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npbmms | How after thousands of years without shampoo and soap, we survived, and now we can't even think in a life without it? | I just don't get it, I was trying to not use shampoo or use less of it, but when I train I really need it the same with soap, I don't understand how our ancestors clean themselves without chemicals that now we have, and I don't know if it's a thing like washing your teeth that actually increase your life expectations. | Biology | explainlikeimfive | {
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"Theres actually studies done that show you dont need shampoo and overuse of it can actually be damaging as it strips, out the natural oils that your hair creates. During quarantine I tested it myself. I went 2 months using only warm water to wash my hair. After about 3 weeks I started to notice that my hair was soft and similar to when I used shampoo and conditioner. However if it got wet it became coarse fast and sweat made it worse fast. Basically the point of my little story is, they are not 100% needed to get by. I only went back to shampoo because after quarantine I did manual labor for a while and the sweat made it mangy looking. A lot of hair specialist recommend not shampooing every day but more every 2-3 days. Shampoo just clings to the dirt and oils to pull them out faster, you can still get clean without it.",
"There's three benefits to hair care: cosmetic oil control, pest control, smell control. Speaking on America's history of shampooing: In the 1700's, lice was absolutely rampant, especially in the wigs men wore. The powder in wigs was partially supposed to act as insecticide but it rarely worked. Women's hair was also regularly lice infested. Women took care of their hair cosmetically by brushing their hair. This distributes the oil evenly from scalp to tip, and since women didn't cut their hair, there was plenty of hair to take the oil. They washed their hair perhaps once every other year. Hats were also huge! In the late 1800's and 1910's, with the advent of plumbing, white ladies would get their hair washed maybe every other week and set in style at a salon. Otherwise they would brush the oil out. Men's hair was short and oiled or waxed. This controlled the scent and made it harder for lice to get ahold of ladies. African ladies were sometimes forced, by law, to wrap or cover their hair. Sometimes they were also forced to relax their hair. Kinky hair is dryer than straight hair, so oil buildup is not as much of an issue. The harsh chemicals that relaxed hair would deal with bugs, but at this time fleas and lice were common issues for all poorer folks. Once World Wars happened, mass produced shampoos became the norm, since lice is a big deal with massive armies. After World Wars, soldiers took the habit home, plus home plumbing was more common so frequent hair washing could be done more often.",
"Bacteria and other microbes cause most illnesses. Average life span has been increasing as we have improved our personal hygeine.",
"A British historian did an experiment recently. She wore a linen shift under her clothing for a month and didn't wash with soap, it drew out all the sweat and bacteria away from her body leaving her smelling fine. She then went a month not washing without the shift and the difference was huge. She stank 🤣"
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npd44y | why around the year 2000 we had to put "www." before each website and now we no longer need to. | I am born in 1999, I remember having to write "www." before my website in the address bar otherwise it would not work. Later in elementary school it no longer needed to be done to access the website. What happened? | Technology | explainlikeimfive | {
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"In the early days of the Internet, it wasn't so clear yet, what everyone was going to use it for. Around the end of the 90s/start of the 00s, it was starting to become pretty clear that web browsers and web pages were going to be how most people and businesses used the internet, most of the time. If you're going to run an internet domain, there are a bunch of different services you can host on it though. You can host a web page, an email server, an FTP server, a Gopher server, or countless other things. Traditionally, you would host each of these things on a separate subdomain of your main domain: URL_0 for your website, ftp. URL_2 for file transfers, URL_1 for an SMTP server, and stuff like that. And sometimes, each of those services would be hosted by a different physical server on a different IP address. Often there would be a forwarder so that if you went to URL_2 you would be bounced to URL_0 , but that was an extra step to set up. As things developed (and as the IPv4 address pool dried up), it became much more common to use virtual hosting, reverse-proxies and similar systems so all these services would appear to be hosted on a single system, which makes it simpler to just create a URL_2 domain and host all the services on that one address. Businesses were also starting to decide arpound the same time that leaving the \"www\" out of their website domain made for better branding.",
"For many sites, the www still works, but it is basically redundant. If every site needs it, then no site needs it."
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npe9n2 | Why does the area around the wound feels itchy when the wound dries? | Biology | explainlikeimfive | {
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"Damaged / inflamed tissue releases histamines, nerve growth factor and other related chemicals. These chemicals help repair tissue damage and magnify the response of nearby pain/heat receptors. When the body releases histamines at/near the sight of the damage, these histamines dilate blood vessels, but ultimately produce the itch sensation."
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npen37 | How does a flash bang work? | Technology | explainlikeimfive | {
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"Sensory overload. Creates a very bright light to temporarily blind people, and a loud bang that gives tinnitus (ringing in the ears) and disables a person's ability to both see and hear opponents, which totally disorientates them until they're recovered.",
"As the name suggest the explosives and the design of the bomb is chosen to create a large flight of light as well as a loud bang. Human sensors are designed to work in a wide range of conditions and will therefore adjust to various levels of sensory input. The mechanisms for this is different depending on the sensors. Firstly the retina in your eyes work by constantly generating chemicals which gets broken down when light hits them which is how we sense the levels of light and actually see. If you see a bright light it will break down all the chemicals in your retina making you go blind until the cells can reproduce the chemicals and you will slowly gain back your eyesight in the darker conditions. At the same time the eye detect the bright light and closes down the pupil. But it is not able to react fast enough for a flashbang and when it reacts and closes your pupil it is too late and you end up with a tiny pupil only allowing a bit of light though to your retina for a few seconds which also makes you blind. For your ears there is two effects going on as well. Firstly the sensors in the ear consists of hairs of different lengths which will sway depending on the frequency of sound. But a flashbang does not produce any frequencies only a large single shockwave. So it is able to set all the hairs in your ears swinging at the same time. It takes a bit of time for these to settle down and actually respond to more quiet sounds around you. So you go deaf for a few seconds. But secondly some of these hairs will be permanently damaged. The effect is that these will send a constant signal to your brain. So when your hearing does return the brain gets the signal that a few single frequencies are still loud, like a whistle or something. The brain actually focuses on these high pitch constant sounds because they are the loudest and tries to make out what it is. And it takes the brain even more seconds to find out that the hairs that these nerves are connected to are actually damaged and it will eventually just ignore them for the rest of your life. First then will the brain be able to focus on the other sounds around you and start analyzing these. There may also be other neurological conditions happening. We do not have the best ability to analyze these situations in a controlled environment with equipment scanning everything that is going on. Our research into epilepsy does show that big sensory inputs to the brain can have effects throughout the brain and nervous system. But these effects are not fully understood if there are any at all or if they are just natural responses to suddenly going blind and deaf while getting stormed by armed assailants."
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npf4zf | Why does a 15 stone adult have the same Paracetamol dosage as a 12 year old? | Biology | explainlikeimfive | {
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"There probably is a preferred dosage for your body mass in many basic medications, but its impractical to cater dosages for every human being for basic meds with high safety levels for the dosages it provides. So just pick a dosage that will work for the vast majority of body masses that is also safe to take. Its safe and does the job so theres no need to look into catering dosage management for wildly different bodies. For more serious medications with serious risks (aka prescribed medication) - dosage does matter purely to reduce side effects and to be effective for what ever ailment the person has. This is one reason why some meds are over the counter - their high safety tolerances for the dosage offered and tends to work for most people. So no need to have multiple dosage options."
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npfan5 | how do loud noises cause problems to your hearing and eventually make you deaf? | Biology | explainlikeimfive | {
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"Inside your ear^1 are tiny hairs that act like microphones tuned^2 to the different frequencies^3 we can hear. Vibrations are carried along the auditory nerve to the brain. These hairs are formed when you are in the womb and do not grow back when damaged^4 . Loud and sustained^5 noise in particular can damage these hairs. Any kind of trauma or internal damage to the inner ear may also cause permanent hearing loss, for example loud impulses (gunshots, explosions) which will tear the ear drum and it may not heal perfectly, penetrating the ear drum (for example with a q-tip) can cause the same. In addition, chronic ear infections are associated with hearing loss. There are more mysterious forms of auditory damage like tinnitus, or ringing in the ears. It is correlated with trauma and exposure to loud noises but we don't have a good understanding of the mechanism by which we perceive it. 1. The hairs are inside your cochlea, a bony snail shaped structure that is connected via the bones of the inner ear to your ear drum. Inside the cochlea is a sac of liquid called the basilar membrane, the hairs live along this membrane. There is a complex electromechanical relationship involved that converts pressure waves into mechanical vibration and finally into electrical pulses along the nerve. 2. Higher frequencies require smaller hairs. These are more fragile, which is why we lose high frequencies as we age. 3. They're actually tuned to a range of frequencies and they overlap. This is why low frequency noise \"masks\" higher frequency noise. 4. They grow back in some animals, like turtles. 5. Like a rock concert, plane flight, or noisy restaurant. So tl;dr there are hairs in your ear that don't grow back, and bones and stuff that can break and won't heal right. Don't stick stuff in there and wear ear protection."
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npfge7 | When we download applications or software from a server, why are we often encouraged to use a mirror site, rather than the "original"? | Technology | explainlikeimfive | {
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"Let's say you owned a store that became really popular. The store only had room for 100 people in it at a time, but as your store becomes more and more popular, people start having to wait outside. You try to tweak the inside of the store and maybe you squeeze a few more people in, but the only way to expand the current store further is to buy the place next door which is REALLY expensive ($1 million dollars). If you did that, you could handle 200 people but then once you hit that limit, you are faced with the same problem and expensive costs. Plus, you have people driving all the way from other nearby cities to come to you, so their trip is lengthy just to buy from your store. You realize that for the same cost ($1 million dollars), you could set up TWO additional stores in nearby cities. So instead of one store that can handle 200 people, you end up with three stores that each serve 100 people. And since the stores are closer to some of the shoppers, it is no longer a really long trip for them. And if you ever need more stores, it is much easier, cheaper, and quicker to buy more stores instead of trying to expand the existing stores. This is the same thing with servers and mirrors. Mirrors are the additional servers that provide the same files, and can provide them at faster download speeds if there is a mirror that is closer to wherever you are. And faster downloads also means the download is FINISHED faster, so that also helps create more availability on each mirror. And on top of it all, it increases reliability because if one server has a critical failure, people can go to a mirror instead of getting mad about being unable to download the file.",
"It’s a way to load balance server load amount multiple servers. Chances are if you are being pushed to a mirror it’s because it’s over loaded. CDN’s are a better way of handling this tbh."
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npgdfw | What is APR % on a car? | Other | explainlikeimfive | {
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"APR - Annual Percentage Rate Also known as \"simple interest\" though it's not really simple. The interest you pay on an auto loan is computed based on the daily balance. You take the APR and divide it by 365 and that gives you the daily interest rate. Each day the interest charge is computed on the balance of your loan that day."
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npgjl6 | Why on old cartoons, did a scenery object look brighter if the characters were going to interact with it? Why would the quality differ regardless? | Technology | explainlikeimfive | {
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"They were being drawn in different layers. Old cartoons were literally drawn on clear plastic sheets like you'd get on an overhead projector. Character's movements therefore had to be drawn and redrawn for each frame. The background didn't. It would stay the same for multiple shots. These different layers would be stacked on top of each other and a picture.would be taken. Then, the character pictures would be swapped out for the next frame. Maybe the background would be moved a bit too. If an object was going to move, it would have to be on a separate layer from the background.",
"The short answer is that background plates were often rendered with different media than the more limited choices available for ink and paint that made up the animation cels. If the director wanted a watercolor look to their scenery, they could get that, but then the animated elements would stand out from their surroundings because the ink and paint you could use on celluloid (cel) was very bright and defined, and therefore created a harsh contrast with the backgrounds that allowed subtle gradations in color.",
"Often the background is painted with water colors. Then characters or anything that has to move is painted with acrylic paint on clear plastic sheets called cells. The Ink and Paint department would try their best to match the colors. Matching the 2 different types of paint colors is difficult.",
"They weren't just brighter. They were outlined and simpler like the characters. That's because the other objects were in the background layer which, unlike everything else, which was penciled and colored in, it was painted."
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nphzj6 | Why are people not supposed to close their eyes or go to sleep if they have a concussion? | Biology | explainlikeimfive | {
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"I think this is old information. I believe the theory was that it’s easier to monitor a person’s neurological status if they are awake. You would notice dilated pupils, slurred speech, trouble with walking/moving (these would all indicate a change in neurological status - the person’s status is declining and they need medical attention ASAP). It is important to note that the medical opinion on this topic has changed. According to the Cleveland Clinic: “There is no evidence to support that waking someone up with a suspected concussion (or not letting them sleep at all) is needed or beneficial. There is also no proof that waking them is going to help them get better faster.” From Kidshealth: “Any child who might have a concussion should be checked out by their doctor or at the emergency room (ER). But it's OK to allow the child to fall asleep. In fact, especially for young kids, it can be hard to keep them awake. After any hit to the head, though, a child who falls asleep and can't be wakened needs emergency medical care. Get help right away if that happens.” URL_1 URL_0",
"It makes it harder for the paramedics and doctors to ask you question if you're asleep. That's basically it. If you're awake you can provide answers. However, after they get the answers they need they'll let you sleep. Your question is based on the belief that if someone has a concussion and they sleep they'll go into a coma. However, you can't prevent a coma by yelling at someone to wake up and slapping them."
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npihqa | Why is water discolored when they’re working on the lines but not normally? | From time to time, we get notified that the town is flushing the lines and water may be discolored until they’re done, and to run the water for 15 minutes. Why isn’t the water always discolored and what causes the discolored water? | Chemistry | explainlikeimfive | {
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"You can replicate this effect at home. Just pick a faucet that you don't need daily, and then don't use it for a few months. When you first run it, you'll have that same \"rusty\" water. There is always a certain amount of rust and sediments in the water lines. But your normally functioning water system is a relatively stable and smooth flowing system. When they open up those huge lines to flush out fire hydrants though, you disturb that system quite a bit. The huge increase in water flow stirs up that sediment that normally happily sets at the bottom of your line, filling the water system with rust and debris."
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npjsp8 | How can a country be in debt to itself | Economics | explainlikeimfive | {
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"A country is made up of people. Think of it like a family. Now think of the Parents borrowing money from the children. So the government borrows money from its citizens and it does this through the issuing of bonds. People then buy the bonds and the government pays them money in interest for doing so.",
"A country is made up of people and groups which can borrow money amongst themselves. A government can borrow money from its citizens, or even parts of the government borrow from other parts. Typically governments obtain loans by selling \"bonds\", an agreement to pay back an amount of money in the future. If you have part of the government tasked with collecting and retaining money for the future (such as Social Security) it makes sense that they would then turn around and buy government bonds in order to slightly grow that money over time in what is usually considered a completely secure investment. So in this case the government owes money to itself because it needs to repay or \"service\" those bonds in the future.",
"So there's 2 main ways in the US, the first is a program has funds set aside . The best example is the Social Security office, they are the largest holder of US debt. You pay into social security and currently it earns more than it pays out. So the extra is invested in funds to grow the amount of money that the fund has. Basically it says okay I will take a million for a road and give you 1.1 million in 10 yrs cause I have earned value off if that road. Why does this happen, well that road needed maintenance, but they couldn't fund it with what was available, that's why you dont want the Social Security part of the regular budget cause it would be vulnerable to political whims, so it's part of the government but separate so it is harder to mess with. The second is a central bank, they are part of the government but separate, there job is to keep control of the money system. They do this through the accumulation of assets, things that can be sold or traded if needed, like gold or silver or foreign currency.the central bank issues currency to try and keep the currency stable and each one is a promise to be able to be redeemed for any for the denomination on the bill. Now the central bank also buys bonds from the Government which it earns interest off of, but if it does to much the currency loses much value, now your currency is always losing value thru inflation,which is why things cost more than in the past. So why cant the government just print money, well it can and it can cause hyper inflation like in Venezuela. But that's why we have an independent central banking system to keep inflation under control"
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npmvcr | why do baseball pitchers not wear some form of protective gear on their heads or face? | Pitchers stand roughly 60 feet from a batter, and a ball comes off the bat at let’s say around 100mph for simplicity They have less than half a second to move and avoid the ball if it just so happens to fly at them. And going off what I’ve seen from clips of it happening people don’t exactly just walk it off so wouldn’t they logically want to wear at least some form of protection? | Other | explainlikeimfive | {
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"Statistically, the likelihood of the ball going in their direction is small. Not to mention, a good pitcher will make sure the ball is hit as little as possible. The ball will almost always go to the catcher.",
"**TLDR:** The odds of being hit at the exact angle of the pitchers face is VERY low. The amount a helmet would mess up a pitcher's visibility or motion is less low. **Slightly more detail:** Most pitches don't result in a hit, and among hits, there's a tiny window of possible trajectories (both left-right and up-down angle) that would result in hitting the pitcher. Pitchers are hit by hard hits a few times a year, out of literally 10s of thousands of pitches thrown, maybe even more. Wearing a helmet would make every one of those pitches worse in exchange for protection from a VERY unlikely event. Pitchers have decided it's worth the risk to pitch better. Like you said, they have \\~no time to duck, so the impact would probably be directly from the front, so they'd have to wear a full face covering like a hockey cage or visor, with a chin strap to keep it on during pitching. That would be pretty cumbersome and pitchers are already super-perfectionists when it comes to developing their particular throw, which is a complex full body motion. Visibility could be an issue too, pitchers are using their extreme peripherals to keep track of baserunners stealing bases, putting more limitations on what kind of helmet/visor could be worn. Personally I think it would take a pitcher being permanently disabled or killed in a game for modern pitchers to consider this or for the league to put in a rule requiring it."
