q_id
stringlengths 6
6
| title
stringlengths 3
299
| selftext
stringlengths 0
4.44k
| category
stringclasses 12
values | subreddit
stringclasses 1
value | answers
dict | title_urls
sequencelengths 1
1
| selftext_urls
sequencelengths 1
1
|
|---|---|---|---|---|---|---|---|
nu8wwo | Why does a full stomach lessen the effects of alcohol? | Is it because the food absorbs the ethanol which lowers its effects on the body? Because that’s what I assumed. | Biology | explainlikeimfive | {
"a_id": [
"h0whkpn",
"h0w6slv",
"h0w6swi",
"h0x2z6g",
"h0wiobb"
],
"text": [
"I once read that it was because when your stomach is empty, the alcohol proceeds straight to the intestines to be absorbed into your blood stream. But if there was solid food in your stomach, you stomach's sphincter would be closed, forcing the alcohol to wait there before being absorbed. This spreads out the absorption time, reducing the intoxicating effects, like others said, but also gives time for some of alcohol to be broken down by enzymes in the stomach and be rendered non-intoxicating.",
"It slows down the intake of alcohol in your small intestine, because alcohol is “watered down” by food, so its effects are lessened and prolonged in time. Otherwise, if you take a shot on an empty stomach, it gets sucked in almost immediately, and all at once, assuring you get a hard hit.",
"Nope. First you need to know alcohol is absorbed in the large intestine rather than the stomach. When you're belly is full it takes longer for the alcohol to get where it needs go go and there's more stuff to deal with for your body. Jn other words your tolerance is the same, stay up long enough and all the extra booze you drank will keep you entertained. :)",
"So basically with drugs the quicker something enters the blood stream the bigger the high. I had a professor explain it to me like imagine getting to 100 mph it feels way more exciting going from 0-100 in 6 seconds than slowly going through the gears. Like others have said the food slows the process of ingestion of the alcohol so you don't a big hit of it at once. You will still eventually get all the alcohol just in a more measured manner so you don't feel the big rush of getting loads dumped into your blood stream",
"Alcohol absorbs into your body all through your GI tract. Your intestines absorb it the quickest, while the stomach absorbs at a much slower rate. When you eat before, your intestines are more full so the alcohol spends more time in your stomach, slowly being absorbed into your body. When you drink on an empty stomach, the alcohol makes its way to the intestines where it's absorbed much quicker."
],
"score": [
88,
33,
27,
8,
7
],
"text_urls": [
[],
[],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
nu9hmk | How do keys in music work? Do they just pick random notes to flat or sharp? And what's the difference between a minor key and a major key? | Other | explainlikeimfive | {
"a_id": [
"h0wdhmj",
"h0weryo",
"h0wefi1",
"h0wiao1",
"h0x3rmz",
"h0wcxtf",
"h0wjmxd"
],
"text": [
"In music a Scale is a set of rules that the notes follow. It tells you what the relationship between the notes are. Jumping from one note to the one right next to it is called a half-step. It means that two notes are right next to eachother. A whole-step means you are jumping over one note, so if youre on a note, and going a wholestep up, that means that there is a note inbetween the two you played. So a scale tells us how far apart from eachother all the notes in that scale are. Theyre the rules. How many Half-Steps, and Whole-Steps there are. I will mark Whole-Step as \"W\" and Half-Step as \"H\". So the rules in a Major Scale are: W, W, H, W, W, W, H And the rules in our Minor Scale are: W, H, W, W, H, W, W So now we know how the notes in our two scales relate to eachother. But we still gotta know which notes we should play!. So we pick one note, that we want to be our \"Root\". This is the very first note in our order, and if we know what the first note is, we know what all the other notes are since we know how far apart they need to be from eachother. So picking a root note is called choosing a Key, the Key is what the first note played is, and the Scale is how far from the first note all the other notes are. So G-Major and C-Major are both Major scales, but their first note is different, and so the following notes are different from eachother. But the distance between them is the same. Going from G to A is the same as going from C to D. Its a Whole-Step. They sound the same, one is just brighter than the other. What key you use depends on which one is the most fun to play, a piano will use more or less black keys depending. Other instruments will be tuned differently, and require different techniques. And a singer will have a specific range of notes they can comfortably sing, which will influence the key that the instruments play in. The difference between Major and Minor is how far the notes are from the root, and generally Major is seen as \"Happy\" and Minor as \"Sad\". So the notes being played in music dont matter, its the relationship between the notes. As long as the distance between all the notes are the same, the song sound the same. Minor and Major are different **Scales**, not **Keys**, so the distance between the notes are different, and so they sound different. As to which keys get sharpened and flattened it doesnt matter, but there is a system. When reading out the notes you want to keep the alphabetic order as good as possible. The notes we play with are A, B, C, D, E, F and G. Ill represent a sharp as \"#\" and flat as \"b\" So if im counting my notes in C-Minor, i can do it like: \"C, D, D#, F, G, G#, Bb\". But it gets messy, i have two D's and two G's, and im missing an E and an A. Hard to memorise. If i choose to flatten those notes instead though i get: \"C, D, Eb, F, G Ab, Bb\". And now its all alphabetical, and no repeat letters. Ab and G# sound the same, which one is used just depends on the alphabet. Makes it much easier to memorize.",
"Think of the notes on a piano. The shortest distance between two notes, for example from a white note to the black note immediately above or below it, is called a semitone. So C - C# or B - Bb is a semitone, and so is E - F and B - C, because there are no black notes in between these white notes. A tone is made up of two semitones e.g. C - D (two white notes with a black note in between) F# - G# (two black notes with a white note in between) or even B - C# (white, white, black). Every major scale has the same pattern of tones and semitones between the notes of the scale, regardless of the starting note. That pattern is tone, tone, semitone, tone, tone, tone, semitone. The easiest scale to visualise this is C major - it's played using only the white notes of the piano, because the pattern of white notes on the piano from C up to the next C follows that same pattern of T T S T T T S (T=tone, S=semitone). This scale has no sharps or flats because no notes need to be raised or lowered to follow the tone/semitone pattern. The next most common scales are G major and F major. If we play all white notes starting on G or F the tone/semitone pattern doesn't work so G major needs the 7th note to be F# to follow the pattern and in F major the 4th note is lowered to Bb. From then on subsequent major scales will add more sharps or flats (but not both) depending on the starting note to continue following the major scale pattern. For minor scales, the pattern is T S T T S A S (where A=augmented 2nd which is an interval of 3 semitones). This is for a harmonic minor scale, which is usually what people refer to when they talk about minor scales. Again the patterns of tones and semitones in each harmonic minor scale will remain the same regardless of which note you start on. Because major and minor keys have different patterns of tones and semitones for the scales they use, this gives them a different sound, or colour, to the listener even if both scales begin and end on the same note. It's why you hear people refer to major keys as 'happy' and minor keys as 'sad'.",
"This is also western music only. I figured that was assumed in major and minor scales. If anyone is familiar with other tradition's music, I'd love to read about it in a comment. (If you look at a picture of a piano keyboard, this will make a lot more sense Notes repeat themselves in divisions called octaves which go from a note to the same note at either twice or half the frequency. This is what going up or down an octave means. It's also what you're doing in the \"Do a deer...\" song where you start at Do and end at a higher Do. Inside each octave there are twelve notes. If you look at a piano keyboard, you'll see the keys are arranged in groups of twelve--7 white and 5 black keys. On a guitar, that's what the frets are, and the 12th fret is one octave higher than the natural string note. The two different keys are how we pick out which of the 12 notes are part of our progression through the octave. It does this by starting at the root note. This is what the C in Cmaj means. It's telling you to start at a C note. (On a piano, this is the white key to the left of the group of two black keys). From there we either go a \"whole step\" and skip a note to get to the next one in the scale, or we go a \"half step\" and use the next one. Conveniently, the piano keyboard is set up for the white keys to be the C major scale. We can now see that to get from one C to the next higher C takes a whole step-whole step-half step-whole step-whole step-whole step-half step, and takes us through CDEFGABC. Let's say we want to work out the E major key instead. We start at E (white key to the right of the two black keys) and follow the whole-whole-half-whole-whole-whole-half pattern. This covers an absolute TON of black keys. These black keys are what the flats and sharps are and we only call it a flat or sharp depending on which letter we call it. If it's a half step up, it's a sharp, and it's a flat when it's a half step down. The other rule is that we don't reuse or skip letters. Our E scale started as E??AB??E since we didn't know what the black keys were. Knowing what we know now, the next note is F. Except it's the black key a half step past the \"regular\" F so it's an F# (or F sharp). The same is true for all the other ones and the full E major scale is EF#G#ABC#D#E. For a minor scale, all the same rules apply other than the different pattern. Minor scales go whole-half-whole-whole-half-whole-whole. It's the same number of steps. It just has different \"stopping points\" for the notes. To see if you get it try the following: * What notes are in the C minor scale? * (Hard mode question) What minor scale has the same notes as the C major scale?",
"thank you for all your explanations... it all makes sense now",
"So different approach here to understand the physics behind it. Notes are just different frequencies. There are certain frequencies that sound good together. For example if you take a base (root) frequency and multiply it by 2 you get a nice sound (the same note just an \"octave\" higher). If you take a frequency and multiply it by 1.5 it sounds nice (perfect fifth). In western music we usually stick to eight of these ratios that we've decided sound good and call this group of ratios a scale. What's with those annoying sharps and flats? Well it turns out that our brains are annoying and the ratios we like don't follow a perfect pattern, so we had to add some sharps, flats, and nudge some other frequencies around a little bit so we could make instruments that are actually playable. Luckily for us our brains don't really mind the slight deviations.",
"Consider from each note to the next (so from C to C#) as an interval. The sharps and flats in a scale are based on the intervals. A major key is intervals of 2,2,1,2,2,2,1. So starting from C, two intervals is D, then E, 1 interval is F and so on. If you were to start from D, then two intervals is E, another two is F# and then G and so on. I can't speak as to why this set of intervals sounds good, and why the minor set sounds sad. But they're not randomly picked.",
"Let’s try this for everyone who’s less musically inclined. Here is a picture I drew of a keyboard on top and how it would look if we were less concerned with playability. URL_0 All the white keys have names (A-G repeating although we often start at C, more on that in a minute). The black keys are called sharps or flats, but for simplicity’s sake let’s call them +/-. So the black key between C and D would be C+ or D- (they are basically synonymous). When we play a scale in music, the most common way we do it is by using the pattern we get when we play all white keys starting on C and ending on C. Look at the bottom keyboard I drew. That means C (skip one) D (skip one) E F (skip one) G (skip one) A (skip one) B C. We call this a major scale. If we start go A to A on white keys this gives us a different pattern that we call minor. If we wanted to start on a different note we have to use the black keys to keep the same pattern. So if we start on G, to maintain the pattern we have to use F+ instead of plain old F. Basically you are transposing so the patterns stay the same but because of the way the keyboard is laid out you have to compensate by replacing some of white keys with black keys. Hope this makes sense!"
