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7mwb60 | When photons hit objects and then come back to our eyes, do they kind of just "bounce" off the object, or are they always absorbed and re-emitted by its atoms? | I was reading about the photoelectric effect, where photons are absorbed by atoms and then re-emitted. But I couldn't really find any information on when exactly this happens. Is that what happens every time light hits something and then reaches our eyes? Or do the photons with improper wavelengths not "fit" and get "rejected", thereby bouncing off and never being absorbed at all? Or is bouncing and re-emission basically the difference between color and shininess, like a pure white object re-emits all photons and a mirror bounces away all photons...or something? Idklol | Physics | explainlikeimfive | {
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"You can picture the process as an absorption and emission, but things in the quantum realm work in ways we cannot easily imagine. Here's a simple depiction. Photons are little pieces of energy: sometimes it looks like a ball, sometimes like a wave I the sea. If a photon encountering a molecule has the right amount of energy (if it isn't too big or too small), an electron in the molecule will accept that energy and become excited, frenetic with that extra energy. Soon after this excitation the electron will get tired and throw away that extra energy in a new photon, as big as the one it previously accepted. This photon may occasionally be directed towards the retina in your eyes and produce an image in your mind. Be aware that electrons are very choosy and won't accept all the photons, but only those with the right amount of energy. This is the reason why a banana is always yellow: its outer molecules have electrons that absorb and emit only photons with an energy corresponding to the yellow color. In fact, for a photon any amount of energy can be put into relation with a different color. There are many processes in which photons are absorbed and emitted by an object, this is just one of them. Metals for example behave somehow differently, but this is a nice example."
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7mwf4w | Why is static electricity more prevalent during colder months? | We've been experiencing a cold spell in Kentucky and static electricity has been building up like crazy these past few days. Why does the cold impact the buildup of static electricity? | Physics | explainlikeimfive | {
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"Its not the cold, its your forced air heating system removing moisture from the air in your home. Ever notice hiw clithes fresh from the dryer spark a lot? Add a humidifier and witness the static reduce."
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7mwgpu | Do video games give you any real life skills? | Technology | explainlikeimfive | {
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"It depends on the video game, but yes they have been shown to have benefits such as.... - Increased hand-eye coordination. - Increased reaction times. - Increased focus/concentration and memory ability. Some have educational value (such as typing games and games focused on topics such as history, language, etc.).",
"Studies have shown that they can possibly help with hand-eye coordination and certain types of problem solving. URL_1 URL_2 They can also help people become more persistent by presenting players with challenging tasks over time: URL_0 So they're potentially somewhat generally beneficial in that they sharpen your abilities a bit. However, it bears mentioning that this is not evidence that games are the best or even a particularly good way to do these things, compared to other activities. Also, games generally don't provide you with actual real-life *skills* per se - Guitar Hero doesn't really help you learn guitar, most driving games don't make you a better driver, and most shooting games won't help you with real-life self-defense. So, there are benefits in playing games, but that doesn't prove that games are the best way to spend a lot of your time."
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"https://www.parentingscience.com/beneficial-effects-of-video-games.html"
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7mwi6g | When something such as a blow dryer falls into a pool of water, why does it electrify the entire pool? | If an electrical appliance falls in to water, I would expect the electrons from the negative side of the circuit to make a beeline for the positive side of the circuit. So why does electricity move throughout the entire body of water, rather than just directly from one wire to the next? I would also assume that the current flowing through the body of water is non-uniform. | Physics | explainlikeimfive | {
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"When an electric circuit is introduced to an alternate path to its source, (in this case through the water as opposed to through the appliance heater or motor, a parallel path is created. It is not accurate to say that electicity follows the path of least resistance. I t follows every available path. The path with the least resistance will have the most current. A short cicuit occurs when an alternate path to current flow exists than has extremely low resistance, the electrical current flow is usually high enough to trip the circuit breaker or blow the fuse. In the case of the electrified water, the current flow is high enough to be lethal, yet not high enough to trip the circuit breaker. That is why in the US outlets located in bathrooms, kitchens and near pools and hot tubs have GFCI protection. If the GFCI senses any current leaving the normal path greater than 5 milliamps, it shuts the power off to the device.",
"This is more or less a myth. It is the current through your heart that kills. The current flows from high potential to low and the path of least resistance will have the highest current and other paths will have lower current. If you are swimming in a pool, you will be subject to small potential differences and the resulting current through you will be very small.",
"The negative side of the circuit(neutral) is tied to earth ground back in the breaker box in your house. In something like a bathtub, the water provides millions of paths to ground which is a much lower resistance path than getting in the neutral wire and running through a hundred feet of copper wiring to get back to the box The water provides a huge parallel path, while the proper return wire provides a very skinny series path to ground",
"There is a lot that goes into this, but you have to keep in mind how the appliance works. Both hair dryers and toasters work by running an electric current through a metal spring or set of wires that heat up due to the resistance and lack insulation so the heat can escape. So once these are in the water - assuming the appliance is still on and plugged in - they suddenly have an outlet for all the electricity being run through those wires. This would be why you normally see the \"suicide in the tub\" jokes or comments having to do with a hair dryer or toaster. Many appliances might short out, but essentially you are running the current directly from the outlet into the water. Electricity follows the path of least resistance when possible and in many cases the water conducts the electricity better than the wires do. (I mean, they are specifically chosen to resist the current and heat up.)"
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7mwit4 | How come soda foams up differently when poured on ice cream? | Other | explainlikeimfive | {
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"Soda by itself has no proteins in it so the bubbles pop almost as soon as they are made. When you pour the soda on ice cream it melts some of it and mixes with the cream. The proteins in the cream increase the strength of each bubble causing them to last longer and so creating the \"foam\" that sticks around longer.",
"My daughter did a science fair experiment to address this. The ice cream that foams up the most and is actually creamer is the ice cream that had the most aeration which is usually the cheapest brand. The carbonated liquid that was used had no bearing on the end product, except for taste."
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7mwmqa | What's the fundamental difference between hand soap, dish soap, body wash, bar soap and shampoo? | Could I bath myself in dish soap? Could I clean my dishes with shampoo? Could I wash my car using hand soap? Is there really a difference between these different forms of soap? | Chemistry | explainlikeimfive | {
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"They're each focused on a different purpose Dish soap should cut through grease and oil, that's its primary job. It doesn't necessarily need to smell nice or be soft on the hands as long as it plows through stuck on grease Hand soap should be decent at getting stuff off your hands, but also needs to be soft on the hands. It should be neutral or smell nice. Shampoo should remove the grease from your hair, but not be so aggressive it dries it out or changes its color which may be acceptable with something like a dish soap Different tools for different jobs. If you want it to be soft on hands then it can't be super aggressive, if you want it to be super aggressive it'll do bad things to soft things like skin and hair.",
"I *have* used shampoo to wash dishes (when traveling). When I was a kid, we used dish soap to take bubble baths."
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7mwp05 | What determines a company's stock price and how can you tell if it's over or under valued? | Economics | explainlikeimfive | {
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"So, a share of stock means you own some fraction of a company. The value of the company is the total price of all the shares put together. So, stock price is directly related to what a company is worth. What makes a company worth something? Profits and assets. The value of a company is basically determined by how much profit the company is going to put out over time, plus whatever stuff / cash the company currently owns. So, it's not always that easy to guess how much profit the company is going to make in the future, which makes stock prices somewhat subjective, and also makes them go up and down depending on how things are going in the company, their market, and the economy in general. Usually, stocks get a price based on how the company is doing, how the market they are in is doing (e.g. a movie studio vs. the film industry in general), and rule-of-thumb ratios that people use to compare the value of one company to another. So if one company is doing pretty well but it's valued at 10:1 stock price : earnings, and its competitors are at 12:1 and not doing as well, you would conclude that company is under-valued. On the other hand, you can look at a company like Uber, and see that they are actually not that profitable, and probably conclude it's over-valued. The reason companies like this have high valuations is investors expect them to make big profits or acquire/make lots of assets (for example, valuable patents) at some point in the future. There are a lot of other ways to judge the value of a company, but at the end of the day it's profits, future prospects, assets (minus liabilities) and various formulas people like to apply to those."
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7mwp6n | Why does removing batteries, and then reinstalling them make the device work for a small period of time? | Technology | explainlikeimfive | {
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"Circuits are designed to shut off with batteries below a certain voltage. When it detects an excessively low battery voltage it turns itself off. That circuit stays in the \"off\" state until voltage is completely removed from the circuit. That circuit also has a range... Say cut off when voltage is below 3V, but only come back on when above 3.2V so that there's no flip-flopping if the voltage is exactly at the cut-off When batteries are no longer delivering current, they do tend to revive themselves. It's possible, with the example above, it got down to 3.0V, triggering the cut-off, then raised to 3.1V, but not above the cut-on. When you remove them, the cut-off resets, then the 3.1V is enough to power it until it goes down to 3.0V again. Sometimes it's possible to repeat this several times."
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7mwr6r | Plasma, in the electrical sense. Why is it its own state/phase? | Chemistry | explainlikeimfive | {
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"Plasma forms when you heat up a gas to really high temperatures. The electrons get ripped away from the atoms due to their high energy. This is called ionization. This makes plasma highly electrically conductive. Plasma is its own state of matter because its properties are so fundamentally different from a gas, in the same way that a liquid's properties are fundamentally different than a solid's.",
"Plasma is different from solids, liquids, and gasses. In a solid the atoms or molecules are fixed in a static structure, and while for instance a conductor might be able to trade electrons between atoms, the nuclei do not move. In a liquid the nuclei are moving around but the atoms or molecules generally are staying stuck together. They are in contact but not fixed in place, and so able to conform to the shape of their container. A gas has mobile nuclei but the atoms or molecules aren't stuck together, instead just bouncing around their container frantically. In the case of a plasma the material has been given so much energy that the electrons are no longer bound to their nuclei. Instead you just have a sort of soup of nuclei and electrons all whizzing about. Molecules are of course no longer possible and there are just elemental nuclei without any exclusive claim to specific electrons."
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7mx176 | why does it hurt more to get hit with things when You're cold | Other | explainlikeimfive | {
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"\"The nerves in your hand get much more sensitive when they're cold. Also, your veins constrict, and blood runs less to your extremities and more to your vital organs to preserve heat. This makes your skin more rigid, which causes pressure to be applied to these already sensitive nerves. So everything is getting less blood flow, which also makes it harder to make precise or repetitive movements. So all these make for a more painful experience when your fingers get hit when they're really cold. Compare the warm, soft hands with good padding and flexibility to cold, rigid, blood-deprived hands.\" That question was aleady asked on this subreddit and if you want to know more about it then you can find your answer here: URL_0"
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7mx2a8 | How can companies come out with very similar products(Google home, Amazon alexa) without infringing on each others patent? | Technology | explainlikeimfive | {
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"Patents must describe, in detail, a very specific technological improvement. They don't just cover the general idea of a product. A computer talking to you has been around for years. A computer understanding speech has been around for years. A computer following instructions has been around for years. Combining these things isn't a particularly novel invention, it's just an application of existing technology - that makes it unworthy of a patent. I'm sure there's some feature of the devices that is patented so the competition can't copy it but the basic idea is nothing new."
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7mx405 | Why are humans the only creatures to wipe their behinds? | Biology | explainlikeimfive | {
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"To my knowledge, we're the only animals to have an exceptional need to do so, due to our bipedal build. Most quadrupeds don't have buttocks of the nature of those created by the way our legs connect to our torsos. Feces drops directly from their anuses to the ground, without need to pass between two large slabs of muscle and fat. Beyond this, the dislike of the odor of one's own feces seems to be unique to humans. While other animals shun their droppings in relation to food, for obvious reasons, many use it to mark their territory, or even their dens. They think, if such a term fits, of this odor as their own personal scent, discernable from the scent of all other individuals of their species.",
"Some animals, like dogs, slightly prolapse when defecating, so the poop doesn't really touch anything else except for their rectum. When they're done, it all goes back inside."
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7mx6gy | How does an IUD work? | Biology | explainlikeimfive | {
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"Yer not alone in askin', and kind strangers have explained: 1. [ELI5: How does a IUD work? ]( URL_3 ) ^(_18 comments_) 1. [ELI5: How do hormonal IUDs release a reliable, steady stream of hormones for years? And do they taper off or just stop releasing hormones? ]( URL_4 ) ^(_3 comments_) 1. [How does a copper IUD work? (ParaGard or equivalent) ]( URL_1 ) ^(_3 comments_) 1. [ELI5: how do non-hormonal IUD's work? ]( URL_5 ) ^(_2 comments_) 1. [ELI5: How can IUDs prevent periods? Where does the uterine lining go? ]( URL_2 ) ^(_3 comments_) 1. [ELI5: What are IUDs? ]( URL_0 ) ^(_4 comments_)",
"There's two basic versions of a an iud; one uses hormones while the other does not. The non-hormonal one simply makes the uterus a non hospitable environment for the zygote, even if the egg gets fertilized. The hormonal one also acts as a physical deterrent, with the added bonus of super slow release hormones making the body think it's already pregnant. Or was just pregnant. Either way, the balance is off compared to a person's \"fertile period.\" Pregnancy takes a lot of pretty precise events to occur. If any of those are wrong, even if the sperm meets the egg the body will reject it.",
"Well, lots of answers from previous threads to answer this, but I'll take a hit at it since I'm bored at work. The IUD, intrauterine device, is a small, T or anchor like piece of plastic/metal/copper that is inserted into the uterus through the cervix. When not enlarging for the purpose of fetus holding, the uterus is actually pretty small, about the size of a fist. When you put an object in it, it makes the uterus a pretty shitty place to be. Pregnancy itself, despite how much we talk about surprise pregnancies, and how much we as a society take it for granted, is a difficult process, and requires a lot of proper steps to take place in order to be successful. Throwing a big anchor, literally, in the way, makes the uterus a hostile environment, and far less likely to indicate to the body that pregnancy is the right move at this point in time. The IUD, prior to insertion, has a long pair of strings attached to the ends of it that are cut down after insertion. Once the IUD is ready to be removed, the gyno reaches in with foreceps, and tugs on the strings. This causes the prongs on the IUD to collapse and then it can be pulled straight out! If hormones are involved in the IUD, as others have mentioned, it essentially works in the same vein as any other same-type hormonal birth control, most commonly by making the uterus extra-mucuousy so it doesn't allow for the implantation of eggs on the lining. Source: Was a army medic and regularly assisted and performed Well Woman's Exams and Birth Control procedures for Mirena, ParaGard, and Nexplanon"
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7mxbgp | What is the benefit of a strong password? | Technology | explainlikeimfive | {
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"When the server gets breached and the database gets downloaded, the attackers now have unlimited attempts to brute force the passwords within that database. If your password is weak then it will be one of the first to fall, potentially before you're notified of the breach. If you use that email and password combination elsewhere then you'll get breached there as well Your strong password argument relies on them not having the ability to spend days brute forcing passwords, this is a bad security assumption. You should always assume the breach and focus on minimizing damages when it happens Every system will get breached, its not a question of *if* merely *when*"
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7mxd3l | While taking a very hot bath I realized I was sweating from the heat. What is the difference between sweating from cardio and sweating from say, a steam room if there even is one? | Biology | explainlikeimfive | {
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"None. Sweat is nothing more than your body pushing out water so that water can evaporate (and cool the body down). Actually it's your body pushing out salts with water following the salts (look up osmosis for more on that)"
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7mxh39 | Why does your body feel weak when you have a fever or you’re sick? | Biology | explainlikeimfive | {
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"It's working to fight it, think of your body as a company with 100 employees, normal operation takes 75, with 25 there as just in case, but when your sick you need 110, 10 more than you have, so they're strapped for 10 people and it's hard to keep up so they do what they can until things calm down and you only need 75 again, sickness is A taxing thing on the body so it slows you down",
"Because you have to use your energy to fight the reason you're sick. Your immune system is using the glucose on your blood rather then your muscles, then you're tired. The same occurs when you eat too much, because your energy is sent to your digestive system and you feel sleepy."
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7mxjqa | What happens if you freeze an acid and turn it solid? Is it still corrosive? | Chemistry | explainlikeimfive | {
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"Acids are acids because they're in solution with water, they have free hydrogen and hydroxides floating around that want to go make friends. When you turn the acid solid, its no longer in a solution. The water forms back up into its H2O configuration and the acids regain their full form. With everything bonded and nothing looking to make new friends the acid won't be reactive Until it starts to melt, then it starts to dissociate and is an acid again",
"Acids without water aren't acids. *edit: as somebody pointed out, there are solvents other than water, but the idea is roughly the same with them* Your normal CO2 is just a gas you breathe out. Dissolve it in water and it becomes H2CO3 - carbonic acid. Very, very weak, but enough to affect your blood pH. Chloride is just a gas. In water, it's HCL, hydrochloric acid. Same with alkalis - NAOH is just white crystals. Mix it water and it becomes a strong base. Touch it and the sweat on your skin will make it into a base and burn you. Both acids and alkalis disassociate water molecules into H+ and OH- ions. It's those ions that burn and react with stuff. Without water, they don't react the same. If you freeze them, they will in general separate from water."
