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ng5114 | why do tall buildings have red lights ontop? Is there a minimum height that this needs to be applied to? | Other | explainlikeimfive | {
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"Because in the dark they can be really difficult to see for pilots of low flying airplanes and helicopters. The fear is that someone flying over a city at night might not see a building and crash. There is a minimum height of 200 feet, set by the Federal Aviation Administration. They have different categories of buildings requiring different types of lights.",
"It’s for planes/helicopters to be able to see the tops of buildings and know not to get too close to the red lights.",
"Tall structures have blinking red lights on top so that aircraft can see them at night. It’s not a huge problem in a major city, but out in the country you can easily crash a crop duster into a radio mast that you didn’t see. FAA mandates tower lights for all structures above 200 feet tall.",
"It's for aircraft, and possibly some other things. Makes it more visible so you don't crash. Generally it would be helicopters that are likely to be in that kind of area at an altitude that could be a problem. There is almost certainly a legal requirement for buildings of a certain height, but that's going to vary by country.",
"Those lights are a signal to low flying aircraft, so they can avoid the structure. Here is a link that shows the types and heights a building may need. URL_0",
"They have red light to avoid collision from airplanes and helicopter, by putting a red light on buildings pilots gets notification that there is some object ahead. This is called aviation lights or Aircraft warning lights . [ URL_0 ]( URL_1 )"
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ng5gri | How do computers work at its most basic level? How did we take physical objects, put them together, and have it so when we press a button, a portion of our screen lights up? And how did we turn this into a code that can be used to make other software? | Technology | explainlikeimfive | {
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"You know how you can use a switch to turn the lights on or off? The switch sits on an electrical circuit and can break it, preventing electricity flow and turning the lights off, or reconnect it, restoring the electricity flow and turning the lights on. Now If you put two switches together on the same circuit, then it will only work (lights on) if both switches are turned on. This is an “AND” gate. If the two switches are connected in parallel, then the lights would be on whenever either of the switches is turned on. This is an “OR” gate. The computer chip is basically millions upon millions of such microscopic switches and gates on tiny circuits.",
"First, the \"theory\" of a computer came well before our ability to physically implement it. Basically, logicians several centuries ago, came up with a way to treat logical statements (statements that can be true or false) as a kind of math, coming up with the field today known as Boolean Algebra. Instead of mathematical operations like ADD and MULTIPLY, we had logical operations like AND and OR. Let's say we have two logical statements we call A and B. Doesn't matter what they are exactly, except that they can either be true or false. I can combine them together with the logical operation AND to make a new statement: A AND B. This new statement is only true if both A and B are true at the same time, and is false if either of them or both of them are false. OR is true if either of its components are true and is only false if they are both false. We also have a third operator called NOT, which basically just inverts a statement. It makes a true statement false and a false statement true. With these we can create more complex operators like NAND, NOR, XOR, XNOR. Turns out, if we treat \"True\" as \"1\" and \"False\" as \"0\" we can make these logical operators behave like mathematical operators (Add, Multiply, etc.) but only in binary (a number system that only uses 1's and 0's). So if we can find a way to implement logical operators with physical components, we can create a machine that can do math. Eventually we were able to do this, first using vacuum tubes and then subsequently with transistors. We can create those basic logical operators, then combine them in ways to do mathematical (and other) operations. We can also feed them back onto themselves to create electronic circuits that can \"store\" values (as long as they are powered), creating memory. With all of these, we have a very basic computer. Basically all it is, is a series of logical operators, implemented with transistors, that take input (in the form of electrical voltages) and produces specific outputs (again, in the form of electrical voltages). All modern day code does is allow us to program computers using easily intelligible programming languages. Other programs called compilers and assemblers take that code and covert it into the machine language that computers understand at this basic level."
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ng6s7d | How do antidepressants remove brain fog, and what does it exactly do that makes someone feel grounded? | I have MDD and anxiety disorder, and got back to my meds just yesterday after a year. I instantly noticed the changes, felt more grounded, less brain fog, and I feel like I'm living in real time and not just floating around. I got my sense of time back. How the hell does that work? | Biology | explainlikeimfive | {
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"Depends what you're taking, if it's an SSRI it stops serotonin from being reabsorbed back into your blood, so there's more of it available to be used by the brain (and other cool stuff). Serotonin is a neurotransmitter, so having more of it means that signals between connections in your brain are easier to pass on. This could be a reason for feeling sharper and less fogged up. Obviously serotonin is involved in a whole boat load of other processes all over the body too, including emotional regulation and even muscular actions (it's been linked to central nervous system fatigue too!).",
"Unhelpful to your question but I always found I had more brain fog on ssri's as well as feeling like I was muted and slow. Always lost track of time being a zombie. It was explained to me that the reaction was due to how my body processed the medication that caused most of the effects. Slight increase or decrease in chemicals in the brain can substantially help or hinder how you function as a whole. Diet and activity levels also play a large role in how anything affects a person. Mindset and Setting also impact in how you react to any drug, even prescribed ones to some extent.",
"This may not be a satisfying answer, but most mental health medications operate by changing some specific aspect of brain chemistry. Your brain is a ridiculously complex web of wires called “neurons”. They send chemical signals (“neurotransmitters”) to each other to create everything we experience: vision, emotions, logic, etc. Sometimes a specific part of that vastly complex web gets messed up. For example, many neurons involved in emotional and mood regulation use a specific neurotransmitter called serotonin, and in some cases the serotonin gets “stuck” somewhere and your brain has trouble getting its signal all the way through. One class of mental health medication (SSRIs, selective serotonin reuptake inhibitors) basically helps “unstick” your serotonin, so your brain can more easily regulate your mood. The dissatisfying part is that, in many cases, we are actually not entirely sure exactly how a certain medication has the effect that it does. We just know it’s effect is useful, and we have ideas about what it is *probably* doing."
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ng74js | how does drag and drop from desktop to browser work? | It's crazy that I can select an icon on my desktop, drag it to the browser window, release the mouse button and the browser will know which file the icon referred to. How is this implemented? | Technology | explainlikeimfive | {
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"Not sure this is at a 5yo level but: Your desktop is just a graphical rendition of a file explorer. When you click and drag an icon it loads a file address into a 'clip board' within the operating system (OS) and when you drop it somewhere it pastes it into the location you dropped it. So, when you drop it into the browser your OS interfaces with the browser program and pastes it where ever you drop it within that program. Edit: It's basically a graphical shortcut to telling the browser to upload a file from the desktop through a file explorer interface.",
"The operating system has an Application Programming Interface (API). It's a way the programs and operating system can interact with each other. Using this interface, the program listens for events from the operating system (key press, mouse move, mouse click, etc). One of those events is the \"drag and drop\" event. The Operating System basically tells the program, \"Hey, I'm dragging and dropping this particular file into your window, do what you want with it\"."
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ng7fc4 | why is it so hard to overcome compulsive behaviours like skin picking? | Just really wondering why people find it so incredibly difficult to stop doing something that's obviously causing them much harm. | Biology | explainlikeimfive | {
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"The answer is in the name: \"compulsive behaviors.\" \"Compulsive\" comes from \"compel,\" which means \"to force (someone) to do something\". Behaviors like these are often caused by anxiety disorders, which mess with the way you think about things. When you have that sort of disorder, it is difficult to deal with these compulsions because it's a little bit like an itch - the feeling doesn't go away unless you \"scratch\" it, so to speak."
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ng7iiu | what happens to unused (but not recalled) products that are pulled from stores? | Bloomingdale's, Target, and Macy's removed ChrissyTeigen's Cravings line from their stores because of her bullying scandal. But I'm curious to know what happens to these types of products once they're pulled? Are they sold somewhere else for a steep discount? Do they just get dumped (unused) in a landfill? Same thing for clothing that is no longer in season/trendy. Do designers just trash them or do they allow them to be resold through other vendors? | Other | explainlikeimfive | {
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"It depends, sometimes the shops have arrangements with suppliers that they will only pay for goods once they are sold, so can return them to the supplier, other times they will resell them to discounters, very rarely will they just trash them."
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ng871t | how does a new born baby knows the breast can feed him/her? | Biology | explainlikeimfive | {
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"For a true newborn, who can’t crawl or move or really do anything. They don’t really KNOW anything. But they are still born with instincts. In this case the instinct to suck on a nipple in front of it/in its mouth. That’s really all they have to do. Babies that you see crawling around or crawling towards/reaching for breasts have just learnt to associate them with food since they’ve been the source of food since, well, they were a newborn.",
"Newborns have a sucking reflex and a rooting reflex. So when a nipple touches their cheek, they turn their face towards it, latch on, and start sucking. This is all instinct. The appearance of the breast helps with breastfeeding too. The areola and the nipple are like a bullseye target."
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ng8kms | why are high pressure zones usually related to bad weather and low to good weather? | Title says it all | Earth Science | explainlikeimfive | {
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"It’s the opposite. Low pressure systems are areas of hot air; hot air absorbs more moisture that eventually has to come down as rain; at the boundaries with high pressure zones it creates winds.",
"Low pressure zones are usually full of warmer air. High pressure zones are usually full of colder air. When a low pressure zone is sitting on an area, they just have some pleasant warm weather, but when a high pressure zone starts moving into that area, since the colder air is denser, it flows in Underneath the warm air of the low pressure zone, forcing that warm air to rise. That warm air that is force to rise starts to cool off as it gets higher, and usually warm air is also full of moisture/humidity. So that moisture starts to condense into clouds, and eventually storms."
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ng8sad | How do we know of planets like alpha centauri that are in very distant solar systems, but are not sure if planet nine exists? | Other | explainlikeimfive | {
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"Planet Nine would be a type of planet that’s very hard to detect from inside or outside a solar system. It doesn’t pass in front of the star so you can’t watch for blinks. It’s not massive enough to produce a major wobble the parent star. It’s not orbiting quickly enough to produce a smaller cyclic wobble in the parent star. It’s too small and/or distant to have a significant gravitational impact on other known planets. So with no gravitational effects to work with, you’re basically left watching the skies hoping it will eclipse random stars and you’ll be lucky enough to be watching at the time. That may take an eternity, if it even exists. The planets we find around other stars all fall into those other easy-to-find categories. They’re massive, they transit their stars, and/or they’re orbiting rapidly. Finding something like Pluto from afar would be impossible.",
"Alpha centauri is a star system not a planet, and is composed of 3 stars. Therefore it is bright and visible by telescopes. It can be observed and tracked. Planet nine on the other hand is a planet and therefore doesn’t emit light. The only way to visibly see it would be if it’s reflecting our suns light. Unfortunately it is very far from us. The only evidence we have (afaik) is an inference from observations of other objects in our solar system."
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ng9elp | In WWII, why do European Army medics do not carry firearms while Pacific Navy corpsmen do? | In Band of Brothers, Eugene Roe and other medics walk unarmed while many Pacific theater films depict medics/corpsmen carrying weapons. In Hacksaw Ridge, Desmond Dos exercises his right as a conscientious objector and elects to not carry a firearm and is somewhat ridiculed for his choice. | Other | explainlikeimfive | {
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"Under the Geneva Convention, combat medics are permitted to, and commonly do carry defensive weapons and still keep their noncombatant status, but lose any protection if they use those weapons offensively. However, that doesn't translate well to real world conflict. Only relatively few nations even adopted the terms of the Geneva Convention, and in a war zone environment there's little sense in going unarmed, even if you're ostensibly a noncombatant. A truly conscientious objector could of course go unarmed at their peril. This was particularly true in the especially brutal fighting of the Pacific Theatre, where combat medics were targeted specifically by Japanese soldiers, and truer still in modern insurgency conflicts, whose belligerents rarely have any regard for the rules of war that protect those medics.",
"WWII medics are designated by wearing an armband and often red cross markings on their helmet. Technically, they are not allowed to be armed, and by not being armed, the opposing side is supposed to not attack them and simply let them conduct their medical duties as they can't fight back. in Europe, generally, the sides respected this and medics were not targeted and thus were not allowed to carry weapons. Not always the case, but this is the usual situation. In the pacific, the Japanese did not care about the medic situation and treated them the same on the battlefield. As such, a medic in the pacific might be armed, though of course, being a medic, they may never actually use their weapon, even if they have one, their duty is to provide medical care, not to engage in fighting. Edit: A side note, a Navy corpsman likely would have had at least some weapons and infantry training before entering the field, in addition to their medical training. An Army medic most likely would not have had any infantry training outside of their basic training. I don't know if this mattered in practical terms more than who you were fighting.",
"Basically it comes down to defining who they are the marines are marines who also tend for the wounded. The army they are soldiers who are trained to be field doctors or field medics as such they are regarded according to the Geneva convention as non-combatants and so are offered some degree of protection by other forces which have signed up to the Geneva convention."
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ng9i0o | Why do people have the urge to use the bathroom when nervous? | Biology | explainlikeimfive | {
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"Because your ancient reptile brain can't tell the difference between anxiety about giving a presentation and fear of being eaten by a tiger. One of the things bodies do in preparation for flight or fight is to evacuate bladder and bowels to make themselves lighter so running away is easier."
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ng9p9c | how does Crypto crashing effect the whole market? | Economics | explainlikeimfive | {
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"In general it doesn't, the market will continue with or without Crypto, the amount of \"money\" in Crypto is relatively small."
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nga0et | Why hasn’t the price of video games been inflated like every other product? | Games in the 90s were around the $50-60 range and have stayed there ever since until recently. Edit: thank you all for the responses 🙏 | Economics | explainlikeimfive | {
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"With the rise of digital distribution the expenses in delivering games has dropped, and many games have added costs in the form of optional things you can pay extra money for. As such, there's a bit of a standard expectation for new games to sell around $60. The first game that tries to redefine that standard at, say, $80, is a game that sells less than the ones it's competing against.",
"Game companies figured out they can just sell an unfinished product for 60, then keep selling updates (fixes) as DLC. Then add in skins, loot boxes, and the like; they are basically printing money compared to the old days.",
"They have inflated. With microtransactions, dlc, season passes, loot boxes, battle passes and expensive special editions. It’s hard to find a game these days that actually costs $60 to own the whole game.",
"Another reason: Video game sales and the potential market for sales have increased massively since the 90s. For example they sold 700k units of Wing Commander III and it was considered a hit while CDPR sold more than 10 million units of Cyberpunk (still a hit despite its problems). Digital distribution has increased revenue of per game sold for publishers. In the past to publish a game publishers typically had to go to wholesalers who then distributed the game to retailers and at every step along the chain people wanted money."
