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n1w8kx | What is the difference between the Classical concept of full employment and Keynesian concept of full employment | I am having a hard time on understanding the concept. I have minimal knowledge on economics and I am seeking here for an explanation about this. Thank you people. | Economics | explainlikeimfive | {
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"In classical full employment, everyone has a job. In Keynesian full employment, everyone who wants a job has a job. If someone is moving from a Walmart stocker to spaceX engineer, it’s probably a good thing that they were unemployed for a month.",
"I'll also throw \"structural un-employment\" which is primarily made up of the time required for job seekers get aligned optimally with jobs. Could be the job search process, could be moving for a better job, could be required gaps between jobs (like garden leave).",
"In classical economics full employment is a long run equilibrium between supply and demand and is basically independent of policy. Keynesian full employment is the level of employment where additional demand side measure (ie the government buying stuff) will drive up prices but not employ more people. Policy wise this is important: Keynes says that the government has a role pushing the economy to full employment, classical theory does not.",
"It's hard to give an ELI5 answer, because that difference is somewhat the whole point of Keynesian economics. Moreover, \"Keynesian\" can mean a lot of different things--what Keynes said, the historical Keynesian school, Post-Keynesians, Neo-Keynesians, and I'm probably missing some. And of these, the Neo-Keynesian flavor is the only one somewhat consistently taught in economics programs. My stab at it: full employment is always \"all people who are willing to work at the current market salary have a job\", the difference is whether or not the market gets there on its own. In classical economics, anyone who wants a job at the current market salary can get one. If anyone doesn't have a job, it's because they don't want to work at the current market salary (i.e. they are voluntarily unemployed). Keynes went \"dude, just take a look out there, people can't find jobs and that's not because they're too greedy or lazy\". His theory is that demand drives the economy and therefore full employment often requires that the government boosts the demand; otherwise, you have involuntary unemployment."
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n1z3d9 | Why do your feet start sweating while still feeling cold when you put socks on to warm them up? | I dont understand why my feet are cold, and than I put on socks/slippers to warm up and than they start sweating but don't feel any warmer... | Biology | explainlikeimfive | {
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"Even when you are cold your body secretes small amounts of sweat. If you add another layer like a sock then it's significantly harder for the sweat to evaporate. Especially tight fitting clothing like bras, underwear, and yes socks. But there's a fairly common condition called hyperhidrosis where the feet and hands create excessive sweat. Fabrics, allergens, and stress seem to trigger it."
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n1z5ii | How can a single layer of onion decompose whilst it continues to grow? | So I have just cut into my red onion and about 3 layers in, there’s a whole layer that is brown, mushy and it smells like pickles. But that is the only layer affected. I know this is can be a common thing. But how does this happen? Will it ever affect the rest of the onion? | Biology | explainlikeimfive | {
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"Instead of cutting into the onion, peel a (healthy) layer off. Then try to peel the very thin translucent membrane that separates that layer from the next. Like a thin sheet of plastic, that membrane is sufficient to block the bacteria that caused the rot from progressing to the next layer. The bacteria happen to only eat the \"layer\" cells, and cannot eat or dissolve the membrane material. Kinda like corn seeds, we can't digest the outer cellulose \"shell\" but the inside is very much digestible. So with popcorn we pop the inside out so it's exposed, and otherwise with corn on the cob we chew to break through the outer shell of the corn seed, so the inside is exposed. Anyway, bacteria that caused the rot in your onion could not get through the thin membrane that's between each layer and the next."
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n1zi36 | Why is it we do things, such as breathing, speaking, and walking without any thought but then the second we directly focus on whatever it is we have to do it manually until we forgot | Biology | explainlikeimfive | {
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"There is quite a benefit to being able to manually control these kinds of actions, and benefit to letting them go autonomous. Being able to manually control walking lets you carefully pick your way through a dangerous area. Manual breath control lets us begin hyperventilating to get lots of oxygen to our muscles very fast. Manual blinking lets us clear junk out of our eyes. Manual tongue control lets us make specific sounds and pick our teeth clean. On the flip side, having to do all the things manually all the time would be extremely taxing, so letting them go autonomous reduces the load on our mind and allows us to focus on things that are more important, like being aware of our surroundings."
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n1zohz | when we feel like “a weight has been lifted off our chest” after being relieved from something, what is that actual weight feeling? | I hope that’s the correct flair, but when we are feeling anxious, or very sad, or scared, or worried, we feel there’s an actual weight on our chest. Then when we get relieved it really feels like the weight has disappeared and we feel light again! What is that “weight” in biology terms? | Biology | explainlikeimfive | {
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"Stress makes our muscles tense and that makes our bodies feel heavy and tired. When whatever is stressing us out is over or gone, our muscles relax from being tense, thus we feel lighter, like a weight has been lifted off of us.",
"That’s the tensing and then relaxing of your accessory breathing muscles. Most of the time when you breathe, you are doing it pretty passively. You don’t really use many muscles to breathe, just your diaphragm. But when you need to, like if you’re running or fighting, you have a whole host of other muscles that can be called in to help. The muscles between your ribs, the ones in your neck and over your clavicle, even the ones in your back and stomach all help. When you get frightened, your whole body gets ready to run or fight. That includes engaging these muscles ready to breathe “more”. Weirdly, that can feel like a band squeezing your chest. The weight off your chest is when everything relaxes again."
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n1zz7n | When driving into a tunnel, why does it take quite a distance in for you to loose radio signal but you don't get it back till right at the exit, not a similar distance to the exit as you lost it from the entrance? | Physics | explainlikeimfive | {
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"It mostly has to do with the way radio receivers work. It uses something called a *phase-locked loop*. Basically, once your car has found the signal it \"locks\" to it which makes the signal clearer even though you might get a few disruptions here and there. This is why you are able to keep hearing the station even after you are in the tunnel a bit. The signal is very weak but your car knows what to do to boost it. But after you completely lose the signal you are going to need a good strong signal to re-lock to the station.",
"For an *actual* like you're five: because it's easier to maintain an existing connection than it is to create a new one.",
"If you’re talking about Sirius XM it builds in a bit of buffering to prevent temporary drop outs, when you emerge there is a delay as it builds the buffer back up. If you listen to Sirius XM on two devices in your house they won’t be in sync because of the buffer.",
"Especially with modern radios it takes a bit of time for the radio to start playing the audio after you have technically regained the signal. This is because it will constantly be seeking for radio stations and when it finds it then it have to make sure to get it tuned inn right. With digital radio it is even worse then with analog radio as it will have to synchronize with the signal in order to decode it. There might also be some buffering in the radio intended for error correction as the digital signal might send out corrections for those radio sets that do not have a perfect signal but this requires that the data gets buffered up a bit. This will cause the audio to play from the buffer for a few seconds after you lost signal and also for the audio to take a few seconds to fill the buffer and do the error correction when you regain the signal before it starts playing.",
"It’s pretty cool actually here in Australia our tunnels have radio wave repeaters that enable the wave to pass through the earth resulting in no loss of signal. This same system can also be used to hijack the frequency of cars in the tunnel to alert of local emergencies such as tunnel fires and car crashes. Doesn’t answer your question but thought I’d still share cause it’s cool lmao"
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n207i4 | How does a DVD work? | Technology | explainlikeimfive | {
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"Imagine that you were trying to tell someone over the phone how to draw a picture. You'd have to describe what you wanted in detail, in a way that they'd understand. You would make instructions and the person on the other side would follow them. That's roughly how a DVD works. We've learned how to take a movie, a series of images and sounds, and create instructions so that the DVD player can create those images and sounds in the right order. It's like a file on a computer. The DVD is full of the files that the computer in the DVD player can understand and turn into a movie. The disc has tiny tiny little holes in it, and the laser in the DVD player shines over those holes and can tell when there's a hole and when there isn't. It's able to use the pattern of little holes and not holes, to read the instructions. It's like a code that the DVD player can understand."
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n21mu7 | How those anti-counterfeiting stickers work? | Isn't it true that everyone can create those stickers? I mean like these [ URL_0 ]( URL_0 ) | Technology | explainlikeimfive | {
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"These types of stickers is designed so that they are quite hard to make yourself. You can not just print them out on a printer but they need to be printed on a press with a very expensive type of die with specific microgroves in them to make the exact fine texture that gives it these effects when seen in different light conditions. So you either have to develop some sort of new technology or you need to spend hundreds of thousands of dollars on making such a die. However when you have that die you could print them out in the millions. This is why it is cheap for manufacturers to make these stickers but very expensive for forgers who only need to make a handful of them."
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n21v31 | How does food get into your bloodstream? | Biology | explainlikeimfive | {
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"Look at your room. See all the toys that are outside of your box. Those toys are like the nutrients in your food. The toys in your box are the left over stuff that your body doesn't need. When we put food into our mouths it goes into our stomachs and our body takes out what it needs and you poop the rest of it out. Which is why I'm throwing away all that shit in your toy box you spoiled ass brat. Now go clean your room.",
"It gets digested, which is to say broken down in simpler chemicals, on the way from your mouth, thru your stomach, little and big intestine. Once in the intestine, the walls begin absorbing nutrients and water; different foods require different digestive treatment until they are absorbable; the first things to go into your blood stream are simple sugars, since they don’t need much to be broken down, then proteins and fats that need not just stomach acid and enzymes but other things like bile and bacteria to help cut them into small pieces."
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n23fbi | .avi vs .mkv | I noticed recently that if I can just rename an .avi file to be .mkv instead it runs fine... can someone explain to me why this works and what the difference between .avi and .mkv is? Is it a bad idea to rename my .avi files to be .mkv? | Technology | explainlikeimfive | {
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"So... you have to understand that avi and mkv are _container_ files... and avi is a proprietary Microsoft standard while MKV is an open one (and its slightly more flexible). Basically every container file contains a video stream, along with one or more audio streams and sometimes other stuff (subtitles whatever). Each audio and video stream can be compressed using various codecs. You can have an avi that contains mpeg video with mp3 audio for example. You can also have an avi that contains h.256 video and mp4 audio. (its been a while since my A/V days so that may not be entirely accurate, but u get the general idea.) So whatever program you used to playback your not-really-an-mkv avi file probably looked inside the file, saw that it was really an avi and just assumed that's what you _meant_ it to be, saw that the audio and video streams were encoded using codecs it understood and just played it anyway. So you lucked out. Im not sure why - unless you have some form of OCD and all your files have to have matching extensions - you'd want to rename all your avi files as mkv, I'd suggest you just leave them all alone.",
"Since they’re encoded completely differently, you can’t just convert the files just by changing the extension. What is likely happening is that whatever program you’re using to open the files is just ID’ing the file type from its encoding and continuing to opening it as MKV. All changing the file extensions will do is cause other programs to take longer to open them and make other, less robust programs unable to do so.",
"It works for you because your player software is able to tell that your .MKV file is just an incorrectly named .AVI. Some players might not be able to play it. So yeah, it's a bad idea to rename .AVI to .MKV. As for the differences between the two... .AVI is an older format and is pretty limited in what it can do. .MKV supports multiple audio and video streams, supports VBR audio, supports very large filesizes, supports chapters, etc., etc., etc.",
".avi and .mkv is file extensions which indicates two different multimedia container formats. A container format is basically the structure of a file which usually contains multiple media streams and their relations. Usually you will find a video stream and an audio stream but often subtitle streams, chapter or scene markers, metadata or additional video or audio streams in the same file. This is why you need a container format to bind these together. The thing is that the file name extension, the three letter name at the end of the filename, is just part of the name. It does give your operatinsystem some hints on what to do when you open it but it have nothing to do with the content of the file. And most applications know better then to trust this extension when finding out what file format it is. Since most multimedia players can handle both AVI container format and MKV container format it will just look at the content of the file to see which one it is and just play it. This usually works for most files but there are some exceptions. A lot of times when someone creates a file format they reuse existing formats. For example text files, compressed archives, image files, XML files, etc. can often be reused to create new file types. However these can also be opened in other applications, it might not make much sense to them as they do not have the right context but they can open them. So when you for example rename a file from say a .pdf file to a .txt file then the operating system will think that it is a text file and open it in a text editor. The text editor will be able to open it since it is essentially text but it will not know how the typesetting works and will therefore just display the raw code instead of the intended document. But as long as you open the file with the right application and that application ignores the file name it should work just fine."
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n23s25 | Why is fried chicken, watermelon and kool-Aid a black stereotype? | Other | explainlikeimfive | {
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"Watermelon: pragmatism meets racism. Watermelon started out life as a way to store water. We bred it to be sweet and artificially expanded the amount of placenta (the red) and bred out the bitterness. It was originally utilitarian good serving a utilitarian purpose. Many plantation owners would allow slaves to grow their own watermelons for their use and sale. It was a convent way to have refreshments without resources. Some slaves were allowed to generate income and resources for themselves on off hours. watermelons were popular due to low resource needs and sale price. Remember this is in the era before sugar was cheap so sweet things were quite a bit rarer. Why did the owners allow it? several reasons. The less you have to invest in your assets the more profit you make. Another granting small freedoms allows for a better means of control - false hope is a bitch there were others and it varied but those were the big 2. Now what about racism. Newspapers spread the popular image and it stuck. In 1869, *Frank Leslie’s Illustrated Newspaper* published a famous caricature of blacks reveling in eating watermelon, this is thought to be the first, and that became the popular perception. It mingled with other racist stereotypes over the years. Fried chicken and koolaid? not a clue.",
"I heard a story about watermelon. In the south, in the past, black farmers were only able to sell watermelon at roadside fruit stands. So it's easy to see how people associated watermelon with black farmers as it was likely many years of seeing them together before white farmers and legislators let up on the restriction.",
"Watermelon came from laws about what could be sold at roadside stands, with blacks being limited to watermelons. Fried chicken goes back to it being a popular food for slaves as chickens were one of the only sources of meat they could grow themselves, and then an early kkk movie showed a black politician eating fried chicken while not working. Kool-aid I'm not sure on.",
"Different reasons, fried chicken used to be a rich person food and the idea that black people were eating it stirred up anger among poor whites. Watermelon was a very refreshing treat for people working out in the southern heat before coolers and bottled water. Kool aid was much cheaper than actual juices so poor people served that to their kids."
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n23ufa | how does gravity effect the amount of pain from falling. For example, how much less would it hurt to fall off a 20ft object while on the moon compared to falling from the same height on earth? | Physics | explainlikeimfive | {
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"Well, it's not the fall that gets you, it's the sudden stop at the end. On earth, objects accelerate \"downwards\" (that is, towards the earth) at about 9.8 meters per second per second. Called acceleration due to gravity. On the moon, acceleration due to gravity is about 1.6 m/s/s. So a fall on earth will get you to dangerously high speeds much soone than a fall on the moon. Granted, falling on the moon takes longer because of the reduced acceleration, but 20 ft isn't high enough to make a dangerous difference. And that's what determines the scope of your injury and agony: how fast you were going when you hit the ground. Check out this nifty calculator I found: URL_0",
"It's going to be really hard or almost impossible to actually give you an answer to this question. You could conduct a force analysis quite easily just by using gravity and mass. But defining pain is impossible so there's no accurate way to say how much more or less something would or would not hurt."
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n24bpm | How come boards used for karate split so cleanly? Are they manufactured in a special way? | Other | explainlikeimfive | {
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"No. They are normal boards. You do have to break along the grain, however, or you'll have a broken hand. There are tricks tho, like putting the boards in the oven on low heat to completely dry them out. This makes it super easy to break, but easy to spot as cheating. I've thrown a couple of people out of tournaments for this.",
"There are also reusable \"Break Boards\" that interlock at the seam that can be used repeatedly for practice."
