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na07vc | What are those white spots at the beginning of the nail? Why do we have/have not them? | Biology | explainlikeimfive | {
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"The white half-moon shape at the top of your nail is called the lunula. It’s part of the nail’s “matrix”, aka the root, where new nail cells are formed. If a person doesn’t have visible lunula at all, sometimes it’s because their cuticle grew over it... but other times it can mean that they have a vitamin deficiency and their nails aren’t growing properly because of it. Your cuticles serve a purpose too - they’re the clear layer of skin over the top of your nail. They protect your newly grown nail from getting dirty or infected."
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na0hgt | What is the reason human brain has shrunk 10 percent in size over the past 30,000 years? | Biology | explainlikeimfive | {
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"Disclaimer: not a professional, just googled it ELI5: We don't know. Like with anything we don't know there are some theories though. Some smart people don't even think that it matters at all. Some other smart people though think we are all in fact getting dumber. Some other smart people think that our brain is getting more efficient and just doesn't need that much space anymore. Others say, it's because of changing outside factors of the earth, like temperature. Or it might be because of the smaller hip sizes of women that make it harder to birth a baby with a bigger head. And lastly some others think that it is a side effect of domestication. Domestication is what we call the change of wild animals or plants intended by humans for our own advantage. You could for example take a wolf that is a bit nicer to humans than others and try to keep it around. It's children might also be nice to you. And it's grandchildren might even be nicer. So in many generations you have a very nice wolf, a dog. You have domesticated a wolf to a dog. And we find that a domesticated animal has a reduced brain size compared to its wild ancestor, even up to 34 percent. I personally really like that theory. We might have become our very own pets. But who knows. [Original source, might also work for ELI5:]( URL_0 ) There are many possible explanations for this, but no one can pinpoint exactly why and how this is happening. The type of matter within the brain that we are losing paints an even more perplexing picture. We see an erosion of grey matter, not white matter. Grey matter contains the cell bodies of our neurons, they are the backbone of our brain. This grey matter accounts for our complex behaviors and abilities that are unique to humans such as language, culture, and writing. White matter is the fatty myelin sheath that covers the axons of these neurons, this fatty substance is a support structure but nonetheless essential to proper brain function. Christopher Stringer, a paleoanthropologist and expert on human origins at the Natural History Museum in London says that “Scientists haven’t given the matter the attention it deserves. Many ignore it or consider it an insignificant detail.” There are many different schools of thought around the matter. Some scientists think that humans are in fact getting dumber. Some think that the shrinkage is due to the more efficient wiring of our brain. Then there are some scientists that think we have simply been domesticated. Domesticated sheep and dogs, for example, have smaller brains than their wild ancestors. Some credit environmental factors, like the heating of the earth, or physical factors, like the decrease in female hip size, which means babies with smaller skulls and smaller brains. Scientists have flipped over every stone to develop different hypotheses but fitting them all together into a narrative that makes sense is the hard part.",
"They've become more efficient and better at problem solving, instead of people survival and sensory based.",
"We don't know for sure, yet. But we lost size, not quality. When we were hunting animals (and been hunted) and gathering berries, we needed some skills like smelling, hearing and finding a good mate. With agricolture we changed the set of skills to include cooking, writing, music, navigating the sea and predicting star movements. So, in my opinion, we shed some extra weight we weren't using that much anyway to make room for something different, like thinking."
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na1avd | Why does reheated meat have to get to 75°C core but you could just eat the cold meat? | When you reheat mince or a burger the advice is to reheat to a core of 75°C. What is the difference between eating the meat cold vs reheating to only 40/50°C assuming the warmed meat is consumed right away. Surely the bacterial growth in the few minutes from fridge to microwave to mouth to stomach wouldn't matter much? | Biology | explainlikeimfive | {
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"Bacteria are like Goldilocks. They like food that isn't too hot, isn't too cold, but is just right. The longer food is in that danger zone, the more bacteria will grow in the food. If you're going to reheat it, you have to heat it past this danger zone and into the \"too hot for bacteria\" zone.",
"The growth is not from fridge to microwave. The growth is from the point that it stopped cooking the first time and dropped below 75C all the way to the point that you raise it above that point again when you reheat it. It is true that refrigeration slows the growth but it does not stop the growth. Ground meats are a higher risk for food borne illnesses because it is basically all surface area. All the interior of the hunk of meat that would be mostly protected from the bacteria growing on the surface has be ripped apart by the grinding process and it all now exterior and exposed to contaminants."
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na2xby | What makes garlic and onion bulbs special that makes them so good to cook with? Is there a reason other than taste that stops me from trying to cook with all the different species of bulbs? | Biology | explainlikeimfive | {
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"The fact that they're both bulbs doesn't mean that anything bulb-shaped is either tasty or safe. Onions and garlic are both in the same family, \"allium\". Several other alliums are also edible and share broadly similar flavor profiles: scallions, shallots, and chives, for example. To be clear though, there are poisonous alliums too - the entire family isn't generically safe.",
"Onions and garlic share a family classification with other types of lilies that have similar bulbs. The problem is that most lilies are poisonous to humans. Onions and garlic are actually the exceptions that we can consume (but they are also toxic to our furry pets). They are unique because they give a onion-y or garlic-y smell while other lilies do not.",
"You wouldn’t want to eat bulbs at random, since some of them are toxic. Daffodil bulbs are toxic, for example.",
"They just have strong umami flavours which come from naturally occurring glutamate. Kinda like how MSG makes food taste better. And they release sugars during the cooking for process which adds to the intense and complex flavours. Also smell makes up a good portion of taste perception,and garlic is fragrant",
"I think you are underestimating the range of species of bulbs we use for cooking. There is only a few that is known to contain poisons but this still do not prevent us from using them in small amounts.",
"I've also noticed that it seems to be the one thing all cultures around the world have in common (when it comes to food) historically. Wonder if they all too the risks by eating the random \"smelly\" bulbs lol",
"Onions are high in sugars, are easy to grow compared to other sweet things and store well. Those factors made them extremely useful essentially as a way to sweeten a dish in a time when sugar was extremely expensive, which is probably the reason they're so ubiquitous in so many styles of cooking. In modern times they've stuck around largely through inertia, and yes, because they taste good. Garlic has always been primarily a flavoring component and it is optional or could be replaced in all but a few dishes (such as toum, a Lebanese sauce of oil emulsified with garlic). Essentially, no, theres nothing stopping you from replacing onions or garlic with basically any other vegetable aside from your liking onions and garlic.",
"Everyone went straight to the botany but the real answer to this question is because onions and garlic are aromatic when used in cooking.",
"They have a lot of sweetness but it's balanced with it's pungency and acidity. It helps to establish a rich base flavor to build upon with the rest of the ingredients.",
"There are definitely serious practical -can last long because they're dry bulbs, even in the days before fridges -super easy to grow in the garden, as animals don't predate them. Also, garlic is easier to grow because it starts as bulbs rather than seeds. Both these things keep prices low I figure that these big deal practical considerations historically kept them popular in the kitchen , and then now it's still a holdover. I mean, at least partly. Nobody can deny their flavors rock",
"So there's too points to this. The first is that not all bulbs are edible, garlic, leeks, onions are some that are. The second is what makes them so delicious and good to cook with. The answer is that we made them so. Almost all crops nowadays have been used by artificial selection. The original bulbs were good, but when we found a bulb that was especially good we started growing that one instead. As the bulbs became more delicious they became good at certain things over others, and we simply kept breeding them to be better for the purposes we used them, making them more delicious and good. This still happens, for example in [the late 90s early 2000s a new type of brussel sprout, less bitter and more tasty was invented]( URL_0 ) leading to the veggie becoming more popular and eaten.",
"Garlic and Onion aren't delicious and nutritious by accident. Edible vegetable used in cooking have been bread to be edible for centuries if not for thousands years. Many less than year lasting plant store energy and nutrients in the root. This reserves can then be used to grow fast during spring to outcompete other plants for sunlight. The energy and nutrient content make them excellent food for any animal capable of digesting them. Of course plants don't want their energy storages to be eaten, so many plants try to make their roots either hard to digest or toxic. So not all roots are edible. Arms race between plants and animals is whole another topic onto itself. But in short humans are able to eat some of the roots, but not necessarily all of them. Hunter Gathers have first eaten these edible roots in the wild. At some point they've started cultivating some of them. With selective breeding they've bred onion which have huge edible bulbs. The same plants have been selectively bred according to different qualities, and because of this there are diverse selection of onion like edible plants."
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na34vk | Why are tags on shirts placed in the back part of the neck? | These tags have annoyed many, yet companies consider this the most optimal place to put them? | Other | explainlikeimfive | {
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"The neck is typically exposed when the shirt is displayed in a store. This provides fast access to the size information for store employees who need to sort them or put higher visibility sizing information on them.",
"Ease of reading them while able to conceal the tag. Most people hold the shirt from the shoulder section in front of them which exposes the neck area thus the tag."
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na40ie | Why do tech companies constantly change their terms of service? | Technology | explainlikeimfive | {
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"There may be new laws they have to account for or explicitly address, there may be new technologies that come into existence or that they want to use and need to cover, they may need to better clarify based on consumer concerns/feedback or lawsuits/threat of lawsuits.",
"Generally it's to account for various laws being enacted or expiring. Say that there's a class action lawsuit against Company X, and the case gets decided upon a particular phrase in the X's Terms of Service, and Company X loses. You own Company Y, and you have that same phrase in your Terms of Service. You're going to want to eliminate that phrase as quickly as possible so you don't also get sued. Or imagine a state passes a law that forbids forced arbitration. You'll need to put an exception in your Terms of Service that say that the forced arbitration clause of your ToS don't apply in that state."
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na50jr | Why the colonial pipeline Hack caused a gas shortage? | Technology | explainlikeimfive | {
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"No, a lot of the company's operations had to be temporarily shut down because the computers controlling various pieces of equipments were [potentially] compromised. As such, oil products weren't flowing from sources near Texas up the east coast.",
"Running a pipeline means, among other things, that you have a lot of computers that help you. Computers that control the valves and the sensors that are spread out across the line. Computers that send and receive commands from the operators. Computers that collect statistics for billing. When your computers are at risk, so is your permit to operate the pipeline...because you will be blind. If something fails, you cannot guarantee that you see the failure. You cannot guarantee that the control equipment reacts as it should on a fault. You risk an environmental disaster that will cost you your company and the rest of it's profitable future, if you get a leak at a time when you can't see it and it gets out in the press and to the overseeing authorities that you knowingly risked a failure. Shutting down was the sensible option.",
"> Are there not manual controls that they can use to get the oil into barrels or trucks? Yea, probably like 3000 manual controls. Which is why a computer has to manage it. Can't have 3000 people standing at each control flipping switches all day. It doesn't scale."
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na5r4c | how the hell do you read those Twitter screenshots? I feel like everytime I see one they are in a weird order, and I never know the chronological sequence of comments. | Technology | explainlikeimfive | {
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"Especially on newer screenshots there will be a white line connecting the profile pictures of the people conversing. Simply read those from top to bottom.",
"It's so frustrating! Doesn't help that after 2 replies Twitter hides the rest and goes \"And here are unrelated tweets, formatted exactly like the replies were!\" Always feels like the conversation just abruptly goes full non-sequitor. I'd say it's the most-frustrating social media format in my life, but nothing will beat tumblr conversations that go more than 5 replies deep and turn into upside-down pyramids of letters",
"Normally, a thread of people replying to each other goes top to bottom. But if you see a tweet \"embedded\" within another (a quote tweet), you read the innermost one first - that one came first, and the user whose tweet you're viewing commented on it.",
"I couldn't finish the one with the vertical humpback whale. Twitter cropped both ends off."
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na5xo6 | Is a hypothesis considered to be null if it creates a paradox? if not, why? | Physics | explainlikeimfive | {
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"No, that is not a null hypothesis. The null hypothesis is that the \"treatment\" or \"change\" made in the experiment does nothing. Like a placebo in medicine, it's the possibility that people will just get better if you don't give them a drug. In physics, it's more like running the experiment with the power off, stuff still happens but it's not a result of the effects of the equipment you're using to generate the experiment.",
"Got a feeling you are confusing two non related things. A null hypothesis, (as I recall from 25 years ago) is a scenario in which the variables in your experiment are considered to not have any influence on results. A paradox is essentially just a contradiction of terms. This is my recollection, feel free to correct me"
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na64h1 | Why can't we use railgun technology to launch satellites into orbit? | Technology | explainlikeimfive | {
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"Low Earth orbit requires a speed of 7800m/s So lets say you have a humongous rail gun that’s 400 meters long. The lazy math says that to exit at 7800m/s, the satellite will be spending something around 0.06 seconds accelerating. That gives you an average acceleration of 130,000m/s^2 That’s 13,250 times earth’s gravity, and your satellite is pulverized.",
"Keep in mind, that going into space is not about getting up high, it's about going exceptionally, ridiculously fast horizontally. So fast that as you fall back to earth, you \"miss\" as the Earth curves away from you. This means that your rail-gun has to launch your satellite at a speed of about 8 km/s. This is 23 times the speed of sound! Rockets only start to hit this speed once they've left the thick parts of the atmosphere. The rail gun has the disadvantage of having the projectile hit that speed in the atmosphere. The result would be an absurdly high amount of pressure, heat, and drag. It's not just not happening.",
"We've [tried]( URL_2 ) several [times]( URL_1 ) at [this]( URL_0 ) point. Turns out its hard and requires a really really big gun. The root of the problem here is muzzle velocity, how can you get something moving at 8000+ m/s? A high velocity rifle round might be 1000 m/s, a high velocity tank round might hit 1800 m/s, but orbital velocities are significantly higher. Light Gas Guns are basically the only way to do this, they require a main explosion that squeezes a chamber of hydrogen or helium gas to build up the pressure and send it shooting down a much narrower pipe at high speed and launch the projectile on the other end. Bad news, they're big and don't work great with massive projectiles. SHARP was a ginormous light gas gun that had a 47 meter long barrel and it was only able to get a 5 kg projectile up to 3 km/s, that's about a third of where it needs to be and only the mass of about 3 cube sats. There was an even bigger version planned with a 3500 meter barrel to get things up to orbital velocity for the low price of $1B Rocket based launches are good for a few reasons 1. They work, we know that by now 2. They don't subject your payload to ludicrous G forces, most are under 3 Gs during launch so you don't need to make your satellite heavy by packing all the holes 3. They can move fairly large things, communication satellites are over 1000 kg these days 4. You aren't forced to launch into a specific trajectory like with a cannon We'll always be looking into space planes and non-rocket space launches but for now rockets work well enough and the price has been coming down for years."
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na6ip2 | If a plane's cargo hold was filled with helium, would it take less fuel to take off? | Physics | explainlikeimfive | {
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"Not much. Helium is lighter than air but the volume of air in the cargo hold is not really significant. Heliums density is around 1/10 of air (at roomtemperature) so even the biggest plane in terms of volume, which is the Airbus Beluga at 2209 m³ would have to lift roughly 2 tonnes less. The maximal weight of this Plane are 220 tonnes so it would only be a difference of 1%",
"Creating a vacuum in the cargo hold would actually use less fuel than filling it with helium.",
"Just by virtue of being less dense, yes it would reduce the aircrafts weight by a VERY slight amount and therefore would require VERY slightly less thrust.",
"Maybe. If the helium was contained in a very, very light bag at one atmosphere, then it would make the plane's interior atmosphere lighter. Not the plane itself, that's all made of aluminum and steel.",
"Assuming the helium was at the same pressure as the air around the plane, yes. Effectively you have designed a rather thin zeppelin type airship. Because the gas in the plane weighs less than the air it displaces, it will have positive buoyancy, and will push the aircraft upwards. As fuel use is related to take-off weight, less fuel will be needed."
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na6onm | Why is it that we enjoy a certain food less if we eat it many days in a row? | Other | explainlikeimfive | {
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"Marginal utility/benefit reduces as you consume some products or food. This is why more will not give you the same satisfaction infact the utility may go on the negative side"
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na7ygp | What’s APR and how does it affect you financially | Economics | explainlikeimfive | {
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"An APR is an Annual Percentage Rate. It’s the rate of interest you will pay on a debt, I.e. loan or credit card."
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na82c5 | How does clicking a link to a malicious website allow hackers to gain control over a computer? | Aren't browsers suppose to be sandboxed? Assuming you never run any file that is downloaded, how does malware go from within the browser to gaining root access and encrypting your file system? | Technology | explainlikeimfive | {
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"There are various ways to break out of the sandbox. Among other things, the webpage can be set to automatically download a file when you load it, with virus files being quite small and quickly completed. Then, it is just a matter of tricking you into opening the payload. Like pretending that your computer has a virus and directing you to download their super awesome virus remover tool. Don't worry, it is all legit, the virus in your computer is just manipulating Windows into thinking our antivirus is a virus, really. Other fun tricks are to spread cheap casual games with an installer that installs special web browsers that allow for foreign code to be run. And yet another exists that runs a Macro (a prerecorded set of instructions) on Microsoft Word, which (you guessed it) runs a virus program. The best way to avoid many of these attacks? Vigilance. 1. Never click any sort of links in an unsolicited email. Not from a stranger, not from a bank, not even from your parents (until you have a chance to confirm they sent it). If your bank sends you an email about your account, type your bank website into the address bar. 2. Never click on ads. Like ever. But especially not when that ad is saying you won a contest, may be infected with a virus, or has a big blinking button that says \"Download\" 3. Never do your personal business on your work computer. That way, if you screw up, it doesn't affect your work, and if someone else screws up work, it doesn't affect your personal business."
