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7br0uq | why does smoking marijuana and eating edibles give you such a different high? | Biology | explainlikeimfive | {
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"Because edibles get processed by the liver and that changes the THC compound to 11-Hydroxy-Metabolite which is stronger, and more psychoactive than the THC that is smoked."
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7br238 | - why does time slow down as you approach the speed of light? | Physics | explainlikeimfive | {
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"When Einstein was first thinking about relativity, he came up with a thought experiment using a a loop of metal on a train travelling near the speed of light. He wanted to see what Maxwell's equations (which describe all of electromagnetism) would say if you ran a current through that moving loop. The math behind that experiment showed that if Maxwell's equations were true, then Einstein's thought experiment would create infinite energy. Einstein thought that this couldn't be true - Maxwell's equations must hold for everybody no matter how they are moving. The only way to resolve the infinite energy problem and keep Maxwell's equations in tact is if the speed of light (i.e. the distance it travels in a certain amount of time) is the same for every observer. Applying more maths, the only way that the speed of light can be the same for every observer (when you change the observer's speed) is for the distance light travels and the time it takes to travel it are DIFFERENT for every observer. Specifically, the math shows that if an observer is moving close to the speed of light (or is watching someone else moving close to the speed of light) they will see that everyone else is moving slower - time is slowing down.",
"u/mr_indigo has a nice answer. The elaboration I'd like to make is on: > the distance light travels and the time it takes to travel it are DIFFERENT for every observer. Time doesn't really slow down as you approach the speed of light -- the better way of thinking about it is that time travels differently for every observer going a different speed. Not only that, but different observers see other observers as having time pass differently too -- they don't actually agree on who has the faster clock. Say you're on Earth and I'm on a spaceship going almost lightspeed. You see my time as slowing down. But from my perspective in the ship the Earth is the one whizzing past me at nearly the speed of light, so your time is what seems really slow to me and mine is \"normal.\" So there's nothing really unique about going near the speed of light that causes time to change -- instead any difference in speed between observers will create disagreement on how time is moving. We just don't really notice at small speed differences.",
"You move in 4 dimensions, and the sum of those speeds is the speed of light. If you're moving close to the speed of light in the spacial dimensions, you slow down in the time dimension.",
"You ever drive a car? Imagine walking on the highway. Everyone would be flying past you, it would be terrifying. You would feel so slow around all the cars zooming by. Now, imagine driving on the highway. All of a sudden other cars don’t seem so fast. You can easily see them and they don’t zoom past you. It’s like they slowed down. Similar concept but things get more interesting at near light speed. It’s like you are going so fast, but because that super fast speed is what’s normal for you now. Everyone else’s speed is sooooo slow that by the time they catch up they have gotten super old."
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7br785 | How does the electron transport chain work | How does it work in both cellular respiration and photosynthesis | Biology | explainlikeimfive | {
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"I'm in medicine, so I'll let someone else more qualified tackle photosynthesis, but for respiration, Your cells break down glucose to generate electron carriers such as NADH and FADH2 (they have actual names, but they're very long and latin and I don't remember them at the moment). These electron carriers then are used by the mitochondria (yes, it is the powerhouse of the cell... We know...) with the help of some special proteins (comlex I/II/III, cytochrome C and Q) to generate a proton gradient across the mitochondrial membrane. Then, these protons are allowed to flow back across the membrane down their concentration gradient through a protein called ATP synthase, which works kind of like a turbine and jams a phosphate onto an ADP, which forms ATP. The ATP can then be used by other parts of the cell to generate energy for various cell processes (DNA/RNA/Protein synthesis, molecule transport, cell division, etc...). It's been a while since I've done plant biology, but IIRC, photosynthesis is basically cellular respiration in reverse. It uses CO2, water and photons (light) to generate glucose."
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7brajw | Why does the wave nature of particles decrease when mass increases? | And, conversely, why does the wave nature of particles increase as mass decreases? | Chemistry | explainlikeimfive | {
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"This is more quantum physics than chemistry. The wavelength of matter is called the De Broglie Wavelength and is defined by the De Broglie equation: λ=*h*/p where *h* is Planck's constant and p is momentum. Planck's constant is on the order of 10^(-34). Due to this you can see that any object with significant mass will produce a very, very, very small value for the De Broglie wavelength. A 1kg object moving 1m/s would produce a wavelength of 6.6x10^(-34) meters. This number is 10^(22) times smaller than gamma rays. So small, in fact, that it becomes essentially non-existent. You will find with every quantum effect, as soon as you move outside of quantum scales the effect disappears."
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7brjob | What causes speech impediments? | Biology | explainlikeimfive | {
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"Yarr! Yer not alone in askin', and kind strangers have explained: 1. [ELI5: Are speech impediments physical or mental? ]( URL_0 ) 1. [ELI5: What causes speech impediments? ]( URL_1 ) 1. [ELI5: How do people develop speech impediments? ]( URL_4 ) 1. [ELI5:How do people develop speech impediments? ]( URL_5 ) 1. [ELI5: Why do people have speech impediments? ]( URL_3 ) 1. [what is the difference between a speech impediment and an accent? ]( URL_2 )"
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"https://www.reddit.com/r/explainlikeimfive/comments/6qmz0u/eli5_are_speech_impediments_physical_or_mental/",
"https://www.reddit.com/r/explainlikeimfive/comments/773j51/eli5_what_causes_speech_impediments/",
"https://www.reddit.com/r/NoStupidQuestions/comments/5s4dzy/what_is_the_difference_between_a_speech/",
"https://www.reddit.com/r/explainlikeimfive/comments/52mkca/eli5_why_do_people_have_speech_impediments/",
"https://www.reddit.com/r/explainlikeimfive/comments/1zv44v/eli5_how_do_people_develop_speech_impediments/",
"https://www.reddit.com/r/explainlikeimfive/comments/2m8siu/eli5how_do_people_develop_speech_impediments/"
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7brxhr | Why does "Stage 1" pancreatic cancer have such a low five-year survival rate? | I searched this, but the only questions that I could find about pancreatic cancer is the "Why is pancreatic cancer deadly *in general*?", not "Why is it deadly even if detected early?" So I am asking it more specifically. So, from my understanding, the reason why pancreatic cancer is so hard to deal with is that you don't notice the symptoms until it's usually Stage III/IV, when it's usually too late to treat. But I was looking at five-year survival for exocrine pancreatic cancer (which is the 85% of all the pancreatic cancer type) at Stage I, and the five-year survival is 14% at Stage I. Stage I is "less than 2cm of growth with no metastasis". With other Stage I cancers having better prognosis, why is exocrine pancreatic cancer hard to deal with it even if found early? Again, I am talking about "exocrine" type, which is the 85% of all the pancreatic cancer type. Also, I am not doing any medical studies - I am using Wikipedia for my sources. [Wikipedia for pancreatic cancer]( URL_0 ) | Biology | explainlikeimfive | {
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"Oncology nurse here! We actually just had an in service about this. The simple answer is because of its location in the body. For one thing, it’s very close to major veins and arteries, such as the aorta, portal vein and mesenteric artery, making it very easy for the cancer to spread far and quickly. It’s also deep within the body, behind and between various vital organs such as the liver and kidneys and intestines. That makes it difficult for surgeons to get to it and surgically removed the cancer, especially if the cancer is close to the major blood vessel mentioned earlier. The percentage of cases found that early is very small as well, because it is usually asymptomatic until the late stages, so when it is discovered early it’s usually a coincidental finding for something unrelated. Treatments such as chemo and radiation also weaken the immune system, which makes cancer patients much more vulnerable to illness and infection. This can lead to sepsis which is can be fatal, but also forces treatments to stop, allowing the cancer to grow further while the patient is being treated for the sepsis/infection. Another interesting thing about pancreatic cancer is that it can grow for 10-17 years before it’s even possible for it to be detected at all, so by the time it is detectable, it is strong and heavily mutated and ready to spread.",
"> With other Stage I cancers having better prognosis, why is exocrine pancreatic cancer hard to deal with it even if found early? Pancreatic cancers tend to be extremely aggressive and prone to spreading elsewhere to hide out and pop up later. I know Stage 1 is by definition \"no metastasis\" but the survival rate indicates the misdiagnosis of Stage 1 is fairly high. Even though it might appear that it hasn't spread because no tumors can be detected it doesn't mean there aren't cancerous cells hiding out elsewhere already."
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7bs9x2 | why does it help to look up when trying to remember something? | Biology | explainlikeimfive | {
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"it's at least partially to reduce stimulus. our brains spend a lot of power processing sight, so someone performing demanding mental tasks will avoid eye contact."
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7bsh1c | We have vitamin A , B, C, D, E and K but not F, G, H, I and J. Why? | Biology | explainlikeimfive | {
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"Vitamins A through E were named alphabetically. Vitamin K was discovered later and is essential in coagulation. But when they name it they spelled it koagulation.",
"Followup question. Why did they decide to have 12 B Vitamins rather than use the rest of the alphabet?",
"To keep it clear, vitamin naming is a mess and changed with time and what part of the world you're in. This is why most scientists do not use the vitamin classification, and rather proper chemical nomenclature. Alright now to the question: most of the latter vitamins (FGHIJ) were compacted in vit b (thus it being called a complex). Also vit B is a mess because most of them changed numbers or in some cases even letters eg. Bm & Bt. There were also vitamins that came after K but no consensus has ever been reached over them. A lot of vitamins disappeared because they were non essential and thus not a vitamin. The whole problem with vitamins is that there isn't a clear definition and was made up a long time ago by people who did not understand the human body that well. TL:DR vitamins changed names and numbers because they found out some of the vitamins weren't actually vitamins, or they were found in the same foods and thus became a vitamin complex.",
"I don't think we have \"found\" a new vitamin in forever, right?"
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7bslc5 | Why do most people have different handwriting if we’re all taught it the same way? | Other | explainlikeimfive | {
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"Handwriting - specifically cursive - is a fluid movement that involves fine motor skills, so is largely unique to a person's hand and nervous system. Education teaches the general shapes to make so that it's legible, but the rhythm of writing, the places that are strongly or lightly pressed, the little flourishes and tactics that make it more efficient for a given hand (e.g., little loops instead of directly reversing direction), etc. are individual. This is not as much of a thing today though due the pervasiveness of electronic communication. Handwriting is primarily scribbled notes in block print. Still distinctive to some extent, but less so than actual \"penmanship.\"",
"Uniform writing takes a lot of time and practice to learn. These days it just has to be uniform enough to be intelligible. If you look at people who learned something like technical drawing; at least back in the day, they learned to all write in the same uniform style."
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7bswtz | Difference between mirrorless and DSLR | I have searched on reddit but most of the information seems a little complicated for someone like me who are not really used to the terms used in photography. I'm looking to get a basic camera in hopes to learn a little about photography and have gotten recommendation from the sales assistant to get a mirrorless camera. I was introduced to both D3400 and A5000 so I'm hoping someone can explain it in layman terms for me to further understand the difference between the both. | Technology | explainlikeimfive | {
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"A mirrorless camera projects onto the sensor at all times. A SLR style camera has a mirror that redirects the image through the lens to the viewer that you use to frame the shot. When you take a picture the mirror flips out of the way so that the image is projected onto the sensor, then it flips back up out of the way so the image can project onto the sensor. Mirrorless cameras tend to be smaller and less flexible on lenses choices, they also perform slightly worse in low light. SLR have more lense choices but are larger and have better overall performance ."
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7bt201 | What makes a reflector reflect? | What/how is it that reflectors catch the light from my car so far away and become so bright? | Physics | explainlikeimfive | {
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"You're probably thinking of a retroreflector. That's a device that uses several reflective surfaces to bounce light back parallel to the way it came. They sometimes look like 3 small squares, all meeting at one corner, repeated many times across the reflector. You can see pictures on wikipedia: URL_0 or URL_1 The reason they look so bright so far away, is that unlike a regular reflective surface, they don't bounce light randomly, or at an angle away but always bounce light back towards its source. Since you're close to your headlights, you see a lot of light. Someone standing 20 feet to one side of your car would see very little light at all from the reflector."
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7bt48w | Why are we conscious about our decisions while most animals are not? | Biology | explainlikeimfive | {
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"That's quite a complex question, and a loaded one at that. Firstly, I'm not sure I quite agree with the premise that most animals are not conscious (even about their decisions). Some animals are able to pass [mirror tests]( URL_0 ), which involve reasoning (the animal is given time to get to understand what a mirror *does*, then gets something drawn on them in a place where they can not see it directly. Some animals go straight to the mirror to check.) Even tiny animals, like the [Portia spider]( URL_1 ) can exhibit complex intelligence. As an example, this spider is known to have a look at its target, and then take a complex 3D detour of the branches, which leads it to attack its victim from a completely different angle - one that is much more suited to attack. As another example, dogs are able to determine the optimal point at which to dive into a lake, if they have to fetch a stick thrown sideways (i.e. not in a straight line). Crows can accomplish ridiculously complex things, and they seem to learn and use their skills deliberately. We can say I'm cherry picking examples, but other, less well known animals are also pretty intelligent - e.g. there was a video of what looked like a sparrow opening supermarket doors by hovering near the motion sensor (seemingly knowing full well what they do). Intelligence is highly useful for survival. Humans aren't the only animals to have high levels of intelligence, though we seem to have reached some kind of critical point, where our intelligence could run away with it. This is essentially the story of civilisation, and if I had to guess, I'd say it has a lot to do with our relatively good combination of brains, vocal cords, and adaptive hands. These allowed for the development of complex language, then writing (which allows knowledge to be shared much more broadly and over long periods of time). As an interesting comparison / thought exercise, read up on feral children, who are those rare cases where children grow up without human contact. In general, once the advantages of past generations' knowledge, early education, and highly optimal development are taken away, we're not all that different in intelligence to other animals."
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7btkuw | Psuedo Forces (Especially Centrifugal Force) | Physics | explainlikeimfive | {
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"A pseudo force or \"fictitious force\" is something that is observed when the frame of reference that you are in is *accelerating*. What you are feeling is not a real force but a reaction (in the opposite direction) to how your frame of reference is accelerating. Elevators are good examples of pseudo/fictitious forces because you can't see outside your frame of reference. When the elevator is moving at a constant speed, it feels the same as if it is not moving. When it is accelerating up from a stop, then you feel an extra force pushing down on you. This is a reaction to the acceleration of the car. The opposite happens you are accelerating down -- you'll feel lighter (almost weightless if the acceleration is fast enough). For a turning car, the acceleration is not changing the speed, but the direction. A car turning to the left has an accelerating vector pointing left. You in the car will feel a reaction force pushing you right as the car turns left. Since the windows are transparent you can also perceive this as you wanting to continue forward while the car is accelerating left. Relative to the trees outside the car you don't feel a force but relative to the turning car it feels like you are being pulled to the right inside the car."
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7btl4s | Why are baby animals cool with humans/other species, but adult animals are not? | Biology | explainlikeimfive | {
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"Most animals have the instinct to rely on larger creatures (usually their parents) to survive. Partially because they are not ready to defend themselves yet. Baby birds can't fly away, baby cats don't have the strength to attack, etc. If you raise the animal from birth, it will think of you as a family member, but anyone else might be seen as an intruder. When they mature into adults, they will still remember you as \"family\", but they might have other instincts that guide them to try and dominate you, which is why that one chimpanzee killed the lady that owned him after many years.",
"I wouldn't say baby animals are cool with people or other animals- they just can't do much. Kittens with closed eyes will spit and hiss as much as their tiny bodies can given a reason."
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7btszr | Difference Between Heat and Temperature | Physics | explainlikeimfive | {
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"You can think of temperature as being similar to the level of water in a bucket, and heat as being the actual amount of water in a bucket. If you have two buckets, they might both be filled five inches deep with water. But if one bucket is much wider, that five inches represents a lot more water in the big bucket than the small one. Adding more water will raise the total amount of water in both by the same amount, but will raise the level more in the small bucket than the large one."
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7bu26d | What's the difference between classic and alternative coffee - aeropress, pour over, chemex? | Other | explainlikeimfive | {
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"Coffee is made much like tea, allowing coffee grounds to steep in water. Aeropress forces hot water through the grounds and a disposable filter. It's kinda like a hybrid between drip coffee and espresso. Pour-over is exactly what it sounds like. Hot water poured over grounds and a coffee filter. You get the idea. Water over coffee grounds. By using differently roasted beans, altering the steep time (time water is in contact with the coffee), the water temperature, and the type of filtering (if any), we change the taste of the result. Beyond that, it's all up to the taste of the individual. I like french press coffee. The filter is metal, so it doesn't absorb the oils from the coffee. I like the taste of the coffee bean oil, but some people don't. I have an aeropress and an espresso machine, and I much prefer the bitterness of espresso (fine ground coffee, hot pressurized steam, steep time very low, metal filter). Try a bunch of different things, and find what you enjoy!",
"I've drank them all. As far as I'm concerned, there are four major means of making coffee - boiling, steeping in hot, steeping in cold, and pressurized. Boiling is the oldest method. You can either add grinds to water in a pot and boil it, or you can rinse grinds with boiling water as in a percolator. Nespresso pots fall in this category, as well as Turkish coffee which the beans are ground into dust and aren't filtered out before pouring and serving. Steeping in hot is the most common. Drip coffee doesn't use boiling water, though it is very hot. The water rinses through the beans in a single pass. Same thing with pour-overs. A French press soaks the beans longer, leading to more extraction of flavorful and bittering compounds, and a plunger separates the two. An aero press is essentially the same thing as a French press, just upside down. Steeping in cold is similar to making sun tea. This is how you make cold brew. Then there is the ideal... Espresso is a method of extraction at ~190F (so not boiling) at 9 atmosphere of pressure. The process extracts not just flavorful compounds but oils as well, the result is a creamy emulsion of goodness, entirely wasted when dumped into an American late or giant American style cappuccino, which is just another late in a different cup and a higher markup. These categories are not in any way official, it's just that every kind of coffee in each of these categories basically tastes the same with only the slightest of variation. I can make you a drip or pour-over that tastes like a French press. I for the life of me cannot tell the difference between French press and Aeropress. I'll grant you Turkish coffee will guarantee a morning constitutional and nespresso pots have no idea what they want to be - it's a cup of coffee with an identity crisis. I'm going to get flamed for this. Most of the methods I'm straining to think of are different presentations of steeping in hot, either dripping water through or soaking the beans before an altogether removal. Very showy, and some people like that, but it makes the same thing.",
"Coffee is made by dissolving the soluble portions of a roasted coffee bean in water. The more hot water in contact with the ground beans, the quicker it dissolves. and the more dissolved into your coffee, the stronger it is (to a point, dissolve too much and it gets bitter) A coffee machine heats water, pours it over the ground beans at a steady rate, and allows the dissolved coffee to flow through the filter into a collection point (carafe or cup). Because it is automated, the machine has the water come out at a steady temperature and rate - fast enough to keep owners happy, slow enough to prevent the filter from overfilling. Pourover brewing just removes the automation. You are heating the water with an outside source (also meaning it can be heated to a greater temp to start) and monitoring the water level in the filter to make sure fresh water replaces the filtered water. Because of your monitoring this process, you can keep water level in the filter full better than a machine, and the solids dissolve faster making stronger coffee faster. Chemex is just a name-brand pourover. They use a slightly heavier filter to slow the process and make the coffee stronger. Aeropress is an inverted French press. Instead of the water flowing over the grounds to dissolve the coffee, the water and grounds are mixed in a chamber, allowed to brew, and then forcibly pushed through a filter to separate the grounds from the liquid. While this process produces coffee faster and stronger, it is also easier to overbrew (making the coffee bitter) and has more particulate matter due to the reusable filters not being as fine as a disposable paper filter (areopress does solve this later issue with disposable filters)"
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7bu2kj | Do some people really have "strong" or "weak" genes? | My new baby is 95% me in looks and disposition. My fiancee's sisters have 5 kids between them, and they mostly look like their fathers. Does her family simply have "weak genes" or is it just coincidence? | Biology | explainlikeimfive | {
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"\"Strong\" and \"Weak\" are poor terms for this. \"Dominant\" and \"Recessive\" are more accurate. Remember 8th grade biology with those Punnett Squares? Some traits are \"dominant\" which means that they tend to show up if someone has them. Other's are recessive which means they tend not to show up as much since you need to have the trait from both parents for it to show. Now Punnett Squares are overly simple when talking about genes but that is ultimately what you are asking. So yes, some genes are \"strong\" but it is incorrect to say that they are somehow \"better\" than other \"weak\" genes. Some genes just tend to show up if present while others do not.",
"In addition to things that people have said about the complexity of determining which genes are dominant or recessive, appearance is going to be polygenic, with many genes interacting to create the end result. I would like to bring up the fact that babies look like their fathers in part to prevent infanticide, because the father is more likely to invest in children that share his appearance and therefore his genes. By the same token, the babies rarely look exactly like their father so that it is harder to be 100% positive about paternity just based on appearance alone, which further protects babies who might have been conceived less honestly."
