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nkv9kc | What the heck happens to sugar when you melt it? | When making caramel, you melt sugar. The sugar starts as a solid, then I believe it breaks down into fructose and glucose before it actually melts, but after it melts it becomes a solid granular consistency again while it is still being heated (WHAT?), and then melts again. And depending on how hot the caramel is when you remove it from the heat determines if the caramel is saucy, chewy, or hard. What causes this behavior? | Chemistry | explainlikeimfive | {
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"Sugar is a fairly complex molecule. And when you heat it up you enable lots of different chemical reactions to take place resulting in hundreds of different chemicals. Some of them do produce simpler molecules like water and carbon dioxide but others produce long complex polymers which gives caramel its unique color, aroma and texture. Depending on the temperature you end up with different types of chemicals."
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nkvniq | if traits can be inherited without affecting your DNA, can we see those traits when mapping the genome? Or do they to under the radar? Do epigenetics ever change your actual DNA? | Biology | explainlikeimfive | {
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"Epigenetics, by definition, doesn't change your DNA coding so it doesn't show up when mapping the genome. It's changes in which genes are expressed, and when and how, which is caused by the chemical soup surrounding the DNA. You can't see that from any kind of DNA sequencing. It's like handing you a hard drive...you can read it, but you don't know which files the user is actually cares about."
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nkwhyc | Why does sugar make things sticky? | Chemistry | explainlikeimfive | {
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"So, firstly, Sugar alone doesn't make things sticky. If it did we couldn't have powdered or granulated sugars, they would all stick together in a solid block as soon as you put them in a bag. What makes things sticky is a mixture of sugar and water. The water is the key part and i'll try and explain why that is by working through a few steps. 1. Water interacts with sugar through hydrogen bonding(more below) and by absorbing hydrogens from the hydroxyl groups that are part of sugar molecules. Hydroxyl groups are a hydrogen and an oxygen, attached to carbon atoms in sugar. Getting them wet can actually create more of those hydroxyl groups. 2. Both of the above interactions serve to modify the [nuclear charge]( URL_0 ) of the sugar molecules. It makes it more negatively charged than it was before. Nuclear charges and dipoles are VERY complicated, but it essentially allows for something called [hydrogen bonding]( URL_1 ) to occur more easily. Don't let the name fool you, it isn't strictly related to hydrogen all the time, it just refers to attraction caused by nuclear charges attracting their opposite charge. Dw too much about it, but also it holds your body together and is involved in every type of chemistry that allows life to exist. 3. We feel that hydrogen bonding as stickiness because it literally is sticky. Those nuclear attractive/hydrogen bonding forces are sticky on a molecular level. edit: sorry it's not more ELI5, i just wanted to make sure people could go read up more if they wanted to.",
"I'll pop in with another point worth knowing, although the video link is more than good enough. \"Sticky\" is not a universal quality. Tape, sugar, and the like is sticky on skin, on a table, on a busted muffler, whatever. However there are plenty of things these adhesives and adhesive-esque materials are not capable of bonding to. Oil your hand up and put on a band-aid: good luck. Adhesion is best considered as a two-way street. The adhesive is sticky to you, but in some physical or chemical sense (or both), if it could talk, it would say you're sticky to it as well.",
"Because hydrogen likes to cling to things. In a dried state, hydrogen is in balance and you’ll notice it’s not very sticky. When in the presence of water - such as the water in your skin - the hydrogen bonds to it. It’s not just the presence of hydrogen though but how much there is in sugar, hence why water which is 2 parts hydrogen and one part oxygen isn’t “sticky” - though as you may notice it does like to cling to your skin. Sugar is 22 parts hydrogen - a lot more to stick!",
"Sugar molecules tend to stick together, which is what allows sugar to form cristals. When diluted in some other substance, like water or sweat, it can't cristalize completely so it ends up making the liquid thicker, and thus sticky"
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nkwsm9 | why the skin gets wrinkled if exposed to water for too long but aquatic animals don't get affected by this? | Biology | explainlikeimfive | {
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"Only our feet and hands become wrinkled when wet, not the rest of our bodies. Specifically, it is the gripping surfaces of our hands and feet, especially the fingers and toes, that get wrinkled when wet. It's not clear exactly why this happens, but it appears to be a way that humans have adapted to make it easier to grip things while we're in the water, by increasing the surface area of the skin where we grab things. Aquatic animals either do not need to grip things (dolphins, fish) or have claws that help them (otters, muskrats). All primates (chimpanzees, macaques, etc.) appear to share this feature with us.",
"It's a neurological response. People with damaged nerves in their hands don't wrinkle, for example. This adaptation is supposedly to help increase grip in wet conditions."
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nkwzyj | The difference between equity and shares | Economics | explainlikeimfive | {
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"Equity is ownership of something. It is how much of the thing belongs to you, vs. belonging to someone else. So, if you have a $500k house with a $300k mortgage, your equity is $200k - you 'own' $200k of the house's value while the bank 'owns' the other $300k (because of the morgtage). This is the crux behind the core financial formula: Assets - Debt = Equity. Shares are just how equity is divided in certain company types. In order to make it easy to calculate how much of a company an individual or investor owns (and make it easy to buy/sell that ownership), the available ownership is divided up into shares, each representing a specific % ownership of the company. If a company has 1,000 total shares and you own 600 shares, you own 60% of the company - or 60% of the total equity. The company will publish how much _total_ equity the company has on its balance sheet (one of the four key financial statements). The individual stockholder can then calculate how much of that equity belongs to them by dividing that equity amount by total shares outstanding and multiplying that by how many shares they own."
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nkx6qg | Are there any random interactions/reactions in physics we know of or should we be able to calculate every outcome 100%? | Physics | explainlikeimfive | {
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"Yes, there are. The most famous of these is half life. The half life of a substance is how long it takes for 50% of that substance to decay. So, if I have 2kg of a substance that has a half life of 10 minutes, in 10 minutes I will have 1kg left - the remainder will have decayed to a different substance. However, if I have a _single atom_ of that substance, there is a 50/50 chance that it will decay in 10min. As far as we know (right now) it is _random_ whether or not that particular atom will decay in the half life. Now, is this _truly_ random or do we simply not understand decay well enough to predict it - well, there is a Nobel Prize in your future if you can answer that question.",
"At the smallest levels we expect almost everything to be probabilistic. In quantum mechanics everything is described by wavefunction which give probability distributions, we can predict probability of measurements but not determine it with certainty.",
"Yes. For example, the path a photon takes through a beam splitter is random (it either passes through or is reflected with a 50/50 probability). This is sometimes used in random number generators to generate \"truely random\" numbers.",
"Oh yes there are. All of quantum mechanics is based on this principle. In QM, we don't calculate the exact values of physical quantities like we do in classical physics. We find probabilities. The equations of motion for a quantum mechanical system yield a (generally time and position dependent) wave function, which in turn leads to a probability distribution. The probability distribution will tell us, at time t and, if applicable, position x, what the probability is that the dynamical quantities of the system will take certain values. It is not physically meaningful to say \"at time t the electron will be at position x\", in quantum mechanics we say that \"at time t the probability of detecting an electron at position x is P.\" Likewise it's not meaningful to say \"this thorium atom will decay in exactly 37 seconds\", or \"this electron will be in the spin up state in 5 seconds\", etc. And it's not that our instruments just aren't sensitive enough or that our physical theories aren't complete enough to make exact predictions or measurements in quantum mechanics, it's that in quantum mechanics it's literally not physically meaningful to predict the value of a physical quantity and instead we can only predict the probabilities of all of the possible values that said quantity can take."
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nkxbs4 | Why does it take more time to fly from New York to San Francisco than the other way around? | Physics | explainlikeimfive | {
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"The Jet Stream Effect. There are (roughly) west-to-east flowing air currents naturally in the atmosphere around the altitude where planes fly.",
"Jet stream and prevailing winds. Those generally go from west to east, and significantly faster than at the surface. For instance, as I type this, prevailing winds over Omaha, Nebraska at 34,000 feet are about 60 knots. Over Aberdeen, South Dakota, they are at about 85 knots, and in both cases going from southwest to northeast. Those winds will help push the plane when going in an easterly direction and will slow down the plane when going west."
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nkxvmb | how does media get their info? | like for example a car accident, how do they know there was a car accident at a place, how do they know who is involved and their personal info to present stuff like "mother of 17 chihuahas ran over cyclist who is also part time panda nurse"? | Other | explainlikeimfive | {
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"Former photojournalist here...... Most emergency services' radios are monitored by news outlets and freelancers. When an incident happens, cameras are dispatched to that incident at the same time. TV and newspaper photographers. That's how they get footage. When that happens, emergency services have media people on staff to give relevant information to news outlets when they have it. Sometimes a press conference is held or the media have a way to contact these officers to get the info they need. I used to be a freelancer for what they call 'breaking news' which is what you described above. I was also a 'stringer' that would take assignments from the newsroom to photograph someone related to a story being done or to feature someone with a photograph. I had portable scanners, subscriptions to services that monitored the radios and sent me text alerts so I knew when they newsworthy events happened for me to get there as fast as possible to get a good photo, hopefully before the competition showed up. I would call the regular newspapers to sell the photos to them. It's not everyone's cup of tea to race towards someone's worst day, take photos of it and then sell them but there's a market for it......or there used to be anyway."
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nkxwl2 | how do sharpening knives work? | I’ve heard someone say that there is a difference between actually sharpening a knife and making it not dull with a rod or something. What is the difference? | Technology | explainlikeimfive | {
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"When a knife is used, the edge accumulates damage over time by either chipping off or bending over to a side. When you use a rod on a knife, you're just pushing all the bits that are bent back towards the center. There won't be an impact to any parts of the blade that are chipped. When you sharpen a knife, you're removing material from the edge to create a new edge. If there are any bits of the blade that are chipped, they'll be removed via the sharpening process.",
"When I knife gets \"dull\", one of two things is happening. - The edge of the knife is still sharp, but it has bent or rolled slightly to one side or the other. [Here is a picture]( URL_1 ). This is known as the knife being out of 'true' - it isn't _actually_ dull because the edge is still there - and can be corrected with a honing steel. By gliding the knife down the steel, the edge is bent back to true which improves performance. This is known as honing - **not** sharpening. - The edge of the knife is worn down and is no longer sharp. [Here is another picture]( URL_0 ). No amount of honing will fix this because the edge is actually gone. You have to sharpen this knife - remove material from the cutting edge to get it back sharp again. **This** is sharpening."
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nky3ic | Uranium-234 has a half-life of 246,000 years. How did we measure that if the technology to do that hasn't been around that long? | Chemistry | explainlikeimfive | {
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"You don’t need to wait 246,000 years to know. You just measure the decay of a know quantity over a known time period and extrapolate that curve out to when you hit 50% decay. For very long half-lives you need a bigger sample and/or a longer test time and/or a more sensitive detector but unless the half-life is so long that you “never” get a decay, you can gather the data and plot the curve with relative ease.",
"The same way a police officer doesn't need to watch your car for 80 miles to know you were doing 80 mph in a 60 mph zone. The speed at which you travel a shorter distance can be extrapolated to miles per hour. The amount of U-234 remaining after X time starting with a known quantity can be extrapolated to show at what point 50% would be expected to remain.",
"In 246,000 years, half a sample will decay. But if you have 492,000 atoms, there’s a good chance that one of them will go *this* year. In a gram of uranium there’s ~10^21 atoms, and so even though any individual atom is likely to last for a hundred millennia, there will be a detectable rate of decay over a much shorter period of time. You count how many decay events your Geiger counter picks up in an hour and extrapolate that out."
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nkyjwt | Why does the body go into a full coma when a specific accident occurs? | Biology | explainlikeimfive | {
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"Theres generally 2 cases. One is some kind of brain trauma. That might be a physical injury, it might be inflammation of the brain lining, excessive fluid causing pressure buildup in the skull, damage due to lack of blood flow from stroke, blood loss or heart attack, or anything else that might result in injury to the brain. When the brain is unable to sustain the processes needed for consciousness we call it a coma. The other case is that doctors cause the coma on purpose, called a medically induced coma. This can be done to prevent pain, reduce movement before and after major surgery, and generally make intensive medical work easier.",
"I think most of the time trauma to the brain causes a lack of oxygen to flow there and the brain isn't able to function. Brain injuries can also cause the brain to not function properly"
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nkz958 | What exactly is the difference between a nation, a country, and a state? | Other | explainlikeimfive | {
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"They all refer to land and people under some form of administration, usually with centralized control, that operates largely independently of other lands and peoples. State often either refers to the operations of a nation or a constituent territory of that nation, though, and does not often refer to a wholly independent region. Country and nation refer to regions that act independently of one another. Country is often used to describe the geopolitical region - that is, the borders. Nation is often used interchangeably, but refers more to the sociopolitical region - that is, the people. The question of what lands *are* independent entities is hard to define, since there is no one organization responsible for them all, though the United Nations tries to fill that role. That's why the UN recognizes a different number of countries than the USA does. Roughly speaking, there are about 200 countries.",
"Nation speaks of the people, country means administration appararus and state means the rule of law",
"A nation is a people and the administration, while a state may be the administration or govt. Country may include land, people and/or govt.",
"Linguistics minor here, to be honest you can use all three interchangeably and you won’t be grammatically incorrect, not the answer you were looking for but just another POV hahah"
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nkzrha | if the earth moves at over 60k MPH, why does it appear slow to astronauts? Is everything relative to the universe moving? And if so, how fast are you really going when floating in space at a standstill? | Physics | explainlikeimfive | {
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"Because the astronauts are also moving at roughly the same speed in the same direction, they only notice the speed difference. There is no telling how fast you are absolutely moving in space, as we can only measure it relative to something else. The only truly set speed is the speed of light. But due to special relativity even that can't be used to measure absolute speed.",
"The movement that you're speaking of is the earth orbiting the sun. Everything in our solar system is orbiting the sun, including the moon, the iss, and the astronauts, so relatively speaking the earth appears to be moving slowly. You can think of it like when you're in a car - no one in the car looks like they're moving at 60mph, because you are too. The entire solar system is also moving as the galaxy rotates, but we don't perceive that either because everything around us is moving together."
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nl0zzd | How can a piece of colored plastic change the wavelength of light? | For exaple when you put a piece of red plastic in front of a flashlight how can the wavelengths just change? | Physics | explainlikeimfive | {
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"They don't - coloured plastic basically acts like a filter. Most light we interact with isnt one wavelength but a combination of various wavelengths, with white light being a relatively even distribution across the visible spectrum. If you shine white light through red cellophane all the non-red wavelengths are absorbed while the red passes unhindered, and you now have a red light.",
"It generally doesn't. The colour red bounces, others don't. That's what makes it red. White(ish) light from a flashlight contains all the individual colours of the rainbow in it all mixed together. [A prism breaks up those mixed up colours]( URL_0 ) - it doesn't make colours, just separates them. If you shine a green or blue light at a red object, it will appear black, or very nearly so since blue is mostly absorbed by a red objective. It might be a tiny bit visible but the majority of that light is absorbed, not reflected.",
"A red piece of plastic is red because it reflects red light. The question is what happens to all the wavelengths of light that is not red. Depending on the plastic and the wavelength it can be absorbed or it could go straight through. So a material will end up being transparent to a completely different set of wavelength then it reflects. The only thing you can say about the light going through red plastic is that it have significantly less red in it then originally. It should also be noted that humans have a relatively limited color vision. We can only see three different ranges of wavelengths and have to interpret the color of the light from this information. So for example a light composed of two different wavelengths may trigger the same cones as another light with a single wavelength. But these will behave differently when passing through different filters. Similarly cameras do not see the same ranges of wavelengths as humans and this is also perticularly noticable if you start filtering out single wavelengths."
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nl11l2 | Why can’t any batteries be rechargeable? Why are there specific “rechargeable” AA, AAA, and other batteries? | Technology | explainlikeimfive | {
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"Batteries use a chemical reaction to move an electric charge. When you're recharging a battery, you're basically reversing the chemical reaction. Not all of these reactions are perfectly reversible.",
"Batteries are electrochemical devices. If they arent connected to a circut the reaction doesn't happen. When you connect them to a circut then then a reaction starts that generates electricity. Rechargeable batteries can react both ways, if you connect them to electricity the reqction will happen backwards. Non rechargeable batteries only work in one direction.",
"It’s not so much that you CAN’T but more that you really shouldn’t and it isn’t worth it anyway. The chemical reaction doesn’t reverse well, and releases significant heat in the attempt. The battery can easily explode, or burst into flames from overcharging and will only partially charge besides. They use different chemical reactions to produce electrical currents. Some reactions more easily reverse than others."
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nl1eet | Can eating organ meat exclusively be bad for you long term? | Biology | explainlikeimfive | {
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"Oh, this is anecdotal but I once overdosed on liver. Vitamin A poisoning. I was eating liver several times a day for at least a week."
