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mwlkxa | How does auto focus in digital cameras and mobile cameras work? How does the program know what it is focusing on and how far the object is and whether it is focusing correctly? | Technology | explainlikeimfive | {
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"Kind of like a trial and error. If the image is too blurry, it will auto-adjust to focus at a further or closer distance, if the image sharpens, and the pixel data from the image becomes more complex (sharpens) than a blurr, it's a good sign that it's adjusting in the right direction. After overcorrecting in one direction and it becomes blurry again, the sensor can determine that it has adjusted too far, and will go back to the sharper image. At least that's how I would design autofocus software on a camera. This may be computationally expensive. I've also heard of range detection like ultrasound in some cameras to determine the objects distance from the lens to determine the proper focus. Then a motor rotates the focus dial on the lens.",
"Followup question. What diabolical bastard made phone cameras like mine, that auto focus to perfect clarity every time, then pop out of focus?",
"You've asked two separate questions here. The first is how does the camera focus. The second is how does the camera know what to (try to) focus on. Let's take them in that order. First, how does autofocus work? There are basically two different types of autofocus technology. One is called **contrast detection** and the other is **phase detection**. **Contrast detection** starts from the observation that, if the object in the picture is in focus, you'd expect to see some sharp edges. So the camera basically looks at the picture, and measures how much contrast there is in the small areas where it's trying to get the focus right. The assumption is that more contrast = sharper edges = better focus. So the camera just focuses the lens in and out, on a sort of trial and error basis, until it gets the highest contrast reading. If it moves the lens and the contrast reduces, it knows it needs to move the lens the other way. If it moves the lens and the contrast increases, it knows to keep moving the lens in that direction until the contrast stops increasing. A couple of interesting observations fall out of this. Firstly, note that contrast detection relies on being able to process and do calculations on the image, so it's strictly for digital cameras only. Old-style film cameras simply can't do this. Secondly, contrast detection requires contrast: it can't focus on smooth uniformly coloured objects. **Phase detection** works differently. It starts from the observation that, if the object in the picture is in focus, then all the different rays of light from the object, which have travelled through different parts of the lens, must all end up in the same place on the sensor. So the autofocus sensor effectively looks at the light that's coming through the top of the lens, and compares it with the light that's coming through the bottom of the lens. If they show the same picture, the subject is in focus. If they don't, then by comparing the two pictures the camera can work out whether the focus is too far forward or too far back, and by how much, so it can tell the lens to go to the correct place directly. Phase detection doesn't have to work directly on the image sensor. It can, but it's only relatively recently that manufacturers have been able to do that. It was more common for cameras to have a separate autofocus sensor. For example SLRs would reflect some of the light down to a sensor in the bottom of the camera, and that would work fine as long as the light path to the AF sensor was the same length as the light path to the imaging sensor. Note also that phase detection works on the light coming through the lens, not on the digital image, so phase detection AF is quite workable in film cameras (and in fact it was invented before contrast detection AF). So that's how the AF works. Now **how does the camera know what to focus on?** With some cameras, you tell it to focus on whatever's in a particular area of the sensor. That's particularly common in 'pro' cameras. These cameras will often also be able to look at the areas surrounding the one you've specified, so that if the subject moves from one area to another, the camera can track it automatically. Most digital cameras also have a set of 'rules' that they use to look at the picture and work out what's likely to be the most interesting or important part. If there's a big area of blue at the top, that's likely to be sky and you don't want to focus on it. If there's a big area of green at the bottom, that's likely to be grass and you probably don't want to focus on it. If there's an oval area of pink in the middle, it might be a face so you might want to focus on it. Obviously this is hugely simplified but you get the idea. These days they can also work out which bits of the picture are eyes, and that's really important because getting somebody's eyes in focus is more important (if you have to choose) than other parts of the face. Does that all make sense?",
"Some cameras use contrast to determine if they're in focus. They look at what's coming in to the camera and does some comparison to see how sharp the image is. If an image is blurry, the contrast (difference in brightness) between two adjacent points will be low, but as the image becomes clearer, the difference in contrast between two adjacent points becomes greater. Side note, there's basically two types of autofocus: Passive and Active. Passive would rely on the camera looking at the incoming light and seeing what the contrast is like (as above). Active sends out a beam of energy (e.g. ultrasonic waves) to determine how far away things are / if anything is nearby to assist with focusing. Some cameras use an autofocus assist beam (i.e. an infrared beam of light to light up the scene) to aid with focusing."
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mwm7nc | How can there be a global water shortage if virtually all of our water is recycled naturally? | There are many articles claiming a global water shortage is near. I understand local droughts and other causes that may affect cities and even countries, but how can it be global? Where is the water going? I can only imagine relatively small amounts for things like nuclear waste. And on that note many times people say that producing beef or almonds or other things waste tons of water, but isnt that water also recycled eventually? | Earth Science | explainlikeimfive | {
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"We are short on drinking ready water where people are, which is how this is measured. (How many people don’t have access to enough water each day)",
"Because global warming is changing weather patterns around the world which means less rain and snow in places where it used to be. It's not that there's less water overall, it's just that changing weather patterns changes where the water is going, which is places were it's either not needed or inaccessible. For example, less winter snow in the Rocky Mountains means less spring and summer water in the Colorado River watershed which provides water for much of The Southwestern U.S., eventually emptying in the Pacific. At the same time, Typhoons in the pacific are getting bigger and more frequent, so there's more water being dumped back into the ocean. In other words, water that used to fall as snow in the Rockies is now falling as rain in the Pacific Ocean where it's unusable. That's a simplistic explanation but you get the drift.",
"All water eventually ends up in the oceans, and we can't drink sea water. We could process sea water to be drinkable, but it takes a lot of electricity so we never built a lot of plants to do that.",
"If the rate at which we consume water exceeds the rate at which water is recycled, a shortage becomes inevitable. It's like spending more money than you make. You'll eventually go broke, no matter how big your savings. This can happen at any scale."
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mwmf84 | Do vitamin supplement dissolvable tablets (eg. Berocca) do anything | Biology | explainlikeimfive | {
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"Vitamin supplementation is only effective if you are deficient on the vitamin that the supplement provides. There are lots of reasons that someone could be deficient in a vitamin, either it isn't in their diet in sufficient quantities or they are bad at absorbing a particular vitamin from their food and require more of it than someone with normal absorption levels. Berocca tablets aren't different than other supplements. If you need something in them they will help. If you are sufficient in all of the offered vitamins then they won't do much. There is a potential for fat soluble vitamins to become toxic if you ingest them in sufficient qualities. It has happened where arctic explorers will be forced to eat one of their sled dogs and have died from vitamin a toxicity after eating the liver. Usually supplements like berocca only have water soluble vitamins in them, in that case your body just expels the excess vitamin along with the rest of it's waste."
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mwmweu | Why do we stutter even though we know exactly what we want to say? | Biology | explainlikeimfive | {
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"Speech is hard. This is what is involved in saying 'twang' > To say the sound /t/ we need a momentary blockage of the airflow with the tongue just behind the teeth at the alveolar ridge. We need blocked airflow but no vocal fold engagement. Immediately after to say the /w/ sound we need to now engage the vocal folds and make an o shape with the lips that then pulls back. We then need to co-ordinate the jaw dropping and lounge moving to the floor of the mouth and back a bit to say the /æ/ sound, while maintaining vocal fold engagement at roughly 110Hz for men, 200 for women. That's the air being forced through the slightly tensed and raised vocal folds to bring them together so that sound passing through vibrates them in a regular pattern. Now let's keep those vocal folds engaged and occlude the mouth again, quickly bringing the tongue up towards the soft palate, further back in the mouth. Also let's lower the velum and open up the nasal cavity briefly so that sound can escape out the nose to make the /ŋ/ sound. All that to say twang. 4 simple sounds in a split second, involving 6 moving parts all with precise co-ordination. And that isn't even taking into account any of the other things you can add on, all the tone and intonation. Language is hard too. That's just the pure mechanics of saying the word. Formulating a whole sentence that is meaningful, conveys what you want to say, makes sense to the listener... it's a lot of processing, at a very rapid speed. Add in anxiety and concerns about social stuff, and we're at a very complex system making a lot of bits move all in co-ordination during a lot of stress. How complex speech is isn't really appreciated enough, we are in awe of people moving just their fingers and feet for pedals when they master the piano but speech involves even more things moving as one in just the right way. And I haven't even mentioned co-ordinating all that with breathing right for speech (which is also actually a major contributor) And so we expect to see a number of dysfluencies, some stuttering behaviours. 1-3% is normal for everybody, usually of the repetition (the sound, word or phrase is repeated) kind with some prolongations (the sound is stretched out). Much more than that 1-3%, or Blocks (when no sound comes out) and secondary behaviors (other behaviours that the person does or that the stutter causes) are where it starts to become a true stutter.",
"It's not my specialist subject at all, but I've read a couple of articles on the subject. To make words come out of your mouth, there is a part of your brain that takes the \"words you want to say\" messages and controls the parts of your mouth, tongue, breathing and stuff to make the desired sounds come out of your mouth. There is another part of the brain that deals with hearing and understanding. That part of the brain takes sounds coming in your ears and identifies word sounds and constructs meaning out of them. When you actually want to speak, both of these processes are working together. In your brain you form the sequence of words you want to say, and send them to the \"make words come out of your mouth\" process. At the same time the \"understanding language\" part of your brain is listening to the actual sounds coming out of your mouth and checking that the sounds it is hearing are a correct representation of what you wanted to say. If it detects something going wrong, it interrupts the making words process and makes you go back a bit and do it again, but right this time. For people who stammer, there is a mismatch in this process. The \"detect a mistake and correct it\" process happens when it doesn't need to happen, and causes a stutter. Of course once the first stutter happens, there is now a genuine mistake, so the process repeats, and you get caught in a loop of trying to correct the error caused by trying to correct the previous error. It is well known that people who are prone to stuttering and stammering only do it in certain situations, for example if they are nervous or in certain emotional states, because in those situations, there is a different threshold for error tolerance. If you are comfortable and with people you trust, your brain just doesn't care as much if it makes a bit of a mistake. If you can't hear yourself speak, then you can't stammer because it breaks the feedback loop. If you are singing, then a different process is taking place. The brain deals with music and language separately. If you listen to a song, for example, it is very often the case that you just don't follow the meaning of the lyrics because your brain is in \"music\" mode rather than \"language\" mode. When you sing, the sound feedback is being handled by the music part of the brain, so the hypercorrection from the language part of the brain doesn't cause the undesirable interruptions.",
"im not sure how ELI5 this can be - as there are MANY different reasons and pathologies for stutters so you'd need many ELI5s for each an every one maybe? Other general comments here are kinda covering it but two people's stutters whilst seeming the same may be due to wildly different reasons/causes.",
"too much neural activity your brain is trying to protect you from messing it up by asking you to shush it cuz you might fail and relive an episode of being a failure in the past, its logic that if you sound weird or not good enough or say something stupid you might not get a chance of reproducing and your genes will leave the gene pool!",
"Yeah I always understood stuttering to be an airflow problem. It’s not a mouth problem as much as almost choking on the air that should be expelled to drive the words.",
"The part of your brain that figures out what you actually want to say and the part of your brain that makes your mouth actually say it are both separate areas, all on their own! That's why you can have a word stuck on 'the tip of your tongue', or stutter over something you clearly have in mind.",
"I’ve had a stutter my whole life, it’s improved a lot but I still have it when I have to say my name. Especially if it’s someone asking me my name at Starbucks or in that kind of setting. I have to say “my name is ___” or “name is ____”. Another weird part of my stutter is I get a word blockage on the last word of a sentence unless someone finished the sentence for me then I can say the last word fine. Brains are weird."
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mwn2ng | why do so many animals yawn? | Wouldn’t it make sense for different species to have different ways of expressing fatigue? | Biology | explainlikeimfive | {
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"Not sure if correct but yawning is done for your body to take in more air and oxygen than with normal breathing. When tired you supposedly breathe slower and so you yawn to make up for the oxygen. So it makes sense that any breathing animal would yawn."
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mwnfug | Why do teeth require so much care to last as long as the rest of our bodies? | Maybe I’m underestimating how much maintenance I put into the rest of my body? | Biology | explainlikeimfive | {
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"Our modern diets include a lot of food items that our teeth have not (yet?) evolved to cope with. We eat a lot more sugar and live a lot longer than our distant ancestors.",
"Like the others say, a lot of bacteria. But also, your teeth can't re-generate, like your bones and skin can.",
"Your mouth is a gateway to a wild amount of different things that can eat away at your teeth. When you eat some candy, your shin isn’t coated with the candy",
"If you ate no, or very little, sugar, then your teeth would require no, or very little, care. Unfortunately, sugar is in almost everything we eat in a modern diet. So we attend to our teeth.",
"As well as what others have said, we frankly weren't designed to live as long as we do now. If you're probably going to die at 40, your teeth may hold out long enough. But these days we can live twice as long at least, and our teeth simply have not evolved enough to keep up."
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mwo0cm | How do Magic Erasers (those little sponge-block things made by many companies including Mr. Clean) work? | Chemistry | explainlikeimfive | {
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"They are abrasive (like steel wool or sandpaper), just a very fine grit. Their amazing cleaning comes from physically scraping dirt off on a very small scale. As an aside, Magic Erasers are way overpriced, you can buy the exact same sponges in bags of like 100 for a few dollars on Amazon (or other online retailer). Search \"melamine sponge\".",
"They’re a super fine sand paper sponge. So, they essentially remove the top layer of the surface you’re cleaning. Would not recommend for glass.",
"They are extremely fine melamine (plastic) “sandpaper”. They should be used with a very light touch, with light strokes, like you’re just trying to touch the dirt, not the item’s surface. If you press too hard or use it on the same area for too long, you will take off the finish and you’ll notice there’s a dull spot on the item now. It’s easier to ruin finish with magic erasers than people think"
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mwoz57 | Why does pressure increase the deeper you go underwater? Is it related to the weight of water above you or gravity? | Physics | explainlikeimfive | {
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"Both? Gravity gives things their weight. When you go deeper under the ocean, more water is above you, pressing down into more water beneath you, and beside you, and all around you. This creates a metric fuckton of pressure, more than enough to instantaneously crush many living things at far enough depths.",
"The weight of the water above you. When you reach the bottom of the Mariana Trench, the weight being pushed on you is like hundreds of elephants crushing down on. But it’s also not just from above—it’s from all around you, from all angles, all the time.",
"The weight of the water above is equal to the mass of the water above multiplied by gravity. If you could be in the same underwater situation on the moon then the pressure would be six times less, even though the mass of the water was the same."
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mwpcnb | Why is uninstalling so much faster than installing something? | The same amount of data is getting added or removed from your system each time I think, so why is removing it so much faster? | Technology | explainlikeimfive | {
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"Because you don't actually delete anything. Data bits aren't overwritten, only the section is declared empty to be overwritten when a new files is saved",
"Data isn't physically deleted, it's just marked to say it can be written over. If you imagine the hard disk as being a blackboard. Installing the program is drawing a complicated image on the blackboard, all different coloured chalks, and all the rest of it. Uninstalling the program is just hanging a sign on the blackboard to say \"Feel free to use this board if you need it.\"",
"All file systems are different but most work a bit like this. When writing data to a device the computer adds the name and length of the file as well as the first place it will write the data into a file allocation table which is basically a list of all the files in your device. Then it copies data it is receiving onto many sectors one the device. Sectors are like sheets of paper that the data is written on. If it gets too the end of the sector and still has more data to write, it writes the address of the next sector it is going to write on. This continues until all the data is written. Uninstalling (deleting) a file is much simpler. It just erases the entry in the file allocation table."
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mwpcuy | Why is it so hard for a camera lens to capture the depth and the quality as seen with a naked eye? | Technology | explainlikeimfive | {
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"The simple answer is that it is just as hard for the eye. Our eyes also have depth of field issues, but we constantly shift the point of focus. Rather than thinking if the eye as taking a photo think of it more like a video camera that can refocus almost instantly. As soon as we look at a blurry part of the picture it immediately snaps into focus. Our brain then stitches it all together so we perceive it as a sharply in focus world.",
"Although good cameras are better than the human eye to capture something, the difficulties to make a good picture are as it follows: * Your eye got a resolution of a few millions of pixels (total amount of \"photoreceptor cells\" in your retina). To get such a good resolution, you either need a giant artificial \"retina\" or a retina with very tiny photoreceptors, both of which are hard to create. * Your brain analyses the picture. Your camera barely do it (and only the digital ones). This makes what you see clearer than what you detect, while the camera usually don't turn the raw measured data into a vectorial picture. * You need to make quite a lot of parameters setting with your camera that are automated in your eye. Like focusing or the time of exposure (well, your eyes don't have any time of exposure IIRC, so that's a thing a camera will have to deal with that an eye don't) EDIT: * and the focal is very different, causing a picture to seems so unlike what you see (think of taking a moon picture with your smartphone camera and how bad it looks? Well it's because there is a such higher focal than your eye, making everything far seems little)",
"I'll answer for the depth part with hopefully easy to understand solution, that doesn't take the physics/biology too literally and only explain the basic concept. Camera only uses one lens and seeing depth requires two points of views (2 eyes). The brain perceives depth from the difference between the two pictures seen by 2 eyes. If you try to perceive distance with only 1 eye open you will notice that it is a lot harder. 2 points of view (or eyes) is required because then the brain can analyze the small differences in light traveling different distance/direction from the same object into your different eyes. There are these virtual reality/3D movies/glasses and the depth in these is created from the different images projected into each eye.",
"If you look at the optical properties of our eyes, they are terrible. But as many here said our eyes are in constant movement and 'scan' our field of vision. Also and most importantly out brain does the main work in our perception. So rather than compare our eye to a single picture you would have to compare it to a series of images that are processed by a computer afterward."