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7bu3wk | How are we able to "dissect" light in order to derive useful information from? (ex. Like light from distant galaxies) | Physics | explainlikeimfive | {
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"Dissect is actually a pretty good word for it. We take the light from a distant object and run it through a spectrum, dividing it into component colors. Along that spectrum will be a number of dark, narrow bands, which correspond to atoms and molecules that absorb those frequencies of light. The strength of the bands tell us which elements are present, and in what proportion. If those bands are shifted compared to what we would see on earth, we can tell if the object is moving away from or towards us."
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7bujyx | Why do some people get hungrier faster than others? | Biology | explainlikeimfive | {
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"Metabolisms. Different people’s bodies burn energy at different rates. There are base genetic facotra but you can also raise your metabolism through exercise. Her body just burns/needs more energy than yours does on a normal basis."
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7bun3j | Food preservation: Why does food begin to taste like 'fridge'? | Most notably is the transformation of flavour in butter. Leave your butter unwrapped in the fridge and it tastes like your fridge. Such is similar to most foods to some extent. Why does this happen? Edit : thank-you all for the replies :) | Biology | explainlikeimfive | {
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"text": [
"Is it because the combined gasses of the foods naturally albeit slowly decomposing swirls around and mixes with the oxygen in your food. The circle of fridge life"
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7bv0ha | How do naps and sleeping make headaches go away most of the time? | Biology | explainlikeimfive | {
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"text": [
"Headaches are usually caused by muscle tension in the head and/or neck. Anything that gets you to relax is likely to release this muscle tension."
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7bv7q8 | What is a Sonic Boom? | Physics | explainlikeimfive | {
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"text": [
"Yo ho ho! Yer not alone in askin', and kind strangers have explained: 1. [ELI5: Sonic Booms ]( URL_1 ) 1. [ELI5: What exactly is happening when a sonic boom occurs and why does it create so much sound? ]( URL_4 ) 1. [ELI5:What actually causes a sonic boom? ]( URL_3 ) 1. [ELI5: Why do sonic booms exist? When something is supersonic, why does it make a loud noise as it breaks the sound barrier (like a whip)? ]( URL_5 ) 1. [ELI5: What exactly are sonic booms? Why do they happen? How is crossing the sound barrier different from any other change in speed? ]( URL_0 ) 1. [ELI5: How does a sonic boom happen and what is it? ]( URL_2 )"
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"https://www.reddit.com/r/explainlikeimfive/comments/20lyia/eli5_what_exactly_are_sonic_booms_why_do_they/",
"https://www.reddit.com/r/explainlikeimfive/comments/1giwn1/eli5_sonic_booms/",
"https://www.reddit.com/r/explainlikeimfive/comments/4uj6x5/eli5_how_does_a_sonic_boom_happen_and_what_is_it/",
"https://www.reddit.com/r/explainlikeimfive/comments/1bet8t/eli5what_actually_causes_a_sonic_boom/",
"https://www.reddit.com/r/explainlikeimfive/comments/4tyzk6/eli5_what_exactly_is_happening_when_a_sonic_boom/",
"https://www.reddit.com/r/explainlikeimfive/comments/2e7uvt/eli5_why_do_sonic_booms_exist_when_something_is/"
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7bvkj6 | Is there any way to solve a cubic equation in the same way you can solve a quadratic equation using the quadratic formula? Basically, is there any 1 formula that can solve a cubic equation. | Mathematics | explainlikeimfive | {
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"There is a [general cubic formula]( URL_0 ), it's just difficult to memorize.",
"In case anyone's wondering: there is also a general [quartic]( URL_1 ) (x^4 ) formula, which runs to a couple of pages of math and has an interesting history of [academic theft]( URL_2 ). [There is no]( URL_0 ) general quintic (x^5 ) formula.",
"It's not exactly 1 formula, but rather a series of steps you can follow. Details are [here]( URL_0 ).",
"Yes. It is [much more complicated though]( URL_0 ), can't sing Pop-Goes-the- Weasel to remember it. Another interesting thing about it is that it has imaginary numbers in it. Often times, when you have a particular cubic and plug in numbers, then the imaginary numbers all cancel out to give three real solutions with no imaginary numbers in their expression. But, sometimes, you can have a cubic polynomial, with three real roots, but when you plug in the numbers into the cubic formula, you still end up with imaginary numbers in the expressions! These are real numbers that can't be expressed (in radical form) *without* imaginary numbers! For example, the roots to x^(3)-3x+1=0. They are all real, but if you [click on \"Exact Solution\" in this Wolfram Alpha computation]( URL_1 ), you'll see imaginary numbers! EDIT: This phenomena is called [Casus Irreducibilis]( URL_2 ). There is a formula for 4th powers as well, but for anything higher, it has been proved that there is no formula."
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"http://www.storyofmathematics.com/16th_tartaglia.html"
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"https://i.stack.imgur.com/M6L8y.png",
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"https://en.wikipedia.org/wiki/Casus_irreducibilis"
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7bvsgm | How can people safely attend rock concerts with a sound level of 140 dB when the pain threshold is around 120 dB ? | Physics | explainlikeimfive | {
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"text": [
"In regards to hearing, it's not safe. Sound that loud for the duration of a concert may result in damage to hearing. Especially if you regularly attend loud concerts, it can result in some degree of hearing loss.",
"People who do that often will also go deaf over time. So it depends on your definition of „safely“",
"You could buy electronic ear muffs? I have some for when I go to the range because I **HATE** having to yell or have people yell at me. You can turn up the volume to amplify people, but it has a decibel limit. That way the shot gets \"muted\" to a safer level. I plan on wearing them to a Periphery concert this month."
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7bw3wi | Some drugs are derived from natural compounds that come from bacteria, plants, and animals. How do we decide which chemicals to test as drugs from these organisms? | Chemistry | explainlikeimfive | {
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"text": [
"Often we target things that already have some property that we want. Penicillin, for example, is thought to have been discovered by accident. Alexander Flemming accidentally left a petri dish open with staph bacteria in it, and it got contaminated with mold. Flemming noted that the bacteria didn't grow next to the mold and hypothesized that the mold was producing something to kill the bacteria. So if we're studying an organism and discover that it has some property we want, we will try to isolate it and test it as a drug. Sometimes it's an accident, sometimes you spend years combining different things and testing all of them until you get something you want. There's a lot of trial and error involved.",
"There is a field of research called natural products discovery. Basically what you do in this research is test loads and loads of chemicals from plants, fungi, bacteria, etc to see if any of them do what you want. The main way to make this less tedious is to not test all the chemicals individually. You start by testing a total extract of the thing you think might have a useful chemical, which contains tons of chemicals all together. If this extract does what you want, you separate the chemicals in it progressively (e.g. by boiling point or molecular size), testing which fraction does what you want at each step. After enough separations, you are left with the single chemical that does what you want."
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7bws5k | What are the blue/green clumps that form in alcohol-free mouthwash after use? | Chemistry | explainlikeimfive | {
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"text": [
"They're coagulated proteins from your saliva that have been coloured by the mouthwash, not bacteria or food debris. If you spit in a lidful of the stuff you'll still get the bits."
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7bwtc9 | Is the universe actually infinite, or does it just go beyond our current observational capabilities? | Physics | explainlikeimfive | {
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"text": [
"We can see to the finite edge of where we can see. We cannot see what's beyond the finite edge of where we can see. We cannot verify that there is infinite space beyond the finite edge that we can wee.",
"If the universe is huge but finite, it would curve. We have detected no indication that it has any curve at all. So it's either at least as much larger than the observable universe as the observable universe is roughly larger than you or me, or it is in fact infinite. Future measurements may be able to detect curvature in greater detail than today, so someday the question may be answered, but until then the universe is practically infinite from our perspective."
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7bwwhe | Why does metal get colder than plastic? | Chemistry | explainlikeimfive | {
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"text": [
"It doesn't. Leave a metal bar and a plastic bowl out at 0 degrees Fahrenheit in the winter, and they'll both end up 0 degrees Fahrenheit over time. But when you with your warm hands picks them up, the metal will cool your hands faster than the plastic will, and so it will feel colder.",
"Metal is a conductor of heat (thermal conductor); the reason it feels cold is because it is more efficiently pulling heat from your body and conducting it into the colder air around you. Plastic is not a good conductor, so it doesn't get as cold or hot as quickly when exposed to a temperature differential; it is considered a thermal insulator. At a more fundamental level, there isn't a really good understanding of what makes something particularly good or bad at thermal conductivity as far as I'm aware.",
"Metals typically have a lower specific heat capacity than plastics. It takes less energy for them to change temperature. So they both heat up and cool down faster than plastics. But if you left both in the freezer for a few days they would be the same temperature."
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7bxlnp | How does fire cause wind? | Physics | explainlikeimfive | {
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"text": [
"As air heats up, it rises. When air rises, other air comes in from the sides to replace the air that went up. As the fire gets bigger the air currents can get more and more chaotic. Wind."
],
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7bxmvy | How does a company benefit from offering its employees discounts on its products? | Economics | explainlikeimfive | {
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"text": [
"Recruiting and retention. A discount is a job perk which draws people to work there. The discount often keeps them there too. This acts to offset the marginal cost of the discount as well because you now have a built-in frequent buyer.",
"I work for the cable company. Receiving comp services means I am familiar with the products, and can therefore educate the customer and recommend other products they may benefit from.",
"They also don’t have the expense of marketing and selling to employees that they have for regular customers, so it’s a perk to attract and retrain with little cost. Additionally, it sends a positive message if their employees use their products themselves, gain first hand using them, act as ambassadors for their employer, etc.",
"In the tech industry (and many others), it's called [\"Dogfooding\" or \"Eating Your Own Dogfood\"]( URL_0 ). The idea is that you want employees to be intimately familiar with your products, and you want to quickly find out what is working and what isn't. You can't always rely on customers to tell you the good and bad things about your products. If a person walks into a clothing store and asks for a recommendation, an employee that owns a bunch of the clothing is going to be able to make better recommendations. It's also much more reassuring for a customer to see employees wearing the clothing of the store they work at rather than the clothes of a competing company. Conversely, if an employee buys a piece of clothing and it falls apart or stretches out, they're more likely to report that back to the store owners compared with a customer who may just stop shopping at the store and not report anything."
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7bxmw1 | Why supersonic planes are designed with Deltawings, and subsonic planes are designed with swept wings? | Physics | explainlikeimfive | {
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"text": [
"Long skinny wings have [less drag]( URL_1 ) for the amount of lift they generate, so they're more fuel efficient. But you can't have a long skinny wing on a supersonic airplane: if the wings stick outside the [cone-shaped shock wave]( URL_0 ) surrounding the plane, they may be damaged, and if not, the flight physics gets much more difficult. So supersonic wings are tapered to stay inside the shock wave cone. They still need enough area to generate lift, though, so they need to be wider from front to back -- thus the delta wing shape."
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7by2ju | How does air conditioning work. | Chemistry | explainlikeimfive | {
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"text": [
"When something boils, its temperature goes down. That's why a boiling pot of water stays at around 100 degrees C, you are putting in heat with fire, but the boiling is cooling it. There are two ways of making something boil, putting in alot of heat, or reducing the pressure. Air conditioners work by reducing the pressure around something that loses a lot of heat when boiled. So the area around that stuff becomes cold and they blow that air into your house. Now they move the boiled steam to another part of the air conditioner. Condensing the steam creates heat, so they put that part outside your house and blow the hot air outside, they then pump the liquid back to be boiled again."
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7byqw5 | what determines if 2 chemicals will or won't bond | Chemistry | explainlikeimfive | {
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"text": [
"Square blocks go in square holes. If the orbitals of one molecule are the same 'shape' and 'size' as another molecule they can fit together. Aside from looking at bond overlap you can also understand a lot of chemical reactions from simple E+M. Opposite charges attract. If a molecule has a part of its body that is a little bit positively charged (maybe there is a carbon next to an oxygen that is slorping up its electrons) than any negatively charged part on another molecule is going to want to stick to it. In the case of something super negative like say the carbon next to a lithium in alkyl lithiums, it will stick and won't come off. At a high level though it's all about going downhill. Whatever increases the entropy of the universe will happen. Period."
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7byzyi | Could a brain transplant actually be possible and would memories transfer over to the new body like a hard drive? | Biology | explainlikeimfive | {
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"text": [
"With current science? No. There are way too many nerves and things we wouldn't be able to connect. Memories would transfer over though because they are all contained in the brain.",
"Right now, we do not have the technology to connect that many nerves. Nerves can heal a bit, but entire spinal cord breaks are beyond our healing capability and our scientific understanding. One day, it might be possible. The memories would transfer with the brain. Memories aren't stored anywhere else besides the brain.",
"Yes. Yes. All your memories are in your brain. In essence, a brain transplant is actually a *body* transplant, taking the entire memory and consciousness of a person and attaching a new body around it. The tricky part is regenerating the spinal cord and assorted cranial nerves. We don't really have the technology to reconnect the spinal cord.",
"A head transplant is being attempted in December. I expect it will be a massive failure. But all the people saying we don't have any clue how to reattach spinal chords.... we're not that clueless. We get better at these types of things every year."
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7bz112 | How does a high change in pressure “turn your organs to jello” and kill you? | I️ just saw an argument about people dying inside tanks during WWII from bombs that didn’t directly hit the tank. Their bodies were fine, but they were dead. Also from what I️ understand this is the same way a high velocity round from a rifle will kill something. The tiny hole from the bullet isn’t the killer, it’s the pressure change, and that’s why slow rounds like hand guns don’t kill as effectively. Is this true? how does pressure change turn you to jello? edit: aiming this more towards the tank question | Physics | explainlikeimfive | {
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"I take it they meant they died from the shock wave. Yes, strong shock waves can kill you, as they act almost like a supersonic brick wall that can enter your body. Hitting a brick wall at high speed would kill you because your organs get squished and stop working. Similarly, a shock wave would squish your organs as it travels through you. It won't literally turn them to jello, but would rather tear them up.",
"water doesn't compress. The Archimedes principle states that pressure exerted on water is spread throughout the whole of the water. you are mostly water. Whatever pressure hits you travels through your body, and anything not water gets crushed. So thats what it means by into jello, your own bodies hydraulic pressure crushes anything not water.",
"[I’m a visual learner so here’s this.]( URL_0 ) Now it’s close to the blast but you can clearly see that the only thing that hits the dummy is the shockwave. I’m also pretty sure this effect is multiplied when in a container like a tank. (like sound) Edit: also check out “ballistic gelatin” gifs to see what is happening when a bullet travels through you. You will immediately notice the massive cavity it forms which implodes then explodes again, really damaging stuff."
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7bz6ps | Why do things get crispy rather than soggy when you cook them in oil? | Chemistry | explainlikeimfive | {
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"text": [
"Any food cooked in hot fat is fried. The method of heat transference is the same whether there’s just a little fat in the pan (sautéing), the fat comes partway up the sides of the food (shallow-frying), or the fat completely envelops the food (deep-frying). When food is added to hot oil (usually 350°F to 375°F), its surface dehydrates. Meanwhile, through a series of Maillard reactions (named after the chemist Louis Camille Maillard), its sugars and proteins break down to create complex flavor and golden-brown color. Browning is quick and thorough because the hot liquid fat delivers heat to even the smallest crevices on a food’s surface. In the initial moments of frying, as the surface dehydrates, it forms a crust that inhibits further oil absorption, while continuing to conduct heat to the interior of the food, where the heat causes starches to gelatinize (as in french fries), proteins to denature (in fried chicken), and fibers to soften (in fried zucchini). Maintaining the correct oil temperature is key to frying. If the temperature drops too low, the crust forms slowly, allowing the food to absorb more fat and become greasy. If the oil gets too hot, the food burns on the surface before it cooks through. [Source]( URL_0 )"
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7bz92g | New credit cards offer me 0% APR for the first 18 months but now the credit account I've held in good standing for years is charging me 22%. Why isn't this the other way around? | Economics | explainlikeimfive | {
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"text": [
"Because the new card is trying to entice to you to switch to them so that later when the APR goes up they’ll make money. It’s the same concept behind cell phone carriers, internet/cable providers, gyms, etc offering amazing deals upfront and then raising the fees later.",
"Because no one would switch from that 0% to the 22% card. They're banking on the majority of their customers either being happy with their service, or too ingrained in their habits to switch cards once the rates go up."