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npmx3j | How does software / firmware physically 'interact' with hardware. | I understand, at least at a superficial level, that integrated circuits contain many many transistors, which act as 'switches' for current flow. By applying a current to the transistor 'base' (or not applying a current), the current flow from collector to emitter can be used together with others for AND, OR, NOR etc, which in turn can be built up to be used for many complex processes. What I don't understand is how the 'program' (software or firmware) can apply this switching signal in the first place. Somewhere there is a physical change- i.e. current is allowed to flow to the 'base' contact on the transistor. How does this happen without a physical switch? What mechanism is in place to allow current to start and stop without a physical interaction? I would love to know in the context of a simple microcontroller, something like an arduino, rather than the complexities of PC. | Technology | explainlikeimfive | {
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"The program is stored as a physical difference. From the moment the software is written to a computer (or read from a disk) it is already a physical voltage in the computer. All that's left is for it to move around via those transistors.",
"Probably easiest to go back to the 8 bit computers of yore... If you are happy with the idea behind how a CPU works. It has a fixed number of instructions each denoted by a particular sequence of numbers. It reads the next instruction from memory. The location it reads from is typically controlled by a Program Counter register. Instructions will tell the CPU to do one of the following: 1. Read from memory to a register 2. Write to memory from a register 3. Manipulate a register 4. Jump to a location (ie: change the value of the Program Counter) The interaction with hardware was achieved in the early days by simply making hardware behave like memory. So writing to location F000 (in hex) didn't write to physical memory but wrote to the Digital to Analogue converter connected to the speaker circuit. Knowing which circuit to activate is done by monitoring the address lines (aka address bus) of the CPU and the R/W (read/write) state. Once the address lines are setup there is a small amount of time during which you can get or set the data. Knowing what data to read or write is achieved by getting or setting the voltages on the data lines. (Aka: data bus) Firmware came about as an abstraction layer. It allowed software to be written that didn't need to know about the physical location of the speaker circuit. Instead it can make a simple call to a firmware function (which is a set of mini programs held in read only memory) Having a firmware means the physical hardware can change without breaking the software that calls it. Which is handy..."
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npn628 | what is the purpose of "folx"? | Other | explainlikeimfive | {
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"Mainly by drawing attention to itself. You write it differently to let people know you absolutely do have trans and non-binary people in mind. But I think that's sort of a faux inclusivity. Because you also imply, that they are not part of \"folks\". It's like \"womxn\". Supposed to be more trans friendly, but really it's just not including trans women in \"women\" again.",
"While the word folks is already gender-neutral, the term \"folx\" is used to specifically display inclusion of gender-queer, transgender and agender folks. In my opinion, it seems to be a non-necessary change."
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npnb37 | How does adding more protons change hydrogen into iron or some other element? | I think it fits both the chemistry and physics tag but whatever. Anyway, how does it work? You have 2 hydrogen atoms together making an hydrogen gas molecule, but the you add 25 particles of positive energy to each of them and BOOM, solid iron. How does adding positive energy changes it? | Chemistry | explainlikeimfive | {
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"“Positive energy” isn’t a thing, unless you’re into crystal healing and chakras. Hydrogen gas is a molecule (meaning it’s atoms bound together). Changing elements is nuclear physics, and we normally just consider atoms on their own. So lets consider one hydrogen atom. It’s a proton (which has positive electrical charge), and will have an electron nearby (negative charge) giving an overall neutral atom. If we add 25 more protons, we’ve made the atom a whole lot bigger, and it’s now Iron. We also need to add 25 more electrons to keep it electrically neutral. Also if you have loads of protons all together it gets unstable, so you also need to add about 25 neutrons to the nucleus next to the protons. Adding all the electrons also means you can do different chemistry than you can with hydrogen. Chemistry is basically just connections between atoms involving electrons. So to answer your question, we aren’t adding positive energy, we’re adding mass. We’re adding protons, neutrons and electrons. Doing that changes the overall mass of the atom."
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npoarb | How can there be dark side of the moon? | So I guess everyone heard that there is dark side of the moon, and that we can never see it from earth. My question is how is that even possible? We are moving with incredible speed alongside the expending universe, then there is earth rotating around the sun, there is earth rotating around itself, and on top of that moon is also sniping around itself as well as around the earth and yet somehow it manages to have perfect synchronization with earth to the very millisecond and millimetre of rotation so that we can never see its other side? What are the chances? or maybe its just natural giving earth gravitation or sth? are all moons like that? | Physics | explainlikeimfive | {
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"The moon is tidally locked so the same side always points at earth. The other side isn’t dark, it goes through the same sunrise/sunset cycle as the side we see.",
"It’s not just coincidence but due to something called tidal locking. The moon used to rotate faster than it currently does and also be closer, at that time it’s rotational frequency didn’t match the orbital frequency and so you could see both sides from Earth as it went around. However like how the moon generates tides on Earth, the Earth generates tides on the moon. This transfers energy from the rotation of the moon into orbital velocity, making it slow down and orbit further out. This continues until no more energy can be extracted, which is when the moon rotates in sync with its orbit. Currently the same thing is happened to the Earth, the tides every so slightly reduce our rate of rotation and increase the moons orbit by a few centimetres each year. If you gave this enough time either the Earth would become tidally locked to the moon, or the moon would escape from Earths orbit depending on the energy involved. We can see and example of this with pluto and it’s ‘moon’ Charon, they are both tidally locked to each other and so the same sides always face each other."
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nppd75 | What is a wormhole? | I'm pretty sure it's been asked before, so feel free provide a link. Preferably easy to read because I'm not native english speaker. | Physics | explainlikeimfive | {
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"Ok, first things first: there is no proof that something like Wormholes actually exists. The only thing wormholes have going for them is, that General Relativity, the best theory of gravity we currently have, does not forbid them, and that some descriptions could, in theory, allow wormholes to exist. However, just because a theory does not forbid an object from existing **does not imply that it actually exists**. Now, that this is out of the way, let's look at the predictions of General Relativity. Bear with me, this might get a bit technical. The conformal [Carter-Penrose diagram]( URL_0 ) of a Schwarzschild Black hole (that is a black hole without rotation and without net charge) maps all of spacetime on a finite diagram. These so-called Carter-Penrose coordinates accurately describe the geometry of the asymptotically flat spacetime outside the black hole (labeled \"Universe\" in the diagram) and the inside of the black hole. However, describing the universe in these coordinates reveals two further regions: one on the bottom of the diagram labeled \"white hole\" and one on the left side. These two regions have never been experimentally observed and are just artifacts of General Relativistic description. The geometry of the white hole would be very similar to that of the black hole, with the crucial distinction that everything within the event horizon must propagate progressively further away from the singularity instead of towards, as in the case of the black hole. That means, everything within the white hole must leave its event horizon in finite time. The region on the left hand side of the diagram similarly shares the geometry of our universe, with the crucial distinction that the time-function t flows in the other direction. If *t* is a time function in our universe, *-t* is a time function in the area labeled \"parallel universe\". It is important to understand, that this diagram does not \"predict\" a parallel universe. It just means, that based on the best theory of gravity and spacetime we have right now, such a parallel universe is not *forbidden*. That is, the geometry of spacetime would allow this place to exist. In the Schwarzshild case, the parallel universe cannot be accessed from our universe. The reason for this is, that lightlike paths (e.i. the paths of objects moving at the speed of light) are tilted at 45° everywhere in this diagram. A consequence of this is, that no observer can follow paths that diverge 45° or more from the vertical line. As you can see from the diagram, in order to pass from our universe into the \"parallel universe\" we would have to follow a path that *is* tilted more than 45° from the vertical line (which would imply faster-than-light travel). Einstein and Rosen have devised a solution of the Einstein Equations that would, in principle, allow a traversion from our universe into the \"parallel universe\". This phenomenon is called the \"[Einstein-Rosen bridge]( URL_1 )\", which are colloquially called **Wormholes**.",
"It is a theoretical area of space which is folded and the two areas of space are connected by a tiny temporary \"tube\" between the two areas of space."
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npqcbe | how does a computer ‘read’ a disk? What exactly is on the shiny side of the disk that is able to be read and over-written by the computer and it’s laser and then play a video game? | Technology | explainlikeimfive | {
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"So Hard Drives, floppies, and most tapes are read magneticly. Think the disk cut like a pizza and then ringed. Each section is magnetically charged. It can be read as a 1 or 0. Lost of 1s and 0s can be converted to data. Disks like CDs and DVDs are a bit different. Think of a spiral groove like on a record. In the spiral there's pits and lands. Basically it looks like Morse code - - - . . - it is also read as 1s and 0s."
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npqei5 | If the timbre of a musical instrument is unique due to the overtones it creates, and overtones are just other frequencies, why do we hear its notes as one unified sound rather than multiple sounds at once? | Physics | explainlikeimfive | {
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"Well even though you can tell of a chord is major or minor etc., you don't really hear the chord as separate notes. The waves of the various frequencies are perceived as one sound",
"Short answer is, because you aren't specifically listening for them. With ear training it is possible to hear overtones to a point. Most easily demonstrated by starting with a sine wave and adding overtones up the series one at a time.",
"Your ear does actually hear the sounds as individual frequencies. However since timbre is very important in identifying what a sound is the brain will interpret these frequencies as belonging to the same sound so it can make sense of it. It is possible to get your brain to interpret the same sound as comming from either a singe or multiple sources but you need to trick it. This is similar to how you can trick the brain into seeing something as either a single or multiple objects. But in general the brain is very good at interpreting different signals as part of the same source so this can be quite dificult."
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nprv0z | How are life expectancies calculated? | I’m for example 32 living in the Netherlands. The average life expectancy is 81.7 years; does that number make any attempt to estimate medical advances during my lifetime? | Other | explainlikeimfive | {
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"No, it does not. Life expectancy at birth uses the current mortality rates *now*, i.e. % chance of dying as a 0-yo in 2021, % chance of dying as 1-yo in 2021, ... Thus it does not apply directly to any generation: if you're 32 today, the relevant information is life expectancy at 32 (i.e. not taking into account mortality before 32, since you did not die!) for your generation: % chance of dying at 32 today, % chance of dying at 33 next year..."
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nprvew | Do humans have innate survival instincts? | Birds innately know how to build nests. Bees can make hives and search for pollen. It’s incredible they just “know” how to do these things. What is the human equivalent? | Biology | explainlikeimfive | {
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"We have lots of survival instincts, from newborn babies instinctively searching for a nipple, to our propensity to pay attention to and protect small, weak creatures with large heads and eyes. We have an instinctual love for water - this sets us apart from our closest cousins, chimpanzees, who due to their denser body structure can not float or swim and have a natural aversion to open water. We have natural love for throwing things - children will throw things given half a chance. To each other, at each other, at anything really. We have a strong natural aversion to the smell of faeces and dead bodies, which sets us apart from animals like dogs, who seem to enjoy the smell. We also have tendency to lean our heads together - almost no other animal does this, and it has been theorized that this helps the harmless head louse spread, which is a sort of inoculation against the much more dangerous body louse. Those are just a few of the ones off the top of my head.",
"The trick with humans is less innate instincts but a more adaptive brain. We also are birthed relatively unfinished, while many animals are basically good to go from the start. But we do have some instincts. The sucking reflex ensures we get milk and the palmar grab reflex is there to hold onto the hair of whoever carries tje baby. URL_0 The feet also have that grab reflex, probably an old thing from when we were apes in trees. One could also argue that our tendency to copy and search for harmony in the herd is an instinct. Our brain overrides these reflexes at a young age. But they do come back in certain brain damage scenarios."
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npryvk | Why is it bad to refill the same plastic bottle? | Chemistry | explainlikeimfive | {
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"text": [
"It is not. It is a psychological marketing trick to increase the sale of bottles. Plastics can leech into the contents (e.g. water) of the bottle if it gets damaged either physically or chemically. But a standard polyethylene bottle will last a very long time when if treated well. Companies have been/tried to have been sued for people using incorrect types of plastic bottles to store thing that they were not originally intended for. Like paint or solvents in old drinks bottles, and this can cause some bottles to degrade faster. So for liability reasons companies also say it's bad, but it's just the standard idiot label. Similar to how a bag of peanuts has a warning that the bag contains nuts. Long story short, it's a marketing trick masquerading as a liability trick, in turn masquerading as a health issue. Be smart, refill your bottles, help stem the plastic tide!",
"It isn't. But the bottle has an expiring date and after that it could be possible that the plastic is weakened and pollutes your water."
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nps255 | How did pigeons/crows that were used for sending messages back in the day knew where to deliver it? | I don’t know if this is a stupid question but I’ve always wondered how they knew where to take the message to. How did they train these birds? | Earth Science | explainlikeimfive | {
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"Pigeons naturally remember where their nest is, and are able to find it by navigating the Earth's magnetic field. In order to send messages, you kept pigeons /away/ from home, and then released them. For example, imagine I am your friend. You want to be able to send me mail by pigeon. So I give you a couple pigeons I raised in my house, and you keep them in cages at your house. When you want to send me mail, you attach it to a pigeon you got from me, then release it. It will find its way home, which is where I am. And I get your letter! That is, unless the piegon gets eaten on the way here...",
"Crows are not used to send messages, only a type of pigeon called a homing pigeon. They don't know where to deliver messages, they only know where there home is (hence the name homing pigeon) so if released, they'll fly home and not anywhere else. If you live in New York and want to send a message by pigeon to Chicago, you need a pigeon that was born and raised in Chicago. Once it's home, it needs to be transported to some other location so it can fly home again.",
"Pigeons are very good at finding their way home. It come naturally to them. So if you take a pigeon born and raised in place A to a different place, it'll be able to fly back to place A pretty easily and quickly. Now all that's left to do is attach a small note with a message, and you have a messenger pigeon. I don't think any other bird has ever been used for this purpose outside of fiction, though."
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npsi0e | How is text to speech generated? | Technology | explainlikeimfive | {
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"The first thing you do is make a voice bank. In most cases this means recording someone say a whole bunch of words and sounds in different ways. Then you have to make a program that can look at text and pick the right sounds from that voice bank. Often this will just be a one to one word match, but for words that weren't put into the voice bank, the program needs to be able to break that word up into its individual sounds (phonemes) and then fetch those sounds from the voice bank and string them together to make them sound like one word. This is what's happening when a satnav mispronounces a place name - the program has misunderstood the sounds of the text it's reading. Because this is quite unreliable, the voice banks that sound most human are the ones with the biggest catalogues of words, generally speaking, so that they can avoid having to construct words from phonemes as much as possible. Many modern voice banks also figure out the intonation of the sentence and pick and morph the words to match that intonation instead of getting a flat, robotic tone."
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npsqls | How does a car's fuel gauge know how much fuel it has? | Other | explainlikeimfive | {
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"text": [
"a small float sits inside the tank connected to a resistor which is connected to the battery, the lower down the ball the higher the resistance sending a higher or lower electrical signal, letting the car know how much is there."