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mwq4i3 | why sometimes we have a feeling that our heart skipped a beat? | Biology | explainlikeimfive | {
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"Your heart throws out an extra beat slightly sooner than it should (PAC or PVC). After this there is a slightly longer than normal pause before the next beat. The pause is what you feel.",
"One reason is that the top of the heart, the atrias, will kinda spasm and won't sufficiently do their job (help fill the ventricles aka bottom/larger part of the heart) which means that the heart will beat as normal but with less volume flowing through into your body. It's called a PAC and it's pretty common and can be exasperated with caffeine and other drugs."
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mwqvpw | Is Sun more like a frozen explosion (held back by it’s own gravity) or is it more like a boiling ball of lava? | Physics | explainlikeimfive | {
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"Its actually more like an implosion held up by the energy coming from its core. Said core fuses hydrogen nuclei together, which produces helium nuclei, as well as a lot of energy.",
"It's definitely not a boiling ball of lava. In fact, if you take a chunk of sun out of the sun, that chunk won't even produce that much heat, because the fusion reaction is not particularly strong. From wikipedia: > models of the Sun's interior indicate \\[...\\] energy production, of approximately 276.5 [watts]( URL_1 ) per cubic metre at the center of the core,[\\[76\\]]( URL_2 ) which is about the same power density inside a [compost pile]( URL_0 ). It's just that the sun is super huge, so all of that total mass and heat adds up."
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mwqxhe | What are flies doing when it looks like they are rubbing their hands? | Biology | explainlikeimfive | {
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"Cleaning their sensory hairs. Most insects have some kind of grooming habit like this for their forelimbs and face.",
"Correct me if I’m wrong but if my childhood’s obsession of animals books serves me well, they are just grooming. Flies need to be quick and any particles (dust, dirt) on their legs or wings will compromise their agility.",
"While grooming seems to be the primary reason, there may be other reasons for the behavior. One idea is that the rubbing helps regenerate an even magnetic field or [remove static]( URL_0 .), giving them improved flight abilities. Another is that they are simply sensing the environment more, kinda how a dog sometimes licks its nose over and over while smelling something. Each \"rub\" may give them a new whiff of the area. These ideas are based on the fact that flies have been found to have built in magnetic sensors that act like [compasses]( URL_2 ) and evidence shows they may even *see* magnetism, even [imprinting beneficial locations to offspring through genetic changes]( URL_1 ) that guide the fly where to go. So keeping their sensors clean may still be only part of what's going on. TLDR: Removing static and getting a better look at where they are.",
"Planning and considering from which angle it can be the most fucking annoying from. Flies are experts in guerilla warfare tactics. Blitz attacks.",
"Cleaning themselves, you'll find cockroaches and house flies groom themselves so often and are cleaner than your house cat and dog"
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"https://www.discovermagazine.com/planet-earth/can-fruit-flies-see-magnetism"
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mwr62j | So many meds warn not to mix with alcohol. Why? What exactly is alcohol doing to make them dangerous? | Chemistry | explainlikeimfive | {
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"The enzymes in the liver which is used to metabolize alcohol is also used to metabolize a lot of different substances including a lot of drugs. When you drink a lot of alcohol you bind up these enzymes preventing them from metabolizing other things. This changes the way that the medicines metabolize over time. The effect is different in different medications of course because they work differently and have different metabolazion pathways. With some medication it might be possible to take more or less medication to get the same effect while in others you can get buildup of toxic metabolic byproducts that should have been handled by the liver. There was also a different reason why people were told to not drink alcohol while on antibiotics. These drugs are often used to treat sexually transferable diseases. And while they might cure the symptoms fairly quickly you can still infect others. And doctors found it hard to get people to stop having sex, especially as people struggling with sexually transferable diseases were often the ones getting drunk on the town and hooking up with people. So they told a white lie and instead instructed peolpe to not drink alcohol on antibiotics which was much easier to for people to follow and helped reduce the spread of diseases.",
"Doctor here. It's mainly due to two properties of alcohol, which can be dangerous if combined with medications with similar actions, simply because the effects will be stacked on top of each other. 1) liver toxicity. Alcohol is metabolized by your liver and may be \"poisonous\" to it in higher doses. Some medications are the same, so combining two substances that harm your liver will obviously increase the risk of that happening. That's the case with isotretinoin (called accutane in the US, I think) 2) Central nervous system depression (in other words, deactivating your brain). This effect explains why alcohol gets you sleepy and also why benzodiazepines like clonazepam or other sleep meds make you sleep. The issue as that, when you combine them with alcohol, this deactivation might be too intense and you might shut down unintended areas in your brain, such as the one responsible for your respiratory drive. That's what happened to Michael Jackson, although I don't think there was alcohol involved.",
"Lots of medications get processed by the liver. Alcohol also gets processed by the liver. So, there's a risk that doing both could damage your liver by overworking it. There's also a rumour that I don't know is true. One of the first antibiotics was used to treat syphilis. Allegedly users were told not to drink because the meds wouldn't work, but the reason was secretly that drinking might lead to them having sex and spreading the syphilis before it got treated.",
"One reason is many medications have negative effects, for example on your breathing and heart rate. Your body does it's best to compensate for this under normal conditions, but alcohol inhibits your body's ability to compensate for the negative effects of the meds, making the side effects much worse and can easily become dangerous, particularly when it comes to breathing and heart rate"
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mwrnap | Why do we pee more often when it's cold? | Biology | explainlikeimfive | {
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"Your blood vessels try to keep blood from flowing to your limbs to preserve body heat. This causes your blood pressure to rise. Your kidneys respond by pulling water out of your blood to try to lower blood pressure.",
"To keep warm, your body does work to raise your body temperature. This is done by increasing your metabolism, shivering, etc. Your metabolism is powered by the chemical adenosine triphosphate (ATP). When it releases its energy CO2 and water are by products. You will breath out the CO2, but the water will accumulate and be processed and stored in your bladder. Literally every process in your body works by consuming ATP. It powers almost every chemical reaction, your muscles, etc. You typically have only about 100g of ATP in your body at any one time, but it is produced and consumed so often, that in the course of a single day you will have produced and used an amount that would total about you own body weight."
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mwspa8 | How does the weighing scale measure body fat? | Technology | explainlikeimfive | {
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"text": [
"By sending a small electric current trough your body. Manufacturer will pretend it will encounter a difference resistance whether it encounter fat, bones or muscles, which is true, but not accurate at all. Truth is, it simply doesn't work and is just marketing"
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mwt6hd | How is it possible to become allergic to something you've been eating all of your life? | Biology | explainlikeimfive | {
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"Tolerance is just as much of an active process as an aggressive immune response. On top of that, the overall functioning of the immune system is incredibly complex, and depends on a massive number and variety of cells/signals working together correctly. Sometimes, things just go wrong. That sounds like an incredibly vague answer, and it kinda is, but you have to imagine the whole thing is similar to a machine with millions and millions of moving parts, or a computer. Little errors happen, sometimes with major consequences."
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mwthsn | Why do we tremble when we are nervous? | Our hands and feet get shaky when nervous , why is that? | Biology | explainlikeimfive | {
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"Your body prepares to deal with the stressor, interpreting the anxiousness as a signal that you'll need to stand your ground or escape from danger. Your muscles become primed to act, leading to a trembling sensation, twitching, or shaking. Tremors caused by anxiety are called psychogenic tremors. URL_0",
"You're not used to the adrenaline. Adrenaline is a drug, but just a hormone that does a series of things in your body, most noticeably, opening capillaries and flooding your body with blood to allow muscles to act more rapidly. If I recall correctly, it also enhances the effects of endorphins, making pain a lot less noticeable/ incapacitating. Just like any drug, though, you can develop a tolerance to it and learn how to function on it. Just like the 60 years old alcoholic never shows signs of being drunk, a person constantly in stressful situations doesn't shake or jitter as adrenaline floods them. Adrenaline also allows the heart to go into overdrive and is used medically in a few conditions in the hospital, but I suspect doctors are very picky and choosey on when to use it and probably want heavy sedatives nearby if they do use it. This is not the same as a fighter in a ring who is comfortable through exposure, but more like the people who have lived in battlezones their entire life. I wouldn't be surprised if the constant exposure to adrenaline also caused permanent damage to their brains like other drugs do a well, but am unsure if any research has been done into the topic.",
"One word: Adrenaline. It rushes through your body when you get scared or are in danger. It messes with your nervous system as it goes through your body which causes the shaking. Adrenaline also does a bunch of other things to our body. Such as increased heart rate and sweat."
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mwtvfc | How does Nvidia DLSS work? | I understand its some sort of AI/network but I don't get how just turning that on for a supported video game give me extra frames. | Technology | explainlikeimfive | {
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"It renders the game at a low resolution and then upscales it to a higher one, in a way that is much less demanding than rendering the game at a high resolution to begin with. The trick is that they upscale it now using a standard image-scaling algorithm, like we've been using since digital images existed, but a special system 'trained' on scaling that specific game. Here's the much-simplified gist of how that works: You have a program whose job is to look at a low-res image and guess what it should look like in a higher-resolution, then output the result. It keeps track of a vast collection of image statistics to help it make that guess. At Nvidia HQ, they run the game and render it twice simultaneously, once at a low resolution and once at a high resolution. A computer looks at each frame of the low-res image, makes its best guess as to what the upscaled version should look like, then makes a few alternative guesses by using slightly different versions of its stored stats. Then it looks at the real higher-resolution image it's provided, checks which guess was closest to that, and adjusts its stored stats to better align with that guess. Next time you feed it that same low-res frame, its guess will be closer to the ideal. Do this over and over and over and over again, and eventually you've got a program that's pretty damn good at turning low-res images into high-res ones. Nvidia then ships the code to users and it can be run on graphics cards that has the special hardware optimized for this. Doing it per-game helps a lot because what works for one game's graphics won't necessarily work for another game's (imagine scaling The Last of Us when the system trained on Minecraft). Now it won't ever be as good as actually rendering the game in the higher resolution to begin with, but if it's done well it can look a ton better than taking a low-res image and upscaling it the traditional way, and it's still a lot cheaper (in terms of performance cost) than rendering it in the target resolution. (This ignores the aspects that are special to rendering videogame assets and not just plain video feeds, but it's Explain Like I'm Five, not Explain Like I'm a Computer Science Student, and hopefully gets the general idea across.)"
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mwu9t7 | Why is it with everything else, the less you use it the longer it lasts, but the human body needs extra work to make it last longer? | Biology | explainlikeimfive | {
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"text": [
"Not really a true premise, think of abandoned buildings. They decay rapidly, and for similar reasons. Both require ongoing maintenance to keep the elements and other organisms from destroying the entire structure."
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mwuj76 | why are some programming languages faster than others? | For instance python is slow and c++ is fast. Why is that? | Technology | explainlikeimfive | {
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"In the specific instance you cited, python is a \"scripting language\" which means that it gets read and executed (interpreted into machine language) line-by-line each time it runs. C is a compiled language, which means it gets converted into an executable file (machine language) before you run it. So basically the line-by-line reading part gets done in advance.",
"This won't be true in all cases, but I'm the case you mentioned it's because Python is an interpreted language and C++ is a compiled language. When the computer executes a Python script it has to translate into another language the computer understands. C++ translates itself to another language when you compile it, and thats what your computer reads. Its like being handed one book in a language you understand (compiled C++ code), and another book with a different language and a pocket dictionary (Python code). You're going to be able to read both in the end, but you'll read the first book way faster",
"People do mention compiled languages vs scripting interpreted languages which certainly is probably the biggest factor but there are smaller significant factors worth discussing. C++ has \"harsher rules\" than Python for instance, at least to the newbie programmer. IMO I prefer to call the C++ rules \"unapologetically simpler\" instead of harsher, but these harsher rules means that the C++ compiler can make a lot of useful assumptions that the Python interpreter cannot. For instance C++ is \"strictly typed,\" while Python is \"weakly typed.\" In Python you can try to assign for instance numbers to strings, mix and match strings and numbers in lists, etc. Python will only catch these errors at runtime. C++ doesn't let you do that, the C++ rules require each variable to have the type it is declared before it is used and then enforces these types for everything from assignments to addition to make sure you aren't adding weird things like strings together. But once the compiler checks all these things, the program it compiles to does not have to check this all at runtime. When C++ is told to add two number variables, it just adds them, Python instead has to check whether the variables you are adding in the first place are numbers and then add them together. This takes a lot more time than the just adding. This is just one example but there are many like it. Another example is that C++ gives the programmer full control over memory and it is up to the programmer to make sure that memory is freed once unused, Python instead has a complicated scheme to make sure memory is freed once unused. To do nearly anything Python often has to do all sorts of checks for all sorts of edge cases prior to doing the actual operation listed on the line. C++ doesn't, its more annoying with its rules sometimes but this is what I mean by C++ being \"simpler,\" Python's rules let you do more but Python's rules also come with a lot of exceptions (pun intended) and Python has to check that its not violating these. Every check adds more time it takes to run. IIRC there is no reason Python can't be a compiled language beside the fact that no one has yet made a compiler for it. But all of this stuff would certainly get in the way of performance compared to C++, so no one bothers to make one.",
"As a general rule the \"closer to the metal\" a language is the faster it is. C++ is compiled down to something the processor can understand on its own and run with very little overhead. The compiler isn't perfect so some inefficiencies sneak in, but it's very minor. Python however is interpreted. What happens is that a different program (the interpreter) reads your python code and on the fly tells the processor what to do and when. This intermediate step of the interpreting the code you wrote and translating it to something the computer understands will slow down the overall program compared to c++ which runs directly on the processor."
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mwurzh | If people only breathe out of one nostril at any given moment anyway... why are blocked noses so uncomfortable, even when only one nostril is blocked? | Biology | explainlikeimfive | {
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"text": [
"Because your body can't switch to that nostril and unblock the damn thing. So your sinus swells up, everything gets backed up, and it's just not a fun time. Horray for spring.",
"You don't only breath out of one nostril. One nostril will be more open than the other, but air still passes through both. When your sinuses swell, they cause the nostril that's already naturally partially restricted to become fully restricted and the asymmetry is uncomfortable."
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mwusc3 | What is plasma, the fourth state of matter? | Physics | explainlikeimfive | {
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"text": [
"Take a solid, and pump a bunch of energy into it. The molecules which were pretty solidly chilling out start moving around a bunch more, and the solid becomes a liquid and it has different properties now. Pump more energy into the liquid until the molecules get way more active, and they'll actually start breaking the liquid apart as they go crazy. Now it's a gas, and it has different properties. Pump even more energy into the gas, and things get so weird that it will *conduct electricity*, which is a hugely different property since gasses are insulators. It doesn't spread out evenly like gasses do, magnetism can have a big impact on it even though it doesn't affect gasses, etc. - so many properties have changed that it's an entirely different state of matter now. That's plasma.",
"Imagine an atom as a living body, electrons are the hands. Electricity can be conducted through you so long as there are free hands to hold it(imagine a lightning bolt) and pass it along. Solid- atoms are all hugging each other for warmth in one mass(if enough hands are free, electricity is passed through, depends on the arrangement) Liquid-atoms are all holding hands and walking around. Switching hands to cross between and such.(switching happens at light speed, so there are usually enough pathways for some electrical Conductivity, but there’s some resistance as hands are occupied with hand holding. Gas- atoms are running around with their hands out, slapping the hands of others(no clear pathways for electricity because you don’t have a hand waiting to receive it. Plasma- hands separate from the body and float around between everyone while the all the body’s are running around. (The hands are free from their prior duties and can now exclusively be used to pass electricity, or high 5, whatever they want. In reality, the hands ARE the electricity, but in order to transfer charge, there has to be electrons that can easily be swapped out for others, so as to let a charge pass through. An electron with a full time job is harder to replace."
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mwvgaf | What are capital gains taxes and what do they do? | Everything i see when i look it up doesn’t leave me confident enough to think i actually know what they are. | Economics | explainlikeimfive | {
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"The capital gains tax is a government fee on the profit made from selling certain types of assets. These include stock investments or real estate property. A capital gain is calculated as the total sale price minus the original cost of an asset. So tax is only paid on the *profit* made from the sale of the asset. It's currently either 0%, 15%, or 20% depending on the income. It is *much* lower than normal income tax. Which tends to result in people who generate their income primarily from investments paying very low tax rates. The current proposal would boost the top-end of the capital gains tax to 43.4%."
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mwvkfk | Why and how did they manage to make every country follow the Gregorian calendar? Even the North Koreans? | I'm aware that most east asian and SE asian countries also follow the Lunar Calendar but even then, the Gregorian calendar is also used | Other | explainlikeimfive | {
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"text": [
"Colonialism and imperialism. Most countries in the world at once point have been either colonized or economically subjugated by a European power. Since up until about the end of the 19th century almost all the world trade focused around Europe and Europe used the Gregorian calendar it ended up becoming a de facto standard world wide."