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na8as8 | why can’t we just plant a huge amount of trees instead of trying to stop CO2 emissions? | It seems to me that most of our governments and environmentalists are focusing on people’s and companies’ reduction of CO2 emissions when discussing how to deal with climate change. This requires a lot of social pressure and people’s sacrifice. So I always wondered if we couldn’t just plant a whole bunch of trees and other plants to solve the problem? I don’t think anyone would oppose that. | Other | explainlikeimfive | {
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"Trees can help to offset CO2 emissions, but they’re not ‘free’ to grow — they require the correct soil and a lot of clean water. You can grow trees where they’re not entirely meant to be growing, sure, but then you have something like Southern California that burns down if someone looks at it incorrectly. It’s also important to note that you can’t cut down an existing forest and then just plant a bunch of trees to quickfix the fuckup — forests are highly complex ecosystems from root to canopy and Chet from Toledo planting 3000 of the same species of spruce tree where there used to be a thriving forest isn’t going to fix anything.",
"Doesn't solve the bigger problems at hand, would just allow humans to continue living unsustainably, if humans are to survive the next century planting a lot of trees is not the first step.",
"Planting trees will slightly help in the short-ish term (20 years). It is unarguably a good thing, but it’s not a replacement for a long-term plan. The first problem with trees is that those ecosystems can only sink so much carbon, after which they release as much as they’re sinking. Each area is a one-time-use that can be undone if not properly managed (side-eyes the Amazon’s management). The second problem is that they’re far too small to counteract our current CO2 production. Humans are releasing something like 6 billion tons of CO2 per year. If each tree takes in 5 tons of CO2 over its lifetime, that drive to plant 20 million trees will sink 1/60 of one year’s global emissions. And it’s easy to say “oh we’ll just do 60 of those every year”, but we would literally run out of land within a few decades. Trees are good for slightly undoing the damage we’ve done, but so far too little to prevent the problem in the first place.",
"Why can't we just hire more firefighters instead of making materials more flame retardant?",
"Where would you suggest we plant these trees and other plants without social pressure and people's sacrifice?",
"Get a big bottle, pour 500ml of water and start pouring 200ml of orange juice and try to pour just as much water to make the orange juice disappear while also pouring orange juice Would be quite hard I think",
"20 companies produce 1/3 of all co2 emissions - the notion that people individually are the main cause is corporate fiction URL_0"
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na91oc | What does “gain of function research” mean in non scientific terms. | Please explain | Other | explainlikeimfive | {
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"It puts a wild virus in a situation that can bring out its nasty qualities so that we can study and prepare for the possibility that it could make its way into humans. Viruses reproduce really really fast. This means they can undergo evolution really really fast. We can expose them to human cells where the individual viruses most infectious to human cells are likely to thrive and outcompete their less infectious cousins. This results in a new virus that is nastier to humans. All this is done to help us understand the threats facing us from wild viruses that could find their way into humans naturally. The contention from some scientists is that this might be more risky than its worth since it would defeat the purpose of the study if a lab accidentally leaked an artificially nasty virus into the population.",
"Suppose you had a regular villainous person that you captured and experimented on to make stronger, faster, smarter, and more evil. In short, suppose you took a regular bad person and made them a supervillain. Suppose further you did this to help figure out how to counter similar supervillains in the future. That’s what gain of function research does for pathogens."
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na9i7o | what is actually OCD? | I know it's much more than "haHa book noT aLlIgnEd With taBle" | Biology | explainlikeimfive | {
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"OCD consists of 2 parts. An obsession and a compulsion. The obsession is usually based around fullfilling some arbitrary requirement to prevent an imagined disaster. The compulsion is the inability to NOT fulfill that requirement. There's a scene in ASIP that demonstrates it perfectly. Charlie's mom flips the light switch multiple times and they ask why she does it and she says \"If I don't do it, Charlie will die\" Edit: the ASIP example is an extreme example, but extreme examples make the best examples because they illustrate diagnostic criteria clearly",
"Like most things nowadays, it's a spectrum. There isn't a nice tidy way of explaining it because it manifests differently in people. Some people have the stereotypical version where they fear contamination or germs, and their compulsion is to wash their hands excessively. Others experience a version called \"pure O\" and that's more along the lines of intrusive and obsessive thoughts about things that scare them. Their compulsion is rumination on said obsession and trying to get to the root of why they think about that stuff. The problem is, there usually isn't a logical explanation, and this only intensifies the cycle because people often attribute a moral failing or something more sinister to the thoughts. It takes a lot of different forms and varies in terms of severity. Some people are able to go on with life without a lot of interference, whereas others have a much more difficult time coping with it.",
"I hate the examples of if I don't do _____ then ____ will die. That is a VERY extreme example of OCD. Almost none of my obsessive behaviors come from a fear of someone dying if I don't do the thing. There are a few related to things needing to be certain ways at work but to be fair, I work in a hospital pharmacy so those fears aren't that unreasonable. I'm talking medications need to be organized and clearly labeled not all the paper clips have to face a certain direction. I do get anxious when I don't have my pen though lol The reason why is because it is familiar and part of keeping everything the same and organized which makes me feel like is important for my job and helps reduce errors. It stops me for a moment and makes me anxious but I can move on. As far as compulsions, these are things you must do repetitively. This would be things like the urge to wash your hands 3 times every time you wash your hands or checking that your door is locked 7 times before you feel comfortable leaving your house. I used to have trouble with compulsions but I've found medications with the help of psychiatrists that help. I do have a few left over such as my need to take 3 paper towels in public restrooms and when I'm super stressed I'll start taking a certain number of steps or chewing my food a certain number of times again. There are many types of OCD including the well know checking, organizing, and cleaning along with the lesser known intrusive thoughts, rumination, and some forms of hoarding. No matter how OCD manifests in a person, it is a serious condition that often takes over their day to day life. It is not a simple desire to have things clean and organized as some ignorant people some to think when they say things like \"Oh my OCD is acting up today!\" when they feel the need to tidy up a bit. Saying things like that reduces the real struggles of someone diagnosed with OCD to just a silly quirk in the eyes of those who don't understand. Please don't do it. Thank you for asking this question and being willing to learn about an often trivialized mental health condition."
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naajon | How is there an average of 12:06 hours of sunlight at the equator? | I was looking at different places on timeanddate and noticed that in Quito the sun is always above the horizon for 12:06-12:08 hours a day. I looked around at other places on the equator and it's the same thing. Shouldn't it be exactly 12 hours? How is the sun up more often than it's down? | Earth Science | explainlikeimfive | {
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"Quito is at a very high altitude. As a result the angle from sea level to the East to sea level to the west is more than 180˚. You see this effect at sunset. On the ground, you've seen the Sun set, but if you look up at the bottoms of the clouds, they are still lit. It takes a few minutes for them to be out of direct sunlight.",
"Official sunrise/set happens when the sun is 50/60 of a degree below the horizontal. That's because the atmosphere make the sun on the horizon appear 34/60 degrees higher than it really is and it's 16/60 degrees from the centre of the sun to its edge. So from rise to set the sun has to go 180 degrees plus an extra 100/60 degrees which takes and extra 6 mins 40 secs. Against this, apparent days are currently a few seconds short of 24 hours because we're farther from the sun than average, but it's not enough to eliminate the above effect.",
"Think about the sunset. The atmosphere bends light so there is still daylight after the sun sets below the equator & daylight just before the sun rises in the morning."
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nab2r1 | - how does one prepare for a tornado? | Earth Science | explainlikeimfive | {
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"1) you'll need an area below ground. If you don't have a basement, you can have a storm shelter installed in your garage or yard for a few thousand bucks. It isnt cheap, but it can save your life. Be sure to register with your local government (most of them have a registry) so they know to come look for you if your house collapses on your shelter. 2) stay weather aware. Watch what's happening on TV, listen on the radio, or tune in the the NWS reports. 3) FFS if there is a tornado coming at you, DO NOT BE THE PERSON WHO STANDS THERE LOOKING OUT THE WINDOW. Get safe. Stay safe."
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nachm7 | Why is drinking 14 drinks in one day worse than drinking 2 each day over the course of a week? | Biology | explainlikeimfive | {
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"Because your liver can only process so much alcohol in a given amount of time. If you drink more than that, then it stays in your bloodstream, being a toxic chemical, making you drunk, and if in high enough concentrations, causing alcohol poisoning.",
"Why is placing 1000 pounds of weight on your foot in one day worse than placing 3 pounds of weight on your foot each day for a year? What your body can handle over time is not equal to handling it all at once. With alcohol, 2 drinks will be processed out of your system by the time you consume 2 drinks the next day. 14 in a short time frame will greatly increase the amount of alcohol in your blood and it will take longer to sober up because it is 7 times more alcohol to process.",
"Each drink raises the blood alcohol content (BAC) by .02. Your body eliminates alcohol at the rate of .01 per hour. So, if you drank 14 drinks over 4 hours, your BAC would be .24. At that level, you would experience stupor, confusion, feeling dazed, and disorientation. Standing and walking may require help, as balance and muscle control will have deteriorated significantly. Sensations of pain will change, so if you fall and seriously hurt yourself, you may not notice, and you are less likely to do anything about it. Nausea and vomiting are likely to occur, and the gag reflex will be impaired, which could cause choking or aspirating on vomit. You would experience blackouts.",
"We eat 21 meals a week, but that doesn't mean we could eat 21 meals in a day. Your body takes time to process what you put into it. If you put too much into it at once, it can't process the excess and it just stays. With food, it stays as fat. With alcohol, it stays as alcohol in your blood, and it also puts a lot of stress on your liver as it's trying to keep up with filtering all that crap you just put into your body.",
"Think of it not in terms of overall amount but in terms of rate of intake and the resulting concentration in the body. Your body has limits as to what it can handle, and consuming too much of anything in one sitting pushes past the boundaries of what your body can cope with."
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nact9g | If lead is a culminative toxin, "there is no safe threshold/amount of lead exposure," and exposure can lead to irreversible tissue/organ/brain damage, why is it so prevalent everywhere, especially in our food? Why aren't we making more of an effort to remove it? | Biology | explainlikeimfive | {
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"Lead exposure isn’t a problem for the average person. It doesn’t get inside you just from being around it. You have to breathe in lead particles. Kids didn’t get lead poisoning from eating lead paint bc they were poor and hungry, it was the lead dust that was created by chipped lead paint, which was often used - and not maintained - in public housing. Kids would chip and peel the old paint, and breathe in the released lead dust/particles. I had to wear a respirator when I worked in stained glass because we use lead solder. Melting it with a soldering iron produces smoke, which contains lead particles. Breathe enough of that in, get dumb. (Also why leaded gas isn’t sold in the US anymore.) The groups in those studies worked with or around lead.",
"Because it cost so much money, that it would require state,or more likely federal funds to remove it... and lead is really only a poor people problem. There was legislation introduced at the federal level to completely fix the problem once, but once they saw how much it cost the opted for a lead abatement program instead."
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nad111 | Why does the conflicting taste of something hot and cold go well together? | I recently went out to eat and I had a very hot brownie with ice cream as my desert. I was wondering that intuitively, hot and cold should not go together well, but the desert was very good. I was wondering why this was | Other | explainlikeimfive | {
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"My best answer would be less about the temperature, and more about the flavor. With a brownie al la mode being a mix of sweet and savory. I think the heat just provides a more pronounced difference in the two flavors. Try fries in a milkshake, it works great.",
"It comes down to competing sensations. Your brain has this ability to normalize repetitive sensations. If you hear a tone for a while your brain tunes it out. If you eat salty things for a while you stop tasting the salt. Your brain craves new sensation. That's why salty and sweet goes so well together the flavors compete and as your brain bounces back and forth between each, it perceives the flavors of both better. It goes the same for hot and cold foods. Hot brownie, cold icecream. Warm cookies, cold milk. Alternating mouthfulls of hot stew and a cold drink. Hot pizza, cold beer."
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nagwn8 | How does injecting heroin (plant matter and more: cellulose, fibers, dirt, tons of impurities) not immediately kill you or cause serious infection? | Biology | explainlikeimfive | {
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"I assume you mean because opiods are deprived from plants that processed opiod drugs like heroin still have cellulose, fibers and dirt but that's certainly not the case. Any of that stuff is destroyed/removed during the drug making process. Opiods themselves are some of the least neurotoxic drugs there is, they cause no brain damage alone when used correctly. Also when injecting heroin it is generally heated up and then soaked into a 'filter' (usually cotton) to help remove any small impurities that might exist and to make it easier to draw into the syringe. Sometimes fibers from the cotton can end up in the syringe and injecting them can make you feel very sick",
"It doesn’t always, as the immune system is amazing. But it adds up overtime with abscesses and endocarditis. That can kill you."
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nah065 | why do people's voices sound different at different times of the day? like deeper and more gravely in the morning, normal mid-day, and softer and more high pitched at night? | Biology | explainlikeimfive | {
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"It’s deeper in the morning because your muscles are more relaxed. I’d guess the opposite is true in the evening. Your voice muscles are getting tired so it impacts your voice."
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nahk4x | What is happening when you press on or rub your closed eyes and begin to see colors and patterns? | Biology | explainlikeimfive | {
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"When you rub your eyes, you are physically stimulating the receptors in your eyeballs that usually fire in response to light. Turns out if you have detector cells *so sensitive* that they fire off in response to being hit by a few photons of light, pushing them with relatively gigantic meat appendages will also set them off. When nerve cells in your eyes go off, your brain interprets that as \"light\". It has no way to know whether those detectors were set off by light (like usual) or by physical rubbing. All it knows is: \"eye detectors report activity, captain!\" \"must be light! Produce visual information from the incoming signals!\" \"but captain, it seems like a bunch of weird random jumpy signals\" \"I love patterns - this must be one of them! Fit the incoming signals to some possible patterns and show those\"",
"What you are seeing are called \"phosphenes.\" Long story short, there are many types. However, when you press on your closed eyes, it affects the cells of your retina and causes you to see patterns. URL_0"
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nahr5n | My husband wants to keep our bedroom door open at night to hear if someone breaks in. I want to keep the door closed because if a fire starts outside of our room, the door will buy us time to escape. Which of these scenarios is more likely? | Other | explainlikeimfive | {
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"Depends on the crime rate where you live, and how often you clean out your dryer lint filters and oily rag collection.",
"Break in. Smoke detectors are there for a reason. Both of you meet in the middle and load the entryways with those squealing alarms that go off when the door or window opens.",
"Well you could take steps to prevent a house fire, or make it far more unlikely at least. You can’t prevent a break in realistically. If someone wants to get into your house they will. Also a break in is statistically more likely, there are only around 350,000 house fires a year in the US while there are well over 1 million home burglaries per year in the US",
"Fire. Can you set up An alarm system for the burglar instead? Maybe a camera?",
"The odds are pretty high that someone will break into your place and set the bedroom in fire if said burglar is also an arsonist. What's the crime rate look like in your neighborhood?"
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nahzob | how do voltmeters, or multimeters that can measure voltage, work? | Technology | explainlikeimfive | {
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"I assume you mean the analogue ones. They run a current through a coil of wire which causes a magnetic field. There's a permanent magnet nearby so this creates a force proportional to the amount of current flowing. Then you have a hinged needle attached to a spring which converts the force into rotation. You can use this arrangement directly for measuring tiny electrical currents, i.e., as a ammeter. If you want to measure voltage, you use a resistor; the current that flows through the resistor will be proportional to the voltage. You can use different resistance values to measure different voltage ranges on the same multimeter; those dials on the front just switch in different resistors."
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nai7yi | How do our eyelids get visibly oily during the day even though eyelids are poreless? | Just something I've been wondering. Eyelids seem to get as shiny as noses even though there is an obvious and huge difference in the amount of pores on these two areas. Where does all the oil come from? | Biology | explainlikeimfive | {
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"text": [
"Eyelids are not poreless. They actually contain the highest concentration of sebaceous glands anywhere on the body. And sebaceous glands are where oil is produced."