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7bz9um | . How are vinyls made and how does sound project off them? | Technology | explainlikeimfive | {
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"text": [
"Sound waves are vibrations. Those vibrations are etched into tracks in the vinyl record. Then when you put a needle into that track and spin the record, the vibrations are transferred into the needle. Just amplify that needle with even a piece of printer paper rolled into a cone and you've got sound!",
"u/PM_ME_A_PLANE_TICKET is absolutely correct! I'd love to get a little more technical. \"How are vinyls made?\" - vinyl as a material (when compared to metals like steel, for example) is very soft. This allows it to be easily scratched by, for example, a very sharp and tiny needle (the recording needle). As u/PM_ME_A_PLANE_TICKET's explanation showed, sound waves are nothing more than just vibrations through a medium--usually air--so something that can respond to those vibrations in kind (like a diaphragm) can essentially \"pick up\" what the sound waves look like and translate them into another form. In our case, the diaphragm moves the recording needle in a reciprocal way (corresponding to the sound waves), and it thus etches the sound wave into the soft vinyl. \"How does sound project off them?\" - well, it doesn't really \"project\". In fact, it's a lot simpler than projection: it's actually the exact opposite of the process described above! In the same way that sound waves can cause a needle to vibrate and etch into a vinyl, a similar needle (the pickup) can \"read\" those etchings in the vinyl and cause a similar diaphragm to vibrate, which then moves the air molecules in the same way the original sound wave did, thus reproducing the sound! It's truly magic."
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7bzafb | why does picking at your skin leave scars and enlarge your pores, but pore strips dont? | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"Pore strips do. You're ripping pus or dirt or hairs or whatever out of your pores and that stretches the opening. It doesn't matter what causes it; it just happens either way."
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7bzppq | Why are cavities black? | I have some small visible cavities on my molars and my dentist never mentions them.... I've read some sources that have claimed it being remineralization of the tooth. Others saying that it's the rotten part of the tooth...What is it? | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"likely what you're seeing is an old filling. amalgam fillings turn black after some time. i seriously doubt a dentist would not mention it if you had a cavity."
],
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7c07hi | Why is suicidal ideation a common side effect of antidepressants? Given it is a common symptom of depression, should the antidepressants not suppress this symptom too? | Biology | explainlikeimfive | {
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"text": [
"Being depressed is more being low energy than being sad. When people take antidepressants, sometimes they’ll go from: “What’s the point of doing anything?” to “I should go do something, I’ll go call my family, that will be good.” But sometimes their energy makes them think: “I should go do something, I’ll take my life, that will be good.” The thing is, suicide is not that easy. Depressed people sometimes struggle with doing their dishes, or changing clothes. Suicide can seem like a really hard thing to do. On Antidepressants, it can then suddenly seem like an easy option. Sometimes reading of suicide will make suicide seem compelling. If you are having suicidal thoughts, call a suicide hotline, please.",
"I've had it explained to me this way: Depression causes apathy and an overall lack of energy, which in severely depressed patients can even lead to someone not even being able to muster up the energy or care enough to kill themselves. Most anti-depressants take 6 weeks to reach therapeutic levels, but your do see minor gains in energy and mood (increasing positive or negative emotions) in this time. Unfortunately, that can mean you have a decrease in apathy, still feel depressed and just enough of an increase in energy to actually commit the act."
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7c0duz | What is a quiet title? | I saw over in r/documentaries Mark Zuckerberg sued for land in Hawaii. They mentioned he sued for quiet titles or using quiet titles. | Economics | explainlikeimfive | {
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"text": [
"A quiet title suit is a suit that asks a court to give a determination about who owns a particular piece of land (or some other piece of property that has a title, but it's almost universally about land). Its purpose is to \"quiet\" any disputes about the land ownership. It's a fairly routine thing to do when there's either a dispute or some ambiguity about who actually owns a piece of property."
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7c0kzp | If companies like Apple and Samsung are in close competition, how does the latter end up making screens for the former (and other similar cooperative business decisions)? | Economics | explainlikeimfive | {
"a_id": [
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"text": [
"Because it makes everyone more money. Apple ends up with better screens and can sell their phones for more, while Samsung profits from selling the hardware to Apple.",
"It's mutual profitability for both companies. Samsung has been making screens, resistors, batteries, and other components for decades. Samsung has also been in the phone business a long time. Companies like Apple would get Samsung's latest and greatest screens just like they'd put in their own Samsung phones because they still make money. If they gave them lesser screens, they wouldn't sell as well, causing for less screens to be made, and less in sales overall. So helping the competition still helps Samsung's bottom line.",
"Also, it's only the phone/computer division of Samsung that 's competing with Apple. Apple doesn't make screens, so it's not like Samsung screens are competing with Apple's. A better question might be if you ask why lots of car companies collaborate and sell basically the same model under different names"
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7c0lcl | Why are there such drastic differences in salaries between different countries? | Economics | explainlikeimfive | {
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"I'm going to avoid discussing service industries, because they are drastically different and less subject to the global market (You can't work construction in Detroit and Munich on the same day) I'm mostly talking tech. The biggest driver of disparity in tech jobs is cost of living. If it costs 2000 a month to live in Boston, and 200 a month to live in India, then salaries will reflect that. Companies aren't in the business of lowering profits to give employees extra spending money.",
"The companies working in this environments have different budget and different workforce demand when employing. If you seek to hire new people you have to offer a salary that will attract them. In Germany this means offering much more than in Poland. As for why the Polish companies don't offer more? Same as anyone else, they won't unless forced to and then you have to consider how much revenue they have and how much they can afford.",
"Labor productivity mostly, highly productive countries tend to have high wages. Take a look at [chart 14]( URL_0 ). 3-2% of long run real GDP and productivity countries that many developed nations experienced for the past 200 years compounds and adds up in the Long Run.",
"No. 1 reason is difference in productivity. If a person in Japan can make 10 goods per hour vs 5 goods per hour in Poland, his wage, everything else held constant, will be double in Japan. Productivity is influenced by almost all key country characteristics, say: Political stability Level of technology as used by companies/govt Social capital (eg can you trust in your fellow human beings around you) Weather Industry development in country Culture Quality of institutions So even if there is perfect human capital mobility and perfect movement of goods (large assumptions), these will not make a person more productive on their own, so the same person could get a different wage in different countries for same type of job.",
"Every company pays every employee (maybe excluding CEO's and other top figures) as little as they can get away while keeping that employee. In some countries that is more, in some countries that is less. it's generally connected to the cost of living.",
"CMIIW but it boils down to how big and developed a country is. It goes back to their GDP which in terms reflect their spending patterns which is affected by tha maturity of market, technology, tax, FP, etc etc For example: a mcdonald staff in lower gdp country will have lower salary than those in well developed country. This is because the people can only buy McDonald's food at a certain price, any higher would make it too expensive hence no people buy them. That's why there is an index for that(big mac index) You just have to think all the way through. An example with $ If you have a 1 staff McDonald's If you sell 1000$ worth of big macs monthly you can only pay salaries so much to have a margin. You wouldn't be able to give your employee 1500$ a month because then your cost will be higher. And at the same time you couldn't just put the price up because no people would buy them if they're too expensive.",
"I think the real question here is \"Why are some countries developed more than others?\" The other answers do a good job of explaining why high development gives higher wages (High development means a lot of labor is far more productive, and therefore more expensive. This then trickles into jobs that aren't dependent on development, because (a) more money in the local economy and (b) you have to pay workers comparably or they change fields) but none really explain why some countries are more developed than others. This is a major question in macroeconomics, but there are a few theories / causes. One of the accepted theories explaining this difference is called \"premature de-industrialization\" [1]. Normally, a developing country moves from a largely farm-based economy to one built on manufacturing. Manufacturing is a good way to develop a strong middle class, as it's both high paying and relatively low skilled. As manufacturing gets more efficient with better technology, though, the number of manufacturing jobs required to make a certain number of goods goes down. This allows people to move into service jobs without decreasing the total quantity of manufactured goods. Finally, the higher standard of living achieved during the shift to a manufacturing economy allows people to invest in education, which further boosts innovation and growth. This process has gone wrong in the third world. Because developed countries have already developed a strong manufacturing sector, especially highly automated or high skill manufacturing, a newly developing country cannot compete. This forces the country to either compete in very low skilled manufacturing (via sweatshops) that pays workers very poorly to compete with the higher technology of the 1st world, or shift into a service-based economy without the strong manufacturing middle class to support it. Another compelling theory is one of institutions [2]. This theory suggests that countries with good institutions see high economic growth, which in turn supports the very institutions that created it. For example, developed countries usually have democratic governments that strongly defend civil liberties and personal property. They also have a strong financial sector that allows for investment, which is crucial to growth. If a company cannot sell shares to raise money or even take out a loan, it's very difficult for that company to expand. At an individual level, the ability to take out loans allows people to buy houses and cars or invest in education. Finally, a well-developed country has a strong education system, with secondary and post-secondary schools creating a much more skilled workforce. These institutions often depend on a strong economy, but are also necessary to maintain one. Finally, no comparison would be complete without at least a passing glance at colonialism [3]. Colonialism, especially in Africa, allowed for the direct exportation of low-skilled labor from underdeveloped countries to more developed countries. (Remember premature de-industrialization? Imagine that, enforced with guns.) This obviously hindered the growth of African nations and increased the growth of nations that owned the slaves. Furthermore, colonial governments were not usually set up as democracies with the native's best interests at heart. A government designed to export wealth to the colonial power is not one that will foster the strong institutions needed for growth. As evidence for this, consider Singapore and Hong Kong. Both were colonies of the British Empire, but the lack of natural resources meant that they were more useful to the British as trade hubs. Thus, no real exportation of slaves, and they founded strong financial institutions and a framework for democracy. 200 years later, they're still very prosperous, while many former colonies in Africa are not. There are of course more reasons (Malthusian traps, initial factor endowments, regional cohesion, capital accumulation, etc), but this wall of text is a little beyond ELI5 already. Sources: 0: I'm avoiding macroeconomics homework by doing macroeconomics on reddit. 1: Rodrik, Dani. “Premature Deindustrialization.” Journal of Economic Growth, 2015 2: Glaeser, Edward, et al. “Do Institutions Cause Growth?” Journal of Economic Growth, 2004 3: Nunn, Nathan. “The Long-Term Effects of Africas Slave Trades.” The Quarterly Journal of Economics, 2007"
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7c0lw8 | What exactly proves the pythogeran theorem to be true? | Mathematics | explainlikeimfive | {
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"Take a square of area c^2 and place that inside a square at an angle so the corners touch the sides of the larger square. [As seen here]( URL_0 ) Each of the 4 triangles have the area 1/2ab combined this is 4 x 1/2ab or 2ab The larger square has the area (a+b)^2 which expands to a^2 + b^2 + 2ab So the large square can have its area described in two ways which are then equal so we have a^2 + b^2 + 2ab (full area) = c^2 + 2ab (small square plus 4 triangles) We can cancel the 2ab out on both sides to give: a^2 + b^2 = c^2",
"God, there are so many proofs of the Pythagorean theorem, both the right-angled version and the general equation. [Here is a slew of them]( URL_0 ) [Wikipedia also has some of them on file]( URL_1 ) In general, you can either use a geometric proof (Similar to what other posters in this comment section have posted) or more pure algebraic proofs that simply rearrange equations known to be true and show that as a result the theorem must hold true as well. Most often you're going to get some mix of the two as those equations are representing some geometric object."
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7c0mb6 | How does valuation work for tech startups? | Like it says in the title, how do people decide how much a tech startup is worth? I've seen countless tech companies that seemingly produce very little but are still valued at astronomical numbers | Economics | explainlikeimfive | {
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"One of the most reliable ways is when a company sells a part of itself in \"funding rounds\". So let's say you have a startup, and you've got a proof of your concept, but you need some investment to push it to the next stage. You will offer a certain stake in your startup to a set of investors (usually Venture Capitalists, so called because they put Capital [money] into fledgling companies [Ventures]). So you say \"I'm going to offer 20% of my business to investors in this funding round. Ladies and gentlemen: start your bidding\". When this funding round closes, your startup will have collected an amount of investment. Let's say it's $100m. It's split across a set of investors, who will each take a segment of the 20% you offered, in accordance with how much of the $100m they put in. But now your company has a valuation. Investors just paid $100m for one fifth of your company. Congratulations, you're CEO of a half-billion dollar firm.",
"Physiologist here who has raised over $10M in early-stage venture and seed-stage capital for startup tech companies. Ultimately valuation is a negotiated value between two (2) parties with opposite interests: 1) the startup's founders who want to argue for the highest valuation possible so that they can raise the money they need to launch the company while retaining as much ownership in the company as possible; and 2) the investors, who want to argue for a lower valuation, so that their money buys the highest amount of ownership in the company as possible (to a certain limit - which is that their ownership isn't so great as to cause the co-founders to become unmotivated to work hard to make the company succeed). There isn't any magical formula for this process. There are two main \"big picture\" variables at play here: 1) the risk that the startup will fail; and 2) the likely future cash flows to the company if it succeeds. Risk is a destroyer of value. The higher the perceived risk to the investor that the company will fail, the lower valuation he/she will place on the company. The lower valuation placed on the company, the more ownership an investor will be able to buy for his investment - and the higher payout he will get if the company succeeds. So…a company that wants to develop a novel drug, for example, is going to have a higher risk than a company that wants to develop a medical device (and has a working prototype). More experienced management lowers risk, first timers significantly increase risk. Coming to investors with just an idea is far more risky than coming to investors, say, with a working prototype of a product that has been through a clinical trial proving its usefulness over existing products. Future cash flows refers to the amount of profit that the startup can reasonable be expected to achieve in the future. A biotech company pursuing a novel diabetic drug might be able to achieve multi-billion annual profits - while a niche software company might only expect to achieve annual profits in the tens of millions of dollars. Comparable deals (valuations placed on similar companies) help, as do financial analysis to define a large \"ballpark\" range of reasonable valuation. Typically, solid biotech/medical device startups that have good management, protectable intellectual property, and a good market opportunity typically see first-round (A-round) valuations in the $1M to 7M range. A few exceptional startups might be able to negotiate a higher initial valuation. Few would ever get investor attention with a lower first-round valuation. The idea, of course, is to \"stage\" the total investment required to achieve profitability. So you might raise a $2M \"A Round\" (first round of investment) on a pre-money valuation of, say, $4M (selling a 50% ownership stake in that company) - then use that money to achieve significant technical and/or business milestones so that you can later go out and raise, say, a $5M \"B Round\" at a new valuation of, say, $12M. The idea, of course, is to use \"expensive\" early-rounds to increase the valuation of subsequent rounds (by lowering risk to investors at the time of investment) so that you can raise additional tranches of cash at less expensive rates (i.e. selling less ownership). All-in-all, though, valuation is still largely achieved through negotiation and shopping the company to different investors. It's a lot like trying to value an antique car - there may be some sort-of comparable sales (not the exact same car, but sales of antique cars that are sort-of like the car you're trying to sell) to help guide you, but at the end of the day, the company's valuation is whatever someone is willing to pay for a portion of its ownership stake.",
"In the tech industry specifically, the valuation relies heavily on competition, total addressable market, volume of active users and magnitude of proprietary assets/intellectual property. For example, Uber received a massive valuation because it was the first mover in a new industry with strong branding position and a massive addressable market. The valuation has been sustained by the sheer number of people who use it.",
"I've worked at silicon valley startups for 10+ years and I can tell you, with my hand on my heart that the numbers for early seed rounds are basically made up. I mean, there's a *logic* at play but it's based on what you're able to raise to deliver a prototype of your vision. If you have an idea for \"umbrella drones\" you spec out your engineering cost to build the devices and a fabrication facility, then you need to hire people so you cost out those salaries, you need office space and marketing etc and you arrive at a number. Call it $2mn. Then you start meeting investors, you give them your pitch which will go something like \"there's 3bn people affected by rain every year, and 1.8bn buy umbrellas every year, which creates an umbrella market worth $4tn / year. We believe we can produce and sell 120k $1000 drone umbrellas / year at a market cap of $120mn, we're looking to raise $2mn in return for 5% as a series A\" etc etc (i'm being flippant, but you get the idea). Investors want to give the least amount of money for the most return at the lowest risk, so they tend to partner up with other Angels or VC companies. So 1 investor might give $100k and someone else might give $500k, but each of those transactions will establish a value based solely on the cost of producing the initial idea (and frequently, just a prototype version of the idea) and the founders ability to sell his pitch. Investors also like to call the shots, so while the founder wants to execute his vision, he still has to go and report back to the VCs on progress (usually via board meetings), if the company is not growing fast enough, or the VCs have started seeing trends in other sectors that will yield a safer return, they can and frequently do, make strategy changes they expect the company to embrace. The founder is free to ignore the request, but he won't get another round of investment from that investor. Profit is rarely a factor in the equation. Everyone *wants* a profitable company but companies can operate solely by raising cash, and they raise cash by talking about their appeal and using metrics that verify their appeal, ie how many users, 40% year on year growth, subscriber penetration, repeat visits, unique impressions etc. It's why twitter, a company that makes almost no money, is worth $7bn. It's madness when you think about it. Once that initial investment is raised, a public valuation now exists and all subsequent valuations are essentially an evolution of it."
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7c0s0s | How would losing a limb (or multiple limbs) affect blood flow and oxygenation of the body? | Biology | explainlikeimfive | {
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"The body has baroreceptors inside the arterial walls which regulate the pressure of the circulating blood. These receptors keep the blood pressure in a specific range via multpile mechanisms like renin-angiotensin-aldosterone, systemic vasodilation/comstriction via nitric oxide etc. If you loose a limb, the blood pressure may rise at first but the body will adapt in no time using these mechanisms. So it wont necessarily effect excercise capacity.",
"It would not have a noticeable difference in many cases, provided its healed properly. Remember, our body is really good at adapting to changing conditions inside and outside of itself. The thing with oxygenation is that our body wants carbon-dioxide and oxygen at the same time. How much we have of both is detected by cells along our blood steam, and then the message is sent to our brain really quickly, and very often. The message is telling the brain how acidic our blood is, and that acidity is the result of having different amounts of carbon-dioxide and oxygen (and other factors, but this is a ELI5); more oxygen makes it less acidic, and more carbon dioxide makes it more acidic . Your blood acidity wants to be a jusssst the right level at all times, so when our cells exchange their carbon dioxide for oxygen, our blood acidity naturally lowers. To counteract this, we breathe in more oxygen, returning it to jusssst the right level. This applies to every little part of our body, from your head to your toe, as all these cells want to live in a comfortable environment. When you lose a limb, you lose the cells which send the message to your brain, along with the muscle, tendon, and other tissues which require that message to be sent. Your brain can only tell how much the messengers want oxygen, not where or how many cells need to be oxygenated. As a result, a loss of a limb makes the body work a very small amount less than if it had that limb. This is also true for blood pressure/flow, because there is less muscle and other tissues to deliver this oxygen to, and take carbon dioxide away from. Would it make cardiovascular exercise easier? It would eventually make no difference, as your brain and heart get used to there being less cells which need monitoring and the transfer of nutrients (not that they can directly measure these in any way). Depending on the amputation (let alone recovery time), your body will change its breathing patterns and heart pressure/beat to be just a tiny bit smaller... probably not even noticeable, and it wouldn't make a difference.",
"When your arm gets chopped off at the rotator cuff, does the arteries and veins in your shoulder reconnect to re-complete the loop?"