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mww6q3 | Why do you get goosebumps when you’re excited or scared? | Biology | explainlikeimfive | {
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"As you know, mammals are generally covered in fur. When mammals are cold, they have a reflex that fluffs up their fur to make their fur coat a warmer insulator, like a thick winter jacket . When mammals are scared, they have a reflex that fluffs up their fur to make them look larger and more threatening, in order to scare off predators or attackers. The way this fluffing reflex works is that there are tiny little muscles in the skin that attach to the root of each hair follicle. When these tiny muscles contract, each hair shaft is pulled upright, and a little bump appears in the skin at the base of each lifted hair shaft. Humans have these tiny muscles in our skin too, because we are mammals covered in fur. It’s just that our fur has become to thin and so fine, that it is nearly invisible, and you can generally see the skin underneath. We have the same reflexes to fluff up our fur as other mammals do, we just don’t have thick fur coats. So what you see is goosebumps.",
"Ever seen a cat raise its fur when agitated? You do the same, minus the fur. Basically it's your involuntary fight or flight reflex, preparing you for conflict."
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mwwoou | What is a 'key change', referring to music? | I know what it sounds like when it is pointed out, but have no idea what it is and how it works. | Other | explainlikeimfive | {
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"A basic example of a key is the key of C. On a piano, it’s all of the white notes and none of the black notes. So a song that is played in the key of C would only use the white notes. There are seven different notes in a key (though many octaves). This is a simplified explanation, as not every song stays strictly within these 7 notes. A key change is when the song moves from the key of C, to (for example) the key of C#. This means that the entire song shifted up one note. Within a key, chords are given Roman numerical identifiers (I, ii, iii, IV, V, vi). The C chord is designated as the I chord in the key of C. If a I chord was being played (C, E, & G notes), this entire chord would shift one note to the right on a piano when the key changes to C#. The I chord now has the notes C#, F, & G# in it. The ii, iii, IV, V, & vi chords all shift up one note too, so the chords remain the same relative distance apart from each other, but the entire song is now higher in pitch. This would all be much easier to explain with a visual aid.",
"When in music you are playing in a \"key\" it basically means that all the chords and the notes played in that song belong to a certain scale. For example, if you are playing a song in the key of G major, all the notes played and the notes included in the chords belong to the G major scale. When you do a key change, you are shifting everything to a new scale. Now keep in mind that what matters in a song are not the notes themselves, but the relationship and the distance between notes. You can play a song in all the keys, and it will still sound like that song (if you keep the same distances between notes), just higher or lower. Usually key changes are done to lift the song upwards (resulting in the same song, just feeling it higher in pitch) or to create wierd harmonies when you are not keeping the same relation between notes and chords of the previous key."
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mwxb3n | Why are paint's primary colors red, yellow, and blue, and light's primary colors are red, green and, blue? | Chemistry | explainlikeimfive | {
"a_id": [
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"text": [
"Paint's primary colors are cyan, yellow, and magenta. Which are the complementary colors to light's rgb. It is my understanding that it is because pigment is subtractive when mixing, since mixing the primary pigments gives you black. Light is additive when mixing, since mixing the primary colors gives you white light."
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mwy7aa | Why is it that when you open your eyes underwater everything is blurry, but when you’re wearing goggles it’s clear? | Physics | explainlikeimfive | {
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"text": [
"This is a fun one. So your eyes have two lenses that it uses to focus light (refraction) into a point in the back of your eye where your optic nerves are. The front one is the cornea, which normally has light travelling through air hit the surface of the cornea, and use the curved shape and greater density to bend the light. But water has about the same density as your cornea, so it can't bend the light as much. The second lens can't compensate, and the light that hits your optic nerve is not in focus",
"Everything bends light a different certain way. This bending happens as light goes into something and again as it leaves. Light bends a certain amount as it leaves air and enters your eye and your eye can easily focus light bent that way. Light entering your eye from water is bent differently and your eye can’t completely adjust for it, so your vision is blurry. Goggles simply provide a pocket of air so your eyes can properly focus the light."
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mwyfsl | Why do bottles filled with water start smelling after a certain amount of time? | Other | explainlikeimfive | {
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"text": [
"URL_0 Here is a Sci-Show episode just about that. But basically most water is at least partially chlorinated and we are used to the taste, but the chlorine and other gasses release from the water into the room over time"
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mwyl90 | is honey really a good substitute for sugar? | i just found out (google search) that honey is 82% sugar. so is this 'healthy sugar'? if there even is such a thing. i always believed honey to be the most healthy of foods, even reading somewhere 'its one of the only foods excess of which is not harmful' but this high sugar content clearly worrying. i regret topping off my foods with it. but now. just too confused. can anyone please help. thank you | Other | explainlikeimfive | {
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"text": [
"The 18% that \\*isn't\\* sugar is generally the bit that's good for you, albeit you still wouldn't want to eat the stuff if you have diabetes. The thing you mustn't do is to use more of it than you would sugar on the assumption it's healthy, though.",
"Excess of honey is *absolutely* harmful. Excess of anything is harmful as a general vague idea, but specifically excess of anything that's almost entirely sugar is *really bad*. You shouldn't regret using honey and it's perfectly good as a sweetener - just treat it as you'd treat sugar. It is definitely healthier than refined white sugar for sure, yes, but in everyday practical terms the difference just doesn't matter that much.",
"I'm not 100% sure of what the question is? But if I'm understanding right, honey isn't healthy. I'm sorry that you were misled."
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mwyzuv | car number plates in the usa | Here in the uk, registration plates come with the car (we have vanity/private number plates you can transfer but as far as I know you can’t buy a car without a reg) do you have to supply your own number plate when you buy one? Is it registered to the car or does each person transfer the number plate when they change vehicles? | Other | explainlikeimfive | {
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"Exact procedures are state-level laws so some of the details vary but in general: Car doesn't come with the plate. You apply for a temporary plate which is literally just printed out on a printer and is good for some period of time while you get your actual plate. If you're getting a new car because for example, your old car got totaled in an accident or is being junked, you can have the plate transferred from the old vehicle to the new vehicle at the DMV - basically transferring the registration from the old vehicle to the new vehicle so the government knows what car the plate is tied to. Otherwise, you apply for a new plate which you either get in person at the DMV or is mailed to you.",
"The biggest difference is that *license* plates—as they're called in the US—are not tied to a particular car in perpetuity like they (typically) are in the UK. When you buy a car you do not have to register it if you don't need to drive it on public roads. For instance a truck permanently kept on a farm doesn't need to be registered at all. That aside, typically when you buy a vehicle in the US it is registered at the time of purchase. The new owner can do this themselves, or if it's bought from a dealer they can usually pay a small fee for the dealer to do it for them. The exact process varies from state to state: the registration of motor vehicles is done under the auspices of the state governments, not the federal government. As such the license plates themselves bear the state's name, not the country's; a car registered in Chicago will have an [Illinois license plate]( URL_1 ), a car registered in Boston will have a [Massachusetts license plate]( URL_0 ), a car registered in Miami will have a [Florida license plate]( URL_2 ), etc. As you can see from the photos I've linked they have unique visual designs and different numbering formats. The only thing about them that is standardized across the country (and Canada and Mexico, too) is the plate's size (6\" high by 12\" wide) and the location of the mounting holes. Also notice that they have adhesive decals with numbers on them applied at the corners: these decals indicate the month and year that the registration expires. The decals and a paper registration certificate carried by the driver are required to prove that the car is properly registered; the plate is not in and of itself proof of proper registration. Before the expiry the owner will have to pay a fee to renew the registration, usually on an annual basis. Some states also require the car to undergo a mechanical inspection for roadworthiness, and/or undergo exhaust emissions testing to ensure the car's exhaust emissions control systems are functioning properly. This is sort of analogous to your \"MOT\", but it's not compulsory in every state. The plates (typically) stay in the possession of the vehicle owner and can be transferred to a different vehicle in their possession. When you sell a car and buy another one you can typically keep the old plates and change the registration so that the new car uses the old plates, while the other party who bought the old car has to get new plates or transfer an old one of their own.",
"In CA, the default\\* is that plates stay with the car. Unless they've changed things, in NY plates stay with the registered owner (transfer to new car, etc) & #x200B; \\*can always pay extra to do it different"
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mwz0uv | Why do belly buttons collect lint?? | Other | explainlikeimfive | {
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"Most hairs on your belly are growing in the direction of the belly button. When wearing clothes that are susceptible to generate lint while you are moving around the lint can only travel in the direction of the belly button, eventually collecting there. Having a smooth, hairless belly should therefore also reduce lint accumulation.",
"And why don't all my t-shirts have a hole in my belly button area?!",
"If you use the pieces of toenail you bite off to scrape it out you don't have to worry about it"
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mwzjns | if advanced scurvy reopens old wounds/scars, does that also happen to stretchmarks? And how deep does the wound reopen? If someone is pierced completely with a spear and it heals, will it open completely through again with scurvy? | Biology | explainlikeimfive | {
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"The reason this happens is because skin is held together by a mesh of structural proteins called collagen. Vitamin C is vital in creating collagen, but also in maintaining it. Wound healing has a great need for collagen, so it brings a bunch of cells to the wound called fibroblasts that produce this collagen, and maintain it. In the severe absence of vitamin C, the fibroblasts instead begin to degrade the collagen structures, basically eating the structure of the skin. This happens only at scars because fibroblasts are far more common in scars than in other parts of the skin. I can't prove it, but my educated guess is that scurvy would not entirely reopen deep wounds. Collagen is mostly found in skin, bone, and tendons, with a bit in muscles too. It's not found much in internal organs. So, the fibroblasts that would destroy collagen will be found mostly in skin and bone scars. Muscles, even those that have healed after damage, would have much fewer fibroblasts, so would take longer to decay. It might happen eventually though if by some morbid method you managed to keep the victim alive long enough for this to happen. As for stretch marks, I couldn't find anything on that, I'd expect because scurvy is found mostly in ships' crews and armies and traditionally, women who had already had children tended not to be crewing ships or fighting wars. There simply wouldn't have been any opportunities for doctors to observe mothers with scurvy back when most scurvy was happening. I don't think these wounds would reopen, because they're not full on wounds, they're a bunch of tiny sub-surface tears that quickly repair themselves. I doubt such things would recruit that many fibroblasts, and they'd leave quite soon after because there's so little damage to repair. Even if they did degrade the collagen, it wouldn't result in open sores, because the wounds are tiny, originate from below, and never breached the surface."
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mwzmzx | What is dirt? I know it’s like pretty much the base for most ground, but what is it made of? | Earth Science | explainlikeimfive | {
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"It's like decomposed plant matter and animal remains and bits of Rock and sediment and minerals and water and poop and hopefully not Styrofoam but probably some styrofoam and space dust and elements and molecules and atoms and ... Lots of different stuff all packed down and intermingling",
"The main components of good soil are: * 45% minerals (mostly in the form of sand and clay (large to smaller mineral particles) * 25% water * 25% air * 5% plant and animal remains mostly in decayed forms Obviously there's an enormous amount of variance in different geographic area's soil, but that's an average for good soil to grow plants.",
"Dirt is just a general term that means many different things. I suspect you mean soil which is a specific thing.",
"At one point, all land above sea level had no animals or plants whatsoever. The land was just rocks and minerals, same as you'd see on Mars or the moon. There was zero dirt. Eventually, plants arrived and took over the land, then animals. Imagine millions of years of fallen leaves, fallen trees, seeds, dead insects, poop, everything that could fall on the land that wasn't rocks. This is dirt."
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mx0oyw | How does the filming work for actors who've spent hours upon hours in makeup? | As an example, Arnold Schwarzenegger spent upwards of 6 hours being made up to play Mr Freeze, which I can understand, but what does the filming schedule then look like? Do they film as much as is possible to limit the time spent on set, or is it just doing what they can until the actor has to go through the process or having the get-up removed again? I'm led to believe Jim Carrey had military training in coping with torture techniques when he played The Grinch, but that could be urban legend, of course. | Other | explainlikeimfive | {
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"It depends on the production, but generally the goal is to film as much as humanly possible with them in makeup to try to reduce how many times they have to go through that process. This means that even after a 6-hour makeup session in the morning, you might be working for another 8 hours.",
"Their days are typically long anyways, so while they're in makeup they film other scenes or building sets. But the guy who played the hell guy, I can't think of his name sat in makeup for 7 hours every day to film those movies.",
"A film day can be mad long. It might be that the person comes in a 5-6am, in make up til midday, then film until midnight, but they don't need every actor every day, so you work it out so they sleep at some point. Some actors actually nap in the makeup chair, which I can't imagine, but it makes sense."
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mx1sv8 | Why do you feel more tired when sunburnt? | Biology | explainlikeimfive | {
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"\"Sunburn\" is another name for \"nuclear radiation damage to millions of cells across a wide area of the body\". 1. There is a flurry of activity by DNA-repair enzymes and other repair processes. 2. Those cells with irreparable damage sense it and commit mass cell-suicide to avoid becoming cancer. Their \"bodies\" then need to be swept up and taken away. All together, that is a massive drain on your immune system and body energy stores. And at the same time, being sunburnt probably means you were outside a long time - which means you're likely dehydrated and maybe muscle fatigued from hiking, swimming etc. Add all that to the radiation damage and it's no wonder you're wiped. & #x200B; Edit: I didn't mean alpha/beta/gamma radiation, it's solar UV (*electromagnetic* radiation from a nuclear explosion) that causes sunburn.",
"Because your body is spending energy trying to heal you. Also swimming is both good exercise and an efficient way to get sunburnt so that may also play a role",
"Damage detected on skin surface from prolonged contact with sun rays. Execute healing and cleanup initiatives to repair damage. Notice: healing requires resources, this process may cause light fatigue.",
"The Sun emits a ton of light particles. Each particle has a different amount of energy, some having enough energy to hurt your cells causing sunburn. The one's that cause Sunburn fall under UV (ultraviolet). When your skin cells absorb this UV light, it breaks apart the structures of these cells. Your body needs to remove this damage and get rid of them. Like any damage your body processes, your skin undergoes inflammation from your damage by the repair cells coming to clean up. When you have a sunburn, you have millions of these tiny damages invoking a very large immune response causing massive amount of inflammation and raising your body temperature. This amount of work is tremendous and makes you tired. Also, the clean up chemicals the cells make to repair/protect you also make you tired and not feel well.",
"Because your body is using all its energy/calories trying to repair the damage you allowed the sun to do",
"You literally have a burn across a large portion of your body. Sometime causing a second degree burn meaning it penetrated the outer layers of your skin to the under layers that are more sensitive to damage. Just like in fighting off an infection if your body is working overtime to repair that much damage it’s going to prioritize energy stores to the cells that need it most.",
"Sunburn is an injury to your skin. When your body repairs itself it diverts resources to that task, causing you to feel tired.",
"Likely due to the dehydration and whatever you were doing that caused you to be sunburned. Plus, that's a large surface area burn, and especially if it's peeling off, that's a lot of water loss from the burned areas of skin.",
"If you really want to be mind blown, getting large tattoos feels much the same, both in skin pain at the tattoo site, and the drained tiredness and malaise I associate with sunburn. In fact, some even call the reaction \"tattoo flu\". Similar thing though, I imagine. Damage to the body, trauma, mild shock, inflammation responses, etc.",
"Will spf help prevent this if I'm also hydrated?",
"Sunburns kill skin cells, causing an acute increase in proteins called interferons (among others). These are proteins that have many roles including anti viral effects. A known effect of interferons that are given therapeutically is extreme fatigue (used to be given in cases of hepatitis infection). Source - I am a dermatologist/immunologist."
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mx2xpf | Why do we feel that tingly pain in the jaw the first time we eat something sweet after our mouth had been neutral for a while? | Biology | explainlikeimfive | {
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"You have three sets of salivary glands in your mouth. The different glands produce different types of saliva (thick, mucousy or thin, watery). You're feeling your submandibular saliva glands doing their job. I often get this pain after eating sweet or sour candies.",
"Your saliva glands are going into overdrive in order to break down simple carbohydrates as quick as possible. It probably has more to do with the last time you had a quick dose of carbs, rather than your mouth being “neutral.”"
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mx36vo | If you own millions of dollars of stocks in 1 company and own like 12 or 15 or 20% of the whole company's value, do you then become part of the board of directors? Is THAT how that works? | Other | explainlikeimfive | {
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"Once you own more than 5% of a public company, you have to publicly declare your ownership stake. To \"automatically\" be able to join a board, you'd need to own 50%+1 of shares to nominate yourself and vote yourself on. But being a significant shareholder may be enough to get other shareholders to approve you as a board member. But most board members are not typically large shareholders, but instead others who have some expertise or insights they can offer as a somewhat neutral outsider... you'll see lots of other company CEO's (often from complementary industries), former politicians who may have insights from the government/regulatory angle, industry experts (ie. professors with PhD's in area), etc. For example, you might see an eCommerce company board that has CEO's with knowledge of logistics/shipping, tech architecture, or marketing/advertising.",
"Not necessarily. Each company has its own bylaws established that govern how the company is specifically ruled, but more or less all of them agree that a majority vote by shareholders is required for more or less all decisions not delegated to say the CEO previously. Usually to get on the Board of Directors, you have to convince 51% of the shares to vote you into that position, but usually if you have 20% of the shares you won't have much of a problem getting that support."