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n24c58 | Why are butterflies so hard to catch? They seem to always know where you're coming from. | Biology | explainlikeimfive | {
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"Butterflies, and many flying insects, are covered with tiny hairs called setae. These hairs play a proprioceptive role, which means they allow them to understand where each of their body parts are. But they also allow them to feel sudden changes in pressure, caused by the wind or a predator approaching. When you swing to catch them, you compress the air between you and your net and send a pressure wave that they react to. Another factor may be their evolved trait of erratic flight, which makes them more difficult for predators (and you) to catch.",
"Butterflies are good at detecting movement. Approach them slowly and you have a far better chance of catching them.",
"Insects have faster reflexes than large animals. Think of spidy sense, the comic idea that the spider has psychic ability. This comes from the fact that If you ever try to catch or smack a fly or any bug, you notice it seems to always jump right before you even start to move your hand towards it. This has to do with our perception of time vs the insect. When you go to quickly slap a fly, you send a message from your brain to your hand to make it move. Your hand begins to move, but it takes some number of milliseconds, maybe even much longer at times, for your brain to see your hand move because the visual message hasn’t been processed by your brain yet. None the less, your hand has started to move towards the fly and the fly has seen it and mentally processed it before you. This gives you the perception that the fly has a 6th futuristic sense since you didn’t even know you spooked the fly due to fact your brain is essentially processing the past, not the current moment. That’s right, the bug is living closer to the true present moment, us humans are living in the past. For larger animals like whales and elephants it’s even worse. All this is because we are big, so it takes more time for nerve signals to travel to our brain, be processed, then travel back to our limbs to commit an action. The fly is small so information travels around its nervous system much faster."
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n253id | Why does Wal-mart have over 20 registers yet keep only a few select open and allow lines to back up? | Other | explainlikeimfive | {
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"Cash registers require people to work them. Stores like Wal-mart only assign people to work based on how expected traffic. If they had people at every register, the line will be taken care of easily but after that, the store will have 20 people twiddling their thumbs. Stores have that many registers to handle days like Black Friday where there is a large amount of traffic. On most days, there are less cashiers because the traffic is less.",
"They are cheap and do not want to pay for employees to run the other cash registers is my guess.",
"The Walmart here keeps getting rid of registers and adding self checkouts. Pretty lame because even those get backed up and people are slower at scanning and bagging their own shit so it takes even longer now sometimes"
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n253w0 | why does a movie filmed in 24 fps look totally fine but a game running at 24 fps look awful? | Technology | explainlikeimfive | {
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"Partly it's the fact that you're accustomed to higher framerates in games than in movies, and in a lot of action games, those tiny fractions of a second really do matter. Probably the major reason, though, is motion blur. Video game rendering generally shows you a snapshot of a 3d world at a single, precise moment, whereas motion pictures shot on film, the film is being exposed for a *duration*, not a moment, and moving objects are blurred along the direction of motion. This helps to visually \"bridge the gap\" between one frame and the next. If you ever watch old movies which feature stop-motion animation or 'claymation', you'll see they have the same weird 'jerky' quality that you feel when playing a low-framerate game. It's for the same reason: the lack of motion blur.",
"Movies can be shot as a slower shutter speed, meaning each frame that contains movement has a slightly blurry effect that makes the slower frame rate appear smoother than it is. Video games produce sharper frames and need to be run at a higher frame rate to appear as smooth in movement."
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n259lp | Why the U.S post a price before taxes rather than like some other countries who post the full price including tax? | Economics | explainlikeimfive | {
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"The sort answer: it's the way prices have traditionally been listed, and nobody wants to break from that tradition. It also helps with consistency, since taxes vary widely based upon where the purchase is occuring. Online stores wouldn't be able to list prices at all unless they knew exactly where the customer lives. Physical retail enjoys being able to charge the same pre-sales-tax price at different stores and advertising a constant price."
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n25ko9 | What is about holding something, eg. sleeping with teddies/stuffed animals at night, makes us feel safe/at peace? | Other | explainlikeimfive | {
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"There are primate studies examining how baby monkeys react to different types of artificial “moms.” They showed that the baby monkeys had decreased stress when they have a furry “mom” compared to a non-hairy but otherwise identical “mom.” Humans probably have a similar mechanism, retained from when our ancestors were more hairy. Furry things remind us of mom ❤️"
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n25wia | Why will a lit light bulb cast a shadow when another light is passed behind it? | Shouldn't the backlight just join with the bulb's light to just make a brighter wall instead of a dark and defined bulb shape? | Physics | explainlikeimfive | {
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"Shadows are not a dark are but a area that is darker than the surrounding. The light will be combined but still were the bulb block the light will be less bright so it looks shaded. If you are out when there is a clear blue sky at the middle of the day and you are shade from direct sunlight the sky will still illuminate that area. The brightness there will be a lot higher you have with indoor illumination. Direct sunlight is 120 000 lux. Shaded from the sun but a clear sky is 20 000 lux. A well illuminated office is at 1 000 lux and a living room with a cosy light level is at 100–300 lux. So when you consider in shadow out during the day is infact a lot brighter then want you consider non shaded indoors, you still think of it as shaded because it is less bright then direct sunlight. So shaded is just less then the surrounding, the amount of light in the shades are can vary a lot. Lets first look at a lamp that off when you have another light source . A incandescent lamp that is almost just glase will bend light not block it but other types will block light. Regardless how it happen can create a area behind it will less light ie a shadow. Then let's turn on the lamp. The light from it is now added to the room and what you see is the combined light from it and the other light source. If it is not a lot brighter than the other light source you will be able to see the combined amount of light is less on some area of the wall. If it is bright enough there will still be some difference in light level but the difference is to small for you to notice it."
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n263xo | scientists found that of alternate realities exist, they’re less than a third hairs width. What does this mean and how does it work? | Physics | explainlikeimfive | {
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"It is based on a theory describing realities laid right over each other, separated by a different vibrational force. So, they would be separated on a minute level due to the difference in frequency. Travel between the two would be impossible, unless a means was developed the ability to enter a tunnel of sorts after achieving a high speed."
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n27b1e | How do we still not know how eels reproduce? | I feel like being something we eat, how in the world have we not found an answer yet? | Biology | explainlikeimfive | {
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"it was unknown for a long time because eels travel a huge distance to the open ocean to reproduce. They also have a bunch of life stages, baby eels don't just look like small adults. People couldn't find any trace of eels breeding at all in Europe, where they were known, and didn't realize that glass eels, elvers and adult eels are all different ages of the same eels in different places.",
"For a long time, it wasn't known how eels mate. Recently, we've observed eels travel to the Sargasso Sea and engage in both courtship rituals and mating. This was only possible thanks to modern GPS trackers."
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n27eyw | Why do we still mine so much iron ore when screp steel/iron for recycling is so cheap it's almost worthless? | Economics | explainlikeimfive | {
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"1) don't underestimate how cheap per ton iron ore mining is. 2) while there is lots of scrap it still wouldn't support more than a few years of iron production before it was all gone.",
"Scrap steel has a very wide range of characteristics and a near-infinite number of contaminants. As such, every “batch” of recycled steel will have some variability. When iron ore is used, the metallurgists who control the refining process generally have significantly tighter range of characteristics in their raw material, and considerably fewer contaminants",
"Because MOAR IRON PLS. It's not as though steel recycling isn't humming along— it's just that we use a *lot* of steel.",
"You're thinking of it from the wrong end. Iron is so common that scrap is almost worthless. The discovery of iron smelting wasn't revolutionary because iron is especially good for anything, but because its amounts are so vast that you are essentially only limited by your ability to smelt it. It's so common that there are no really serious estimates of its reserves, as it's one of the elements that rocks are made of. We would have to literally dismantle the planet to run out of it. This is why iron scrap is almost worthless.",
"Because there's still a market for \"fresh\" iron. There also needs to be enough getting discarded to the recycling to support the demand for material to make new things. For example a car might make it to the scrapper after just 15-20 years, but a machine tool like an engine lathe can keep over a ton of metal tied up for 50 years or more easily as long as the owner takes care of it. When it comes to steel more specifically, there's a lot of grades of steel both regular and stainless, and not every company needing steel for whatever they're doing will just specify \"steel, any kind.\" They might specify 410 stainless, so unless what's in the scrap bin is 410 and can be recycled and sold to them, they'll just go get \"new\" steel.",
"In the USA the majority of steel produced domestically is from recycled materials. Something like 70%. We still import a lot of steel from china and other countries, who also recycle a fair amount themselves. We could theoretical meet the demand for steel with 100% of recycled materials, but that all depends on how easy it is to get to the source of scrap, how much of it there is to be gotten and how much you want to pay somone to chop it up into manageably small pieces, then drive it over to you in a truck or a train car. We'd also runnoit of scrap in a fed years. This also assumes not one bit is wasted which isn't going to happen in the real world. Ships sink to the bottom of the ocean to say the least. You might for example, be willing to pay a higher scrap price if you're buying from a company that just tore down a steel sports stadium and they can ship you 50 tons a day for the next 5 years. Plus steel from that is likely to be clean and fairly high quality. So in the us the supply of recycled scrap mainly comes from easily accessible streams such as drop ends from sawing of linear stock from manufacturers, leftover skeletons after parts are cut out of sheets, scrapped vehicles, swarf from large machine shops. Demolished buildings, etc. Whereas some products for steel might end up in forms of places where it's just not economical to recover. For example, steel rebars embedded in concrete. Definitely takes a lot of time and energy to crush the concrete and get the rebar back out, again, and you won't get that much material back to show for it."
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n27qop | Why can’t freshwater fish live in saltwater (and vice versa)? | I was trying to read about why freshwater fish die in saltwater but it was still a little confusing to me. | Biology | explainlikeimfive | {
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"Speaking strictly of salt water or fresh water fish.. its more of an osmosis process.. Salt water fish cells have a high concentration of salt.. when put in fresh water, the cells get too much fresh water in them and takes the salt out, they get too bloated and die. Fresh water fish cells have the completely opposite issue.. so when in salt water, their cells will get too concentrated with salt that they will get dehydrated and die. Sometimes you see fresh water or salt water fish in brackish water ( the point where fresh water and salter water start mixing). They can hang out in the water for a while.. but eventually have to go back to the respective waters or die. There are other fish such as salmon, steelhead, sturgeon and others and go back and forth between the too.. they are called Anadromous fishes. ( but most of them are born in fresh water, go out to the ocean, go back to fresh water to breed and die) Source: my bf is a hard core Fishman. His fish knowledge is immense. Edit: words, and more updated info from bf who loves talking about fishes..🤣🐟🐠",
"A living cell is designed to work at specific conditions: the chemicals that make up a cell perform best at certain temperatures, with certain concentrations of chemicals, etc. This also applies to how much salt is in the cell: living things need a certain amount of salt in them in order to survive. Even if the amount of salt inside the cell stays the same, the amount *outside* the cell also matters: if the fluid around the cell is saltier or less salty than the cell itself, the cell can dangerously shrink or swell as water flows through the cell's membrane toward the saltier side. Living things have different ways of keeping the right amount of salt in their body, but they're tuned for the environments they live in. For instance, humans' urinary systems help keep the proper amount of salt in the body if they eat or drink most things, but they're unable to get rid of enough salt to survive if a human drinks nothing but seawater. Similarly, most freshwater fish aren't suited for keeping salt out of their body if they swim in sea water, and most salt water fish can't keep enough salt *in* their bodies if they swim in fresh water."
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n28j15 | Why is one 100% polyester fabric different than another 100% polyester fabric? | What I mean is that I have a favorite 100% polyester pillowcase- it stays cold. It's like a slick soft kind of pillowcase. But I have *another* 100% polyester pillowcase that stays warm and is less soft. If they're both polyester, why wouldn't they feel/act the same? | Chemistry | explainlikeimfive | {
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"Polyester is just the name of a certain type of material. There are actually lots of different polyesters, each with different properties. It's sort of like how we say that something is plastic, but clearly plastic water bottles are made of all kinds of different plastics. It's just a catch all term, you'd have to know the specific kind of polyester that your fabrics are made of to know if they are *exactly* the same.",
"Because polyester is a class of fiber, not a fabric. The only thing the tag tells you is the source material. How the fibers are threaded and how those threads are woven determine the fabric. Just as wool quality differs from sheep to sheep, so too does the processes of synthesizing polyester fibers yield different nuances and qualities. Once you have fiber, You spin it in some way to make thread or yarn. You then weave thread or yarn to make a fabric. There are dozens of different ways to weave threads. Consider dupioni vs taffeta. Both silk, but with very different properties. A felt flannel shirt is traditionally wool, which might be the same as your snug socks, but they are strongly differentiated by weave. Now consider a 3-piece suit, which is also wool, also very different. Look at say... denim jeans and a bedsheet. Both typically cotton. Etc. Anyway— hope that helps."
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n28jse | Why is it not possible to recreate a dinosaur if its DNA was found? | Biology | explainlikeimfive | {
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"DNA doesn't stick around for very long. After about 500 years there's nothing left. Anything that could have been salvaged from it is long gone.",
"Even if we found some dna that has miraculously survived, it would be like finding a hundred peices from one of those 10,000 piece mega jigsaw puzzles. We might be able to tall that it is a jigsaw puzzle, and maybe we could say in very broad terms what the picture is supposed to be, but we would be completely unable to finish the puzzle, or even identify what should go in the missing pieces. A huge amount of our knowledge of say, humans, comea from sequencing and studying a huge number of complete genomes of different people, and even then, we are only just starting to edit and change human genes. We would be flying blind with dinosaur dna."
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n299ex | Why is the color blue so hard to recreate compared to other? | I’ve heard that it took a very long time for scientists to figure out how to make, for example, blue colored lights. Why is blue harder to make compared to other colors like red or green? | Chemistry | explainlikeimfive | {
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"Well, there are two answers here. Blue dyes are hard to make because the color blue doesn't naturally occur basically at all. This is likely because it wasn't beneficial for things to look blue in nature. The only occurrences of truly blue things occurring in nature are because of light striking a surface a particular way, like how the wings of a butterfly are actually colorless but their shape basically only reflects the color blue. This picture shows the weird shape that butterfly wings have that makes this possible. This is maybe a little too complex to eli5, but it's pretty! URL_0 As for why it took so long to make blue lights, the answer is completely different. What you are talking about are LEDs. Really, we could just take any old light and put blue dye on the bulb and it would look blue. But scientists took until well into the 80s and eventually some time in the 90s to make a blue LED. The reason is because, again, the materials that make this possible are rare. Let's talk about how an LED works and why it emits light. Everything is made of atoms. Atoms have electrons that they like to keep hold of. But, when you have a lot of atoms in a solid block (like in an LED), they sometimes can lose electrons and these electrons just kind of float from atom to atom, doing their own thing. It takes energy to make an atom \"forget\" about that electron. This why you need to plug LEDs in to an outlet for power! Now, eventually that electron will find a place to settle down and let an atom take it. When it does this, the electron will lose that energy that it gained. The amount it loses depends on the material the electron is in. It just so happens that energy and light are related so when the electron loses that energy, it actually releases light. So, the amount of energy that electron loses determines the color of light it sends out! The problem for scientists was that materials with the correct energy to do this were very few and far between as nature just doesn't really seem to like the color blue, *at all*. For a while it seemed impossible. In fact, we basically had to make our own material to do this called Gallium Nitride. It was a massive breakthrough at the time. Red and green LEDs on the other hand were found almost immediately because it just so happens that silicon (one of the most abundant materials on earth, also happens to be a type of material called a semiconductor which makes all of this possible in the firstplace), gallium arsenide, abd another special material indium gallium arsenide (both being studied heavily in the 50s and 60s for their really awesome properties, also semiconductors) have energies that correspond really well to red and green. So they were basically discovered and manufactured immediately. EDIT: added why red and green were so \"easy\""
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n2ad4s | how are gorillas and similar animals taught sign language? | Biology | explainlikeimfive | {
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"Usually they show an object, show the sign, and the gorilla repeats it for food. It’s debated whether they are actually speaking the language or just trying to match patterns for food.",
"They aren’t. At least not in the way you probably believe. Gorillas don’t compose sentences. They can be trained to repeat patterns and expect results, but they aren’t using human language in any meaningful sense. It’s similar to training your dog to bark when they want a treat. There’s a great podcast with an episode about this: URL_0"
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n2ax04 | I have several questions regarding medical oxygen cylinders and the air we breathe. | Other | explainlikeimfive | {
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"> What does a medical oxygen cylinder contain ? Pure oxygen or just air ? Pure oxygen. Regular air wouldn't help at all, because those who need oxygen presumably already have access to regular air. They aren't scuba divers. > If it contains pure oxygen, then why we say pure oxygen can be toxic ? That doesn't make any sense to me. Pure oxygen does have problems long-term. However those problems are much less than asphyxiation, and those using oxygen are doing so because they have problems absorbing oxygen through normal breathing so they won't be getting the full effect of pure oxygen anyway. It is mixed with regular air until they can get normal blood oxygen levels, they aren't over saturated like if a normal person breathed pure oxygen."
