moved it."
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mjy47y | What would happen to us if we no longer produced cortisol? | Biology | explainlikeimfive | {
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"You would die, its called acute adrenal failure. Severe weakness, confusion, pain, vomiting and diarrhea, loss of consciousness and/or delirium would hit beforehand. Eventually a critical organ would fail due to low blood pressure and then you die URL_0",
"Overnight drop from normal to absolutely zero cortisol? You’re going into shock and dying without medical intervention."
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mjyqx7 | What are SDKs ? | In game development. | Technology | explainlikeimfive | {
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"When you make a videogame you don't normally write every single part yourself. Usually you have an engine, where someone else wrote the stuff that handles a lot of the parts. The engine is that, and the API is the way your programs interact with that, but the SDK is the actual software you run on your own computer to write programs to interact with it. It's rarely 100% strictly necessary, but it's generally all set up in a sane way to write programs in a way that works with all the libraries and hardware and stuff without you having to figure it all out yourself. Like it's not the software that runs on the playstation specifically, it's the software that runs on your computer that has all the setup to write programs that will run on the playstation and all the compiler settings and stuff built in"
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mk0fk1 | How come when a shark devours a rotting whale carcass it doesn’t get sick like a human would? | Biology | explainlikeimfive | {
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"Some do. But also sharks stomachs have different digestive juices than ours and it helps kill the bad bacteria.",
"Different species have different biology. Specifically different gut bacteria and stomach acids. The bacteria in the rotten whale flesh is counteracted by what's in the sharks gut. If I eat a dog turd I could die but my puppy does it everyday.",
"Same way coyotes and foxes can eat carrion. Their stomachs are different. Humans have extremely sensitive stomachs compared to other animals because when we started cooking our food, that extra energy that used to go towards digestion and fighting bacteria in our guts went towards developing our brains",
"How do you know Brucey Bruce doesn’t get food poisoning?",
"Don't Icelandic humans devour rotting shark carcass if it has aged long enough?"
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mk0qgu | Why is it bad to put defrosted food back on the refrigerator ? | Biology | explainlikeimfive | {
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"It's not. It's usually bad REFREEZE defrosted food. This is because food can survive 1 round of the water within it crystallizing, but 2 rounds of crystallization will ruin the texture of almost anything. Once defrosted food is thawed, it MUST be refrigerated, unless it is being cooked immediately (or it's something that doesn't require refrigeration, like bread).",
"Taste and texture aside: Every time you freeze or reheat food it passes through the danger zone. This is the temperature where food borne pathogens can thrive. The longer its in this zone, the more chance of food poisoning occurring. Keeping food below 40F and above 140F (5C and 60C respectively prevents or inhibits If you don't reheat your food to 165 degrees F then any potential food borne pathogens will still be there. Soon as the temp falls below 140 they'll start to grown again. Since cooling food takes time, re freezing (or even refrigerating) already frozen once food puts it back into the danger zone. Any food that's been in the danger zone for more than 2 hrs is considered no longer safe. Unless you own a blast chiller, it's going to take probably around 30-45 mins just for your single portion to cool down and be out of danger. The bigger the portion, the longer (the chef world uses ice wands in big batches of soup in an ice bath to rapidly cool if we don't have a blast chiller, and even then it can take an hour to get below 40degree - an hour for a 5 gal bucket sitting in ice water up yo its rim with a gigantic frozen plastic wand in thr middle of it too) Source: chef for 10 years and ServeSafe Certified for all of that."
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mk0tbw | Why are drone batteries so big but have the same amount of mAh ? | My drone battery is huge but has 5000 mAh and my phone is way smaller and has 5500 mAh. Why is that? | Technology | explainlikeimfive | {
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"Check the voltage. If you wired multiple of your phone batteries in series, the pack would have a higher voltage, but the same capacity in terms of current."
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mk0vzg | If a bear can consume excess calories and hibernate without food/water for weeks, why cant we do it? | Biology | explainlikeimfive | {
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"URL_0 this is an interesting story of a man who fasted for 382 days. We need water and a few essential nutrients, but we CAN fast for long periods if we have enough fat reserve."