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7c0xk0 | Why are bubbles round? | Physics | explainlikeimfive | {
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"Not all bubbles are round but for to answer the question it is a force called surface tension. It pulls the molecules tightly together and the closer they pull the more compact they are leading to a spherical shape. A sphere is were you achieve the tightest possible grouping of particles.",
"The surface tension of water makes it much like a balloon. the surface want to be as small as possible, but the volume of air is still constant because it can't get out, so what happens is that it goes towards the shape that has the smallest surface area, given the constant volume, which is the sphere. A balloon isn't perfectly round because it has the opening and the rubber might not be equally thick everywhere, but a bubble becomes perfectly symmetrical because there is no reason any side should be favored over another, so everything is evenly distributed. (Gravity might make it slightly thicker at the bottom I suppose, a bubble is so thin and light that the gravitational force is very small and hardly noticeable)"
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7c11u8 | What is happening to my floor? | Other | explainlikeimfive | {
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"I think you have a water damage. If you look at the chair-leg you notice a water puddle. You hearing water might be another indicator, as well as the wood bending. Contact your insurance (by god i hope you have one) or your landlord if he can be held accountable for such a damage (depends on your country of origin/the contract). If you have underfloor heating it is very likely that such a pipe leaked. If you live on ground floor it is possible that your foundation is not sealed anymore. If you live above ground floor and do not have underfloor heating maybe some pipe running through burst. Best inform your insurance company or landlord first. This is going to be expensive."
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7c128q | Why is it that I️ can go the entire night without peeing while asleep, but as soon as I️ wake up I️ have to run to the bathroom immediately? | Biology | explainlikeimfive | {
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"During sleep at night, antidiuretic hormone releases and keeps the water in your body by limiting the filtration speed of your kidneys. You dont produce much urine, hence you dont have the urge to pee and dont wake up. This mechanism is disrupted in diseases like diabetes or chronic kidney diseases and you wake up just to pee which is called nocturia.",
"During the duration of sleep you do not pee (hopefully). However, your kidneys are still filtering your blood (hopefully). When you wake up you have not peed for the duration of your sleep and therefore have to pee."
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7c1bak | What are benign tumors and why/how do they grow if they aren’t cancerous? | Always kind of wondered about this. Thanks! | Biology | explainlikeimfive | {
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"Tumors are excessive tissue growths in places which you dont normally expect and they are named after what they're made of (myoma: made of muscle; lipoma: made of fat etc). Of course there are other tumors named differently but i'm telling only this part to create a general sense. Malignity/benignity concept is used for a few reasons which refer to the risk or danger a tumor has for the human body. For example if a growth invades the surrounding tissues and disrupts the normal physiology it is considered malign(or cancerous). Or it can effect the neighbor tissues not by invading but pressing on it (like in the brain). Some can be functional tissues and secrete hormones which disrupt the bodies' phisiology(like adrenal or pitiutary glad tumors etc). Benign tumors generally dont cause any harm to the body except maybe some cosmetic problems. They dont have the potential to turn into malign processes so generally thats why they are called benign.",
"Cells have to follow certain rules in a healthy individual. For example, a particular cell may: 1) only survive if surrounded by cells like it, 2) only survive if one side is facing one environment, and another side is facing another environment, 3) obey an intercell signal to terminate, and 4) not try to increase the amount of blood supply in the area (i.e. vascularize). To be a \"cancer\" a particular cell may need to break all of those rules (and others). A benign tumor may just break, e.g., #2 on that list. So it will grow without regard to its orientation, but it will not grow away from its tissue type and it will obey signals from the body to terminate. Cancers often result from an accumulation of mutations. Each mutation may disable a different rule. When enough rules are broken, the cell can grow in parts of the body it has no business growing, and it can threaten the person's life. A benign tumor is one that can either be on the path to danger (precancerous) or unlikely to ever become dangerous."
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7c1r0f | How do explosions trigger car alarms? | Technology | explainlikeimfive | {
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"Most car alarms detect movement on the car, like when someone tries to break in. If it is too sensitive, it can be set off by someone leaning on the side. An explosion sends out a massive shockwave, which shakes the car and sets off the alarm.",
"When an explosion occurs, regardless of the source, it creates a shockwave. In large explosions, say like a nuclear blast, shockwaves can level cities/infrastructure just as well as the actual blast itself. Shockwaves can also kill people caught in them if they're powerful enough. When a bomb goes off, lets say in a terror attack, the blast will do immediate damage (likely with fragmentation, being a terror attack and all) while the shockwave will cause massive infrastructure damage. Windows will be destroyed, barriers and fences too. The effect of the wave crashing over a car is what sets off the alarm, since it's enough force to physically rock the vehicle/impact the sensors that trigger the alarm."
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7c1s3b | How can a hydrolic press break a diamond? | Physics | explainlikeimfive | {
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"Hardness basically describes which substance will *scratch* more easily, but not which will crush the other. A piece of glass can easily cut a beef roast, but if you throw a beef roast at a glass window, the window will smash to bits while the beef remains intact.",
"Hardness =/= toughness. Hardness is a measure of an objects ability to resist being deformed. If you press into a diamond you won't make a dent because its atoms are packed incredibly tightly. The same inability to deform is what causes hard objects to be brittle. Generally speaking, harder objects tend to be more brittle. Being inable to deform under stress means there is only one other option: breaking. So, while you can pretty much never scratch the surface of a diamond no matter how hard you press into it, you can fairly easily shatter the entire structure with a hammer.",
"Diamond is very hard, but it's not infinitely strong. If you crash a metal car into a metal pole, both get bent but the stronger pole bends less. Diamonds, alas, are crystals so they don't bend. When their strength is exceeded, they fracture or shatter. When you try to crush the diamond at first you see the steel deforming but at a certain level of force the diamond fails.",
"Diamonds are one of the hardest materials on the Mohs scale, which is defined by what materials are able to scratch other materials. So in that sense, the diamond would scratch the press metal, not the other way around. Hardness as represented by the Mohs scale doesn't capture the full picture, though. Even though it's difficult to scratch, diamond is decently brittle, meaning that it's fairly easy to apply enough force to cause it to shear along one of its crystalline planes. Believe it or not, it's possible to break a diamond by stepping on it on a hard floor - you don't even need a hydraulic press."
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7c1um3 | what is it about electricity that makes it so dangerous to the human body? | having electrical work done on my house today & this thought popped into my head. edit: just wanted to say thank you to everyone that has replied to my post. even though i may not have replied back, i DID read what you wrote & just wanna say thanks so much for all the info. i learned alot of something new today 😊. edit #2: holy crap guys. i have NEVER had a post garner this much attention. thank you guys so much for all the information you have provided even if i havent personally replied to your comment...i have learned a ton reading through everything, and its much appreciated! | Biology | explainlikeimfive | {
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"Your body uses electrical signals in its nerves, which is why electricians are told it's better to brush a suspect wire with the back of your hand (so the involuntary cramp pushes your hand away rather than clamps on). The major way people die from electric shocks is if it goes through the heart. Your heart is a finely tuned machine that does not appreciate a sudden external signal saying contract all muscles. If you're lucky, your heart resumes beating with its normal pattern. If not, hope someone around knows CPR. Incidentally, this is also a bugbear for medical shows - the device with the paddles and the shouting clear doesn't restart the heart, it stops the heart and is used when the rhythm has gone wrong (called fibrillation). The heart can then restart itself with the correct rhythm (hopefully). Edit: thanks to the 5000 electricians who have correctly pointed out that devices exist for checking if a circuit is live. Use a device if you have one (and if you haven't got one, why are you working on your electrics?). The only time that tip saved by bacon was when I found an unknown wire in my loft. The main house breaker was off, but it turned out some enterprising previous owner had hooked the loft lights up to my neighbours power. 240V is unpleasant (and made my hand & arm contract fast enough to bruise all my knuckles on a joist).",
"The human body is not a perfect conductor for electricity and when electricity encounters resistance it generates heat. If you happen to become a part of an electrical current of a high enough amperage(the measurement of an electrical current), you could be severely burned. More importantly, electricity causes muscle contractions. Since our body controls its muscles through the nervous system with electrical signals, an overload of these signals might cause serious contractions and even paralysis. What’s worse is that this could even cause your respiratory system to fail and ultimately stop your heart.",
"There are two things really. One of the biggies, is that often electrocution over rides conscious muscle control, and so the person who becomes electrocuted is unable to let go or jump back out of harms way once it starts. They may be thrown clear by their own muscles spasming, or they may instead grip the wire even tighter. 1. Your autonomous nervous system such as heart beat and your internal organs, uses electrical impulses to keep everything working. Electrocution can interrupt or over ride these signals, preventing the heart from beating correctly or sometimes stopping the heart all together. In order for this to happen, the electricity must pass over the critical chest area and vagus nerve. For example touching a livewire with both hands would form a connection from one hand, through the arm, chest, and out the other arm, stopping the heart. Grabbing it one handed might cause it to form a circuit going up the arm, down the side of the body and through the feet. It doesn't take much amperage for this to happen, but it usually requires high voltage. Also alternating current is more disruptive to the body than direct current, and more likely to electrocute somebody even at lower amps and voltage. And #2 Amperage can cause burns. The same action that causes the filament in a light bulb to glow bright orange, causes your body tissue to get hot and can cause electrical burns as the rapid influx of electricity pushes past the electrical resistance of the body and creating heat in it's wake. These types of electrocutions may not stop the heart, but may literally cook the body. People who get electrocuted and have to have limbs amputated, are usually the ones who were burned by high amperage but not long enough to kill them. Direct Current with low resistance and high amperage can cause electrical burns to a person just as readily as alternating current can. Amps kill and amps burn. Even a lower voltage direct current could burn you readily if the amperage is high and resistance is low. This is also responsible for the numb tongue you get when licking a 9v battery. The tongue completes the circuit and begins to be burned, which causes us to yank the battery away before any real damage is done.",
"There are two things that make it dangerous. First, if it takes the right path through your body it overpowers the proper signals from your nervous system causing heart to stop beating or beat too rapidly and weakly to effectively pump any blood. It can also mess up the signaling in your brain, rendering you brain dead. Second, if you have a power source able to supply high current and you connect something with some, but not very much, resistance across it a lot of power will go into it and it will heat up really fast and possibly explode. Short circuits are typically what causes this.",
"Lots of talk here about stopping hearts, burns, etc. Those are the kinds of effects from lower amounts of power, like household electrical outlets. Once you get up to larger amounts of power ( for example a piece of equipment touching an overhead line, or giant cable that power buildings), your heart stopping is the least of your worries. Your heart will be cooked far beyond well done before it even has a chance to stop. It would cook you instantly from the inside out. A downed live power line can kill you even if you are standing ten feet away, and you can be electrocuted by standing with your legs too far apart.",
"Electricity involves energy transfer. Anything that transfers energy is dangerous. Falling off a cliff. A fire. But our muscles and nerves basically run on electric potentials, so electricity can easily disrupt them...including the heart.",
"This will get buried but hopefully someone reads it. I had an electrical engineering professor talking about how the heart muscle uses electrical signals to trigger different events within each heart beat. I think there are two signals that are meant to be timed slightly off from each other, and this timing is almost perfectly synced with a standard house outlet that operates at 60hz (in the US). So electricuting yourself with AC power really fucks up that heart signal and you heart loses its really important timing. Sorry I'm not more knowledgeable on this but the person I learned this from was.",
"A couple of things. First your nerves make you do things like contract muscles. The signals get passed through the movement of ions that creates an electrical potential (voltage) that causes a reaction to do something like constrict the muscle. If you create that voltage in another way than moving those ions naturally, your muscle still contracts. This causes bad things to happen like injury from your muscles contracting, or contracting and relaxing quickly in the case of AC. You can end up sending yourself flying, or causing other damage. Your heart is also a muscle so it can disrupt your heart by screwing up its rhythm by forcing it to contract and relax 60 times a second. The next part of it is that as current passes through something with high resistance it creates heat. This can cause burns, burns are generally bad, but electricity can burn you inside. But that's basically it, it interferes with signals traveling across our neurons, this on its own is temporary, but the physical response, like our muscles all contracting and throwing us backwards can be damaging, or our heart going into fibrillation, can be very dangerous or life threatening. Then, it causes burns as it travels through your body to ground, these burns can be internal, and a lot of things internally handle being burnt a lot worse than your skin can handle it. High voltage AC is dangerous because it will make you go flying and make your heart go into fibrillation, and you can get burned. High voltage DC is dangerous because it will cause you to grip tighter on to whatever you grabbed on to to, and you will be unable to let go while you cook, and it can stop your heart. These aren't the only things that they do, but it's the gist of it. You don't want voltages higher than a few mV at most generated by external electricity or it will cause your neurons to fire inappropriately. You don't want enough current to go through your body that your resistance adds enough energy to start reactions that shouldn't be happening, like proteins reacting and denaturing. \"Electricity\" isn't dangerous. The problem is it's required for our bodies to function. But because our bodies rely on electrical potentials to be a certain way, having that potential change because of something outside of our body makes that not work. Otherwise it's not electricity that's damaging us, it's heat caused by that electricity. The wrong kind of electricity at the wrong place is dangerous. But that's like saying what is it about gasoline that makes it so dangerous to a car? It's not dangerous to a car, it's necessary for a car to function. But if you go to a gas tank, and fill every crevasse your car with gasoline, that's not good. Not because the gas is specifically dangerous to cars, but because while the car needs gas, it needs to have areas without gas, it needs gasoline vapors to ignite, not liquid gas in the engine, it can't wash the windows with gasoline instead of wiper fluid, it can't vent exhaust when that's filled with gasoline, and a spark from the battery or spark plug can cause the whole car to burst into flames. Like gasoline, electricity can cause burns/heat to pretty much anything. Like the engine in a car needs to have a particular ratio of gasoline to not-gasoline to work properly, the human body needs a particular combination of high and low electrical potentials to be in a working state. If you stick your fork in an electrical socket, that's pretty much like going to the gas station and pouring the gas all over your car. Neither are a good idea, but it doesn't mean gasoline is particularly dangerous to cars.",
"One of the biggest dangers of electricity is the burning. But because your heart beats with the use of electrical pulses your body creates, once electricity enters your body from an outside source, at sixty cycles per second, your heart will try to match those cycles. Which can easily and quickly burst your heart",
"The issue isn't that electricity is particularly dangerous. The human body has electric receptors in it, basically little ports that electricity turns \"off and on\" in a sense. The issue with being shocked is that your body suddenly gets all these signals from an outside source. It then contracts muscles that shouldn't be contracting. The most dangerous one here is your heart, which can mess up your hearts pattern, and kill you if it doesn't restart properly. Imagine a top spinning. I suddenly add a fan blowing across it. Then I take the fan away. The top might fix itself and countinue spinning, or it might topple over. Top = your heart, fan = electricity.",
"In general high energy is dangerous. This could be electrical, gravitational, kinetic, whatever. The reason power lines are dangerous is that they have enough energy to fry you like a christmas tree. Humans are actually highly resistant to Electrical energy, skin is not conductive. Note: there could easily be a fluke, our nerves use electrical signals & the right jolt at the wrong spot could have a bad effect.",
"First of all, the passing current can \"hijack\" the transmission mechanism that regulates your muscles and make them contract for extended periods of time. This means that a current as low as 1 mA passing through your chest can stop your heart and/or your lungs from functioning correctly. The other dangerous aspect is the heat which is produced by the current flowing through your body, which can be enough to cause severe burns to skin and internal tissues. The reason your body heats up when current is passing through is that the electrons continuously bump into the atoms in your body, transferring energy in the form of vibration (which is heat).",
"One of the main reasons why 60 hertz alternating current is so dangerous is that that frequency is close enough to our heart frequency that can seriously impact your heart. Almost any other frequency would be safer, like 80 hertz. And supposedly, one of the main reasons why the powers that be went with the more dangerous 60 hertz was because of the recommendation of Thomas Edison, who was still quite influential at the time. And the reason he went with that frequency was that he was doing everything in his power to shut down alternating current because it was in direct competition with his direct current system. He recommended the worse and most dangerous frequency in order to do political and economic harm to the people whose alternating current had beat his system out of these huge contracts. He was a seriously miserable prick.",
"As an apprentice, I was taught that, once shocked, anything less then 347V will cause you to pull away, anything more then 347V will repel you. 347V is the dangerous voltage, because it specifically will cause your muscles to contract and grab the wire. And, even though amperage is the most important thing, an hour grabbing a wire at even a low amperage will fry you. FYI, look up. If you're in an office, there is a high probability that those lights run on 347V. If you ever work on something live, where there could be 347V, have a spotter. \"Your job is to stand there at the bottom of this ladder (it was wood) and, if I jerk and don't respond, kick the ladder out from under me. I may break a rib or something, but I'll live.\" -Journeyman to me at my first job.",
"There are 2 issues: Electricity traveling through your body creates a lot of heat. This can cause sever burns, both outside and inside your body. In your nerves the body sends electrical signals to command certain moves. This is also the reason why you would see someones muscles move when under electricity. This causes 2 issues: 1. You can't control your muscles, which may cause you to be unable to remove yourself from the source. 2. It can cause serious issues to certain muscles, like your heart. If electricity passes your heart, then it may stop pumping, causing you to die. A defibrillator would use this method to help a heart to start pumping again. Thus it's not only important how dangerous the electricity that's flowing through your body is, but also where it flows. It's also dangerous to touch someone in a situation like this, so helping may be difficult.",
"Physiologist here: Electricity is dangerous for three (3) major reasons. First, the proper function of your muscles and nerves (and this includes your heart muscle) depends on having the right amount of charged particles (mostly ions of sodium, potassium, and chlorine) on the inside and outside of cells that make up these structures. Electricity, or more specifically, electrical current, is a movement of charges. Current running through your body can perturb these charged ions in a manner that can cause all or part of a cell (muscle or nerve cell) to have a different distribution of charged ions at its cell membrane. This can have the effect of causing a muscle/nerve cell to contract/fire (or stop a muscle from contacting/firing). The net impact on the heart, for example, can be to desynchronize its firing muscle cells - causing the heart to be unable to contract in the specific coordinated manner required to effectively pump blood. If this happens, your heart isn't effectively pumping blood - and you soon die. Similarly (and secondly), current passing through the brain can disrupt its function. You need your brain (among other things) to tell your diaphragm to contract and cause your lungs to fill with air (breathe). So electric current passing through your brain can cause you to stop breathing for a long enough period of time for you to die. Thirdly, when electrical current runs through the human body, a lot of heat is generated. This heat destroys/damages cells and causes burns just as fire or boiling water would cause burns to the tissues of the body. So, even if the electrical current doesn't disrupt the function of your heart/brain, electric current traveling through the body can still inflict life-threatening burns."