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n2b3qd | What are Implicit Biases/Stereotypes? | I tried looking up the definition of this phrase online, but anything I could find on it just made me more confused. Could someone please help me out and explain the concept to me in simple terms? \-Vic | Other | explainlikeimfive | {
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"The idea behind implicit bias is that we hold certain beliefs that affect our behavior without our knowledge and that these biases can be detected by certain tests. However, the original research into implicit bias has since been debunked and its continued use falls into the category of 'pseudoscience'."
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n2cfoe | Why do rockets have to go around in orbit and do a bunch of squiggly maneuvers to get to the moon? Why cant they just go in a straight line? | And by straight, i mean, just... Point the nose of the rocket towards the moon and keep steering till you get there.... | Physics | explainlikeimfive | {
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"Pointing directly toward the moon and turning as the moon orbits would use soooooooo much fuel. There is no drag in space, so if you can accelerate in a way that gets you to where the moon will be by the time you get there, you can turn the engine off and just wait. Also there are no squiggly maneuvers, I'm not sure what you mean. The process to get to the moon is 1. Orbit Earth 1. Accelerate away from earth at the right time so that you go where the moon will be 1. face backwards and \"accelerate\" to slow down so that you orbit the moon instead of shooting past it. [Here's a gif]( URL_0 )"
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n2cio4 | How does a folded sheet of paper 42X be the distance to the moon? | Mathematics | explainlikeimfive | {
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"if the paper is folded 42 times, then there would be 2^42 (=4,398,046,511,104) layers of paper. Standard office paper is 0.1 mm thick. So 2^42 / 10 = 439 billion mm, / 1000 = 439 million meters, / 1000 = 439,000 kilometers, which roughly matches the 405,000 km to the moon (at the farthest point in its elliptical orbit) Shameless stolen from: URL_0",
"Each time you fold a sheet of paper it doubles in size. Obviously you can't ACTUALLY fold a sheet of paper 42 times, but if you could, here's how it would work: if 500 sheets of paper are about 2\" as you say, 1 sheet would be 0.004 inches. 1 fold would make 0.008 inches (0.004 * 2^1) 2 folds would make 0.016 inches (0.004 * 2^2) so 42 folds is 0.004 * 2^42 = 17592186044.4 inches = 277,654.45 miles. The distance to the moon is 238,855 miles (give or take, depending on orbit)",
"Everyone is giving the mathematical variables for the paper thickness being doubled 42 times, but if it helps to think of it \"backwards\",take the distance to the moon and cut it in half 42 times. For me this is easier to visualize, and if you have a tape measure, you could go around and measure the length of a wall or any object. After you have the full measurement, retract half of the tape measure and see how many times you can reel in half of the tape measure. You'll find that for any object in your house you can probably only cut the distance in half so many times before the tape measure is all of the way back in",
"It’s exponential. Every time you find it, its thickness is multiplied by two. This starts out slow but goes faster and faster. If you start with a thickness of 1, then folding one gives a thickness of 2. Folding again makes it 4, then 8, 16, 32, etc. Do you see how the thickness increases more for the later folds? After 10 folds you have a thickness of just over a thousand. After 20 folds we’re already at over a million. The amount of folds doubled but the thickness went up *much* more than double. After 42 folds the thickness is over 4 trillion (short scale).",
"A paper can be folded at 6 or 7 times at max.... right?",
"What does the thickness of 500 sheets of paper have to do with anything?",
"Because each fold doubles the thickness, not just adding one paper. So the first fold is 2 papers thick, the second 4, third 8, and so on. You'd reach about 500 pages thick about 9 folds in. (512 to be precise) So to reach the folds to the moon you'd just have to take the distance to the Moon, divide it by the thickness of paper, then find the first power of 2 that's greater."
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n2cqo5 | Why did the life expectancy for people with down syndrome increase from 25 years in 1980 to 60 years today? | I read that it was largely due to the end of the inhumane practice of institutionalizing people with Down syndrome but i don’t really understand what this means. | Biology | explainlikeimfive | {
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"A lot of people with Down Syndrome have a number of other health problems besides the cognitive issues that people mainly notice. For example many have a heart problem, atrioventricular septal defect. If untreated or poorly treated, this can lead to a very early death. There are a number of other health problems they can have. With better health care, they will live a lot longer. They’re getting better health care now than they used to. They’ve stopped the institutionalizing so much and now often mainstream them as kids, which has had great results.",
"Back in the day, these people were thrown in institutions where the most minimal levels of care were provided. There was also a large aversion to mentally handicapped individuals and society was mainly ok with these people being swept under the rug to keep up appearances. Hence the life expectancy being so low",
"The reason their life expectancy extended is the same reason life expectancy in general has been extended: medical advancements. People with Downs Syndrome have a great many health issues. They now no longer die from heart failure in infancy, or severe GI infections, or things like that. Institutionalising disabled people was not - and is not - in and of itself cruel. The problem was with the nature of the institutions themselves, although in general people always did their best according to the wisdom of the time. Modern group homes are a much better environment for people who cannot live independently, although they can still fall prey to abuse or mismanagement.",
"During WW2 in Germany and I believe Austria, many kids and babies who were institutionalized for disabilities were killed by being out outside without sufficient clothes so they would get pneumonia and die. Institutions tend to be mental hospitals or called insane asylums. People there get maintenance care at best.",
"The life expectancy of the patient with downs syndrome has increased because the medical system is much better at treating the immediate and chronic problems of these patients. We’re simply much better at keeping them alive day by day. The issue of institutions is debatable. Without proper care, life expectancy in a poor home will be poor. In a good institution with good care will be good.",
"Previously they were dehumanized and treated like a \"slightly less than human\" (names like retard, mongoloid or other derrogatory terms were used\\*) and they were marginalized. Even their families sometimes would regard them as \"a punishment from god on the family\" sometimes. Honestly, i doubt such a family would want to spend resources in someone who'd not \"get married and have kids\", \"not make them proud\". Let alone that their own development was impaired by social stigma. They were segregated and had to study in \"special classes\" which further stigmatized them in the eyes of society. With that they were practically always dependent on their families which would sometimes not care much, and sometimes even feel relief when they died. They have feelings too, they're people with feelings. I can hardly imagine how depressed they might have been living isolated and stigmatized. *(\\*Or the terms were coined and then became therrogatory)*"
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n2d7cq | Why is castor oil made from ricinus not toxic, and can prolonged use cause toxicity? | Biology | explainlikeimfive | {
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"The poisonous substances (Ricin mostly) aren't in the oil but rather the solid parts of the plant. So when pressing the oil out they stay in the remaining plant matter (wich therefore can't be fed to animals like you'd usually do with such remains) Ricin doesn't dissolve in oil (but in water)"
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n2dw0m | What’s the stuff that falls off the hot metal in metal forging? | It’s super satisfying watching metal get shaped into whatever it’s going to end up being but there’s always like thin layers of metal breaking off the second it gets crushed again ? I’ve always wondered this hmm. | Chemistry | explainlikeimfive | {
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"That's called scale. Its an oxide, and basically a layer of rust from the heat. It doesn't \"look rusty\", but it indeed is a layer of iron oxide. Every time you heat the metal, you loose some metal to oxidation because of the composition. Its mostly iron with some carbon and other things. Forging temperatures require oxidizing flames (as in forced air) of sorts to make the flames hot enough to make metal malleable, and those oxidizing flames oxidize the metals themselves.",
"What’s the difference between scale and slag then?",
"Scale, hammerscale or mill scale, formed when hot iron reacts with oxygen in the air. It is an iron oxide (mixture of oxygen and iron), similar to rust but different. There are several iron oxides of which rust is one, scale is actually a mixture of several. The iron-oxygen reaction takes place a bit differently due to the high temperatures at play. It looks a bit different but has similar properties to rust. Although it provides some environmental protection, this outer layer on hot worked steel is generally undesirable. Most steel is taken through a pickling, flame cleaning, blasting, or some other cleaning process afterwards to remove it. It's basically rust's cousin.",
"Scale. It is the surface material that oxidizes from the air. It is also why flux is used, because that Scale will prevent proper forging/make inclusions which could ruin the piece.",
"Surprised no one mentions how painful scale can be once it lands on your skin. Spent 7 years working in an industrial forge. Scale is thin and if it lands on your skin it almost instantly cools and sticks to your skin. Meaning not only did you suffer a fairly severe burn but now you have to peel the scale off your skin which removes any remaining living tissue with it. I have my fair share of scale burn scars as a reminder of the 7 years I spent squishing metal for a living.",
"To a 5yr old , When iron or steel is hot enough to glow it rusts almost instantaneously and when the metal is being worked it squishes and the rust crumbles off like a dried out layer of a biscuit , as others have said flux is just a chemical that coats the metal and when hammer forging its responsible or the “sparks” that shoot off , which are really just red hot liquid flux not metal splashing around",
"bare metal, exposed to the air, will react with the oxygen in the air and create oxide of some sort. thats what we call rusting. heat speeds up most chemical reactions, so often when metal is hot enough to forge with, its oxidising almost instantly."
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n2e1gj | Why do small flags fray at their ends but larger flags stay intact? | Other | explainlikeimfive | {
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"Larger flags take higher amounts of wind to get them to move. Flapping in the wind is what causes flags to fray. So smaller flags provide less resistance and so flap more and thus the fraying."
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n2g857 | Why do we have so many copyright issues compared to the past ? | We used to be able to see all sorts of videos on YouTube with official music and other stuff. I saw a woman get copyright claimed for playing Moonlight Sonata which belongs to the people. Streamers could also play music all they want and not get banned for it. But in the last years, everything has changed. How and why? I do support and want the artists to either get credit or payment for their work, but the current state is kind of ridiculous. | Other | explainlikeimfive | {
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"Two big things - one there are a lot more people making publicly accessible content now. Where there used to be a few folks making a mix tape once a year for their friends or personal use, or duplicating technology required owning a printing press, now everyone has a channel or five. Computers can now automatically recognize protected content. If you own copyright on something and want it to be protected, you can have computers watch for it being used without authorization, and automatically send take down notices. If you're a content host, you probably want to do that for your hosted content so that you're not going to get a claim against you. More folks infringing, and easier to find them."
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n2girf | What is an NFT? | Other | explainlikeimfive | {
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"Okay, an NFT is a NON-FUNGIBLE TOKEN. This little thing is an online receipt. Let's take the Mona Lisa for example. You say to a guy, \"hey, I wanna buy the Mona Lisa!\" and this guy says \"sure, pay X amount and I'll hand you a receipt\". So, you pay X amount and you get this lil receipt that says you own the Mona Lisa. That's stored away in a cupboard in amongst all of these other cupboards, except the cupboards are the internet. However, you ask for the Mona Lisa because you've bought it, but this guy is like \"no, you don't own the REAL Mona Lisa, you own the Mona Lisa\". So what you've done is bought the off-brand version (online) instead of the real thing. Also, the guy you paid doesn't really own the Mona Lisa. And every time you buy one of these Mona Lisas, you basically destroy the environment a little bit. Anyway, NFTs also cause greenhouse gas emissions and a lot of people disprove of them. The TLDR is that you're buying an online version of a product and it says you own it, but you don't own the real thing. Edit: these are commonly used with GIFs from artists or album covers and such! Edit 2: I misspelled non-fungible as non-fundable.",
"An NFT is a non-fungible token is a unit of data stored on a digital ledger, called a blockchain, that certifies a digital asset to be unique and therefore not interchangeable. NFTs can be used to represent items such as photos, videos, audio, and other types of digital files. An NFT is a digital asset that represents real-world objects like art, music, in-game items and videos. They are bought and sold online, frequently with cryptocurrency, and they are generally encoded with the same underlying software as many cryptos. Physical money and cryptocurrencies are “fungible,” meaning they can be traded or exchanged for one another. They’re also equal in value—one dollar is always worth another dollar; one Bitcoin is always equal to another Bitcoin. Crypto’s fungibility makes it a trusted means of conducting transactions on the blockchain. NFTs are different. Each has a digital signature that makes it impossible for NFTs to be exchanged for or equal to one another (hence, non-fungible). One NBA Top Shot clip, for example, is not equal to EVERYDAYS simply because they’re both NFTs. (One NBA Top Shot clip isn’t even necessarily equal to another NBA Top Shot clip, for that matter.) Source: URL_0",
"You take a picture with a digital camera. Instead of saving it to your storage unit, you save online permanently on a list that says YOU (and only you) own it and it's authenticity to it (this is the block chain). You then can sell that ownership of your picture to the highest bidder, and transfer authentic ownership in exchange for a digital coin. The list is updated with the new owner. How am I doing Block Chain bois?"
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n2gj38 | . How its possible for the light to travel constantly with out stop slowing down from the most old galaxies? | Physics | explainlikeimfive | {
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"Light is special because it has no mass and always travels at, well, the speed of light. This is one of its fundamental properties due to the laws of physics. You can’t really compare light to say, a spaceship, because it’s just not the same thing. But almost anything can move long distances in space without slowing down. By default, things continue moving at the same speed they’re already moving unless something acts to slow them. On Earth, everything needs to fight air resistance or water resistance or friction with the ground to keep moving. But in space there’s nothing to bump into (at least it’s very rare to hit something) so if you do nothing, you keep moving.",
"Gravity or with what energy still move at same speed?",
"Because everything travels at 3x10^8 m/s through spacetime. Objects with mass have this 'velocity' pointing so they move entirely or mostly in the 'time' direction (a stationary object is moving at full speed through time, but not at all through space), while photons and massless particles are heading in the 'space' direction (really fast in space, not so fast in time). Like a ship sailing North at a fixed speed, if it turns to point more Eastwards, its Northwards speed decreases as its Eastwards speed increases, but its overall velocity is unchanged. Here, 'North/South' is analgous to moving in time and 'East/West' is analogous to moving in space. This quite nicely captures why space contraction and time dilation occur (though it does ignore all the details). Hopefully ELY5!",
"Things that have no mass MUST travel at the speed of light. It's simply a written rule of the universe."
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n2gr8u | Human Speed Limit | Physics | explainlikeimfive | {
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"A little above 10 meters per second (roughly 36km/h or 20mph) as proven by Usain Bolt. Before him scientists believed the limit was a little below 10m/s",
"aiming for an ELI5: humans have a power limit based in the biochemical process which uses chemical energy to move. there are 4 main fuels that the energy factories in your muscles use and the muscles move between these at all stages. the first is primary fuel for sprinters (ATP- > ADP+P) but you dont have much of it stored (a max of 10seconds for bolt types, only a few seconds probably for the rest of us 3-6). (this reaction releases 24.64 watts/kg the second systems is the anerobic conversion of glycogen, this makes less power that the 1st (13/5 Watts/kg) but you have a larger store of glycogen. the by product is lactate as this process only part burns the fuel. the lactate part burn fule builds up and you feel that as burn in your legs. training can increase your tollerance to this burn nd increaste your removal of lactate as a fuel in other muscles. this system can carry you for 400-800 meters. the third system is the aerobic breakdown of glycogen. this fully burns the glycogen to carbon dioxide and water. this needs oxygen which you inhale and puff out the carbon dioxide. you have a large stockpile of glycogen (a couple of kilos perhaps) so this process can run for a couple of hours. when it runs out 'you hit the wall' and become very tired and less powerfull. this system can make 7.76watts/kg. the 4th system is only able of making 2.36 watts/kilo of power, but aerobically burning fatty acids. this being much less that the systems 1 to 3 is why after glycogen runs out you perform less strongly. the upside is that you have loads of this fuel, many days worth, it also needs a lot of oxygen. so to answer your question it depends on the length of the 'race', as we are looking at pure speed then you could perhaps assume its all down to the first system, ATP- > ADP+P. if you then look at Bolts 100m dash, he averages 22.5watts per kilo. the model in the book 'secret of running' shows that the max power for an hours effort is 6.4 W/kg and this match's the World records in various sports. so basically the answer is what /u/luckbot said and is backed by biochemistry. other than improvement in shoe and track design it isnt going to get much faster.",
"One way is to observe a sprinter's max acceleration and try to model what their speed would be if they could sustain that acceleration for a lot longer."