],
"score": [
409,
13,
6,
5,
5,
3,
3
],
"text_urls": [
[],
[],
[],
[],
[],
[],
[
"https://imgur.com/a/tRcOOpF"
]
]
} | [
"url"
] | [
"url"
] |
|
nuacpd | Why are the first pair of leaves on plant seedlings not considered "true leaves"? Are they just for "decoration"? | Cotyledon (the first pair of leaves) on plant seedlings often look very different from the eventual plant leaves. If they're not "true leaves," d o they not photosynthesize? Then why are they green & look like real leaves? | Biology | explainlikeimfive | {
"a_id": [
"h0wdwwd",
"h0wdz9u",
"h0whhwj",
"h0wdxa7"
],
"text": [
"They are real leaves. They simply are help the plant establish itself before the energy in the seed runs out. That is why they are so small and go away so fast.",
"They are real leaves and works very similar to the other leaves coming later. But they are also very different in that they are very simlpe in structure and can not grow very big. The seed usually do not have enough neutrition to grow a proper stem, roots and leaves. So these cotyledon leaves requires much less neutrition to grow and will give the seedling enough energy and carbohydrates to grow into a proper sapling which will grow the real leaves with the complex structures that is more efficient and can grow much larger.",
"They are the plant equivalent of baby teeth. The first leaves are functional, but are intended to provide food to the plant early on until it develops enough to grow its own proper leaves.",
"They are the embryonal leaves, meant to boot-start photosynthesizing which then provides further construction material for the plant to build itself. They may or may not look similar to the “true” leaves, which grow later using the carbon fixed by those first leaves. They are called “true” leaves, because an adult tree can have literally millions of them in its lifetime, and they are all the same, but the first two are different."
],
"score": [
28,
27,
13,
5
],
"text_urls": [
[],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
nuam13 | How do contact lenses stay put when we swim? | How do contacts stay in place when we swim? Shouldn't the water disrupt the surface tension between our contacts and our eye? Does it actually disrupt that surface tension and people i know have been super cautious? | Chemistry | explainlikeimfive | {
"a_id": [
"h0wek7s"
],
"text": [
"Water would need to get between the lens and your eye in order to pull it off. since contact lenses are directly contacting your eye, water can't get in. so ti can't pull them off."
],
"score": [
3
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
nub1h1 | How are large pieces of plywood made if they're even longer than tree trunks? | Technology | explainlikeimfive | {
"a_id": [
"h0wgoca",
"h0wggu7"
],
"text": [
"Plywood is made by gluing together large sheets of wood that are made by [peeling off the diameter]( URL_0 ) of the log, then cut to size and layered with the grain going in opposite directions,for strength.",
"Plywood is made by plying off a sheet of wood from the trunk. This looks very similar to how you would sharpen pencils and you end up with the long sheets of wood. You often see this in the plywood as the wood grain pattern is repeated over and over which is because it is all from the same tree but at different depths. In addition to this plywood is glued together allowing them to just put multiple plies next to each other. The glue and the other layers of ply will make it strong enough."
],
"score": [
18,
3
],
"text_urls": [
[
"https://youtu.be/eF5LVBW1vl8?t=106"
],
[]
]
} | [
"url"
] | [
"url"
] |
|
nub1xt | where does watery snot from a runny nose come from? | I am always surprised at the amount of watery liquid that comes from noses when it's cold outside or due to allergies but where is that stuff coming from? Like is there a reservoir of fluid somewhere in the head, or is it being glooped out of cells or out of the blood stream? Or something else?! | Biology | explainlikeimfive | {
"a_id": [
"h0wggu6",
"h0wl5ko"
],
"text": [
"It's mucus, which is secreted by the mucous membranes in your nose--all the individual cells contributing a little bit, which is why there can be so much.",
"Cells in the internal lining of your nose contain water (like all other cells really; life requires water), and they use that water and some chemicals to make and excrete sticky but watery mucus. It serves to stick to and flush out whatever it is that your body thinks is in your nose that shouldn’t - viruses, allergic particles, dead cells from infection etc."
],
"score": [
3,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
nub5fc | What is the survival strategy of moss? It seems to be everywhere, especially when there is shortage of resources. | Earth Science | explainlikeimfive | {
"a_id": [
"h0wo9pq",
"h0wzgdp",
"h0wj21o"
],
"text": [
"Well it depends are you talking about a moss or a lichens? Mosses tend to grow in moist environments where lichens (which are a combination between a moss and a fungus) tend to grow in dry places. Mosses will grow on the trees and ground and thats where they get their nutrients from, vs lichens that grow on rocks. Lichens breakdown the rocks that they grow on and that is where they get their nutrients. They literally eat rocks if that isn't a neich im not sure what is.",
"You're thinking of it like every creature, plant, insect, etc. has a business plan. Some things like moss Judy move into spaces randomly and out-compete everything else by needing virtually nothing.",
"I don't have a degree in biology, so someone might be able to explain it better, but basically evolution has allowed this organism to thrive in environments where resources are scarce. And being able to thrive in resource scarcity actually is an advantage, as there is usually less competition. As the character Ian Malcolm so eloquently put it in Jurassic Park: life finds a way."
],
"score": [
36,
6,
5
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
nubv9l | What's The Difference Between Software And Firmware? | Hardware is the part of the device you can touch, software the the part that makes it do stuff, so where does firmware fit in? Is it just a subcategory of software? | Technology | explainlikeimfive | {
"a_id": [
"h0wk74o",
"h0x1upw"
],
"text": [
"Firmware is software installed on hardware for the express purpose of telling the operating system or other components how it should use the hardware.",
"If you look at a Hard Drive. HDDs have their own circuit board with a processor, memory and motor controller and are pretty much a separate little computer on it's own. The software that runs that mini system is called firmware and isn't stored on the main computer or on the motherboard and very seldom (if ever) needs to be updated."