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ngae0d | How come when you multiply a number by 0, it always equals 0? | Mathematics | explainlikeimfive | {
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"Youre multiplying it 0 times tho. Think of it this way. If I gave you $0 three times, how much money would you have? Or if I gave you $3 zero times?",
"Because there are ZERO groups of whatever number is being multiplied. Like looking at your dining room table and saying, \"...I have zero groups of 75 pizza rolls each.\" Sadly, an empty table.... **based on a true, tearful story of how I longed for pizza rolls one Saturday at 2:00am**",
"If you have 1 basket with no eggs in, you have no eggs. If you have 7 baskets with no eggs in, you still have no eggs. If you have 7, 250 baskets with no eggs in, again, you still have no eggs, just a lot of baskets. It doesn't matter how many zeroes you have, it is still just zero.",
"> wouldn't you have what you started with? You didn't 'start' with 3, because you're trying to approach it like addition. In 3+0 you start with 3 and add 0. In multiplication, you start with 0 and add 3 to it repeatedly until you have reached the desired multiple. So, 3x0 is 0+nothing. 3x1 is 0+3, 3x2 is 0+3+3, and so on.",
"> If I multiply 3 X 0 how come the answer is not 3? I am multiplying the number 3, 0 times. Wouldn’t you have what you started with? You're not \"starting\" with anything. All you have are two factors. It makes no difference whether I hand you 0$ three times or whether I hand you 3$ zero times. You always end up with 0$.",
"Multiplication =/= addition. Use bags of apples as an example. If a grocery store sells bags of apples in 3s, then one bag equals 3 apples. Say they want to know how many apples they sell in a day. Instead of counting each individual apple, they can just count the bags (much easier number to manage). So if they sell 1 bag, they've sold 3 apples. 3 (apples) x 1 (bag) = 3 (apples sold). If they sell 10 bags, then they've sold 30 apples. 30 (apples) x 10 (bags) = 30 (apples sold). If they sell 0 bags, then they've sold *0* apples. 3 (apples) x 0 (bags) = 0 (apples sold).",
"“If multiplication tells you how many times to add a certain number, then multiplying by 0 means that you have nothing to add because 0 means nothing. So, 3 * 0 means that you are adding 3 zero, or no, times. ... You get 0 because you're still not adding anything. Nothing added to nothing is still nothing.” From URL_0 If that makes sense and helps you understand it a lil better"
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ngbjzl | Why do psychiatric hospitals work? Won't people act completely different when they are taken out of their familiar enviroment? Or when they are after the treatment thrown back into their 'old lives'? | Other | explainlikeimfive | {
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"Usually the main interventions offered by psychiatric hospitals are providing a safe environment where inpatients can be monitored and kept safe in a way that's not possible in the community, and regular medication (particularly for psychotic/affective illnesses) that eventually stabilise a patients mental state until theyre safe to be discharged home However, It's true longstay psychiatric admissions can be deskilling in terms of ability to manage day to day life. I live in the UK and its common for a psychiatric admission here to last a couple of weeks or a month (though obviously every case is different), even for psychotic/affective illnesses",
"Inpatient stays at a mental hospital aren't going to fix all of a person's problems, that's not what they're for. The point is to get the person to a point where they aren't a danger to themselves or others. Ideally, after discharge, a patient will do intensive outpatient followed by regular, long-term therapy.",
"What exactly do you mean? I think this varies from country to country. If you don’t want to be in hospital, the only way you’ll get in against your will is either self-endangerment (suicidal) or against others. If this is the case, most patients aren’t able to „hide it“ for a long time. But some people really are able to suck it up for a few hours or days, so they’d be released earlier. The chance that they’re coming straight back then, is high. This is called revolving door effect If this is really bad, you’d be medicated against your will - > the possibility that you’ll leave the hospital in a different state of mind is very high than most of the times, as antipsychotics (for example) change their point of view. Imagine psychosis like there’s a filter over reality and the AP will make these go away. If this happens (compulsory drugging) patients will likely stay around 6-8 weeks, at least If the situation isn’t too dangerous for you or someone else, you’d be released. This could also sometimes mean, that people will still be sick and act different to what they did, before the disease. So both is possible. There are also treatments, where the patient is at home and he or she would be visited once a day. It’s also possible that you’d get a help system, like Social individual case aid, social workers, therapeutic shared flats, legal guardians.... If you’d have to take medication after hospitalization, depends on the diagnosis. For example patients with a drug-induced psychosis would get medication for a few days and then MOST of the times their condition will brighten up. A patient with schizophrenia will most likely have to take medication forever, either pills or a depot (injection ever few weeks) But base line: if you’re really diseased, you won’t be able to act different for a long time and would fall back into older patterns. This also all comes down to the specific person and also diagnosis. But I’m not sure if I got this question."
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ngbvho | Why do our legs tap up and down when we're nervous or just whenever? | Biology | explainlikeimfive | {
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"When our minds and emotions have excess energy from stress or nervousness, it is common to release it in the form of movement. Sometimes it’s leg or foot tapping, sometimes it’s pencil or pen tapping (hand or finger movement), or for others it’s letting their mind race with other distracting thoughts.",
"Being nervous triggers your fight or flight response which sends adrenaline through your body. The adrenaline makes you want to move, but if you're just sitting in a chair, the best you can achieve is fidgeting such as leg tapping."
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ngbzye | Whats peoples logic behind if you hit something and it might've broke or something doesn't work like intended to just hit it (again) to "make it work again" | Other | explainlikeimfive | {
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"Same logic as \"guess it's free\" when the item doesn't scan at checkout. Just poor dry humor lol. Dad jokes and such. Sometimes when you hit something that isn't working it'll work again though, I've witnessed it. Loose pieces can fall back where they're supposed to be with a little impact. Probably not so much with newer technology since connective pieces are more delicate nowadays but with radios, old TV's, VCR's, etc. It's totally possible",
"It's called percussive maintenance and it's the first thing you learn in a lot of trades because it often actually works. Sometimes you need to just knock a cog back in place or smack something to make 2 wires touch. In England the saying is \"if in doubt; give it a clout\"."
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ngchqm | why the color of flames depends on how hot it is (red-orange-yellow-blue..) | Physics | explainlikeimfive | {
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"For this you need to look at thermionic emission and the basic structure of an atom and specifically its electrons. Electrons in an atom are in different orbits or energy levels. For an electron to move up a level it needs more energy put into it. When it falls down from a higher energy level it has to release energy as a photon. Keep this in mind. As a metal is heated it’s atoms start to jiggle about more vigorously. Eventually even electrons gain enough energy to start moving up energy levels and then cascading down. This cascade results in the emission of photons of light. Now at lower temperatures the electrons don’t go very high so when they drop they emit low energy photons which are red light. As the temperature is increased they jump higher and fall further so the energy increases. If you remember the electromagnetic spectrum as wavelength decreases from red to blue, the energy increases. Some non eli5 explanations if you want to pursue this further [link]( URL_0 )"
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ngdjm8 | What is a nuance? | Other | explainlikeimfive | {
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"Sorry for the unclear post, but i confuse myself when trying to come up with the question even"
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ngdpk2 | Why do anxiety attacks happen randomly? | Other | explainlikeimfive | {
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"Your body is pretty much busy with doing the stressful tasks you are doing in that moment. Whenever you rest your body let's all the anxiety lose. Almost like people tend to get sick/headaches etc. during vacations because the body finally has to time focus on its actual problems. Get your adrenaline levels down. Do some exercise, drink less coffee or coke, meditate. Give your body a chance to do something else with the built up energy."
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ngignl | how those encased in the Pompeii volcano were encased so perfectly? | Biology | explainlikeimfive | {
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"The bodies were covered very quickly with ash and lava. And while people died instantly from this it takes time for a body to burn up. There is a lot of mass and a lot of water that needs to be heated first. So the lava had time to cool and harden around the bodies first. Especially those covered in the colder ash which compacted around them and sintered to stone from the heat with their dead bodies inside. In this rock there have been little oxygen and microbes to decompose the bodies. The heat have also caused some of what was previously biological material to survive. However most of the bodies that can be seen today are castings of the voids left by the bodies.",
"A \"pyroclastic flow\" (what killed most of the people in Pompeii) is a searing hot cloud of gas at several hundred degrees and rolling down the mountain at hundreds of km/h. When that hit the city, anyone outside of a bunker would have been killed almost instantly where they were, one breath of the cloud pretty much liquifies your lungs. Over the next few hours and days, ash from the volcano settled deeper and deeper, burying the bodies of the already-dead people. That's the trick, they were already motionless and stiff when they were encased. And then what they were encased in too - a thick layer of fine ash that packed in all around them and then compacted further under weight and time, sealing the bodies in a solid mass."
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ngiqoj | Why a piece of microfiber cloth cleans a wet surface better when it is already wet than when it is dry. | Technology | explainlikeimfive | {
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"Water sticks to water! It's why droplets form - each water molecule is sticking to the next. If you wipe up a mess with a damp rag, the water molecules in the mess stick to the water molecules in the rag."
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ngix1b | Vasovagal response and what prompts it | My son (16) fainted the other day when he had a blood draw. He has never had a similar response to the sight of blood or anything. | Biology | explainlikeimfive | {
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"The autonomic nervous system is responsible for maintaining a lot of the normal day to day functions of your body, including blood pressure. When someone vasovagals, the autonomic nervous system misfires and is temporarily knocked out of balance which causes not enough blood to get to the brain thus leading to fainting. There are many things that can cause someone to vasovagal. The blood pressure sensors in the arteries can be too sensitive in some people to the point where wearing a shirt with a tight collar or tie could cause someone to vasovagal. Exercise could cause someone to vasovagal. Situational vasovagal syncope is when a specific situation causes someone to faint. Some common examples are during urination, after coughing, or fear of a painful stimulus (like blood draws). It doesn’t necessarily happen every time and there are some factors that could contribute to it being more likely to happen, like being dehydrated and having a slightly lower blood pressure.",
"I had a vasovagal response after something stupid: the Tower of Terror ride at Disney World Resort. I wasn't scared during the ride, but the unpredictable up-and-down motion caused my body to tense up, and when I got off the ride I was pale, sweating, nauseated, and almost passed out. I have doctors in my family and they were certain I had clenched my b-hole too tight, causing the physical reaction and blood pressure loss. It sucked. I felt sick for about an hour afterward."
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ngje3r | Why do companies continue to install bloatware on devices? | Technology | explainlikeimfive | {
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"Because while *some* people complain overall people still buy it. People complain about microtransactions in games all the time but *a lot* of people still buy the games and buy the microtransactions so why would the company take them out. Financially, it doesn't make sense. Bloatware is similar in that people complain but it doesn't stop them buying it and forgetting about it. Some people may even enjoy it."
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ngjp3r | Exponentiation | The naive explanation of exponentiation is always given as repeated multiplication: * 2^3 = 2 * 2 * 2 * 10^4 = 10 * 10 * 10 * 10 etc etc. But while that works for integer exponents > 0, it's obviously not applicable to exponents that are negative, fractional or zero. Negative exponents map to division intuitively enough I guess, but N multiplied by itself zero times is not 1, after all, and how do you multiply something three quarters of a time? So since 'repeated multiplication' doesn't capture the whole concept... what exactly *is* exponentiation, in and of itself? What concept does capture the general case? What's the big-picture elevator pitch that covers all of it? (I don't need educating on what the other kinds of exponents represent, I'm looking for an overarching concept of what the beast looks like from a distance) | Mathematics | explainlikeimfive | {
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"After you \"invent\" exponentiation-as-repeated-multiplication, you notice it has a very useful property that x^(a)\\*x^(b) = x^(a+b). (e.g. 2^(3)\\*2^(4) = 2^(3 + 4) = 2^(7)). Negative, fractional, and zero exponents are all created by taking this important property and \"seeing where it goes.\" For example, I don't know what 3^(1/2) is, but 3^(1/2)\\*3^(1/2) must be equal to 3^(1/2 + 1/2) = 3^(1). Well, that's true for sqrt(3) as well, so 3^(1/2) must be the same as sqrt(3). And I don't know what 5^(-1) is, but 5^(-1)\\*5^(1) must be 5^(-1 + 1) = 5^(0) = 1, which is the same thing as if we had multiplied by 1/5 (and so on).",
"Fractional exponents can be explained by multiplying many times as well. What number do you need to multiply by itself to get x? x^1/4, so x^1/4 is effectively x multiplied by itself 1/4 times, you’d need to do it 4 times to get x. Then fractions like 3/4 are just a combination of x^3 and x^1/4",
"It for the most part, if not all parts (I'm not too deep into this), is (repeated) multiplication. a^(b) is simply a product consisting of b numbers of value a. **Positive integer exponents:** a^(2) = a\\*a a^(3) = a\\*a\\*a = (a\\*a)\\*a = a^(2)\\*a a^(5) = a\\*a\\*a\\*a\\*a = (a\\*a\\*a)\\*(a\\*a) = a^(3)\\*a^(2) We see the general rule: a^(b)\\*a^(c) = a^(b+c) **Negative integer exponents:** Using the same examples above we also see: a^(5) / a^(3) = (a\\*a\\*a\\*a\\*a)/(a\\*a\\*a) = a\\*a = a^(2) We see the general rule a^(b)/a^(c) = a^(b-c) This rule also directly shows the case for zero: a^(0) = a^(b)/a^(c) for b=c follows a^(0) = a^(c)/a^(c) = 1 Also from this rule we can get a, so I think, nice visualisation: Positive integers increase the 'product length' in the numerator, Negative integers increase the 'product length' in the denominator of a^(b)/a^(c). & #x200B; **Fractional exponents:** a^(1/2) = a^(1-1/2) = a^(1)/a^(1/2) = a/a^(1/2) Thus it follows a^(1/2) = a/a^(1/2), multiply both sides by a^(1/2) and you get a^(1/2)\\*a^(1/2) = a. We have shown that a^(1/2) is nothing but a different way to represent sqrt(a), all through multiplication. We could go on to show that a^(b/c) is simply the c-th root of a to the b-th power.",
"Other comments cover how we define rational exponentiation (e.g. a^(b) where b is a rational number). If b is an irrational number, though, we still need to do more work to define a^(b). It's not really that deep, though—we just define an infinite sequence of rational numbers x1, x2, ... etc. that approaches the irrational number b, and then define a^(b) as the limit of the sequence a^(x1), a^(x2), ..., a^(xn) as n goes to infinity. If you want a really really really broad overview of exponentiation that's very theoretical, I think the best place to start (which is definitely not really ELI5-level) is with some calculus: consider the differential equation f'=f, i.e. consider finding some function f that is its own derivative. Under the initial condition f(0) = 1, we have that f(x)f(c) is equal to f(x)+f(c) for any arbitrary c, because they have the same value at x = 0, namely, f(c) (this is the uniqueness property of differential equations—if they're equal at any given point, then they're equal everywhere because the differential equation specifics exactly how the solution can change from that given point). But c is arbitrary, so we can really write that f(x)f(y) = f(x) + f(y) for any x, y. This looks an awful lot like the exponentiation property a^(x+y) = a^(x)a^(y). Now we can just define the unique solution of the differential equation f' = f with initial condition f(0) = 1 as the function exp(x). This is a perfectly good definition—exp(x) is simply defined as the solution to this differential equation with f(0) = 1. We can then deduce that exp(x) = 1 + x + (1/2!)x^(2) + (1/3!)x^(3) + ... (on and on to infinity) This is how we can really define the exponentiation function without any reference to repeated multiplication—it's defined by the solution to the differential equation f'=f with f(0) = 1. (In standard notation, it happens that exp(x) = e^(x). But this is a *consequence* of our definition of exp(x)... this is NOT how we define exp(x). In fact, it's more precise to say that we define e^(x) as exp(x), rather than the other way around.) For exponents with different bases, we just define a^(x) = exp(x ln(a)), where ln(a) is the natural logarithm of a... this definition agrees with the traditional conception of exponentiation (i.e. exp(x ln a) = e^(x ln a) = a^(x)), and entirely avoids the ambiguity caused by the repeated multiplication definition of exponentiation."
