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nd9x00 | Where does new water go when it enters a container that already contains some water? | While giving my daughter a bath, she asked if water sinks or floats and I wasn’t quite sure on how to answer. Where do the new water molecules end up when it joins with other water? | Physics | explainlikeimfive | {
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"You can answer your daughters question through a simple experiment. Add dye to the water you will pour in then pour the coloured water into the other bottle filled with plain water. You’ll see some interesting patterns form as the water continues with the same momentum then eventually all the water will be the same colour.",
"Assuming its all the same water, the new pour will just disperse into the existing body, with how that happens mainly being determined by the physics of the act of pouring it. If the two waters are different in terms of temperature, amount of dissolved solids in it, chemically, etc, etc then you could end up with some interesting behaviors. Softly pouring fresh water over sufficiently salty water can result in distinct layering of the two kinds of water in the tank, [an effect well exploited by the film industry back before they had computers to make any kind of visual effect involving clouds]( URL_0 ).",
"Could sink, float, or somewhere in between. Velocity and angle matters on how the water molecules are affected by the resulting current. The easiest way to show this is to drop a few drops of food coloring into the water.",
"Lots of variables here. Flow. Volume. Direction. Even temperature can effect how the 2 fluids would act"
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ndaftu | why does your voice sound weird then you talk into a fan? | Other | explainlikeimfive | {
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"Because your voice is sound that is carried through the vibrations of the air. The fan disrupts the air, and in doing so disrupts any sound that is being carried through that air."
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ndanbt | Why exactly do people die of old age? | Biology | explainlikeimfive | {
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"Entropy. Things wear out, be it gene replication, organs, or the brain. When this gets to the point where the body cannot function well enough for these organs to keep the person alive, they die.",
"Death by old age is a misnomer. Prior to wide spread medical care and autopsies old people died and no one knew why so they called it \"death by old age\" Nobody dies of old age specifically, it's that you are more likely to have certain lethal conditions when you are older. The body wears out, the immune system is weaker, and you get prone to certain types of conditions. Today Death by Old Age medically speaking is considered death by one of 3 conditions in the elderly. Cancer, Respiratory disease (pneumonia, etc), and heart failure/stroke. There's plenty of other ways to die, but those 3 are the most common causes of death in people that are older. The chances of getting cancer increase as you age, because there that much more of a chance of random replication failure in your cells, exposure to radiation, chemicals, etc The heart only has so many beats in it's life, and accumulated damage and artery clogging adds up Respiratory disease is the most common way of death due to a weakened immune system."
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ndbrpg | How does the sleeping brain retain the intentions of a person's conscious self (like not moving all or part of the body, or waking at a very specific time) and then actually carry them out? | Biology | explainlikeimfive | {
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"This is actually pretty easy to explain to a five year old: The brain doesn't sleep. It is still fully functional while you sleep. It's just not processing information the same as when you are awake. Think about critters like bats that hang upside down to sleep; same thing. I'm not sure neurologists can explain out the actual (complex) mechanism by which this happens; there is alot about the brain that we do not understand.",
"Can't answer the first part properly, I'm really not specialised in sleep. For the second part, it's because we have an internal clock that is synchronized on the natural sunlight, with the help of this clock your body knows more or less what \"time\" it is and that's why you can wake up regularely at a given time without the need of an alarm clock. It doesn't work every time because depending on your level of stress, fatigue it can disturb it. Alternating between night/day shift at work disturb it as well.",
"I also want to know this. I never use an alarm clock, but will tell myself I want to wake by 4 am and I wake around 3:45 am and slither out of bed (so as not to wake my sleeping wife)"
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ndcfem | How are we good at determining how full a container is just by holding it? | Basically the title. When we pick up a sealed container with our hands, say, an oxygen cylinder, most of us can determine how filled it is. But how? | Other | explainlikeimfive | {
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"You can feel the center of gravity of an object, because simplified that is where your forced applies. It is basically the rotational axis of an object. You can test this by suspending something a disc in water and then weighing it down with coins on one side. It will always spin closer to the coins. Now the center of gravity does not equal the fullness of the container, but we can approximate it, the heavier the substance, the easier. A container that is empty will have its normal center of gravity, but one that is half-full will have it shifted towards the filled half."
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ndcjqr | how do Air Fryers work? | Technology | explainlikeimfive | {
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"It's just hot air spun around by a fan, the same as what's called a convection oven. Nothing is really fried. It's a marketing trick because people like fried food and the spinning air makes the food crispier than non-moving air.",
"It suspends the food in a mesh basket inside a chamber. Hot air is blown inside similar to a convection oven, except in an air fryer air can flow under the food since it's suspended in a mesh basket.",
"There is still an important concept missing from the other explanations. Oil plays a large role in how an air fryer works. To start, let's look at how an oven, convention oven, and deep fryer work. An oven and convection oven both cook food by heating air and having it circulate around the food. Convection ovens use a fan to move air around, but a regular oven doesn't. However, a deep fryer uses an electrical heating element to heat oil. The oil is hot enough, and contains enough energy, to cause the water in the outer layer of your food to flash into steam. This is how fried foods get a nice crunchy crispy exterior. Onto an air fryer. Instead of heating a giant container full of oil (which can be really dangerous and generally splatters badly when food is added to it), a small amount of oil is added to the outer layer of a food. A quick shot of cooking spray is sufficient. The air fryer then uses circulating hot air to heat the oil, which in turn heats the food. This is how it fries foods. Without any oil, it's essentially a convection oven."
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ndd3cn | What causes different types of airplane turbulence? | Realized while flying recently that there are lots of different “kinds” of turbulence. Sometimes it feels like you hit a pothole, sometimes it feels like you’re almost free falling and sometimes the airplane feels like you’re driving on a really bumpy road. Does anyone know what outside factors lead to the plane responding in these different ways? | Physics | explainlikeimfive | {
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"If you feel like you hit a pothole that is most likely due to a gust, basically a strong wind. If you feel like you’re free falling, that isn’t really unique to the air flow, you can usually feel it on take-off just because of the transition between configurations of the plane and the decreasing rate of climb. But you might also feel it if you hit a gust that pushes you down. So the pothole and the free fall is essentially just from a strong wind in a certain direction. The bumpy road would be caused by highly turbulent winds (turbulence itself is just chaos in a fluid, all wind can be considered a form of turbulence but weather can make winds more energised on smaller scales) which results in lots non uniform smaller gusts all over the plane.",
"Not surprisingly there are a number of reasons. The most common reason for turbulence is unstable air. Often found near thunderstorms. Unstable air is typically caused by temperature variations in the air. A common way this occurs is through something called daytime heating. The sun heats the ground, the ground heats the air. Hot air rises and you have unstable air. Add some moisture and you have the makings of a thunderstorm. Additionally you can get turbulence from the terrain when strong winds roll along the countryside and the lay of the land affects the wind. Mountains are another big factor. Also, a strong change in windspeed or wind direction in a short amount of time (we call this windshear) can also cause strong turbulence. This can happen low to the ground or up at altitude. There's also wake turbulence as well but that is less common as it's easy to predict and avoid. It's hard to really tell what type of turbulence you're experiencing based on how the bumps feel."
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ndda66 | Why does it hurt to look at the sun/strong lights? | The title pretty much says it. My best guess is that it has something to do with overload or something, but I have a hard time understanding why light would cause pain. | Biology | explainlikeimfive | {
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"Your eyes can be damaged by excessively strong light (for instance, staring at the sun). Life in general evolved pain so that living things could learn to avoid harmful things. Your ancestors who stared at the sun until they went blind all died. Your ancestors whose eyes hurt when they looked at the sun for more than a second or two lived."
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nddezt | Why do scars show more the older you get? | Biology | explainlikeimfive | {
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"Well your skin is less elastic, has less collagen and changes quite a bit as we age especially if you smoke and or have sun damage from actual tanning or just being outside alot. So depending on what type of scars you are referring to, old acne scars can appear worse. I dont know about other types. Newer injuries to the skin would result in more scarring than when you were younger.",
"Can you provide more details? Are you talking about existing scars become more obvious or new scars show more in older people than younger?",
"To my knowledge, your body produce radicals and antioxidants. Basicaly, antioxidants are the ones heal your body in many ways(aging, scars etc.) and until the age of 25(?), antioxidants outnumber radicals. After the age of 25 your radical production starts to increase and aging starts. At the same time your antioxidant production starts to decrease. Once radicals start to outnumber antioxidants in your body, you start to have wrinkles, your eyesight lowers, your reflexs starts to slow down which means your reaction time gets slower and slower. And obviously your wounds get healed in a longer time period. It seems like a lot but this process isn't happening in a short period of time. Basicaly this is a process goes on your whole life, starting from birth to death. P.S. This might not be the only cause. This was a project which I did in highschool.",
"Collagen (the stuff that holds your skin together and makes it firm and smooth, and also what forms the bulk of scar tissue) in skin breaks down as you age - this is also what causes wrinkles. Interestingly, it's the same principle behind scurvy. Collagen needs vitamin C to chooch, so if you don't have enough, all your old scars start to... open back up.",
"Same approximate age as you and most of my scars have diminished with time... And I am absolutely covered in scars (as in 30% or so of my body is scarred from ant bites as a child and I lived a very rough early life with many physical injuries and even a couple deaths). Could be because I have naturally high cholesterol (low LDL, though) and have always been a fantastic healer."
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nddia1 | How do smart watches/wearable fitness trackers work? | Monitoring your heart rate seems simple enough, but how do they formulate information about your sleep, calories etc.? | Technology | explainlikeimfive | {
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"The data you put in and analysis of movement metrics and heartrate. For example, if it knows your height and weight, when you go for a brisk walk it can detect the walking motion and rough speed, sometimes including GPS data, then combine height + weight + type of activity = decent approximation of calories burned. For sleep, it detects position (you lying down), the types of motion, and heart rate, and can make educated guesses about when you were sleeping. Here's a *really* detailed look at the sleep data interpretation: [ URL_0 ]( URL_0 )",
"They typically use an accelerometer to detect orientation and movement and monitor how it changes over time. For example, an Apple Watch guesses that you are standing when the watch face is perpendicular to the pull of gravity and the appropriate side, based on how you told it you wear it, is pointing down. If it detects a similar orientation but swinging back and forth and also detects the shock of your feet hitting the ground, it is generally safe to assume you are walking. Combine that with the barometer detecting an elevation change and it knows you’re on stairs. Detecting a rise in heart rate and it can deduce that you may be exercising."
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nddni2 | How do planets...exist? Meaning...how are they not hurtling through space like rouge planets? | So, in the sun centric model, the planets revolve around the sun like an elliptical right? How come this model isn't moving left to right or up and down? For some reason this bothers me. | Physics | explainlikeimfive | {
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"The reason is simple - all of the planets in our solar system were formed at the same time from the same ball of matter. Why does that make them exist on the same plane? Well, you take this ball of matter (mostly hydrogen gas), and in the center is where you're going to get the sun. Some of the matter is rotating clockwise, some is rotating counterclockwise about that center. Just by random chance, you'll have a little bit more going one way or the other (CW or CCW). As gravity pulls everything together (and form the sun), conservation of angular momentum means that slight bit of extra rotation is going to speed up - like a figure skater pulling their arms in for faster rotation. So... gravity pulls this ball together, but instead of all collapsing to a single point (the sun), it kind of \"pancakes.\" So you get the sun at the center, and the rest of the pancakes become the planets. They all exist on the same plane and orbit in the same direction because they were formed from the same \"pancaking.\" Oh, and our current planetary models say that the solar system probably formed with twice as many planets (maybe more) and then gravitational disturbances flung those extra planets off into deep space... and that deep space is probably littered with these extra planets, hurling through space.",
"It's moving, first the planetary orbits are not in 2d so is not like every planet in a given solar system is orbiting in the same level or plane at the same time, more over our entire system (and every other system) is always orbiting or moving around the center of mass of our galaxy."
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nddwa7 | most of the screens we look at are 2D, what makes our brain perceive it as 3D or normal images? | So I recently started watching anime and one thing I notice is it's a 2D art style and still I rarely find anything unusual. Fights are beautifully animated and so is the scenery. And I realised most of the screens are 2D but we don't notice any difference. Do our eyes just adapted that style or our brain tricks is to perceive it that way? | Biology | explainlikeimfive | {
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"Your eyes/brain only see 2D as well... however there are numerous depth cues that the brain uses to interpret the 3D world around us. One of those depth cues is stereoscopic vision, where each eye sees a slightly different image and the brain deduces depth information from those image differences... however there are numerous other depth cues. Size and shadows tell us about depth. A 3D image of a sphere looks \"3D\" because it has shading and shadows. A 2D screen can present a lot of these depth cues which help our brain interpret 3D."
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nddwfw | How does your brain 'realize' that you're home? | Like after a road trip if you're asleep, on that final turn towards your house you'll wake up. How does your brain know that you're almost home? Edit: I'm 99% sure it's not a coincidence because even when I'm driving with other people who obviously wouldn't drive the same way as my parents, I still wake up at the same turn into my neighborhood every time. I could be dead asleep for the entire ride and I'll still wake up. Also doesn't matter which direction I'm turning from | Biology | explainlikeimfive | {
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"Selection bias, how many times do you wake up half way through the trip and just go back to sleep? How many times do you wake up and stay awake but discount this experience? How many times does your dad slam on the brakes turning into your street just for a laugh? Basically you are only counting the times you wake up near home as an event while discounting all the other events.",
"The parts of your brain that process input (sounds, smells, acceleration, etc) never turn off, even when you're ignoring them, even when you're asleep. And every part of the brain has memory, that's how brains works. So if done something many times before and you associate those sensations with something important, (e.g: \"I'm almost home\"), then you've effectively trained your senses to recognize the environment, which can be especially effective with them working together. These systems can wake you up... Which, again that's kinda the whole point. If you've decided that getting home is a reason to wake up, then your brain can handle the mechanics of making that happen, assuming you've taught it what getting there feels like. It's not a perfect system and I'm sure you get false-positives all the time, which you'd just shrug off without knowing why you awoke. You brain certainly can't leave you a note detailing how it came to it's conclusion.",
"Usually it’s the shift in speed that wakes you up. Generally in long trips you’ll be driving fast on the freeway but then you drop down to 20/30 mph as your near home and your body can sense that change. Either that or the driver and anyone else awake in the house make subtle changes as you turn into the neighborhood. Maybe they wiggle a little more or they let out a big sigh or relief.",
"I kinda feel the same.. I drive all the time, my wife & children will somehow wake up when we’re within the vicinity of our home. At times, I’ll try my best to not wake them up by consciously try not to do sudden braking etc but they somehow will wake up before reaching the gate. Funny thing is they slept like a baby when i stop at traffic lights somewhere away from home. I guess it’s human instinct that cannot be explained scientifically..",
"Usually you travel on a highway for the most of the trip. You go faster, rarely stop, there are no intersections or hard turns. But this changes when you drive off the highway to get to your home which (presumably) is at some distance from the highway. There is a change in speed, stops and turns frequency.",
"We are derived from animal types that learned to go back home from the far away hunting grounds. There may not be one simple answer, but all our senses come together to remember home. Memory palace memorization techniques take advantage of this."
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ndeeoz | What do protons do when electrons flow? | I know that current is the flow of electrons so what are protons/neutrons doing when electricity flows? I was learning the band theory of semiconductors earlier and it briefly mentioned something about protons moving in an opposite direction to electrons but I don’t understand it well. Can someone help me? Why is electron flow emphasized of protons also flow? Thanks! | Physics | explainlikeimfive | {
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"I think you've misunderstood something you've read. Protons do not move when electricity flows. Not only are they locked into the nucleus of the atoms of the material, they're nearly 2000 times as massive as an electron and thus far more difficult to move. In a semiconductor you have the concept of \"electrons\" and \"holes\"--when an electron moves in a semiconductor it leaves an atom with an incomplete electron shell behind, which is a \"hole\" ready to accept an electron from somewhere else, but that has nothing to do with protons moving.",
"Nothing. They stay where they are, aside from tiny vibration due to heat, sound, and stuff like that (basically molecular/atomic vibrations and phonons). The positive \"holes\" in the atoms/molecules are gaps left by the moving electrons and that the upstream electrons move into as they flow."
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ndejbh | Why are swear words even a thing? | Other | explainlikeimfive | {
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"Pretty much we just arbitrarily deemed certain words to be rude or offensive. Like you could say feces or poo or number two on tv, but say the word shit and it's a fine from the FCC for you. At its core it's about a societal expectation of politeness."
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ndem5j | how our bodies produce mucus. | Wondering how there are never ending boogers when one has a sinus infection. | Biology | explainlikeimfive | {
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"Water and other stuff (I think white blood cells) gets pulled from your body and made into snot: mucus discharge and yellow/green/brown puss. The dirt/dust in your nose also contributes. Runny nose and fever (if you have one) are why you need water (and nutrients) when you have a sinus infection."