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naijgi | Why do news stories about new major diseases treatment (cancer, AIDS, and etc) end up as a story and not become widely used? | Technology | explainlikeimfive | {
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"COVID not withstanding, it normally takes many years from a cure that works in a lab to turn into a cure that your doctor can prescribe you. The whole testing and approval thing takes time normally. There is also the problem that science reporting in mainstream media is terrible. The take things out of context, remove all qualifiers and come up with the most attention grabbing headline possible. Of course the press offices of universities and institutions aren't any help in this either. If there is a for profit company involved especially one seeking investors they will overstate things even worse. Some researchers may go \"we found promising results that may eventually lead us to a path to a potential cure for x\" and you read in the newspapers \"researchers found cure for x\" Despite all that we doe end up with improved treatments for all sorts of diseases all the time. You probably won't hear much about them unless you or someone close to you has that disease and you pay attention.",
"There's a bunch of science related reasons behind why but I'll go with the media angle. MAJOR BREAKTHROUGH ANNOUNCED! sells ad space, sells papers, sells whatever. PREVIOUSLY ANNOUNCED BREAKTHROUGH WAS A DEAD END! admits that your media outlet sucks at fact checking and not many people would care anyway because it's not click baity enough.",
"The vast majority of groundbreaking new disease treatments end up as dead ends for one reason or another, but when a promising new treatment fails to deliver, that's not news."
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najbqj | Why do opioid painkillers give us constipation? | Biology | explainlikeimfive | {
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"Opioids obviously block pain signals in the brain. At the same time they slow down signals from the central nervous system. That second effect is the \"high\" opioid abusers are seeking. Either way a secondary effect it slows down the movement of stool through the intestines. Part of the job of the intestines is to absorb nutrients and water from the processed food, now stool. That process doesn't slow down because of the opioids. So the stool eventually becomes too dry and compacted to move through the intestines well, thus constipation."
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nak3kv | How does Disney recycle animations from one movie to another? | I watched this video, that shows side-by-side comparisons of animations which were recycled by Disney in different movies: URL_0 As you can see, the movement and framing are practically identical in the clips, but the characters’ looks sometimes vary. For example, Little John has other clothes than Baloo. How is this recycling done? Presumably, iy saves Disney time (and probably money) to use the “same” animation, but there are still some changes made to the recycled scenes. What does the process of changing the scenes look like? | Technology | explainlikeimfive | {
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"Most of the work required to make animated movies is to figure out the motions of the characters. There is a lot of little details required to make the characters move in a realistic way. Once all the movements were figured out the process of actually drawing the characters is much easier. You are just looking at referance drawings and filling inn all the details on the scetches from the animators. What Disney did a lot was to reuse the animations from earlier films and just have the artists draw different characters on the same scetches. This means you do not need animators for these scenes and they can spend more time making the new animations for other scenes instead.",
"By tracing them. These were hand drawn animations, with each cell a picture drawn by a talented animator. So, they could use tracing paper and copy the rough outline of the image from the previous film, which would still be in Disney's storage somewhere, and then make this light changes to adjust it to be the new character for the new film. Reportedly, the process of tracking down the animation from the previous film and then having to slide the ultimate with so much of a hassle that animators felt it would have been easier to just redo it from scratch, but orders are orders."
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nakvtb | Why would the market fall on fears of inflation? Doesn't inflation mean the dollar is worth less so shares would be worth more? | Economics | explainlikeimfive | {
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"There are a number of causes of inflation, but there are two of them that connect to the minimum rate of interest expected by banks: If demand for goods in the economy rises faster than production can expand to respond to it, you can see price increases. And if lending increases, then because banks can effectively create money by lending and then trading the asset created by that debt between them, they can create more dollars, or whatever your currency, than would otherwise exist, as people spend money that only exists because the bank lent it. Obviously, these can connect, if people spend the extra money on consumption, but you can get one moving without the other. The central bank can help reduce this by raising the interest rate it charges to banks in *its* accounts they all have, and shift the general rate of interest charged up, often because they will make debt products that are explicitly designed to track that measure. The hope would be that this changes saver's calculations of whether they want to spend this money now or wait until it grows, and also make people less willing to take on debt. This has three effects on the stock market, **firstly**, business lending becomes more expensive, so companies cannot borrow to invest, or to buy their own stock, and existing debts take more money, meaning they have to redirect money away from shareholders, lowering the expected rate of return on stock. **Secondly,** that effect of borrowing becoming more expensive generally causes many people to spend less money, and budget more to interest payments, which can end up reducing economic growth as well as inflation, hurting companies. **Thirdly,** for very high interest rates, people can just stick all their savings in a savings account, rather than in the companies' shares directly, getting most of their return through loans that go to those businesses rather than owning shares. The first two are mainly what you'd see, people can fear less economic stimulus from cheap debt. There's many reverse effects to though, like government debt, that often doesn't even have an interest rate, just flat payments, looking really promising as an investment when inflation is really low, so shares can go up or down in response to higher inflation, depending on what else is going on.",
"\"Worth more\" is the issue. A dollar today, and a dollar one hundred years ago are the same number but the dollar a hundred years ago buys more stuff, so it's worth more. Just because the number on the currency goes up, doesn't mean it worth more. It's relative to how much stuff that number can get. Hard assets, like land, have intrinsic value that hedges them against changes in currency values. Not 100%, we still see crazy prices in property but more than something like bonds or options contracts which are explicitly in future dollars. As far as market movement, market movement is always more about emotion, than logic. Fear of anything, drives down market prices."
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nale3i | When somewhere on our body got injured like cut or bruised, why can’t our brain just switch off and keep the nerves idle on the injured area temporarily so that the person won’t feel any pain? | Biology | explainlikeimfive | {
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"That would just increase your chances to injure yourself again. Pain serves a very important function: **\"There is something seriously wrong here!\"**, and, by extension via operant conditioning: **Better not do that again!/Better stop doing that!\"**. From an evolutionary perspective you could say that pain responses increase fitness, as they have a higher change of getting passed to the next generation. A human without pain responses will quickly leave the gene pool.",
"In my mind, that would be like taking the batteries out of your smoke detector because you don’t like the sound it makes when there’s a fire. It’s a warning and a call to action - just like pain is. I don’t think it would be wise to turn it off.",
"Pain is important, it tells you something is wrong. It makes you care for that area, if you dont feel pain when you are cut there is nothing making you keeping that area safe. In the wilsd this may mean you dig in the ground with your cut, or touch other things. Constantly tearing it open, and introducing bacteria. If you are unlucky you die from that. Basically, back in the wild people who didnt feel pain would have suffered a higher risk of death due to infection/not healing. If they suffered a higher death risk they would not survive long enough to have a child. If they do not survive long enough to have a child, the genes that \"turn off\" the pain could not be passed on, so now most people feel pain, since that was a survival requirement, except some few with a condition. Nowadays however we dont really \"need\" it all that much, assuming we keep our stuff clean, and dont exert pressure on our wounds. But pain is an indicator something is wrong, and needs to be fixed, and a wound hurting when you touch it is good to indicate that touching/pressuring it will increase the time it takes to heal. This is also why we dislike pain, since if we enjoyed it and actively sought it our survival chances would be lower, leading to those genes responsible for us liking pain not being passed on.",
"Well, depending on the scenario, the brain can issue instructions to various glands to secrete things like adrenaline and other powerful chemicals, to dull pain for a period of time, but this is usually a temporary thing, and it kind of has to be. The brain issues pain signals because it believes, as a result of information it gets from the nerves, that your body is in danger of serious and irreparable harm, unless you STOP MOVING AND GET HELP! For example, if you bruise your arm trying to elbow strike a tree, but your body lets you ignore that pain easily, theres nothing stopping your stupid, idiot self, from continuing to smack on that tree until your arm breaks. Similarly, there is nothing stopping a person with a cut making their situation worse by opening the skin wider, except PAIN. Pain will stop you doing things when your reasoning mind won't, which makes it really effective at keeping people alive. The problem comes when the brain cannot tell the difference between a pain signal from a healthy nerve that is urgent and incredibly important, and a false positive from a dead nerve, or an unfortunate but unavoidable real signal from a trapped nerve. The reason people have trouble with this part, is that they don't understand the relationship between nerves and the brain well enough. That's not to say you have to be a neurologist to understand this stuff to a useful degree, but you do have to abandon certain preconceived notions. The brain does not have control over the nerves in the body. Any of them. For any reason. The brain receives information from the nerves in the body, deciphers that information, and sends out chemical and electrical impulses to the various parts of the body, muscles, glands, organs, IN RESPONSE to information from the nerves. The brain cannot, independently and under its normal operation, \"create\" or \"prevent\" pain signals being sent by the nerve, OR prevent itself responding to those signals. The brain is often referred to as the control centre for your body, but it really, REALLY isn't. All it does is collect, decode, process, react to and store information that the body provides it with, about its circumstances. All the conscious stuff, the ability to know that this pain is to do with a dead nerve cluster, but that other pain is from a coffee table you just walked into, NONE of that happens in the autonomous brain. That is all CONSCIOUS mind stuff, and your conscious mind has absolutely no ability to hijack the autonomic systems of the body, to switch individual nerve clusters off. None at all. You cannot tell your brain to stop telling you about the pain from the dead nerve cluster, and your brain won't figure it out for itself, because absent the conscious intelligence you have, its just a bag of damp meat in a fluid filled space in your head, that can perform some impressive functions automatically. If people could just decide that this particular pain is a bug or a glitch in the system, and shut that channel off, it would be great in some situations, and in others, would result in things like people just ignoring pain from rapidly growing tumours, thinking they are just trapped wind or something stupid. That's why the brain doesn't have an override switch, and why you have to go the medical technological intervention route, when dealing with trapped nerves.",
"From an evolutionary perspective, pain is really useful. In response to an acute injury, feeling pain is a great signal to tell you to not do the thing that just hurt you again and to tell you to look after the bit that's damaged until it's healed. And we know this function of pain is really well retained (i.e. we'll never unevolve a pain response) as people who don't feel any pain don't usually live that long.",
"My arm went through a window when I was 11. Completely opened the skin from wrist to bend. Felt no pain at all. Surprised to see the inside of my arm tho 🥺. Dr. said adrenaline protected me to prevent panic.",
"Why would it? Pain exists for a reason. It tells you something is wrong and you need to fuckin move quickly to fix it. If you didn't feel pain, you'd probably end up cutting your fingers off or something without even realizing it",
"A lot of people think leprosy makes people's body parts fall of: Actually it's a disease that attacks the nerves, so you can't feel pain in extremeties. Every little unnoticed cut can then get infected... There is no evolutionary pressure to \"turn off\" pain, sadly, and a lot to keep it on and terrifying",
"It’s possible to develop mental fortitude to the point of not experiencing pain in an unpleasant way.",
"Let me ask you something: have you ever pushed through something? How much farther would you have gone if you just stopped being bothered by it? We humans have a frustrating tendency to overexert. Keeping the nerves going and complaining is an effective way of forcing us to at least calculate if we should keep going or if it would be better to stop. If we had the ability to just stop feeling, we would probably injure ourselves.",
"Neuropathic pain PhD here. The comments saying that pain is an evolutionary advantage are correct, pain exists to warn us of anything that can cause tissue damage/injury. The experience is unpleasant so we avoid it. The reason pain persists after injury is to deter wound interference and promote wound healing. Part of this process is also reduced pain threshold (so touching a wound hurts whereas touching normal skin doesn't normally hurt) and sensitisation of the surrounding area. Normally once the wound has healed the pain stops. Lots of comments arguing against the advantages of pain are about chronic neuropathic pain (NP), which is pain that persists after an injury has healed, or in the absence of a stimulus altogether. It is neuropathic because the neurones sending the signal don't switch off after healing. This is a maladaptive consequence of the pain system, and in short we don't know exactly how it happens or how to fix it. It's a very common problem, with many causes including diabetes, MS, traumatic injury, cancer/chemo and surgery, which is part of the reason why it's so hard to figure out. NP has huge socioeconomic implications and there is lots of research going into it.",
"Be honest. Would you get up from the computer to put out a grease fire in the kitchen if the smoke alarm went silent after 10 seconds?",
"A bit extreme, but have you seen the girl with a condition where she feels no pain? You can get an idea of why it’s important. [YouTube link]( URL_0 )",
"years ago read the following book about leprosy and why it is important to feel pain, - if you don't you hurt yourself and that is why a lot of people with leprosy have amputations - not because of the decease, put they hurt themselves and don't feel the pain, and then get infected - etc. URL_0",
"Your brain sends pain signals to keep you aware of where you are damaged, this helps stop you damaging it further by, say, hitting it again or leaving wounds open and prone to infection . Having said that you *can* tune out the pain with meditation or focusing on something else. Your body does this automatically if you are full of adrenaline because there is an emergency. For instance if you get stung by a bee and also break your arm you won't notice the pain from the bee sting. If you cut yourself while urgently taking your baby to hospital you won't feel the cut until the baby is with the doctor.",
"Well I must admit I have been accident prone all my life. Once my sister pushed me out of a moving car when I was 6, busted arm and a lot of stitches in my head. Fell face first into a metal garbage can from falling out of a bunk bed, busted lip and needed a lot of stitches. Broke both legs at different times once in a ball pit and once driving and got sandwiched between two idiots,and the clutch popped my leg! The best was I was cutting ground meat and the knife slipped and I had a complete flexor tendon lacerations on all four fingers needed surgery and 72 stitches, also hand therapy for 9 months. Recently as a heat stroke and fainted and busted my four front teeth on the floor, the dentist said he had this only happened to one other patient and that lady was screaming bloody murder, he said I was unusually calm and must have a very high pain tolerance! I just know that when you REALLY hurt yourself your brain keeps you calm and you don’t really even feel the injury ya know ya hurt because ya feel kinda high and really calm 😎At least this is my experience"
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nanohi | What are SPACs (Special Purpose Acquisition Company) and what do they do? | Economics | explainlikeimfive | {
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"When a growing company wants to go public as an IPO, the traditional process requires a lot of disclosures, accounting, paperwork, filings, legal fees etc. as the company readies itself for public stock sale. This can take a long time and be costly. n alternative method is a SPAC. This kind of company raises money from (usually very well heeled) investors with the goal of short circuiting that process. The investor money is pooled and a SPAC is formed that does nothing, but announce plans to acquire other companies. The SPAC then goes public with a very simple IPO (simple because the company does nothing, yet). Then the SPAC acquires a real company that wants to go public. Now the stock in the SPAC is really just the valuation of the acquired company and the acquired company is for all intents and purposes public, skipping all of the usual process.",
"SPACs are companies created to invest in other companies without telling you what they will invest in. It’s kind of like going to a Michelin restaurant and ordering the tasting menu. You don’t know what you’re gonna get, but you trust the chef.",
"They raise money in a public offering, and then spend that money to buy a venture funded company. This allows some efficiencies over the traditional process for taking the company public, which can benefit the owners of the company being acquired. It also allows more people to participate in buying a company than the traditional initial public offering process, which may make more capital available or at least spread out the profits more fairly.",
"They are a regulatory loophole to fleece the public markets. They bypass disclosure requirements and allow private companies (shareholders) to offload their bad investments onto public markets. Historically they perform terribly but banks and private company shareholders are eager to do them before the loophole closes.",
"Say you want to get investor money to buy dodgy stocks, but you don't want any of that pesky regulation that comes with an IPO, you create a SPAC, take their money and then once the company (or companies) you invested in start to tank, it's not your problem.",
"In my limited, up-close experience with one of these entities, the SPAC was a way to IPO a company under terms that were so shitty for retail investors, that a conventional IPO approach actually failed right before being launched just a year or so prior. The SPAC approach allowed a PE firm to offload its debt in the to-be-acquired company to ~~suckers~~ er, retail investors who bought into the new company, probably not realizing they were just buying a shit-ton of the PE firm's debt, and a company with limited upside that never would have attracted much interest as a conventional IPO. EDIT: I realize this sounds cynical but I really mean it. I have no idea why these are even legal.",
"A SPAC is a company whose business plan is this: - First, you raise a pile of money from investors - Second, you go through the process of becoming a public company and getting listed on a major stock exchange (NYSE, Nasdaq) - Finally, you use your pile of money and publicly traded status to convince a successful private company to merge with you Until you complete the final step, your business basically does almost nothing: You have a CEO, a couple dealmakers, maybe a handful of contractors for accounting and IT. You mostly sit on your pile of money. Once the deal is finalized, *technically* the target company you acquired ceases to exist. But in practice, the combined company continues right where the target left off. The combined company's first move is to basically become the target company: Usually the target's executive team takes over management, your CEO and dealmakers exit the company, the company renames itself and changes its branding to the target, your shareholders only get a small percentage of the combined entity in exchange for your pile of money and publicly traded status, and it's business as usual for the target's employees, customers, suppliers etc. The publicly traded status is the main incentive for the target company to go through with the deal. It basically trades away a piece of itself for the ability to quickly become publicly traded (and the pile of money).",
"Taking a company public (making it so that ordinary investors can buy a piece of it) is a complex and slow process, with strict rules e.g. about what you can say about your future earnings. An SPAC is an \"empty container\" that goes public without a specific operating business -- their business is to hunt for another company. So the SPAC does the slow and complex part of going public up front, and a lot of the strict rules don't matter because there's no specific future business. Later, the SPAC merges with a private company, usually with an additional investment round to go with it. The private company becomes public without a lot of the restrictions. People who bought shares in the SPAC end up with part of the formerly private company, as do those that joined the additional investment round. There are other common features, like if you have an SPAC share and you don't like the target, you can dump your share and get your money back. Whatever way a company becomes public, there are people who seem to disproportionately come out ahead. People argue a lot about whether IPO \"pops\" and greenshoes and other things are bad, or are necessary features to do good, but different paths to the public market do favor different groups of people. The mad rush to create SPACs and celebrity-branded SPACs should be a clue that all may not be level for the ordinary investor. One good (and entertaining) newsletter that over the past few months has talked a lot about SPACs is Matt Levine's Money Stuff. Usually very entertaining and informative and accessible."