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ngknbj | How does our brain creates hallucinations and illusions? | For example see a shadow of a person that doesn't exist but our brain thinks it does. | Other | explainlikeimfive | {
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"Your brain is constantly guessing at reality and creating images out of light waves. Hallucinations are images created either based on a miscommunication in the brain or when the brain is trying to protect you.",
"Imagine if you had a 2000 piece jigsaw puzzle and only put together the border with a few spots in the middle, but you've done the puzzle before so you can roughly visualize what the whole thing is going to look like. That's what happens with your brain/eyes. What your eyes actually sense are just borders and random splotches of color (light waves) in the middle. Then your brain takes that data and fills in the rest of the picture from memory which is what you end up actually 'seeing'. Hallucinations happen when your eyes sense ambient light particles or get incomplete data, and your brain accidentally fills it in with the wrong picture. Likewise, hallucinatory drugs basically work by making your brain really bad at guessing the picture."
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ngkqjg | What is it in the cells of certain lizards and amphibians that allows them the ability to grow back limbs? | Biology | explainlikeimfive | {
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"DNA. Humans have genes that allow them to repair cuts to skin, muscle, and various other kinds of tissue. Lizards just have genes that code for growing a tail back if it gets cut off in the same way you have genes for growing new skin when you cut your skin."
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nglvhp | Why do flies seem to only want to fly near humans despite there being an entire world around them? | I don't get it. A fly will get into your house and want to buzz around your head instead of trying to escape, go somewhere else or just chill. There has to be a scientific explanation. | Earth Science | explainlikeimfive | {
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"The scientific explanation is. Flies have found that humans produce food. And when flies have food they can lay eggs near said food so their offspring has a greater chance of living.",
"Is that true or do you only notice the ones that are around you and not say the five that are resting on the outer wall of your house?"
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nglw19 | Why do shoes without support hurt your feet, but you can walk around barefoot just fine? | Biology | explainlikeimfive | {
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"Your foot isn't the same as your neighbor's. Shoe manufacturers are looking to provide a comfortable fit for the largest audience, the average person. If your foot is different in any meaningful way, that means an off-the-shelf shoe will be uncomfortable. My brother is \"flat-footed\". He needs a special insole to be comfortable. Usually an aftermarket Dr. Scholls. I don't have \"flat-footedness\", I have a \"comfort\" foot, which is a special designation in footwear. I need a little more padding than most people. My sister doesn't need either arch support or extra padding. She's just fine picking a shoe off the shelf and expecting a comfortable fit for the life of the shoe. & #x200B; All of us are perfectly fine walking barefoot. It's just the shape of the \"standard shoe\" bothers both my feet and my brother's feet. It puts more pressure on our \"weak spots\" than a perfectly flat surface dose. Imagine being barefoot and walking on a surface that mimicked the sole of your shoe. Because shoes are formfitting, they'd be pressing into your arch or your heel or the ball of your foot, or even constraining your natural toe spread.",
"no one is walking around barefoot all the time tho. if you walked barefoot on a hard surface all the time your feet would hurt. the human foot was designed to walk in dirt, sand, and occasionally a rocky surface. the wrong shoe can change the way someone walks and the amount of pressure on each area of the foot. also, the bottom of the shoe is not rounded like your foot. when wearing shoes your foot hits the ground differently. the shoe might also stop the correct joints from moving at the correct time, if at all. in short, shoes restrict us."
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ngm06q | Why is alcohol always labeled as a depressant, when it can often make people feel much more lively, uninhibited, etc. when drunk? | Biology | explainlikeimfive | {
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"It is a depressant because it depresses your nervous system, so it is named that because of how your body reacts to the alcohol, not because of how it makes the person act.",
"Alcohol is technically a “biphasic” substance. This means, to a certain point, it behaves like a stimulant. This is partly where the term “catching a buzz” comes from. Up to a BAC of about 0.06, you feel effects akin to a stimulant. After that it behaves as a depressant",
"Depressant simply means it slows or depresses the central nervous system. The technical term is CNS depressant which mean central nervous system depressant. Alcohol like opioids and benzos slows the firing of synapses in the brain leading to slower brain function which in turn leads to a slowed nervous system. Lots of cns depressants make you feel stimulated oxycodone ketamine and pcp being some big name ones",
"This is a language issue. \"Depression\" has two meanings. 1. Extreme sadness or apathy. 2. Reducing or pushing something down. Consider: A \"*depression* in the ground\" isn't a sad area, it's a hole. A \"tongue depressor\" doesn't make your tongue sad, it's a tool that pushes your tongue down in your mouth. When alcohol is called a \"depressant\", that's using definition #2 as well. Alcohol \"depresses\" your central nervous system. It depresses your inhibitions, your heart rate, your breathing, your focus. Aka it reduces/slows those body functions."
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ngmkc2 | what is the difference between the various "moving" pitches in baseball, i.e. the slider, the cutter, the curveball, and the breaking ball? | Physics | explainlikeimfive | {
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"It’s the: movement, the break, and the speed. Let’s list them according to speed. A cutter traditionally is faster than a slider and a slider is traditionally faster than a curveball. So a hitter gets synced, used to, to the speed a pitcher is throwing the baseball. If the pitcher consistently throws the same speed, the hitter should have a better chance at hitting the ball in play. So the pitcher will vary the speed of their throws to “unsync” the hitter. Another thing the pitcher can do is throw different types of pitches to further “unsync” the hitter. This is where throwing a cutter, a slider, and a curveball come into practice. A curveball, does just that, it should curve as it is pitched from the pitcher to the hitter. This gives the hitter the impression that the ball is going to cross the batter’s box in the top left corner upon leaving the pitcher’s hand but it curves upon entering the box and enters the box outside the bottom right of the box, thus “unsyncing” the hitter. This dramatic shift from the pitcher’s release to where it lands in the box is known as the break. The overall change in direction is the movement of the ball. The slider does not break as much as the curve, and a curve can curve in many directions; where a slider is generally flatter but sometimes can be slightly vertical, but it can move just as much. The cutter generally does not break as much as the slider but like the other two it can move just much. Remember though, there are the varying speeds of the different types of pitches. So when all the different combinations of speed, movement, break, and pitch type are changed up it leaves the hitter guessing and that is why a hitter hitting 30% of the balls thrown at them is considered a great player!"
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ngn2iq | Why does air at 80F feel warm whereas water at 80F feel cold? | Physics | explainlikeimfive | {
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"Because you don't feel the temperature of *things*, you feel the temperature of *your skin*. In other words, the thing you're touching needs to change the temperature of your skin for you to feel it, and the quicker/more efficiently something changes your skin's temperature the ***more*** you'll feel that thing's temperature. This all depends on the ability of the thing to give/remove thermal energy to/from your skin. Liquids are generally good thermal conductors, which means they quickly/easily give/take thermal energy and therfore rapidly change the temperature of what they're in contact with. Water is a liquid and therefore removes/gives thermal energy from/to you skin quicker than your body can replace/remove it, so you readily feel its temperature. Gasses are generally poor thermal conductors, which means they slowly give/take thermal energy and therefore sloooowly change the temperature of things they're in contact with. Air is a gas and therefore your body can replace/remove thermal energy faster than air can give/take it, so you will feel its temperature to a lesser degree. If there was a material that could not transfer thermal energy at all, even if it was 100,000C, you would not *feel* its temperature because it would not change the temperature of your skin. Alternatively, if there was a material that conducted (moved) thermal energy insanely fast but it was just 1C hotter than your skin, it would feel pretty warm because it would rapidly impart thermal energy to your skin, and thus would quickly and effectively change the temperature of your skin. Additionally, the greater the temperature difference between two things, the quicker they will exchange thermal energy. So, for example, air close to your body temperature will conduct thermal energy from/to your body slower than air that is significantly colder/hotter than your body's temperature. We also have to consider that your body actually has to expell thermal energy to maintain the right temperature because it's constantly generating its own thermal energy. In other words, your body needs to give off heat to stay at 37C, and if it's surrounded by something that inhibits the removal of thermal energy, your skin/body temperature will begin to rise, causing you/your surroundings to feel hot. Remember how air is a poor conductor, especially if its near-body-temp? If you're surrounded by (stagnant) 80F air, that air is actually going to *trap* thermal energy around you and subsequently your body temp will rise. Conversely, water, even if its near-body-temp, removes thermal energy from you body quicker than your body replaces it, therefore reducing the temperature of your skin and making you/your surroundings feel cold(er). EDIT: Changed fluid to liquid.",
"Your perception of \"hot\" and \"cold\" is greatly influenced not simply by the temperature of your environment, but in how quickly it can draw heat away from your body. This is why 80 degree air temperature with a breeze \"feels\" colder than one without, even though the air is the same temperature. The ability of a substance to absorb heat is known as its *heat capacity*. This is the amount of energy required to raise the temperature of something. The heat capacity of water is about four times that of air. This means that, as air and water draw heat away from your body, the air's temperature near the surface of your skin will rise much faster than water. Once the material touching your skin (be it air or water) reaches the same temperature as your skin, it stops drawing heat away. Basically the water stays colder longer and therefore draws heat away from your body more quicker, creating a sensation of being colder."
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ngn75i | why are catalytic converters so valuable and worth stealing? | Is there a black market for them? Why do cars need them? Can we protect them, somehow? Thanks! | Technology | explainlikeimfive | {
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"They have a small amount of various precious metals. This makes them expensive. Factory cats can cost a few grand so thieves steal them and sell them for less than oem but at quite a good price. Scrap recyclers will usually pay 100 or so for each one because they can refine the metal if needed. Most of the scrap places, around me atleast, don't bother refining them and instead sell them to junkyards or various places online.",
"They're an easy part to steal, since it's on the outside of the car and you can sawzall one off pretty quickly. They're an expensive part, because they have small amounts of very expensive metals, which convert some of the more harmful exhaust products into less harmful ones. Cars don't need them to run, but they do need them to meet emissions requirements. And short of mounting some sort of shroud over the entire exhaust system, which would add cost and complexity to the car, there's not a whole lot you can do to protect them. Hence, worth stealing and easy to steal."
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ngnbz3 | Why are you not supposed to pick a cold sore? Does it make it spread? | I have always been told to not lick them, and it seems gross, but also incredibly difficult to avoid. I don’t get them often, but when I do it seems like it speeds up the healing if it stays moist. Edit: title says pick but I meant lick, still ELI5 to both | Biology | explainlikeimfive | {
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"Cold sores are a type of herpes virus (in the same family as chicken pox, shingles, and genital herpes). The virus burrows into a nerve and lives there, occassionally coming out to the skin and causing a herpes sore. During this time (and for a few days before the sore appears) you are able to \"shed\" the virus. That is, you can spread it to other places on yourself or to others through direct contact. Licking the sore could cause the virus to find a home on your tongue or another place in your mouth or lips. Touching the sore and then your nose or eyes could spread the virus there as well. Kissing, performing oral sex, and sharing cups and utensil with another person can also spread the virus. Usually people just get cold scores, but someone with a weak immune system could get a really bad outbreak, and babies/young children are greatly at risk. Moisture doesn't necessarily speed up healing, but dryness may make the sore crack and cause a larger or deeper ulcer. Using a lip balm made for cold sores is a good way to keep the area moist. Your saliva is honestly not great for moistening lips as it evaporates quickly."
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ngnftz | Why do raisins (and almost all dried fruit) upset my stomach but grapes do not? | Biology | explainlikeimfive | {
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"This sounds like the sort of thing you should probably be discussing with your doctor. It sounds like a medical issue."
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ngopaq | ; What is A1C and why even with changes in diet and medication it's so hard to lower once it gets high? | Biology | explainlikeimfive | {
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"Blood glucose is a real time snapshot, if you will, of your given level of sugars within the blood. Normally the body is able to regulate the amount of sugar within the blood by means of two mechanisms (for the most part) controlled by the pancreas. When blood glucose is low, glucagon stimulates the liver and muscle to turn stored glycogen into glucose that is released into the bloodstream. When glucose is high, the pancreas releases insulin to instruct the body to allow glucose into each and every cell as well as store additional sugars as fat or glycogen. A1C is a historical measurement of how much glucose red blood cells have been exposed to over time. The typical red blood cell lives for about 120 days. When blood sugar has remained high over the life of the red blood cells, they are highly glycated (the impact of glucose on the red blood cells). An A1C test is also known as a glycated hemoglobin test for this reason. Typically insulin either from the body or injected will reduce blood sugar for the short term. Some insulins are long acting while others only last for a short time. Blends are also available. When the body has become resistant to the effects of insulin, blood sugar will remain high leading to the glycation of the hemoglobin in the red blood cells. This is not something that can be undone. A1C levels will not be reduced until blood sugar is maintained at a lower level for at least as long as it takes for new red blood cells to be created. TL,DR: high blood sugar \"stains\" red blood cells in a way that cannot be washed off resulting in a given A1C level. Red blood cells live for about 120 days. A1C levels will not be reduced until a large portion of \"stained\" red blood cells have been replaced by the body over the course of most of that 120 day window while blood sugar has also been kept to a more manageable level. Source - I am a full time paramedic and triple major pre med student who loves, lives, eats, and breathes this stuff. If you want or need any additional clarification, I would be happy to help without going into biomolecular/biochemistry level detail.",
"A1c is sugar bound to the hemoglobin in your blood. (The name comes from technical chemistry.) This bonding lasts a while, and the rate at which it happens depends on how much sugar is in your blood over time. The more sugar is in your blood, the more of your hemoglobin has sugar attached, and the higher your A1c. Because the bonding is long-lived, A1c effectively measures your average blood sugar over a long period of time, typically months (i.e., about the lifetime of a red blood cell). That makes it useful for telling where a diabetic's blood sugar has been for months prior to the blood draw. It's hard to lower because diabetes is relatively hard to treat, because diabetes isn't just unhealthy body chemistry - it's irreversible (or at least hard-to-reverse) damage to certain parts of the body that manage blood sugar as a result of unhealthy body chemistry."
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ngpnaw | The meaning of abstraction and concretization? | I really can't understand it but I have some thoughts and I don't know if I'm right: For example I have an engine, just a simple engine you see in cars. So if I try to ***abstract*** then I'll go into the details like "this engine contains of several parts and I'll go into the details about this pretty crankshaft"; In case of ***concretization*** I'd just say "das shit moves the car". | Other | explainlikeimfive | {
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"That's about right. Except that it's the opposite. With abstraction you don't care what's in there, you have an engine, you don't know how it works internally, you just know what it does and how to use it. With concretization, you \"make it concrete\". It is not just an idea anymore, you have the entire description of what it is, how all the pieces work internally, there is no mystery anymore.",
"If anything it's the opposite of your example, and then you would be pretty spot on honestly. I'll start with an example from math called *topology* (don't worry about it at all) but in topology a donut and a coffee cup are identical. Why? Because they each have one hole. As far as topology is concerned that's all that matters. That would be an abstraction. The idea of a thing with one hole. A concretization would be an actual donut and an actual coffee cup. Which are example of something with one hole. So using your example an engine would be \"a device that converts one form of energy into motion\" Any device that has that property is an engine, nothing else matters. Concretization would be an actual engine, with its gears and pistons and what not. & #x200B; Some more examples might be the idea of the color yellow. That's an abstraction. and a concrete object would be an actual wall that is painted yellow. Or the idea of baseball, again an abstraction. A concrete object would be an actual game of baseball.",
"Abstraction means moving from **specific** things to **general** things. For example, imagine a tree. \"Tree\" is an abstraction: it sets aside the specific details (is it a pine tree? a birch? a palm? where is it? how tall is it?) in order to extract a general idea (has wood, probably has leaves, is probably bigger than grass). To take a palm tree and a pine tree and extract the idea of \"tree\" is abstraction. Concretization is moving from **general** things to **specific** things. For example, in the last paragraph, I took the *general* idea of 'abstraction' and concretized it into the specific example of trees. That made it easier to understand, because it let you work with things rather than ideas for a moment. Any given tree is a concrete example of the abstract idea of 'trees', any given bee is a concrete example of the abstract idea of 'bees'."