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7mxka1 | Why is most food acidic rather than alkaline? | Is it just that alkaline things don't taste nice so we don't eat them? Are three loads of foods that are alkaline? | Chemistry | explainlikeimfive | {
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"I'm not an expert but there are at least a couple reasons: 1) Alkaline stuff tends to taste really bitter, rather than sour (acidic) and people tend not to like that 2) Alkalinity (at least on the scale of alkalinity where you'd have something not harmful to eat) is not generally as good at stopping harmful bacteria from growing as acidity. Again, not an expert, might be wrong.",
"Living things in general are more resistant to acids than alkali's, for a variety of reasons. Not only does this mean that alkali foods are more dangerous to eat, relatively speaking, but it also means that alkali foods are less common in the first place. Since food is for the most part made of things that used to be alive, and alkali's are more dangerous than acids to living things, living things are more prone to using acids than alkali's for all sorts of purposes. Both of these reasons mean that there are simply less edible alkaline foods than there are acidic foods."
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7mxpbg | how does pyrite naturally form perfect (?) cubes? | How does such a seemingly "unnatural" shape come about naturally? Also, are they really perfect cubes or close enough? | Chemistry | explainlikeimfive | {
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"Yer not alone in askin', and kind strangers have explained: 1. [ELI5: How does iron pyrite form into a perfect cube while in the ground? ]( URL_3 ) ^(_2 comments_) 1. [ELI5: Why some minerals like pyrite are found in such peculiar shapes? ]( URL_1 ) ^(_12 comments_) 1. [ELI5: How can you procedurally form a cube in nature? ]( URL_0 ) ^(_6 comments_) 1. [ELI5: How do large crystals form? ]( URL_2 ) ^(_5 comments_)"
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7my4gr | How do grocery stores get fruit/vegetables that are out of season? | Other | explainlikeimfive | {
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"It's less complex than you'd imagine: most often, they are imported from distant countries with different weather. In a few cases they are simply stored in warehouses -- apples, for example, can be kept for months in the right conditions.",
"Out of season essentially means out of the ideal growing time There are a few ways 1. Out of season in one country can mean they are in season in another country (i.e. when it's summer in the northern hemisphere, it's winter in the southern hemisphere) so they import them 2. Some farms can grow fruit vegetables indoors or use extra fertilisers, etc to grow them when they are out of season 3. Some fruits / vegetables can be frozen, dry stored or preserved using enzymatic preservatives meaning they can be kept in a warehouse until needed.",
"Many things are grown in giant heated greenhouses and polytunnels. There are also different varieties of produce which are grown at the beginning, middle and end of season. Things such as rhubarb are forced to grow and then discarded. Carrots are covered in straw and harvested when needed. Apples are kept in a giant fridge for about a year before they get sent to stores so there is a supply year round. for other items such as raspberries they are grown abroad and imported. Bananas are picked green and put in giant warehouses before a small amount of gas is released to start the ripening process. Its a small world when it comes to produce."
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7myrb6 | Why do you become tired after a big meal? | After every big meal , I become very tired and wondered why. | Biology | explainlikeimfive | {
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"digesting a big meal takes a lot of energy and you body have a limited amount of energy to spare. So your body redirect a big amount of its energy to the digestive system, leaving less energy to the muscles and other body functions, which is somewhat similar to when you've exercised and spent a lot of energy."
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7mytov | Why is it the same set of hands (mine) that can quickly slice a potato or cheese into perfect thin parallel slices can't seem to write legibly or draw a straight line with a pen despite long practice? | Other | explainlikeimfive | {
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"It's all about muscle memory. You stopped practicing your handwriting while it was still terrible. So when you write, your mind just falls back on the movements it's used to. If you practice writing slowly and legibly every day, tolerating only the neatest writing, your muscle memory will eventually catch up, and your legible writing will get faster and faster. I used to have the same problem. I practiced daily for three months before I was satisfied enough to take a break. I still have lots of room to improve. But my handwriting is way better than the chicken scratch I used to produce.",
"Your grip on a knife is sturdy and rests well within the entirety of your hands. The grip on a pencil is gripped by (generally) two fingers and a thumb with tensed muscles and resting only on the back of your joining thumb and index muscle. More precision is needed for smaller muscle groups to keep steady.... That's the best I got"
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7myy9i | 6 Fingers is actually a dominant trait. Why aren't there more 6 fingered people? | Biology | explainlikeimfive | {
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"Dominant does not mean common. Dominant just means that it'll win out over recessive. How common a trait is has nothing to do with this. It depends on how many copies of that gene version are in a population. There is a detailed explanation here: URL_0 Short version is that despite a trait being dominant it will only show up when that gene is present. Since the actual gene for polydactyly is so rare not many people receive the gene and exhibit the trait,",
"I'll just post the answer I wrote the last time this came up. In short: \"dominant\" and \"recessive\" don't affect how prevalent an allele becomes- that depends on whether they're advantageous or not. Even though 6 fingers is dominant, it doesn't make its possessors more successful in having children. The number of 6-fingered people started out low, and since there's no advantage to having 6 fingers, their proportion remains small. \"Dominant\" and \"recessive\" simply describe how two alleles interact with each other. A dominant allele may be disadvantageous- in which case it would slowly die out. It might simply be rarer- when most of the population has recessive alleles, the dominant allele doesn't increase in number as quickly. That's the simple description- let's look at it closely! ## Alleles The DNA of humans (like most animals) is paired up. We have two copies of each gene. Each copy doesn't have to be the same, too, and we can have two different versions of the same gene. Each version of a gene is called an allele. ## Dominance When an allele is dominant, the organism takes on that trait even if it has another recessive allele. For example, there are 3 alleles that determine your ABO blood group: A, B, and O. A and B are co-dominant, and O is recessive. So if you have one A allele and one O allele, your blood type would be A. A is dominant over O. Similarly, B is dominant over O, and having one B and one O allele would give you a B blood type. ## Frequency Nevertheless, the O blood type- two O alleles- is much more common in human populations. Why? In this case, having A/B/AB/O blood types doesn't really affect your life. You wouldn't expect someone with an AB blood type to be more successful in life than someone with O, for example. Thus over the generations, there isn't any pressure that makes people with O blood less successful. So if a population starts out with a lot of O blood people, chances are that two people meeting and having kids will both be O type- and all their kids will be O type. So it just happened that we started out with relatively lots of O type people, and the proportion stayed that way! The same goes for having many fingers on each hand. It's simply much more common to find 5-fingered people, even though having 6 fingers is a dominant trait. ## More reading URL_1 URL_0",
"There are many times where a dominant trait is rare. For example, dwarfism is dominant, while lactose intolerance is recessive. It really all depends on luck and how common a trait is. For example, if you killed everyone with 6 fingers for multiple generations, you'd more or less erase the gene from the gene pool.",
"If a dominant trait is not prevalent in a gene pool it is likely because it is either harmful or there is a sexual selection bias against it. 6 fingers is likely the latter"
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7mz6lx | Why Does Cold Air Hold Less Moisture than Warm Air? | With the big drop in air temps in the northern US, I got to wondering about this. I’ve read that people get itchy dry skin in the winter because cold air doesn’t hold as much moisture as warm air does. Assuming that’s true, what’s the reason for it? | Physics | explainlikeimfive | {
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"The temperatures we like are very close to the temperatures where water condenses from a vapor (gas) to a liquid. Colder temperatures, like the ones outside now, are below the temperature where water condenses and even below the temperature where it freezes. When the water freezes, it falls out of the air. When that air with no water is drawn into out homes and offices (so we have fresh air to breathe) we warm it up. While warming it up would allow it to hold more water in the vapor state, that doesn't make water appear spontaneously in the air. So we have warm, but very dry air, unless we have special machines that add water to the air as they warm it.",
"Water molecules in water and ice are bound to their neighbors. If they get enough energy, they can escape and go into the air. If they are in the air and hit a surface (that includes dust particles - surfaces are everywhere), they can get trapped again - which is more likely if they have a lower energy. Hotter temperatures means the molecules have more energy. Water molecules are more likely to go into the air, and less likely to go out of it."
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7mz7wp | How can someone who is unconscious survive for a long period of time underwater? | I posted the link for context, but this happened recently near my hometown. Assuming the boy really was underwater for 30 minutes, how was he able to survive? Or is this just a case of those who were present not tracking time well because of the situation? **Edit: I thought I pasted the link on my phone, but I guess not, here is the actual link URL_0 And as people have commented it was a pond that had been frozen over** | Biology | explainlikeimfive | {
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"**TW: drowning, going to get a little graphic for the sake of the explanation.** So, you're at the local swimming pool and you inhale some water. The water goes into your lungs, prevents you from inhaling air, you panic, and your whole body rapidly expends what little oxygen you have as you thrash about, and you quickly lose consciousness. Over the next couple of minutes your oxygen starved brain begins to shut down, all functions begin to cease, and your heartbeat stops. You died! Now, you're walking along a frozen lake bed in a horrid Siberian winter, because invading Russia in winter is a great plan. When suddenly, the ice below you cracks! You plunge straight down into water colder than your ex's feet in the darkest hours of the night. This causes you to rapidly lose body heat, which *slooowwsss dooowwnnnnn allllll ttthheee proooceeesssesss iinn yyoouurr boooddddyyyy*. You can't thrash, your muscles won't respond, your metabolism slows as the temperature decreases, your heart begins to pump more slowly... As your head hits the ice above you, you black out, the stress on your body too much. You died! But wait, your body doesn't **need** oxygen. What would it use it for? Your heart isn't beating, your brain meat isn't shooting the rest of you with electricity, your muscles are completely limp, you aren't even supporting yourself, you're just floating in the water. You're essentially hibernating like a bear. Suddenly, the minute or two of air that you had lasts for much much longer. Your brain still has all the things that it needs, hell, it was just about to tell your heart to beat, all it needs is for your body to be warm enough that the neuron can fire. Meanwhile, a lonely peasant saw you fall through the ice, they're running towards the lake, knowing where the safe ice is, they sprawl across the ice, grabbing your thick coat and slowly dragging you from the depths. But the air is still terribly cold, you're not breathing, but your eyelids twitch, so they drag you towards their home, laying you by the fire. You gradually begin to warm up, your brain remembers what it walked into this part of your body to do, and sends the impulse to your heart to contract. **Lub** Sluggishly, your heart contracts, your blood thick, and tepid. **DUB** But the rythm is kept as the impulse from your brain kick-starts the SA node (what pacemakers were invented to fix), and your heart begins to beat again. Your body begins to function once more as your blood warms. Your savior has been pumping your legs and bashing on your stomach in a crude attempt to get you to - *Blaaaaagggfhhhhhhhrurfjdjsjebfiebdugmanrp* Vomit. Well, to get the water out of your lungs. Enough is expelled through hacking and coughing that you manage a few shallow breaths, oxygen returning to your blood, the CO2 being expelled. Over the next hour your body begins to recover and you wake up. You're in a cabin, but you died. Why are you naked? And comfortable? And who's spooning you? Wait, are you the little spoon? Hmmm, it's kind of nice to be the little spoon for once... Wait, who is that? Turning over, you see the one who must have saved you, did you die? Or did you just start living? Annnndddd that's what happens when I try to ELI5 after prepping for DND. Hopefully it was illuminating, it was fun to write. **TL;DR** You drown when you're warm, you use up all your oxygen trying not to drown, or simply through your body's normal metabolism, and your brain dies. You drown when you're cold, and your metabolism slows down so much that your body *can't* use up the oxygen, the reactions that occur simply don't work at the low temperature. So you go into stasis, under the right conditions, your body will start working again. Your brain still has oxygen, it is still trying to do what it is supposed to, it's just too cold. Warm it back up and it will work fine.",
"The problem with drowning is that you're no longer able to breathe. The mechanism is that new oxygen is no longer brought to the blood and carbon dioxide is no longer expelled, which causes the organs to begin failing. However, the rate at which your organs stop working is not uniform. A person near death in a snowdrift may appear to have no heartbeat, but spontaneously revives when they warm up. That's why it's popularly said that \"you're not dead until you're warm and dead.\" In ice-cold water, the brain is preserved for longer than under ordinary conditions. Although brain damage is occurring, a person can often heal or adapt to a small amount of damage without a permanent loss of function. You didn't link to the article, but I'd guess that's what is occurring here.",
"When you're unconscious, your heart rate and respiration slow down dramatically. However, that's not enough to keep you alive because you can still inhale water and drown. Instances when people survive despite being underwater for so long nearly always occur when the person is submerged in very cold water (e.g. a frozen lake or river), which slows down all metabolic functions, including cell death from lack of oxygen, dramatically. The combination of being young, tough, lucky and being submerged in an ideal environment to prolonging survivablitly allow the human body to be preserved for a relatively long period of time."
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7mzgui | How do high blood pressure medicines help reduce blood pressure? | Biology | explainlikeimfive | {
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"Couple of ways. High blood pressure mostly comes down to the heart pumping harder/faster, blood vessels squeezing harder (blood vessels have a little lining of muscle), and salt/water balance. The body controls all this in a couple of complicated ways. Let's cover the most common groups: * Calcium channel blockers (like amlodipine) stop blood vessels from squeezing down as tight by working on that little lining of muscle. * ACE inhibitors (like lisinopril) stop part of a signal relay that normally tells blood vessels to squeeze down and tells the kidneys to hold on to salt and water. Angiotensin receptor blockers (ARBs, like losartan) are really similar, but work on a different part of that relay. * Thiazide diuretics (like HCTZ) are interesting. You'll mostly read that they make you pee off salt and water, so you have less blood in your vessels, meaning lower blood pressure. There actually seems to be a lot more to it long-term, but it's not ELI5 (they don't even explain this part well in med school.) * Beta-blockers (like metoprolol) block signals that tell the heart to beat harder and faster. * Alpha-blockers (like prazosin) block signals that tell blood vessels to squeeze down. They act on a different part of the same big system as beta-blockers. * Central alpha agonists (like clonidine) act on the same system as alpha and beta-blockers, but instead of blocking the signal, they trick the brain into not putting it out to begin with. In general, what we've realized is that blood pressure isn't always the thing to focus on. Some drugs that decrease blood pressure don't make you live any longer, or have fewer heart attacks and strokes. (Alpha and beta blockers are both great for a lot of other problems, but not great if high blood pressure is the only one. Thiazides, calcium channel blockers, ACE inhibitors and ARBs are all cool.)"
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7n05ju | How our lungs prevent/eliminate dust ? | Biology | explainlikeimfive | {
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"Your nose and trachea are lined with tiny hairs, cilia, which are covered in sticky mucus that traps most dust from getting to the lungs. The cilia in your windpipe are always doing a wave, so to speak, that pushes stuff up and out.",
"It's not very complex. Your lungs are lined with goo (mucus) and the dust sticks to it. This dirty goo is pushed out by tiny hairs and by coughing.",
"we have these filters in our lungs similar to air filters in cars, and every day we clean it out with mucus",
"As people have pointed out there is mucus to trap dust and whatnot and little waving hairs to push said mucus up to be swallowed/coughed up (the charmingly titled mucocilliary escalator). Of note those hairs die off if you're a smoker (so badness stays in you lungs) and grow back and work again once you stop, hence why a newly quit smoker may get one hell of a cough as they are clearing out a lot of built up debris."
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7n0cft | Defecating and the associated physical and emotional response. | Biology | explainlikeimfive | {
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"This could be a symptom of Irritable Bowel Syndrome or something similar. You may want to speak to your doctor. (Sorry if this breaks the rules, I’m just worried about OP.)"
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7n0hu3 | The moment any of my fruits start rotting, fruit flies would appear out of nowhere. Where do they come from? | Biology | explainlikeimfive | {
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"Their eggs are already in the skin of the fruit and they hatch from there. You can prevent them from hatching by thoroughly washing your fruit and/or putting them in the fridge since fruit flies need room temperature to hatch. Edit: freezer != fridge",
"What is the best way to wash your varius fruits and vegetables?",
"They normally are in the skin of the fruit or, like microorganisms, in the air, as Pasteur's experiment suggests."