],
"score": [
9,
4
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
nubw9x | What is intersex? | I keep looking on google but I don't understand | Other | explainlikeimfive | {
"a_id": [
"h0ww32f",
"h0wkgen",
"h0y8i42"
],
"text": [
"Okay so imagine this. Let's say you were a girl and you knew yourself as a girl for most of your life. Growing up you did all the girl things that girls do. And then one day you find out that you're infertile and you will be so for life. The doctor does an X ray and finds out that apparently you have testes where your ovaries are supposed to be. Doctor says \"this can't be right\", does a chromosome analysis, finds out you have XY chromosomes You're technically a man if we go by simply chromosomes and gonads. But how's that possible? it's not true, you look like a girl, walk, talk and act like a girl. How can you be a man?! Outrageous! Here's how: you have androgen insensitivity syndrome. You have a genetic mutation that makes you literally immune to testosterone. Which means no matter how much of the stuff your body makes, none of it activates any receptors and it gets converted to estrogen instead. So now you have undescended testes and an actual vagina and uterus and the full kit basically, but not the ovaries. You are now one of the few people on earth who is sexually ambiguous enough to be classified as a 'intersex'. There are many people born this way and they are usually unable to fit into the box of male vs female. There are many conditions that can be characterised as intersex. Hermaphroditism, Klinefelter syndrome and AIS as mentioned above, to name a few",
"Intersex is a person born with atypical sex characteristics or ambiguous ones. Who constitutes as intersex is debated both medically and in intersex fields. There are various intersex syndromes. So, they could have ambiguous genitalia. They could have a penis but XX chromosomes. They could have a vagina and a prostate gland, etc., or any combination thereof. Some people say that since hormones are a sex characteristic, people who are assigned female at birth but have high levels of testosterone (or vice versa) technically fit the medical criteria of intersex, but that is heavily argued for and against.",
"Wow something I actually know about. So I'm intersex, and i didn't find out until a year into my male to female gender transition. The overwhelming majority of intersex people never find it. It is usually internal and only discovered during autopsies. Having different genitals externally is incredibly rare. For me, they found out once a doctor noticed my hormone level were strange. They eventually figured out I have ovotesticular disorder. This is just one of many possible intersex conditions. That means in the womb, my gonads developed both testicular and ovarian tissue. That's why, as a teenage boy, I developed C cups and had hips. Most people don't have their hormones closely monitored, and it's possible that many cases of infertility are the result of an intersex condition."
],
"score": [
32,
18,
3
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
nuc4o3 | Why can't anyone reduce an air conditioner or refrigerator down to truly portable size? | There seems to be a lower size limit for conventional, compressor-based refrigeration. The result is that portable cooling devices are always simple fans, or at best, evaporative cooling units. What prevents conventional refrigeration and air conditioning from working at sizes much smaller than a dorm refrigerator? | Technology | explainlikeimfive | {
"a_id": [
"h0wmn8m",
"h0wnp7e",
"h0wohp8"
],
"text": [
"Are you talking about walking around with a personal A/C unit strapped to your back and keeping you cool while you move about your day? The main issue is the fact that you'd basically be conditioning the atmosphere around you and net no benefit. A/C units work because they take heat from one location and exhaust it in another (window unit sucks room air into the fins, transfers the heat the the refrigerant, the now cooled air is blown back into the room, and the hot refrigerant is then cooled by the outside air and the cycle repeats). If you don't have a closed environment to pump the cooled air into and a separate environment to pump the heated air into you're just spending energy for no net gain. In order to have a mobile, air conditioning unit that you can take around with you, you'd basically have to wear a suit that traps the cooled air against your body to benefit you.",
"The HVAC system in a modern vehicle is not only portable, it’s about as small as practically feasible. The compression required by the system demands a fairly strong power source to drive the refrigerant pump. It’s not just a fan.",
"Cooling cycles don't generate cold. They simply move away heat, and thusly they need a hot side. Which means for these things to have any effect at all you need to be able to place the hotside outside of the room/system that you want to cool. If the entire device has a small form factor this wouldn't really be possible"
],
"score": [
14,
10,
6
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
nucabz | why do we make faces doing doing activities that don’t involve face, like writing with tongue sticking out, playing guitar, or trying to recall something vague? | Biology | explainlikeimfive | {
"a_id": [
"h0worpi",
"h0wr2gz",
"h0x1a9i"
],
"text": [
"There's a really, really close connection between *thinking* and *language*. Some believe that our species didn't actually become the clever monkeys we are until we started forming languages which helped us to cooperate with people we don't already know and trust. Point being from the moment you're born your mental development is closely tied to some kind of language learning, and no matter what culture people are raised in, facial expressions and body language are parts of how we communicate. So when your brain is doing X, and calling up all the memories necessary for X, and invoking all of the muscle memories it associates with X, it's not going to filter out irrelevant information or \"noise\" unless that \"noise\" actually interferes with doing X. Why the *specific* expressions associated with those particular deep thought processes, I don't know. Maybe writing invokes a lot of memories of talking, and sticking out your tongue is a comfortable way to stop it from waggling around in your mouth while you try to form the words you're using.",
"Imagine what communication would be like if you had to \"manually\" tell your face to make each and every expression all the time. We can exert a lot of control over it. But the default do-nothing setting is for your face to communicate without you thinking about it. This means you make faces constantly no matter what you're doing, even when nobody is around to see it. -- *That sticking your tongue out expression isn't really about the writing action. People who do that do it when they're puzzling over something, like what to write, or how to assemble a folding Ikea table. I'll hazard a guess that it's an unconscious signal for others to wait a bit and not interrupt. Because that's the message I get when I see it.",
"Contrary to other answers, isn't it (also) the following? Namely: In the motor cortex in your brain, areas that control the face and areas that control the fingers make up the biggest part of the motor cortex, and are also closely next to each other: [ URL_1 ]( URL_2 ) So: If you're writing or playing an instrument, and you're trying your absolute best at it, \"your brain\" does its best to activate that part of the motor cortex as hard as it can, so that some of the \"brain activation\" spills over/spreads to neighbouring parts in the motor cortex, and thereby activating muscles in your face. & #x200B; Edit: This article explain a similar effect (better explained and better sourced) in regards to [Why We Make Funny Faces When We Lift Weights?]( URL_0 )"
],
"score": [
29,
7,
3
],
"text_urls": [
[],
[],
[
"https://thebarbellbeauties.com/why-we-make-funny-faces-when-lift-weights/",
"https://personal.utdallas.edu/\\~tres/integ/mot2/2\\_08.jpg",
"https://personal.utdallas.edu/~tres/integ/mot2/2_08.jpg"
]
]
} | [
"url"
] | [
"url"
] |
|
nucc6v | How do spam callers call you from fake numbers with area codes that are relevant to you? | Technology | explainlikeimfive | {
"a_id": [
"h0wmpxw",
"h0wogc0"
],
"text": [
"The phone system is intentionally set up to allow spoofing the number you're calling from. Imagine you've got a business with multiple office locations. Whenever someone makes an outbound call, you want the caller ID to show your businesses inbound number. This is why you can spoof caller ID. As for how they get relevant numbers, it's because of the information collected about you along with your number. They may, for instance, scrape Facebook for hometown info and full in area codes to match. These spreadsheets of information get sold and traded around many times.",
"Phone spammers operate on the internet. There are exchange services between VoIP and PSTN networks, so they're making internet calls into the phone system. It is a feature of the phone system that they transmit a caller ID when they establish the circuit from caller to callee. It is a feature of the phone system that you can specify your own caller ID. This has a legitimate business application - call centers can have hundreds or thousands of numbers, but they want to present a uniform callback number to be identified by, and callbacks can route through their private exchange. So spammers have automated a system where they will present your area code, and then the rest of the number can be effectively random. The idea is to make you believe the call is local, and therefore somehow relevant to you, like it's a local business or neighbor. That might have been more effective 30 years ago, but since the age of the cellphone, I had a Chicago area code and lived in Portland. I don't think I've ever known anyone who actually had an area code in the area they actually lived. So if I get a call from my area code, I know for sure it's spam. As a bonus fact, by federal law, all calls must be connected. This goes back to the early days of the telephone network, when the military needed a reliable national network. They didn't want to deal with competing networks where your call would be connected only if you called from the same network, so it was a mandate that calls had to be able to cross networks and be connected, and carriers couldn't intentionally degrade connection quality or anything. So the phone companies know when a call is spam, but up until very recently, they've had very little they could do legally to stop them. You have to receive the call, and you have to be the one to decline it. But what they did manage to do is if a call is coming from an internet exchange, it's almost certainly spam. In that case, they can at least warn you that it's potentially a spam call. And this also works by blacklisting. A legitimate exchange business would keep spammers from using their service, and companies that use VoIP and don't want to be flagged as spam will pay money to use an exchange in good standing. Oh, and there are online services, they take a few steps to setup, but you can route calls through them, and what they do is any restricted or spam number, they can strip away the fake or restricted caller ID info. This is more helpful with restricted numbers and weird people you might know calling and harassing you. For spammers, this will get you the outgoing number at the exchange. That might not be a valid incoming number, so you probably can't call it and connect, and it certainly won't call back to the person on the internet. And it will also strip away the legitimate business use case. So if your bank were to call you, you wouldn't know them by the call center number they called you from, and you wouldn't necessarily know who to call back if your call was interrupted."