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ndetci | How exactly does electricity "know" to not flow backwards in a transmission line (or circuit)back to the source? Why does it move in one direction? | Physics | explainlikeimfive | {
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"Similar to air flowing through a hose on a machine, the end it's coming from has something pushing it along (a generator). This generator is making a voltage potential, and the place it's going to has a potential of 0 (it goes into the Earth after going through your stuff). Just like that high pressure air wants to go to where there's low pressure to even out.",
"Think of it like water: water flows through the path of least resistance If you dump water out of a bucket at the top of a slope for example, it will flow downward, not necessarily in a straight path, but following areas that have less impediment Likewise, electricity will flow from higher voltage to lower voltage = there is higher voltage behind it and lower voltage in front of it. The system operates on a push-pull, tension-type approach.",
"It doesn't. And, in fact, assuming that electricity doesn't bounce back is a wrong and potentially destructive assumption. A huge part of electrical engineering on circuits boards is making sure all the components are impedance matched to avoid reflections. Any AC transmission line needs to have good impedance matching or energy reflects back from where it is supposed to exit. Well you might as, what happens when it gets back to the other end? Well some passes through and some reflects back. There are a lot of partially correct answers here",
"It doesn’t know which way to flow. It flows from high voltage to low voltage, just like air and water flow from high pressure to low pressure, and heat transfers from a hot surface to a cold one."
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ndfqs8 | what is the "risk-free interest rate" and why could it be anything else than zero ? | I know this rate plays a huge role in pricing financial products. So much that it stunnes me we don't have a fundamental grasp on it. My naive guess would be, it must be zero all along. Then again, it might depend on the strictness of "risk-free". crossing the road is not riskfree. Are financial products better described by a risk profile ? | Economics | explainlikeimfive | {
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"It's basically considered 'Risk Free' because there's not a possibility it won't be paid back. It exists mostly in theory, but then has correlation in reality. Basically think of it as saying if you had $10,000 and I told you you're not allowed to spend it for 1 year, how much would the market demand to do that? Assuming zero risk, what would you charge to delay the use of your own money? The most common risk-free rate refers to US T-Bills though, which is basically as close to truly zero risk as you can get. There's essentially no chance the US Government won't pay back your money on a 30 day T-Bill. Even if they had to just print the money, they'd pay it. And if there was ever a chance that the US Government did not pay back a 30 day T-Bill, then it's quite likely at this point you've been killed or irradiated enough to die soon and the US Dollar no longer exists."
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ndgxwz | Why is there a lot more smoke (steam?) after you turn off the heat when cooking on a frying pan? | Physics | explainlikeimfive | {
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"There's not more steam, but colder steam, thus more visible. Water steam is mostly transparent. When it get colder, it's like clouds : liquid water in very small particle floating around appearing whitish.",
"You see it more for the same reason that rain in our atmosphere occurs. When cold air hits hot moist air, the moisture in the hot moist air condenses just like how when you have an ice cold drink in a cup in the summer, water condenses on the sides of the cup. So when the burners are producing heat on the stove, the humid air coming off the pan is surrounded by hot air and doesn't produce visible vapor. When the heat is turned off, the pan and the hot evaporating water coming off of it is the hottest thing around, and hits the cooler air in your kitchen, condensing and creating the visible effect."
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ndh7n9 | When we're out of the house and there is sudden need to discharge, why is our body feels like "excited" when we're just metres away from the toilet and we have to run? | Biology | explainlikeimfive | {
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"Your thoughts can influence your physicality. I’m assuming you’re talking about having to pee, by the way, but the words discharge and excited make me feel like maybe you have some other issues going on in which case you’ve got a whole different problem. Anyway, think about how you can stop yourself having to pee by not thinking about it. It follows logically that you can make yourself have to pee worse and worse by continuing to think about it. You have to be so bad when you’re only meters away because all you can think about is finally getting to... discharge I guess. I suppose that’s pretty exciting.",
"It's called \"Proximity Incontinence.\" No problem holding your excretions when you're running around during your busy day, but as soon as you are approaching the safety and relaxation of your home, suddenly your bladder and your sphincter relax and are ready to let go. It's a psychological phenomenon and you can learn to override it and make conscious efforts to strengthen your resolve to wait until you get to the toilet."
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ndifcb | how is towing a parked vehicle not theft? | Other | explainlikeimfive | {
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"Property owners have a right to remove unwanted or unauthorized vehicles from their property. It can be crappy but ultimately it's not illegal, and the vehicle owner has ways to recover the vehicle.",
"Tow companies are licensed to tow vehicles from places they have parked illegally or without authorization from the property owner. They also notify the owner of the vehicle via registration records and provide a way for them to recover the vehicle."
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ndij98 | Is the smallest thing smaller than the biggest thing is big? | Other | explainlikeimfive | {
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"Well the smallest thing we have theorised is the plank length which is 10e-34 metres. The biggest we know of is the observable universe which is 10e26 metres. So from our perspective which is around 10e-1 metres, in terms of orders of magnitude the plank length is “further away”. edit: if we follow this logic, (to answer your original question within the confines of ELI5) yes."
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ndiup2 | How do wildlife documentary makers remember which animal is which? | Like they name a tiger Simba and then they go "Now Simba must be exiled because he didn't do this" How do they now which one is simba? | Other | explainlikeimfive | {
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"The filmmakers spend a ton of time around these animals. Far more time than what you see on the screen, For every minute of footage that airs, the camera person might have shot hours of footage. They may also have had to spend a great deal of time slowly acclimatizing the animals to their presence so they can get close enough to film. In that time, they can notice the differences in the animal's appearances that you or I don't notice casually. For example, they might notice small size differences or differences in facial features or coloring that aren't obvious to someone not paying much attention.",
"They film tons of footage. They review the footage. They decide which narratives they can squeeze out of the footage. They edit and do commentary on the narrative. Only if they get lucky does the narrative fit what really happened. Most of the times it's just completly fabricated. It's a business",
"Same way people with identical pets. Or people that breed animals can. Ypu spend enlugh tine arounf an animal and you *know* them. Knlw their habkts know thwir little ecfentricities. Know the sound they're makimg. One of my pets is talking right now in a different room and i know exactly who it is and what he wants and that when i go to give it to him i knlw exavtly how he'll react."
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ndmek0 | How does calculator know and use pi if even super computers can't know all the digits. Does it use like first 100 digits? | Mathematics | explainlikeimfive | {
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"Probably way less than that. For any real-world application, even a few decimal places are totally sufficient. Use 6 digits, and the circumference of a kilometer-wide circle is less than a centimeter off the true value. That's already better than most measurement methods. And additionally to that, computers in general can't handle infinitely precise numbers. If you do the right calculations, the error could stack up, but in this case you rather use mathematical tricks to simplify the calculations first, before using any hard-coded numbers.",
"If you press Pi and then Enter, it will probably display a short sequence of pi. Thats what is hard coded into the calculator.",
"Pi is whats called an irrational number, this means that it never repeats, this also means its infinitely long. Noone will ever be able to know the whole of pi, since it never repeats and goes on for eternity. But, you dont need to know the whole of pi. Just a small number of it is needed. For example, for us to calculate the circumference of the known universe to within the width of an hydrogen atom, we only need 39 digits of pi. NASA only uses 15 or 16 digits for their space missions, it doesnt have to be exact, just very close. A millimeter of miscalculation here or there wont matter, since human error will account for much larger distances. So a calculator doesnt need to know the whole of pi, 15 digits of pi would be enough to launch a space station, and most people dont need to be more accurate than that (i hope?).",
"Even if you wanted to send a rocket to a point somewhere in the known universe, 100 digits of Pi would already be overkill. A normal calculator works just fine with ~10 digits",
"If you want to see how many digits it stores, subtract the first number, then multiply by 10. Repeat until it runs out of numbers. eg. assume calculator actually had 3.1415, but it only showed 2 decimals at a time, so all you see if 3.14 3.1415 (calculator shows 3.14) 3.1415-3 = 0.1415. (calculator shows 0.14) 0.1415 x 10 = 1.415. (calculator shows 1.42) 1.415-1 = 0.415 (calculator shows 0.42) 0.415 x 10 = 4.15 (calculator shows 4.15) 4.15-4 = 0.15 (calculator shows 0.15) 0.15x10 = 1.5 (calculator shows 1.5) 1.5 -1 = 0.5 (calculator shows 0.5) 0.5 x 10 = 5 (calculator shows 5) 5-5 = 0 (calculator shows 0) And you are done. Calculator only showed 3.14, but you can figure out the unseen numbers. It can also be done more efficiently, a lot more efficiently, but I was trying to lay it out :).",
"May I provide an engineering perspective? We don't need infinite precision in pi; we just need *enough* for the job at hand. Say you have a 3\" wide hole, and you need a bolt that goes through with 1/64\" clearance on either side. To calculate the size of the bolt, you just need pi to enough decimal places that any error is going to be much less than 1/64. (1/64=.015) So, 3/3.14 = .95541, and 3/3.1415 = .9549 The difference between the two is only .0045, which is less than our required tolerance, so two digits of pi suffices in this example. Now, say you need a match tighter than 1/64. Say you need a tolerance of 1/10000, or .0001. Then 4 digits of pi would not be enough. In fact, even five digits of pi would leave you with an error of .0004. In this case, you would need six digits of pi to get to your required tolerance. In space flight, you might need pi to hundreds of digits if you're going to calculate where Pioneer might end up in another 50 years to some reasonable degree of certainty. But for most earth-bound applications, 10 or 15 digits is more than enough precision.",
"Other people have really good explanations, but I want to talk about error. Using the first 2 digits is fairly accurate for most calculations. The error introduced by using is negligible (about 0.051% error) which becomes even smaller if you use pi approximations in trig functions like Sine, Cosine, Tangent, etc which you usually will be doing with pi. Ex: sin(90) = 1, but sin(90.1) = 0.99999848. The error we willingly introduced (90.1 instead of 90) is about 1.1111% error, but the error in the output comes out to be 0.000152%. In general, introducing error into a system can compound itself as you carry that number further into your calculations. But the trig functions are a special case where they are not sensitive to error. Since pi is frequently used in the trig functions, the digits of pi don’t really matter in most cases. An example of how much error is okay, think of 1/2 an inch of error and apply to context. Landing a spaceship on the moon and being off by 1/2 an inch in the landing is amazing. Building a patio with one side 1/2 inch short is acceptable if it was a DIY project, though you might notice it eventually. However, I’d start panicking if my dentist told me he was 1/2 an inch off in the root canal. Source: I’m an engineer in training, so I am okay with errors and being close enough within context.",
"Most calculators internally use more decimal places than they display, it's how the displayed figure is rounded.",
"As a mechanical engineer, what is OP talking bout? Pi is 3, right?",
"The calculator only does arithmetic to about 12 significant figures. There is a mathematical theorem by Fermat which states the equation x^n + y^n = z^n has no solution when x, y and z are positive whole numbers and n is a whole number greater than 2. Andrew Wiles proved the theorem in 1995. From [Homer’s Last Theorem]( URL_0 ) In the Simpsons “The Wizard of Evergreen Terrace Homer appears to have found an exception to the proof 3,987^12 + 4,365^12 = 4,472^12 If you try it on a calculator it will appear to be true. *Simpsons writer David Cohen obviously knew that Fermat’s equation had no solutions, but he wanted to pay homage to Pierre de Fermat and Andrew Wiles by creating a solution that was so close to being correct that it would apparently pass the test if checked with only a simple calculator. In order to find his pseudo-solution, he wrote a computer program that would scan through values of x, y, z, and n until it found numbers that almost balanced. Cohen finally settled on 3,987^12 + 4,365^12 = 4,472^12 because the resulting margin of error is minuscule—the left side of the equation is only 0.000000002 percent larger than the right side*",
"Loads of people have already stated this, but a calculator will have the first few digits of Pi hard coded into it. You can find out how many decimal points by multiplying by 1000000 then subtracting the digits before the decimal point.",
"Your calculator is built using a processor that does math using the binary system. It all depends on the length of the binary registers (i.e. how many bits are used to store each number). But, it's an informed guess that they chose to store one full register worth of decimal places. If the calculator uses 64 bits to store the number, then it has about 16 decimal numbers of precision^[1]. [1] [stackoverflow]( URL_0 )",
"URL_0 If you used 40 digits of pi you could calculate the circumference of the entire visible universe — an area with the radius of about 46 billion light-years — \"to an accuracy equal to the diameter of a hydrogen atom.\"",
"My math teacher said your calculator uses a taylor polynomial to find pi and other irrational numbers.",
"It probably uses as many digits that will fit into 8 bytes of memory. That’s about 15 digits (including the 3 out front). Computers use a fixed number of bytes for all non-integer numbers. It doesn’t matter if it’s 5.0 or 4.1 or 6.789543 or pi or the square root of two. That’s probably 8 bytes (15 digits), but on some older machines it could be 4 bytes (7 digits).",
"How many places does your calculator display? That should be enough.",
"A lot of things are some approximation. A good research topic related to this Taylor series/McLaren serious.",
"So pi in a Ti83 is stored as: 3.1415926535898. I figured this out by doing pi -3.1415926 and it told me it was 5.35898*10^-7.",
"Its not calculating anything. Its retrieving saved data. & #x200B; Copy pi to a million digits and put it in notepad. Save it. Open that document up and ask yourself if the computer calculated that number when you opened the file???",
"You don't need many digits of pi for accurate calculation. To calculate a circle with circumference equal to the observable universe, that is accurate to the smallest thing, a hydrogen atom, you would only need 39-40 digits of pi. Most things are much smaller and don't need to be as accurate. URL_0",
"You ever see the video [*Powers of 10*]( URL_0 )? Remember, each additional decimal digit of Pi is a factor of 10 additional precision. NASA only needs 14 decimal digits. The diameter of the universe, to the precision the width of a hydrogen atom, needs only 39 digits. Think about it: 1/1,000,000,000,000,000,000,000,000,000,000,000,000,000 is hella small / hella precise.",
"As others have already mentioned, the calculator stores only a finite number of digits of PI. If you want to know *exactly* how many digits, you can look it up in the manual. For example, in the [manual]( URL_0 ) of the **Casio fx-991EX** it says on page 14: > pi is displayed as 3.141592654, but pi = 3.14159265358980 is used for internal calculations. For programs on PC we can look into the [Intel Developer Manual]( URL_1 ), volume 1, subsection 8.3.8 (page 219): Approximation of Pi > The numerical value of PI can be written as: Pi = 0.f \\* 2^(2) where the fraction f is expressed in binary form as: f = C90FDAA2 2168C234 C > > The internal approximation Pi of the value π has a 66 significant bits. Since the exact value of π represented in binary has the next 3 bits equal to 0, it means that Pi is the value of π rounded to nearest-even to 68 bits. So interestingly, on 64bit systems, pi is saved with 68 bits.",
"For many calculations, a calculator may only need a dozen or so digits of π to get an accurate answer. However, there are some calculations that require many more digits. The trigonometric functions are periodic, with period 2π. To calculate the sine of 9.999999999•10^(99), you need to calculate the remainder when that number is divided by 2π (and then the remainder is used in an engineered polynomial that approximates sine or in some other algorithm for computing trigonometric functions, such as CORDIC). Now, somebody normally should not be taking the sine of a number that large. There are various numerical problems that arise using numbers that large. However, that is the user’s problem. If they give us a number and ask for the sine, we want to calculate it accurately. (And sometimes large multiples of angles might arise through manipulating various trigonometric identities, and they will largely reduce if the calculation is done correctly. So we want to try to do a good job.) So, for the sine function in a calculator to work well, it has to be able to calculate that remainder accurately. In effect, that requires having over a hundred digits of 2π—in addition to calculating 100 integer digits of a number around 10^(99)•2π, you need more fraction digits to calculate the residue accurately. Usually, that information is not stored directly as digits of 2π. Depending on the hardware available, it may be stored as pieces of prepared reciprocals of 2π (or related numbers like π or π/2). Whatever data is needed, it is computed when designing the calculator, using extended-precision software, and stored in the programming of the calculator. Additionally, if we wanted to be fancy, we do not need to store the digits of π in order to have them available when we need them. We know ways to calculate the digits, using series that add up to π or other methods. This is how extended-precision software obtains π—it calculates as many digits as needed when they are needed. It can never calculate all of them, but it can calculate as many as you need at the moment."