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nl1lki | Why do babies instantly cry after being born? Are they constantly crying while still in the womb? | Biology | explainlikeimfive | {
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"So babies cry when they come out only SOMETIMES. The doctor forces the baby to cry by patting it's back hard because there's a chance it could have blood or placenta in it's throat and the doctor wants the baby to cough it up. When the baby comes out already crying it's most likely because of pressure from being pushed out of a small space. Making them cry also kind of kick starts their lungs like starting a car",
"Babies are crying at birth, or a doctor wants them to cry, so they will take a lot of deep breath‘s in to inflate their lungs, close their patent ductus arteriosus, and they begin circulating blood at a faster rate. Most babies have blue extremities because there’s no blood flowing to them. Crying gets the oxygen flowing the blood going and all the extremities begin to turn a normal color.",
"I have had two babies. One came out crying and one didn’t. Most do, probably because they’ve come out of a nice, warm bath in a dark and comforting environment - into the cold and bright outside. Also, babies do cry in the womb! They don’t make any noise because they don’t yet have air in their lungs but they practice all of those baby things before they’re born.",
"Sudden cold. Noise. Sensation from being touched and moved. And it probably fucking hurts like a bitch squeezing through the birth canal. Your skull is literally misshapen. Regardless of the elasticity of it at that point, can't feel good...."
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nl3i4l | Why are there women's shoe sizes and men's shoe sizes instead of just standard universal sizes? | Biology | explainlikeimfive | {
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"There are universal shoe sizes. The common system in Europe is the length of the last in pairs points that is 2/3 cm. The system is used for men's, women's and child shoes. US use the light in barleycorns that is 1/3 of an inch but the subtract 24 for it for men and 23 for females and 11 2/3 for children's sizes. I have no idea why there is a male and female diffrence.",
"Because they can sell more things if they are gendered, because it discourages people from sharing."
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nl3l3y | Why do complex numbers figure in Quantitative Finance? | The last time I studied math was when I was 17. Thus I'm innumerate. [This Quantitative Finance answer]( URL_0 ) uses complex numbers and mentions Fourier Transforms. But how can complex numbers appear in Quantitative Finance? Obviously, most financial variables can't be complex numbers — prices, interest rates, inflation rates, rates of return can't be complex numbers! | Mathematics | explainlikeimfive | {
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"In Fourier space the imaginary part of complex numbers gives us cycles and repeated patterns. This is because e^(ix) = sin x + i cos x These trig functions allow you to express things in terms of frequencies (like notes of music), in frequency space instead of as events in time. It’s a very powerful way of describing repeating events."
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nl3vtw | Since glasses make your vision near perfect, will a person with near perfect vision putting on your glasses have your vision? | If I had perfect vision and put on a persons glasses would my current vision be similar to theirs? | Biology | explainlikeimfive | {
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"No. Glasses are correcting the lens of your eye not focusing the light into a point at the back of your eye correctly. They are either going to shift the focal length forwards or backwards. If someone puts on your glasses it's going to be blurry, but in the exact opposite way. Think of it like stilts. If you're four feet tall and wear foot tall stilts you'll be 5 feet tall. If a 5 foot tall person puts those on they'll be 6 feet tall, not 4.",
"No the glasses are made to correct the bad shape of their eyes, moving their eyesight to “less near sighted” or “less far sighted”. So if you use them when your eyes are already the correct shape then the “correction” will actually push you away in the other direction; “less near sighted” glasses would make you “more far sighted” etc."
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nl3w3a | What are drivers? Why do they need to be updated so often? Why are they even called drivers? | Technology | explainlikeimfive | {
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"Drivers are an interface between the operating system and the hardware. The operating system doesn't know how to operate every piece of hardware, so it needs something in between. I guess it's analogous to different cars having the same interface (steering wheel and pedals) even though under the hood they might operate completely different (gas or electric or rotary engine etc). They are called drivers because they drive or control hardware."
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nl4pe7 | What makes depressed people unable to function? | Other | explainlikeimfive | {
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"So you probably think you wash up your dishes because you're a great person who just knows that they need to be done. In reality you do them because your brain rewards you afterwards by feeling good about doing it even though you may have hated actually doing it. When someone is depressed they either don't get that feeling or not much of it. It can be pretty hard to motivate yourself to do something if before you do it you feel like shit and after you do it you still feel like shit. Depression can also make you feel like you can't do something. That you're a failure. With this it can be hard to motivate yourself to do something if you believe that you'll just fail at it.",
"Its a kind of apathy. Nothing matters. There's nothing driving you to do your dishes, and even if you do manage to do them, you won't feel good for doing it. Low neurotransmitters across the board, poor diet, and lack of sunlight or activity can all compound to make a mild depressive episode into a major depression.",
"A common misconception is that depression simply relates to being \"sad\" and while yes, that's an obvious outward perception there's more to it than that. It's waking up after a full 8 hours sleep and still being tired. Exhausted even. It's knowing you really should shower but having no motivation to do so. Feeling swamped and like there's loads to do, despite having nothing needing done. To overuse a cliché, it's a rollercoaster. But you don't get to see where the dips are or even if there's a climb coming up again. You kinda stop caring about things and it can become very difficult to bring yourself to get them done. Source: I have Depression.",
"When you’re depressed there’s a lack of dopamine in the frontal lobe of the brain. This is more than just about ‘feelings’. Low levels of dopamine literally cause these brain cells to die at an accelerated pace. The brain stops functioning properly and a highly depressed person can’t even fully think what they need to get done or how to solve current problems. It’s not their choice. Also, the motivation centers are in the frontal lobe. Your brain is a computer, you may think you have full control over it but you do not. When your brain breaks, you break.",
"I guess I'll stay with a friendly reminder that this question...isn't exactly appropriate for this sub because the answer is going to be subjective. Depression manifests differently for different people and there's no real hard and fast rules. However, to take my best stab at it, a really common symptom of depression is the despair that your circumstances can never improve, regardless of the effort you put in. This is what drives people into isolation and all of the other big negatives associated with depression, and very often allowed people to rationalize not cleaning because it's a \"waste of time\" or something similar. I personally only own 1 of each standard dish such that if I want to eat I HAVE to wash my plate and silverware every time. When I had a whole cupboard of dishes, even seeing 3 plates and bowls in the sink waiting to be washed could start to feel overwhelming. It's not just laziness (I'm an auto mechanic and certainly work hard enough throughout my day), but the idea of putting in effort for something that only benefited ME would fill me with anxiety. I should be spending that effort on OTHER people in order to.... Whatever my depression wanted to say at the time. Usually something like, \"prove I'm a good friend\". It's difficult to explain in the simple terms that are the main point of this sub. I would recommend perhaps r/askreddit for a further dive into this.",
"There are quite a few factors that can cause this, and the lack of function can be one, all, or some hideous combination inbetween. I will describe a few of the ones that have affected *me*... I don't know them all, and I imagine other answers may cover those gaps. Quick preface, I have clinical depression (I'm being treated though!) and have experienced some of what I'm about to describe - but depression hits and affects everybody in slightly different ways. My experience is certainly not universal, is what I am saying! ***Executive Dysfunction*** Numero uno on our list of suspects. \"Executive function\" refers to the systems in the brain that help people take action in moving towards a goal. The goals can be as high-reaching as \"graduating from university\" or as common as a list of daily tasks, wanting to read a book, play a videogame, etc - it's things we know we **need** or **want** to do. And one of the main types of properly-working executive function is \"**self-motivation**\", which is the ability to take care of tasks when there's no *outside* consequences. And this is what gives important tasks a mental 'weight' that actually pushes us to do something. For example, if you have no visitors, nobody would see your stack of dirty dishes (no external consequences), but you'll do them anyway. Executive ***dys***function, on the other hand, is the failure of those systems to work correctly (if at all). Tasks and goals no longer seem... well, to have weight. They don't necessarily seem any less *important*, but the 'weight' of that importance isn't there. We know that the dishes need to be done, or the trash needs to be taken out, or whatever, but the 'weight' of that task (normally provided by the self-motivation system) simply doesn't *exist*. So we can consciously recognise that something is important, but subconsciously (where the 'executive function' systems operate) the importance itself doesn't hold any mental value, or weight, and so our conscious brain saying that something is important and we need to do it becomes an insubstantial, almost ghostly voice. It can be as loud as it wants, but it still can't move me. You know the line from Mulan, where the Emperor says \"No matter how the wind howls, the mountain cannot bow to it\"? The mountain is our subconscious brain, the bits that provide motivation. The wind is our conscious brain. Properly-working executive function is the wind tossing sticks of dynamite. & #x200B; ***Self-Worth*** And number two, closely tied with number one. Depression makes your own personal value crash, really hard - so taking care of yourself becomes a task that is *too* heavy to do. Why would you polish a turd? There's no point in doing any of this stuff, because at the end of the day, *I don't value myself*. I just can't summon the energy to care, because I would rather do literally anything else and escape into a fantasy where the world (and myself) isn't made of shit. & #x200B; ***Missing Reward Systems*** So, another one of the brain's subsystems is the 'reward loop'. You accomplish a goal, your subconscious rewards you with feel-good neurotransmitters. The neurotransmitters are picked up by receivers, and this detection is interpreted in our heads as the good feeling. This is tied in with executive function that we discussed above. Depression can affect this reward system in two ways. It can (1) reduce the amount of, or entirely prevent, the neurotransmitters from being produced and emitted, or (2) it can affect the *receivers* that detect the neurotransmitter's presence. In the second case, the receivers can simply be unable to detect the neurotransmitter's presence (this is really common in meth addicts, I believe?), or simply become much less sensitive - so our subconscious can be yelling all it likes that we did a good job, but we can't *hear the message*. The end result is that doing tasks that we need to just doesn't feel like an accomplishment. We know it needs to be done, but we also know that we won't feel better once we've done it, so why bother? Instead, we do stuff that is better at generating the feel-good signal (the neurotransmitters). Stuff we *want* to do, because it generates *such* a strong signal that even our dulled, blind and deaf receivers can detect it - or the signal is strong enough that even the really damaged producers can produce some of the chemical.",
"In the grand scheme of things, it doesn't matter as a depressed person. Everything takes a lot more effort to do and without the dopamine from feeling like you accomplished something. When the mind/body is in that state we tend to take the path of least resistance, just to make it through."
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nl58ca | What is Bayesian statistics, and how is it different from regular ol' statistics? | Mathematics | explainlikeimfive | {
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"Bayesian takes into account what you already know. In its simplest form, it can change the odds of something occuring",
"Ultimately, they come up with the same results but they are different ways to think about the same problem. Frequentism tends to think about things like \"If I flipped a million coins, how many of them would turn up heads?\" Bayesians tend to think about things more like \"If I was to flip a coin a million times, how sure can I be about my prediction for how many turn up heads?\"",
"Bayesian statistics actually has a lot of common sense. Let me give you an example. Let’s say you are trying to navigate a town, and you need figure out which building you are at. You are given a map, and you see there are 100 buildings in the town. Without any prior information, you would say there is 1% chance you are at any building. After you walk around and observe your environment for 15 minutes, you gather new data and now you believe there is 5% chance you are at building 1, 5% chance at building 2, 0% you are building 3, 10% you are at building 4, etc Then you walk around for another 15 minutes, which allow you to gather more data to update your belief. Now you think there is 25% chance you are building 1, 0% you are building 2, 0% chance you building 3, 50% at building 4, 5% at building 5, etc In Bayesian statistics, your belief is stated as a probability distribution. The shape of this probability distribution is changed each time you gather new data. The more data you have, the more narrowly shaped the distribution is, which is a mathematical way of saying you are more convinced about something. The alternative is called frequentist statistics. They solve the city problem by asking , if I am at building 1, then how likely is my observation; if I am at building 2, then how likely is my observation now; if I am at building 3, how likely is my observation now. Finally, after repeating the process for all 100 buildings, they pick the building with the highest score. In short, they score all 100 buildings, then pick the building with the highest score. The frequentist statistics is all about finding which parameter has the biggest score (known as likelihood function)."
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nl5dor | If atoms are too small to see, then how can we see anything? | I'm lead to understand that atoms are too small to be seen, as in light couldn't reflect off them or some such situation. If this is the case, and all things are made of atoms. Then, how can we see anything at all? | Physics | explainlikeimfive | {
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"Think of it like looking at a single grain of sand from a mile away compared to looking at an entire beach from a mile away. It's just a matter of how good our sight is. Light reflecting off the single grain of sand will be too little for our eyes to perceive it as an object, but put billions of them together and enough light will reflect off them all for us to perceive it.",
"Individual atoms are too small for light rays to interact with, let alone be picked up by your eyes, but when you put a bunch of them together they do form a surface that light can bounce off of. Kind of like how you can't see an individual house from space, but you can see cities."
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nl5xxy | How does the moon control ocean tides? | Something I know is factual yet I do not fully understand | Physics | explainlikeimfive | {
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"text": [
"Gravity. The moon is over 300,000km away, but its gravity still tugs on the Earth, moving the tide in and out as it orbits the Earth. This diagram gives a good visual explanation: [ URL_0 ]( URL_0 )"
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nl5za2 | Why does squinting improve your ability to read things ? | Other | explainlikeimfive | {
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"You can make a camera without any glass by using a pinhole instead. Look up \"pinhole camera\" to see how the light is focused by going through a small opening. When you squint, you are effectively creating a \"pinhole\" lens that focuses the light rays simply by virtue of going through a small opening. Bright light helps by making your pupils contract, also creating the pinhole effect. If you are a camera buff you know that using a small aperture opening will make more of your picture in focus. You can also create a pinhole with your fingertips and look through it to bring things into better focus.",
"Squinting hard can also alter the shape of your eyeball, so if you are nearsighted, you can get some focus improvement that way."
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nl66mu | when a wound is healing why is there a tingling feeling around it? | Biology | explainlikeimfive | {
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"text": [
"The nerves in the wound are also healing and connections are being reestablished. Also the healed skin under the scab is pushing it off and sometimes that results in nerve tingling."
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nl672q | Why is it easy to get your head stuck in a narrow space, but difficult to get it out? | Other | explainlikeimfive | {
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"The head is shaped kinda like an egg. Notice how one end of the egg is a bit wider, and then it tapers at the other end? That wide part is basically what the jaw and ears are. It's easy to push the head in because of that nice taper, but it is hard to pull it out because the wider part of the head contains the jaw, ears, or nose that can get in the way.",
"Your ears basically work like barbs, when you pull your head out. When you push your head forward into something, they'll flatten to the sides of your head. But once you pull your head out they have to fold forward over themselves before you can get out again."
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nl6eiq | Why can’t we just pump man-made ozone into the atmosphere in order to fix the holes in the ozone layer? | Earth Science | explainlikeimfive | {
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"A couple of reasons. First, ozone is quite unstable. It breaks down quickly in the atmosphere. The ozone layer is constantly replenished, but any individual ozone molecule lasts a matter of ~~weeks~~ (edit: days! The lifespan is shorter than I thought.) Two, the ozone layer is very high up. It takes a long time for air at the ground to mix up to that altitude - longer, as it turns out, than ozone lasts. We actually do create a lot of ozone at ground level: it's a significant pollutant. But it doesn't get up to the ozone layer. And three, the problem isn't *getting* the ozone: the problem is that certain pollutants, which *do* last a long time, speed up the rate at which it breaks down."
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nl6lj7 | If the earth is a closed ecosystem, how can there be water shortages? | Water shortages are prominently discussed in the news and by environmental activists, but I’ve always been taught that nothing on Earth can be created or destroyed..? Shouldn’t Earth have exactly the same amount of water on it now as it did 5000 years ago, and as it will in 2080, regardless of how much I water my lawn or how long a shower I take? As someone who tries to behave in a ecologically responsible manner this has been bugging me. Any takers!? | Earth Science | explainlikeimfive | {
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"There are *clean* water shortages and areas where there is drought. There is the same amount of actual water on the planet, but in some places the water available is polluted or there may be farms built in areas that expect there to be ample rain but because of shifts in weather patterns there is none.",
"There's no shortage of water. There's a shortage of \\*fresh drinkable\\* water. There's also mal-distribution...we don't have water in places that we want it. Earth actually gains water over time from incoming ice from space and burning hydrocarbons, and loses it to space. Cleaning dirty water, or desalinating salt water, is very energy intensive and difficult on a mass scale, and natural sources of drinkable water are very rare and hence very valuable. \\*That's\\* what you're using up when you water your lawn or take too long a shower.",
"It's not so much a concern of *using up* all the water, the problem is one of allocation. Not all water use is equal, and water diverted from a river or pumped from an aquifer can take months or years to replenish itself. And that doesn't even begin to address the issue of downstream (literally) impacts of, say, a dam in one country completely stopping a river flowing into another, or the inefficiencies involved in cleaning and treating gray or black water to responsibly return it to the environment.",
"They're referring to freshwater sources. You're right that it's a closed system. But underground fresh water reservoirs (aquifers) take a lot of rain over a long period of time to replenish, if they can at all. Thats where the shortage comes from, it's really more like \"water that is potable and easily accessible shortage\"",
"1- the earth isn’t a perfectly closed system, and the saying “matter cannot be created nor destroyed” doesn’t mean water stays as water. It’s like burning a log, if you collect 100% of the smoke and heat and light, you have the material to recreate the log again. Water can be changed into different materials that require energy to revert 2- water shortages could be based on that a certain area is having a dry spout when that water could just be elsewhere 3- using water for showers makes in undrinkable. The water needs to go through some sort of filtering process to return to drinkable water, and that usually takes a massive amount of energy."