],
"score": [
3,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
nuclq1 | in tv shows how much of the next season they film while filming the previous one, for continuity reason and stuff, or how they make them transition seamlessly? | Because for example if you don't film part of the season 2 while filming season 1 how you can make the actors look just the same in the next seasons, especially when the episode is like cut in half or the next season start just after the first? | Other | explainlikeimfive | {
"a_id": [
"h0wp0ho"
],
"text": [
"Given the large break in between seasons, it is highly unlikely that any filming for a future season will be going while at the same time filming for a current season. For a TV Show, you're almost certainly only ever filming one episode at a time, as you have production schedules to meet and a single episode requires weeks of production around it. Continuity is maintained simply by paying attention to it and hiring staff to enforce it. The producers and writers will typically come up with what is known as a \"show bible.\" It's like the written wiki for that show, updated and maintained as the show progresses. That covers continuity at a larger level. Episode-to-episode is usually because you have a somewhat static pool of writers. They develop a collective tone and continuity over the series, which is why many series can change drastically if they writers change. Lastly, in scene-to-scene you have specific staff members whose job it is to make sure things look the same from shot to shot (since not all shots are done in show order) so that continuity is maintained."
],
"score": [
8
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
nucrzu | How do deep sea fish exist and how do they survive the harsh 4000m deep sea pressure? | Biology | explainlikeimfive | {
"a_id": [
"h0wouli",
"h0wovjx"
],
"text": [
"Fish are full of water, unlike land based mammals full of air, thus deeper water pressure equalizes them out internally",
"The pressure inside the fish is the same as the pressure outside. Water doesn’t compress very much so water can squeeze in at huge pressure, but fishes cells and tissues are full of water, so they don’t get squished. The only reasons humans can’t cope well with high pressures is our bodies are full of air in certain places like the lungs and sinuses and inner ear, and these gaps would squish inward under high pressure. But with the right compressed gasses to breathe and the right cautions traveling up/down, humans can tolerate a pretty large amount of pressure too. At 100 foot depth which humans can dive to, pressure is already 4x greater than the atmosphere yet it’s survivable."
],
"score": [
5,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
nud0xw | What causes the foam when boiling pasta? | Chemistry | explainlikeimfive | {
"a_id": [
"h0wr503",
"h0wsr91"
],
"text": [
"It's the starch that's seeping out of the pasta and mixing with the water. The same thing happens with potatoes which are also very starchy. Sometimes the left over starch water from boiling the pasta is used to make pasta sauces as the starch helps with the flavor and consistency of the sauce.",
"When you boil water, the water at the bottom of the pot is hotter in comparison to the water at the top. Since the bottom most layer of water is in contact with the bottom of the pot, it boils instantly, and when it boils, it creates bubbles of water vapour. This is why hot water has bubbles coming out of it. As with pasta, you may have noticed that the bubbles are a lot smaller and foamier looking. This happens because of the starch in the pasta. When you boil starch in a pot, some of it dissolves into the water, thereby creating pasta water. Some of this starch gets so hot that it rises to the top and creates a layer of hot starch that prevents water vapour from escaping, creating a foamy appearance. Fun fact: since the water vapour is trapped under the starch, the pasta water gets superheated. Which means, if you wanna scald someone horribly, boil some pasta, or rice or potatoes for 15 minutes and throw the water at them. All that pent up steam immediately escapes along with the boiling water. Double damage"
],
"score": [
4,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
nud51h | What exactly is “imposter syndrome”? | So I have my issues (much like anyone else), but someone described them as having imposter syndrome and I’m not exactly sure what that is. A cursory google didn’t really explain much so here I am! | Other | explainlikeimfive | {
"a_id": [
"h0wqzcd",
"h0wsq49",
"h0wtpu0",
"h0wr0qi",
"h0x1e62"
],
"text": [
"It's when you don't believe you are where you are because of your knowledge or talents. Like you don't deserve the job you have or the position you are in. Another way to think of it is when people like you, but you think it's undeserved (you're an imposter). The feeling your own merits couldn't possibly be the reason good things happen to you.",
"Imposter syndrome is feeling like you're underqualified for the position you hold. You feel like you've skirted by mostly by lucky happenstance, and that you don't actually have the skills to succeed in your position. You feel like you're going to be found out at some point and lose everything.",
"Imposter syndrome is an informal term (it hasn't been formalized as a diagnosis yet) where a person believes that they are unworthy of the things they have achieved and will be found out. Essentially a person, usually high achieving, feels like they got where they are due to luck or circumstance rather than skill or hard work, and that this is going to be discovered, that they will be revealed as an \"imposter.\" Most people are going to feel like this at some point, but there are some people where it is pretty constant and really causes them a lot of stress.",
"Imposter syndrome is basically the feeling that you are where you are in life not because of your own hard work and accomplishments, but because you've been lying through your teeth and that you're afraid people will pick up on it eventually.",
"Believing you're a fake, you don't deserve to be where you are etc An example would be a doctor, or research scientist, believing he or she only got to where they did by luck or personal connections etc and not by the merit of their work, their intelligence, how hard they work etc It's basically the feeling you *would* get if you did actually go and take a job you were unqualified for -- except (I would assume) the syndrome applies to people who are qualified yet still feel it, otherwise it's just kinda the truth xD"
],
"score": [
56,
14,
4,
3,
3
],
"text_urls": [
[],
[],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
nud63i | Why did old TVs require that the channel be on 3 before accessories like VCRs and game consoles could work on them? | Anyone who grew up in the CRT era of TVs remembers that you had to turn the channel to 3 before you turned on the VCR or game console. Otherwise, the picture would not work. Why was this so necessary? Edit: woah this blew up while I wasn't looking! Thanks for the replies! | Technology | explainlikeimfive | {
"a_id": [
"h0wsq4b",
"h0wt8d5",
"h0x4h1t",
"h0x4htp",
"h0yb1y6",
"h0ws1bx",
"h0xmibf",
"h0x3njm",
"h0x8dpi",
"h0xi5sh",
"h0wrffj",
"h0x0doa",
"h0xer6x",
"h0y3vo7",
"h0x4lzg",
"h0yoos4",
"h0xt0kf",
"h0x1nhl",
"h0yff8x",
"h0x3gjs"
],
"text": [
"Channels on old CRTVs that had TV *tuners* are basically different frequencies that you tune your TV to, like how you turn your radio to a specific frequency to pick up a channel you wanted to listen to. Edit: it was channel 3 (or the selectable alternative to avoid interference) because the NES/VCR had to be talking in the same \"language\" (channel 3 frequency 60-66 MHz, channel 4 frequency 66-72 MHz, or channel 5 frequency 76-82 MHz depending on where you live and which had the least interference for you). Back in that day we had no way of transmitting the image and sound from the game console or VCR directly to the TV like we do today with S-video, component, HDMI, Display port, etc. So the simple solution was to turn the image and sound into radio ~~waves~~ frequencies and transmit it to the TV like a TV station. To comply with Federal regulations this TV signal from the console would have to be very weak so that it wouldn't interfere with any other signal. This means that the console could only transmit the signal a few millimeters to centimeters. To get around this limitation they used coaxial cable to carry the signal but you still had to tune the TV into the frequency the console/VCR was transmitting at. This guy does a good job explaining that a NES and similar devices are actually mini TV transmitter stations. [~~ URL_0 ]( URL_3 ) [ URL_1 ]( URL_4 ) (I'm not sure what's going on with URLs today, people are saying my link is broken but when I click on their links, I get the exact same URL that I posted...) Edit: this really blew up. To clarify some things: * I accidently put radio ***waves***, the NES doesn't transmit (yes it's a transmitter) radio waves, it transmits electric Radio Frequency (RF) to the RF modulator/adaptor that translates that signal into the frequency range used by the selected channel. (There's probably something I don't understand about this as I understand modulation is changing the frequency rate to transmit more and varied information u/maxwellwood did a great job expounding on this [here]( URL_2 )). * Technically speaking anything that transmits electric RF also inadvertently transmits radio waves in the form of electromagnetic RF radiation. This is mitigated. Blocked by what is known as shielding. * Yes, I know about the two screw antenna connection. Technically, a coaxial cable is that two screw connection bundled into a single, shielded cable with a universal/standardized connector. * Yes, you can transmit your game console's frequency over the air to your TV with the appropriate Electric RF to electromagnetic RF amplifier. All electric RF produces radio waves as far as I'm aware whether on purpose or not. Doing this while remaining in the grey area of legality in most countries would get you a pretty crappy signal to the TV though at any distance you couldn't just use the cable. * All cables used to take audio/video (AV, A/V) from a device to a TV is a transmission of data regardless of electric verses electromagnetic.",