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7n0iff | Why do establishments make bathroom doors push to go in but pull to come out? Why not make it pull to go in and push to go out and avoid touching the door with your clean hands? | Other | explainlikeimfive | {
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"I've seen them both ways. In general, doors that open to hallways are put in so they don't swing into the hallway. It's a safety issue; you don't want to hit someone. Having the entrance a push makes it easier for you to enter the bathroom without contaminating the door if you are going in to wash something off of them. Push doors have the hinges and lock on the inside, so you can't be locked in. Many public bathrooms also tend to have drinking fountains, closets, or other utilities near them; having the door open outward makes the wall there dead space. This is more important in a corridor, less so in a bathroom section which is likely just a corner anyway.",
"It is a common safety requirement to arrange the doors that way to prevent an inaccessible obstruction stopping someone from exiting the building. Imagine if a cart or something was placed in front of a bathroom door that opened outward and then a fire alarm went off. Those in the bathroom wouldn't be able to open the door and the cart would be on the other side of the door!",
"Oh! I can answer this! I recently started a job in HVAC engineering (kids, avoid this industry if you have a mechanical engineering degree). Typically the air that's pumped into rooms (supply air) gets there via diffusers. Once the air is there it needs to get out of the room so it can either reheat or cool down again. That's where returns come in. Returns are typically just an opening in the tile ceiling, or in the case or a restaurant just an opening on the back of the HVAC unit. A tenant space is designed to have neutral or slightly positive pressure. That way opening/closing doors isn't a hassle, among other reasons. If it's slightly positive it'll keep cold air from getting in during the winter months when an outside door is opened. Bathrooms are a bit different since that air is smelly and gross and no one wants that air getting into their space. An exhaust fan that vents to the roof is put in the bathrooms. The return air in the bathroom does not even mix with the other return air. The exhaust fan's cfm (cubic feet per minute, the unit of measurement used to describe the volume of air put into the space in a certain amount of time) is typically 50-100 depending on the size of the bathroom. The supply cfm to the bathroom is typically 35-80. This puts the bathroom at a negative pressure, which keeps the nasty are inside the bathroom. What does this have to do with doors? Well when you enter the bathroom and you push the door IN that pulls the clean air into the bathroom while pushing the dirty air into the bathroom. When you leave and you pull the door, same effect. It's all about keeping the dirty air within the bathroom. What I don't understand is why don't all restaurant bathroom doors have that foot handle where you can pull it open with your foot. Makes it so much easier. Edit: I'm not 100% correct, as expected. It actually has to do with the egress of the door swings and other accessibility concerns. Neat!",
"How much dirtier is a bathroom door than a regular door?",
"So you don't nail someone with the door. knocking over a tray of food or causing legal issue. My guess, anyway.",
"Because unless you actually make contact with an observable amount of human shit, the toilet door is not going to make you ill. Johnson & Johnson would have you believe otherwise, though. There's a reason they make a lot of money selling sanitary products that most people don't really need.",
"Here’s how to use the bathroom in the most sanitary manner: 1. Do not use the urinal to pee. Urine splashes back on you. So stand as far back from the urinals as possible and just let loose like a fire hose. 2. The better option for maximum sanitariness is to use the stall. Kick open the door. Seat down? Don’t touch it. Stand as far away as possible again.Pee all over it. Then kick the flush. Or don’t flush. Don’t worry about breaking anything because fuck everyone. 3. Wash your hands for 2 seconds. 4. Dry your hands with the paper towels, use towel to open door, throw your filthy towel on the ground. You are now the cleanest most sanitary person in the world. Enjoy your day touching knobs and money and hand rails that are all perfectly germ free. Not like that gross bathroom with piss everywhere and dirty towels on the floor",
"Because never in the history of ever has anyone ever caught anything by touching a fucking door handle. For god's sake stop being neurotic. Downvote all you want. Toilet commercials aren't actual biology lessons. Sheesh.",
"What about those who reeaalllyyyy reaaallllyyyy have to pee. Easy open push doors are a lifesaver.",
"I took an architecture class in Korea, so it may be different, but we were told it was so you could stop the door with your foot if someone accidentally comes in on you while you’re on the pot. House doors also follow this rule in Korea.",
"Fire code. Doors shouldn't open outward into areas that may be trafficked in an emergency situation.",
"There are foot pulls that can be mounted on the bottom of a latchless door to open it hands free. I don't know why you don't see them more often. I've only seen them a few times in the US, I know the Smithsonian Air and Space Museum Udvar-Hazy Center has them, but other Smithsonian museums do not!",
"Many are pull to go in. At least in offices. Bathrooms are kept at a lower pressure than the common area by extract fans. This prevents the smell leaking into the common area. The door is pull open so it's held shut.",
"So how do you push doors without hands? I’m genuinely curious",
"Because when going out you could slam the door in the face of someone?",
"There is a code of buildings. It’s not a choice, but they have to build accordingly to get a license for business",
"basic rule here in Finland is that doors inside are installed so that they won’t block path towards emergency exits and exits should be always pushable so you can run out. I think there was a EU policy also which was about the same.",
"I’ve always said when I open a bar (never going to happen) you can’t get out of the bathroom until you’ve washed your hands. If you try and not wash your hands sirens go off alerting everyone to what a dirty bastard you are. The amount of people who don’t wash after going to the toilet never ceases to amaze me. Obviously I haven’t thought this whole system through but whatever.",
"Why have doors at all? Changi Airport's toilets have no doors. There's a chicane for privacy, and that's it. Cheaper, and more hygenic. Plus, no likelihood of a swinging door hitting someone.",
"You’re still using your hand to push a door that 1000 other dirt bags touch. Also it’s basically a safety hazard. Can’t have Jim Bob ramming a door into a waitress while she’s carrying 5 plates of hot cheese soup.",
"Some people have you her on the issue but let me clarify. It is neither building nor fire code that makes a bathroom door swing in the direction of egress; however, the building code does specify how far a door is allowed to swing into a corridor or space. For instance, a door cannot obstruct the means of egress width by more than 7 inches when fully open and cannot obstruct the means of egress width by more than 1/2 in any position. That is why most doors in corridors or other confined spaces open into the space. When you have a door that provides access to a room that can by occupied by more than 49 occupants, then he doors must swing in the direction of egress and two doors must be provided for said room or area. A recessed doorway is very common in this application. It is also an economical and architectural decision to have doors swing into a bathroom so there is more usable floor space for movement and patrons. I believe every chair in a bar or restaurant is worth 10s of thousands of dollars per year, so even one more chair makes a huge difference.",
"Maybe it's because most bathrooms were built before everyone had a weird obsession with germs.",
"Depending on the building occupancy it has to do with code. Like some people have said they don’t want it swinging open into a hallway during a fire and blocking it. So in some buildings no one had a choice and in order to get occupancy from the municipality the building has to be completely up to code.",
"it's usually a space efficiency thing. the corridor leading to the bathroom has other doors usually (the other bathroom door for the opposite sex, or leading to the kitchen or back of house, or store room, etc.), so having a door swing out into that would either be a safety issue, or require the corridor to be wider than minimally necessary. compare that to the inside of the bathroom, the bathroom door can swing into that space. doors usually only need to open into the direction of escape when the occupancy load is greater than 50 people, so it doesn't apply here since toilets are considered as a temporary (non-simulataneous) space which are not expected to have people there for extended periods of time",
"I’m actually qualified to answer one of these! Two main reasons: One is that a door swinging outward will create a barrier in a hallway that is possibly being used by people to exit the building in an emergency. Two is that due to the required clear floor space around plumbing fixtures for people with disabilities, there’s actually more room to swing the door in, and since when the door closes (which it will so you can go to the bathroom) all the floor space is freed back up, it makes sense to have it swing in. There’s a couple other minor things such as in a hallway there’s usually very little wall space. The wall either turns or there’s another door next to a door. On the pull side, you want to have some wall, 12 - 18 inches depending on the controlling agency, so that someone who needs the extra leverage can put a hand on the wall to push off of as they pull open the door. Source: am a licensed architect"
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7n0jdt | How does a voltage divider actually work? | Physics | explainlikeimfive | {
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"It's possibly easier to consider an old-fashioned slide potentiometer that we used at school years ago, rather than discrete resistors. A length of resistace wire is fixed stretchad out along a piece of wood and one terminal of a battery connnected to each end. Connect one probe of a voltmeter to one end and slide the other probe up and down the wire. When the two probes are at the same end, naturally there is zero volts measured. When they are at opposite ends, it reads the full battery voltage. At intermediate positions you get intermediate voltages that go continuously from 0 to V in proportion to the distance. So you have a continuously variable divider where Vout = Vbatt x (separation/total length) and thats equivalent to the resistances either side of the slider. That setup is exactly the way a volume control works on a radio etc. the slider runs along a carbon resistor track and passes a signal on that is a proportion of the feed source.",
"There are two voltages at the divider: the voltage across the whole thing and the voltage at the midpoint. The midpoint voltage must be less than the voltage across the whole thing (because of Kirchoff’s voltage law), and that voltage is determined by the ratio of the device values. Why? Because there’s one current flowing through both devices. The voltage across each device for that current is given by its resistance value. In fact that’s the definition of resistance.",
"My highschool physics teacher had quite a good ELI5 explanation for this. Imagine electricity is just a bunch of big dudes that love lifting stuff. Their voltage tells you how much resistance they can still 'pick up' and their current tells you how many dudes there are. Remember: V = I*R and I = V/R So a high resistance means not very many dudes will walk but their capacity of lift is high and low resistance means there are a lot of dudes but they do very little work. (Sort of, I know this doesn't tell the full story) Now what happens in a voltage divider? You have two resistors in Series. When the dudes walk over the first resistor they pick up some resistance and thus their capacity (V) goes down. Then when they pick up the next resistor they are saturated and V=0. So would you look at the Voltage in-between the resistors you will see the dudes there can still pick up some more, but not everything. Thus the voltage is 'divided'"
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7n0my5 | How does plastic packaging prevent bread going stale? | Bread usually goes stale when left out in the air for long periods of time, so how does putting it in relatively air tight packaging prevent it going stale, when it is still sitting in a ‘chamber’ full of air? Is it because a small amount of air can only give the bread a certain amount of ‘staleness’? | Chemistry | explainlikeimfive | {
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"Because bread does not stale just when moisture leaves the bread. It's a common misconception. When you cook starch, it gelatinizes. It takes up water, swells, and softens. When it cools, the starch recrystallizes becoming hard, creating that stale bread feel. Moisture can slow this down, like the inside of that plastic bag, but bread still stales in moist environments. Staling is most dramatic when the bread surfaces are exposed outside of the bag. [ URL_0 ]( URL_0 ) The process is called starch retrogradation if you want to research more about it. The other comment is really really wrong. Refrigerated bread stales fastest, but inhibits mold growth. Freezing your bread halts the recrystalization process entirely, making it better suited for long term storage. Reheating a stale piece of bread with soften it again. You haven't added moisture back into the bread, it's just the starch gelatinizing again. In fact, you lose more moisture through heating the bread again."
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7n0s2r | Why is it common for women to get a UTI after sex if they don't pee after, even though their vagina and urethra are separate? | Biology | explainlikeimfive | {
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"They are separate but close enough together that fluids can get in there and the motion can irritate the urethra. Also the urethra some women have is very short making them more prone to infection; peeing helps get stuff out. Edit: I don't word well.",
"If you're going for PIV, you will most likely spent a lot of time rubbing the shaft of your cock along the urethral entrance as you go back and forth (it's situated between the clitoris and vagina). This will end up with some amount of lube, sweat, sexual fluids, whatever being pushed up there. Urinating after sex flushes it back out before any consequences can take hold."
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7n0v8i | How does a finger print sensor work? | Technology | explainlikeimfive | {
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"When you take a close look at your fingers, you’ll notice that there are very small ridges on them. Everyone has a slight difference between the heights of these ridges, the distances between them, and all the empty spaces or unique points of these ridges. When you use a biometric system to record and use a fingerprint scanner, you often have two systems: an Optical and a Capacitor scanner. Optical scanners work by shining a bright LED light over the finger placed for scanning, and takes what is essentially a digital photograph of the finger print. The ridges closest to the scanner will reflect the most light, and the depths and curves will usually reflect less. The scanner records these “images” and sends the data to a computer that calculates the depths and distances between ridges, that are again, unique to (almost) everyone. The second type of scanner, a capacitor scanner, is more commonly found in phones and various tablets, and is more commonly known. These work by using a capacitor that stores a current, and another computer that measures these currents. When you place your finger over a plate where the capacitor is working, the ridges closest to the plate will affect the conductivity of the capacitor, whereas the air in the ridges between will leave it relatively the same as before the finger was placed. A computer records these changes, and because each distance and curve between ridges are different, the recorded difference will be different. This is how your electrical “fingerprint” is recorded! Edit: I didn’t expect this to blow up so much! In regards to all the interesting questions, I will get to them as soon as I can, and read up on the topic to make sure I’m not spouting none sense. I’m currently slammed at work, but I will make time to answer you all. :)"
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7n13zd | When we cry, what is the purpose of the tears? | Biology | explainlikeimfive | {
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"From what I understand, the brain releases a hormone that causes you to produce tears, and it's often released in tandem with the same hormones that register sadness. Interestingly enough, tears from sadness, and tears from cutting onions have vastly different chemical makeups.",
"And what about babies? They cry when they're hungry, angry, hurt, sad, constipated, you name it. Source; I just babysat my 16 month old nephew who cried because he DID NOT want his bottle."
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7n1kxm | why do private residences have doors that open into the building, but commercial buildings have doors that open out of the building? | Other | explainlikeimfive | {
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"Private residence doors open inward because it is safer. If someone knocks on the door you can open it a small amount and remain behind the door. It's more difficult for someone to push the door open against your weight than if you were opening outward and they grabbed it. Commercial doors open outward for fire safety. The door opening outward means in a stampede it can still open and not block people from exiting."
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7n1lg3 | Why does the skin under your nails need your nails to protect it? Why and how is it different to the rest of your skin? | Biology | explainlikeimfive | {
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"You have it the wrong way round. That skin is sensitive because your nails grow over it, so it never needs to get as tough as the rest of your skin. You may not think of nails as that important because, as an evolved Human, you don't use them much in day-to-day life, but look at how other species use them. That's what they're there for - not to protect skin.",
"Nails are not only really for protecting the skin beneath them. They are more like tools attached to your body. With them you can for example grab small things more easily or dig better with your hands. See other animals like mouses, who have nails like we do, but in other shapes, which allows them to do things more easily than they would be without them.",
"I googled more information about the nail bed when I had my left index nail removed. When it was removed the skin was soft and sensitive, like when you trim your nails too close to the quick, but all over a huge area. This skin’s job is usually just holding on to your nail and guiding it to your fingertip before letting it go. So when it was removed there was this huge sensitive part. But after a few days the former nail bed toughened up and was no different than the rest of the skin on my finger. I learned first hand just how important nails are when I had my left index removed. I did not expect how difficult it would be to pinch things or pick up small objects or press buttons. Even if we are not using our nails the way other mammals do, to dig holes or climb trees, they are still important for giving structure to our fingertips."
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7n27mn | When nuclear bombs are tested over water, what happens under the water's surface? | Physics | explainlikeimfive | {
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"The water's surface is vaporized immediately due to the extreme heat. Those water vapors travel upward and mingle with all of the radio active particles before going far up into the atmosphere. Those tiny water vapors carry radioactive particles with them until the vapors condense and fall as a rain drops. Then you have radio active rain."
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7n2kmz | why vision gets distorted when hot and cold air meet | Physics | explainlikeimfive | {
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"Light travels at a slightly different speed through hot air than through cold air. This causes the light to bend, like it does in a lens.",
"A good comparison is to the surface of a body of water. Since light travels differently in water and air, you can see the barrier between the two clearly. The same exact thing happens with hot air and cold air. The light is traveling differently through the two, so you can see the area where they mix. The mixing of hot and cold air can even resemble the shimmering of water since air is a fluid (fluid means something subtly different from a liquid) and moves in a similar fashion to water",
"Great question! I guess you can start with thinking about what temperature is. When something is hot, the particles in that material are moving faster on average than the particles in something that's cold. Because the particles are moving faster, they bump into each other more frequently and tend to have more space between any two particles. When things like gases (for example) are transparent, they can slow down light and bend it by an amount which is directly proportional to their density. Since a hot material like hot air has more space between its particles, it has a lower density than cold air, and they both bend light by different amounts. When the two gases mix, they make images seen through the mixture appear distorted as all the rays of light coming from some object behind the mix aren't traveling parallel. I should say that I have no idea why exactly light bends when it passes through a material boundary at some nonzero angle from the perpendicular, so I might go start my own ELI5 post.",
"The same reason a straw appears broken in a glass of water. Hot and cold air have different index of refraction, causing light to travel at different speed. This difference cause the rays of light entering the mixture exit at different angles. Watch this video: URL_0 Extra fact: the same principle of Snell law also explains how optical lens like those in eye glass and telescopes work by bending light.",
"Snell's Law. Light *always* travels the path of leaat time. Just like how light is \"bent\" when entering water, the difference in density (how close atoms/molecules are together) affects the path of least time. Imagine you're knee deep in mud and there is a road a few feet away from you with a finish line at the end. You and a friend want to race to the finish line. Do you run straight to it through the mud or take a different path to get to the road where you can run full speed? Here is an excellent video [3blue1brown]( URL_0 ) For the untrusting: URL_0",
"Light travels at a constant speed in a vacuum only. In materials, it slows down. If it transitions from one material to another *at an angle*, it bends to a new angle based on that incident angle and the relative refractive indexes. The refractive index is how much slower light travels than a vacuum. By definition, vacuum is always exactly 1.0. Glass is as high as 1.5, light travels 2/3rds the speed in glass. Which is why you can make a lens, bending the light! Diamond is 2.4, thus it bends light in remarkable ways, which is why we value it. Air at 0C 1atm is 1.000293... only a SMALL amount of difference over a vacuum. At 25C 1atm, it drops to 1.000277. Also water vapor- dry, not cloud droplets- has a different refractive index (can't find it). These aren't very noticeable close up unless the air is VERY hot (gas stove burner), but hot air does create dramatic mirage effects across large distances.",
"Imagine light hitting a glass block at an angle. It refracts as it enters due to a change in speed due to a change in density. Like a lens. At different temperatures, you get different density air, so as light passes through, it refracts in a similar manner to above.",
"Great question! I am a aerospace engineer working on a field called Aero-Optics. We study essentially this phenomena. This occurs because as two glasses of different temperatures mix, the mixing becomes turbulent. The turbulent mixing causes density to fluctuate throughout the fluid. Fluctuating density manifests and fluctuating index of refraction. Index of refraction dictates the speed of light through the medium. You constantly have different small pockets of varying density that are changing in both time and space. This causes the waviness. This is ALSO what causes the “mirage” affect of a road on a hot day, or the “waviness” about a flame."
