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7luxow | Why do people wake up very early after a night being up drinking? | Other | explainlikeimfive | {
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"Alcohol is a depressant, which means it suppresses certain kinds of brain activity. It begins by suppressing judgment and inhibition, and at higher doses will suppress brain stem functions like balance, coordination, and even life support. Your brain will compensate for this by releasing excitatory neurotransmitters to overwhelm the depressant effects of alcohol. Unfortunately, this self correction takes awhile to stop and start. In the morning, when the alcohol is out of your body, your brain is still flooded with excitatory neurotransmitters, causing you to wake up."
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7lv8ni | Why do so many car commercials try to appeal to viewers emotionally rather than advertise features of the car? | Other | explainlikeimfive | {
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"Because that's how advertising works best. Human decisions are built on emotions and how you view yourself more than on logic. A lot of the psychological theories used for advertising are based on the theories of freud and the subsequent work of his nephew, Edward Bernays. EDIT: for more try here : URL_0",
"Because that's what works. The average person doesn't care about the technical information. They care about the brand name and how it's made to look.",
"A car is a way to express the type of person you want to be perceived as. They're selling a lifestyle not a car."
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7lvdsf | How do Liquid Crystal Displays (LCDs) work? | Technology | explainlikeimfive | {
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"Basically, there is a backlight behind everything. Infront of the backlight are 3 layers of 'pixels', red, green and blue. Each pixel in each layer allows light (from the backlight) through when a electrical current is passed through (or in some cases, not passed through). These colours 'mix' and through the help of a polarising filter you get what you see on your monitor.",
"Let's look at light. Light can be thought of as a series of waves. Normally, the waves are moving at all sorts of angles. You can pass light through a *polarizing filter* which straightens out the light waves in one plane. It does this by blocking the some of the light and letting only some through. Sort of like having messy hair and then combing it straight. If you take 2 polarizing filters, but turn the second one 90 degrees, you can effectively block *all* the light. Got it? Ok. Years ago, smart researchers figured out a way to make a material polarize light when electricity was run through it. This was liquid crystal\" . Power off= no polarize. Power on: polarize. So, combine that material with a normal polarizing filter (turned 90 degrees!) and you have created an electric light blocker! So, now you have a way to block light. Take 3 very small versions of this (call them LCD pixels)... and put a red, green, and blue filter in front of them. When you put light behind it and turn off the power to the 3 pixels, the light from behind shines through and lights up all 3... producing red/green/blue light...which you see as white light. Now, power up the pixels. You can now block the light selectively. If you have enough of them (large LCD display) , and a way to control them (computer/electronics) you can create any image you want.",
"I'm going to talk about the plain gray/black LCD displays, like you'd see on an old-school digital watch or calculator. Liquid crystals only allow light to pass that is oriented in a particular direction, but that direction changes when electricity is applied to the crystals. On top of the crystals, there is a piece of glass that also only allows light with a particular orientation to pass through, but electricity doesn't change that direction. When the electricity is off, those two directions line up, so that light in that direction can pass through. But when the electricity is on, the two directions that can pass are far different from each other, so the light that can pass through the glass can't pass through the LCD, and vice versa, which means that the combination of the two of them is opaque. In practice, the crystals are contained in a substrate that keeps them in particular locations, each of which can be electrified individually. They have tiny, nearly invisible wires running to each of those locations to provide the electricity."
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7lwbft | What is terminal velocity and how does it happen along the vertical axis but not the horizontal plane of motion? | Physics | explainlikeimfive | {
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"As you move through the atmosphere, the air causes a force known as drag. You can feel drag if you stick your hand out of the window as you're travelling in a car. Drag is related to the speed an object is moving through the air. The faster you move, the more drag you experience. If you are falling, accelerating faster and faster, the drag you experience also grows. Eventually, the force of drag matches the force trying to accelerate you (gravity in this case), and you experience no further increase in speed. This is known as terminal velocity. Terminal velocity can and does happen along horizontal planes as well as vertical. Ironically, it is experienced in planes. This is the reason jets travel so high. The get into the thinner air so the drag is less (and the terminal velocity is greater).",
"If you had a constant force acting horizontally and a consistent source of friction applied, would have a terminal velocity horizontally... but not really something commonly encountered.",
"**What is terminal velocity?** Terminal velocity is the highest velocity you can naturally achieve by falling. In this case \"terminal\" means \"last\" and not \"deadly\" like it sometimes does. As you fall, you have to push air molecules out of the way; if you fall faster, you have to push the molecules harder. Because of the third law of motion (equal and opposite reactions), that means those air molecules are pushing back on you too. The force of this push back is called Air Resistance. When the force of air resistance (which is slowing you down) equals the force of gravity pulling you down (which is speeding you up) you've reached your terminal (last) velocity because your air resistance was only increasing because your speed was increasing. **Why doesn't it happen along the horizontal plane?** The short answer is because there's no force of gravity in the horizontal plane. I said earlier that terminal velocity was the highest velocity you can *naturally* achieve. The reason I used the word \"naturally\" was because terminal velocity only considers when there are *only* two forces on the falling object: Gravity (pulling down) and Air Resistance (pushing up). You can go faster than terminal velocity if you added another force in the downward direction (like a rocket, or a spring-loaded launcher), it's not an absolute limit. Adding a new force doesn't completely get rid of terminal velocity though, it just moves it further down. Eventually the air resistance will catch up to the added force and your object will stop accelerating (although it'll be going faster than if you hadn't added the extra force to it). In this way you could come up with a different term (I'm sure there is one) that is essentially \"terminal velocity, but with more forces involved\" and you could apply this to the horizontal axis; but Terminal Velocity as it is only applies when there's just gravity and air resistance."
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7lwbs0 | how does a stove fan convert the heat rising from the stove that they sit on into electricity to drive the fan? A thermoelectric fan I believe it is called. | Physics | explainlikeimfive | {
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"if it's thermoelectric, then it uses a peltier device. which is a semiconductor that generates electricity when there is a difference in temperature between the two sides. the other type of stove fans are not thermoelectric but rather mechanical. they work by using a sterling engine which also capitalizes on the difference between two areas having different temperatures.",
"I don’t know about this kind of fan, however if it works with heat maybe it is a peltier device"
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7lwqnx | Why does the stream of water from a faucet get thinner as it gets lower? | Physics | explainlikeimfive | {
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"The rate of flow (liters per minute or whatever) depends on the width of the flow and its speed: a high-speed narrow stream can carry the same volume as a slow wide one. Gravity causes the speed to increase as the water falls, so it must get narrower in order to maintain the same flow rate everywhere along the stream.",
"Free falling water is accelerating due to gravity. The water is coming out of your faucet at a constant volumetric flow rate, so the cross-sectional area of the stream must reduce as the velocity increases."
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7lx4f0 | How do cough medicines work? | Biology | explainlikeimfive | {
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"Cough mixtures marketed for a chesty cough often contain expectorants and/or mucolytics. Expectorants such as guaifenesin are supposed to assist with loosening and coughing up mucus. Mucolytics such as bromhexine may thin the mucus in the airways and make it easier to cough up. Basically it thins out your congestion to make you cough it up and spit it out."
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7lx6us | Does the number of blades of an electric fan affect its "wind power"? | Physics | explainlikeimfive | {
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"Not necessarily. Once the air starts moving its inertia will maintain the pressure difference and the flow, at least until the next blade moves past. You need more blades if you want to maintain a higher pressure difference, because otherwise the air will start to push back before the next blade sweeps through. Pedestal and ceiling fans aren't going just fur velocity of air though, they want volume, which can be achieved by making them bigger. If you wasn't a faster breeze you can alternatively make the blades spin faster. Spin then fast enough and you don't need more blades because the ones you've got don't give the air enough time to push back before sweeping through again. You also get high air velocity with it. It friends on what you need. PC fans need high airflow and pressure to squeeze air through small areas, but they don't have a lot of power and need to be cheap so they use lots of blades. Pedestal fans are more about volume and being cheap, so they are larger and plastic but with slower speef to cut down on volume. Big outdoor fans may be designed for larger areas where sound isn't such an issue. Faster, stronger, smaller blades for a longer 'throw' will work.",
"The difference is only slight. Based on law of diminishing return, an input to increase output only slightly increases near steady state conditions. Say you have to wash the dishes, and you use a drop off soap. The soap takes off 40 percent of food off the plate. If there was a direct proportion, another drop should take 80 percent of the food off another plate but you notice only slightly difference. The next plate, you add another drop and again it's only slightly better. At one point you realize six drops off soap is the best results even if you added more. In contrast to this, if you had a 3 blade fan at a given rpm and you add one more blade, the mass increases requiring more power to maintain rpm and drops efficiency, but you notice a little more air. One more blade, and the mass goes up, power efficiency decreases, and flow only increases slightly. In HVAC, these differences can be seen by the fan affinity laws. While these types of fans are typically centrifugal, an increase in diameter increases number of fan blades (this depends). Not to get overly technical, to double your air volume, you have to double your diameter of the fan (increase of blades) but it also adds 4x the pressure and 8x the power required assuming constant rpm. I found this paper that shows experimental results (not mine). URL_1 URL_0 Edit: The engineer in me wants me to say that this assumes blades with the same geometric profile, with same experimental variables, and work constructed with quality",
"I dont see any other comments so maybe people are shadowbanned? Anyways the flow generated by the fan is a complex matter based on blade shape, material properties, motor properties, as well as RPM and ambient conditions. In the case you described the result is entirely dependent on the shape and material of the blades. Intuitively one would expect that having more mass (more blades) moving around at the same RPM would result in higher flow, however poor blade design could cause this to result in turbulence/interference that actually will lessen the flow! So it is very important to do testing in these situations. Thats why we have wind tunnels!"
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7lx9lb | Why aren’t dominant traits always more common than recessive traits? | Biology | explainlikeimfive | {
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"Dominant traits aren't preferentially passed along between generations, they just express more strongly if they are passed down. If a dominant gene is rare, it may continue to be rare unless there's some selective pressure killing off animals without it.",
"\"Dominant\" and \"recessive\" simply describe how two *alleles* interact with each other. A dominant allele may be *disadvantageous*- in which case it would slowly die out. It might simply be rarer- when most of the population has recessive alleles, the dominant allele doesn't increase in number as quickly. That's the simple description- let's look at it closely! ## Alleles The DNA of humans (like most animals) is paired up. We have two copies of each gene. Each copy doesn't have to be the same, too, and we can have two different versions of the same gene. Each version of a gene is called an *allele*. ## Dominance When an allele is *dominant*, the organism takes on that trait even if it has another *recessive* allele. For example, there are 3 alleles that determine your ABO blood group: A, B, and O. A and B are co-dominant, and O is recessive. So if you have one A allele and one O allele, your blood type would be A. A is dominant over O. Similarly, B is dominant over O, and having one B and one O allele would give you a B blood type. ## Frequency Nevertheless, the O blood type- two O alleles- is much more common in human populations. Why? In this case, having A/B/AB/O blood types doesn't really affect your life. You wouldn't expect someone with an AB blood type to be more successful in life than someone with O, for example. Thus over the generations, there isn't any pressure that makes people with O blood less successful. So if a population starts out with a lot of O blood people, chances are that two people meeting and having kids will both be O type- and all their kids will be O type. So it just happened that we started out with relatively lots of O type people, and the proportion stayed that way! The same goes for having many fingers on each hand. It's simply much more common to find 5-fingered people, even though having 6 fingers is a dominant trait. ## More reading URL_1 URL_0",
"Suppose a mom flower is red and if bred with other red flowers produces only red offspring. This is called 'true breeding' because no other colors pop out of these pairings. Suppose a dad flower is yellow and if bred with other yellow flowers produces only yellow offspring. Imagine an offspring flower that inherits one color gene variant from its true breeding red mom parent and one color gene variant from its true beeding yellow dad parent. A flower cannot be both pure red and pure yellow, so this situation has to resolve somehow. If the offspring turn out red, we say red is dominant to yellow. The offspring has a yellow gene variant, but it is not expressed because the dominant red variant overrides it. Now, to answer your question: Dominance has nothing to do with the frequency of the gene. Suppose there are 7 billion flowers on the earth, but only 10 of them have the red variant. Well those 10 will certainly be red, but it's not common. What happens in the next generation? The offspring of the red flowers will also be red. But if the red flowers bred with yellow partners (likely), they will also carry the yellow allele. When they have offspring of their own, there is a 50% chance that they will pass on the yellow gene variant rather than the red. Why wouldn't the red allele slowly increase in frequency and become fixed in the population? Well, what if yellow flowers prefer yellow mates to red mates? What if a predator (a bird, say) can see red flowers more easily than yellow? What if the red gene variant also causes failure to thrive? Or, what if there is nothing giving one a particular advantage over the other? In that case which becomes more common than it was in previous generations is more or less a matter of chance.",
"When you are working with a large population, it ends up working out that the dominant *allele* (copy of a gene) doesn't become more common unless it gives a survival/reproductive advantage. If you are already familiar with Punnet squares, Khan Academy has a whole group of videos to explain population genetics: URL_0",
"Yer not alone in askin', and kind strangers have chimed in: 1. [ELI5: if blue eyes are recessive then how did they manage to originally spread to so many people? ]( URL_1 ) ^(_39 comments_) 1. [ELI5:Why haven't dominant genes completely replaced recessive genes through evolution? ]( URL_0 ) ^(_19 comments_)",
"Certain phenotypes (appearances) may be less desirable to mates (e.g. dwarfism) even though it may be dominant. In addition, these traits could reduce the survivability of the individual. Overall, natural or mate selection does not favor the trait in the current environment.",
"Say for example that there's a dominant gene that causes offspring to miscarry with 109% mortality rate. The fact that it's dominant doesn't change the fact that it'll get bred out. The same principle applies for less extreme examples.",
"They aren't. Some recessive traits have advantages and therefore are more common. In nature this might even result in animals with the dominant trait dying off and then you never see that trait again. Some genes are simpler than others and it's just one thing or another. Other things require several genes to control, it's not a case of this or that.. but could be this, that, the other, or the other.. and so forth. A good example of this might be horse color. Chestnut is the most recessive color but very common, White (which is extremely rare) is the most dominant color of all.. grey is otherwise thought of as a dominant color (and I note grey and white are not the same).. but of course you can also have black, bay, buckskin, and a ton of other colors in horses. When you breed two things together if they both have recessive genes that is the only gene the offspring can get.. simple... with dominant genes the genotype of the parents is more complicated.. both parents might have 2 dominant genes. One might have 2 dominant genes and one might have 1 dominant gene and 1 recessive.. or both might have 1 dominant gene and one recessive.. ONLY in the last pair would the offspring have a chance of getting 2 recessive genes and therefore it would have the recessive trait. It's a 1 in 4 chance of that.. but of course it won't happen in the other scenarios."
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7lxc8j | Why are pianos and organs tuned differently? | Other | explainlikeimfive | {
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"They are tuned to the same sequence of tones/frequencies. Music written for one can be played on the other with little or no adjustment. The chords and keys and keyboards and the notes each relates to are identical from one to the other. That said, a piano uses strings that are activated by a little cloth hammer. It is a bit like a guitar on the inside, the difference is you use a keyboard to plunk each string instead of a pick or you finger. Organs push air through pipes, like a flute or a clarinet. Each pipe is [essentially] a whistle or a foghorn that plays one note. Some organs use electric speakers, but the principle is the same--a tone is transmitted directly to the air with no strings involved. There are (literally) no strings attached.",
"Organs are a bitch to change the tuning of: the process involves changing the length of every single one of those goddamn pipes. Tuning a piano involves turning a bunch of screws, which still sucks, but much less. Basically every other instrument is tuned a hell of a lot easier. That 400-year-old pipe organ also generally does a damn fine job of providing all the music one needs without needing *any other* instruments, thank you very much. If it should require some accompaniment, then that accompaniment can retune its own damn self (away from that new-fangled A440 pitch standard they only came up with in 1835) to the arbitrary standard of the barely-tunable musical instrument taking up half the room."
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7lxhvy | How cold does it get in a man-made vacuum chamber? | Physics | explainlikeimfive | {
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"That depends on the temperature needed. Vacuum isn't cold, in and of itself. The small amount of gas in a vacuum chamber can have whatever temperature you want and radiation can be used to warm up any other objects inside.",
"Vacuum doesn't have a temperature. Objects in a vacuum could be hot or cold. Overheating is even potentially an issue in something like circuitry because vacuum functions as an insulator."
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7lxosk | How exactly does Alka-Seltzer make someone feel better? | I see people taking Alka-Seltzer for many different ailments, including hangover. How does putting bubbly water in your stomach make you feel any better? I feel like it would make me want to throw up even more. The same with heartburn. What else is in Alka-Seltzer to make people feel better? | Biology | explainlikeimfive | {
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"1. It contains an alkalizer that neutralizes excess stomach acid. 2. It also contains aspirin that helps with aches.",
"It's just a combination of antacid and aspirin. Aspirin can reduce pain and fevers and antacid can help settle an upset stomach. Edit: The fizz is from sodium bicarbonate and citric acid combining with the water to make an antacid."