"Very similar to those audio device adapters which transmit on particular FM station frequencies, it's a very very localized pirate radio station. Except the switchbox was a direct interface to the antenna input, and did not transmit into the air. Channel 3 is a particular frequency and was commonly unused in most places (over the air) so there would be less interference/collision. If you area did have a channel 3 over the air then you had the choice of 4. And no market had channels immediately next to each other due to bleed-over, so if you had a 3 you didn't have a 4 or if you had a 4 you didn't have a 3. Usually the channels were 2,5,7,9,11 or such, nicely spread out, many markets didn't have a 3 OR 4 at all. Of course when over the air was mostly replaced by cable, there was less need for channel separations. And digital has no neighbor-bleed problem at all.",
"Older TV sets did not have inputs for devices. They could only display pictures that came in as TV signals. So the devices had to emit a TV signal. TV signals have to be on some channel. By convention channel 3 was used (only a few areas had a Channel 3 station).",
"When TVs were invented, it never occurred to the manufacturers that they could be used for anything besides broadcast content from regional television stations. That's what they are set up for: VHF broadcast reception within several predefined channels. When the first home video devices were invented (VCRs, computers, video games, etc) the only way for your television to recognize the signal was if the device in question created a signal identical to what the broadcast station would create. Conveniently, most televisions had the ability to connect an external antenna in the back. All your device had to do was convert the desired composite video into an NTSC broadcast signal with appropriate levels, and feed it into an antenna cable, which you wired directly to your television. The last step is telling your television where to find the signal. Most devices broadcast on either channel 3 or channel 4, and there was usually a switch on the back to choose.",
"Here's a cable TV company [\"Keep It On 3\"]( URL_0 ) customer education series of commercials from 1995, produced so that people with cable boxes didn't tie up the Customer Service lines, and trigger truck rolls, just because they didn't have their damn TV sets on Ch 3. OK, I made this. I went nuts. Managers gave me this assignment, they expected just a single commercial, perhaps with a service tech, wearing hardhat, standing in front of his van, saying: \"Please keep your TV set on Channel 3.\" Instead they got this.",
"You would have your normal cable line that had all the channels on it. You would plug this into your VCR. You plug another cable from your VCR into your TV. When your VCR was idle, it would just forward the signal from its line in onto its line out. However, when your VCR was on, it would interrupt the signal for one channel and put its own signal on that channel instead.",
"Is this a US spesific thing? Cause I had several CRTs growing up, the oldest one being from the 70s (which only has 2 tunable channels), and every one of these would work directly with game consoles.",
"Can someone explain like I'm 5 instead of talking about switchboxes, frequencies, bleed-over, accessories and TV transmitters. Fack",
"It's a cultural thing. In the UK we had two dedicated AV channels which didn't take up existing channel slots. And as far as I can tell, this is still the case for TV that don't have digital channels built into them.",
"I never got this - all the analogue CRT TVs I had were tunable, I used to put the console on channel 6 because we had 4 TV channels and I'd put the VHS on 5. Did American TVs not let you do that?",
"The accessory had a built inn TV transmitter. It would not output a high power signal so you could not use it to transmitt the signal over the air very far. But if you connected it to the antenna cable in your house it would be picked up by the TV. You would often be able to select what channel to transmitt on which would have to match the channel on your TV. But some channels such as channel 3 and 7 were common ones. This would be so that you did not accidentally transmitt on the same channel as your local TV station as then you would not be able to watch this TV station.",
"The joy when you found the right channel and you could hear the music and see Mario jumping around. You can hear it in your head now, right?",
"each channel is a different frequency. let's pretend that you have three people sending notes to three other people, but they're couples, and you can't mix the notes up. you mark each note with a color. now each person knows which note is theirs when they arrive frequency is how they're all sent together but the tv can know how to separate the channels old tv's didn't have extra inputs. it was the antenna or nothing. so you have to get a splitter so you can have more than one thing going in. and to the tv, it doesn't know what's connected. it just looks for the tv signals, so basically a signal that has all of those frequencies (like the colors in my example). so the vcr and nintendo and such all came with their frequency set to use the frequency that channel 3 is. (but not all, some used different ones, but not often) so, to be clear, let's say in the people example, let's say these notes are like the written subtitles for the different tv stations. you now get a new source of subtitles, how about a nintendo game. you just know that all extra sources send notes with a red label. so to view these outside sources of information, you have to go to the red note guy, as he is receiving them. and in the same way, the tv just thinks you want to watch whatever is being broadcast on channel 3. it thinks you're receiving this from the antenna. it doesn't know that you have a vcr or nintendo i think either 3 was the least used tv channel or maybe it was set aside for this purpose, but it's what everyone used for extra sources of media",
"Atari 2600 had a switch for 3-4 in case the channel 2 in the area was too strong and interfered with 3.",
"You used to have to hook up consoles to TVs using something called an \"RF adapter\" - radiofrequency adapter. This adapter would sit between antenna/cable and your TV. The way it would work is it would knock out the signal on that channel and replace it with that from your console. These adapters were noisy and sucked. For car audio, before aux inputs became standard on cars, they used to sell adapters that worked in a similar manner - you'd plug them into the cassette tape in the stereo, and they'd broadcast a really strong signal on a certain FM channel and occlude whatever was supposed to come over the radio that way, and those adapters also sucked and were noisy.",
"I don't feel like the other answers here really make this as simple as it could be, so I'm going to summarize my [video]( URL_0 ) on the topic: Televisions sold prior to the 2010s were mostly intended to receive a picture sent by a TV station over radio waves, called a \"signal.\" There are multiple TV stations in every town, so to keep signals from interfering with each other, they use a process called \"modulation\" which lets all the stations send the same kind of television signal, but using radio waves of different \"frequencies.\" A TV set can receive signals of many frequencies, then choose one and ignore the rest. This is called \"tuning,\" and it's how you choose one program to watch out of the many available. TV stations all use standard frequencies, to make sure every TV can receive from every station, and for convenience those frequencies are given numbers, and called \"channels,\" so channel 3, 4, 5, and so on, are always the same frequency no matter where you are. Although you can make a TV signal that isn't modulated, which we started calling \"composite\" when it became popular, there was nowhere to put that kind of signal into many TVs made before the late 80s. Old TVs only understood how to receive pictures on the standard TV station channels. To solve this, VCRs and game consoles all contained tiny \"TV stations\" that produced a very weak signal - too weak to travel through the air, but strong enough to be recognized by your TV if you put it into the antenna input. Your VCR had to send the signal on one of those standard channels, so the manufacturers chose channel 3, because it was available on every TV ever made, while some other channels weren't. Sometimes you already had a channel 3 in your town, and that could cause interference, which is why you could also switch your VCR to channel 4. Because of how television signals work, there can never be a channel 3 and 4 in the same region, so if you already had a real channel 3 station in your town, you'd use channel 4 on your VCR, and vice versa.",
"In France you had to set an unused channel and turn this $@?! wheel indefinitely until you see a scrappy picture.",
"You only had to do that when connecting via the TV's antenna or coax jack. With any other inputs, like composite or s-video, you did not. As for why, it's self-evident, don't you think? With the tuner input, stations are selected by channel. Your VCR or game console \"station\" can't broadcast on EVERY channel, so you have to tune into its channel.",
"Didnt have to be 3. You could use any channel. My house used channel 8 for whatever reason for the vcr/console. Channel 3 wouldn't have worked as here in the UK we have ITV which is traditionally associated with channel 3 following BBC 1 and bbc2. We also have Channel 4 which would obviously be tuned to 4 and later came channel 5 which you would tune to 5.",
"In the US it seems that each channel had a very specific part of the frequency spectrum. 3 or 4 was usually empty so that was a good place to put in the console. The Console/VCR was setup to \"broadcast\" to that frequency. As far as I know, in the NL where I grew up, there was no standard channel distribution - you had to look up the frequencies in a little book and setup each channel separately. Probably because it's a small country and there is no need for many overlapping broadcasting areas."