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ngrx4p | How are rainbows formed? Why do they only form occasionally? | Physics | explainlikeimfive | {
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"Rainbows are water droplets acting like a prism and splitting white light (like sunlight that contains the entire visible spectrum of light) into bands of the different wave lengths. In case you don't know, the wave length of light determines what color it is. More energetic light has smaller wave lengths and is blue-er, while light with less energy is longer and red. We only see a limited segment of the electromagnetic spectrum, which includes radio waves, micro waves, visible light, ultraviolet, infa red, and x rays, all arrayed according to wavelength with visible light somewhere in the middle. Tl;dr any time water gets atomized it'll happen if you look from the right angle. Play around near sprinklers when the sun is low, find the right angle you'll see rainbows. Also rainbows are circular, you just usually don't see the whole thing."
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ngt2x9 | What are the colored balls on power lines? | Whenever I see large power lines here in California, there are almost always brightly colored balls strung along the lines. Are these to warn aircraft or something else? | Other | explainlikeimfive | {
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"They're called visibility marker balls or marker balls. You'll often find them near mountain passes, in the deep valley areas, near major freeway crossings and around airports. They weight about 17 pounds each. The marker balls are placed on power lines to make the conductor crossings visible to aircraft.",
"For helicopters and aeroplanes to be able to see the line. But also meant to deter birds from sitting on wire and breaking it.",
"It is very hard to see wires from the air due to them blending in with ground clutter. The best one can hope is to see the pole lines (pilots are taught to cross over the polls and no in between them). Those pole lines don't exist when power lines cross valleys. & #x200B; Wire strikes were such a problem and danger, accounting as the most common cause of aerial accidents in the late 70s for helicopters, that manufactures added wire cutters to helicopters to make such incidents survivable. A [wire strike protection system]( URL_0 ) is found on nearly all helicopters in the world now"
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ngt913 | What causes an aorta to rupture? | Biology | explainlikeimfive | {
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"Depends on circumstances, but unless it’s trauma induced, an [aortic dissection]( URL_0 ) likely preceded the rupture. This is because dissection cause the layers of the aortic wall (the lumen) to splice, exposing the outermost layer to the tensive pressures of systolic blood pressure (the temporary increased pressure due to the heart contracting). Dissections can occur as the result of natural diseases, the most common of which forensic pathologists will place under the umbrella phrase “hypertensive and atherosclerotic cardiovascular disease,” a combination of the natural diseases of high blood pressure (hypertension) and ‘hardened arteries’ (atherosclerosis)—in this case involving the aorta—another disease of the cardiovascular system that can be caused by another multitude of pathophysiologic sequelae (the most common causes are aging, high cholesterol or hyperlipidemia, diabetes, and smoking). My disclaimer at the beginning (“unless it’s trauma induced”) neglects to explain the fact that often trauma can make it easier for a diseased, dissected aorta to rupture, in which case any resulting death is considered traumatic with the cardiovascular diseases being contributory. To my knowledge there is no empirical data that can reasonably assist in differentiating whether a healthy aorta would rupture under compressive forces X or tensive forces Y compared to a diseased aorta being subjected to the same forces. So, any death due to aortic rupture in the presence of a traumatic force will be traumatic in cause and manner, with any presentation of disease being secondary. Absent any circumstance of trauma, however, natural ruptures will always be primarily the result of the underlying disease, whatever it or they may be."
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ngtfv2 | How does the concept of "Buy one get one free" works in marketing? How does this strategy prove profitable for companies? | Economics | explainlikeimfive | {
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"Option 1. The cost of the two items is profitable or at least breaks even, at the sale price of 1 (ie it costs the seller $1 for one item they the sell for at least $2) Option 2. Loss leader- you come in to buy the special and walk out with other items that are more profitable.",
"Ever wonder why they make you walk past all those shelves to buy something? People aren't good with the small purchases. By offering 2 for the price of one supermarkets are trying to entice you by making you think that you'll be saving (which you are) but by buying that, they make profit by making you buy something which you normally wouldn't buy. Furthermore they lure you into their shop, like bait lures a fish, past all their shelves. Then you see and scoop up all their other discounts, making them even more money. TL;DR it's a supermarket ploy designed to make people impulse buy.",
"Most of the other answers are good but miss something. A lot of bogof offers are on items near end of life, and this offer can get some value out of it rather than discarding."
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ngvloj | Why is it easier for people (kids notably) to put their head between two bars but harder to get it out? | Physics | explainlikeimfive | {
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"The top of the head is rounded, making it easy to gradually bend bars apart a little to allow the head to slip past. The jaw, on the other hand, is a jutting and angular bone structure. It’s hard to get that to slip into a gap without a lot of pain and risking injury.",
"A big part of the problem with children is that they get impatient. An adult is likely to take time to try different ways and angles of getting their head out. A child will panic much more quickly. This leads to difficulty getting them out because they won't stay still, but also it causes them to resist your efforts. As noted by someone else, they are also more likely to keep pushing if the bars are giving enough to allow them through. Adults have enough experience to stop trying.",
"My story is a little different. When I was a small child, my mom came out and found me on the front porch with my head between the metal bars of the railing. \"DON'T MOVE!\" she commanded. Soon the family and eventually neighbors were gathered, expressing concern. Everyone had their own pet suggestions to get me out -- my head was buttered, hands and a car jack were tried to bend the bars, and so on. But my head simply would not fit though the bars, period. Throughout this process, I kept trying to speak, but was silenced or ignored. Eventually when there was a pause, everyone being momentarily out of ideas, I spoke up again. \"Why don't I just get out the way I got in?\" And then I stepped my entire slender body back through the bars, to the same side my head was on. I'd never gotten my head through the bars in the first place...just my body. I wasn't even stuck...just very obedient."
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ngw8ou | how does some dinosaurs get transformed into fossil fuel while others are perfectly preserved? | Biology | explainlikeimfive | {
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"They didn’t. Oil is principally formed from microorganisms like algae and plankton falling to the bottom of the ocean over hundreds of millions of years. Coal is formed from vast forests of tree like plants that grew in swampy areas for millions of years before there were microorganisms that could break down their woody structure and cause decay. Over time layer on layer built up. In both cases these layers would be buried by sediment and heat and pressure took over the process.",
"Fossil fuel is not primary made of dinosaurs. Fossil is from Latin fossilis that mean \"obtain by digging\" so they have the same name because both are found in the ground not because the creation was related. Coal is was formed from trees in low-laying wetland, something similar to peat moss but with trees. 90% of the coal is from the Carboniferous and Permian periods, both are before the emergence of dinosaurs. Petroleum (Oil) was primary formed in the age of the dinosaurs but from zooplankton and algae in large shallow seas. The oxygen level in the was very low on the bottom or sediments cover stuff there faster then they could decompose. Dinosaurs lived on land. There was large sea reptiles back then but they are not dinosaurs. Because relative few dinosaurs would float out and settle on the sea bed very little oil is mad of dinosaurs. So the condition where you get dinosaur fossilization is not the same as where petroleum was formed.",
"It is a common misconception that fossil fuels are derived from animals. For the most part it comes from plants, algae, microbial organisms. When the organic material becomes buried under sediment, over time the heat and pressure increase and the organic materials break down into simpler forms, a kind of hydrocarbon soup we call crude oil, natural gas etc. Depending on the environment it can also turn into peat instead of petroleum. Peat could eventually form coals and tarry petroleum like substances if given enough time, heat , and pressure.",
"Dinosaurs don't get converted into fossil fuel, trees get converted into coal and algae get converted into oil. 66 million years ago or earlier dinosaurs died and were eventually covered up and left mostly fossilised bones, some in tar pits left more remains, but not much more. Some animals from much more recent past like mammoths were encased in ice and remain fairly well preserved, but mammoths are not dinosaurs. URL_0",
"Fossils and hydrocarbons are not the same thing and are produced in very different conditions. Hydrocarbons, occur when organic matter of any kind is deposited into Anoxic conditions. The lack of oxygen means the organic material is preserved and doesn't decompose (into Co2). Over time layers and layers of mud locks that organic material in place. Millions of years later it's buried deeper and deeper and heated up, the organic material is slowly converted into Hydrocarbons.",
"Everyone here is talking about fossil fuels but nobody about preserved bones… The thing is that vast majority of dinosaur bones have decomposed completely and the very few remaining ones are only there due to lucky combinations of conditions that prevented decay or made bones petrify. I went to a palaeolithic archeological expedition once and I must say that whatever bones we could find, even though they were 1000s times “younger” than dinosaurs, were in BAD condition - barely holding together and almost crumbling when you touch them.",
"When I was younger I used to think that oil came from dinosaurs. I had a hard time undertanding how SO MANY dinosaurs ended up dying in exactly the same spot in order to create an oil reserve of 100 of millions of gallons of crude. Then I did a little research online and discovered it wasn't dinosaurs but just organic matter, accumulating over millions of years and lord knows how much pressure, to create the oil reserves."
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ngwog7 | why are gluten free pastas so much more "sticky" and guey when they don't actually have gluten? | Gluten free pasta when cooked is sticky, gluey, pastey and is extremely popular. I find it to be too Gooey to enjoy but the wife and I are wondering why is it like that and regular pasta is not when cooked. | Chemistry | explainlikeimfive | {
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"Gluten-free pasta may lack *gluten*, but it does not lack *starch.* Starch mixed with water makes a gluey paste of the sort you describe coating the gluten-free pasta. Non-gluten-free pasta also has starch, but the structural mesh of gluten running throughout the dough acts a sort of \"cage\" that largely traps the starch inside and prevents it from leaching out into the cooking water, where it can then form the glue. But gluten-free pasta doesn't have gluten, so there's nothing to stop starch from leaching out in much larger quantities, making way more glue.",
"Pro-tip - cook gluten-free pasta really al dente. I mean you probably do that for all pasta, but al dente gf pasta is indistinguishable from al dente normal pasta. GF pasta overcooked by 30 seconds is mush.",
"To add to the other answer, gluten won’t make things sticky or guey but actually more stretchy and pliable. This is because gluten is formed of long chains of molecules. When kneading bread you’re developing gluten and increasing the chain lengths. You don’t want to do it too little or the bread won’t have good texture, but also not too much because the bread will be way too chewy. When making a cake, the fat (oil or butter) actually prevents the gluten chains from growing too much which would make the cake chewy and not moist and crumbly. Mmm cake",
"It sounds like you're eating (or making) overcooked GF pasta. It's only sticky or gluey when it's overcooked, IME (and I've been GF for about 8 years now). As someone else mentioned, timing is critical for cooking GF pasta - you can't let it overcook, or sit in water with the heat off while you get other things ready. I prep everything else and use a timer, and pull it off the heat and drain the pasta when it's still somewhat \"toothsome.\" Thirty more seconds and it's a mess. Also, the brand of GF pasta matters a lot. After a lot of experimenting with different brands, I only use Barilla because the pasta tastes the most like regular wheat pasta and is easy to cook. Bionaturae is one brand that I tried that was nearly impossible to get right. Target's Good and Gather brand usually works okay (but I have a suspicion it's repackaged Barilla, they're so similar). I thought the Tinkyada brown rice pasta was awful; I don't care how supposedly healthy it is."
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ngx5hm | Why is pi irrational ? | Mathematics | explainlikeimfive | {
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"A number is irrational if you can't write it as one integer divided by another (4/5, 3/7, etc.) The *proof* that pi can't be written this way is pretty hard to ELI5, but the very-general, very-vague outline goes as follows: * Let's pretend we're in a world where pi **is** rational * Then those two integers I just talked about do exist * Look at this fancy formula I created using those two numbers. By the way, it has some fancy properties. * Uh-oh. Those fancy properties means there must be an integer that's still positive but less than 1. That's clearly wrong. * Hm... our reasoning must have gone wrong somewhere, but where? * The only thing we didn't justify was that pi is rational, so we must have been wrong from the start. * Therefore pi is irrational",
"Do you mean what makes it irrational, or why does it happen to be irrational? If the latter, the simple answer is that there is no particular reason for it to be rational. Also there are infinitely more irrational numbers than rational ones (as in, for every rational number there are infinite irrational numbers), so the likelihood of a random number being irrational is very high.",
"Pi cannot be represented as a ratio of any two whole numbers, i.e. pi is never equal to a/b, where a and b are whole. This property makes pi irrational. There are several known mathematical proofs of this fact but I don’t think I can eli5 any of them. They all use some relatively advanced math and are neither particularly short nor easy. Pi is also not just irrational, but transcendental, meaning that it cannot be found as a solution to any polynomial equation with rational coefficients. This puts pi apart from other irrational numbers like the square root of two, which is a solution to, for example, the simple equation x^2 - 2 = 0. Coincidentally, unlike pi, proving the irrationality of the square root of two is quite straightforward. An interesting open question is whether the digits of pi have the same frequency of occurrence in its written sequence. Numbers with such a property are known as normal."
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ngyef3 | When our fight or flight response is triggered, how does our brain decide if we should fight or if we should run away. | Biology | explainlikeimfive | {
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"The parietal cortex and the prefrontal cortex basically are responsible for judging risk and reward so calculate what to do in an incident, however these parts of the brain are not fully developed until about the age of 25 which is why young people don't always make good decisions in a crisis situation. URL_0",
"\"Is that bear bigger than me? Can I *actually* knock out that guy with a gun before he shoots me?\" A lot of it is gonna be based on a person's personality and the nature of the threat. And it's not a perfect decision-making process because people still wind up getting killed in situations like that, sometimes unavoidably.",
"There are a number of processes involved. The amygdala lets the hypothalamus know something's going down, which then triggers the stress response in your body, including the production of adrenaline your body needs to take on the challenge. In an instant, you need to size up the situation and rely on what you know about all of the different factors to decide the best option. What's the risk of fighting? What's the risk of *not* fighting? If your house is on fire, you'd flee and get yourself away from the danger without question, right? But if, say, a relative or pet was trapped inside, you'd probably balance the progression of the fire, where they were, and might very well go back in there to save what's important to you, even though you're putting yourself at risk. Your prefrontal cortex does a lot of work in a very short amount of time. Not everything is as dire as a burning building but our brains don't know that. There are a bunch of health problems that come along with having that stress response but not physically using it."
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ngzfo7 | Why is it so much easier to iron a crease into a shirt than iron it out again? | As title please | Physics | explainlikeimfive | {
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"Because there's no easy way to \"invert\" a crease in fabric. You can't get flatter than flat. When you iron the crease in, you're folding the crease through 180 degrees. When you try to iron it out you're opening both \"legs\" up 90 degrees to each side then trying to press it flat. So a lot more stress went into the bend to set the crease than you can put in to remove it."