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7lxt7e | why a small movement in earth's rotation makes a large difference in temperature at different times of the day. | I am talking with a 'flat-earth' believer on another board. He asks why a small movement in earth's (supposed) rotation can increase the heat from the sun from morning / evening to mid-day. Forgive me if this has been asked before, I did search but did not have much success which is probably why my explanations of the above are not working. | Physics | explainlikeimfive | {
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"Point a flashlight at a wall. You know the flashlight is delivering 'x' energy to that circle. Tilt the flash light at an angle. Now the circle stretches out into a bigger oval right? But it's still just delivering x energy, so there's less energy per unit of 'area.' The sun hitting the earth impacts things the same way. A ~30 degree angle, iirc, effectively halves the amount of energy being delivered to a spot. But I agree with the others, if this guy has the capability to believe in flat earth, you may as well bang your head against a wall as talk to him.",
"Flat earth believers cannot be persuaded with reason. Don't waste your time. But the answer is partly that things take time to warm up once the Sun is on them, and partly that at noon the Sun is at a steeper angle, therefore filtering through less atmosphere before reaching the ground.",
"Problem number one: you're talking to a flat-earther. Just so you know, he's probably not even serious. I have yet to meet someone that's both sane, and earnestly believes that hypothesis. I hate those guys... my heart is beating a little faster in anxiety just thinking about them. I wish I could afford to round them all up, take them to the South Pole (past their stupid ice wall), just to make the point. The heat of the day is primarily due to how long it takes things to heat up. Just before daybreak is usually the coldest part of the day because it's had all night to cool. At noon, yes, the light is hitting more directly and the heat from it is most intense. It's *getting warmer* most quickly at this time, however, despite that, it's not the hottest part of the day. Rather, it's usually mid-afternoon, before sundown, that a given area sees its highest temperature, because it's been warming all day. If you want, check out an hourly weather forecast for a sunny day (try 85251, Scottsdale). 3-4pm is when it finally reaches its hottest.",
"URL_0 This is a photo of how the angle affects the distance-- it's a lot easier to see how the angle we are at relative to the sun could make the sun so bright during the afternoon and dark at night",
"Ask him , \"Why doesn't the sun fall down?\" And \"What causes the sun to rotate around the North Pole?\" Once he denounces gravity, you can go ahead and tell him he's full of shit, and you never want to talk about this shit again.",
"Tell him to light a candle. Then tell him to stick his hand near the candle. He will find that its is hot. Now tell him to put an object infront of said candle at the same distance he placed his hand. Then tell him to put his hand infront of the object. He should find that the candle doesn't feel as hot. This works just like the earth rotating. When in direct exposure to the sun it gets more energy therefore more heat. When its night the sun is blocked by the other side of the earth acting like the box in the above experiment. Also dont waste your time arguing with idiots. Your time is important and this person is not worth the effort. You cant fix ignorance sadly."
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7lxxrl | What happens inside of our body when we take medicine that is not necessarily needed? | Biology | explainlikeimfive | {
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"The medicine still does its thing: a decongestant will still constrict your blood vessels (to no noticeable effect), a pain reliever/anti-inflammatory will anti-inflame (to no noticeable effect), etc. Your body will work through it like it would if you were sick, except you won't notice most of the effects. If you're taking NyQuil just to get to sleep, get yourself some sleep medication (like generic Unisom). Those have either diphenhydramine (Benadryl), or doxylamine (the stuff in NyQuil) alone, which sounds like what you really want to be taking. Also consider something else, because long-term that's no good. Go to sleep later when you're naturally tired, do something non-electronic that makes you sleepy (books really do it for me), etc.",
"First, medication does not \"go where it is needed\", rather it goes everywhere in the body and does what it does in all those places. Some areas of the body might be more sensitive to a particular drug but the drug is present all over. So when you take a drug when not needed the drugs just do what they always do, regardless of if that is helpful. Taking Nyquil as a sleep aid is a pretty bad idea because of all the other drugs in it which cause undesirable side effects and strain on your body. Instead just take a sleep aid drug directly if you must.",
"> What exactly happens in our bodies since that medicine is mostly to help battle cold/flu? specifically, it's to battle the *symptoms* of a cold. It does the exact same things in your body whether you have a cold or not, like suppressing histamine receptors. However, since you don't have the symptoms to fight, you won't notice relief from them.",
"Thank you everyone for the response. To clarify, I am aware that there are actual sleep aids out there as Zzzquil and Unisom. I am only actually taking the Nyquil every once in a while because it is just available. Not as often as the post makes it seem. I just actually wondered since it was specifically for cold/flu if it affected me. Thanks again!",
"Just get some melatonin from any pharmacy, that's what your body already naturally makes to make you fall asleep",
"I highly recommend doxylamine if you're not sick and just looking for sleep (it does tend to be more expensive though). I don't know if its just me, but that stuff always does a much better job not giving me a tired feeling the next day like benadryl but works just as good getting me to sleep",
"It's important to note that those medicines do not attack bacteria/viruses. NyQuil is a combination a few medicines, (acetaminophen [a pain reliever], [sometimes] phenylephrine, an antihistamine [can reduce effects of allergies], and dextromethorphan [may mitigate coughs]). Each has its own effects, such binding to a receptor and causing or stoping the receptor from activating. Those actions are largely independent of actually being sick, and the antihistamine has a general side effect of inducing drowsiness (and is sometimes used by itself for that purpose)."
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7lxyuo | Is "heat" basically just lower-frequency light? | Physics | explainlikeimfive | {
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"There's two things to consider here that get a bit confused by the terminology people use. There is 'temperature', which as you would expect just means how hot something is. This is not the same as light, it is basically a measure of how much (on average) kinetic energy each molecule has. Then there is 'heat' or 'heat transfer' which refers to thermal energy moving from one place to another. There are 3 ways heat transfer occurs, conduction, convection, and radiation. The third one, radiation, is what you are thinking of, and refers to heat transfer via electromagnetic radiation. A hot body will actually emit radiation at a wide range of frequencies, but there will be a peak in the distribution ( URL_0 ) and that is the frequency where most of the heat is being radiated. For example when metal gets red-hot that is because the visible range of frequencies dominates at that temperature.",
"Radiative heat, yes. For example, if you step out of the shadow into the sunlight and you immediately feel the warmth of the Sun, that's caused by radiative heat transfer in the form of light from the Sun. It's not *just* lower-frequency light, but the overwhelming majority of it here on Earth is. Conductive and convective heat, however, is not \"light\" per se.",
"The basic principle is that every body that has a temperature above 0K will emit electromagnetic radiation. This radiation is emitted at a whole spectrum of wavelengths. Some guy named Wilhelm Wien made [this awesome graph]( URL_1 ) that shows the intensity distribution for different temperatures. **Most heat at lower temperatures is indeed radiated through frequencies below those of visible light.** If you look at the graph for 5500K however, it almost perfectly aligns with the 390-700nm range for visible light. Coincidence? Of course not! [The sun's surface temperature is around 5778K!]( URL_0 ) Life evolved to percieve the frequencies that are present in our environment, which is super cool IMO. Of course, we have invented/discovered other sources of that same visible light, but that's why the visible light spectrum is what it is: it's determined by the sun's temperature. **So yes, heat radiation is just low-frequency light, because visible light is actually just heat radiation from the sun.** (Btw, radiation isn't the only way heat is transfered: conduction or convection are the other options)"
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7ly6nr | Why don’t the rich seem to pay their taxes? | Economics | explainlikeimfive | {
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"What are you referring to? Rich people pay very large amounts of taxes. Is there some story you could link us to that explains your question?"
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7ly70p | What exactly is Santa Tracker, “tracking”? | Other | explainlikeimfive | {
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"The NORAD radar system is very advanced and can track Santa’s sleigh with ease. When he comes over the pole, the Air Force will scramble jets to escort him through our airspace.",
"Santa. It's tracking Santa. You can see the reindeer and the magic behind his sleigh as the flies around the world giving presents to good little girls and boys. He's is over Freetown right now which means he will be here soon so so if you expect to see any presents tomorrow morning you need to go to bed. It is past your bedtime and Santa knows when you're awake. Go to bed."
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7lybc5 | what is glaucoma | Biology | explainlikeimfive | {
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"Your eye has two chamber which are separated by the iris. That's the colorful part of your eye. The chambers are filled with fluid that's continuously produced and reabsorbed at the same rate. The chambers are connected by the pupil, that's the black hole in the middle of your eye. The fluid in the chambers is produced on the backside of the iris, you can't see this part. It then flows through the iris to the chamber in from of the iris and is absorbed all along the outside edge of the iris. Glaucoma is a disease you get when the pressure in the chambers is too high. This can be due to to much production or, more commonly, because the fluid can't leave the chamber because the small channels for resorption are blocked. This high pressure then leads to damage to optic nerve, which is at the back of the eye. You can image it as pressing your eyeballs into your skull with your fingers, obviously this is not good for the eye. That's why it hurts to do so. Over time this damage to the optic nerve can destroy it completely and lead to blindness. Glaucoma is treated by reducing the amount of fluid that's produced with drugs or by allowing more of the fluid to be absorbed by clearing the blockage. This can be done by making the iris contract, thereby making the pupil smaller but also moving the tissue of the iris from the outside edge towards the inside, thereby clearing the blockage of the absorbing tissue on the outside edge of the iris. Surgery is also available which can open up the blockage mechanically with a knife or a small tube to allow the fluid to drain. I hope this helps you and I'd be happy to answer any further questions!"
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7lycb6 | How does an electricity company know how much electricity you use? | Other | explainlikeimfive | {
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"The meter measures both voltage and current going into your building/home/whatever to calculate the amount of electricity you're using. Voltage remains the same, but the current flowing in does change when something is drawing electricity from the circuit. > ...and the amperage depends on the appliance (it doesn't change in the house circuit but in the appliance itself) Ah, but it does: your house circuit is only pulling the current it's using, it's not constantly doing this. When you switch on a bulb, the amount of current you're drawing from the mains increases.",
"It measures the current and the voltage and determines the power usage from that You can measure current by putting a tiny resistor in the path and measuring the voltage across the resistor or by looping wire around the current carrying wire and inducing current in the loop. Once you've got the current and voltage you multiply them together and increment the watt-hour meter at the right rate Good power meters also measure the voltage. Voltage should be constant but can drift or just be a bit off. 120V countries could have 110-130V at the outlet so assuming 120V can result in inaccurate power measurements"
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7lycvg | What is the strategy behind football players always running straight into the pack of opposing players, gaining just 2-3 feet? | Other | explainlikeimfive | {
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"Football is very much the game of inches. Rushing the ball is slow and takes a lot out of your players, but its consistent. You are going to gain yardage, and as long as you can get first down its progress. Throwing the ball is risky if its an incomplete pass there is no progress, and if your QB gets sacked you lose yardage. This isnt even considering the possibility of getting intercepted, which is an instant turn over.",
"It's the oldest and safest play in football, and sometimes you only need two feet. No fancy shifts in the blocking. No dangerous laterals, screens, or pitches. No running backwards. No throwing the ball up for grabs. Just two thousand pounds of power. There are other \"up the middle\" run plays that do involve more complicated blocking schemes to try and open up a gap, but when it's 4th and a foot the power run is the best call. Those plays also keep the defense honest. If they're not concerned about the possibility of a power charge they can swap out some of the heavy run blocking D-linemen with smaller, more nimble linebackers and defensive backs to better cover the pass and the outside runs."
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7lyddw | If Cosmic Microwave Background Radiation (CMBR) is the first light from the Big Bang , how can we see it if it travels in a straight line? Surely it would be at the edge of the universe, unless reflected? | Physics | explainlikeimfive | {
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"The big bang occupied all of space. Not a particular location. As such, there is always some light that was at the proper distance from us to be getting here \"now,\" whenever now is."
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7lysoc | why does only empty space expand during cosmic inflationary expansion? Why are occupying objects unaffected from expansion ? | I remember reading a comment on this Subreddit where someone wrote that expansion should not be visualized as the boundary of the universe expanding but as the fundamental physical spacetime fabric itself expanding. When I rescale a picture or blow up a balloon, everything on the surface gets larger. So why is only empty space and distances being enlarged, why not physical objects too? | Physics | explainlikeimfive | {
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"Because there are forces that pull in the opposite direction such as gravity, Nuclear Strongforce and electromagnetism. You actually need to get pretty far away before the expansion of the universe is significant enough to not be counter acted by some force. Even Galaxies that are close together like the Milky Way and other galaxies in the Virgo Super cluster are close enough to resist the expansion of the universe.",
"The expansion of space freaks us out because we hear that things are moving away from each other faster than the speed of light. And that's true, but it's only true if they're 4.5 gigaparsecs away from each other (the [Hubble radius]( URL_1 )). That's a long distance. The \"occupying objects\" you're talking about aren't 4.5 gigaparsecs in diameter. I'm 5'9. If it takes 4.5 gigaparsecs to be expanding by a speed of light, how much am I expanding? Speed of light/4.5 gigaparsec * 69 inches = 3.78390698 × 10-18 m / s 3.78 millionths of a millionth of a millionth of a meter per second. That's not going to pull me apart any time soon. I may stretch like a spring, but I'll also collapse like a stretched spring, less violently, but as a function of the same forces. The speeds people talk about in the metric expansion of space are only impressive when you consider the metric expansion of the entire Universe and not little pieces of it. Though being that the expansion of the universe is accelerating, it may eventually accelerate to the point that even the little pieces of the universe accelerate away from each other fast enough to cause a [Big Rip]( URL_0 )."
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7lytmb | How can alcohol withdrawal or detox kill you? | Edit: I’m not an alcoholic, I just couldn’t find concrete answers anywhere. 😊 | Biology | explainlikeimfive | {
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"Alcohol activates a receptor in the brain to tell it to be sleepy and drunk. In long term use, the brain doesn’t want to be sleepy and drunk all the time, so it does three things to maintain a normal awake/alert state: 1. Gets rid of some of the receptors that alcohol acts on 2. Gets rid of some of the normal brain chemical that says “be sleepy/sedate” at normal times. 3. Increases the normal brain chemical that says “be awake and alert and active” When you stop drinking, you now have fewer receptors for chemicals saying “be sleepy” and also less chemicals saying “be sleepy” and also more chemicals saying “be alert and active.” The result? Seizures. Lots and lots of seizures. Which are basically just too much brain activity. Which use up the sugar and energy in the brain and produce poisonous waste products in amounts too high for the body to get rid of it.",
"The way a body works is to try to maintain what's called \"homeostasis\", which means that all the chemicals in your body are being replaced at the rate they're being removed. Now, alcohol (and other drugs) either mimics chemicals in your body, break down into chemicals that mimic chemicals in your body, or do a job that a different chemical in your body would do. Because of this, your body stops producing those chemicals (in order to maintain the right levels of them) when you have the drug in your system. However, it takes some time when you STOP putting the drug in your system for your body to realise this and start making those chemicals again. This is why withdrawal commonly feels exactly the opposite of how the drug feels: when you're on a drug, you have extra chemical making a good feeling happen, but when you \"come off\" the drug, you have less of that chemical, so you go in the opposite direction. And, if the delay is too long (and the chemical in question is super important), you can run out completely and die.",
"When you go into withdrawal of a drug, then you typically get symptoms opposite of what the drug does to you. For example, lots of opiods cause constipation, so one symptom of opiod withdrawal is explosive diarrhea. As far as I know, alcohol is for unknown reasons anti-epileptic. So when individuals are experiencing extreme alcohol withdrawal, then they can sometimes go into seizures and die.",
"I have gone through severe alcohol withdrawal. It starts with jerking awake despite not being able to sleep. A weird pit feeling in your core, and the anxiety is... indescribable. Then pretty soon you think you hear your neighbors talking, or your roommates are home, or you respond verbally to questions that were never asked.. auditory hallucinations were huge. Starving but you can't eat, water hurts your stomach, then you seize up, this happens forever until you can get some pho. Solid food seems to feel like a baseball in the gut. I landed in the ER probably 5 times. Librium supposedly helps but I didn't notice. You have suicidal thoughts. Get professional help if you're getting off the sauce.",
"There is a great sub here on reddit that is called r/stopdrinking if you are experiencing alcoholism, or just want some moral support and not feel the anguish of \"being alone\". They are really supportive, I lurk there alot"
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7lytnb | Why aren't the lenses in glasses made as thin as possible from the outset? | Physics | explainlikeimfive | {
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"Many of the materials with a higher index of refraction are very expensive, or may only be supplied by one supplier, driving up costs. It's fairly safe to assume that many people could not justify spending a lot more for those materials, and will accept a thicker lens that costs a lot less. In addition, some high index materials may result in a more fragile lens, or have notably worse issues with chromatic abberation, which are not desired by some.",
"They're usually ground and polished from a flat blank: casting doesn't give a precise enough shape. The different thicknesses require using different kinds of plastic: the higher the \"index of refraction\" of the material, the less deeply curved the lens has to be, so it doesn't have to be made as thick. That said, if your optometrist is asking several hundred dollars more for high-index lenses, you might consider an online eyeglasses site. I don't want to promote specific companies on ELI5, but the pair I'm wearing now (nearsightedness plus astigmatism, high-index, antireflective coating) work beautifully and cost me $43."
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7lyxn6 | What is the difference between bleached & unbleach flour | How should I choose one over the other | Chemistry | explainlikeimfive | {
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"From The Kitchn: “Technically, all flours are bleached, but it's the process by which it happens that sets these two types of flour apart. Bleached flour is treated with chemical agents to speed up aging, while unbleached flour is bleached naturally as it ages.” Whew, that was a tough google."