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ndmghl | How are manufacturers able to manufacture really small cpu transistors? | Technology | explainlikeimfive | {
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"Photolithography. You know how a projector can take a small image and turn it into a massive projected image? You basically do that in reverse, large designs which get focused down and etched into the silicon by bombarding it with light.",
"They use chemicals to build a thin layer, use light to burn it off in places, then more chemicals to actually modify the exposed parts of the chip (e.g. acids to create channels for conductors). The advantage of using light is you can shine it through a bigger guide (that creates the necessary patterns) and reflect it down to a very small size.",
"This is a very complicated question since modern processors take like 3 months and over 1000 steps to make, but ill do my best to skip all the detail and make it really ELI5 They use special chemicals and light to draw a pattern, or mask, on the silicon. They can then modify or remove the parts of the silicon that is not exposed. This process along with several other specialized processes for each step is repeated to modify the silicon to make transistors, replace parts of it with wiring to connect everything and then build a big stack of wiring on top of it that connects it all to the rest of the computer. They key processes used are: Lithography (drawing a pattern with light and chemicals) Implant (modifying exposed silicon by adding trace amounts of other atoms to it) Etch (removing exposed silicon (or other materials) by either chemical solutions or chemical plasmas) Deposition (depositing a film on the silicon, sometimes to fill in silicon that was removed with etch, sometimes to make a new film that will be etched to have something else filled into it) Polish (smoothing out the wafer after various steps make it rough or deposit too much material)",
"You know how you can use a magnifying glass to burn stuff by concentrating rays in a tiny area? Manufacturers use a magnifying glass with a pattern on it, then the concentrated rays burn out very tiny patterns in a tiny area. The burnt areas have different physical properties to unburnt areas, and with the right pattern this creates a transistor.",
"Lithography is the term your seeing over and over here. But it's not as simple as everyone is making it sound, it's a really amazing process to generate appropriately small wavelengths of light. Eli5 version is, imagine light is like a marker, you can only make lines as thin as your marker tip, in order to make a smaller marker tip they use one marker (a laser) to make a new marker that's smaller, by shooting a laser into a perfectly round ball of tin, that tin then emits new light if a smaller wavelength (aka smaller marker) Search youtube for euv"
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ndmlkj | Why do ships leave calm paths in the ocean? | As the title says, when a ship goes by it seems to leave a trail of calmer water, why is this? | Physics | explainlikeimfive | {
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"Waves are water that's travelling on top of the rest of the water. They don't just form, they are created by something pushing the water (usually wind). So when a ship goes through water, it pushes the waves to the side (due to the shape of the hull being designed to cut through the water) or just flattens the water, leaving a calmer patch behind it. Unless there is really strong wind, once a ship has travelled over a section of water, it'll remain flat until either wind creates new waves or waves from outside the calm zone move into it, which usually takes a while as the wake from the ship (the turbulent water) acts as a barrier."
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ndmvqp | Why do we mess up something when people start watching us how we do it? | I mean my mom can cook but if any of us go near her she gets panicked and chases us out. This happens to all of us, we naturally prefer people not to stare at us when we do something, it increases anxiety and stress. | Biology | explainlikeimfive | {
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"Anxiety makes you tense, rigid and shaky. It makes you overthink and rely less on muscle memory. Anxiety is a response to a percieved threat. Its there to help us, but can have the opposite effect sometimes. In our society things like status, skills, intelligence, knowledge, \"being right\", fitting in with the norm etc. Are highly valued, these are values we think of as positive. And if we possess them, chances are we will be treated better. If the stray from the norm, or are wrong, or quirky, or do things differently, or make mistakes. Chances are we will be made fun of, and be treated worse. When someone stares at you, your brain realizes that they will be able to pick up on any small thing you do. Any mistake, or difference. It causes the idea of a threat to form, and so your body activates a fight or flight response. Shaking, increased heart pressure, sweating, quicker breathing. These are things meant to prepare you for something physicaly demanding. Sweating to help you cool off if you decide to run or fight, heart pressure heightens to provide more oxygen for your organs, and quicker breathing to provide the oxygen for your blood. Your body may release adrenaline, and adrenaline makes you shake. These are all there to provide support for a percieved threat, but its a response that is not adapted to our society. Back when we were hunter gatherers, being shunned might mean you would have been kicked out of the tribe, and youd get eaten or starve to death. Today it may just mean you get mocked. Its a result of the insane amount of progress thats been made the last 20 000 years. But when you are alone, there is noone to judge the process you have gone through. Only the finishes product, you can do anything you want in the actual process without consequence. Its why you get nervous when showing something youve made, or when you cool a new food. Its also why you get that sinking feelinc when someone tells you youve done a bad job."
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ndmysm | What causes Hand, Foot, and Mouth disease to localize on such specific body areas? | There can be atypical breakout areas, but what causes the sores to commonly appear on the hands, feet, and mouth area? | Biology | explainlikeimfive | {
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"A lot of infectious bacteria have specific receptors on their surfaces that recognize similar ones on specific cell types, which is how UTIs localize on urethras. That may be a part of it!"
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ndnurt | why do we have to wipe our bums but animals don’t? | Biology | explainlikeimfive | {
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"Well this isn’t specific to humans. One contributing factor is that we are erectus, or bipedal. Meaning our butt cracks are smooshed together since we are not on all 4’s. But again, some animals still have to do it. Even dogs for instance need their glands “expressed” which is like a butt wipe of sorts. Many animals throughout the kingdom require some form of poo cleaning",
"Well for starters I think this can be simply answered by stating the observable obvious. We have muscle and adipose tissue that extends past the point of excretion. This is not so for animals such as, dogs, birds, or fish. Other primates who do, baboons come to mind, are likely pretty smelly.",
"Another answer is diet: your poop's consistency depends on what you eat. Ever notice that sometimes you poop and when you wipe, it comes clean, but other times you poop and when you wipe, it's messy? That would be the reason."
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ndnyde | What was the Watergate Scandal? | Other | explainlikeimfive | {
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"President Nixon sent some dudes to break into the Democrat offices in Watergate to photograph documents and plant listening devices on phones. They got caught and eventually an investigation began. The Nixon administration attempted a coverup and basically did everything they could to not cooperate with the investigation. Nixon lied all over the place and the impeachment process began, his public support eroded, and he resigned from the presidency.",
"The president got caught spying/putting listening devices in his opponent’s rooms/workplace. He got caught and resigned before impeachment . The building was the Watergate building hence the name, Watergate Scandal. Edit: fix an error",
"Tl;dr: President Nixon's 1972 re-election campaign broke laws to help him win, hiring some ex-CIA and FBI people to illegally spy on the Democratic Party. They got caught. Nixon won the election in a landslide, but as more details came out the scandal didn't go away, and Nixon ended up resigning before he could be successfully impeached, due to trying to cover-up the cover-up of the crimes. ------- In 1968 Richard Nixon won the US Presidential election, but with only 43.4% of the popular vote and 301 electoral college votes, against the Democratic Party candidate's 42.7% (with an independent candidate getting 13.5% of the vote and 46 electoral votes). When seeking re-election in 1972, the Campaign to Re-elect the President decided to cheat, to secure their win. As part of their plans, they hired some ex-FBI and ex-CIA agents to come up with a plan to bug the offices of the Democratic National Committee. On 17 June 1972 5 individuals (mostly anti-Castro Cuban activists, but with an ex-CIA agent) broke into the Watergate complex (a series of office buildings in Washington DC) with the aim of wire-tapping phones in the DNC's headquarters, located in the building. Due to a bit of bad luck and some incompetence from their look-out they got caught by the police. Nixon himself was probably not directly involved. The leader of the group had ties to the Nixon Campaign. In response, the Nixon Campaign began a cover-up operation, destroying evidence, lying about investigations and even kidnapping and beating up the wife of Nixon's campaign chair (and former Attorney General) to keep her quiet (she knew one of the burglars). Despite direct evidence linking the Campaign to Re-elect the President to the burglary, and suggestions that this was part of a widespread series of criminal activities against his Democratic Party opponents, Nixon was successfully re-elected in a landslide, with 60.7% of the popular vote, carrying 49 states (all but Maine, and DC) and winning 520 electoral college votes. But the scandal didn't go away. The burglars were convicted, but their dies to the Nixon Campaign were investigated, particularly by the press. And later, by the Democratic-majority Senate (the Senate being 56-42-2 after the elections). President Nixon started trying to cover-up the original cover-up of his campaign's involvement, and got caught. In particular, a special prosecutor was appointed to investigate, and on 20 October 1970 President Nixon ended up effectively firing his Attorney General and Deputy Attorney General as both refused to fire the special prosecutor (although his Solicitor General did). But due to the backlash against that, he had to appoint a new special prosecutor who indicted and convicted several people in relation to the cover-ups, and named President Nixon as an \"unindicted co-conspirator\" to their crimes (believing that he couldn't prosecute a sitting President). The next big problem for the President was that he had kept tapes recording what was said in the Oval Office. Once the public found out about these, there was a lot of pressure to have them released. In April 1974 the Nixon Administration released edited transcripts of the tapes, but in July the Supreme Court voted 8-0 that the tapes themselves had to be handed over to the special prosecutor, were made public and were fairly damning - both in relation to the specific scandal (covering up the cover-up of the burglary), and Nixon's views in general. Within days the House had issued Articles of Impeachment against the President, and shortly afterwards one final tape was released, which revealed a conversation Nixon had days after the burglaries, in which he discussed covering up the crime. With that removing any argument he wasn't involved, impeachment was almost certain, and Nixon resigned as President, to be immediately pardoned for any crimes by his successor, Gerald Ford. ------------- The Republican Party learned a lot from the Watergate scandal; the importance of controlling narratives, to keep lying, not turn on fellow Republicans, not keep recordings of the President's crimes, and that a President can pardon his allies and co-conspirators for their crimes and get away with it. All of this helped save President Trump from a similar fate (although, obviously, he lost his re-election despite the crimes and cover-ups involved in his first election and re-election campaign)."
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ndomgc | How do body fat scales work? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Fat tissues are much less conductive than muscles. Body fat scale runs a very weak current through your body and calculates the fat mass by comparing the outgoing and incoming current."
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ndowyy | How does the body recover from a short period of poor diet and exercise? (Specifically the heart) | Let’s say someone ate poorly (high fat, junk food diet) and exercised very little for 5-10 years in early adulthood. But maintained a fairly balanced lifestyle and healthy weight afterwards. Would the body “recover” from the negative effects of being overweight or does the lifestyle change simply pause the negative effects from increasing? | Biology | explainlikeimfive | {
"a_id": [
"gybras4",
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"text": [
"Some of the negative effects take quite some time to reverse, but they are mainly capable of being reversed such as cholesterol-containing deposits (plaques) in your coronary arteries.",
"Mostly the body will recover. If someone is extremely overweight/sedentary some diseases can start which are non-reversible, like CHF, fatty liver, and enlargement of the heart muscles. But those are extreme cases. Generally speaking clean living will get the body back to \"normal\" albeit slowly in some regards. It is markedly harder with age, though, and bad habits become harder and harder to break. Which is why it's best to learn healthy habits early and make them lifelong.",
"Not a doctor, but the answer is certainly a bit of both. Buildup of fat tissue in the body from eating high-calorie foods can be easily reversed; it’s just the body’s way of storing energy for later. Buildup of sodium in the body can be reversed as well, since sodium routinely exits the body through urine. However, some of the conditions that arise from long periods of unhealthy lifestyle can cause irreversible damage, such as diabetes, hypertension, malnutrition, etc. Explaining why each particular condition is reversible or not is very complicated, and different for every case, but typically it’s a function of how quickly the body is able to get rid of certain substances, and whether they act by changing an environment or just straight up destroying it. You can think of it like alcohol. You drink every once in a while, you’ll be fine. Even if you’re an alcoholic, you can recover with minimal side effects if you do so within a couple years but it will be difficult to do so. However, as soon as you start to develop liver cirrhosis, that damage is never going to heal even if you stop drinking.",
"I just wanted to say that we have very different definitions of “short periods.” I was thinking you meant a couple of weeks, not 5-10 years. Good think you clarified!"
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ndpdes | Why are babies so much more flexible than adults? Why do we get less flexible over time? | I recently rolled my ankle in soccer due to a tight calf muscle. My therapist says that most adult calves are tight and that regular stretching is essential for physical activity. Then I saw a baby with his foot near his head in a stroller... I know he didn’t stretch to be able to do that. | Biology | explainlikeimfive | {
"a_id": [
"gybspy1",
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"text": [
"Babies have less actual bones in their bodies and way more cartilage. As we grow that cartilage turns to bone. For example, Babies have no kneecaps. Babies also have more water in their bodies.",
"In addition to the other comment (fewer fully set bones, gotta get through that vaginal canal somehow), yes we do get less flexible over time as well. The primary reason is scary tissue and adaptations in fascia and collagen fibers. ELI5 time: you have a brand new sheet of paper (musculoskeletal system), it is perfectly smooth, sharp corners, and lays perfectly flat. Being a 5 year old, you naturally grab it and crumple it up into a ball (adaptations to imposed stress). Your mom comes by and un it and smooths it out the best she can (natural recovery to soft tissue), but it's not QUITE as smooth, flat, or even the same dimensions as before. Now imagine doing this every day for decades (pretend it's incredibly resilient paper that won't tear). Now, you're a lot older than 5 and you don't have your mom fixing things like she used to because you live in your own place (why you continue to crumple the shit out of a piece of paper that is a scientific marvel is beyond anyone's guess). Each of those times you crumpled it up added another few new wrinkles that you can't seem to smooth out, shortening the X & Y dimensions of the paper."
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ndqjvr | ground coffee is not soluble to water. What makes instant coffee be "made from real coffee beans" when it is soluble? | Chemistry | explainlikeimfive | {
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"Ground coffee contains insoluble compounds, but these never actually reach the coffee you drink (unless your filter folds in on itself, hate it when that happens). So all the parts of a coffee bean that coffee is made of *are* soluble, and if you can isolate these from the insoluble parts - say by running water through some ground beans, and then using a vacuum to cold-boil off the water - you can get a solid that's fully soluble and contains.... *almost* all the parts of coffee beans that coffee is made of. Boiling off the water will also boil off any volatile compounds that give coffee a part of its flavour. I'm sure instant coffee companies do their best to try and replace them, but... Well, that's why instant coffee taste like instant coffee.",
"Ground coffee is is used to make instant coffee. We make coffee by pouring hot water over/through the grounds. Instant coffee uses the same principals, but on a large scale to produce coffee concentrate (really really strong coffee). Then, that concentrate is dehydrated and broken down into smaller granules. Instant coffee is just redhydrated, so it completely dissolves. The grounds used to make it were already discarded before it made it to the store shelves.",
"Instant coffee: Cook coffee, freeze dry it. So you basically just get dehydratet coffee that you rehydrate with hot water."
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ndr14b | - How do people/computers calculate further digits of pi? | I saw recently that you would only need 39 decimals of pi to calculate the diameter of the observable universe to the margin of a single hydrogen atom. So then how in the world do people make the calculations to find more digits of pi? How did we get to so many? | Mathematics | explainlikeimfive | {
"a_id": [
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"text": [
"Historically, people used the following methods: 1) Measuring 2) Calculating the areas of many-sided polygons, using them as an approximation to a circle 3) Using a number of different formulas that expressed pi as an infinite sum or product, and just kept adding additional terms; for example, the [Leibniz formula]( URL_0 ) which is a very simple result that says 1 - 1/3 + 1/5 - 1/7 + 1/9 - ... = & pi;/4 We now have 4), an [explicit formula to compute whatever digit of pi you want without having to calculate the preceding digits]( URL_1 )",
"One of the cool things about Pi is that it tends to pop up in unexpected places in math. It turns out that Pi can be reached by a ton of different formulae. For example, Pi = 4 - 4/3 + 4/5 - 4/7 +... By calculating more and more terms of this series, you get values closer and closer to the actual value of pi. In practice we don't use this series, because it takes a long time to converge (you need to add a lot of elements for each digit you want to calculate). There are other, more efficient formulae which computers use."
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"https://en.wikipedia.org/wiki/Leibniz_formula_for_%CF%80",
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ndt2uw | why it’s so hard to make shampoo bars and conditioner bars that are just as good as the bottled liquids. It seems to me like it should be just as simple as not adding water. | Chemistry | explainlikeimfive | {
"a_id": [
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"text": [
"It's not hard but it's not practical. A pre-made liquid is easily applied to hair down to the scalp. Even dry shampoos come in powder form for this reason.",
"A couple of things: 1) Liquid shampoos can contain things that are liquid at room temperature or drying would damage like plant oils, root extracts as well as some liquid chemicals that help it foam, clean, and stay fresh. 2) Even if the only liquid the shampoo requires is water, rehydrating takes time, and also surface area both of which don't really work ideally in a bar form."
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ndtdu9 | Is there a reason we have 2 nostrils? | Biology | explainlikeimfive | {
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"text": [
"Short answer - This gives us a better range of smell. Long answer - 2 nostrils effectively act like two noses. Due to some biological mechanics, usually one nostril allows less air to pass through than the other, with the nasal flow switching every few hours. The sensory cells in our nose sometimes require more time to identify certain odors, and a low-airflow nostril gives them more time to be detected, giving us a better ability to detect scents. Vsauce also has a video on this I think"
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nducm8 | Edible plants and fungi. I assume we used to determine if a food was edible by trial and error for most of the past. How would we determine newly discovered food edible today without jeopardizing health or life? | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"The same process still applies, many survivalists have it memorized and use it in the field. It's called the Universal Edibility Test. It's a several step process that takes most of the day to accomplish. First, you seperate out the various parts. You need to test roots, leaves, stems, buds, and flowers independently, because sometimes one part will be poisonous while another isn't. You give each bit a good smell. Strong and unpleasant odors are usually a bad sign, and if you're in the field you'll just generally discard them without further testing. You test for contact poisoning by placing a tiny piece on your wrist for just a moment. If it burns, itches, numbs, or breaks into a rash, you just discard it. Then you boil each bit individually. Test each piece by briefly touching it to your lips, and then waiting 15-30 minutes to see if anything happens. After that, you can take a small piece into your mouth, chew a couple of times, and hold it in your mouth for 15-30 minutes to see if anything happens. If it's bitter or soapy, you just discard it. If there's no reaction at all, swallow it and wait the rest of the day. If there's no ill effect after several hours, you can assume this part of the plant is edible. Repeat the process for each individual part of the plant. Many plants have both edible and inedible parts to them, so this can take several days. As far as fungi goes... just don't. If you're in the field and you can't determine the exact species of mushroom you're looking at with 100% accuracy, don't touch it, don't eat it, just leave it alone. There are many kinds of mushrooms that are edible in one circumstance, but poisonous in another. Hen mushrooms are safe, but if they're growing on a conifer or cedar tree, they're poisonous. There are scientific tests you can do on mushrooms to determine their exact chemical components and identify if any of them are poisonous, or if they combine to create something poisonous, but if you're out in the woods it's a better idea to just leave them alone."