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n2h3r5 | How oil contamination makes paper transparent? | I am just wondering how oil stain over paper makes paper transparent but water cannot do it? Thanks for your answers in advance! | Physics | explainlikeimfive | {
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"You can see through most liquids. Paper is full of tiny holes. The white fibers will reflect light making it bright and not see thru. When oil goes in, the white fibers no longer reflect light, and the oil fills all the holes. Now you can see through the paper as all the holes are filled in and light doesn't bounce around randomly. Light goes through something - and it's shape can adjust the light. That's how circus mirrors, magnifying glasses, and eyeglasses work - these have smooth surfaces. When it's a rough surface - the light bounces around and you no longer see through it. Oil or was can easily smooth the surface."
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n2houk | Why does the brain need to have a larger surface and not a larger volume? | I was reading the Selfish Gene and I got to the part where the autor says that the human brain stores data much more efficiently and has a much more complex retrieval mechanism of memories than a computer counterpart. If storage and access are the goals, wouldn't a "smooth" brain make more sense? | Biology | explainlikeimfive | {
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"Only the surface of the brain (oversimplifying but generally correct) has the cell bodies where 'meat' of the brain actually is. It does all the processing and thinking. The rest of the brain is just wires that connect the bits of the surface together. Having a really folded brain means that these connections don't have to be as long.",
"Its a logistical problem. What limits the brain is not how much brain cells you can pack into your head, but how you can feed all those cells. The brain cells get nutrients from blood, but blood cant flow freely into the brain - its absorbed via the surface of the brain. Thus, the larger the surface, the more nutrients can be absorbed, and the more braincells you can have. If your brain was a smooth ball, the cells further inside would simply starve (and die from their own excretions, which wouldnt be properly removed)."
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n2i2s8 | Why do people in old photos (early to mid last century) appear so much older then they were at the time? | I always wondered, why in many of those pics, men and women look already middle aged, when they were in there early 20s or so. Clearly these few decades can't be enough to make such radical morphological shifts | Biology | explainlikeimfive | {
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"This is mostly due to the perceptions of the observer. You, as the viewer of the photo, already have preconceived notions of what people should look like based on hairstyles and clothing. Check out live concerts from the same time period, you may find that video will give a better impression of age.",
"Just a general sense of taking care of your body. Such as proper exercise, Skin care ie. sunblock. A huge difference in skin appearance is cigarette smoke. And generally less stressful blue collared jobs like mining and industrial work. - just look at pictures of individuals before and after war to know that jobs play a big role. Lastly proper dental care. Heathy teeth play a big role on your jaw line and face structure."
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n2ipo0 | Why does water poured onto already moist potting soil soak in faster than water poured onto completely dry potting soil? | Earth Science | explainlikeimfive | {
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"When the soil dries completely there are hydrophobic residues on the surface that prevent the water from being absorbed until the surface tension is broken. ELI5-er: When the soil dries completely, waxes and oils in the soil protect the surface. Kind of like the way it is hard to wet a new towel. Source: asked this exact question in hydrology class once.",
"Wet soil clumps, creating gaps for the water to pour into. When the soil dries it separates again and spreads out to create a broadly uniform layer (thanks, gravity!). That makes a barrier for the water."
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n2ixa0 | why do we open our eyes wider when surprised or scared? | I just spotted an old video of my son at about six months old. I was making raspberry noises and each time I did he looked classically startled, with big wide eyes. It got me wondering: did he learn that? Is it innate? Why? | Biology | explainlikeimfive | {
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"Wider eyes and dilated (i.e. biiig) pupils make it easier to soak in more visual information. This is important for quickly assessing the surrounding environment for fast reactions. This is important for survival in surprising / scary situations as it helps us react faster. That's also why blood vessels dilate and you see more blood flow to your limbs. To help them react quicker to perceived threat/danger (which is an element of surprise/getting startled). In your case it's probably more a matter of getting more alert for something your on expects / wants perhaps. To find the source of something you really like."
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n2iyoc | how does an engine brake work? | Technology | explainlikeimfive | {
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"A normal diesel engine works by sucking in air, compressing it, adding fuel, which burns and expands - producing power, and then expelling the exhausts gases. If you stop adding fuel, it takes energy to compress the air, but you get 99% of that energy back when it expands again. Instead, after compressing the air, the valves open and release it, making a farting sounds. Now you've wasted all that energy, slowing the truck down.",
"An engine requires a lot of energy to run. There is a lot of resistance as the metal moves through the oil films and all the auxiliary services like water pumps, oil pumps and alternator use some energy. In addition when the engine is running it will move air from the intake, compress it and release it into the exhaust. This too requires a lot of energy not only to move the air but when you compress it the air heats up and gets cooled by the metal in the piston, cylinder and head. So the air pressure drops a tiny bit which means that it does not push the piston down with the same force that the piston used to compress the air. Engine braking works by putting the car in a low gear and release the throttle therefore cutting the fuel supply to the engine. The wheels then have to drive the engine instead of the other way around and the car will slow down due to all the energy required to run the engine. This is usually a preferred way to brake, especially for longer distances. Firstly there is a lot of mass in the engine so it does not change speed as fast. And because the braking force is dependent on the speed of the engine you do not get sudden changes in braking force which can make the car uncontrollable. Another advantage is that normal brakes have a very small area to get rid of its heat so they tend to heat up if you use them too much. However an engine have a huge radiator, fan and water cooling to prevent it from overheating. So it takes much longer for the engine to overheat then the brakes when going down a hill. Engine braking is often used by trucks to help them reduce their dependence on their regular brakes. In these trucks there is often valves in the air intake or exhaust to further convert the energy to heat and noise."
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n2j0y5 | Why Positive charges always are on the upper side of cloud and negative charges below it ? | What happens if lightning occurs by those positive charges ( I saw a news where lightning hits 5 km away from its origin, they said it is due to positive charges )? How lightning happens during volcanoes eruption ? | Physics | explainlikeimfive | {
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"So a thunderstorm has two parts that form lightning, an updraft and a downdraft. These are massive columns or air moving up/down. When that much air is being moved around it is easy for dirt or sand or dust to be picked up and thrown into the storm as well. When bits of the particulates collide they start to build up a charge, this happens enough times and you can have such a large difference in charge between particles that you get lightning. Now for the question, positive charges are not always on the top actually. There are 3 types of lightning, cloud to cloud, cloud to ground, and ground to cloud. All of these decided by where the charges are. While cloud to ground is the one we tend to notice the most it is definitely not the only kind. Same thing with volcanoes as well, so much ash rubbing against each other that charges are formed and lightning goes off, however that tends to be in the smoke column so technically cloud to cloud lightning."
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n2j8fo | how does decaying fruit/veg help soil? Can it restore soil? | Biology | explainlikeimfive | {
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"I made a [image album]( URL_1 ) of a edible garden I made from 100% recycled/salvaged materials. Built straight on top of previous lawn. [Here]( URL_0 ) is another album of a tiny garden that I built straight from burying raw organic trash. Atoms are not created or destroyed, they can be recycled through 'nutrient cycling'. This also means bags of leaves, and grass clippings people through out are worth hundreds of dollars if you wait a few months and have sunlight and water.",
"The nutrients in fruits and vegetables are broken down to create a thin upper layer called humus which obviously is very rich in nutrition and helps seedlings and such to grow smoothly. Even while in soil erosion this upper layer gets removed thus highly degrading the fertility of soil. So yes decaying fruits and vegetables with plenty of other organic material can restore the fertility of soil."
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n2jh7u | Why can't we dispose of non recyclables in a volcano? | Earth Science | explainlikeimfive | {
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"They would burn up and the fumes would be released into the atmosphere. If we are going to burn the rubbish anwyay, we might as well save the expense of shipping it to the nearest volcano (which might be on a different continent) and the danger to the people doing the dumping, and just burn it in an incinerator. Burning it in an incinerator allows us to use the energy produced by the fire to power the electrical grid, and have filtration systems to remove the more harmful/toxic fumes produced.",
"Because it burns up in the surface of the lava and the toxic gases get released into the atmosphere, same as when you simply set it on fire.",
"It would be a pretty expensive and hazardous operation to transport millions of tons of trash to a volcano every day to dump it. There have been some small local efforts at this but nothing major. But your concept is not that foreign. We do install trash incinerators which creates conditions pretty close to those in a volcano in order to reduce the amount of trash. These are not without problems though. Nobody wants them in their back yard due to the smell and gasses they emit. And the remaining ash still contains some quite nasty chemicals and minerals that needs to be handled properly. You would have similar issues if you threw it in a volcano as well. The gasses would still escape and the ash would eventually make its way to the surface."
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n2jie0 | Why does 50% volume on video and music players not sound half as loud as 100% volume? | Usually if a video is too loud, 75% sounds almost the same as 100% and only at around 30% there is a noticeable difference in volume. | Technology | explainlikeimfive | {
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"Human hearing is complex. For something to be perceived as twice as loud, it needs to be 10 dB louder, which is 10x power. But to be 4x louder, it's 20 dB louder which is 100 times as much power. So it really depends how the player has implemented it's volume slider. If it does it linearly, i.e if you have it at 50% it just multiplies the audio signal by 0.5, then it's be way to sensitive at one end and not enough at the other. So the volume slider should probably be linear in dB.",
"Human hearing works on a logarithmic scale while usually the player volume bar is on a linear scale. In really simple terms, you have to use multiplication instead of addition. To put it in numerical terms with an example: \\- Start with volume at 10% and move to 20%. The value has been multiplied by 2. To increase the perceived volume further by the same amount, you have to multiply again. So the next step is 40%, then 80%. Working with your numbers, going from 100% to 50% doesn't halve the perceived volume but it reduces it by some amount. If you want to reduce it again by the same amount, you have to go from 50% to 25%, then 12.5% and so on. Since you are on a logarithmic scale and addition has been replaced by multiplication, it's hard to provide a meaningful definition of \"half as loud\". This is highly subjective and difficult to put in numbers."
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n2jui3 | - I recently read an article stating all human life began in Africa and branched out, but if thats 100% true, why are there different races?? | Biology | explainlikeimfive | {
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"This is a common question here. Humans are constantly evolving still today. In Africa dark skin helped prevent sun burn and skin cancer. When people migrated north there was less sun so that wasn’t as much of a concern, but a lack of vitamin D made white skin more useful. With languages and general face shapes that just happens because isolated groups of people slowly have random changes that add up over time.",
"There are no human \"races\". It's not a scientific term used in biology. There are simply humans with different traits.",
"Theres more genetic diversity between different groups of chimps in the same valley than different ethnic races of humans. Although we appear visually quite different at times, we are all the same.",
"Evolution has two parts to to: genetic mutation and spread. It’s the first of these you’re forgetting. Somebody’s DNA gets randomly damaged or copied incorrectly (i.e. mutates), and the mechanism for transporting brown pigment into the eyes no longer works. Bam, you now have the first “blue eyes” gene in Europe. Many of that original person’s descendants will inherit that same blue eyes gene. Mutations that are helpful in surviving to raise lots of healthy children will become the majority population quickly, those that are bad spread slowly, and those that are neutral spread randomly. Skin tone varies from region to region and pretty frequently shifts. In places near the equator, mutations that build up pigment in the skin are favored, since that layer of pigment helps shield your skin from sunburns and skin cancer. In places near the poles, pale skin mutations are preferred, since skin cancer isn’t as much of an issue it’s more important there to absorb light for good vitamin D production and not waste resources manufacturing all that melanin. Language is pretty similar. It went faster when there wasn’t any global communication and people rarely left their tribes. Tribes introduce new slang, words shift meaning or slowly drift to develop accents. Over long periods of time you get a new language. Now “yeet” is a casual word for throw, and nobody would be caught dead using “gay” to mean “joyful” unironically.",
"Dogs dude. Think of dogs. There is a huge variety from selective breeding and they essentially came from wolves. Humans did this too. Not necessarily consciously but by tribal allegiance. A family with a different eye shape becomes successful and has many offspring. You're not entirely wrong about \"races\" because the same meaning applies. When people talk about race, they're talking about tribes. Genetically we are essentially the same, but tribally we are different.",
"> If we all stem from the same DNA, the same continent, the same place, then how are there different races? Mutation + different selective pressures in different populations. Example, the need for lots of melanin in the skin diminishes as a population migrates away from the african savannahs due to more clothes being worn to deal with the weather (no just cold, very sunny deserts require more covering, counter intuitively), making the dark skin associated with sub-Saharan Africans a waste of biological resources, and thus favoring less prominent melanin production. For example, the mutation that enables lactose tolerance in adults only seems to have become prevalent in Europe and the Mediterranean within the past 20k years due to some particular selective pressure in that region. Now consider that Humans spread out from Africa somewhere between 500k and 2m years ago, forming various semi-isolated population groups that didn't interbreed terribly much. A hunter gatherer is in western Europe is not likely to take a wife from the eastern side of the Ural mountains, let alone Japan. > Lets not even get started with languages, we all started with the same grunts and sounds, how did there become a thousand different languages all over the world? Especially if we all originated from the same cradle of life. This is mostly similar to how racial traits developed. Mutation + isolation. Languages mutate over time, and historic populations didn't have the means of mass communication that might motivate linguistic convergence. For instance, compare Shakespearian English to Modern English, where a difference of only 500 years makes them nearly unintelligible. Then consider again the fact that populations moved out of Africa, a whole continent with lots of internal geographic divides to create mostly linguistically isolated populations to foster language divergence before the migration to the rest of the world, at least half a million years ago. That is a lot of time and space for languages to mutate and drift without much pressure to converge."