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nl6s8d | - Why does peroxide poured into a cleaning case to clean your contact lens turn to water overnight, but the peroxide left in the bottle does not? | Chemistry | explainlikeimfive | {
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"Peroxide, given the chance, will slowly decompose into water and oxygen. This process can be sped up by a catalyst (the platinum disk in the case), especially if the catalyst is heated. At low concentrations, this is fairly slow and pretty benign. However, more concentrated peroxide (sometimes referred to as high-test peroxide) decomposes so violently that it can be used as a monopropellant in spacecraft, such as Soyuz descent module. It also powers the turbopumps and vernier thrusters on the R-7 (Soyuz) booster."
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nl6th2 | What the heck do birds and bees have to do with “the birds and the bees?” | Other | explainlikeimfive | {
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"text": [
"They both breed prodigiously. A long time ago, bees were not understood as they are now and worker bees were thought to be male. The queen bee popping out babies was thought to be a result of her having copious amounts of sex with all her workers. Birds also have lots of sex around mating season. Their songs are effectively “hey, wanna hook up?” calls."
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nl6wap | How does our brain know to not fall out of bed when we are sleeping? | Biology | explainlikeimfive | {
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"text": [
"Contrary to popular belief you are not unconscious when you are asleep. Your brain is quite alert but doesn't bother waking up your conscious mind unless it has to. This means it's taking in information from the outside world including keeping track of where it is in relation to other things. If you start to roll over and you feel the edge of the bed you'll stop rolling over."
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nl8nl0 | How can we tell whether a sound originates in front of us or behind us, when it's equally distant from both our ears? | Physics | explainlikeimfive | {
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"The tragus is the little stick out part on the head/face side of your ear canal. It helps you differentiate high and low sounds, and the conch, and the way it is shaped, helps determine the distance and relative position horizontally. There are many fascinating facts to found about the stately ear, perpetual miss congeniality in the facial feature beauty pageant."
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nl8p0x | Why are the photos of the universe oval shaped and not perfect circles? | Physics | explainlikeimfive | {
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"It's a map projection, not sure if you have ever heard of that in regards to maps and globes. But if you take a sphere there is no way to flatten that out without gaps or distortions. One of the least distorted projections is called the [Mollweide projection]( URL_0 ). Which looks like an oval. The oval-shaped photos of the cosmic microwave background, the closest thing to a \"photo of the universe\" we have is that kind of projection. That's because we are taking pictures in every direction so we end up with a sphere. Which we then have to project on a flat surface to make a map.",
"The same reason that maps of the world are often oval shaped -- because it's a projection. We're looking outward at the universe as if it's a big sphere, and we're inside it, looking out at the inside surface of that sphere. But to show that on a 2D surface like a book or a screen, we need to use projection somehow, which will always create some distortion."
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nl9361 | How does indexing the internet work? Like, what does a search engine like Google do to retrieve millions upon millions of websites? | Technology | explainlikeimfive | {
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"text": [
"Internet search engines employ what are called \"spiders\", automated programs which will index web pages and follow links to find *more* pages, gradually working their way across the internet to find everything which can be found. Usually when people publish web pages to the public they will want those pages to be indexed so they can submit the addresses to the search engines directly, giving the spiders somewhere to start."
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nl980u | Why does the US use Fahrenheit instead of Celsius to measure temperature, and what are the advantages of using Fahrenheit over Celsius? | Other | explainlikeimfive | {
"a_id": [
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"When your mom tells you that your shirt is inside out before school, and you respond \"gosh, I know. don't tell me what to do\". Now you must keep it inside out, even if it isn't the right way and you want to switch it. Because you can't be wrong. Like that."
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nl9w7v | How does a person survive a lightening strike? | Lighting strike contains around 10 giga watt and 300 million volts so how does a man survive that without getting roast. URL_0 | Earth Science | explainlikeimfive | {
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"Direct lightning strikes are quite rare--usually what happens is that the lightning strikes the ground and the electricity travels along the ground and zaps anyone close by. Or the lightning strikes a tall object, say a tree, and an arc of electricity strikes a person standing beside the tree. The energy of the strike is far less by the time it gets to said unfortunate person. So how do people survive direct strikes? Well lightning isn't really like other electrical currents--think of it as more 'spread out'. When lightning strikes you, it actually travels over your skin (called 'flashover'). When you stick your fingers into an electrical socket, you're making direct contact with the source--so the current hits you in a much concentrated way. Lightning is also *very* quick--what causes burn damage is the heat of the air around the lightning, but because it's so quick it doesn't do too much damage. The biggest cause of death from lightning strikes are heart failures--cardiac arrest as the jolt passes through you. Edit: Sorry, forgot to say--obviously a portion of the current in a direct strike will go through you too. That's what causes the cardiac arrest, because it travels through your nervous system etc.",
"The short answer is that the energy goes through them, the same way a current goes through a cable without burning it. The human body is not designed to pass through electricity like a cable though, so there is a good chance that some of that energy actually damages the body.",
"There are at least two kinds of lightning strikes. First, there are thin 'feelers' that branch multiple ways between ground and cloud. These feelers don't carry much current. When the feelers make a connection between ground and cloud, the 'main bolt' will go through one of them. This main bolt carries an enormous amount of current, enough to heat the air to make it expand a create a loud boom - a thunderclap. Most people who are hit by lightning are hit be 'feeler' bolts. While it is incredibly dangerous and painful, it is very survivable. Surprisingly, even being hit by a main bolt can be survivable, only less so. The bolt will take the path of least resistance. If you are wet (which you tend to be in a thunderstorm) this means it will pass mostly through the skin, bypassing internal organs like the heart, thereby sparing them. Finally, not all lightning strikes are direct hits. But even a near miss can be dangerous and painful with one of nature's most powerful phenomenon.",
"My friend got struck by lightning then his ex girlfriend (who dumped him) won the lottery shortly after.",
"Electricity prefers to follow the path of least resistance to get to the ground. In most cases this will mean that the lightning will travel over your skin to get to the ground rather than going through your body, burning your skin but leaving you otherwise unharmed."
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nl9ytq | In Hawking radiation, how does one of the particles getting sucked in let the other one get away? | Physics | explainlikeimfive | {
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"text": [
"The problem you are having is that this idea is a simplistic explanation that hawking came up with to try to communicate this idea. You will need to dive a little deeper to resolve the issues this visual gives you. Short answer to your question is, it doesnt, there isn’t really particle pairs being created *in the way you are thinking* . We say that for every particle there is a field associated with it, when there is no particle that field hovers around 0. Never exactly zero due to uncertainties. There is no reason in this instance to favour either the particle or anti particle and so you can think of each empty bit of space as having equal “chances” or equal “amounts” of each as if they cancel out. even though the field is hovering around 0. This is still a bad picture if you start asking more technical questions but is a little better. Im not sure how to explain this without knowing what you know or dont know because quantum field theory is not the most normal language friendly field. Now what about the actual Hawking radiation? Well when the black hole comes into being, you can think of it as “disrupting” this “hovering above zero” for the fields in empty space, so they don’t perfectly cancel out anymore. This leads to what an observer would see as a particle being emitted from outside the event horizon. Never at the event horizon always outside it. Its important to remember that only the distant observer looking at the black hole would see radiation. If you free fall into the hole you will find the radiation is essentially undetectable (not zero as some popular science claims). If someone again sees the issues with this explanation, of which there are many, and wants to get more technical, im happy to answer.",
"There are three possible outcomes when a pair of particles appear near a black hole: 1. Both get sucked in. The particles annihilate, no change to the mass of the black hole. 2. Both escape. The particles annihilate, no change to the mass of the black hole. 3. Only one get sucked in, the other escapes. This means there is now mass outside of the black hole that appears to have been created from nothing. Mass is energy, and energy can't be created from nothing, therefore the black hole must have lost mass equal to the escaping particle."
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nla26r | What is happening in our brain when we're trying to remember something but can't, and then it suddenly comes back to us when we actively, consciously put in the effort to remember it? | Biology | explainlikeimfive | {
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"gzhhvzl"
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"I hope you don't know how memories work, because I'm gonna tell you anyway! As simply as I can put it, a memory occurs when your brain reactivates neurons in your head the same way they were activated when that event actually happened. What you sensed, what you felt emotionally, all recreated to remember what happened! (Again, as SIMPLY as I can put it) Activating neural pathways reinforces them, making them less susceptible to being lost, since your brain is constantly rewiring itself and creating new neural connections, (again, in a SIMPLE sense) Trying to recall a memory can take some time for your brain to connect all the dots, and light up the pathways that have since been weakened. Trying \"harder\" can certainly make a difference, but really what you are doing is minimizing distraction long enough so that the memory can get resparked"
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nla754 | Why are pills usually the same size for different sized people? | I’m eating pollen medicine. They are small pills and I should eat one per day. I realized that I, as a big dude has the same dose as a small tiny woman would have. One pill per day. Even if I have three times the mass. Why is it this way? | Biology | explainlikeimfive | {
"a_id": [
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"Some medications, like anaesthetic, are usually given as individual doses because it’s typically injected, and the effectiveness is based off of body size. But things like antihistamines target specific areas and don’t get effected by body weight, so you can take the same amount as a much smaller person with pretty much the same effect",
"I am a tiny woman, and I often get \"rare\" side effects or only need a half pill depending on the medicine. I believe the \"one size fits all\" dosages are heavily skewed towards mens' needs. Here is a (US-centric) article on the history of womens' lack of participation in clinical trials [ URL_0 ]( URL_0 ) tldr: \"it has been acknowledged in recent decades that clinical trials have notalways adequately enrolled women or analyzed sex-specific differencesin the data\"",
"Medications - especially the ones that doctors trust patients to take unsupervised - are formulated with big safety margins on both sides. Firstly that taking one or two or even the whole bottle too much won't kill you / do lasting harm (unless you do it repeatedly) and that the medication will be effective even if you're overweight or have issues effecting absorption (like they assume you're still likely to drink milk close to taking an antibiotic). In hospital - where you are dealing with medications that need to be more precisely administered - part of the nurse's duty is calculating the precise dosage taking your weight into account. And the hospital is controlling your diet so you won't have had things like milk, grapefruit or alcohol that can interfere with medications.",
"> One pill per day. Even if I have three times the mass. Why is it this way? That is not the norm, so there can't really be a generalized answer to that. Best thing to do in your case: ask your physician!"
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nlacu5 | why do the interiors of Banana become wet when you cut them but not wet when you pull them? | Biology | explainlikeimfive | {
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"gzhioa9",
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"When you cut them you rupture the cel walls and the cytoplasm inside spills out. When you break them the cells remain intact and are only pulled apart from one another.",
"Bananas are made of tiny structures that are full of fluid. When you cut it, you either cut these structures or, most likely, you crush them as the knife goes through, releasing the fluid. When you break the banana, the structures just separate from each other because their bond isn't that strong and the fluid stays intact inside them."
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nladlc | how do radiation measurement units work? | ive been watching lots of videos and documentaries about criticality incidents, meltdowns, etc and i keep hearing about different units like sieverts, rads, gray and others(?) but i have no real clue what they actually mean or how bad the doses/amounts were | Physics | explainlikeimfive | {
"a_id": [
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"A lot of your confusion comes from the fact that for any quantity in this field there are *TWO* units of measurement. For example, *Becquerel* and *Curie* both measure the same thing: for a given amount of stuff, how many of its atoms will decay per time unit. One Curie is equal to 37000000000 Becquerel, which is equal to 37000000000 atoms decaying per second. Becquerel is the SI unit and the one you should be using. Then there are *Sieverts*. Sieverts are a measure of how much damage your body receives from radiation. Most radiation sensors will be able to measure Sieverts. Sieverts replace the older unit *rem*, Roentgen Equivalent Man. Then we have *Gray*. Gray is a measure of how much energy is absorbed from the radiation. The *rad* is an older unit. You should use Gray, not rad. Finally there is *Roentgen*, which is no longer used and there is no equivalent SI unit. If you see someone using Roentgen, smack them upside the head with your geiger counter.",
"**Dose** basically measures energy absorbed from radiation per mass in a target body. This is important to know because radiation damage is proportional to the amount of energy deposited into the \"stuff\" (mass) that something is made of. The **Gray (Gy)** is the *absorbed dose unit*. It's the simplest to define: a dose of 1 **Gy** means 1 **Joule (J)** of energy has been deposited for each **kilogram (kg)** of mass in the target. So if a 10 **kg** target absorbes 5 **J** of radiation, it has received an *absorbed dose* of 2 **Gy**. The **Sievert (Sv)** has the same *units* as the Gray, **J/kg**, but it's defined differently. It's the *equivalent* or *effective dose unit* and is used to measure the relative severity of the same *absorbed dose* (measured in Gy) but for different types of radiation and/or body tissue. For example the 2 Gy dose described above would be more damaging to our bodies if it came from neutrons than from gamma rays, and also more damaging if it hit your lungs than your skin. Each of these scenarios have an associated *weighting factor*. Gamma rays have a *radiation weighting factor* of 1, but alpha particles have a weighting factor of 20. This means that 2 Gy of gamma rays has an *equivalent radiation dose* (H) of 2 **Gy** × 1 = 2 **Sv**, but if it were alpha particles the equivalent dose would be 2 **Gy** × 20 = 40 **Sv**. You then do the same to factor in tissues, multiplying the equivalent dose by the *tissue weighting factor* to get the *effective tissue dose* (E), also measured in Sv. Skin has a weighting factor of 0.01, for the lungs it's 0.15. These numbers are selected such that if you add up the weighting factors for the whole body you'd get 1, because if your whole body absorbes a dose the effective tissue dose would be the same as the equivalent radiation dose. A 2 Sv *equivalent dose* would be a 0.02 Sv *effective dose* if it hit the skin, 0.30 Sv if it hit the lungs, and 2 Sv if it irradiated the whole body. To put these final numbers into context, 1 Sv of dose is **A LOT**. The annual effective dose limit for a radiation worker is 20 *thousandths* of a Sievert per year (20 mSv/yr). For the public it's only 1 mSv/yr. If you received a dose of 1 Sv in a year, you're in trouble. Because dose calculations and measurements often end up dealing with such small numbers, it can be convenient to have another smaller unit to make the numbers easier. The **rad** is just this, it's 1 hundredth of a Gray. This means a dose of 20 **mSv** would be the same as a dose of 2 **rads**. Rads aren't commonly used because its an old unit, nowadays **Sv** is the standard, so you shouldn't get used to using them though."
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nlarpo | Do animals other than humans repeat patterns mentally? e.g. getting a song stuck in one's head | Biology | explainlikeimfive | {
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"It is very hard to say because we have not been able to ask the animals themselves. However we do see a lot of the same behavior patterns in animals as we do in humans. Especially in dogs which we do a lot of interaction with we can see things like obsessive compulsive disorders, depression, dementia and other mental ilnesses that we have in humans. So it is fair to assume that animals can also get songs and such stuck in their head just like humans."
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nlaydi | How do our voices change as we age? | Obviously a 20 year old is going to sound much different in 40 years. What causes this? | Biology | explainlikeimfive | {
"a_id": [
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"Sounds, including your voice, are caused by vibrations. Vibrations are modified by several factors: the mass of the moving object (heavier things are harder to accelerate aka change direction quickly), the size (larger objects take more force), the tension or restoring force (stronger forces will shove the object back to neutral faster), and so on. That's why tightening the strings on a guitar raises the pitch, and heavier strings are used for the lower bass notes, and acoustic instruments get larger the lower the pitch they're designed to create. As you get older your vocal cords increase in size (larger & heavier = slower = lower pitch), the resonant cavities in your chest, sinuses, and mouth get larger (lower pitch), and the tension of the cords changes."
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nlb9h9 | why is volume smaller than 1mililitre measured in miligrams | Why does medication use mg and does this relate to ml? If miliGRAM is for weight, why is it used for liquids which are a volume? Example: my cough syrup comes in 200mL bottle. It states for every 5ml of liquid, there is 100mg of some active ingredient. So does that mean in 5ml, .005ml is that active ingredient? Tldr why does it switch from ml (volume) to mg (weight). Also if anyone knows why sometimes it's mL Vs ml I'd love to know too. | Mathematics | explainlikeimfive | {
"a_id": [
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"The active ingredient is a solid. You can add solids to liquid and then they dissolve. That doesn't mean that the solid wasn't a solid when it was measured out to be added to the liquid. Like would you measure the sugar you add to your coffee in mL? No, you'd measure it in weight.",
"It's not about volumes less than 1ml being measures in mg it's about the dose of the actual ingredient being a mass, dissolved in a volume of liquid. Mg is a measure of that mass, and ml is a measure of the volume of the liquid. The active ingredient is the medicine, which is dissolved in the liquid around it to make it drinkable. It says the amount of medicine in mg because that *mass* is the value that matters, it is the dose of the actual solid medicine you will be getting. In this case 100mg of the medicine is dissolved in each 5ml of liquid, so there is 4000mg (4g) of medicine in the entire 200ml bottle. You can't necessarily say 0.005ml of the 5ml of liquid is taken up by the active medicine, because that depends on something called the \"displacement value\" of the active ingredient (this is a measure of how much space/volume 100mg of it takes up when dissolved in a liquid). This won't be on the bottle, as it is only of interest to manufacturers/pharmacists. Edit: to answer the second part both ml and mL are correct and mean the same thing, no difference between them.",
"The cough syrup is a liquid, therefore it is usually measured by volume. The active ingredient is most likely a solid dissolved in the liquid. Solids are usually measured by weight. The Litre is one of those rare units where it is acceptable to use both L (upper case) and l (lower case) as an abbreviation, so both mL and ml are correct."