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mk0ze4 | Where are the asteroids that made the craters on the moon? | Other | explainlikeimfive | {
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"Likely they got broken apart and the parts are mixed into the moon dust, or bounced back into space. Similar to what it would look like if you threw a snowball at the ground.",
"Mostly vaporized. Asteroids are moving at several kms per second, that's a lot of kinetic energy that gets converted to heat in an instant. The rest gets ejected out, forming the walls of the crater and spraying out beyond the rim."
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mk12jf | When downloading multiple files, Why some files are slow in downloading but other files are faster in downloading? | Technology | explainlikeimfive | {
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"There are a handful of reasons, the ones that came to mind for me are : 1. Your software downloaded of choice (whether it be a web browser, Steam or other game launchers, FTP programs, etc) could be prioritizing items based on when you started downloading them. 2. Your connection to the individual server one of your downloads is on is better or worse than the rest, so you have to wait longer for the packets to arrive, slowing down the download speed. 3. Your HDD/SSD can’t keep up with all the downloads at once, so it slows some of them down to make sure everything is downloaded correctly.",
"When you download a file, the server you're downloading it from doesn't know how fast the connection between it and your computer is. All it knows is that if data packages are lost on the way, it's probably sending it too fast and needs to slow down. There are different ways that servers can deal with it, but the common strategy is to start low and increase rapidly until it loses packages, then it cuts it down and increases the rate more slowly, rinse and repeat until it can maintain a speed close to the limit. This is why you can often see a sawtooth pattern on plots of download speeds. The problem with this is that servers sending data can't talk to each other and agree to split the middle. Instead, they tend to steal each other's share of the pie through this constant game of increase and decrease. That is why you often end up with one download being way faster than another. However, this problem can be fixed on your end: Many applications that download or stream files allow you to limit download speeds. So for example if you're downloading a big game on Steam, you can limit the maximum download speed through the settings menu. Some routers also allow you to set more detailed rules for internet traffic, but that's beyond eli5.",
"There's several possible bottlenecks, each of which will determine what file gets downloaded fastest. 1. The download servers. If the servers are fairly slow, your computer might be able to download faster than they (together) can upload. In this case, you'll just download every byte of data as it's sent, and the speed is determined solely by how fast the server can upload. 2. Your internet connection. Most internet connections can only handle a limited amount of traffic. In this case, the ISP decides which download server's data reaches your system first. Most likely, it'll give the physically closer server its bandwidth first, meaning that a nearby site (or one large enough to afford servers in every location, like Google) will get a faster download in this case. If there's spare bandwidth (or your ISP decides to split your connection more equitably), you'll get data from the other servers. 3. Your mass storage device (I.E. hard drive or SSD). An SSD probably is going to be faster than the internet, so it'll save data as it arrives (though it'll group data into blocks large enough to write all at once, to save device wear). But, because hard drives really don't like jumping around, they'll have to prioritize based on what's convenient for the device. That means writing the file that's nearest whatever the drive is already reading/writing first, only switching when it runs out of data in that location. Of course, depending on how your mass storage driver works, it might quietly cache the files in RAM if they download faster than your device can handle, and then write them the moment the disks aren't busy doing something else. This'll let the system completely ignore your hard drive's speed limitations, but might stop working if you fill up your unused RAM with downloaded data that hasn't been written yet."
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mk1d26 | why do we still send humans to space occasionally and not the robots? | Other | explainlikeimfive | {
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"As a general rule; robots are amazing at very specific things, humans are good at a huge range of things. Also having humans up there allows us to study the impact of microgravity on said humans",
"What? We do send robots far more often than we send humans. Robots are good at doing specific repetitive tasks that you've designed them for. But general AI is not currently a thing so robots are bad at coming up with creative solutions to unexpected problems. Actually, that's not even accurate: they're not bad at creative solutions, it is literally impossible for them to perform tasks they weren't specifically programmed to perform. Also, the main reason we send humans into space is because it's cool and we like doing it. It's great to look at photos or videos of people on the space station and think about how cool it would be to go up there yourself. Watching a video of actual humans bumbling around on the actual Moon is instantly more engaging than watching a robot do it. People seem to have this idea that space agencies about NASA are all about finding the most efficient solution to any given problem. They're not. Outreach is part of the goal and always has been. That's why they let their astronauts goof around a bit and do silly things with no scientific value. Showing videos like the one of the hammer-feather drop experiment on the Moon, or Chris Hadfield filming a music video in zero gravity, or whatever, is a good way to get the public engaged in science and encourage an interest in space that you don't get to the same degree with robots."