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naodnn | Why do glass bottles have to be “recycled”? | Why can’t companies just sanitize and refill them? | Other | explainlikeimfive | {
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"Some do - beer bottles for instance are reused that way. But there are a lot of those. For the most part, there are small numbers of a lot of different bottles scattered across the country, and collecting, sorting, and then returning those to the specific places that use them is not economically viable. Easier and cheaper to melt them down and make new stuff.",
"They can be but it only works at a local scale. In college, the store near my house sold milk and juice in heavy glass bottles that you could return to the store. There was a deposit of 50 cents on each bottle to encourage returns. The local dairy would pick up the empties when they delivered new milk, wash them, and refill them. In order to be reusable, a glass bottle has to be thick enough to survive being banged around with other bottles and heat sterilized many times, so they're pretty heavy. If the manufacturer is shipping their products long-distance, the cost of collecting empties, cleaning them, and shipping the heavier bottles both directions is a lot more than the cost of buying new bottles. There are very few small, local producers of milk, juice, and other beverages (except micro-breweries) these days so products have to be shipped a long way. Most beer bottles and other glass containers are currently made to survive just one trip from the factory to your house and they're as thin and light as possible without being too easy to break. As a homebrewer, I have to be careful which bottles I use because the really thin bottles can explode if the pressure inside is too high.",
"In The Netherlands, you pay 10 cents extra for most types of beer bottles. You get that money back when you return it to the store.",
"You also have to consider how many of them end up broken before they get back to an actual recycling place (or the manufacturer if you want to insist on reusing them). You can't do anything with a broken bottle besides melt it down and start over.",
"When I was a child, we did this here in the States. Your \"pop bottles\" were all returnable/refundable. You would buy a six-pack of Pepsi or Mountain Dew or whatever your soft drink of choice was and then drink them. The empty bottles were put back into the six pack flat and returned to the grocery store where you would get a nickel back for each one (some states gave more, and those were usually listed on the top of the bottle). The bottling company would pick them up, sanitize and refill them at their plant. We did this all the time. I had an uncle who would go along the road side and collect unbroken refundable bottles for spare change (he was just a kid at the time, too). I seem to recall this phasing out sometime in the early to mid-80s with the onset of plastic bottles and aluminum cans becoming more popular. I'd say storing bottles for this purpose takes up a lot of real estate and probably isn't as efficient as just manufacturing new plastic bottles and aluminum cans. Good memories, though....",
"They can but for all but the smallest operations it’s usually not worth it. A factor to consider is space. Empty bottles still occupy a bottle’s worth of volume. A bunch of bottles in a bag or box further take up space because they don’t fit evenly together. Hence the difficulty of the scheme in Seinfeld to bring deposit bottles and cans from New York to Michigan to take arbitrage advantage of Michigan’s ten cent deposit (vs NY’s five cent); the only way they could make it profitable was if Newman got his hands on a mostly empty mail truck and did it under the cover of a normal mail run. There are ways to minimize that volume logistically, but the simplest and most effective way on any kind of large scale is to smash the bottles to compress the volume the constituent glass would take up. That being said, the milk delivery process of yore used* to be exactly this. You got fresh milk from the dairy in glass bottles, and you’d leave your empties on the porch or in the box for the milkman to retrieve and bring back to the dairy on his run. *Well, still is. It’s just not as common as it used to be, but many smaller dairies still do home delivery of milk and milk products the way they used to.",
"This used to be the model - there were local bottling businesses everywhere. Deposit bottles would be collected, cleaned and reused. But there were many, many fewer brands and sizes of soda to deal with. And the deposits on the bottles used to be a much larger portion of the price of a bottle of soda, making them more valuable."
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naoe6d | What maps do pilots use? | If the Earth is round, which I think we can all agree on, how do pilots of planes and ships know how to navigate? If flat maps can't display the correct distances, does that mean they have special maps for that? | Earth Science | explainlikeimfive | {
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"A flat map can display correct distances. The scale is just not the same for all part of the maps. You have to compensate for it but it is quite possible. For Mercator projection the scaling [looks like this]( URL_0 ). The Mercator projection was created for sailing because it preserves angles. If two lines cross at 32 degrees on a Mercator map that still do that if you draw them on a globe. It preserve angels and shape locally, this is called a conformal projection. A course with a constant bearing is a straight line on a Mercator map. The Mercator projection was created in 1569 for use in navigate because of it's properties. The compensation you need to do for distance is relative simple to do. Angle conversion would be a lot more troublesome. Today there is lots of computer that you can use for planning that do all use spherical coordinates internally. Just test [ URL_1 ]( URL_1 ) and click on stuf and the PLAN and you will se the the great circle path between the points with correct distance.",
"The \"flat maps can't display correct distances\" only becomes a problem when we talk about large distances (order of magnitude of the earth size). Pilots can use local maps just fine as all other vehicles (think of Canada: they have no problems using maps even though their country is displayed relatively distorted on a map). There are of course \"special\" maps, but that's more a thing of what objects are drawn (e.g., a ship captain might be more interested in the water currents and depth as well as lighthouses, and not so much in the restaurant in the centre of an island, pilots care about flight corridors, cars about streets and so on). Edit: corrected mistake, \"globe\" to \"map'"
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naoizh | What does a degrowth global North look like? | URL_0 | Economics | explainlikeimfive | {
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"I mean, the idea is that emissions are tied directly to economic activity, and thus if you have less economic activity, you necessarily have less emissions. Mathematically and economically, it makes sense, and both the 2008 and 2020 recessions are pretty good proof of the concept. The problem in figuring out what it \"looks like\" is because it largely assumes that things currently done in the global North can be equally done in the global South, which...is not likely. Further, a lot of what the global North currently produces goes a long way towards keeping the global South functioning (e.g. Brazilian Ag functions because of American petroleum exports; without those exports, Brazil essentially can't grow food because of how poor Brazilian soil is). Thus, what it ends up looking like is highly dependent on if it *works* or not. At best, you get a long-term deflationary economy, poor economic growth, and decreased spending. At worst, the above effects trigger a much stronger economic shock, at which point the economic system outside of North America basically collapses."
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naphe1 | What is Hedging with respect to Future and Options? | Any trader who could dumb it down with an example? | Economics | explainlikeimfive | {
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"You go to Vegas one summer and bet $100 on the Packers to win the next super bowl. The bet pays $1,000 if you get it right. Flash forward to next January, the packers have won the NFC and are playing against the Chiefs in the superbowl. Now, depending on the outcome of that game, you're either going to leave with $1,100 (the $1,000 you win, plus your initial $100 back), or $0. You decide that is too much of a gamble, so you hedge your initial bet by making a new bet against it. You bet $500 that the Chiefs will win the game. It pays an even $500 if you get it right. Now, if the Packers win, you end up with $600 (the $1,100 minus the $500 you lose on the new bet). If the Chiefs win, you end up with $500 (from the new bet). With just the 1st bet, your 2 options were either $0 or $1,100. Once you placed the hedge bet, your options are $500 or $600. Either way, your expected win amount (assuming the game is a toss up) is $550. But with the hedge, you're taking less of a gamble and can better predict the amount of money you will wind up with.",
"Hedging in it's simplist form is buying a financial instrument that will benefit if your other holdings decline. Example: If your invested in a broad market index fund but you think the market could see some downside, you may buy call options on something called the VIX. The VIX is commonly called the fear index or volatility index. If the market begins to crash, then the VIX will go up.if you own call options then your option value should increase which will offset (or hedge) against some losses on your primary holdings. Think of option hedging as a form of insurance. If your wrong, then you've just paid a premium to have had the hedge. But if you're correct then you will have successfully reduced the negative impact to your underlying portfolio. Think about car insurance. If you never have an accident, then your premiums for that year are gone. But if you do have an accident then your insurance will help to reduce your loss. It's the same general concept."
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naqtyu | How does rubber go from liquid from a tree to being a tire or a rubber band? | Technology | explainlikeimfive | {
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"Rubber is mixed with various fillers, oils, resins, and anti-oxidation chemicals to get the right consistency and then a final mix of sulfur curing agents is added. When heated under pressure, the sulfur molecules crosslink the rubber molecules together, turning a bowl of rubber spaghetti noodle molecules into a solid and impenetrable molecular chain-link fence. This process is called “Vulcanization.”"
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naqxqj | How can one pipeline deliver different brands and octanes of gasoline? How do they separate them at the destination? | Technology | explainlikeimfive | {
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"All of these folks saying pipelines only deliver crude oil are incorrect. While that is the most common scenario there are some large pipelines that transport gasoline and diesel refined products along with typical crudes. These pipelines are batched systems and the operators account for an interface mix of the products (transmix). This is a sacrifical cut of a lower quality product to maintain the quality of the higher value product. The batch train lineup in the pipeline is carefully scheduled to avoid contamination.",
"There is an interface of the different fuels, like diesel and gasoline. They do mix a little but due to the different densities they stay pretty much separate. When the product (s) gets to a tank farm they will run that interface into another tank then likely introduce that into a diesel tank because the volume in the tank will dilute that interface and still.keep the product in spec (I mean a huge tank with thousands and thousands of gallons). I have worked where a pipeline comes into a tank farm and this is how they receive the different fuels. Like I say some mixing does occur but it's diluted in the large tanks. They will typically not interface with regular gas and premium because the density is too close and they would mix more. Edit This is for fuel pipelines, I am.not sure how or if they separate crude in the pipes.",
"They either use the mix or they will put in a \"pig\" a larger rubber stopper to separate the mix...",
"The pipeline only carries one thing, gasoline. After it comes out of the pipe additives are put in by the customer to raise the octane rating, add cleaners and detergents, etc. But every gas buyer is getting exactly the same gas out of the pipeline.",
"They can insert a pig into the pipeline, the pig goes between the different fuels. Example pig seen here: URL_0"
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nar6q9 | How does the contact lens stay in the center of the eye and not go anywhere in the white part when already worn? | Biology | explainlikeimfive | {
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"The cornea sticks out of the eyeball just a little bit and the contact lens is designed to fit over that shape. If you have astigmatism, It might not stick out as much or too much or is just a bit misshapen so that it is harder for the contact lens to stay.",
"The optometrist who prescribes them performs a contact lens fit as part of the eye exam, to be sure they fit properly. The eye bulges out a little in that spot due to the cornea, the clear part of the eye in front of the iris and pupil that does most of the focusing of the light that enters the eye. A contact lens is designed to fit over that shape. Most contacts are made within a few variations in size and shape, so that one of the combinations of options is likely to fit most people. Think of it like having S, M, L, and XL shirts: one of the standard sizes is likely to fit most people. A good fit is tight enough to stay in place well and not cause ulcers by moving around too much on the eye, and loose enough to let a little of your eyes’ tears underneath to lubricate and nourish the eye and to not damage it by digging in to the cornea. The doctor checks for these conditions during the fitting (as well as other factors like how likely you are to take care of them properly and what your use/lifestyle is, to recommend ones made of materials that are better for how you will use them). Some people have corneas too oddly shaped to wear normal contacts. Keratoconus, for example, is a condition of the eye that causes the cornea to grow out into a cone shape instead of the normal sphere. A nice normally rounded contact lens won’t stay put over a conical cornea; think of it like trying to balance a bowl on a traffic cone with highway traffic roaring by. So mild to moderate stage may wear special scleral contacts that are larger, covering some or most of the whites of the eye (called the sclera) as well as the cornea, in order to stay on and also to help constrict the abnormal growth of the cornea.",
"When the optometrist makes your prescription, they include your eye measurement, and prescribe you a contact that fits to your eye size/shape. It doesn't move outside of external force because it's fits your eye, just like if you get the right size pants they don't fall down.",
"It doesn't always. I had to have one I couldn't find, fished out of the back of my eye several years ago. I thought I lost it, but no, it was clear around behind where you couldn't see it. I never wore contacts again. I didn't like them that well anyway.",
"It's pretty rare, but contacts also can slide off the center of my eye. I remember a few high school wrestling matches where I lodged a contact way up inside my eye."
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narnvb | why do antidepressants decrease your libido? | I thought this stuff was supposed to make me feel good | Biology | explainlikeimfive | {
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"Depression involves a chemical in our brain called Serotonin being out of wack. Several types of anti depressants work by affecting how our bodies interact with serotonin in an attempt to bring it back in line to normal levels. However, like a lot of chemicals in our body, serotonin doesn’t just do one thing, it is involved with a bunch of things. It helps regulate mood (the main issue with depression) but also affects stuff like appetite, sleep, and libido. Our brains are stupidly complex and we don’t fully understand them. Because of this, we can’t really target mood regulation super well and just shotgun serotonin into the brain and hope for the best. This typically helps with depression, but can also affect the other stuff that serotonin does.",
"To add to the good explanations, antidepressants are not supposed to make you \"feel good\". It's supposed to make you feel *not depressed*. While feeling depressed isn't a good feeling, feeling \"good\" isn't simply the absence of depression. This is a cheesy metaphor, but think of clouds in the sky. With the clouds, everything is filtered through them and days aren't as bright. Things seem more the same. If you take them away, you can clearly see a sunny sky, a moonlight sky, or a dark night sky before the moon as risen. Taking away the clouds doesn't change what's going on in the sky behind it. Alleviating depression doesn't make everything sunny all the time; it reduces the impact depression has on how you view/feel about everything. Then yeah, as everyone else noted, side effects of messing with brain chemistry can do annoying things like decrease your libido. Or mess with your appetite, or give you weird thoughts that are different than the weird thoughts from your previous depression.",
"Antidepressants mess with the chemical balance in your brain, and libido is controlled by, well, chemicals in your brain. By messing with the happy/sad chemicals antidepressants also reach into the horny chemicals, so libido is lowered but your general happiness is higher"
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narwix | What causes the light of the sun to have different angles when it shines through clouds? | As the sun is so far away it should only go 1 angle, right? | Physics | explainlikeimfive | {
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"Yes, light from the sun is effectively parallel. The reason it doesn't look parallel is due to perspective. You know how when you [look at railroad tracks]( URL_0 ) the tracks seem to get closer to each other? It's the same thing with beams of light.",
"The angles aren't different. They appear to diverge because in geometry the rule is that parallel lines that move away from you or toward you will always appear to diverge. Train tracks are the easiest example of this.",
"It’s an optical illusion: the sun’s rays that we see are near enough parallel. Just like when you look along parallel railway lines, they appear to meet in the distance, the same is true with the sun’s rays. The difference is, our brains interpret the sun’s location as just above the clouds, rather than an incomprehensible distance away. The rays that we interpret as shining down through the clouds are actually shining at a very shallow angle, and are very much longer than we interpret them to be, making the perspective view so pronounced."
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narwv6 | asphyxiation build up of CO2 | apparently the chocking sensation is a build up of CO2 in your body, not a lack of oxygen. but how come when i breathe out and then hold my breath i get that sensation until i breathe back in again? | Biology | explainlikeimfive | {
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"> apparently the chocking sensation is a build up of CO2 in your body, not a lack of oxygen. Yes. CO2 is actually mildly toxic; the distressing feelings associated with asphyxiation are entirely caused by your body sensing and reacting to carbon dioxide, partially in an effort to force you to breathe, and more generally is related to what is called nociception, or the reaction to noxious stimuli. The other side of this is that you *don't* get this reaction if there's no CO2 involved, which is why pure nitrogen can actually be relatively dangerous; it can displace oxygen, but because nitrogen is functionally inert none of your body's CO2-based alarms will go off, so you won't know what's happening until it's too late (and, in the grand scheme of things, is actually not a terrible way to go out). > but how come when i breathe out and then hold my breath i get that sensation until i breathe back in again? Your body is continually dumping CO2 into your lungs; the act of breathing just exchanges the gas in your lungs for fresh air."
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nasgux | How is π (3.141) equal to 180° in radians ? | I mean pi is an irrational number so how is it equal to 180 degrees ? How do we know it ? | Mathematics | explainlikeimfive | {
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"Because a radian is **defined** as being 360° divided by 2π. We didn't \"discover\" that's what it was, we made it so that it was so.",
"A circle is defined as being 360 degrees, or 2π radians. Thus, by definition, π radians is *precisely* equal to 180 degrees.",
"I think this gif on Wikipedia demos it pretty well. URL_0 URL_0 #/media/File:Circle_radians.gif Angles are a real thing. And we need some way to measure them that we can all agree on. So at some point we started using 360 degrees to mean an entire circle. It's an arbitrary number, we could've picked 100, or 1000, or any other number. 360 is just nice because our brains can easily divide it by 2,3,4,6,8,12,10. But we didn't have to call them \"degrees\" and we didn't have to make them 360. We just decided that one degree is the angle needed to make 1/360th of a circle. Pi is the name for a special irrational number. Pi is defined to be the ratio between the circumference and the diameter. It is also the ratio between the half diameter and the radius. Since the radius is defined as being half the diameter. The circumference is defined as being the distance around the edge of the circle. The diameter is defined as the longest width of the circle straight through the middle. Someone decided that the word radian is defined as the angle needed to make 1/(2*pi) of a circle. So one radian of angle would get you to the point that traveling one radius of the circle would get you. In other words, you need 2*pi radians to to make the entire circumference of a circle. Or pi radians to make half a circle. Which is 180 degrees in the other way of measuring angles. So basically pi radians and 180 degrees are two different ways of saying half a circle's worth of angle. Because that's how degrees and radians are defined.",
"It comes from how radians are defined. One radian is the angle on a circle whose arc is one radius in length. Therefore a whole circle is 2pi radians and a half circle 180 degrees) is pi radians",
"Because a circle is split into 2*pi radians. This means that pi radians is half of a revolution which is equivalent to 180 degrees. They are effectively just different units for the same measurement (an angle). To convert from degrees to radians you divide by 180 and multiply by pi."