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7lz4d1 | Why would a company want to go Public? Why would you want to answer to shareholders instead of customers? | Economics | explainlikeimfive | {
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"There's an old joke that helps explain it. Old enough that the numbers are probably completely wrong, but this is the way I learned it: * Up to $1,000,000 a year in sales, a company is run by its founder(s). * From there up to $5,000,000 a year in sales, a company is run by its banker. * After that, a company is run by its lawyers. And the reason behind the joke is that the larger a business gets, the bigger the loans they want to take out, and the bigger the loan, the harder it is to borrow. A small business borrows money the way you would to buy a car or a house: the founder takes out one or more personal loans. He maxes out his credit cards, he takes out another mortgage on his house, he borrows money from every friend and family member. But there's a limit to how big you can get off of that kind of informal lending. Sooner or later, you need to issue commercial bonds. Which you, as a non-banker, can't do. So you partner up with a commercial bank, and they underwrite your bonds. But first, they tell you what you have to do to your business to make it eligible to issue bonds, to make ratings firms willing to give you a decent rating. If your business keeps getting more and more successful, there will come a time where no bank is big enough to underwrite the kind of commercial bonds you'd want to issue. You need to borrow more money than that. And there's only one way to do that: sell off part ownership in your company. But the legal requirements that are put on publicly owned companies are complex enough that, at that size, you have your own in-house legal department, or a are paying a huge retainer to a law firm. And from then on, you run every serious decision past them, so that they can tell you whether or not it would get you in trouble with stock market regulators.",
"Going public brings in *a lot of fucking money*. For example, the Facebook IPO brought in about **90 billion dollars**. This lets founders & early investors get some of their money back and freely trade shares of the company. This gives the company the capital to expand and grow.",
"It’s a good way to get a serious money infusion. You sell off part of the ownership in your company in exchange for cash."
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7lz7pg | Why does alcohol cause a burning sensation? | Biology | explainlikeimfive | {
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"We have reseptors (named VR1) that respond to heat. Think of these as small thermometers. These small thermometers gets more sensitive when they get in contact with alcohol, witch means they think they are at a higher temperature then they really are! This \"hot\" signal is sent to the brain, and precieved as a burning sensation."
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7lz8g1 | How do places like call centers have outgoing calls with the same identity (one phone #), but at home if someone is using the line we can't make calls? | Technology | explainlikeimfive | {
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"It’s just a simple trick performed by call center software. The outgoing phones are all assigned a single identity that masks the actual number to display on the recipient’s caller ID. This is similar to how companies can use one mass email system to send millions of emails with specific or variable from names and from addresses, even though they are coming from the same IP address. Source: mass communications tech for a large organization"
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7lzbhf | What's the difference between sympathy and empathy? | Other | explainlikeimfive | {
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"the differences between the most commonly used meanings of these two terms: sympathy is feeling compassion, sorrow, or pity for the hardships that another person encounters, while empathy is putting yourself in the shoes of another.",
"I have sympathy for my wife when she suffers a menstrual contraction. I have empathy for some poor kid who annihilates his testicles landing a bad railie.",
"Sympathy: \"Wow, that sucks. Glad it never happened to me.\" Empathy: \"Wow, that sucks. It also happened to me.\"",
"This [video]( URL_0 ) walks through the differences really well. Since I first saw it, I try to keep it in mind and strive to be empathetic instead of sympathetic.",
"Sympathy is feeling an emotional bond with another person so you understand how they feel and share their feelings in’s detached way. Empathy is feeling their feelings in more-or-less the same way. So like a doctor friend of mine was taught in med school to have sympathy, not empathy, for patients. An example is if a patient is distraught by some negative medical news you’ve delivered. A sympathetic doctor will understand why they’re distraught and be concerned about helping them. An empathetic doctor will be distraught,too, so much so that he/she can’t be a comfort to the patient. They’ll nerd comforting themselves."
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7lzbi6 | How do whistles work? How does air going through a tube create such a sharp tone? | I know there’s a weird hole in it, but I don’t understand what about the air particles going through makes vibrations that hit our ears. Thank you in advance! | Physics | explainlikeimfive | {
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"Air moving over openings creates vibrations that can be audible. Think of a really windy day and your windows make a low humming sound during the big gusts. Or maybe you have a chimney that does the same thing. Faster air + smaller openings increases the frequency of the vibrations, and in turn, the pitch of the sound."
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7lzdn8 | If the atmosphere is 78% nitrogen why did life develop to use carbon dioxide and oxygen rather than nitrogen? | Biology | explainlikeimfive | {
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"Nitrogen is pretty inert when it comes to chemical reactions. It will naturally form a triple bond with itself and its pretty hard to get it out of that state. Even if you have a lot of nitrogen in the air it pretty much just binds to itself and refuses to react with anything.",
"That is how our atmosphere is today, as life developed it was quite different. When life first developed there was a LOT of CO2 in the atmosphere and nearly no oxygen. Life back then didn't even use oxygen, at least not how we do today. In fact, the first organisms to photosynthesis are believed to have caused a mass extinction due to how drastically they changed the atmosphere as atmospheric oxygen was toxic to many organisms at the time. If anything, the Atmosphere today owes much of it's current status to life rather than the other way around. Edit: Wanted to say thanks to everyone who went into greater detail and gave a name to the great oxygenation event, especially those who posted sources. Secondly, to the few who mentioned it, the properties of Nitrogen also play a big part in this but when I originally commented there were already answers addressing it so I answered it from a biological stand point. I acknowledge that the chemistry angle of this is also very much right.",
"Nitrogen gas (N2) has a covalent triple bound. This is really really really ridiculously strong and makes doing any chemistry with nitrogen gas really hard (in fact when chemists need to do stuff in a non-reactive atmospheres they frequently use nitrogen). Splitting that triple bound is so hard that basically the only things that split nitrogen gas on the entire planet naturally are lightning and nitrogen fixing bacteria (such as those that hangout in the roots of legumes and make them great sources of protein). Getting that N2 triple bond to break and converted to a bioavailable form requires really really complicated enzymatic chemistry that is difficult to evolve and does not work efficiently in the presence of oxygen. Basically things that can split N2 can’t survive well in an aerobic atmosphere which is a pretty major limitation (the bacteria do survive nicely in the root nodules of legumes that evolved a nice system of incorporating these bacteria in a largely oxygen free environment). Bioavailable nitrogen (NH3/NH4+, NO2 and NO3) is one of the most significant factors limiting the primary productivity of an ecosystem. You need nitrogen to make protein and every living thing needs protein to build enzymes and structures. Things like legumes that can fix nitrogen from the air have massive advantages over other organisms in nitrogen limited environments and introducing nitrogen fixing plants to places that didn’t have them to begin with has wrecked ecosystems across he world. The Haber-Bosch process and the development of nitrogen fertilizer basically allowed the world to get this many people because without nitrogen fertilizer our agriculture yields wouldn’t be able sustain 7 billion people. Oxygen on the other hand is super easy to do chemistry with, in fact it’s a little too easy and oxygen sometimes reacts a little to indiscriminately (see rust). CO2 is harder to use than oxygen but still easier than nitrogen. Photosynthesis does some very complicated chemistry to convert CO2 into useable carbon and O2 but even photosynthesis sometimes gets messed up by oxygen’s tendency to react with everything. Sometimes the main enzyme in photosynthesis accidentally grabs an O2 instead of a CO2 which sucks for the plant as this doesn’t net any energy. Some plants evolved a cool new type of photosynthesis that solves this problem by only doing photosynthesis deep inside the leaf with little oxygen around to make it more efficient (that second type of photosynthesis is basically way more efficient in every single way we’ve tested yet most plants still do the first type for some reason which is a major mystery in plant biology). TL;DR: nitrogen gas is very inert and the chemistry to make it bioavailable is really really hard and the only chemistry life has evolved to make nitrogen bioavailable doesn’t play nice with oxygen which is a problem in atmosphere that contains a lot of oxygen. Oxygen is super reactive and easy to use to do lots of chemistry (it’s a little too easy and actually causes a lot of problems). CO2 is somewhere in the middle (much closer to the N2 side of things) but photosynthesis is pretty neat and works well. TL;DR(TL;DR): It all comes down to thermodynamics in the end. Edit: random spelling and grammar things",
"Oxygen is a really great chemical for causing chemical reactions. Carbohydrates (what food is made out of) have a lot of energy in their bonds, and can be used to power things (like your car). Carbon Dioxide, on the other hand, is an incredibly boring, stable, and low energy molecule. Your body uses oxygen to force a reaction which turns carbohydrates into boring carbon dioxide. The difference in energy is something you get to keep, and you use it to power your body. This process is called *cellular respiration*, and it's the same reaction as setting fire to a pile of logs, it just happens at lower temperature inside your mitochondria. The reason oxygen is so great is because it has one of the highest electronegativities of all the elements (it's close to the top right on the periodic table). This means it is powerful at coming into a party alone and stealing all of your girlfriends (You're hydrogen, and your girl is carbon: there's probably a better metaphor). It produces a lot of energy this way, and your girlfriends like him so much that they're never coming back. Fluorine might be even better than oxygen, but there isn't a lot of that floating around in our atmosphere, so we haven't evolved to breathe fluorine (there may also be more practical reasons why we don't breathe fluorine). This is also part of the reason CO2 buildup in the atmosphere is a problem. It takes incredible amounts of energy to get our girlfriends back from oxygen, the Chad of the periodic table. Edit: I forgot to answer part of your question. Nitrogen is the emo guy standing in the corner. Noone is leaving with him. Edit II: Carbohydrates, not hydrocarbons.",
"Chemistry. Oxygen is what allows animals to function because it reacts with everything. It is essentially a highly volatile poison that we have adapted the use. Nitrogen is inert which means it can’t be easily used for energy to make animals move.",
"It’s sort of like saying “There is vastly more water on earth than gasoline. Why is it that we’ve developed cars that run on gasoline and not water?” Water has little potential energy that’s usable for chemical reactions compared with gasoline. The same is true for nitrogen relative to oxygen.",
"I'll start with oxygen and finish with CO2. Organisms obtain useful energy through chemical reactions that move electrons from high energy states to lower energy ones. Oxygen is abundant and a really great electron acceptor so transferring electrons from, say, a sugar molecule to oxygen atoms is easy and has a high energetic payoff. The most well known process to do this is called [aerobic respiration]( URL_1 ) and in this system the oxygen atoms used as electron acceptors are converted to CO2 and H2O. Organisms able to use this oxygen-dependent process generally outcompete organisms using less ideal electron acceptors and as a result they spread over evolutionary time and came to dominate earth. CO2 is trapped (fixed) by photosynthesis in essentially the reserve process and this requires an energy input. Free electrons removed from water molecules by the sun's energy are bound up along with the carbon atoms from CO2 to produce large carbon-based molecules like sugar. This represents an energy store that the plant can later degrade (through aerobic respiration) to free up energy in a useful place and time. There are a few living organisms that do use nitrogenous molecules, and various other atoms, in processes equivalent to those I mentioned above. They're only \"better\" in very specific circumstances so that's why they're fairly rare. For example, there are bacteria that use [iron atoms instead of oxygen]( URL_0 ) and others that use [sulfur]( URL_2 ).",
"Lot's of good answers, I'll add that carbon is the stuff of life because it's a universal middleman. It's a perfect scaffold for complex molecules, nothing else on the periodic table works that way. The next best thing would be silicon, which doesn't work.",
"Carbon lends itself to far more varied compounds than nitrogen. Carbon is tetravalent, whereas nitrogen is generally trivalent. That means carbon likes to have four bonds per atom and nitrogen likes three (usually - nitrogen can also be pentavalent). As such, carbon is the basis for all life that we know of. Its tetravalent nature makes it perfect to form large and stable molecules. Molecules that just don't form with other elements.",
"As an interesting aside: Nitrogen atoms like each other. They *really* like each other, and want to form pairs, and stay together forever and ever. Keeping them separate by forcing them into other structures often *does not end well* because they will just break any bond, crush any structure, and not give a flying fuck about how much mayhem they create in the process, just to get back together, quickly and with great release of happiness and energy. And that is why *a lot* of explosives are basically rickety molecular scaffolding with the purpose of keeping a few nitrogen atoms just far enough to stay separate while they're in storage, but close enough to react as soon as a spark or a bit of heat gives them a slight push. This is why we got *nitro*glycerin, and tri-*nitro*-toluene (TNT). And why for example detecting nitrogen via portable spectroscopes is a possible strategy for identifying explosives in airport security.",
"Oxygen is like harnessing an elephant: It's a bit risky since it might rampage through your village but if tamed it's an incredibly powerful tool since it has so much energy and utility. Nitrogen is like a sloth, it's not dangerous but it also has very few practical uses since it has very little energy potential.",
"During the Carboniferous period (~300 million years ago) the atmosphere was so oxygen rich that insects got bigger to decrease the risks of oxygen toxicity. That was around 30% atmospheric oxygen levels.",
"From a medical POV nitrogen is necessary for breathing. It helps the body produce a product called surfactant which essentially keeps your alveoli (lung sac thingys) from collapsing. Nitrogen washout is no bueno.",
"actually the first organisms on earth didn't use oxygen and in fact, oxygen was toxic to them. then along came some bacteria which produced oxygen as a by product, raising atmospheric oxygen content to the point that it killed all the other bacteria , eliminating the competition. after this all life required oxygen.",
"Actually, nitrogen is vital to life on earth, just look up the term “nitrogen cycle.” Here’s a random quote: “Nitrogen is so vital because it is a major component of chlorophyll, the compound by which plants use sunlight energy to produce sugars from water and carbon dioxide (i.e., photosynthesis). It is also a major component of amino acids, the building blocks of proteins.” URL_0",
"Nitrogen isn't used when burning things, essentially. Sugar is the fuel source of all living things. Everything that we eat that gets used for energy has to be broken down into sugar so our cells can use it. Plants use photosynthesis to create sugar so they can burn it later. Sugar is a hydrocarbon, much like gasoline or kerosene, and when it's burned it requires oxygen and produces CO2 and H2O. To create sugar from photosynthesis, you need CO2 and H2O. Nitrogen isn't used in combustion, and therefore doesn't work as a fundamental energy storage mechanism.",
"Carbon is \"convenient\" because of the way it bonds to chemicals that allow for complex things like DNA. Oxygen makes water that dissolves at lot of chemicals and allows reactions for life as we know it. Just as silicon has issues in oxygen (a science fiction story had a silicon \"lifeform\" exhale silicon dioxide). As other have said - nitrogen is pretty stable. What nitrogen you need is already bonded to something else. There are some ideas of what a creature that lives on ammonia would be like but it would be so alien that it couldn't live in our atmosphere (pressure and chemistry would kill it)."
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7lzr12 | if you do use a single can of paint to coat a room, is it the equivalent of shrinking the volume of the room by the size of the inside of the can? | Physics | explainlikeimfive | {
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"Yes, maybe depending on how the paint reacts. It may be more if it swells while drying or less if there is something that will evaporate out like water leaving it less than the original volume. Assuming that the act of drying doesn't make the paint thicker/thinner it would be as you say."
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7lzs8r | Why do officers in world war 2 use only a pistol while the soldiers get to use rifles and machine guns. | Other | explainlikeimfive | {
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"text": [
"Rifles are for engaging targets (shooting people and stuff) at a significant distance. That's not the main job of an officer -- their job involves strategy, tactics, and command and control.",
"If an officer is actively engaged in a firefight, many people have already failed. An officer's job is to make command decisions about where the unit under them goes. They're not even the ones that (generally speaking) directly control the soldiers actively fighting - that's what higher ranking *enlisted* soldiers are for. An officer should be a fair distance away from the direct fighting where they have the safety and security to make informed decisions about what to do next. A high-ranking enlisted soldier is there to say, \"You four soldiers go around this building to flank the enemy while I take these eight soldiers and hold this line to distract them,\" while bullets are flying around them. An officer is there to say, \"There is an enemy infantry unit advancing our direction that will arrive in three days. We have to protect our supply lines, so send a unit here and here, and keep these units here to protect our front line.\" While it's important for an officer to be battle-hardened enough to make command decisions even under the stress of fighting and shooting, it's also in the military's best interest to keep them as safe as possible so they can worry more about their decisions than not getting shot. It's also important to protect them since they will have more information about what's going on and what should going on, so if they die the unit might not have clear direction on what to do next. To that end, officers don't need rifles. Rifles are heavy and cumbersome, so it would just get in the way when the officer is going about doing their duties. Officers are also going to have guard details with them or very nearby in case of an emergency, and those soldiers will absolutely have rifles. All of that said, officers do still spend time near, and often *on* the front lines directly involved in fighting. Leaving them defenseless would be dumb. So they carry pistols for their own personal protection in case they do need to do some fighting."
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7lzv4t | Why does sticking one leg out from under the blankets mske your whole body feel cooler? | Biology | explainlikeimfive | {
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"The blood in your body carries much of the heat from the core of your body out to your extremities, when you stick a foot out it cools also cooling the blood in your foot. That blood then travels back through your core to get warmed up again then back through your foot to \"release\" that heat.",
"Yer not alone in askin', and kind strangers have explained: 1. [ELI5: Why does sticking one leg out from under the covers transport me from Mustafar to Hoth? ]( URL_4 ) ^(_15 comments_) 1. [ELI5 Why is it that both legs under the covers is too hot, both legs out too cold, but one in one out is prefect? ]( URL_0 ) ^(_4 comments_) 1. [ELI5: Why does sticking one foot out from under the blankets prevent me from getting too hot? ]( URL_5 ) ^(_14 comments_) 1. [ELI5: why does uncovering blankets from your feet cool you off so quickly? ]( URL_3 ) ^(_2 comments_) 1. [ELI5: How is it that I can keep a leg out from under the covers and my body temperature evens out, but if I'm sitting on the couch with a blanket on my lap, the top part of me is cold? ]( URL_1 ) ^(_1 comment_) 1. [ELI5:ELI5: Blanket on, feels too hot. Blanket off, feels too cold. One leg out, feels perfect. Why is it so? ]( URL_2 ) ^(_4 comments_)"
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"https://www.reddit.com/r/explainlikeimfive/comments/2awkl8/eli5_why_is_it_that_both_legs_under_the_covers_is/",
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"https://www.reddit.com/r/explainlikeimfive/comments/4dphy5/eli5eli5_blanket_on_feels_too_hot_blanket_off/",
"https://www.reddit.com/r/explainlikeimfive/comments/6plcgh/eli5_why_does_uncovering_blankets_from_your_feet/",
"https://www.reddit.com/r/explainlikeimfive/comments/2n9txp/eli5_why_does_sticking_one_leg_out_from_under_the/",
"https://www.reddit.com/r/explainlikeimfive/comments/ke7i5/eli5_why_does_sticking_one_foot_out_from_under/"
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7m0cwe | Why do people immediately gag/throw up when they touch their uvula with their finger, yet not as much when the uvula touches the back of your tongue? | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"The purpose of the gag reflex is to stop you choking on foreign objects in your mouth. Obviously your tongue is not a foreign object so it would be a pretty crappy mechanism if it was unable to distinguish between your own tongue and a foreign object."