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ndue44 | Why do Japanese people have a hard time pronouncing the L sound? | Other | explainlikeimfive | {
"a_id": [
"gycny8o"
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"text": [
"Because L does not exist in Japanese. Same reason native English speakers struggle to pronounce Ć/Ћ in Serbian or LL in Spanish."
],
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ndueg9 | how does yeast make bread dough increase in size? | Biology | explainlikeimfive | {
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"text": [
"Yeast is a microbe, and it consumes the sugars in the dough. As it does this, it produces gas as a waste product, which inflates the dough and let's it rise as it essentially fills with air. That's why bread dough has lots of air pockets in it."
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ndus2g | How did people in ancient civilizations cut their nails? | Other | explainlikeimfive | {
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"text": [
"Knives and scissors have been used for thousands of years. Specially designed knives and scissors came around sometime in the Ancient Egyptian era. It was seen as a sign of nobility, and was quite fashionable for the wealthy to emulate. Having nicely trimmed, shaped, and painted nails meant you didn't have to work for a living.",
"They usually didn’t need to as there was much more hand labor involved and their nails would naturally break or wear down when crawling through the forest or hunting or beating down an enemy tribe member with a club."
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ndwbcy | What's the difference between a server and a cloud when it comes to data storage? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"A lot of people are telling you what makes up \"the cloud\", but I think it is more instructive to talk about how the term was intended to be used. In the past when a company wanted to do something involving computers such as build a billing system for multiple store locations, they would draw up a big diagram for how their system would work. This would include everything involved, from the devices used by the workers at the locations (thin client, thick client, etc), the network topology, etc. A major part of that was figuring out the hardware requirements for their own billing server, where it was going to be housed, who was going to maintain it, etc. Instead many companies in the modern way of doing things will have that part of the diagram pointing towards a literal line drawing of a fluffy cloud. This is because the server is housed \"in the cloud\", which is to say they will pay a different company to provide computing resources and management. After all, if you own a chain of coffee shops you probably don't want to be building out a server facility, you don't have that talent on payroll. So \"cloud computing\" isn't really a technology as much as it is an organizational concept."
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ndx48h | Why aren't the bots ruling the trading markets? Just buying as soon as the curves are going up and selling as soon as it's going down? | Economics | explainlikeimfive | {
"a_id": [
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],
"text": [
"They are. [High frequency trading]( URL_0 ) (HFT) algorithms make huge amounts of money for big banks. HFT algorithms have access to retail trading data and use that to get in before individual traders can see whats happening and make thousands of trades a second.",
"They are. Have you seen the numbers of transactions certain companies (hedges funds) make and how long it takes for them to do it."
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ndx618 | Why exactly does friction between some materials screech so awfully loud? Is it just due to hardness? | I can see how a rough, heavy cast iron pan rubs so loudly on a metal burner rack, but chalk and a blackboard are both pretty smooth. What gives? | Physics | explainlikeimfive | {
"a_id": [
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"text": [
"Noise from friction comes from vibrations creates as the materials runs past each other’s. Imagine dragging a stick across a metal fence making a rattle. If you did this very quickly it would sound like a continuous sound rather than a rattle (not a great analogy sorry). In the case of chalk, it’s made of calcium carbonate which is very soft in comparison with the black board. In this case the friction is enough to shear off chalk material onto the board."
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ndx6g9 | what would happen if the government sent everyone a $1,000,000 check? | Economics | explainlikeimfive | {
"a_id": [
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"text": [
"Massive inflation. Even when everyone has a million bucks, the amount of products in the market remain the same. Let's say everyone tries to buy a $10,000 car. There are only 10 in the shop, but 1000 people looking to buy. How do you decide who gets it? Most likely, someone will offer to pay more for the car. The price will rise until only 10 people are willing to pay the price (maybe $500,000). So, massive inflation. There are other problems too, but this is the main one."
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ndxb4v | What happens if you're really muscular and have a low body fat percentage but still classified as overweight/obese? Do you still develop health problems? | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"No. This is part of why a lot of people say BMI is a bad thing to use. It was originally designed to be used on groups, as a fast way of estimating on average the health of a large number of people at once. It wasn't really meant to be used on individuals, but because it's simple and fast gets used on them despite not being meant to be used that way. Some athletes despite being in good shape, are classified as overweight by BMI, because BMI only cares about how heavy you are and not about how much of that is fat versus muscle."
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ndxe3d | Why do balloons "pop" when a pin goes into them, rather than the pin create a bung like say a screw in a car tyre would? Also, why does putting a bit of tape on the balloon first change the result? | Physics | explainlikeimfive | {
"a_id": [
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"text": [
"Balloons are made of thin material. A small puncture lets the air out, and the force of that air escaping tears the hole wider and wider in a split second, tearing the balloon apart. Putting the tape on acts as a reinforcement, stopping the tear from expanding.",
"So it basically relates the the thickness of the material in question? As such a car tyre is thicker and therfore has the time to plug before tearing away from the piercing object? I had a feeling it was something like that but wasnt 100% sure! Thanks for the answer!"
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ndxf61 | Would gravity change as you get closer to Earth’s center? | Physics | explainlikeimfive | {
"a_id": [
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"text": [
"Yes it does. The force of gravity comes from the mass of all the rock under your feet. If you start digging down there will be rocks over your head pulling you upwards and less rock under your feet pulling you downward so the force of gravity is reduced. If you are able to get to the center of the planet there is just as much rock in all directions so the force of gravity is zero.",
"Just to add some extra detail for explainlikeim17, the [shell theorem]( URL_0 ) proven by the man Newton himself states that a shell of a sphere of any size and thickness will have no gravity on the inside. So if you stand inside of a huge inflated basketball, you will feel no gravity from ut. The proof is calculus, but you can also imagine it as a version of two inverse-squares equalling each other, which is how Newton proved it. Now, if you imagine the earth as a bunch of concentric shells (like a jaw breaker with different flavors), it is clear that gravity goes down as you tunnel through the center of the earth/shells. There is a second part of the theorem that deals with outside of the gravity from outside of a shell or sphere, which is the intuitive gravity that you understand from planets."
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ndxi3v | What is the biological reason that we are able to grow long strands on our head? | Biology | explainlikeimfive | {
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"text": [
"The strands of hair from our scalps/heads grow longer because the hair follicles there have a much slow \"turnover rate\" programmed into them than the hair follicles in, for example, our arms. In other words, your arm hairs fall out much more frequently, so they don't have the chance to grow as long.",
"The reasons posted so far go into the biological mechanism for the growth of hair, but I’ve yet to see a why. One theory is that hair can be a great external indicator of your physical health and thus your suitability as a mate/partner.",
"Hair growth occurs when a protein begins to accumulate from the hair follicle. This protein accumulation is what you see as hair strands. This accumulation/growth happens in cycles. 1. In this stage hair grows from the follicle. Can last around 2-5 years. 2. Temporary stage for hair follicle to renew itself after doing all the work. Lasts 2-3 weeks 3. Dormant stage when the grown strand remains as it is. Around 3 months. 4. The hair sheds off. Hair on different body parts have varying lengths simply because they spend different amounts of time in stage 1 i.e. growth stage. Longer time spent in stage 1= longer hair. So hair on the head spends a longer time in stage 1 than hair on other body parts. Now what determines the time spent in stage 1? That's due to certain signals sent to the hair follicle which tells it to start or stop. These signals are dependent on genetics, age etc. Which is why people of a certain population seem to grow longer hair or hair growth reduces as you age."
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ndy7fb | How do anchors on yachts work and how can they hold a whole boat when they lay on flat sea ground? | Technology | explainlikeimfive | {
"a_id": [
"gydawme",
"gydnxer"
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"text": [
"That's not how anchors work. They act to hold one end of a heavy chain so that the ship can lay it out on the bottom. The chain applies the forces that keep the ship in the right area.",
"Firstly, the horizontal forces acting on a boat aren’t as big as you might think. Certainly less than the weight of the vessel. Then consider the shape of an anchor. In all cases they are designed so that if you pull them horizontally they dig into the ground. The further you pull the deeper they dig. So suddenly you aren’t just trying to pull the anchor, you are trying to pull all of the ground that it is under. You can imagine that an anchor doesn’t have to be buried very deep before the amount of ground you have to pull far exceeds any force you can apply."
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ndz7jr | if animals don’t know what they look like, how can they tell which animals are the same species as themselves? | Biology | explainlikeimfive | {
"a_id": [
"gydhf16"
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"text": [
"I’ve wondered about this in relation to dogs. How does a chihuahua look at a St. Bernard from a distance and think “dog!”?"
],
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ndz89q | If all the cells in our bodies are replaced every seven years, how do we retain memories with replaced brain cells? | Biology | explainlikeimfive | {
"a_id": [
"gydhi7z"
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"text": [
"> If all the cells in our bodies are replaced every seven years They're not. The rate of cell turnover and replacement varies drastically depending on the type of cell. Tissues that experience high wear-and-tear are replaced frequently, while others are replaced rarely or never. Skin cells are replaced on the order of days or weeks, red blood cells on the order of months. Neurons, however, stick around for pretty much your entire life."
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ndzw32 | How can a pig transform into a wild boar? Pigs released into the wild can drastically change their characteristics in a short time. How does this happen? | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"Genetic they are very similar we raise pigs in a manner that doesn't allow them the wild tendencies and mannerisms. (If you've ever been around wild hogs, you know that's a good thing.) Primarily being used to humans, and the domestic lines have added a good amount of weight and heavier bones. They are still the same Bush critters though and will turn on you if they think you might be eatable.",
"They don't really. Pigs are usually slaughtered before they're a year of age. They're kept in an environment where they're constantly fattened up, medicated and taken care of. The males are castrated long before they're slaughtered. When those pigs escape into the wild, their hormonal change significantly changes. They'll have more physical exercise, more stress hormones, more opportunity to develop sexually and so on. And that does change the way the pigs look. They'll grow more hair, they'll be leaner and more muscular and over time. Generations of wild pigs will emphasize the genes that help them survive in the wild better rather than the ones that made them better hogs for slaughter. They don't resemble wild boar though. If you look at pictures of actual wild boar rather than domestic pigs, you'll see that wild boar are much more compact with thick bristly fur."
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ne0hfm | Why cant we retain all our memories and experiences as we get older? | Biology | explainlikeimfive | {
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"text": [
"I like to look at our brain like a peace of paper. When your born its empty,clean, pretty. Everyday your writing on that peace of paper and it get full. When your old, all the paper has been written on and some sentences cant be read. Its okay be those sentences are there. They existed but just cant be read. You might have spilled coffee over the pages. You can't read them but you know their there. It must be weird having memory lost.",
"It's not so much that we can't as it is that we don't have a need to. It has to do mainly with the way our brain stores memories in the first place. Over millions of years or biology developed a punishment/reward system to drive us to seek things that help us survive and avoid things that inhibit our survival. The positive or negative labeling of memories is a result of this system, and all memories are stored with some type of emotional association. When we are young many things we experience are new and exciting, and the emotional tags, either positive or negative, are also more intense and varied due to this novelty. As we grow older, however, individual events become less novel because they more often relate to previous experiences and are less likely to be stored in memory as they are less useful in terms of survival. This doesn't mean you are unable to remember things as you get older, as there are ways to train your brain to maintain neural plasticity as you age, but due to the fact that you're not experiencing as many new or intense things, especially not things necessary for survival, your brain has no need to expend the energy required to create long-term memories. Neurons are too costly to make and keep them for no reason."
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ne0rrb | What causes inflation? | Economics | explainlikeimfive | {
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"text": [
"Inflation happens when the overall amount of money in circulation increases faster than the overall amount of goods and services increases."
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ne0tqk | Microwave ovens cook things by shooting radio waves at food, right? So if I put something small in the microwave, and it doesn't catch many... microwaves, are the other microwaves wasted, or do they play some other role? | Physics | explainlikeimfive | {
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"Microwaves bounce around the interior very quickly so your item has a lot of opportunities to \"catch\" those waves. But some proportion of them are instead going to be absorbed by things like the walls of the microwave or the magnetron itself. Heating up the magnetron is usually considered to be a waste so those waves are not useful.",
"Microwave ovens create what are called standing waves. Basically they're pockets of high energy areas throughout your microwave, and the fact that they're called \"standing\" means they aren't moving, or are moving slowly, which is why there's a turntable in most modern microwaves. As the table turns, it moves your food through the pockets of high energy where the water in your food absorbs some of it, heating it up. Surrounding the entire cooking area is a thing called a Faraday cage, which is shunted to ground. This gives the excess/unused energy a place to go (to ground). So yes, the energy not being absorbed by your food is wasted."
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ne13im | Why are there many plants that can be grown in a greenhouse, but some, like ramps and truffles, that can only be grown in nature with conditions that can’t be mimicked in a greenhouse? | Biology | explainlikeimfive | {
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"Truffles are the mushroom of a fungus that is symbiotic with the roots of certain trees (most notably oak and hazel). They take up to a decade to become established (and you have to grow the trees too). this obviously requires a rather large space and oak trees need temperature variation anyway so being in a greenhouse wouldn't really help in the first place. Truffles can be cultivated, and are cultivated, but they are cultivated in forests not greenhouses. Ramps (and wild ginseng) are slow growing specialists in forest understories. The bulb/root takes several years to mature and (in ginseng anyway) is considered more flavorful/powerful because it has matured slowly in the relatively harsh conditions of the wild. You could raise these in greenhouses but....first of all, like oak trees (and many other fruit trees and berry bushes) they are adapted to seasonal climates and need to be cold in the winter to mature properly. The whole point of a greenhouse is to keep things from getting cold, so there's not much point. You can grow them in a suitable patch of forest after sowing them there, but you have to wait for them to grow to maturity which takes up to a decade. Also farmed plants can lack the marketing power of wild ones (wild ginseng sells for much more)",
"Truffles can be cultivated, and regularly are. The catches are: * They're very picky about the environment they're growing in which includes the soil, trees, etc. and that's a lot of factors to cover. You can't just build a greenhouse or just plant them wherever you are. Some places just won't work. * They take several years to develop, so you need to go through a ton of work and money to get set up and then you might find out 10 years later that they didn't grow after all. Womp womp.",
"The ELI5 version is that you CAN grow ramps and truffles in greenhouse. The reason why you DONT is because 1: the environment it needs is quite specific, unlike alot of green house plants, from soil acidity to humidity, you need to control it to a much higher precision. This means a extremely complex climate control system and not just a glass room. 2: its a fungi that grows on tree roots so you need trees. Which means a big green house. 3. it takes a long time for it to grow, + big house + all that expensive equipment, unless you have money to burn, simply cultivating them in the wild is MUCH cheaper.",
"Maybe someone could answer this. Can truffles grow anywhere? Say northern Scandinavia?",
"Because truffles grow on the roots of hardwood trees. Hardwood trees take decades to grow and can't be grown inside a greenhouse due to their size. URL_0"
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ne1ul4 | Why do some products like TV remotes still use infrared while everything else is moving to Bluetooth? | Technology | explainlikeimfive | {
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"\"If it ain't broke, don't fix it\". IR remote control is simple, robust, low-tech and extremely widely established. It just works, every manufacturer has experience with it and has the supply chains set up. You only change it when there is real benefit in doing so. For example, if you need to send more or more complex data than \"button has been pushed\". One such thing might be a remote that gives haptic or optical feedback, or has a pointer-style functionality on gyroscopic basis. All of that needs more data connectivity than IR can provide, and therefore manufacturers switch to BT.",
"There’s no interference with IR, and it uses a fraction of the power needed for radio signal.",
"Bluetooth is expensive. IR is cheap as hell. IR is just a LED light. Bluetooth needs an encoder, radio transmitter receiver, software to do handshaking and pairing,",
"First is the principle of \"if it ain't broke, don't fix it.\" Infrared remotes have been around for 40 years and work just fine. Infrared is also cheaper and less power hungry."