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nh05cu | Why is it not possible to create a perpetual motion machine with permanent magnets, that can exert a continuous force to a magnetic turbine to power a generator to gain infinite energy? | Physics | explainlikeimfive | {
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"Because energy is conserved. We don't know how to create it or destroy it, we just know how to transform it. As far as we can tell, this is a limitation of the physics of our universe, not a human/technology problem. So if we're getting energy out of a device it has to be coming \\*from\\* somewhere and the system you're talking about has no energy input and only a finite amount of energy stored in the magnetic fields. In the particular case of arrangements of permanent magnets, you can always setup an arrangement that applies a \\*temporary\\* force, but there will \\*always\\* be a position with no net force. The turbine will rotate until it reaches that point, then stop. That initial rotation is powered by energy in the magnetic field that you put there when you arranged the magnets. Once you use it up, there's no more force and no more energy to extract.",
"If you're using a permanent magnet to spin something, you only get one \"push\" out of the magnet before the object falls into the most stable location. You can see this with fridge magnets; push one into another, and the free magnet will move away **and stop**. Unless you keep moving the first magnet, the second magnet will stop moving. Hence, you have to continuously put energy into one part of the system (the magnet you're holding) in order to get movement/energy out of another part (the free magnet getting pushed).",
"Energy cannot be created or destroyed - it can only change forms. This is a law of physics. Even if you could create a machine that _perfectly_ conserved energy - there was zero energy loss during that machines function (impossible) the second you start _extracting_ energy from that machine to do work, you lower the energy in that system. Eventually, that system will run out of energy. A perpetual motion machine that ran forever _and_ could have energy extracted from it would be required to create energy - and that violates physics as we understand it.",
"As you know, magnets will exert a push/pull force depending on the alignment of the north/south poles. In practice, if you made this machine, imagine you have 4 permanent magnets around the sides of the chamber with 4 magnetic vanes on the turbine. At moment one the magnets will repel the turbine and cause it to spin, at moment two the turbine will reorient itself so that it's exactly in the middle of the push/pull force and it'll stop moving, so no more power being generated. Since the permanent magnets are fixed, that's end of story. Now, if you used moving magnets on chamber, so that you could keep reorienting them with respect to the turbine, then you'd have a system where the turbine would continuously spin. You could achieve this by using alternating electro-magnets so that the poles keep going north/south in a cycle constantly pushing the turbine. This is an everyday object called an electric motor, the electromagnets are converting electrical energy into mechanical energy in the turbine. We use this for electric cars, drills, screw-guns, fans/impellers, etc. So this absolutely exists and is extremely efficient. This isn't perpetual energy because there is a loss of energy due to heat/friction in the rotating turbine, the electrical energy put in will be less than the mechanical energy put out. So in your theoretical machine, you'd be putting X electrical energy in, converting it 0.8X mechanical energy, then harnessing that mechanical energy back into .6X electrical energy. Does that make sense?",
"I’m going to assume that the magnets are pulling on the turbine towards them? The problem is that they will also pull on the bits of the turbine moving *away* from them. This will cancel out any further motion."
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nh0e1w | Why does using Mobile Data in smartphones consume more battery than using WiFi? | Technology | explainlikeimfive | {
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"Mobile data must transmit/receive data through cellular towers, which may be quite a distance away (a few miles, or even farther). WiFi service, provided by a WiFi hotspot/router, are usually much closer, within 10-100 feet. It takes more energy for the phone to send signals to the distant tower than to the nearby WiFi router.",
"Say you're in the countryside and you see your friend a couple of fields over. You want to talk to them. You could either shout the message directly, or give them a call on their phone. Which is easier? Mobile data is like shouting. Your phone can do it, but it's \"talking\" to the internet via a tower that could be far away. Wi-Fi is like calling your friend. Your device is talking to the nearby router and letting that carry the signal to the internet, so your phone doesn't need to \"shout\" as loud."
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nh1380 | Nuclear Reactors | Physics | explainlikeimfive | {
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"Nuclear engineer here. The only real difference between a nuclear power plant and, say, a coal power plant, is the source of heat. A coal plant burns coal to boil water into steam which turns a turbine and makes electricity. A nuclear plant uses the heat produced from a fission chain reaction instead. The advantages to this method are numerous. Firstly, the fission reaction is far more energetic than any chemical reaction, so nuclear fuel is highly energy dense. An amount of nuclear fuel the size of your pinky could provide more electricity than a barrel of oil. Also, because no combustion occurd in this reaction, and all waste products remain inside the fuel rods, there are no greenhouse gas emissions to worry about (well, there's some steam, but that's not really a concern). The main disadvantage of nuclear power is that the waste products can be very hazardous, and if the plant is mismanaged, it can release significant amounts of radiation to the environment. This means that the nuclear power industry is very tightly regulated, which drives up the cost significantly. It is worth mentioning that nuclear is the only power industry that is responsible for paying for its waste. Most countries do not charge coal plants for their carbon dioxide discharge, or require solar panel companies to pay for the recycling process for failed panels. The cost of nuclear power is relatively fixed because the fuel is so cheap. It costs about the same amount of money to keep your nuclear plant around whether it's making power or not, so nuclear wants to be running at 100% power all day, every day. This makes it a poor choice for \"following the grid\" (ramping power up and down to match the total demand required by the population)."
],
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9
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nh1p1l | When milk turns into yogurt, why does it get thicker? | Biology | explainlikeimfive | {
"a_id": [
"gytrgcx",
"gyujx9q"
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"text": [
"The milk is given specific bacterial cultures that coagulate certain parts of the milk ( milk solids) eventually this thickens and separates from the liquids in the milk and you get yogurt. This is also why yogurt is touted as a probiotic.",
"It’s a good idea to start by identifying what you’re really asking! Let’s start with a “natural” or “home made” style of yogurt. Most people will add specific bacteria to the milk (lacto bacteria). These bacteria will “eat” the milk sugars and other food sources. Happy bacteria reproduce and produce more bacteria! As they have little baby bacteria, they consume more and more of their food source. But! What eats must poop!! (Metabolic byproducts). One of these byproducts is lactic acid, which changes the properties of the milk as the pH drops (this is that sour note you get when milk starts to spoil). Since these bacteria are not pathogens (bacteria that makes you sick), as they grow they make acid, the acid drops the pH of the milk and this (aka fermentation) process creates yogurt! Now, as some have said, people can also add thickening agents like corn starch. These are used to give the desired texture of the products you love so much! Hope this helps!"
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nh2vo4 | When you don’t get sun exposure where does your tan go? How come your skin gets lighter? | Biology | explainlikeimfive | {
"a_id": [
"gytzzli"
],
"text": [
"The epidermis is continually regenerating itself. Old skin cells at the surface are lost and are constantly being replaced by new ones at the lower level. Basically your skin gets completely replaced every few weeks."
],
"score": [
7
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nh38s9 | what's the reason needle shock causes the body to pass out? | how could that be helpful in a fight or flight situation to shut down and become incapacitated? | Biology | explainlikeimfive | {
"a_id": [
"gyu085b"
],
"text": [
"If you're talking about people passing out from needles, then that's *not* helpful, to anyone. But the body needs oxygen to work right, and when people get anxious about an injection they oftentimes start to hyperventilate (breathe very quickly but take in short breaths) or hold their breath and subconsciously forget to breathe, and that winds up causing them to faint."
],
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7
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nh3b66 | How do bots work? | And I don't mean like spam bots. I searched this sub and couldn't find much. For example, I see people tagging u/ savevideo or u/ savephoto, and just saw one "shakespeare bot" that repeated a comment but in "shakespeare language." Are these real people? Im assuming not, but on the video one I think, I saw the "user" post they got banned. So I'm a bit confused? ELI5 I'm fairly new here | Technology | explainlikeimfive | {
"a_id": [
"gyu1vsb",
"gyu26b2",
"gyu25yt"
],
"text": [
"A bot is just a program running on a computer somewhere--it could be a server in the cloud, a desktop/laptop, or I suppose you could even do it on a smartphone if you were so inclined. Reddit has the \"normal\" interface where you go to URL_0 and you see the posts and comments laid out on the page, but it also has a computer-readable format that just packs the data in nice easily digested chunks. 3rd party Reddit apps tend to consume that interface and apply their own formatting. A bot will also use that interface and check for whatever trigger the programmer sets it to. Sometimes that means checking every comment looking for certain phrases (e.g. the ubiquitous grammar correcting bots that are quickly banned because they're stupid and add nothing to the conversation). Many will periodically check for username mentions, then jump to whatever comment mentioned their name. Once the program has detected its trigger it does whatever it was programmed to do. Simple bots may just reply with a canned message. Marginally more complex would be doing a find-replace, a unit conversion, or looking up a keyword in a database (this is common on competitive card game subreddits like /r/mtg where bots are made to facilitate calling out a card by name, then the bot will look up a link to that card and post some relevant information from it). The sky is the limit here--a bot could take in an image of a chess board and tell you the best next move, or take in an entire news article and run it through a pile of AI to spit out a summarized version of the article. When that processing is done the program then usually posts a comment. Technically the bot can interact with reddit in any way a human can, but certain interactions are bannable (e.g. posting the same link all over the place, upvoting/downvoting).",
"Reddit has an API (Application Programming Interface) which is basically just a web page meant for software to read and interact with, rather than a human. In Reddit's case, it's a series of pages where a program can read comments or other information, then post their own comments, without having to deal with the fluff of the visual aspects. In the Shakespeare bot's case, it's basically asking Reddit every few seconds for \"all the posts in a specific set of subreddits,\" which reddit gives it. The program, which is running on its creator's computer, then does some processing to figure out which comments it wants to reply to and what it will say, and then uses the same API to reply directly to the original comment. However, in order to do this, the bot itself needs its own account, with its own credentials (username & password). The bot sends this information along with the contents of its post so that Reddit knows what username to associate with the bot. This also gives Reddit the power to ban a bot as if it were a human, because to Reddit's servers, they're basically the same thing.",
"Those bots either search all of Reddit (with some subreddit exceptions) for their summon word (or sometimes on specific comments like haiku bot which looks for words with specific syllable combinations) or wait to be summoned by being tagged. Then when that happens they run code to do their thing, like for Shakespeare language it replaces words based on context, and save video generates a link to where you can download Reddit videos."
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nh3s3r | How are the close up shots in various National Geographic shows or in shows like Perfect Planet shot? | Other | explainlikeimfive | {
"a_id": [
"gyu3l4e",
"gyu3aej"
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"text": [
"Option 1: Extreme telephoto lense. The camera is more like a telescope, and is much further away than you think. Option 2: Stealth and automated cameras. There's no human nearby; the camera was left behind and the animals naturally wandered close by to observe without scaring the animals. Option 3: Patience and exposure. The camera crew sat in an environment for days, weeks, or months until the animals were confident enough to wander closer. Option 4: Staged Shots. You're actually seeing an animal in captivity, such as a research & conservation center, and the animal has been positioned for the shot in a controlled environment.",
"Usually these shots taken are from a decent distance away using a special lense. Think of those guys in the NFL with those mega scope looking cameras on the sidelines."
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nh3sxt | Why do sudden hits on certain parts of the body cause death? | Other | explainlikeimfive | {
"a_id": [
"gyu4i44"
],
"text": [
"It's mostly because it restricts blood flow and damages blood vessels, going to the brain. My relative had his neck hit by a piece of rock while driving and the doctor said the only reason he was alive is because of his thick, muscular neck, which acted as a protective shield. I would like to recommend everyone reading this to exercise your neck and grow some muscle. Could save your life one day. I used [this]( URL_0 ) neck training plan."
],
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"https://gumroad.com/a/56038515/paDrs"
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nh3voi | Why are Harshad numbers interesting in mathematics? Which applications do they have? | They are also called Niven numbers | Mathematics | explainlikeimfive | {
"a_id": [
"gyu57wk"
],
"text": [
"They're \"interesting\" because they have a property which people have found interesting. Math is more than just what can be applied to the real world. In fact, many people prefer math that has no application to the real world. Basically, they are divisible by the sum of their digits, which doesn't appear to be very common. So finding and testing for them is a minor challenge people have found interesting."
],
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4
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nh3z0v | How does the human body figures out what is "food" and what is a "liquid", how does it sort it out? | This is something that has always puzzled me. How does your body understands that these minuscule substances (like spices or seeds) aren't liquid but instead considered food, and, how does it manages to sort out everything when your stomach has a bunch of things on it at the same time? | Biology | explainlikeimfive | {
"a_id": [
"gyu4m35",
"gyu7kjl",
"gyu5j1g"
],
"text": [
"Just mashes it down, add some acidity and enzymes, then absorbs the amino acids, specially packed fat, and simple carbs into the bloodstream",
"Solid and liquid food/drink enter the body through the mouth and are chewed into a fairly smooth mixture there. From the mouth they pass down to the stomach, where a combination of acids, enzymes, and physical churning breaks the food down further, both chemically and physically. From the stomach, the food enters the small intestine. A bit of further chemical breakdown happens here, and nutrients are absorbed from the food into the blood through the walls of the intestine. From the small intestine the remaining unabsorbed and indigestible parts (fiber, seeds, etc), as well as the water enters the large intestine. The large intestine absorbs most of the water, passing it into the blood, and the remainder is passed out as feces. Meanwhile, your kidneys are filtering your blood to eliminate wastes produced by your cells and to maintain your blood at the right level of saltiness. As they filter, they excrete water filled with wastes and salt, which goes to the bladder for storage and is then excreted as urine. TL;DR...there's not a single step where everything gets sorted, it's more like an assembly line where different parts of the food get absorbed (or not) at different stages. And urine production happens off on a separate assembly line.",
"It doesn't sort it out. Everything gets dumped into a pool of acid (stomach), which breaks everything down into small chunks. The acid-food-soup is passed on to a long tube (intestines), where the acid is neutralized (bile), and the nutrients and most of the water gets sucked out. The remaining solids get packed together into a larger mass for disposal later on."
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nh4cq3 | Why we bob our heads to music we like? | Biology | explainlikeimfive | {
"a_id": [
"gyuruv7"
],
"text": [
"From what I understand, music is full of a lot of information. When you listen to music all that information going through your brain is a lot to process, so your brain does a trick where it out sources some of that processing work to different parts of your nervous system/body. That’s why we nod or tap along with a song. It’s also where the urge to dance comes from."
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nh4lw3 | why do we like being scared? Like watching horror films or playing horror games etc. And also is it the same reason why you like to be chased as a kid? Like playing tag/tip | Biology | explainlikeimfive | {
"a_id": [
"gyuexfz"
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"text": [
"When you get scared, you experience adrenaline. It makes your heart beat faster, increases your blood pressure etc. it also releases “feel-good” endorphins and dopamine. These are natural pain-killers in a human body that are similar to the drug morphine. They decrease discomfort and bring about feelings of well-being and euphoria. Euphoria is a feeling of intense excitement and happiness. This is why you enjoy being scared and yes, as a kid games such as tag also gives an adrenaline rush which produces the same effect!"
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nh5ni6 | if your voice sounds different to you than it does to everyone else how do people get good at impressions? | Other | explainlikeimfive | {
"a_id": [
"gyuf3w4"
],
"text": [
"Some people may have less difference between what they hear and what others hear. This makes it easier for them to change their voice to match someone else's voice. Other people can figure out the differences between what they hear and what others hear and compensate. For example, recording their voice and playing it back or practicing with another person. With trial and error, you can change your voice to \"sound\" correct to others."