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7m0edd | Why are schools strict on females showing shoulders and exposing skin? | Other | explainlikeimfive | {
"a_id": [
"drqfoy2",
"drqg4an"
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"text": [
"Because they seem to believe the archaic and stupid notion that all teenage boys are slavering hormonal beasts and the mere sight of even the tiniest bit of skin will put them into a lust filled rage and they won't be able to learn. You know, since the only education that matters is the male's.",
"Because a teenaged girl can always come to school naked enough that anyone would understandably complain, and while that is an edge case, the rulebooks need a threshold to forbid, and this threshold has to be arbitrary."
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7m0lu0 | Why do companies expect people to give 2 weeks notice before quitting but won't give 2 weeks notice before firing or laying people off? | Other | explainlikeimfive | {
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"Because Americans don't, generally, believe unions are a good thing. In countries with strong unions, the company is required to give the same notice as the employee.",
"Many companies do give you warning before laying you off, but it depends on corporate culture. If you're fired, it's generally because you did something bad, and in that case you didn't earn a warning. If you did something really bad like threaten someone, they want you gone immediately. You're not actually required to give a two weeks notice. Most of the US uses at will employment, which means either side can terminate employment for almost any reason. It's just nice to do so your employer can start hiring or training a replacement. It also makes it easier to get a good reference later.",
"In Australia, for fulltime and part time workers, they have to give the required notice and you work for that tome OR they have to pay you for that notice period if they don't want you to work it. Casuals are different, they fon't get any notice, nor do they have to give amy to leave.",
"I believe the firing part depends on the reason for the dismissal, also firing a person could leave someone wanting revenge and allowing said person to remain on the premises with access to stock, customers and/or sensitive data isn’t wise. Most companies expect you to give them notice and this is written into employment contracts, I would imagine it’s to give the company suitable time to find a replacement. As an aside I once worked for McDonalds and I quit and advised them I would not be working my notice, I was told I would forfeit my holiday pay. I doubted the validity of this claim and said I don’t mind as I quit right now. Once I got paid it was sans holiday pay, so I requested a copy of my signed contract and nowhere did it state I would lose my holiday pay. I proceeded to contact HR and they stated it was a system error. Strange that the system error appeared to coincide with what I was told. Moral always read your contract.",
"I think the concern is that people who have been told they are being fired don't make the best workers. Some companies actually escort people out when they give notice, for the same reason, but others don't, since many workers are motivated to want to leave on good terms."
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7m0zf5 | What is the leading theory / theories regarding creation of our solar system / universe / etc within the scientific community? | Other | explainlikeimfive | {
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"Thanks to a guy called u/BadAstronomer, AKA Phil Plait, for most of this information. I knew only the most rudimentary of things before, and used to even be scared of the concept of such a huge universe before I saw his videos. Scientists still have very little idea as to why the Big Bang happened. We do know that many black holes are in the centres of most galaxies, certainly the largest like the Milky Way and Andromeda. They, plus the mass of stars and gas near the centre provides something for the whole thing to orbit around. As for the solar system, that used to be a rather large cloud of gas and dust sitting around about 5 billion years ago. A supernovae happened nearby, which because of the insane pressure in large star cores, generates many of the heavier elements, and that supernovae also disrupted the balance in that cloud, and in the centre, it began to coalesce into a star. This took some time. It got hotter and hotter and denser and denser until it had enough pressure and to initiate hydrogen fusion in the core. That is the definition of a star. Stars have something called a steller (when we talk about our own Sun, we usually call it a solar) wind that blew away the remaining gas and dust nearby to the outer parts of the solar system. The other planets began to coalesce in similar ways, but got nothing even remotely close to enough to be even a brown dwarf, let alone a star. Jupiter's birth is a bit disputed, we don't know whether it ever had a core, and if so how it formed. The gas and dust was blown too far away for the four rocky planets to collect any kind of impressive atmospheres like even the Ice Giants of Neptune and Uranus have, but they did still have some. The Asteroid belt was constantly disrupted by Jupiter's massive gravity, and was probably in part swallowed up by it, leaving Mars relatively small, and unable to form any sort of planet that has no other objects of similar size within it's orbit, part of the definition of a planet. It actually seems like Jupiter moved inwards towards the Sun (a process that actually happens to many gas giants like Jupiter in exoplanet solar systems), but was stopped by Saturn's gravity from going too far. It was just trying to eat up as much as it could. Saturn, Uranus, and Neptune began to move further out from the Sun, towards their current positions, and that seemed to disrupt the Kuiper Belt and the comets around it. And that also began to send a lot of asteroids and comets into different orbits. I'll get to that later. Earth got it's start pretty early, but a few tens of millions of years after it's birth, a massive protoplanet named Thea slammed at it in a low angle collision, blowing apart Thea and taking a good part of the Earth with it, and the crust of the earth liquified into lava, that coalesced into the Moon, but that Moon was pretty near the Earth, so the Earth cooked the moon, making the far side of the moon's crust thicker. Remember the asteroids moving around from last paragraph? That slammed into the Moon (and Earth), which couldn't penetrate, only crater, the far side, but broke through the near side's thinner surface, bubbling up Lunar lava, which made the Maria we see today. Tidal forces moved the Moon away from the Earth and also tidally locked the Moon's faces. The Earth cooled down and also got a lot of water from comets, and it looks like some organic molecules too, and maybe although disputed, basic forms of life. Mercury was formed just as a basic coalescence of rocks, but it's orbital period isn't tidally locked to the Sun the same way. It's a 2:3 resonance, not like the Moon. And it's been that way since. Venus once was much cooler, its clouds much less of a problem, and had oceans of liquid water and maybe life. But the Sun began to heat up, due to the hydrogen fusing into helium which increased the pressure, and pressurizing gas leads to gas heating up. The Sun eventually boiled away the oceans, and water vapour is a strong greenhouse gas, and the rocks even began to have greenhouse gases boiled out of them too. Plate tectonics, what may have once been, stopped. We have a few ideas as to why Venus rotates retrograde and so slowly, but the giant impact hypothesis, IE a big object turned the thing over, is popular. The Solar wind also blew away lighter elements in the Venusian atmosphere, leading to only the heavier ones like sulfur dioxide. Any core of iron providing a magnetosphere that may have provided a shield went away when the rotation slowed, exposing the planet to even more rays. Mars once had oceans of liquid water too, and maybe life as well. But for some reason, it's magnetosphere stopped, not sure why, and the sun blasted away with the solar wind anything keeping the planet tempurature regulated. The water evapourated over the eons, and is lifeless today. The Saturnian moons likely are stopping the rings from forming into a moon themselves, they've locked them into positions where they can't move. Uranus likely got whacked, hard. And that would be why it spins sideways. It's much colder, and so methane is much more common in its atmosphere. Neptune's moon Triton looks like it might have been a dwarf planet captured from the Kuiper belt, which probably explains why it orbits retrograde. The Kuiper belt is probably too close to Neptune to form a proper planet, and the objects that are there have to be far away from Neptune to not get thrown out of orbit. The Sun's Ort Cloud is much more populated than the math would suggest. The Sun's been orbiting for a pretty long time though, and has passed by other stars. Maybe that's where the extra comets are from. Good enough answer?"
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7m11m7 | How can a smartphone camera, with such a small lens, detect different levels of depth to apply a portrait effect? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"1 - The device identifies what is in the first plane (using the parallax effect of dual lenses/sensors, similar effect with dual pixel sensors, or AI with single lens/single sensor) 2 - Whatever is not in the \"first plane mask\" is blurred by software after the actual image is taken - the background is captured with good focus (unless the main subject is so close that auto focus really creates the bokeh by itself), the blurr is \"photoshopped\" automatically afterwards.",
"Ta da! A blog from Google about the technology. Long story short: dual cameras or convolutional neural networks. URL_0"
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7m19lb | Is there an absolute hot or max | Physics | explainlikeimfive | {
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"text": [
"No, there is an absolute zero because you can only take energy out of system until there is none left, but you can always add more energy"
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7m1euo | Can you make a ethnic group lose it's citizenship, making them a stateless ethnic group? | Other | explainlikeimfive | {
"a_id": [
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"text": [
"It has happened before, yes. Another example I can think of that occurred recently is when [the Dominican Republic revoked the citizenship of thousands of people of Haitian descent]( URL_0 ). That said, I can't say if it will happen to your ethnic group. It's not something that's very common because it obviously causes all sorts of problems, but it can occur."
],
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"https://www.theguardian.com/world/2015/nov/19/dominican-republic-violated-human-rights-haitians-citizens"
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7m1fs4 | Why is it that when you turn on a heater and suck in the air coming out of it, it feels dry? | Biology | explainlikeimfive | {
"a_id": [
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"drqw0kz"
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"text": [
"Hot air has a higher capacity for water. So if you heat up a volume of air the *relative* humidity goes down even though the absolute amount of water stays the same. Therefore the warm air can take up more moisture and that can come from your skin and other tissues, so you feel that it's drying you.",
"Hot air is less dense. The particles in the air are farther apart and can accomodate more water molecules among them, compared to cold air. So when hot air touches you, it absorbs some of your water and you feel like you are drying."
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7m1p6d | How do hiccups begin? | Biology | explainlikeimfive | {
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"text": [
"Yarr! Yer not alone in askin', and kind strangers have explained: 1. [ELI5: Why do hiccups happen and how can I easily get rid of them? ]( URL_8 ) ^(_60 comments_) 1. [ELI5: Why do hiccups occur, what causes it to stop, and why does it sometimes hurt? ]( URL_0 ) ^(_ > 100 comments_) 1. [ELI5: Hiccups ]( URL_2 ) ^(_13 comments_) 1. [ELI5: What exactly are hiccups, and what causes them? ]( URL_1 ) ^(_4 comments_) 1. [ELI5: How and why do hiccups happen? And why does \"scaring hiccups away\" work, but only sometimes? ]( URL_4 ) ^(_4 comments_) 1. [ELI5: Why do you get hiccups every now and then? What is its purpose? ]( URL_6 ) ^(_1 comment_) 1. [ELI5 What are hiccups and how are they caused? ]( URL_7 ) ^(_1 comment_) 1. [ELI:5 Why do humans hiccup? ]( URL_3 ) ^(_11 comments_) 1. [ELI5: What causes us to get hiccups ]( URL_9 ) ^(_14 comments_) 1. [ELI5: Why do we hiccup? ]( URL_5 ) ^(_54 comments_)"
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"https://www.reddit.com/r/explainlikeimfive/comments/5ckxdi/eli5_why_do_hiccups_occur_what_causes_it_to_stop/",
"https://www.reddit.com/r/explainlikeimfive/comments/2hsy0d/eli5_what_exactly_are_hiccups_and_what_causes_them/",
"https://www.reddit.com/r/explainlikeimfive/comments/4tppxx/eli5_hiccups/",
"https://www.reddit.com/r/explainlikeimfive/comments/y90ww/eli5_why_do_humans_hiccup/",
"https://www.reddit.com/r/explainlikeimfive/comments/14fqrj/eli5_how_and_why_do_hiccups_happen_and_why_does/",
"https://www.reddit.com/r/explainlikeimfive/comments/1vwpos/eli5_why_do_we_hiccup/",
"https://www.reddit.com/r/explainlikeimfive/comments/mht0z/eli5_why_do_you_get_hiccups_every_now_and_then/",
"https://www.reddit.com/r/explainlikeimfive/comments/17afq6/eli5_what_are_hiccups_and_how_are_they_caused/",
"https://www.reddit.com/r/explainlikeimfive/comments/1n2qsn/eli5_why_do_hiccups_happen_and_how_can_i_easily/",
"https://www.reddit.com/r/explainlikeimfive/comments/69ryyz/eli5_what_causes_us_to_get_hiccups/"
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7m1uru | How can Tesla's Grid battery solution can make sense when it can power 30k homes for only one hour? (South Australia) | Technology | explainlikeimfive | {
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"You’re definitely right, the battery system won’t stop a full blackout. Instead its purpose is to help buffer out periods of very high load until the power stations can respond.",
"Batteries in a grid help to smooth out the difference between \"real\" power production and demand. Power production from coal plants, natural gas, wind, hydro, or solar. And demand from your house. Traditional power production plants take a VERY LONG TIME to turn on and off. And demand can go up and down in an instant. So what happens when everyone turns on their AC over summer? Well the grid says shit there is too much demand, let me turn parts of the grid off to reduce demand and we get blackouts. The battery comes in to play here, and becomes instantly another power source until more power generators can be turned on. Lets say the reverse happens and there isn't enough demand, in a normal grid we just burn that energy because we can't store electricity. If you are into bitcoins you just mine bitcoins. With a battery you dump electricity into the battery for use later. TLDR: You are not suppose to run on the battery all the time, it acts like a temporary solution."
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7m22pn | Why does cross breeding work between certain species but not all? | Biology | explainlikeimfive | {
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"text": [
"Your genetic code is like a recipe, a series of biological steps that describe how to make you you. Your unique recipe is created by going through your parents' recipes, and at each step choosing at random from your father or your mother. If both of your parents are German chocolate cakes, their recipes are going to be very similar and most the steps are are going to be the same. Maybe one uses a darker chocolate or has more pecans, but isn't going to matter too much which parent you get which step from. If one of your parents was a red velvet cake instead, the recipes are different, but still pretty close. There is pretty good chance you'll still get some sort of cake out of the combination, but it is going to be a pretty unusual one no one has ever seen before. But if one of your parents was a banana cream pie, those recipes are too different. When you try to combine them, you are probably just going to make a mess, and not get any sort of edible dessert out of your efforts.",
"What type of animal have you been trying to impregnate?",
"The genetic code has to match between the parents in order to create a viable offspring. Pretend like a hypothetical genome has 100 pieces. Species A has piece #1 code the heart, piece #2 code the brain, and piece #3 code the mouth. If both parents' species code things the same way, then the heart, brain, and mouth will all be coded like either parent, or something in between either parent. And assuming both parents were viable, the offspring will be as well. Species B, however, has piece #1 code the acid glands, piece #2 code the beak, and piece #3 code the tentacles. If an egg from A was fertilized by a sperm from B, the code would result in none of those organs being coded for. In fact, the very code that tells the newly combined cell to begin dividing would probably be in different areas of the DNA and the cell wouldn't even start dividing."
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7m251p | what happens if a child is never potty trained? Will they eventually learn on their own? | Biology | explainlikeimfive | {
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"I would imagine, like anything else in life, they would learn from how other people react to what they are doing. If people act with disgust for example they probably will get the idea. If a person is isolated from any human contact I would imagine they will do what suits them best. They probably won't want to crap in their own bed because it smells, etc."
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7m2a29 | Why are games from Japanese developers notoriously difficult/or include a difficulty setting higher than most games? | Other | explainlikeimfive | {
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"I can't say with certainty, but I would conjecture that it ties into Japanese culture similarly to some of their ridiculously hard game shows. If you've ever seen Ninja Warrior or some of the more obscure Japanese game shows, their difficulty is all kinds of insane."
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7m2ebi | Why don’t airports and air travel companies update from the staticky ATC systems to something that is able to be more clearly heard and understood. | Technology | explainlikeimfive | {
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"text": [
"Your cellphone also loses signal if it goes into a tunnel. Your cellphone is fm radio, pretty, nice, but weak signal. Plans are on lower frequencies, AM radio. Shittier quality but a much stronger signal strength."
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7m2jul | Why does pouring soda into a glass create foam when sparkling water doesn't? | Chemistry | explainlikeimfive | {
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"text": [
"Soda is stickier than water. Foam is the fluid sticking to escaping gas. Water slips off bubbles really easily but the soda doesn’t.",
"Yarr! Yer not alone in askin', and kind strangers have explained: 1. [ELI5:Why does carbonated water not foam when poured like beer and pop do? ]( URL_3 ) ^(_8 comments_) 1. [ELI5: Why do some sodas (like Coke) produce a lot of foam when it's poured into a cup, from say, a can, while other sodas (like Sprite) don't produce nearly as much? ]( URL_1 ) ^(_12 comments_) 1. [ELI5: How come carbonated water doesn't foam up like pop/soda when it's poured? ]( URL_2 ) ^(_4 comments_) 1. [ELI5: Why does Coke fizz so much when poured, when other sodas don't? ]( URL_0 ) ^(_4 comments_)"
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"https://www.reddit.com/r/explainlikeimfive/comments/7lsa9w/eli5_why_does_coke_fizz_so_much_when_poured_when/",
"https://www.reddit.com/r/explainlikeimfive/comments/5ppui9/eli5_why_do_some_sodas_like_coke_produce_a_lot_of/",
"https://www.reddit.com/r/explainlikeimfive/comments/5l19pv/eli5_how_come_carbonated_water_doesnt_foam_up/",
"https://www.reddit.com/r/explainlikeimfive/comments/30gujy/eli5why_does_carbonated_water_not_foam_when/"
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7m2tf7 | Why does the temperature at which you cook your food matter? | Biology | explainlikeimfive | {
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"text": [
"Most cooking methods involve blasting the outside of the food with heat, so the inside of the food is insulated from the heat. If you cook at too high a temperature, the outside will start to burn before the inside is fully cooked. You need to cook at low enough temperature that the whole thing is cooked without burning.",
"Cooking serves different purpose : * killing bad things that are present in your food : here you understand why temperature is important. Just like you won't die in a hot bath, bacteria won't die at 30°C. * changing texture and taste. Here, we are looking at chemical transformations. Just like when you touch a hot metal rod, you won't burn yourself until a certain temperature is reached. Therefore to obtain a sear on a steak, having your cooking pan blazing hot is necessary."