],
"score": [
8226,
596,
329,
156,
120,
28,
22,
21,
21,
16,
15,
10,
8,
4,
4,
4,
3,
3,
3,
3
],
"text_urls": [
[
"https://youtu.be/8sQF\\_K9MqpA~~",
"https://www.youtube.com/watch?v=8sQF\\_K9MqpA",
"https://www.reddit.com/r/explainlikeimfive/comments/nud63i/eli5_why_did_old_tvs_require_that_the_channel_be/h10vhzt?utm_source=share&utm_medium=web2x&context=3",
"https://youtu.be/8sQF_K9MqpA",
"https://www.youtube.com/watch?v=8sQF_K9MqpA"
],
[],
[],
[],
[
"https://www.youtube.com/watch?v=QYOImTAV4Zg"
],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[
"https://www.youtube.com/watch?v=8sQF_K9MqpA"
],
[],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
nudn3p | What exactly is genome sequencing and why is it important? | Biology | explainlikeimfive | {
"a_id": [
"h0wuwfu"
],
"text": [
"A genome is a map of an organism's DNA, and sequencing is the process in which science can tell what genes do what to the body as it grows. For example, one set of genes when organized a certain way, tells the body to grow sharp pointy teeth, while a different way has the body grow a normal chicken beak. By sequencing the genome, we can find problems in DNA, and even try to edit the DNA to remove those problems. Allergies, propensity for cancer, nearsightedness, even predisposition to obesity and diabetes can all be linked to parts of your DNA, and knowing what part does what helps us treat and understand."
],
"score": [
3
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
nuduvk | How do batteries 'store' electricity? I understand that if you put electricity into a battery, the electric stays there, but how does that work? | Technology | explainlikeimfive | {
"a_id": [
"h0wvii8"
],
"text": [
"It's chemistry. There a many different kinds of battery but in general they have two metal plates, called \"Cathode\" and \"anode\" or \"negative side\" and \"positive side\", respectively. Between these plates is an unstable chemical that given the chance wants to react with the cathodes and anodes, releasing electricity as it does so. The reaction will only proceed if the battery is placed in a circuit where it can push it's electricity through the circuit. In other words electrons need to be able to leave the battery via the cathode plate and fresh electrons need to be pushed into the battery via the anode. If electrons can't leave and be replaced, the chemistry can't occur and the battery remains charged. Overtime, as the electricity is produced, the chemical reaction slows down and eventually stops, in other words, the battery is \"dead\". The chemicals in some batteries can be reset by applying an electric charge, backwards. They can then be reused and recharged again and again. Other chemistries don't allow this and once depleted are replaced."
],
"score": [
14
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
nudzwe | What physically is the difference between a charged particle and a non-charged particle or electron? | Physics | explainlikeimfive | {
"a_id": [
"h0wvvi4",
"h0wvyav",
"h0wwhob",
"h0x19gl"
],
"text": [
"The difference is that charged particles have charge. Charge is just a fundamental property of a particle that measures its interaction with the electromagnetic force.",
"You can't have an electron without charge. Charge is intrinsic to the particles, if you change it enough to not have a charge then it becomes a different particle. A proton for example with a positive charge is composed of two up quarks and a down quark. A neutron with no charge is composed of one up quark and two down quarks. An electron is elementary, it has no smaller parts.",
"\"Charge\" is a fundamental property of an elementary particle, along with its mass and another property called \"spin.\" Sorry to say, but the physical difference between a charged particle and a non-charged particle is simply that: one has charge and the other does not.",
"You've got to understand that somewhere at the bottom of physics there has to be something that is both the what and why at the same time. We call these the fundamental interactions. We call them fundamental because we have been unable to divide them in any way. And the thing about the fundamental interactions is that they are the reason for themselves. For instance a nail stays in a board because of friction not because it's a nail, so that's something that does something for a reason that is not itself. But charge is charge. The reason for charge is charge. Charge basically claims the space around the particle and imbues that space with a tendency to do things. In particular if two like charges are brought into close proximity they both generate a force that repels each other. If unlike charges come together the imbued force attracts. And we know this is because the constituents of things like electrons and protons and neutrons, that is the quarks, have fractional charges that either add up to 1, -1, or 0. You're asking why, but that is the why. So as you work your way down through physics everything is caused because of something. A happens because of b. B happens because of c. But at the very bottom the four fundamental interactions happen because that's what they do. They're actually lots of places in your life where you hit these fundamentals. Why are all positive numbers greater than zero? Well that's just what it means to be a positive number right...? Meanwhile, we may one day find out the charge has a 'why'. If we do discover that some property of quarks does something weird to spacetime the blah blah blah that thing I can't imagine that causes charge then that will become the why and that thing I can't imagine right now would become the new fundamental interaction. So it's a good question, and it's a question that I'm sure someone somewhere is still studying and hoping for a higher power to particle accelerator to probe into, but for right now it just seems to be the rules."
],
"score": [
10,
8,
3,
3
],
"text_urls": [
[],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
nue6x1 | Why do we feel hot when it's 37°C outside when our bodies are running at that same temp anyway? | Biology | explainlikeimfive | {
"a_id": [
"h0wx4uc",
"h0wxnz3",
"h0wxwt5"
],
"text": [
"Because our bodies are constantly creating heat, and if the heat can't go outside, the body starts heat up more. To counteract this, we sweat.",
"Primarily because your body is always generating heat, and always trying to maintain that 98.6F/37C temperature. Your body is much better at generating heat than it is at dispersing heat, and it primarily disperses heat by sweating. Sweating coats your body in water which can cool you off IF the ambient temperature is lower than 37C. But if both you and your environment are 37C, there’s no cooler s place for your body heat to disperse into, and so sweating doesn’t work nearly as well.",
"Your body produces heat, even doing nothing. Just lying down you produce about 60 Watts of heat, just from being alive. If you can't lose that heat to your surroundings you will heat up. The two main ways of losing heat is radiation and convection. When you are the same temperature as your surroundings, you cannot radiate away heat: you receive it as quickly as you get rid of it. So your body keeps cool by making you sweat a lot, this cools you through evaporation. However, at that temperature your body is operating close to its limits. To stop you from doing unnecessary activities and risk overheating, you body makes you feel sluggish and uncomfortable."
],
"score": [
20,
9,
5
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
nuephm | Is there a limit to how bright things can get? | Physics | explainlikeimfive | {
"a_id": [
"h0x24n9",
"h0x2sgx"
],
"text": [
"Yes and no. Yes, because human eye’s can only perceive brightness to a certain extent. No, because the brightness of something does not care how much of it can be perceived by the human eye.",
"The only real limit is the total amount of available energy. The Big Bang was, in practical terms, the brightest thing that ever happened. It released all of the energy that currently exists in the universe as (sort of) light (What, exactly, happened is really technical. You can look up timelines on the Big Bang and see at what point the energy turned into matter and how.) Supernovas are the brightest things that currently still happen- a massive amount of their energy is released as light. When black holes eventually decay- far, far into the future, long after our sun is dead- they will be the brightest events in the universe. On Earth, the brightest things you're going to see are nuclear explosions, which release their energy primarily as gamma radiation (ie, light) which then turns into heat when it is absorbed into the immediate environment, which in turn creates a shockwave as the superheated air expands."
],
"score": [
57,
12
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
nug2ep | How much radiation can kill you? | please explain it in a scale that i can understand, also im asking because im doing research on nuka colas and seeing how much radiation it actually has. | Biology | explainlikeimfive | {
"a_id": [
"h0x7klz",
"h0xd067"
],
"text": [
"This chart is probably the best explanation/comparison that I've ever seen : URL_0",
"To add, there is the minimum lethal dose that will kill by the action of the radiation itself, and higher doses kill more quickly. However, repeated smaller doses (smaller than the minimum lethal, but still very large) can also be deadly. Lower doses can be deadly as well, causing (or significantly increasing the chances of) cancer or other major issues, and radiation burns in the lungs from inhaling ash can kill just by interfering with the lung function."
],
"score": [
15,
3
],
"text_urls": [
[
"https://xkcd.com/radiation/"
],
[]
]
} | [
"url"
] | [
"url"
] |
nugnlo | How is it possible to gain weight overnight ? | Last night I used my scale and saw that I was 92.7 Kgs. Right after that I went to bed, slept a good 8 hours without waking up and without eating or drinking anything. This morning, I stepped back on the scale after peeing. It showed 93.2 Kgs. How is that possible considerating I had 0 food / liquid intake between my two measurements ? | Biology | explainlikeimfive | {
"a_id": [
"h0xbj28",
"h0xbu9w",
"h0xn0po"
],
"text": [
"Scales are sometimes wrong for obscure reasons. Mine, for example, shear off 0.5 kg whenever they are next to a wall.",
"Measurement slop - or you changed into heavier pants. The scale is displaying a measurement down to 0.1kg but if you really inspect the manual I’ll bet it’s actually only rated as accurate to +/- 0.5kg. You will always lose weight overnight, exhaling carbon dioxide and water.",
"As folks have mentioned, your scale is at fault. Besides the scale just having slop, another thing to look at is the floor beneath the scale. If the floor is soft, or you move the scale between uses, or it’s on a hard floor but one that has give (ie, a flexing floorboard), those things can all influence measurements. Or you’re a sleep eater. They exist!"