],
"score": [
8
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nh5uix | What exactly is sound? | I am learning sound engineering and would like to understand more about the physics behind sound. So every sound (musical note) has a wave equation? However, two C5 from two different instruments have different timbre; are the wave equations for them thus different? | Physics | explainlikeimfive | {
"a_id": [
"gyufc8k"
],
"text": [
"Sound is vibrations in the air. Different instruments have different timbre because of their different ways of making sound and the shape of the instrument itself, the waves are indeed different. Just like how different people have different voices, the sounds originate from slightly different places in their throat (pitch of their voice) and vibrate through their skulls slightly differently (things like nasality are also here)."
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5
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nh6s74 | If you spray a bee nest from a far distance with a hose, how do the bees know to find you and not string the hose itself | Do they just assume the nearest person is responsible for the magical stream of water? | Other | explainlikeimfive | {
"a_id": [
"gyukfqe",
"gyukvkg"
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"text": [
"If they are upset they swarm out of the nest. Some bees can see darker colors like a bear and will sting that. Some bees can detect carbon dioxide from our breath and will sting that. Some bees will just sting anything that moves. Some bees memorize what it looks like outside their hive and sting anything new.",
"The \"stinging frenzy\" that you are thinking about does not happen until one or more bees has already stung someone and released the pharamones that activate the aggressive reaction from other bees. The Killer Bee is the exception to this rule. They have evolved a more proactive reaction to threats and water is not needed to start it. Still pharamones are the key factor with them as well. So a single bee needs to be directly attacked or hurt or threatened and it will sting, usually killing itself in the process. When the stinging sac is activated pharamones from sac are released into the air and it's the GO light for any other bees in the area to attack the object nearest the sting sac of pharamones. If one were to place pharamones on a tree, they'd try to sting a tree. Do it on a car, they would try to sting a car. Bees are not smart and don't decern things like you or I If you spray them with a hose they release a pharamone as well, but its more like a search and destroy any moving thing, from this post on Now see top of my post"
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nh75as | Why do firehoses flail around with such immense force if nothing/nobody is holding them steady? Is it the water itself “pushing” on the spout of the hose as it comes out? | For clarification I know that fire hydrants release water with insane pressure, I’m just wondering what exactly about that water pressure causes the hose itself to become a wacky-waving-inflatable-arm-flailing-tube-man. Thanks! | Physics | explainlikeimfive | {
"a_id": [
"gyuoi5c"
],
"text": [
"Yes, the water coming out of the hose works exactly like the thrust from a jet engine. It creates a force on the hose, trying to push it in the opposite direction of the water flow. This causes the hose to move, which changes the direction the water is shooting from second to second, changing the direction that the hose is getting pushed, ending up with a bunch of random flailings."
],
"score": [
23
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nh7cro | If depression is caused by chemical imbalances in the brain, how can having bad things happen to you cause it? | I often hear about external things causing depression, but I always thought that depression was caused by exclusively internal things and separate from anything that's actually happening in your life. On a separate note, how can things like exercise and therapy help with it? | Biology | explainlikeimfive | {
"a_id": [
"gyuo7gn",
"gyuolif",
"gyupdbo"
],
"text": [
"Bad things make for bad chemicals, and a long streak of severely bad things can make for a lot of bad chemicals. Some people can cope with a lot of bad stuff happening (it’s called psychological resilience), while for some other people the limit after which they’ll spiral into depression is lower. Exercise and therapy are supposed to help with making good chemicals to restore the balance.",
"Those chemicals in the brain (like dopamine and serotonin) are caused by feelings/emotions and IRL situations. Confidence, anxiety, loving and trusting yourself all influence those chemicals. When you exercise your brain releases a chemical called dopamine and endorphins . They’re basically what makes u happy",
"There are both genetic factors that can increase the chance of developing a depressive disorder, and things that can happen to a person that can cause them. Depressive disorders have been known to change the brain, both in form and function. There are a wide range of different options for therapy, which usually work by trying to change the ways you think, or perhaps breaking down emotional barriers. Exercise is just one of many ways to stave off depression. It, along with other activities, releases happy chemicals in the brain. It's a complex subject that is far from being fully understood."
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nh7gfp | some species (invertebrates, arthropods and certain fish etc.) see in Polarized vision. I’ve seen images but how does it work and what are the benefits of it? | Biology | explainlikeimfive | {
"a_id": [
"gyuoz3e"
],
"text": [
"Reflections changes the polarization of light. So it is easier to distinguish reflected light from direct light. You can even buy polarized sunglasses which will give you the same ability. It makes it much easier to for example look into water because the sunlight that is reflected off the surface is filtered away."
],
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|
nh7l3j | Why do we have random flashbacks about bad memories, only to physically hit ourselves in the face? | Other | explainlikeimfive | {
"a_id": [
"gyuqlz1"
],
"text": [
"wait, are you literally hitting yourself in the face when you have bad memories? if you're not trolling see therapist, that's not normal."
],
"score": [
9
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|
nh8e12 | if you buy a house and theirs a HOA in your area and you refuse to join , follow their rules etc. What can they actually do. | Other | explainlikeimfive | {
"a_id": [
"gyutkqe",
"gyuto23",
"gyutxmo",
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"gyuu9gk",
"gyuxz10"
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"text": [
"You agree to abide by the HOA bylaws when you buy the house there. You cannot buy the house if you do not agree to them. If you do not pay the monthly/annual dues and do not keep your property maintained according to the rules or make modifications to the house that violate the rules then they can legitimately take you to court and in the worst case get you kicked out of your own property.",
"Joining the homeowners association is legally put into the contract you have to sign if you want to own or rent the property. In that contract, you give them the authority to punish you if you break the rules, anything from being fined to being evicted. If you don't sign that contract, you don't get to have the house. That being said, the majority of homeowners associations aren't actually that bad. It's just that no one goes online to talk about getting a polite reminder to mow the lawn, so you only ever hear about the extreme cases where the people running the HOA are so concerned about making sure that the neighborhood looks good, so that property values stay high, that they become obsessive and tyrannical.",
"When you buy a house it's already part of the hoa, and purchasing it means you joined. It is a legal contract and breaking a contract has legal repercussions. Mostly it's going to be fines which you are obligated to pay. But you can go to jail if it goes far enough. URL_0",
"So you have to join as a condition of buying the home. There are some exceptions but those are few and far between so can be ignored by far and large. If you break the rules they can fine you according to the local regulations and if you don’t pay you can be removed and forced to sell.",
"As part of the house purchase agreement, you have to accept that you are joining the governing HOA and are legally bound by its rules. You sign documents to the effect during the closing. They can fine you, put a lien against the property, even foreclose for lack of payments.",
"You can't not join. The deed to he property itself has what called a restrictive covenant that the owner will abide by the HOA bylaws. Naturally, one of the bylaws is paying dues and not paying them subjects you to further fines which are enforceable in court. The rest of their powers are controlling the outside of your house. Not that they wouldn't regulate the inside as well, but trespass prevents them from being able to observe it. And outside doesn't just mean the home's exterior. They can forbid fences or hedges, putting in a garden to grow food, getting rid of flowers/shrubbery around the house, swimming pools, and storing boats or other recreational vehicles outside the garage."
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nh8i0l | What is the "safest" way to receive the hit from a car running you over? Would it be feasibly safer to jump into the windshield? | Physics | explainlikeimfive | {
"a_id": [
"gyuv43f"
],
"text": [
"Most standard cars (not SUVs) are designed to strike you fairly low and then roll you over the bonnet and push you to one side, this is relatively easy to survive. Vans, trucks and SUVs have squarer fronts which hit you high up and push you back away from the vehicle this easy relatively difficult to survive."
],
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6
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nh8td5 | why does chronic excessive drinking change how you look? | Biology | explainlikeimfive | {
"a_id": [
"gyv3i3o",
"gyv3a0i",
"gyw3fta"
],
"text": [
"Collagen is a protein in your body that helps hold things together. When we build a big house we use a scaffold to hold things up and collagen can act like that scaffold. But when you drink a lot of alcohol, your body produces a lot of free radicals which act like darts. As these darts get more common, they start to punch little holes in the collagen scaffolding until it gets weak which means your skin starts to visibly sag and not appear as tone. More of a ELI8 but I hope it works.",
"Alcohol is hard on you. It’s a little bit poisonous. Your body has to work hard to filter the poison part out, and that makes harder to filter out all the other wastes and toxins from your body, so your body never quite works as well at keeping you healthy. Alcohol does a lot of other things to your blood vessels and skin, and your body gets worn down.",
"what's going on when people's heads get really big and red from excessive drinking?"
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nh8tgn | how do telescopes see so far away? (Literally explain like I'm a 5 year old lol) | Other | explainlikeimfive | {
"a_id": [
"gyuwfif",
"gyuy57i",
"gyuwj2j",
"gyuxvny"
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"text": [
"Our eyes don't shoot out beams of something in order to see, instead light coming from a source bounces off things and is detected by our eyes when it arrives. A telescope then acts to collect light over a larger area than our eyes, and focuses this light into a smaller area to be viewed.",
"Telescopes do 2 things. The first thing is that you'll notice the front lens of a telescope is BIG. Telescopes and cameras and other lenses work just like the lens of your eye - the bigger it is the more light it can let in. So a telescope can see things that are much darker then your eyes can. The other thing telescopes do is magnify, meaning the thing you see at the back end looks much much bigger than it does to your eyes. So they can see things that are dim, and they can zoom right in on details. The light from far away objects was always there, you just need good optics to be able to see them.",
"The things telescopes can see are very far away, but also very big, this means they end up being not *too* small in the sky. The issue is they are very dark/dim and still quite small, telescopes solve both these issues. First telescopes have large openings in the front and large lenses/mirrors, this gives them a large surface area over which they can collect light, the larger the telescope the more light it can collect. Secondly they magnify the image of the objects, spreading it out and making it larger and easier to see.",
"A telescope uses a system of glass lenses and mirrors to expand a small area of incoming light, and then refocus it to the size of the eye piece for viewing. For glass lenses, the first lens expands the light, and the second lens shrinks that expansion back down to for your eye. For mirrors, they take a large area of light and through the curve of the mirror, focus all that light into a small area, which is then reflected into your eye. The larger the mirror/lens system, the farther it can look. Today’s telescopes (at least in space) are also, or at least were, limited to the resolution of their sensors, and clarity/precision of their lenses/mirrors."
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nh96lk | How do people at cern "get" the protons to put in the large hadron collider? Like ik it sounds stupid but it's been bugging me for ages like can they just capture them out of the air? | Physics | explainlikeimfive | {
"a_id": [
"gyuypl3",
"gyv0m67",
"gyuyus4",
"gyv1nmo"
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"text": [
"Hydrogen is a proton orbited by an electron. [Apply strong electricity]( URL_0 ) and the electron is \"stripped away\", \"ionizing\" the hydrogen into just a proton (nucleus) with no orbiting electrons at all.",
"They have a duoplasmatron! Which is a cool name for \"metal box that uses a high voltage to rip the electrons off hydrogen\": [ URL_0 ]( URL_1 ) So, they start with hydrogen gas. The duoplasmatron takes off the electrons and spits out about 70% of the remaining protons as a beam to the proton synchrotron. That accelerates the protons. Then they go to the super proton synchrotron. Which accelerates them more. \\*Then\\* they go to the Large Hadron Collider. The same proton sources feeds a bunch of other stuff at the same facility.",
"Hydrogen atoms are basically 1 proton and 1 electron. Stripping away electrons is fairly easy. Your question is still not answered though, as I don't know what the exact process is to make sure exactly how many protons to accelerate for the final bang, or if it's rather a constant stream.",
"The LHC doesn't collide protons for the most part, they use lead atoms for lead-lead collisions but also do some lead-proton collisions. To get yourself some raw protons you take some hydrogen gas and hit it with a lot of radiowaves so the electrons get enough energy they just leave their host atom. You can separate the protons out with a magnetic field and then launch them on their way. They'll get their hydrogen gas from an industrial supplier who is most likely getting it from cracking methane (CH4) and then purifying it so its all hydrogen. Particle colliders generally launch streams or clouds of atomic nuclei at each other because they have a pesky habit of missing so you have to shoot a ton of them at each other to get even a single collision. When they hit they become this blob of wibbly wobbly energy that isn't really protons and neutrons anymore and will manifest as any combination of particles with the right energy which is how we find new heavy particles that don't last long."
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nh9i4r | Why do we sometimes read things, but forget to comprehend what we just read? | Other | explainlikeimfive | {
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"Disclaimer: I don't specifically work in a field dealing with this, but I have colleagues that do and I've been interested and asking questions lately, this is my take of how reading works and what goes into learning from texts. I believe it largely has to do with reading being a lot more complex than we take it for. A whole lot goes into even reading this sentence. You have to recognize the letters, decode what sounds go into each syllable, then figure out the word. Once you have the word in mind, you have to pick out its particular meaning. You then string together all the words in that sentence to try and see if the meanings you picked out for each word make sense together. Punctuation factors its way in as well at this step. Now you summarize that sentence into a thought, and each of the other sentences found in a paragraph. You take those thought and you should be trying to summarize them into what that paragraph is trying to tell you. Now you've understood the smallest amount of what's on a page. Just now you did that complex set of multi-step operations several times. It takes A LOT of brain power, but most of the time it's pretty subconscious. But if at any step there is a snare, for example not knowing a word, or not having a grasp of the concept a sentence is trying to convey, your brain has to spend more power trying to pull meaning out of the jumble. That's usually what causes the issue your describing. Your brain is trying to spend brainpower on something but you don't have the OOMPH to spare. You could be distracted, tired, emotionally drained, or a combination there of. And if the brain power isn't there for say, giving meaning to the sentence, all you did was look at and recite words. At that point it wouldn't matter if they were English, Chinese, French, or a Cypher like rot13, they were meaningless to you and you can't synthesize, that is to say learn, something from nothing."
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nha53a | Why do formula 1 cars use super slick wheels? | Other | explainlikeimfive | {
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"Well, in F1, grip is super important. And the only contact point with the ground are the tires. Slick tyres gives the car a bigger contact space with the ground and therefore more grip than a tire with treads. The reason road cars need to use tyres with treads is to get rid of the water so they can reach the tarmac and have grip in all weather conditions.",
"The grooves in your tyres are only there to displace water. It's the rubber touching the road that counts. That being said the compound is key. Racing slicks are extremely sticky and once warmed up they try to preserve that heat either by wrapping the tyres up in thermal blankets while off the track or when on the track they try to keep momentum going to keep the tyres warm. Cold tyres don't grip well. This is why drivers can sometime struggle to get up to speed after a sudden slow down until they get the heat back in."
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nhbduf | Why does the seconds hand appear to move backwards when you first glance at a clock? | Biology | explainlikeimfive | {
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"This is known as the \"stopped clock illusion\" and most people see it as a long pause of the second hand rather than it actually moving backwards (but some do see it moving backwards). It comes from the way our brain edits out blurry input from moving eyeballs. When you first look at a clock or watch, your eyeballs moved to get the clock or watch in frame, and the movement produces a blurry image for a split second. Once your eyes stop moving, there's a clear image for your brain to process and it literally overwrites the blurry image with the clear image. But now the clear image is \"what you see\" for a few milliseconds longer than you really saw it, so fast moving things (like a second hand) appear stopped or slowed (and in some cases, moving backward) for very brief time - basically the time of the blurry image is replaced with the non-blurry image. We don't notice this without some fast moving and expected thing in the image (like a second hand)."