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n2klk3 | What is the use of the guy with the stick in an orchestra? | Other | explainlikeimfive | {
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"Without him the players would run home. The threat of the stick is the only thing keeping them in their seats.",
"The conductor is the main reference point for the people playing instruments to follow. They basically give subtle instructions and keep the timing with hand gestures and the stick. they just control the ~100 people involved. That way the players don’t have to have to look frantically at their neighbours if they forget something or lose track. They just make the orchestra not fall apart after 2 minutes lol The job is considered so important that if something were to happen to the conductor, the first violin is supposed to get up and take their place",
"The conductor guides the musicians as they play. S/he keeps time for everyone, directs players or sections to start playing, stop playing, play louder, play softer, etc.",
"The conductor sets their tempo or speed for the song. Puts an emphasis on their choice of instrument by telling them to play louder or softer. Here's a decent example with a familiar song. Watch how the conductors hands guide the musicians. URL_0",
"The [conductor]( URL_0 ) uses visual cues, sometimes their voice, to lead the various parts of the orchestra successfully. They often help set the timing of the performance and smoothly introduce or phase out other parts to provide a rich experience for the audience. They are not completely necessary, however when multiple musicians work together, especially very large ones, it is easy for timing mistakes and poor execution as a group effort. In modern music, and small bands, the conductor is replaced in favor of everyone playing in time with a specific member, usually a pianist or drummer. In some cases, a backing track might be used for more precision for each member.",
"he is the director. in rehearsals, he's boss, he gives direction to the players as they learn the music since he's the one that can hear the ensemble and knows all the individual parts. For the actual performance, a professional musician should not need someone to tell them to get louder or accent a note as you see them making elaborate gestures to crescendo and such, thats mostly for show. Thats all been planned in rehearsal, but its part of the process that many conductors are very enthusiastic, because a metronome dude is boring. but they may need to make sure certain events align to things happening on stage (if there is a stage performance they are playing along with).",
"An orchestra is too big for the musicians to play in tight rhythm. You might assume that the problem is that they can not hear everyone else which is part of the problem but the main issue is that sound takes some time to go from one end of the stage to the other end. So by the time you hear the musician on the other side play the note it is too late to play yourself and if it is a fast note he might even have stopped playing the note by this time. So instead you have a conductor in front who everyone looks at and follows his rhythm. There are also other uses for a conductor. He is the only one in the orchestra who hears the music from the perspective of the audience so he is able to listen to any imbalance or other problems in the music and then correct the musicians. This is especially true during practice but even during performances the venue might have changed, the public changes the acoustic, the humidity and pressure changes how the instruments sound, the musicians is in a different state of mind, etc. So the conductor is able to gesture to musicians any corrections while they are performing in front of a crowd.",
"Conductors play various roles simultaneously: 1) **They are the \"metronome\" for the orchestra.** They keep time during the performance so everyone doesn't get lost. Why don't they just listen to each other? They could, maybe, but that is increasingly impractical the bigger the orchestra. It is better to have one central point of reference. And it helps for that to be a visual signal. Light travels faster than sound; relying on sound in a large concert hall means things will be delayed and out of sync. 2) **They are the \"sound guy\" for the orchestra.** Make adjustments \"on the fly\" to the volume of different groups of instruments. Again because it's hard for the performers to hear themselves and each other. The conductor hears things similar to how the audience will hear them, and knows who needs to be louder, who needs to be softer. 3) **They are the \"boss\" or \"director\" of the orchestra.** This has not mentioned so far but is probably the most prestigious and important role. Usually, the conductor is the person who's been leading the orchestra's rehearsals for the past however many weeks or months. Providing instructions, making changes, determining the overall shape and feel of the performance. Like the director of a film or play, making creative decisions behind the scenes. 4) **In some cases, they're the \"DJ\" of the orchestra**. They can \"remix\" on the fly, if it's a more improvisatory setting like a jazz orchestra. For example the conductor can point out who the next soloist will be. Or tell two people to trade bars of solos. Or arbitrarily decide to repeat a section one more time, or go back to a previous section. Similar to point #2 but with even more options.",
"The conductor usually has a specific movement in their hands that give the orchestra the tempo and sometimes the intensity of the piece of music being played. If you watch their hands movements you can get an idea of how the song is too be played. So imagine if they were playing a quiet and slow melody the hands might be graceful in movement and flowy. If you had something like 'In the Hall of the Mountain King', you'd see more deliberate movements, very rigid. As the song gets faster, you will see the movements become more deliberate and intense. The orchestra/band sees this. They too are following the tempo and movements with the same rigidness and intensity. The power in the stick Edit: word(s)"
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n2l0a3 | How do companies make money by selling shares? | I’m trying to understand what’s the point of going public and selling shares of a company after the initial IPO. From what I understand, a company makes money by having investors invest in their company during an IPO. The investors make their money back if the stock goes up after the IPO. But how does the company continue to make money off its shares once it’s already public? I get more confused when I see huge companies do stock buy-backs. The stock price goes up but what changes for the company? | Economics | explainlikeimfive | {
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"When a company does an IPO (Initial Public Offering) they sell the shares on whatever exchange they listed on (NASDAQ, NYSE, etc). The company gets this money. What's happening is the owners of the private company are selling some or all of their ownership of the company to the public. After that, they don't get money when the shares are sold. The only way they can make more money by selling shares is by releasing more shares. However, there are consequences to this because it can dilute the value of existing shares, making them worth less. The reason they do this is it can raise a crap ton of money to invest back into the business."
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n2l5qi | How are video game AIs programmed? Is it a just a long series of "If Then" statements? Why are some AIs good and others terrible? | Technology | explainlikeimfive | {
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"While the other comments are true and most games do operate off shifting \"states\" and such, there's one more advanced technique that some games use called \"Goal-Oriented Action Planning\", or GOAP. In GOAP, AI consists of two things: things it wants to achieve (goals), and things it can do to change itself or the world around it (actions). An AI is given a set of goals (kill the player, stay alive, etc), and long lists of actions that it could do (move, shoot, reload, etc). The AI then decides which goals it should be going after, and calculates what actions it could be doing at any given time to satisfy as many goals as possible. For example, imagine that an AI soldier is hunting the player, who is somewhere on the other end of a warehouse. The AI's goals are (from highest to lowest priority): * Stay above 10% health * Kill the player * Keep the player in view * Avoid the player's line of sight * Keep its weapon loaded The AI's actions are (in no particular order): * Move to a specific spot * Shoot gun (kills the player, but only when gun is loaded and the player is visible) * Reload (keeps the gun loaded) * Jumpkick player (kills the player, but only when the player is visible and right nearby) * Use a medkit (gives health back) At first, the AI can't see the player. None of the actions it has at its disposal let it kill the player at that moment in time and it's not losing health, so it doesn't bother with those goals and instead tries to get the player into view. Once it sees the player, it realizes that the \"shoot gun\" action would let it kill the player, so it stops moving and starts shooting. If it runs out of ammo and the player isn't dead yet, then it can no longer shoot, so it stops trying to kill the player, moves somewhere to avoid the player's line of sight, and reloads. If the player takes the AI's health down to 10%, it remembers its highest priority, stops shooting, and uses a medkit. If the player gets too close while the AI's out of ammo, then it jumpkicks the player instead of reloading. Process repeats until the player is dead. The cool part is that the programmers don't have to code the nitty-gritty of any of this. All they have to do is decide the AI's list of goals, decide what each action requires and satisfies, and which actions each AI has. The AI then decides the rest on its own. What's more, you wouldn't have to change much to create a vastly-different enemy. For the example above, imagine that the \"Avoid line of sight\" goal was second on the list instead of fourth. Suddenly your brutish soldier AI is doing everything it can to lurk out of sight, only stopping to attack the player once the player has lost track of it. Whole new enemy, only one (1) line difference. If you want to read more, I recommend [this guy's website]( URL_0 ) and the papers he's written on it.",
"It is more or less just a string of priorities tied to set objective, yes. And It was in one of the Halo games that the difference in bad / good enemy AI is not based on any command strings, but the amount of time you need to deal with the enemy (i.e. larger health pool makes enemies look smarter).",
"An absolute base AI could be made from if-then-else statements but to have AI people consider good there's many systems layered on top of that to give a little more realism, things like having a \"state\" like relaxed or alert and shifting priorities and decisions by shifting states etc., and can include even things like altering the breadth and depth of vision cones so an actively alert enemy will be paying more attention as well as looking at spots identified as a hiding place instead of just doing a back and forth patrol etc. There's a YouTube channel called AI And Games that does a lot of exploring on AI in regards to videogames specifically as well as mapping out the specific ways specific games do their thing."
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n2ntiu | How is stamina(endurance) built? | I understand how muscles are made stronger. But i don't understand how stamina is built. Because it doesn't feel like the body would microfracture the heart? How does exhaustion play into it? Is all exhaustion equal? If I get exhausted playing Beat Saber for example, is that as effective as getting equally exhausted running? It doesn't feel like it would be. Does gaining more endurance increase your energy/calorie consumption? | Biology | explainlikeimfive | {
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"In general building stamina and endurance is done by improving your body's capabilities of supplying your muscles with oxygen and energy and also by the body getting more efficient at transporting away waste products from the muscles. When a muscle contracts it requires energy and oxygen which is consumed. This results in waste products being created which need to he transported away. So by increasing your stamina or endurance you simply improve the body's capabilities in this regard. Your endurance and stamina will vary slightly depending on what you exercise. If you run or do cardio you improve the hearts capability in pumping blood which results in more oxygen and energy can be transported to the muscles. Your leg muscles also get better at consuming the energy and oxygen more efficiently so it utilises the energy and oxygen pumped by the heart to a greater extent. If you instead of running lift lighter weights with more repetitions your heart doesn't get much better at pumping blood, but your muscles will still get more efficient and that muscle gains more endurance. If you do high intensity training like running intervals your muscles consume more oxygen than the heart can supply it with. When the muscle is forced to work without oxygen it will start to create a lot of lactic acid and eventually the muscle won't be able to contract any more until the lactic acid has been transported away. So this type of training will again improve the muscle efficiency so it takes longer before the lactic acid starts being produced. Also the muscle gets better at disposing of the lactic acid so you can keep working out for longer and also need less time to recover between exercises. So not all exhaustion is equal. If you work up a high pulse like when running your heart gets stronger and better but you won't be able to do much more bicep curls or push ups. Similarly if you do push ups you will exhaust your arms and chest but not improve your heart, so you won't get better at running by doing push ups."
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n2ogrt | How an underwater wave sinks a submarine. | Physics | explainlikeimfive | {
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"Actual submariner here. There are very many factors at play here, so we may not know an exact answer, but undersea “waves” that we might see during a seismic tsunami event, or surface storm like a hurricane or typhoon can move the submarine around in the water like anything else. For those of us piloting a submarine, maintaining depth is a balance of factors from the angle of our planes (similar to a plane’s wings) as well as the water/air ratio we maintain in our ballast tanks to obtain our desired ‘buoyancy’, or our ability to maintain a desired depth with minimal work on the planes. Subsurface disturbances or waves can affect our ability to pilot the submarine safely. Sometimes we can get to a deeper depth to avoid a surface storm, but if an event is severe enough, it’s possible to lose control. A mixture of conditions, improper training, or bad decisions could have a catastrophic effect."
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n2op77 | why are there a huge amount of different insect varieties, like in ants, but only a small amount of different varieties in animals such as crocodiles? | Biology | explainlikeimfive | {
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"Tiny changes in those small animals allow them to fulfill different niches and avoid competition. A tiny change in a crocodiles morphology wouldn't do as much the separate it from the other croc species. Ex. A slight change in the size of a birds beak (I know I changed examples but still) will change its primary food source. A small change in a crocs mouth.. will still make it be a top predator.",
"I think its about the size of animals, there aren't as many possible niches for large animals like a tree browser like a giraffe, also bugs can be specialized for a very small area like a specific tree",
"There’s lots of great answers here. I’d also like to add that short life cycles and large quantities off offspring offer a large pool for desirable mutations coupled with more opportunities to perpetuate those mutations."
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n2oxil | How and why did the number 13 become such an unlucky number? | Other | explainlikeimfive | {
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"We’re not actually sure why 13 is a famous unlucky number in the west. It appears to have got to be a popular thing sometime in the early 1900s but they history of it before then isn’t really known, but it popped into the social world around then and took off. But 13 isn’t the only unlucky number. Go around to other cultures and you’ll find they’ll have various lucky and unlucky numbers too. In the west, lucky and unlucky numbers are sorta “fun” things, but go to Asia and lucky and unlucky (or auspicious) numbers have much more cultural significance.",
"You should have asked when and where, because those answers are easier. It was somewhere around New England, and some time in the early 1900s. That's about as much info as anyone can actually find, the rest is pure speculation. The Unlucky 13 thing is a purely American phenomenon, and people can only guess at its origin. There's one theory that suggests Judas Iscariot (not to be confused with Judas Priest) was the 13th apostle, but that doesn't hold water because someone would have probably figured it out sooner than almost 2 thousand years later. There's another theory that the 13th law was omitted from Hammurabi's Law Code, but that one falls flat because none of those laws were numbered. It might be connected to the original 13 British Colonies, but again... why did it take so long and what the hell is unlucky about that? The theory that makes the most sense (to me, anyway) is that 12 is a very natural number, which means thirteen is unnatural. 12 months in a year, 12 hours in half a day, 12 beers in a 12-pack, 12 eggs in a dozen, the 12 Days Of Christmas, and so on. 12 is a nice even number that everyone seems to like. Of course, this theory makes perfect sense to me because my invisible friend just plain hates odd numbers. No idea why, he won't say."
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n2pnic | Why is it while driving and not paying attention, you can suddenly snap out of it and have no clue where you are? | Biology | explainlikeimfive | {
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"When we first are learning to do something, we have to expend a lot of conscious attention on it. Once we get used to something, we can basically \"downgrade\" it to automatic sub-conscious actions, like muscle memory. When we get used to driving, we can do the basic steering & operation of the vehicle essentially automatically...we don't need to focus conscious attention on it. As a result, the thing we \\*are\\* consciously focusing on (our \"locus of attention\") can wander to other things that don't involve vehicle navigation. When you suddenly pay attention enough to ask \"Where am I?\" you don't have any continuous stream of position like you would if you were paying attention and have to figure out where you are. Until you do, you literally don't know where you are. Allow me to stress that basic operation of the vehicle is \\*not\\* the same as \"driving\". Driving safety \\*requires\\* conscious attention because you need to be constantly looking for threats and assessing how you might avoid them, which you can't do automatically. So if you lapse into the \"autodriving\" state it can be extremely dangerous. Your reaction time to unexpected things goes way down.",
"Answer from a neurologist: While it's completely normal to \"zone out\" and have your body go on \"auto pilot\" while you're driving, it is NOT normal to feel unfamiliar with your surroundings (unless, obviously, you're somewhere new) when you \"wake up.\" In a post below you said: \"it's really strange that roads I've been on a million times look completely foreign at first when snapping out of it.\" This is not normal. How long does this sensation last? If I were you, I would talk to a doctor about this, especially if similar things are happening when you aren't driving. This sort of thing can be seen in several types of seizures. BTW I can't diagnose or treat an illness over the internet, so this is not to be taken as medical advice; hence why I stress the importance of seeing your own doctor(s)."
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n2pow8 | How did they achieve realistic movie CGI in the 1990s when computers back then were primarily 486/Pentium based and 3D acceleration came later? | I've seen movies like Jurassic Park and Deep Impact, and am wondering how they achieved such graphical feats that still look realistic by today's standards when computers then are achingly slow compared to what we have nowadays. | Technology | explainlikeimfive | {
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"Jurassic park, specifically, used practical effects rather than just CGI. Those dinosaurs were either puppets, animatronics, or dudes in costumes.",
"Proper computers had accelerated graphics even then --- I think people mostly used SGI for that. More importantly, this only matter for _real-time_ graphics --- when making a movie, rendering the scene can take much longer than the scene itself, so you can have a slower computer (you also have many of them and render different frames in parallel).",
"The rendering (the process of making the actual image itself) times for cgi for films in that time would be weeks, months, for a single scene, now those times would be drastically reduced to produce the same images. But a big help, particularly for Jurassic Park, was that the cgi was mostly to enhance the animatronics and puppets, rather than being the entire final image."
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n2pvht | how can car airbags inflate when they’re under a solid plastic dashboard? | Technology | explainlikeimfive | {
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"text": [
"The plastic has lines on the inside that you can't see that are significantly weaker so it will split apart and let the airbag out. [There's a Slow Mo Guys video showing airbags deploying]( URL_0 ) and you can see that the cover on the front of the steering wheel breaks into two flaps that move out of the way. The plastics have intentional breaking lines built into them so that you don't end up with a chunk centered over the airbag just getting blasted into your face by the small explosion in your dash",
"Because they are explosively inflated with a pyrotechnic device. They blast the plastic cover panel out of the way as they inflate."
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n2qapr | water is transparent right, so when we put on the tap or see a waterfall, it turns white, why is that? | Physics | explainlikeimfive | {
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"Air bubbles are mixed into the water. Depending on the temperature of your water from the tap, it will be air and sometimes minerals in the glass.",
"Air bubbles and turbulence. When the Reynolds number (density * volumetric flow rate * characteristic length / viscosity) of water reaches a certain number (over 10,000), the water molecules move about in a chaotic fashion, so you can't see through it. Reduce the density, flow rate or characteristic length, or increase the characteristic length, and you'll see [laminar flow]( URL_0 ), which is how you expect it to act.",
"A 'white' surface is what we see when all the light hitting something gets bounced back, but scattered in different directions. All other colours are what happens when light hits something, and a little bit gets absorbed. Water doesn't absorb a noticeable amount of light. But usually it also doesn't scatter light - it just lets the light through. However, when light moves from air into water, or the other way around, it bends a little. This is why we can see water even when it's still. Water faucets and water falls are mixtures of water and air, with loooots of little bubbles. Every time light moves into or out of one of those tiny bubbles, it gets bent a little. Since there are so many bubbles, a lot of the light ends up scattered back at us, just like a white surface. As a side note, when light gets bounced back but *not* scattered, you get a reflection."