],
"score": [
16,
8,
3
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
nuhfkh | - Why do meteors always streak across the sky and never seem to come straight at us? | I saw some explanations of this earlier but they didn't add up to me. Given how thin the atmosphere is compared to the size of our planet it seems statistically improbable that most space stuff would just skim the outer edge. If the case is that Earth is colliding with relatively static space debris that is in our orbit (like when we see regular annual meteor showers) then why aren't the streaks in the sky all oriented the same same way, but instead seems to come from all different directions, yet almost none of those directions appear to be coming right at us? | Earth Science | explainlikeimfive | {
"a_id": [
"h0xgwgz",
"h0xik8p",
"h0xft5w"
],
"text": [
"Ever see one of those [coin donation things]( URL_0 ) that looks like a big round shallow funnel? You start your coin rolling around the top and it goes around and around the funnel, losing height over time, seeming to travel faster and faster as its path gets tighter and tighter? Yeah - gravity is like that. It's called a 'Gravity well'. The center of the funnel? That's earth. The gravity well is HUGE relative to earth itself. Think about it - the moon is trapped in our orbit (actually it's very slowly escaping). The moon is 180,000 miles or so from us. That's how big our gravity well is. When an object gets close to earth and is moving slow enough to get trapped in our gravity well, it starts to get pulled in but the object doesn't just veer off it's current course and start plummeting at us, it spirals in, getting closer and closer, but going around and around, so that the angular impact with the atmosphere isn't unlikely, it's inevitable. In fact, having something come \\*DIRECTLY\\* at us from space is what's almost impossible. Why? Well - space is huge. I mean - freaking insanely big. And there's stuff flying around it in every possible direction, but in our solar system it's mostly all going around the sun the same direction as the planets - but I'm getting off point. The point is - with stuff able to come at us from every angle, and with us being this tiny, tiny little target in space - but with a much bigger gravity well. Almost everything coming towards us is going to hit our well, not us.",
"With the Earth moving through space at the speed that it is, and in orbit around the sun, it's very unlikely that a meteor will have the speed and \"aim\" required to hit us directly, which would cause it to \"come straight at us\". What tends to happen much more often is that the meteor is going a speed that falls within an appropriate range, and is aiming in a direction to hit a much larger target: Earth's Gravity well. It then gets caught and is pulled towards us until it enters the atmosphere at a curving angle and burns up across the sky. A meteor coming right at us would be like shooting a bullet from 200 feet away, and hitting a bullseye on a dart board moving sideways at 100 miles per hour. It's not very likely. It can happen, of course! But it's much more rare.",
"They do come straight at you, but if they are randomly distributed across the sky then ones coming straight towards you are fairly rare. The main reason you might believe they don't is that a meteor heading straight towards you is much more difficult to see compared to one streaking across the sky, it's trail will be very short and it might just look like a star fading in and then out."
],
"score": [
14,
4,
3
],
"text_urls": [
[
"https://www.youtube.com/watch?v=T0uwtmHt0v4"
],
[],
[]
]
} | [
"url"
] | [
"url"
] |
nuhrun | Why do wild animals sometimes save humans? | Other | explainlikeimfive | {
"a_id": [
"h0xjg6u",
"h0xj84h"
],
"text": [
"Many animals have social and/or parental instincts that kick in when they see/hear another member of their species in distress. Sometimes these instincts are a little too broad and they mistake a floundering animal that’s sort of similar as one of their own and try to help. Something like a dolphin or a horse with significant social behavior will naturally try to assist their own struggling friends and family, and may extend that courtesy to you if you’re looking particularly horse-like today. A crocodile has minimal social structure and is more likely to kill another injured crocodile - and will definitely extend that anti-courtesy to you instead.",
"I think their are too many variables to give this a well informed answer. But it lots of cases I would imagine it comes down to a natural drive we all have to aid and support the kin around us. While it all looks very different from animal to animal, many branches of the evolutionary tree and evolved to prioritize companionship and reciprocation of aid."
],
"score": [
9,
4
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
nuifls | what is that body experience that occurs when your falling asleep and it feels like you fell down hard and why does it happen? | Biology | explainlikeimfive | {
"a_id": [
"h0xmyhw"
],
"text": [
"It’s called a hypnic jerk (or many other names) and it isn’t anything serious. The majority of people report this experience right before falling asleep, and no one knows for sure why it happens. But there’s some competing theories. One is that it is an involuntary reaction to you heart rate slowing down. The theory is that sometimes when you fall asleep your heart rate quickly decreases, and that this triggers a response that something is wrong and you do that jerk that quickly wakes you up/speeds up your heart rate again. Another theory is that it is left over from our tree climbing ancestors, that our ancestors would jerk awake before falling asleep, which would help check that they were sleeping in a spot on the tree where they wouldn’t fall out and get hurt. Another theory is that things like anxiety, stress, or even working out right before sleeping all cause it. No one really knows for sure."
],
"score": [
6
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
nuj6r2 | Why is there such a thing as a “feels like” temperature? For example, in NYC, it’s 91 degrees today but the weather app says it “fees like” 99 degrees | Earth Science | explainlikeimfive | {
"a_id": [
"h0xq8w6",
"h0xqll0",
"h0xrtv0",
"h0xqlf1",
"h0xyzio"
],
"text": [
"A large portion of that has to do with the humidity in the air. 90⁰ with 10% humidity feels way different than 90⁰ with 95٪ humidity. The air can only absorb so much moisture based on its temperature. If it's hot and humidity, it's hard for the sweat on your body to evaporate. Since it's not evaporating and cooling you, it feels hotter than it would if the air was dry.",
"It's because the human body cools itself off via sweating, which can be much less effective in high humidity. Our sweat needs to evaporate off our skin to cool our body, but if there is a ton of water already in the air the sweat doesn't evaporate as readily and we can overheat easier. So scientists did a bunch of studying and modeling on the human body, how sweating works, etc, and came up with a general model for how humidity effects the \"average person\", it's not super futuristic science and needs to be taken with a grain of salt but we basically have a scale that says from humidity 20-40%, add 5 degrees F to the thermometer temperature, for 40-60% at 10 degrees, etc. So if in NYC the thermometer reads 91, and the humidity is 50%, the scale says add 8 degrees for a \"feels like\" temperature.",
"It is a calculated temperature based on humidity and wind in addition to the actual measured temperature. This is because we get cooled down by wind and when we sweat. But if the wind is calm and the humidity is high we do not get cooled down in the same way. So even though it is 91 degrees your body will experience it the same way as if you would in a 99 degree low humidity indoor environment where your body is allowed to sweat effectively.",
"Because what it \"feels like\" to you depends on your ability to sweat and cool off when the sweat evaporates. Literally your skin gets wet with water from the sweat, and the wind blowing \"forces\" it to evaporate, and the water \"sucks\" the heat out of your body to use as energy to go from liquid phase to vapor phase. That's how you can be \"ok\" in 100+ degree temperature outside, which is hotter than your body temperature of 98 (Fahrenheit). So basically a 91 degree humid air with no wind will feel equivalent to a 99 degree dry+windy day.",
"Your body does not sense temperature. Your body senses the rate of heat transfer to your surroundings. This is why grabbing a bag of ice from the freezer feels colder than a freezer meal in cardboard packaging. Your body feels heat leaving your hands and finger tips and tells you about it via the sensation of cold. It's a function of how fast the heat is leaving. Touching 30F cardboard is almost negligible because cardboard is a poor conductor of heat. Touching 30F ice feels very cold because ice conducts heat extremely well, and has a large specific heat, so it'll absorb lots of heat before changing its temperature much. So for the \"feels like\" temperatures, it's a function of how quickly your body sheds heat to the air around you. In areas with very low humidity, sweating is a very efficient process. If you increase the humidity percentage, your body can't shed heat as well because sweat doesn't evaporate as quickly. In addition, the air itself now holds more moisture, which holds more thermal energy. Surprisingly, humid air actually transfers heat less efficiently than dry air (even though water transfer heat better than air) and this is because water vapor changes the thermal properties of dry air. Because the air transfer heat more poorly, your body can't shed heat as quickly. The end result is your body feeling like it's hotter outside because heat isn't leaving your body as quickly, which is perceived as hotter ambient temperatures."