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npt7tu | Why do computers/art programs still have problems with sorting colours, even when they have explicit options for it? | Technology | explainlikeimfive | {
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"For a computer, a color is a number. Traditionally they are stored as their Red-Green-Blue values, let's say \"0\" meaning none of that color and \"255\" meaning as much as possible from this color. If you now tell the computer to sort by color, it will simply sort by number. Since red is the first part, it will first have all the colors with no red in them, and at the very end those colors with a lot of red in them. That means that in between \"no red, a little green, fully blue\" and \"no red, quite some green, fully blue\" there will be other colors like \"no red, a little more green, no blue at all\". This makes sense for the computer, but looks awful to the human eye. The question you need to ask is: How do you sort colors objectively?",
"This is a very complex subject. Color, as perceived by most humans, is a mixture of four types of excitations, one for each of Red, Green, Blue, and non-colored brightness. Of course, these regions [overlap]( URL_0 ) and that complicates matters further, but let's ignore that. The thing to realize is that \"color\" (as seen by humans) is 4 dimensional (note, this can vary between 1 and 5). Four dimensional things are hard to imagine, so let's ignore the rods, leaving a 3D color space, which we can model as a large cube made of regular dice. How do you draw a 1D line through that 3D cube in a way that \"seems right\" to a person's subjective experience of which colors are close to each other? No matter how you draw the path through the dice (and I encourage you to play around with various ways to do this), there will always be dice (colors) that are nearby each other in the larger cube, but yet far apart on the 1D line (sorting). In short, there is no natural sorting of colors, so all sortings have problems of one sort or another. We can even throw out computers, people have the same issues. Imagine being in an art class and being asked to design a color wheel. Now you're projecting the 3D color space onto a 2D canvas, how do you do that? One common solution is to make a circle with the colors in rainbow order. But where on this wheel is brown? Brown isn't there, because the rainbow order circle does the 3D to 2D projection by eliminating brightness information and brown is secretly just a different name for dark orange (seriously). By a similar token, almost none of the colors of a sunset show up on the wheel, if you had a paint of one of those colors, where would you put it? Somewhere between yellow-orange and blue-purple? Problem is, those colors aren't next to each other on the wheel. Okay, so the wheel is bad, but so are all other projections, because fundamentally the projection from higher to lower dimensions loses information in a way that directly experiencing the colors does not."
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nptfj3 | why does ice form on meat when defrosting in a metal bowl with water. | I usually thaw frozen meat in steel bowls, full of water. After a while, when you flip the meat over there is a large chunk of ice that forms on the bottom. How is this happening? | Physics | explainlikeimfive | {
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"text": [
"If the meat is considerably below the freezing point of water, it can freeze water that’s contacting it. Tiny ice crystals will form on all sides, but the ones that form on the bottom can’t immediately float away and melt again."
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nptito | How are 'dark numbers' (in e.g. crime statistics) calculated? | Other | explainlikeimfive | {
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"text": [
"It depends very much on the specific statistic. However for unreported crimes it's fairly simple, at least for the UK. There's a survey conducted called the British Crime Survey. (I assume this doesn't include Northern Ireland; I'm not sure if they have their own equivalent.) This survey asks people if they think they have been a victim of a crime, whether or not they reported it. Now of course there are still problems with this - eg. people may not understand exactly what is and isn't a crime, or they might be reluctant to talk about certain experiences. There are also gaps - eg. crimes with no immediate victim (like drug smuggling) or crimes that don't direct affect individuals (like some kinds of corporate fraud). However it generally gives a more accurate picture of actual prevalence of most crimes than reported crime figures."
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nptuq2 | Why is upload usually much slower than download? | Technology | explainlikeimfive | {
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"text": [
"In simplest terms it's just a commercial consideration; most people are consumers of data hence their bandwidth is down and rarely up. It would be wasting limited bandwidth guaranteeing a fast upload speed that's rarely, if ever, used. Those who need a lot of upload capacity are, largely, businesses or content creators of some kind. Therefore they'll be offered different rates to consumers that unlock faster uploads (and will have the capacity, and desire, to pay for it). In simple terms it's a 'fake' throttle but a reasonable one I guess.",
"The signals can only physically transport so much data, and *most* people tend to download way more than they upload. So they need faster download speeds and the companies have structured their systems around that. With fiber optic it is a moot point, the speeds are the same just because of how that technology works."
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npu8ut | Why do we not feel pain while asleep? | For instance ive recently injured my elbow from a bad fall it is extremely painful to the touch, but when I sleep Ive noticed Im not woken up by the pain. I usually toss n turn a bit in my sleep so theres no way Im not rubbing or bumping my elbow to some degree. | Biology | explainlikeimfive | {
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"I'm glad you aren't feeling any pain from your elbow while you sleep, but I've been woken up by pain plenty of times.",
"You do. You just don't remember it later, because you don't form memories while sleeping. This is just like how anesthetics likely work."
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npv5c7 | Why do we squint when we try to focus on something? | Shouldn't it make it harder to see or do we do it to block out anything outside the focus-area? | Other | explainlikeimfive | {
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"The smaller the iris (or aperture on a camera), the less critical the lens/focusing needs to be. A pinhole camera has such a small opening that it can focus without a lens at all. Our eye focus is not always correct for whatever reason so squinting will always make things sharper. The trade-off is that it also gets darker as less light can get in.",
"[Link]( URL_0 ). TLDR: it changes the shape of your eye and blocks some of the light so it’s less scattered.",
"Squint does two things. Blocks unnecessary light from flooding your eye, making it easier to see the thing you want (like lowering the sunvisor while driving a car) Secondly, the gengle compressions compresses the eyeball allows the eye to focus on items typically too close or two far away. This will happen naturally, but you don't really think about it."
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npvazy | How does the internet work in practical terms? On what does it rely physically? | Technology | explainlikeimfive | {
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"text": [
"Physical computers. When you visit a website, it's essentially a set of files and scripts that you download and run locally on your computer. Those files are stored somewhere in the world on a server. A server is basically a big storage computer. Ie. it's not used by a person for personal computer stuff, it just sits in a big room full of other servers holding files. When you type in a web address into your browser, it sends that address to a DNS server. A DNS server is kind of like a phonebook for the internet. You ask the DNS server \"send me [www. URL_1 ](https://www. URL_1 )\" and the DNS server tells your browser the address of a server that holds the files for [ URL_1 ]( URL_0 ). Now that your browser knows where those files are, it gets in touch with the webserver that holds those files and downloads those files to show you in the form of a website. In the early days that was all a website was really. A bunch of text and pictures plus instructions for how to showcase these to you. Modern websites are a lot more interactive. Some websites don't just send you files and text but also scripts that run locally on your computer. Some websites run software on those servers. That way you can send a request for a website, but you can also send a request for the server to do something for you. Like, find a book on amazon. As you can imagine, it takes an enormous amount of servers to store all of the content on the internet. All over the world, there are cavernous halls filled with servers. Many websites are stored in several places all over the world so that DNS server, that phonebook, can direct you to the nearest one for the fastest server. But when you get right down to it, the internet is just a bunch of computers full of files and scripts with a clever system for making it possible for you to retrieve those files from all over the world just by asking for them using your phone or laptop.",
"The Internet relies on data sharing agreements between commercial telecommunication providers, and government providers in some countries. You subscribe to a particular Internet Service Provider (ISP), and your computer sends data to them. They share it with the other ISPs to allow it to travel to the ISP serving the site you want to visit, who provides it to the servers running the site. Returned information follows a similar path back to you.",
"The internet is a giant “network of networks”. So, what is network and how can you build your own internet? Imagine you want to connect your computer to another one. In its most basic form, you just put a cable between them and that’s it. Congratulations, you’ve got a network!. Add some networking code and both computers can now send and receive data from each other. Soon you realize that it would be cool to have all of the computers in your house connected. You could connect every computer to every computer, but the amount of cables would grow exponentially by each new computer on the network (since each computer would have to be connected to every other computer). You realize that this would be much better if every computer were connected to a single device that handles the data routing between each computer. Lucky for you, somebody has already created such device. It’s called a “router”. Even more, since having cables all around is annoying, this router comes with WiFi, which works the same way as cables but uses invisible radio signals instead. Now you have your whole house connected together! But what would happen if you decide to go even more ambitious and connect your Router to your neighbor’s router? Well my friend, now you’ve got a “network of networks”. The computers on your network can send and receive data from your neighbor’s computers. Now let’s take this further, shall we?. Let’s put a bigger router on the street and connect the routers of each house to it. And why not make a giant router for the whole city and connect each street’s router to it? You can now see how the “network of networks” starts to grow. Add a giant Router per City, State, Country, Continent and connect them together and you’ve got the biggest network of all: the internet. With this approach, you can now send and receive data from every computer in the world. To facilitate this process, you probably have an ISP (Internet Service Provider) that gave you a router and handles the connection between your house and a more general network. Interestingly, there are ISPs of ISPs. So there are consumer oriented company’s that handle this kind of domestic usage for you, and then there are other company’s that handle connections between country’s in the other end of the spectrum. The wider the scope of each network, the more data it has to handle. So you are gonna need way bigger cables and routers for handling the connection of a whole City in comparison to the ones in your house. Further more, you can make multiples routes between two networks in case one of them stops working (for example if a cable breaks). Bonus: When you visit a website (which is just one usage of the Internet, as a more general thing), your computer goes network after network until it reaches the computer where the website is located. The website itself is just some files, code and data in another computer. How big sites like Google, Netflix, Facebook etc, handle huge amounts of data and deliver them super fast to your house anywhere in the world is a whole engineering problem to solve, but the general idea remains the same. Bonus 2: In case you were wondering how mobile networks like 4G work, they function very similar in essence as a giant WiFi."
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npvtnd | "According to all known laws of aviation, there is no way a bee should be able to fly. Its wings are too small to get its fat little body off the ground. The bee, of course, flies anyway because bees don't care what humans think is impossible." So, how DO bees fly? | Physics | explainlikeimfive | {
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"text": [
"That's a decades-old myth that doesn't hold any water. People do know how bees fly, and they do not defy any laws of aviation. You can read more about the origins of the myth and the actual science to it here URL_0",
"If you think of bees as tiny little airplanes, then the math doesn't work and they shouldn't be able to fly. The flaw in that concept is that bees are, obviously, not tiny little airplanes. Bees don't fly the way that airplanes do; bees fly the way that bees do - by flapping and rotating their wings at the same time.",
"This idea was based on an incorrect model of how insect flight works (obviously, as they do fly!) It was later realized that bees actually get two pumps out of their wings with each beat. They push their wings back, then rotate them and pull forward at a new angle so they're still pushing down. It's kind of like how you'd move a knife to smooth icing as you sweep across a cake in both directions. I'm sure there's a lot more involved in the ways bees fly, but this was one thing we didn't notice initially that helps to explain how they do it.",
"By not using the laws of aviation. Don't know why anyone would think it'd be a good idea to apply the laws of mechanical flight to a biological creature. bees fly by moving their wings up and down and rotating and twisting them while doing so. This creates enough lift for them to fly even with heavy loads of pollen. Nothing mysterious about it."
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npwe1a | what caused back injury when lifting something heavy in the wrong way? If we over work other muscles it’s just sore for a few days. Also, how does a weightlifter’s belt prevent injury? | Other | explainlikeimfive | {
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"The back is mechanically complex, and there are lots of ways you can injure it. What you are probably thinking about is a ruptured disc. Think of your spine as a stack of tuna cans, with squishy bags of jelly between each pair. Your back can bend because the jelly squishes, and the bags are stretchy. If you put too much force on the stack though, the bag will break, and the jelly will squish out. Now your cans get closer together - that space is used to allow your nerves to branch off from your spinal cord, and if they get pinched, you've got major pain. The weightlifting belt helps with this. Your spine isn't the only thing that supports the weight. Your abdomen does as well, like a big inflatable bag. Your body wants to increase the pressure in that bag when you are bearing a lot of weight - this is why you hold your breath and bear down when you lift something heavy. The belt helps maintain that pressure, which supports your spine and prevents injury.",
"The muscles help to stabilize the spine. Picking up by bending over and or twisting can cause the “cushion” in between your vertebrae (bones that make up your spine that incase all your nerves (how you feel pain)) to bulge out of place. When this happens it can pinch the nerves. This is a pain that even oxycodone can’t help. Nerve pain can be completely disabling. The back brace helps to support your lower back more than just your muscles can and causes you to have to squat vs bend and also keeps the natural curve in your spine. Core exercises and proper body mechanics are the key to keep back injuries from happening. I spent the last several weeks on painkillers and steroids so I could walk again after a L4 bulge( bulge, herniated disc and slipped disc are used to desribe the same injury) Didn’t really do anything specific to damage it. Just some yard work, moved a bunch of mulch and concrete pavers and then sat with bad posture, once it becomes inflamed it just keeps pressure on the nerves, pressure on the nerves makes it more inflamed, Just gets worse. Some people recover on their own, some people don’t. I hurt for two weeks but it was bearable, then painted my sunroom. That night I hurt so bad I almost called an ambulance. I couldnt walk at all and ended up in the emergency room that morning. Just layed on the floor biting down on a towel screaming every time I moved. Also, since it is your spinal cord it could pinch a nerve that causes terrible pain further down your body along with the back pain. I had a slipped disc in my upper neck a few years ago ( I’m 38) and it made it to where I could barely move my arm. Most people with a lumbar injury( lower spine) have pressure on the sciatic nerve which runs down your leg all the way to your foot, (known as sciatica ) that shit sucks."
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npwp5j | How do eggs work? How come sometimes a chicken lays "normal" eggs that we eat, and how come sometimes it lays eggs with a baby chicken inside? | Biology | explainlikeimfive | {
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"When a hen has access to a rooster, she can lay fertilized eggs. When she doesn't she lays unfertilized eggs. Egg farmers scan all the eggs that are laid, and sell the unfertilized ones in the grocery store. Fertilized ones are hatched, and the chickens sold/used to grow chickens for meat."
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npx0j7 | how stuff gets buried over time. Like shipwrecks get buried so deep in sand that they need to be dug out, and ancient artifacts and ruins tens of meters underground. | Earth Science | explainlikeimfive | {
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"A lot of things gets burried in themselves. The roofs and walls of buildings collapse over the foundations trapping whatever is inside under rubble which turn to dirt when it decays. The upper decks on ships will also collapse down over the rest as it decays. In addition the wind blows sand that have eroded from mountains over the ruins where they are deposited. Rivers floods bringing inn silt and mud covering the ground and the ocean floor. The ocean currents push sand around and even onto beaches. This is how things gets covered over time. Places which do get covered tends to get covered more and more over time while places that gets uncovered and eroded tends to get eroded more over time. There are plenty of shipwrecks and ancient cities which have been just destroyed by the elements due to their locations. We have seen huge container ships run aground against cliffs and have been turned to dust by the waves in a few short years along with the cliff faces around it. But these are not the type of ship wreak we uncover a century later."
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npx1fr | Hawking radiation | So I need to do a presentation about Stephen Hawking tomorrow. I have his life pretty much down but since its for physics I also will need to explain a bit of Hawking radiation. If anyone could help that would be great. | Physics | explainlikeimfive | {
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"According to Quantum-Field-Theory the vacuum is filled with random creations of particle and antiparticle pairs that immediately destroy each other again so we don't notice them. But near a black hole the gravity gradient is so steep that one particle can get absorbed while the other gets away. Simply by conservation of energy the black hole has to lose some mass for the particle that was just created and doesn't have a partner to annihilate with. So these particles fly away from the black hole taking some of it's mass with it. That is the hawking radiation.",
"If you have a string, it can have certain kinds of vibrations along it. If you hold that string fixed at a certain point, certain kinds of vibrations (the ones that involved the string moving around at the point you're holding) are forbidden, so the vibrations around it will change accordingly as those modes die out. This is how string instruments work - you hold the string, and as a result only higher frequency vibrations are allowed when you pluck it. A quantum field is not a string, but it is a continuum with waves that can propagate and vibrate, much like the vibrations along a physical string (but in 3D). The black hole event horizon acts like your hand - the field is cut off from the field inside, so these vacuum vibrations have to change in response. It turns out that some of the resulting vibrations look like particles leaving the black hole. Interestingly, a lot of these vibrations are quite far from the event horizon - most of the particles originate within a few times the black hole's radius, not directly at the horizon. Now, I'm sure you know that quantum theory and general relativity are not compatible, and this is an attempted fusion of them. This makes the prediction slightly controversial. However, for big black holes, the gravity at the event horizon as actually pretty weak (at least by the standard of what goes on inside), and weak curvature make fusing the theories much easier. So this is seen as a relatively reliable prediction. I should note that the common picture of virtual particles is not taken that seriously. Virtual particles are not really first-class objects of quantum field theory, they are a mathematical tool to analyze vibrations in the field. Indeed you do get this picture of negative-energy particles falling into the black hole when you apply the trick, but it is the field behavior and the eventually observed real particle that are actually fundamental to the theory."