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7m2tif | Why does our voice change when we close our nose? | Physics | explainlikeimfive | {
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"text": [
"Your voice is the result of a bunch of interactions of different sound waves bouncing around inside of your mouth and sinuses; closing your nose means it'll bounce back some waves back into the rest of the system, and others will be absorbed into your nose and go nowhere. Changing the way the sound waves bounce around changes the actual sound you get."
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7m2tpr | How do the bets in the middle of a craps table work? | Other | explainlikeimfive | {
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"text": [
"There are two basic bets in the center: the hard way and proposition bets. The hard way bet is that the shooter will roll a certain combination of dice faces before rolling a 7 or any other combination. For example, the 5-5 hard way will win if 5-5 comes up, but will lose if 6-4 comes up or the shooter 7s out. Proposition bets are that the next roll will be whatever you bet on. So if you bet on 6-6, you will win if 6-6 comes up and lose to anything else. Same with any 7."
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7m2xsp | why does whipping creme “whip” and become thick, but milk or half and half doesn’t? | Been making homemade whipped creme for years, but today I accidentally used half and half and wondered why it wasn’t whipping. Why does heavy creme become thick when you whip it? | Chemistry | explainlikeimfive | {
"a_id": [
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"text": [
"Milk and (dairy) half-and-half don't have enough fat to bind with the proteins to get thick and creamy when whipped. When you whip cream it traps air, and that's what makes it into whipped cream. That's really all it is.",
"When you start whipping whipping cream, your goal is getting it to foam up. It foams up because the fat in milk is mostly \"triglycerides,\" which is stuff that foams easily. If you take out the fat, you take out the triglycerides, and there's no reason why it would foam up anymore. When you whip up the fatty milk into a foam, you're also damaging these \"triglycerides.\" If you keep whipping the whipped cream, you'll keep the molecular changes, but you'll also slowly let all the air that you whipped in escape. At this point, you have whipped cream that's had all the air squeezed out of it: butter."
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7m4gg2 | Do the IoT devices or sensors have to have IP address functionality in their firmwares? Or do they have to use the Internet Protocol Suite? | Technology | explainlikeimfive | {
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"If they are using IP (e.g. TCP/IP or UDP) then yes they need their own IP address. They have the IP address handling and the network stack in their firmware. Many IoT devices even run little mini linux distros inside them as \"firmware\". Source: work with IoT stuff",
"They don't *have* to, you could have a house full of sensors using simpler protocols and one or two relays that speak IP to do the \"cloud\" stuff, but it's common anyway, at least partly because the programming is easier for many developers.",
"An IoT device needs to have an advanced enough processor embedded in it to handle *some sort* of networking. It doesn't necessarily have to be a full TCP/IP stack, it could use some simpler network locally and have a more powerful local controller/hub bridge the gap to the outside world.",
"You can have 1 item that acts like a server that all the clients talk to on their own protocol (MODbus, CanBus, LonWorks, Honeywell SDS). That one server like item might be the only gate keeper with regular tcpip protocols",
"Most do, but it is not required. Many devices from the IoT ( a term I don't really like for its vagueness ) are in fact based on some variation of a Linux kernel. You might not be aware of this, but developing a platform where you can just build applications to actually do stuff with your sensors is actually a difficult challenge. To ease that, a lot of manufacturers will start with some existing stuff and it just happens that Linux is pretty much ubiquitous in this domain. So most devices will have a full IP stack because they run a stripped down Linux, which they do because no one wants to start from scratch. EDIT: At some point, to be on the \"Internet of Things\", you'll need an IP address, but it is possible to have several devices connected to a single hub within a building without internet. Zigbee is a protocol that allows this : URL_0",
"It is not necessary to have IP addresses for each IoT device. The data to and from the device can be directed using only the MAC address of the device. Every piece of networking hardware has a MAC address to uniquely identify it.",
"Other have this mostly covered, but another point is that any new IoT device is likely to be IPv6 compatible where each network has the capacity of the entire IPv4 space (~4 billion addresses), ~~so it makes sense to just give them an IPv6 address.~~ edited for dumb",
"Additional questions How does IOTA change all this, or is this a completely different thing than the question?",
"They need to be assigned an IP address, yes. This IP wouldn't be defined in the firmware though, it would likely be assigned via DHCP. Instead, the device would have a set MAC address, which defines the \"name\" of the specific connection. Basically, a device says, \"Hey interwebz, I'm [mac address]. Give me an IP address!\" Router says, \"Sure, how about [open IP address]?\" Device says, \"Ok, I'll use that one!\""
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7m4o9o | what is a byzantine rhyme scheme? | It's what critics describe does a problem with Eminem's Relapse album | Other | explainlikeimfive | {
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"text": [
"It's using the adjective \"Byzantine\", which means excessively detailed or complicated, referencing the byzantine administrative and governmental system which was absurdly bureaucratic, complicated, and unwieldy. They are saying the rhyme schemes Eminem employed where way too complicated or overly drawn out, reducing the quality or accessibility of the album."
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7m4s1a | what will happen if I put a new battery alongside an almost dead battery in a toy or remote? | Technology | explainlikeimfive | {
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"text": [
"It depends on the toy. If they are in parallel (both plus sides connected to each other, both minus sides connected to each other) you rapidly charge (or try to charge) the old one while rapidly discharging the new one. In the best case you just break the batteries, in the worst case you start a fire with toxic materials. Don't do that. If they are in series, the voltages just add. The toy might work or not depending on the toy and the batteries, but even if it works, it won't work long as the old battery will stop supplying a sufficient voltage quickly.",
"Here's the thing about an almost dead battery. Whenever you put a load on a battery there is a voltage drop. The closer to dead the battery is, the larger the drop. So if a new battery is 1.5V it may be 1.4 when under load. A dead battery may have 1V but drop to nearly 0 under load. So 2 new batteries in series would be 3v no load and 2.8 under load. 1 new 1 dead would be 2.5 no load, 1.4 under load. So most of the time a dead battery is not doing any good, and if anything is just doing harm be draining the good battery.",
"I had a atari type game it was just a joystic and buttons with a few games and you plug the cables into the tv and it took 4 batteries but i found out you only had to put 2 and it would still work i thought it was pretty cool i dont know the answer to your question but i just wanted to share that",
"Assuming they're in series, which they usually are. Imagine you have two 6-foot ladders, and you attach them together end-to-end to reach your 12-foot roof. After a certain amount of usage, the ladders break and become unusable. Since you are always using both these ladders at the same time to reach the roof, they break apart at the same time. Attaching a broken ladder to a new, 6-foot ladder won't help you reach the roof. You need two new ladders. Here, a 6-foot ladder is a working battery, a broken ladder is a dead one, 6-feet is the voltage of each battery, and 12 feet is the voltage the device requires."
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7m4sbe | Why is it not illegal to kill smaller animals such as rabbits, squirrels etc and insects when it is illegal to kill larger animals? | Other | explainlikeimfive | {
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"It has less to do with the size of the animal, but has to do with the species endangerment. For example, hunting deer is perfectly acceptable in most places even though they are larger. Small animals like rabbits, squirrels, etc, are no where near extinction and are varmints compared to larger animals like tigers and rhinos that are closer to extinction.",
"Technically it is illegal depending 9n the context. Cruelty to animals is a crime. Now hunting animals is regulated, so that right there can get you in a load of trouble. The hunting is determined by how prevalent the animal is to maintain a steady number. Smaller animals breed much faster than larger ones and thus their numbers grow far faster. For the time it takes for one deer to be born and grow to adulthood easily 100 rabbits could be born and grow up. So hunting rabbits is much more lenient than hunting a deer",
"It's not illegal to kill larger animals, and it's not legal to kill smaller animals. Not exactly. If you kill squirrels, rabbits, etc. without a hunting license, and out of season, or kill too many, then it's illegal. If you have a hunting license, and the appropriate tags/specialty license, and it's the correct season, you can legally hunt deer, elk, prong-horn antelope, bear, cougar, etc., although there is a total bag limit that varies by state. Check with your state department of natural resources for exact hunting regulations. There are many animals that simply are not legal to hunt, period. Insects aren't mammals or birds; there generally aren't regulations About killing then unless they're endangered."
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7m55vt | What are undersea cables? What is their purpose, how were they built, and what would happen if they were cut? | Technology | explainlikeimfive | {
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"> What are undersea cables? Thick cables that are under the ocean, exactly what their name suggests. > What is their purpose? We're using one right now to communicate over the internet assuming you aren't in the US. They provide the communication connections across the oceans, or at least they did until satellites became a thing. > How were they built? [Here you go]( URL_0 ). They basically just used modified ships and dropped it in. > What would happen if they were cut? Well there are several of them so cutting one would only reduce bandwidth. If you cut all of them you would break the internet and a lot of other communication techs since those cables are kinda important for that."
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7m57ks | Difference between LED, AMOLED, LCD, and Retina Display? | Technology | explainlikeimfive | {
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"So these are terms that refer to some fundamentally different things. I'll throw a few other terms in the mix that will hopefully clarify things: ###Display Technology * Cathode ray tube (CRT) where an electron beam is used to excite colored phosphors on the inside of a glass screen. You may have heard it referred to as a \"tube TV\". This is pretty old stuff, and is the earliest display technology for TVs. * Plasma displays, where a gas inside each pixel is made to glow. This is now pretty outdated, but still way newer than CRTs. It was especially common back when LCD TVs were new, and lower quality than they are today. * LCD (liquid crystal display). This is the most common type of display tech for televisions. There are three different colors of pixels (red, green, and blue) that can be made more or less opaque to let through light being created by a backlight behind the screen. The combinations of red, green, and blue can be used to form millions of different colors. * AMOLED (active matrix organic light emitting diode). Each pixel is made of of individual little lights that don't need a backlight. This is newer, and is being used in a lot of newer phones, but is still very expensive for large TVs. ###Backlight technology Note that backlights are only needed for LCD displays * Cold cathode. This uses a light similar to the overhead fluorescent lights used in stores and office buildings. * LED. This uses LEDs (light emitting diodes) to provide the backlight. Newer TVs will have hundreds of individual LEDs to provide even lighting and the ability to dim different sections of the screen to provide better contrast. ###Other stuff * Retina Display. This is just a fancy Apple buzzword for having lots of pixels that are really tiny, so you can't see the individual pixels on the screen even when you look pretty closely.",
"Retina display refers to a display with pixels small enough that the human eye is physically incapable of distinguishing the difference between adjacent pixels, at a given distance. This is kind of funky because our eyes don't work with pixels but it's probably a decent approximation. LCD stands for liquid crystal display and basically works by having pixels made of liquid crystals and by applying a certain voltage they will let through different amounts of red green and blue light. The light comes from a backlight (typically one or many LEDs these days). OLED stands for organic light emitting diode and has tiny colored LEDs in each pixel. This is why a black pixel can emit zero light unlike an LCD which just attempts to block all light from the backlight. I'm not sure what AMOLED is and I just came here for karma, not to do work.",
"Retina Display is not a technical designation, it's a marketing term. There are numerous display resolutions available in PCs (FHD, QHD UHD, etc) and Apple wanted to have a trademarked way to describe their display resolution that nobody else could legally use to make it sound like a unique offer. Depending on the device and screen size the term \"Retina Display\" can refer to significantly different resolutions and varying pixel density, though generally it means the pixel density is high enough that you cannot make out individual pixels at standard viewing distance. The Microsoft version of this is \"PixelSense\", which is again a marketing term rather than anything that has technical meaning.",
"Something relevant that hasn't been explicitly mentioned is that AMOLED black = nothing. That's why blacks look so good. It's in Samsung products but also Google and Apple",
"I have to deal with display technologies all the time in my line of work. Here's the major points: **LCD** is like an image being illuminated by a backlight. The backlight can mean that the viewing angles aren't necessarily fantastic and if the backlight is poorly done it can be viable around the edge. This also means a true black isn't achievable. However, more recent LCD display technologies like IPS and PLS, use larger RGB sub pixels and vastly improve uppon the technology. **LED** just means the backlight being used is LED lighting. **OLED and AMOLED** are essentially the same, the only difference being the way the transistors are handled. These screens don't need backlights- they make the light themselves. These are a hot newish technology because we can make them bright and we can make them thin. But they have some huge problems. The blue diodes we use in OLED decay at a very rapid rate. Have a Samsung Galaxy S5 and beyond? Pull up a full screen all grey image and you'll see the issues: burn in and a warmer (orange) color shift. Have an iPhone X? You'll see these problems more and more the longer you have your phone. It's a pretty bad technology in that regard. Far worse than we had with Plasma. It's important to note that OLED screens are not built to last. And though they're touted as high end, we have still not created a great version of OLED. OLED does have the advantage, like laser projection, of being able to display a true black. **Retina Display** doesn't mean anything. It's a silly Apple marketing term that just means more pixel density, but it's not even properly defined. Basically by Retina, Apple means any display technology (and they do mix them) in a device, but with pixels small enough to look smooth. It doesn't mean more resolution (because their phones actually have pretty poor resolution.) It just means decent resolution per inch. **Quantum dot** isn't one you asked about, but it's one to keep an eye out for. It can't, in its current consumer state, display a true black like OLED. But it has better accuracy at high brightness, it can get brighter, and most importantly, it doesn't suffer from burn in. With more development, it has the potential to be the OLED killer.",
"LCD and LED are screens with white backlights, which have moving lens (pixels) that physically move to bend the light from the backlight and produce color AMOLED have no backlight. The pixels are organic and produce their own light. This allows the screen to be thin as well as produce true blacks. Retina is nothing more than a marketing term. Apple uses regular LCD/LED and slaps on Retina to make it sound more appealing",
"There's a whole bunch of different display technologies out there today. LCD (liquid crystal display) being the most common. As the name suggests, you have some electrically sensitive crystals that can polarize light when you pass a current through them. Sort of like a high tech Venetian blind. LCDs don't produce light on their own though. (Think the original Gameboy.) So they need a backlight to make the screen visible. Originally they used bulky CCFLs (sort of a cross between a neon lamp and a florescent tube), but were eventually replaced with LEDs. These were marketed as LED TVs to differentiate them, and make an easier upsell. The main advantage with LEDs is you can make thinner, more energy efficient displays. Nearly all LCD displays use them now. The problem with LCDs is they can't display true black. The best ones can block most, but not all light from the backlight. So blacks will always look a bit washed out, resulting in reduced contrast ratio and colour accuracy. CRT and plasma displays can produce true black, but they have their own shortcomings in regards to size and power consumption. OLED is the next gen technology to replace them. OLED stands for organic light emitting diode. They're tiny LEDs made using an organic material that emits light in response to electrical current. An AMOLED display is a matrix of these, with each sub pixel (the red, green, or blue bits of a pixel) being its own individual OLED. They generate their own light, so a backlight isn't needed. And since you can turn them off completely, it can display true black. Hence better colour accuracy and contrast. Using organic materials also allows for thin and flexible displays. They do have some shortcomings though. They consume more power than LCD panels when showing a lot of white, like a text document. There's also lifespan issues with blue OLEDs. Lastly, they're quite a bit more expensive than LCD displays. Though prices have dropped significantly in the last 10 years. A Retina display is just a marketing term Apple used when the iPhone 4 first came out, to differentiate it from older devices. Basically anything with a 264ppi (pixels per inch) display or higher. Which is basically every phone now. At that point, the individual pixels are so small that that the average person would be unable to see the individual pixels at the closest comfortable viewing distance. A lot of low resolution LCD displays had a noticeable \"screen door\" effect, including early iPhones and the OG iPad, which is what the high PPI displays sought to address.",
"LCD and LED are mostly the same, both being LCD panels. The difference is the backlight technology. Displays listed as LCD use fluorescent tubes to light them where as LED displays use LED lights to light them. They have their strengths and weaknesses, LED is generally considered better as they are often brighter, more energy efficient, and can sometimes utilize dimming zones to improve contrast. AMOLED is Samsung's OLED technology. OLED is unique where instead of the image being lit by a light behind the screen, each pixel produces its own light. The main advantage to this is near perfect blacks since pixels showing darker parts of an image can show less or even no light at all unlike LCD or LED. They can also be very energy efficient, only turning on parts of the screen that are needed. Retina display is Apple's term for a high PPI/DPI display, which means more than average pixels per inch. A retina display is usually LCD or in the case of the iPhone X, AMOLED. A higher DPI generally means more detail for the size of screen. It's not anything special, there are many displays out there that are higher DPI than Apple's retina displays, Apple just has a special word for it.",
"As an Electrical Engineering student and avid graphics geek, I love this stuff! Great question :D **Displays** Computer screens are made up of a grid of \"pixels\", which are little tiny colored squares. Think back to [Super Mario 8-bit]( URL_0 ), see how you can see all of the squares in his body? That's because your GameBoy's pixels were pretty huge. The pixels in your computer now are really tiny, which is why we get smooth round shapes. In [old computer screens]( URL_3 ), pixels used to either be \"on\" or \"off\", either lit up or dark. This meant you could only have black and white images on the screen. **Nowadays, our pixels light up in any combination of colors.** How do they do this? One way to create any set of colors is to use different combinations of [Red, Green, and Blue light]( URL_4 ). You can make just about any color by combining these three colors. So a trick that you can use to create a colored light is by shining a red light, a green light, and a blue light right next to each other at different intensities. If they're small enough that your eye can't tell them apart, all your eye will see is the light combination. In fact, [that's what pixels look like up close]( URL_1 ). **The difference between types of displays is how they use those tiny colored lights to create colors.** * An **LCD** display has a backlight behind everything, and it controls the color by blocking different amounts of each color of light. This means that \"black\" on an LCD display still looks kind of bright. * An **OLED** display is dark by default, and turns on tiny little colored lights in different amounts to create different colors. * An **AMOLED** display is a type of OLED display. It allows you to access and control pixels faster than other types of OLEDs (PMOLEDs), which allows you to have bigger displays. * A **retina** display is a fancy Apple marketing term, meaning the [pixel density]( URL_2 ) is higher. Basically, this means everything is higher resolution, so your eyes are even less able to see the little tiny pixels. It's like going from 8-bit to 16-bit.",