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mk1nw2 | Why do we need to stretch our muscles? In the wild we wouldn’t have time to stretch before running from danger so shouldn’t our bodies be ready to move optimally whenever needed? | Biology | explainlikeimfive | {
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"We don't and static stretching is highly discouraged. What we do need to do is \"warm up\" the muscles. This entails some minor activity to increase blood flow to the area. This helps protect the muscles when in use. If you stretch a \"cold\" muscle you're more likely to cause tears and further injury.",
"Warm up before, stretch after. Warming up serves as a low intensity precursor to high intensity movement. It allows muscles to be oxygenated and warmed so that fibres can be stretched. Animals often move for periods at a time at low activity, keeping them warmed up in case of high activity because the need to conserve calories. Stretching precents muscle shortening due to training or strain. Animals often stretch after rest but because we train for performance, we need to stretch ao that we do not lose range of motion. Not all of our physiology is figured out yet but stretching afterwards prevents issues such as spasm and tears wgile warming up promotes range of motion and performance.",
"Your question assumes that in the wild we would have the same \"baseline\" activity that our modern advancements has allowed us. We rely on transport to get us anywhere, where as in the wild we would have to walk for everything, even the fact that we turn a tap and water comes out has removed the need to go and fetch water. Some rural villages have a 25km walk everyday, just to get their daily water needs. In contrast we sit 8+ hours a day in an almost static position, we use tools to carry our loads, we have effectively reduced our bodies baseline ability and fitness level, which leaves us in a position that our muscles are just not used as much as they should be to allow for impromptu bursts of effort. In short we are chronically unfit in comparison to how fit we would be with a lifestyle in the wild. But that being said, on a biological level, our brains (in comparison to wild animals) consumes a massive portion of our daily energy requirements (I believe its something like 1/3), and because of that our bodies are constantly optimising its energy allocations. If something isn't being used, and it is considered non-essential, the body starts reducing the resources it allocates to those non-essentials. This is why people who are bed ridden for extended amounts of time, develop muscle atrophy, because the muscles are not being used. This is obviously an extreme example, but essentially this is what our modern day life of sitting behind desks, and transportation has done to our muscles as we don't demand much from them on a regular basis. Stretching comes in and engages the muscles and makes sure that we are forcing the range of motion of the muscles as well as the nerves which is trying to counter the hours of inactivity. These stretches shouldnt be done cold, as that can lead to damage, but after some light activity we have increased the blood flow, and then proceed to stretch and warm up the muscles and nerves before putting full exertion on the muscles. Stretching is effectively the hack we have found to counter the lack of physical activity our modern lifestyles have created. Anyway, that's as close to an eli5 answer I can think of...",
"It would be wasteful and difficult to keep a body at optimal for rapid motion all the time. This would be like keeping a car engine running all the time. It wears things out and wastes fuel. Stretching and warming up is a way to protect yourself. In an emergency you can, of course, do stuff immediately - it comes with higher risk of injury which wouldn't matter much if, for example you need to escape from a chasing lion. But if you're exercising, there is no reason to risk injury."
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mk3gbp | why when at high altitudes does water bottles, chip bags, etc. expand to maximum capacity? | I recently visited some national parks in California and in sequoia national park, the water bottles, chip bags, sauce packets were all expanded to the point it looked like they could explode at any moment. Why is this? | Physics | explainlikeimfive | {
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"The air pressure outside drops the higher up you go which causes the bag to inflate with the about of air pressure inside. Sometimes if there isn't enough room to expand, the explode.",
"When you change altitude, the density of the air outside the package changes, but the density if the air (or in the case of the chips, nitrogen) does not change because it is sealed. The difference in the pressure will cause the package to expand or contract, depending on whether the outside pressure has increased or decreased. For example: last week I was in the mountains and had some water, then put the cap back on. Later in the day I went home, near sea level. The atmospheric pressure in the mountains was less than it is at sea level, so the bottle had contracted and shrunk, looking it it had been squished. When I opened the cap, there was a hiss as the pressure inside and outside the bottle became equal and the bottle popped back into its normal shape."