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npx4se | what happens to vaporised rock? Scientists always say that X amount of tons of rock vapourise when a meteorite hits. But where does it go? | Earth Science | explainlikeimfive | {
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"At first it is spread through the atmosphere like any other gas. But eventually it does start to cool down. As it cools down the rocks will start to condensate into tiny droplets smaller then grains of sand. They are small enough for the wind to carry them along. Eventually they will end up on the ground in some form or another like all other sand. But depending on how much there is a lot of it can still be in the atmosphere spread around the world for months. The closest we have to this effect we have experienced is during volcano eruptions when similar vaporized rock might be part of the eruption and create huge dust clouds or even clouds of tiny droplets of molten rock. There is even one famous airliner which ended up flying through such a cloud of molten rock."
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npxbe1 | How Does Venus still have an atmosphere if it doesn't have a magnetic field? | I've googled and read several articles and/or explanations and I'm still having trouble understanding. How does Venus still have an atmosphere without a magnetic field like Earth? Especially when Mars lost its atmosphere precisely because it doesn't have a magnetosphere either? | Physics | explainlikeimfive | {
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"It does have one. It's just a lot weaker than ours. But to really answer your question, the atmosphere itself generates a much stronger one. The ionosphere reacts with solar winds and generates an EXTERNAL field. It's not as protective as ours overall, but pretty freaking cool",
"There are several things working in the atmosphere's favor. 1. Solar wind interaction with the dense atmosphere does create a magnetic field, albeit a much weaker one than the one protecting Earth. That helps mitigate a lot of the losses. 2. The atmosphere itself (mostly CO2) is of a much higher molecular weight than just O2 and N2. This also aids in mitigating the losses as it is harder for these gasses to escape the atmosphere with it's fairly large gravitational pull compared to Mars or Mercury. 3. There is a lot of volcanic activity on the surface. This activity creates more atmosphere which helps replenish what is lost."
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npxnqg | After drinking lots of water in one sitting, why do we urinate little and often, instead of all the water at once? | Biology | explainlikeimfive | {
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"The process of liquid through the body is as follows. Though the mouth, to the stomach, to the small intestine, to the large intestine, to the blood stream, to the kidneys, to the bladder. Then out through the urethra. Once a lot of liquid enters your system your body knows it has more than it should/ it needs. So your kidneys kick on and start filtering excess liquid out of the blood. Your body knows itll be doing this for a while so you need to urinate. however your kidneys are the \"bottleneck\" in this system. And can't actually filter at the rate you uptake liquid. So you can't just piss it all out at once."
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npxz1y | how indoor plants became indoor plants when at one point in time there was no “indoor” | Biology | explainlikeimfive | {
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"They live outdoors in the environment they come from they're only indoor plants in environments that are not the same as where they come from",
"Indoor plants are called as such due to their nature that they don't require glamorous amount of sunlight. Commonly called as shade plants, they thrive more under the shade. And I'm pretty sure there have been sources of shade in nature for them to evolve that way.",
"“Indoor plants” are just plants that have been put in a pot and moved inside. You can grow almost anything inside if you know what you’re doing and manage it properly. There are full-on indoor forests in some very large atriums. The point is that there’s not necessarily anything special about these plants. However, much like with dogs, some plants have been selectively bred to achieve a specific criteria (light, water, care requirements, size, etc.) that make them better houseplants. This is artificial selection, though, and doesn’t”t happen under natural conditions.",
"Its typically when the plant is being grown outside of it's normal climate. For example, if I took a plant that's used to growing on the forest floor in the Pacific Northwest, its going to have a hard time growing outside in south Texas. If I moved it down there, I keep it as an indoor plant so that it doesn't get fried in 100°+ sunlight."
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npybls | When we send messages and posts in places like a Discord server, where are they stored? Will we ever run out of space? | Technology | explainlikeimfive | {
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"They are stored on the server of whichever messaging platform you're using. Discord, Facebook, and any other service has server space where they store everything you send. To answer the second question, probably not. They will just buy or build more servers."
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npyjr7 | why does wine go bad when exposed to air, but when air gets through the cork in tiny amounts it ages? | By this logic, opening wine would age it...but the flavours don’t develop like they do from real aged wine.. | Chemistry | explainlikeimfive | {
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"You got something backwards in there. It's doesn't get O2 through the cork, it gets O2 FROM the cork. It's a finite amount of oxygen contained withing the compressed cork itself, thats why they seal the bottle with wax or a metal wrapper outside the cork. You want a little O2 for the nice slow oxidation of compounds in there to age properly, but once it's sealed the outside air isn't getting in. Letting it breathe when it's open aims for a different reaction with other compounds, and its much more dramatic. But let it go on too long and the wine will be real nasty. So both aging and breathing aim for oxidation reactions, but different compounds at different rates for different goals."
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nq0bzu | How can sugar act as a preservative when it feeds bacteria and mold so readily? | Biology | explainlikeimfive | {
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"If you have enough sugar or high enough concentration, the bacteria/mold can’t survive. Water (technically, all solvents, but water is the liquid in question) undergoes osmosis, which means that it tries to flow across membranes from areas of high water concentration to low water concentration. It will continue flowing until the concentration on both sides of the membrane are equal. So if a bacterial/fungal cell lands on a bed of pure sugar, the water will flow out to try to equalize the sugar concentration. This is basically impossible, so the bacterial cell ends up losing all its water and dying.",
"Sugar is hygroscopic that means it absorbed moisture from the surroundings. The result is if you have a high enough sugar concentration like in honey it will suck out moisture from bacteria and fungus (mold is fungus) cells. They can no longer grow because they like all líving things need water for the cells to function. So if you mix sugar with water it is the perfect food for bacteria but if there is not enough water the sugar might instead kill the bacteria.",
"It is also hydrophilic meaning it absorbs a large amount of water. Once moisture levels drops to a certain level it will preserve food.",
"Too much of anything is a bad thing. While bacteria would love some tasty sugar, most organisms would rapidly dehydrate in a syrup. Osmosis would pull the water right out of them"
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nq1df6 | I have read that steel manufactured before atomic testing began is sought after for various purposes because it isn’t tainted by radiation. How would steel that exists on the surface be less affected by radiation than iron deposits in the ground? | Physics | explainlikeimfive | {
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"The iron deposits we find in the ground is just fine. Even refining the iron ore to iron metal does not contaminate it, mostly because this process uses fossil coal. The problem is that converting the iron to steel involves pumping compressed oxygen into the molten iron to make it react. And the compressed oxygen is made from the atmosphere and is therefore contaminated with various different isotopes. Most notable small quantities of cobalt-60 which binds to the iron in the steel.",
"As part of the process of turning ore into steel we heat the ore up incredibly hot and then \"blast\"(which is why steel is produced in a blast furnace) air through it which causes the oxygen in the air to react with and carry off some of the impurities like carbon. When you're \"blasting\" air through you're also depositing some of the elements that are floating around in the air. That means that Trace radioactive elements put there when we detonated nuclear bombs are deposited in the steel",
"In particular they're talking about steel in ships made - and sunk - before the various atomic bomb tests in the late stages of WWII and thru the 50s. Water is a reasonable absorber of radiation from atmospheric nuclear bomb tests, so the steel that is already at the bottom of the ocean would have gotten very little if any of the radiation. Note that we're obviously talking about the ships that were deliberately blasted by nuclear bombs on the surface and _then_ sunk, like at Bikini Atol; those received _quite a bit_ of radiation."
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nq1lfz | When do plants release oxygen during photosynthesis | If plants need glucose and oxygen for cell respiration how can the plant afford to release oxygen? | Biology | explainlikeimfive | {
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"Not all glucose gets used in respiration. Much of the glucose is turned into structural material. Just like us, plants grow, and the mass for that growth comes from food. Plants happen to make their own food through photosynthesis. So the plants “exhale” oxygen when photosynthesizing, and then use some oxygen when respiring. But since not all glucose goes into respiration, not all of the exhaled oxygen gets used."
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nq1uok | Why is cranberry juice the go-to recovery drink after donating blood? Is there a science-related benefit over apple or orange juice following a donation? | Biology | explainlikeimfive | {
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"The main thing is that you want both fluid and sugar. The benefit to cranberry juice is that it's more shelf stable than the others. In many cases it's cheaper as well. Often, however, they use whatever juice they have on hand.",
"Fun fact: in Austria (outside a pandemic) you get a choice of sparkling water, cola, or grape juice (both unfermented and fermented), plus a snack. But I've never seen any apple, orange, or cranberry juice. So probably no blood-related scientific reason.",
"I’ve only ever seen orange juice, so maybe it just depends on the organization/location you donate.",
"I've donated blood eight times and they gave us orange Hi-C every time. It's been like 15 years since I donated, so maybe the science changed, but I've never heard about cranberry juice being the thing to drink after donating. It seems like a poor choice because people need fluids and sugar then and most people don't even like cranberry juice. I think it's gross."
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nq28fw | Charcoal vs. burnt food - carbon | What’s the difference between burnt food and charcoal? Wouldn’t they both be carbon? Charcoal is good for you, but burnt food is bad. Why? | Chemistry | explainlikeimfive | {
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"Charcoal is carbon formed in the absence of oxygen, whereas burnt food is oxidized. Burnt food isn't super unhealthy to eat, you'd have to eat a lot to make you sick, but in general you want to avoid [oxidative stress]( URL_0 ). Charcoal isn't necessary healthy on it's own, either. It absorbs things quite well, so if you're healthy, eating it will just cause it to absorb whatever you ate, not terribly helpful. However it's great if you accidentally swallow something poisonous or toxic."
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nq2bz0 | How are phone numbers created ad why do they need a country code? and wont we run out of phone numbers eventually? what happens then? | title says it all. I've been starting to wonder about how phone numbers work. Also could i create my own number with it's own country code? | Technology | explainlikeimfive | {
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"In order to receive phone calls all the phone systems in the world needs to configure their systems to route calls to your phone number in the right direction. It is too much to expect to have all the phone systems in the world add all phone numbers in the world to their configuration. So instead we have a system where the phone systems only need to look at the first digits to know roughly in which direction it will need to route the call. The country codes are defined by the International Telecommunications Union. The country code +1 is assigned to the Federal Communications Commission but they work with similar agencies in neighboring countries. Other countries have longer country codes. The numbers are further divided into several area codes. There have actually been some cases of countries running out of phone numbers. Or more commonly they make a system of phone numbers which does not work as the population changes. The thing is that there is no limit to how long a phone number can be. Some systems have technical issues with long numbers but there are phone numbers in use today that are over 15 digits long. And the FCC have reserved several area code for various changes to the current system.",
"a phone number is just a string of digits, from 0-9 inclusive (meaning it includes 0; there are 10 digits here). Phones in the US use 7 digits, without the area code. That means there's around 10 million possible phone numbers. Once you include area codes, that maximum number of phone numbers increases to 10 billion, because there's 10 digits. This means the US has more total phone numbers than there are people alive on the earth, on a technical level. Outside of that, things get a bit awkward when you consider global phone numbers. Because there's some countries like India that can have 13 digit phone numbers; and then some small island nations that barely need more than 4 digit phone numbers, just because of differences of population & size. You most likely couldn't create your own number with it's own country code, by yourself, without a lot of effort for it to get recognized by the global telecommunication companies - and even if you did, they'd probably charge some massive fees that wouldn't be respectably \"possible\" for a single person (nor would it be \"worthit\" if it were for just a single number, on their end)."
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nq2vn6 | Why do we use such complicated methods to execute prisoners? Can’t we just give them a handful of sleeping pills? | Other | explainlikeimfive | {
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"Well sleeping pills are terrible at killing people for one. Usually you need something like alcohol to compound the effects. In the end result it's still not a pretty way to go, I'd prefer a bullet to the head. The idea behind the drug cocktail used is to anesthetize the victim first and then kill them. It's debatable how well it actually works. I personally would probably choose a shotgun to the head over the chance of being paralyzed, aware, and slowly choking to death since I can't breathe anymore. Also keep in mind that's not the only method used. New Hampshire and Washington allow hanging. Mississippi, Oklahoma, and Utah allow firing squads. Electric chair is allowed in Alabama, Florida, South Carolina, Kentucky, and Tennessee. Ultimately we use a the lethal injection as a way to try and pretend it's a humane death. It's just to assuage the guilt of pro-death penalty advocates and the executioners themselves. There's no other reason. As if that somehow absolves killing someone.",
"Cruel and unusual punishment Many of the \"traditional\" methods of execution such as the electric chair or firing squad could be considered less humane or cruel methods of punishment because they can cause unnecessary suffering. Being shot for example doesn't necessarily kill you instantly. The US doesn't intentionally torture its prisoners either... unless you're unlucky enough to be in Guantanamo. Lethal injection occurs while the person is anesthetized so they don't feel and pain or panic during the process. However there have been a few notable incidents where it was botched. Personally I would probably prefer to be hanged or have a .45 cal bullet through my brain. Interestingly though hanging is still on the books in the US as a means of capital punishment, predominantly in the military. The last person to be hanged in the US was in 1996, and the inmate chose that means over lethal injection. Contrary to popular belief hanging does not cause you to slowly choke to death, when done properly it breaks your neck and kills you instantly. Perhaps the most famous people to be hanged in the 20th century were the inmates of Spandau prison, ie the Nuremberg Trial Nazis.",
"Most widely available \"sleeping pills\" are formulated to be less toxic than, say, the barbiturates of the 1940's and 50's. Taking enough to reliably kill you is chancy and unpredictable. However, it is a mystery to me why (assuming that we want an option for state-sponsored killing at all) we don't simply use opiates. A large enough dose of morphine, administered gradually by IV, is guaranteed to kill anybody. And it not only doesn't cause pain or agony, it puts most humans into a blissful state. Some might experience transient itching or nausea, but as the blood level increases, those symptoms disappear. Morphine is readily available, effective as a single agent, and easily administered. And if the idea of death row inmates being allowed a moment of bliss makes people uneasy, then nitrogen inhalation also rapidly leads to death with neither pain nor pleasure involved. In my opinion, the state should not be forcibly ending any human's life. But if a prisoner prefers death to, say, life in prison, then they should have access to a simple, cheap, foolproof means of ending their life.",
"Taking a very cynical view: The “complex” forms of execution with multi-stage drug cocktails are done to make it look less like an execution and more like some sort of medical procedure where the “patient” dies on the table. We have a lot of quick and effective ways of executing people, quicker and more reliable than an intravenous drug cocktail given by an untrained prison guard who botched finding a vein. But they *look* like deliberate killing. Shooting, gassing - both quick and effective. As violent as a firing squad is a half dozen rifle rounds to the chest and there’s seconds on the clock before the person is dead. But it’s messy and is very clearly an execution. Similarly - flood a gas chamber with CO and the condemned will fell mild nausea for a few seconds before passing out. We know this because it’s what people who have narrowly survived CO poisoning have reported before they passed out. Similar effect with replacing Oxygen with Nitrogen for a low oxygen chamber - there are very few symptoms, none painful, with mild nausea being the most severe, for ~20 seconds before unconsciousness kicks in. But again - this is very clearly an execution. Instead we strap people down to something that looks a bit like an operating table and have someone carry out what looks like a clinical medical procedure."
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nq36h5 | how do pregnancy tests work? | Biology | explainlikeimfive | {
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"When someone is pregnant they produce a hormone they would not produce otherwise, you can find that hormone in your urine so pregnancy tests have something that reacts when it spots that hormone in your urine and something that tells you when the reaction was spotted."
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nq37fs | What are the small bumps around our nipples for? | Biology | explainlikeimfive | {
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"text": [
"Those are [Montgomery glands]( URL_0 ) that secrete oil to keep the nipple lubricated."
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nq4ios | If radio waves and visible light exist on the same spectrum, why can't you tune a transmitter to get it to shine? | Physics | explainlikeimfive | {
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"Your antenna isn't efficient at generating waves that small. Antennas are optimized for a certain size range. AM antennas are big and transmit around 1 MHz which is waves around 300 meters. FM antennas can be much smaller and work around 100 MHz / 3 meters. If you tried to get an antenna that's good at broadcasting FM to instead broadcast 2.4 GHz for WiFi it would do terribly and you'd barely get any signal out no matter how much energy you pumped in. Similarly a microwave antenna is meant for 300 MHz-300 GHz, trying to get it to blast out Near IR at 400 THz is going to be terribly inefficient, and trying to get it to generate blue light at 770 THz is going to be even worse You instead need to use transmitters and antennas optimized for the frequency you want to work with, its incredibly hard to build anything that can work effectively across an order of magnitude, let alone 6 (300 MHz to 400 THz)",
"Pump enough power into your radio transmitter and it'll eventually glow. That said, it's from internal resistance heating due to the massive current load, and nothing to do with the antenna performance itself. It's like saying the resistance coils on my electric cook top are better transmitters than an FM radio because they can transmit from nothing, all the way up to visible light. Completely different physics, and now I'm spending too much time explaining a bad joke so I'll just stop."