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mx3hah | Wouldn't a truck without its back "facepnant" if the driver stepped on the breaks suddenly? | edit: Agh, typo in the title, I meant "faceplant". [This]( URL_0 ) is the vehicle I'm talking about, I know NOTHING about cars or such, so I turn to random strangers on the internet, only hoping I won't be called names. Wouldn't the speed and inertia send the truck forward if it stopped suddenly? Or do these trucks have a system that would prevent such scenario? | Physics | explainlikeimfive | {
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"Something tips over if its center of gravity is pushed far enough over its footprint on the ground. The lower the center of gravity, the harder it is to do this. Those trucks have a fairly low center of gravity and the weight of that little bit on the back isn't trivial. You would probably have to be going faster and breaking harder than it is capable of doing to make it fall front-ways."
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mx3lls | Why do we develop food intolerances (lactose, gluten, etc.) as we grow older despite regularly consuming them as children? | Biology | explainlikeimfive | {
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"I'm a Medical Laboratory Scientist, and lots of my schooling revolved around learning a shitload about immunology. So this is going to be more like ELI18, because the human immune system is wack. Wall of text warning and I can't TL;DR this. Please anyone who reads an inaccuracy or inconsistency correct me. Also I wrote this on my phone and it took a long time so I hope it helps. So there's different reasons for the various things you mentioned. Let's start with lactose, which is a sugar that needs to be broken down by an enzyme called lactase into glucose and galactose in order to be absorbed by the intestines. Some people do not produce sufficient quantities to break down the sugar, however bacteria in your gut *are* able to metabolize lactose, and their consumption of it causes a fermentation reaction, which is the cause of the signs and symptoms of lactose intolerance. So this is an enzymatic insufficiency. Gluten intolerance is a complex spectrum of disorders, lots of scientific debate is still ongoing to better understand. Coeliac's disease is understood to be an autoimmune disorder. Autoimmune disorders are diseases where *your* body makes antibodies against your own tissues by failing a process that classifies things as yourself or foreign. In Coeliac's your body damages your intestines because of a reaction to gluten. This causes you to be unable to absorb nutrients So when your immune system \"sees\" something as a threat it makes antibodies that bind to the \"enemy\". How does it do this? An antibody is a protein made by your immune system to bind in a \"lock and key\" fashion to proteins on the surface of threats known as antigens. This binding causes a cascade of various responses from other elements of your immune system. Part of which is the inflammatory response, which is managed by a type immune cell called t-cells, their destructive processes damage the villi in the intestine. Other allergies such as shellfish, peanuts, or anything like that, is caused by an over reaction by a class or immune antibodies known as IgE antibodies. There are five common classes of immune antibodies IgA, IgG, IgM, and IgE. IgE is known to be the antibody that's most heavily involved in allergic reactions, causing a cascade of cellular and chemical responses. This can cause a variety of things to happen, like hives, rash, itching, or even anaphylaxis. Once again a protein on the surface of some food you've eaten is perceived as a threat. Each consecutive exposure causes increasing overreaction by your immune system. As for why this happens more as you get older, it could be sample bias, it could be repeat exposure that wasn't initially severe enough to be noticable, or changes in your immune system, natural over the top allergies. Also people who develop an autoimmune disease are at an increased probability to develop another autoimmune disease.",
"Your body has a rulebook called DNA. This rulebook has certain timers built into it. Because of these timers we grow when we're little and stop growing when we hit our early 20s. Lactose is a sugar found in milk. Our body mostly needed it when we were breastfed, but not once we grew up. So to be efficient, our body stops making it easy to digest Lactose at an age that we no longer consume it/have access to maternal milk",
"ELI10 1) Partly because when we are young we have little controll over what we eat. We all had that one kid inour class who would throw up at the drop of a hat. As these kids grow older and become in controll of what they eat they realize that they may have low level alergies and intolerances. 2) In terms of gluten intolerance or an allergy to foods there is also your immune system at play. Our immune system is really good at destroying things that could harm us like bacteria, viruses, and other bad things. Our immune system is so powerful that when it messes up it can actually harm a person more than help them. Two common ways our immune systems harm us is in the form of **allergies** and **auto-immune disease**. Both of these frequently develop or worsen with age. An allergy is when our body kicks into attack mode against something that isnt dangerous like pollen or peanuts. Attack mode means swelling and heating up so the immune system can do its job. In mild cases your body itches, but in dangerous cases your body swells. Every time your body is exposed to something you are allergic to there is a chance that the reaction will be worse than last time. so a kid who has a mild egg allergy as a kid might become deathly allergic in adulthood. An auto-immmune disease means that your body accidentially creates weapons against itself. These weapons are antibodies. When your body is exposed to a new type of virus or bacteria or immune system, through trial and error, develops a specific type of antibody that can destroy it. Sometimes, for reasons that science doesn't totally understand, our immune system might accidentally make antibodies that attack our own cells. Celiacs is the name of the auto immune disease that is triggered by gluten. Celiacs can develop at any point in life.",
"When I was diagnosed as a coeliac, the Dr explained that it was like male pattern baldness: the faulty gene is already in our DNA, but there's no way of knowing until the symptoms appear. It's just a ticking timebomb. What makes coeliac disease even harder to diagnose is that it has dozens of unrelated symptoms, none of which are *guaranteed* to appear. The only way to confirm coeliacs is to take a biopsy of the intestine, which is usually only used as a last resort. So someone could have been a full blown coeliac for years until they finally get the biopsy done (I had about 3 years of tests, which is actually pretty quick. I know people who were waiting 20+ years). So, between faulty genes, and the length of time it takes to get diagnosed, you're likely to be aware of it much later in life.",
"I binge drank a ton of beer one day, and had a stomach ache, diarrhea and fatigue that lasted like 7 years. It was like a 7 year hangover. I thought I just fucked myself up permanently, until I did some research and tried a gluten free diet and it completely changed my life! In my case, it kinda makes sense, you binge drink a poison and your body learns to hate the poison."
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mx3yja | Why are the hottest/coldest days of the year not the same as the solstices? | Earth Science | explainlikeimfive | {
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"Basically, thermal capacity. The oceans and land masses have to warm up/cool down, and that does not happen immediately. At the winter solstice, the oceans are still warmer than what they would be if the temperature was constant during the entire year. It takes about one or two more months for them to reach their lowest temperature, and by that time the energy coming from the sun starts warming the oceans up again.",
"Temperatures depend on a wildly chaotic combination of natural events, time of year, and fluctuating weather patterns. The sun is only part of it. Picture a cannon that shoots paint at a wall. The cannon is loaded with the exact same powder charge each time, and an identical paint can is used. Each time it's shot, it will leave a different splatter of paint."
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mx40rk | What are our eyes doing when we make our vision blurry? | When looking at an object we can make our sight blurry intentionally. For example if I'm looking at my laptop screen I can stare at it a make it seem blurry, sort of like loosing focus. What are our eyes doing when we do this? | Biology | explainlikeimfive | {
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"You change the point of focus. This is done by squeezing the lense to change it's shape. EDIT: the lense in your eye, using the muscles in your eye! You can do the same thing by holding a finger ~30cm(1 foot) infront of your face. While looking at your fingertip you will notice that everything else seems blurry."
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mx4vd5 | Why does head butting someone hurt the head butted more than the head butter? | Biology | explainlikeimfive | {
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"A properly executed headbutt strikes the victim in the soft part of the face, that is the nose and mouth, with the hardest part of the attackers head, that is the crown of the head, or the forehead just below the hairline. It doesn't really have anything to do with adrenaline, or how angry someone is, it's about technique. It hurts the victim more because the attacker is striking their soft vulnerable parts, the thick crown of the skull is much less prone to injury from a strike like this than the mouth and nose."
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mx5cay | Mole Hairs | ELI5: This is gross but how come a hair that grows out of a mole is longer than any other hair in the nearby vicinity? | Biology | explainlikeimfive | {
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"A mole is a small cluster of specialised skin cells called melanocytes. Usually, melanocytes are spread out evenly, but now and again they clump together and form a mole. A melanocyte’s job is to produce melanin, which is the pigment or colour in your skin. This is why moles are dark, and also why you can get moles by being in the sun. Hairs that grow from a mole are affected by this melanin just like skin is. Melanin makes hair darker and coarser, and longer. The structure of these “mole hairs” is more like the hair on your head (or pubis) than the hair on your arms or legs."
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mx69gt | why does the brain think of alternative scenarios to the negative interactions ,events that happened ? | Biology | explainlikeimfive | {
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"So, the brain is a learning machine. It takes what has happened, analyzes the situation and outcomes, and thinks of a different way to handle the situation. This is for next time. Say if you knock someone’s water over, your brain will analyze that to see what knocked over the water and if it could be avoided."
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mx7cg6 | If potable water is so important why do we use it on our toilets? | Or maybe it's just my country, idk. | Other | explainlikeimfive | {
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"We have an easy access to large supplies of fresh water delivered through a large and complicated infrastructure of pipes. Creating a completely new and separate system for just toilet water would cost a lot of money and take a lot of time both for the initial build and its maintenance.",
"You'd have to have double the plumbing infrastructure, double the pumps, double the water towers, to go only to toilets. Fresh water is important, but copper in the pipes is also important, the time it would take to double the infrastructure is important, lots of things are important.",
"What else are you going to use? Most homes, for cost reasons, aren't built with a facility to collect waste such as shower/sink drain runoff for toilet use",
"Having a single source of water is simpler and carries no risk of contaminating drinking water by hooking up to the wrong supply. If toilet flushing water came from a separate unsafe for drinking supply it opens up the possibility of accidentally connecting the drinking taps to bad water instead of potable water. Also while toilets are about 1/5 of residential water use, residential use is a small fraction of the total water we use. Nearly 2/3 of our water is used for generating electricity and irrigating crops, so any savings from toilets will be a fraction of a fraction.",
"We wouldnt necessarily need all new plumbing. We could just use the gray water from showers, sinks, and dish water. We did that in the military in the poor countries around the world. Saves so much water and electricity. Now sure how we could exactly install in already built houses, but new houses we could have a sump like container either placed underground or in garage with an overflow pipe. Use the outflow pipes to the sump and pumps could be used to push to toilets. If too much water is introduced to the sump, an overflow pipe would be used to pump to the normal sewage pipes."
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mx7s6q | How do planets bend time? | Physics | explainlikeimfive | {
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"Gravity, as far as we know, is caused by distortions in spacetime caused by mass. Since it's a distortion of spacetime it impacts both: space...which is why things are \"pulled\" towards planets, and time...clocks run slower near big masses. There's nothing special about planets in this respect, it happens with all masses, but planets are the largest masses except stars and black holes so it's more pronounced near them. \\*Technically\\*, just moving your watch near a stack of free weights causes it to move a little slower, but it's such a small effect that you can't measure it. On the other hand, GPS satellites have to correct their clocks for the distortion caused by being in earth's gravity well (and for the distortion caused by how fast they're going).",
"I may be wrong about this but I believe this is more or less how it goes. Imagine you have a flat surface, like a table. You place a circular glass somewhere on the table and surround it with 12 marbles the same size as each other, so that you have a circle of marbles touching the outside of the glass. This glass represents Earth. Each of these marbles represents one hour on Earth. You then place another ring of marbles around the glass, but 6 inches away, still with the glass directly in the center of the circle. This ring represents outer space very far away. This ring has 36 marbles in it. All of the marbles in both rings are numbered and in order. Next, take a 6 inch pencil and and place it in between the rings so that it is touching the top marble (Marble #1) against the glass and is pointing directly upwards toward the top marble on the bigger ring (Marble #1). Then, wait 1 minute. Now, rotate the pencil around the smaller ring so that it is facing directly away from the second marble in the smaller ring (Marble #2). Now, which marble in the top ring is being pointed to? You'll see that it is probably Marble #4. So, in the time that it took you to move the pencil from Marble #1 to Marble #2 in the smaller ring, which was 1 minute, the pencil moved from Marble #1 to Marble #4 in the bigger ring. Remember, each of these marbles is equal to 1 Earth hour, so this means 1 hour that passed on Earth was equal to 3 hours that passed in outer space. This is what is known as \"time dilation\". Time closer to a big object (the glass) moves slower than time would when far away from the big object.",
"One video I highly recommend you watch is „Why Gravity is not a force“ from Veritasium. URL_0 You have to think about time and space being directly connected. You can‘t just bend one you have to bend both. Again all mass bends spacetime. Not just planets but also black holes, stars and galaxies.",
"I should preface this with the idea that gravity is the expansion of space-time, outward from things with mass. No need to get into potential subatomic causes. Imagine it as “space pressure”. The rapid and constant expansion of space-time near bodies of mass can only be absorbed into the greater fabric of space-time at the speed of light. Because it’s happening all throughout the body of mass, if you’re not part of the surface mass, you are constantly surrounded by expansion. Like how a group of people radiating heat will put off a more heat at the edges than any single person because they are absorbing more than they are emitting on one side. Because of this there is a kind of “back-pressure” of the space-time expansion and space-time doesn’t have energy type storage properties. It “stores” the build-up by “zooming in” on the space-time that’s there, effectively creating a Doctor Who police box, space is it’s quite literally bigger when you are closer to mass. The difference with the police box is that instead of a barrier that separates the bigger inside from the smaller outside, it’s a gradual increase. It’s not noticeable with size of objects being transferred from one area to another because their size and shape is determined by atomic bonds that adjust accordingly. But the time effect is observable through atomic resonance comparisons. Time will go slower, but if you could compare the sizes of the atoms side by side at the time, the faster one would be slightly smaller, as well as the container it’s in, the person holding it, and so on, that is until you brought it back to earth, then it would be the same size as the other one. This is different from time dilation related to relative speed. Time moves more slowly as you approach the speed of light, it also moves more slowly close to mass. I imagine you may be able to find a happy medium of relative time by going a certain speed at a certain orbit?"
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mx82ve | How computer really work? because for me, its like a magic! please | Technology | explainlikeimfive | {
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"This isn't really an ELI5 questions. This is more like the subject material of two college courses.",
"You know how when you want to store the number 13, you write the digits 1 and 3 next to each other on a piece of paper? Well the computer does the same, but sadly it does not have 10 digits to work with like we do. It is based on electricity, so it only has two states: on and off. Well, we made the computer quite smart because it takes those two states and translates them into two separate digits: off becomes 0 and on becomes 1. Now we just gotta come up with a number system that uses only those two digits. Lucky us, there is one, it's called base two or binary. So our number 13 written in binary is 1101. The number only and uniquely written with 1s and 0s. So now since we based our system on the on and off system, we simply have two cables turned on, one turned off, and then another one turned on. 1101. That's how the computer has short-term memory of stuff like numbers. For long-term stuff, it needs something more permanent than electricity. Magnets! The computer has a bunch of magnetic disks and instead of having power off for a 0 and on for a 1, it instead leaves a tiny mark on the magnetic disks if a 1 is supposed to be there and nothing if a 0 is supposed to be there. Then, later, it has a tiny arm that goes to different spaces on different disks and can detect the presence and absence of these tiny marks and boom, you read binary from the magnetic disk. This was trying to cover your specific questions, as the topic itself is very broad. If you have any further questions feel free to ask in a response to this."
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mx9961 | Why does carbonation hurt your mouth? Why does it burn your nose when you burp? | Biology | explainlikeimfive | {
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"Carbonating water actually produces a compound known as carbonic acid. It is a weak acid and is what causes the burning sensation you feel."
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mx9i3r | Could you catch a bullet in space after a gun has discharged? Do guns operate the same with little to no gravity? | Physics | explainlikeimfive | {
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"No. It will rip through your hand just as easily as on Earth. The force from a gun comes from the explosion of gunpowder (and its modern counterparts) behind the bullet. This shoots the bullet out the barrel at high speeds. This will happen with or without gravity. Whether a gun will fire in a vacuum is a different thing, but after it gets fired, it's the same. Once you have a moving bullet, it will just stay moving until another force hits it, aka, your hand, which will react in exactly the same way as it would on the surface.",
"Gravity has nothing to do with how guns work. It does have influence on the bullet path (it curves it). In space, far from any other source of gravity, the bullet would just go straight. You should not try to catch it...without air, it’s going faster and stays going fast “forever”."
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mxahvt | How important is it to stretch after sport? Almost all the fittest people I know never do cool downs after training and such. | Biology | explainlikeimfive | {
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"I was taught in both competitive gymnastics and personal training to do cool downs after stuff. Why? It transitions your heart back to an appropriate pace. It stops you from fainting. It improves flexibility in a way that preworkout stretching doesn’t. And it just feels nice",
"Hunter gatherers even do cool downs by having rest days. Do they stretch? Well, they retain most of their flexibility well into adulthood because their activities require flexibility. For example, they squat instead of sit in chairs, they climb instead of use elevators, etc. You should stretch.",
"If they are super into this, or professional, they may have other ways to do cool downs that work for them. I run a lot, as does my wife. After a good run, or jog, we slow down, then walk. Maybe sit for a bit. That's our cool down. I would assume ppl newer should really follow all the recommended guidelines, but as you start to do it regularly, you can begin to figure out what works for you. I mean, if you're basing this on someone who's been doing this for years, then I would assume they have their own routine and it works. They probably don't deviate much. While a person who's only been doing it a few months should follow all the guidelines because they don't want to suddenly shock the system, wind up in pain or whatever, by cheating the steps. Edit: Can also depend on what the activity demands too.",
"How old are you/they? The older I've gotten, the more important stretching has become, and the more I've needed warm-ups/cool-downs. It's also more important when you spend more of the day being sedentary."