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mk3l6q | Why is it worth it for companies to take your money for gift cards or virtual dollars for spending later? Sometimes they'll even take $40 and give you $50. What's the benefit to them? | Economics | explainlikeimfive | {
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"Something like 10-15% is never cashed in. Lost cards and expiration dates give them a profit.",
"A few things. Gift cards are often gifts, strangely enough. A chance to reach a new customer. The company usually won't need to actually sell $50 of product to make a profit, they may still make profit or break even at $40. There worth the risk to them. Not all cards are used. Free money. Payment for gift cards is upfront. They can then use this money immediately to reinvest, or even as a kind of interest free borrowing I guess. Almost all cards will have terms that can be quickly abused. Especially if the company goes in to administration. The first rule is obviously expiration date. But there have been companies recently that have refused to honour any cards since they went in to administration. Others have said they are immediately halving the value. Now this doesn't strictly benefit them, as being in administration is very bad news, but it does let them mitigate risk.",
"Because very often people never wind up using the gift cards or virtual dollars which basically means free money for the company that sold them.",
"First, gift cards don't involve companies actually giving you money, only providing you a future discount. There is sufficient margin for goods or services provided that the company would still make profit. Then, gift cards ensure that you will make a future purchase for a price that exceeds value of the gift card - pretty hard to hit $50 exactly and purchasing something worth $49 will feel like losing $1, so people would rather use the card for a $89 purchase. Also, selling gift cards means interest-free money now, with services provided at a later date."
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mk3qw6 | Why are different types of cheeses cut into different shapes? i.e. provolone is always circular | Other | explainlikeimfive | {
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"The shape of cheese comes from its design. Before molds Cheese that is a disc is more structurally sound so as the cheese hardens it is held together, cheese in the shape of a disc also makes the salt content even and the mold that grows to evenly distribute. When making large quantities of cheese before modern machinery the wheel shape also helped to move large quantities of cheese by rolling them. All these together have given cheeses their traditional shape based upon the specific cheese. Today though it’s mostly just tradition as we have ways of combating all the above circumstances.",
"There are different methods curing cheese to get different flavors, some are hand formed and uncured, snd then sold whole (fresh mozzarella), some are molded in a large wooden mold and then unmolded, stacked and aged, then cut into wedges for sale (Cheddar or Parmesan), some are kneaded, hand formed into sausage or ball shapes, tied with string and hung up to cure or be smoked (provolone.)",
"It depends on the size of the cheese wheel: If it's a small one, you can buy it whole and get a round cheese. If it's very big, it gets cut into slices or blocks, for example, and you can buy a small part of that big cheese wheel. My personal observation is that size correlates with age and cheapness, so an expensive young cheese tends to be sold whole while cheap old cheese is sold in smaller parts."
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mk3tig | - If sheep have to be sheared or the overgrowth will cause problems. How did sheep survive before they were domesticated? | Other | explainlikeimfive | {
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"We bred them to grow extreme amounts of wool, wild sheep do not grow wool like that. This is true of just about all domesticated animals - we have bred them for traits we find value in, and that can be detrimental to their ability to survive in the wild.",
"> If sheep have to be sheared or the overgrowth will cause problems. How did sheep survive before they were domesticated? Sheep in their current form did not exist before humans. Every plant or animal in your life that has in some way been cultivated or domesticated, from strawberries to bulldogs, is a **human creation**, made possible by genetic modification via selective breeding over hundreds and thousands of years. The predecessors of modern sheep did not have the almost pathologically extensive growth rate of wool for which their modern cousins have been selectively bred."