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nq58qb | Why does our body shake when we’re scared or nervous? | Biology | explainlikeimfive | {
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"Adrenalin surging through your body and your muscles twitching in response to the excess of the fight or flight chemical.",
"Your body is evolved to consider only one kind of threat: something trying to eat you. What do you need to be prepared to do if something is trying to eat you? Kill it or run away. How do we prepare for that? Get those muscles primed and twitching with a rush of adrenalin!"
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nq69qq | How people in space age slower than people on earth if time on earth goes slower than the time in space? Shouldn't it be the other way around? | Physics | explainlikeimfive | {
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"There's two competing versions of time dilation when you go to space. 1. Special Relativity- that says that the observer who is moving has a slower clock. The faster they move, the slower the clock. 2. General Relativity- much more complicated, but the overall effect is that close to a huge object, time slows. The closer and huger the object, the slower the clock. When someone talks about time dilation, they often are *only* referring to the special relativity version, as introducing GR is confusing. In the specific case of a GPS satellite having to accommodate for both, GR has a larger effect, so the clock of a GPS is ever so slightly faster than an equivalent atomic clock on Earth. If the satellite were moving faster, or the Earth less massive, it would be different, and SR would dominate.",
"You're mixing your frames of reference here. Time runs slower on Earth than in free space (like the area between galaxies) because the Earth's gravity well slows time as it bends space. Astronauts don't travel into free space. They stay **very** close to Earth. The Earth's gravity curvature at the ISS is almost the same as at sea level. In order to avoid falling to the Earth, space travelers/satellites have to be moving very fast to the side. This high orbital speed also impacts time, due to relativity."
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nq7gst | What exactly is a spark, and how does it occur? | Physics | explainlikeimfive | {
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"It depends on what kind of spark you're referring to. If you mean the sparks you get from a firework or from striking steel and flint for instance, the spark from a firework is a small mote of burning chemicals and the spark from the steel is a small piece of very hot steel. If you mean a spark like what jumps from your hand to a doorknob and gives you a shock; certain conditions can cause your body to pick up a static charge, essentially loose electrons from the environment. When you touch a conductor, like the metal doorknob, the electrons jump from you to the doorknob, causing a visible (and tangible) discharge.",
"It is a build up of negative electrons. You can experience this by walking across a wool rug in bare feet. The charge builds up in you. Then when you come close to something like a doorknob, a little lightning bolt will form as the charges equalize."
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nq91nc | How can we be sure that super colliders work the way we want them? | Recently, Ive seen some news about new discoveries based on data from super colliders, which might suggest that there is something wrong with the current models of the muons they were experimenting on. As best as I understand it, they are able to make a theoretical prediction, do an experiment, collect data, and see if the two match. I also know they repeat the experiment many times, and could redo it at different locations, to make sure its not just some software bug of malfunctioning hardware. However, all of the people I've seen talking about it seem to think that the theory around these particles itself is wrong, since the results don't match perfectly. In the end though, the information about the muons has to be measured in some way. How do we know the the theory behind how we measure muons is not wrong, and that its the theory of what muons are that is flawed? | Physics | explainlikeimfive | {
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"Well the theory of how we measure them is based upon how we think they act, so it's not like those are two completely separate problems. But in regards to this latest anomaly, my understanding is that the tests are seeing the expected byproducts of these particular collisions and those byproduct particles are reasonably well understood and they're fairly confident in what they're seeing. The issue is that the ratio that those two byproducts are being produced seems to be slightly different than the prediction. That doesn't completely rule out some sort of experimental error, which is why they're going to do more testing, and hopefully either figure out what the problem is, or just build more confidence in the fact that muons are acting unexpectedly."
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nq9xjj | (Spoilers for a 22-year-old movie.) At the end of Fight Club, Project Mayhem is successful in blowing up the buildings where the debt record is stored. Since my knowledge of economics is extremely limited, can someonewhy this plan would've or wouldn't've worked? | Economics | explainlikeimfive | {
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"No company that has any data worth anything has it stored on single servers in a major city. They have backup plans and failsafes in case something like that happens. The plan would not have worked"
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nqa18s | Why are some elements (like astatine) that are close to the last stable element more radioactive than elements farther away (like curium)? | Physics | explainlikeimfive | {
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"It comes down to how neatly you can pack the required number of protons and neutrons together into the nucleus. There's a balance between the electromagnetic force pushing the protons apart and the strong and weak nuclear forces holding the particles together. The geometry with the very large number of particles of heavy nuclei (210 for astatine) is complex and it turns out that, sometimes, larger numbers of particles are actually more stable. Imagine trying to pack 210+ balls neatly into a spherical arrangement, given that there are two types of balls and one of these (the proton type) needs to be as widely spaced as possible."
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nqaypd | Are women’s X chromosomes both the same? If they are different, does that affect how genes are passed down? | Biology | explainlikeimfive | {
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"No, like all pairs of chromosomes we have, there are slight differences between the two copies due to one coming from one parent and one from the other. The genes that are passed down aren't really any different from any other chromosomes. A process called \"recombination\" will basically cut the two copies at random places and then splice them together, so you get an X chromosome that's part of one copy and part of the other. That's what then gets passed to an offspring. Each offspring gets an X chromosome that's spliced together differently.",
"No, the X chromosomes are different. Good example I am familiar with is Hemophilia. It is a bleeding disorder attached to the X chromosome. Mother has 2 X, let's say a \"good X\" with no Hemophilia, and the \"bad X\" with the disorder. (I am not inferring a person with Hemophilia is bad in some way, just using as an example) Father gives his X or his Y chromosome, both \"good\". First potential child is a female that receives mothers \"good X\" and father's only X = no Hemophilia. Next Child is female and receives mothers \"bad X\" and father's only X = she now carries the Hemophilia Gene plus has the same chance of passing along that \"bad X\" to future kids. Next Child is male and receives Mothers \"good X\" and father's Y = no Hemophilia. Last child is male that receives Mother's \"bad X\" and Father's Y = he now has Hemophilia and will for sure give that \"bad X\" to any female children. Mother's different X chromosomes absolutely affect how that particular gene is passed down.",
"They are each coming from different parents, so they are different in that regard. They will contain the same genes, although they may be different versions of those genes."
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nqbx4h | - how does sunscreen work? | Chemistry | explainlikeimfive | {
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"Sunscreen prevents the harmful ultraviolet rays from the sun from damaging your skin. There are 2 types of sunscreen, chemical sunscreen and physical sunscreen. Chemical sunscreen contains chemicals that undergo chemical reactions when they absorb the ultraviolet radiation and release it as heat from you skin. Basically, the layer of chemicals absorbs the UV rays instead of your skin. Physical sunscreen, also called sunblock, contains minerals like titanium dioxide or zinc oxide that block the UV rays from your skin by reflecting them.",
"Sunscreen prevents ultraviolet light from reaching your skin which causes damage to your DNA which could cause cancer. It works by absorbing the ultraviolet light in the same way a black car would absorb all the visible light that hits its surface.",
"It works like paint. In ultraviolet wavelengths it's opaque, but it lets visible light through. As for how THAT works, in each chemical substance there are specific energy levels for electrons that are valid, and only if the difference in energy between two of those valid states matches the energy of the photon can it be absorbed. Different substances have different valid energy levels, so they absorb and reflect different colors. If they don't interact at all with light of that wavelength, we call them transparent."
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nqc0mm | How are solid state batteries different from current lithium batteries, and why are they better? | Technology | explainlikeimfive | {
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"Ssbs do not use a toxic liquid electrolyte. Without that, dendrites can't form and kill your battery over time, or short it and make it explode. They are safer, can last a lot longer, and can be recharged many more times than normal batteries.",
"Hypothetically, a solid state battery can be safer and lighter (or rather, more energy per weight) than a lithium ion battery. As far as I know such a battery hasn't been perfected yet. Energy capacity for the most advanced solid state batteries is still very low, and costs are very high. It's more of a \"maybe in the future\" thing and still very much in the development phase where lots of really cool sounding ideas end up dying in the crucible of real world application."
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nqc2aa | Why does a 25lb dumbbell dropped from 1ft up high hit the floor "harder" than someone who weighs over 150lbs and jumping more than 1ft? | Physics | explainlikeimfive | {
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"The dumbbell is more or less completely rigid. When dropped it doesn't deform, so it lets all of it's energy out on impact. With the person, we have our legs to absorb the shock, which lessens the blow to the ground, not to mention more surface area on the person. Same principle behind crumple zones in a car, really. If you hit a brick wall with a car that doesn't deform it's going to hurt a lot more than if you hit the same wall with a car that does deform.",
"A dumbell has almost no \"give\" when it impacts. In contrast not only do people typically have squishy flesh on their feet and cartilage in their joints, they also bend their legs a bit to absorb the impact over a longer period of time. The dumbell is also more dense than a human so the impact force tends to be concentrated onto a smaller area. This is important for the resulting damage to the floor surface from the impact.",
"Dumbbell tends to have a smaller area, so the impact is more focused. Person tends to dampen the impact with their knees or their soft feet/shoes and water body which spreads the impact out over a longer time. Compare a 25lb dumbbell to a 25lb water balloon for example.",
"If a person would keep his legs tight and stiff and then land on his heel, it would be a harder solid impact. But a human that jumps uses several muscles, tendons and joints to dampen the impact it starts with the foot, where the arch of your foot is like a spring that dampens .. then the bones in the foot and tendons around them widen to further spread the impact. Next up is the achilles tendon which is just a big rubber band that absorbs the energy from the impact and together with the ankle joint serves as a big spring/lever when landing. We usually land on our forefoot and not the heel. Next is the knee that by folding absorbs another amount of the landing shock. Your calf muscles and thigh muscles also absorb a part of the shock, but they are more designed to provide power for motion. Lastly and the most important muscle in running, walking and jumping is the glutes .. your bum is a very large muscle that is used as a huge shock dampener. So when all these elements work together, they absorb and lessen the shock of the body weight. If you want to see a good example of everything working together in perfect synchronisation, look at a cat and how soft it can land, even from a relative high height."
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nqdhft | Why can we feel a fan blowing air from the front, but barely feel it sucking at the back? | Physics | explainlikeimfive | {
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"Outflow is getting pushed in one direction while inflow is grabbing from everywhere. That's why a vacuum can go from doing nothing to being stuck on your hand, drapes, carpet, etc. Goes from a small pulling force all over to all the pulling force being just at the opening.",
"Imagine the airflow looking kind of like a mushroom, with a very wide top (suction) and a very narrow foot, the push.",
"I stumbled upon this and thought why not try to answer it. URL_0 The air that's blown against your hand is directly hitting your skin, where you feel it. This also feels cold, because the air is directly taking away any moisture and warmth radiating from your hand. On the reverse side, you barely feel it because the air isn't hitting your hand, but being drawn from around it and between your fingers. If your hand had many holes in it, like a colander, you would feel it much easier. This is why it feels so weird. Picture above to illustrate. & #x200B; Hope my answer is satisfactory! :3",
"The air pushed out the front maintains a tighter stream than the air being pulled in the back, which means it has a greater velocity. The total volume of air moving is the same, but in the back it's being pulled from a much greater area. Basically you can think of it pushing a stream forward that tends to stick together for a distance like water from a hose. However, at the back you just have a low pressure zone where air is being pulled from the top, bottom, sides, and rear to fill in space where that air was removed.",
"What freaks me out is when every so often, though the fan is still turning and connected to the power, there will be a little gap that lasts a few seconds when I can't feel the wind. I now keep a Bic lighter by the fan so I can light it and see if the flame moves, so I know I'm not losing my mind.",
"Imagine you have a balloon or plastic bag filled with water. If you poke a hole in the bottom the stream of water comes out pretty fast, but looking at the water level in the bag it will look like it's barely moving. Same with if you put your hand in front of the stream of water, you'll feel it hitting you, but if you stick your hand in the bag near the hole you won't feel any suction. The fan is pushing in one very specific direction (the hole) but is pulling from the whole area behind/around it (the entire bag).",
"Say theoretically you have a fan that sends 1 cubic meter of air per second, let us say it does this by sending it at 1 meter per second through a 1 square meter of area. The behind of the fan will have to bring the same amount of air per second than the output you have, so it has to send 1 cubic meter of air per second. But the behind of the fan is not limited by the area the blade covers, it can come from pretty much anywhere so it has a much bigger area. So if the area air can get into the fan is 4 square meters and only 1 cubic meter goes in per second then the speed of the air behind it has to be 0.25 meters per second,so the air doesn't move fast behind the fan. Think of the fan sort of like a wind funnel, the area to get into a funnel is way bigger than the area to get out, you are slowly shoving the air into the funnel and it comes out the other end going way faster because all the air that got in needs to get out at the same rate. Just like when you press your finger on the water hose, the water needs to speed up because it needs to go at the same rate it was going before but through a smaller area, the fan concentrates the air that should have otherwise gone through a bigger area and pushes it through a smaller one at higher speeds.",
"in addition to what is already explained, there is another fact that is important: your touchsense is trained on gripping things. it realizes the power an object or in this case current has got, as long as it is a pressure. detecting a sucking force does not have much use according to evolutionary progress for a human or even a primate. mostly, its enough to realize, when it ended. therefore you feel blowing air much more than sucking air.",
"The sensory neurons that make you feel stuff respond to pressure. -When air is blown at you it provides pressure that the cells can pick up. -When air is sucked away from behind you, no such pressure is applied, meaning you won't feel it.",
"My friends and I used to blow weed smoke through a fan that was pointing out the window. We realised early on that you have to blow it right into the back of the fan, otherwise Jon's dad would storm the room asking why the house smells of weed.",
"Because fan blades can be designed to push air out in a certain direction or concentrated location/area. This could certainly be done in the other direction where the there is localized negative air pressure but the consumer would not understand because they are buying something that they think should blow air at them. This gets really funny when the fan is not focused in either direction but is simply moving air (like HVAC). You can get the impression that it is not blowing hard enough. It is."