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n2r0g8 | why is a part of the umbilical cord left on a newborn baby? Why not just cut it all the way to where the belly button will be? | Biology | explainlikeimfive | {
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"It falls off naturally in a few days. If you cut too close, you risk hurting this process and damaging the baby. It is normal to leave a stump so this can occur naturally and correctly.",
"Once you've tried to cut a thick flesh tube off a wriggling baby having spent the previous 12 hours without sleep or food while your partner screams, you'll understand why they keep a decent gap between the child and your scissors.",
"When cutting the cord, you need to place a clamp of some kind between baby and where you cut (best practice used to be two clamps baby side, one placenta side, and cut between them, but I haven't seen that pushed for a while). You do this to stop massive bleeding, which is bad for babies. Obviously, you need to have space to place the clamp(s), so you physically couldn't cut right up to the umbilicus.",
"Where the belly button starts and the umbilical cord ends is not exactly clear and you wouldn’t want to risk damaging the part of them that will be attached for the rest of their life I could go into more detail but I’m explaining like I did to my four year old who asked this exact same question"
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n2sasw | Watching House M.D. The line came up that the person was on dialysis for her kidneys but they don't for the liver. Why can't we? | Biology | explainlikeimfive | {
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"The kidneys are incredibly complex, but their purpose is simple - they remove water + toxins from the blood, and then reabsorb just water back into the blood. That's a simple job we can replicate with machines. The liver breaks down fats, creates new chemicals, attaches to the common bile duct, and a whole host of other functions, which are impossible for us to duplicate.",
"The kidneys filter out the the water in your body and extracts toxic elements and removes excess water so that you can urinate the toxins and water out of the body. The liver doesn't do that and does a vast range of other functions none of which dialysis helps with."
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n2se2p | Why are we able to blink so fast? | How are we able to consistently blink so fast? If so, why can’t our other muscles move that fast with such consistency? | Biology | explainlikeimfive | {
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"There’s almost no mass in your eyelids. Muscles are basically constant force machines... they can move *very* fast on their own but they can only go as fast as the thing they’re attached to can accelerate. And most things you pull with muscles have a lot of mass, relative to the muscles. Eyelids don’t."
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n2sxwd | If I tan easily does that mean my skin is damaged faster? Does sun tan lotion negate all damage from the sun? | Biology | explainlikeimfive | {
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"Hi! This is a really good question. While I can't answer your first question, I can answer the second one. The way most sunscreens work isn't by repairing damage, but by blocking the sun's UV rays. Basically, all light exists on a spectrum of colors. Past the colors we can see is ultraviolet rays(UV rays). They are at the end of the spectrum, indicating that they have the most energy. UV rays are radiation, so thats how they damage your cells. If you block those rays out, they aren't going to damage your cell's DNA and give you cancer. While sunscreen is very effective, even high SPF can't filter out 100% of UV rays, so you will still be absorbing some, but not enough to cause significant damage. **This is also assuming you apply enough of it and reapply frequently.** Sunscreen can't repair pre-existing damage or heal sunburn, but it can ensure that more damage does not happen. I hope that made sense. Just make sure you apply a sunscreen with at least SPF 30, preferably every day to minimize everyday exposure to UV rays. :)"
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n2tbcj | How can a nuclear explosion be strong enough to burn a shadow of a person into a building but not destroy the building? Is it just heat/light and not force? | Would a person safely behind a building be okay, but a person at the same distance from detonation while in the open be vaporized? Are all the "Nuclear shadows at Hiroshima" pictures at a specific limited window of distance from detonation? [ URL_0 ]( URL_0 ) I associate nuclear explosions with obliteration of their surroundings, like this. Is this inaccurate? What goes further, the burn/vaporization distance or the shockwave/explosion distance? | Physics | explainlikeimfive | {
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"They weren't vapourised. The light and radiation from the explosion burnt the area around that person's shadow. Where their shadow fell on the building, footpath, steps, etc was protected by the person's body and so leaves what looks like a shadow. It's just that everything else around the shadow was bleached by the light.",
"An atomic bomb explosion has at least two distinct phases: the flash burn and the traditional shockwave. The flash burn is an intense flash of light/heat that lasts about a thousandth of a second. It's able to reach only the surface of objects and isn't able to travel through a human body. That's what caused the shadows. For relatively small bombs like the one used in hiroshima and nagasaki, the damage distance is about the same. With larger bombs the flash burn damage travels farther. The shadows of hiroshima are far enough from the source of the explosion for buildings to survive. Hiding behind a building would have saved from the flash burn but not from the following shockwave.",
"Well the shadow is literally the part that isn’t burnt. Everything around it is burnt. The human is in the way and blocks all the initial burst of hot gas, particles and radiation that would leave the burnt appearance on the building behind them. For Nagasaki and Hiroshima, those detonated high above the city, so whatever super vaporising solar sphere of instant atomisation death would not have reached the ground. Instead the people would be have been hit by superheated air that gave them super severe burns and radiation sickness. Very few were thanos snapped. These people died far slower deaths. (I’m only saying very few instead of nobody because if they were vapourisrd then we literally have no evidence left of them). Then the bodies were removed and all that was left was a shadow on the wall from the blast. At Nagasaki people 2.6 miles away received burns from the initial flash. At Hiroshima all buildings except the reinforced or earthquake resistant ones within 1 mile were destroyed. It’s obviously a question of magnitude, it takes more energy to topple a building than give a person burns."
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n2tnaz | Why and how, given that there's no nerves in our brain, do some headaches feel like they are located inside our head rather than on the surface? | Biology | explainlikeimfive | {
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"So, pain receptors are not what feel pain. Your pain receptors are activated by stimulus, and they send a message up to your brain. Your brain analyses this message, and *it* is what decides that you are indeed feeling pain. You feel pain with your brain, not your pain receptors. But without pain receptors to feed information into your brain, how do you get a pain sensation? Well, your brain is the boss. It can make you feel whatever it wants to. It can interpret what is going on however it wants to. And sometimes that means “my head is aching”."
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n2twau | OK. This is hard to explain. But it has to do with gravity in spaceships | So, we see lots of films where the crew has artificial gravity by their spacecraft rotating at some predetermined speed. But there is no gravity in space. And since the ship has to rotate on some sort of axis what makes the axis 'heavier' or fixed for the rest of the ship to rotate? If it works like a windmill, what is 'holding' the axis in place to create the spin? | Physics | explainlikeimfive | {
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"> And since the ship has to rotate on some sort of axis what makes the axis 'heavier' or fixed for the rest of the ship to rotate? It isn't rotating on an axis like it was anchored there, it is rotating on *its own* axis. Imagine a basketball spinning, tossed into the air. It is spinning around itself, the axis of its rotation is within itself. That is how the spaceship is spinning as well. Typically the design is a big ring with the axis of rotation being in the center. This is so it can connect to the rest of a ship which isn't spinning, as the central axis would be relatively stationary.",
"First of all the notion of \"there is no gravity in space\" is wrong. (Well geavity \"in\" space isn't correct anyways but that's beyond this eli5 I guess) Not only are all objects in some way shape or form in space, but gravity itself doesn't just magically stop somewhere. Instead it gets weaker but is still present. Astronauts on the ISS don't feel \"no gravity\" because there is none, they feel no gravity because they are in constant free fall. The ISS literally has to move at 27600km/s in order to not drop back on Earth. Just like the Earth has to move at roughly 30km/s in order to not fall into the Sun. Now into your actual question. Which I don't quite understand, I think. The spaceship simply rotates around its own axis, just like the Earth rotates about its axis. It's not anchored onto some rotating motor, instead one could foe instance expell something from the ship in the opposite directionof the desired rotation. Imagine you're in space, holding both your arms stretches out and you have a spray can in each. Now if you spray forward with your right hand and backward with your left hand, then your body starts spinning. In this case your rotational axis would go from head to feet and you would rotate to your right. The same can be applied to bigger objects such as a spaceship."
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n2vh2p | How does allergy medication work? | Biology | explainlikeimfive | {
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"Allergies are the over-reaction of your immune system to allergens (dandruff, hair, pollen, dust, etc.,). This over-reaction triggers your body's defense mechanisms causing you to get itchy, have a runny noise, sneeze, and cough, as those are things that can rid the allergen from your body. Allergy medications work by blocking the parts of your immune system that signal those defense mechanisms. Different medicines target different parts of the immune system, but histamine is one of the main contributors to the allergic response hence why many allergy meds are called anti-histamines.",
"Severe allergic reactions are caused by an antibody called immunoglobulin E overreacting to what it thinks are infections and causing excess histamine to be released which in turn can cause severe reactions possibly leading to anaphylaxis. So anti histamines stop the histamines what they don't do is combat the thing you are allergic to they just minimise your reaction to it. URL_0"
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n2vvsc | Why is grass usually cool even when it's super hot outside? | Biology | explainlikeimfive | {
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"Grass requires a sizable amount of water to remain green and healthy through hot days. For example, the 123 golf courses in the Palm Springs area in Southern California use 25% of the region's water supply: URL_0 Water can hold a lot of thermal energy. Watering the grass and soil acts as a heat sink, making it hard to heat up the ground to higher temperatures on hot days. Plants also convert sunlight into food rather than heat. An area of concrete will just absorb sun and get hot while the same area of grass will turn part of the sun's energy into food so it will not be as hot.",
"Grass is primarily made of water. Water is a material that has a high specific heat meaning it takes a lot of thermal energy to heat up to a certain temperature. Something with a low specific heat, like metal, transfers heat really quickly and takes much less thermal energy. Think of objects as batteries for heat. A cubic meter of water at 20°c is storing a lot more thermal energy than a cubic meter of steel at 20°c.",
"First, Grass constantly evaporates water at the surface, which pulls more water from the ground and transports the nutrients up. Evaporative cooling lowers the temperature. Second, the irregular shape of grass makes for very little contact area with your skin when you step on it. This reduces heat transfer and gives the impression of a lower temperature."
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n2waw9 | What is National Debt and How does It differ From Personal Debt? | Economics | explainlikeimfive | {
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"The US Treasury issues debt instruments called bonds. A bond is a promise by the government to repay the cost of the bond, plus interest, at a later date (10, 20, or 30 years). People buy these bonds because they are an incredibly safe investment. The US government always honors its bonds. The biggest single holder of US bonds is the US Social Security Administration, and the majority of bonds are owned by US citizens and US companies. International companies and foreign governments also invest in US bonds, because they are such stable investments. The interest rate on US bonds is often very close to, or even less than, the inflation rate. Which means the US government actually stands to make money on some bonds. So a country's debt isn't really like personal debt at all."
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n2wfst | what is an NFT | Technology | explainlikeimfive | {
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"NFT, known as Non-fungible token is fundamentally anything that isn't a currency. Let me put this in 5 year old explanations for an ease of understanding. I'll start with what is \"fungible\", because that's our keyword here. Fungible is essentially anything that can be easily replaced. For example, a penny is considered fungible because it can be easily replaced by another penny. So when we talk about non-fungible, we're talking about something that is very unique. Something that cannot be replaced. For example, say you created an art picture. You didn't copy anyone(more or less) and you made it with your own two hands and a creative unique mind. It's unique. Non-fungible. It cannot be replaced. Sure, you can copy and slap it on t-shirts or anything, but it wasn't originally created by you. To certify that an artwork you created is unique and an original, we slap a tag on it that says \"hey, this art right here is made by this person and it is an original!\". And that tag stays on it \"forever\". This tag is essentially an NFT, A Non-Fungible Token. As for why this exists, well I'm not exactly certain but I can imagine it's so we don't get fooled with fakes with modern art or something digital. Let me explain. Imagine Leonardo Da Vinci in modern times with all this cryptos and technology. Everyone loves Leonardo's work and would spend a pretty penny for his work. He creates the Mona Lisa and he puts a Non-Fungible Token on it. That Mona Lisa is now very unique and an original because of that NFT. Now imagine someone simpleton decides to make his own Mona Lisa and imitates Leonardo's work down to the last stroke. This simpleton has created a very identical Mona Lisa that you can say that this simpleton's Mona Lisa can be passed off as Leonardo's work and make tons of money off of his name. BUT WAIT, that identical Mona Lisa doesn't have a NFT and because there already is a Mona Lisa that already has its own NFT that belongs to Leonardo, the identical one can easily be known as a fake and cannot be sold(or at least for the same value the original would). And also we'd probably applaud and then berate the simpleton for being a Leonardo copycat because society and technology. So yeah. NFT. It doesn't have to be art specifically. It can be anything that's unique(hell even a tweet apparently). The value just depends on a variety of factors.",
"imagine a jpeg with a Bitcoin attached to it. Not a literal Bitcoin that has a known monetary exchange rate, but a digital code that only your jpeg has. So... like a watermark. A unique watermark on a jpeg. Now you can claim that your jpeg is rare and valuable, and sell it to a speculator for tens of thousands of dollars. Oh, and generating that unique watermark uses more electricity than a small city."
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n2x0xk | Are photons physical particles? As in could I grab one out of the air and hold it? | Physics | explainlikeimfive | {
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"Photons are... weird. The short answers to your questions are: yes, they're physical particles; no, you couldn't grab one out of the air or hold it. Photons have no *inertial mass*, so they're not made out of \"stuff\" in the sense we traditionally think of it. They're really packets of energy. But energy is basically the same thing as mass for... reasons... so they still react to other matter in ways that mass does. Which is why they can be reflected (mirrors) or refracted (look at a straw in a glass of water)."
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n2x7hu | Does glass experience damage at a cumulative rate where slight damage 2 months ago can accumulate to damage/stress fractures or if I drop my phone does it depend on the direct and singular fall? | I work as an smart phone repair tech, and was wondering, if I drop my phone 5x in a month do all the previous drops damage my phone to an unnoticeable level that eventually reaches a breaking point, or does only the acute fall dictate the damage (I know most phones have a robust glass, does this change the glasses historical tolerances? | Physics | explainlikeimfive | {
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"Yes, virtually all materials experience fatigue damage; small growth of micro cracks whenever they’re loaded up. Brittle materials, like glass, tend to be better about this but it still happens."