"\"retina\" is merely a term coined by Apple that is essentially 300ppi. Pixels per inch. Back when the iPhone 4 (I think) came out. It was highly praised for it's high resolution and super clear display. Basically most phones, even budget phones nowadays are \"retina\" displays because the screen has so many pixels that it's very clear and sharp. This is a term coined by Apple. So if you see shit like \"it doesn't have a retina display\" it's a load of BS.",
"Here's an actual ELI5 without technical jargon: LCD = A panel of dots blocks light in certain areas to make a picture. Behind the panel, the screen is all white all the time. That's called the \"backlight\". (Side note: \"LED\" without the O refers to using a LED backlight on an LCD display, unlike previous displays that used a fluorescent light bulb for the same thing - more energy efficient. Fancy LED-lit LCDs can actually dim certain areas of the backlight so it's not \"all white all the time\", mostly to save even more energy.) OLED = instead of blocking the light, a panel of millions of tiny lights makes up the image directly. That's why they're so crisp and clear. But because they're individual lights, lights left on all the time will become dimmer over time, leaving a \"burn-in\". (Side note: you ever seen an electronic billboard on the road? Those are LED, using millions of full size LEDs (like those indicator lights on your TV and modem) to make a picture, but since you're viewing it so far away, it looks like a single big image. It's fun to get close to one some day! OLED is just a really, really tiny version of the same idea.) Retina = just a display (of any type) that has individual dots so small that your eye (retina) can't tell the difference between them.",
"LED: Light Emitting Diode. These are typically used for backlighting in modern non-OLED displays. They're capable of emitting a very pure, white light, they're very power efficient, and they turn on instantly, unlike older cold cathode backlighting. AMOLED: Active Matrix Organic Light-Emitting Diode. This is a screen which is comprised of what are essentially many tiny green, red, and blue LEDs. Because these light up on their own, no backlight is required - and they can be turned off completely, giving them the deep blacks they're renowned for. LCD: Liquid Crystal Display, which is a more conventional type of screen technology. Liquid crystals get manipulated by electricity to change their color. They do not emit light by themselves, necessitating a backlight. Because of this, you cannot get perfect blacks with them. Retina's basically just a marketing term Apple uses for a certain amount of PPI (Pixels per Inch) on a panel/monitor. In most of their products, Apple uses IPS displays, which are a type of LCD panels. IPS panels are unmatched in terms of color reproduction, but since they require a backlight, you cannot get perfect blacks with them. IPS and (AM)OLED panels both have their advantages and disadvantages. As I previously mentioned, IPS panels have more accurate color reproduction, while OLED panels have deep blacks and more vibrant colors. However, unlike IPS panels, OLED panels are also more susceptible to burn-in and mura (uneven colors). OLED panels also tend to use a Pentile grid, which uses twice as many green subpixels as red and blue ones. This effectively lowers your resolution by one-third, and many people argue that you don't truly get the advertised resolution on, say, a 1440p Pentile AMOLED panel. [Here's a traditional RGB grid next to an AMOLED grid. RGB looks much better.]( URL_0 ) Thankfully, resolutions on phone screens are so high nowadays that this is practically a non-issue. I might've gotten some of this wrong, but it should be mostly correct!",
"Retina != a display. It's marketing. Anyway. LCD == Liquid Crystal Display. A large lightsource, in the back of the display (a backlight) or around the edges provides white, multicolored light. Each pixel, or rather color sub pixel, is controlled by a pair of polarizers. Think of polarization as a direction, it goes through a polarizer, it has a polarized direction, call it up or left (it's actually quantum blah blah blah not important right now). Now that it's gone through one polarizer, it's chance of going through the second depends on the \"direction\" of the second polarizer. If the second polarizer's direction is parallel to the photon's (they're both \"up) the photon goes through. If it's perpendicular (the photon is up and the polarizer is left) the photon doesn't. If the direction is \"somewhere in between\" the photon has a chance of going through, dependent on how close its direction is to the polarizer's. If the polarizer's direction is halfway in between, it let's half of the \"up\" photons through and blocks the other half. A liquid crystal display has controllable polarizers. Each little pixel has 3, one for red, green, and blue, that change to let in however much red, green, or blue light you want going through to the users eyes. All this complexity means you get lightleak, or photons bouncing around and through pixels you don't want and blah blah blah. But it works. OLED, or AMOLED (Same thing really, for this purpose) uses something far simpler. Run a current through an organize compound (the O stands for organic) and it emits a specific color of light, easy. The brighter you want it the more current you run through it. You can turn it off completely by not running any, no lightleak. Just same as above, you run three colors (red, green, and blue) per pixel (dependent) and combine to get whatever color you want."
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7m5d63 | What makes us want to watch bloodshed among other people? | Other | explainlikeimfive | {
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"It might not be the violence itself that is the attraction, but intangible things most human societies attach to violence. Think about the military. The military is always shrouded in values such as honor, courage, and integrity. Military personnel are highly respected and valued. In the US and in most other nations, the military is the most trusted institution-even more so than democratically elected representatives. But think about what the military actually is. It is the main purveyor of violence for a nation. Militaries exist to do two things primarily-kill people and blow things up. War is almost always imbued in romantic sentiments like glory, as well as masculinity. Consequently, young men are attracted to war and the military-not necessarily to the blood and gore, but to the romanticism and glory of the battlefield. The kids in school are \"proving themselves\". They fight to show that they're tough or that they won't take any shit from people, that they can defend themselves. This is most pronounced among kids who come from backgrounds where they feel the need to defend themselves in the first place. Among some people, physical toughness and brutality are signs of strength and manliness. By fighting, they gain followers, sexual partners, and in other times and places the loot from pillaging. Fascination with gore might be something else-it might have to do with trying to make sense of our own mortality. Gore reveals that we are, after all, just flesh and blood and that we could in one accident or tragedy, be gone. Look at the imagery of religion-it is extremely gory. The bloody, crucified Jesus, the graphic images of martyrs, the ritual of drinking Christ's blood out of a chalice and eating his flesh. Its no wonder, considering one of religion's primary tasks is to deal with the fragile, temporal nature of our earthly existence."
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7m5ewz | Why is it that when we urinate and it is yellow it represents dehydration, but when we urinate and it's clear it shows we are hydrated, even though the same amount of urine comes out each time? | Biology | explainlikeimfive | {
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"Color indicates the (lack of) water. Meaning you evacuated stuff that wasn't water. Meaning dehydration.",
"Hydration affects the frequency that you need to pee. Each batch of piss is a similar volume because the urge to pee is affected by things like the volume of your bladder. More hydrated = more pisses per day. The volume of diluents (yellow stuff) excreted per day will presumably be the same regardless of hydration. So, the amount of diluent per piss will be greater if there are fewer pisses.",
"Your body gets the urge to pee when your bladder reaches a certain level of fullness. That means that whether you're dehydrated or not, when you need to go you're likely to go about the same amount every time. You might not be noticing that you're going to the bathroom *less often* when you're dehydrated.",
"Take 1 cup of water and put a drop of food coloring in it. Then take a gallon of water and put the same drop in it. Which one dilutes the color more? When you're well hydrated, there's more water which dilutes the stuff in your urine that gives it color. When you're dehydrated, there;s less water, so the waste is more concentrated."
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7m6io9 | how do drug purity tests work when testing drugs like cocaine and mdma? | Chemistry | explainlikeimfive | {
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"The test kits include specific molecule which change the active ingredients in the drugs to other molecules which have specific colors. It may also have molecules which will interact with common adulterants to provide other information about how the drug is cut. If you don't get a strong color indicated by the test it will often be because of impurities cutting the drug. You can use other tests to test for common adulterants if you want to figure out if they're benign (i.e. cocaine cut with sugar) or scary af (cocaine cut with Levamisole). That being said, the only way to know for sure is to use something like a mass spectrometer to measure the contents exactly.",
"There exist very questional field tests for \"purity\" of heroin in which you apply a reagent to a specific amount (100mg?) and gauge its purity against a chart of how deep the color change is. I don't know how many drugs they exist for. But a test more ably done in the field rather than a professional lab is the addition of various reagents such as Ehrlich's. This effects a color change which you can compare to a chart. URL_0"
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7m6jwo | Why does maturity of sperm matter when a drop of semen can impregnate a woman? | Biology | explainlikeimfive | {
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"Odds of survival. Mature sperm is more likely to survive the trip up the Fallopian tube to the egg. One single sperm cell CAN impregnate, but the odds are against it by design. The female reproductive system is hostile to sperm (acidity, etc.) to weed out damaged or incomplete candidate cells."
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7m6mak | Why do birds repeat sounds and tunes? | With all these videos of pet birds doing cool sounds and tunes, I don’t know why birds do it. Is it for fun? Communication? Tell me how it is please! | Biology | explainlikeimfive | {
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"Some species of birds use oral communication for some of their social interactions, mostly (a) warn others about incoming danger, (b) let others know where they can find food, (c) attracting a potential mate, (d) others. Think of it as a language. When humans are born, they don't know any words from the womb, they learn them by exposition. It's the same with birds, they learn all the whistlings and chirps they make from exposition, they have the ability to listen to a sound and reproduce it to some degree, for them, it's a survival situation. The songbirds that appear on videos are reproducing the sounds they hear because they think they will be useful for a future social interaction, whatever it will be. If the tune doesn't serve any useful function, it will be rapidly dropped. I remember reading an experiment where they taught a set of tunes to some parrots, they liberated them to the wild, the original parrots taught the tunes to the wild parrots but, because it didn't have any use in that society, all the parrots quickly forgot it and stopped singing it altogether."
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7m6x21 | How does the Scottish central banking system work and how is it connected to the British central bank? | Economics | explainlikeimfive | {
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"There is no Scottish central bank. Its central bank is the Bank of England, which despite the name is the central bank of the entire UK. Some commercial banks have the right to issue banknotes in Scotland, but these are still British pounds, the same currency used in the rest of the UK."
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7m6z1g | How do we know that two identical snowflakes have never existed and never will? | Chemistry | explainlikeimfive | {
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"The reason we can say no two snowflakes are identical with such high confidence is due to the absolutely disgusting number of possible differences that can occur in the formation of a snowflake. To put it into perspective, take a deck of cards and shuffle it. Statistically speaking, the order in which the cards end up (from top to bottom or bottom to top) has never existed in the history of mankind. This is because a deck of 52 cards can have 52! (52 factorial) different ways to end up after being shuffled. Thats 8,065,817,520,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 different combinations, and thats just with 52 variables (cards), this number is so big that our monkey brains actually don't understand just how big it is. Assuming \"identical\" here means down to a molecular level, then the formation of a snowflake would have millions, or billions or trillions of variables, i.e a number so big (1,000,000,000,000!) that we can just about say \"yea that's not happening, wrap it up and go home\"",
"We don’t in the sense you are thinking of. They mean statistically negligent. Like if I told you that you would never get struck by lightning while winning the lottery. Technically speaking there is a chance, but the odds are so low we are comfortable verbally using a definitive statement.",
"The statement is trivial if you think about it. No two objects of that size are ever going to be ‘identical’ without some qualifiers, at what size-scale do you stop comparing them...atom by atom?"
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7m7cg1 | How is the nose connected to the mouth and the ear? Why is it that blowing your nose will block and your ear and yawning will release the pressure? | Biology | explainlikeimfive | {
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"The eustachian tube connects the pharynx to the middle ear (otherwise fluids would build up in that otherwise closed space between your ear drum and cochlea).",
"When you blow your nose, you are likely creating high pressure inside your mouth/nose. This is forcing air into your Eustachian tube and into the middle ear. This tube isn't open all the time, you've forced it open with the air pressure. Now the pressure inside your ear is higher than the pressure outside, which stretches your eardrum, making it less able to vibrate in response to sound waves, so your hearing gets muffled. Yawning/opening your jaw wide/chewing manually opens the Eustachian tube, allowing the air pressure to equalize."
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7m7cvn | How does male voice change post-puberty? | Biology | explainlikeimfive | {
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"Take a rubber band and stretch it out, then blow hard against it - it'll make a humming noise as the air buffets past it. The pitch it makes will depend on the combination of the band length and the tension you put on it; the shorter the band and the higher the tension, the higher the pitch. Vocal cords are pretty much the same thing only made of meat. (a lot better optimised, but the same principle) During puberty / adolescence, the larynx in males become larger and the vocal cords become longer, and so the tones they produce become lower."
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7m7fu3 | Why is eating too much after a long period of starvation dangerous? | Biology | explainlikeimfive | {
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"This is an extremely difficult to answer question in a manner for a 5 year old to understand because it requires a basic biochemistry background to understand but here it goes: In starvation mode your body is conserving energy. It takes a little energy to digest food and get things going. To make this energy your need the elements potassium, phosphorous and magnesium (how and why is beyond the scope of this question) Since you have starved, your body's supply of potassium, magnesium and phosphorous are low and are supplying energy to the necessary functions of your body for survival. When you eat, the demand for energy increases to the point where your body cannot produce the necessary energy to digest the food (you lack the 3 key elements in sufficient quantities). Your blood levels of potassium, magnesium and phosphorous go into dangerously low levels that cause cardiac arrest, irreversible neurological problems (because your body's reserves of those elements gets immediately depleted while your gut tries to make the digestive acids, bile, energy for movement through the GI tract). This is **\"refeeding syndrome\"** Hope this helps",
"It’s called “refeeding syndrome” When you’ve been starving/deprived for a long time, your body shuts down everything it can get away with. Growth, reproduction, anything that can go offline or run at bare minimum will start to do so. Remember that physical processes (including digestion) demand energy and nutrients to do, which a starving body can’t spare. Everything has to go towards the absolute essentials, keeping the heart and brain going. If you were starving and were suddenly given a lot of food (especially rich food) *your body wouldn’t know what to do with it*. You’re still in starvation survival mode, so non-essentials like digestion are basically ignored. If they function at all, it’s bare minimum. All the food overloads this barely functioning system.",
"I tried that. Fasted for 11 days, and went too fast to glorious meat meals! But the day after I started puke and poop from diarrhea like never before. I got to the point I thought whats the point of drinking if it just go right through the system to vomit and puke? I started to get dehydrated and dizzy, and the worst stomach pains you can imagine! So I got to the hospital to get intravenous hydration and some pills to help disgestion. I got better after one day, but never been in worse pain! So start careful eating after starvation or fasting!",
"Because your body isn't used to eating anymore so when you eat a lot your body gets shocked and you poop yourself to death.",
"“Refeeding syndrome” This is why people who suffer from severe anorexia often must go into psych rehabs with specialized ED treatments. Not everyone will require a tube but the amount of doctors and nutritionists it takes to make sure just one patient is getting the right intake of carbs, calories, nutrients, proteins, and especially water intake is seriously important. Doing an internship now for my dueling undergrad in social work and pre med in a geriatric continuation of care. The nutritionist is a boss and she doesn’t mess around. I’ve seen her go on rants about what will or will not happen to the patients body should they continue xyz and it’s admirable. Food choice is one of the most personal things we do for ourselves.",
"When you've been starved for a prolonged amount of time (10+ days), your body's stores of various nutrients become depleted. Phosphorus, magnesium, and potassium are typically the highest of concern because these regulate muscle contractions (including heart, lungs, etc). Although your body stores (in the muscles and liver mainly) of these nutrients can be low, your body uses all that it can to keep blood levels within a normal range so that your heart, lungs, etc can continue to function normally even when your body is starved, or even emaciated. Now, introduce a high carb meal... Phosphorus, potassium, and magnesium are all used in breaking down carbohydrates to make energy. Since you have very little stores of these available, they are instead pulled from the blood to be used for carb metabolism, which then causes the blood levels to significantly drop to dangerously low levels. That can then result in a heart attack. This process is called refeeding syndrome. There are other complications with this including: fluid retention (which can cause heart failure), Wernicke's encephalopathy (a person becomes very confused due to thiamine deficiency), and high blood sugars. There are several things we do in the hospital to minimize the risk of refeeding syndrome, but main thing is to slowly introduce carbs, replace electrolytes (supplement or IV) and give a thiamine supplement.",
"It is due to the Refeeding Syndrome. When a person is starved, the body switches from sugar to fats and protein as fuel. Also, many minerals and electrolytes are being used up, even if it appear to be of normal levels in blood. Insulin (a hormone to control sugar levels in blood) levels are also suppressed because there's very little sugar. Then, when you feed the starved person with a lot of food, the insulin level rises, to help use the sugar that is now available. This also cause the body to start regenerating the fats and proteins that was used up earlier. Those processes requires a lot of the minerals and electrolytes that are already depleted. The cells' fuel, called ATP, is also affected as the processes above and ATP both competes for the same thing (phosphate), which is a bad thing. Also, as minerals and electrolytes are pulled into the cells, the levels remaining in the blood plunges. This can have impact on how the heart functions and affect its normal beating, and also increases the risk of dying. Thus, never give a starved person normal quantities of food, or their body cannot handle it and start causing harm. You don't want the body to immediately start making the proteins and fats before the electrolytes and minerals level returns to normal (for the body as a whole, not just for the blood)."