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nqedgq | astrophysics question: age of universe vs. size | Physics | explainlikeimfive | {
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"Nothing can travel faster than light speed relative to the space it's in. But the expansion of space itself has no such limitation (it isn't a physical object and, as /u/blueparrotfish below notes, it's not even technically a speed!), and the current expansion is effectively much faster than light speed if you're observing objects far enough away from us. If it helps, think of the expansion less as \"space getting bigger\" and more as \"rulers getting smaller\". If you measure the same room with an ever-shrinking ruler, the room looks like it's getting bigger, in a way that varies depending on how far away things are from you. For example, suppose you have a 1 meter ruler. You have two stars, one 2 meters away and one 4 meters away (but remember, you *mean* two *rulers* away and four *rulers* away respectively). Now, suppose your ruler \"shrinks\" to 1/2 meter over the course of one day (in the original measurements - but because this is what you're using to measure, that 1/2 meter is now one \"new meter\" as far as your measurements are concerned). You now use your ruler, and you find that the first star is now 4 rulers away and the second star is now 8 rulers away. You say \"oh, the first star was 2 meters-from-one-day-ago away a day ago, and is now 4 meters-as-I-measure-them-today away, so that star has moved away at a rate of 2 meters/day\". And the second star went from 4 meters-one-day-ago to 8 meters-today, so you say it moved at 4 meters/day. The stars didn't exactly move - the space between you just got bigger. And you can tell because how fast stuff moves away from you is proportional to how far away it was in the first place - you're not *adding* distance, you're *multiplying* it by an ever-increasing amount. If your ruler shrinks fast enough, the distance between you and another object can grow arbitrarily fast (which, counterintuitive as it may seem, is not the same as the object *moving* arbitrarily fast: velocity is *not* the rate of change of distance in this context!). ----- As for why we can see those distant objects: the light they emitted left at a time when the Universe was much smaller, and covered the distance at a rate that kept it juuuuust ahead of the expanding distance between us (basically, it's at a distance where the expansion was adding distance at some large fraction of *c*, but the light was closing it at 1c). Any light that wasn't close enough to outpace the expansion was lost (to us) forever, and the objects that emitted that light are now unobservable (i.e., outside our observable universe).",
"The universe is in a constant state of expansion, and that expansion can happen faster than the speed of light, so even though light has only been able to travel 13.8 billion light-years since the big bang, the space itself has expanded faster than the speed of light. Joe Rogan just had Neil deGrasse Tyson on and asked him this very question! Hope I helped :)"
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nqf2bm | If we use degrees ( ⁰ ) to measure angles, why do we also use degrees as a measurement of temperature? | Mathematics | explainlikeimfive | {
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"The most basic meaning of \"degree\" is \"An individual step, or stage, in any process or scale of values.\" There are 360 degrees in a circle because there are 360 individual steps. (You can fine-tune a degree using arcminutes (1/60th of a degree) or arcseconds (1/60th of an arcminute, or 1/3600th of a degree). Similarly, there are steps in temperature. 1 degree Celsius is ever so slightly cooler than 2 degrees Celsius.",
"The word itself means little more than 'step' or a fixed amount of change. It has the same roots as the word 'grade'. It is used in many fields to describe a change of something in known fixed intervals like 1/100 of the difference between the temperature of water freezing and boiling or 1/360 of a full circle. Even an academic degree falls into that category somewhat as it is a fixed step on your way of achieving mastery in a subject. The word graduate and degree both come from the same root word of taking a step. The degree word and ° symbol originally came from use in angles and was later used for other things like temperature. One weird fact is that degrees of an angle are subdivided in minutes and seconds like hours are. Half a degree is 30 minutes of an arc and 1/3600 of a degree is one arc second. Minutes of an arc were marked with a ' and seconds with '' to show that they were the first and second subdivision of a degree. Based on that first and second notation a raised zero was used for the degree itself. You still see this sued today with geography where locations are given in degrees, minutes and seconds for example 40° 41' 21'' N, 74° 2' 40'' W would be one way to describe the location of the statue of liberty in New York. When people starting taking down notations for temperature in various scales they reused the degree symbol already used in angles, since they considered it to be broadly the same sort of thing. Thankfully none of those scales use minutes and seconds to subdivide them.",
"\"degree\" means a small increment. For this reason \"degrees\" by itself is NOT a measurement of temperature. Degrees Celsius are small steps of the Celsius scale. Degrees Fahrenheit are small steps of the Fahrenheit scale.",
"If you don't like measuring temperature in degrees, then the Kelvin scale is for you! Temperature is given in Kelvins, *not* degrees Kelvin.",
"To be pedantic, the symbol you use is a superscript zero not a degree symbol, which is a perfect circle. ⁰ vs. °"
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nqfzn6 | the difference between a producer, recording engineer, and mixing engineer? | In a typical music context - i.e. rock/pop band looking to record an album, what role does a producer play and how do they work with recording and mixing engineers | Other | explainlikeimfive | {
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"For a rock band, a recording engineer is responsible for getting good recorded material and is concerned with acoustics in the room, mic placement, etc. The mixing engineer takes the recorded material and edits it, i.e., sound levels, effects, and giving an overall polish to the music. The producer is present at all stages and is the musical leader making suggestions and adding ideas, much like a director in a film. In smaller studios, these may be the same person."
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nqhc4l | How do restaurants calculate how much their dishes should worth? | They bought the ingredients with a certain price , then they cut them up ,mix them up and then cook them just eyeballing the ingredients. So how do they calculate to price their dishes when converting from ingredients to a dish? | Economics | explainlikeimfive | {
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"First of all, things aren't \"eyeballed\" in restaurants. Everything is measured/weighed and prepared in portion sizes for consistency and to minimise waste. For example if you order a pasta dish, the chef cooking this will have portions of pasta pre-weighed and ready to cook at his station, each portion will weigh the exact same amount so each dish served will be the same. There is a basic fomula for food cost calculation and I'll break that down further. Basically how ever much the ingredients cost to cook one serving multiplied by 3. Then you can add a dollar or two to make it a more round number or fit in better with the rest of the menu pricing. OK let's break this down. I'll use a cheeseburger as an example. Each cheeseburger has a bun, sauce, pickles, onions, one slice of cheese and one burger patty. The burger patties each weigh 130 grams. Each container of meat weighs 5kg and costs 100 dollars. 5000g/130=38.46 but we round up to 38.5. You can make 38.5 burger patties from 1 container of meat. $100/38.5=$2.59 per patty Buns cost 50 cents each One block of cheese slices costs $30 containing 100 slices so 30 cents each One portion of pickles and onions costs 25 cents One portion of sauce costs 10 cents. 2.59+.5+.3+.25+.10=$3.74 One burger costs $3.74 worth of ingredients to make. Times that by 3 and you've got $11.22. Now that seems like an odd looking price for a burger so we are going to charge $12.50 So it's really just basic math.",
"There are other costs as well. Operating costs such as ingredients (as u have said), utilities, worker salaries and shop/outlet rental have to be taken account as well. There may be advertisement or any association fees that may be incurred too. The owner should calculate how much cooked food he should sell to not only cover the costs and also turn in a profit. The owner also needs to maintain food quality, and the price competitive so there will be customers! For example, let's just say, a restaurant owner knows he needs to sell 100 plates of fried rice monthly to stay afloat. So this is the target to meet every month.",
"You assume restaurants are using “cost+” method for pricing. Most likely they price what the market will bear. If you can sell a meal for $25, why would you price it at $10? Similarly, if you priced everything at $75, will you have enough people coming in? So they look around other restaurants, decide where they want to positon themselves and estimate what would that mean for their revenue and can they cover the costs and generate profit.",
"The cost of ingredients is a pretty small part of the costs for a restaurant. They also have to pay for the space, upkeep on equipment, and for the people who make the food. This is especially true for \"basic\" ingredients like vegetables and pantry staples. So long as you've portioned out any meat, fish, or other fancy/exotic ingredient (saffron, truffle, nice booze, etc.) it doesn't really matter if you give the customer a plate with 25% more carrot than usual."
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nqiewz | what is the difference between Eastern and western medicine, besides the obvious geographical location. | Other | explainlikeimfive | {
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"There are two things that will be helpful to understand: (1) There is no one singular “Eastern medicine” and (2) not every culture has the same relationship with medicine as is becoming common in the west. it is not that there is “Western medicine” and “Eastern medicine”, instead there is a growing practice of **evidence-based medicine** that is becoming the standard throughout much of the developed world and then there are traditional remedies or traditional medicine that has not yet met or been tested to a scientific standard of evidence or has been tested and cannot meet a scientific standard. For example: Reiki (the Japanese traditional practice of laying on of hands) is not evidence based — But neither is chiropractic medicine which originated in the west (although the founder claims to have received this knowledge from “another world“). Sometimes these traditional remedies are tested and become part of the evidence-based practices. Sometimes they are not able to meet these standards but are practiced anyway. That’s where helpful thing to understand (2) comes in and it’s something I didn’t understand until I spent time living in China. In the East, there is a pervasive culture of medicine as spiritual/ritual not really intended to purely heal the sick so much as intended to ease the suffering of both the patient and the family who feels a need to “do something” about a loved one’s suffering. There is a second social function similar to keeping someone in your thoughts and prayers or lighting a candle for someone that this set of “Eastern medicines” holds within cultures more common to the East that causes there to be a larger emphasis placed on practices that don’t necessarily meet evidence-based medicine standards but do meet this social need. This is what people are trying to get at when they say “Eastern medicine is more holistic”. In the west, we have appropriated some of that culture without really getting the context and you’ll see all kinds of misinterpretations packaged as “Eastern medicine” and held up to the standards of “Western medicine” efficacy as if they were both medicine in the same sense but merely from different places.",
"The philosophy which underpins most eastern medicine is the practice of treating the whole person, and not just the symptom. Western medicine believed in the inquiry and examination of the physical body and its symptoms and using a scientific, evidence-based diagnosis of health, using clinically-proven treatments."
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nqiuja | Moving between two different points in space-time and the observed effect. | Okay, I couldn’t fit my questions into the title but here goes. Considering Einstein-Rosen Bridges (or any form of wormhole) exist. From what I’ve gathered, in the night sky we are viewing billions of galaxies which are millions/billions of light years from us. This tells us that we are viewing said galaxies as they were/looked in the time that it took the light they were emitting to reach us. My first question: is the assumption that some of these galaxies have already merged/joined other galactic groups etc. plausible? My second and what the original post is about: if wormholes (faster than the speed of light) were to exist and take us to e.g a galaxy that is 2 billion light years from our solar system, would we be travelling to the galaxy as it looks in the night sky or how it is in its circumstance? I apologise in advance if this comes off incoherent but I genuinely have been thinking about this for days and couldn’t find any similar posts online on the same query. | Physics | explainlikeimfive | {
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"So, your question is twofold, and currently only has been answered in theoretic physics, which isn't exactly the most practical of things to answer questions... But I'll try to answer both, based on your example based on the second one, as this will simplify my answer a lot: > \"Let's take a wormhole (Einstein-Rosen Bridges) that is located 2 billion light-years away [...]\" Question 1: **Is the assumption that light reaching us implying that these galaxies may have merged or joined other galactic groups already plausible?** That's the easy question to answer, really. The answer is factually... \"It depends.\" Only those that had a collision course 2 billion years back technically will be merged/joined up. Think of it as an infinite pool table (and ignore friction, because you're in space): If you hit a ball in a path clear from the other balls, straight to infinity, and the other balls aren't ever moving into its trajectory, then you won't have a collision, thus you won't have a merge/join up event. Now think of each of those balls as galaxies' full gravitational field: Two galaxies that never enter each other's gravitational well cannot join up. Question 2: **If wormholes were to take us to that galaxy 2 billion light years ago, would it be how it was back then, or would it be how it actually is right now?** Now, that's a question for the ages. **Literally.** Einstein-Rosen Bridges are considered a speculative thing, due to their potential implication for time travel, but let's keep it simple for a simple explanation: An Einstein-Rosen Bridge is not a wormhole in \"space\", but rather a wormhole in \"spacetime\". That's a big difference, and here's why: Two ends of a wormhole aren't necessarily at the same time period as each other. For instance, if you were to be on side A, you could be near the Earth in 2021, but on side B, you could be 27 billion years in the future, looking straight at the Earth from there, and see what happens to in 25 billion years in the future (yet, while looking through the wormhole, see us as we are now, in 2021). **This differs from a space-only wormhole, as those are exclusively from \"now\" to \"now\", and would lead you to see the destination as it is now, not as it was 2 billion years ago (which is what you see in the night sky), or how it was/will be at any other time period.** This seems like a bit of an overstatement in how stuff could affect time travel, but it could also end up in a situation where a series of those wormholes, taken in a correct order could theoretically bring you from Earth in 2021, to Earth 1910, and you could then create the weird paradox of \"how would time travel work, even\"? I... I am no expert physicist, and most of that is from a lot of well-educated guesses, a lot of sci-fi material, and a more in-depth google search than I should admit to. I hope that helps.",
"You would be traveling to \"wherever\" it exists in 4D spacetime. The time component could be anywhere forward or backward from our own."
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nqkllz | Why do text-to-speech apps for nonverbal people cost hundreds of dollars? | Technology | explainlikeimfive | {
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"Because that’s what the seller wants to price them at. The market is small, and they might be interested in recouping the investment quickly, there might be no competitors, or hard to get, substitutes are basically not having an app, etc etc etc."
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nqlb4m | What Is the Federal Funds Rate? | Why is it so important that every news site write about it if it changes. | Economics | explainlikeimfive | {
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"The federal funds rate is the interest rate that banks charge each other to borrow or lend excess reserves overnight. Law requires that banks must have a minimum reserve level (held by the Fed) in proportion to their deposits, so if they are below this minimum reserve, they can short-term borrow from other banks that have excessive reserves. The rate matters because an overnight loan between banks is probably one of the _safest_ loans one can make (beaten only by US government bonds, but those are for longer duration). When evaluating whether or not to make _other_ loans to non-banks, the bank does a risk/return analysis - does the amount of money that I will make from the loan offset the risk the lendee won't pay me back, and how does that amount of money compare to my other loan options? Since bank to bank loans are low risk, banks would only want to loan to others if the rate of those loans is _higher_ than the interest rate the banks would pay for the overnight loans. The higher the funds rate, the higher the interest rate for other loans has to be in order to compensate for that risk. In practice, this means that when the Fed Funds Rate changes, every other interest rate is going to change in accordance."
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nqlmb2 | Why does not getting exercise make you eventually get hypertension, but getting a lot of exercise regularly makes you have lower blood pressure? | Moving around a lot to lower your blood pressure, and your blood pressure rising when you're not moving much just doesn't seem logical to me at all. | Biology | explainlikeimfive | {
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"If your arteries are clogging due to plaque formation/cholesterol, that makes it harder to pump blood throughout your body. Therefore, the pressure myst be higher in order to force blood through the narrower arteries. If you’ve exercised a lot and don’t have that buildup, your arteries are wider. Your heart doesn’t have to pump as hard, which means your blood pressure is lower, since there’s less resistance to the flow.",
"Exercise doesn't lower blood pressure in the short term. Regular exercise will have the long-term effect of a stronger, more efficient heart: > Regular physical activity makes your heart stronger. A stronger heart can pump more blood with less effort. As a result, the force on your arteries decreases, lowering your blood pressure. URL_0",
"You have to think beyond your heart. They don’t call it the heart system, they call it the cardiovascular system - and there’s good reason for this. The heart is the primary pumping mechanism yes, but along the way there’s an elaborate system of one-way valves and musculature that forms a secondary pumping mechanism. When your muscles contract, they push blood through the system all by themselves. The more you’re moving the more effective this system becomes. It all combines to take a lot of the load off the heart and keep the pressure in the system low. When you don’t move, the heart is the only pump and it’s trying to push blood through miles of narrow pipes all by itself. This requires higher pressure and strains the heart."
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nqmenh | Why is drinking alcohol and taking Tylenol together dangerous? | It's well known that you shouldn't take these two together. Why? | Biology | explainlikeimfive | {
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"Pharmacist here. Ethanol and Tylenol aren't processed by the same enzymes. Tylenol's (paracetamol) toxicity is due to its secondary metabolism by an enzyme (CYP2E1), which in normal conditions only accounts for a little percentage of it. Ethanol acts like an inductor of that CYP2E1, increasing its presence and making it more active, thus increasing the secondary metabolism of Tylenol. That secondary metabolism results in a toxic compound responsible for the hepatic damage. Edit: that CYP2E1 is also the responsible of a Tylenol overdose, because meanwhile CYP2E1 isn't inducted by ethanol, the quantity of the toxic compound increases proportionally to the quantity of Tylenol in the body.",
"They both cause stress on the liver in order to be broken down and removed from the body system. Taking both, together, is putting two heavy stresses on that organ simultaneously. Too much stress at one time or too much constant stress on an organ causes organ damage which may not be reparable."
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nqmprn | Why does the current in a transformer not follow ohm's law or the AC equivalent of it but instead runs on the principle that Pin=Pout? | I've seen many people question the same thing and the answer is always that Pin=Pout. But why and how is it possible that the current isn't proportional to the load and decreases (in a step up transformer) when it should increase? | Physics | explainlikeimfive | {
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"The transformer certainly follows the AC equivalent of Ohm’s law (current is voltage divided by impedance), but for an ideal transformer, the resistance of the transformer windings is assumed to be zero. So ideally, no power is dissipated in the transformer itself. However, if the transformer secondary is connected to a simple resistor as a load, then the resitor will follow Ohm’s law. And an ideal transformer will deliver all electrical power supplied to the primary into the load. Hence Pin=Pout. A real transformer will have power losses in the resistances of the windings as well as eddy current losses in the core.",
"Conservation of energy. Ignoring losses for a moment, the energy going in at any given moment must be equal to the energy coming out, and thus the rate of energy in must equal the rate of energy out. Rate of energy is power. Power is voltage times current, thus for Pin to equal Pout then Vin \\* Iin = Vout \\* Iout (ignoring the trig component for a moment and just looking at the simplified circuit).",
"The current in a transformer does follow Ohm's law. Let's take for instance an ideal voltage step up transformer, it takes 12 volts input and converts it to 120 volts output, now Ohm's law comes into play to conserve energy. In order to step up the voltage the current must decrease proportional to voltage change, from our example our input current will be reduced with the ratio 12/120 or .1, meaning 12 volts 1 amp in equals 120 voltages .1 amp out, the power remains the same."