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mxama7 | People say that big corporations don't pay their fair share in taxes by using loopholes. What exactly are these tax loopholes? | Economics | explainlikeimfive | {
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"If a company declares a loss one year, they can count it against their taxes in following years. They can also deduct loses on assets, meaning that a company can buy an investment declare the value its lost over time against their taxes. This is what Amazon has been doing for the most part. Despite the companies immense size and growth, on paper at least they are losing money because they keep reinvesting their profits into the company. Giving stocks out to staff and executives is tax deductible So is giving to charity, which is partly why all big companies are associated with a charity. But the big one is foreign subsidiaries. Companies open up offices in countries that have very low corporate tax rates and declare their profits in that country. This is why countries like Ireland have so many Corporate headquarters located there.",
"The Government wants business to do stuff, like open a factory in a poor part of town. Since businesses don't just obey orders from the central government in the US (not a communist country), So Congress tries to **~~bribe~~** entice the business by offering them a tax break. Some of these are employment specific, allowing them to deduct the salaries of new employees hired to work in the new facility. Businesses do this, when it's worth it, and if they do it enough, they can use the loophole constructed by Congress to pay no taxes. It's totally paying their fair share, because Congress built the loophole, not the company."
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mxbmte | Why do migraines make you nauseous ? | Biology | explainlikeimfive | {
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"There are theories about how the vagus nerve is responsible for the nausea. Breathing techniques have proven effective in reducing it. Try 7-12 (practice when you can): Breathe in for about 7 seconds and out for 12. on outbreath you may have to purse your lips to slowly deflate. Imagine the last of the air going out through the soles of your feet until the diafragm is completely relaxed / belly empty of air. It also lowers heart rate and bp, releases endorphines and adjust the balance between O2 and CO2 in the blood. Simultaneously you can use your fingers to press from both sides on the meaty area between the thumb and index finger. It’s supposed to hurt a bit. This alone reduces nausea.",
"Gosh. I needed info on this. The headache doesn't kill me but the nauseous paralysed me completely.",
"The thing is, we don't know. Migraines are really not understood well. It's not really known what causes them or why the symptoms that occur during them occur.",
"Humming can also help. It releases cortisol and soothes you. A quick way to shrink the vessels is to put an ice pack on the back of you next and swing your arms around to get blood flowing. I personally think the nausea is from different pressures in different parts of your head. I was sent from the er to an eye dr to have the pressure checked in my eye balls. I know when the flashing kaleidoscope lights start that it’s time to get somewhere dark, cool and quiet. Hate those suckers.",
"Not answers, but interesting fact: Some medicine used to treat migraines, such as triptans, work to increase the amount of serotonin in your brain. However, the side effect of increasing serotonin in your stomach is nausea and is consequently a side effect of triptans. Oppositely, some nausea meds, such as ondansetron (zofran), work to reduce serotonin for nausea, but result in the side effect of headaches. So it is possible that serotonin issues are happening all around the body, with levels high and low in the wrong places, causing both a migraine and nausea?",
"I can't say for sure because migraines aren't totally understood, but I'll do my best! I believe there's 2 main reasons. 1. The headache isn't the only hallmark of a migraine headache... most people have sensitivity to light and sound, some dizziness, and just like you said, nausea. Many people (myself included) get this funky thing called aura too, either just before or during the migraine. That's a bunch of weird neurological symptoms that usually have to do with your eyes--seeing flashing lights or bright spots, having ripples in your vision, losing your depth perception, or even going *very temporarily* blind in one or both eyes. Any of that can get super disorienting, and brains hate being disoriented. Kind of like getting sea sick. The horizon looks straight and level, but your body is rocking and swaying... the brain doesn't like conflicting information and throws a hissy fit! 2. This is a little more science-y. Serotonin is a neurotransmitter. A chemical that works on nerves and helps them 'talk' to each other. You've probably heard of it in the context of mental health, how serotonin in your brain affects your mood. But oddly enough, you have *way more* serotonin in your *gut* than in your head. Serotonin has a lot of jobs, but one thing it does is constrict blood vessels, or make them tighter. This can hurt, especially if it happens really quickly. One of the biggest theories that doctors have about how migraines work revolves around serotonin shrinking those vessels and causing a headache. Since it's working on vessels in the brain, it could cause those other symptoms too, like seeing weird things. But if the serotonin in your *brain* is acting funny, it would make sense that *all* of the serotonin in your body might be acting funny. The rest of it is in your abdomen... so nausea or even vomiting would fit. Hopefully that's fitting for ELI5, and hopefully it answered your question a bit! Oh and as a bonus fact: There's a such thing as *abdominal migraines.* The same intense pain, but located in the abdomen instead of the head. Usually abdominal migraines are suffered by children who have grown up family members with regular migraines. Then when the kids get a bit older, they stop having stomachaches and start having the headaches instead."
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mxbz08 | the difference between protein, carbohydrates and sugars in regards to energy for the body. | Biology | explainlikeimfive | {
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"Proteins are composed mostly of amino acids, and they have to be turned into glucose by removing the amino (nitrogen) group from them, then splitting that into ammonia (which gets excreted) and a \"carbon skeleton\" which is basically just a carbohydrate and can be processed in the same way. This is a very small part of energy production, though, unless you're deliberately eating a keto diet or something like that. As for carbohydrates (and sugars, since sugars are just simple carbohydrates), those get converted into three types of simple sugar (glucose, galactose and fructose) by digestive enzymes. The glucose goes directly into the bloodstream while the other two get converted to glucose in the liver. This is why simple sugars are bad for diabetics, because they get dumped rapidly into the bloodstream, while fructose (e.g. fruit sugar) is a little bit better because it takes time for it to get converted in the liver."
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mxc5is | if granite is an intrusive igneous rock that forms below ground, why do things like the Sierra Nevada range exist? | Earth Science | explainlikeimfive | {
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"Here's a timeline Granite forms in hot spot - > granite moves with continental plate - > continental plate hits oceanic plate/other continental plate - > all the rocks get thrust upward into into a mountain range - > all the rock above the granite gets worn down by erosion - > granite on the surface. Granite is a very strong rock, and so it doesn't wear down quite as easily as others, leaving large portions of it on the surface or poking out."
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mxcnve | Do Predator Animals Think Their Prey is Stinky? | Biology | explainlikeimfive | {
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"It's impossible to say for certain what something smells like to another animal, both because it's impossible to compare pure sensations (\"qualia\") between people, let alone animals; and also because their brains are set up very differently than ours regarding smells. Having said that, though, I feel quite confident telling you that everything about a prey animal smells *great* to a predator. Your tiny little olifactory lobe (looks like a little flap of skin on the underside of your brain) gets all excited when you walk into a house where somebody's cooking a tasty dinner. A lion's olifactory lobe (a great big knob towards the front of their brain that makes up a solid quarter of their brain volume) is going to get similarly excited just being a hundred meters downwind of a delicious buffalo calf. Of course, animals with massively better olifactory processing are also able to differentiate smells much better than we can - one smell doesn't \"mask\" another so much, in the same way that a bright light doesn't necessarily \"mask\" everything else you can see. However, even if they do detect something they don't like (I think that's unlikely), that's just part of the experience of smelling prey, which is part of the experience of getting fed, which is pretty great."
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mxcupf | Why does slowing down audio sometimes deepen voices, but sometimes not? | Technology | explainlikeimfive | {
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"Sound being deep or high pitched is based on the frequency of the sound. When you slow down a recording it basically also slows down the frequency of the waves that make the sound and so it gets deeper. I have never experienced a situation where slowing down a recording didn't deepen the sound so I can't speak to what is going on there."
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mxdxdr | What is happening on a cellular level when your body gains cardiovascular endurance? | This is probably a poorly written question but what is happening to the body as we gradually get better cardiovascular endurance. What has to happen for someone go from running a mile to a marathon? | Biology | explainlikeimfive | {
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"Your heart pumps blood more efficiently. Effectively, a singular beat of your heart is capable of moving the blood in your body a further distance; meaning, you are capable of circulating oxygen throughout your body with less energy needing to be inputted for additional beats. Similarly, your lungs begin to draw more air with less effort and tire less easily from deeper, heavy, more cumbersome/wasteful breathes. Both of these things in combination means that your body will overall produce less Lactic acid, and consequently feel less sore by continually pushing the boundaries and capabilities of your body. Eventually you build the capacity to “be able to take the next step” in running to be able to compete for a marathon. In fact, most marathon runners I know who run them for enjoyment and pushing themselves say they train just shy of a true marathon (who has the time of true capacity built for it outside of Olympic athletes?) 15,16,17 miles for training and letting the adrenaline of “runners high” carry them to the finish."
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mxe2rr | Why do we break things when we are furious? | Other | explainlikeimfive | {
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"Most people don't break anything. I would say it's a pathology that's exaggerated by the media because of the drama. That said, we are all susceptible to making bad decisions when we are emotional. Rage is one of the emotions that can especially consume us to the point where we can't focus on anything else, and hence can't assess the outcomes of our actions clearly. The breaking of stuff is then a mix of needing to direct our aggression into action, and disregard for the consequences of doing so. That aggression can make us physically violent is likely due to genetic links, because those who fought others were at many times in our evolution more successful in survival and/or breeding offspring than those who did not.",
"I don’t think it’s everybody, just people with anger issues. I’m one of those people. The trick is to remember that you’re the one that will have to clean it up, so you’re only fucking your own angry self over. That and focusing on breathing instead of the thoughts racing through your mind. Another handy trick is to focus on your senses. Think of 5 things you see, 4 things you can hear, 3 things you can feel, 2 things you can smell and finally what taste do you have in your mouth. I’ve never made it past 4 without being calm again.",
"I'm not sure what context this is, seems pretty general, but I feel it's important to note most people don't do that. If you've ever read Why Does He Do That by Lundy Bancroft you will find that many destructive and abusive people do it for many reasons and excuse it as being out of control, when the opposite is true. These abusers are in control, have perfected their systematic abuse, and target and tailor their abuse to their specific victim. Some people here have said evolution or fight or flight or what have you, but when it comes to abuse and destruction, context means a lot and that seems really reductive. If you are in a situation where someone is constantly destroying your possessions or others, you should get out of that situation immediately. If you are looking for an excuse as to why you yourself destroys objects in anger, you should get help. There is actually not an excuse for it in normally functioning adults.",
"I'm gonna leave this here until an expert answers. We, human beings are wired to express things or emotions in action. Be it rage, sympathy, love, or any other feeling. When we are furious or mad, our feelings get converted into action, and breaking (or throwing) stuff can release the stress.",
"Firstly should be noted that not everyone breaks things because of anger. Now to the actual part of your question. If people are not emotionally and correctly regulated as children when dealing with overwhelming feelings, they don’t learn how to self regulate and such will create strategies to release tension and unregulated emotion. I.e breaking things."
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mxeor0 | What happens in your brain when you can't remember something that you are certain you know? | I was trying to remember a word that I've used numerous times. The word took me about 2 days to remember. It was chronic, as in my chronic back pain. I knew it started with a c and I knew what it meant but had a very hard time remembering what it was. I also knew some words that were similar but not quite correct. What was happening in my brain to cause this? | Biology | explainlikeimfive | {
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"Memory recall can be inhibited by similar but incorrect things. In this case, similar but wrong words. But you could also get memory inhibition from similar but wrong locations when trying to remember where you went \"that one time.\" Memory inhibition is the technical phrase. And it's an important part of memory: our memories would be useless if we didn't have a way to tell them to shut up except when we need them. But we're not perfect, so sometimes we inhibit the wrong one. Oops. I think the basic background to explain why this happens is to keep in mind the brain is very interconnected, and when you store/retrieve memory, it's not the same as looking at a photo of something you saw. my background is psychology, not necessarily hardcore bio, just so you know. So my knowledge of the biology is mostly functional for specific aspects of perception and memory. Memories are reconstructive: it's more that you save some key features that remind you of the context, and then when those features are activated (by the environment, or you actively trying to recall), you reconstruct what you think happened. During this process, you fill in missing details and may not even be aware of it (studies show confidence in your memory of something isn't correlated with accuracy, so feeling confident isn't a good indicator of how good the memory is). Well... what happens if the features of memory A are *really* similar to memory B? You may accidentally retrieve memory B. In the brain, this is likely related to neural inhibition. Activating pathway B to retrieve the wrong memory is reducing the signal from pathway A. So the info is there, it's just not strong enough to get retrieved into conscious experience. Other reasons for inhibition include just not activating enough features to \"find\" what you're trying to remember. E.g., it's easier to remember something if you're in the same context of when that thing happened. That includes physical environment and psychological environment: it's easier to remember things that make you angry when you *are* angry."
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mxes46 | If fruits are already sweet, why do they put sugar in fruit juices? Is it because of the sourness or maybe there's another reason? | Other | explainlikeimfive | {
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"Because more sugar tastes better than less sugar. If they could inject sugar into fruits, they would do that too. Modern fruits already tend to be sweeter than their historic counterparts.",
"It's not actually that common to add sugar to fruit juices, at least not anywhere I've lived. Could it be a cultural thing?",
"Sugar is a preservative. Keeps the fruit juice from going bad longer. Sadly sugar testes good and the quantity used has grown over the years.",
"Mass market brands aren’t working with super ripe right off the tree fruits. They use manufactured concentrate that’s made from fruit purchased with price as the primary concern. But then they can mask the lower quality of the fruit (and the taste of any added preservatives) by adding additional flavorings and sugar. This method also removes any quality variability from the available fruit and makes sure that each batch tastes exactly the same.",
"Sugar is cheaper than using good quality fruit. Keep the masses addicted to nutrition-less sugary drinks If you like real fruit juices, make it yourself."
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mxf5lv | Why is foam white no matter the color of the soap? | Physics | explainlikeimfive | {
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"Because colour comes from how light is reflected off surfaces. Any time there's a change in the medium the light is travelling through, such as the change between air and water, some of the light bounces off, some of the light changes angle of travel but keeps travelling in roughly the same direction, and some of the light is absorbed by the molecules of the new medium. Also, light has a property called wavelength, which is measured numerically. This wavelength property affects how the light is reflected, refracted and absorbed: For any given medium change, some wavelengths will bounce off, some will change direction, and some will be absorbed, and each of those wavelengths will do that to a certain degree. The \"colour\" of light is the result of our brains interpreting the wavelengths it is made up of. Light that contains lots of different wavelengths looks white, while light that only contains wavelengths of certain bands will look coloured. Lots of short wavelengths with no long wavelengths looks blue, lots of long wavelengths with no short ones looks red, and middle wavelengths with few short or long ones looks green. Intermediate combinations of wavelengths look the colours between these. For example, some long, some mid, no short will look yellow or orange. Also, purple is a trick of the brain, and it happens when the eyes detect both long and short wavelengths, but no middle wavelengths. So, let's imagine you have a bar of soap. This bar of soap is a kind of middle blue colour. It's not super dark, but it's not super pale either. It is very blue though, no purple or cyan tinges. This happens because when you shine a white light on the bar of soap, the middle and long wavelengths (the green and red ones) get absorbed by the soap, while the short wavelengths (the blue ones) get reflected. We see only the reflected wavelengths. About 50% of the short wavelengths are reflected to create that middle-strength blue. Hopefully that should make a bit of sense. Now, let's imagine you have a liquid soap, that's the same blue colour, but also transparent. This is doing much the same thing when it comes to light, but instead of being absorbed, some of the wavelengths pass through the soap, bounce off the sink surface beneath it, travel back up through the soap and then travel towards your eyes. You still get a blue tinge, because a lot of green and red light is still being absorbed by the soap, but enough is being let through that it also lets you see the stuff beneath the soap. Now, foam is kind of cool. Foam is actually a bunch of absolutely tiny bubbles, and a bubble is a thin layer of water with a hollow interior, and both the water layer and the air interior are transparent - they let some light through instead of absorbing or reflecting it. Light that passes through a bubble will hit a lot of surface changes. There's the surface change from the outside air into the water layer, then from the water layer into the inside air, then from the inside air into the water layer again, then from the water layer back into the outside air on the other side. That's four medium changes, and remember that each time light changes medium, a portion of it will bounce off. If say 10% of light bounces off each time light moves between air and water, then each time, only 90% of light passes through. After 4 transitions, a total of 35% of all the original light has bounced off a surface and back towards the light source. Get a bunch of bubbles, like foam is, and you've got hundreds of thousands of opportunities for light to bounce off. Almost no light is getting through, even though the air and water are transparent. The role soap plays in bubble formation is that it acts kind of like layers holding the water in a bubble shape. It works similarly to how oil behaves in water, forming its own balls of oil instead of mixing with the water. That happens because the oil molecules are something called hydrophobic - they don't like water and will try to hide from it inside a big ball of oil. Soap molecules are cool, in that one end of them hates air, and one end of them hates water, so when presented with both air and water, the soap molecules spontaneously organise themselves into something called a bilayer: Two rows of soap molecules that trap a layer of water between them, with their water-hating ends pointing out to hide from the water and their air-hating ends pointing in to hide from the air. [Here]( URL_0 ) is a kind of OK diagram of that. The molecules responsible for the blue colouration of the soap aren't involved in this process though, and water reflects light of all colours, so the special property of only reflecting blue light ends up lost when the soap molecules are mixed with water and air to make foam. Those blue colour molecules, which aren't the soap molecules but instead a dye molecule put in to make the soap look blue, are just tinging the foam a pale blue colour, as the water bubbles are doing loads of white reflection, but scattered blue dye molecules do still absorb some of the red and green.",
"Because many colors of light blended together look white and the bubbles are bouncing those colors in all different directions.",
"Light bounces off of objects until one colour sticks. Foam is made out of lots and lots of little objects, so the light bounces in all sorts of different directions. A colour cannot stick, and so it looks white.",
"It isn't. But, the foam may be *lighter* - a lot lighter, even - than the soap because it's diluted with water.",
"Imagine looking at a bubble, and how its got all these different kinds of colours on its surface, the reason for this is different thicknesses in the bubble. Now imagine soapy foam, it's a multicolored bubble, but there's thousands/millions of them... your eyeballs aren't equipped to see such detail, so it gets \"averaged out\", and with the combined effects of the light being scattered through all the bubbles, we interpret it as white... which is a good approximation for \"all the colours\" in our brain"
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mxf9jh | What is actually happening when you get a kink in your neck, and why can they sometimes last for 5 minutes or 5 hours? | You know when you first feel that twinge and you’re scared to move either way for a brief second. Why is that spasm set off sometimes and not other times. | Biology | explainlikeimfive | {
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"Soft tissues in your neck get squeezed around, moved and pinched between the joints in your neck. If they bulge far enough they could possibly pinch a nerve and that’s when you get pain in your shoulder blade, shoulder and down towards your hand. The tissue might only move a little or a lot. If it’s bad enough and bulges a lot it can obstruct your movement and be hard to reduce unless you know how to treat/help someone. Other times it may be only a little displacement and probably goes away on its own with just general activities of daily living. This is very distilled down to keep it simple but it boils down to soft tissue getting moved around and pushing on surrounding tissues creating pain and stiffness. Source: I am a conservative orthopedic specialist and treat these problems for a living.",
"I am genuinely curious as well. I used to get these a lot, and once had one so bad I actually had to go to prompt care. X-ray showed nothing but MRI later showed I had a bulging disc in my neck. I never found out the reason why they hurt so bad. Side note: once I started doing yoga every day and watching my posture, my neck got exponentially better. Daily forward folds saved me lol.",
"There’s kind of two different scenarios. One is when you muscles pull, that will feel like a Charlie horse in your neck, or if you have over worked it, it will hurt when you move and turn your head etc. The other scenario is a what us Physical Therapists call a “facet lock” where your spine is slightly out of alignment. That can be caused by a strain, it will feel like you have a “lock” or “block” that mechanically you can’t move a certain way. The strain should resolve with stretching or heat or just when the muscle calms down. The facet lock will have to resolve spontaneously or with a manual therapy or manipulation by a practitioner such as a PT or chiro.",
"In essence kink is a overactive muscle. That can usually be caused by over work or strains like pulling the muscle etc. Every time you use a muscle, it damages it. This is why you can build muscles for something over time, because despite how much effort is being applied, the muscles are still having to work. When muscles tear, the body will try to fix the tear. That process creates a little knot (comprised of collagen and such to repair the muscles) in the muscle that needs to be broken up either through stretching, or physical means like a massage. Eventually the body will catch up on dealing with the waste products associated with the repair, but the lymphatic system is a manual pump that needs muscles to be moving in order to move the waste product to your lymph nodes, which is why it can take so long to clear up if you aren’t moving, drinking enough fluids, or massaging the area. An ELI5 in truth is that your body is like a road. Overusing it can cause ruts (or a crash) in the road that need to be fixed, and the people that need to fix that will back everything up causing massive traffic jams on the road that cause a lot of pain in the neck for those involved. Without someone trying to push those workers along (massage, stretching, etc) they can take hours to fix the problem and move along."