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7m7taz | Has pregnancies (in humans) always taken 9 months? Is there any possibility that the development time could increase or decrease in the future? | Biology | explainlikeimfive | {
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"For reference, our closest relatives have gestations of 230 (chimp) and 257 (gorilla) days, compared to our 270. Rhesus monkeys gestate for 164 days, baboons for 187. Our gestation time has slowly lengthened as we evolved to be a larger species, and could feasibly continue to do so. Essentially, bigger animals need longer in the womb. Judging by the 8 month chimp, and the 8.5 month gorilla gestations, it has at least been close to 9 months for as long as we've been recognisably human. Where it gets interesting is whether or not this span will make an upward or downward trend in the future- and I'd estimate upward. The average height of a human has increased greatly over the past century due to availability of nutrition. Larger mothers have larger children, which would hypothetically need a longer gestation. However, this is environmental, and hasn't necessarily been selected for in our genes. Humans have also hit a roadblock on gestation- we're limited by the size of the birthing canal. Our massive brains need to develop, and if they were any larger at birth, we wouldn't be able to be born. (This is why human babies are so helpless- that giant brain is basically a blank slate at birth because it wants more development time, but can't get it in the womb.) With increased availability for C-sections these days, women having very large babies can still safely deliver. And these over gestated children, which otherwise wouldn't be born, are able to survive and enter the gene pool. All of these lean towards a longer gestation. However, at the same time, medical advances mean that children who are born prematurely are also able to survive and enter the gene pool when they otherwise wouldn't. So all up, I don't think we'll see much change in our gestation time in a hurry. Over a few million years, it might move a week or two either way. tldr; a) No, with a but, and b) yes, with a but."
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7m8bpq | The difference between drugs like cocaine and amphetamine and their seemingly more dangerous big brothers crack cocaine and meth amphetamine? | Chemistry | explainlikeimfive | {
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"For crack vs cocaine: normally, cocaine exists as an ionic salt, mixed to an acid salt (such as hydrochloride salt). By mixing the salt with a very strong base (with a higher PH than the cocaine), the cocaine is deprotonated, and effective converted into a form that can stand by itself. The process of freebasing can be used to purify the drug to a degree, and the product can be smoked (as cocaine salt decomposes/burns before it can be be vaporized). There is a structural difference between methamphetamine and amphetamines, the presence of an extra carbon atom and associated hydrogens (aka a methyl group) at the end of the chain. This product is typically a abused more frequently, but clandestine synthesis of meth from amphetamine is not common, as synthesis from other precursors, could be easier.",
"Crack can be smoked, which is faster-acting than other methods of getting drugs into the body. The history of considering it \"worse\" than other forms of cocaine is less about the drug and more due to the populations/areas where crack is popular-- among African-American people, or in areas where they live. Methamphetamine is chemically different than other types of amphetamines, of which there are many. Think of the difference between fructose (fruit sugar), sucrose (table sugar), and lactose (milk sugar)... they are all sugars, which gives them similar names and they fill a similar place in our dietary needs, but they taste different and the body interacts with them differently. Some people can't even digest lactose and it makes them sick. Similarly, methamphetamine may not come from the same source as other types of amphetamine, and it's not just a different method of getting the same drug into the body, like crack cocaine is. It's more potent and longer-lasting. It also has a bad reputation due to its association with poor people (because it can be manufactured) or serious criminals (due to the opportunity to manufacture and sell it)."
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7m8lvu | The different types of fats, trans fats, saturated/unsaturated, etc, and which ones are "good" or "bad" | Biology | explainlikeimfive | {
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"The other answers in this thread are right from an organic chemistry perspective, but you are asking about it from a medical/health perspective. Saturated and trans fats are bad, and unsaturated ones are good. Imagine you eat a burger. it goes in your mouth, then to your stomach, then your pancreas releases a bunch of enzymes that break it down further and it gets absorbed in your small intestine. It crosses the border of your small intestine into your blood. Then the carbohydrate, fat, and protein filled blood goes to your liver. Then the liver does different things with it, but ultimately it converts all the excess protein, carbohydrates, and various types of fat into the standard type of fat that your body uses for storage. Then it sends it out to different parts of your body for storage (like your butt and thighs). But now say that the liver wants to withdraw fat from the bank and use it for energy. It needs a molecule to go to the fat cells in your butt and withdraw the fat and bring it back. This molecule is called a high density lipoprotein (HDL or good cholesterol) and it is made out of unsaturated fat. The worst thing about fat is not that it makes you look unhealthy. It's that it clogs up your arteries, which means your heart has to work harder to move blood around, which can result in heart failure. The chunks of fat can also break off and cause heart attacks and strokes. The best thing about HDL and the unsaturated fats they are made of is that HDL goes around and scrapes off the fat stuck in your arteries. So monounsaturated fats, polyunsaturated fats, and omega fatty acids are considered good because they help make the molecule that removes fat from your body. The other kind of fats help deposit more fat in your body."
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7m8oqc | Why does our skin have any amount of electrical resistance? | Biology | explainlikeimfive | {
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"text": [
"Because almost every substance in the universe does. It's an *exceptional* case for something to have none -- such a material is called a *superconductor* and is extremely hard to make. Currently every known superconductor only works when quite cold."
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7m8pbh | can someone explain how and why analogue is different than digital in context of computer processing power? | Technology | explainlikeimfive | {
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"Analog-- I want to tell you the number 82. So I shine a light towards you at 82% brightness. You observe the brightness and write down what you see. Digital-- I want to tell you the number 82. So I blink a light on-and-off 8 times, wait a second, then blink it another 2 times. Advantages of analog-- what if I want to tell you 82.5? I just make it a tiny bit brighter. Easy. Disadvantages of analog-- accuracy. If there's fog in the way or I'm just not that good at judging brightness, I could interpret your 82% brightness as 80% or something. Advantages of digital-- accuracy and repeat-ability. I can tell the next person 82 using a similar code of blinks and as long as I don't **completely screw it up**, they'll know I mean 82 and pass it along to the next person who asks for that information. There's no worry about a minor imperfection adding a little inaccuracy here, then more inaccuracy at the next step, then more... as long as each step does it right, you can keep sending the signal and it will be exactly the same as it started out. Computers could not work with analog signals at the level of performance they do now. They're too fast and inaccuracy would be severe. There is also no such thing as 100% accurate analog signals. How can I know you meant 82% instead of 81.9999%? With digital, the signal is preserved as long as it's intact. We lose the ability to transfer information like 81.9999% unless we previously agree we're going to send over 4 decimal places of precision. That's a pain in the ass. But we can make that work. We can't make uncertainty or inaccuracy work at a speed of GHz (billions of operations per second).",
"First: The basics. Digital computer can \"understand\" 2 values: 1 and 0 (ON and OFF). Analog computers can \"understand\" several values: Low thru High. Basically it operate on mathematical variables in the form of physical quantities that are continuously varying. For example, an analog computer may work with temperature values, voltages, pressure, etc. Regarding processing power, The digital ones can take measures with binary values (Combination of ones and zeros). For example: To process \"5\" (FIVE) on a digital computer the binary value is 101. On an analog computer the plain and simple value of 5 is entered in that state. So, as you can see, part of the processing power on a digital computer DEPENDS how many bits can candle the processor. Old computers had a 8-bit processor. New ones have a 64 bits processor, That means, the processor could process ANY value between zero and 1,844,674,407,3709,551,615 at the time. Analog computers are able to process any value (depending the precision) at the time. Back in the 60's, Analog computers were more \"powerful\" than any 8-bits computers but as technology advanced, digital computer became faster with more bits to process. Still to this date, we have analog computers, the simple one that we still using is [this ruler]( URL_0 ).",
"Computers are digital, they can’t comprehend analogue signals. Any analogue signal must first be converted into a digital approximation for the computer to understand and store. To that end... there’s no such thing as a “difference in processing power”, as analogue signals don’t exist from the computer’s point of view. A higher resolution digital approximation of an analogue signal will have more samples, and contain more data, so you need more processing power and storage to have more accurate representations. (E.g. a 48 kHz .wav is larger than a 32 kHz .wav of the same song, as its digital approximation of the sound wave is higher resolution) The same applies to images."
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7m9dr8 | What happens to the skin when you form a friction blister | The skin bubbles up almost immediately after doing something repeatedly, like say twisting a screw driver, and puss fills the pocket. What exactly is happening to the skin? | Biology | explainlikeimfive | {
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"Your typical blister is from some sort of rubbing or friction that causes the upper layer of skin to separate. Think... rubbing the ends of a plastic bag with your fingers to separate the two layers. In that pocket that's been created, serum (or pus, or blood) fills the cavity."
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7m9hpx | How do calluses form so quickly ? | I was gifted a violin yesterday, and ended up practicing for about 7 hours. My fingertips stung pretty badly by the end. This morning, I noticed that the skin on my fingertips had toughened up a bit and, 5 more hours of practice later, they barely hurt at all. How did this happen ? | Biology | explainlikeimfive | {
"a_id": [
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"When skin is met with direct ongoing pressure (pain, damage, etc), it starts to basically make more skin on the top layer to protect the inner layers. It doesn't happen overnight, but they can form rather quickly. The proof is in how at first your fingertips hurt but the next day it wasn't that bad. Your skin created a tougher layer of skin on the areas it was hurt (your fingertips) to protect it from any future damage that could happen."
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7m9kom | Why are cells so small and why can't they be huge? | Biology | explainlikeimfive | {
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"Because as cells get larger, their interior mass increases faster than the surface area of the cell membrane. This means that at one point, the amount of membrane would not be sufficient for servicing the entire cell interior. Not enough oxygen/water/sugar could enter the cells through the limited protein \"doors.\"",
"Some cells are huge though! Eg, some of your nerve cells can be really long: in these cases, they try and keep the volume small by being thin and long. It helps with fast signal transmission between your feet and brain. Big bird eggs or dragon eggs(definitely exists :D) are a single cell. They don't need to do the things that normal cells need to do. Instead they just store all nutrients in it, which is why it's huge.",
"The size a cell can achieve is constrained by several factors, some more important overall, some more important depending the function of the cell. The main constraint is the rate at which nutrients, waste, and signal chemical can move across the membrane of the cell. Imagine you have a cell that produces energy from acquiring sugar and produces a waste. If the cell is bigger than necessary, it will take a long time for the nutrient to travel from the membrane to the respective organelle where the production of energy will take place. Just like that, after the energy is produced, it will take more time and energy than necessary to take the waste outside of the cell. Another constraint is associated with differences in concentration of chemicals inside and outside of the cell. A lot of important cell functions are dependant on having *x* amount of chemical *A* inside the cell and *y* amount of chemical *B* outside to create a gradient, which helps with the transportation of chemicals across the membrane, sometimes being used as a way to produce energy! (see: Na-K pump). Finally, one of the most important constraints is the amount of liquid a cellular membrane can hold. Cellular membranes are made of lipids and are fairly thin compared to the size of the cell overall. Think of them as a balloon, you can hold a little amount of liquid with no problem but the more liquid you're holding, the more likely it will be for the balloon to break apart. Fun fact: Not all cells are tiny, some can be very large, specially neurons, which have to send a signal from the place a stimuli is taken to the brain. For example, giraffes have neurons as long as the length from their toe or tail to their brain, which, incidentally, makes them a little slower than animals with shorter neurons. Another fun fact: There's a unicellular organism called [*Syringammina fragilissima*]( URL_1 ) which can grow [up to 8 in]( URL_0 )! That's quite a lot for unicellular organisms since they're usually in the microns (millionths of a meter).",
"For cells, the rate that materials can be passively or actively transported across the cell membrane is a function of the surface area of the cell. However, assuming a spherical or similar shape, the volume of the cell increases much faster that the surface area of a cell would increase. This places an effective limit on how large a functioning cell can be."
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7m9w4z | What can't you taste the sweetness in drinks after eating something sweet? | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"The receptors in the tongue after a brief time are unable to keep processing the taste. So you stop tasting. They essentially get tired and stop sending the signal to the brain that what is in your mouth is sweet. After another brief time without that taste, the receptor resets and you can taste it again.",
"Your taste like you other senses primary detect changes. You dont sense smells after a while. Like if you cook at home and burn the food, after a while you will not smell it but if you exit your home and spend a short while in clear air you will smell the burned food when you return. Touch work the same. You feet the chair when you sit down on it but then you will not notice it. Event sight and hearing work that way to different degrees."
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7ma0fq | What exactly makes cooked food more nutritious? | Chemistry | explainlikeimfive | {
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"Cooking food just makes things easier to digest. Meaning your body can absorb more nutrients from them.",
"It depends on the food. It's not necessarily the case that cooked food is more nutritious. It might have the same nutrition, or less, or more. If it has more, it is likely due to the cooking process altering or breaking down structures that are hard for you to digest, making it so that you digest more than you would from the uncooked food (i.e. instead of breaking down in your gi tract, it passes out intact as poop).",
"Living things run on sugar. When you digest food, you eventually break it down into sugar which feeds your cells. Unless you are eating raw sugar, your body has to convert your food into sugar so your cells can use it. Luckily, the plants and animals we eat also run on sugar. However, the sugar in plants and animals is usually stored not as sugar but as a different chemical which is more stable and easy to store (like how you can stack plastic cups so that they take up less room). Animals store sugar as fat, and plants store it as starch or celulose. When you eat plants or animals, you are mainly eating the storage chemicals which need to be broken down into sugar so your body can use it. This takes extra work and energy. This means you have to use energy to extract energy from food. In some cases, it takes more energy to break down (digest) food than you get out of it. For instance, if you ate only cucumbers or lettuce, you would starve to death, because these foods are hard to digest and you actually use more energy than you gain. Cooking for helps to break down the complex molecules in the food so that they are easier to digest. This means you can get more energy eating the food, because you use less energy to digest it. Cooking food was important to humans developing as an intelligent species, because our big brains require so much energy. We couldn't get enough nutrients to support our big brains if we just ate uncooked leaves or raw meat. Note this is the ELI5 answer, there is also a lot of other stuff going on regarding protiens and and other nutrients that I do not mention.",
"Well obviously if you cook something it will degrade in some sense. For the most part cooking a vegetable for example does NOT make it more nutritious. In fact the longer you cook vegetables the worse off you'll be in a health sense. Though you can prep vegetables and food differently to make the most of the \"healthy compounds\" you desire in a food, but then it will come at a cost of degrading other aspects/nutrients of that particular food. URL_2 URL_0 (Not a great source) URL_1 (Not a great source)"
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"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2722699/"
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7ma356 | Why does it get more difficult for men to pee as they get older? | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"Benign Prostate Hypertrophy, in other words, prostate enlargement. The cause of this is unknown. Bladder stones can also cause difficult urination, but they're less common.",
"Your urethra(the tube from your bladder to your penis) runs through your prostate. When men get older almost all of them will develop a enlargened prostate. This causes the lumen of the tube to get smaller and for the opening from the bladder to the urethra to get smaller and less accessible as well. This causes symptoms like: starting is harder, lesser pressure and little drops following when you are already done peeing. This is one of the main causes for older men to sometimes have difficulty peeing. It is one of many more though."
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7maeok | Why do you hear a little bit of static in headphones whenever you plug them into a device or unplug them? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Headphone jacks have circular conductors the length of the jack. As you insert it they rub against parts of the socket meant for the circles higher up. They thus get a slight amount of power unintentionally that creates a bit of noise."
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7maiib | why is there “cold air” that emits from someone who just came from outside? | I’m currently sitting in a chalet at a snowboard/ski park and, although there is no door near by (sitting on upper level), people who have just been outside seconds earlier emit a really chilly breeze when they walk by vs. people who have been sitting in the chalet for a while. How does this work? | Physics | explainlikeimfive | {
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"This is due to how heat transfer operates. Heat tends to move from places where it is hot to places where it is cold in order to equalize the temperature. Now technically there is no such thing as cold but rather it is an absence of heat, so that \"cold breeze\" you feel is actually them stealing your heat not them blowing cold on you. Their clothing is very cold from being outside in the low temperature so when they come inside their clothes remain cold until warmed by their surroundings. You happen to be the warm surroundings that the clothing absorbs as they walk by.",
"Cold objects actively sap thermal energy from outside themselves until cold object or creature is in balance with it's surroundings.",
"Their body is actually cold from being outside in the cold. When they go inside, their body cools the air around them and creates a draft. Similar to putting water in the freezer. When you pull the water out of the cold freezer, the water(ice) is also cool, and you can put it into warm drinks to make them cool as well."