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nasz42 | Trying to choose between these LED therapy device options and understand why 1 is better than the other | Technology | explainlikeimfive | {
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"There's [no evidence they actually work]( URL_0 ), so you're probably wasting your money."
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nat84k | why Planet Fitness advertises itself as a “judgement free zone,” but then also has an alarm installed at all its locations that effectively judges anyone for being a so-called “lunk”? | Other | explainlikeimfive | {
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"What's the deal with no gallon water jugs either?",
"The lunk alarm is more how someones actions are disrupting others use of the facilities rather than making a judgement about their body type etc. If you are banging weights around then the loud sudden noise is highly disruptive to other users, whether the term lunk should have been used, but it is probably better than the selfish bastard alarm.",
"\"Judgement free zone\" doesn't mean \"disruptive jackasses welcome\". The \"lunk alarm\" is there to stop people from slamming weights around, shouting for attention, etc. They're trying to make the gym a chilled out environment, and the alarm is their way of sending a \"hey, knock that shit off\" message - this is not them judging the *person* at all, simply trying to prevent the *behaviour* that they don't want."
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nate9f | What is protein folding and how does it work? I have tried to understand and can get the concept. | Chemistry | explainlikeimfive | {
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"Proteins are made of smaller molecules called amino acids that your cells bolt together in a long chain. The proteins don’t stay in a long noodle-like chain though. Each amino acid has a different structure and this gives it a unique electromagnetic effect on the other amino acids around it. Under the combined effects of hundreds or thousands of individual amino acids, the long chain twists and rotates and folds into a complex three-dimensional shape. This shape is very important, as it determines whether or not the protein actually functions, and how effective it is. This shape is also *enormously* complicated to figure out. You have to sequence out how your body is building the protein and in what order, and then calculate how the thousands of competing electron clouds around each atom twist and pull the molecule into shape. It’s a problem that requires vast computational power to solve, these are the most complex molecules in the universe."
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natlz2 | Why do we get angry when we're hungry? | Biology | explainlikeimfive | {
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"Your brain uses fat and sugar for energy, when it doesn't have enough fuel, it sends a stress signal. The anger or sadness you feel is a response to that stress signal. Do you know about the fear/stress response?",
"The brain is sending the necessary signals to fix whatever is wrong. In this case you can't relax and pretend things are fine, because you need food, so the mind makes sure this is the case. It's the same with all emotional responses, being for a reason, only we've created such an unnatural environment that it often gets confused. Depression and anxiety are other examples of your bio-feedback going haywire, often because of poor diet/exercise, or hereditary imbalances. Food though? Food is something we've always needed and always will and because we feel our stomachs growl its a lot easier to pinpoint the reason that we feel awful."
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natyoo | why is it we as humans need to warm up or stretch before exercises, but we never see other animals do the same? | Biology | explainlikeimfive | {
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"Animals aren't as sedentary as humans are nowadays. They move a lot more and are more active, so they're always \"warmed up\"."
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naubwu | Why does hot coffee that goes cold taste bad, but iced coffee or cold brew taste fine? | Other | explainlikeimfive | {
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"Ice Coffee is cooled down immediately after brewing so the oils in it have not evaporated away, and other compounds have not oxidized due to exposure to air. It is still fresh and so still tastes good. Standard hot coffee that is allowed to go cold in your cup over the course of an hour or more has had more of the oils evaporate due to being at a high temp longer, and had more of the compounds oxidize due to sitting for an hour or more. The temperature is a very small factor in it starting to taste bad, it effectively going \"stale\" or the coffee equivalent of going flat over time is the factor.",
"As an old nurse, I can tell you that coffee at any temperature is acceptable. We often pour coffee that we don’t get to for an hour or more. ❤️☕️",
"long time specialty coffee barista here. \"specialty coffee\" is used to denote high-quality beans that are sourced directly from farms, not bought on the commodity markets. the roasters we worked with were extremely dedicated, and the product was often very different than what most people are accustomed to. a light-roasted high quality coffee should have a color like tea, a clean body (not thick!!!!!!!!), and a juicy, flavorful, sweet flavor. good coffee is truly more like tea than the coffee you'd get at starbucks or dunkin donuts, to the point that those latter drinks are almost unrecognizable as coffee to me. here's my point. if you're drinking GOOD coffee, it tests *best* at lower temperatures, somewhere between hot and room temperature when the flavors have had time to develop and it reaches a temperature that won't scald your taste buds. it will continue to taste good as it turns lukewarm and cool. so if your coffee tastes bad when it's cooler, it was never good coffee to begin with. as such, i cannot really answer your question, as the premise of the question (\"hot coffee that goes cold taste\\[s\\] bad\") is itself flawed. but i'll try to answer somewhat. iced coffee that you get at many shops is simply yesterday's brewed coffee poured over ice. if that tastes good to you, then that's great, i'm jealous! at best, it's tolerable to me. i make no apologies for being a snob so save your breath if you want to call me out on it. cold brew makes good coffee because for whatever reason the low temperatures never extract some of the harsher notes from even low-quality coffee. i suspect that most places are doing a better job at filtering cold brew, because partly why warm coffee that goes cold tastes bad is due to unfiltered solids continuing to brew, leaving bitter/sour tastes.",
"Our coffee maker doesn’t have a heating element and instead stores the hot coffee in an insulated thermos carafe. Even when the coffee goes cold it retains its flavor quite well. The open top glass carafes that sit on a hot plate are death to good coffee.",
"In general, when food or drink is hot, the flavor is mellowed out, and when it's cold, it's intensified - and that's especially true with bitter flavors. With hot coffee, since we want it to be served hot, we brew it to an intensity that tastes good at that temperature. When it cools down, it ends up tasting too strong and bitter, because those flavors are intensified past where we wanted them. When we make iced coffee or cold brew, we brew it to an intensity that tastes right when it's cold *and* diluted with ice. So we engineered it to have a good flavor at that temperature - if you took an iced coffee and heated it up, it would actually taste *too* mellow and diluted, compared to what you'd expect from a regular hot cup of coffee.",
"Coffee from a gas station that cools down tastes terrible because first its low quality, and second, its over cooked sitting in the machine ready to serve. I make high quality coffee via pour over method, and when it cools, it tastes different than when it was hot, but not at all bad. The difference between the two is astonishing. Ive had gas station coffee that tasted fine hot, and like a tire cold. This doesnt exactly answer your question via chemistry, but I suspect if you're running into this situation, lower quality coffee is part of the equation.",
"We brew coffee and then put it in the fridge when it cools off a bit. Flavor is amazing and no bitterness. Don’t put ice in it either as it waters it down nor do we add sugar/milk. We started this by accident after having to run to the hospital after making a fresh pot of coffee. Didn’t want to toss it and didn’t want to leave it on the hot plate, so we put it on a hot pad in the fridge. Sometimes I’ll get new/different brands and taste them hot then cold to see how much the flavors change."
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naujov | Why Are Most Animals Sclera (whites in humans eyes) Not White and a Different colour? | Biology | explainlikeimfive | {
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"Usually they’re fairly dark for camouflage and UV-resistance purposes. Humans and some other social animals have developed brighter sclera, presumably so that other members of our species can more easily identify exactly what we’re looking at."
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nauuky | why do we hate the sound of our voice when listening to a recording? | Biology | explainlikeimfive | {
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"Fun fact. The voice what you hear from recording is your real voice. Have you ever tried recording the voice of someone you know. You will notice that the recorded voice of that person and their voice what you hear directly whenever you are talking to them is the same... Meanwhile yours are not. It is because the voice you hear whenever you speak is a bit pitched. It is more \"mature \" or deeper. The reason behind this is this. You hear your own voice differently because it hits you directly. It comes from you and there are other paths within your head leading to inner ears where those voices of yours could very well travel. So all in all the recorded voice of yours is the \"real\" voice what everybody jis hearing whenever you speak The voice what YOU are hearing when you speak is the altered voice. as you hear it kind of differently. Funny isnt it?"
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naw1ai | why do people panic buy and hoard when supply would be OK otherwise? | Economics | explainlikeimfive | {
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"Because just beneath the veneer of civilization most people are just stupid greedy primates ready to split your skull for *their* banana.",
"Tommy Lee Jones said it best in Men in Black. \"A person is smart. People are dumb, panicky dangerous animals and you know it.\"",
"In game theory, it's called the [prisoner's dilemma]( URL_0 ). It's globally better if no one panic buys than if everyone panic buys. But individually, it's always a better choice for *me* if I panic buy. Using the example in the wikipedia page: * if you don't panic buy, my options are -1 (don't panic buy) or 0 (panic buy). * if you panic buy, my options are -3 (don't panic buy) or -2 (panic buy) So if there's no way for us to coordinate and no punishment for me if I panic buy, I'm *always* better off if I panic buy. Even if it would be better for both of us if we coordinated to stay calm.",
"Generally it's not people buying a huge amount, it's mostly lots of people buying slightly more than normal, in this case either filling up sooner or topping up instead of just putting $20 worth in. Everyone buying slightly more causes the supply issue.",
"Lotta people saying selfishness but that's not the whole story. When resources are scarce for an unknown amount of time the one who has the most is least likely to die. It's engraved in our dna to put oneself before strangers. It's illogical and kinda sucks but sometimes survival instinct prevails over higher reasoning.",
"We have a massive empathy problem here in the US. We'd rather have it and not need it than let someone use it when they need it.",
"Experience. A lot of people remember the last real fuel shortage and during storms we see fuel and basic good shortages too. The fuel shortage today isn't just from panic buying. It's price rises. Gas was like $2.90 a gallon last week and it's over $3.20 near me now.",
"Because you are making a guess as to whether *other* people are going to hoard. If they do in sufficient numbers, then you won't have what you need. At that point, you may as well just try to be one of the ones who got there first, so the poor guy who is at the end of the line gets the shaft and not you. Basically, because you can't guarantee that people are going to coordinate, it becomes a mad dash."
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naxicb | what is a lymph node? | I spent a night in the hospital last weekend because they thought I might have appendicitis (luckily I didn’t). I spent the night getting morphine and nausea meds and they released me to go home the next morning. I went to the bathroom and when I looked in the mirror I noticed around my neck and jawline were really swollen but not really painful. I showed my MIL who is a nurse and she said it was my lymph nodes that were swollen, meaning there might be an infection. We called the hospital but they said not to worry about it but if it hadn’t gone down by Monday to get it checked out. Luckily the swelling went down and I’m fine but I still don’t really understand what a lymph node is to begin with. | Biology | explainlikeimfive | {
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"Have you ever wondered what happens to all the fluid that leaves your cardiovascular system (heart, lungs and arteries) to reach your muscles and tissues? The answer is, Lymph Vessels! Without over complicating things, your lymph nodes that are located all around your body (spleen, neck, tonsils, groin, armpits) and help regulate your lymphatic system and fluid, which helps get all that fluid that has left to get to your cells, to get back to your heart. In this context however, you're more likely to be interested in their Immune function. A number of really important Immune Blood Cells (T Lymph, B Lymph etc.) reside in your Lymph nodes, think of them as little 'Test Labs', when a pathogen enters your body, the lab sends some specialists to the site of infection, to do some \"field work\", but they also, rather importantly, start work in the lab, testing out how they can kill the pathogen. It's during this testing that your Lymph nodes swell, due to the increased flow of fluid to the area. This is also why your lymph nodes are often the first indication of illness, as they become swollen oftentimes before you become symptomatic."
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naxkpk | How do magnets work? | Physics | explainlikeimfive | {
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"Okay, magnets and magnetic fields are really weird and are actually tied together with electric charges, and there’s two main kinds you’d deal with on a daily basis. First, and electromagnet. Moving electrons (or moving negative charges) generate an electric field around them, so if you have a straight wire with current running through it, a magnetic field that runs in circles centered on the wire runs around it. If you then coil that wire around something like a nail, you can turn that into a magnet by turning it on, running current through it, and generating a magnetic field. Then there are magnets like Bar Magnets, the stereotypical ones you see painted red and black with a North and South Pole. These magnets have magnetic fields because of an interesting physical property the material has. Normally the electric fields of an item’s atoms are all pointed in random directions, but in magnetic items all of the electric fields are actually aligned with each other. These electric fields then generate (or go hand in hand with) magnetic fields, which is how these things generate their magnetic properties. Fun fact about electromagnets, all electric motors are electromagnets, but instead of using the current to make something magnetic, they use it with something that is already magnetic, to where when the electric charges generate the magnetic field, the magnetic field causes the magnetic item in the center to spin, creating the motor. And, generating electricity works in the same exact way just backwards, spinning a magnetic field (so spinning a magnet) inside a coil or wires will generate an electric current in that wire. This is how turbines change spinning energy into electric energy."
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naxpxo | I have heard that the IOC takes a big amount of the Olympic profits, while the host tends to go into debt. Why do they need so much money and isn't it possible for it to go to the host? | Economics | explainlikeimfive | {
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"> Why do they need so much money Corruption > and isn't it possible for it to go to the host? Very much so.",
"They take as much as they can because until recently, getting the Olympics was considered a big honour and an opportunity to boost tourism. Lately, the IOC has had a hard time finding cities willing to play by their rules. The reason that the 2022 games are in Beijing is because literally the only other place in the world that wanted it was Astana, Kazakhstan. The next two Summer Games after Tokyo will be in Paris and L.A. since they both have a lot of existing facilities that won't likely be abandoned after three weeks.",
"> isn't it possible for it to go to the host? Well, yes, of course. It's not like it's a universal law of the universe that the IOC is owed a bunch of money. But that's the agreement that the host and the IOC made, and so that's how it goes, just like any contract or agreemet. Why does the IOC want a bunch of money? Because everyone wants a bunch of money. You, me, the IOC, the host, that guy across the street. The host is simply just hoping and betting that they get their money from tourism and national advertising from the games long after the games are over."
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naxxtp | How Does Flight Pricing and Fluctuations Work? | I don't understand this at all... I have never booked my own flight before and am trying to budget a vacation. 1 premium economy seat from Toronto to Tokyo was $1,800 last time I looked and now they are $4,000??? How does this work? Am I doing something wrong? How can it change so drastically when I looked LAST WEEK | Other | explainlikeimfive | {
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"People here are mostly wrong. Flight pricing is pretty insane. Airlines are *extremely* competitive on price and fluctuate their prices of each seat and route continuously, not just day by day, like nonstop. They have automated algorithims that take into account what seats are left, what class and so on. They also look at every other flight they have and every other flight every other airline has, on every route, and they try to make an \"optimal\" price point for their ticket to meet some goal they have--which may not be \"highest profit\". They may be even cutting prices (to take away from other airlines) or raising them if few seats are available, or lowering them if they would to avoid risk and sell the flight. Or any number of changes to make it how they want to position their pricing structure. And for complicated reasons, usually a flight wants to be slightly overfilled with passengers. That is position it so that you sell just a few more tickets than you have space, as some people will cancel or change flights or not make it-- but again, this is a usual case, and on some routes it will not be the case and they have other priorities--they may not even care how many people are on a flight if they need to get planes to places. It's not just \"supply and demand\", its absolute nonsense to say that, absolute nonsense-- its incredibly complex algorithms that take many many things into account. In rare occasions you can see flights have massive fluctuations like you saw when some market factor changes. What that change is though, is hidden to the public eye. However, as general rule, one that can certainly be broken though, booking less than a week to departure, prices often increase, as people's willingness to pay increases (and many of these flights are sold to businesses, which will pay more) and longer out, flights tend to be more steady in rates. Businesses tended to be airlines most valuable customers (along with rich people paying for high end services), so they banked a lot on that seats would be available at increased rates to \"last minute business travelers\". During covid, this has gotten destroyed as few business travelers are traveling. **tl;dr**: Airline tickets are dynamically priced for market conditions and can lower, raise or anything based on things that are going on. Supply and demand is only one factor",
"Generally, the closer your booking date and flight date are, the higher the prices. You basically pay for the convenience of having an earlier flight. Lower prices from sales or promos are mostly due to unoccupied seats in a flight, airlines would rather sell these spots at a lesser amount than leaving them vacant."