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mk40r3 | Why do some drugs such as Trazodone/Gabapentin calm or put you to sleep at lower doses yet have opposite effects at higher doses? | Chemistry | explainlikeimfive | {
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"Edit: I thought I was in the r/askscience sub lmfao sorry I am not a scientist but I have wondered the same thing before so I did a little research. Take anything I say with a grain of salt; just trying my hand at this. > Although its mechanism of action is not fully understood, the main pharmacological action of trazodone is blockade of the serotonin 5-HT2A receptor (1mg of trazodone roughly blocked half of brain 5-HT2A receptors). Increasing trazodone dose (50mg) causes antagonism on histamine H1 and α1-adrenergic receptors. The blocking of the 5-HT2A, histamine H1, and alpha receptors is thought to produce the hypnotic effect reported for low doses of trazodone (25–100mg).11 At these low doses, trazodone induces and maintains sleep without causing daytime drowsiness or tolerance, mainly because of its short half-life (3–6 hours). [Source]( URL_0 ) I found this info on trazadone but haven’t looked into the other substances you mentioned yet. So what I took away from this is that while the exact mechanism of action of trazadone is still unknown, we DO know that only as little as 1mg of it can produce the hypnotic effects that combat insomnia. Also, at higher doses trazadone will act as an antagonist to the histamine H1 and a1 adrenic receptors. This is where it goes over my head but I think that the interference of one or both of these receptors could produce an effect on your body that makes the hypnotic effect less viable. I believe agonism of the histamine receptor causes hypotension so the antagonist response could be hypertension which in turn would make it harder to fall asleep. I have no idea what antagonism of the adrenic receptor would constitute. Another substance that works better at lower doses is Melatonin btw. I hope someone more qualified than myself comes along to answer your questions! :)"
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"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5842888/"
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mk41bo | Veins carry blood, so why do we bleed when areas that don’t carry veins are cut (skin) | Biology | explainlikeimfive | {
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"There are three types of blood vessels: Arteries carry blood from heart to organs. There's large pressure inside of arteries, so if you cut open an artery, the bleeding will be pretty massive. Veins carry blood from organs back to the heart. They're low pressure vessels, so the bleeding is much slower, though if you hit a major vein, it's still pretty significant. Inside of organs, arteries split into capilaries. Those are the tiniest blood vessels, so small that the red blood cells have to go through them one by one. These vessels are everywhere and there's an enormours amount of them. And that's what gives rise to the bleeding when you cut a place where there are no vessels visible.",
"> Veins carry blood, so why do we bleed when areas that don’t carry veins are cut (skin) Most of your tissue is connected to your circulatory system in one way or another, not via veins or arteries, but via capillaries. If a cut bleeds then some form of blood vessel has been opened.",
"Evert cell in your body is connected to a blood vessel but there are many different kinds of blood vessels. Most cells are next to really tiny blood vessels called capillaries. Think of it like roads, the big blood vessels are like interstate highways. Most people don't live next to them. Instead those highways branch off into much smaller roads and individual houses end up next to tiny little roads. Veins are just the blood vessels going from your cells towards your heart. Arteries are the blood vessels that go from your heart to your cells."
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mk4tml | Why does a shower makes you feel good and how is it helpful when you’re ill? | I always heard (and felt) the benefits of showering to relax and it has always made me fell better when ill. Why is that? | Biology | explainlikeimfive | {
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"text": [
"Steam. Helps with breathing as it opens up your airways. Heat of hot water relaxes muscles.",
"It used to be thought when you had a fever the increase in body temperature was enough to destroy the pathogens in your body while not harming normal body cells. Now the prevailing idea is that in order to increase the body temperature enough to kill pathogens you would absolutely kill body cells as well. Which is why a high fever is such a bad thing. So why do we have fevers? It's through this it actually opens things up in the body and gets the fluids moving faster. Really normally the body does this to try to remove the heat actually, however it also allows the body's immune system to work better by allowing it to move around the body faster and with less obstacles to put it simply. So by having a hot shower you are sort of replicating this effect and heating up your whole system helping things get moving and reinvigorated."
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mk54z3 | - Why do soft drinks taste different from a can, bottle and fountain? | I know formulations can differ from country to country but don’t understand why the same drink in the same country can taste so different depending on packaging. | Chemistry | explainlikeimfive | {
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"A soda fountain is mixed on the spot with water and carbon dioxide provided by the restaurant, with concentrated flavoring provided by the beverage company. Even if the soda fountain avoids big variations in how the soda is mixed, you still have different tap water that could affect taste. You can filter it to try to make it more consistent but there’s still a lot of variation possible. Cans are actually lined with plastic on the inside so you shouldn’t have much flavor added to the drink by the container, or if you do it shouldn’t be too different from a bottle. But you can still taste the metal of the can on your lips. Bottles may let light in which can cause many changes over time, and carbonation levels could be different too.",
"In the case of soda fountains, the final product is prepared on-site. The soda fountain does not have a tank full of Coca-Cola that feeds the dispenser. Rather, the soda fountain has a tank full of concentrated Coca-Cola syrup, a CO2 canister, and a water line. When you dispense Coca-Cola into a cup, the soda fountain is carbonating the water with the CO2 canister, and then mixing-in a small amount of concentrated Coca-Cola syrup. The soda fountain actually has many different tanks full of concentrated syrup - usually, one for each type of soda. If the syrup tank becomes empty, then the corresponding spout will only dispense carbonated water. I prefer the taste of fountain sodas over canned or bottled sodas. The freshness really makes a difference!"