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7n2kq0 | If the ice caps melted, would the oceans be colder or warmer? | Other | explainlikeimfive | {
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"You can sort of think of it like a glass of ice water on a hot day. Ice water is 32°F (0°C) even when the ice is melting. However, once all of the ice melts, the heat is no longer just melting the ice it is instead heating up the water.",
"Not a scientist but I read somewhere that when the ice melts the additional water creates more overall surface area of water. That additional surface area is more water the sun can heat up.",
"The world in general would get warmer because of the reduction in the albedo effect. URL_0 ELI5 The ice caps reflect some of the light from the sun back out into space while water in the oceans absorb most of the sunlight that hits it. At a global scale reflecting sunlight means less heat, absorbing sunlight means more heat.",
"Warmer. If the ice caps melted, it would likely be caused by, or at least in tandem to, rising ocean and atmospheric temperatures, which means the ice caps are melting because the ocean is warmer, not the other way around."
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7n2kxs | How come you can have a good or bad sleep? | Biology | explainlikeimfive | {
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"Simplest answer: variance. Better answer: there are multiple factors involved. Light sources in the room or before you go to bed mess with melatonin production, which signals your body to sleep. If you wake up in certain parts of your REM cycle, you'll feel groggy instead of rested. Nightmares can make you tense during sleep, which makes some people less rested. Alcohol interferes with sleep quality. And I've heard that sleep you get before midnight is twice as restful as sleep you get after midnight. The effects of stimulants shouldn't be underestimated. The half-life of caffeine is about 6 hours. This means that if you have a cup of coffee at 2 or 3 in the afternoon and go to bed at 8 or 9, half the caffeine from your afternoon coffee is still in your system, interfering with your sleep. And the list goes on...",
"Imagine you are a phone with a rechargeable battery. You use energy throughout the day and every night you need to recharge your battery or else it will be dangerously low the next day or even dead. For some people, they have batteries that need only 5-6 hour charge but for the average adult an 8 hour charge will get you through the day. The tricky thing with charging your battery though is that the battery doesn’t charge right way when you plug it in. The charging cable has to be inserted for around an hour and a half and stay connected for a full charge. Sometimes you forget to put the charging cable in all the way. It starts to charge but then disconnects itself and you don’t get a full charge. Most nights the charging cable goes in all the way and the battery is able to reach a full capacity."
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7n2l7t | How does carbonation aid with an upset stomach? | Biology | explainlikeimfive | {
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"A lot of times nausea is caused by your stomach being very full, not necessarily just with food but also with air. If you have a bit of soda it can make it easier to burp and release some of the gas in there which puts pressure on the top of your stomach and nerves that make you feel uncomfortably full and nauseous. Release some of that air and there is less pressure and less nausea.",
"It doesn't. People say flat ginger ale helps with alleviating nausea symptoms. Ginger has been studied to have anti-nausea properties.",
"I'm pretty sure the relief people feel from drinking say sprite or ginger ale comes from being able to burp and release excess gas buildup alleviating a little bit of pressure in the persons stomach.",
"Carbonation stimulates the pyloric valve (the sphincter between the far end of the stomach and the small intestine), allowing it to open longer than it usually does. Carbonation allows you to empty the stomach more quickly in the proper direction. Other ingredients (ginger, for example) may be helpful, but plain carbonated water does the trick, too.",
"To everyone saying it doesn't help- that is a narrow view. One sip of diet soda can help with nausea I sometimes get in the mornings. Sometimes I also get very nauseous along with the urge to sneeze. When I sneeze, the nausea is instantly gone. I've never met anyone else with the same symptoms.",
"You may be thinking about soda water. Years ago people that had eaten too much or for whatever reason had an acidic stomach would go to the drug store soda jerk and get a soda water. Back in those days every drug store had a food bar where you could sit on a stool order a sandwich and a soda and eat it there. The high school aged kid that worked behind the counter was called a [\"Soda Jerk.\"]( URL_0 ) I'm old enough to remember when this was common. The soda water was carbonated but the carbonation is slightly acidic. The soda (think: baking soda) on the other hand is an alkali (opposite of acidic). A soda water had a duel function, it would make you burp and the soda would counteract the excess acid in your stomach. Today we can make soda water with a big tablet. The brand name is Alka-Seltzer.",
"Wait, so why does the “plop plop fizz fizz” shit work?",
"It works for me too, but I can't find any scientific reason. Maybe I just find soda comforting. One possibility is that your nausea can come from low blood sugar, which is fixed with soda. That said, even diet soda helps me eat when I normally can't",
"Haven't read every comment, so sorry if this has already been said, but another benefit of soda with an upset stomach is the folic acid. Drinks like Coca-Cola have so much sugar in them that your body should naturally reject it like poison. Folic acid is a chemical agent in drinks like these because it keeps you from throwing up. Offsets all of the sugar."
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7n2nz3 | What is mental hygiene and how to perform it? | Other | explainlikeimfive | {
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"Mental hygiene is not a term of art as far as I know. Therefore performance of mental hygiene depends on your definition. I tend to think of it as training your mind to serve your highest good. What habits of mind increase or decrease your well being? For me, mental hygiene is remembering to practice gratitude and compassion. I'm sure the internet will give you lots of other ideas about how mental hygiene can be defined, and how to perform it in your daily life.",
"It is the erroneous belief that performing mental gymnastics, like solving puzzles, can somehow impact your greater cognitive function. Studies have shown that these activities only make you better at those activities. So, to answer the second part of your question, you don't."
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7n33qt | Why are bridges more likely to freeze than a normal patch of the road? | Physics | explainlikeimfive | {
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"Because there is cold air both under and over the bridge and it cools down faster than the regular pavement where the ground is still warmer than the air. So in essence, the highway doesn't freeze as quickly because it is being kept warmer from below. Edit: for those that are saying that it is because the ground insulates the pavement, that is not correct. The ground transfers heat to the pavement by conduction.",
"Because the cold air flow under the bridge causes the temperature to lower faster as opposed to the road that has only earth underneath",
"Bridges are suspended above the ground. The ground holds some warmth. The air around the bridge will get much colder than the ground the road is on.",
"The pavement on the ground is insulated, earth and soil make pretty good insulators. Bridges and overpasses are surrounded by air, which isn't such a good insulator allowing those parts of the road to become colder, and more prone to icing up.",
"A \"normal\" patch of road does not get affected by severe weather like a bridge due to the insulating effect of the ground. A bridge is exposed to the elements (i.e. cold air) on all sides and all angles because it is suspended in the air. A patch of road is only exposed to the elements from its surface."
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7n378j | What is reactive power in electricity? | Physics | explainlikeimfive | {
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"Computer engineer here. Apparent power = reactive power + resistive (or work) power. Since power is a bit of a tricky concept for laymen to understand I'll use the term energy instead. They are not the same thing; power is the time rate of change of energy and energy is power integrated over time. In electrical applications, resistive energy is any use of energy that increases entropy. Energy that is used to light up a light bulb is resistive energy; energy that is used to generate heat is resistive energy; energy that is used to turn a motor shaft (once it is energised) is resistive energy. Reactive energy on the other hand is energy that is stored in an electrical or magnetic field. Capacitors store energy by creating a charge disparity between two metal plates. An applied electric force pushes electrons onto one plate, and the coulomb force (electrons repel one another) from those electrons pushes electrons off of the other plate. This occurs until the coulomb force from the electrons (or lack thereof) is sufficient to oppose the electric force pushing them on. When the external electrical force is removed, the opposing electrical force remains; the energy stored in the capacitor can then be released. Inductors are more difficult to understand, but they store energy in a magnetic field by capturing changes in current. The more rapidly current changes, the more energy is stored in the inductor. The closest mechanical analogue that I can think of is a flywheel but even that's not entirely accurate. Just like capacitors, energy stored in inductors is still electrical in nature."
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7n3800 | Why do you have to eject a thumb drive before removing it from your computer? How does not ejecting damage your computer? | Technology | explainlikeimfive | {
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"Imagine someone is writing on a piece of paper. By asking the computer to remove the drive you are letting that person finish their sentence and the writing makes sense to the next person reading it. By yanking out the drive without telling the computer, you are ripping the paper from that person whilst they’re trying to complete their sentence and you’ll end up with missing words.",
"It can't damage your computer, but it can damage the file system on the thumb drive. When you eject, it closes any open files and finishes writing any data before saying it is safe to remove.",
"To improve system speed and drive performance operating systems typically buffer at least some of the writes to a drive. For example if an application wrote 1 character at a time and that was replicated by the OS into changing 1 byte at a time on the harddrive it would be exceptionally slow and downright damaging to SSDs. Since there is a buffer of some data (both file data and the various meta data that says where files are and what their properties are) you need to be sure that it has all be written to the drive before it is ejected.",
"It doesn't damage the computer, but it can damage the data. Thumb drives don't read/write instantly. If you've written a large chunk of data to the drive, and then a little later you want to remove it, the computer could still be in the process of actually writing the data to the drive. Ripping it out in the middle of that could leave your drive in a funny state, with parts of files written. Ejecting is just warning the computer, and giving it a chance to tell you \"hold up a sec, I'm not done with it.\" USB drives are much faster than they used to, and if you haven't written anything or used the drive in the last few minutes, chances are it's safe to just rip out. The computer may whine about it but most likely it wasn't actually writing anything still.",
"It doesn't damage the computer, but it can damage files on the external/thumb drive. Basically, the operating system may delay writing to the drive because it's busy with higher priority tasks. By telling the OS you want to remove the drive, it will finish the write and then let you know it's now safe to remove the drive."
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7n3hab | What causes light to travel at different speeds through different mediums? | Physics | explainlikeimfive | {
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"There are several different models that describe how this happens. I'll try to give one that I think is relatively intuitive. Light is made of particles that act as waves. These are wiggles of the electromagnetic field. The atoms/molecules of a substance also wiggle around in the substance due to their energy and the forces between the molecules. This is called 'lattice energy'. It can also be described using waves. When the waves from the light wiggling are added together with the waves of the lattice energy wiggling, you get a whole new wave. This is sometimes described as a new particle that's a combination of lattice energy and a photon, which is called a 'polariton'. Massless particles always move at the speed of light, but a polariton has mass, so it must move slower. This speed is dictated by exactly how all the waves add up, which is dictated primarily by the structure of the substance and how the molecules in it interact with each other. What's good about this model is that the polariton is what goes slow, since we aren't regarding the light as a photon anymore, we can still say (at least in some sense) that it always travels at the speed of light. Contrary to some popular posts that show up in this sub, the slowing of light in a material is not caused by it bouncing around in the material or being absorbed and re-emitted."
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7n3o0l | Why is HF so dangerous when it's a fairly weak acid? | From my chemistry knowledge HF is weaker than HCl yet it is common to find bench grade HCl, why isn't it the same with HF? | Chemistry | explainlikeimfive | {
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"It reacts with damned near everything and seems to especially like breaking down organic compounds. It reacts with metals creating all sorts of halite salts which are also toxic.",
"We often used high concentration HF acid to etch and structure glass (quartz/borofloat/pyrex) in the cleanroom I used to work. From a chemical perspective HF is incredibly dangerous because it easily penetrates your skin and starts interfering with some of your biological processes. Among other things it binds to calcium ions in your blood, which hinders cell metabolism and may cause cardiac arrest (rule of thumb was that a 10x10 cm exposure area was potentially fatal). I also seem to recall being told it may react with the calcium in your bones and make your bones brittle beyond repair around the exposure area, but I am not sure and fortunately we had no accidents during the time I worked there.",
"\"Strong acid\" and \"weak acid\" are technical terms that denote aspects of how the acids dissolve in water. Weak acids can be dangerous at high concentrations. Just look in your kitchen. Household vinegar is about a 5% concentration of acetic acid, lemon juice is about 5% citric acid. These are perfectly safe concentrations - you can even eat them. Kick those concentrations up to 90% and you need fume hoods and rubber gloves to safely work with them.",
"In terms of physical chemistry, hydrofluoric acid is a pretty weak acid. This is because, unlike hydrochloric acid, most of the HF does not dissociate into a fluoride ion and a hydronium ion, the latter of which is responsible for the reactivity of most acids. Hydrogen Fluoride whether in gas or in a solution, however, is **extremely poisonous.** This is for two reasons. The first is that Hydrogen Fluoride is soluble in oils as well as water, and being a small molecule it can easily pass through the skin into the blood stream, and into tissues. More importantly, it easily complexes calcium ions, rendering them unusable by the body. Calcium is used by body systems in a huge number of ways especially as a signalling ion. Your body depends on calcium levels being very tightly controlled. Exposure to HF causes tissue necrosis, hypotension, breathing difficulty, paralysis, and cardiac arrest. Worse, one of the first symptoms can be numbness in the effected area so your may not notice that your skin is peeling off. The reactivity of hydrofluoric acid is not due to it's acidity, but rather, due to it having a higher electron affinity than oxygen. So it can steal electrons from oxygen, thereby replacing the oxygen in normally highly stable/inert substances like silicon dioxide, and rendering them much more soluble."
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7n4ba3 | What causes that "sick person" smell? | Biology | explainlikeimfive | {
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"Bacteria waste as they replicate, consume, and (essentially) defecate. Don’t think about it",
"Phlem, bile, the urea in sweat - all tend to build up depending on the condition. People with severe health problems have trouble with basic hygiene so they have more B.O. than a healthy person. As GlossyProse pointed out - if you have an infection, bacteria are using your body as both food and a latrine. Some conditions have unique odors caused by symptoms of the disease.",
"When I had lymphoma, my mom always told me I had a certain ‘sickly’ smell. I was still showering and cleaning and not vomiting on myself. She just said I smelled sick (this was before diagnosis). Then years later when she got cancer, I knew exactly what she meant. So I’m fascinated with this answer bc I do believe there is such thing as a sick person smell.",
"My Grandma had a stroke but lived about 5 months afterwards, albeit bedridden. I visited her daily to check on her but also to give my mother a break from sitting with her mother in law up to 15-16 hours a day. Grandpa was almost 90 so he was no help really and Dad was still working. The day that she died she looked the same as the days and weeks before but there was a weird smell in the room. I cant really describe it other than to say it was sweet, but not a good sweet smell (?). Mom called me aside and said that she didn't expect Grandma to make it much longer. I didn't ask why... but she was right, at about 4 that afternoon she passed away. A few years later she mentioned that she had been in the room with 2 relatives when they died, her aunt and my grandma. She said that she knew when they were near death because of that smell. (Ill also add my mom is a saint for taking care of her MIL in her last days like she did. She cared for her just like it was her own mother) TL;DR-Sick people have a weird sick smell but people close to death have an even weirder smell."
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7n4d9y | How can forensics tie a bullet to a specific firearm? | Can forensics tie a bullet to a specific gun? like a 9mm bullet from glock 19 #1234. Can forensic science actually do that or is it hollywood bs? | Technology | explainlikeimfive | {
"a_id": [
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"It's Hollywood BS. A comparison to a ballistic forensics database has never yielded a positive match (Maryland has maintained one for years and gotten no tangible benefit from it). A US National Research Council Study concluded (from [wikipedia]( URL_0 ): > The United States National Research Council released a report in 2008 that endorsed the investigation of microstamping as an alternative to ballistic markings. **It had concluded that a national database of ballistic markings is unworkable and that there is not enough scientific evidence that, \"every gun leaves microscopic marks on bullets and cartridge cases that are unique to that weapon and remain the same over repeated firings\".** It described microstamping as a \"promising method\" that could \"attain the same basic goal as the proposed database\".[14] Microstamping is the laser etching of unique identifiers onto the firing pin, and it has independent problems of its own; namely that firing pins are a bit like tires, they're an easily changed consumable on most firearms like tire is a consumable on cars -- it's like requiring laser etching on tires so you can more easily identify what car was used in a crime.",
"Actually can. Each firing pin has a distinct strike on a casing like a thumb print. Barrel rifling also varies so finding a bullet and casing basically tells you exactly which gun fired the bullet",
"Real-world forensics cannot. Even if the chamber of a gun is rifled, the machine-produced rifling will be uniform across that make and model of firearm. This means the absolute closest you could actually get even in the best case is that you know **a**, say, Glock 19 shot the bullet. But it could be #1234 or #3456 or #Cookie. And you wouldn't be able to determine which of those it was. But most guns, especially non-rifled firearms, don't leave such marks. So it could be a Glock or a Remington or a Smith and Wesson.",
"If you're saying that you can take a bullet, examine it and tell you which handgun in the nation fired that bullet, that's Hollywood BS. However, if you have a bullet and a suspected gun it was fired from, you can say with a certain amount of certainty that this was or was not a bullet fired from that gun. It's never, \"I'm 100% certain this bullet was fired from this gun.\" It's more like a partial fingerprint where you can use statistical analysis to determine the likelihood that a bullet was fired from a given gun. This certainty can be increased if the gun barrel has any unique flaws or marking patterns on the bullet that make a false match less likely."