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ne5894 | Why do some foods freeze well and others don’t? | Biology | explainlikeimfive | {
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"Sometime it is how you freeze it. Normal freezers produce larger ice crystals and will turn veggies and fruit into mush when thawed. Those large ice crystals basically puncture cell walls and the water pours out when thawed. Imagine a bunch of ziplock bags full of water and those are the cell walls. Then the tip of a knife is an ice crystal and poke a bag and watch the water pour out. Now to get around this you need extreme cold. Liquid nitrogen works. You can freeze a strawberry with that and then thaw it and it will have pretty much the same texture. Why because at extreme colds ice crystals have less time to form and are smaller not every cell wall gets cut open.",
"The different contents of items may have different freezing points, plus some contents may want to separate naturally. Ice cream is a great example. If you leave it out to melt, the fats and the water will separate (just like oil and water). They will still separate when frozen, but much more slowly. This is why if you leave ice cream in the freezer for too long, the fats and water separate more and more, and you have two frozen parts instead of a nice mix - the frozen milk fats (the goopy stuff) and frozen water (the ice crystals). There are similar dynamics at play with many items. When the moisture wants to freeze in something like bread, it separates out and freezes on it’s own, this means less moisture is left inside the bread making it hard and dry, and ice accumulates outside of the bread - AKA, freezer burn."
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ne59fr | Why does water stop boiling when you lower the heat source (but is still more than the boiling temperature)? | I have observed this while cooking, but if you boil something at high flame and then turn the flame low, the liquid stops boiling. E.g. Water boils at 100C. On high gas, it starts boiling. That means the water temp is now 100C. Then if I lower the flame, the water stops boiling even though the flame temperature is greater than 100C at all times. At high flame, the water has reached 100C, so if I lower the flame the water temp should still remain 100C. | Physics | explainlikeimfive | {
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"As you apply more heat to 100C water, the temperature of the water actually does not increase beyond 100C. The excess energy is released as steam. This also explains why removing the heat source causes the water to stop boiling nearly immediately - there is no more energy being added, so no more energy needs to come out.",
"The pot of water is losing heat by several methods. The big ones are evaporation and conduction through the sides of the pot to the colder air around it. If the flame isn't putting in enough heat to overcome the losses to the air, the temperature of the water will drop until it's at a new lower temperature where those losses match the input from the flame.",
"While the flame is over 100 degrees, the air surrounding the pot is much lower and constantly trying to cool the water. The heat you're adding with the fire has to be more than the cooling effect of room temperature air, otherwise the water temperature will decrease.",
"> but is still more than the boiling temperature That is the key mistake here - the water is no longer at a boiling temperature. Since the temperature of the water is constantly being cooled by the air and even the pot holding it, the lower fire means that the water is now being cooled faster than it is being heated.",
"When your pot of water reaches 100 C it doesn’t turn to steam all at once. It take additional energy to convert the water from liquid to gas. This is called the latent heat of vaporization. It takes a lot more energy to turn water into a gas than it does to heat it from room temp to a boil.",
"Water will boil to the boiling temperature and not higher. You can't increase temperature above the boiling point. In normal pressure thats is. As soon as you remove it from the heat source it will stop boiling but stay just below it boiling temperature for a while."
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ne5fuq | What is the minimum size a particle can be and still have a specific location? | In other words, at what size does a particle switch from local to nonlocal (ie, collapse)? I Googled both versions of the question but didn't find anything (but maybe I'm posing the question incorrectly). | Physics | explainlikeimfive | {
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"There is none. Even large objects have quantum uncertainty in their location, it's just that the uncertainty gets vanishingly small the larger the object. It all depends on what level of precision you want."
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ne5gdq | How are data/files recoverable off of a computer after they have been "deleted?" Is this just Hollywood trickery? | Edit: Fantastic answers, thanks all for the insight! | Technology | explainlikeimfive | {
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"Imagine your hard drive as a big notebook. When you want to write something, your operating system finds either a blank page or one that has junk it can erase and writes the data there. But in order to find that file later, it needs to write a \"table of contents\", a list of each file with the page number it belongs on. When you go and delete a file, your OS is lazy and just erases the filename from that table of contents. That means that the data's still written in the book, the OS just doesn't know where. So data recovery folks will just ignore the table of contents and go look through the pages one by one till they find the data they want to recover. There's also ways to recover data even if you told the OS to go erase the actual data, very similarly to how using an eraser on pencil still leaves indentations and smudges where the writing was.",
"When you delete a file, all you’re really doing is saying “this isn’t needed, it’s OK to overwrite” but that doesn’t mean it immediately is reused. Think of it like checking out of a hotel room. You’re key no longer works, but the room remains as you left it until housekeeping needs the room and makes it up again.",
"For mechanical hard drives, to save time, instead of writing zeroes or random data on top of an existing file, typically just the reference in what essentially is a giant table if contents is erased. To the OS, the results in the same effect: that space now contains no data of any importance and is available for future use. However, unless something else is written to that space, the physical location that file formerly resided in the disc surface will contain the data that previously was that file. Software tools can instruct a drive to go to that specific location and read what's there even if the OS thinks there's nothing of importance, and the previous file can be recovered if it is still there. For an analogy, think of just erasing a single line out of the table of contents of a notebook, instead of also going to that specific page and erasing the data itself.",
"When A file is deleted off of the computer hard drive, most times all that is happening is that the title of the file and its location on the disk are erased from the File Allocation Table. The file itself still resides on the disk and can be recovered with the right software. This is why the department of defense Recommends that you wipe the drive completely three times in order to destroy any and all information that is on it before donating, or even destroy the disk completely to prevent the information from ending up in the wrong hands. Edit to add: DOD Specs 5220.22-M specifies that you should write a random character in every space on the drive 3 times to assure that it is not recoverable. I worked in the Justice Department and we would wipe all drives three times random and then one MORE time with all zeros as some software would view 'random' as 'not wiped.' All zero's in every space took care of this bit.",
"When you delete something, the operating system marks it to be overwritten on the hard drive and hides it from being seen or accessed. If it never gets overwritten, then special software can go in and unmark it and allow it to show up again. Deleting something by overwriting the bits with ones or zeroes is called \"wiping\" the information and is done with sensitive or classified material.",
"Usually, when a file gets deleted, the only thing the computer does is it throws a tarp over the data and hangs a sign on it saying \"VACANT\". All the data is still there. This is why deleting even really huge files is basically instant, because nothing actually got deleted, it just got flagged as vacant space. When you use programs that inspect your computer's storage, they have to trust the operating system to tell them which files are actually there or not. When the OS sees the \"VACANT\" sign, it skips it over and reports no files there to programs. If a program wants to write new data there, the OS will happily write new data completely over the old stuff as if it wasn't even there. There are special programs that don't go through the operating system's normal channels and check the storage directly themselves. They see the \"VACANT\" sign and instead of pretending there are no files there, they cast off the tarp and find all the old data. If you want to truly delete a file, you have to tell the operating system to not only mark the data as vacant, but to write new data over top of all the old stuff. Manually erase it. You can write whatever you want, but customarily one would write a bunch of binary zeroes over the old data. Doing this is often referred to as \"zeroing\" the drive. In some cases even this doesn't fully delete the data, though. On spinning hard disk drives, the platters that store the data store it as tiny magnetic charges all next to one another. Writing new data on the disk over top of old data in theory should flip the charges around perfectly, but it's not always so perfect. A shadow of the old data can be found on the old drive if you inspect it with very special tools. This technique can be used to recover data from platters that have even been zeroed out the long way. One also has to be worried about so-called \"bad sectors\". That is, chunks of the disk are reported to the computer as corrupted, failed, or damaged, rendering them inaccessible by normal means. Any data that is in a sector that goes bad will basically stay there (assuming it isn't damaged by whatever caused the sector to fail). Special tools can scan these failed sectors and recover data left on these too. If you want to defeat these kinds of data necromancy from ever bringing your data back, you may want to zero-out up to a dozen times in a row or more. Or you can just straight up physically shred your drive platters into bits or destroy it by other means. Completely destroying the physical disk is the only way to ensure beyond any doubt that the data is truly gone. It's just more time consuming to do, especially at the scale of a large office that could be dumping hundreds of these things all at once, so it rarely gets done. So no, this isn't entirely Hollywood trickery. If it's the first kind of deleted data I mentioned, this is something you can easily do at home with some readily available software. The other, more specific kind of data recovery is also possible, but I understand it is very expensive and doesn't always work. The exact nature of the recovery might be embellished for a show narrative, as all things often are, but it is rooted in some reality."
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ne5qt8 | using “royalty-free” beats for monetized YouTube video? | Other | explainlikeimfive | {
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"While a royalty free licence can be sold for a one-time payment, the rights holders can also choose to grant that license free of charge if they so wish. The site terms, as you've described them here, seem to suggest that's what they offer. (That's also assuming the site is above board and they own the appropriate rights to what they provide) Edit: I've just taken a look at their terms, and one caveat I'd note before you use their content is that they \"reserve the right to refuse / revoke use of [their] music **for any reason**\". They list some examples of pretty severe circumstances in which they would exercise this right, but in theory they could do so on a whim, and you'd potentially find yourself losing rights to your own work, or forced to pay royalties after all. Not trying to suggest they have any ill intent, but just something to be aware of - even if the current operators of the site are all honourable folks, who's to say it won't come under new ownership at some point?"
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ne5s8n | Why can't fungal toenails be completely removed? | Is there a reason extremely fungal toenails cannot be removed and have their nail matrix destroyed? It seems a lot of care is to do yearly trimming/drimmel | Biology | explainlikeimfive | {
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"The fungus is in your blood stream. I had my nails so bad I never knew why so many of them were even still hanging on. My doctor prescribed a heavy duty antibiotic I think it was terrafine but I am sure it is close. It was a ninety day course and I had to get a blood panel test to check my liver once a month on it. After the meds I had been warned I would not see any improvement for months. The doctor did well and everything went as he predicted. It even got rid of some athletes foot I had as well."
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ne6imx | How are we able to notice immediately when wearing stereo earset in the wrong side? | some stereo earset doesn't have obvious Left Right marking and wear it in the wrong side. But i could immediately notice when playing the music. Do left and right ear has different hearing characteristic? | Biology | explainlikeimfive | {
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"When some music of mine was in the final stages of mixing, we were all listening back to one of the songs. There were doubled vocal tracks, one on the left, and one on the right. I told the mixing engineer to switch them around. We all agreed that it was better after it was switched but couldn’t say why that was. It’s hard to know what it was that made me want them switched around. My best guess is that as people who read left to right, we want to hear the sound that happens first (even if only by a millisecond) in the left ear so the music is moving left to right."
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ne6ry8 | Why can't we swallow rapidly? | Biology | explainlikeimfive | {
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"Swallowing is quite a complicated process--it involves the movement of a large chunk of thyroid cartilage and also requires the passage through to the windpipe to be closed off, to avoid food or water getting in there. That all takes time. If you try to short-cut it then it won't work very well--I'm sure you've choked on something when you tried to swallow it too fast.",
"Not an expert, but maybe also an evolutional solution to humans not dumping food down to stomach too fast. Some food has to be broke down before by crushing with teeth and adding saliva is the beginning of digesting. Otherwise dropping large chunks of unprocessed food material fast on stomach would make the digestion harder."
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ne6w0o | how does my heart beat 100,000 times a day for 80 years without getting tired or messing up? | it just amazes me. i thought the heart was a muscle. it never stops. | Biology | explainlikeimfive | {
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"The heart is a muscle, but it's a different type of muscle from your skeletal muscle. Cardiac muscle cells have 10 times as many mitochondria as your skeletal muscles. Mitochondria are basically the \"power plants\" of your cells that break down glucose into energy. Because they have so many mitchondria, they have a basically endless supply of energy. Also, the heart beats rhythmically, with different parts contracting and relaxing at different times, so when one part is contracting, the other part is not doing anything, meaning every part of your heart gets a \"micro-rest\" during each heartbeat.",
"Your heart creates its own energy that prevents it from getting tired! It also has special things in place to make the job of beating easier like its sack full of fluid that surrounds it and prevents friction when it beats.",
"Hate to break this to you but your heart might well not do that without messing up at some point. And the reason it can do is if that if it couldn't, you wouldn't be here. It's evolved to have a number of facilities to keep it going, from the second it first beats in your mother until the day you die. It's not alone, however. There are all kinds of pumps, sphincters, muscles, etc. that have to work 100% for you to stay alive, everything from your lungs and the way they inflate to the valves that control air intake into them and the muscle tissue that pulls them open to \"suck\" in air. Hundreds of tiny autonomic systems. Your pupils in your eyes. The mechanisms in your existing muscles to keep them working. Your entire digestive system is far more complicated than the heart. The only real difference is that you don't \"feel\" your heart, unless it's in real dire straits, so you don't feel pain / tiredness in your heart, lungs, stomach, lymphatic system, etc. so you don't notice. You'll just think that your body is tired or that you're \"out of breath\" because the message is sent by other means rather than you directly feeling your lungs getting tired from too much exertion."
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ne7m8g | How Does One Go About Doing CPR, On Someone With Large Breasts Or Implants | Other | explainlikeimfive | {
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"Exactly the same as on someone without breasts. It's not acknowledged because it's not relevant at all. Also, it's not illegal to expose a nipple if you're trying to save someone's life. Indecent exposure does not apply in that situation.",
"If you haven’t retrained since you were a child, it’s probably not valid. You have to renew CPR certification every 2 years. So be careful- could save a life, but also end up with a lawsuit."
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ne7mjs | Biologically speaking, what makes someone take longer to ejaculate than others? | For example, I have a friend who needs at least an hour to do his business. But I could be done in less than 10 minutes if I wanted to | Biology | explainlikeimfive | {
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"An hr? Either someone's not doing it right or isn't as sensitive. More than likely just a white lie, lots of dudes say it takes that long, but realistically you shouldn't expect more than 20 minutes of constant activity. 10 minutes is fair, but since foreplay is part of the game, 20-30 minutes is totally normal. Shit, I have trouble going too early, so don't feel any sort of bad about it, consider yourself lucky"
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ne84xh | Why are nevada test sites not as radioactive as Chernobly | Chemistry | explainlikeimfive | {
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"Because in Chernobyl there was 190 metric tons of uranium which the vast majority was thrown all over the place, where a nuclear bomb might have 2 or 3 kg of nuclear material. So to get the same amount you need to detonate over 60,000 bombs. Edit: oh and forget to mention a lot of tests in Nevada were underground which contained the radiation as well. So that helps prevent the area getting to radioactive.",
"While they are both radioactive events, they occur in very different ways with different intended results. A bomb uses a small amount of radioactive material (typically a few kilogrammes worth) as the fuel, with the intention of using up as much of it as possible to create the explosion - spreading radioactivity is a side effect of creating a very big bang, which is the primary intention. The Chernobyl meltdown on the other hand was a runaway nuclear reaction creating a steam explosion in a reactor - so there was a lot more radioactive material to start with (to be used as a fuel source in an ongoing reaction), and this fuel wasn't used up as part of the explosion, but instead stayed intact as the explosion blasted it out over the immediate surroundings.",
"Bombs work different than meltdowns. A meltdown works like a dirty bomb. No atomar explosion but nuclear material thrown around far and wide. Bombs instantly split much of thr fissionable material thus leaving alot less radioactive particles. Also the radioactive particles that are creates by a bomb explosion have usually very short half lifes."