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nay27r | Boolean algebras | ELI5: Boolean algebras what is it and what’s a good way to memorize the process of it. | Mathematics | explainlikeimfive | {
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"Boolean algebras are systems where you take propositions which can have true-or-false values, and assign them symbolic names, as if they were math variables. Like maybe we decide A is \"it's raining today\" and B is \"the grass is wet\". These statements can then be combined in different ways, using connectives like \"and\", \"or\", and \"not\", to make compound statements. If we decide that the & symbol means \"and\", then we could write \"A & B\" to mean \"it's raining *and* the grass is wet.\" Or maybe we would like to write something like \"It is not true that it's raining *and* the grass is not wet.\" After all, it would be very weird if rain were falling but the grass were dry! We might decide that the ~ symbol means \"not\", and then we can write that sentence with a formula like: \" ~(A & ~B) \". But another way of saying the same thing, would be to say \"Either it's not raining, or else the grass is wet.\" Can you see why these two different formulations would mean the same thing? If the | symbol means \"or\", then we could write that sentence out as: \" ~A | B \". The point of boolean algebra, is that it's a set of rules which lets us *transform* a statement like \" ~A | B \" into \" ~(A & ~B) \" or vice versa, so that statements which are logically equivalent to each other can be switched around however we like. It's kind of like regular numerical algebra,where if someone says \"x is 5 more than y\", you can do some rearranging and say \"that means y must be 5 less than x\".",
"Boolean logic determines whether a set of data, typically a few variables, is true or false. 1 = true, and 0 = false. Boolean algebra determines whether this data is true or false by putting it through conditional statements (in Computer Science, I refer to these as \"logic gates\"). These conditions include simple comparisons; \"AND\", \"OR\", \"NOR\", \"NAND\", and \"XOR\". AND will set a statement as true if all of the variables in question are equal. Suppose we have two variables: A and B. A = 1 B = 1 An AND comparison is written as multiplication, so the expression \"A x B\" is symbolic of saying \"Do we have A and B?\" Well we know A = 1, and B = 1. 1 x 1 = 1 A x B = 1 We have A, and we have B! This statement is true. Let's change the value of B to 0. 1 x 0 = 0 A x B = 0 We have A, but we do NOT have B. Therefore, the statement is false. Let's look at OR gates, which are represented by addition. Let's keep the same variables as last time, A = 1 and B = 0. 1+0 = 1 A+B = 1 We have A, but we don't have B. However, we only need one OR the other. Therefore this statement is true. Let's change A to 0. 0+0 = 0 A+B = 0 We do not have A, nor do we have B. Therefore, this statement is false. The statements NAND and NOR are the same as their original respective statements, however the answer is inverted. A statement that would typically be true would be false, and a statement that would typically be false would be true. XOR is an \"exclusive or\". This means that the statement needa to be a true OR statement. Suppose we have A = 1 and B = 1. We have the statement: A XOR° B We know A = 1, so in a typical OR statement the result would be true. However, B = 1, so the result is false. Let's change B to 0. 1 XOR 0 = 1 A XOR B = 1 We have A, but we don't have B, which means the XOR is true. Apologies if this takes up a lot of screen space. I hope this helped! °XOR has a special character that I can't type right now. It's a circle with a cross through it"
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naynm0 | why gasoline explodes while lighting a fire and lighter fluid doesn’t? | I’ve seen a few videos recently of people pouring gasoline on fires and having it not just catch on fire but actively explode. Advice on the internet seems to be to never use gasoline for a fire, only lighter fluid. From personal experience, lighter fluid doesn’t really explode, it just burns. What’s different about gasoline? | Chemistry | explainlikeimfive | {
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"Gasoline also \"just burns\", just more violently than lighter fluid. If you look into the [naming conventions]( URL_1 ), burning very fast is called deflagration, and actual explosives detonate. In any case, the *why* is down to the chemistry of burning - how fast oxygen in the atmosphere can react with the carbons and hydrogens in the fuel or explosive, to form carbon dioxide and water vapor. Even [iron burns]( URL_0 ) if oxygen can get at it efficiently enough. A majority of the explosives that detonate are made of chemicals that have the oxygen right there, built into the chemical formula, so that the burning reaction is fast enough to be a detonation rather than a \"burning\", and oxygen from the atmosphere is not needed for it.",
"It comes down to volatility. Gasoline is less stable than lighter fluid because that's what it's designed to do. Gasoline is designed to explode in an engine and has a much lower flash point (temperature of ignition) than lighter fluid.",
"Gasoline evaporates much more quickly. Flammable liquids like gasoline and lighter fluid can only burn when mixed with oxygen in the air. If you are brave, you can put out a lit match in liquid lighter fluid (but please don't try it.) So it's the evaporated fumes, mixed with air, that burns so rapidly, and gasoline makes a lot more fumes because it evaporates so quickly. Gasoline also has loads of energy. One cup of gasoline has the explosive energy of seven sticks of dynamite. (That was a public-service message when I was a kid.) FWIW, if you squirt lighter fluid on an open flame, it *will* make an impressive fireball. I burned the backs of my fingers pretty badly during the Texas ice storm in February, using lighter fluid to try to keep the wood stove lit. Never squirt any liquid accelerant on an open flame."
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nazw0n | What do the songs we like do to our brain that makes us like them and why does it differ from person to person? | Biology | explainlikeimfive | {
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"Musical taste is generational, and cultural. To avoid deviating too much from eli5 territory, it has to do with sound waves. The sound waves have ups and downs, they look like mountains and valleys. A soundwave has a frequency, the word frequency by definition just means \"how often something repeats\" so the frequency of a soundwave tells us how ofteb the mountains and valleys repeat. If its a high frequency soundwave it means it has many short, but often repeating mountains and valleys. If its a low frequency it means it has longer, less often repeating mountains and valleys. In music, the word melody means \"sounds that are played after eachother\" and harmony means \"sounds that are played at the same time\" (like a chord) Generally the sounds that we find \"harmonius\" or consonant, are sounds where the frequencies of the sound waves align. This means that the two sounds being played together, has the top of their mountains meeting at a close point, and so its valleys. A soundwave with double the fequency will always align, even though one of them is higher. This just means that for every 1 mountain and vallet for the lower soundwave, there is 2 mountains and valleys for the higher. The octave is double the frequency, and is considered the most harmonious. But if you play frequencies where the mountains and valleys do not allign, it will often sound like the sounds clash. This is called dissonance, and its the reason why a miss-played note in a song sounds very out of place. However, dissonance is not always bad. Music generally works by building tension by using dissonance, and then resolving that tension with consonance. Songs are kind of like telling a story, you cant just have the good parts, there needs to be some tension as well! But its also very very cultural. Ive described music out of the western 12-tone equal temperament system but there are many many more systems in the world, with different notes. This is why middle-eastern music may sound out of tune for someone who is not raised there. But if you grow up with that kind of music it sounds very natural. Thats not to say it sounda bad for you if you are not raised in the middle east, but it explains why other cultures music systems may sound \"out of tune\". Its just because we have not been raised with that music.",
"I'm not sure about this but I'd say listening to the music releases dopamine and other chemicals in the brain. Maybe it differs from person to person because of what type of sounds and music we heard growing up during our formative years."
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nb0yd9 | Why does overstressing your back muscles (bad posture) make them weaker? | Normally, if you overstress a muscle, it gets stronger. But if you have bad posture, causing you to overstress certain back muscle groups, you get back pain. Then the physio gives you exercises to "strengthen" those muscles. How does that work? | Biology | explainlikeimfive | {
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"Over stressing a muscle means that muscle is engaged. If you're not keeping your back straight, the muscles responsible for that action will not be engaged, making them weaker. Your muscles get stronger by using them.",
"Bad posture isn't caused by overstressing muscles, but by underusing them to the point that they atrophy and become weaker over time.",
"If you hunch over you use a different set of muscles than if you use your back muscles to keep your back straight. Not keeping your back straight and depending on the hunched over muscles, will therefore make the muscles straightening your back weaker (by not being used as much as they should) At least this is my understanding",
"Muscles have a length/strength relationship. Muscles at the end of the range in which they work are less strong than when they are in the middle of it. So lengthened Muscles due to bad posture can be less strong. The better answer for posture is lack of use, not over lengthened, as mentioned before."
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nb1189 | why do we never see clouds form, and why do they always appear to be at the same height? | Earth Science | explainlikeimfive | {
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"Cloud formation is relatively slow; if you're not staring at the sky and paying careful attention, you won't notice a cloud growing larger (or smaller, for that matter). Clouds are generally pretty far away, so they look like they're all around the same height. But I've definitely seen clouds that are well above/below another set of clouds. It's just that there aren't many reference points in the sky for you to regularly notice that the clouds today are higher/lower than the clouds yesterday.",
"We do, it just happens relatively slowly, and clouds are constantly on the move. If you watch a timelapse video of sky you'll normally see clouds starting to form. As for the same height - of you're talking about flat-bottomed clouds, the atmosphere isn't one static layer of gas. It has layers and currents of different temperatures and humidity. Hot air rises, carrying moisture with it. When it reaches a layer where the air is cool enough for the moisture to start to condense, clouds form - and is why clouds look like they've got flat bottoms."
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nb23gr | why does most mammal species have a pair number of breasts? why do human individuals commonly have 2? | Biology | explainlikeimfive | {
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"Mammals generally have bilateral symmetry so pairs of breasts fit in with that general layout, humans rarely have more than twins so extra breasts would not be an evolutionary advantage."
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nb2omr | How exactly are certain weapons banned from being used in war? | What makes things like poisonous gas or some firearms banned? Most importantly, why would nations play by the rules? Bonus question: what exactly is a war crime and how is it punishable? | Other | explainlikeimfive | {
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"Why would anyone play by any rules or laws? Enforcement. If one person uses the things, then everyone who agreed gangs up on them.",
"Most \"banned\" weapons have a reason. But they're only banned if others choose to enforce that ban. Basically the idea is that if you used banned weapons, the rest of the world will turn on you and that won't be good. The idea is to keep everyone in check. If you use a banned weapon, you're taking a risk that others aren't gonna be happy. Whether or not anyone cares enough to do anything though, is up in the air. Poison gas / chemical weapons got real nasty in WWI and the big issue is that against an equipped army, they aren't particularly effective, except as a first use when they're not expecting it, otherwise you can prepare for it. All it does is make the army prep for chemical warfare and cause additional, unnecessary burden and suffering against soldiers, civilians, and the environment. Chemical weapons are also pretty nasty in their effects, but mostly, its really nasty and its not really \"better\" than other weapons, so no need for them to be used. To my knowledge, no specific firearms are banned, I'm not sure were you got that from. The most prominent things that are banned are chemical weapons (and bio weapons), certain types of bullets which are hard to extract fragments or bullets that expand when hit, and laser weapons specifically made and used to permanently blind enemies. Some countries have voluntarily put self-bans on various other weapons, but this is far from as universal as the ones above, for example, many nations, but notably not the US, China, or Russia, have agreed not to use anti-personnel land mines. \"war crimes\" are mostly an unrelated topic to this question, so you're better off posting that on your own.",
"> What makes things like poisonous gas or some firearms banned? Because they cause undue suffering even beyond what you'd normally expect in war. > why would nations play by the rules? Because those that don't want horrible weapons used on them will abide by the agreement to not use them on others. > what exactly is a war crime It's any crime that is directly attached to individual or group actions related to actions taken in war. Often they are things that are unusually horrible, target innocents intentionally with no clear benefit, or violating whatever laws, treaties or international agreements on conduct during war. > how is it punishable? Depends on the crime and the country doing the enforcing, but usually they are enforced by the winning side(s) of that war.",
"Mutually agreed by most 1st world countries. Failure to comply results in the U. N. ganging up on the user, but if you look at Syria's use of banned chemical warfare on its citizens you'll notice that the U. N. turned a blind eye to it."
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nb33g6 | How does the optical illusion where something looks like it’s spinning slower than it is work? | Biology | explainlikeimfive | {
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"Cameras only capture a limited number of images (frames) per second. Imagine you have an object which spins one and a quarter times between each picture. This would look exactly the same as if it was only spinning a quarter turn per picture. Similarly, if it turns 3/4 of the way each time, it would look the same as spinning a quarter turn backwards. If it spins exactly a full turn it'll look like it's not moving at all.",
"You're right it's hard to describe. If you want to learn more or look up examples, this phenomenon is called **aliasing**. It's a result of how video cameras work. It takes still pictures at a constant rate. This is [easier to explain with a picture. Consider this:]( URL_0 ) A disk like a wheel is spinning **clockwise.** Each picture is one frame of the video. Between each frame, the wheel spins just less than one full rotation. Now think about what happens when you watch those frames. It will look like the wheel is spinning counter-clockwise, and much slower than it really is. Between each frame the wheel does 90% of a forward turn, but that looks exactly the same as 10% of a backwards turn. That's also why as a wheel speeds up, on video it sometimes looks like it slows down more and more, stops, then starts spinning the other way. It goes from slightly less than one rotation per frame to exactly one per frame, then slightly more. This aliasing effect only happens in video, usually not in real life. In real life it rarely happens, and would be the result of a flickering light creating the same \"strobe effect\" as the video frame rate. Outside in steady sun, it doesn't happen."
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nb3qjg | why do we sleep? | Other | explainlikeimfive | {
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"The honest answer is: We don't understand sleep very well. We know a little bit about how our brains work, but there is a lot about them we still don't understand. Sleep seems to act like the reset button on our phones. After our brains have been \"running\" for too long, they need a break. While our brains are still active during sleep, it's not active in the same ways as when we're awake."
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nb50qc | - Heat & Light from stars | Sun which is a star emits light and heat. The universe has stars bigger & brighter stars than the sun. 1) So do bigger stars emit more light and more heat ? | Physics | explainlikeimfive | {
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"Yes. Larger stars produce more heat and light. There are a bunch of different conformations depending on the life cycle of the star. Our own star for example, in several ~~million~~ billion years will burn through all it's hydrogen and start burning helium. At that point, it will blow up large enough to swallow the inner planets, making more heat and light. Edit - wrong order of magnitude for years. Edit 2 - URL_0 .",
"You guys are awesome, thank you for all the information. Cheers",
"Set your hose to a [spray setting]( URL_0 ) and spray your dog right next to you. Depending on how close your dog is to the hose, it may get 100% of the spray or something close to it. Now spray the same dog but further away. Your dog now takes up a smaller wedge of the spray, and thus gets wet slower than when he was taking up nearly 100% of the spray That's the effect distance has on the total heat/light of stars. We're relatively closer to the sun than most other stars, so it's more akin to getting hit by a hose up close. Even if a star was bigger and brighter than our sun, that's a bit like being hit by a fire hose instead of a garden hose. Yes it'll soak your dog a lot faster if it was right next to it, but the further away the fire hose gets, the slower it'll soak a dog."
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nb56mm | Why does toilet water move when it's windy outside? | I live on a condo and noticed that the water in the toilet bowl was slightly moving (kinda like waves) and was fascinated. So i started paying attention to it more and noticed that it would do that only on windy days, the windier it was, the more it moved and would sometimes start to resonate which blew my already blown mind! | Other | explainlikeimfive | {
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"There is a vent that goes through your roof and is connected to your plumbing drains. It facilitates the water draining to the sewer or septic. Wind blows over it and creates oscillations in the connecting plumbing.",
"[This is the typical sewer pipe setup]( URL_1 ). The water in your toilet bowl and in the U pipe under your sink prevent the sewage smell gases from getting into your rooms. However, these gases must be released or pressure will build up, so there's a pipe vent going to the roof. So when the wind blows strongly outside, there's a bit of a [chimney effect]( URL_0 ) and some of that atmospheric wind \"pressure\" pushes on the water in your toilet bowl a little bit, enough to create waves.",
"Interesting. I've never noticed this! Now I'll be staring at my bowl when there is a wind storm. If I had to hazard a guess it may have to do with the air pressure difference between outside and inside sort of like a barometer. Or it could be your building is slightly shifting in the wind depending on how tall it is."