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7manhh | Why only 5 countries have the power of veto in the UN? | Other | explainlikeimfive | {
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"When the UN was founded the 5 most powerful nations (Winners of WWII) at the time had no reason to join. They would be giving up power and authority to a foreign governing body and the risk was just not worth it unless they had some kind of control in said governing body. Since the UN does not work at all if even one of the powerful nations was not a member concessions were given and they were given permanent Veto power on the UN council.",
"A bit of history. After the first World War, there first came the League of Nations (set up in 1920). The main goal of the LN was to prevent another world war from happening. Obviously, that failed. In fact, the LN was in general fairly useless, and part of the reason it lacked any real power to do things is that several of the main world powers either didn't join or joined only for a short period of time. Now, after the second world war, when the UN was formed, they obviously wanted to avoid the failings of the League of Nations. It was more than clear that for it to have some form of power, you really need all the big world powers involved. But the USA, for one, only was going to join if they had the option to veto. And if you give the option to veto to one world power, the other big ones want one too. The UN decided though that it was better to have these five nations involved and give them a veto that they might occasionally use, rather than have them be absent completely and have the UN fall into the same state of uselessness as the League of Nations. The idea is that the countries weren't going to be using their veto all the time and having the veto at least got them to the discussion table. Better to have them there and veto once in a while, than not have them there at all which would've been the alternative.",
"They won WWII and created the UN with them at the top, they were not apt to give any of the lesser countries or the losers of the war a say. The overall goal was to create a forum so that a huge war like the last two didn’t happen again, the best way to do that was to have the big boys at the table"
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7mat0f | How do the anti-theft systems at store exits/entrances work? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"There are little tags inside the devices that emit a reply radio signal when they’re subjected to another, higher power radio signal on the correct frequency. If you shoplift an item, this tag is still active and the sensors you walk through can detect it. When you check out, the cashier runs your item over a device that detects the tag. When the tag is detected, the device emits a very high powered pulse that burns out the tag, deactivating it. This is the “bong” you hear sometimes. This pulse does a good job of demagnetizing credit cards, so that’s why there’s signs saying keep them away."
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7mb8cn | Hockey vs Football Helment | Why are hockey helmets and football helmets so different? I know concussions are a relevantly frequent problem plaguing not only the NHL but hockey in general, so why not adopt the bigger helmets used in football instead of their smaller ones? Thanks for any answers | Other | explainlikeimfive | {
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"Hockey helmets are more about not getting hit by a puck. There are rules about hits to the head which try to mitigate incidences where concussions can occur. The helmet needs to be smaller and lighter so that it doesn't inhibit a player's performance because unlike football where you are running anticipated routes in short bursts there is a lot more time playing between stoppage times and the situations which players are in are constantly changing making players have to keep their heads on a swivel; a larger helmet would just get in the way."
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7mbmu4 | how does fast charging work | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Fast charging works by providing a different voltage or having a lot of current available. It requires a special charger that can work with the phone. The phone and the charger negotiate what type of power will be used Phones still support the standard 5V 500mA charging that's been standard for a long time so they can charge off of any charger. If you restrict it to just working with fast charge chargers then only your charger works with your phone and when you go on a road trip with a friend you won't be able to use their car charger The point of standardizing on USB charging was so any charger works with any phone, making phones only accept their own fast charge breaks that standardization and puts us back in 1998"
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7mbutz | Why does shining a blue laser at an LED turn it on? | Technology | explainlikeimfive | {
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"text": [
"I'm assuming it was a white LED. They work by shining a blue LED at a phosphor which causes it to emit a mix of red and green light. Together with some of the blue, they mix to make white. Any blue light shining on the phosphor will make it glow to some extent. The blue laser is intense enough to make it apparent."
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7mc2lp | What is the point when a material bends too far and it cannot be made the same and what is happening to it physically to make it that way? | Physics | explainlikeimfive | {
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"text": [
"That is what is called plastic deformation. The material exceeds the stress the atomic bonds are capable of withstanding which causes the material to deform and eventually break. When a material deforms and returns to its original shape, it is called elastic deformation. During this, the stress is not large enough to break the atomic bonds in the material and it is able to retain or return to the original shape."
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7mc71m | Sharpe Ratio | Sharpe Ratio is widely used for investment performance measurement and measures excess return per unit of risk for a portfolio: (Portfolio Return - Risk Free Rate) / (Standard Deviation of Portfolio). However, I'm having a hard time explaining it to my finance illiterate younger brother. How would you explain it so that a five year old would understand? It can be in the form of dumbed down analogies -- I've been stuck for a week and can't figure out how to explain this in extreme Layman's terms. | Economics | explainlikeimfive | {
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"text": [
"Have you ever played [Rainbow Road]( URL_0 ) on Mario Kart? It's basically a really narrow winding track with no edges. It's pretty much the hardest level in the game. You drive your kart around the track, but it's really easy to fall off the edge. If you do, you are rescued, but you lose valuable time. Now say there are four players. 1. One driver drives really fast, but keeps falling off the cliff and getting back on. So sometimes they are driving max speed and sometimes they are going 0MPH. 2. Another drives really slow and almost never falls off. 3. Another driver goes slow and still falls off. 4. And the final driver drives fast and doesn't fall off the side of the road. Who is the best player? Obviously the person who drives fast and doesn't fall off the cliff is the best because they will reach the finish line first. Who is the worst? Obviously the person who drives slow and falls off. But what about the other two? Is the slow and steady tortoise player better than the fast and non-moving hare style player? In the game you can just look at the lap times, but in real life, there is no finish line. It's just a never ending track. So you need a way to compare the two strategies. The Sharpe ratio allows you to do that. Imagine four investors. 1. One investor makes really risky investments. Some years he makes a lot of money and some years he loses a lot of money. 2. The second investor makes really safe investments and hardly ever loses money, but makes money very slowly too. 3. The third investor makes low risk investments, but still loses money. 4. The fourth investor makes high growth investments, but they are also low risk. Like above, the fourth investor is the best and the third is the worst. The other two are in the middle. And the Sharpe ratio is the way to figure out who is best. So there are three components of your equation. Portfolio return is pretty simple. It's how much money they made with their investments. Next, subtract the amount of money they would have made in the least risky investment possible. Making $100hour sounds awesome, but what if it turns out minimum wage is $99/hour? It's not so impressive that you made $1 an hour more than the minimum. Now on the bottom is the standard deviation of portfolio returns. If you make 10% one year and lose 10% the next year, that's more volatile and risky than if you you make 5% one year and lose 5% the next year (-10% to 10% is 20 percentage points wide vs. -5% to 5% is only 10 percentage points wide.) So the higher the number on the top and lower the number on the bottom, the better the investment. The top number tells you about how much money you could make, and the bottom number tells you how risky it is. A high Sharpe number means they made a lot of money with a small amount of risk. 2/1 would be a great number. Meanwhile, if the Sharpe ratio is 1/3, that would mean they had a highly risky set of investments, but still didn't make very much money. That's bad. Meanwhile, the last two investors (Mr. High Risk High Reward and Ms. Low Risk Low Reward) might both end up with the same Sharpe ratio."
],
"score": [
6
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"text_urls": [
[
"https://www.youtube.com/watch?v=kO920gPFW2Y"
]
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} | [
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"url"
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7mc9k3 | Why is mold acceptable in some foods, such as cheese, but not in anything else? | We're able to enjoy something like blue cheese dressing, but once mold shows up on bread, it's no good. Why is that? Thanks! | Biology | explainlikeimfive | {
"a_id": [
"drswwag",
"drsxl9s"
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"text": [
"Some molds create toxins that are harmful to the human body. The molds that cause many types of cheese (such as the blue cheese dressing you enjoy) do not create the harmful toxins. Mold on many other foods don't necessarily indicate danger just a lack of freshness (fermentation happening, change in taste, texture, etc.) and are perfectly safe to eat but if you have other food options you will likely throw it away because you probably have enough money to not eat moldy bread.",
"Think of mold as you would mushrooms. Some are safe to eat, others can harm you. Mold types is by no means random, you can't have mold that grows on vegetables be the same that grows on cheese, and so on. As far as why mold has become acceptable in cheese compared to other food products with safe amounts of mold in them, it comes down to a couple things. The first and easiest answer is that certain cheese's with mold taste better to people compared to the non-moldy counterpart. Two it's easier to store moldy cheese for longer periods of time compared to something like bread which grows mold extremely fast, and to boot doesn't taste any better by having it."
],
"score": [
39,
16
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
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7mciaw | If amber lensed computer glasses reflect the blue light, why aren't they blue? | The way I was taught how light works in school is that an object absorbs all color that it doesn't reflect. IE an apple absorbs all light except red, which it reflects, therefore the apple is red. If amber lensed computer glasses (like these ones [here] ( URL_0 )) are supposed to deflect the blue light why aren't they blue? | Technology | explainlikeimfive | {
"a_id": [
"drt04ar",
"drszpa4"
],
"text": [
"They're not reflecting the blue light, they're absorbing it. And all other colours except amber. So amber is what you see coming through them as well as bouncing off them. When light is absorbed it is used to vibrate the molecules that make up the glass. This makes it slightly warmer, but not so much you'd notice, normally.",
"Amber lenses *absorb* the blue light, blocking it from coming through. They don't reflect it."
],
"score": [
7,
3
],
"text_urls": [
[],
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]
} | [
"url"
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"url"
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7mcilq | Why does the body hold onto excess calories and turn it into fat instead of just getting rid of it with waste? | Biology | explainlikeimfive | {
"a_id": [
"drsy9pl",
"drt6v8t"
],
"text": [
"Because a long time ago food didn't come so easily to our ancestors. Your body holds onto the excess as fat to use as a reserve for times when food is hard to come by.",
"Evolutionarily speaking, it was not that long ago that the idea of \"excess calories\" being a bad thing was unheard of. Even a few centuries ago, all but the most wealthy could and did face the risk of not always having enough food to go around, especially in the leaner months of winter or a bad harvest. In the last few centuries we've had a massive number of advancements in the quality of life and how easy and plentiful food can be, as well as the high caloric content in a lot of it. So our bodies just have not had *near* enough time to evolve or adjust to the point of not thinking \"better hold onto this, never sure when the next meal will come.\""
],
"score": [
57,
6
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7mcjfu | How do they air movies on TV and still fit it at even time slots regardless of the film's length? | Obviously a movie can be any length - but on TV they always seem to be in even slots rounded to the nearest hour/half hour/ten minutes even with commercial breaks included. How do they fit these movies on schedule without compromising some bits from the film? | Other | explainlikeimfive | {
"a_id": [
"drsyt75",
"drsyn0b",
"drsyoa4",
"drszkvg"
],
"text": [
"They can edit the film to cut insignificant parts, speed up the playback ever so slightly, adjust the number and length of commercial spots, credit speed.",
"Look at the beginning of the film. A lot of the time there will be a disclaimer that says the film has been edited to fit the TV screen and \"to run in the time allotted\"",
"A lot of movies have TV \"cuts\" that are cropped to come out at an even time. You'll see a lot of them speed up the credits or have shorter opening sequences. You can also join the next show in progress if you have to. Station I work at doesn't air movies, but we do the latter with sports, since they never come out to an even time.",
"They do compromise. TV cuts are always edited unless the network claims otherwise. Then they pad with commercials."
],
"score": [
17,
11,
8,
5
],
"text_urls": [
[],
[],
[],
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} | [
"url"
] | [
"url"
] |
7mckta | In the tornado, was the death of the Wicked Witch of the West indicating that Miss Gulch actually died in the tornado? Or did she ever come to get Toto and it really wasn’t happily ever after? | Other | explainlikeimfive | {
"a_id": [
"drszrqg"
],
"text": [
"Follow up question. Why did dorothy, a girl from rural kansas, not just go straight for the storm shelter? Why did she go inside the house looking for Aunt Em? I mean, she SAW the tornado!!! Where the hell does the think Aunt Em is?"
],
"score": [
7
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7mcnsb | You couldn't kill bacteria with 102° water, so why does your body heat up while you're sick? | Biology | explainlikeimfive | {
"a_id": [
"drszz6v",
"drszlje"
],
"text": [
"It doesn't incinerate the bacteria, but it does make life harder for them. It weakens them, without being so hot as to kill your own cells.",
"The higher temperature boosts your body's immune system. It's more effective at higher temperatures. Of course, it's a fine balance, because above 105°, the heat starts causing serious brain damage."
],
"score": [
5,
5
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7mcwam | How come objects that are far away in mirrors still appear blurry, despite the mirror being flat? | I'm nearsighted, so things in mirrors appear really blurry as if they were far away even though the mirror is a flat surface. | Physics | explainlikeimfive | {
"a_id": [
"drt1zaw",
"drt2r2v"
],
"text": [
"We are able to see objects because we can see the light that is reflected off of an object. When you look at an object, you are seeing the light that hits them and then it travels to you and hits your eyes. The same is true for a mirror, except it has to hit the mirror first and then your eyes. The light is still traveling the same distance (a little more distance actually) because it has to go from the object, to the mirror, then to your eyes. Even though the mirror is right next to you, the object that it is receiving the reflected light from, the object you are trying to see, still has to send its light a distance to reach you, making it seem the same as if it was far away when seen in a mirror.",
"Because the objects that you look at by looking in a mirror are still far away. The mirror doesn't bring them any closer. You aren't looking AT the mirror, after all; you are looking at the light coming from far away that the mirror reflects."
],
"score": [
6,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
7mcxvy | Why does your skin show your sun tan / burn so much more after you shower but not if you were to just jump in the pool? | Biology | explainlikeimfive | {
"a_id": [
"drt23ly"
],
"text": [
"When you shower, you scrub your skin with soap and a wash cloth or loofah or something similar. This exfoliates the top layer of skin, leaving the tanned layer underneath. You don't do quite as much scrubbing in the pool."
],
"score": [
4
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7md00u | How do spray on anesthesias work? | Like the ones used by dentists. | Biology | explainlikeimfive | {
"a_id": [
"drt2hng",
"drt50i0"
],
"text": [
"> How do spray on anesthesias work? There is no such thing as a spray on anesthesia as anesthesia is a state someone can be in. It is like saying \"How do spray on sleeps work?\" Instead you are probably thinking of spray on analgesics. In general a topical analgesic involves the use of chemicals which can be absorbed into flesh and will interfere with sensation in various ways depending on the particular type being used. For example lidocaine blocks the sodium channels in nerve cells which prevents the propagation of nerve signals which convey pain or other sensation, resulting in a numbing of affected tissues.",
"I'm going to guess you mean anaesthetic, which is a term used to describe topical analgesics. Well... They work the same way any form of externally applicable anaesthetics work. They include chemicals which can be absorbed or penetrate the skin, fat and be absorbed. The thinner the skin (e.g. inside the mouth), the less penetrative these need to be and the denser (more effective?) the applied analgesic compound can be. As an example, lidocaine products won't work on thicker, multi-layer skin areas such as your fingers, but work inside your mouth. The fact they're sprayed on is irrelevant, mostly, as it's indifferent from application directly to the skin. The only distinction is from those which are injected below the skin layer."
],
"score": [
6,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
7md2nc | What is the thing about hyper loops that keep them from actually being a reality | Technology | explainlikeimfive | {
"a_id": [
"drt2qsd",
"drt2o2k"
],
"text": [
"> What is the thing about hyper loops that keep them from actually being a reality The whole not existing thing is what it really comes down to. We don't have extensive tubes of near vacuum running across the country to desired destinations. We don't have a reliable way to propel a capsule down such tubes which would keep it from rubbing against the walls of the tube and destroying itself. We don't have a reliable way to keep the inside of said capsules pressurized and livable for passengers. We don't have a way to power such capsules through their journey. We don't have a way to deal with potential emergencies such as a stuck capsule, a tube breach, a capsule breach, or any of the other as yet unexpected problems which might occur. And of course we don't know what we don't know about technologies which don't yet exist!",
"Testing, research, energy efficiency, mass adoption. Hyperloops are in the very early stages of development. They are being invested in by a small number of people, which means that limited resources are being put into doing the design and testing required to scale up any designs. Energy efficiency is more of a personal opinion of mine. I think that hyperloops are a good concept, but keeping a 1, 10, 100, or 1000 mile long tube vacuum is not going to be an easy task. Nevermind engineering such a tube, which could in theory be done. Imagine the maintenence. Mass adoption is the other issue. As of now, it's marketed as a potential solution for individual travel, not group travel. But really, for it to pay for itself every it's going to have to adapt to a larger market, and not just cater to a few very wealthy individuals who participate in the project because it's a novelty."
],
"score": [
3,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7md4a8 | Why we still use towers to broadcast signals (radio,cell phone, etc). Why not small antennas that could be built anywhere with wires buried in the ground. | Technology | explainlikeimfive | {
"a_id": [
"drt2txv",
"drt2y6r"
],
"text": [
"Cost. It's cheaper to build a smaller number of antennas in locations that allow sharing -- this usually means putting them high up so their signals can get past obstacles. One phone antenna tower may serve users across up to 100 square kilometres. (Typically fewer, but still a large area.)",
"> Why we still use towers to broadcast signals (radio,cell phone, etc). Why not small antennas that could be built anywhere with wires buried in the ground. Tall towers are capable of transmitting signals long distances over a large area without having to actually go to those areas and build infrastructure directly. They are in one location which can be provided with power and maintenance with relative ease. Small antennas built all over the place would require going all over the place to build them and maintain them. Feeding them with wires buried underground also requires digging up huge amounts of the ground which, news flash, isn't easy. Dirt tends to be heavy and any time you want to start digging it becomes a huge problem. How do you figure you are going to dig a trench straight through a neighborhood, through people's yards and houses? Think you can run it down a road which obstructs traffic while you do it, requires approval from the local government, and all the while you are dodging other buried utilities such as water or gas lines? In contrast you can just build a big tower and blast radio waves through that neighborhood without any fuss at all."
],
"score": [
7,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
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