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7c270i | Why do fire alarms ring in 3s? | You know, it rings 3 times, and then where it would ring the 4th time there's some silence and then it starts ringing again. Why do they do that? | Technology | explainlikeimfive | {
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"The Temporal-Three alarm signal (a.k.a T-3) pattern is a standard pattern used by alarm manufacturers. It is one of the alarm patterns that is designed to let people know what type of emergency there is. T-3 (three alarm sounds followed by one silent count) is the standard signal for \"Fire in the building\". There are other standard alarms as well. For example, T-4 (4 alarm sounds followed by one silent count) is the standard for Carbon Monoxide alarms.",
"* the alarms are coded, different rings mean different types of emergencies * it makes the alarm stand out more * it makes it clear this is, in fact, an alarm, not some other kind of noise"
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7c2tjw | What causes you to sometimes have a sudden urge for a very specific thing to drink? | I'm pretty sure this is normal for everyone but one day at work I may have an extremely strong urge to buy a Fanta from the soda machine, and another day a Coke. One day you can have a sudden irresistable thirst for orange juice and you empty that box as if it was your last action on this earth. One day it can be just water. Always been curious if there is an explanation for this sudden craving for a specific thing to drink. | Biology | explainlikeimfive | {
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"Not sure if there is anything more specific to drinks, but I've always been under the impression that when your body craves something it's because it needs it. Thus why pregnant women sometimes have such strange cravings (because their body is experiencing strange nutritional drains and trying to compensate). Your craving for orange juice could really be a craving for vitamin c or citric acid or something, and your craving for water could be because you're just dehydrated, etc. Don't have any actual sources to back this up, but it's always made sense to me, more or less."
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7c2vzn | What makes rape victims often stay quiet for so long? | Other | explainlikeimfive | {
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"Rape is a very, very difficult crime to prove. People have consensual sex all the time and before someone can be locked away for rape you have to be able to prove (~~\"beyond a shadow of a doubt\"~~ \"beyond reasonable doubt\" is the usual standard) that the sex that you had was nonconsensual. Imagine going to the police and being like \"So I met this guy at the bar, and we were having a good time. I even went back to his place with him, but there were red flags everywhere. I called an uber to go home, but he forced himself on me before I could get out of there.\" The next question the police will ask is about evidence. They obviously can't arrest someone just because, and that's the tricky part. Rather than screaming and fighting, some people just freeze up when threatened. How is an investigator supposed to tell the difference between a rape where the victim froze and consensual sex? It's he-said-she-said, and we can't convict anyone on that. It's an uphill battle the whole way, combined with the trauma and pain that a victim now has to cope with every day. Most don't bother. Thankfully that's changing. Statistics nowadays show that victims are more likely than ever to report sex crimes and that police and other groups are much more likely to open a serious investigation than they were a few decades ago, but it's still very difficult.",
"shame and embarrassment. We often blame the victim for getting raped and not the rapist for committing the act. You've just been physically violated, perhaps now carrying an unwanted pregnancy, and now everyone is scrutinizing why you were walking home alone in that short of a dress, ask if you told him no, ask why you didn't fight back. It's pretty bad for male victims too. There's the stigma that guys can't get raped. That ranges everywhere from that guy being told he's a weakling to saying he can't be raped because all guys enjoy sex. I mean, even in your own question you're equating weakness to female anatomy and inconsideration to male anatomy.",
"Rape is hard to prove, it is one of the few crimes that can look exactly like a consensual activity. Even if there is physical evidence, it will often come down to a he said she said situation. And when the rapist is in a position of power where they can retaliate, it can be in the victims best interest not to report. In addition, human nature is such we want to believe in the lesser evil. It is more comforting to believe a victim is lying than that a friend is a sexual predator. There is a natural inclination not to want to believe the more serious threat. Finally, due to double standards in sexuality, women who have sex out of wedlock are often viewed negatively. She might not want it on record that she went to the apartment of a stranger, consensually got naked and into bed, and only changed her mind after he didn't have a condom. Unfortunately, many believe at some point consent becomes unrevokable, sometimes even when it isn't explicit given. Recent surveys have shown a surprisingly high number of college students, men and women, believe you are obligated to have sex if a date buys you an expensive dinner. Extending this a little further, men are often portrayed as hapless slaves to their lust, with wanton women using their wiles to bend them to their will. A woman who has claimed to have been sexually assaulted is often seen to have encouraged it with her behavior or acted consensually and is using the threat of accusation to get what they want. Places where this culture exists can be very harsh on victims, ostracizing them even if they win their case. Finally, sometimes they are not really victims. They aren't lying, but memories are fallible and can drift over time. A consensual situation they wound up regretting can in their mind evolve into a non-consensual one.",
"Hm, I have no experience in this subject personally. I would say it has a lot to do with bunch of feelings and justifications but the most simple would be that there is shame and embarrassment to overcome but to a larger degree I think it is a concern of not being believed while simultaneously wanting to 'move on' with their lives and not be stuck in something so horrible. To ELI5 my point, your in school and a bully starts picking on you, stealing your stuff, beating you up, and being an overall POS. What makes you not want to go to authorities? For me it was the fear of not being taken seriously, victim blaming that comes up every time, the bully (abuser) not being punished, and finally I just wanted to be away and forget it all and saying anything about it would mean that I would be putting all of that under a microscope for myself and it would be my life for a long time. Something I want distance from suddenly becomes my existence day after day.",
"Let's not talk about rape. Let's talk about something simpler. Let's say I loan you $400. But when I ask you to pay me back, you say \"That wasn't a loan! It was a gift!\" Now, I **know** I didn't agree to give you a gift. But I also didn't make you sign a promissory note, or draw up a document. So it's my word against yours, isn't it? What can I do? Well, I can tell our friends that you didn't pay back a loan you made me. But you could just as easily say that I gave you that money, and now I'm just going through regret over it and trying to take advantage of you to get my money back. You could say that I'm just being dramatic about the whole thing, that I made it all up to get attention or sympathy. (or to get money from our friends!) Say I tell my friends that you took my money and never paid it back. I bet a lot of them would ask why I don't sue you in court, use the law to get justice. But I'd have to go talk to a lawyer, ask a bunch of questions, take time off from work to testify in court, and even then, there's no guarantee (because it's my word versus yours) that the judge would rule in my favor. ( 1 ) Even though going to court isn't a great option for me, if I **don't** go that route, people are going to think that maybe I don't think I could win in court, which means they'll think maybe I'm lying about the loan. Meanwhile, you're pissed off at me, because I've told all our mutual friends that you never paid me back. So you tell them all I'm a liar, and an Indian Giver, and how I've got so much money I'm just giving it away to everyone, but somehow you're being unfairly singled out. Our mutual friends, meanwhile, might wonder if it's ever safe to accept any gift from me, or if I might be lying about other things to get attention or sympathy or money. And we're talking about you stiffing me on a loan here! Now mix in questions about how rape victims \"should\" look or act or sound, about issues of consent and how it does or doesn't work, about social stereotypes around women and sex and trust, about false accusations and whether being accused of rape is as bad as actually being raped, about people lying to gain advantage, and you can get a sense of how bad it gets. Footnote # 1: small claims court actually **does** assume large transfers of money are loans unless they are expressly documented as gifts, which is different than criminal law cases where the standard for guilt is much higher."
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7c30qh | Where and why do you use the i, the Imaginary Number ? | Mathematics | explainlikeimfive | {
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"Dynamics and circuits, as well as process dynamics are major points. Basically anywhere that feedback exists and you need to calculate it you will incorporate i into your calculations.",
"One common one is AC circuits with capacitors and inductors. If you've got a circuit with a bunch of resistors, 4 caps, and 3 inductors you can solve it with a 7th order differential equations, that'll probably take a few days, or you can use \"phasors\" which uses i to represent phase shifts due to the caps and inductors. This let's you just add, subtract, multiply, and divide complex numbers(a+bi) to solve it. You can do this in minutes and not hate your life Complex numbers are used for cyclical events like AC circuits or Dynamics in mechanical systems",
"Copying an earlier reply of mine: First of all, I hate the name \"imaginary\" numbers, because it leads to all kinds of confusion where the concept is actually quite simple. Starting with counting numbers: 1,2,3... But what if you want to have numbers in between? Does that make sense? Well, we could do 1/2, or 13/29 or 2353/3535 or whatever *rational number* you want, because we are extending the system in useful ways. For centuries there was extensive debate over whether zero or negative numbers really \"existed\". It seemed meaningless to talk about having \"less than none\" of something. But regardless of philosophy, negative numbers are *useful*. If zero is sea level, land is positive, underwater is negative. How could bank balances work without negative numbers? Nobody could keep track of credits and debts. A greek mathematician was (according to legend) drowned for showing that *irrational* numbers existed, that there were numbers (like the square root of 2) that could not be expressed as a ratio of two integers (counting numbers). His \"friends\" could not bring themselves to believe that such numbers existed, even when faced with incontrovertible proof that they did. But such irrational numbers are extraordinarily useful, the square roots of non-square numbers, pi, e, all of these are irrational, and I bet you know that a circle's area is pi*r^2. Bam, irrational number being useful Which brings us to Imaginary numbers. Simply put, imaginary numbers are another useful way to extend our number system. Negative numbers let you solve x+2=0. Imaginary numbers let you solve x^2 + 2=0. Imaginary numbers, and real numbers are the two starting sets that when combined make up *complex numbers* which are simply real and imaginary numbers added together. Generally, complex numbers of the form a+bi are visualized as coordinates on the [complex plane]( URL_2 ) more like (a,bi). This plane has real and imaginary axis, and all complex numbers can be expressed as a location along those two axis. This is mathematically interesting in and of itself, for instance squaring a complex number tends to rotate it in the complex plane, and playing around with where numbers rotate to, and how far away from the origin (the zero point where the axis cross) you can get some [interesting pictures]( URL_0 ) with some very [interesting properties]( URL_4 ) But enough high concept and abstract math, how about some real-world applications? Imaginary numbers are used very often in various applications in physics. Much of the usefulness comes from Euler's Forumla: e^ix = Cos(x)+i*Sin(x) This means that you can express something that moves in a wave or cycle like a sinusoidal function as an exponential function. Often one or the other of those is easier to work with mathematically, so you can freely transform back and fourth. For example, the [Schrodinger Equation]( URL_1 ) which describes how quantum ~~particles~~ waves move, is formulated with imaginary numbers in it Depending on the specific situation, solutions to this equation may either travel indefinitely--in which case the sin/cos terms describing a traveling wave are used--or die out, where exponential decay is used instead. Another interesting example is refractive index, which describes how light interacts with matter. Most normal materials have a positive refractive index, meaning that light bends [like this]( URL_3 ) when traveling through the material. Some exotic materials have negative indices of refraction, meaning that the angles in that picture would be on the other side of the center line. Furthermore, you can have a positive imaginary reactive index, which when you work it out (I did this problem in a physics class last year :P) means that the material is absorbing light, and not all of the light that goes in comes back out. Finally, you can have a negative imaginary index, meaning that the light that goes in becomes brighter when it comes out, which sounds strange, but that is exactly what happens in a laser. There are many more examples of real-life applications of imaginary numbers, you just have to know where to look. Once again, imaginary numbers were invented because they are *useful*. You'd be surprised how many real-world advancements were made because some crazy math guy came up with a bizarre new idea."
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7c32kh | Different interpretations of probability ? | What are frequency interpretation and degree of belief interpretation in probability ? | Mathematics | explainlikeimfive | {
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"Frequentists view probability as ratio of some machine of sorts. Throwing a dice for example is seen as a machine which 1/6th of the time gives 2. You can know this ratio by doing repeated tests on it and checking how the results turn out. Which makes sense. But this way of thinking sort of collapses when you're asked to make probability estimates of things that only happen once. Like, lets say olympics. Each competitor is currently in unique place in their own career, some are completely new faces. You can't just repeat these same olympics over and over the get frequencies of each competitors successes. So in a way, the whole frequentist way of thinking collapses and you simply can't make statements like \"this guy probably wins\". Which is where Bayesian way of thinking pops up. It treats probability not as some ratio of an abstract machine you need to study, but rather as your degree of certainty that some event happens. If you believe, for whatever reason, that some event is likely, bayesian system enables you to measure exactly how strong this belief is, and how it should change as you receive new information. The outline I'm familiar with is that bayesian interpretation of probability is mainly used in cognitive psychology and AI research because it provides guidelines to how one should react to new information. All other times there is little harm in treating probability as a ratio of some weird machine you may or may not understand."
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7c3acd | How is TV static from the big bang? | Physics | explainlikeimfive | {
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"Most of the TV static is from the amplifier itself; only ~1% of that is cosmic background radiation. CBR is spread across a pretty wide band, 0.3 GHz to 630 GHz, which broadcast TV is within that band. It's also really quiet, which is why almost all the static is local (part of the TV circuit itself) electrical noise.",
"It's residual energy that is still dissipating. In the grand scheme of the universe our lives are a mere split second, there are things at work that are bigger and take longer then we can comprehend.",
"I'm guessing your really asking how there could still be left over effects from the big bang. Static exists because TV antennas pick up light waves of a certain frequency that overlap with frequency of waves from somewhere out there in space. It turns out those waves from out there are actually the big bang happening. **How could the light from the big bang be just reaching us now?** Well, light travels fast - but it turns out something travels faster - the expansion of space itself. [inflation]( URL_0 ) is the process of more space being created between the stars. Have you ever asked where the big bang took place? Like, what park of the sky it would be in? Well, it was all of space, so it took place everywhere. Everywhere was just a lot smaller back then. As all of space expanded away from itself, some parts actually did so at *faster* than the speed of light. This means there are parts of space who's light will never reach us and some parts (going a little slower) who's light is only now reaching us. The electromagnetic radiation (light waves) from the dawn of time travel across the universe to come to rest in your antenna and make a gentle hiss and some soothing snow."
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7c3qp4 | Why are flying planes louder when it is cloudy? | ...especially if they are in or above the clouds? | Physics | explainlikeimfive | {
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"text": [
"Sound travels better through humid air than dry air. This is because humid air is [less dense]( URL_1 ) than dry air, and so [absorbs less acoustical energy.]( URL_0 )",
"While this is an interesting observation, unfortunately it's not necessarily true everytime. Just like any mechanical wave through the mass of a material, the speed and the energy dissipated by _per unit distance_ is dependent on a massive number of factors, the temperature/mositure content/density, the wind direction, speed of the object producing the sound, the type of sound(pitch and timbre, will change with engine type). And obviously a plane will not necessarily take the same route in a active weather that it will take through a clear sky. So what you observed, in your individual particular case was a mixture of the above humongous number of factors, some increasing loudness, some decreasing it. If I have to take a blind bet? I'll blame density, convective currents and a higher throttle. Sound not only travels faster and loses less energy through a less dense material like humid air, now the density difference between ground air and air at the height of the airplane is weaker, so upward currents are slower and are taking away lesser energy away from the engine sound. Also a plane will be at higher throttle to maintain the same pitch, as lift produced per square inch is now lesser in humid air. How about you repeat the observations several times, alongwith some detailed weather reports? It will be VERY interesting to check out what is it in your area!"
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"https://www.sweetwater.com/insync/effects-of-temperature-humidity-live-sound/",
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7c3w7w | How much info can a website glean from websites open in other browser tabs? | Technology | explainlikeimfive | {
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"Websites can't see what you're doing in other tabs, as that would be a major browser security issue. However, many websites contain Facebook \"Like\" buttons, or Facebook comments sections. If you're logged in to Facebook (even if you don't have a tab open to Facebook), the Facebook elements on those pages can see that you're logged in, and Facebook can keep track of what websites you visit.",
"Generally no. A browser code cannot access another window tab..... unless that window/tab is opened by this window/tab's code. That's not how Facebook gathers it's data. They gather data because other websites embed Facebook code for serving ads and someone pays them to do it. So when you go to URL_0 , that site tells your browser to go run code from Facebook that records your IP, device, browser, and other info and that you visited URL_1"
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7c47hw | why is having your neck broken so often fatal? | Biology | explainlikeimfive | {
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"Your spinal cord that connects your brain to body (especially your diaphram ) exists in middle of your neck. Break the neck and you stop breathing because your brain can't tell your diaphram to contract and release and open your lungs to intake air.",
"I think it damages your spinal cord which is how your brain tells the rest of your body to do things.",
"If you break your neck up high enough and sever the spinal cord, your spinal cord will no longer be able to send signals to your lungs to breathe, and to your ribs to expand and contract with your lungs. Notice that Christopher Reeve used a machine to aid his breathing for the rest of his life after his accident (where, because it happened at a large event, he got medical attention almost immediately after he was injured, which likely saved his life). If you don't get medical attention right away, you will likely die shortly.",
"Your neck is the highest point on your spine before you reach the brain. People who have broken their back in different places will get paralyzed in different ways depending on how far down the spine you've severed the spinal cord. & nbsp; For example, mid to lower back might paralyze you from the waist down, but further up toward your neck could paralyze from your shoulders down. If you break your neck, you risk paralyzing your entire body, and potentially further up towards your brain. You could lose control of your breathing, sight, etc.",
"Easier: Breaking your _spine_ causes problems. You damage the nerve INSIDE the spine, and you cut off all communication with anything that specific location and everything below it gets cut off. This is why the spine is so protected. If for example I was to break my spine at say my waist, I would not be able to move my legs and likely my bladder, some intestine, etc. You cut off the neck communication you cut off communication between the brain and all the body. That includes all things like lungs, etc. Only thing that survives is the heart because it causes its own beating with its own special nerves. Nothing else can get instructions so nothing else moves. To note, all damage to the spine does not automatically cause ALL the problems, but depending on how much nerve was damaged inside the spine is the extent of the paralysis."
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7c4h09 | How does certain medication/supplements that you take 'under your tongue' work? | Biology | explainlikeimfive | {
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"text": [
"The medication absorbs/passes through the mucous membrane under there. There are a lot of blood vessels under your tongue, so it's able to get into your blood stream faster than if you swallow it and it has to go through your digestive track."