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mk58h9 | How does a country switch its official language? | When the ottoman empire turned to turkey they switched the language from arabic to turkish and when the soviet union collapsed the countries it produced switched from russian to an independent language. But how does that process work , we're talking about millions of people switching their language. | Other | explainlikeimfive | {
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"I can speak for the Soviet Union, having been born in it. Bilingualism, and trilingualism in some places, was already the Soviet norm so at the official level, all it took was to remove Russian from official use in places that didn't choose to keep it official alongside their language. Those that kept it, such as Belarus or Kyrgyzstan, didn't have to change anything. There are major differences across the ex-USSR in the proportion of local language vs. Russian usage in everyday life, but even native Russian speakers were taught the local language at school. Language rights and the level of official recognition of Russian continue to be highly contentious issues in some of the former Soviet republics that dropped Russian; Belarus stands out as having the opposite problem—Russian drowning out Belarusian in much the same way English is drowning out Irish in Ireland. In the end, no-one really had to learn another language overnight.",
"The country switches the official language by declaring it. From then on government documents are now in that language. In the cases you mentioned, the majority of the population already spoke the one they switched to as their native language, and may have been less fluent with the previous language"
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mk6ks3 | What is happening on the atomic level when materials get squashed or stretched? | When you stretch a rubber band, or a t-shirt or any material; what is happening on the atomic level that allows some materials to extend whilst others break? Likewise: what is happening when you squash sand or plasticine? What is happening that allows it to bind together regardless of how it’s deformed? | Physics | explainlikeimfive | {
"a_id": [
"gtehhgj"
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"In events where there's only a physical change (i.e., no chemical reactions), the effects are happening on an intramolecular level. Intramolecular means: interactions between molecules. In addition to the forces that bind atoms together into molecules, there are forces that bind molecules together into solid objects. When you apply a mechanical force to an object, you're stretching or squishing those bonds. Oftentimes the result is that the molecules align themselves in a new way. The following points apply mainly to polymers (including rubber and plasticine, I believe.) Sometimes a long, folded molecule will unfold and extend when you apply a tensile force. Sometimes a material will be composed of many long chains that all attract each other weakly, and when you pull on the material with enough force, the chains will slide past each other. (The chains go from being aligned \"side-by-side\" to \"head-to-toe\", lengthening the material.) Sometimes a material will be composed of long, randomly oriented molecular chains, and when you pull on the material, the chains align themselves in parallel. Conversely, when materials are compressed, molecules can fold up, squish closer together, and reorient themselves to accommodate the force. Metals are a little different. Their crystalline structure means their constituent molecules/atoms align themselves into planes. The planes are able to slide past each other in response to a force, but defects in the crystal lattice can hinder that sliding motion, decreasing the metal's malleability/ductility and causing it to break instead. Metals are also usually comprised of sectors of differently oriented crystal structures called grains. These grains can also slide past each other and align with each other in response to a stress."
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mk6z0q | Why do different compunds made out of the same or similar atoms have fundamentally different properties? | Total chemistry noob here. I do kinda understand how compunds form, but why do they behave so different, e.g. even if just one out of 8 atoms is switched out for another while the rest stays the same. | Chemistry | explainlikeimfive | {
"a_id": [
"gte8em9",
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"text": [
"Because of the shape of the atoms. Like carbon is used for both coal and diamond, but the shape of the diamond molecules is worth a lot more.",
"Fundamentally, much of that determines a compound's properties is the shape of a molecule, as well as the different types of bonds formed. Each element will form bonds of varying strength with each other element, so the order and positioning of atoms can drastically change the properties. For example, a highly polar compound, where positive and negative ions are separated on either side of the molecule, will tend to have a higher melting and boiling point because each molecule will rotate until it's strongly attracted to its neighbours. A compound with the exact same elements, but structured in such a way that it isn't so polarized will have much weaker attractions.",
"The shape of the molecules, and what it's components are, will largely determine the properties of the material. In a lot of cases, similar molecules will have similar properties, such as methanol and ethanol. In other cases, the difference is more dramatic (methanol and methane)."
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