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7n4hhg | Despite its very large population, entrepreneurial culture and rapidly developing economy, why are so few inventions/innovations coming out of China? | Economics | explainlikeimfive | {
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"text": [
"It’s pure economics. I’m a national economist so here is my take. This is still up for discussion. China is focused mostly on production. Where many western nations are focused on R & D. This is why, when you look on clothes or even your phone, it’ll usually say ‘produced in (Taiwan, India or China)’. Besides this. Many innovations are actually made in China, however since their population and internal market is so large, they usually go to self production purposes. The innovations are simply not competitive on the international market. Would you buy a phone, completely designed and produced in China? No, I thought not. As stated prior they can supply their own demand. Imagine a little country like Denmark, we can’t self supply, since we can’t produce a vast amount of different demanded material to supply our own demand. We haven’t got a large enough labor force compared to the amount of different products demanded. Now see China, they have an almost equal amount of products demanded however their population is 200 times bigger. The same goes for the US and EU on a general basis. So China is simply not specialized for international innovations."
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7n4mvt | Why do men cradle their balls when they are doing nothing but sitting around on the couch or trying to go to sleep? [NSFW] | Biology | explainlikeimfive | {
"a_id": [
"dryzzl0"
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"text": [
"Im a girl and I tuck my hands in my thigh/ crotch when I'm trying to sleep or just lying around. Its warm. Thats it"
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7n4nn8 | How is the Criterion Collection able to restore movies that are 50 plus years old to Blu Ray quality? | Technology | explainlikeimfive | {
"a_id": [
"drz07pu",
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"text": [
"35mm film still has more detail contained on it than any digital camera can capture. It captures far more texture and nuance, this is why some directors (Tarantino being a popular example) still use \"real\" film. This is comparable to the old records vs. digital format debate in audio recordings. Celluloid film does have a tendency to break down and degrade over time, but it can be \"remastered\" and digitized, often to considerably better quality than it would have been originally (as seen through an analogue projector). For example, I was watching reruns of the original Star Trek run on the BBC yesterday. These episodes never looked better! Not just the remastered \"cgi,\" but every shot was crisper, cleaner, and better colored than I remember them being originally. Edit: 32-35mm (I was a projectionist for Pete's sake, I should know this!)",
"Boils down to: How many megapixels does film have? Infinitely many! It’s because the image isn’t divided up into tiny squares (the pixels) and is perfectly smooth. Film is far more detailed than digital as it’s analogue so it’s a good source for making better and better versions."
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7n4p2m | If water activity is the driving force for microbial growth in food, how can broths have such a long shelf life? | Biology | explainlikeimfive | {
"a_id": [
"drz0xhi",
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"text": [
"Because they are boiled (to kill bacteria) then sealed. No new oxygen, and very very few microbes to start.",
"They do not. Once opened, a broth has a very short shelf life unless refrigerated or frozen. As with all canned goods, broths in a cans or jars are sterilized after closure, so no living microbes are present."
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7n4snj | How is yeast harvested? | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"Yeast is fairly easy to culture/cultivate, all you need to do is feed it sugars and a few key nutrients and minerals such as phosphate. Apparently it's common to use molasses as a food source for the yeast. Interestingly, yeast is considered a facultative anaerobe and it actually grows and multiplies best in the presence of oxygen, by carrying out aerobic respiration. It only switches to alcoholic fermentation if oxygen runs out, in such conditions it grows very slowly. However yeast has a much higher tolerance for alcohol than most organisms. The yeast is taken from a small starter culture that's maintained in a lab under strict sterile conditions. The starter sample may be only a few grams. It's tested for quality, genentic purity, and the presence of other microorganisms. It's transferred to a semi-seed step carried out in a sterilized vat of several hundred liters. The seed culture and a few dozen liters of a dilute nutrient solution are added. Oxygen is slowly bubbled through the solution to keep the yeast from producing alcohol which slows it's growth. Every few hours more nutrient solution is added, and the yeast multiplies rapidly. This takes around a week. The yeast multiplies from a few grams to several kilograms. The semi-seed culture is then divided and transferred to large batch or \"trade\" culture tanks of hundreds of thousands or millions of liters. This may be done at a separate facility. The culture process is basically the same, but it's not practical to use perfectly sterile conditions at this point. Nutrient solution is added periodically, and air is bubbled through. The yeast grows from a kilogram or so, to dozens of tons. The last step is to centrifugally filter the yeast from the tank solution, creating a thick yeast concentrate. This may be dried under controlled conditions, frozen, or bottled in liquid form."
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7n5nhx | How does gravity keep us on earth? | Physics | explainlikeimfive | {
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"text": [
"The question is rather, why does gravity keep anything on anything (because the law of gravity applies to every mass object in the universe). Nobody 'really' knows what gravity is. Just that when something has mass, it has gravity. The bigger the mass, the bigger the gravity (e.g. the sun has a lot more mass than Earth, so the sun has bigger gravity). On the moon, which has a lot less mass, the gravity is not as strong. A black hole, which is really just a really **really** massive the star, the gravity is so strong that not even light can escape it (which is why we perceive it as a 'black hole'). Some think gravity is an effect of mass distorting space-time. Where there is a mass large enough, space bends around the mass, resulting in gravity. Some think it has to do with energy, if something has a lot of energy, it attracts stuff. And some even believe that there are these particles called 'gravitons', which get emitted by an object of mass and pulls stuff towards them. All just theories though (Einstein has a pretty cool one). Figuring out how gravity works (and if we can simulate it), will be the biggest achievement humanity can dream of, and it would launch us into a new type of civilisation.",
"Gravity is a force that acts and attracts between every object in the universe with mass. On a small scale it makes very little difference but on a large scale, like planets, they attract with a lot of force. So earth attracts humans with a large force so keeping us on the surface."
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7n5nq2 | How does radar work? And why can you only pick up objects on radar if they are above a certain latitude? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Radar is just just radio waves that get sent out, bounce of an object, and return to the receiver. Radar can detect objects at any altitude as long as there's nothing in the way. So for example, radar can't detect something on the opposite side of a mountain, and can have trouble picking up planes at very low altitudes because of ground clutter (trees and hills and such that get in the way or create noise that hides the plane) but radar can be on the ground or the sea looking up or in the air or space looking down.",
"As a former 14E (PATRIOT radar and fire control) soldier: * Yes, as long as there is nothing between the object in the air and the emitter, it can see the object. This includes rain clouds. * You can't see below your wavelenght - the distance over which the wave's shape repeats. Most air traffic control radars are 1–2 GHz 15–30 cm wavelength. * The return (the radiation sent back to the emitter) suffers from the inverse square law: energy sent out is inversely proportional to the square of the distance . When the energy bounces off the object/target in the sky it is received inversely proportional to the square of the distance. Air search/fire control radars require a lot of power. * The radar \"gun\" used by police has a narrow beam and since the distances are smaller it can be made less complex than an air radar but they use the same frequencies as many air search radars."
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7n5y25 | How can we discern between light arriving at Earth that has been redshifted and light that simply is just that wavelength? | Physics | explainlikeimfive | {
"a_id": [
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"By looking at the wavelength of the light. The emission spectrum of stars have peaks that correspond to the elements in their photosphere, and we know what those emission line wavelengths [should be]( URL_0 ).",
"Certain elements always give off (or always absorb) light of specific wavelengths, so we know to expect particular patterns of light coming from a star at very specific wavelengths.",
"[Look at this image.]( URL_0 ) You know immediately that it’s a photo of a rainbow and that someone must have inverted the hues because rainbows are always the same colours—the properties of water and light make it so. It’s like that with stars. The properties of stuff that makes them up and the laws of physics dictate that they look a certain way. We found [Fraunhofer lines]( URL_1 ) in the light from the Sun. Then we found similar lines in other stars. They had the same relative spacing but were shifted a little compared to the Sun’s. The simplest explanation is that they are made of the same stuff as the Sun but moving toward or away from us."
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7n6cld | How does an audio equalizer actually WORK? (Not how do I use one) | I already know how to use an equalizer either on a mixing console, or a parametric EQ in a DAW. But from an engineering perspective, how does an EQ actually work? If I wanted to build one, what's the general concepts I would have to know in order to build one? How does an equalizer actually differentiate the frequency ranges, and then boost the tones within those ranges? Since it is all one single audio stream, how does it differentiate/modify the ranges within the same stream? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"It is all just [filtering]( URL_0 . By careful selection and placement of time-based elements in your circuit like capacities and inductors, you can filter out frequencies. In essence you can think that a capacitor takes a certain amount of time to charge. When fully charged, the capacitor acts as an open circuit and does not let any more current flow. Frequencies that are too fast will not let the capacitor charge/discharge between cycles, giving you what’s called a low-pass filter (it only lets low frequencies through). In general you can create most types of filters in circuits, but modern equalizers will do it with dedicated chips or even in software. The mathematics behind filtering is Fourier analysis, and most Fourier transforms have a circuit equivalent."
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7n6fk9 | Why do our public universities spend enormous sums of money on football/basketball coaches? Why do they need athletic teams at all? Universities should focus on education. | Other | explainlikeimfive | {
"a_id": [
"drzexl0"
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"text": [
"Money. People watch sports, which earns them more money. Money they can then put into education."
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7n6h5l | How does fermentation of food manage to attract the "good" bacteria? | So today, I took my first step into the world of fermentation and I got some sauerkraut going. It got me thinking; what attracts the good bacteria to the cabbage, opposed to attracting harmful bacteria? Generally, leaving food out at room temperature for extended periods of time isn't a good thing in regards to food safety, but why is it okay with fermentation? | Biology | explainlikeimfive | {
"a_id": [
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"It's more like it doesn't provide living conditions for bacteria that's bad for you. Typically you will find lactobacillus in sauerkraut the same type of bacteria in making yogurt, kefir, and kimchi. That doesn't mean you're not going to eat other bacteria with it. Most of the bad bacteria is dealt with by the process - proper cleaning of the product, salt (which deteriorates cell walls), and acid production (from the fermentation itself). Improper creation of any of these can create better living conditions for bad bacteria.",
"When you make saurkraut you start by pouring salt water over everything, right? The lacto bacteria can live in a high-salt environment. The bacteria that make food spoil, can't. Same with other lacto-fermented vegetables, like pickles, kimchee, etc, they start with salt water."
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7n6j4g | Why do bodies feel heavier when limp? | Biology | explainlikeimfive | {
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"A conscious person who is being carried won't want to be dropped. They can help position themselves in a way that keeps their center of gravity in line with that of the person carrying them.",
"Ahoy, matey! Yer not alone in askin', and kind strangers have explained: 1. [ELI5: Why is dead weight (unconscious person) so heavy when the person's weight doesn't change? ]( URL_5 ) ^(_ > 100 comments_) 1. [Why do you get heavier when you go \"limp\"? ]( URL_4 ) ^(_2 comments_) 1. [ELI5: How exactly does dead weight feel heavier then an actually weight? ]( URL_0 ) ^(_4 comments_) 1. [ELI5: Why do you feel heavier when you let your body go slack (deadweight)? ]( URL_1 ) ^(_4 comments_) 1. [ELI5: Why do people feel heavier when asleep compared to when awake? ]( URL_3 ) ^(_4 comments_) 1. [ELI5: Why are unconscious bodies so much 'heavier' than conscious ones? ]( URL_2 ) ^(_11 comments_)"
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7n6odw | What is falsetto, and how is it different from normal singing? | Are their specifics on when high-pitched singing becomes falsetto? | Biology | explainlikeimfive | {
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"text": [
"Your normal voice is modal. It's \"the optimal combination of airflow and glottal tension that yields maximum vibration.\" It's basically the way you hold your vocal cords to give yourself the maximum vibration. Falsetto is when you vibrate \"the ligamentous edges of the vocal cords, in whole or in part.\" This create a higher pitched sound. So the normal voice uses the mucus membrane part of your vocal cords to produce sound. Mucus membrane is the kind of tissue you feel on the inside of your gums. It's different from ligamentous tissue, which is the tough fibrous elastic tissue that connects bones and cartilage inside your body. So if you are using your normal, comfortable voice, it's going to be modal since that's the optimal balance point for making a vibration. If you purposefully try to speak in a high pitched voice and end up using the ligamentous part of your vocal cords, it's falsetto. [This video has a lot of great examples of someone using his modal and falsetto voices.]( URL_0 ) You can really tell the difference between the way they sound.",
"Yo ho ho! Yer not alone in askin', and kind strangers have explained: 1. [ELI5: Falsetto ]( URL_0 ) ^(_1 comment_) 1. [ELI5: Why can we have falsetto, and how do they work? ]( URL_3 ) ^(_2 comments_) 1. [ELI5:What's the difference between a guy singing falsetto and a man with a high vocal range? ]( URL_4 ) ^(_2 comments_) 1. [ELI5 falsetto. ]( URL_6 ) ^(_._) 1. [ELI5: What's happening when our voices go into falsetto? ]( URL_1 ) ^(_2 comments_) 1. [How can you tell the difference between falsetto and a wide singing range? ]( URL_2 ) ^(_1 comment_) 1. [ELI5: When singing, what is the difference in how your \"head voice\" and \"chest voice\" are produced? ]( URL_5 ) ^(_3 comments_) 1. [ELI5: How come you have that break in your voice that separates falsetto and normal voice? ]( URL_7 ) ^(_13 comments_)",
"So there have been a few very good technical explanations in this thread but they don't really ELI5. So here goes. When you normally sing in your natural range it's the comfortable singing you can do from your chest (or throat if you're a screamer) and generally produce volume with. Falsetto is when you get to the point where you can't sing higher comfortably anymore as it feels you're straining your voice and end up pitching flat, so you sing more out of your mouth. It kind of feels like changing gears. You can then sing a few notes higher, but you do lose volume (and unless you've trained yourself properly, you can also lose some vocal control). Your voice sounds more thin and airy when you sing falsetto. Of course, certain people, like operatic singers, are specifically trained to be able to sing in falsetto and have it sound almost indistinguishable from their normal range Source: am a natural baritone and all pop music by men is written as if it's meant to be sung by castrati. Also, have an opera singer for a sister"
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"https://www.reddit.com/r/explainlikeimfive/comments/55s42a/eli5_whats_happening_when_our_voices_go_into/",
"https://www.reddit.com/r/NoStupidQuestions/comments/7i42fm/how_can_you_tell_the_difference_between_falsetto/",
"https://www.reddit.com/r/explainlikeimfive/comments/48hjm6/eli5_why_can_we_have_falsetto_and_how_do_they_work/",
"https://www.reddit.com/r/explainlikeimfive/comments/7k316g/eli5whats_the_difference_between_a_guy_singing/",
"https://www.reddit.com/r/explainlikeimfive/comments/5nreiy/eli5_when_singing_what_is_the_difference_in_how/",
"https://www.reddit.com/r/explainlikeimfive/comments/1o1dqe/eli5_falsetto/",
"https://www.reddit.com/r/explainlikeimfive/comments/7iso0a/eli5_how_come_you_have_that_break_in_your_voice/"
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7n6ydq | Why drug dealers would agree to be on those VICE shows | Other | explainlikeimfive | {
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"Journalistic integrity has existed throughout the centuries, protecting sources to get to the truth. Vice is offering anonymity to get the story. Ego is what likely keeps the dealers willing to tell their story in disguise just to be on television. I imagine it appeals to the rush of the drug dealer lifestyle some people who thrive in that community come to expect and enjoy on some level."
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7n782d | How is Planet Earth the series filmed? | Other | explainlikeimfive | {
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"over a very long time. They have behind the scenes on the blurays! Almost more interesting than the actual series.",
"It’s a number game ultimately. Hundreds of camera crews working round the clock to get the smallest details. They recoup costs by selling the footage they don’t use, or creating secondary series’ (like blue planet for example). They also provide the majority of amazing shark footage for discovery channel’s shark week."