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nlb9iw | why is it that so many games have separate server regions for Korea and Japan when they’re right next to each other? | Technology | explainlikeimfive | {
"a_id": [
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"Korea has different rules and laws aboth video games and having sperate servers for those that speak different languages is always a plus",
"Korea and Japan have a bit of a rocky history between each other, but there is also perhaps a more pressing reason: The Japanese speak Japanese, and Koreans speak Korean. Just because they are somewhat geographically nearby doesn't mean that you can drop them in a game together and have any hope they can effectively communicate with each other!",
"The reason is actually because there are so many more players in Japan and Korea that a single server would struggle to handle them all. Splitting across language and legal lines is just an obvious place to divide. The same doesn't happen in Europe that often because the player count for these games is lower."
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nlbpyx | How is light actually reflected at the right angle? | If photons aren't directly reflected but absorbed then reemitted, how do they obey angle of reflection? How does the atom know? | Physics | explainlikeimfive | {
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"Reflected light is like throwing a ball at a wall, it will bounce off at the same angle. It is not absorbed and reemitted. Scattered light is absorbed and reemitted; that’s like throwing a ball at a crowd, and whoever catches it can throw it anywhere they like. Some crowds are dense and they throw more balls back.",
"The more I googled it, the further into quantum mechanics the answer was getting. In short, you cannot describe the process just as \"an electron in an atom absorbs a particle then re-emits it\", it would be inaccurate. Due to the quantum nature of these particles (especially photons) you have to remember that a photon is an electromagnetic wave. And if it hits a reflective surface with atoms arranged in a mostly regular way (a single atom will scatter the light, not reflect it) it is [reflected as a wave]( URL_0 ): due to the wave having a certain size, different parts of it get re-emitted at slightly different times and it cancels out in all directions except the reflection direction. It's still not entirely accurate but I'm afraid there's no simple explanation beyond this point without going into quantum effects that I don't understand well enough to explain accurately."
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nlc5ee | How do life rafts and inflatable jackets self inflate? | Physics | explainlikeimfive | {
"a_id": [
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"text": [
"They have a canister of compressed air attached to them. When you trigger the inflation the compressed air from the canister is used to inflate them."
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nld943 | Why is blood in the ventricles dangerous? | Why is one type of bodily liquid - CSF - fine (even needed) in the ventricles, while another - blood - is potentially deadly? | Biology | explainlikeimfive | {
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"Are you talking about the ventricles of the brain or the heart?",
"I mean I'm not sure about specifically that part of the body, but any body fluid in the wrong place is dangerous. It's the wrong consistency, doesn't have the right nutrients needed for that area and potentially has dangerous bacteria in it. Like its ok for sweat glands and pee to have bacteria floating around in it. It is not OK for CSF to have it.",
"First off, the blood shouldn't be there and if it is - that's indicative of some kind of damage somewhere else which in itself may be the bigger problem. Secondly the blood can clot in the CSF conduits, this can cause hydrocephalus - this is a condition where pressure builds inside the brain inside the CSF system causing damage. Finally the breakdown products of any blood clots may inflame the lining of the ventricles which affects the adsorbsion of CSF and again can lead to hydrocephalus."
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nldylb | why is burning calories such a slow process compared to accumulating them? | Biology | explainlikeimfive | {
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"Because our bodys are meant to live for a while when no/ little new calories are available. And if there is food available, it has to be used efficiently, saved as fat for the next famine. It's not like our metabolism knows that the probability of that happening is rather slim and that the dangers of being overweight are a more pressing issue.",
"Think of it like how a car is designed to be refueled. You can fill a gas tank in under 2-3 minutes mostly while it takes hours of driving to consume that gas. This simply makes sense - humans (until very recently ie few hundred years) had to do manual work for long periods just to grow/catch/earn enough food to survive. It wouldn't make a lot of sense if the human body had to take many hours away from their productive efforts simply to consume food.",
"> why is burning calories such a slow process compared to accumulating them? You are thinking about this the wrong way. Your body is a very efficient machine that burns just as many calories as it needs. This is a fairly consistent amount of calories that you can estimate by [using a calculator]( URL_0 ), and you can then confirm by weighing your food and weighing yourself for a couple of weeks. The rate that your body burns calories can be increased slightly by your activity level, but there are limits to how much you can increase it. So if you eat only as many calories as your body needs, burning them is not a slower process than accumulating them - it is the exact same speed. If you eat fewer calories than your body needs, burning them is a faster process than accumulating them and you lose weight. If you view food as nothing more than fuel for your body that takes time, money, and effort to consume, the question then becomes why do people expend more resources than necessary to consume calories they don’t need and their bodies can’t burn?",
"We have evolved in environments where obtaining food is often difficult, and the processes of obtaining food required using a lot of energy. Therefore there was selection pressure in favour of minimizing the calories we need to get stuff done, and maximizing the energy we obtain from food. The trouble is that now many of us live in environments where food is very easy to obtain, and we don't need to actually use our bodies very much in our day to day lives."
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nled8j | Why do lips get drier the more you lick them? | Biology | explainlikeimfive | {
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"text": [
"by liking the lips you remove the fat layer that protects them from outside, exposing them to a faster evaporation.",
"It's because the saliva you put on your lips evaporates very quickly because it's warm. This dries out your lips. It's a real thing, not just a trick of the mind."
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nleysv | What is torque? | I'm currently doing a motorcycle mechanics course, and no matter how many times I read about torque, I cannot understand it and forget what it is after each time I've read it. I think what's missing is someone explaining it to me in really slow, simple terms. | Physics | explainlikeimfive | {
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"Torque is the measurement of twisting force. So when you turn a wrench, you apply forcein a twisting mannner on the bolt. This is torque. Then the engine is on, is twists the crank shaft. This is torque.",
"Torque is a rotational force. It differs from the force required to push a block uphill because it includes a distance component. On a consistent incline, the work in Newtons required to move the block is constant. Removing a bolt however can be easier with a longer wrench because the force is measured in Newton meters. Applying one newton of force at 1cm is significantly less then one newton of force at 1m EDIT: Consider using a socket by itself to loosen a nut, then use a socket wrench to rotate the socket. You can easily see that the wrench requires less force to rotate the nut because it is applied at an increased radius.",
"The other answers here are okay but they sort of hit the mark slightly off. Torque IS a \"force\" that causes rotation. It's confusing to use the word force like this because you can generate a Torque using a Force (Torque, τ, is proportional to radius, r, from the centre of rotation - e.g.: length of a wrench when tightening a nut - to the (linear) Force, F, used to generate the Torque - e.g.: you pushing on the wrench - and the sin of the angle, θ, between the lever (the wrench) and the axis of rotation (lengthwise along the screwthread) - you mostly don't need to worry about the last one though) (τ = r*F*sin(θ)) The way I like to think of it is \"A Torque is to a Force, like rate of spin is to velocity.\" It's basically the same thing, but distinct in that it is angular (circles'n'shit), not linear.",
"Stick your left index finger out. Twist it with your right hand. That's torque. All the little explosions in your engine push on parts of the drive shaft that are off center, applying torque."
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nlh0b5 | Why are images of transparent blue men so common in futuristic/scientific illustrations? | I work for a science communications organization and we've all noticed the 'transparent blue man' trope. You know, a bald male figure with lightning or something shooting out of his head and DNA in the background. I would love to know how this began - was there an original image that inspired it? Is it Dr. Manhattan-related? Why is he blue and not green as early computer imagery would have suggested? | Other | explainlikeimfive | {
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"It's for a couple of reasons mainly. For one, it's the most easy to identify colour for people suffering from poor eyesight and potential color blindness. Secondly, It's the color less likely to glitch when projected on a screen."
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nlht1s | supergroups in biology | I'm taking an accelerated bio course and I have been trying to understand a quick grasp on the role of supergroups in biology. Are supergroups just unicellular eukaryotes, i.e. protists? How is this different from Kingdom Protista? | Biology | explainlikeimfive | {
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"Supergroups are gathering of groups that are in general larger than kingdoms For instance, all animals and fungi plus a few other things are in one supergroup (multiple kingdoms) All plants, green algae, and red algae are another super group (again multiple kingdoms) But in some cases a single kingdom is divided into multiple supergroups. Part of this is because eukaryotes got all tossed in the kingdom protoctista simply because they weren't plants, fungi, animals, or bacteria. Same with procaryotes, as we found things that were like bacteria but weren't bacteria we needed to split those into supergroups This is to better reflect their actual shared ancestry"
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nli9qd | how does the mechanical watches work? | I mean where do they get the energy from to power themesevles? | Technology | explainlikeimfive | {
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"There are manual wind watches, but those aren’t super common anymore. A lot of them today have a little weighted piece of metal on a rotor that’s usually on the bottom of the watch (and a lot of times visible if the bottom is glass/crystal). That weighted piece of metal spins around when you move your arm which spins the rotor. That spinning of the rotor is what compresses the spring. So you basically just charge it by wearing it. It’s also why some fancy watch cases rotate, that way they’re spinning that weight and rotor even when it’s away, which is usually considered better for the watch and means it won’t run out of juice and have an incorrect time if you don’t wear it for a little while.",
"There is a coiled spring. When you wind the watch, it tightens up the coil which then creatures the force necessary to power the gears."
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nlie3t | Cameras confuse the hell out of me. | How do they work? Is it glass or mirrors or something? It’s so confusing | Technology | explainlikeimfive | {
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"Curved glass (a lens) is used to focus light onto a photo-sensitive surface - film for traditional film photography, a sensor for digital. Oftentimes this light is reflected off of a mirror inside the camera body for design considerations.",
"For normal film cameras, it's like this. The camera is just a box that keeps light out. Inside that box, there's a roll of film. This film is basically a specially treated type of paper (not really paper, but it's made of cellulose, which is what plants are made of). The film is treated with several different chemicals, which react when they are exposed to light. If you were to take that film and just look at it in your living room, the amount of light would be too great. The chemicals would react immediately, changing the color of the paper until it was completely black. The chemicals are designed to react with only a very small amount of light. The front of the camera has a shutter on it, a mechanical device that opens and shuts very quickly when you press a button. The shutter is designed to let the right amount of light in, so that the chemicals don't \"overexpose\" the film. For a normal camera, it's open for just a tiny fraction of a second (but if you're a really good photographer and know what you're doing, you can mess with the shutter speed and change that -- for instance if you wanted to take pictures at night). There's also a lens, a curved piece of glass, that focuses light onto the film. There's also a mirror in there that reflects the light up to an eyepiece, so when you put your face up to the camera you can see what the picture will look like before you press the button. When you take a picture, a piece of film is in the correct position behind the lens so that the light in front of the camera is focused right on the film. You press the button, the shutter opens and closes very quickly, and now the film has been exposed. The chemicals react according to the level of light they were exposed to. This results in a copy of the image being \"burned\" into the film. This copy will have reversed color (brighter light causes it to burn more, causing a darker image). This is why film negatives have their colors reversed. Then there's a little lever or wheel or other mechanical piece on the camera that you can push. This little thingy pulls the film forward, so that the next frame of film is in the right spot behind the camera lens. When you're done taking pictures, you retract the film into its protective case, where it's nice and dark. You remove it from the camera and then take it to be developed. The developer goes into a \"dark room\" where they use a special type of light that doesn't react with the film, but the person can still see. They then basically reverse the process, projecting light through the film negatives to put an image on a piece of paper that has been similarly treated. You have to wash off the chemicals and wait for it to dry before the picture can be taken outside the dark room.",
"If you really want to blow your mind, take a piece of thin cardboard and punch a medium sized hole in it (like the size of a sharp pencil lead). Hold the cardboard over a table or something under a light fixture. Move it up and down until you can see the projection of the light fixture on the table. Light is so weird.",
"Digital works something like this: Imagine this thing called receptor. It's a square which tells how much light hits it. From 0 to 100%. This would give a image of resolution 1x1. If you arranged 100 of these in a 10x10, you get a 10x10 resolution image. Increase the quantity and the kind of light they receive and you get a camera like the one in your phone."
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nlimsq | How come water based liquids sting wounds but oil based liquids or ointments don’t? | Chemistry | explainlikeimfive | {
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"Our bodies use water, in our blood, as the main fluid to move stuff around. So water is special to us in a way that oils are not, when water touches our wounds, it's sort of like the right plug fitting into the right outlet. Our nerves, which are exposed in a wound, use chemicals called \"ions\" to transmit signals up to our brain. When water touches an exposed nerve, if that water contains too many ions (like salty water) or too few ions (like distilled water) it can cause the nerves to misfire and transmit a signal to the brain that we perceive as \"stinging\". If the water has just the right ion balance, which we call \"saline water\", it wouldn't trigger that sensation."