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nhbu5o | How does Decaf coffee work? Like isn’t caffeine naturally in the Coffea plant? | Biology | explainlikeimfive | {
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"There is indeed caffeine in coffee beans. And when you brew coffee you extract all the caffeine with the flavors and colors in the beans. But there are some solvents which will only dissolve caffeine and not any of the flavors and colors in the beans. So if you brew using these solvents instead of ordinary boiling water then you only get the caffeine. What you are left with is coffee beans with all its flavors and colors but with only trace amounts of caffeine.",
"The raw beans from when they are grown are pretty soft and permeable. They soak these beans in a solvent that dissolves caffeine, so the caffeine just dissolved in the liquid then the beans are taken out and washed of the liquid.",
"One way is to wash the beans in liquid carbon dioxide. This has to be done in a pressure chamber since carbon dioxide cannot be a liquid at atmospheric pressure. Caffene is soluble in carbon dioxide, but most of the other flavour compounds are not. When the washing is complete, the pressure is released and any remaining carbon dioxide quickly evaporates away.",
"Yes. Most of the caffeine can be extracted at a lower temperature and time than most of the good flavours. This is done in advance with differing methods. The result is mostly-normal tasting coffee, missing most, but not all of the original caffeine content. It’s a sweet spot between strength and flavour but some of the naturally-occurring caffeination remains intact, as you expected. Nothing beats the taste of the real thing on the first extraction.",
"Yes, caffiene is naturally in coffee plants, but, caffiene is also water soluble. This means that for decaf coffee, green coffee beans (before roasting) are soaked in water or steam and the caffiene can be extracted. The green coffee beans are then let to dry out back to thier normal moisture level, and processed into coffee normally.",
"Indeed. Caffeine and related chemicals are found in all parts of the coffee plant. They are particularly concentrated in the seeds however the outer fruit containing the seeds also contains some caffeine. Ripe coffee berries can be pressed for fresh juice which I have heard is pretty good and gives a bit of a kick like tea or coffee. This is a byproduct of some processes used to refine and seperate the seeds. There are several methods to used to remove caffeine from coffee. The simplest is to coarsely crush green coffee beans and rinse them in cold water at a few degrees C, then press the grounds to remove the cold solution, then repeating this a few times. This takes advantage of the fact that caffeine is more soluble in cold water than most of the flavor compounds in coffee. This removes most of the caffeine but leaves most of the flavor. You can then dry and finish roast the coffee. Another common method is the \"Indirect solvent Process.\" The green beans are brewed in hot water which is then filtered out, producing essentially a strong coffee, though green coffee isn't terribly good tasting. The resulting brew is then chilled and mixed and stirred with a hydrocarbon solvent like dichomethane or xylene. Neither of these are soluble in water and thus float to the surface as an oil layer. Caffeine is a lot more soluble in DCM or other such solvents than water so most of the caffeine is removed fron the brew, which then can be pumped off as a seperate layer. The brew is then heated which boils out traces of the solvent remaining in the brew which you don't want introduced into the coffee beans. The hot water is then recycled to brew more green beans. Because the recycled water is still rich in coffee flavors but is only poor in caffeine and a few other compounds, so overall not much flavor is lost from the beans. Usually the coffee beans go through 2-3 sucessive steeping steps after which about 97-99% of the caffeine is removed. The discarded solvent which is rich in caffeine but also contains some of the flavors may undergo a third step to selectively remove caffeine from it in turn. After which it can be heated to boil it off in a closed container and remaining flavor compounds can be added back to the coffee. The solvent vapor is piped into a condenser as a gas then chilled and condensed back into a liquid, so it too can be reused. You don't want to simply vent that stuff to the atmosphere. Again, the green beans, caffeine removed, are dried then roasted before being packaged for sale. Another method uses CO2 at high pressure. When pressurized, CO2 becomes a liquid although at ambient pressure it can only exist as a solid or a gas. By tweaking the pressure and temperature you can control the solubility of caffeine in the liquid CO2. The liquid CO2 is passed through the green coffee then scrubbed with water to remove the caffeine. Once the pressure is reduced the CO2 bubbles out of the water."
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nhcp58 | Dropping anchor when you get the spins | When you lay down after drinking a few to many, why/how does putting one foot on the ground (dropping anchor) stop the vertigo (spins)? | Biology | explainlikeimfive | {
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"Your sense of balance is based on feeling and the more points of contact you have the better your balance. (2 feet better than 1) When you lay down drunk you lose this reference and touching the floor gives you a point to refocus."
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nhcz6i | If gravity is not as a force, but a consequence of masses moving along geodesic lines in a curved spacetime then what is a Graviton? | Physics | explainlikeimfive | {
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"That's the entire reason quantum physics and general relativity don't get along. If quantum physics is right, gravity is a force that must be mediated by a particle...we call that particle a graviton. We've never been able to isolate one but the Standard Model has a very good track record of predicting particles that we later find, so this isn't necessarily an issue. If general relativity is right, it's not a force but warped spacetime. One (or both) is wrong. They can't both be right in their current formulation. A graviton makes no sense under general relativity, but we don't have a theory of quantum gravity that \"looks like\" general relativity at large scales (where we can do very successful experiments) but still plays nice with quantum physics."
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nhd7q7 | Why is Internet Explorer still around, what kind of applications or businesses still use it? | Pretty much the title | Technology | explainlikeimfive | {
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"For example I worked in a company that used some house developed software for the product database, and that only really worked in explorer, redeveloping the software would be expensive and licensing a third party software would also be very expensive, basically if it ain’t broke don’t fix it",
"IE was around for long enough, and for a long time was the only browser with really solid enterprise support, that a ton of early corporate web applications were written for it and used custom IE functions that aren't present in any other browser. I used to work somewhere that the entire CRM software was a highly customized version of Siebel and it only worked on IE. You don't just roll your entire CRM suite without being \\*really\\* sure it will work, and the business case to roll it is always terrible...it's always cheaper to keep IE than to rewrite the software. Eventually you get forced into it when Microsoft sunsets it, but you hold out as long as possible. For mission critical applications you're way more concerned about stability that \"latest technology\". IE has been really stable for a really long time.",
"The company where I work does CAD drawings using an obsolete program called CADKey. To look at these drawings, we use a program called Autovue, that for some, reason doesn’t seem to work with modern browsers. Internet Explorer is the only one. We use IE to quickly look through these CADKey files. That being said, our IT dept is looking into ways to do this without IE right now..."
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nhdgvw | Why does marijuana give you dry mouth, even when it’s taken in an edible form? | Biology | explainlikeimfive | {
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"When THC binds to the endocannabinoid receptors on your salivary glands, it “reduces the amount and increases the viscosity” of the saliva they secrete — hence the dry, sticky feeling inside your mouth.",
"Marijuana’s active compounds, known as cannabinoids, affect the human body by binding to cannabinoid receptors. [This study]( URL_0 ) demonstrated that salivary glands have cannabinoid receptors, and that cannabinoids decrease saliva secretion by binding to those receptors. Presumably, the cannabinoids are getting to those receptors through the bloodstream, so any method of getting cannabinoids into your blood would have this effect."
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nhdreb | Why does oil not evaporate like water? | Chemistry | explainlikeimfive | {
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"Oil has a much higher boiling point. That basically means it's molecules need a lot more energy before they can convert to a gas. Water boils at 100C. Oil, depending on the type & purity, is more like 200-300C. As a result, at the same temperature, a lot more water molecules will be going fast enough to escape than oil molecules. This means the water evaporates \\*much\\* faster. The oil still is evaporating, it's just so slow at room temperature that you don't notice it much."
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nhdvvc | How do Bug Sprays kill bug's? | Biology | explainlikeimfive | {
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"text": [
"Most insecticides contain nervous system toxins, chemicals that bugs don't have any way to metabolize which mess up their central nervous system. Mammals are more sophisticated and live longer, so we have mechanisms to remove these toxins."
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nhe3qw | Why does a big stick helps a tight rope walker with their balance? | Physics | explainlikeimfive | {
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"It helps them control their center of gravity. If their body moves one way they move the bar the other way to keep the mass centered.",
"Newton's third law of motion: > For every action, there is an equal and opposite reaction. If you want to go left, you need something to push to the right. If you want to go right, you need something to push to the left. That pole is something to push. An umbrella is also often used.",
"Also increases their inertia, or resistance to positional change, which would decrease the reaction time they need to compensate for winds gusts and other balance issues."
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nhednc | How does echolocation work in animals such as bats? Does human echolocation work the same way? | Biology | explainlikeimfive | {
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"Echolocation is fascinating and part of a whole field of research known as neuroethology. In the simplest terms, bats make a click at a specific frequency and wait for the sound wave to bounce back. The echo will his either the right or left ear first and thus inform the bat of the direction of its target. Human echolocation is much rarer, and as far as I know is usually seen in blind individuals. There have been a few studies which show that in these echolocating humans, it’s actually the vision centers of the brain being activated and not the hearing centers. This would suggest that in a blind individual, the brain has repurposed the real estate for seeing into an echolocation center."
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nhf74b | What’s the cause and effect of an iceberg breaking off? | I saw on the news that the world’s largest iceberg in Antartica broke off. 1. How does this happen? 2. What are the consequences of this happening? | Earth Science | explainlikeimfive | {
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"Ice sheets move. As new snow falls in the elevations it compresses into ice and gravity carries it downhill. Slowly, but inexorably. The end of the ice sheets stick out over water. Ice has weight, even though it can float. When it extends to a point where enough of it extends past land the weight can contribute to it, quit literally, snapping off. Warmer temperatures can and do contribute to and potentially aggravate this process, but the basic mechanics are above. As for what happens, the new iceberg drifts, melts, breaks up, drifts more and eventually melts."
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nhfl58 | How is rice so cheap to produce considering how much work there is to harvest it? | I read online that it takes 4 months to harvest it from seed and even then you'll only be able to harvest a handful of rice granules, which isn't really enough to be self sustaining if growing it at home. On farmland, it also seems like tedious work to produce such a large volume of it given that the rice plants are cut by hand. | Economics | explainlikeimfive | {
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"Waiting for it to grow is not difficult work and can be done easily by a single person. They basically just have to spray pesticides occasionally. Also, the cheap rice is not cut by hand. They have big machines that drive through the field and harvest it. [Rice harvest image]( URL_0 )",
"Rice in paddy fields requires very little effort between planting and harvesting the reason for the flooding of the fields is to keep down weeds and other things which might interfere with the crops, so it is really cheap to grow."
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nhfpwf | What is it about Styrofoam that gives smaller pieces such a high static charge? | Physics | explainlikeimfive | {
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"Their lack of weight. Basically, the bigger pieces have the same property, but you dont notice since they dont stick to everything. Gravitiy is a really weak force and small things with a big \"static charge\" will be affected more, by the forces involved in that, rather than gravity. Or magic I dunno really.",
"Surface area relative to volume/mass likely plays a role to some extent. An electrical charge likes to spread out as much as it can, subject to other concerns like trying to equalize if possible. With a larger piece of styrofoam you can carry a much larger charge but the charge is spread out over a larger surface area. Meanwhile it has to contend with a much higher mass. So any given piece of surface has a smaller charge and more weight to hold.",
"Styrofoam is very electrically insulating, so once random electrons get stuck on the surface, they don't want to move around, this combined with its surface roughness means that it is very difficult to get charges off Styrofoam. The reason smaller pieces stick to things so well is because as things get smaller they have increased surface area per volume. The static force is proportional to the amount of charges on the surface, which is proportional to the surface area of the piece, where as the force of gravity is dependent on the mass which is proportional to the volume.",
"Just for general education, if you’re talking about the white foam that is composed of little white beads molded together- that’s not styrofoam, it’s expanded polystyrene. Styrofoam is blue extruded polystyrene (not expanded), and is a trademark of Dow.",
"There are two aspects which contribute to it. The first is that the polymer is actually not very conductive to electron flow, so if charge is accumulated, it does not quickly dissipate (does not drain to ground). Another aspect is that the structure is simple and includes a side benzene ring which allows for excess charge to be distributed in a cloud over a large area (in effect, adding a single electron sees the charge get shared among six carbon atoms so there is no big charge disparity at the atomic level but there is a charge disparity at the molecular level). When several rings are aligned on the same side of the polymer chain, you can get a charge distortion, a negative zone at surface which isn't stable, really, but lacks enough energy to be forced to escape (flee, spark, go to ground). It is similar, in some ways, to how clay minerals often behave (charge is unevenly distributed across the structure) and will flocculate (glom together from electrostatic forces). It isn't really that it has an extraordinarily high charge so much as the mass of the styrofoam is small so the force caused by the presence of charge seems large for the volume. There is a surface charge; it isn't huge (won't shock you when electrons jump) but it is \"Huge\" relative to the mass."