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7c4md5 | Why does bread get tough when left outside a bag/box for some time, but crackers get soft in the same situation? | Chemistry | explainlikeimfive | {
"a_id": [
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"text": [
"Bread has a lot of moisture (google says 40%). So, leaving it out leads to the liquid evaporating out and drying out the bread. Crackers have very little moisture, that's why they can last much longer than bread. So, when you leave them out, they absorb the moisture from the surrounding environment."
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7c5aaf | Why is stomach acid unable to kill the bacterias that cause foodborne illnesses? | Biology | explainlikeimfive | {
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"text": [
"It kills off some of them, but not 100%. For example, I read that you need to ingest around [a million individual]( URL_0 ) *E. coli* or cholera bacteria to actually get sick from them. The more bacteria there are, the greater likelihood that one or two will pass through the stomach quickly enough to survive it. There are other bacteria that have adaptations allowing them to survive. For example, they might form spores. Spores are kind of like a state of suspended animation for the bacteria, where they aren't really doing anything, but as a result are more durable. Other times, there isn't even any bacteria present. A lot of bacteria produce substances that cause irritation to humans, and are more able to withstand heat than the bacteria themselves. So if you have a piece of food with tons of bad bacteria growing on it, and you cook it, all the bacteria will die but the stuff they secreted will still be there, and will cause disease in anyone who ingests the food."
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7c5d1l | Why are karats only up to 99% purity and not 100%? | Chemistry | explainlikeimfive | {
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"You aren't able to remove every little bit of the various metals which are in a gold bar. By in large, no chemical process produces 100% purity. When they 'filter' out the different metals, some are left over due to random disorder in the system. The metal alloy slowly gives a higher content ratio of gold as others are processed out, but you can not say its 100% gold. Imagine you have a ball-pit with walls full of red, green, and yellow balls. This ball pit has a fan below it, and so the balls fly up and down, and hit the sides, hit each other and are just moving all over the place. You've found that the yellow balls have Velcro on them, so when you drop a large Velcro ball in there, they all bind to it. This large ball is easy to take out, because you've tied a string to it, and when you remove it, there is a lower amount of yellow balls than before. There are still yellow balls, but there is a lower amount. If you do this for every colour, you'll soon find you can't remove all of the balls, and so it is not worth your time. The second thing you notice is that the yellow balls add a preferred property to your metal; say they make it more colourful in the ball-pit. You would want to keep some to preserve this property, because it creates a better ball pit. For some alloys (metal mixtures), they do this as well, as things such as gold are very malleable, and an alloy can make it stronger. *This is not really what they're doing when purifying gold, but its a good relevant thing to note."
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7c5mbi | how does hand soap go from liquid to foam? | Chemistry | explainlikeimfive | {
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"text": [
"A special valve in the pump assembly injects air into the stream of soap as it exits the nozzle of the pump."
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7c5s96 | Why is the sound of someone snoring so annoying when we're trying to sleep? | Biology | explainlikeimfive | {
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"text": [
"I imagine it's at least partly because the sound is irregular. Traffic, air conditioners, and rain are very rhythmic. Predictable sensory input is input that our brain ignores, which is why you only smell things for a short period of time. Snoring is jerky and hard to predict so you never adjust. I could also be wrong."
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7c6mug | Why do we continually need to search for new porn to arouse us? What exactly is it that eventually drains all previous porn off its original arousability? | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"Much in the same way we don't watch the same exact TV show episode daily, why we don't wear the same exact outfit daily, don't listen to the same song over and over in perpetuity or eat the same meal over and over in general. Your mind does not derive any more stimulation due to over saturation. The mind generally craves innovation and stimulation as humans. When it becomes repetitive and the brain stops signaling stimulation for viewing, your mind craves for something different to reach that stimulation level. Edit: I am sure somebody can breakdown the exact science in the brain.",
"I think it's the novelty of it. And access. If there was less access, people would watch the same scenes over and over and over and over and over again."
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7c6wre | Grid Computing as it applies to a business setting | So my understanding is that it's basically a network of computing devices, but how does this help businesses as far as data mining and data science goes? Specifically, what about grid computing is advantageous to business? | Technology | explainlikeimfive | {
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"Not many businesses use this technology. The idea is to take extremely large computation jobs, and spread them out across many computers in multiple locations. This way they can get done faster than by just using one roomful of computers. And otherwise idle computers can help out with the computation.",
"Grid computing is useful since it utilises idle computers to perform complex tasks, think of it like if you had 100 weak workers just sitting there but instead you go and find 1 very strong worker and pay him to finish the job, it would be a waste of money since you're already paying the 100 workers, instead you could just divide the complex task between the 100 weaker workers who would finish the job in the same time. So grid computing could save money and also would utilise the full potential of resources a company possesses."
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7c78et | why is it that fire normally burns orange? Why isn’t it blue, green, or purple? | Chemistry | explainlikeimfive | {
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"text": [
"The color of a flame depends on what is burning and how hot it is. Most flames come from burning carbon based fuel (wood, wax, etc) and these things burn orange/red/yellow. The higher the temperature the whiter the flame. Other chemical substances simply burn different colors than carbon. This has to do with the amount of energy given off as something burns."
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7c7brc | Why does a company or any organization still need accountants? Why cant every transaction be recorded in a computer and entered into the books automatically without needing a person to do it? | Economics | explainlikeimfive | {
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"Well, many companies do fully automate their accounts already, e.g. they may conduct all their business through an enterprise platform like [SAP] ( URL_0 ). But there are still questions about how to interpret the law and categorise things within such systems. Laws, regulations and accounting standards can change, and questions about how to organise finances can get really complicated for a large company, and some accounting practices are optional, meaning accountants can advise on what to do to make the balance sheet look right.",
"I was financial manager for a Student Team for a year so I did this stuff small-scale, but I think my experience should be extrapolatable to larger corporations. The general answer is that a lot of it is already automated (calculating taxes etc.) But bookkeeping is such a 'human' thing. The software we used managed to automatically book things like Diesel onto the right books since it recognized the resellers, but for example a random receipt from a DIY store, no computer can figure out where that product was used for, meaning you need a human to read the receipt and figure it out. Then there is all the dealing you will have to do with creditors, special prices, package deals, special circumstances, etc. All stuff software can't do at the moment, you would need a really good AI for that.",
"Automated bookkeeping is something that a lot of programming hours have been used on, and is a major industry in itself. There are a number of different issues that need taking into account: **Paper is still an important way to exchange accounting information:** Just in travel expenses alone, all the receipts from meals and similar expenses make up a huge amount of paper. Sometimes a payment is stipulated as part of the text of a contract, without a separate receipt. **There are no widely-accepted international standards for accounting information interchange:** if you get an invoice from a vendor, or send one out to a customer, it will likely be as a PDF with that company’s document design on it. Whilst there are several different competing standards for things like electronic invoicing - at least one was made by the UN and standardised by ISO as far back as 1987 (UN/EDIFACT INVOIC messages), and as recently as 2015, the ISO has standardised OASIS UBL as a file format - none have made the leap to being the main way to interact between companies. Even banks don’t all present bank account information in a standard format that a program can import! **Every country has different rules for what should be on an invoice and how it should be presented:** for example, tax breakdowns, exchange rates, item descriptions, and so on. In Spain, there is a concept called a “suplido” that doesn’t even have an established English translation (the closest is the phrase “expenses disbursed on your behalf”), and they need to presented differently on an invoice. **Existing systems to deal with the disparity of paper and file formats are unreliable, and expensive:** generally these require some sort of OCR for paper based formats, and some sort of Machine Learning processing that identifies the likely location of key accounting criteria (company name, invoice amount, tax amount, etc). Companies like Kofax make a lot of money out of these solutions, but they are generally not affordable for small businesses. **Existing ways of forcing electronic information interchange are regional, or industry based:** many large companies require all their vendors to send invoices through a specific system using a particular document format. Often it’s proprietary, or more recently, it’s a website where the vendor has to type that information in by hand. Some countries have enacted laws that require public procurement and invoicing to happen using electronic formats, but, crucially, each country’s format is different, and some don’t even have the ability to use electronic invoicing. The EU attempted are trying to harmonise this with PEPPOL, but even that is just one region, rather than something that the major trading blocs have agreed to use on a global scale. Of course, these are mere technical issues, there are a number of other problems: **There needs to be processes in place to verify that accounting data is valid:** in larger companies, this generally takes the form of a purchase order, whereby someone inside the company types in accounting data as part of an order telling the systems what to expect from an invoice, and if an invoice arrives that agree with that PO, then it is matched and accounted for. If it arrives erroneously, or doesn’t arrive, then these things need to be dealt with by humans. **Accounting Data has an analytical component:** generally companies wish to know how much they are spending on specific categories of product or service, or how that is divided into departments or business units. This sort of analytical data changes from company to company, and is difficult to standardise on. In larger companies, the Purchase Order generally carries enough information for this analytical data to be accounted for. **It’s not all invoices:** Bookkeeping also involves accounting for stock, asset tracking, payroll, credits and other liabilities, notifying banks of things like invoices that need factoring, talking to customers who are late in paying their invoices, preparing and verifying tax statements and monthly, quarterly and annual accounts, and dealing with a big influx of data. A large part is automatable. But the general disparity of data means that there need to be people available to deal with the outlying conditions and the small irregular occurrences. That being said, the main issue here is that **People still need to type the information in:** at some point, even if it’s just a cashier typing into a till, or an account manager typing into a purchase order, that information needs inputting at least once. Most automation is based on the idea of removing repetitive inputting of the same data. That being said, if an accountant doesn’t do it, someone else will, and that someone else has other jobs to do. Which leads me to: **Bookkeepers are cheap:** sometimes it’s cheaper to hire a bookkeeper to perform a task than it is to give that task to someone who is paid more to do tasks that are more productive or generate value for the company. A CEO is not going to type in the invoices he generates because he can be more productive and generate more income doing other jobs. Fewer bookkeepers are needed as time goes by, but a lot of things still need to happen before their need is eliminated completely."
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7c7s9j | why is it more instinctual to hold our breaths while lifting something heavy, than it is to breath properly? | Biology | explainlikeimfive | {
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"text": [
"when lifting an heavy object, your body needs to become rigid enough to lift such object. So you start tensing your muscles to create a strong enough structure capable to lift. Breathing involve the diaphragm to expand and retract the rib cage. in order to do so, the upper chest needs to be \"soft\" enough to allow the contraction and expansion. This goes against the \"rigid\" stance that is needed to lift the heavy object and this is why we stop breathing while lifting."
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7c806a | Why is it damaging to battery life to charge up when it’s not completely run out? | Technology | explainlikeimfive | {
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"dpnu5wm"
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"text": [
"In modern batteries, that's not true. Older batteries technologies had that \"memory effect\" that forced you to discharge it completely before recharging, or you'll lose capacity. The cause of this effect is related to the chemical processes that take place inside the battery when it discharging and recharging, and are quite complex to ELI5..."
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7c86w2 | If you put tires on your car that are larger than the ones from the factory, would you actually be going slower than the reading on your speedometer? | Physics | explainlikeimfive | {
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"text": [
"No, you'll actually be going faster. The speed is calculated based on the OEM tire size, whereas if you put a larger tire on, there is more circumference so the hub will spin slower, yet will be traveling the same speed. You can have it recalibrated fairly cheaply.",
"Example: Your car comes with factory-installed tires that are 21.8 inches in diameter. That means the circumference of each tire is 68.5 inches. Now let’s say you want to replace the stock tires with new tires that are 24.6 inches in diameter. Each new tire has a circumference of 77.3 inches, which means it travels almost 10 inches farther with each complete revolution. This has a tremendous affect on your speedometer, which will now indicate a speed that is too slow by almost 13 percent. When your speedometer reads 60 miles per hour, your car will actually be traveling 67.7 miles per hour! [source ]( URL_0 )"
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7c90cb | in places where doctors can prescribe marijuana for medicinal purposes, how do they get dosage and frequency correct considering the variety and efficacy of all the strains of the drug? | Biology | explainlikeimfive | {
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"It is not prescribed the same as other medications. The doctor doesn't fill out a prescription and have you take it to the pharmacy. Instead, they simply give you a \"recommendation\" granting you access to possess it legally. It is mostly on the patient from that point to make decisions about which strains may alleviate their symptoms. The Doctors and staff at the dispensary can provide some insight as to which strains may be more effective and what dosage or method of intake might be best, but a lot of it is research and first hand testing to see what works best for the individual.",
"They don't prescribe you an amount or a strain or anything like that. They recommend that, if you don't have experience with marijuana, you start out with 5-10 mg of an edible, since edibles both allow you to control your dose more and have a longer, flatter high (I refer to it has being 'medium' rather than 'high'). They also suggest the amount based upon the persons gender, height and weight, and that you do it with someone, again, if this is their first time. However, this is when you are in talking to the doctor. Once you have your prescription and go to the store to actually buy it, chances are, your first time, you're going to spend a good 10-15 minutes talking to the purveyor about different strains and what you want. Assuming you are going for the flower (or bud) rather than edibles, they're going to talk to you about different THC levels and strains and try to find what works best for what you want. Each person is different in both how they react and what they want out of it, because one of the benefits to it is that the experience and medicinal qualities can be very personalized.",
"My mom went to a dispensary recommended by her cancer doc, that specializes in managing pain. They extract oils and mix to specifications for the chemicals known to alleviate pain, the first one she got had to be tweaked. I assume they QC the amounts using standard lab equipment. She started with one drop and then 2, to get the dosage right. Prior to that, she was on opioids which were making her even more nauseous and not helping with pain. MM gave her a quality of life in her last years and months, I can’t believe there is even and debate to give patents access especially with how bad opioids are.",
"Doses aren't as important because you can't OD on it. If you take too much you'll just get hungry and pass out.",
"That's a huge growth area -- scientific research on dosage and strains. I watched a great lecture series on medical marijuana last spring -- early research at a Canadian hospital shows that one puff of a measured dose about the volume of the white of a fingernail gets you pain relief without the high. Video is online, not sure I'm allowed to link it. In Canada, the industry feels like when we were in the early years of the dot com boom. So much energy, so many needs for growing a brand new industry.",
"LOL, no. In Cali at least, they just give you permission to buy MJ. That's it. It's up to you to figure out the dosage, type (edibles -vs- smoked), etc.",
"Cannabis is still a schedule I controlled substance, and as such, cannot be 'prescribed.' (Drugs like Marinol notwithstanding, but that's a completely different conversation.) In states where medical cannabis is legal, doctors can give you a 'recommendation' to use medical cannabis, which you present to a dispensary or delivery service to buy whatever you want."
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7c936w | How does your nasal passage close based on which position you sleep in? | My nose is stuffed up and when I lay on my left side my passages clear up momentarily then slowly my left passage closes up. And vice versa for my right side. It's infuriating. | Biology | explainlikeimfive | {
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"text": [
"The slow creep of snotbergs downward with the help of gravity and time. Called nasopharyngeal mucosal drift. This is why you should always swallow."
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7c94kv | Panic Attacks | Biology | explainlikeimfive | {
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"Hi there, Therapist here, and also have had panic attacks myself. It is common that many people will experience a panic attack at some point in their life without having an anxiety or depressive disorder. A panic attack is simply the activation of a person’s fight or flight response without a true life-threatening stimulus. The symptoms that people experience are a result of the adrenaline in their system and if a person was injected with adrenaline they would experience those same symptoms. Physically: people often experience chest tightness or pain, a feeling of shortness of breath, dizziness, sweating or feeling hot, shakes limbs, knot in the stomach, or nausea, increased heart rate. These things are all accounted for by your body preparing to fight or run. Mentally: people often experience extreme fear, feelings of dread, racing thoughts, worry that they’re having a heart attack or dying, worry that they’re going to pass out, worry that they will go crazy, worry that they will lose control. The “full” panic attack typically lasts about 15-20 minutes, as that is how long adrenaline takes filters out through the blood, however people often feel anxious and shaken after the fact (another effect of adrenaline leaving the system) which can sometimes cause them to hype up their feelings of anxiety again and release more adrenaline as their mind fears there is more danger. Generally, (not accounting for pre-existing medical conditions that would be exacerbated by spikes in blood pressure or heart rate) they are not harmful physically, just extremely uncomfortable and leave you feeling scared. Evidence-based treatments include: cognitive-behavioral therapy (changing behaviors by changing thoughts), medication, or a combo of both. Panic, anxiety, and depression are very treatable behaviorally.",
"\"Oh... I can feel my heart pounding. Here we go again, crap. Does my left shoulder hurt? Seems like it aches... no, no, I'm having a panic attack. I'm fine, stop being stupid. But it does sort of ache, and my pulse is really high... let me check it. No, stop it. You're fine, just breathe through it. Think about something else. The left side of my face is feeling numb... maybe it's a stroke. I should check my eyebrows in the mirror... can I still say words without slurring? Let me check... no... no stop, you KNOW this is a panic attack. You're being stupid, these happen twice a week. God I feel light headed, am I sure my eyebrows aren't drooping?...\" Repeat for 1-5 hours."
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7c99ju | Why it's more pleasant/ichy when someone lightly touch our body than when we do it ourselves? Shouldn't it be an identical sensation? | Biology | explainlikeimfive | {
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"You're brain is wired to respond more to unplanned stimuli. When you touch your own skin, the brain knows where and when it will happen. When someone else does it, your brain can't tell and reacts stronger"
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7c9qyz | What make objects 'bouncier' than others? | Physics | explainlikeimfive | {
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"That's an extremely broad question that brings up many answers, but usually geometry, and materials. Round shapes filled with air, like balls tend to be bouncy because when they hit the ground, the air compresses to a higher pressure, and then when it returns to it's original pressure it bounces back. If you are talking about rubber versus hard plastic, usually you are talking about rubber being made of long chains of organic molecules, that can be thought of like a bunch of strings tangled together in a ball. If you pull at opposite ends of the ball, strings will slide past each other and stretch out to an elongated shape versus the coiled up shapes they started in. Chemical bonds and van der waal's forces can pull them back to their original shape. Hard Plastic tends to have their long chains of organic molecules so tightly crosslinked to other molecules that they can't slide past. Think of them as being more heavily knotted tangled jumbles of string. Hope that helps some, although I'm not sure it is a clear definition.",
"The scientific name for 'bounciness' is the coefficient of restitution. It's influenced by two main things; how much an object deforms when it hits something, and how much energy it loses in that process. Something very hard like a rock, loses lots of energy when it deforms but is very hard so overall can seem 'bouncy'. A superball deforms a lot (relatively) when it hits something but doesn't lose much energy, so is also very 'bouncy'. What influences how much energy something loses during impact is a much more complicated question. Source: have a PhD in how materials and construction influence impact behaviour."