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nliql6 | Why, although planes are highly technological, do their speakers and microphones "sound" like old intercoms? | EDIT: Okay, I didn't expect to find this post so popular this morning (CET). As a fan of these things, I'm excited to have so much to read about. THANK YOU! | Technology | explainlikeimfive | {
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"I’m a commercial airline pilot and there is a lot of misinformation here. First of all, 99% of the time we’re on VHF AM, not HF AM radio like people have suggested. Second of all, the radio has nothing to to do with the intercom anyways. The real reason is weight. Good speakers are heavy and the fuel to carry those around for the life of the airplane costs thousands to millions. TLDR; Good speakers are heavy and cost too much fuel to carry around.",
"*TL;DR - the speakers, microphones, and all of the plane's audio systems have a narrow frequency response in order to maximize intelligibility over the aircraft's AM radio equipment and between crew members in noisy environments like the cockpit.* Their audio systems, generally speaking, are all on an older, simpler analog standard, for important reasons. The main issue (everything else stems from this) is that the radios they use in the aviation band (~118-136mhz) are AM radios (like AM broadcast radio, or like CB radio). This is weird, because almost everybody else uses FM (like FM broadcast, or like walkie-talkies) at those \"VHF\" frequencies because of the better audio fidelity and noise suppression. However, when two radio operators accidentally talk over one another at the same time (\"double\") using FM, the result is a garbled mess in which neither one of them is guaranteed to be intelligible. (A comparable effect would likely happen with some sort of digital audio transmission.) When two operators double using AM, the result is often just hearing both of them at the same time, so pilots and air traffic controllers can still at least make out what one or even both operators are saying. *Edit: there's been some discussion of this in the comments. If the two AM carriers aren't exactly the same frequency, yes, you may get some nasty interference sounds. All I can say is... FM doubling is a lot worse than two AM transmissions that are tuned to exactly the same frequency. [Further info.]( URL_0 )* So getting back to the audio quality of aviation audio systems: if you're using AM (amplitude modulation), you only want to invest your radio amplitude into audio frequencies that are useful and important to understanding a voice. (This band pass filtering doesn't really matter for FM transmissions, which is a larger discussion.) When, as a ham radio operator, I use amplitude-modulated voice communications to talk to someone in e.g. New Zealand from here in Montana, I limit the audio frequencies I transmit (and receive) to about 150 through 3,000hz. When someone talks, you hear sounds all the way from 100 through 20,000hz, but only about 15% of that range is really crucial to understanding what they're saying. Investing radio power into transmitting all those other audio frequencies is basically just a waste of your radio power, and is likely to get lost in radio noise, anyway. So, the microphones that pilots use, any audio processing, and even the headphones/speakers, really don't need to be very high bandwidth like the speakers/headphones you'd want for hi-fi music listening - they're all geared for maximum intelligibility in the presence of noise, not maximum audio quality. And hence you get \"from the flight deck\" or flight attendant messages over the intercom that sound like low quality audio - it's all part of the same audio system the pilots use to communicate with ATC, one another, other planes, the crew, etc.",
"Small cheap speakers sound bad. Small cheap microphones sound bad, but are very durable. It's not worth the cost, weight, and maintenance to get better audio since there's not much benefit to it in the first place. Good audio doesn't really contribute to a good flight in a way that's worth any of the costs.",
"Commercial Airline Captain Checking In ! ÉDIT: thanks for all the upvotes and badges < 3 Many considerations : - in aviation and aerospace we need to make sure safety related equipment are reliable. That is why multi million dollar planes are equipped with sometimes CRT screens : they don’t break at the first turbulence. Same for the intercom in the cabin : we could install Bose PA speakers but you’d need to make sure first they are designed to be fail proof. We still do check them as part of the cockpit preflight because we need to know in case we do need to announce a no-time emergency (like « emergency descent ! » or « EVACUATE ») they were at least working. I personally listen to it on my mixer to be SURE they work when I use them - laws : they have to follow a specific standard that is very precisely required and there must be only a handful of makers on the market, just like my plane the B737 has only two providers of autopilot controls. In particular there is a need of everything in the plane to be ignifuged to retard fire in case one breaks out. There must be design specifications for, for example, working through interferences, not breaking during a spike surge of electricity (we do connect and disconnect several time a day massive generators of 400hz 115V Ac generators from the planes or the onboard generator or external ground generators and each time a solenoid jumps and spikes can go through the electric busses and would maybe fry mainstream grade equipment) - money : there are certainly weigh considerations for EVERYTHING on board. This equipment is not exempt and modern grade equipment that are not designed with weigh in mind can’t find a buyer from Boeing Airbus or the new competitors. Mind you, a big American airline decided to remove 1 or 2 olives per on-board meal after the first oil price crises : they estimated it saved them half a million dollars in fuel a year. There is no little savings when it comes to weight on a plane. - and finally probably the most likely reason why PA speakers don’t upgrade : Certification. Every system on a plane, every sticker, is certified. Next time you go to the toilet check the stickers : they have a number somewhere that links tl their certification. Each plane is designed with specific design plans and the most basic of its structure is part of the certification. That is notably why you pretty much never have a window perfectly adjusted to your seat : they are designed by Boeing but every airline chooses the seat configuration. The cell stays the same. Now I’m not 100% sure of it, but the speakers might be tied to the plane type. When a plane is upgraded to a more modern one like the 737 which cames from 200 (legacy) to 300 (classic) to 800 (Ng) and now max (-8), at each time the manufacturer can only modify 25% of the désign or the planes is deemed needed a new certification which means a whole complete flight test campain which is extremely costly and also means pilots need to train for the new type instead of a short transition called « difference training ». Since most of this is taken by the update of the wing design, engine, systems here and there that improve fuel efficiency and comfort, a PA speaker is probably last on the list. Mind you the overhead panel controls of the max are still the same as the -200 for some parts because changing it would mean the plane needs a new certification and although it’s 2021 the max doesn’t have push buttons with lights like the new planes because companies have too many of them to want to pay for the transition. Notably Southwest pressured Boeing to not modify the overhead to a modern styled one for this reason alone. Trust me, we pilots would love a redesign of the cockpit that is old fashioned (albeit cool because of that) and noisy for a more modern and quiet one, so if those controls are not updated, the PA will be last Given all that though, each generation of planes gets better on all parameters and I would bet a B787 sounds better than a B727 in the cabin - unless the PA makers have stayed the same ? TL,DR : reliability, laws, weight, R & D, certification, cost to airline training due to said certification",
"While poor comms can be a problem, in general the actual quality that the pilots/ATC perceive is higher than the recordings you’ll find online. The online recordings are generally made with volunteer receivers in areas of poor reception whereas the ATC transmitter sites are professionally set up on top of mountains/towers etc. Pilots do sound more muffled if they’re wearing an oxygen mask (fighter pilots or airlines under emergency) or pressure suit (U2 pilots).",
"Most commerical planes are ancient, in terms of technology. Everyone assumes they are the height of technology but there is a good chance, depending on the route (in the US at least) the plane you're flying in is 20+ years old. Many of them are designs that are even older than that. Look how long the 747 has been flying lol",
"Aircraft Technician here, I’ll presume your asking this question from the perspective of a passenger on a large transport airplane. It’s all about expense, the manufacturers build airplanes the operators will buy, the operators don’t care about PA sound quality. It’s designed to meet the minimum requirement at the lowest cost. Some aircraft that have been designed more recently like the A350 and B787 will probably have better PA audio quality due to advances in technology, but it’s still going to be cost driven. Older aircraft PA systems usually will not be upgraded if they continue to meet the minimum requirement, again due to cost. All this talk about AM and FM frequency bands is lol, there is a very specific HF and VHF frequency range for aircraft communication with Air Traffic Controllers. HF is for long range communication when aircraft are transiting an ocean, VHF is used while over or close to land. This has everything to do with the wavelength of the frequency and nothing else. The sound quality on these transmissions is normally higher quality then regular cabin announcements, because the type of communication on these radios is important for safe operation of the aircraft, thus the operators are willing to pay more for it. Also, any overlay these frequencies may have with AM or FM radio frequencies is coincidental, it’s not important information to answer your question. You’ll also notice the sound quality in the cabin is better when the aircraft is on the ground as opposed to inflight. One, the cabin air pressure is different in flight and this affects the way we perceive sound due to the different pressure in our inner ear. Second, the aircraft smashing its way through the atmosphere creates a lot of air friction and noise near the cabin doors due to the irregular shape of the interface of the fuselage skin and door skin, and some small air leakage at the door seals. Third, nearly all of the PA microphones in the cabin are right next to the doors, so they pick up all the back ground noise of the doors.",
"They make you sit in the cheapest, most uncomfortable, seat possible and you wonder why they don't have high-quality audio? Corporations will do anything to save a buck.",
"Another reason that I don't see mentioned is that there really is no reason for high fidelity in a comms system. The system they have is good enough for understanding what's being said, anything more would just raise costs in an already expensive industry",
"Petition to stop all pilots from needing to report every little detail to passengers; unless there is an emergency or change of plans. I do not know of anyone that gives a damn about airspeed or outside temperature. All the pilots are doing is waking us from our rest.",
"So to all the commercial airline pilots that are chiming in, here is a bit of advice. Figure out what you are going to say before you start talking. \"Hi! this is John your ahhhh pilot here. We are going to be ahhhh flying to ahhhh Albuquerque and we expect the flight to ahhhhh take about ahhhh 3 hours and ahhhhh...\" I don't know about the rest of you, but every damn flight... which is strange because I rarely fly to Albuquerque."
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nliu0v | Why can't we revive a deceased person by making their heart beat again (e.g. by using an artificial heart)? | Biology | explainlikeimfive | {
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"Sometimes we can. People have their hearts restarted or put on a bypass machine until they can heal or have surgery. Usually you have to be lucky enough to be in a hospital when that happens however. If your heart stops your brain is going to have about 3 mins before brain damage sets in. After 9 minutes the brain is essentially dead and revival isn't possible.",
"When the heart stops, cells in the rest of the body die. If the heart was restarted, you've only fixed the cause of the problem, not the effects of the problem.",
"As other posters said, once the heart stops pumping, oxygen is no longer circulating to body tissues and they begin to starve and die. An imaginary clock starts once this occurs and you have between 3-5mins before the damage is irreversible even if the heart were to restart (no one truly knows exactly how long and it varies by age, how healthy the person is, temperature, and other factors... But it's minutes at best.) Another reason that has not been mentioned already is when you die, blood is no longer moving (i.e. being pumped by the heart). Blood that slows down or stops moving begins to form clots inside the vessels, especially smaller ones. This initial process starts relatively quickly with the blood becoming thicker as microclots form. This also factors into the problems resuscitating someone who has been dead for minutes. Thick or clotting blood cannot be pumped effectively even if you restore pump function. When CPR is performed on someone whose heart stopped, it is essentially doing what you are asking. It's an artificial means of maintaining the pumping function the heart is no longer doing while using other medications and interventions to try and restart the heart or reverse the underlying reason it stopped in the first place. With few exceptions, CPR or artificial cardiopulmonary resuscitation often fails and even for a witnessed cardiac arrest IN THE HOSPITAL (where you assume CPR starts almost immediately, and access to resuscitative medications are readily available) the chance of successfully reviving someone who later goes back to a normal life is somewhere around 25%. It is even worse if it is unwitnessed or occurs outside the hospital. I am a doctor who works in an ICU and do CPR frequently as part of my job. It's unfortunate we do not have more tools or better ways of reviving people but one thing healthcare workers hate is how Hollywood portrays CPR (and defibrillation/shocking the heart) as magical tools that always bring someone back from death. Its portrayal on TV or in movies is often completely opposite to how it is in reality.",
"If somebodies heart stops pumping blood. This also stops oxygen from getting to organs. So after a while those cells start breaking down and dying off. So if you were to do this to somebody who is dead for more than a few minutes (yes its that fast) there is only a small chance they will be “alive” and even then then will have massive damage to the brain and other vital organs. The only way this would be plausible is if the person they do this on dies in the hospital and everything to perform the transplant is ready to go right that second. On top of that the bodies immune response will likely attack the artificial organ causing further problems. If you have any questions feel free to ask",
"You can. it's just you have to be able to open them up and insert the artificial heart all within 3-5 minutes of them dying. CPR / defib machines can in some very lucky cases restart someone heart which **is** bringing a dead person back to life. No heart beat = dead. One of the reasons it doesn't matter if you break bones etc while doing CPR because you are dealing with a corpse and nothing can make it any worse than being dead. First aid instructor qualified to teach the defib machines as well.... though we are not really meant to mention the corpse / dead thing when teaching this as it's considered a bit off putting telling joe public to go mouth to mouth with a corpse, it's referred to as the \"victim\"",
"My brother’s wife had a heart attack last month and he was unable to perform CPR because he’s disabled and couldn’t move her to a hard surface. EMS was there within 8 minutes but it was too late. They were able to get her heart beating but test results showed that her brain had gone without oxygen for too long and she would never resume consciousness.",
"You are cooking. Suddenly the food catches on fire. You stop the fire. The food is still burnt. (Although sometimes you can salvage the food)",
"Look up ECMO. My dad had a severe reaction to blood products during a \"routine\" surgery and his heart & lungs started shutting down. He was flown to the nearest hospital and put on an ECMO machine that allowed his heart and lungs to rest and heal. He used to be an okay dad but after his near-death, he is now an awesome dad and grandfather!",
"Brain death. Anoxic (lack of oxygen) injury to the brain happens within minutes. Since blood delivers your oxygen, the lack of beating leads to lack of oxygen very, very fast. It's the reason why those who have cardiac arrest with a returning heartbeat, but no neurologic function, are placed under cryotherapy (not freezing, but targeted temperature management to several degrees below body temperature). We're trying to decrease all those breakdown metabolites that start to occur within minutes of the brain losing oxygen and starting to die. Oxygen and minutes are everything. CPR (cardiopulmonary resuscitation) should actually be called cardiocerebral resuscitation, or CCR. You are pumping blood to the coronaries of the heart by doing CPR, but you are also getting some vital blood to the brain with each set of compressions."
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nljdk9 | How do explosives (grenades, artillery, dynamite, etc.) actually kill you? | Physics | explainlikeimfive | {
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"There’s generally three ways. The easiest one, which requires the least explosive, is via shrapnel. Basically, you encase the explosive with a material that’s designed to shatter into sharp, deadly shards. When the explosive goes off, these shards are ejected away from it at high speeds, and when they hit a body it causes massive damage by cutting, crushing, and disconnecting various body parts. Shrapnel has a few limitations - structures tend to block it and the lethality of shrapnel decreases with distance. So it’s best used as a precise anti-personnel weapon - hand grenades being a great example. You’re not going to knock down a building with shrapnel alone. But you can kill and maim the people inside and establish yourself in it with shrapnel. The second way is through heat and fire. This one is where an explosive is used to disperse an incendiary material across an area. Here, the explosive is really the delivery system, and the payload is a slow but hot burning material which then damages and kills through obvious means. The last way is through air pressure. For this, you’re looking at bigger explosives which have an explosive yield big enough to turn air itself into a lethal weapon. At high yields, explosions create a shockwave. This shockwave can impart a massive force on a person, which can damage or even crush bones and organs depending on the size of the shockwave. A shockwave of about 75-80 G’s will kill some 50% of adults it contacts. This is a more complex calculation, depending on the explosive yield of the bomb and the distance from explosion a person is. Bombs also destroy structures - even if the shrapnel, heat, and air pressure don’t kill you, a bomb can collapse the structure you are in, crushing you or suffocating you. There’s also some less conventional bombs which spread toxic or deadly materials throughout an area. For instance, a dirty bomb is one which explodes to spread radioactive material in an area. It’s not a nuclear weapon, but it spreads radioactive substances which can kill. Nuclear explosives are a different story, especially within a certain distance. Within a few hundred feet, a human body will be vaporized by the intense electromagnetic energy released by the bomb. The heat and light from these weapons can be more intense than that of the surface of the sun.",
"sometimes its from the shrapnel tearing through you or it can be from the shock wave many casualties from the German v2 rockets didn't have any marks on them the shock wave just ruined their insides killing them almost instantly",
"It depends. There are two primary effects caused by explosives: blast and fragmentation. Fragmentation comes is a couple flavors. There is primary fragmentation, which is the parts and pieces of the explosive device, and secondary fragmentation, which is made up of parts and pieces of things around the explosive device. These are thrown at high velocity by the explosion. You can think of these as a whole bunch of bullets that are different sizes travelling at different speeds. Similar to real bullets, if you get hit in the right spot by one or enough spots by a lot you will die. Blast is the compression wave created by the explosion. Similar to fragmentation there are different types. The wave through the air is called a shock wave. The wave through the ground is called ground shock. If its in water, its also a shock wave (shock waves travel much faster and stronger through water than air though). The shockwave is able to do damage due to two reasons, we have hollow spaces in our bodies and our flesh has an elastic limit. The hollow spaces allow for damage because it creates a compressible area, whether the area was meant to be compressed or not. The elasticity of flesh comes in because there is only so far tissue will stress before ripping and taking damage. Strong shockwaves travelling through your tissues can stretch tissues beyond this point, primarily in internal organs (they aren't really meant to stretch much). Another way that shockwaves deal damage is they can throw you around. So even if the blast doesn't damage you enough internally to kill you, it can still throw you into a concrete wall like a rag doll.",
"The lethal effect comes from the shrapnel. If a grenade explodes, the metal casing of the grenade is fractured into hundreds of smaller bits that will be blown in every direction, inflicting major damage on anything that happens to be close by.",
"Grenade deaths are usually from shrapnels being scattered at a high speed. For artillery, if you're talking 'bout the big guns like on tanks and ships, AP (armor piercing/penetrating) rounds will directly ram you to death, HEAT rounds will melt you with boiling jets of high temperature, HESH rounds will cause a shrapnel-like effect and hit you with scorching pieces of your now-broken vehicle armor. Depending on proximity, just the shockwave alone from the explosion can kill you"
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nljz38 | In cell fractionation, how come no cell organelles break in the process of homogenization or under the influence of immense gravity? I feel like no organelle should stay intact in an extreme condition like 20,000g. | Biology | explainlikeimfive | {
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"They're floating in liquid, so the pressure is very evenly distributed. At 20,000g the hydrostatic pressure can be really high but it's almost perfectly even over small distances, like the size of a cell or organelle. So it's being squashed evenly from all sides and there's no shearing/tearing force to break it apart. The only way it should do anything is if you get to such a high pressure that molecules start changing phase."
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nlkjb1 | Why are alkaline noodles chewy? | Chemistry | explainlikeimfive | {
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"Alkalinity causes more water to be absorbed into the noodle flour to break down more starch. The broken down starch gels with the protein (gluten) to strengthen the noodle. This strengthened noodle structure is firmer and has a \"chewy\" bite."
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nlknv5 | Why are flights from NYC to Boston 1.5 hours long when they should only take around 20-30 mins? | The flight distance from NYC to Boston is around 190 miles. Assuming a passenger jet can travel at 500mph, shouldn't it take only 20-30 minutes to travel the distance, instead of the usual 1-1.5 hours? | Other | explainlikeimfive | {
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"Flight times are counting \"block time\". This is the time from when the blocks are removed from the wheels of the plane at the gate and it can push back, to the time the plane enters the gate at the destination and has the blocks put back on its wheels to stay in place. This means that taxiing time, waiting for take off clearance, etc., is all part of a flight time.",
"Lots of good answers here, but basically the plane isn't going 500mph for the whole time it leaves the terminal until it arrives at the next terminal. Think of it this way; You work 10 miles from home, the speed limit on the road to work is 60 miles an hour, so you should be at their door 10 minutes after you leave your door? No. Because there's time invloved in getting from your door to the car, getting to the highway, getting up to speed, getting off the highway, driving to the building, parking the car, leaving the car and getting to the door.",
"Mainly due to the routing. We are not really allowed to fly direct from say JFK to BOS. This is due to the amount of air traffic and airspace between the two. So generally you will get routed away from the incoming flow, and have to avoid military and outbound traffic from other airports. So even though the straight line distance may be 150 Miles, the actual route of flight could be 250 or 300. Same with altitudes, We can't just fly there at 5000 feet, and actually that would take longer as we are limited to 250Kts below 10000 feet, so generally we will fly around 17-21000 feet due to speed and traffic and airspace. & #x200B; Source am airline pilot.",
"Becuase medium and large airliners dont take direct routres, the idea is that all air traffic is done in corridors, which are flight paths calculated to be the lowest cost, insurance reasons and such, also like that all airports have take off and landing corridors, meaning that before going to its destination, a flight must leave an airport in a specific path until it reaches its designated altitude and then it can head out in the direction its supposed to go. So basically, even if the distance is 190 miles which is around 20 minutes in the avarage cruise speed of a normal airliner (around 500-600 MPH), the landing and take off manuvers are around 25-30 minutes each, between the landing/take off window, the designated corridors, line up manuvers and such. So on a 6-8 hour flight its not a big deal, but for a short city hop, it can be annoying.",
"This is like asking, \"if my car can go 0-60 in 3.9 s, why does it take me 30 seconds to pull out of the driveway?\"",
"Board, taxi, take-off, turn around to face the right direction, flight time, circle the airport, land, taxi, arrive at gate and wait for bridge, unboard.",
"1. Time doesn't just include flight time. It also includes time the plane spends taxiing to the runway for takeoff and to the gate after landing, being pushed-back from the gate for takeoff, waiting to takeoff, etc. 2. Plane doesn't travel at cruising speed the whole flight. It takes off at around 150mph give or take some speed depending on the wind and how heavy the plane is loaded, and when it's climbing to cruise altitude it starts off flying at around 200 - 300mph shortly after it takes off and gradually gains speed. Plus there's also the speed it flies when descending. 3. Routes aren't in a completely straight line."