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7n7g8i | How does rabies induce hydrophobia? | Biology | explainlikeimfive | {
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"Rabies causes extremely painful muscle spasms in the neck and chest when swallowing. So every time they take a drink or even swallow their own saliva it is extremely painful. In later stages of the disease even the thought or sight of water can cause the muscle spasms. So there is an aversion to the stimulus that causes the pain (water) and they become hydrophobic. Edit. Spelling",
"In rabies act of swallowing causes sudden and extremely painful spasms of diaphragm and other respiratory muscles. Pathological muscle spasms are corelated with damage to nucleus ambiguus (nuclei of nervus vagus) done by rabies virus. View or sound of water cause fear of that pain. That fear can itself induce spasms or even epileptic attack. Besides of hydrophobia pathognomonic (that is proper exclusively) to rabies is aerophobia- the same symptoms may be caused by flow of air on ill person's face. It isn't caused by increased salivation. Both symptoms have the common cause- damage to nucleus ambiguus.",
"Thank god for *Michael Scott's Dunder Mifflin Scranton Meredith Palmer Memorial Celebrity Rabies Awareness Pro-Am Fun Run Race For The Cure*",
"Michael Scott’s Dunder Mifflin Scranton Meredith Palmer Memorial Celebrity Rabies Awareness Pro-Am Fun Run Race for the Cure",
"I always thought micheal was speaking nonsense when he said that during the run when jan offered him water"
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7n8l3h | Why are there areas of turbulence in a flight and other areas without, even if it is at an altitude above the clouds? | Physics | explainlikeimfive | {
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"turbulence usually occurs to differences in air temperature, which causes differences in air density. the abrupt changes then cause abrupt changes in airspeed and therefore altitude. it's like running through water, then syrup, then air, then water again.",
"Turbulence is essentially rapid changes in the motion of air around a plane. Close to the ground it can be caused by the air being slowed down by friction, or being diverted around buildings or mountains. Under clouds it's usually because of hot air rising and cold air sinking next to each other, so a plane goes quickly from going up to going down. At high altitude you can get \"clear air turbulence\", which is dangerous because it's hard to detect and predict. Sometimes you find it at the edge of jet streams, where very fast-moving air meets relatively slow moving air. When a plane moves from fast air into slow air, the air moving over the wings slows down, so the wings produce less lift. That's when you get the horrible dropping feeling!"
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7n9glm | what's the difference between controlling the volume on the PC and controlling the volume on its speakers? | Is there a difference if I have the volume set at 1 on the audio source (PC) and at 100 on the audio output device (in this case, the speakers), and vice versa? | Technology | explainlikeimfive | {
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"The difference is the signal to noise ratio you end up with. Keeping the PC volume low and then cranking up the speaker is like recording someone speaking softly outside and then amplifying it: all the background noise gets amplified too. Keeping the PC volume high and turning down the speaker is like recording someone speaking loudly, and playing it back quieter: their voice was loud compared to the background, so it sounds better. You can't straight up max out the PC output because it's designed to be able to power headphones and small speakers on its own, so it can be turned up \"too high\" and cause distortion. You want to turn it up as high as you can without getting distortion on loud sounds, and then adjust your speakers to taste. This sort of volume control is really important in areas like... oh, electric guitars, where the sound is overdriven, and distortion is often desired. Loud amp, quiet guitar vs loud guitar, quiet amp makes very different sounds."
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7n9m6f | Why does America send so much aid around the world when it’s own people have a massive homelessness, drug, healthcare, infrastructure problem? | Economics | explainlikeimfive | {
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"Foreign Aid is to a large part a geopolitical tool. It also has a humanitarian aspect, but mostly it is political. This is not only about America (USA), but an answer in general. You are making sure countries are pro-you and stabilised (edit: regarding the *government*), people from there do not move (for example as refugees to \"you\"), countries are influenced culturally as you want, you ensure economic access, ensure the geopolitical grasp in that area (which explains when the aid is taking the form of military items or money for military). All those things are \"pro you\", but you also want them to be \"contra other geopolitical and local players\". Furthermore, a lot of that money goes back into your own companies. Especially regarding infrastructure (and military) projects which are usually done by large companies - and those are not from the place you're giving the money to.",
"We send less than 1% of our budget out in aid around the world. Such an amount would not begin to address the issues we have domestically that you name, but it does generate goodwill with other nations while doing a not more to help that nation than it will do here so it is considered a good thing.",
"So first, America doesn't actually send a bunch of aid around the world. We spend about 1% of our federal budget on foreign aid. For America, that's almost a rounding error. Second, it engenders good will in other nations and is just the right thing to do. If you have that much wealth that you can afford it, it's the right thing to contribute and get other countries to like you. Lastly, and probably most importantly, it's a national security priority. People turn to things like drugs, crime, revolution, and even terrorism when they are poor and feel like they have no other alternatives. So, every dollar America sends to other countries helps to stabilize those countries. By fighting poverty, disease, and starvation overseas, we help stop people from feeling desperate enough to turn to violence and harm America and her allies.",
"1. It doesn't. The amount of foreign aid the US gives is not impressive. It's around 1% of the country's GDP, below the UN's guideline and less in absolute amounts than some other, smaller countries. (Last I checked some years ago, Japan gave more aid than the US did, despite having smaller population and economy) And of the aid America *does* give, a huge chunk goes to comparatively wealthy countries like Israel, which isn't really humanitarian aid at all. 2. It's not one or the other. If this aid wasn't sent out, I can guarantee you that it wouldn't be spent fixing America's health care or homelessness problems. And likewise, if there was any political will towards solving these problems they could be solved without cannibalizing foreign aid. It's not like America has a fixed budget for humanitarian purposes. The budget for foreign aid is very much separate from that for domestic health care or infrastructure. 3. the money quite simply goes farther when you help developing countries. For not a lot of money, you can feed *a lot* of people in countries with famine. Helping Americans is comparatively more expensive. 4. it is something of an investment as well as aid. If other countries are more stable and prosperous, they can buy more American goods, for example. And with luck, they might even be grateful and become an ally of America's. And, of course, stable countries aren't a threat to world security. Imagine, for example, if a saner, more humanitarian policy towards Korea back in the day, could have prevented North Korea from becoming the problem that it is today. (Of course we don't know what would have happened then but broadly speaking, helping other countries become more stable, safe and prosperous *often* means they won't end up run by maniacal dictators)",
"Your first assumption is that money will solve the homeless, drug, or any problem. That has not been proven and there is a mountain of evidence to the contrary. Your second assumption is that 'lesser' problems shouldn't be addressed until 'greater' problems are fully solved. By this logic, police shouldn't investigate theft until all rapes and murders are solved.",
"The aid we send isn’t nearly significant enough to tackle any of those issues. But aid gets brought up because it sounds wasteful (yer helpin’ other countries that are full of foreigners), and it’s far easier for politicians to attack foreign aid and pander to xenophobic bases than it is to scrutinize defense spending.",
"I think that foreign aid is basically bribes and payoffs to get foreign leaders to do what we want them to do, or to help governments that we like stay in power. Governments are not benevolent. They do what they think is in their own best interest, and they don't just hand out money because they are nice.",
"I'll probably get downvoted again about this, but anyone you see that is actually homeless (as in sleeping in the streets) is in one of three groups. 1) Mentally ill and refusing/unable to accept treatment. 2) Substance abuser refusing treatment. 3) There by lifestyle choice. Crusty punk, bohemian, transient, etc. I work for a non-profit and we have very well-funded resources to help this population, they just refuse to participate for one reason or another. Living in a neighborhood impacted by \"homeless dumping\" really opened my eyes to this issue. As others said, throwing money at the problem won't change anything. The only solution for the addicts at least is harm-reduction programs that will give them access to their drugs in exchange for living in a halfway-house. This is a political tough sell in America at the moment. Re: Healthcare and infrastructure, we have the best in the world if you can afford it. This is the unfortunate side-effect of capitalist societies.",
"Homelessness isn't as big of a problem as you think. It's currently solvable with the resources we have now in a lot of areas - a big part of homelessness is mental health and addiction. Aside from that, we have a drug, healthcare and infrastructure problem mostly due to one political party refusing to modernize. Our healthcare is expensive because one party is lobbied to keep it expensive - it earns private companies billions. Our drug problem is because we're conditioning addicts to be criminals and not helping them. It makes money. Also, opioids are vastly over prescribed. Infrastructure spending isn't done because we run out of money to do so by giving corporations kick backs. There is no push and the few pushes are done with kickbacks for corporations, not to improve things. Basically, half of America wants to look to the future, the other half wants to keep things as close to the 1950s as possible. Foreign aid isn't a lot of money and a good chunk of it comes back to us in one way or another. We don't want nations to destabilize in the era of the nuclear bomb.",
"It's a quandary that we believe that our own people should pull themselves up by their own bootstraps but don't have that same feeling for people in other countries. The Marshall Plan, one of the first large-scale foreign aid efforts ($140 billion adjusted for inflation) by the US was done to keep countries from falling to the Communist ideology after WWII. The idea that throwing money at people so they don't become our enemies have had mixed results, at best.",
"Mostly so that country will keep buying more American wheat, corn, aircraft, pharmaceuticals, heavy machinery, industrial products, banking services, telecommunications services, energy services. America's problems with chronic underemployment and trade deficits would be far worse if we didn't in a sense pay these countries to keep doing business with us.",
"Even poor countries that receive aid send aid (or try to) in order to bolster their perceived stature. With the US in particular, there's an idea that if we weren't involved in other countries' affairs it would leave a vacuum for another superpower to do so. One theory of international relations is that the world is most stable when there is only one supreme superpower. They believe the world was more stable when the United Kingdom was that superpower and when it meddled in other countries' affairs, a period they call Pax Brittanica. Essentially the superpower balances power in all other countries, not allowing any other country to gain too much influence or any to grow too weak, which would allow another country besides the superpower to exert influence over it. The US sort of filled that role, particularly the second World War and following, but it's very ambiguous now what the US's role is or should be."
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7n9ogj | How is "realistic" water rendered so smoothly in realtime | I'm talking mostly about videogames, but the question applies beyond them. It seems like rendering water and fluid physics in realtime would be a very intensive task, especially when it must interact with other objects seamlessly. At the very least, there are an enormous amount of polygons in play. How is it rendered so smoothly and in such high fidelity in modern applications? | Technology | explainlikeimfive | {
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"Currently, water is not modelled as a fully interactive fluid simulation. The fluid simulations you'd see if you searched for them on YouTube are small simulations rendered for a long time in something like blender. They're not rendered in real time. Water in a video game is pretty much just a mesh that may move and reflect stuff to show the surface, but there isn't really anything to it under the surface besides filters to simulate the lighting effects of being underwater. Objects don't typically interact with it as if it were a continuous liquid."
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7n9p3g | with glasses, can e.g. watching tv worsen your eyes? | Biology | explainlikeimfive | {
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"text": [
"No. The reason your vision goes bad is because they grow into an incorrect shape. Looking at a television isn't going to cause that to happen, and incorrect glasses are just going to cause eye strain."
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7na1fr | How does 'swatting' work | Other | explainlikeimfive | {
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"text": [
"Swatting is the practice of making a fake 911 call reporting a gunman, hostage situation or similar, with the aim of getting a SWAT team to raid a streamer's location. The SWAT team believes they are heading into a very high-risk situation involving lethal weapons, so they are obviously a bit on the edge. According to police rules of engagement, they should only open fire if someone's life is in danger, but during raids they need to make the decision on whether to open fire or not within fractions of a second. So, if they saw a person holding an item that they misidentify as a weapon, or have a person fail to comply, they may perceive it as a lethal threat and react by firing."
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7na4ni | Why instant coffee is water soluble, but coffee grounds aren't? | Chemistry | explainlikeimfive | {
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"Instant coffee is made by brewing coffee at a very high heat and pressure, then spraying it out of an orifice into a heated chamber where the water instantly evaporates, leaving behind just the coffee solids. Instant coffee is just dehydrated brewed coffee, where as the coffee grounds are just the ground up coffee beans."
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7nacsj | Why is it harder to kick a football farther in cold weather versus warm? | Physics | explainlikeimfive | {
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"A few reasons, 1 the skin of the football is less elastic, and 2 the air is more dense giving more drag and 3 depending on when the PSI was checked too, if the football was pressurized at room temperature, the pressure inside the ball will drop when its cold, making it under inflated."
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7nafkd | inflation in venezuela? | Economics | explainlikeimfive | {
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"Venezuela's economy relies heavily on oil, so when oil prices plummeted a few years ago, they couldn't make enough money from selling the oil to pay their national debts and to pay for their extensive social programs. So instead of borrowing the money from another country or the IMF, they decided to just print more money. This causes runaway inflation which caused the economy to tank.",
"Venezuelan here. Interesting and accurate insights have been provided but do not sidetrack one reason as important as the others: Venezuelan socialist regime readily destroyed the domestic industry, progressively displacing the origin of consumer goods to a foreign one. This added weight to an already burdened economy which relies on oil exports.",
"The Venezuelan economy is/was heavily reliant on oil, especially since, as a socialist state, the health of the economy is even more closely tied to the government than in a capitalist system. When oil prices plummeted, the funds available for the government did as well. This severely limited Venezuela's ability to pay its debts, as well as maintain the various social programs it has. So, the government had two options: either cut the programs, introduce \"austerity\" measures, until the economy was better(this has its own problems, but that's another story), or they could print more money to pay for its expenses. This is what Venezuela did. Unfortunately, when you print more, its worth less, and in addition, the value of a currency is largely based on what the markets view as its stability. Since Venezuela was having major problems, the currency was valued less and less, so the government printed more and more. But this caused the currency to be worth less... repeat."
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7nai1x | How do email spam filters work? | Technology | explainlikeimfive | {
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"I’m by no means an expert and hope this will tide you over until someone more qualified arrives. I believe it’s a sort of artificial narrow intelligence, that is created with a set of known spam senders, a blacklist if you will. The AI then learns from your habits, like what you delete without reading, what you mark as spam etc. This means it will improve over time.",
"It's a many-faceted approach and a constant battle. In the email servers I run, every email that comes in is scored and past a certain score, the email is flagged as spam and quitely tossed. The scoring goes through a few steps 1) Greylisting. Anytime something connects to my mail server, if it hasn't gotten a recent connection from that IP, it rejects email from it saying \"Try Again\". Proper email servers will wait a couple of minutes and retry, spam-generating bots will move on. 2) IP Address check - Is the source IP from overseas? Is the source IP part of a dynamic IP pool, like an ISP dialup or DSL pool? Is the source IP already part of a black list. All of those add to the scores. And then it uses things like SPF and DomainKeys to cross check the sending IP address with known mail server IPs for the domain in the sender address. 3) Heuristic algorithms. Analyzes the subject and body of the message. Does it contain phrases like \"B1GG3R P33N3R 4 U!!!!!!!!\" or \"I am Prince Ububu from Nigeria\"? And then finally, I maintain my own blacklist of sender addresses. THere's a few companies and people that I had dealt with in the past that would not honor unsubscribe requests from, so I just black hole their emails completely."
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7nalt4 | What is a "magnetic wave"? | Everything I read about photons says they're a electric wave plus a magnetic wave, but nothing ever explains what that means. An electric wave seems clear enough, like it's a transferal of a packet of electric energy from one point to another. Fine. But what the hell is a magnetic wave?? Like, the object receiving the photons receives a small amount of magnetism, so iron would be attracted to it? Or the object is magnetically attracted toward the light source? Or the photon's magnetic wave itself attracts iron towards itself as it travels? | Physics | explainlikeimfive | {
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"The waves in question, carried by photons, are called electromagnetic waves. They are the same thing, fluctuations in the same field. The movement of charge produces the \"magnetic field\". Attracting metal, through ferromagnetism or its friends paramagnetism, diamagnetism, and antiferromagnetism, is more a property of those materials than of the field itself.",
"To understand what electric and magnetic waves are, you should first understand what the electric and magnetic fields are. Imagine all of the space around you is filled with little arrows that can be pointing in any direction in 3D space: up/down, left/right, forward/backward. This is what a field is. The electric field in a space is affected by electric charge. A positive charge will have the arrows all point away from it. A negative charge has them pointing inwards, [just like this]( URL_2 ). A magnetic field works the same, but with magnetic things, [just like so]( URL_0 ). Importantly, these two fields are coupled to each other. If there is a change in one, it will affect the other. In an electric generator, magnets move near wire, the magnet's effects on the electric field around the wire causes electricity to move through the wire. An electric motor does the exact opposite. A wave in one of these fields is just what it sounds like: a wave. It's where the vectors along some direction in space are alternately going one direction then the other [like so]( URL_1 ). For a photon, that wave is moving through space, so the part that was up, then turns into a down, then back into up, that is, it's changing. Since it's changing, then there *must* be a change to the magnetic field there (we could describe it just the opposite way too). This is why we talk about it as the electromagnetic field together, because they affect each other so strongly. So what happens is that the electric field wave and the magnetic field wave run together at a 90 degree angle to one another, [just like this]( URL_3 )."
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7naq4r | Why do soccer players and their teammates always protest yellow/red cards, when they never get overturned, anyway? | Other | explainlikeimfive | {
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"They like to be dramatic. They also fall on the ground writhing in pain trying to get penalties called only to pop up absolutely fine 4 seconds later.",
"Because soccer is a physically exhausting sport without breaks. A person's already stressed trying to formulate game plays and coordinate their motion to execute those plays, so when something like a yellow/red card comes out emotions are bound to run high. It's a way of letting out some of the frustration that's pent up, too. Plus sometimes the cards are just legitimately based on a BS call that the referee made without all the information, and it's human nature to not want to be unfairly judged for something you didn't do.",
"You're also trying to work the refs for future calls. So maybe if you protest a close call, you can get the next close call to go your way (so it's \"fair\"). It mostly never works because refs know what you're doing but it doesn't hurt you why not at least try it."