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mxfm3g | Why does the room spin when you've drank a little too much? | Biology | explainlikeimfive | {
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"I don’t know the exact science but if I recall correctly when there’s too much alcohol in your blood it actually diffuses into the liquid filled part of your inner ear. That’s the part your brain uses for balance, and because alcohol is a different density than the fluid, it disrupts the fluid causing it to move even when you’re completely still, the fluid moves the little hair like structures in the inner ear and those structure send a signal to your brain that tells it you’re moving or spinning. The fluid in your inner ear and those hair like structures are the same reason we get dizzy but goes away shortly after we stop when we spin in circles too much, the fluid starts moving continuously in a way that your brain can’t figure out how to balance properly and the fluid needs to run out of momentum and settle somewhat before your brain can figure out the balance thing again."
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mxgq2c | why does it take time to fall asleep and we can’t force it consciously? | Other brain activities like focusing, reading, remembering and so on, can be triggered actively whenever we want, but we can’t decide when we fall asleep. Besides some specific conditions must be fulfilled, like being tired, in a relaxing position, appropriate light... | Biology | explainlikeimfive | {
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"Maybe because sleep is not the same type of brain activity. Quite the opposite, sleep is a major change in brain activity. We are evolved animals but still animals. A lot of those conditions are evolutionary adaptation for survival. On the other hand there are techniques and routines that help people fall asleep faster. A common problem is a tendency to engage in thoughts and worries. That’s a bad habit that can be trained out.",
"To fall asleep your mind needs to be fatigued, the neurotransmitters in your brain should have been depleted and there should be no or minimal external stimulus like a quiet place and dim or no lights. This is because our brains have something called the Reticular Activating System. This is a network of fibers that sends information to the brain and different parts of the brain get stimulated in return. The brain can be stimulated by stimuli like light, sound, pain, heat, cold, anxiety, excitement; none of which let us sleep since it fires the brain. So if you work out and tire yourself or meditate, which calms you down, (controls the firing of the brain) you could sleep at will. There are plenty of things that can be done to help one go to sleep by calming down the brain or tiring it.",
"I would like to point out that you do not have to be tired to sleep. In fact, with training, you can sleep as much as you want, whenever you want, as quick as you want. Some branches of military even train their soldiers to sleep under just about any circumstances, quickly. You basically need to turn your brain off. Sleep is kind of like the opposite of conscious thought. We tend to think of being tired as required for sleep because we usually sleep when we are tired but this is because it is easier to fall asleep while tired since being tired causes your brain to be less active. You can read more [here]( URL_0 ). Edit: I learned about this when I was suffering from extreme depression and anxiety due to a bad divorce. Meditation is a great tool to help with falling asleep faster."
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mxgzrw | how do devices that use batteries, like phones, know the percentage of the charge remaining? | Technology | explainlikeimfive | {
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"Hi :-) TL;DR: A full battery has more volts than an empty one. So for example, 4.2v=100%, 3v=0%. But it's not linear. & nbsp; Voltage of a battery drops when discharged over time. Some phone apps (or programs for your laptop) will even let you see the voltage. You probably have seen the 1.5 volt label on regular AA/Mignon alkaline batteries. It's actually a little higher initially. Then it will gradually go to 1.4...1.2v. Once it reaches 1 volt or less (drop off happens more suddenly), many devices stop working. Battery testers or battery circuits measure this voltage (or any $3 multimeter can to some extend if you add a load). Same with lithium batteries. Some may be labled 3.6V, but when full, they're over 4v. Under 3v they would get damaged, so devices (or a circuit on the battery pack) will cut off. This is the reason why old phone or laptop batteries will sometimes cause the device to just shut off at, say, 20%, as the old battery's voltage will drop unexpectedly fast compared to a new one (EDIT2: And when the load is high). So the percentage is just a \"guesstimate\" using the common discharge properties of a battery. Some smart programs will recognize old battery behavior though and compensate. EDIT: [Example discharge curve of an alkaline battery]( URL_0 )",
"the less charge a battery holds, the less voltage it outputs. the device just checks the voltage and determines the percent.",
"The battery pack or the android main board has a \"battery fuel gauge\" IC which keeps track of the charge state of battery. You cannot achieve that level of precision by only measuring voltage. Basically, it uses fuel gauge. There are several algorithms for Li-Ion chemistry, and the gauge might use one or more of them.",
"To be a little more more ELI5 than some of the other comments, a battery is like a water balloon. When the battery is fully charged, it's like having a water balloon that is full to bursting. When you let the water out, it comes out harder and faster when the balloon is full than when the balloon is almost empty. The phone looks at how hard and fast the water is coming out to figure out how full the balloon is."
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mxhti1 | How can trees be leaf-less all winter and even turn grey/brown but when spring comes they get small green leaves starting to grow on the edges of each branch? | Sorry if this has been asked before I wasn't sure how to put it in words or if there's a name for this phenomenon, I see trees with hugh branch structure all grey but with small almost un-noticeable green leaves, do trees hibernate in winter? Thanks! | Biology | explainlikeimfive | {
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"Trees that hibernate during winter are called deciduous. These plants do this to conserve energy for when they need to produce fruit, aromatics etc which takes a lot of energy."
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mxhxgs | How come you need anti-rejection drugs for a lung transplant but not for something like an aortic graft? | Watching an old episode of MASH and they're taking an artery out of one guy and putting it into another. How can they do this without fear of rejection when things like kidneys or lungs need to have anti rejection drugs for life? | Biology | explainlikeimfive | {
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"You can’t. Don’t rely on television for accurate medical depiction. When someone needs an aortic graft, doctors take a cylindrical metal mesh and place it inside the weak part of the vessel. This stops the vessel from literally exploding by giving it a lot of support. If the aneurism has already burst, they sew it closed again and then place the mesh inside. This is very hard to survive - it’s something like 10% survival rate from a burst aortic aneurism, if that. I know a man who had an aortic aneurism rupture while he was in hospital waiting to have his aneurism sured up, and they couldn’t save his life. If you need a human vessel to replace a completely shredded blood vessel, they take one from your leg. That is how you get around rejection."
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mxi9ev | how does the brain store the meaning of words in your head? | Does it link words to pictures in your mind? So there is a mapping from the word "owl" to a picture of an owl in your head? Can I also add that I don't think this mapping involves word definitions, so for example the word owl won't map to the word definition of an owl since you need to define words in the definition itself. This causes a never ending chain as you keep having to define words in further definitions. | Other | explainlikeimfive | {
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"You gotta think of your brain like a file cabinet that stores all the words you know and has files on the things that a make a word have a meaning. This includes relationships between words/ideas, sensory info, similar words or things, sounds, usages, and all that. Then there’s pathways that form between what you hear/see and where the file is stored in the mind. The word owl would definitely map to the definition of an owl (big, nocturnal, hunter, wise, feathery, bird, bitey, 360 head spin) unless you didn’t know what an owl was, in which case you’d maybe try and figure out if an owl if something that sounds like the word ‘owl’, find a word that sounds similar and maybe come up with a wrong definition and start to build inaccurate files on it. I don’t know if this is allowed, but the non ELI5 word for this is psycholinguistic processing and it relates to the way words are stored and retrieved in the mind.",
"Think of it as if the word \"owl\" (or whatever word you choose) evokes an image in your conscience through, as you say, mapping (neurons talking to each other). But it is not that simple. The same word can evoke different images depending on your situation, and obviusly depending on the person. For example if I say home you might evoke your home, but I will evoke mine. Moreover, if you live in a flat for example, you may evoke your flat or your parents' house. About the definition... It is very uncommon that the brain evokes a definition without you purposely wanting to do so, because you have to search (literally, you search in your storage of info) the words to describe it, so it is less efficient and more conscience-driven. Hope it helps!",
"Haven’t seen anybody bring up the schema theory yet. This theory of memory does a really good job of providing an image of the structure and relationship between short term memory (STM) and long term memory (LTM). The first thing you should know is a schema. Essentially, a schema is a bundle of information that is stored as one unit in your LTM. For example, the actual word ‘owl’ is only a small part of the ‘owl’ schema in your brain. This helps explain why, when you think ‘owl’, information from multiple contexts are brought up and readily available (what an owl looks like, sounds like, where it might live, maybe you even have the tootsie pop owl from the commercial right on the tip of your tongue). Second, keeping in mind that schemas are their own discrete units, related schemas (like ‘owl’ and ‘feather’) can be pictured as linked like kindergarteners holding the same rope on a field trip. When a specific schema - let’s say ‘feather’ - is pulled out of your LTM up to your STM, all related schemas including ‘owl’ aren’t necessarily pulled up with it, but are closer to your consciousness than a totally unrelated schema, like ‘railroad’. There’s a lot more to schema theory than I explained here, and it’s all very interesting - I recommend checking it out. Thank you for coming to my TED talk.",
"I am helping a woman recouperate from a stroke that really hammered her language area (so she has Aphasia).... and it is fascinating how her brain works I can see how it finds old memories and can’t form new ones and where connections are or are not made.",
"Images? Lol:) Some of us have no linking of an image to anything at all. If I think of an \"owl\", then it links to the concept of \"what an owl *is*\", e.g bird, can fly, silent in the air, flexible neck, etc. At no point is an image involved. I am curious how you mind deals with the definition of words that are concepts - have no image. E.g Logistics, Faith, Calculus, Like, Fear etc? r/aphantasia"
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mxjk2v | Why do we get put off from doing things when someone tells us to do something? | Biology | explainlikeimfive | {
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"People, especially in a culture where high levels individualism is valued/seen as a virtue, like believing that they have control. If you do something because you want to do it or you decide to do it, you are exercising your control over the environment. So, if you decide to do the dishes, some part of your brain is like \"Cool, I get to decide when the dishes are done. This makes me feel in control and powerful.\". So, you get up and walk to the kitchen to do the dishes, and on the way someone says \"Hey, can you do the dishes?\". That part of your brain now has a conflict - are you doing it because YOU decided to do it, or because someone else told you to do it? It doesn't make you feel as in control or powerful."
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mxjrmz | Why does a sharp nail split wood and a blunt one wont? | I have always been taught when putting a nail into wood which could split, you should tap the point of the nail to dull it first. I have done this enough to say it works. A blunt nail will not split wood when a sharp one will. | Physics | explainlikeimfive | {
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"Think of wood like a bundle of tubes. Tree vascular tissue (generally) all runs one way (knots are where branches were and curves are natural as not all trees are straight), which is why wood splits in one direction. In really simple terms, a sharp nail forces between the fibers of the wood which forces them apart. Blunt nails break some of the fibers while still retaining enough pressure to hold in the wood."
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mxk3g4 | Why is there a limit on how much money can be printed in a Country/Region? | Economics | explainlikeimfive | {
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"I would guess, inflation? A lot of money = money isn't worth as much."
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mxk3vz | In a F-14 Tomcat, what does "Goose" do? | In the movie *Top Gun* we see pilot Maverick with his offsider Goose. The F-14 clearly needs a second man; but the A-4 does not, nor does the ~~Mig-28~~ *F-5E.* The F-15 and F-18 comes in both one and two man variants, but I don't think I've seen a two man F-16. Modern MiG's and Sukhoi's seem to be one man fighters. | Technology | explainlikeimfive | {
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"The aft seat in a Tomcat is for the Radar Intercept Officer. They're responsible for communications such as satellite linkage etc., and jamming enemy radar as well as operating their own radar. They may also handle the weapons systems. Offloading some of these duties to a second person allows the pilot to put more focus into what they're doing. It is also helpful to have a second pair of eyes to establish and maintain visual on an enemy craft. A lot of modern craft that have tandem seats also have multi-function displays that allow cockpit customization, and each crew member can optimize what displays they have to play to their individual strengths.",
"Goose was the weapons systems officer ( URL_0 ). Some aircraft don't require an additional officer to manage the weapons either because they are not intended for the same high-intensity dogfighting that requires all of the pilot's attention or because the avionics are more advanced and support the single pilot better. And more importantly, Goose was a damn good man.",
"In Jets that usually have 2 officers, the 2nd officer does things so that the pilot can focus on piloting: keep track of targets, adjust weapon loadouts, operate the radio, etc. Remember that the number one cause of plane crashes is pilot error. We no longer see many fighter jets with 2 officers because we now have more capable computers that can do all that. When a jet does come in a 2 officer variant it is most likely a trainer.",
"\"Goose\" is a Radar Intercept Officer, RIO. the thing about the Tomcat, and older aircraft like the F-4, was that the radar was so complex that a second crewmember was needed so that the pilot could concentrate on flying the aircraft. so basically, a RIO was for operating the radar and other systems the Tomcat used to detect enemy aircraft and give the pilot the information he needed. there´s much more behind that, but this covers the basics. nowadays, many of the stuff that needed to be handled manually is now done automatically which is why you see two-seat fighter aircraft only when they do challenging stuff like air-to-ground operations (F-15E) or something like that. otherwise, trainer versions of said fighters like an F-16B or F/A-18B are also twin seat"
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mxltxh | Why are some solids transparent and some opaque? | Physics | explainlikeimfive | {
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"The structure inside the object is a certain arraignment of atoms/molecules. If that structure happens to have the right spacing for visual wavelengths of light to pass through, its transparent. I"
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mxm168 | Why can't you taste anything when you plug your nose? | Biology | explainlikeimfive | {
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"Because your nose is around 60-70% responsible for 'taste' the food you eat releases chemicals that travel up to your nose. Receptors there pick up those chemicals and signal them to your brain"
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mxm41m | How accurate are daily weather forecasts? | How can meteorologists predict weather forecasts with accuracy? After how many days out do forecasts lose accuracy? What factors make weather forecasts hard to predict? | Earth Science | explainlikeimfive | {
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"3 days in general the time at which forecasts break down, due to the inherent chaotic nature of weather by the time you get to 3 days the random nature of the system tends to reduce the accuracy to a level too low to be significantly useful.",
"It's partially done by looking at historical norms for the region (e.g. you know it's more likely to rain when the wind is from a certain direction etc), and partially done by using big computers to analyse weather patterns and predict how they'll change. Accuracy for short-term forecasts isn't really guaranteed after three or four days, though, and that's because the weather is a chaotic system--that doesn't mean it's entirely impossible to predict, but that the slightest error in your starting conditions will rapidly diverge from the actual weather. To give an example: let's say you had a magic device that could measure the wind speed, temperature and air pressure at every point one metre apart in the atmosphere. You feed those values into a perfect supercomputer that can exactly simulate every interaction there is and let it run. The resulting prediction will \\*still\\* be totally wrong after a month, because you didn't measure the bits in between those 1m points and have no idea what was happening there!",
"Pretty accurate. Meteorological predictions are made on data collected from decades even centuries of research and with the help of extremely intelligent super computers. Inspite of this there are some errors which can happen & do happen all the time. By rough estimate, you'll get right predictions 22-25 days a month."