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nqn8m8 | How does suturing veins prevent blood from leaking out? | As the title stated, how does suturing veins prevent blood from leaking out? Wouldn't the gaps between the sutures and holes from sutures cause continuous or more bleeding? | Biology | explainlikeimfive | {
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"Blood has its own built in plugging mechanism. They’re called platelets, they constantly circle around the blood stream, and when the interact with a cut/hole/damage to the blood vessel they start to clump/tangle up with other platelets, causing a clog that seals the damage and stops the bleeding. So when you suture a vessel shut, you’re taking a really big hole/cut and making it a smaller hole/cut by pulling the edges together. This help slow the flow a blood by making the hole/cut smaller. Then, the platelets in the blood naturally finish up the job by plugging any of the small holes/cuts/opening that remain.",
"Often you're trying the suture around the vein to close it off (like a rope around a hose). Therefore there aren't any holes from the needle.",
"End to end suturing of blood vessels uses very tiny stitches, and there is either a tourniquet above the area or both ends of the vessel are clamped while this happens. Veins are lower pressure systems, so once blood flow returns, they might seep a bit, but that's when clotting takes over the attachment point. With arteries, it's riskier, and usually only for smaller vessels - say hand reattachment that involves suturing veins, arteries and nerves. Even tinier stitches. There are also stapling systems for larger arteries. But mostly the damaged area is taken out and each end is tied or stapled off completely. The body will start producing new blood vessels, ancillary flow is an amazing way the body adapts to loss of original pipes."
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nqnt3j | How do animal moms know when to stop breast feeding and move onto solid food? | So how do mother mammals know to stop attempting breast feeding and start giving solid food? Especially so for species where the mother does most of the hunting like lions? | Biology | explainlikeimfive | {
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"At some point their offspring stop digesting milk properly, so they have no recourse but to move on to solid food. It’s called lactose intolerance and it’s the default state of mammals. The fact that lactose tolerance is rather widespread in adult humans is an evolutionary trait linked to animal husbandry.",
"Mother cats have an instinct to bring dead — and later alive-but-injured — prey animals for their kittens to eat and play with. They will teach their kittens that prey animals are edible by eating them in front their kittens. And they will teach their kittens to hunt prey by letting their kittens play with the injured prey animals. Once the kittens are old enough to start hunting for themselves, mother cats basically just abandon their kittens. A rapid shift in hormones after a certain number of weeks causes the mother cat to stop producing milk and also to almost entirely stop engaging with their kittens. Some mother cats will even become hostile to their kittens in order to force the kittens to leave. It is also around this time that the kittens develop a natural intolerance to lactose and so literally cannot drink milk without getting sick."
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nqoqyf | why nuclear bomb tests don’t cause nuclear winters and other effects from nuclear bombs? | Technology | explainlikeimfive | {
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"They do cause all the same effects as a nuclear weapon dropped in war. The only difference is one of numbers. It is anticipated that if nuclear war ever occured that the involved nations will launch all of their available weapons. In the case of the U.S., Russian, and China this total will be in the thousands. There have been quite a few nuclear tests performed over the last 80 years, but they were spread out over time and still don't approach anywhere near that total.",
"The idea of \"nuclear winter\" was based on what might happen after an exchange of thousands of weapons aimed at major cities that resulted in massive uncontrolled fires that burned for weeks or months. Even in that worst case scenario it's debatable whether the climate impacts would be so drastic.",
"The number. This possible doomsday scenario was is if one superpower launches all its nukes to wipe the other. Once that was initiated, the other would see it coming, but not be able to stop it. The only response would be to launch thier thousands of nukes back. The majority of two vast continents getting nuked within the span of a day would completely destroy the US and Russia and have untold ecological problems for the rest of the world.",
"We haven't done nuclear bomb tests in like 30+ years, and even then during the final years of nuclear testing they were all done underground. Besides that, the idea of a nuclear winter is just *one* hypothesis about what would happen as a result of a large-scale, widespread nuclear war. And it requires the explosion of *many, many* nuclear devices at one time to create the amount of dust and dirt and debris that would cause such a nuclear winter (though there's debate about whether that would happen). Individual nuclear devices are not enough to cause a nuclear winter. Besides that, nuclear testing *has* caused serious issues, such as long-term radioactive contamination of certain areas (look at the testing grounds in Kazakhstan), electromagnetic pulse effects that destroyed satellites in space, and accidental radioactive spread over civilian populations at some points. A lot of these mishaps and consequences shaped nuclear testing agreements and protocols, so that we *wouldn't* repeat those mistakes again.",
"They have plenty of effects, you should look them up. Nuclear winter requires a large number of bombs detonating simultaneously, around the world, kicking up enough smoke/ash/debris to block the suns radiation and lower the global temperature.",
"The “Nuclear Winter” scenario assumes that the bombs will be used on cities, burning vast numbers of buildings and starting Hiroshima-esque firestorms all around the world. The smoke and soot from global destruction clouds out the sun and lowers global temperatures. Isolated tests in the middle of nowhere don’t have that effect. After the 1960s, the world powers conducted most of their nuclear testing underground to better contain fallout and maintain secrecy.",
"Nuclear winters require a massive amount of dust to be carried up into the upper atmosphere and reduce the amount of sunlight reaching the ground. A single nuclear weapon may carry some dust into the upper atmosphere, but not enough to create a nuclear winter. In addition most new tests are carried out underground so no dust is carried up into the atmosphere.",
"They do cause all the effects of Nuclear explosions otherwise they are pretty poor tests, just not the winter. That's why they are done in the middle of deserts, or underground, or ion uninhabited stops in the Pacific. The winter is caused when enough bombs go off that so much dust is thrown into the atmosphere, the sun is effectively blocked out, thus the temperature plummets globally.",
"Nuclear winter would have been the result of thousands of bombs which would in turn cause fires and produce smokes that cover sunlight around the planet. Nuclear tests were either done underground or on deserts where there's nothing to burn. Depending on what element the bombs were using the radiation can stay there for minutes or for years, some places that were used do still have faint traces of radiation from the 60s but it's a dessert so nobody lives there."
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nqqruo | when viewing a sheet of transparent glass or a mirror from it's side profile, why does it appear green in colour? | Physics | explainlikeimfive | {
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"The iron oxide that gives glass the green tint isn't there on accident, it's added to make the glass easier to melt in large batches. Glass melting furnaces produce almost all of their heat in the form of infrared light. This is a problem when you want to heat up something transparent, because the infrared light will go right through it! It just heats up whatever is behind the glass. That makes it take a very long time to melt the glass. Iron oxide is added because it is a cheap way to make glass absorb a lot more infrared light. It has the side effect of making the glass slightly green, but this is fine most of the time. You can buy iron free glass if you need your windows to be perfectly colorless, but that glass is more expensive because it is harder to work with.",
"Different metals dissolved in glass give different colors. For example, gold will give you red glass. Iron will give you green. The green tint in glass is typically from iron impurities.",
"Because glass isn’t perfectly transparent. We see color based on what wavelengths of light get absorbed by and object and what get reflected. We think glass is perfectly clear letting all the light pass through it, but in reality is reflects a little bit more of the green spectrum than everything else. With a thin sheet of glass it isn’t enough to notice, but when the glass is really thick, like when you look down it the long way, you absolutely can notice the difference."
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nqr3ii | why do gaming laptops perform significantly worse on games when running on battery as opposed to it being charged? | Technology | explainlikeimfive | {
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"Running a lot of the components, such as the GPU, takes lots of power. The computer will try to minimize battery drain when unplugged, and thus won't fully utilize the hardware. I'm sure you can change this behavior in your power settings. However, your battery will probably drain *very* fast.",
"A battery has a maximum draw capability, they generally are not capable of providing enough overall power to run all components at maximum capacity when running purely from battery. Pulling too much power from the battery too quickly can damage it just like charging it too quickly can. As others have stated, the power plan on a laptop generally works to run even lower than maximum draw while trying to find a good balance of runtime and performance, but this can be changed to the detriment of one of those two criteria."
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nqrvex | why does squinting seemingly make stuff less bright, even if your pupil isn’t being covered in the slightest? | Biology | explainlikeimfive | {
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"The whites of your eyes have little to do with what you actually see. The pupil of your eyes is responsible for receiving light and transmitting it to the brain to be perceived as vision. Squinting changes the angle of the lens of your eye overlying the pupil, causing light to be refracted differently to certain areas inside of your eye, some of which are better at detecting brightness of light, while others are better at detecting color and overall acuity (sharpness) of an image. If you wear glasses for nearsightedness (trouble with distance vision), you can actually improve your distance vision slightly through squinting -- it bends the light in a way that partially corrects the lens abnormality in nearsightedness. If you only have a mild case of nearsightedness, squinting can almost correct it entirely (but will cause eye strain and other issues doing it all the time). All your glasses (or contact lenses) do in these situations is add another lens with a correction factor to cancel out what your lens isn't doing properly and hence correct your vision."
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nqrz9h | What happens, physiologically, when a person faints? | Biology | explainlikeimfive | {
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"Fainting is caused by a loss of blood flow to the brain usually caused by low blood pressure. Our brains need a lot of oxygen which is carried by blood, so if it senses it isn't getting enough, it triggers you to faint. This makes you go from standing up vertically to being horizontal very quickly, and your body no longer has to fight against gravity to get blood to your brain and assuming there are no underlying conditions or if there are that they are treated, you will regain consciousness pretty quickly."
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nqsy41 | Why does heat cause some objects to become less sticky, whilst other objects become more sticky? | An example of a material that becomes more sticky when heated is some kinds of plastics, whereas honey becomes less sticky when heated. | Physics | explainlikeimfive | {
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"Room temperature plastics are probably solids, and they get sticky when you heat them up because they start to melt. The liquid part is the sticky part. Room temperature honey is already a liquid, and when you heat up a liquid, it lets it flow faster, making it less sticky."
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nqtsze | Why does the magnetic strip on cards need to be swiped quickly? Why won't it read if inserted slowly? | Technology | explainlikeimfive | {
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"The reader keys off changes in the magnetic field of the strip. You need to move fast enough that the change happens quickly enough for the reader to recognize it as a change. If you go too slow, the change is so gradual that the reader doesn’t see the “edges”. The changing field is what activates the electronics in the read head. Imagine a bar code blown up to thousands of times normal size…you could be standing on a bar but it would just look like a giant black expanse and you wouldn’t realize you were standing on a bar code. Swiping slowly makes the stripe “bigger” from the reader’s point of view.",
"It's mostly because when you move faster you move more evenly. If you go slowly you actually introduce a lot of variation into your movement. When you swipe quicker it's far more likely that it's an even and consistent movement. The reader can deal with huge variations in the \"width\" of data, but it has to be consistent throughout the swipe.",
"The magnetic strip reader is sensing the changes in magnetic field as the card moves past it, and is trying to interpret that as a series of values. Because the card will be moving at various different speeds it actually needs to consider multiple possibilities from what it senses; if it senses a magnetic orientation of north for a period of time that might mean one value is north if the card is moving quickly, or two places are north if it is moving slowly, etc. The greater a period of time it needs to consider the larger the number of different speeds of swipe are possible. The card reader also at some point needs to come to a conclusion about what card was swiped. It can't do this until the maximum period a card can be swiped has elapsed, so letting someone take 10 seconds to slowly swipe a card would not only mean the reader needs to consider every possibility from the extremely slow to the fastest reasonable swipe, it also would take 10 seconds to finish reading a card swiped at a normal speed. It has no way of knowing if the user has finished!"
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nqusoq | What happens in the body that causes seizures during alcohol withdrawal/detox? | My dad had a seizure while going through withdrawals when I was younger and it was horrifying. When he came to, he looked like he was drunk again despite not drinking at all that day. Can someone explain this to me, please? | Biology | explainlikeimfive | {
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"There's a receptor in the brain called GABA-A. It's inhibitory, meaning it reduces the electrical signals in the brain. Alcohol and benzos activate the GABA-A receptor. These drugs have an inhibitory effect on the brain (they are \"downers\"). However, when you use these drugs for long periods of time, the brain will produce less GABA-A receptors. This is called desensitization. If you stop using the drugs suddenly, your brain now has a GABA deficit. It has a shortage of inhibitory signals, which leads to *dis*inhibition. The number of electrical signals increase, and you have a seizure.",
"As for the part about him appearing drunk after the seizure, that's likely because he was in a [postictal state]( URL_0 ). The symptoms (confusion, nausea, drowsiness, etc) are similar to those of someone who is intoxicated."
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nqvdqz | Why does the washing machine take twice as long with hot water then cold? | Technology | explainlikeimfive | {
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"You could have a clogged screen on the inlet of your hot water line to your washing machine. It's an easy thing to check and fix. Turn off the water feed and disconnect the hose at the washer. Look inside the washer inlet for a screen just inside it. Gently clean the screen off with some spray cleaner and a coton swab. Reassemble the hose and washer and turn the water back on. Source; I've had to do this a couple of times on my machine over the years. It greatly improves the water flow.",
"Because it needs to heat the water before washing and cool it before rinsing (machine depending). Heating water takes energy and the more of it there is, the longer it takes. So that's why it takes longer in general. Some will add a bit of cool water near the end of the cycle so that by the time everything is rinsed and spun, it's all easy peasy."
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nqvkf2 | How does your body adapt to avoid dizziness when you get dizzy often enough? | So, I was a high-level gymnast for many years. Something I've noticed since stopping is that I suddenly get dizzy again, and sometimes even get the "sinking" feeling in my chest if I flip around too fast. When I was a gymnast, I was able to do practically anything I wanted without getting dizzy, and **never** got the "sinking" feeling. I know that these are tied to the fluid in your head, but how does the body adapt to avoid these feelings when they're repeated often enough (during, for example, gymnastics over many years) | Biology | explainlikeimfive | {
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"In general you don't sense *things*, you sense *changes* in things. If something happens often enough, you \"stop sensing\" it. If you keep sending the \"dizzy\" input to your brain, eventually your brain will filter it out. That's why a pool can feel chilly when you first get in, but then you don't notice the temperature at all after a while."
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nqvuq3 | How is it possible to get pregnant while on your period? | Biology | explainlikeimfive | {
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"Some of the explanations here are plain wrong (sorry folks). Technically, a pregnancy can't start while you're menstruating, because ovulation results in the release of hormones that inhibit menstruation. It's more accurate to say that it's possible for sex during menstruation to result in a pregnancy. Your fertile window begins a few days before ovulation, because the sperm can survive in there for a while. So if you have a long period (bleeding for, say, 7 days), and a short cycle, and you have sex toward the end of your period, you might ovulate while there are still some living sperm left.",
"The first explanation seems just wrong, because, as you said, it wouldn’t be an actual period. The second explanation makes sense, because sperm can survive there for a few days. It actually normally takes a day or two to travel from vagina through cervix then through uterus then into the fallopian tubes where it might or might not meet the egg. It is possible for the sperm to take more time than average to make that journey, or maybe it can also just hang out in the fallopian tubes for a short while. So if intercourse happens at the tail end of the menstruation, and the woman happens to have an early ovulation, then it would theoretically be possible to get pregnant."
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nqw2yy | why cant you just inject blood with an extremely high oxygen level to resuscitate them | Im taking when they’re not already dead, just unconscious or not having the ability to breathe. Or maybe with cardiac arrest and you inject the blood while doing chest compressions. | Biology | explainlikeimfive | {
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"The problem isn't just insufficient oxygen, it's also that CO2 builds up in the blood and makes it overly acidic. You'd have to run the blood through a scrubber to replace the CO2 with Oxygen, but those machines are very expensive ([ECMO]( URL_0 ))",
"Your blood carries oxygen chemically bonded (weakly) to hemoglobin, not free oxygen gas. Injecting oxygen directly into the blood creates bubbles in your blood, which can kill you by plugging/blocking blood vessels. There \\*are\\* machines to directly infuse oxygen into blood (and remove CO2), as mentioned by /u/jmlinden7, but they need a ton of surface area (basically, an artificial lung) to work, they don't just stick an oxygen hose in."
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nqw6ez | Why are IPv4/IPv6/NetBIOS addresses and names needed in networking when every device has a unique MAC address? | Technology | explainlikeimfive | {
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"The MAC address does not give any description of where the device is located or how you can send a packet to it. If we were all just using MAC addresses for all traffic then every router at every ISP needs a list of all the devices in the world and where to find them. This would be extremely difficult to maintain. The current system of addresses is based on the geographical and logical location in the network. A router only needs to look at the first bits of an address in order to know where it should send the package next. You can compare it to a post address. We technically do not need to write the street name, post code and country on every letter we send in the mail since most people have a unique name. However it is very helpful to the post office to know if the receiver is living on the other side of the city or in the next country. The way we have it now they can only look at the post code and sort it into rough boxes that can be sent in different directions. A post office in New York City does not need to know your street address in Los Angles and only need to know what post code range is used for the west coast cities.",
"MACs only work on a lan level, ARP tables arent sent across the network. Routing subnets is easier than mac tables, also for security reasons, its easier to assign/change/reassign IPs than unchanging MAC addresses. The list of reasons why IPs are needed is longer than the character limit for a comment.",
"A MAC address is a thing called an unroutable address. An IP address is routeable. It's not at all clear from just looking at the addresses but IP addresses actually have a thing built-in that allows them to be logically divided into smaller parts called subnets. This allows IP addresses to be logically subdivided so it's easier to find a device by it's IP address. MAC addresses don't have this, they are just a unique identifier for a device. To make this easier to understand imagine you want to visit somebody. Their address is 3746729924. Their neighbors address is 27319, the house across the street is 9887372838276618. The address numbers are given out essentially at random so there's no way to find out where these addresses is located based on just the number. You would have to wander around the country until you happen across it. This is how a MAC address works. Now imagine you are given the address of 300 Kitty Street, Dog Town, Florida. You don't know where this is located but because you know how addresses are formated you can more easily find it. This is how an IP address works.",
"Let's say a MAC address is the name/surname of the computer. (And work only on LAN) Imagine how complex or inefficient would it be if a computer needed to know each MAC adress in the world.",
"MAC is like your DNA, it uniquely identifies you. But good luck trying to send someone a letter addressed with their DNA. IP address is like your street address. It pin points where you are right now. The post office (the network) knows how to get mail to your house. When you move you change your address, just like your phone connecting to free Wifi at Starbucks."