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7naqdu | Why does Coke (or any soda) taste a lot sweeter when it’s at room temperature, compared to when it’s cold? | Chemistry | explainlikeimfive | {
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"Coldness numbs the taste receptors on the tongue and mouth. It can hide a variety of sins (think chilled booze shots instead of room temperature ones). It can hide sweetness (here), bitterness (iced coffee versus room temperature coffee -- heat can also mask these flavors), etc. Also, room temperature soda gas less carbonation. Carbon dioxide forms an acid in solution that can balance sweetness. Flat soda at any temperature tastes sweeter than carbonated soda at the same temp.",
"Physiologist here: Short answer: receptor-binding thermodynamics. ELI5 Answer: The sensation of \"taste\" occurs when certain molecules in a drink/food each bind to a certain taste receptor in the taste bud of your tongue. These molecules are whizzing around in the fluid you eat, and when they collide with its receptor, in just the right orientation, then bind to a receptor and activate it. That activation causes a nerve impulse to be sent to the brain - where the overall pattern of all taste receptors that are activated enable you to discern one taste (pattern of taste receptor activation) from another. The higher the temperature, the faster these taste molecules are whizzing around in the fluid that is in your mouth. The faster these molecules move, the greater likelihood (in a given period of time) that a taste molecule has collided and bound to its taste receptor on your tongue. The more taste receptors that are activated, the greater the sensation of taste. So, you could, for example, increase the sensation of sweetness by adding more sugar molecules to the drink (more molecules, more binding, more taste sensation). You could also increase the temperature (molecules moving faster means more binding and a greater taste sensation). It's all due to the physics of molecule binding at the atomic level."
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7naz5e | Why does heated frothed milk taste better than heated non-frothed milk? | Chemistry | explainlikeimfive | {
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"When you heat something, the molecules diffuse faster and you are able to taste a more upfront flavor. When you aerate something you also develop more subtle flavors Same reason why someone swirls their wine - to add air and increase area (the wine clinging to the inside of the glass increases surface area). In relation to this, the addition of heat creates a better flavor profile by increasing surface area from the air as well as develop flavor from it with the heat diffusing more flavor molecules ata faster rate. In contrast to this, if you freeze something, the flavor profile is muted from the freeze and the density makes it difficult to open up."
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7nb3gh | Why do many people see a white light during a near death experience? | Biology | explainlikeimfive | {
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"They don't. It's purely anecdotal. A handful of people will claim that they saw a \"white light\", or a \"tunnel with shapes at the end\" or \"the face of grandpa Joe\" etc. And then it becomes representative of the whole experience because of the next point. [It becomes a narrative trope]( URL_0 ) that writers in all forms can use as an easy way to describe their characters experiencing a near death experience, or played or laughs as that trope is subverted, etc. Which means it's then put in enough works as to enter the public conscious. But it's ultimately bogus. Anecdotal evidence is not the same thing as evidence.",
"Doctors believe that before you die there is a large surge of electrical energy in the brain as the brain begins to lose oxygen. EEG's have also shown increased brain activity a few minute before death. This is what probably causes the white light."
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7nbn7h | Since One Year Equals One Revolution Around The Sun, Shouldn’t We All Celebrate New Years At The Same Time Regardless Of What Timezone You Are In? | Other | explainlikeimfive | {
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"> Since One Year Equals One Revolution Around The Sun, Shouldn’t We All Celebrate New Years At The Same Time Regardless Of What Timezone You Are In? No, because a year *doesn't* equal a revolution around the sun, it equals a specific number of days. That the length of our year is calibrated to as closely match our revolutions around the sun in order to keep the seasons from wandering isn't relevant to the definition of when a year starts for a specific location in the world.",
"You're overthinking this and trying to be pedantic about what the holiday celebrates. It's celebrating the calendar rolling over. Calendars are based on local time & every other celebration we have is based on local time, why would New Years be different? You'd have to pick somebody's timezone to base the counting on & any selection is completely arbitrary. People want it to happen at a time for them that allows them to celebrate properly. Nobody wants to be stuck with a \"New Years\" celebration that makes them get up at 6a."
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7nbsxi | How can you determine the location of a fault line by just looking at a topographical map? | I've lived around mountains for a decent part of my life and this just doesn't make sense to me. They seem so contorted and fragmented that it shouldn't be so simple to tell where a fault is and it's type by just looking at the landscape (or a topographic representation of it). | Other | explainlikeimfive | {
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"Not all mountains are directly the result of a fault. The Cascades in Washington state are mountains, but the fault causing them is off the coast. Mountains in Hawaii are not the result of a fault, and some of the mountains in SoCal are traced by faults. One of the best places to see the effect of a fault is to look at the Wallace Creek formation in eastern San Diego county. The creek bed is offset, as are some of the mountains. In other words, if you imagine a hill like your finger, the tips are moved left/right from where they used to be, and it is obvious."
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7nbv5z | How do so many of Americans veterans end up homeless? | Other | explainlikeimfive | {
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"Plenty of people join because they'd be homeless otherwise. If you've got no real skills, live in an economically depressed area & have a shitty family that doesn't want to support you, joining the military doesn't seem like such a bad idea. If you don't learn any useful skills while you're inside, things aren't going to be any better when you get out. Couple that with injuries, psychiatric problems & the rampant alcohol abuse in the military and you've got a problem. The fact that US has done everything possible to dismantle social services over the last 30+ years and things are particularly grim.",
"I've searched tha seven seas fer an answer. Yer not alone in askin', and kind strangers have explained: 1. [ELI5: Why America has so many homeless veterans ? ]( URL_4 ) ^(_18 comments_) 1. [ELI5: Why are there so many homeless veterans? ]( URL_2 ) ^(_61 comments_) 1. [Why are there so many homeless American vets? As a foreigner, I'd expect them to have a load of money as compensation for having fought at wars ]( URL_3 ) ^(_30 comments_) 1. [ELI5: why there are so many homeless vets in the USA? ]( URL_1 ) ^(_3 comments_) 1. [ELI5: Why is the rate of homelessness in the USA so high? ]( URL_0 ) ^(_94 comments_)",
"A fair number of veterans, notably combat veterans, have PTSD, which can make it very difficult to hold down a traditional job. It can also cause the victim to turn to alcohol or drugs for relief, which is a reason why veterans have some of the highest rates of addiction. Addicts are also very present in the homeless population, both because their addiction makes it difficult to work, as well as the fact that most addicts will spend whatever money they get on drugs/alcohol, before even food or shelter. Some veterans joined the military out of high school, and if you are not in a specialized position in the military or a place of leadership, it can mean that you may not have many skills that are applicable in the job market, a market that more and more favors those with college education. If you were a standard infantryman, the number of transitive skills could be few and far between."
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5rchdd | Why is the top button hole for most shirts horizontal as opposed to the usual vertical button hole? | Other | explainlikeimfive | {
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"The top button hole is horizontal to provide the most support or resistance when you tilt your neck forward and backward while the vertical lower button holes provide resistance to being pulled apart from the sides",
"~~The strip of fabric with the buttons in it (caller the placket) is typically made separately and then attached to the shirt. By making the bottom button stand out in some way, the person who sews the placket on to the shirt can very quickly determine which end is the bottom and which the top, saving a few seconds every time. Eventually those seconds add up to more shirts being completed in the same amount of time.~~ Oh shit, I misread the question. I thought you were asking about the bottom buttonhole."
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5rci62 | How does the body induce orgasm? | This is directed at the male anatomy. I'm looking for someone who works in medicine or biology, specifically. How does the body know to induce orgasm after x amount of strokes? What is the nature of the actual sensation? What causes the sensation to happen after enough stimulation? Why does no amount of stimulation in another area of the body (an arm, for example) induce an orgasm there? | Biology | explainlikeimfive | {
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"First of all, let's understand that sexual stimulation entails not only physical sensation, but also mental interpretation. Stimulation without mental lust does not result in an orgasm. A good way to prove this is by a simple visualisation exercise. Try to visualise a stimulus that you subjectively perceive as sexually *un*desirable, even repulsive. Imagine being stimulated by this object or person, you will not be able to orgasm. The biological mechanism of sexuality (and the mental aspect of it) is as follows. Sensory stimulation (from any part of the body) reaches the spinal cord, which is then processed in the sensory cortex, which is connected to the limbic system. The limbic system is responsible for the *emotional interpretation* of the stimulus. If it is perceived as sexually arousing, a genital respons will ensue, which is erection. Erection is a parasympathetic response, while the ejaculation itself is sympathetic. If the sexual stimulation is continued, and desire and arousal are high, eventually a threshold will be reached and dopamine will be released at once in the nucleus accumbens of the reward center in the brain, which is responsible for the rewarding feeling, while simultaneously the sympathetic nervous system reacts by inducing an ejaculation. Internal male genital organs (prostate, seminal vesicles, bulbourethral gland, ductus deferens) will all start to contract and push out this mixture of different substances that make up sperm (only 5% of sperm actually entails sperm cells, the rest is protein rich viscous liquid substance). OP stated that no other area in the body can induce orgasm. This is false, stimulation in another area of the body *can* indeed induce an orgasm due to the mental interpretation of the act. For example, a typical sensitive spot is the inside of the neck. Some people are able to get orgasms just by sensual stimulation in the neck. This does not count for all body areas, since some areas are better sensibly innervated (lips, inside of neck, inside of thighs, feet, ears, etc.)."
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5rclvd | The difference between an Officer and an Enlisted person in the army | Other | explainlikeimfive | {
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"Rank, basically. The lowest officer rank is higher than the highest enlisted rank. Normally officers have some authority or are in command in some capacity, and are better trained in leadership and management. There's also such a thing as a non-commissioned officer or NCO (which aren't usually considered \"officers\") which refers to the higher ranks of enlisted personnel like corporals and sergeants.",
"A commissioned officer (lieutenant, captain, colonel, general, etc...) is a member of the military that derives his or her authority from a commission (formal appointment) issued to him or her by the head of state. In other words, he or she derives his or her authority from the state. Commissioned officers are generally in positions of management and leadership rather than positions of specialisation. However, air forces are often an exception to this. Non-commissioned officers are enlisted personnel (corporal, sergeant, warrant officer, etc...) that have obtained a position of leadership or authority through experience and promotion through the enlisted ranks. However, even the most senior NCO is inferior in rank to the most junior CO. In practice, commissioned officers give general orders to non-commissioned officers, who in turn give specific orders to junior enlisted personnel under their command in order to facilitate the execution of the general orders that they were given.",
"This is the case for all branches, not just the Army. By all means please correct me or add to this guys, I've been drinking and just threw some stuff down (was sailor). To become one: The biggest difference is that becoming an Officer requires a college degree and becoming Enlisted does not. This is not ALWAYS the case as senior enlisted have opportunities to become officers later on through various programs, however, the vast majority of officers have a 4 year degree. Responsibility: Officers are like executives in the private industry. Take a fast food place for instance. The young enlisted would be the burger flippers and cashiers, mopping the floor, etc. The senior enlisted would be like the manager. An officer would be someone who owned or oversaw the operation of that restaurant and/or several more as well. The treatment: Enlisted boot camp is 50-100 dudes/ladies all staying in bunks a few feet from each other in a row getting yelled at constantly and treated like babies. You know nothing as a newly enlisted military member and you'll be treated as such. You need to be broken down and taught everything. Officer candidate school (officer boot camp) is like a cross between college and boot camp. Instead of a huge room full of bunks where you'll be scrubbing the floor with toothbrushes and sleeping feet from other people, you share a dorm with usually 1 other person. Not nearly as much breaking down and being treated like a child. You're treated more like an adult and taught how to lead more so than follow orders. You'll still be yelled at and have to get up early and run a ton, but it's night and day different from enlisted boot camp. The pay: You can look this up yourself. Officers make a lot more money. Google \"Military Pay Charts 2017\". Very briefly I'll go into it, an E1 right of boot camp will make about $1450 a month. An O1 will make about $3050 a month. E1 being the lowest enlisted rank, O1 being the lowest officer rank. Source - Recently separated Navy E6"
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5rcmdv | The Nuclear Option | What is it? I looked it up and i know a little, like the fact that it allows senate to just need a majority vote. Can someone ELI5 on it? Can the senate use it to pass a supreme court nomination? | Other | explainlikeimfive | {
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"Although I think there may be different specific versions, the nuclear option basically goes like this: The filibuster isn't a law, it is a rule of the Senate (and, more specifically, an interpretation of a rule of the Senate). A Senator can ask for the presiding officer of the Senate to explain/decide on the meaning of a rule. That decision is binding, so long as a majority of Senators don't vote against it. That vote on whether the interpretation is binding can't be filibustered. So, the nuclear option is to use a procedural move that can't be filibustered to end the filibuster with a majority vote."
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5rcnl7 | If the American president has to be born in America (or at least to American parents), and Cabinet members are in the line of succession to president, why can Cabinet secretaries be non-American born? | I have two degrees in political science, and never thought to ask this! | Other | explainlikeimfive | {
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"If a Cabinet member is not American born, then they can't be president. The Constitutional requirement wins. It's a risk of appointing such a person into the line of succession.",
"If a person is not a natural-born citizen or is otherwise ineligible for the Presidency, they are excluded from the line of succession. For example, Secretary of the Interior is nominally eighth in line for succession, but former Secretary Sally Jewell was disqualified from succession because she was born in England. As a result, Secretary of Agriculture Tom Vilsack was eighth instead of ninth.",
"Succession is spelled out in the \"Presidential Succession Act of 1947\" which was passed at the urging of President Truman. When FDR died in 1945 everyone noticed that the \"Presidential Succession Act of 1792\" (the one in effect at that time) was a little out of date. The Act states that \"...shall apply only to such officers as are eligible to the office of President under the Constitution\"."
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5rcq73 | When planets are visible from earth, why do they appear as stars to us on the surface of earth? | Physics | explainlikeimfive | {
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"They're reflecting light from the sun, just like the moon does. Now imagine that the moon was much further away- you wouldn't see all the craters on it. You'd just see a white dot, which could look like a star. That's the same thing that's happening with the planets. They're just so far away that they look white."
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5rcxq9 | What is the difference in a child's brain where they enjoy simpler forms of entertainment? | There is an outoftheloop thread about hour long indian animation and nursery rhyme songs. One example is this: URL_0 Reading the thread it seems many adults have to suffer from the enjoyment children are having of these videos. But it makes me wonder why do children enjoy these simple forms of entertainment? Why not better animation or faster paced action? Or more advanced songs?(Not necessarily complicated but more professional) When I was a kid I had pretty much no choice in the matter. Though I don't think I ever enjoyed them I remember hiding away from everyone and playing with toys by myself while others were watching Sesame Street, I think I always hated Barney as well. But other people used to enjoy those songs as kids, but now don't enjoy them at all. I think something happens to the brain that brain that turns something that they once enjoyed into something so utterly annoying. What is that something? | Biology | explainlikeimfive | {
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"Children have limited experience because they've only existed for a few years. As they get older and get exposed to more complex ideas and themes. They desire more complex presentations.",
"It's a few things. Babies and toddlers take comfort in repetition. It's how they go through their day (usually with a schedule which brings security and structure) and it's how babies and toddlers learn new things. If you have spent any time with a baby they love the \"I dropped my toy from the highchair game\"- they learn about cause and effect; the sound the toy makes hitting the floor, and usually how their parents react to the game. They think it's hilarious! It also allows toddlers to start to learn/pay attention to take in new information each time. So while watching the same show or reading the same book over and over again might be boring and annoying to us they will start to anticipate things and then start to learn/memorize new parts. It's exciting for them to start to remember things and get them right! If your toddler asks for the same book over and over next time try changing a important detail and the child will probably correct you. Basically repetition brings comfort, security, trust, learning, memorization and anticipation. You can google toddlers and repetition for more info... Source: mom of a 4 year old boy and almost 2 year old girl..."
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5rd3n1 | Could stone be forged like Metal is? As in heat it to the required temperature to liquify, then pour that (lava) into molds? | Other | explainlikeimfive | {
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"That's not forging, what you're describing is \"casting\". Forging involves 'hammering' an object into shape. Casting involves 'pouring' a liquid into a mold. The classic way to 'cast' stone is via \"sintering\" which is a process where you take a powder and heat it until the particles all stick to each other (think firing clay). Fill your mold with powder and something to hold it together and heat it in some sort of kiln. You can do what you describe, it's pretty common in the ceramic arts. Glass casting goes back at least to the Roman times. The process for a 'stone' wouldn't be too different (I've poured lab-made 'lava' on several occasions). There are also guys out there who literally go out and scoop lava (actual lava from a volcano) into molds.",
"Forging, as others mentioned, is the process of heating and hammering a piece of metal until it is of shape. Forging doesn't work well with stone, as the materials we think of as stone are almost always very brittle. Solid materials come in one of two very broad categories: stretchy and brittle. Usually, stretchy things are weaker, because of the very nature of being stretchy; you're pulling material apart. Brittle things are usually stronger, because their atoms make a very stable structure. These are broad generalizations, of course. Metal, at certain temps, gets very stretchy, but doesn't become liquid. The bonds between atoms start to weaken due to all of the energy everywhere, but the metal hasn't hit melting point yet. This allows us to hammer it into a certain shape, which also kind of kneads the stretchy bonds into a shape that is very stable when it cools down (tempering) Stone materials never really hit the same stretchy-but-not-goopy stage metals do. They go from pretty solid to pretty liquid in a very short temperature range. When they're solid, they are brittle; their bonds are very stable and arranged just so. If you hit a brittle material, it will not stretch; it will crack, like glass does, because it's bonds cannot stretch. There are all sorts of deep-down atomic reasons for why some bonds will stretch and some will not, but for the most part, stone is in the latter category."