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n2yrt9 | Why are all our fingers diffrent sizes? | Biology | explainlikeimfive | {
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"The human hand is remarkably different from that of other primates, with shorter fingers, a smaller palm and a significantly stronger thumb; of course, the most notable feature of our hands is the ability of the thumb to perfectly and comfortably oppose (come into square contact at the tips) each finger of the same hand. While we can’t know with 100% certainty all the factors that led to the evolution of our hands, it would seem it all revolves around this perfect opposability, and the various advantages that provides in certain scenarios, that has dictated the length of each finger. It’s not entirely clear when the modern human hand appeared. Prior to a recent discovery, the consensus was about 800,000 years ago. However, after finding a third metacarpal with a *styloid* (lump at the base) dating back to 1.4 million years ago, scientists are now wondering if the modern hand evolved even earlier. The hands of our ancestors millions of years ago were much like those of modern chimpanzees, whose hands, palms and fingers are much longer, and thumbs are much smaller and weaker. Evolved to accommodate knuckle walking and climbing through trees, their fingers are curved, and the tips lack the broad bones (*apical tufts*) to support the highly sensitive, wide fatty pads of human fingertips. Altogether, this produces a hand that works very well for hooking onto horizontal supports (e.g., tree branches) but can easily lose its grip when waiving a stick and has little strength or precision when attempting to squeeze or pinch. Compared to this poor-gripping, relatively awkward paw, our hands have much shorter palms and fingers. Our fingertips have strong supportive bones on top of which are broad, sensitive, fatty pads that will accommodate uneven surfaces. The palm also has added fatty pads, some of which provide further protection for the hand, and also aids in gripping. The bases of the thumb, second and third fingers have all been strengthened to withstand greater stress, and in fact, the thumb has three muscles attached not seen in chimpanzees: the *flexor pollicis longus*, *flexor pollicis brevis* and *first volar interosseous*. Together, these make for a significantly stronger thumb that, along with some modifications to certain joints, allows for full, comfortable opposability. Researchers have focused on several theories to explain why these changes occurred, and one of the most popular is that a better, stronger, finer grip was needed for making better tools and thus those who had such a grip had a distinct advantage in this way and others were selected out. Using stone tools dates back to about 3.4 million years ago, and around 1.7 million years ago, more refined (but still crude) tools, like axes and cleavers, had appeared. Over the next million or so years, tools became progressively more refined, while the hand evolved to its modern state; since hand strength and dexterity are required to make and use better tools, it is thought that the advantages the latter provide led to the evolution of the former. Another similar theory holds that our hands evolved thanks to the advantages this provides in accurately throwing and clubbing things. In support of this hypothesis, scientists point to the fact that there are two main prehensile (gripping) actions of a human hand: one that grasps with precision and one that holds with power. The precision grip is perhaps best illustrated as the way a pitcher holds a baseball, while the power grip can be seen in the way a man holds an axe. According to adherents of this theory, without the evolved, long and opposable thumb, and precise control of fingertips, a primate couldn’t throw with much strength or accuracy. Likewise, without the vice formed by the thumb overlapping the fingers, and its new powerful *flexor pollicis longus* muscle and the additional fat on the palms, an axe would easily slip from the hands of a primate (as is sometimes seen with chimpanzees wielding sticks). A third, equally violent theory acknowledges both of the first as potentially contributing factors, but notes that neither explains precisely why the hand holds its present, relatively stocky shape. Claiming however, to have the key to the “[geometry]( URL_1 )” of our hands, adherents of this theory note that the human hand only becomes a truly strong weapon when it is formed into a fist. They also identify several facts in support: (1) chimpanzees cannot form a good fist; (2) the smaller surface area of a fist delivers a blow with greater force; and (3) the way the bones are arranged when one makes a fist imparts even more force on the victim. And it is the precision with which the bones are aligned that the researchers feel most bolsters their argument. When clenched in a fist, there is no space inside, and this is because of the precise lengths of the finger bones; in addition, the excellent support provided by the thumb is due to the fact that it is precisely the right length, and begins at just the right place on the palm. [ URL_2 ]( URL_0"
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n2z1np | Why do images of earth from space not contain satellites and other space junk? | Earth Science | explainlikeimfive | {
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"I think you're really underestimating how big Earth and the space around it are, and how small those things are in comparison. Also for image satellites it might be more desirable to pick a lower orbit, where there's less of this stuff in the way. On the off chance that something *is* in the way, they might discard the photo and get another one on the next pass.",
"Why do photos taken from your phone don’t contain every spec of dust in between the camera and the subject? As explained by others, they’re either too small to even be caught by the camera, or when they do photobomb a picture they’re just discarded",
"> Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space. - The Hitchhiker's Guide to the Galaxy",
"It's a bit like saying \"why don't you see people in images of the earth?\" There's some huge scales going on here.",
"Think about a mini van. That’s about the size of some satellites, but a good reference point. Some space junk is bigger and a whole lot is smaller. Ever been in an airplane and looked out the window? That’s 40,000 feet (about 7-8 miles). Could you see a mini van on the ground from that distance? Nope. Low Earth orbit starts at about 150miles up. The diameter of Earth is almost 8,000 miles. So to get a full picture of the Earth you have to be far away, and all the objects orbiting Earth (except the moon) are infinitesimally small in comparison.",
"Answer this: \"Why do images of Earth from space not contain trucks?\" Because they're too small and spread out, right? Except there are way more trucks than satellites, AND each truck is bigger too! So you've answered your own question. They're smaller than a pixel in a pic that fits the whole earth.",
"I am one of those newspace satellite engineers, specializing in developing the EO payloads. The distance argument is the strongest one, but there is also the factor of light. The lighting conditions have to be just perfect, angle of sunlight, the shape and surface on the debris and camera position. The smaller size does not actually matter when there is perfect reflection as that would still fill the pixel up. Think taking a long exposure of the sky, the star is smaller than a pixel but still can be seen in the image. This is true as the background is the void of space, not the case when looking at Earth. It can still happen that the background is well lit and the debris is seen as a dark spot. A 10cm debris at 300km being imaged at 400km orbit from a satellite that is doing 30cm resolution on earth would surely see it. But most often it would happen over sea or such where the earth image is not of use. Besides, most satellites do 20m - 1000m resolutions, the sub-meter things are very few, and they will have more problems when there are 60000 new satellites up there. But lighting conditions are still important to actually affect the data meaningfully. The problem is much worse for telescopes on ground as they have really high resolution and smallest of the debris can light up with even a fraction of the light. There is a [study]( URL_0 ) that says, they would eventually even reflect man-made light going off earth.",
"ELI5 If there are one million ants per human on earth, why can't I see them from my window seat on a flight?",
"Another thing is there are around 34,000 peice of space junk larger then 10 centimeter most of those are tracked and URL_0 we are not talking about the first stage of a Saturn V rocket we are talking here small pecies of things. Each one of these have an orbit that can be tracked and monitored. So say that you have a debris field of space junk at altitude 100 miles above the earth's surface you would program you satellite to avoid that area. Spacecraft the pilot would do this. So first you are already avoiding the area that junk is in and then you want to take a picture of the earth's surface you point the camera towards the earth and take the picture while having avoided ever being near the debris in the first place. There have been times when debris has been captured on film. Look up the black night satellite for a good read. Also the camera resolution along with lighting angle of the sun shadows might not be able to illuminate the debris near you. Hope that helps. *edit due to spelling."
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n2z1yp | why can pain sometimes be overwhelming? Doesn’t you body create the feeling in the first place? Can’t it just not? | Biology | explainlikeimfive | {
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"Pain is your bodies way of telling your brain that what’s happening to your body is bad and needs to stop."
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n2zqjn | Why is salt the only rock regularly ingested by humans in its pure form? | Biology | explainlikeimfive | {
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"Salt is actually a mineral, whereas a rock is a composite of multiple minerals and other substances. We can also consume other pure minerals safety in moderate amounts like gold and silver. Salt is uniquely tasty, soluble and cheap, so it’s generally the only mineral we eat in its raw form regularly."
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n2zyej | How does an enclosed environment like a birds egg support a growing animal compared to a mammalian womb? How are waste products removed, are there hormones involved and how does the embryo receive oxygen? | Biology | explainlikeimfive | {
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"Egg has two layers. When egg cools after being laid, the inside layer shrinks a bit, making an air pocket. Egg has garbage sack called an allantois. Garbage sack does gas exchange through the air pocket and tiny holes in egg surface. Garbage sack holds liquid waste. More or less. Edit: several people have expressed concern about eating the garbage sack. Because egg has no baby chick, garbage sack has no waste",
"Because an egg isn't a closed environment, especially compared to the reproduction of eutherian animals as ourselves. Hard eggs are obviously an incredibly successful way to reproduce it gave animals the ability to colonize the land and diversify, it has existed for hundreds of millions of years, and is used by vastly different organisms today. Though eggs do create certain vulnerabilities they definitely work! Eggs contain layers, as the egg forms and hardens a pocket of air is created directly under the shell ,which is porous, and allows the embryo to receive a constant source of oxygen and ventilation of CO2, all the nutrients it needs to develop to hatching is contained in the yolk which the embryo subsists on. Although they are both similar forms of reproduction in technical form; placental mammals are far more complex and a born far more developed. These traits, present in all mammals, are only possible because the greater nutrients and protection offered by developing slowly, protected within our mother, until we are too big for her to support have made mammals incredibly diverse and successful on Earth.",
"Hey guys, OP here. To answer your question yes, I do remember learning about egg development in primary, but it goes as far as : \" at this time, eyes develop. At this time, the beak develops, an egg needs to be warm\". And that's about it. I do have some knowledge in development ( community health nurse and currently pregnant with my first child). So I know a decent amount about human gestation, its just eggs seemed like such a blindspot for me. Right now, this fetus requires so many calories and resources to grow, and an egg is just so.. comparatively bizarre. Thanks all for all your insights!",
"One thing no one has mentioned that I vaguely remeber from a class about birds in took was that they make certain waste products into more stable, less toxic forms. Like nitrogen into a solid form instead of urea. Apparently thats the solid white stuff in bird poop that can be made into fertilizers/explosives? These are 10 year old memories dont listen to me.",
"Basically, an egg is a self supporting system with a built in supply of food and a built-in bathroom with ventilation. Fertilized eggs are basically born with a little live cell from when it is laid, and, at this point, warmth from the nest and the brooding as well as oxygen that comes in through the pores of the eggshell help support the growing chick. Inside the egg, there is enough supply of nutrients for the chick to grow, and a waste disposal sac as well. In mammals, this is the job of the placenta and the mother. Carbon dioxide also passes through the pores in the eggshell. Eventually, the chick outgrows the shell, and is developed enough to hammer through it with it's beak. For the first few hours of life, there is enough of the food storage left from the egg to sustain the chick, connected to it's belly, called the yolk sac.",
"You can see the waste sac in a live egg here: URL_0",
"It looks like most of the question has been answered. But one thing I havent seen in the comments yet(might've just missed it), is that a bird egg is MUCH larger than a human egg. Human eggs are about 100 microns in diameter, or about as wide as a hair. It can barely be seen with the naked eye. Because of that, the embryo must develop with an attachment to the mother in order to receive nutrients. On the other hand, a bird egg is, well, about the size of a baby bird. It has enough room to carry all the nutrients needed for development without feeding from the mother.",
"Also very cool, the evolutionary leap from egg to live birth is not large. In just a few generations and it can switch",
"As a side note, and fun fact I learned while my wife was pregnant, unborn babies drink their own urine in the womb"
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n305ge | What determines if a metal produces an oxide layer? | Chemistry | explainlikeimfive | {
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"Firstly how reactive it is to oxygen. A metal like gold is practically inert and so won’t readily oxidise in air. Where as something like sodium or aluminium will oxidise very quickly. Secondly the physical properties of the oxide. Aluminium oxide isn’t water soluble and is fairly hard so sticks to the metal very well, on the other hand rust on iron is very weak and will be quickly eroded, revealing more iron to oxidise and losing much of the material.",
"I can't really do it for an actual 5 year old level, but here is an explanation: They all produce an oxide layer (noble metals aside) What matters is whether it's protective or not. By that I mean: does the oxide coating protect the underlying metal from further oxidation? And whether it does or not turns out to be largely a function of how much volume change the material undergoes when it oxidizes. If the volume change ratio is above and close to 1, it's protective, if it's any amount under, or over by too much (I forget the exact ratio, 1.5 or 2 or something?) It's not protective. Volume ratio of Aluminum to its oxide : protective Volume ratio of iron to it's oxide : not protective The mechanical properties of the oxide also have an effect if there is any sort of rubbing or wear on the surface (protective oxide that keeps getting rubbed off is not super effective) And if there is anything like salt water around, all bets are off, it'll corrode, \"protective oxide layer\" be damned!"
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n312d7 | What do the numbers mean at a dentist check-up? | Is it identifying the tooth and giving a numerical score or something else? | Other | explainlikeimfive | {
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"Do you mean the numbers which the dentist reads aloud to their assistant while your gums are being checked around each tooth? The dentist is measuring how deep are any gaps (pockets) in your gums, at the base of each tooth. These pockets are places where bacteria may settle and cause tooth decay or gum diseases. Healthier gums fit snugly around teeth. The deeper are the pockets, the more risk they present."
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n31unz | Why does it hurt your ears to listen to loud music in headphones in a quiet environment, but it doesn’t hurt to listen to the same volume in a louder environment? | Biology | explainlikeimfive | {
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"The ear tries to protect itself whenever it can, if it senses a loud sound, it reduces sensitivity to the ear drum, making the sound appear quieter. This process takes a little bit of time, so if an instantaneous loud sound occurs such as you quickly turning up your volume, the ear doesn’t react quickly enough and gets overwhelmed. As gas lawn mowers are generally loud, having one running for a minute or so while you find your favorite playlist is enough time for ears to reduce sensitivity to eardrum. Sealing ear buds are a good option for listening to music while mowing the lawn as they block out more outside noise than regular over the ear headphones do, this will allow your to listen to music at a quieter level, protecting your ears long term."
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n32914 | Why does genital size on humans vary so much from person to person but the rest of our organs are relatively the same size? | Biology | explainlikeimfive | {
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"Some people have long fingers, some people have big heads, or small ears. Some people have feet that are a bit bigger than their height would suggest. Some people (and some races) are on average taller than others. With genitals you’re only noticing it because our culture has an obsession around genital size.",
"You're not talking about all genitals, you're just talking about one organ in particular. Nobody compares uterus size, prostate size or ovary size, only one organ is measured by size. That organ you're asking about is our good friend and our true master, known as the penis. The little general. And the answer will both shock and fail to impress you. The answer is because they don't vary in size very much at all, and because size literally doesn't matter to the females of our species. Lemmy explain why... A guy's size can only be truly measured when that thing is standing at attention. In default resting mode, it can look like anything from a limp eel to a little pimple, but erect most of them are roughly the same size. There are a few notable exceptions like Jay-Z or Tommy Lee, but those are the exceptions and not the rule. I'm considered a small guy at 5.5 inches, but a guy with just over 6 inches is considered gifted by the gods. That's not much of a difference at all, especially when you consider where it's designed to go. The female counterpart organ, also known as the vagina (or the Great Divide, the Happy Valley or the baby cannon), is an organ that even modern science can't fully explain. It's made of highly elastic tissue, elastic enough to fit an entire baby through the opening, yet when it's in default resting position it's only 4 inches deep (for a big one) and the inside walls are all touching each other. Even if after girl gives birth to her 10th baby, her VJ will quickly return to its natural size and shape. While the external appearance of the vulva may be altered by childbirth, the size and function of everything will not. Think about that... 3 to 4 inches deep, inside walls touching each other, and the rest is all elasticity. If you put your smallest finger into there, you can touch the sides in every direction and almost reach the bottom. But given enough time and effort, that thing can stretch out enough to fit a whole baby through it. No guy, not even those freaks of nature, can come even close to the size of a baby. Penis size does matter, but it turns out it only matters in the locker room.",
"They all vary. If you dont focus alot of attention on those other parts you dont notice the differences."
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n32s50 | why isn’t there an ‘absolute hot’? | Physics | explainlikeimfive | {
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"Temperature is roughly \"average kinetic (movement) energy of particles\" Since energy has no upper limit temperature has none either. There is a lower limit because every particle can't have less than 0 Energy.",
"There is: URL_0 . As we've never experienced it, it is the theoretical max temperature."
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n33b65 | How does heartburn imitate arrhythmia? | I read that the most common heartburn symptom is a sharp pain in your chest, but for me it always feel like my heart starts to beat irregularly. It used to trigger panic attacks for me. (I don't have arrhythmia, but I do have reflux.) | Biology | explainlikeimfive | {
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"The esophagus (where reflux or GERD manifests after acid travels in a reverse direction from the stomach) travels in very close proximity to the heart as it goes from your throat to your stomach. Irritation of the esophagus may lead to some minor irritative symptoms of the posterior (back side) of the heart, including palpitations or feelings that are like palpitations. It's difficult to say whether this is from the esophagus moving in response to the irritation and pressing on the heart or if it is coming from the heart itself.",
"I experience this too - not heartburn, but weird heart-type feelings arising, we're pretty sure, from acid reflux. I found out about the acid reflux from a throat scope I requested because I'd been more often having to chew food (particularly breads and meats) very ridiculously thoroughly to prevent it getting \"stuck\" and having to swallow water to force it down - which is REALLY uncomfortable when it fails, btw. That plus heart palpitations/anxiety symptoms, though every time I'd get a checkup or an EKG they'd go \"yeah you're strong as an ox.\" Pantoprazole has been a life changer in that regard - that plus regular cardio (I'd just been lifting before... why mess up gainz, I thought) to get the weight down."