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mxm8uq | What exactly is a partial derivative? | What exactly is a partial derivative? I have a basic idea of a derivative i.e, I know that dy/dx is rate of change of y with respect to x and that it represents the slope of a curve Thanks! | Mathematics | explainlikeimfive | {
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"It’s still a slope. But when you multiple variables then you have a surface instead of just a curve. You can hold all but one variable constant then take the derivative to find the slope in only one direction.",
"ELI5 example: Nickels are worth 5 cents and quarters are worth 25 cents. So if you have n nickels and q quarters, you have a total value of 5\\*n + 25\\*q cents, or v(n,q) = 5n + 25q. The partial derivative of v (with respect to one of the parameters) tells you how much it increases for an increase in that one parameter. There's a different partial derivative for each parameter. Here we have 2 (number of nickels and number of quarters), so there are two partial derivatives: If you add one more nickel, the value goes up 5 cents, so the partial derivative of v(n,q) with respect to n is 5 (or dv/dn = 5). Similarly, adding one quarter gives 25 more cents, so dv/dq = 25.",
"When explaining things I like to use a practical example. The ideal gas law is written as PV=nRT and we will rewrite it as P=nRT/V so we now have a function where Pressure (P) is expressed as an equation related to three variables the number of moles of a gas (n) the temperature of a gas (T) and the volume of the container (V). Now if n and V are constant than the equation is just expressed as a function P(T) and the derivative P'(T) can be expressed as dP/dT but if there is more than one variable we cannot take a single derivative. Remember that the derivative is nothing more, and nothing less, than the rate at which the equation is changing. For a multi-variable equation that equation must be broken down into components expressed as a vector. These components are the partial derivatives. Consider again our example P=(nRT)/v since it is a function P(n,T,V) it would be expressed as three partial functions added together. So P'(n,T,V)=pP/pn+pP/pT+pP/pV (actually signified by a lowercase delta but I don't have that on my phone's keyboard). Which is found by essentially pretending the other variables are constant. So pP/pn is (RT/V)pn, pP/pT is (nR/V)pT, and pP/pV is (-nRT/V^2)pV.",
"The partial derivative is the same, but instead of a curve, you have a 3D surface. Now, to calculate a derivative, you need a trace or slice through the surface reducing it to a line. If you have a function f(x,y), then the partial with respect to x at (a,b) is the slope of the line where x=a. Similarly, the partial with respect to y at (a,b) is the slope of the line where y=b.",
"For functions with multiple independent variables f(x,y), f(x,y,z), etc. when you take a derivative you need to specify which variable you're differentiating the function by, so basically which independent variable you're using to measure the function's rate of change. So for a function f(x,y) you have partial derivatives df/dx and df/dy. For function f(x,y,z) partial derivatives df/dx, df/dy, df/dz and so on. You can imagine for a function f(x,y) say the function is entirely flat when moving along the x-axis, no change in f(x,y) whatsoever, in which case df/dx = 0 saying there's no change in f(x,y) with respect to x. Conversely say there's a great amount of exponential change in the function as you move along the y-axis so you're partial derivative there could be df/dy = e^y . This is just to highlight that partial derivatives for different variables can be drastically different depending on the function."
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mxn4wh | How do people skip stones on water? Does the stone shape matter? | Physics | explainlikeimfive | {
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"Whenever something is entering the water it needs to push the water out of the way in order to sink. If the object is traveling fast, the water exerts a large amount of pressure on the object, resisting its entry into the water. If something is falling straight down into the water this causes the water to feel like a tremendous slap, but you still make it through because your direction is straight into the water. But if you have a lot of HORIZONTAL velocity, this impact of energy can be enough to bounce you back out of the water because you don't have a lot of downward velocity to break through that impulse of resistance energy. So you will end up skipping back out, then back down. If you still have too much energy, it will continue again and again until your horizontal velocity lowers enough to permit entry through the resistance. So, the shape of the object matters because the shape is what causes the amount of resistance. A large flat object meets a lot of resistance to entering the water. So that's why you usually look for flat stones to skip. A more aerodynamic shape, like a bullet, will also be more hydrodynamic, allowing it to enter more easily and less likely to skip. Almost anything blunt will be easier to skip than something sharp."
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mxpeg1 | Why do olives go in martinis and what does it actually do to the drink? | Chemistry | explainlikeimfive | {
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"Most martinis are 97-99% gin or vodka. So, the garnish, is just to add a subtle flavor. Appearance is a factor as well.",
"Usually brined olives so adds a bit of salt. It isn't going to add much flavor since it doesn't really have time to soak. Looks cool? Maybe to eat after/as you drink for that salt kick.",
"You can put some of the brine into the martini. It's called a dirty martini. Adds a slight savory salty note.",
"I have a friend who likes the salty taste of olives in beer too, for much the same reason as martinis",
"They're there to make the drink more fancy and what they *actually* do to the drink is make it more fancy."
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mxpi7h | How do floors bend/shake but not break? | I’ve had a bizarre phobia since I was young. I do not trust the structural integrity of most buildings and am always worrying things will collapse/break. One thing that really triggers my anxiety is when I can feel a floor shaking. If my one year old, 25 pound son can run by and make the floor shake, how can it hold substantially heavier items (like a fridge, washer, etc.)? Please only reassuring comments - I can’t handle this phobia getting any worse :) | Other | explainlikeimfive | {
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"Strength has almost nothing to do with flexibility/stiffness. A steel cable is incredibly strong but flexible as a noodle. A glass rod is as stiff as you could wish but easily broken by hand. You’re worried about things breaking...that happens if the load gets bigger than the thing can hold. The safety factor of buildings is extremely high... they can hold far more load than they ever see in normal use. Flexibility actually *helps* the building be stronger... it lets the load balance out and spread around to be carried by more of the structure. We don’t *like* flexibility, because we evolved walking on solid ground and it feels weird to us, so building designers intentionally make floors stiffer than needed to be to make us comfortable but this has nothing to do with structural weakness. Building things to be both really strong and really stiff can be done... but it’s almost always extremely *heavy*. This is why concrete or stone buildings are so massive and stiff. Wood or steel construction is much more flexible, and light (“more airy”) but no less strong.",
"It's good when things bend, because they're avoiding breaking! Wood is a great building material because it is flexible and can take the stresses we put on it as walls and floors for years! Wood also vibrates in ways that make it better for musical instruments than, say, concrete. I don't really know why that is and I am not smart. But so your floor boards will bend and also carry shockwaves. The floor shaking from someone running on it is just vibrations. If it's shaking in an earthquake, that'd be something to worry about, but even then, buildings are designed to move a little so they aren't brittle. Skyscrapers sway like mad in the wind or when the ground moves, and they don't fall. I hope this is helpful!",
"All forces cause some bending in structural members. Everything is, to some extent, like a spring. A 25 pound object hitting the floor can exert hundreds of pounds of force. This force causes a small but not unnoticeable deflection of structural members - a tiny fraction of an inch of movement. Since it is an impact, the force is brief, and vibration is caused, making this small movement even more noticeable to you as it happens over and over during the vibration. A much heavier object will cause more deflection of the supports, but still well under the amount it would take to cause a yield. Wood, the main structural element of most buildings, can bend a huge amount before it breaks. This is extremely useful, since it means that wood can withstand those huge force spikes from impacts, while something even stronger like glass would break from an impact.",
"If it helps to ease your phobia, you might consider the vibrations you're hearing and feeling as ripples on the surface of a pond. That's pretty much what they are. When your son runs across the floor, what you hear and feel is those ripples traveling through the floor (and the air) and bumping into your body. Have you ever seen a picture of [the inside of an acoustic guitar?]( URL_0 ) Check it out. It looks cool. That's basically what your house is. If you rapped your knuckles on the \"floor\" of that picture, you'd hear quite a loud sound as the vibrations traveled around, but there would be absolutely no danger of your knuckles breaking through. You'd have to hit it incredibly hard with your fist to break through. And a guitar is very thin wood held together with only glue! Your house is made of, and held together by, much, *much* stronger materials."
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mxpwaw | Why do we like the music we like? | Other | explainlikeimfive | {
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"i dont really have the expertise to comment on the whole question, but it is thought that the pleasure we get from music comes from a sort of Reward system, from within the brain. Your brain guesses where the song will go next, and if it is right, it will reward itslef with dopamine, similarly to why we find jokes funny, but in that case, it's the brain being surprised by a completely different outcome, that triggers dopamine secretion. I'm sure musical taste has a lot to do with pattern recognition as well, but like I said, I'm no expert :).",
"Not an expert, but my favorite explanation of what music is is a solution without a problem. I've heard there's a lot of overlap between math and music and so listening to a song is similar to solving a puzzle only you don't have to think to come up with the answer. My theory is that depending on your own personal mental \"structure\", you need a different \"formula\" from everyone else that resonates best with you. And the more music you listen to, the more complicated and unique this formula needs to be to bring you the same satisfaction.",
"Nolan Gasser, one of the founders of Pandora Music wrote a book recently called “Why You Like It.” URL_0",
"Musician/composer here. I feel like a lot of these answers here are just guesses of why there’s different taste in music, rather than the proven explanation. In psychology, there’s a trait known as the mere exposure effect: When an individual is exposed to a stimulus (music, film, food, etc.) repeatedly over time, that individual likes it more after experiencing it over and over again, than just the first time. Even if they disliked the stimulus the first few times. So rather than explaining the complex differences in genres here, I’ll make an analogy to music using food. Each genre is like a different regional style of cooking; BBQ, Italian, Cajun, etc. etc. Yes there’s individual differences between individual dishes within these broader categories, but food within one of these categories will be similar to other dishes in the same category. Like individual songs/pieces in a larger genre. Someone who grew up in a place where say, BBQ, is eaten frequently, will probably really like BBQ food, as that’s what they grew up with. (Mere exposure effect at play.) Now let’s say that person moves to a different town when they get older, that Cajun is really popular in. The different spices, sauces, types of dishes and more may be too different for that person to like, but maybe a specific dish or two taste alright. Due to the mere exposure effect, that person will like that specific dish more and more, as they get used to the different ingredients and learn what to expect; they may even branch out to more Cajun dishes!! This is just like music and other experience we have during our lives. The more familiar you are with it, the more you tend to like it. Like food, music has many different styles, and some are more similar to others. Being familiar with a genre tends to let you ‘understand’ (using this term loosely) a new-to-you song that fits that genre, better than someone who never has heard that genre. And so you will probably like it, while the other may not. There are so many different genres, sub-genres, artists, composers, bands, instruments, and musical systems across the world, that it is likely you are only exposed to a small handful compared to the larger picture. Others may be only exposed to a completely different handful. This is what leads to our different musical tastes. And in a way, you can ‘learn’ to like a genre or piece by using the mere exposure effect, by listening to it several times.",
"I dont think there is an ELI5 answer. I mean have you noticed literally everyone has different tastes in music? I'm an identical triplet who is a former music teacher and all three of us have very different tastes despite the fact that we are genetically identical and spent the first 18 years in the same house. I'm also the only one who studied music. I tend to think the opposite of a lot of the comments here. A lot of the music I like is because it breaks expectations. So from a personal and cultural perspective nobody agrees on everything or maybe even anything. From a purely mathematical reason the fact that sound is a wave does matter. If you've ever noticed that two instruments playing out of tune don't just sound bad; you can actually hear the conflicting waves almost fighting with each other. It sounds like beats (this is essentially where the waves briefly clash and cancel each other out). Most cultures avoid having waves that clash with each other. Most cultures still have dissonant intervals but in western music they're a means to drive things forward. They need resolving to a more pleasant group of notes.",
"A lot of it is simple association. Education (about music) will tend to lead you to enjoy more complex, interesting music (classical, some world, some metal, some hip hop, progressive, etc). Pop (top 40, easy listening, etc) is often looked down on because it can be made by algorithms and is very often just a product, but its simplicity still allows almost anyone to enjoy it. Hating on pop is more of an intellectual choice than a matter of taste (Phrasing, but you get the idea). If you grow up listening to country and associate it with good times, you're more likely to enjoy it (until you see the above). If you were an angry teenager and listened to hard/angry music then, you'll still probably have some appreciation of it even when you're older.",
"I think /u/Default_Male_Orc gives the best answer. Rewarding music tends to balance novelty and familiarity. Expectation fulfillment and subversion. It's a good guess that some of our preferences are influenced by physics (frequencies that are simple ratios of each other have less destructive interference). Some are influence by our biology (we can experience synchronicity with rhythms on a similar scale to our heartbeats, walking pace, etc). Some preferences are influenced by fulfilling / subverting the patterns we expect to hear (based on what we've heard in the past). If this is the case, genres can be thought of as common ingredients that tend to pair well together because of physics, biological factors , and path dependence (i.e. because of exposure to patterns \"A\" and \"C\", I come to the experience primed with expectations about \"B\"). Genres then become families of recipes that cluster around modes of physical experience (and of course their attendant emotional states).",
"I link music enjoyment to how much you had fun while hearing it. A lot of my music tastes came from gaming and in those games there'd be a soundtrack that stuck with me because I'd hear it through moments of enjoyment. Same reason pop music is popular for people at parties, they can connect hearing the song to a having good time etc."
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mxqf67 | - Why does it sometimes become colder in the morning just as the sun comes up? | Earth Science | explainlikeimfive | {
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"The earth is always losing heat to space, right? So throughout the night it gets colder. The first second the suns shines on the surface it will deliver just a bit of energy, not enough to compensate for the loss, so it will continue cooling, slower, until the amount of energy given by the sun is equal to the energy lost to space. & #x200B; In my experience its about 0.5 to 1 hour after sunrise in the tropics, faster in the equator, slower in the poles. But of course there are winds, tides, and other effects that make everything more complicated, but that's mostly it.",
"Well, right before the sun comes up is the coldest it gets. The temperature falls continuously after the sun sets, if you account for movement of the air and stored heat in the ground. The phrase “It’s always darkest before the dawn” isn’t true, but “it’s always coldest before the dawn” is true."
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mxr36e | How do chickens “sync” their eggs? | I’ve seen friends post photos of chickens who disappeared and come back with a clutch of chicks. Assuming one chicken, laying one egg a day, how does a broody mom come back having hatched 3-5+ in a given cycle? Do other mothers sometimes contribute to a clutch, too? Do they hatch progressively or sync up a bit, does the mother hen manage the eggs to get them all the same “amount” of incubation as to have them hatch out nearly the same time? | Biology | explainlikeimfive | {
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"A hen can lay a clutch (5-7) over a few days. They rotate the eggs in and out of the center to evenly heat them, so slow/quicken the development.",
"So I have a hen who’s sitting on some now. A Hormonal change in the chicken is triggered by a few factors. Increase daylight, seeing or hearing other chicks, and watching a clutch of eggs accumulate all factor in. The hens lay eggs for a few days, then one hen will decide “I’m ready to be a mother now” She then will sit (if she’s committed) the 21 days till they hatch. She will start incubating them all at the same time. Sometimes hens will continue to lay after she’s started sitting. In those cases those chicks are delayed by a few days. Once the older chicks hatch the hen may sit for an additional day or two, but after that she’ll be done."
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mxrkvr | How much of a big deal would it be for lunar orbiters to take a 90deg turn so that their orbit avoids the dark side, the comms blackout etc? | Physics | explainlikeimfive | {
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"To do it once, it's not a huge deal. That's called an \"inclination change\" and it's among the more efficient types of orbit change, but it still requires a change in velocity (not speed, but direction) and that requires fuel. And fuel is heavy and expensive to get to the moon, so precious. The issue is that flipping to a 90 degree orbit only temporarily solves the problem, because the moon is rotating so an orbit that avoids the dark side will be right over the dark side in a week (1/4 rotation). You need to get into what's called a \"sun-synchronous\" orbit, which is slightly angled so that your orbit precesses just enough to oppose the moon's rotation. You can do it, but it's a very specific orbit, not just a simple inclination change."