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7c9zbk | Why do we use proof for alcohol on alcoholic drinks when we also use percentage of alcohol by volume? | Chemistry | explainlikeimfive | {
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"I believe proof is a different measure stemming back to the days when you couldn't just accurately test the exact composition of the drink or consistently manufacture it to a standard. Its just stuck since then. If I remember how it works correctly, its a measure of how a mixture of the drink and gunpowder react when exposed to a flame. The weaker the drink, the slower the mixture burns. Why the measure is used only for liquor, at a guess wine and beers alcohol content is too low to even allow the powder to burn and hence fails the test outright.",
"For the same reason we list the volume in both ounces and milliliters: different people are familiar with different systems."
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7ca0d1 | What is ventricular tachycardia and how dangerous is it? | Biology | explainlikeimfive | {
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"SVT, or *supraventricular tachycardia,* is a condition where the two upper chambers of the heart (the *atria*, which are above the *ventricles,* giving this its name) sometimes beat too fast for the ventricles to keep up, and this means there's less fresh, oxygenated blood moving through the heart and around the body. Ventricular tachycardia is similar, but it involves the *ventricles*, the bottom chambers of the heart. Those are the chambers that pump blood out, and if they're pumping too fast they can't get as much blood out as the brain and body need. Ventricular tachycardia can possibly lead to *ventricular fibrillation*, which is when the ventricles simply vibrate and quiver, without fully pumping. This is dangerous, and it can lead to death from lack of oxygen to the brain."
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7ca1ti | What is the current layman's description of an atom that the scientific community deems acceptable? | When I was in middle school they told us that atoms consisted of electrons orbiting around a nucleus that itself primarily consisted of protons and neutrons. When I got to university they told us that was wrong and said something like the electrons are moving so fast it can't be determined exactly where they are at any given time and that it was more like a probability cloud. Does this mean that a given electron itself does not exist at any one particular place at some given time, or is it that it does, we just can't determine exactly where it is because of either limitations with current measurement technology or theoretical limitations with measurement technology in general? When I looked up the wikipedia article on atoms it seems to repeatedly refer to electrons as being bound to a nucleus rather than orbiting a nucleus. Do scientists now think that it is inappropriate to refer to electrons as orbiting the nucleus? | Physics | explainlikeimfive | {
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"When we are schoolchildren, we are generally taught that subatomic particles like electrons are little spheres orbiting around the nucleus in an atom. But that isn't correct. Subatomic particles aren't little spheres, they are more like matter waves. There's simply no way to pin down the exact position of an electron in an atom, because it has no exact position. What's the exact position of a wave? Making matters worse, the uncertainty principle tells us that there's a chance that a given electron isn't even within the atom at all, at least for a brief time. There's a very very very small chance that an electron from an atom in your nose could be found on Mars! (Of course, it would be hard to tell, since all electrons are identical.)",
"If we use your Middle School understanding of an atom, we can just very slightly alter it to make it \"more correct\". \"An atom consists of electrons \"moving\" around a nucleus primarily consisting of protons and neutrons. and is the smallest significant unit that comprises an element e.g.; \"one atom of hydrogen\" is the smallest unit we can have that is definitely still hydrogen.\" The only reason your Middle School understanding has to be changed is that electrons don't behave like \"little planets orbiting the nucleus of an atom\", and they don't \"bounce around like billiard balls\" against the extant radius of the nuclei's electromagnetic force, they just kind of \"wander around\", tending to favor positions closer to the nucleus.",
"It's not a measurement problem. Whilst electrons *are* moving fast, the 'probability cloud' bit of your question is at the heart of the matter. At the levels of atoms, nature is fundamentally fuzzy - no matter how good the resolution of any equipment we use, the location of an electron at any one time is a truly random thing. We can use the probability functions of quantum mechanics to say there is a lot more chance it will be here rather than there, and that's how we come up with [electron orbitals]( URL_0 )."
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7cahvw | In Pre-Calc we’ve been dealing with sine, cosine, tangent, cotangent, secant, and cosecant waves. What are the actually telling me, what is the purpose of putting numbers in front of them (2sinx or sin2x) and what would I use them for? | Mathematics | explainlikeimfive | {
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"2 sin x is the same as 2 * sin(x). sin 2x is the same as sin(2 * x). The items I show in parentheses here are the inputs to the *sin* function. The other random 2 at the beginning, outside those parentheses, is multiplying the *output* of that function."
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7cakmq | Why waves ? All energy transfer in nature from one point to another happens in waves. Light, sound, even gravity travels in waves. Which fundamental property of nature is responsible for wave like nature ? Are there other non-wave like ways to transfer energy from one point to another ? | Physics | explainlikeimfive | {
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"The short answer is probably pretty unsatisfying: because that's the way it is. There is no reason that light, energy and everything else *has* to move in waves. In fact, some really smart people (such as [Isaac Newton]( URL_3 )) initially thought that light was just particles that moved in a straight line. However, eventually we observed phenomena like [diffraction]( URL_1 ), which posed a serious problem for the idea that light is just a bunch of particles flying through the air. However, diffraction and other such phenomena are easily explained if light is a wave. So light must be a wave? Not so. Albert Einstein came along and solve the problem of the [photoelectric effect]( URL_0 ), which he did by assuming that, instead of waves, light actually *was* just particles flying around. So who's right? Those who observed diffraction and said light must therefore be waves? Or those who observed the photoelectric effect, and said that light must therefore be particles? The answer is, both and neither. And an [experiment]( URL_2 ) was done that showed just that. Turns out, light is not a wave, although it acts like a wave sometimes. And light is not a particle, although it also acts like a particle. It's something totally different. All mass and energy in the universe is now understood to have wavelike and particle-like behavior. So no, there is no way to transfer energy that avoids the wave-like nature of mass-energy.",
"Waves are a metaphor we invented, to describe the way that forces travel through space -- from one spot to all the adjacent spots, or all the adjacent spots in a particular direction. The way our universe works, forces always travel through space. Many (like magnetism and gravity) spread at the speed of light, though some (like sound) spread much more slowly.",
"It’s not really waves but something else entirely. They behave according to an equation that sometimes acts like a particle and sometimes a wave- it’s just a quantum oscillation. The reason it does is because it does. All we really try to explain is the what not the why."
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7cbbje | What is "Brainfreeze"? | Biology | explainlikeimfive | {
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"Your brain uses the temperature sensing nerves at the back of your throat to judge extreme cold. Those nerves are relatively deep in the body while still exposed to the outside. If they're cold, your environment is likely *very* cold. Your body raises its internal temperature to compensate. Specifically, it increases your brain temperature. It's a fever, but instead of helping the body kill germs, it's protecting your brain from extreme cold. Ice cream and smoothies and other frozen treats are very new on a biological time scale. When you eat too much of it too fast, your body responds like it would in extreme cold. This is why pressing your tongue against the back of your throat helps. Tongues are warm and full of blood, and they help return those nerves to normal."
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7cbog1 | Do atoms ever actually touch each other? | Physics | explainlikeimfive | {
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"> Do atoms ever actually touch each other? It depends what you mean by \"touch\". Likely what you are imagining, some sort of hard surface contacting rather than field interactions, is a complete fiction. Atoms are not composed of things with such surfaces, they simply don't exist. When you really get down to it electrons, protons, and neutrons are all composed of particles that are just fields themselves. So atoms which interact via electromagnetism from their electrons are \"touching\" in the only way that really exists."
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7cbsl4 | Why do showers make us feel better? | Biology | explainlikeimfive | {
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"Warm water relieves muscle tension Shower sound provides a soothing effect for the mind. Being naked and alone makes you feel vulnerable but you're in an enclosed space which makes you feel secure",
"Physically because warm water relieves tension in your muscles. That is a relaxing feeling. The sound of the water flowing is also consistent and relaxing. Mentally showers are nice because they've been consistent your entire life. They are something that basically never changes no matter how much the rest of your life changes. They are something you can always \"go back to\" and you know what to expect. It is like your own little safe space."
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7cbt9r | The difference between melody and harmony. | Other | explainlikeimfive | {
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"Melody is a sequence of notes. Harmony is when multiple notes at the same time sound good together. When you sing a song by yourself, you sing the melody. When you have a choir singing along with you, you get harmony.",
"I️m no expert but I believe a melody is the “tune”. So the consecutive notes to make a song. A harmony is when two different, complimentary notes are played/sung at the exact same time to create a harmonious sound."
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7cbukb | Why are motherboards green? | Economics | explainlikeimfive | {
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"Cheap solder mask Green is a very very common color for solder mask for double sided boards and has been the most common color for decades. Billions of PCBs are made with green solder mask so it's super cheap. Boards can come in any color. Many premium boards come in red, black, or blue. They can afford the extra dollar for non-standard solder mask",
"In a past life I applied solder mask and we had yellow, blue, red, and green solder masks but green was the industry standard and we had several types. Just as a quick primer, one type we rarely used was UV hardened so we'd slap film on the silk screen to block out the areas we didn't want the soldermask to go on (think T-shirts), apply it to the board board each side and then cure it right away, but most were photo sensitive so we'd silk screen the entire board, put it in the oven and let it set, then take it to a non-UV room, apply film one by one and expose it, develop it, then put it in the oven to harden. The next step after solder masking was hot air leveling where solder would be applied to all the exposed copper (holes, surface mount locations, etc.) and the last step was to apply the white silk screen with all the tiny writings for components. White was used because it gave the most contrast but we had any other colors requested too and if the board was yellow, we'd use black, etc. So that it's not always green, but it is most of the time - but why? Originally,the masks used a base resin that was a brownish yellow and a hardener that was a deeper muddy brown so it's likely just coincidence. All chemicals have natural tendencies. As to why green is still used and preferred, that comes to the last steps, final inspection, testing, and later assembly which is its own world. Imagine starring at board after board in a QC room under a giant magnifying glass with lights. You need to be able to see all the lines so it can't be too opaque but it can't be too clear and bright or it'll create eye strain. Green seems to accomplish that well. So a few reasons: 1. Green creates contrast 2. Green is easier on the eyes 3. Green helps hide minor imperfections on the fiberglass board 4. It's cheaper to stock one color and application process and buy wholesale than having 10 different colors each with its own slightly different method of application requiring changing of your silk screen. 5. It's tradition."
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7cbwjv | If sound travels faster through solids than gasses, how come when there are solids in the way (i.e. walls), one can hear less? | Physics | explainlikeimfive | {
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"Whether you can hear a sound or not has nothing to do with the speed of transmission at all. It has to do with how much of the sound energy gets through the material to your ears. Some materials absorb sound energy the way a pillow absorbs the kinetic energy of an object.",
"sound does travel through solids faster, but it doesn't switch from air to solids very efficiently. If you started a sound by vibrating the wall of a building, it would travel very efficiently, but if you just started shouting at the wall, it wouldn't travel very well at all.",
"Sound doesn't travel the same in all solids or all gases. When sound moves through the air directly into our eardrums, the vibrations are directed into the ear, where it vibrates the drum and inner ear bones. When it hits a solid object, it similarly vibrates the object, with some of the sound repelling back (causing an echo) and some of it potentially passing through the object. The thicker the object, and dependent on the material it is made from, those vibrations are less likely to pass all the way through the object to vibrate the air on the other side (allowing you to hear it) Foam materials and uneven surfaces are especially bad at passing through sound because the vibrations come in randomly and the foam itself is stretchy, which muddles the sounds. It's why recording studios use those cross-patched walls. The shape prevents the sound from even reflecting."
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7cbxl7 | Why are most animals seemingly unaffected by / unafraid of the presence of most other animals but immediately flee at the sight of a human | An example of what I mean would be why birds and squirrels or a deer and a hawk or a dolphin and a sea turtle coexist within close range unphased by each others company, but flee when they see a human. | Biology | explainlikeimfive | {
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"Eyeballs. Predetors usually have their eyeballs on the front of their heads (think human, wolf, lion) where prey have their eyeballs on the side of their heads (think deer, rabbit, mouse). It's like a big red flag for animals.",
"It's because humans don't follow the rules. Every animal has a personal space bubble and they do \"alarm\" signs to show when another is getting in their bubble. Example: A Robin is hunting worms. A deer is walking in the area. The Robin will stop feeding and look up at the deer. If the deer notices, it will shift course and go around the robin. If the deer doesn't notice and keeps heading towards the robin, the robin will stand up a little taller and maybe pump it's tail or fluff it's wings, using motion to show the deer, and any other animals, that he is not being respected. (Check out starting at 2:22) URL_0 If the deer keeps coming, the robin may jump a couple feet to the side or into a bush above the deer's head - a larger motion to show alarm. Other animals will notice this and look in that direction (the same behavior the robin first used to get the deer's attention.) If the deer would have started running at the robin, or jumped at it, the Robin would fly further up into the tree and given off a little \"chirp!\" alarm while pumping it's tail and maybe wiping it's beak on the branch, using movement and sound to show alarm. Making noise is dangerous for animals, so it's only done when absolutely necessary to alert all the other animals around it. (around 3:26 in the video, you can hear the robin chirp when it flies off) Birds close to the robin will fly up and observe, and the birds a little further away will stand up and look. This creates pockets or bubbles of alarms around the landscape - the stronger the alarm, the bigger the bubble. Humans now, we don't see the robin stand up and look at us. We don't see it stand taller, or take a few steps to the side. We don't see it fly up just above head level. When we notice a bird, we get an alarm because we startled it pretty bad, causing the bird to fly up and tell everyone about it by alarming. We don't follow the common courtesies of the natural world and so animals can't accurately predict our behaviors. This scares them, so the scream in panic. If you slow down, walk slowly and quietly, and walk around the birds when they show the first stage of alarm - the standing up and looking - you can move through the landscape without setting off alarms. If you want to learn more about this or have questions, let me know - I teach it occasionally, as well as other survival skills, and enjoy spreading it around. Tl;dr: We are rude, don't follow the rules, and this scares animals. EDIT: a good starter place for this type of awareness stuff: URL_2 and a shameless plug for URL_1",
"They know a predator when they see one. You think rabbits or deer hang around long when they see a wolf?",
"Could we be creeping them out just by our posture and walking style? We humans are afraid of snakes and spiders I guess due to how 'not natural' they appear...",
"I always suspected it was something to do with the fact that man is the only predator that can be dangerous at range. Animals have learned that humans are dangerous at what would be a safe distance from another predator. Just a thought though. It’s not based on anything.",
"I think its actually just fearing what they're not used to seeing. I've worked in the woods, the more accustomed to humans animals are, the more likely they are to stick around. I've had packs of wolves flee and never be seen again almost a mile away from me. Yet, if I lived in their territory, I bet I'd have numerous/less positive experiences. I've worked in the oil and gas industry in northern Alberta. I'd have jobs so remote, I'd have to be flown in with one other person by helicopter. When I'm working out there, I don't fear bears at all. They'll never stick around long enough to harass me. I know they'll watch me, but are so unsure of what I am that they won't go near me. Then if I'm working on a plantsite, I have to be much more wary. I've had a bear come right up to me and try and pick a fight (he'd come about 10' from me, stand on his hind legs, and slap the ground). That bear was used to the mannerisms of people, and didn't see them as a threat. I've had moose and elk watch me while I was working. A fox and a coyote have also followed me around before. Usually in that case there was human activity nearby. The ones that I'd only briefly get a glance of were in remote locations. With animals, its always important to be aloof. Your actions dictate their reactions. They really don't know how to interpret people. So people that run away? You're food to them. You stand your ground but don't make aggressive actions/startle them? They'll probably leave you alone. In NA there's only two animals I'd run from: bull moose in rutt (October) and pissed off wolverines. I wouldn't run from a Kodiak bear or a polar bear either, but I wouldn't like my chances if they were hungry and I didn't have food to distract them with. Curious cubs are another thing to look out for. They don't really have the fear mechanism that older bears have, and just want to come say \"hi\". Momma bears really aren't as big of a threat as people may assume. It's usually the bears that you don't see that are the ones people should worry about. E.g.: if I come across a momma with her cubs, I'm slowly backing out and don't really worry much. But if I come across a momma and not know that she has her cubs nearby, that is much more alarming.",
"Why so many complicated responses? The ELI5 reason is natural selection. Humans are incredibly dangerous and unrelentingly cruel. Animals who DIDN'T flee from humans got killed, either for food or sport, and never had offspring. Only those with an \"irrational\" fear of humans passed on their genes. In cases (now extremely rare) when humans have encountered a population of animals for the first time, the animals ignored them completely, and were quickly slaughtered as a reward.",
"Humans are not somehting you want to be around. We eat anything and everything we can catch, which is everything. Other animals evolved instinct to stay away.",
"As some people have said one reason is familiarity. A few decades ago some researchers were trying to get dolphins to speak English(I know it’s crazy) but I read that they had to go to a specific spot in the ocean that dolphins were already used to humans at. If they just found dolphins anywhere they probably wouldn’t cooperate.",
"We smell like a chemical shitstorm to them. Even before we were drowning in Listerine, nicotine and Old Spice we smelled different. We smelled like fire and something that eats flesh. Also, we are way, way taller than most predators. We are extremely loud as well. Most wild animals are not looking at our eyes to assess danger. They usually know to run way before we're in range to do something like that. It's primarily scent and our size. People always smell like they are stalking an animal when they're trying to stalk an animal. Just doing that (stalking) releases semiochemicals from our glands that Bambi can smell loud and clear. Domestic deer and elk don't act the same way because they equate our scent with food.",
"The answer is evolution. Imagine if some weird, 2 legged alien showed up and had some weird stick thingy in its hand. You are curious, but keep your distance. Then boom, you're dead and don't even know how it happened. The animals who survive are the ones who run from the spooky alien that can kill things instantly from long distance.",
"Most animals are afraid of, or at least wary around, things that look strange or unfamiliar. And compared to other animals, humans look *really* weird, with our bipedal walking and our clothes and stuff. We also surround ourselves with strange things like cars and tents and food in weird smooth containers. Animals learn to associate humans with strangeness, so it makes sense that they'd be wary. Also, most mammals at least learn from their parents' behavior. If they see their parents are wary around humans, they will learn the same. And animals that are afraid of humans tend to be more likely to survive. We don't *like* animals being comfortable around us.",
"As someone who also flees at the sight of other humans (situation permitting) it's probably because humans are dicks, on average, and they'd rather not roll the dice.",
"I think this video is relevant here: [Man vs Lions. Maasai Men Stealing Lion's Food Without a Fight!]( URL_0 ) Watch the hunters body language and lions confusion. Amazing stuff!",
"If I approach deer in a UTV(Razr or whatever), they just seem curious and don't instantly flee. Maybe because they don't know what the hell it is? If I stop and get out, they run!",
"So if I wear a mask that shows fake eyeballs on the side of my head I should be able to approach safely? Many times it seems that the animals escape without even being able to see your head directly, perhaps because they are triggered by sound cues or similar.",
"Animals will of course be afraid of humans if they have seen humans act aggressively toward them before. But I think you’re asking why do they do it in the first place? I’m guessing it’s because when they see a human, they’re seeing something they don’t normally see. The default action then is to flee. The reason I think this is the case, is because in my neighborhood there are lots of deer despite the fact that I live in a city. These deer are generally not afraid of us, because they see us all the time."