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nqx0c6 | What is the difference between pragmatics and semantics? | Other | explainlikeimfive | {
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"To be pragmatic is to do what is sensible and necessary, rather than what might be fun or exciting. A pragmatic person will spend an evening doing laundry, even if it's not very fun, because they know it's important to have clean clothing. Semantics is the branch of linguistics that deals with the meaning of words or concepts. Such as how \"poop\" and \"shit\" mean the same thing but have very different tones and uses."
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nqxe8k | is there a medical/physiological reason why male birth control doesn’t exist yet? | Biology | explainlikeimfive | {
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"Everyone else here is talking about hormonal birth control, but that’s WAY less likely than vas-occlusive contraception like RISUG. Basically, they can inject a polymer into the tube that carries sperm and can remove it if you feel like having a baby, so more like an IUD than the pill. It’s in Stage III clinical trials now, so we’ll see it at some point in our lifetimes.",
"It is both more difficult and less desirable. For women, birth control works by hijacking existing hormonal cycles. Without tampering a woman's body will naturally build a lining in the uterus into which an egg can implant when fertilized. After an egg is implanted the body will react by thickening the lining to prevent more eggs from implanting. If no eggs are implanted the lining will be shed in a period to start the cycle over again. Birth control uses the natural hormonal signals to thicken the existing lining before any eggs can be implanted, and then letting off the hormones to allow a period. Because the thickening hormones were active throughout the cycle the periods are typically lighter, and the hormones are more stable. For many women this means less hormonal side effects such as PMS and a less painful period, so they would desire to take birth control regardless of its contraceptive effects! In contrast male birth control would need to find a way to prevent the formation of sperm and/or prevent them leaving the body. Unfortunately there isn't any natural cycle to hijack; men are adapted to making sperm constantly and expelling them as needed. If they aren't used the body will even purge the old ones reflexively! A simple hormone to stop men making sperm isn't something that is immediately evident and may simply not exist. Furthermore men do not in general experience any undesirable side effects from the production of sperm, so there are no anti-PMS or less painful period benefits to be had.",
"I took part in a male birth control trial. It was a gel that was rubbed onto my back once a day. It was very similar in look and smell to hand sanitizer. It was called Nest if I recall.",
"The male hormonal birth control that exist right now are generally using MPA as the main effector. This drug is more commonly known to be the drug they use for chemical castration. It's not an off switch for sperm production or fertility, its an off switch for the entire testicle. MPA alone has the effect of destroying libido, decreasing muscle mass and even causing dangerous mood swings, not to mention that if taken for long enough, the effects can become somewhat permanent. To offset the immediate effects, pharmaceutical companies will try including other hormones or just straight up steroids. Often causing more problems and further complications after the drug is stopped.",
"Women naturally have a \"turned off\" state in pregnancy, which pauses your normal period cycle and release of eggs. Most female birth controls are designed to take advantage of pregnancy hormones and trick the body. Similar to an actual pregnancy, things can restart once the body comes back to normal. Men on the other hand continually produce sperm. There's no such toggle built in there. So male birth control has to get creative to be effective yet avoid long-term effects. A few do exist now and haven't been shown to be much worse than female BC, but it's harder for them to get approved for public use. There's also a lot of situational bias at play too; it's not as if the issue exists in a vacuum. Female birth control, despite its side effects, is a high priority to keep on the market due to its medical necessity for many people; male BC doesn't have that edge. Men that don't want children already have a simpler, safer and more reversible surgical BC option than women (vasectomy), lessening the necessity by another step. And just culturally male BC has way more of an uphill battle right now since it showed up late and goes against the current social norms.",
"Hormonal birth control for men essentially has the same problems as hormonal birth control for women. But with women the risks are measured up against pregnancy, which can be very risky, whereas men don't have that risk. 'This podcast will kill you' did an episode on the pill which explains it in more detail.",
"If I was a woman, there's not a chance I hell 'd EVER trust a man that says they're on birth control.",
"Stopping 1 to 3 eggs being released monthly is easier than stopping the 1500 sperm created every second. They are in development,but none have been approved. I'm sure you'll hear that they created one but stopped because men whined about the side effects. This is a lie motivated by gender politics. The study in question was stopped because a third party oversight panel found issues with the methodology. In this study they did report higher numbers of and more severe side effects however males dropped from the study in the same numbers that females dropped from similar studies The most interesting and promising male contraceptives are vasalgel and similar products.",
"What has not been addressed in the thread as far as I can see is medical ethics. Every medical intervention will have some degree of risk and negative side effects. Pregnancy and childbirth is very risky and dangerous for the health of the patient, so preventative care for that condition is considered a worthy tradeoff for the risk of side effects from birth control intervention. Men can't get pregnant, so interventions only cause negatives to their bodily health. Some may be willing to take the risk for the benefits, comforts, and conveniences of birth control, but a doctor can see allowing risk with no chance of improved overall health outcomes as unethical. And no, doctors aren't going to clinically agree that living with children is a long term health risk.",
"There are a bunch of things being investigated that prevent the sperm from fertilizing the egg, prevent motility and other sperm functions URL_0 It isn’t really that far away, but it is kind of held back by the market predictions - i.e. that people who can get pregnant dont trust the people who can’t get pregnant to make sure they dont get pregnant.",
"The side effects for a daily male pill are significantly worse and in some it could cause permanat sterility. I haven't read about it since 2015 but it is a much more complicated than the female birth control pill. Edit: The others reason is that the female birth control pill creates progesterone, which is a naturally occuring chemical in the body that atops ovulation. It is basically mimicking a biological function while the man one is not",
"Vox does a cool series about this on Netflix called explained about birth control. It exists, but men won't take it because they experience the same side effects as women and it was decided it wasn't marketable."
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nqxey2 | Are there any benefits or drawbacks of sleeping completely flat, without a pillow? Or is it personal preference? | Other | explainlikeimfive | {
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"It is best for your anatomy to maintain a neutral spine. That being said, most pillows give you the opposite result. They elevate your head disrupting your spine’s natural position. And that’s why you keep hearing people say, although not frequently, that pillow aren’t “good” for your posture. You can apply the same analogy to the mattress. When I was backpacking in Thailand and South Asia several years ago, I had the great pleasure of sleeping on rock hard beds. It was almost like the mattress didn’t exist. I got used to it pretty quick. But one thing I noticed was the positive effect it had on my posture. I was standing up straight like my spine had been replaced with an iron rod. I now sleep on a firm mattress and a stiff but “thin” pillow. But imho it really comes down to personal preference as pillow or not, it won’t drastically change your life.",
"Acid reflux/heartburn gets worse when you lay flat. Gastroenterologists recommend patients sleep at an angle using blocking under the bed or a wedge pillow. Not a problem for everyone but I can't sleep flat."
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nqxpzs | How exactly does the math of RSA encryption work? | So, I'm very familiar with the general concept (well...sort of) Person A and Person B both have public/private keys. Both public keys are made public (duh) to make it possible for both parties to decrypt it. Person A sends off a message encrypted with their private key, which can be decrypted by Person B using their public key. Vice versa for Person B sending a message. The problem that I can't seem to understand, though, is how exactly that...works. Because logically (to me anyway), if something can be done, it can also be reversed. How does the math of RSA ensure that this isn't the case and that the encryption is asymmetrical rather than standard and symmetrical? I assume the math behind it is incredibly complicated, but I just can't seem to wrap my mind around the logic on a mathematics-based operation behaving like this since (to my knowledge) math is pretty symmetric in nature. | Mathematics | explainlikeimfive | {
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"I think there's a minor misunderstanding. When A wants to send a message to B, A encrypts the message with the public key of B. Then B can decrypt the encrypted message using their own private key. The general idea behind the math is as follows. The message m is written as a number (recall data can be represented in a computer as a binary number made of 0s and 1s). Then, we choose whole numbers e, d, and n such that m^(e*d) = m modulo n. We use e as the public key of B and d as the private key of B. That is, if we multiply m by itself e*d times, we get back the original message m. This is modulo n which means the number line wraps around every n numbers. We can compute x modulo n for any whole number x by taking the remainder of x when we divide by n. The encrypted message is m^e modulo n. A can send this as e is the public key of B which is public knowledge. Then, to decrypt m^e modulo n, B can use their private key d and multiply m^e by itself d times to get (m^(e))^d = m^(e*d) = m modulo n. To be secure, RSA relies on it being really hard to find d such that m^(e*d) = m modulo n given e, m, and n. The current best approach I know to recovering d is to factor n into its 2 prime factors. Note n is generated as a product of two primes. That is, n is a whole number prime times some other big whole number prime. Then, knowing these prime factors, we can easily generate e and d in the same manner that B would have used to generate these keys for themselves originally. So currently, the security of RSA rests on it being really hard to factor big numbers in general like what is used for n.",
"I randomly generated 2 prime numbers, multiplied them together and got 2100164884403801796476253999141832323244096220555409904678799655053853703740023011519520700517368942818811769887651080129051716351348401464777825499748179148567. Can you tell me what those numbers were? You can use a computer. It took me seconds to generate and multiply those numbers, it will take you far longer to factorise them. If you make the numbers bigger it will take my basically the same amount of time to multiply them, but it will quickly take hundereds of yours for you to factorise the result. This is an example of a mathematical operation that is easy to do but very hard to reverse.",
"As a very oversimplified explanation, when encrypting something, ideally you want some type of problem that is very work intensive to solve, but at the same time, very easy to check a solution of. One example would be various puzzles, where you can almost immediately see if a solution to the puzzle works, but the amount of computation to derive a solution is insanely hard. In this sense, the keys are solutions to the puzzle. And depending on the design of the puzzle, there can be multiple keys. For example, if I have a number with only two prime factors, one factor can be one key and the other can be the other key. When the system checks against the key, it will see it a factor and is thus valid.",
"> Because logically (to me anyway), if something can be done, it can also be reversed. Maybe logically to you, but incorrectly. Some things are far easier to do in one direction than another. You can make a cow into hamburgers fairly easily, but it would be quite a challenge to turn hamburgers back into a cow. In a similar way, public key crypto relies on that some things are far easier to do in one direction in math than in the other one. RSA is based on just such a thing, prime factorization. A prime number is just a number that can't be expressed as a product of two smaller numbers. So 4 can be expressed as 2*2, so it's not prime. But 5 can't be expressed in such a way, so it is prime. Next, multiplication is easy: 43 * 71 = 3053 is easy to calculate. However the problem of \"I multiplied two prime numbers together, and got the result 8051, what are those two numbers?\" is a far trickier one."
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nqy9us | how does “connected, but no internet” work on computers and other technology?? | for context, this just happened to my computer, and i’ve always wondered how it was possible for something to be connected… but not connected | Technology | explainlikeimfive | {
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"It's connected to the local router (like paired, similar to a Bluetooth connection), but the router isn't receiving any information from outside",
"It's a bit like roads. You can have a few dirt paths that connect your main house with your shed and your garden plot, but those paths don't directly connect to the main road. You have to go through your house to get to the main road. If the path from your house to the main road is blocked, then you can go anywhere on your property (your network, all the devices on your WiFi or ethernet) but you can't go anywhere off the property (the internet).",
"Okay, like you're 5. Imagine being stuck in a room with a lot of other people, but no one has cell service. You can talk to all the other people in the room as much as you want, but no way to talk to the outside world. In this scenario you are the computer. The other people in the room are other devices on your local network. The cell phones are the internet."
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nr1oau | What makes sounds sound different from each other besides frequency, like what would for example be the difference between me slapping my table or a persons voice? | Physics | explainlikeimfive | {
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"Pretty much every sound you will ever hear is not just one frequency, but a whole bunch of frequencies. Sound can be represented as a spectrogram, showing how much sound is present of all frequencies. A C note on two different instruments will share the same main frequency, but have a whole host of variations of other frequencies. The amount and frequencies also vary over time. A major difference between a jet engine and a distant gunshot, for instance, is the suddenness and echo of the latter."
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nr24o4 | How does sun screen work? | Chemistry | explainlikeimfive | {
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"Sunscreens only block ultraviolet lights, since that’s the part of sunlight that causes sunburns. Since sunscreen doesn't absorb visible light, it appears clear when put on your skin. But with the help of a [modified camera that sees UV light,]( URL_0 ) you see that the sunscreen looks like black grease paint. It appears black in the UV camera because it's absorbing all the UV light that hits it, just like black paint looks black because it absorbs all the visible light.",
"Let's start with \"what causes a sunburn?\". Your skin gets hit with sunlight and you see the bright sunlight hitting it. But that bright sunlight isn't what causes the damage. What you don't see is the types of sunlight that our eyes can't pick up on. One of these types of light that we can't see is ultra-violet, and it has a fair amount of energy in it. So when it hits your skin and you don't have any protection, over time, that energy kinda wrecks important and complex stuff that makes up your cells (in sort of the same way a fire that's too close burns your skin). The ultraviolet light damages the cells that make up your living skin, and causes them to turn red or blister or peel. Sunscreen is like a wall that doesn't let quite as much of that invisible, damaging light through. Apply it and it dries into a sort of invisible armor that our eyes can't see... but that ultraviolet light (which our eyes also can't see) can't get through. So our skin doesn't get as damaged, and we don't get \"burned\"."
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nr37ry | Do photons follow a sinusoidal path? | Does a single photon moving through space in an overall straight line actually trace out a sine wave, turning left and right as it goes? | Physics | explainlikeimfive | {
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"They are waves - they do not follow waves. It is an oscillation in the direction of a field, not an oscillation in position. They move in a straight line.",
"No, a photon does not move in a sinusoidal path. A photon travels in a straight line from source to destination, and the \"sine waves\" that you are thinking of are simply a *representation* of the electromagnetic field that the photon is made of. The oscillation of the electromagnetic field describes the *properties* of the photon (frequency, polarization, and velocity), not its actual physical movement. Part of the difficulty in this is that a photon is *both* a particle and a wave at the same time. It was a massive logical leap when it was made, and it's still counterintuitive today, but it is fact and has been verified time and time again.",
"Here's my best attempt at explaining Quantum Field Theory to a five-year-old: Think of a large pool filled with water. If the water is very still, you can barely see it's there. However, when the water is disturbed (or \"excited\" in the case of a field), you can observe the ripples as they move through the water. If you create a very large disturbance in the water and the ripples splash against something, it can create individual droplets that appear visually separate from the rest of the water. Now imagine that droplets are more or less likely to be created at certain points in the ripple (I.E. closer to the centre of the ripple, or at the peaks rather than troughs). The droplets aren't guaranteed to appear at any point, but the *probability* of them appearing at certain locations is higher than others. The ripple represents the \"wave\" portion of light. The sine wave that we represent light as is a *wave function*. Like the ripples in the earlier example, a photon (our metaphorical droplet) is more likely to be found at certain points in the probability wave (ripple). Just like the droplets only appearing when the ripple splashes against something, photons only exist at the moment that they are observed. Imagine this as a ripple in the photon field, where photons only pop in to existence when the wave \"splashes\" against something (like other particles). Hope I did okay!"
],
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nr3pcn | Why do we get goosebumps when we’re cold/afraid/whenever else we get goosebumps | What purpose were goosebumps supposed to serve. Do they even do anything? Also how do they work? | Biology | explainlikeimfive | {
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"h0ebo1y"
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"text": [
"It is thought that it could be an old reflex from our ancestors. If we had a lot more hair and a stronger goosebump reflex it would cause all our long body hair to stand up which can both keep us warm and make us look larger to an enemy."
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5
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