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5rd8i0 | How is YouTube a sustainable business model? If view count remains constant but video storage costs continue to increase, wouldn't this lead to a permanent loss? | Let's assume that in 2020, YouTube maintains a daily view count of 500 million per day. However, they also keep old videos on the site that aren't generating views. Don't these "dead videos" eventually accumulate and overcome the profit margins with cost of storage? | Technology | explainlikeimfive | {
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"Storage costs are going down exponentially. Every year the cost of storing 1 GB of data is half what it was the previous year. YouTube loses money every time someone uploads a long video that nobody watches, but it doesn't matter because they make insanely high profits off of the top 1% of the most popular videos. As long as YouTube is a good place for popular videos, the business model is sustainable. If it turned into an unpopular site where people just uploaded their personal videos but nothing popular or viral ever went there, it'd lose money.",
"As of the last time Google released any financial info about YouTube (early 2015) was that it was not a profitable business unit to operate. However, since then, most analysts are thinking Youtube is now profitable due to them selling way, way more ads than in previous years. Google has really taken a strong effort to get advertisers on Youtube, and the latest analysis thinks they will likely be profitable during 2017. However, in completeness, even if it was a money loser, Google would continue to operate it, as it provides benefits to google's other services. They (like many businesses) are willing to take losses in their left pocket to reap bigger profits in their right pocket"
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5rdp0j | Why do we feel a lump in our throat when we hear upsetting news? | Biology | explainlikeimfive | {
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"This is called a \"globus sensation\". > The exact cause of globus sensation is uncertain. Some specialists believe that it is due to a problem with the co-ordination of the muscles involved in swallowing. Many muscles are involved in swallowing and they need to tense and relax in the correct sequence for swallowing to occur normally. In someone with globus sensation, when they try to swallow saliva, some of the swallowing muscles may not relax fully and so the sensation of a lump in the throat occurs. However, when food is swallowed, the food stimulates the muscles in a different way and normal muscle relaxation occurs. URL_0",
"Dunno but ive got this thing called globus pharyngeas which basically means i constantly have that feeling, its theorized that its an anxiety induced disorder. First occurred two years ago during a period of severe anxiety and never went away. Its much worse when im anxious. After a while i learnt to live with it, and now i dont really notice it unless anxious.",
"I looked this up a while ago - just went back. Summary: it's not really a lump, we just think it feels like one. Very interesting. Link = URL_0 As Nick Knight explains for The Independent, your autonomic nervous system - the overarching system that controls other nervous systems like the sympathetic nervous system - kicks into gear, and causes a bunch of different reactions inside your body depending on the circumstances. This is the same system that controls your 'fight or flight' response along with other unconscious body functions like digestion. When this system switches to hyper mode, it first sends out oxygen all over your body to make it easier for you to punch something in the face, or run away in the opposite direction to safety. To spread oxygen to all of your muscles, your body must first breathe it in. In an effort to take in more air, the nervous system tells the glottis - the opening in your throat that ushers air into lungs without taking food with it - to stay open for as long as possible. In other words, your throat opens wider than normal because a bigger opening means more air. You don’t actually feel your glottis opening wide. If you did, everyday life would feel awfully strange. What you do feel, though, is muscle tension caused by your body trying to keep your glottis open even when you swallow. Normally, when you aren’t crying, your glottis opens and closes when you swallow all day long. This ensures that food and spit go one way and air goes the other, with no mix-ups in between. But, when you cry or are on the verge of crying, your glottis is trying to stay open, but gets forced close every time you swallow. This tension messes with the muscles in your throat, giving the sensation of a lump. The lump feeling is actually referred to as globus sensation, and it happens to everyone in these stressful situations. Normally, this feeling dissipates quickly once you calm down and your glottis goes back to functioning like it used to.",
"I always get this when watching sad movies. I then pretend to girlfriend that I'm totally fine",
"I thought this was just one of the many fight-or-flight responses. Anxiety or panic tends to have a few physical symptoms, almost all of them to enable you to be more mobile, that is increased oxygen intake, increased heart rate, increased blood flow, and evacuating the bladder and bowels. I always assumed that the lump in the throat was part of the esophagus widening to ensure plenty of oxygen was getting in.",
"Does anyone else also get a strange tingling sensation in their head when they hear upsetting news?",
"According to Traditional Chinese Medical theory (very ancient), that sensation is called \"Plum-pit syndrome\". It is caused by emotional disturbance which effects the smooth flow of qi, resulting in stagnation of qi and phlegm in the throat. Why the throat? I don't know.",
"In traditional Chinese medicine this is called Plum pit syndrome. It is associated with stress and anxiety. They have good herbs and treatment for it."
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5rdvd0 | Why urban centers tend to be more liberal, while rural sectors tend to be conservative. | Other | explainlikeimfive | {
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"One explanation is the distribution of the electorate. Urban areas = more people = more diversity. Second, more people = more votes = more diverse voting public (i.e. opportunity for multiple political identities/opinions/leanings, etc). States with higher populations also get more votes. States like CA (with many cities) and NY (with one dense city) get more representatives in the House and more electoral college votes in presidential elections than, say, low population states like MT or WY. Now, obviously people move around over time, so this is why we have a census every 10 years - to update voting districts and the distribution of votes for elections. Two things for you to dig deeper: * [A 2016 episode of WYNC's Podcast More Perfect]( URL_0 ), which describes a supreme court ruling in 1962, Baker v. Carr and addresses the question you are really asking: are rural area votes versus urban area votes being fairly re-districted between the two? Crazy good episode. It raises some truly fascinating questions about the court and it's power to decide elections. * A [collection of UMich 2016 election maps]( URL_1 ) helps draw out the urban/rural distinctions more clearly, revealing they are much more nuanced than simple red/blue. Scan through each map, but be sure to get to map 6, which is at the state-county level and includes purple to show how close the vote leaned left/right. Note how the urban areas tend to actually be purple...not 100% blue. It isn't so much that urban areas are more liberal, as it is they just have more people which means opportunity for more opinions."
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5rdvng | How do tiny snails end up in fish tanks even though no snails are put in? | Other | explainlikeimfive | {
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"Live, fertilized snail eggs would have needed to be introduced somehow. Snails often lay eggs on plants, so if there are live plants in the tank, it could have been from them. But anything *could* have had snail eggs on them (gravel, tubes, decorations, etc.) if they weren't sterilized first."
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5re0bo | Who, or what, finds and puts together the information on sites such as URL_1 and URL_0 ? | Technology | explainlikeimfive | {
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"Short answer: Mormons. Why? Members of the Church of Jesus Christ of Latter Days Saints believe that they can be baptized on behalf of their deceased relatives. Part of that process involves meticulously documenting who has proxy baptisms done for them so that nobody gets doubled up on. Like most Christians, they believe that Jesus will be back soon and He's going to help them make sure they don't miss anybody. How? As part of that ambitious effort to essentially map out the entire human family tree, resources like the above mentioned serve as searchable archives of public records such as birth, death and marriage certificates as well as census records. Many of these records exist in hand-written form only. To deal with this huge barrier, all of the documents are scanned into a database and volunteers from around the world (mostly Mormon) painstakingly type out the image text so it can be digitally searchable. TLDR: Mostly Mormons do it, some are employed by those websites, many are just volunteer enthusiasts.",
"I did! They have a volunteer base that reads documents and then keys in relevant information. I went through 50 or 100 WW2 era German documents from the Warsaw Ghetto I think it was. Sad, but I read German and I felt like I should help. I also did some union membership cards from Wisconsin. They have a lot of files to download and work on!",
"The records was previusly in churches, hospital records and stuff. And a great deal of effort have been put into digitalizing it all. (University Genealogy studies mainly) Initiatives made by past relatives (such as mine - [ URL_2 ]( URL_1 )) that have been going since 1918 and uses tools by URL_0 TLDR: They make use of the public records made by the Genealogy societies and university studies",
"My dad. He isn't mormon, but he is fascinated with where he comes from. His hobby has taken him all over the country. When he finds a lead he goes to the last known location of that possible ancestor, checks the cemeteries and libraries for documents. Once he is sure of the lineage he adds it to his tree. Some lines he has been able to take back a thousand years.",
"There's a National Genealogical Society and one for pretty much every US state as well. Most accredited genealogists have accounts on sites like these to edit and create family trees. For instance, my mother has researched our family back to the 1700s in Europe and it's almost entirely trackable on Ancestry.",
"I used to work at an archive in London that was digitising its collections of workhouse and asylum records. The job was both incredibly fascinating but also very repetitive as you turned page after page and took a high res photo of each. Some of the books are in bad condition and couldn't be looked at by the public. It's fabulous that they are accessible now and to people all over the world.",
"I had a great friend in college who got his history degree. After college he worked for URL_0 at the National Archives scanning documents and archiving them for the website. Seemed like a pretty good gig for a while.",
"Hi, I created a throwaway so as to not 'out' my main account, but I worked as product manager and business analyst doing this for almost a decade for URL_4 (by a very large margin, the largest.) Despite the current most popular response, Mormons make up a tiny fraction of the genealogical community (not even 1%). Most of the space is occupied by archives and libraries on one side, and private companies on the other - although FamilySearch, the Mormon genealogical wing, is fairly large. There are 4 main items which come together to actually make the process happen. 1) Acquisition of content 2) Digitization of content 3) Transcription/digitization and clean-up of data 4) Publishing of content and data The first step, in many ways, is the hardest. Teams of content aquisitionists spend years cultivating relationships around the globe looking for content sets which will fill in gaps in available records sets or add more information to existing ones. Early on in the internet-genealogy era, this was primarily from large federal archives in the US and the UK - thinks censuses, social security records, and so on. These are easy, well indexed, and well understood and usually came on microfilm, which is extremely cheap to digitize. As time has gone on, attention has shifted to state archives, which often have microfilm or microfiche, but increasingly collections were loose paper - which is very expensive to digitize, but collections are usually in good repair. As those have been exhausted, or local privacy laws prevent their digitization, it's shifted to church records, smaller archives, private collections, and some interesting ancillary collections like digitizing yearbooks. From the beginning of the negotiation of a contract to its close can easily be several years, even for a small collection of images. Usually the contracts will include a company (like Ancestry) digitizing and indexing the records free of charge to the archive, with some type of exclusivity contract preventing the archive from giving/selling the images to competitors for a handful of years, while the archive is still free to serve the images to their patrons all they want. Exceptions to this are items like the release of the 1940 census where the federal government managed digitizing the images (although it was outsourced to a private company to actually do the work) and companies had to pay to get access to the images all at the same time. The second step, digitization of the images, is one of the most fascinating, in my opinion. Very common types of formats for genealogical content are: Microfilm, Microfiche, Index Cards, Loose paper, news papers, maps, and books. For Microfilm and Microfiche there are excellent mostly automated machines for scanning this content. It's usually scanned as a 'ribbon', which means in a 1000 ft reel of microfilm, it gets scanned as a single 1000ft long image, and is sliced into individual images/frames later. For books, if the book isn't unique and super old, usually the binding of the book gets cut and it gets scanned in a high-end sheet-feed scanner (these can often do 200+ pages/minute). For books which are too old or unique/rare, they will get scanned in special cradles with two DSLR cameras looking at opposing pages. This is very expensive and very slow (think 2,000 images/day.) Images then usually go through a very rigorous audit/edit where extra space is cropped, color might be fixed, etc. Usually there is a zero tolerance policy for poorly scanned images - they get sent back to the archive for a rescan. For URL_4 , there are hundreds of people around the world involved in this process at any given time. Third, When the images return, they go to be transcribed/indexed. The content has to be analyzed as a set to understand what type of content is actually contained. It's not uncommon to scan a collection of Birth records, only to discover it contains Marriage and Death records as well, which requires the transcription project to be adjusted to account for this. Content is usually sent to overseas vendors for this process because it is less expensive, but most importantly - they tend to be significantly better/more accurate than westerners. Groups like FamilySearch, however, do this entirely via a volunteer force using a double-key/arbitrate process. So as each type of content in a collection is analyzed, each type of form must be accounted for, and a definition of what content is wanted/needed is written up, usually with rules as to accuracy levels required. When it returns from transcription vendors, a pretty extensive audit is performed to look for mis-transcriptions, incorrectly marked forms, missed data, etc. When transcription completes, the data still needs to be massaged. For example, \"Texas\" might have been keyed as \"Tex\", \"Texas\", \"Tx.\", \"Tx\", \"Tejas\", etc. All of these need to be normalized to \"Texas\" so that it is actually searchable as a state. Algorithms are also run to look for odd patterns such as names with many consonants in a row in non-Welsh collections, or a large portion of the names having mis-matched genders. Ie. you would expect most 'John's to be Male - but if most show up as a female, there was probably a major mistake in transcription. Families will be linked together as a 'group' at this point, instead of just a bunch of individuals. For some types of content, image-by-image form recognition is run so that the images can be overlaid with transcriptions and labels when a customer looks at them. Finally, fourth, the content gets published and made searchable. This is a fairly complicated process for large datasets. URL_1 , for example, has more than 19 billion records in almost 33,000 different collections. You can search them all in a few seconds. If you want to known more, there are a series of Ancestry blog posts about the scanning/digitization pipeline (not written by me) from a few years ago here: https://blogs. URL_4 /ancestry/2013/4/10/our-image-processing-pipeline-the-good-the-bad-and-the-ugly/ https://blogs. URL_4 /ancestry/2013/04/20/image-processing-at-ancestry-com-part-2-living-in-the-mesosphere/ URL_3 https://blogs. URL_4 /ancestry/2013/05/13/image-processing-at-ancestry-com-part-4-microfilm-scanning/ URL_0 URL_2",
"Combo of volunteers and paid staff read original documents and transcribe them into digital format so they can be searchable. Can't speak to URL_2 but I have done this for URL_1 . URL_0 I have not transcribed any source information but have created family tree there and matched source docs to the tree individuals.",
"A big source of the records they have are national and state-level archives. For example, they get census records, Civil War, and Revolutionary War records from National Archives. From states, they can get things like marriage licenses, birth/death certificates, and probate records (things like wills and estate papers). I work for a state archives, and Ancestry pays for us to make copies of the records for them to digitize and index. In my opinion, the indexing is one of the hardest and most time-consuming things they have to do to make the records usable. Just take a look at some of the millions of pages of records they have, many of which are hand-written. Sometimes the writing is poor or simply unreadable, so the transcriptionists have to make judgment calls about what they think certain words or names are. Then that information has to be paired with the digitized records in their database so that people can search for them.",
"People like my mom. Which falls under the category of mormons. She spends all day once a week doing genealogy work at a Mormon library that has access to all sorts of databases. She also uses whatever free time she has. It's her main hobby. A lot of retired people ( especially but not exclusively Mormons) do it too."
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5re3kb | What is the process behind counting TV votes? (As seen in talent shows, etc) | Technology | explainlikeimfive | {
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"Normally you phone into a number which will play an automated message before ending the call. From the production side of things they can see the number of calls to each number. This is a pretty standard part of telephony technology and is used in virtually every call centre for recording stats. If required they could report on unique calls vs total calls to get an idea of how many times people are voting multiple times etc."
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5re890 | Georeferenced Images | What does georeferencing really mean? How is it done? Recording latitude / longitude data when the images are captured? Is the latitude / longitude / altitude data always stored in EXIF? Or are there other possible formats? | Technology | explainlikeimfive | {
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"If you have pictures from your last vacation, it could be nice to know where they were taken, couldn't it? So, the camera - if it has an GPS - can record where the pictures was taken and store it together with the image. Such as in the EXIF header. This is sometimes called geotagging. If you on the other hand have a scanned map of a city for instance, and want to show your position on the map using GPS, you must tell the map software what position in the real world the pixels of the scanned map represents. This is usually done by selecting a few points on the map, enter the real world position for those points and let the software figure the rest out. This is georeferencing. Of course, if you buy aerial photos over a country, they are normally georeferenced already. There are tons of formats for this too"
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5rec91 | By what mechanism does the body force you to take another breath after you've held it for a long time? | Biology | explainlikeimfive | {
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"O2 levels in the blood fall. CO2 levels rise. Acidity of blood rises. Hypothalamus in the brain can detect this change, notifying the brain the O2 levels are getting dangerously low. Instincts kick in, and forces the diaphragm to take in another breath. Correct me If im wrong please (I might be)"
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