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n33ozy | - why can medication injected into your bloodstream via a shot be administered pretty much anywhere on your arm (or leg, wherever), but blood is always taken directly from a vein? | Biology | explainlikeimfive | {
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"The shot you might be thinking of is actually an intramuscular shot, not an intravenous one. They usually choose the deltoid or the gluteus muscle into which to inject it. It doesn't go directly into your bloodstream, but rather sits in the muscle, which then slowly picks the medication up via its capillaries, returns it to your veins, and then to your heart so it can be circulated throughout your body. Blood is taken from veins because they are easily accessible in several locations on the body and they are a low-flow/low-pressure system. Taking blood from an artery could result in the formation of a hematoma or uncontrolled bleeding, since that is under direct pressure after the heart pumps.",
"For injections you have 3 different methods (that I know of) for placing medication into the body. The method you're thinking of is intramuscular or IM. IM shots are injected into a major muscle group. It uses the tiny blood vessels in the muscle called capillaries to slowly diffuse the medicine into the blood. The kind used to take blood out or inject the medication directly into the bloodstream is called intravenous or IV. The needle goes into a blood vessel to access the blood stream. The inner elbow joint is used simply because it's the most convenient for the doctors and the patient. The veins are close to the skin so the doctor doesn't need to use a big needle to reach them. Finally we have interosseous or IO. This is used in emergencies when the doctors need to get the medicine into the bloodstream immediately or they can't find a vein for whatever reason. They take a drill with a hole in the center and drill into the shin bone. From there the medicine is injected directly into the bone marrow. TL;DR you're thinking of IV injections directly into the bloodstream. The some vaccines and medicine just go into the muscle."
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n34cf9 | Why has the US not been able to end the war in Afghanistan after so many years? | Other | explainlikeimfive | {
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"The big issue is that to win a war you have to be able to achieve your objectives. However the objectives that the US have with their Afghan war can not be achieved with military forces. They want to end the Taliban rule and replace it with a US friendly democratic rule. The problem is that there is no US friendly democratic rulers who are capable of stopping the Taliban from returning. A big part of the issue is that the Afghan people hate the way the US have taken their country by force and is continuing to exert violence towards the Afghan people. Even if the US admits defeat and retreats out of Afghanistan then there is nothing preventing the Taliban from taking control which would be unacceptable for the Americans. So of the two options available the best one for the American forces is to just continue their occupation indefenantly and hope for something to change."
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n34ery | On statistical maps for obesity, diabetes and low income there is always a very high percentage at the border between AZ and New mexico. Why is that so? | Other | explainlikeimfive | {
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"Poverty and obesity/diabetes go together because lower quality of food is cheaper. Also, if you are poor you are more likely to have experienced trauma and depression issues. Stress eating is very common. As for the geographic area you speak of, in areas where there is less development and fewer job opportunities the land is cheaper and so is the cost of living. Concepts like that can keep people trapped because they can't make enough money to move somewhere else even if they wanted to so they just stay put."
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n35gr9 | Why does squinting help you see better? | Biology | explainlikeimfive | {
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"Here's an excellent explanation from an opthamologist with an awesome sense of humour... URL_0",
"The part of our eyes that sees is actually in the back of the eyes. Think of it as pixels of a screen that the brain puts together to give a complete picture. The job of the lens in the eye is to direct light into those pixels. People with impaired eyesight usually have a lens that struggles with directing the light. As a result, each \"pixel\" recieves light from multiple directions and this gives us a blurry image. When we squint or look through a small hole we decrease the amount of light entering our eyes. By doing so we also decrease the total light getting from multiple directions at each pixel, producing a clearer, yet dimmer image.",
"This is a little tricky to ELI5, but squinting reduces the \"aperture\" or opening for light to pass through. A smaller aperture makes it easier to get an image in focus. This requires more light (squinting in the dark just makes things darker), but it helps compensate for issues with the lenses in your eyes. There is a way of taking a photograph with no lenses, by putting a piece of (unexposed) film in a completely sealed box, then poking a pinhole in the box across from the film. The result would be a normal photograph. Lenses are useful to get more detail at one specific distance and to adjust the field of view (telescopic for a narrower but distant view, wide for a wider view). But, that also means that the \"focal point\" -- the place where all the light meets at a point after going through a lens -- changes, and so the lenses also need to adjust the focal point to hit the right place on the back of your eye, or the camera sensor, or the film for old cameras. (If you did not know, your eyes work just like a camera, but with biological instead of chemical film or electronic sensors.)"
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n35he6 | Why does swishing mouthwash remove more debris from your mouth vs water | Other | explainlikeimfive | {
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"Swishing with mouthwash does not remove more debris from your mouth than water. It just leaves a minty aftertaste."
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n36136 | Why is it that when two singers hold notes, but one is slightly off, you can hear "vibrations"? | Physics | explainlikeimfive | {
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"The difference between the pitch (frequency) of the two waves produces what is knows as a \"beat\". It's just the sum of the two waves.",
"Musical notes are expressed scientifically in cycles per second. The commonly accepted middle A note is now 440 cycles per second. (This has changed historically, but that matters not to this discussion.) Middle A is the one in the middle of a piano, as is also accessible by pretty much all musical instruments. We theoretically hear a range of sounds from 20 cycles to 20,000. When two notes are blended they create a sum and a difference. Thus, 1000 cycle note against a 1001 cycle note produces an additional 1 cycle note and a 2001 cycle note. You hear the 1 cycle note as a \"vibration\".",
"This phenomenon is known as \"beats\". If you add together two sine waves with two different frequencies, the resulting wave looks like [this]( URL_0 ). If the two frequencies are very similar but slightly different, the \"inner\" wave on that picture has a frequency half way between them, but the \"outer\" wave has a very low frequency. If you studied trig identities at school, you can show this using the sum-to-product formula. With most sounds you can't actually hear the individual peaks and troughs of the wave because they're too close together, but with beats the frequency of that \"outer\" wave is so low that you can actually hear it getting louder and quieter. Fun fact: if you wear earphones with a slightly different frequency note playing in each ear, you still hear beats, even though in this case the notes are only combined together in your brain. This is called \"binaural beats\" and there are plenty of audio clips on the internet displaying it.",
"Ask a guitar or bass player to tune their instrument using harmonics, or look for a video on YT. There are specific places on the neck of the instrument where a different kind of tone will be produced if you lightly place your finger, rather than pressing all the way down on the string. If you play a harmonic on the fifth fret of the lowest (by pitch) string and the seventh fret of the second lowest string, the two strings ringing together in a specific way. If either string is even slightly out of tune, you'll hear that warbling \"wah wah wah\" noise you're thinking of. To tune the instrument, you adjust the tension on (usually) the higher pitched string using the tuning peg until the 'wah wah wah' sound goes away. Unfortunately, this only works to get the instrument into tune with itself, so you need to be pretty sure that the low E is at least close to in tune before tuning the rest of the strings to be in tune with it. Why/how does this work? It's easiest to visualize if you picture the strings as sine waves. If you pluck a string don't have it fretted, picture it moving like a jump rope, from one end to the other. When you fret a string, you keep the portion above where you're fretting from rotating, so you rotate a shorter portion of the string, making the sound a higher pitch. When you play a harmonic, you don't really fret the string; you place your finger above a fret, gently touching the string. When you pluck it, not only does the portion you plucked vibrate, the portion above where you're touching it vibrates as well. The relationship between the lengths above and below your finger is such (mathematically) that the peaks and valleys of the two lengths line up, making the combination of notes pleasant to the ear. When you do it to two strings at once (specifically one string at 5 and the next highest at 7), the math between the two strings at the two places means that if the peaks and valleys of the 4 vibrating lengths isn't just perfect, the peaks and valleys don't all line up, and you hear dissonance, rather than a pure chiming ring. That dissonance is the wah wah wah noise. So bringing this back around.... that's what you're hearing if the singers voices aren't perfectly in tune with each other... the dissonance between the frequencies of sounds, where the jump ropes aren't lining up."
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n36gyk | Why do some power cables not have a ground prong? | For example, my electric shaver cable only has two prongs. Without a ground prong, doesn't that mean it could shock me if something went wrong with the electricity? | Technology | explainlikeimfive | {
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"The ground wire is meant to save a user from getting shocked when the metal outside of something gets electrically charged. This is not possible in case of an electric shaver since the outside is mainly made out of plastic and the blades are (probably) isolated from the electrical bits.",
"The ground wire is supposed to connect to any pieces of metal you might touch on the appliance. But your electric shaver is most likely made of plastic and therefore there is nothing to connect the ground wire to. Similarly there is no way that an issue with the wiring in the shaver will cause the electricity to flow to your body because everything is made of plastic.",
"All of the other responses give the correct technical answer. The term used to describe such tools is “double insulated.”",
"It's not always necessary. If your shaver has a plastic case that's considered insulation enough, and there's no sensitive electronics inside needing it either."
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n36p5t | How and why did horse domestication become a thing? Was it before or after people learned to ride them? And most specifically how did humans decide that was a thing/point of travel/ good idea? | I’ve searched in this forum and really couldn’t pinpoint an answer. My gut tells me it might have been a side thought after being able to farm and harvest crops, or maybe even domesticate smaller animals. But from what I picture in movies and tv shows, it seems like we were riding horses before any kind of domestication. I greatly appreciate any foresight into this, or sources I can look up to read into further. TIA so much for your insight and time! | Biology | explainlikeimfive | {
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"Take a read, {{Who Ate the First Oyster?: The Extraordinary People Behind the Greatest Firsts in History}} It discusses the domestication of animals amongst many other firsts.",
"On a side note, plant and animal domestication is probably a lot older than you think. We domesticated dogs about 15k years BCE and cattle 10k. Evidence of horse domestication is relatively recent at 5K or later."
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n36pvk | How come people don’t sneeze when they are sleeping? | Biology | explainlikeimfive | {
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"Well, it’s kind of impossible. Sneezing is a reflex, and the brain requires quite a bit of stimulation to actually trigger it. When you’re asleep, the part of your brain that should tell your body it’s time to sneeze becomes much less active - it’s resting, too. So yeah, you can sneeze in your sleep, but it’s usually during the light stages of sleep or when you’re already waking up.",
"I’m pretty sure they do. Or if they do.. the act of it wakes them up... so they aren’t asleep anymore."
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n36y91 | Why does space appear colorful in long exposed pictures but appear black and white to naked eyes? | Never seen any colors during the night time but the space photography appear colorful. | Other | explainlikeimfive | {
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"Your naked eye is not sensitive enough to pick up the faint light over the vast distances. Those pictures are normally taken with pretty fancy telescopes.",
"There are multiple exposures taken through various filters. The individual exposures are post processed to make the colors more vivid, then the various exposures are aligned and combined into a single vivid photo which looks pretty. Originally this was done to show how the glowing gasses around the object were distributed by the type of atom that was glowing. The public now expects these stellar objects to be vivid and colorful. They usually are not. It’s called false color.",
"Also keep in mind that a lot of the pictures you see from long exposures have been processed. Heavily. Any image you see that is taken using a IR/UV/XRAY/ < insert non-visible type of light here > is being presented to you with color added post processing. Someone basically selected a color they liked and used it to stand in for that wavelength. They also often take images of the object using a single visible light wavelength as well. Then the images are combined to present the pretty colored images you are familiar with. This is not the true color of the object however, there is a lot of visible light information that is not included. Edit: Below info is for one of the most popular and familiar nebula images: The Pillars of Creation. \\ > The picture was taken on April 1, 1995 with the Hubble Space Telescope Wide Field and Planetary Camera 2. The color image is constructed from three separate images taken in the light of emission from different types of atoms. Red shows emission from singly-ionized sulfur atoms. Green shows emission from hydrogen. Blue shows light emitted by doubly- ionized oxygen atoms. Text excerpt from the description of the image linked below (link to text below link to image): [ URL_3 ]( URL_0 ) [ URL_2 ]( URL_1 )",
"These strucures in space are really not bright enough for our eyes to see them. The photos you see are taken by adding together a lot of images, or exposing the camera for a long time. It reminds me of those scenes in movies where they look out the window of the spaceship and see a whole galaxy. First they would need to turn off the interior lights to see anything, and that whole galaxy would be very faint."
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n379sg | I have 4 young plants in a vase. One starts losing strength, space is running out. I take it out of the vase. The other plants now battle for their space and grow stronger than the first plant killed. After a while, one remains. Do plants eat each other's roots? How do they take the space? | I can't find anything about this anywhere in any language that I know. | Biology | explainlikeimfive | {
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"Each plant's roots need a certain amount of space to ensure adequate nutrient and water absorbtion from the soil. If it's cramped in there, all of them are getting less than they need. This is also why you have to keep transplanting your plants into larger and larger pots as they continue to grow, because they've \"outgrown\" the one they're in.",
"I believe it starves the other of nutrients. Somethings in nature can even send out chemicals to near by things and kill them off."
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n37h9l | What causes sadness on a chemical level? | Happiness is regulated by serotonin, motivation is regulated by dopamine. So what chemical causes sadness in the human brain? What exactly happens in our brains chemically when we feel a sudden pang of sadness due to, say, the death of loved one ? | Biology | explainlikeimfive | {
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"The same ones, lack of dopamine/serotonin will impact your humor and cause what we define as sadness…"
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n38bzm | how do we measure the size of planets and other entities like black holes that are extremely big? | Earth Science | explainlikeimfive | {
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"We can measure how big it looks in the sky, and then using its distance calculate its size. We know the relationship between distance and relative size. For example, if someone is 6 feet tall we know how big they'll appear to be if they are 100 feet away, 1000 feet away, a mile away, etc"
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n38g5k | why are so many death row executions by lethal injection botched when vets can peacefully put animals “to sleep?” | I know this is a heavy topic, and for the record I don’t support the death penalty, but I’ve always been curious. How is it that we can “put to sleep” pets and farm animals so they peacefully drift off, but so many death row executions end in a lot of pain for the person being executed? I’ve also heard of issues with the government even acquiring the drugs needed for lethal injections. Why can’t they just use whatever they use for dogs and cats, but at a higher dose if needed? Again, I know this is a dark topic, and I don’t want the government executing anyone, but I’ve always wondered about this. | Biology | explainlikeimfive | {
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"Euthanasia of animals is performed by medical professionals using specialised euthanasia drugs with names like Fatal-Plus, Lethabarb, etc. These drugs are generally super-concentrated solutions of sodium pentobarbital (on the order of hundreds of milligrams per millilitre) in some kind of medical setting. Executions, by contrast, are performed by prison officials using whatever drugs they can get their hands on, including by ordering them from [UK drug wholesalers operating out of the back of a driving school]( URL_1 ). The people who perform executions are not medical professionals. Often, they are amateurs who quickly find out that killing a fellow human being, no matter how heinous the crime, is more than they can handle. [Quoth Jay Chapman, the man who invented lethal injection,]( URL_0 ) \"It never occurred to me when we set this up that we’d have complete idiots administering the drugs.” EDIT: Formatting."
],
"score": [
3
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"text_urls": [
[
"https://www.nytimes.com/2007/02/11/magazine/11injection.t.html?pagewanted=3&_r=0",
"http://news.bbc.co.uk/today/hi/today/newsid_9342000/9342976.stm"
]
]
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| [
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|
n38h1q | What happens to light after it hits the retina and initiates a nerve signal? | I’m labelling this as physics rather than biology because **I’m not asking about how our body uses the light to create an electric signal, instead I’m interested in where the light that has entered the eye and hit the retina then goes after the process?** I hope that’s clear. | Physics | explainlikeimfive | {
"a_id": [
"gwo872k",
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"text": [
"The light is absorbed to create that electrical signal and to my recollection it also generates a small amount of heat. So the photon itself is converted entirely to heat and (electrical) energy, there is no \"light\" left to go anywhere, it's in a different form altogether. Light that isn't absorbed in this way is reflected back out, which is how we can see eyes and even into the eye with the right equipment.",
"It's gone. It's absorbed by the retina. That's how vision works in the first place. You can't not ask about how how the light creates a signal because it's the same thing as what you're asking."
],
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28,
4
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