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nlkv7y | Why do some carrots float and other sink in the same water? | Other | explainlikeimfive | {
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"Carrots are a fibrous root crop that is similar to wood. Depending on the makeup of the individual root it will have a different buoyancy likely because of the internal openings present in each root. If the openings are large, it will trap more air and increase the buoyancy. If the openings are tight or closed it will sink for lack of buoyancy."
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nll6yc | Why does the liver have so much more regenerative properties than other organs? | Biology | explainlikeimfive | {
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"Firstly, the liver is not a mechanical organ like the heart or kidneys. It’s functions are based entirely on chemistry, not on structure. Any liver cell anywhere can do what a liver cell does. So, if you remove a piece of the liver, the liver still works. This would not work for a mechanical organ like the heart, because the structure of the heart is absolutely key to how the heart functions. If you remove a piece of the heart, you fundamentally alter its mechanical properties. Secondly, the liver is primarily tasked with de-toxifying toxic chemicals, and so it is constantly exposed to toxic chemicals. This constant exposure to toxins causes constant damage to liver cells. So liver cells have to constantly replace themselves as they become injured or killed in the line of duty. Put these two facts together (the shape and placement of liver tissue is irrelevant and liver tissue has a high rate of cellular regeneration), and it adds up to the fact that the liver can regenerate itself far beyond what most other organs are capable of.",
"Doctor here, so the regenerative capacity of any organ depends on the presence of these cells that we call \"stem cells\". They're present in quite a few organs like the skeletal muscle, to some extent in the heart muscle as well! They are called satellite cells too. These cells remain dormant for the most part. So everytime some cells die, it is the job of the stem cell to divide and replace the lost cells. Now this regenerative capacity is close to absent in the nervous system. There are claims that nerves may have some regenerative capacity but it's negligible. Muscular tissue has limited regenerative capacity. Now the liver, has the highest regenerative capacity as an organ. This regenerative capacity stems from the concept of your DNA being able to get copied multiple times. As we grow old, the replications decrease and eventually, our cells die more than they replicate and we ultimately move towards senility. So, if you were to have, let's say a benign tumour that was occupying a part of the liver, you can remove it and the liver would grow back to its original size. That's why liver transplants are so widespread. Not to say that it is an easy task, given how transplants CAN get rejected, so, it's still tough but very commonly done. I hope this answers your question"
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nlm6yp | When a company gets bought out, how do they (the bought company) decide where the money goes? | Economics | explainlikeimfive | {
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"> Is it split among the owners? Shareholders? Those are the same thing. This is where the money goes; ownership is being bought so the people who have it are the ones who get paid for giving it up. > Employees? Hah! Not unless they own stock. > Used to pay off existing debt? Used to pay off employee redundancies? Nope, the company is now owned by the company that bought it out, including any debts they may owe.",
"The shareholders get the money depending on how many shares they hold, sometimes they may get shares in the new company instead of cash. Any debt is transferred to the new company along with the assets."
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nlnqgr | Why can standing in one place for too long make you faint? | I read in [ URL_0 ]( URL_0 ) that standing in one position for too long could make you faint. | Other | explainlikeimfive | {
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"Your heart is good at pushing blood through your body, but doesn't pull it back. By the time blood gets through your arteries and capillaries, there isn't much pressure left to push it all the way back to your heart through your veins. To get around this, your veins have valves to prevent blood from going the wrong way, and the contraction of your muscles helps push blood back to your heart. If you stand for extended periods of time, blood ends up in your feet and lower legs where gravity prevents it from getting back to your heart. If you were walking around or moving, even fidgeting a bit, it would be enough to push the blood back to your heart. If you're standing still with your knees locked, your leg muscles aren't doing much of anything and blood can't get back to your heart. Eventually this lowers your blood pressure and not enough gets to your brain which causes you to faint."
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nlo8wr | If in most cases "death" directly implies the lack of oxygen supply to the brain then why can't we develop a technology that directly provides oxygen to the brain in worst-case scenarios to prevent any shortage at all? | I'll make my question a little more clear. As far as I read, whenever a person is about to die, all that's happening is that their heart stops beating which in turn stops the brain's access to oxygen. I read that it is possible to revive a dead person within 3 minutes of heart-beat-stopping as the brain usually has a 3 minute backup oxygen supply. Why have there not been any research or investments in developing a technology like the "defibrillator" which revives the heart, but instead to keep the brain alive? Also, question part 2: why does the brain die in 3 minutes? Why can't it be revived? | Biology | explainlikeimfive | {
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"There are technologies that provide oxygen to your brain/body after your heart has stopped. How do you think they keep people alive during heart transplants that take hours? The problem is that these machines aren’t small or portable. And to use them you have to tap into the blood vessels that travel to and from the brain. In order to artificially pump oxygen through the brain. So, even if you were able to take the large machines in hospitals that replace hearts, and make it small and portable. You would still have to have emergency responders cutting open the patients neck in order to insert the tubes in the necessary vessels leading to the brain. This would be a very dangerous and complex thing to do, even in an emergency room. This is why chest compressions, which pump the heart by hand, are recommended for any amateurs/normal people trying to help someone with a stopped heart. It’s an easy and minimally invasive way to keep blood flowing to the brain.",
"Your brain consumes a lot of oxygen, both to power thinking itself and to do all the other things cells need to do to live. If you completely run out of oxygen, it basically sets off an unstoppable chain reaction of failures within a cell that ultimately kills it; even providing new oxygen won't fix it when all the other cellular machinery is broken. Now, you're right that the brain does have roughly 2-3 minutes of oxygen, but that oxygen is contained within the blood that pools in the head when the heart stops. Getting the heart and lungs working again (or manually doing that for someone with CPR + Rescue Breaths) as soon as possible is the best way to keep the brain alive (because that's already their job). While the technology to bypass the heart and lungs exists already, it's used only in surgical applications such as a heart or lung transplant, and takes time to get set up by a surgical team. There are some circumstances where the brain can be kept alive for much, much longer after the heart stops, even without a doctor's intervention, but it almost exclusively involves drowning in icy water. The drop in body temperature *before* the heart stops lowers your brain's need for oxygen significantly. Unfortunately, we can't do this reliably for other causes of heart failure because it's physically impossible to cool the body fast enough to save the brain *after* the heart has already stopped.",
"Defibrillator doesn’t actually start a stopped heart it fixes the rhythm or at least tries to, if your hearts not beating at all it doesn’t work. To keep the blood flowing you’d need a full on artificial heart. Theres no magic way to oxygenate brain cells without flowing blood.",
"We do have a technology which can provide oxygen to the brain keeping someone alive until whatever cause their heart to stop can be healed. It is called chest compressions. Whenever someones heart stop you have to apply chest compressions to keep their blood flowing providing oxygen to their brain. And continue to do this until professionals arrive and take over. When they are able to find out why the heart stopped and fix this then the heart will resume is rhythm and chest compressions are no longer needed. If you are on a movie set this is easy because you can just use a defibrillator and it somehow magically fixes any issues if it is convenient for the plot. However in real life this is not the case and the defibrillator is not used unless someone is found to be fibrillating. The brain needs oxygen because all the neurons use a lot of oxygen. Unlike muscle tissue neurons do not have their own local supply of oxygen on hand and need constant oxygen from the blood. And unlike muscle tissue and most other tissue the neurons in the brain are not redundant as the connections made by each single one may potentially be critical for a memory or a skill. So without oxygen the neurons in the brain starts to die and the brain starts to degrade. After about 3 minutes it is likely not enough remaining of the brains neurons to get it working and repair the damage.",
"May I take a different tack here? I think the oxygen question issue has been addressed quite nicely by many responders. With that said, I think OP is perhaps tugging at the sleeve of a larger question: what are the possible interventions to slow down, stop or reverse the death process? I recall this story about scientists observing a \"death wave\" of biochemical activity once a worm dies. Fascinating stuff, and perhaps once the exact nature of this process is fully interrogated, we can do more to prevent humans from dying. URL_0 .",
"So we already do have the technology. Its what life support is. Machines that perform vital functions to keep someone \"alive\". One of the issues is time. You literally have to have the person in the room, with the equipment ready to hook up in order to have a chance at getting things started in time if they crash completely like that. Another issue is cost. Running that equipment and professional monitoring for the patient is expensive. Even prior to U.S. medical care mark ups (if you are in the U.S.). Next is what's the point? If you can't fix/repair the issue that caused them to need the machines in the first place, what's the point of keeping them in that state? On top of that is the actual issue of what is \"dead\". There are varying medical criteria for it that have changed over the years as technology has changed and made certain definitions obsolete. Lack of a heartbeat is still often used as a definition for \"dead\". However now you can bypass a person's heart, cut it out, and replace it with a new one. The person obviously isn't dead, even though some will state they were technically \"dead\" during that time because they had no heartbeat. This is also delving into the difference between practical definition and technical definition. Say someone is decapitated. At what point are they \"dead\"? Is it the moment of decapitation, the point when the heart stops beating in the body, or the point when the eyes or mouth stop moving? Or maybe later when the brain actually experience metabolic \"death\" after passing out from lack of oxygen. For part 2: The brain uses a LOT of oxygen. It also has no capacity to store it for shortfalls. It is dependent on fresh oxygen being supplied via the bloodstream to remain functioning. You can't revive it because at a certain point the cells actually die and just pushing more oxygen and such to it don't change anything because there is nothing left to use it."
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nloo49 | Why do some flies just circle around the middle of a room all the time? | I cannot think of a single way this would benefit them in terms of survival. They're harder to kill, but they're not getting any food at all, are they? | Biology | explainlikeimfive | {
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"2 possible reasons I see - first, flies often fly in circles near food sources in an attempt to get a mate to notice them. Second, it may essentially be a bug (pardon the pun) in their software. Insect nervous systems are very simple and they're often more easily understood as complex biological robots than as having cognitive thoughts like other animals. Keep in mind that \"rooms\", that is to say four walls and a ceiling, arent natural environments that flies are used to dealing with. The circling then could be due either to the neural circuits that keep the fly from running into obstacles getting stuck in a loop since there's always a nearby obstacle (a wall), or, since many insects navigate by keeping a fixed position relative to the sun or moon, it could be confused either by the light in the room or by the lack of a light as strong as the sun."
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nlotu2 | Kinetic energy and Potential Energy. I sort of get in context what they mean, but... help me understand please. | Physics | explainlikeimfive | {
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"Kinetic energy is the energy of movement. When a baseball is flying through the air, it's got kinetic energy. Potential energy is a little weird. Basically, when you're in a situation such that a thing would move if only it was allowed to, its potential energy is equal to the amount of energy it would have taken to get it up to wherever it is. In this case, imagine you picking a baseball up off the ground. Its potential energy is equal to the amount of energy required for you to have lifted it in the first place.",
"Kinetic energy is the energy that an object which is moving has. Potential energy is effectively energy which is stored and could be released. Imagine a ball standing at the top of a hill, it isn’t moving so has no kinetic energy, but because it’s high up it has gravitational potential energy. If you nudge that ball it will start rolling, as it rolls down the hill it will accelerate due to gravity and its gravitational potential energy gets converted into kinetic energy."
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nlpzou | How did scientists exactly figure out what organelles do; how did they test this? | Biology | explainlikeimfive | {
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"This is sort of a general answer, but sometimes they would find out the function of an organelle by removing that organelle. Through different scientific procedures they could remove an organelle and see what function that the cell would lose, and then they’d sort of connect the dots that that organelle was responsible for that function-so when it was removed, the cell lost that function."
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nlqqp2 | Why are seagulls so aggressive and competitive to each other for food, yet stupidly stark sqwaking when you give them food. | Like they immediately start yelling when you give them food, thereby drawing the attention of all the nearby seagulls. But then they get all mad and start chasing each other away. Homie why did you alert them in the first place? | Other | explainlikeimfive | {
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"It's a habitual learning from when they are chicks. Baby birds that can't yet fend for themselves have to make noise to get fed by their parents. If they don't they don't get fed and for many species it sticks with them for life.",
"It's an evolutionarily beneficial development for prolonging the species. Compete when food is scarce, but distribute when it's abundant."
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nlr256 | Why are humans the only animals that wear clothes? | Biology | explainlikeimfive | {
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"Humans are naked apes. We've evolved to not have fur all over our bodies likely was a way to keep ourselves cool. Humans are also one of the few animals with sweat glands all over our bodies. As a result we're marathon runners, able to run long distances to tire out prey. This works great when you are on the plains in Africa but without fur we are pretty exposed to the elements. As humans migrated across the world we developed clothes to keep ourselves warm and dry. It's not really a stretch when you realize that our earliest clothing was made from animal hides. Our ancestors realized the prey animals were keeping warm and their fur was the secret to that, so wearing their fur to keep warm was a logic decision.",
"There are plenty of examples of animals using \"clothing\" in the sense of \"whatever covers the body,\" like with hermit crabs appropriating shells or certain spiders cloaking themselves with silk. \"Clothing\" in the sense of a shirt you wear is a lot more complex than that. Very few animals have the faculties to use even rudimentary tools, and making clothing that is actually useful enough to be worth all the hassle is so difficult that you pretty much need to have human levels of intellect to try. Even if it is incredibly useful to be able to adjust to a wide variety of environments on the fly, evolution just does the bare minimum for survival, so for everyone but humans that means making do with fur and not trying to embark to Antarctica.",
"The easy answer is that we humans are the first animals to evolve the emotion of embarrassment.",
"Not an expert but back in thea days (thousands of years ago) we needed to keep ourselves warm and probably found out that a protective layer could keep you insulated and warm. It probably wasn't meant to hide anything in the early days, just practical."
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nlr7qx | Why do humans enjoy eating hot/spicy foods? Is there a biological reason? Do other species eat jalapeños, for example? | Biology | explainlikeimfive | {
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"Most things don’t like spice. Bacteria don’t like spice, so humans put spice on food to keep away pathogens like bacteria. The people who liked spice ate good food and lived, the people who did not like spicy food died of food poisoning. However, in colder places like europe, they didn’t need spicy stuff as much because it was colder, and the world is your refrigerator.",
"Peppers are spicy because they don't want land animals to enjoy eating them: pepper seeds are destroyed by their digestive systems. Spicy peppers do want birds to eat them and spread their seeds though, because the seeds can pass through the bird intact and grow new pepper plants. Birds can't taste spicy."
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nlrv86 | What (physically) is the hard knot in your stomach when you get anxious? | Biology | explainlikeimfive | {
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"The “tied up” feeling we know all too well is actually an ancient physiological response to threat. The intelligent design of our organs pushes blood away from digestion because, in essence, digestion is needed less for survival than being able to run away or fight. So the feeling you have is the body moving blood from the organ elsewhere.",
"The autonomic nervous system in the brain regulates your organs and the fight or flight response. The knot, is part of the fight or flight response. The fight or flight response has different manifestations. It is triggered by fear, stress, and general illness. A side note, if it gets stuck ‘on’ from too much stress, it causes problems like ptsd."
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nls6f8 | How is earth not completely covered by mushrooms yet? | It disturbs me that fungi are just so infinitely better at regeneration and spreading their kind all over the place but still they didn't dominate whole earth, nor even a country sized terrain. I know they're "everywhere" but aren't they supposed to be like filling every square meter of every possible surface with such capabilities? If they are in fact not that good at regeneration and spreading themselves, how good are these properties of them in reality? Just knowing of their existence makes me chill. | Biology | explainlikeimfive | {
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"Fungi *are* basically everywhere, but usually only in microscopic form (like yeast). But, and this is the key, other life is everywhere too and there's only so much food and water to go around. Everything starts with the sun (although technically you could start from hydrothermal vents, but that's besides the point). The sun provides energy to the plants and the photosynthetic bacteria and algae. Without them, there's no food for anyone. Too much of anything else would choke out the plants, which would then starve out the rest of the food chain. So, plants evolved defenses against fungi taking their spaces, taking their water, and trying to digest them while still alive. Animals also don't want to be eaten, so we evolved immune systems to keep the fungi out until we're dead. And bacteria, they directly compete with fungi for everything. With three major factions of life all in direct competition with fungi, it's no wonder that they haven't completely taken over. In fact, it's those same limitations that stop plants, animals, and bacteria from exponentially replicating too.",
"Fungi don't produce their own food/energy from the sun like plants, they get it by breaking down other things. So their growth is actually limited by the successful growth (and death) of other organisms, like plants, they can then use for food. If they grew so fast or so widely they out-competed plants for space or sunlight, their food source would be limited as a result. The most successful fungi might spread widely but don't grow that large, because they need to live within the limits of the available nutrients."