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mxrq37 | Are the high-quality streams of a live sports broadcast recorded and stored somewhere? | I was watching a soccer match and this struck me: is the live high-quality broadcast stored anywhere or is it just streamed? I suppose it needs to be stored somewhere to make highlight reels, but wouldn't this storage take up TBs of space and therefore not be economical? | Technology | explainlikeimfive | {
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"Most broadcast networks save everything. Yes, it's TBs of space but compared to the budget required to make the broadcast in the first place a stack of TB storage drives, especially at scale, is peanuts. It would be certainly be less than 1% of the overall budget. YouTube is storing far more than all the sporting events that have ever happened and they can pay for that just off ad revenue.",
"Most OTT (over the top) video broadcasters hold on to the raw recordings. There’s a lot of value in these recordings beyond just the original sports broadcast. Say a famous sports player passed on. There’s a lot of value in replays of their past games. The revenue stream goes beyond just the broadcast itself. It extends to include syndication, royalties, etc. The videos are stored offline, yes cost is a big issue, but there’s usually a method to the madness. Hot storage for most recent videos, warm storage for older ones and Cold Storage for archives. There are those that store everything on cloud and some that store everything on site and there are those in between. It depends on their production workflow and their demands for the footage in those workflows and businesses. Modern broadcasters will balance the type of storage they have with the cost to own and operate them. Overall they make more money than they spend. Their profitability allows them to spend what they need on the right type and amount of storage they need. It grows constantly, but usually the tech develops fast enough that the cost of storage per TB reduces over time with higher storage densities, better workflows, better tech etc."
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mxrwmr | What makes sugar a bad carbohydrate if you work out? What distinguishes bad and good calories? | Chemistry | explainlikeimfive | {
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"There is no bad is good carb. It's marketing bs. There are complex and simple carbs. Complex take longer for your body to break down, so the energy is released slower. Sugar is a simple carb. I'm not clear on the timescale differences between releasing energy \"fast\" or \"slow\". For weight management (including working out to build muscle or lose fat) all that matters is calories. The type of carb is irrelevant. (Though you generally feel less hungry with complex carbs). There may be issues with blood sugar levels for diabetics, that's a slightly different topic."
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mxs0gb | Why does food taste different at different temperatures? | Like for example, room temperature bread + cold butter & cheese vs a grilled cheese sandwich. Or raw carrots vs cooked carrots. Etc. | Chemistry | explainlikeimfive | {
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"It depends on the food. Some flavor compounds break down or evaporate at high heats, which is why onions taste different when cooked. Cheese tastes different when melted because the fat can more readily be tasted. Sometimes chemical reactions cause new flavor compounds to be in the food. This includes caramelization which turns sugar into caramel, and the Maillard reaction which is a reaction between sugars and amino acids. Certain compounds also cause your tastebuds to react more intensely when hot and certain others cause them to react more intensely when cold. So your example with the grilled cheese has both Maillard browning from the butter and bread contacting the hot metal, and the more readily available fat from melted cheese."
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mxs5kq | Why are we drawn to shiny metal objects and prone to adorning ourselves with them? | Other | explainlikeimfive | {
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"Shiny rocks are usually hard to find, if I have shiny rocks it means I have something special and stand out.",
"Status, so says our scheming hierarchy brain. “People will see all the jewelry I have and know my wealth allows this. Since I can spend so freely I must have a lot of money, which means I’m important in some way.” Strength, so says our Caveman Brain. “I wear the bones of those I have defeated and skins of beasts I have killed. I can protect what is mine, and all who see me will know this.” Sex, so says our Monkey Brain. “I have wealth, as shown by my abundance. That wealth makes me a more suitable mate because I can provide. This will make me more appealing to the opposite sex.” Shinies, so says our goblin brain. Shiny rocks and metals make the click-clack sound. Must have more. *All* the more."
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mxshlo | Why can’t you boil a sponge to sanitize it? | Googling repeatedly tells you to just buy a new kitchen sponge, never boil them because it doesn’t work. But why wouldn’t it clean them? | Biology | explainlikeimfive | {
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"Boiling or microwaving will KILL the bacteria. What it won't do is REMOVE the dead bacteria. That means there is dead biological material that's just food for more bacteria. The more you sanitize the sponge, the faster more new bacteria will grow... ELI5-when you kill bacteria it becomes bacteria food. Edit: Wow. So. Heat, UV, bleach & desiccation(alcohol/sanitizer) can all kill bacteria. But there is no practical way to clean the material out of the deep pores of a sponge without destroying it. Nothing is as good as a clean sponge. A short video of a single celled organism dying that demonstrates this concept: URL_0 DISCLAIMER: I am by no means a subject matter expert nor do I represent big sponge corp.",
"[A study]( URL_0 ) found that it didn't really help in the long term, even if it did have an immediate impact - and, in fact, it might make it *worse*. > Sanitation by boiling or microwave treatment has been shown to significantly reduce the bacterial load of kitchen sponges and can therefore be regarded as a reasonable hygiene measure. However, our data showed that regularly sanitized sponges (as indicated by their users) did not contain less bacteria than uncleaned ones. Moreover, “special cleaning” even increased the relative abundance of both the *Moraxella–* and *Chryseobacterium–*affiliated OTUs. Presumably, resistant bacteria survive the sanitation process and rapidly re–colonize the released niches until reaching a similar abundance as before the treatment.",
"I guess I take them for granted when I work for the US’s largest dish scrubber company. We hve bags of them that they give you to take home and pass out to family.. When I asked an engineer this they said: Microwaving and boiling do sanitize better than no measures at all but you don’t kill everything in them and they repopulate quickly. Boiling and microwaving also don’t release the trapped food particles inside that lead to future infestations.",
"The secret I've found to long lasting good smelling sponges is to always rinse them out after use, wring them out, and store them so they can completely dry out (I have a basket that suction cups to my sink). None of this boiling or dish washing needed.",
"Wait- can’t we just have the sponge drink some bleach before we boil it?",
"It would clean it temporarily however you would weaken the structural integrity of the sponge by boiling it causing it to rapidly deteriorate.",
"Tried boiling, microwaving, washing in dishwasher, washing in laundry, soaking in bleach. None work. The cleaned sponge seems \"fresh\" for a day maybe then stinks again. Only solutions I've even found is to replace it",
"For how long should we use a sponge? I've been using the same one for months.",
"LPT: Buy biodegradable sponges, and cut them in half. The smaller sponge is easier to handle and it makes the whole sponge last longer!",
"When you are using a sponge, most likely you will be using some form of grease and antibacterial agent. i.e soap. (which breaks the lipid layer of some bacteria) so to sanitize the sponge is kind of like pulling down your pants to fart. its pointless. You arn't eating off of the sponge, bacteria presence on the sponge could result in weird smell, but you could just replace it for under 1$ instead of spending upward of 30min to try and sanitize it.",
"Here's a thought: those bacteria are always present anyway and it's really the soap and water that actually matter. Sponges are really just there to scrape the stuff off that's hard to remove and shouldn't be relied upon to remove bacteria. You microwave a sponge so it doesn't stink. Not so it has no bacteria.",
"Does anyone have the specifics about our use and discarding of sponges? Somewhere I read we are creating significant environmental damage by throwing so many sponges away.",
"I rotate 2 sponges. Every day one goes in to the dishwasher and the other comes out. Everyday my sponge is like new.",
"Most Sponge are from synthetic materials and we fill the landfill with a lot of it. Can i recommend you to use loofah instead? Its from a kind of melon and i have been using it for more than 5 years and cleans dishes without issues. Its pretty large so you can cut it into 2 and when you feel you need to replace it just wash it clean off detergent and chuck it into the compost.",
"Does no one use silicone sponges/scrubbers? They aren’t as abrasive but nothing a good soak can’t fix. Mainly I just wash my dishes right after I’m done using them. They don’t harbor bacteria in the same way as a traditional sponge, dry fast and are easily cleaned/sterilized with boiling water. People say they require more soap because they aren’t absorbent which is probably true but I’ve got a good touch on my soap dispenser to get just enough soap on the silicone sponge to clean dishes without being wasteful.",
"Better question: Why do people still buy sponges (aka soft cesspools)?",
"I run my sponges through the dishwasher with my dishes. They stay clean, fresh, and smell much better. They also last longer.",
"Or just use a dish brush, so simple. Works better, doesn't smell needs to be replaced about twice per year.",
"Just don't use sponges. There are so many other more sanitary cleaning devices for a kitchen.",
"I haven't owned a sponge in ages. Entirely unnecessary. Why even botj with one at all? Dishcloths and scrub brushes are easily cleanable, less wasteful and more sanitary",
"Just take an old coffee can, fill with water and pour one cap top of bleach in it. Throw your sponges and dish rags in there at night. Unless you are camping, who is the hell is boiling sponges!?",
"Can anyone just answer the question-should I be throwing my sponge in the dishwasher to clean it or nah? I read half the comments but I only read one super efficient person that mentioned this",
"It doesn't matter if your sponge is dirty. All that matters is that it is a delivery vehicle for soap so food debris can't stick to surfaces in oily, un-dry-able spots. It's the drying of the surface that really kills things. If your butthole could effectively deliver soap the way a sponge could, it would be ass effective.",
"Boiling works, but just not as well as licking your kitchen sponge clean every month or so.",
"The food that bacteria colonize on is still there after you boil it. It will just recolonize shortly afterwards.",
"OK, there is a difference between sanitizing and cleaning. You can sanitize a sponge but not get it clean, and I will point out that it does not matter if the sponge is clean or sanitary. A sponge is a mechanical device intended to remove physical contaminants. It's not a sanitizing device. Does anyone here use a sponge for the *final* wipe of a plate/dish/glass? It will be rinsed and dried. The drying cloth and/or rinse water quality are MUCH more important, as well as the surfaces you dry them on. When the sponge has physically deteriorated, throw it out..."
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mxsuys | Why are teeth so vulnerable? There's nothing else, that I have to take care of 3 times a day and go to the doctor 1 time a year. | Biology | explainlikeimfive | {
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"text": [
"The main problem with our teeth is our diet. Scientists have studied ancient skulls and discovered that while tooth decay was a problem it was orders of magnitude less common than it is today. Today we eat a lot of refine sugars and that in turn feeds bacteria in our mouths which make acid that destroy our teeth. That's why we need to go to the dentist so often. Soda is by far the worst thing we've invented as far as our teeth go, because it's just liquid sugar suspended in carbonic acid. But good oral hygiene is very important to your health, even if you ate no refined sugars it would still be to your advantage to go to a dentist regularly. You just wouldn't get as many cavities."
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mxt3ys | Why do you get that feeling when someone is staring at you? | Other | explainlikeimfive | {
"a_id": [
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"text": [
"Most likely confirmation bias. You subconsciously notice someone looking your way (seeing them in your peripheral, or noticing their head is pointed in your general direction), so you look up to see if they're looking at you....they see you move so they glance directly at you (movement tends to draw attention) and suddenly they \"were staring at you\". What you don't notice, is all the times someone is staring at you and you never notice (or \"have a feeling\"). And you tend not to remember the times you have the same feeling, look around, and nobody was looking at you.",
"How do you stop \"looking\" at someone? Lately at work my eyes keeping locking at this person. Doesn't matter what I'm doing. I could be at break staring at my phone then for no reason I would raise my head and lock eyes with her as soon as she enters the room. Or I can be walking out the door, I look to the right and there she is again. How do you stop it? I also have no interest in her.",
"You don't most of the time :) I have played with this idea using rear view mirrors and angles and stuff. Mostly if the person can possibly use the whites of your eyes to guess the direction they seem to notice but if you have, for example, sunglasses or stare at them so they can only see you in a mirror (and I suspect therefore can't quite guess where you are looking) they don't react. Just my thoughts, no science. I spend a lot of time in the backseat of the car.",
"This has been tested, and people are in fact not able to \"sense\" when someone is looking at them. When you control the environment fully, people don't notice when they're being watched if there's no clues. When people do \"sense\" that they're being watched it's pretty likely that they noticed it in some mundane way, like maybe at the edge of their vision or in a reflection, and just didn't consciously register."
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mxt782 | Can you turn full cream milk into semi-skimmed or skimmed by simply adding water to it? (UK milk terminology used). | Chemistry | explainlikeimfive | {
"a_id": [
"gvr34kt",
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"text": [
"You can turn it into semi-skimmed by adding skim milk to it. You can't turn full cream milk into skim milk though, the fat has to go somewhere.",
"No the point is that fat (cream) floats on water so by drawing a skimmer across the top you remove the cream, but leave the other parts of the milk intact."
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mxuex7 | Why does going outside when it’s sunny/turning toward the sun trigger a sneezing reaction? | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"ELI5: For some people the nerve that tells your brain about what you see is really close to the nerve that tells your brain what your face feels. When the nerve from your eye to your brain activates very strongly (such as going from a darker place to a really bright place) it can accidentally make the nerve that tells your brain what your face feels activate too. This only happens to people who have these nerves close together. Your brain tries to make sense of the weird feeling this causes as a tickle in your nose and that makes you sneeze. Advanced version: An anatomical variant exists that places CN-II adjacent to CN-V2. When a large enough stimulus (such as sudden exposure to bright light) causes a large depolarization of CN-II in individuals with the aforementioned variant, it can inadvertently trigger depolarization of CN-V2. This is interpreted by the brain as irritation in the distribution of CN-V2, which then triggers the sneeze reflex. This whole process is referred to as the photic sneeze reflex."
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mxufor | Why does putting a wet paper towel around a can in the freezer cool it so fast? | Physics | explainlikeimfive | {
"a_id": [
"gvr9oio",
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"text": [
"The water transfers cold into the can faster than air. Or, said more correctly, the water draws heat out of the can and into the surrounding (freezer) air faster than the aluminum is able to do it on it's own. Think about it like this. If you have a wet paper towel that's been sitting out on the counter all day (so it's room temperature), and you put your hand on it, does it feel colder, warmer or the same as putting your hand on the (dry) counter or a room temperature soda can? It feels colder because it can extract the heat from your body faster. Same reason a marble kitchen table or leather couch feels cold even though they're the same temperature as everything else.",
"There are two types of heat transfer: conduction and convection. Convection is when an air current goes past something of a different temperature; think of a cool breeze or a warm clothes dryer. Conduction is when two masses are in direct contact with each other. Think of putting your hand in cold water or accidentally touching a hot pot on the stove. Conduction is MUCH more powerful. Now air, by itself, is actually a pretty good insulator; it doesn't absorb much energy (low thermal mass). A can in the freezer is limited in how much energy it can transfer to the air right next to it. (A blower would help, replacing air that has been slightly warmed by the can with air that hasn't.). Wrap it it a wet towel, though, and suddenly the can is exchanging heat with something which can absorb a LOT more energy. That's enough to explain why a can gets cool quickly when immersed in icy cold water (and why the cans in the slushy bottom of the insulated bin are coldest, as the gaps between the ice cubes are cold water and not air) but doesn't fill out the whole picture. So, the next question is where the energy goes from the towel. That's explained by evaporative cooling -- when water evaporates, it carries off the energy it takes to transform water into water vapor. So, you get conduction between the can and the towel, and a mixture of convection and evaporative cooling between the towel and the freezer air.",
"As /u/Alexis_J_M comment has already explained, it does cooling by evaporation. There is one more factor: A fridge contains quite dry air, because water in the air would freeze out. The dryness makes the water from the towel to evaporate faster. Evaporation needs heat, and the heat is taken from the can."
],
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mxulnj | What does the combined sun and moon represent in Spanish decorations? | Other | explainlikeimfive | {
"a_id": [
"gvrlc9j"
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"text": [
"Pretty sure it is related to Islam (religion). Spain was conquered by an empire that followed that religion in the 700s."
],
"score": [
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mxwfdy | how does light know the fastest path to travel? | I was reading about Fermats’s principal of least time and what I’m getting from it is that light follows the path that takes the least time. This is contradictory to the previous notion that light travels in the straightest path ever, so how exactly does light know which way will be fastest? | Physics | explainlikeimfive | {
"a_id": [
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"text": [
"The straightest path is the fastest path. Light doesn’t ‘know’ that the straightest path is the fastest path, it just so happens that the straightest path is - in all cases, the fastest path between two points in space.",
"Light behaves like a wave, so it actually goes down *all* the possible paths with the same endpoints. It doesn't \"know\" which will be fastest like electricity doesn't magically know the path of least resistance."
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mxwh2x | what actually cases the pain that comes with being hungry? | Biology | explainlikeimfive | {
"a_id": [
"gvrpoal"
],
"text": [
"The physical sensation of hunger comes from the contraction of the stomach muscles. They are triggered by the hormone ghrelin - also known as the hunger hormone. Ghrelin is known to be rise after a period of not eating and once the individual is fed, ghrelin levels start to drop to their lower levels. Until you get hungry again. Check the [Ghrelin]( URL_0 ) wikipedia for some more info."
],
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mxwi4h | Why do you get drunk faster after a massage or working out? | Biology | explainlikeimfive | {
"a_id": [
"gvrx4pc"
],
"text": [
"I can think of a few reasons; 1. Usually after you work out and/or have a massage it has been longer since you have eaten and your stomach is emptier. Obviously drinking on an empty stomach is more immediately and dramatically intoxicating. 2. Working out dehydrates you and depletes electrolytes, which also makes you more susceptible to intoxication. 3. Both working-out and massages increase blood-flow and circulation, which can increase overall respiration, which in turn can cause your body to process the alcohol quicker."
],
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mxwsl1 | What really is information/data on an atomic scale? | How come a combination of atoms can lead to information being stored in a computer or a brain? | Physics | explainlikeimfive | {
"a_id": [
"gvrpq1v"
],
"text": [
"Information is an emergent property, it isn’t a “thing” in the same way protons and electrons are. We can for instance assign meaning to an arrangement of matter and it now “holds information” despite nothing at all actually occurring to the matter in question. For example we might point at a flag and say “If the enemy is spotted and trouble is coming, lower the flag to half-mast to indicate distress. If the flag is up you are fine.” Nothing changed with the flag itself yet it now holds information."
],
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4
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