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nhgmdn | When you’re boiling a pot of water, right before the water starts to boil if you watch carefully at the bottom of the pot there will be tiny bubbles that form and disappear. Why do they just disappear instead of floating up to the top once they’re already formed?? | Physics | explainlikeimfive | {
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"Finally something I can answer lol. So the heating element (or fire if you use a gas range) is obviously very hot. Much hotter than the 100 degrees C water needs to start evaporating. As you heat up the pan, that heat from the stove goes to the pan and subsequently, starts heating the water. The water at the bottom of the pan will heat up much faster than the water at the top of the pan (since it takes time for the heat to go up the water). As the bottom of the pan gets to 100C and water starts boiling, that bubble (steam, aka water vapour and not air (though there is some small amount of it)) will start rising but immediately get in contact with more water that is not at 100C yet (further from the bottom of the pan), and 'cool' down and that water vapour will go back to liquid and the bubble disappear. As you keep heating it for longer, you'll notice the bubbles get higher and higher before they disappear up until they can reach the very top and start bubbling and you'll say it's boiling. You'll also see these bubbles on the walls of the pan since the heat from the bottom of the pan can conduct through the walls of the pan and heat from the sides, and those will also be much hotter than the water itself. Fun fact, if you want your water to boil faster, you can agitate the water as it heats up (mix with spoon or something) and it will help the water at the bottom to mix with the water at the top and transfer that heat faster. EDIT: The laSt part about cooking was not 100% corrEct aNd therefore, I removeD it. as poiNted oUt by others, cooking has other processes coming in play such as maillarD reactions and hEat destroying pathogenic germS.",
"Small bubbles of water boiling - but during this time not all water is 100° C so not all water is at boiling temperature. The little bubbles of steam travel up and the water above it at a bit lower temperature cools the steam down back to water, so they don't escape from the top.",
"I'm a materials engineer so here goes. Water boiling is a phase change reaction. In any phase change there has to be nucleation of the new phase in the current phase. Nucleation basically means small (sometimes spherical) bubbles of the second phase trapped in the first. Since all reactions are governed by kinetics and thermodynamics both, it is possible that a reaction may be thermodynamically favorable but not kinetically. This means, right before the water boils, it has enough energy to turn into vapor, but it does not have enough to escape the liquid Also, there is a critical nucleation size, beyond which the second phase is stable in the first one. This is due to the different internal and surface energies of the 2 phases. Simply, when 2 phases are in contact, they have some surface energy. Both phases also have some internal energy. Both these energies are negative (so higher means more negative) If the surface energy is higher than the internal energy, the nucleus will be stable and grow. OTOH, if the surface energy is lower, the nucleus will collapse. Again, kinetics says the reaction should probably happen, since we have enough energy to grow a nucleus. But until thermodynamics comes in and says \"you have crossed the critical nucleus size, you may grow further,\" the nucleus will always collapse on itself",
"A follow-up question on the same lines Why then do the bubbles appear to form at specific single points at the bottom of the pan? It's like a steady stream of bubbles from that location. Based on the answers I went through this thread bubbles form because the vessel is heated and so adjacent water turns to vapor, but then why only specific locations?",
"To further expand, there’s different ‘regimes’ of boiling. As the bottom surface is heated above the boiling point, we don’t actually see any bubbles until the surface is a few degrees past boiling. The larger the temperature difference, the more bubbles we see form and eventually make it to the top. This is what we refer to as nucleate boiling. If the temperature of the surface gets too high, a stable vapor film actually forms over the surface and traps the bubbles. This is referred to as film boiling. [Boiling curve]( URL_0 )",
"TLDR for the whole thread.....the bubbles (water vapor) get to cooler temps away from the heat source and the vapor reverts back to a liquid. Oy vey",
"Good question! The bubbles you are at the bottom are actually not the same as the bubbles that you are thinking of! The one that you're thinking of are air bubbles, when you put a straw into the bottom water and blow air into it, the air gets pushed into the water and rises to the top. When you boil water, some of the water at the bottom of the kettle gets so hot they turn into steam! Steam looks exactly the same as air, but with one exception - they like to give out heat and when they do, they shrink and turn back into water. So just as the water starts to boil, these tiny stream bubbles form, but since it is surrounded by water that's not yet at boiling temperature, they almost immediately shrink and turn back into water. This process repeats until all water in the kettle gets to 100 degrees C, when steam can't shrink anymore, and start rising to the top!",
"Interestingly, if you use cold water and watch as it slowly heats up, you will see bubbles form that DO make it to the top. Air dissolves more easily in cold water. As it heats up, the air has to come out. These bubbles will often sit on the bottom of the pot until they're big enough and float to the top. Typically they are all gone by the time steam actually starts to develop (the disappearing bubbles).",
"A more physics oriented answer: The hot war turns to gas which forms a bubble there are two competing forces making the shape of the bubble: the vapour expanding with temperature and the surface tension of the water squeezing it. When the vapor cools as it moves away from the hot bottom it take on which ever shape is easiest to maintain. For lower temperatures this results in the surface tension winning out and collapsing it (this is why water is loudest just before it boils), when the bottom of the pot is hot enough the expansion of the gas wins out and the bubbles just get larger until they reach the top (this is known as boiling)"
],
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nhgusw | Why does our vision keep spinning even if we stopped moving? | Was just spinning randomly in my kitchen and wondered why...when I stop moving...my vision still is weird for a few moments as if I was still spinning around in circles? | Biology | explainlikeimfive | {
"a_id": [
"gyw9284"
],
"text": [
"When you were spinning around, the fluid in your ears semi-circular canals kept moving around. The semicircular canals hold these tiny stones, otoliths, that shift when the fluid moves. These stone hit cilia, tiny hairs, in your ears that are sensitive to motion. When these hairs move, they send a signal to your brain that says motion is happening. Part of our balance is achieved by the ocular-vestibular (eye-ear) relationship (ever notice how it’s harder to stand on one foot with your eyes closed?). So, your eyes are trying to “correct” motion that your brain is being told is happening by your inner ear."
],
"score": [
5
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nhhuxw | Why is it so hard to wiggle my toes individually? | It takes a lot of concentration to get some toes to even move at all. It’s frustrating if you try to command some of these piggly wiggly’s to move. | Biology | explainlikeimfive | {
"a_id": [
"gywdx2t",
"gywll6w"
],
"text": [
"The big toe is controlled by its own tendons, the other 4 are controlled by their own interconnected tendons.",
"Did you just listen this week's freakenomics podcast episode as well? Apparently the shoes we are wearing are partly to blame and also because we don't have practice with it. So start trying to pick up marbles with your toes"
],
"score": [
12,
3
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nhi2py | How come there isn't an imaginary system for dividing a number by 0, while there is one for taking the square root of a negative number? | Mathematics | explainlikeimfive | {
"a_id": [
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"text": [
"So, it boils down to one thing: Allowing division by zero completely and utterly breaks mathematics. Literally 2=4 now and 21334124234 = 9.45412231. Every number is equal to every other number and you just can't get anything useful done. But imaginary numbers (which by the way is a terrible name it's not more \"imaginary\" than any other number) don't do that at all. They are formalized and it doesn't break math at all.",
"There can be - the extended real lines add an infinity, and extend division by zero to equal infinity. This still leaves 0/0 undefined, but even that can be defined in a consistent way if we want. The issue is simply how useful it is. In the complex numbers it is no longer true that sqrt(ab) = sqrt(a) * sqrt(b), which is an annoying thing to lose (along with some other exponent identities), but not that big of a deal. What we gain is enormously useful, since all sorts of cyclic phenomena are well modeled by complex numbers. By extending into the lines with infinities, we lose core division identities - it's no longer true that a * (1/a) = 1, because allowing 0 * (1/0) = 1 creates contradictions. The division operator makes more intuitive sense (since 1/0 certainly feels like Infinity), but it means division is not always the opposite of multiplication, so actually doing algebra becomes more difficult. This is still sometimes useful, but mostly only in analysis (higher level calculus) and a few very abstract physical models.",
"Taking the square root of an imaginary number works within regular math. The imaginary number i is just equal to the sqrt(-1), which algebraically is a-ok so long as it doesn’t need to be evaluated. You can do useful math using i and it’s not a whole new system. Dividing by zero just makes no sense. How many groups of 0 can you make out of x number of items? (A way of thinking about division). The answer is infinite- or maybe it’s 0? Maybe there’s 1 group, but no matter what it’s up for debate (to some extent) and dividing by zero, algebraically, is not useful. Also, if you could divide by zero, you can prove that any number x is equal to any number y, and x and y could be -39104 and 2 respectively tl;dr: imaginary numbers follow the rules of algebra. Dividing by zero is against the rules because the result just can’t be determined, and it wouldn’t be a useful system"
],
"score": [
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|
nhionx | How is it possible for a vinyl record to perfectly reproduce the sound of a musical instrument just by rubbing grooves in it? | Technology | explainlikeimfive | {
"a_id": [
"gywjats"
],
"text": [
"Because sound is waves and the grooves are miniature versions of those waves that get amplified back to the real sound. It’s literally that simple."
],
"score": [
7
],
"text_urls": [
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]
} | [
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|
nhip00 | Is Moore's law still applicable today? And is there any limitations to just how small a transistor can actually get? | Physics | explainlikeimfive | {
"a_id": [
"gywy55k",
"gywkhlp",
"gyxkb8u"
],
"text": [
"It is common consensus among the Computer Engineering research community that Moore's Law, doubling the number of transistors in a chip every 18 months, is dead as of the mid-2010s. There are multiple reasons for this, but one of the biggest is that smallest transistor sizes today, 10s-100s of atoms wide, are extremely difficult to produce without errors (intolerable variations in size and electrical properties). As a result, chip producers have fewer good chips to sell and the chips aren't cost-effective to produce. They (Intel, Samsung, Global Foundries, TSMC) can make chips with smaller transistors, but advances in chip manufacturing to make it financially worth it have slowed well below the rate predicted by Moore's Law. An inaccurate illustration: if your transistors are 25-atoms wide, a manufacturing defect of merely 5 atoms changes the electric property by 20%. It is unclear whether single-atom or sub-atomic transistors are possible. In my opinion, the areas of focus in computer hardware development are shifting away from reducing transistor sizes (\"technology scaling\"), and so consumer-grade, mass-produced < 1nm-tech chips will not be produced in our lifetime. I hope I'm proved wrong. Source: Am PhD student in the field.",
"For now, yes. We can still expect the transistors in a chip to roughly double every two years. But there is a limit and we are getting somewhat close to it, so it’s not really clear how long it will continue to apply. Basically, if you imagine transistors as a switch that open and closes, once you get small enough the electricity will just sorta teleport across it even if you try to turn it off. That keeps it from being very useful. Using other kinds of materials than silicon may help, and even after that we’ll probably still be able to find other ways to make computers more efficient, so it’s not like they’ll be the end of computer advancements. It just means we might have to get more creative and might not make big leaps at quite the same rate.",
"Moore's law always was only an observation. People started to call it a \"law\", like it followed some kind of rules, but that is not it. A long time ago transistor count increased because new functions were added. Nowadays, the transistor count increase is mostly cache."
],
"score": [
52,
37,
3
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"text_urls": [
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|
nhjwrv | How do apps like Google translate, or Google maps monetize themselves? | Technology | explainlikeimfive | {
"a_id": [
"gyws86b",
"gywz3ui",
"gywrszf",
"gywwpe1"
],
"text": [
"Google makes most of its money through advertising but not every service has them. Some products like translate are offered for free as a way to entice users to join the Google ecosystem where they can be served ads and/or to collect data which can be used to target advertising.",
"Google gets a lot of data from less-monetized apps (some of these have monetization, just not for the end user like someone performing a search) to feed into or improve their monetized ones. It’s not so much a separate, non-profitable app and more a part of an ecosystem where they have highly profitable apps. They can also sell parts of the information they worked to develop to third parties like satellite imaging. Google earth has an image subscription you can buy which is part of their practice of selling access to their APIs to developers. Businesses also license google to use maps professionally. I’m pretty sure a lot of translation tech is also licensed to third parties and sometimes used in machine learning to improve other app/future ventures which feeds the whole ecosystem. They also sell the the government. URL_0",
"they don't. They don't have to. google can offer some stuff for free with no obvious monetization because google makes so much money off of other services. The more people use google maps, the more people use google search, which they do monetize (by filling it to the brim with ads)",
"Many of Google maps features are APIs that developers have to pay a subscription to use. The user can use everything for free, but developers who incorporate these features to their websites/app actually pay money to be able to provide them to their users."
],
"score": [
8,
6,
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],
"text_urls": [
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"https://www.forbes.com/sites/thomasbrewster/2020/10/13/cbp-spent-2-million-on-google-maps-for-a-massive-surveillance-tool/"
],
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} | [
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|
nhka75 | If I refract sunlight through a prism in a way that the same rainbow stays on my skin for a long time, what kind of burn would I get? | Does the prism also refract UV light and IR light? How would that effect the light and therefore the skin? | Physics | explainlikeimfive | {
"a_id": [
"gyws0is"
],
"text": [
"If the prism is transparent to UV, yes, it would refract UV the same way (and the UV part of the spectrum would lie, invisibly, off the purple part of the rainbow). (That said, lots of glass is opaque to UV.) You would get a sunburn that is progressively worse the bluer in the spectrum you get, starting with no burn in the visible spectrum and ramping up as you leave the visible for the ultraviolet."
],
"score": [
22
],
"text_urls": [
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} | [
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nhka7i | How do Birds lay eggs without the shell breaking, and how do they pass such massive eggs? | Biology | explainlikeimfive | {
"a_id": [
"gywu5lo"
],
"text": [
"The shape of an egg is really good at supporting pressure. It’s fairly easy to break an egg by hitting it in one spot, but try squeezing an egg in your hand, and it won’t break. As for passing eggs, the size of an egg in relation to a chicken’s cloaca isn’t that big compared to the size of a baby’s head in relation to the hole it comes out of."
],
"score": [
5
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"text_urls": [
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} | [
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|
nhkfv1 | Why does OC/Pepper spray make it almost physically impossible to open your eyes? | I get that it's supposed to burn; but how does it effect the muscles that actually stop you (or most people) from being able to open your eyes? | Chemistry | explainlikeimfive | {
"a_id": [
"gywwato"
],
"text": [
"The irritant itself doesn't injure or affect the muscles, it's your body's reflexive reaction to some irritant. It's called a blepharospasm. A blepharospasm in response to some irritant is a protective reflex meant to protect your eyes from further damage. Squeezing your eyes shut can also stimulate tear production which will help clear the irritant out of your eyes."
],
"score": [
7
],
"text_urls": [
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} | [
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] | [
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nhknud | Under what circumstances do people blanch vs. blush? | I hear that both happen due to the fight-or-flight response. How can this be? Was I misinformed? | Biology | explainlikeimfive | {
"a_id": [
"gywur7k"
],
"text": [
"Blanching is caused by vasoconstriction- your blood vessels in the skin contract to force blood to your essential organs and muscles where it is most needed typically in a fight or flight situation. This is caused by adrenaline and cortisol release - 2 hormones which the brain triggers in stress. Blushing is a little more complex and not fully understood. It occurs mainly in emotionally stressful situations (embarrassment etc), and is hypothesised to be a rebound of the typical fight or flight situation where a physical response is not possible as described causing vasodilation- blood vessels expanding."
],
"score": [
3
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"text_urls": [
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} | [
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nhlhri | How does a logic diagram work to add numbers in a computer? | Technology | explainlikeimfive | {
"a_id": [
"gywysip"
],
"text": [
"Numbers are represented in a binary form in a computer, meaning that every digit in a number can only ever be either 0 or 1. Zeroes and ones are held equivalent to False and True correspondingly. And you can work with False and True using logic. For example, if you need to add two whole numbers, then you start from their last digits. Applying the XOR logical operation to them gives you the last digit of the sum (0 xor 0 = 0, 0 xor 1 = 1, 1 xor 0 = 1, 1 xor 1 = 0). Applying in parallel to them the AND logical operation will give you the carryover to the next digit (1 and 1 = 1; equals 0 in all the other cases). Putting the necessary amount of XOR and AND gates in a sort of a chain for carryovers will let you calculate the sum of any numbers up to a certain size."
],
"score": [
3
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"text_urls": [
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nhlq6c | Why Microsoft shutting down Ms Explorer, instead of re-naming Ms Edge | Technology | explainlikeimfive | {
"a_id": [
"gyx043b",
"gywzxuh",
"gyx071z"
],
"text": [
"Assuming you're talking about the Internet Explorer - it simply is a completely different program from Edge and is being deprecated. I suppose \"Internet Explorer\" has some brand recognition that could be otherwise utilized, but since that brand recognition is mostly **negative** it makes sense to not just rename the different (better) product. It would end up being confusing anyway - why would you rename Twix to Snickers, just because you decided to no longer produce Snickers?",
"Explorer isn't Edge, Edge is Edge. It would be very confusing to rename an old product to the current name of a new one, as they would presumably need to rename Edge to something else (and have everyone think Explorer was Edge), or have ambiguity about what program anyone was talking about. Another benefit of them producing a new program with a new name is that people will readily understand it is different. Explorer is certainly a well known name but it isn't recognized by all as a *good* program to say the least. Microsoft doesn't so much need to worry about their ability to get the name out into public recognition, so shedding a checkered history is likely more valuable.",
"Rebranding. Explorer had so many ups and downs in its history that the brand name is blurred. That is, you say \"MS Explorer\" to people, and you don't know what their internal reaction will be because you don't know what history they may have had with it."
],
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