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nlsbi8 | As hard as it is to doctor counterfeit bills that look real, why hasn’t anybody mastered the art yet? | Economics | explainlikeimfive | {
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"Counterfeiting isn't hard because it is physically demanding or requires decades of training. It is hard because replicating official currencies is an extraordinarily resource-intensive process, requiring clandestine access to special equipment, chemicals and money-laundering capacities. It is simply not economically feasible unless you have the resources of a small country or a large criminal network at your disposal.",
"Australian here. We use polymer banknotes. They have a lot of security features in them such as: You can scrunch them up and they return to normal They have a certain feel to them. They have clear windows. 3D images when you tilt the bank note. A flying bird when you tilt the bank note (as in it flaps its wings). A bird which changes colours as you tilt the bank note. Numbers which reverse when you tilt the bank note. Microtext on the bank note. Fluorescent Ink That's a lot of things for someone to master. It's also very expensive.",
"new tricks and technologies are constantly being developed to detect counterfeit bills. bills are sometimes changed so old counterfeits become useless. the money itself is also made to be very difficult to duplicate. basically, making a genuine copy is so expensive that if you had that much money you wouldn't need to counterfeit money."
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nlsmru | . How the photons carry the informations so we can see them? | Physics | explainlikeimfive | {
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"The photons \\*are\\* the information. We \"see\" when a photon whacks into the receptors in our eyes. The energy from the photon triggers a chemical reaction that our nerves can pick up. The photon isn't carrying information other than \"I'm a photon of such-and-such wavelength (color).\"",
"Photons don't carry information. A photon is just a particle with a particular wavelength. (In reality, photons are both particles and waves, simultaneously, but the ELI5 version doesn't need quantum mechanics!) It's our eyes and brains that turn that into information. The retinas of our eyes \"catch\" photons that hit them and detect the wavelength. The signal of all the photons we \"catch\" are processed a little bit in our eyes and then sent to part of our brain called the visual cortex. The visual cortex acts kind of like a computer and crunches all that incoming data to make a picture. There's nothing inherently blue about photons we see as blue, but that's the way our eyes and brains perceive wavelengths of 400 to 525 nanometers. There's nothing inherently different about a blue photon bouncing off a blue shirt, emitted from a screen showing blue text, or coming down from a blue sky."
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nlsqll | why is there no birth control pill for men? | Biology | explainlikeimfive | {
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"Theres vasal gel. A cheap one time fully reversible chemical vasectomy but of course the FDA wont approve it and pharmaceutical companies wont push for it because it's cheap and one time.(actually it lasts about 10 years.) There are male BC under trial now but nothing approved yet. male BC has to stop the production of millions of viable sperm. Female bc has to prevent the implantation of one or two fertilized eggs into the uterine lining. One of those is relatively much easier than the other.",
"The thing is, it isn't fairly simple. You have to look at the differences in the male and female reproductive cycle. A woman releases a single egg every month, so all a birth control pill for a woman needs to do is to stop that one egg. Men, on the other hand, make thousands of sperm every \\*second\\*. It's quite difficult to stop that process without using such high doses of hormones that it creates serious side effects. A number of drugs have been tested, many of which produced a serious decrease in sperm production, but that's not really enough of a reduction to be viable as a birth control solution if there are still millions of sperm per ejaculation. The odds may be lower, but no one wants a birth control pill that's, say, only 75% effective."
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nlsziz | when you cook meet to it’s specific “safe” temperature, does all the bacteria die at the exact moment it reaches that temperature or is is a steady death? | also why do different meats have different temps | Other | explainlikeimfive | {
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"They don't all die at the same instant. Every different bacteria has a different time/temperature curve...longer exposure to lower heat will result in just as much kill as shorter exposure at higher heat. This is how pasteurization works in beer/milk (low temperature, long period). Depending on the bacteria, they get \\*happier\\* as you increase from freezing-to-fridge-to-room-to-slightly-warm. Then they start to die. Like /u/Lurkesalot said, up around 165F they're basically all dead so you don't need to stay at that temperature for any period of time. At boiling they're all stone cold dead, hence boiling water to make it safe(er). But if you're at, say, 150F you may need to hold there for a longer period to get the same amount of dead bugs.",
"Different meats carry different pathogens. Certain harmful bacteria die at different temps but all die at over 165."
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nlt7kj | What does the "post-" refer to in musical genres like post-rock or post-punk? | Other | explainlikeimfive | {
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"In art you can have a movement, and when that movement ends you can have a related movement that is inspired by, but distinct from, that movement. In painting for example there was impressionism, which was then followed by post-impressionism. In many forms of art there was modernism, followed by post-modernism. With post-rock and post-punk, they are musical styles influenced by rock and punk (respectively) but distinct from those styles.",
"It means after, so the genre that evolved from Punk. Usually when you identify a new genre there are enough defining features that you come up with a new name, I think they call it Post-Punk because it's still very iterative of Punk, the influences are still very obvious. There aren't any conventions though with music genre naming, it's not scrutinized like Latin names for animals. In the early 00's every scene was popping out hardcore derivatives with the 'core' suffix, some of them stuck, some didn't. Deathcore is still widely used."
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nltxk8 | How do people do absurd things in public, like Eric Andre for example, and seem to not care at all and have no hesitation. From yelling and doing obnoxious things. | Other | explainlikeimfive | {
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"Eric Andre and the jackass crew are getting paid hundreds of thousands of dollars to act a fool keep in mind. I'm relatively introverted but I think if you are being paid and have people affirming you, you get over shyness real quick.",
"1) They make a lot of money off it. 2) They have security on hand who can step in if things go south. 3) They have good lawyers who can shield them from any legal ramifications. 4) They work in places like NYC and LA where it's not all that uncommon for people to be doing absurd things in public and filming it. Basically, they have every protection in place that's possible to ensure the safety and well-being of the actors, which makes it a whole lot easier to be absurd and obnoxious without having to face the same type of consequences your average person doing it might. Edit: formatting"
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nlu1a9 | what the calibers like .45 or .50 mean and why is the .308 such a specific number? | Other | explainlikeimfive | {
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"It’s the diameter of the bullet in inches. So a “50 cal” is actually shoots a bullet that’s 0.50 inches wide, and a 308 shoots a bullet that’s 0.308 inches wide.",
"Its just the Diameter of the bullet in inches. The history of the .308 is a little muddy on why it exactly happened exactly the way it did. It came after the 30-06 which was just .3 in diameter cartridge. With new types of gunpowder being produced Winchester arms found out they could get similar ballistic of a 30-06 in a shorter round. Why they decided to make it slightly wider is anybody guess, but it was most likely to stop people from loading the new cartridge into older guns, most likely could not handle the pressures.",
"If I remember correctly, the caliber refers to how many inches in diameter the bullet is on the tip, so a .45 caliber is a .45 inch bullet in diameter. A .50 cal is a half inch in diameter (AKA, really phuckin big) this is pretty standard for pistol rounds. Now this is the part I'm fuzzy on, if I remember right, longer caliber numbers are used for long barrel guns, and the .308, being a rifle round, has the extra number to denote that, along the lines of 30-06 and the .700 magnum. Please, correct my errors if I'm wrong. I'm just a redneck gun nut.",
"I feel like your question has been answered but as for the \"such a specific number\" part, remember that guns are typically machined goods with milling and broaching and all that. It's common in a machine shop to use measurements in thousandths of an inch, so specifying .308 specifically wasn't really out of reach for machinists and their tools. It's actually pretty easy to find calibers measured in thou like .338 Lapua Magnum, .454 Casull, or .303 British) since the tools for that kind of precision have been around for a bit over a century now. Also note that there's at least a few calibers I can think of immediately that are hundredths of a millimeter, (7.62, 5.56, 7.65 Parabellum, 7.35 Carcano...) .01mm is about four tenths (.0004 inches) so technically it is even *more* specific."
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nluqlo | How do people with amputated Appendages (Arms mainly) control prosthetics to the point where they have control of the prosthetic fingers? Awesome technology, seems it's only getting better, but was wondering how the connection is made when they attach the prosthetic like a glove. | Technology | explainlikeimfive | {
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"A robotic neuroprosthetic (a prosthetic that you can move with your brain) works by implanting electrodes in the brain on specific locations where your brain will activate when you are trying to move the missing limb. Your brain has a designated “motor centre”, where the signals to move come from. When you move, your brain sends a message from this part of your brain down your spine to the nerves in the body part it wants you to move. Those nerves activate your muscles, and they contract, which moves your body part. When you lose your body part, you do not lose the accompanying part in your brain that was able to move that body part. It’s like having a remote without the television. The prosthetic is attached in place of the natural limb, and the electrodes are attached to your brain. These electrodes are able to sense your brain sending those messages. The electrodes are activated by the brain’s messages, and the prosthetic moves."
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nlvkzm | Coproducts | Hi, I'm an armchair mathematician (that is, I don't study it) and I've recently been playing around with formulæ using $\\prod$ and $\\sum$ (ie, ∏ and ∑ , if LaTeX isn't supported here). In the dictionary of LaTeX symbols, there is a symbol that looks like ∏ but flipped upside down and called a 'coproduct'. What is this? If you had the following formula, how would you calculate that out? & #x200B; Formula (LaTeX): $\\coprod\_{n=1}\^{3}(n)$ Formula (in words): The coproduct from n=1 to 3 of the formula «n» & #x200B; Obviously, abstract maths can be challenging for a 5-year-old, so I suppose this is less of an ELI5 and more like an ELI'm-a-high-school-calc-student XD | Mathematics | explainlikeimfive | {
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"Coproducts aren't an operation on numbers, but on mathematical structures. They are related to products of mathematical structures. For example, the [Cartesian product]( URL_0 ) is an operation combining two sets into a single set of ordered pairs. This notion of a product of structures can be applied to many different types of structure, not just sets, by looking at the abstract properties of the Cartesian product and generalizing them. Coproducts happen when we take these defining properties of products and \"flip them backwards\" in a certain sense. This yields a different sort of operation for combining structures. Like with products, coproducts may be different for different types of structures, but all share certain abstract properties. An example of a coproduct is the [disjoint union]( URL_1 ) of sets. For example, the coproduct of {0,1,2} and {1,2,3} is the set {(0,0),(1,0),(2,0),(1,1),(2,1),(3,1)}."
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nlvryp | Why do storage devices always seem to lose storage? | I bought a 64GB micro SD card for my switch and once I inserted it, the system tells me I had about 60GB. I've noticed USB devices do the same where if I buy a 32GB one, I would only have about 28GB to use give or take. Where does the extra storage go? | Technology | explainlikeimfive | {
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"When you buy a 64 GB SD card, you're getting 64 gigabytes of storage. That's 64,000,000,000 bytes, since 1 GB is 1,000,000,000 bytes. However, when Windows shows storage, it shows it in the approximate binary equivalent, gibibytes (usually abbreviated GiB to avoid this exact issue). One gibibyte is 2^30 , which is slightly more than 1,000,000,000 bytes. 64 gibibytes is 68,719,476,736 bytes rather than 64,000,000,000. That means your 64 GB SD card will be displayed as only 59.6 GiB. Similarly, a 32 GB USB drive is only 29.8 GiB. You also lose some storage to formatting, but the gigabyte vs. gibibyte issue is by far the biggest contributor to the difference.",
"There's been some disagreement about the correct unit of storage and how to name it. Computers have historically used a binary variant of the scientific prefixes/terms kilo (thousands), mega (millions), giga (billions) etc. They're binary machines after all, and circuitry would use a power of 2 for communication. A kilobyte would be 2^(10) = 1024 bytes. However the proper scientific definition would be 1000 bytes exactly. The term \"kibibyte\" has come about to represent the 1024 variant. It's turned into a mess of some hardware makers and software makers using different numbers in different contexts. A 32 GB SD card probably means 32,000,000,000 bytes (approximately... it's never exactly a round number like that). However Windows probably reports a gigabyte as being 2^(30) bytes = 1,073,741,824 bytes. If you put these two different interpretations together, windows reports the card as being 29.8 gigabytes. Even computer experts *hate* this differentiation. For example, an old 3.5 inch floppy disk held 1.44 megabytes. That's 1440 kibibytes... or, 1 megabyte = 1000 kilobytes but 1 kilobyte = 1024 bytes. A 650 MB CD-ROM holds 681,574,400 bytes, but a 4.7 GB DVD holds around 4,700,000,000 bytes (rounded). Ugh.",
"The units that the device manufacturers and the operating system in the computer are not the same. Kilo is a prefix for metric units and means 1,000 and has been used since 1795. Mega for 1,000,000 was added in 1873. Giga for 1,000,000,000 and tera for 1,000,000,000,000,000 was added in 1960 Computer memory is addressed binary so it is multiples of 2, not 10. 1024 is a multiple of 2 and people started to be called 1024 a kilo because it was very close in size The same way you get a * mega of 1024*1024=1,048,576* * *gigi 1024*1024*1024=1,073,741,824* * *tera 1024*1024*1024*1024=1,099,511,627,776 For giga the variant with 1024 is 7% larger than the 1000 variants The storage medium is sold with units using 1000 and it tends to be stated on the packaging and websites of the manufacturers Operating systems tend to use the 1024 definition. So a 64 GB memory card will be 64\\*1000^(3/10243) =59.6 with the 1024 usage 32 GB will be 29.8. So there is not extra storage but different units. The file system will use some space but it is not a lot."
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nlwns6 | Why can’t we deliberately make people acquired savants? | I’m talking about Jason Padgett. He got assaulted, got a concussion and woke up a maths genius who could see geometry. Why can we not induce this state in a persons brain deliberately? | Biology | explainlikeimfive | {
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"because we dont actually know what specifically happened to those people. we know that got a brain injury, but we dont know what area of the brain was hurt. it would be really stupid if we unknowingly started manipulating people’s brains, potentially ending their life.",
"We don't know the Brian that well, and the research methods needed to gain that knowledge would be inhumane and unethical with our Current level of technology. What happened to him was a fluke, a very rare phenomenon. We don't have enough people like him to properly study it, and intentionally causing brian damage to study it would be really vile.",
"Well, the simplest version has two main reasons. The first, the brain in question is simply structured differently, as in particular regions are larger or smaller, which you can't really do to a normal, already developed brain. The second, whatever strange phenomenon that affects a savant brain is simply too complex or obscure for us to even detect or understand in any meaningful way. Edit: we could likely learn a whole bunch more a lot faster about our brains, and many other things, if we abandoned things like ethics. Let's not go down that road!"
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nlwq10 | What does it mean when the FAA downgrades Mexico's aviation safety rating ? | Other | explainlikeimfive | {
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"The statement from the FAA is that Mexico's aviation association (AFAC) didn't meet the standards set by the UN in the last inspection. The concerns were about the regulations and enforcement of those regulations being insufficient, not a specific problem with plane safety. There is an unofficial statement that it was related to insufficient number of inspectors and insufficient protections against from \"political interference\". (see [ URL_0 ]( URL_0 ) ) What it means practically speaking is that there are new limitations on flights between Mexico and the US: 1. **No new routes or services can be added.** So if a Mexican airline has two daily flights, one at 8am and one at noon from New York to Mexico City, those can stay, but they can't add another one at 10:30am if they don't already have one, and they can't add any flights to Cancun if they don't have them. 1. Routes mean from one city to another, e.g., from LA to Cancun 2. Services means flights within a day (I believe it means a specific time too, e.g., the 7am service to Mexico City) 2. Tickets on Mexican airlines can **no longer be booked under the name of a US airline**. Sometimes when you buy a flight through one company (like Delta, a US airline), you are actually booking a flight on another company's plane (like Aeromexico). 1. This is referred to as \"code-sharing\" 2. Delta and Frontier both have a code-sharing agreement with a Mexican airline (Aeromexico with Delta, Volaris with Frontier) 3. When airlines have the same safety rating, this is allowed. Now that they do not, the US will not allow US airlines to sell tickets with their own airline's name on it if part or all of the flight is operated by the Mexican airline 3. **Flights already purchased will be mostly unaffected;** potentially some tickets (those booked via code-sharing) will be reissued under the Mexican airline operating the flight instead 4. You can **continue to book tickets on existing routes and services** on Mexican airlines from the US Other countries in Category 2 (below the Category 1 ranking) include Bangladesh, Curaçao, Ghana, Malaysia, Pakistan, Thailand, Venezuela and parts of the Caribbean. Most countries with international flights are Category 1 (the highest ranking). There are only two Categories. This has happened before (in 2010) and Mexico's Category 1 ranking was restored 4 months later after adjustments were made.",
"It means that the FAA has less trust in the AFAC (Mexican Federal Civil Aviation Agency) due to their history of incidents, so they are restricting the interaction between Mexican airlines with the US. Basically, if you and your siblings are US-based airlines, this is your parents saying \"We don't want you to hang out with those kids anymore, they're a bad influence.\""
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nlx6d5 | Why do you want to control your breathing while working out? | Biology | explainlikeimfive | {
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"> Wouldn’t inhaling and exhaling as often as possible mean more oxygen for muscle to work? Inhaling and exhaling quickly (Hyperventilating) can actually cause so much venting of the CO2 in your blood that it changes the PH balance to acidosis. CO2 is acidic, so vent a large part of it from your blood unexpectedly before your body has a chance to restore the PH balance leaves it alkali. This can actually cause people to pass out, which makes it a sort of a self fixing problem since that stops the hyperventilation long enough for PH to get back in balance. This is why breathing into a bag helps people who are hyperventilating. That makes them reabsorb some of the CO2 so they don't pass out. That's at an extreme you probably will never have to worry about reaching during a work out however. If I had to guess, I would say having a restricted breathing regime during work out helps one focus on the task at hand while not neglecting to breath every so often. The high energy demand of working out makes focus difficult, so having a simplistic game plan helps one focus on accomplishing the routine while meeting one's oxygen demands.",
"It controls your heart rate and gives you a rhythm. Too much oxygen makes everything work too fast and you get lightheaded."