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ne8gre | Why do arm/leg muscles strengthen from repetitive use, but our wrist/hand muscles only seem to be damaged by it? | Biology | explainlikeimfive | {
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"Repetitive action in those kind of counts without recovery can damage anything. People commonly get worn out shoulders, knees and ankles from repetitive action for a few common examples. Excercising has specific forms meant to help protect joints and connective tissues. Repetitive activity, be it clicking, doing the same thing over and over on a factory line or a lot of sports activities typically does not and often involves doing that one motion for hours on end, hundreds or thousands of times, day after day instead of a relatively small number of reps before shifting to a different activity. Tldr; it's just too many times, too often and usually it's the joints or connective tissues that really suffer.",
"we do strengthen wrist and hand through repetitive usage. THE BIG PROBLEM, is that you give leg and arm time to recover post usage by not using them. Where as gamers don't really stop to it it time to rest, thus damaging the muscles. And also wrist contain much less muscle than arm and leg due to it being a joint.",
"You are misunderstanding the causes of carpal tunnel. Pro gamers are also trained so they don’t develop carpal tunnel. Carpal tunnel isn’t a condition that occurs due to repetitive use of muscles. It happens due to bad positioning and arm posture. This is analogous to a person with no training trying to lift something heavy with the result of a pulled/broken back. A properly trained weight lifter could safely lift the object but if someone with the same strength lifted the object with poor posture, they would break their back. Alternatively, someone working in housekeeping can also easily break their back from repetitively bending over to fix the bed sheets should they practice poor form. In the hospitality industry this is the most common source of injury amongst housekeeping staff. So in relation to playing long hours of video games, practicing poor posture and improper arm movements and practices on a regular basis can result in carpal tunnel. You should also periodically stretch your forearms and fingers before, after and during gaming hours. Fingers can certainly be strengthened. I would know, I used to sports climb competitively. The only problem with finger strengthening is that if done unsupervised or without the proper knowledge, you can seriously injure your fingers permanently because our hands and fingers have more important nerves that won’t heal as easily as a sprained leg or dislocated arm. Uncommon Knowledge: Pro Gamers(even chess players) actually hit the gym/exercise as much as they play video games. A healthy body makes a healthy mind and gamers certainly use a lot of their mental energy.",
"Someone weight training to strengthen their arm muscles isn't doing hundreds of movements per minute. If you were clicking the mouse at the same speed as the guy is pumping his iron then you would be very unlikely to get RSI, but because you're doing it as rapidly as you do then it causes damage. To use an analogy: if you're driving along with the engine in your car doing 2000rpm then it'll be fine. Try and take it up to 8000rpm and chances are you'll damage something, even though the engine is doing exactly what it was doing before, only faster.",
"I'm going to add to the other, very good answers that it probably has something to do with the fact that there is no resistance which is key to strengthening. When you're gaming you're effectively rolling the mechanics or your bones and joints back and forth over and over again, the muscles aren't really being trained or strengthened, they're simply twitching back and forth. This will probably lead to more wear and tear than strengthening, but probably really good twitch responses which is where they would improve, but long term being able to twitch and react real fast isn't going to be of much use and will likely just cause wear and tear.",
"They don't get damaged by it. They get damaged by overuse just like muscles would do. Can you do 500 sit ups every day? Yeah good luck walking after 3 months whem the fibers tear up completely. If its used properly and not overused it will not get damaged. Same goes for wrist and fingers.",
"Others have given excellent answers but an additional issue is how our hand and finger anatomy is set up. It takes a LOT of muscles to do all the motions a hand is capable of: each finger can go up, down, left, right, and has three sections that can (theoretically) move independently, plus the thumb can be moved to an opposite (opposable) position, plus the wrist can change the orientation in a nearly 100 degree cone. The hand is capable of incredibly delicate motions (like picking a single flower without crushing it), broad ones (like pushing open a door), and strong ones (like holding a 50 pound weight or supporting the entire body while climbing). There's simply no way to get all the muscles required to fit into a small enough package entirely within the hand. So instead a bunch of the muscles are in your forearms. You can test this out by gripping your arm below the elbow and moving your fingers around, or looking at the underside of your wrist while you move them. The muscles pull on long tendon \"cables\" that run through your wrist and connect to various points on the fingers. Some compromises have to be made though. Some can't be moved entirely independently, and at some angles strength and dexterity aren't the best because the cables are bending around sharp turns. But the biggest one is that all of these cables have to go through a small channel in your wrist that ALSO has to be small and flexible if it wants to move as well. So these \"carpal\" wrist bones have a tunnel in them, and those cables are packed in there and can be moving backwards and forwards and sliding past each other constantly. But if one of them gets irritated it will swell... which makes the space in the carpal tunnel smaller, which inflamed them, which causes them to swell, which narrows the space, which restricts their motion and inflamed them, which... you can see how it spirals out of control. So it's not the muscles that are getting weak, it's the connections between muscles and joints that are getting irritated and if not given a chance to heal will only become worse and worse. That's why proper posture and wrist alignment is so important."
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ne8o9q | what does crunch company - crunch behaviour mean ? | i dont understand what this means at all, people ask if the company youre working is crunch wtf does it mean? but really explain it to me like im five years old | Other | explainlikeimfive | {
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"Crunch culture is right before the deadline to a major project takes full priority of your life. You ignore your kids, spouse and other commitments to finish a project that has a very hard deadline. Usually workers in this type if situation work 12 hours a day 5 to 7 days a week to make the deadline.",
"Crunch is largely specifically related to software development, and even more directly to video game development. The basic definition of crunch is \"extreme overtime worked to meet deadlines\". If an average work week is around 40 hours over 5 days, crunch is sometimes up to 120 hours over 7 days. Depending on the project and the amount of work that needs to be done, these conditions can be maintained for months on end. Some companies are notorious for going even further, such as renting nearby apartments for workers to sleep in rather than them spending time commuting to and from work. Sometimes, crunch is voluntary. Developers put a lot of pride and even self-worth into a project. A small change in sales or reviews for game projects can mean the difference between getting a contract to make another game or the whole company closing down. No one wants to be the one member of the team seen as putting in less effort than others, or feel regret after the fact that they could have done more, but didn't. Other times, crunch is mandated by the employer. Even though the workers are still only getting a salary intended to cover a 40-hour week, the company will pressure workers to stay late, not take breaks or weekends, and work longer than anyone thinks is reasonable. Crunch can start a year or more before a deadline, sometimes in the form of \"pizza nights\" or \"crunch prevention\" - the thinking is that if you overwork now, you can prevent more overwork later. Ultimately, the problem comes down to the unpredictability of software development and the unmoveable nature of release dates for products. Something has to give, and advertising and company reputation are very valuable elements that are seen as more important than the health and sanity of the workers. In many places where software development is a major industry, there is a cultural belief that each worker should feel lucky to have their job, and that they could be replaced by a person more willing to crunch if they don't go along with the scheme."
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ne8wco | Neural networks/Machine learning | I'm a student of computer science, so you don't need totally ground level resources, but I'd like some really dumbed down explanations of neural networks. All help is appreciated, thank you :) | Technology | explainlikeimfive | {
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"A neural network mimics the function of a human brain. You take a very simple unit and call it neuron. It has several Inputs, one Output, weights that multiply the inputs with a constant, and an activiation function (a simple one would be sum(Inputs) > constant but often we use something smooth like a tangens) Okay this alone can't do much. But if you connect many of them they can learn to solve tasks through abstraction an pattern matching. You connect many of these neurons in several layers and then alter their weights so that the whole networks gives you a good output for the given input. So as an example you want to check if pictures have trees in them. So first layer receives raw pixel data and generates outputs that could for example be areas of dominant colours. The next layer takes this and outputs areas it recognizes as certain shapes. The next layer then looks for shapes that might resemble trunks and crowns, and then the last layer only generates a binary output \"Tree/No Tree\" You don't define how the network shall do that, it decides itself what kind of abstractions it uses (and it's almost impossible to figure that out) During the training you just wiggle the weights around until the number of correct guesses is maximized."
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ne9mto | Why does a cough tend to linger long after a cold is gone? | Biology | explainlikeimfive | {
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"Your lungs are made up for loads of tiny pockets called alveoli, if you cough a lot theres a potential for a little damage and reduced lung capacity. Combine that with airway and bronchial irritation and you get a hard time breathing and a lot of forced air. This causes you to try to clear your airways by coughing, and the cycle continues. Now for most people this isn’t much more than a day or so. But for someone with asthma or someone like me with reactive airway “disease” it can last weeks. Go see a medical professional and there is a good chance you can get an albuterol inhaler to help you stop coughing. As someone who has dealt with that a lot trust me I can sympathize. Lmk if you have any more questions about my experience with crappy prolonged symptoms :))"
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ne9tfw | Does Liquid IV hydrate you more than as if you are drinking regular water? If so, how? | Biology | explainlikeimfive | {
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"It's basically electrolytes to make water \"isotonic\", wich means the electrolyte levels (salts/minerals) match the ones of our body. When you drink regular water it doesn't match the mineral concentration your body needs so some excess water is flushed out (same if too much minerals are in it though). So yes, you get more hydration by drunk volume. But thats really only a concern when you have limited water with you, otherwise you can just drink more and let your body solve it themselves."
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neakw0 | what does a shark “feel” from magnetic fields that allows them to navigate by it. | I recently read an article about a shark using the Earth’s magnetic field to navigate great distances across the world’s oceans. I’ve always been curious about this. Does the magnetic field give them a physical sensation or tingling in their brain or is it more of driving a subconscious instinct? I guess the same would apply to a bird or a butterfly or any other creature that uses magnetic fields to navigate. | Biology | explainlikeimfive | {
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"What do you feel when you're sensing light or sound? It would probably be similar for a shark and the magnetic field. It's probably impossible to tell what an animal senses with a sense we don't (really) have. But just by examining our other senses, we can get a glimpse of how senses that we don't have might feel.",
"I remember reading an article a few years ago about a guy who invented a \"compass belt\" - essentially a belt with a series of rumble motors around it, which would vibrate to indicate north. He said that once he got used to the sensation it became almost subconscious, and he found it vastly improved his sense of direction and position. I imagine animals that have the ability to detect magnetic fields \"feel\" a direction in a similar sense."
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neapj1 | why does the graphics rendering of night scenes more demanding than day scenes in games? | This may not apply in all games but I've played some games with day/night cycles, but overall the experience I got was that most of the time, when during night time, the game had FPS drops lower than day time. For example, I played NFS Heat and I get around 30 fps at day. When I play at night, for some unknown reason for me, it drops about 5-10 fps at most. It's a very shallow question I know, but I would love to get an answer from y'all since this has been one of those things you can't really shake off your mind | Technology | explainlikeimfive | {
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"I would guess it has to do with the number of light sources in night vs day. Daylight is usually just a single sun source, whereas the night scenes have a ton of different color neon lights and stuff. They *should* bake a light map so that its less intensive but I think those games like to use a lot of dynamic sources that will change reflection bounces based on movement in the scene rather than being statically painted. You should be able to lower graphics settings to get less dynamic lighting (look for a setting like Global Illumination or something along that line)",
"It most likely has something to do with how the game handles reflections and shadows, but this will vary greatly on a game by game bases."
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neapu5 | Why do some vegetables or fruits come in a variety of colors but others don’t? | I must have missed something in biology class, but this question popped up in one of my group chats and it’s been stuck inside my head. Why is it that, for example, peppers can be either green, red or yellow, and same goes for apples, but bananas are only yellow? I know that certain varieties aren’t available everywhere so maybe I haven’t seen them, but I’ve never seen a red zucchini before. Can someone explain this? | Biology | explainlikeimfive | {
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"Bananas are green before they are yellow. And pigments change as the hormones in the plants change. Ripening hormones are released and that signal cells to create pigments. Those pigments attract seed dispersers, usually animals that eat fruit. Then those animals spread the seeds around and create new plants. They either spread them by eating them and pooping them out in a new location or by getting the seeds stuck to them and dropping them off somewhere later. But the important part is just that natural selection causes specific relationships between plants and the animals that they rely on for seed dispersal. Whatever color attracts the most effective seed dispersers will be more successful and have more seeds spread, carrying that color gene. So the pigments are determined by genetics, and the genetics are spread around by the animals that are attracted to those pigments."
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nebhad | How do massive trees transport oxygen gas to their deep roots? | Biology | explainlikeimfive | {
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"They don't - the roots absorb small amounts of oxygen from the soil. This is why you can drown plants by submerging their roots. If you've seen a submerged Mangrove you'll notice they have the ends of their roots poking out of the water. Good quality soil is porous and has oxygen exchange both for plant roots and soil microbes."
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nebk54 | Why are we more likely to be allergic to something like nuts or wheat than we are to other food? | Biology | explainlikeimfive | {
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"It's a thing of probability. You're probably allergic to a host of things, but you never come into contact with said things, because its not a common part of your diet. However, allergies to nuts and wheat are very common in our perception because both nuts and wheat are commonly consumed in the western world. You might be allergic to durian fruit, but you wouldnt know that until you eat them. However, durian fruit arent that common of a food in the west, so a lot of people who are allergic to it would go their entire life without knowing."
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neblsu | How do trees talk to each other using mycorrhizal fungi? | Biology | explainlikeimfive | {
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"The mycelium stretch out across the root systems of multiple plants and plant species, and help to carry chemical messages between them. It's hypothesised that the fungi help to maintain the health of the trees in order to ensure they (the fungi) get the carbon and sugars they need to thrive. Two authors to read on this are Peter Wohlleben (who coined the term 'wood-wide web') and Suzanne Simard."
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nebs9c | Why are humans depicted in paintings from ancient civilizations like different than now? Weren't there artists who could paint realistic paintings? | Weren't there artists at that time who could draw humans for what they actually looked like. For instance, look at the paintings of kings from the 17th Century or before. | Other | explainlikeimfive | {
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"What you might consider \"a realistic picture\" is actually fairly divorced from the perceptive experience of seeing a human face or figure in motion. It's not actually intuitive to imagine and execute an ideally framed and posed static human figure in flat lighting. A *lot* of artistic theory had to be developed to get to a stage where we might consider art as truthful representation as opposed to symbolic shapes. There also had to be technological leaps: devices like the camera obscura and other machinations with mirrors helped early Renaissance artists freeze a frame to preserve fine detail. Even today if you asked an accomplished painter to paint a model human from memory, they'd struggle. We needed to develop artistic traditions like using models or photographic references, and for many human cultures the idea of sitting still and staring into space for a whole day so your face and shape could be accurately recorded would have been farcical.",
"The purpose of art isn't always meant to be accurate and realistic. The Renaissance really saw the growth of art method and the adoption of styles that closer replicate real life, including professional studios and guilds, the use of models, perspective drawing, paints and oils, etc. There's a huge difference between the work from someone who is a full-time painter who learned his art from a master over many years, and a monk who spent years copying out the Bible and adding caricatures in the margins.",
"A picture gives information. The information an artist from a long time ago wanted to transmit might be very different from what we want to transmit now. For example, if you’re using a picture to tell a story (helpful if most people can’t read), and you only have one surface because the equivalent of paper is rare, you’re going to put most of your time and skill into getting the story told in a fixed space.",
"One potential answer is lenses. The technology to make high quality lenses first emerges in Holland and Italy during the 15th century. These allowed artists to project images of a sitter onto a canvas and to sketch the main lines and shades, giving the hyperrealistic paintings the renaissance became famous for. (It's also worth noting that many of the paintings involve subjects where this technique would be particularly effective, like shiny armour in a darkened room with a single 'spot' source of light. A renaissance artist's studio would have resembled a photographer's studio today) On the other hand, Classical Art (and some [Egyptian Art]( URL_1 )) made sculptures that are near perfect, and their mosaics are also close to realism, and that can't be explained with lenses. I think it's clear that stylisation played a significant role: it wasn't just that people *couldn't* do 'realistic' (that is, as we know from photographs) portraits, it was that they weren't trying to. They were often aspiring to something else: to show the power of a ruler, to represent the Gods, to communicate something or exhibit a particular aesthetic sensibility. The Greek philosophy of art (Plato and Aristotle) *did* expressly see mimeticism (looking-like-the-thing) as being the purpose or measure of good art though, which explains why Greek and Roman mosaics, sculptures, and [sarcophagi paintings]( URL_0 ) are as realistic as they are.",
"Can you go draw a hyper realistic depiction of the world? If you're anything like me, then no you probably can't. You gotta learn the techniques and practice first right? All these techniques you can just find online nowadays were discovered by someone and perfected by others. Ancient peoples may not have had all the tricks and tools that we modern humans take for granted.",
"One way you can look at it is that realistic drawing and painting is a language that needed to be developed over centuries to reach the current level of sophistication. The rules of good grammar seem obvious once you’ve learned how to speak fluently, so children who make grammar mistakes seem quaint or unsophisticated, as their mistakes seem obvious to the more fluent speakers. Simply learning the rules of an already existing language when you are surrounded by fluent speakers is relatively easy and almost every child does this eventually. That is a totally different thing than reverse engineering a visual language from scratch, which was what the process of discovery of the rules of realism was. As mentioned by others here, humans didn’t have mirrors for a long time, photographs are a relatively recent development technologically. Translating a 3D scene to a 2D surface is incredibly challenging and not obvious at all. How many kids draw in correct perspective innately, using vanishing points and foreshortening? Probably zero. If left to their own devices, how many kids would spontaneously develop those techniques on their own if they were never exposed to more sophisticated art? I’m a professional artist and it took me years of practice to be able to draw and paint fairly photorealistically and I had the benefit of the entire history of artists before me, as well as patient art teachers. All the techniques are easy available to study online these days, but what percentage of the population can draw a recognizable portrait? Probably a low percentage. That’s because drawing realistically is hard even if you know the rules!",
"My history teacher taught me that ancient Egyptians realized how perspective worked, but that the way in which they depicted people, where both eyes, arms, legs, etc. were visible at all times, was because it was necessary to depict all of those parts as a sort of blueprint. Presumably the perceived risks could be that incomplete bodies would be given to those depicted in the afterlife. As such, it could have been a practical choice rather than an artistic one or one of limitation.",
"Because it depends on what the painter is trying to do. Realism may not be the aim - it may be more about projecting an ideal type (typically of monarchy or nobility) or conveying a set of ideas about society and the place of the subject in it - for example the king as a blend of Solomon and Joshua. So what we see as distortions carry meanings according to widely-held archetypes. Often these are lost, but sometimes we can reconstruct the underlying patterns. Even where realism can be done, it may not be - Romans were realistic in their ancestral portrait-busts, but imperial imagery is more stereotyped.",
"Is it not possible that the really good ones just didn't survive as they were done on perishable materials? Thinking about rare survivors like the Portrait of the Boy Eutyches [ URL_0 ]( URL_0 ) which look like 17th century paintings as well as other 'Fayum' portraits [ URL_1 ]( URL_1 )",
"Egyptian paintings stayed almost *exactly* the same over 3000 years. It hard to explain such a tiny degree of variation over so many artists and over so much time. I watched a documentary where an archeologist argued that the art style of Egyptian paintings were strictly enforced by the religious authorities. Unfortunately, I can't remember the name of the documentary or the archeologist.",
"Until the Greeks, the idea of humanism wasn’t particularly valued. The time, costs, and effort required to make artwork meant that artists focused on cultural significance over physical representation (also heavily limited by resources like pigment). Vénus de Renancourt is a 23000 year old totem of virility (there are quite a few Stone Age Venus totems ranging from 25000 years ago), as such you have emphasis on the breasts and hips. These sculptures share a striking resemblance to our own perceptions of the human body with regards to emphasis and importance. I can’t find the exact source, but there was a psychological experiment where they mapped the human body with regards to importance, the hands, head, eyes, sensory organs, and reproductive systems were much larger than other areas. This is akin to most stages of art development as well, novice and intermediate artists will often draw the hands, eyes, and head larger in proportion. (Sensory homonculous) Christianity and the concept of god as human (Jesus) led to more life like depictions of ourselves and gods. The flatness in perspective is attributed to an idea of how it was thought the human eye saw things, like an inverse projection. Humanism made a major comeback in the renaissance, the explosion of scientific and technical development emphasized humanity as having a likeness to the gods, as a result the gods became more human and a pinnacle of human form developed. This has shifted over time with different forms, like the more portly Rubenesque forms, or the masculine dominated forms of Michelangelo. Furthermore we got the camera obscura, the pinhole camera, which allowed artists to directly trace over projections. Something interesting to note is the number of left handed depictions of people during this time, likely because this method mirrored the subject. TLDR: art is a time consuming and expensive process, as such we focused of representation of significance. Technological and philosophical growth lead to more human centric representations.",
"Basically because of the lack of medium (paper, canvas, etc) and tools (brushes, pens, etc). Ancient civilizations did not have medium and tools readily avalaible for an artist to spend hour and hours practicing till they were able to perfect themselves enough to capture a realistic depiction of a person. This basically changes siginificantly during the Renaissance, where these tools became more common.",
"A number of reasons: Style. Different people/eras have different preferred styles. Materials. Not every era had access to good paper, brushes, etc. Colors. We take for granted that we have access to every color under the sun, but that simply wasn't the case back in the day. Some colors weren't available, or they were so expensive as to be basically unavailable. If you don't have access to, for instance, red, painting a realistic portrait is hard.",
"A lot of it was cultural. A lot of medieval art favoured expressionism over naturalism or realism, particularly religious works as it was more important to evoke feeling and encourage individual interpretation of the biblical stories than anything else. But if you look at a painting of Henry VIII (early 16th Century) or the tomb of Richard I 'The Lionheart' (12th Century) you'll find they did do realism in certain instances, where it was deemed important to capture something as it appeared properly.",
"What they are trying represent is different. Frequently, The largesst person in a picture was the most important, not because they were tall.",
"Also a little bit of painting the beauty goal that everyone was trying to reach at the time and lack of knowledge about anatomy.",
"There's styles people liked throughout the ages, but mostly remember that artists couldn't have as much time and materials to practise as today. Lots of the good ones were sponsored most of their lives, before that became a habit the ones available might not be as good.",
"it's mainly related to the Fall of Constantinople in 1453. that was when all the ancient texts on Euclidean geometry were brought back to Europe, which enabled people to calculate proportions and angles. one of the earliest examples of hyper-realistic art in the modern times goes back to Albrecht Dürer, who lived at the beginning of the 16th century",
"Depending on the era, it’s intentional. In the medieval period, the influence of Christian religion affected the way artists painted. The physical body was sinful, so artists did not 1) study anatomy nor 2) make any effort to paint realistic human figures. That’s why you see highly realistic depictions before and after, but then you have a block of time when skilled artists painted like kindergartners.",
"Perspective drawing was only made popular after the Dark Ages in Europe. I'm sure some people could do it, but the focus was more on capturing a larger scenario like a battle or a royal ceremony than depicting a photorealistic apple, y'know? Arts like painting and drawing weren't sponsored or even encouraged as a practice until patronage was possible (in a society with unequal wealth distribution funny enough), so likely nobody had the time, money, or resources to develop their own style of what we consider \"realistic\" art.",
"I've read a bunch of these comments, and think most of them are accurate. The one that I think is missing though is the quality of the materials at hand. I don't know that even the greatest artists of today could do a very realistic painting with what was basically finger paints made from mud. And if they can, I'll bet it'll take them a long time. Just going by what I've seen elsewhere on reddit, artists will do amazing work with just a ballpoint pen, but put in 200 hours. Not something you can really afford to do on a cave wall.",
"A lot of ancient paintings are riddled with symbolism and superstition. Several periods of egypt held that leaving off a limb in the image of someone was a big problem, hence a lot of the weird profile stances, for example. They were also often as much utilitarian and stylistic as they were art, intended to tell a story. Anime/manga isn't hyper realism but it's a huge art style in many cultures at this point and as much as we laugh about things like weird hair=protagonist those tropes convey an immense amount of information to the viewer without a single written or spoken word, which is a big deal in minimally literate cultures. Tldr; yeah the renaissance in particular saw a big uptick in realism but it has as much to do with not TRYING to be hyper realistic and thus not needing to figure it out as it did with not being able to."