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nb5mw8 | Why our body rejects organ transplants from others but not blood (of the same type)? | Biology | explainlikeimfive | {
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"Red blood cells have very few marker proteins on the outside (A, B, O are the classifications for these). Organs, however, are chock full of cells that have marker proteins all over them. So it's much more likely for the immune system to trigger on all of those (foreign) marker proteins compared to the few that are on the red blood cells.",
"Well there are reactions to blood transfusions, even those that are matched. But organs have more cells than blood so the match has to be more specific. Some organs are trickier than others when looking for a match. This is pretty general, if you could elaborate a little on your question I could go into more depth.",
"Most of the answers above are to some extent right, but none is - imho - sufficiently explaining the issue. Obviously, this is a very complicated topic and no ELI5 abswer can cover the whole of it. However, I'll still try to give a brief overview. So every cell in our bodies expresses different surface antigens. The most important one un the context of organ transplantations is the MHC (major histocompatibility complex; \"histos\" being greek for tissue). MHC are actually found in all vertebrates, I think but I'm not 100% sure. However, they are definitely found in humans, and there they're called HLA (human leucocyte antigen; because they are easily isolated from leucocytes and play a big role in their regulation as well). This MHC is sort of a passport of a cell that indicates it's human. Also, these structures differ from individual to individual, so it's not only a passport telling you it's a human cell but also telling you what country (aka individual body) the cell is from. Now in a living body there's always leucocytes all over the place that constantly check cells' MHCs/passports. If a cell does not have an MHC, it is killed, as there's definitely something wrong with it, e.g. it might be a cancer cell. If a cell has an MHC but it's different from the one of the body the leucocytes are from (e.g. the recipient's body), it will also be killed. To simplify and further stick to the passport analogy, if the police (leucocytes) find a cell without a passport (MHC), the cell is killed, and also if they find a cell with a passport from a different country (MHC, but different from the host body's MHC), the cell is also killed. That's why we try to match organ donors and recipients to have their HLAs (the human version of the MHC, if you remember) match as best as possible in order to prevent immune reactions against the donated organs. Also, this is the reason why we give immunodepressant medication, in order to reduce the host's leucocyte reaction to the donated foreign cells. Basically, it's like giving the police donuts so they get lazy and don't do their job anymore because they're busy pumping their carb intake up with the donuts. The mechanism behind blood transfusion is a little different. The ABO system works in a way that you always have antibodies against all antigens you do not express yourself, regardless of whether you've been transfused blood before. Think of it like a country (body) in which the cops (antibodies/immune system) are fighting mob bosses (A or B antigens/blood types). Generally, the cops would attack all antigens, both A and B. However, if the country (body) collaborates with the A type mob bosses (i.e. the person is blood type A), the cops know the A type mob bosses and don't attack them anymore. Thus, such an individual can safely be transfused with type A blood cells. However, if the cops come across a B type mob boss (i.e. blood transfusion of type B blood), they will fight the B mob boss and kill him (aka hemolysis, which has all kinds of bad implications come along with it). Similarly, in a person with blood type O, there's no mob bosses the country is collaborating with, so the cops will fight any mob boss they find. Thus, people of blood type 0 can only receive blood transfusions that aren't mob bosses (i.e. transfusion of type 0 blood, erythrocytes of which express neither A nor B antigens). People with blood type AB have, to stay in the analogy, collaborations with both A and B mob bosses, so they can receive both type A and type B blood as they know both antigens/mob bosses and thus won't fight them. As for why the HLA reaction does not occur with blood transfusion, it seems there's a relatively small amount of HLA molecules on the surface of erythrocytes (red blood cells) thus mitigating the effect. However, there are reports of reactions happening. For further reading, if you're interested: [Article on clinical relevance of HLA in blood transfusion]( URL_1 ) [Some general information on HLA in the context of blood transfusion]( URL_0 ) Sorry for having written a whole novel in this comment; I wanted to take the time to explain it somewhat exactly, as the question touches two quite complex topics. If anything is unclear or there are further questions still to be answered, ask away! Edit: Found another review specifically on the topic of HLA sensitisation in blood transfusions: URL_2"
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nb5nbk | How do nutrition labels even work? | I have a bottle of flavored water (0.68 cents at Wal-Mart, because I’m worth it) and it has 3 servings. If you drink 1 servings worth, you get exactly 0 calories and 0% everything else. But if you drink all 3 servings, you get 10 calories and about 10mg of sodium. How is that possible? I know there’s sometimes really small amounts of things like sodium, but isn’t that usually denoted as “ < 0%”? | Other | explainlikeimfive | {
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"If an item has less than five calories in it, it can be listed as \"zero calories.\" In your example, the drink likely has about three calories per serving or something like that. Basically, it's all round numbers, and the rounding can be weird sometimes.",
"Anything under a certain amount can be left off the nutritional label. This is why ketchup doesn't list cockroaches as an ingredient, even though they regularly end up in the batches."
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nb7qx5 | why do we say “uhm” when we’re thinking? I’m multilingual and it seems to apply to most languages. What makes it so “universal”? | Other | explainlikeimfive | {
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"Uhm and similar sounds are [filler words]( URL_0 ). Their main purpose is to signal that the speaker isn't done speaking. Often times we need a half second to think of what we want to say next. If we let that moment fill with silence, others may take that as a sign we are done talking and then start with their own thread. Filler words serve the purpose of signifying we have more to say. This is a universal problem. It is not surprising other languages have come up with their own filler words. Eliminating filler words from important speeches has the benefit of making the speaker sound more worth listening to. Someone who is used to being worth listening to wouldn't be worried about others interrupting their speech with their own. So we naturally give more weight to those who don't use filler words. In day to day conversations between friends though, filler words serve an important function.",
"IIRC it's called a \"verbal filler\" basically you make a noise like \"uhm\" or \"ahh\" while thinking to send a signal to your conversational partner that you are still speaking you are just trying to fond the word. My Chinese teacher taught us that in Chinese they tend to fill these gaps with the word \"Zhege\" (这个) over and over.",
"Are these filler words universal, though? I thought that one of the things that makes someone seem like a native speaker or not is whether they use the right filler words.",
"Its not universal. I'm more likely to say \"aaayyye\" than \"uhm\". Other filler sounds include \"shhhh\", \"tatatata\", \"dadada\", \"zzzzeee\" All depends on the speakers culture and language.",
"If your mouth is completely relaxed you just make this shwa sound, also called the neutral vowel. When you close that completely relaxed mouth it will make an mm sound. So uhm is about the lowest effort sound you can make, ideal as a filler."
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nb7z12 | what about a weighted blanket makes it so calming? | I know it releases hormones, but why? | Biology | explainlikeimfive | {
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"It isn't that it releases hormones. Compression lowers blood pressure which can calm anxiety and help put people at easy.",
"Humans tend to sleep better with pressure on them from blankets. It can also lower anxiety. It makes humans feel more comfortable. One theory on why we evolved this way is that humans used to sleep together cuddling as a group for safety. It was easier to stay warm and to not get attacked by animals when sleeping together like that. Lions do something similar. So, we feel calm relaxed and sleepy when a weighted blanket simulates the feeling of cuddling with someone for warmth and safety."
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nb877h | How can physicists determine the distance of a distant galaxy, billions of light years away, when space time is warped? (ie. light coming from these distant galaxies is bent throughout its path to Earth) | Physics | explainlikeimfive | {
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"There are a lot of different methods astronomers use to measure distance of very distant things. The short answer is that light doesn't bend much at all when going through empty space, so they just have to pay attention to where it does bend and they can figure out how it traveled. The longer answer is outside the scope of ELI5. But if you're curious, look into the distance ladder. Basically, knowing more about closer stuff can help us compare them to farther away stuff, and we keep building that up like a ladder.",
"I kind of understand your point-of-view here. I think the mistake you're making is thinking that warped space is somehow juxtaposed to straight space. It isn't. There isn't a shorter straight line to draw between two points versus the longer curved warped line. The curved line is the only line that exists and thus the only distance that exists. There is no straight vs curved contrast that we can make that might confuse the issue."
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nb8i2z | What does the weather forecaster mean by dewpoint? How does it relate to humidity? | Chemistry | explainlikeimfive | {
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"There is pretty much always water in the air. Humidity tells us how much water is in the air, relative to how much *could be* in the air. The amount of water that *could be* in the air depends upon the temperature of the air. So, let's say it's 75 degrees out and the humidity is 80%. If the temperature dropped, the humidity percentage would go up, even if the actual amount of water in the air did not, since the maximum amount of water that *could be* in the air has decreased. So, what happens when the air cools down so much that it hits 100% humidity? If it cooled down any more, there would be more water than the air can hold. At this point, the water in the air drops out as a liquid, forming fog or dew or rain, so that the humidity never rises above 100%. The temperature where this happens is the dew point. For almost any amount of water in the air, there is a temperature where it will reach 100% humidity and liquify. So, for any humidity/temperature pair, there is a dew point where the water in the air will start to drop out.",
"Dewpoint is the temperature where air can no longer 'hold any more moisture. When it reaches this point water collects into dew. Humidity is a measure of the percentage of moisture the air can hold. The warmer the air is the more it can hold. Cold air can hold less moisture. This is why a cold object like an ice drink will get dew on the sides. The air hits the cold object and suddenly grows cold, the moisture in the air collects on the object, creating liquid."
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nb8t1j | Why does water expand on freezing while other substances contract on freezing? | Chemistry | explainlikeimfive | {
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"When a substance freezes, it is because the molecules are no longer vibrating as much and are allowed to settle down into a more orderly state. That orderly state is usually one where the molecules are closer together, as the forces between them pull them together. However, these forces usually also pull them into a specific pattern. This is a crystal. [Here]( URL_0 ) is a diagram of ice's crystal structure. While most substances tend to settle closer together, in order to achieve its crystal structure water molecules must actually spread out a bit. By allowing them to organize themselves into this structure (which is what happens when they cool off), they organize themselves into a fairly spread-out pattern."
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nb93wm | How would have Pangea been formed when modern day maps show the tectonic plate borders expanding over the land? | I know this is poorly worded, so sorry about that. Modern tectonic plate map: URL_1 Pangea: URL_0 Shouldn't the borders have collided to stop the land from touching? | Earth Science | explainlikeimfive | {
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"URL_1 When two plates move towards each other, one Plate slides under the other and melts into the Mantle URL_0 When two plates move away from each other, Magma rises and creates new crust. The Earth's crust is constantly recycling itself.",
"Plates moving away from each other are making new ocean floor between them, that crust (under the water) didn't exist during pangea."
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nb98b9 | Does the speed of the internet depend on quality of the LAN cable? | Technology | explainlikeimfive | {
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"Kind of. In theory yeah different cables will handle different data rates. Making sure the cables are installed properly (no twisting, listen to the minimum bending radius, terminate properly) will help In reality I really can't see a LAN cable being the weak link for an internet connection, not unless the cable is outright faulty. For an internal intranet then maybe. Or maybe even an industrial office with internet. But a standard residential property I don't see it being an issue.",
"Your speed is only as fast as the slowest link. For example if you are using a cat 5 ethernet cable (rather than a cat 5e or cat 6), you are going to be limited to 100Mbps. Some cables are also shielded better than others, which prevents interference and improves performance.",
"Depends on lots of things. There are shielded lan cables because electromagnetic interference can induce unwanted noise into your cables. There’s different categories of cables to support various bitrates. For the last 20 years cat 5 has been sufficient, but in the last 10 years we see more cat5e, and lately people are building houses with cat6 or even 7 just to future-proof. If you have fiber-optic internet, a cat5 cable might be a bottleneck. If you’re at all concerned, get a good shielded cat6 cable and see if you have better speeds or less drops."
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nb98zv | How are URLs guaranteed to be unique across the Internet? | For example, what's preventing me from creating a GoDaddy account and making my own domain called URL_0 ? | Technology | explainlikeimfive | {
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"Ultimately, the Internet Assigned Numbers Authority (IANA) which sold GoDaddy the names they can assign. GoDaddy won't sell you URL_0 because they *can't*, and the DNS servers won't accept your claim of the address. The internet functioning depends on all these organizations working together, but you could totally do this within your own personal network. If you wanted to host your own DNS server and direct URL_0 to your own machine, then go ahead. But you can't do this for the internet at large, and if anyone tried they would be cut off from the rest of the internet in short order."
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nb9uqn | How is it possible to convert a 30fps video into 60fps? | I've seen some videos that were originally 30fps get converted into 60fps, and it looks totally normal. Where do the new 30fps come from? | Technology | explainlikeimfive | {
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"It’s a technology called interpolation. An FPGA (typically) at the frames either side of the one it wants to create, then predicts where things should be based on the motion in the past and the future. Then it draws the missing frame. As for it looking normal? Them’s fightin’ words."
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nbb3fy | Why cant gas cars use diesel and vice versa? | Technology | explainlikeimfive | {
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"Gas cars can’t use diesel because it doesn’t burn as easily and the engine won’t run well, furthermore it’ll ruin your catalytic converter While Diesel engines could in theory run on anything that burns, they are designed to take diesel fuel which is much more lubricating than gasoline, so the pump will break along with other stuff They both might run on the wrong fuel for a while, but not well and not for too long",
"Okay found the same post made a few hours ago"
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nbbjob | Why are black holes theorized to be infinitely dense instead of just an incomprehensibly large number? | It honestly seems easier for me to assume that something is just so incredibly incomprehensibly large or dense then it would be to try and say something can be physically infinite | Physics | explainlikeimfive | {
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"We don't know whats inside a black hole. Our known laws of physics don't work there. But if we apply the physical laws we know then it would get infinitely dense because it's impossible to have any distance from the singularity since it's gravity is so strong. (It's force is greater than the forces that repel particles from each other) The thing is at small distances and high gravity we'd need to combine quantum physics with general relativity, we would need a theory of quantum-gravity. And this could easily say something completely different happens, without any need for infinite density. This is basically the holy grail of theoretical physics. All the theories like string theory, M-theory or supergravity try to solve this and find a \"theory of everything\". As long this is unsolved we can only speculate what really happens inside.",
"The error with this logic is the fact that we know of no mechanism that would stop a black hole from collapsing further. In general, things like stars have a finite density because there is some balance between an external force (gravity) trying to collapse it, and an internal force that pushes against it. The earth doesn't collapse because of the immense pressure and heat inside of it. Stars don't collapse because the energy generated in their cores acts against the gravitational pull. Neutron stars have something called degeneracy pressure that prevents them from becoming even denser. If an object is compressed enough such that the gravitational pull is stronger than all those mechanisms listed above, the object will keep collapsing until it literally cannot collapse any further. By that point, it is infinitely dense because all the matter inside of it is concentrated in an infinitely small point."
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nbbowa | Some countries can be referred to as 'The Motherland' and others as 'The Fatherland'. What leads to this difference? | Other | explainlikeimfive | {
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"Some languages have both. In the Dutch language, fatherland refers to the relation of a person with their country of origin, while motherland refers to the relation of a country with its colonies or overseas territories."
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nbbvog | Why can't different species impregnate eachother? For instance, a German shepherd can breed with a pug, but can't breed with a deer. | Biology | explainlikeimfive | {
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"There's ways that egg cells recognize viable sperm cells. They use proteins that link together in order to make a working connection. Think of it as studs on lego blocks, you can build with all kinds of lego blocks because they all fit together. Lego city, space lego, though they're different sets their studs are all the same. Now try to click some mechano on to lego. It won't stay put, the studs, (proteins) won't fit together. So all dogs are basically legos, but horses or cows or sheep or corn, different building systems. All made of plastic but with diffrent kinds of studs to lock in to place. & #x200B; Some species are still fairly close, like lions and tigers, horses and donkeys, think of those like Legos and megablocks they'll fit together, but what you wind up with isn't really structurally sound.",
"Amount of DNA is different. The genes on chromosomes are different. Gametes of different species do not have the right proteins to recognize each other and fuse. Mating behavior and mate selection between different species are too different to allow for breeding."
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nbcf7q | Why do you feel nauseous when overly hungry, which can prevent you from wanting to eat? | Biology | explainlikeimfive | {
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"There’s acid in your stomach that helps break down food. The amount of acid builds up if you haven’t eaten in a while. It’s this excess acid that causes nausea."
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nbcr9w | What is instantiation, explained to a non-developer? | Technology | explainlikeimfive | {
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"Instantiation means creating something using a mechanism to create it with certain constraints. Imagine having a 3d Printer File. Actually printing it would be instantiating (creating an instance of) that object.",
"When you instantiate something, you're creating a copy (an instance) of something. It's analogous to having a blueprint of a car and then producing (instantiating) vehicles (i.e. the copies/instances) from said blueprints.",
"A class is a box. When you press the blue button, [you *instantiate* a Mr. Meeseeks object]( URL_0 )."
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nbculz | How is the weight of the planet Earth calculated? | Earth Science | explainlikeimfive | {
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"The way it was first done with any accuracy was with the [Cavendish experiment]( URL_0 ) in 1798. This used several large lead balls and measured the force of gravity between them, i.e., how much one lead ball attracted the other. This tells us how strong gravity is for a given mass at a given distance. And we also know how strong the earth's gravity is and how far it is to the centre of the earth. So now we can use [Newton's law of universal gravitation]( URL_1 ) to work backwards to find the earth's mass."