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7cc0wd | Why does 3G suck now? | Technology | explainlikeimfive | {
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"3G used to be the flagship signal, it had all the bandwidth dedicated to it and late 3G signal could hit early 4G speeds. These days its the fallback signal. If you're getting 3G it means that the tower is either too congested to serve everyone 4G and had to demote some people, or your signal is too weak to support 4G so it dropped you to 3G to give you a better Signal to Noise Ratio In either case, it means something is going wrong and you're not going to get the 10+ Mbps 3G of old and will instead be getting the 1 Mbps 3G of really old because this frees up capacity on the tower and is less sensitive to noise TLDR - Modern 3G sucks because you only get put on 3G when conditions suck",
"Since no one has explained this like any 5 year old could understand: Carriers (phone service providers like AT & T, VZ, etc.) have certain amounts of radio frequencies (think highways for cars ) that they can put all their phone users (drivers) on. They paid the FCC (or whichever national governing body) a ton of $$ for the highways. Billions. Some are wider and can fit more cars at once at faster speeds. Some are narrower and can still go fast, but with lest cars. Some go really long distances but slower speeds. Some really short distances lighting fast. You get the idea. The reason 3G sucks now is three fold. 1). Had all networks remained the same, phones today require more data (more cars) for the same perceived information (think 1080p streaming, sending 12+ MP pictures, higher screen resolutions). Previously, phones were lower quality and data was less intensive. So that in itself would lead to a slight slow-down (maybe 10-15%). 2). The introduction of LTE required a new way in which data is sent / received (think higher speed limits which require robot-like precision of lane-mergers) so the networks themselves had to add bulk on the backend to support LTE on top of 3G. This back-end complexity itself creates network congestion (again, another 5-10%). And now the big one combined with the previous two 3). Radio frequencies were reallocated (highways opened, and some shut down/moved). The carriers took old frequencies (10 lane super highways) that were dedicated to 3G and repurposed them for LTE, leaving 3G on the two lane country roads (metaphorically and physically, ironically). So when LTE super-highways are in gridlock and you have to bump down to 3G, it’s like a winding backroad that you’re stuck on. Yea you move...but at 40mph max and it’s a longer route. TL;DR: 3G used to be the super-highways of carriers’ networks, but that connection type has been shoved off in favor of LTE and now it’s like driving a country road. Even if no one is on it, you’re slow.",
"3G and 4G phones can handle more than one download stream for faster speed. Although LTE is faster than 3G, network carriers are allocating more network bandwidth and capacity to LTE. As LTE is allocated more bandwidth to service more 4G phones, that takes away 3G network capacity. So where you might have had two download streams on 3G five years ago, the network bandwidth for that extra download stream is now running on 4G LTE. Here's an article covering the disappearing 2G and reduction of 3G: URL_0",
"Most 3G towers were converted to LTE as most phones support the tech and everyone wants \"the fastest\" connection. The remaining 2G towers are converted to look like 3G service, but aren't so great. & nbsp; Simultaneously, cell phones use the internet more and more. Every program that requires communication with a server (which is most everything) eats your bandwidth. & nbsp; Furthermore, wireless devices have become more common. As such, the towers have to handle more connections, handoffs, signal collisions, and frequency issues. In areas with dense population clusters, it is easier to put up more cell sites. & nbsp; Finally, unless cell providers upgrade to true 4G (100Mbps throughput), they are perfectly fine will selling service and claiming that it is \"fastest in the nation\" or \"most reliable\" or \"largest coverage\". Most cell providers share each other's towers.",
"Another factor is that your phone is likely 1080p or higher thus pulling more bandwidth than your lower resolution 2012 phone likely did.",
"> 3G used to be the flagship signal, it had all the bandwidth dedicated to it and late 3G signal could hit early 4G speeds. > These days its the fallback signal. If you're getting 3G it means that the tower is either too congested to serve everyone 4G and had to demote some people, or your signal is too weak to support 4G so it dropped you to 3G to give you a better Signal to Noise Ratio > In either case, it means something is going wrong and you're not going to get the 10+ Mbps 3G of old and will instead be getting the 1 Mbps 3G of really old because this frees up capacity on the tower and is less sensitive to noise > TLDR - Modern 3G sucks because you only get put on 3G when conditions suck What /u/mmmmmmBacon12345 is saying is partially true, in theory. A large extent of it is that carriers have repurposed segments of their 3G spectrum to serve the 4G demand. 5G will be a little different, when it comes, because its frequencies are wildly different to support the insane amount of bandwidth it pushes. In the future, expect 5G to serve larger data needs, 4G to serve basic consumer needs [of course will probably be marketed under a different name, but same basic technology]. Source: former employee for two of the top three US based carriers. Sorry Sprint, you're 4.... 4ever",
"There’s only so much spectrum available in the 700, 800, 1900 and 2100 MHz bands that are common for phones. The carriers pay 10s of $Billions for more. They can devote it to 2g, 3g, 4g LTE. Adding more cell towers helps some, as they can reuse the same frequency slice three towers over. But there’s not enough to go around. They have turned down 2g and repurposed it, forcing people like my mom to replace really old handsets. They are now reallocating a lot of 3g to LTE so it can be used for data. Plan on 3g going away in a few years, and this will just provide better LTE, so it’s fine for anyone with a newer handset.",
"Think of it like TVs. 3 years ago, 1080p HD TVs were all you can find on shelves. Nowadays, 4K has taken over, and 1080ps are getting more rare. Why would companies produce more 1080p TVs when 4K is the new standard? The simple answer is that 3G coverage is reduced. In a competitive market, technology improves. Why maintain 3G coverage when 4G is the new standard?",
"I'll add one other tid bit as a former cell phone tower worker who was a part of 4G and LTE upgrades. Many of the upgrades we did adding LTE antennas, fiber, RRH's, etc. Also called for upgrading antennas on 3G and 2G however the companies didnt want to spend any more money on those old technologies. They constantly sent broken antennas, coax jumpers, etc. or the old coax connectors on the tower would be shot and they would not want to pay to fix any of it, therefore, adding the new antenna many of the times made those frequencies run far worse. It was bad. Edit: sp. Edit 2: Also: A lot of those RF engineers they hire are idiots. A lot of the times when they would have us change out antennas for old tech they would have us change their directions and downtilts for, \"optimization\" but I can't tell you how many of them were changed so they were shooting straight into the ground, a ridge or a giant empty nothingness instead of a populated area.",
"Ok, let me explain here. Radio spectrum is prime real estate for carriers, its real hard to acquire since everyone wants the best bandwidth. LTE propogate radio signals on 700MHz frequency becuase 850/1900 is taken by 3G. This puts carriers in tough position because they can't turn up LTE without taking 3G down on 850/1900. Since internet speed is becoming a norm faster and its getting real hard to keep 3G running beyond 10Mbps. With that said, 3G has become a neighbor where 4G borrows some sugar when it cannot handle capacity. 5G is coming, soon 4G will become that neighbor. source: capacity engineer",
"It's because operators are harvesting spectrum bandwidth from 3G and using it for 4G. In terms of Verizon's 3G, they use to have multiple channels of evdo so lot of bandwidth dedicated to 3G and not much data demand so whoever was using internet, they were getting decent speeds; currently Verizon only have 1 channel available for 3G in major cities as they are using rest of the spectrum for 4G, so now if you are dropping to 3G, you are competing with every one on 3g for resources on that 1 channel. Source: I am Verizon System Performance Engineer",
"I've read a few answers now and I'm thoroughly disappointed so here goes: One would assume 3G *means* 3G and that however fast 3G was, back in it's hayday, is THE 3G speed. That's not the case. 3G, 4G, and LTE all describe different standards for mobile telecommunications. When 3G was the latest and greatest, telecom companies **dedicated the majority of their bandwidth** to it. When the 4G standard came along and they adopted it, they started dedicating more bandwith to it and less to 3G. So if you think *geez I don't remember 3G ever being this slow* then you're not mistaken. It wasn't that slow. 3G describes a standard, not a speed. If all the telecom giants randomly decided to solely support 3G *now*, it would be a lot faster (but not as fast as the latest standard). Edit: if you don't know what bandwith is, it's basically the pipe that data flows through. More bandwith==bigger pipe. Telecom standards==rules for data flow.",
"Here in Germany with 1 bar of 3G/H I can do pretty much everything, watch YouTube, browse Facebook, Google. With LTE things just go faster and are better quality (YouTube)",
"3G was the fastest speed in the US in 2012, at least for wide use and adoption. Now 4G/LTE is the standard, and the signal it puts out drowns most 3G signals, besides which companies are slowly shutting down 3G as 4G matures more fully.",
"Back when 3g was a thing everything was only in like 480p for smartphones, so of course it'd be easier to stream Netflix or YouTube to it.",
"I have a theory that mobile carriers have just transitioned 4G to the 3G network, and 3G is now basically the old 2G / raw mobile data. In a few years they'll roll out 5G and it'll just be 4G rebranded.",
"As applications get more advanced they need better data connections. Back when 3g was the best it was good for the applications of the day, however it's maximum speed wasn't good for modern applications, so as things advanced 4g became the standard and the speed that 3g provided wasn't sufficient for good application performance.",
"Because 4G is actually the old 3G. 3G is just two dudes with microwave ovens shooting microwave rays into town.",
"QoS. 3G is now only being allocated certain amounts of minimum bandwidth so that the rest can go to 4G.",
"Cell tech here. I work on the network connecting towers. To be absolutely blunt, 3G is going to be unilaterally turned off within 5 years. 2G will stay put. The reason is because 3G is mediocre with data speeds in comparison to LTE and 2G is widely used by IOT. Its not worth it to keep an aging technology around that doesn't help us out much.",
"I work at one of the largest cellular tower operating companies. I can tell you it is mainly because 3G is being phased out, most of my new Verizon and AT & T builds have been 4G/4G LTE only. On a lot of the existing sites, they remove capacity on 3G to make room for 4G equipment. This results in lower coverage and capacity for 3G, and 4G traffic given priority.",
"Former network specialist for a telecom company here. I’m seeing some wrong answers on this thread. I️ don’t want to get too technical so will give a very simplified answer. - there are lots of caveats to the question, but,...to simplify the answer: there is less bandwidth allocated to former G networks now. Every time a new “G” network is rolled out, the old network loses resources. As hardware is upgraded to newer generation networks, the bandwidth allocation is moved to prioritize the new G network.",
"In the UK EE went around upgrading thier masts to 4g. This fucked the 3g signal for non 4g phones. At my olds house 4g on the new upgraded mast (nearby) has never worked and 3g is now appalling. We have gone from being able to phone in the house to making a call standing on the rock pile at the end of the garden to get a signal. EE said have a booster in your house but it will cost £100. And that's how you change to tesco (O2) asap. Thankful for good old landlines",
"One aspect that nobody has addressed yet is that \"bars\" are meaningless. Different models of phone & different carriers have different systems for how empirical signal strength in dBm translate to \"bars\". It's very possible that \"3 or 4 bars\" meant a MUCH stronger signal on your other phone than it means today. For a fair signal strength comparison you must go deep into settings (or install an app) that shows you dBm. I'm currently at \"2 bars\" at -115 dBm. This is in addition to all the other points people have made here which are also valid.",
"I'm posting this because I don't see it clearly articulated elsewhere here and I've dealt with your problem a lot here in New Zealand. It's a real problem in many rural areas that don't yet have 4G coverage. *Why is 3G network speed often worse than ever these days?:* The issue is usually **radio network congestion** caused by too many cellular devices being connected to the same cellular tower sector as you. By congestion, I mean too many cell phones, tablets, cars and other mobile devices that are connected to the same radio transceiver on the same tower as you're currently using when you notice the apparent slowness. In these cases of congestion, you'll find it especially bad around schools, large concert venues, or anywhere where large numbers of people (and devices) periodically congregate. You won't usually find this level of congestion in city centres though, as they normally have more tower sectors on each tower to handle more connected devices. The reason you notice the problem only when connected to the 3G network and not when connected to the 4G network is because the 3G radio frequency band is much smaller than the 4G one and if you slice up the 3G band into a tiny slice for each of the thousands of devices that are sharing your tower sector, they all get such a small slice that their data speed drops a lot and their lag increases. This happens with 4G too, but because the frequency band is so much bigger, even a small 4G frequency slice is still big enough to maintain a usable data connection for surfing the internet or most normal stuff people do with their mobile devices. The solution is for your service provider to install more 3G tower sectors to share the load, or to install 4G tower sectors so you can switch to the much bigger (and faster) 4G frequency band."
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7cc1s3 | Is it smarter to get a new, cheap car or continue using an old one that needs repairs constantly and the price only gets higher? | Other | explainlikeimfive | {
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"The best bet is to buy a 3-5 year old highly-rated URL_0 5 yeats old, a car will still have most modern safety and luxury features, have about 10-15 years of low maintenance life ahead, and cost about 1/2 the price of new.",
"Have her track the monthly cost of maintenance and upkeep and repair. If it works out to be more than new car payments would be (which are covered under a warranty for repairs, and generally more efficient and reliable) Then the obvious solution is to replace the car.",
"market research has suggested that buying a 10 year old car and selling it five years later is the most cost-efficient way to own a vehicle. Just don't buy brands that are known for bad reliability. Buy a 10 year old toyota and the only difference between it and a new toyota is less fancy stuff on the dashboard."
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7cc35d | How do “Self-Healing” products work? | So I recently stumbled upon a bag that could “heal” itself with the help of our own body heat. I also have heard about an LG phone with a similar tech that could heal dings and scratches on its back by simply rubbing the affected area. How is this process able to occur? Thanks | Technology | explainlikeimfive | {
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"These materials are usually made of very springy polymers (aka plastics, but I refrain from using that term outside of this aside, since it's not entirely accurate). The process of creating the object they're in, puts them in a \"desired state\". When you do work on the object, such as scratching it, or giving it a mild cut (on self healing cutting boards), the springyness of the polymers will cause them to return to the shape of the original object. Sort of like how we humans typically have desired state of being in bed, and go to great lengths to return there."
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7ccmjw | how do Uhaul and car rental companies get their cars and trucks back when they are dropped off in different states or cities? | Other | explainlikeimfive | {
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"Because other cars and trucks are being driven from other cities to that location. It's a constant network of vehicles flowing in and out. I'm sure if there's too much of an imbalance between locations they transfer vehicles without them being rented. But that is easy enough.",
"Ideally, there is enough balance that a return trip brings the vehicle back. That's the reason you see so many out of state license plates in a lot of rental places, they just keep the car and hope another car will make it back. If not, the next option is to pay customers to do it. If you want a one way rental from Atlanta to Detroit in the dead of winter, you can get a killer deal compared to going the other way. Finally, they put a bunch of guys in a van, or even use a trailer to bring them back. Note that if you take a car from NY to LA, no one is likely to come all the way back to get it. If LA has too many cars, they will send some to Vegas and Phoenix. If NY has too few, they'll get some from Philly or Buffalo. Eventually, surplus cars will flow to the places there is demand, and it will all even out."
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7ccoj8 | How do thermostats work? | I recently replaced the batteries in my thermostat and you have to just remove the whole thing from the wall- it wasn't even connected to the wires in the wall.. so how does it communicate with those wires? How do the wires make the furnace or whatever turn on? If you have the thermostat set to say 21C, how does it know when to turn on the fans if the house goes below 21C? | Technology | explainlikeimfive | {
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"Traditionally, thermostats *were* connected to those wires in the wall. Those provided power & allowed the thermostat to send control signals to the furnace to turn on or off. They worked by various, fairly simple, mechanical methods to complete a circuit that turned on the furnace. Since yours *isn't* connected to the wires & takes batteries, it's probably just a remote control for your actual thermostat - probably using radio to communicate with a base station. It might have temperature sensors, it might not. There's no real way to tell without knowing more about how your home is set up.",
"Older thermostats used a [spiral shaped bimetallic strip connected to a mercury switch]( URL_0 ). Since different metals expand at different rates when heated, the bimetallic strip would make the spiral tighter or looser, tilting the switch and completing a circuit with the furnace to it would start up. Eventually the room would heat enough to make the strip curl the other way, breaking the circuit and making the furnace stop. You changed the temperature by rotating the whole mechanism so mercury switch would break the circuit at a different level of thermal expansion. Modern thermostats and furnaces are electronic. The thermostat has a computer than monitors the temperature, and sends on and off signals to the furnace, often wirelessly. Since they are more responsive, to prevent the furnace from cycling too often, they are typically programmed to bracket a temperature. You set it to 21 C, it turns on when it drops to 20.5 C, and back on when it reaches 21.5 C."
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7ccrvz | Why can't a person, that has suffered from hypothermia, be revived? | Other | explainlikeimfive | {
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"Defrosted? Are you talking about hypothermia or being frozen? In the case of hypothermia a person can be revived from a pretty low temperature with varying odds of success. It gets difficult the lower you go because in general the biochemical process to make your cells and organs function only work efficiently (or at all) in a pretty narrow temperature range. Once out of those range they may not all be able to start back up again. If you're talking about being frozen it's similar but even harder. The processes don't just slow to inefficiency they stop entirely including brain activity. There might be some way to systematically jump start them again, but it's well beyond any technology we currently possess. Besides that, the process of freezing a body in the first place can very easily cause a lot of the cells to rupture as the water in them expands/freezes. If that happens to many of your cells and there wouldn't be a body to revive at all, you'd have freezer-burned steak.",
"Sometimes they can, there have been hyperthermia victims who have survived over an hour without a heartbeat. Under normal conditions, your brain cells start to die after about 4 minutes. Even when frozen, they comes a point where there has been so much damage you can't be revived."
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7ccw26 | How does sunscreen work? | Chemistry | explainlikeimfive | {
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"Two ways. 1. They contain a substance that is opaque to UV light, so it just reflects off you. Titanium dioxide and zinc oxide are common ones. These are highly effective, but have the disadvantage of being messy and can wash off in water. 2. They contain a substance that absorbs UV light. Avobenzone and Oxybenzone are common ones, among others. These are also highly effective and have the advantage of being basically invisible and they don't wash off easily, but they are broken down by the UV light they absorb, rendering them ineffective after a couple hours, so you need to reapply them often to stay protected. The most effective sunscreens use both of these methods."
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