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nec5kx | The Importance of the Fibonacci Sequence and why it even matters if it does | Mathematics | explainlikeimfive | {
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"It's not really important in itself, but it's a simple example of a \"recurrence relation\" or \"difference equation\", i.e. a system whose state changes in discrete steps according to a formula that uses the values from previous steps. These have extremely widespread applications throughout maths and science - you can use them to model real-world phenomena, or to calculate approximate solutions to problems. > Also, why does the sequence start with 0? Why not -3 which is the sum of -2 + -1? You can start Fibonacci sequences with any other pair of numbers if you want. Some properties of the sequence change, but others stay the same regardless of which numbers you start with. There are also generalizations of the Fibonacci sequence, such as the Lucas sequence, where instead of simply adding the previous two terms, you multiply them both by some specific number first. > Additionally, I see the pattern / spiral in nature too. Why is it a spiral? Can all spirals be placed on top of the Fibonacci sequence? A particular kind of spiral called a logarithmic spiral is commonly found in nature. There is a specific logarithmic spiral called a \"golden spiral\" that is related to the Fibonacci sequence - for some reason there is an urban legend that golden spirals are especially common in nature, but they actually aren't.",
"Worth checking this out URL_0 . But to summarise it’s a useful sequence that appears in nature and is used in many fields. Additionally if you divide one number in the sequence by the one before it you get an approximation to the golden rato. The further in the sequence you do this the more accurate you get."
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necvvo | How do calculators find out the square root of a number? | Mathematics | explainlikeimfive | {
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"Depends on the calculator, but here’s one approach, illustrated for square root of 100 1. Make a first estimate (eg half it, your calculator might make a better guess though) = 50. 2. Add that guess to your target divided by that guess, and halve. So (50 + 100/50) / 2 = 26. That’s your next estimate. 3. Continue until the difference between succeeding estimates is small (again depends on your device). 50 - > 26 - > 14.9 - > 10.8 - > 10.03 so it’s getting there very quickly. Edit: as the other poster said, the actual algorithm used by any given calculator may be a lot more sophisticated.",
"Numbers in computers are represented using the \"significand\" made of significant digits and the base two \"exponent\" which tells how big the number is. For example, 96 is 3 * 32 or 1.5 * 64 and will be stored as 1.5*2^6 with 1.5 as significand and 6 as exponent. Square root of 96 is then computed as the square root of 1.5 (as read from a table in memory or with a simple approximation algorithm) multiplied by the square root of 2^6 which is 2^3 or 8 in decimal. Edit: the approximation algorithm is far out of reach for an ELI5, there are many variations described here : URL_0 For an ELI45withaPhD on some computation hacks involving simple functions like square root, you can also read : URL_1",
"Even though Wikipedia has a gift for explaining it in a way nobody but mathematicians can understand it, many of the methods are really simple: 1. Make a guess 2. Repeatedly adjust the guess until you come closer. You can easily check if you're above or below the correct number by squaring (multiplying your guess with itself). Let's say I want to calculate the square root of 99. I guess that it's 1. That's off by a lot, but that doesn't matter. 1 * 1 = 1. That's less than 99, so 1 is too small. Let's double it. 2 * 2 = 4. Ok, 2 is still too small, let's double it. 4 * 4 = 16. Still too small. 8 * 8 = 64. Still too small. 16 * 16 = 256. AHA! This is now bigger than 99. That means the square root is between 8 and 16. Let's try something in the middle. 12 * 12 = 144 Ok, so the square root is smaller than 12, but bigger than 8. Let's try something in the middle. 10 * 10 = 100 Ok, so it's between 8 and 10. 9 * 9 = 81 Ok, between 9 and 10. 9.5 * 9.5 = 90.25 9.75 * 9.75 = 95.0625 9.875 * 9.875 = 97.51 9.9375 * 9.9375 = 98.75 We now know it's between 9.9375 and 10. The middle between that is 9.96875. 9.96875 * 9.96875 = 99.37 So it's somewhere between 9.9375 and 9.96875, and if you want to know more exactly, you repeat this a couple dozen more times and you'll have an answer that's precise enough for the number of digits your calculator can display. As you can see, we got a pretty good answer with a few steps that I could do manually This is called a binary search, and works for many other problems too. The actual algorithm uses a smarter way than \"halve the difference\", I'll write up an example once I'm out of bed and have a real computer and keyboard instead of a phone."
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nedh4z | Why do we have kneecaps bur not elbow caps? | What benefits do knee caps provide and would they be beneficial on the elbows as well? | Biology | explainlikeimfive | {
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"The knee cap isn't primarily for protection, although it may seem that way. It's there to provide more leverage for the muscle that extends the lower leg by increasing the angle it acts at. This is extremely useful in a species that developed as long-distance runners, as humans did. It wouldn't be very useful on the arm because extending the arm isn't an action that benefits from extra leverage--if you could somehow have one on the \\*inside\\* of the arm then that might help, but since that would also get in the way of the action of closing your arm, it would probably be more harmful than helpful.",
"Your knees are under significantly more stress than your elbows since they constantly have to support your weight while you’re walking around. So there’s more need to support all those tendons and stuff there than there is in your elbow. You’re also more likely to just hit your knee since your legs bend forward. Plus, a leg injury is probably a much more certain death sentence than an arm injury. Neither is great, but if you can’t run you’re an easy meal."
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nee2ij | If nearly everything has “cancer causing chemicals” in them, how haven’t more people developed chronic diseases as might be expected? | We’ve all seen the “chemicals known to cause cancer or reproductive harm in the state of California” warning, from our literal refrigerators to other appliances, from plasticware we use to eat to laundry detergent and our body soap. So I would love to learn about how people can and do live full, generally healthy lives using these products when these toxic chemical warnings scare the heck out of me! | Chemistry | explainlikeimfive | {
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"For cancer to form multiple cellular safety mechanisms have to fail. The body is pretty good at detecting and eliminating cancer cells and DNA replication also pretty robust (but not perfect because perfect copies don't allow for evolution). Cancer causing chemicals just make damage to DNA and therefore mutations more likely and will therefore increase the risk of getting cancer over time but it's all a game of chance.",
"Well, more people have actually developed chronic diseases and or cancer than you might expect. According to estimates from the International Agency for Research on Cancer (IARC), in 2018 there were 17.0 million new cancer cases and 9.5 million cancer deaths worldwide. By 2040, the global burden is expected to grow to 27.5 million new cancer cases and 16.3 million cancer deaths simply due to the growth and aging of the population. 1 in 3 people is actually expected to have cancer at some point in their life. I say that again. A third of the entire population is expected to get cancer at some point in their life. URL_0",
"A chemical can be known to cause certain types of cancer if you're exposed to a large quantity of it, but it *can* be safe in moderation or small doses. There are lots of things we understand about the world around us, even the food we eat, that can help us stay informed about how and what we eat. Like fatty red meats can be really unhealthy when you're eating a lot of them, or candies and sweets and sodas that are rich in sugar. These also cause different illnesses and disease if you're not careful with them."
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nef0us | why did two sexes become necessary for procreation instead of one that handled both aspects? | Biology | explainlikeimfive | {
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"genetic diversity. what you suggest is asexual reproduction which many bacteria and some aquatic life here and there do. the issue is that every copy is more or less identical to the first. why is that bad? well, a single disease could now wipe out an entire population. more so no form of reproduction is without glitches here and there and now that bad trait will be copied for every and the species ability to survive decreases. sexual reproduction ie mixing of two brings in a lot of diversity in the gene pool. yes certainly you can get all the worst traits mixing but you also get a case where all the best ones can mix and you get a super awesome offspring who will go on to likely make more super awesome offspring. that's why sexual selection is such a big thing. they want the best mate to ensure their offspring has best chance of surviving. why mutts ie dogs of unknown breeding are usually much healthier than purebred dogs. they are mixed with everything and are likely to be really hardy and resistant to a lot of stuff.",
"For the same reason you don't have kids with your mother. You need to diversify your gene pool or you'll just come out with slightly inferior copies, and eventually will only produce inbred and genetically stunted copies.",
"Some species have more than two sexes. One species of fungus has over 20000. It's all about giving the offspring a wider variety of genetic information to build from. A faulty gene from one parent can be patched with a good one from the other.",
"Two sexes aren't actually necessary. There are many creatures that reproduce asexeually and do fine. There is this hideous tick that just clones itself and is about to become a problem in the Eastern US. Several species of long tailed lizard in three southwest have no males. But asexual reproduction carries a risk. There is very little (if any) variation among individuals of species that reproduce asexeually and that makes the species very susceptible to extinction when environmental conditions change. So that tick will not last long as a species. When something evolves to kill it, they will die. In a species that reproduces sexually, there is enough variance among members that it is more likely that at least some individuals will survive a pathogen and reproduce. For example, humans are largely immune to leprosy. The individuals who were susceptible did not often reproduce, so their susceptibility was not passed on to future generations.",
"Hybrid vigor. Well, that's something else but the idea is the same. Mixing genes from the same species corrects mistakes as well as introducing potentially positive mutations. Cloning has the drawback of cloning errors as well so we don't want that and it's why you don't want kids with your close family members... unless you do."
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neg584 | How and why does music influence our moods the way it does. | It seems to be hardwired into most people, but I don’t see how that is possible. Also, why are there people that do not experience any emotion when listening to music? | Other | explainlikeimfive | {
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"I think you can TLDR this in two ways, and fair warning, my own thoughts are interspersed: 1. Biological/neurochemical pathways 2. Anthropological significance Long version: 1.Biology: our brains break down sound in a ton of different ways and send out all of the parts of a song to different places (including the place that makes us feel stuff.) We can think about this like all of the ingredients in a sandwich: * Bread = our ears - the things that capture the sound * Ham/Turkey/Tofu/Chickpeas/whatever protein = our cerebellum - the thing that decides where information gets sent off to. The biggest, but most densely-packed (neurologically) part of our brain. Keys into a song's rhythm - the bass, the drums, fast or slow tempo * Cheese = auditory & prefrontal cortexes - the things that assess sound and memory (along with a lot of other stuff.) Focuses on melody, loudness and helps us to predict what the next bit of the song might be (like in a pop song when we expect the next chorus - it's pattern recognition of what already came before) * Lettuce = our hippocampus - the thing that helps music \"stick\" in our brains - our memory center. This is how we can at least vaguely remember a song after hearing it one time * Tomato = our amygdala - the thing that makes us feel stuff. This is the area that takes in all of those different parts and translates that to an emotion. It does this using neurotransmitters, which are hormones that make us (broadly) feel happy, scared or sleepy. A reason why some people might not feel anything when they listen to music has been shown through study to connect to lower connection between the auditory cortex (where sound is assessed) and part of our limbic system that controls dopamine (the neurotransmitter that makes us feel happy.) Less dopamine = less happy/indifferent. This takes us to: 2.Anthropology: since prehistoric man, we have used music to imitate other life, express ourselves and celebrate various rites and passages. * Prehistoric man used unsophisticated instruments (like things made out of cave bear jawbones) to recreate nature sounds. This might have helped them hunt or just appreciate nature - both eating and enjoyment are happy things (total speculation, personal theory) * After that there are a lot of suuuuuper old accounts of people making and playing music to commemorate things like births, deaths, harvests, general merriment, etc - they were a form of expression or accompanied forms of expression like theatrical plays. * This is important (once again, totally my opinion) because from an evolutionary/civilizational perspective, this is a hand-me-down, learned behavior - to engage in and appreciate music. Our ancestors celebrated the equinoxes by playing music, dancing and probably getting drunk. Hey! Who doesn't love a holiday party with bad renditions of \"Jingle Bells\" in the background? (Answer: no one. Well, hardly anyone. There's always the oddball :) ) Really, this is the basis of what my answer comes down to - there are *reasons* why our brains \"do\" music, but I think how we absorb and interact with music is largely something we've all internalized through the ages along with something that we put our personal spin on. We are, after all, the ones who decide what we like around us when we're happy, sad, angry, etc. And then we just pass it along."
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negda7 | Are human brains really blank canvases at birth? | Biology | explainlikeimfive | {
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"No. Evolution has pre-programmed us with a lot of instinctual behaviors to help us survive our first few years of life. These behaviors, such as crying, suckling, etc. are not learned. Additionally, your brain also develops a rough \"template\" for how you will eventually develop, with a lot of functionality pre-made (basic understanding of senses, basic ability to move, etc.) and more somewhat determined by your ability to produce neurotransmitters (such as someone with dopamine and serotonin production issues potentially being at elevated risk of depression). Scientists are still unraveling the mess that is the human brain to sort out which parts of our minds are genetic/innate and which parts are learned behaviors. Still, there's pretty strong consensus that at least a large minority is innate."