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nbf84w | | What is the ‘event horizon’ as described by Stephen Hawking and what does it mean for time, space and light? | *Edit* Thank you to everyone for the enlightening responses, I’ve learnt many many things and many have them have been in such clear terms that a giant idiot like myself has been able to understand. The internet is excellent at times. | Physics | explainlikeimfive | {
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"The closer you get to the centre of a black hole, the stronger it pulls, and the faster you need to move to escape that pull. At some point the speed you need to escape its pull becomes greater than the speed of light. Because speed of light is the fastest speed anything can move with, nothing can escape it. This point is what's called event horizon.",
"Event horizons are definitionally a boundary beyond which events cannot affect the observer. Specifically, this is a concept that applies to black holes - in an ELI5 sense, imagine a marble in a deep pot with a curved bottom. By swirling the pot around, you can get the marble to climb the walls, but imagine that this pot had sides so steep and tall that no amount of swirling could get that marble out. If one were to imagine that marble is a photon, the highest point you could get the marble swirling would be the event horizon - if anything, marble, spaceship, rubber duck, were to get into the pot beyond that point, it doesn't matter how fast it's going, it's stuck in there. Since light itself can't escape the event horizon, you can't actually see or even detect what goes on beyond that point - and due to relativity (if someone figured out an ELI5 on relativity, that would be entertaining to read) the closer an object got to the event horizon, the slower it would appear to go, so someone watching something go over the edge would just see it slow down to a complete stop as it entered. Black holes are wild. EDIT: Kurzgesagt came out with a really neat video on this topic a few weeks ago - [check it out]( URL_0 )!",
"Event horizons are the \"edge\" of a black hole's...blackness. It's the point where the black hole's gravity becomes so strong that light (and by extension everything else) can't overcome it and gets pulled in, leaving only black nothingness. This leads to another important aspect about black holes: The actual black hole object (the singularity) is an infinitely-small chunk of mass at the very center, and the hole part that we see is just an illusion, created because all the light that would otherwise travel to our eyes is being sucked into the hole. Another important thing: If you were to fall into the black hole (assuming you weren't ripped to shreds first), time would pass normally for you, and you would watch the universe shrink away behind you until you were surrounded by darkness and/or ceased to exist. Someone *watching* you fall in would see a different thing though. They would watch your descent slow down the closer you got to the event horizon, because the light \"image\" of you falling would become more and more distorted the closer you got. This would continue until you froze in-place completely, at which point you would just kinda fade away since the \"image\" of you falling in, also falls in with you. And one last important thing: Most black holes have event horizons a few dozen miles wide at most. [But some, at the core of very bright galaxies, are orders of magnitude larger than the largest stars, and could swallow solar systems whole.]( URL_0 )",
"Its the place where information can only be pulled farther into a black hole. Time, space, and light, pretty much immediately lose any relevance of what they were before crossing this boundary. In our observations of what we think is a black hole, we are really only seeing the smear left over by the stars and gas and matter heating up as they approach the horizon.",
"I just had to explain this to an actual 5 year old a few months ago. Told him that a black hole sucks up everything, including light, which is why it's all black. The event horizon is the point of no return. Once you cross that point, there's no escape. You'll stretch like spaghetti and time will slow down and then you're gone.",
"Think of this way: You throw a ball vertically up on Earth.. It goes a fair distance then falls back down on the ground. You need to throw it at 11.8 km/s or more for the ball to \"escape\" Earth and go into Space (I'm ignoring air resistance here). Similarly, on Moon, you'd need to throw the ball at 2.38km/s, since Moon's gravity is less than Earth. This is known as the Escape Velocity. For our Sun, the Escape Velocity is 615km/s, ie, anything coming out of the Sun slower than that will \"fall\" back into the Sun. Escape Velocity also depends upon your distance from the gravitation source(center of the cosmological body, usually). So if you throw the ball from an airplane 35,000 feet in the air, the escape velocity required will be slightly low. Now think of this way: Event Horizon is the boundary _around_ the black hole where the escape velocity is 3x10^5 km/s. Does this number look familiar to you? It's the velocity of light. It's also the Universal cosmological limit, meaning nothing can travel faster than that. You can work out the next conclusion on your own but I'll write it here: Since the escape velocity of a black hole at event horizon is \"c\", nothing escapes it, not even light. (Simplified explanation of course)",
"Think of it like getting your hoover and a piece of lint. Place the lint on the ground and turn on the hoover, slowly edge the hoover closer and closer. The event horizon is the point at which the lint is pulled into the hoover and has no chance of escaping the suction. Scale this up to the black hole and not even the fastest things in the universe can escape.",
"The event horizon is the last point at which light can escape the blackhole, if it goes any closer, light will be sucked into the blackholes singularity (center of the blackhole) and its lost forever.",
"Nothing goes faster than light right? So anything, including events, can only go slower than light. If you slow down light (like a black hole) or stretch space fast enough (like our universe), there's a point where light cannot reach you. If light cannot reach you, nothing can, including any information about any event. From your point of view, there's an invisible line beyond which you cannot see. Kind of like the horizon on earth. An event horizon.",
"The best explanation of an event horizon I've ever heard is this analogy. Let's say you are in a canoe on a river. A little way down river is a waterfall. Right now you are safe and can paddle in either direction. As you get closer to the waterfall the river picks up speed. For a while you will be able to paddle against the current and get to safety. But at some point the current is going to be moving faster than you can paddle and you are going to get pulled over the waterfall. That point is call the event horizon. Same thing applies with black holes. It's the point at which there is no escape and you're going to be sucked into it.",
"Think about the surface of a trampoline. When you roll a ball on a trampoline, it goes in a straight line. But if you sit in the middle and somebody tries to roll the ball across, it will instead curve inward towards the low point. The ball didn't change, but the shape of the surface changed. From the point of view of the ball, what is \"straight ahead\" looks like a curve to us. Mass does the same thing to three-dimensional space that you do sitting on a trampoline: it creates curves. Things that look like they're traveling in a straight line start to take a curvy path when they're moving near mass, because space is curved. Back to the trampoline. With no weight on the trampoline, it doesn't take a lot of effort to make the ball reach the other side. Just a little bit of a push and the ball will roll the rest of the way. But as we add mass to the center, there's a \"pull\" for the ball to \"fall\" into the center instead of reaching the other side. If you want the ball to not get stuck in the middle, you have to roll it harder. More mass means you have to add more energy to the ball to stop it from falling into the center. At some point you've added so much mass to the center, and the curve has become so steep, that there's basically no amount of energy you can give the ball so it can reach the other side (assuming you don't break the trampoline, and don't just throw the ball over the hole). In other words, from the point of view of the ball, *all straight lines lead to the center of the trampoline*. No matter what angle or how much force, the ball will go into the middle. This is a black hole. A black hole is a place in space where there's so much mass that all straight lines go into the center. Everything that's inside cannot get out. The point of no return, the place where all those lines start bending inward, is called the Event Horizon. Outside the Event Horizon you can still be on a bad line and fall in, but there are some options to go elsewhere. Once you cross the Event Horizon, however, you're out of options. At that point you are going into the middle.",
"ELI5: it is a cliff, the edge of the world, where everything that ventures beyond the edge falls down and is gone forever. Even light can't climb back up.",
"The \"edge\" of a black hole at the point where you wouldn't be able to escape from the force of gravity of the black hole. An orbit just above that line would allow you to escape, but on or in the line and you fall into it.",
"When we're talking about black holes, the event horizon is the area of space that is so curved that all time-lines point towards the centre of the black hole. In practice this means that nothing can escape from within the event horizon, not even light. Once something crosses the event horizon it can never escape the pull of the black hole.",
"You probably know that a black hole is a massive thing that has lots of gravity. You probably know that it's called a \"black hole\" because it has so much gravity, that light can't even escape it (so it looks like a \"black\" \"hole\"). Well, obviously there's things around it and light that passes by it, so not everything in the universe is trapped by it, just stuff at a certain distance. Well, that distance from the center of the black hole at which stuff (including light) are simply trapped by the pull of gravity and can't get back out again is called the event horizon. It's not really the physical edge of the black hole itself, but it's the ledge / point of no return, where something can never escape and will forever fall towards the center."
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nbg84j | Ram Swap, turning Storage capacity to RAM | 1. How RAM and hard drive differs, and how is it possible to use them interchangeably? 2. This recently blew up in the android community, apparently this is not a new thing, so why is it not done earlier to cut costs as higher ram variant cost significantly more than the lower variant? | Technology | explainlikeimfive | {
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"1. RAM is random access memory. It is the very fast, but impermanent memory that your applications use to do stuff while they are running. ROM is read only memory. It is used to store data that is not ever changed and only accessed - like an old video game cartridge. They are not interchangeable. 2. A RAM swap file is a portion of the hard disk that is used _like_ RAM when a system runs out of available RAM for its programs. The advantage is that the swap file prevents programs/OSs from crashing when there is no RAM to allocate, but it is _much, much_ slower than RAM so it is only used as a last resort.",
"ROM stands for Read Only Memory. Information is burned into the chip and cannot be updated. That would make it useless as RAM. RAM stands for Random Access Memory, the main type of memory used in computing systems because anything could be stored and retrieved from it over and over again."
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nbh0qs | Why do some sounds and feelings, like running your nails on a chalkboard, give you that shivering feeling everyone hates? | Biology | explainlikeimfive | {
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"The best answer I can think of which may or may not be correct is because of innate behavior. Thousands of years ago our ancestors had harsh living conditions and the most cautious survived. When they heard or felt something off they freaked out because it doesn't belong, hence they became alerted from the threat. Even though we have nothing to fear from the sound of nails on a chalkboard, it is something that doesn't belong, causing us to think back to our innate behaviors of survival. Like Lovecraft once said, \"The greatest fear is the fear of the unknown.\""
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nbhur4 | ; If we can stop hearts during open heart surgery and restart them with medicine, why are cardiac arrests commonly fatal? | Other | explainlikeimfive | {
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"text": [
"When your heart is stopped during open heart surgery, it is extremely controlled. You don't eat before the operation, the exact amount of sedatives required are calculated, and you have a dedicated team of professionals monitoring you every step along the way. Even then, they're somewhat risky procedures and deaths happen. When your heart stops when you're NOT at a hospital surrounded by people dedicated to helping it start again, that were planning on your heart stopping - outcomes become far worse.",
"Stopping the heart stops the blood flow. In a surgical setting the heart (and often the lungs too) is bypassed and blood is pumped mechanically to keep the other tissues alive. If your heart just stops while you’re watching TV at home, you’re usually dead before they can get you hooked up to the cardiopulmonary equipment.",
"It’s the difference between a car crash in everyday life and a car crash planned by stunt people. One is planned and controlled by professionals, with contingencies and failsafes, the other is unpredictable, spontaneous, and often occurs without medical help right there."
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nbhvxu | where do tears come from? | Biology | explainlikeimfive | {
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"text": [
"We have three separate glands responsible for creating good quality tears. The meibomian glands produce the oil in our tears. The lacrimal glands create the volume of tears. The conjunctiva, the clear tissue covering the white of our eyes and inside our lids, produces the mucus. My wifey is an ophthalmologist.",
"Just like sweating the answer is glands. We produce liquid to keep our eyes lubricated, when we cry we are stimulating the gland that produces this secretion and it overproduces, leading to droplets forming and then falling across your face, mainly when you observe the way the tv series Game of Thrones was slaughtered in the final seasons.",
"Tear ducts do not produce tears, the are a channel to drain the eye from extra liquid into the nasal cavity. So the ducts are the reason the nose starts to run when you are crying not the source of the tears. Tears will flow out on your skin because the tear ducts can't drain them away fast enough. The tears are produce in the Lacrimal gland that is above the eye to side of the head. The connection to the eye cavity is interlobular ducts. They produce liquid all the time to lubricate the eyeball. They take water from inside the body just like sweat glands. It is not just water but antibodies and other stuff that has a antibacteria effect. If you goolge foe the \"Lacrimal gland\" an look at images you can see it on the side of the eye behind the eye lid. Lost of the images you see it if it is enlargeds and operations to fix it. So do not search for it if image like that distube you This is [a good drawing]( URL_0 ) where A is the Lacrimal gland that produce the tears and C & F is the tear duckts."
],
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nbj9in | Why is light bent around a hot surface? | For example, I look towards the roof of a black car on a sunny day. The background has enough contrast to notice that the light looks wavy from the radiated heat coming from the roof. How does light get bent by the heat? | Physics | explainlikeimfive | {
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"text": [
"The hotter air gets, the less dense it is (which is why it rises. high density sinks, low density rises). When the density of the medium light is traveling through changes, it refracts a bit. Like when you go underwater in a swimming pool and look at something above the water, it's not in the exact place you're looking. It's at a slight angle. It's the same with light traveling through air that has a lot of different temperatures."
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nbjt63 | | Why is purple a very common alternative color for a lot of vegetables and fruits (onions, cabbages, potatoes, dragon fruit, etc)? | Purple do be pretty but why does it seem to occur naturally in nature? | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"Fruits and vegetables can get a red/blue/purple colour from a chemical called anthocyanin. Along with helping your body deal with inflammation, anthocyanins can help protect the plant itself from cold temperatures and to absorb chlorophyll through its leaves."
],
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nbk0bu | how does hunger work? | Sometimes I don’t eat anything all day and don’t feel anything, and sometimes I’m full and still feel hunger | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"There are two separate feelings you need to differentiate. The first is feeling full, which is when you eat a lot of food until you can't fill your stomach any more. You can however still feel hungry in this case depending on what you eat. The other feeling is feeling satiated (not hungry). In order to feel this you need to eat enough food to fill your stomach to a certain degree but also eat enough nutrients. In particular you need to eat enough protein and certain fats. These nutrients are needed by your body and there are special nerve receptors that won't stop sending the \"I am hungry\" signal until enough nutrients have been consumed. Depending on what you eat you will also stay satiated for a longer time as certain combinations of food will inhibit the bodys ability to digest and make use of the nutrients. For example if you eat 4 eggs for breakfast you will feel satiated longer than if you eat 4 eggs and a piece of white bread. The white bread disrupts the bodys ability to digested and make use of the nutrients and thus you will feel hungry sooner."
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nbkkwf | On a chemical level, what differentiates carbohydrates, protein, and fat? | Chemistry | explainlikeimfive | {
"a_id": [
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"text": [
"Lots. They are fundamentally different classes of molecules. Carbohydrates are heavily hydroxylated hydrocarbons (that is, lots of -OH groups. They often form small rings. Your body digests them for energy. Proteins are fragile and complex structures formed from chains of amino acids (nitrogen-containing acids) which are then folded into a unique form so that they can serve specific functions in the body. Fats are long oily acids (long-chain hydrocarbons with a small acid group on the end) which are bond to a glycerol molecule on one end."
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nbkm2u | if something is freeze dried can it melt? | Chemistry | explainlikeimfive | {
"a_id": [
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"text": [
"Freeze drying refers to the process of extracting the water from something by freezing it, then lowering the air pressure so that the ice formed by the water sublimates (goes directly from solid to gas). The end product is extremely dry, but can be rehydrated. Many backpacking/camping meals are freeze dried, as removing the water drastically lightens the weight of the food. Once it has been dried, the food can be stored at room temperature in an airtight container (the food will begin to re-hydrate just from the humidity in the air). So, it won't melt in the traditional sense, like an ice cube melting, but it can become quite soggy if left out in a humid environment."
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nbknn0 | Why is the tennis scoring system the way that it is? | Like why does it go from 15 to 30 and then to 40? | Other | explainlikeimfive | {
"a_id": [
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"text": [
"It comes from the scoring of [jeu de paume]( URL_0 ), basically the ancestor of tennis. First service was made from 60 feet, you scored one point you could move forward 15 feet, second point another 15 feet, and third point a final 10 feet. 15・30・40. Edit: ok, so this was how it was explained to me when i played tennis, and i got curious and tried to find a definitive source about it... but apparently the definite origin is lost in history and people were already conjecturing about it in the 16th century. So.. take it with a grain of salt.",
"There are a few theories, but none of them have any definitive proof. Tennis is so old, the origins of the rules have been lost to time. Your question was being asked 500 years ago, and they didn't have any luck finding the true answer either."
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nblr6k | Why does it take longer for wounds inside your body to close than wounds outside it? | Since external wounds are exposed to, well, the outside, shouldn't they heal slower? Why is it that internal wounds take longer and sometimes may not even heal at all without medicine, like fissures and canker sores? | Biology | explainlikeimfive | {
"a_id": [
"gy00u7d",
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"text": [
"It generally has to do with moisture. If the wound is wet the infection has an easier time to survive. Drying out a wound reduces the ability of the bacteria to survive. In fact, this is why dries meats do not rot. And why mummies exist.",
"Moisture slows down clotting, which is responsible for stopping bleeding and starting the healing process. This is why suicidal individuals may slit their wrists in a bathtub full of water; submerging the wound in water will reduce the clotting rate, increasing the chance that the victim \"succeeds\"/bleeds out before they are found/saved."
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nblvpj | - Has there always been the same amount of water on earth and if yes, where is the water when there is drought in certain areas? | Earth Science | explainlikeimfive | {
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"text": [
"Apart from some very minor inputs and losses to and from space, yes the total amount stays the same. Over geological time water moves around between various “reservoirs” in the oceans, atmosphere, ice caps, deep aquifers, living organisms etc. For example, during Ice Ages, more water is locked up in ice and so sea levels drop. During warm periods, more water is in the atmosphere so there’s less in the ground. So the water isn’t really added or subtracted from the earth as a whole, it’s just redistributed into different parts of the earth’s systems.",
"Roughly the same, yes. In a drought in a certain location, there might be heavy rains and flooding in another location. The Earth is a big place.",
"Remember that water is just H2O and is being produced and consumed by various natural and man made processes every day.",
"Generally the amount of water on earth has been the same throughout human history. When there's a drought in one area. There will be more mousture somewhere else. But that doesn't necessarily mean it's flooding somewhere else. During the last ice age much of the worlds water was tied up in icepacks and glaciers."
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