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nlxig9 | How can USB-C standard be updated to now support 240W power delivery when the plug size and number of pins don't change? | Technology | explainlikeimfive | {
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"More voltage Quick Charge and USB Power Delivery aren't stuck at 5V like old USB devices were The current USB Power Delivery spec allows for 5, 9, 15, or 20 Volt supplies and up to 5A on the 20 Volt supplies for 100 watts of power The new spec supports up to 5 A at 48 V for 240 Watts which is handy for quick charging of laptops and the like. The cable is mainly limited to 5 amps of current because there are only a couple pins providing the power, but there's decent space in there so we can crank the voltage up a bit to sneak power through, just need to make sure charging stops if something gets wonky so buy good chargers",
"When two devices are connected, they negotiate power delivery. When a cable is plugged in, the power delivery pins are set to 5V, 2A, 10W. Then other pins receive a message that indicates the version of the protocol. In the first version, a device then sends a message that indicates which one of the five profiles to change to (the sixth was unused). These are specific power delivery amounts - 10W, 18W, 36W, 60W, 100W. The second version of the standard allows the device to select a specific voltage (5V, 9V, 15V, 20V), and then provides a way to fine tune the wattage from there. The messages allow 0.5W changes to the power delivered. The third version allows even finer grain control. The messages allow 20 mV changes to the power delivered. The fourth version, the new one, allows a larger range of voltages up to 50V to be selected. The other device has the opportunity to say it doesn't support the version requested. The devices will see if they both support each version, newest to oldest, until they can agree on a version or the basic 10W is used."
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nlxwbt | Why does earth’s axial tilt affect our climate significantly more than perihelion even though the latter brings us 5 million miles closer to the sun? | Earth Science | explainlikeimfive | {
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"Solar power radiated per unit area decreases with distance from the sun in accordance with the surface area of a bounding sphere at that radius, proportional to r^2. So, from perihelion to aphelion, the ratio difference in energy intensity is 91.4^2 / 94.5^2 , or about a 6.5% reduction. Conversely, the intensity of radiation striking the Earth's surface is proportional to the sine of the angle of incidence. The Earth is tilted approximately 23.5°, but that swing is either side of the equator from winter to summer, so the effective difference is actually double that. This corresponds to about a 27% difference in energy intensity from winter to summer at either tropic. So, the axial tilt represents over four times as profound a change in energy input as is caused by the change in proximity to the sun.",
"There’s more to it than extra hours of sunlight, as the previous posts have noted. If that was the only factor, then the arctic region would be the warmest place on Earth in summer since the sun never sets. But this obviously is not the case. No, the more important factor is the angle of the sun. When sunlight hits surface at a lower angle it is less intense. Imagine sunlight to be a series of parallel beams. When the sun is high in the sky, a given number of beams hits a smaller area of Earth. When the sun is lower, that same number of beams is spread over a greater surface area. So each square mile of surface is receiving less energy from the sun in winter as opposed to summer. And back to your original question, this energy difference percentage wise is much more significant than a few million miles more distance.",
"Our average distance is 93 million miles, so 5 million isn’t a huge change. The tilt of our axis however cause the north or south hemispheres to receive more sunlight during the summer. The change can be by several hours of sunlight each day depending on the location."
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nlyfb3 | Why do all stringed musical instruments produce the same notes in the same picking spots? | Physics | explainlikeimfive | {
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"They don’t. Unless I’m not understanding your premise…for example, if plucked or bowed, the third “fret” on the bottom string of a violin produces a B flat. The third “fret” on a bass violin produces a G. The third “fret” on a cello produces a E flat.",
"It all has to do with the concept of resonant frequency. First talking about strings, when you put a finger on say a guitar fret for example, you are essentially determining the length of the string that can actually freely vibrate. In this case, that length is exactly from the fret to the base of the string. When you pluck the string, which is just adding energy to the system, the string vibrates back and forth at a specific frequency, called the resonant frequency. The reason why it is this specific frequency is because it is the most efficient way for that string to disperse the energy and return to a lower-energy state. Resonant frequency (in a string) depends mostly on the length of the string and the tension of that string. This is why you can change the notes by selecting different frets (length change) or by tuning the guitar (tension change). The resonant frequency for a wine class or pipe is also the frequency (or set of frequencies) that most efficiently disperses the energy. With more irregular shapes like wine glasses and pipes instead of strings, more important factors that determine the frequency / frequencies are the geometry of the object (analogous to length) and the material that the object is made of (analogous to tension)"
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nlyfxh | what is a NFT? Been seeing a lot in the news about videos and pictures being sold as NFT | Technology | explainlikeimfive | {
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"text": [
"All you need to know is that NFT’s are terrible for the environment because of the exorbitant amount of energy used to create them. Stay away."
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nlzc2f | Is there something surrounding the universe? | Sometimes I’ll hear that the universe has a shape, or I’ll hear discussions about whether the universe is finite or infinite. But to be considered a shape does it have to have a surrounding environment to contrast from? Like if I’m looking at a sphere I can tell it’s a sphere by looking at where the boundaries of the object end and the rest of its surrounding environment begins. Does the universe have a surrounding environment that allows for that contrast to be made? | Physics | explainlikeimfive | {
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"Usually when talking about the shape of the universe, they’re talking about how space time curves. It’s...complicated because it involves extra dimensions that aren’t intuitive to us. But basically there’s three options for the universe. Either it’s ‘flat’ and has no curve, is a ‘sphere’ and has a positive curve, or is more of a ‘saddle’ shape with a negative curve. Which shape it has depends on how dense the universe is. We don’t need to see all of it to tell if it has a curvature, it’s just geometry. If the universe is curved, triangles don’t have 180° like they do if it’s flat. The earth is a good example since it’s a sphere. If you were on the equator and walked to the North Pole, then turned 90° and walked back to the equator, you could make one more 90° turn to get back to where you started. You just made a triangle with 270°. You don’t need to see all of the earth to do this, and it wouldn’t look curved while you were walking since it’s so large. But you’d be able to tell it’s curved just by measuring stuff on it. This is called non-Euclidean geometry, and a curved universe would be non-Euclidean. The universe is really big though. Really really big. So it’s hard to measure anything like that. We’ve tried and found that it’s mostly flat, but there’s still a margin of error that would leave room for it to have a small curve (positive or negative).",
"There's this nice book by Lawrence Krauss called [A Universe From Nothing]( URL_1 ) which explains the shape thing quite nicely. It says that if you take a triangle and add up it's 3 angles you should always get 180 degrees, no matter what triangle it is. Yet, this only applies to flat triangles. If you draw a triangle on top of a sphere, you'll get a larger total than 180 degrees. Imagine if you took the Earth as a sphere and put a point on the North pole. Move down South from there to the equator and put another point there. Now move a quarter of the way around the Earth's equator and put another point there. You now have 3 points which form a triangle covering an eight of the Earth (8 such triangles will cover the Earth. Yet the angles at each point are 90 degrees, which add up to 270 degrees (see [here]( URL_0 ). Likewise, you can put a triangle on a saddle and get angles whose total is less than 180 degrees. Now Einstein's theory of general relativity tells us that drawing a triangle in our universe might not have angles which add up to 180 degrees, which would mean that it's somehow curved. You can measure this by measuring the angles between 3 stars. It turns out that the angles do add up to 180 degrees, which means that the universe is 'flat'. The book then goes on to say that a flat universe can be created out of nothing whereas any other kind of shape would require a cause."
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nlzhh5 | Do orbital planes in space tend to be flat like movies and games suggest? If so, why? | My extent of experience with space travel is Kerbal Space Program and Interstellar. & #x200B; EDIT: I should specify, I mean, in a solar system, and the solar systems themselves. They all orbit. Do the orbiting entities tend to actually inhabit a similar flat plane (like the tracks on a record)? | Physics | explainlikeimfive | {
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"Yes, actually. The reason is due to angular momentum, and the conservation thereof. Picture a pizza maker tossing the dough in the air: as it spins, it flattens out, and it tends to form a disc with everything in the same plane. This is roughly the same physics at play in solar system formation: as the proto-star collapses, gravity and angular momentum combine to force everything into a flat, planar disc.",
"Yes, all of the planets have less than 7 degrees of inclination. With only Mercury having above 4 degrees. The idea is that when the solar system was forming, there was all sorts of dust going at ever inclination. Eventually though the high inclination objects hit other objects (or got dragged by their gravity), these encounters averaged out their inclinations. So eventually all the inclinations got averaged out and we get the flat disk of planets we called the ecliptic."
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nm0alf | Why do people say vinyl records are higher quality? | Other | explainlikeimfive | {
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"It’s mainly because of the “loudness wars”. Read more here. URL_0 Record companies figured out they could increase the volume on Band XYZ’s song. Therefore on a radio, Band XYZ’s song would be louder than Band ABC, and theoretically get more attention. By increasing the volume, they removed a lot of the dynamic range. Dynamic range being the difference in volume between different instruments and vocals. For instance, say Band XYZ really wanted the guitars to be louder, and the drums to be quieter and the vocals somewhere in the middle, so they master the album that way. Then someone else comes in and says “screw that, make everything loud” for the purpose of grabbing more attention on the radio. The “loudness war” began, and people who have higher end audio equipment immediately hated most CDs because almost all mainstream music was being released this way, and when a “remaster” came out, almost always it was just taking the original recording, and making it louder, and the mainstream perception was louder = better. And from a sound quality perspective, it’s not.",
"\"Quality\" is extremely subjective. If we consider pure audio fidelity then digital audio in a suitably high sample format is as close to perfect as humans can perceive. Vinyl records are not even close to being a flawless representation of the original audio, but that isn't necessarily what the consumers mean when they say \"quality\". People may subjectively prefer the distortion introduced by vinyl, and/or like the rituals associated with the medium. So if they say vinyl is higher quality in the sense of being the best way of recording and reproducing the exact sounds of the original performance, they are just flat wrong. But if they just mean they subjectively prefer it then it is their opinion.",
"Some audiophiles will step in and crush me but the theory is analog music followed a wave with near infinite variation. Digital is stepped. Divide a hundred by ten so there were only so many variations. Now digital can be divided by a thousand or whatever the current iteration is. Probably more than our ears can distinguish but we tend to stick to a previous knowledge when we get stuck on something",
"I dont know about the technicals of it all but there is something about placing that needle on the record, hearing that little crunchiness. The music flows so smooth and rich. Just so much more pleasing to the ears."
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nm11d9 | how do beans cause so much more gas than other foods? | Biology | explainlikeimfive | {
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"Beans have a thin layer of stuff like wax that coats the outside and makes them shiny. This wax isn't food so it goes through your whole system without digesting. The different parts of your stomach and good bacteria in your guts transform it and change it many ways but it's still not absorbed as food and it causes the bacteria to make gas. You can make beans in a way that washes off the wax but it's not easy and sometimes takes an entire day just for one pot of beans.",
"To some degree it depends on your gut microbiome. If you eat beans more regularly you will have bacteria that are good at digesting them and won't be as gassy"
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nm15a6 | What is the link between serial killers and lack of empathy and why does being void of emotion instill a desire in someone to hurt or kill? | I've been watching this Youtube channel 'JCS - Criminal Psychology' lately and it got me wondering why serial killers behaviour is always linked to having a lack of empathy. Are all humans just sadistic killers at a base level without emotions in the way? If there's no logical reason to hurt somebody then why do serial killers do it if there's no emotional reason to either? | Other | explainlikeimfive | {
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"tl;dr - People who lack empathy (psychopaths) don't always kill but psychopaths with serious childhood trauma tend to kill. Serial killing is associated with a lack of empathy because empathy makes you feel bad when other people feel bad. Does everyone who lacks empathy kill? Not at all. Many people have what's considered psychopathy but they lead (mostly) ordinary lives. Like I mentioned in the tl;dr, psychopathy combined with childhood abuse or severe trauma can result in killing. Some kill and feel little emotion afterwards, some kill from anger, some for pleasure. If you're interested in noncriminal psychopathy, here's a video you might like: URL_0 Source: URL_1 (Iceman Interview)",
"There's a difference between lacking empathy and being void of emotion. If you lack empathy you can still feel emotions for yourself, so you can get a thrill out of killing people. With that in mind think of it this way, most people that feel bad about harming others won't harm others, so the majority of people that harm others for fun will be people that don't feel bad about it. That doesn't mean every person that lacks empathy will be a serial killer, just that serial killers will tend to lack empathy. Kinda like seeing most basketball players are tall, doesn't mean that shorter players can't play basketball or that if you are tall you play basketball, just means that being tall is a favorable trait for basketball. Not feeling bad about killing others for fun is a favorable trait for becoming a serial killer."
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nm1jia | What is most basic but irrefutable argument that the earth revolves around the sun and not vice versa? | Earth Science | explainlikeimfive | {
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"If the Sun and the Earth were the only two bodies in the Solar System, then there would be no difference between Earth orbiting the Sun and the Sun orbiting the Earth. From an external point of view they would look the same. But there are other bodies in Solar System, and they all orbit around the Sun as well. If you try to claim that any of them (other than our Moon) orbit the Earth, then you end up with a bizarre orbit [like this]( URL_0 ).",
"You can mark the position of venus & Mars each night without any special equipment. If you plotted their positions properly you will see strange retrograde movements that don't make sense at first. But if you model earth moving around the sun and those other planets also moving around the sun everything fits perfectly!",
"The path of the other planets in the sky. At times they change direction and go back in the direction that they were going. This is explained by the planets orbiting the Sun. Say you're watching Mars. We go around our orbit faster. So as we catch up to Mars it looks like it's going in its normal direction in the sky. However, as we pass it is then looks like it's moving backwards as we overtake it. As time passes through it looks like it resumes its normal path through the night sky. This can't be explained by the Sun orbiting the Earth.",
"Suppose you're on a spinning roundabout. Assume you won't get dizzy. You have a ball and you want to roll it forward in a straight line away from you, so you push it forward. However, you see the ball curve away from a straight line. You may initially think that's strange, because you just pushed the ball straight forward, yet there appeared to be something pulling it in one direction. You ask your friend, who is standing by the roundabout what she saw. She says that she saw the ball move in a straight line with respect to her. You want to know what's going on, so you start doing some physics. You see that, because you are rotating, there is some extra force that pulls the ball into a curve with respect to you. Now that you are inspired, you decide to see if you can calculate the path the ball will take, from your perspective. You note that you can perfectly well predict the curve of the ball if you take into account this extra force. You start discussing with your friend what is the best way to describe the motion of the ball: From her perspective, or from your perspective. You quickly agree that it's easier from her perspective, because from her point of view, the ball is just going straight, whereas from your perspective you have to do a lot of maths to find out what curve the ball is going to take. In the end you conclude: The ball goes in a straight line when viewed from someone standing still next to the roundabout. & #x200B; Now to translate all this to the solar system. If we were to calculate the orbits of planets with the earth's perspective, we would get many extra forces pulling and pushing the other planets. We could in principle calculate the orbits from Newton's laws and they would look strange, as others have pointed out. The simpler approach is to say that we put a stationary point of reference at the centre of the sun and have a much easier time calculating the orbits. In physics (and I think in science in general) it's common to take the simplest model that does the job and so we say: \"The planets follow elliptical orbits when viewed from the sun as a stationary point of reference.\", in the same way we said \"The ball goes in a straight line when viewed from someone standing still next to the roundabout.\" There is a subtlety that I do want to point out: In this simple case, we assume that the sun is a stationary reference point. However, in reality, the sun also wobbles a bit. This would in fact complicate our approach a bit again, and we would need a different stationary reference point, around which the sun also orbits. But let's just call it a day for now."
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