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nehcv6 | Why do colors fade out when things (e.g. textiles) are left out in the sun? | Chemistry | explainlikeimfive | {
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"The colors in things like dyed fabrics are made up of a lot of tiny particles that are bonded to the fabric. UV light from the sun can break up the particles and bonds over time, which removes the color from the fabric. Basically, it gets old and crumbles away",
"Sun see colour particles having fun times with fabric. Sun is jeolous. Sun sends UV goons with big sledge hammers down to the pillow. UV goons have field day when sledgehammers. Pillow colours no longer vibrant, because sun is jealous. **^(Sun is bad. :()**"
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nehjdh | Why can only men grow bushy beards? | Biology | explainlikeimfive | {
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"It's a testosterone thing. Male hormones promote facial (and other) hair growth. That's why it starts at puberty. Some women who have unusual hormonal situations can also grow beards, but most will take steps to remove their facial hair as it is societally frowned upon in western cultures.",
"Body hair growth is modulated by a signalling molecule in the body called DHT. DHT is manufactured from testosterone. Although women have some testosterone, men have a hell of a lot more of it, so a lot more to convert into DHT. Women could theoretically grow bushy beards if for example a mutation greatly increased testosterone levels or caused a bug in DHT processing that made low levels of DHT cause a lot more hair growth than intended. This is why trans men can naturally grow beards just from hormone replacement therapy: More testosterone is added to the body, which means more DHT, even though the genes that would produce testosterone are much less active."
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neinxf | How does insulin price gouging work? Shouldn't competitors be interested in selling for $1 less until it gets close to actual cost? | Given that its insulin and not some new pharmaceutical, I assume the method of making more is available to everyone? | Economics | explainlikeimfive | {
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"You're assuming insulin is insulin. Unlike aspirin which is aspirin, the different insulins on the market are not all the same, and what works well for one person may not work well for another. (Chemically they are different). There are widely available, *relatively* cheap insulins on the market, but they might be too fast/slow acting, require too frequent injections e.t.c. If the only insulin that works well for you is a relatively recent one still under patent, then you're at the mercy of whatever the manufacturer wants to charge.",
"Don't forget that insulin is not just a single generic drug/formulation. The big players are constantly updating their products, which allows them to maintain a monopoly on their flagship products. A third party generic would inevitably be a substitute for an old version, not the latest. So then the question is how much value consumers place on the improved clinical outcomes of the newest, best insulin products. Clearly a lot of consumers value them enough that they don't buy the generics which are available.",
"First, the science of making more, as in a general understanding of the process, yes is well known. BUT, the machinery, assembly lines, techniques, and methods needed to actually carry out that chemical process are trade secrets (owned by each private manufacturing company) and not well known. So a company that wanted to start making insulin yes doesn't have to start from completely nothing, but would still need to invest a lot of time/money into research and development to get that manufacturing process up and running both efficiently and on a large scale. So, for a company that doesn't make insulin to start making insulin on a large scale, it'll likely take a lot of money for them to get started, something companies aren't willing to due unless they know for sure that it'll be profitable. So that leaves the current companies making insulin (In the USA, which is what I'm basing this off of, but the story is similar across the world). Of which, there are only 3 serving the USA. ([ URL_1 .)]( URL_0 .)) So those three companies don't really face a lot of competition, the USA is large enough where they all can make a profit, and it isn't like there are a dozen other companies trying to undercut them. It is a lot easier to fight/keep track of 2 other fighters in a fight than 20 others. This also means that prices aren't in as much competition, all three companies can see that while yes, they could slash their prices and try to steal a bunch of business from their competitors, their competitors could just slash their prices to match in a price war. With the end result being they're all still charging around the same amount as each other, all just significantly less than before, so all 3 of them are making significantly less money.",
"Sometimes, Companies can come together to form something like a monopoly. It doesn’t make sense to try and undercut each other when they can form an alliance and agree on a price. Veritasium has a video on this. It is slightly different, focusing more do on the dearth of innovation, but still does talk about competitors working together: URL_0",
"Monopolies and corporations straight up murdering people in the name of profits. Wall street has been buying up drug manufacturers for years until they own them all, then raising the prices between 800-2000%. These are practices that would be banned by any honest government. The US government… well that’s the only first world nation in the world that does not negotiate drug prices. For example that $300 USD vial of insulin is $30 canadian dollars and they are still turning a profit. People die so wall street can buy yachts. And FYI, the #1 expense of drug manufacturing is advertising, not R & D. That insulin was also invented by canada so you can’t blame that at all. They GAVE AWAY the patent because it was too important to monetize. Countries like Canada also got smart and BANNED advertising of prescription drugs. Your doctor can decide what’s right for you or research it online. Saved billions.",
"Hey, Econs major chiming in. In an industry, if enough key companies work together and controlled most of the supply, they can form a cartel and all promise each other to set prices artificially high. So, even though the actual products might be very cheap / easy / abundant to manufacture, the key companies all working together mean that they can set prices at whatever they want. Why do they work together instead of undercutting each other's prices for more sales (and thus, more profits)? Because of 2 reasons: 1. All the companies can profit much more if they price gouge. They all know this, so no one would want to price cut. Eg: OPEC tripling the oil prices because they formed a cartel. 2. If one company price cuts, their competitors will price-cut them. This leads to a price war, where the prices (and profits) will fall until only the \"biggest players\" can afford to cut prices below their competitors costs (due to differences in production technology) or sustain losses long enough to drive them all out, leading to a monopoly. So the big question is: Is this legal? Absolutely not.",
"Why sell for less and compete, when we can both sell for the same high amount and each get rich? I want to be rich more than i want you to be poor. So, instead of dropping my price to put you out of business, I'd prefer it if we could both fix a high price. The end result is the same, but instead of selling for bottom dollar, we both sell for more.",
"In part, they're taking advantage of patients not shopping around as much as they could. For a market to be truly competitive, consumers need to have \"perfect information\", meaning they have to know all the options that are out there and how much they cost. Since diabetes is such a high-stakes problem, most patients are probably just doing whatever their doctors tell them to do rather than doing their own research. The reality is, a number of the major drug makers offer chemically identical \"approved generics\" that cost half as much as the brand name drug a doctor prescribes, and a pharmacist can substitute these drugs in without asking the doctor. In other cases, there are other brands that are much cheaper than the one prescribed, but a patient is unlikely to know that these are options they could discuss with their doctor. There are also programs that can limit the cost of insulin for the uninsured. URL_0 The healthcare market is full of cases where \"imperfect information\" allows prices to get out of control. For example, even when people have the opportunity to choose their own insurance plan, who could possibly have the time and brainpower to research which plan offers the best type of coverage for the range of disease that they personally are likely to get?"
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nejivs | Why are electrical wires made up of loads of tiny copper fibres instead of one fat copper wire? | Title essentially. What advantage does having loads of fibres have over one solid piece? Flexibility? | Physics | explainlikeimfive | {
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"Solid wires are difficult to bend and limits how tight of bend you can make before damaging the wire. Solid wires also are heavier since they have metal filling the spaces between the bundle of thin wires. With that said, for high current applications, you still need solid wires to transfer the power without excessive losses.",
"You can get both types. Generally speaking the thicker the wire, the more current it will be able to safely carry, but yes it's less flexible. By having many strands the idea is that you get the best of both (with individual strands breaking not leading to a total failure). As a result the wire within the walls is usually thick, single core (because it never has to move) with only the cabling that gets manipulated by people needing the flexibility that many strands provide.",
"You’ll see there are many types of wire. You’re referring to stranded wire. (See Under “Forms of wire” URL_0 ). In terms of mechanical properties stranded wire is more flexible and pliable making it easier to handle. It’s not so rigid. In terms of electrical properties it seems to be better for high frequencies"
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nejqj7 | What causes canker sores? | Biology | explainlikeimfive | {
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"They have many different potential causes....minor injuries, SLS from toothpaste, food sensitivities, stress, hormonal shifts, lack of certain vitamins, allergic response.....you would have to monitor when you get them and trace that back to potential causes."
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nek88g | During Hyperinflation, How is the Public Made Aware of Lost Purchasing Power so Quickly? | Economics | explainlikeimfive | {
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"You buy something on Monday and when you go to buy it again on Wednesday it’s dramatically increased in price. Generally there’s no snail mail, email or vmail notification…",
"The prices of things you buy regularly such as food, gas, cleaning supplies, etc go up rapidly. You can literally buy something on Monday and buy it again a few days later and it be more expensive.",
"If it comes out of the blue, then you'll notice it when suddenly lots of products are constantly out of stock. That's a major sign of sudden inflation, *or* a general drop in productivity, or both. That's how we realize that money is currently overvalued - there is more money than there is things to buy with that money.",
"Most people are well aware of the prices they pay for frequently bought items: Bread, a pound of hamburger, a gallon of milk, gas prices, etc. These frequently bought items are also the ones that tend to go up the most quickly during an inflationary period because these are things people need. If the price of a Fender Standard Electric Guitar goes up by 30% in a six month period and I've had my eye on one, I'd likely decide I don't need it. (Supply and demand, keeps the price from raising too quickly). But I can't decide that I don't need a gallon of gas or a loaf of bread if I'm trying to get to and from work and if I have a family to feed. I'm going to buy those things, no matter the price. But I will notice them. Not only that, but if my whole grocery bill increases by 10% over a few months and if my gas increases similarly and the same with other items I purchase, then I'm going to have to economize somewhere. My budget won't allow me to continue to buy everything I've been buying."
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nemle5 | If insulin wasn't patented originally to help save lives, why is it multiple 1000's of dollars a prescription in the US? | Other | explainlikeimfive | {
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"Insulin was patented. Banting and Best sold their patent to the University of Toronto for $1 so that the information would always be available to the public. Banting and Best's method of extracting insulin was to use the pancreas from cows and pigs at slaughterhouses. This is kind of slow and inefficient and can't produce nearly as much insulin as the world needs. Modern insulin is all produced synthetically, using microorganisms that have been implanted with human DNA. Those processes are much more efficient and make better quality insulin than the method of extracting it from slaughterhouse animals.",
"1) The insulin produced today is not created with the same process as the insulin produced by the $1 patent you're referring to, and the new processes are patented differently, and are more expensive. 2) The purpose of pharmaceutical companies is not to help save lives, it is to make money, and when you sell something that someone needs in order to not die, you can charge a lot for it, and they'll pay you anyway. 3) Insulin doesn't cost thousands of dollars. [You can look up pricing for different delivery methods]( URL_0 ) (Pen, vial, etc) and even without insurance you're looking at less than $200 for a vial and less than $400 for the pen system. Those are still VERY high prices for something you can't survive without, so I'm not saying it's not an issue, but the number you've heard is also not correct.",
"Hint: It's only really thousands of dollars in the US. Everywhere else, it's a normal, affordable price, despite them paying the same patents on the modern methods of production. Which tells you that the cost has nothing to do with the patents, nothing to do with insulin production, and everything to do with where you live.",
"I use about 40 units a day in my pump. I know others that require 200. Each person is different. Average retail price for one vial is $350 for one of the most widely used types. I am fortunate to have good insurance so my copay is only $25 a month. It is only expensive because big pharma is a greedy bitch!",
"I am thoroughly confused here. Insulin was originally patented for that exact purpose. A prescription in the US is expensive, but not thousands of dollars. What exactly are you asking? And yes I am someone that relies on insulin to survive daily.",
"At this point it’s raw, unfettered greed. The processes for creating insulin today are not that different than they are 10 or 20 years ago. If anything, manufacturing costs are lower today than 10 years ago. But in the minimally regulated US prescription market, which even includes an inability for the government to negotiate prices, pharmaceutical companies have been going on a rent extraction frenzy. If some entity has what you need in order to live, and there is no control in pricing, you’ll pay whatever they ask for the lifesaving treatment. Person who was most infamous for this was Martin Shkreli, who jacked up the price of out-of-patent medication Daraprim (Pyrimethamine) 56x, from $13.50 to $750 *per pill* for a medication first patented in the 1950s. Hospitals report needing up to 100 pills per treatment battery in particularly stubborn cases.",
"FDA rules. Insulin of the newer types is a complicated enzyme. In order for a generic company to legally sell it in the US they have to prove it is identical to the brand version. This is time consuming and very expensive so most companies don’t try. Thus a few companies have a monopoly on legal insulin and insurance companies have to pay what they say."
],
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"text_urls": [
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"https://www.goodrx.com/blog/how-much-does-insulin-cost-compare-brands/"
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|
nen7tm | How come AB+ can only donate blood to other AB+ people, but AB+ plasma is universal? | Biology | explainlikeimfive | {
"a_id": [
"gyhgtu1"
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"text": [
"So blood type compatibility involves two things: 1) Stuff dangling off the surface of blood cells. 2) Antibodies which are found in the plasma. If you have \"Type A\" blood that means you have \"Type A\" dangly bits on your blood cells. Your body also will make antibodies for any things it doesn't recognize, so if you have Type A blood you will have Anti-B antibodies. if Type A blood meets Anti-A antibodies then bad things can happen. So if you're just transferring plasma what you're really worried about is antibodies. If you take Type-AB blood then it won't have anti-A or anti-B, so it won't react with type A or type B blood cells. The +/- thing (known as Rh factor) works the same way, with + people making the dangly bit on their blood cells, and - people making the antibody."
],
"score": [
6
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"text_urls": [
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nen8ut | Why does magnetic levitation require electromagnets and doesnt work with standard permanent magnets? | Physics | explainlikeimfive | {
"a_id": [
"gyh1cbz"
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"text": [
"It does actually work with permanent magnets, but maglev trains use a combination of both in order to propel the train forward by switching the polarity on the electromagnets. It still uses permanent magnets to hold the train up."
],
"score": [
3
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"text_urls": [
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nenaov | How are (traumatised) rats dealt with after Psychology experiments? Can they be reused for further experimentation? | Hi, Basically I am curious if rats who have been used in psychology experiments can be reused for other experiments. If not, how are they dealt with afterwards? | Other | explainlikeimfive | {
"a_id": [
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"text": [
"To be honest, ethical guidelines are so strict (at least here in EU and the UK) that it's extremely difficult to get any approval for traumatic experiments Those that do get approval only get it for a very small number of the animals with no room for slip-ups But to answer your question, it depends on the type of experiment done on them. Lab rats are specifically bred and usually don't last for many years (most age related studies I've seen have had at most 2-2.5 year old mice/rats). Keeping them alive is also costly in maintenance (no disease spreading, keeping them fed, healthy and active etc). So, unless those animals can be used in other experiments, often times experiments end with culling the mice/rats usually via chloroform and saving samples of tissues in cold storage for future reference Edit: disclaimer, my work is with molecular biology and data analysis, so the mileage in psychology may vary"
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9
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nenqje | - I know what a Fibonacci Sequence looks like 1 - 3- 5- 8- 13 (etc) what does it have to do with conch shells, sinewaves and sunflower seed pods? | For a bit of background; I often see what seems to be a mindless name-check every time there’s a picture posted of anything resembling a spiral. I’ve also seen plenty of pictures of the “perfect ratio.” What I’ve never seen is anyone explain how those four relate to each other. | Mathematics | explainlikeimfive | {
"a_id": [
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"text": [
"If you take the ratio of consecutive terms in fibonaci numbers the number converges to golden ratio (e.g. 2/1, 3/2, 5/3,..., you missed the two there) I do not know the sine waves, but for shells (such as nautilus shells) when you draw a line from the center, the ratio of the consecutive radii (the length between the center and the intersection between the line and spiral) is also golden ratio. For the sun flower seed pods, it is said that the number of seeds in each consecutive circle is the neighboring fibonaci number, but I do it think that is true.",
"All of those follow a shape called a [logarithmic spiral]( URL_0 ). Logarithmic spirals are characterized by something called the growth factor which effectively determines how quickly the spiral grows outwards. If you draw a logarithmic spiral using the golden ratio as the growth factor you get something called the golden spiral which is fairly close to some spirals in nature (though not exact). The golden ratio is related to the Fibonacci sequence because the ratio of two sequential numbers in the sequence approximates the golden ratio. It should be noted that there isn't anything particularly special about the golden spiral over others (with one exception being that it is the most efficient way to distribute seeds when growing outwards). Most occurrences of spirals have absolutely nothing to do with the golden spiral or Fibonacci sequence, at the turn of the 20th century there was a lot of pseudoscience created around the Fibonacci sequence and golden spiral about it being very important in nature or particularly beautiful but there isn't actually evidence to back this up.",
"Others have already said that the Fibonacci sequence relates to the golden ratio. This Numberphile video describes why the golden ratio is found in nature so much: URL_0 To try and put it short, it's the number that can be repeated the most without it getting close to another number. But the video explains it much better.",
"> What I’ve never seen is anyone explain how those four relate to each other. Because, by large, it is a mindless name-check. Most of the stuff you see associated with Fibonacci or the golden ratio is just easily disproved bunk. This makes it hard to sort out what true and what is just a myth. Of the ones you mentioned, the only one grounded in reality that I can tell is the sunflowers. And the arrangement of the sunflowers follows a Fibonacci sequence in that is what results in the densest arrangement of seeds and therefore a greater chance of reproduction."
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