],
"score": [
13,
4,
3,
3,
3
],
"text_urls": [
[],
[],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
nujfle | Why do the eyes and nose water when we yawn? | Biology | explainlikeimfive | {
"a_id": [
"h0xueqi"
],
"text": [
"When your yawn, a lot of muscles in your face contract or get squished, this then squishes the ducts/glands that store and produce tears/mucus, pushing some of it out. Like gently squeezing a water balloon."
],
"score": [
11
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
nujqk6 | what's the difference between browning and burning food? | Like its all just a maillard reaction right? just to differing degrees | Chemistry | explainlikeimfive | {
"a_id": [
"h0xtsab"
],
"text": [
"No, it isn’t all just the Maillard reaction. The Maillard reaction in the terms of browning food happens as a chemical reaction between amino acids when there’s is enough heat energy to drive it. When things start to burn, it’s no longer the Maillard reaction, it’s now a pyrolysis reaction. Which is essentially the heat causing the molecules themselves to start to break down into smaller parts. This is the same reaction that happens when you burn a piece of wood, heat + fuel + Oxygen produces CO2 gas, water vapor, and leaves behind blackened remains that either are not fully oxidized (not fully burned) or are the remnants of what can’t be burned."
],
"score": [
16
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
nuk77w | How do apes maintain their muscles with barely any rest? | I know the amount of muscles they naturally have is mostly genetically determined, but how do they keep these muscles considering how they barely have any rest in between physical activities? How are their muscles able to repair themselves so quickly? | Biology | explainlikeimfive | {
"a_id": [
"h0xwl2e"
],
"text": [
"Apes aren’t as active as you think they are. They spend a lot of their time grazing and lazing in a fairly small area. The troop’s total territory may be multiple square miles but they don’t patrol it daily."
],
"score": [
9
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
nuk8ea | How do ants actually like “stick”to walls? | Chemistry | explainlikeimfive | {
"a_id": [
"h0xxgju"
],
"text": [
"They have tiny little claws. Put an ant leg under a microscope and you’ll see a bunch of tiny little claws that they can used to grab onto/hook onto things. Ants also have (Varying a bit from species of ant to species of ant) tiny hairs, adhesive pads, and suction-cup like structures on their legs that help them climb on close to any surface."
],
"score": [
7
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
nukaeg | why is it unhealthy to stare at phones for long periods of time (like on social media) but healthy to read books? | Technology | explainlikeimfive | {
"a_id": [
"h0xxa88",
"h0ybzhy",
"h0xwqze",
"h0y0hsz",
"h0yko3c"
],
"text": [
"Instant gratification is one concept related to this question. When reading a book, your brain is engaged in an activity that requires critical thinking and patience. To find out the ending to the book you have to finish it. The brain is ultimately rewarded with the satisfaction of completing the book and interpreting its meaning. This is delayed gratification. Social media is an activity that requires no critical thinking. It rewards your brain every 5 seconds by giving you “stimulating” information rapidly. This is instant gratification. One fear is that we are losing our ability to simply exist in our own skin and we use the instant gratification of phones to distract our minds. Also, it’s possible to have an actual addiction to social media.",
"Because smart phones are the popular technology. Go back a generation or two and kids were told they'd ruin their eyes from too much reading and they should go outside instead. Go forward a few generations and people will be told it's unhealthy to spend too much time on the holo deck and they should be using their phones instead.",
"it’s just the mental health component of excessive social media use that is bad. A lot of people cannot handle constantly comparing themselves to others and seeing everyone’s life highlights while they scroll through it on a tiny phone. I also believe the human brain cannot handle being exposed to so many people’s lives and feeling a little involved in it.",
"A few things. The main ones I can think of are quality, light, and positioning. Quality: books go through a quality control process. Books have publishers and editors who have the job of making sure the books are good. The language is correct, and the facts are true. Meanwhile, a load of the internet doesn't have this. So, on average, books are better intellectually than the internet. Obviously there are exceptions. The are a lot of really good, stimulating things online. And there are a lot of books that are pure mince (50 shades of twilight). But on average, books are better (at least historically). Light: screens can mess up your sleep cycle. They give off blue light (as part of the white light). This tricks your brain into thinking it's daytime, making you less sleepy. This is why looking at screens before bed is bad. Meanwhile, books just reflect the light in the room. Positioning: phone screens are small. This means we hold them close to look at. This can strain the muscles in our eyes, which can cause damage.",
"Staring at screens is unhealthy for many reasons, it can cause eye fatigue and headaches due to the flickering and blue light emitted by screens, that books do not. A screen to you looks flacid and constant, but infact if you take a slow motion camera it is actually constantly flickering and emitting \"blue\" light which is highly fatiguing on the eyes. Books do not do this at all, as they are, well not screens. This is why blue light lense glasses are excellent for office workers especially, it blocks out the Blue light and can deter headaches and eye strain."
],
"score": [
58,
16,
13,
11,
3
],
"text_urls": [
[],
[],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
nukj17 | If muscles can repair themselves after exercise, and bones can repair themselves after breaking, why can't we repair whole limbs that are lost? | Biology | explainlikeimfive | {
"a_id": [
"h0xyecd",
"h0xyptx",
"h0xyu81"
],
"text": [
"Because that repairing requires a starting point. Pretty much all repairs in the body start at what’s left of what broke, and move out over the damaged area. Bone starts healing at the remaining bone and moves outwards over the break. Skin that is cut/scraped off heals from the edges of the cut in. Muscles that have damage heal from the surrounding muscle cells dividing replacing damaged ones. If you completely lose a finger, you might get some bone growth and skin growth over the end of what’s left, but there’s nothing else left to grow out too.",
"Because there's a difference between fixing a break in something and completely replacing it. A leg isn't just some muscle and bone thrown together. The bones fit together in a particular way. The muscles are woven in to the bone, and the circulatory and nervous systems (blood vessels and nerves) are delicately woven throughout. Maybe another way to think about it would be fixing a house. If you break a few floorboards, it's easy enough to cut a couple of new ones to fill the hole. If a wall gets busted up, it can be rebricked and plastered to fit in the same place. But if you bulldoze a house, there's no scaffolding or framework to work from. You need to start from scratch, with the floor, the walls, and also the plumbing and electrics that go through the floors and walls.",
"Bashing the dents out of an old car and trying to build a car from scratch are two very different activities. Bone and muscle repair relies on living cells near the damage to replace the damaged cells in roughly the same positions that they should be. The repair job doesn’t require the cells to specialize into new tissue types or follow a complicated build plan. It’s just ordering a muscle cell to copy itself to fill in a space right next to it. Generating an entire new limb means trying to order multiple types of cells to construct a totally new formation. Obviously it *can* be done because they did it once, but the elaborate set of instructions and procedures that controls this is run just once and then disabled while you’re still a fetus. We haven’t yet found a way to selectively enable that process and get it started again. It’s disabled for good reason - you don’t want cells randomly trying to grow new arms in response to minor damage."
],
"score": [
11,
6,
3
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
nukyc3 | How is the galaxy suspended in space? | Physics | explainlikeimfive | {
"a_id": [
"h0y0hdb",
"h0y01dx",
"h0y0j2s"
],
"text": [
"It’a not suspended. To be suspended assumes there’s a point to which something is attached and is hanging freely under the influence of gravity. Galaxies (and everything else in space) exist where they are because their mass creates gravity that affects them and everything else. The same reason that planets in our solar system stay in their orbits around the sun is the reason our and other star systems hang around each other in little clumps and those clumps hang around together in bigger clumps, who are all revolving around more and more mass that forms the center of the galaxy. And so does our and all other galaxy interact gravitationally with other mass and clump where they do.",
"You have to put a force on something to move it. Other galaxies have gravity, which makes space things move. Galaxies push on each other and move through space and sometimes each other",
"They’re not suspended in space. Galaxies are bound together by gravity, and some galaxies are close enough to other galaxies to form clusters that are also bound together. However they are not suspended; they are traveling through space (quite quickly)"
],
"score": [
9,
6,
5
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
nulmtd | Why is a high surface to volume ratio important to cells? | Biology | explainlikeimfive | {
"a_id": [
"h0ybgy8"
],
"text": [
"The cell must pull nutrients from the outside and push out waste. The rate that this happens is based on the amount of surface area of the cell. Maximizing the surface area is the best way of ensuring that the cell gets enough nutrients and can excrete waste."
],
"score": [
5
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
numaem | How come one cherry can taste incredibly sweet and another from the same tree can taste incredibly sour ? | This is actually a question from my 6 year old that I realised I didnt know how to answer | Biology | explainlikeimfive | {
"a_id": [
"h0y7lkh",
"h0y9i75"
],
"text": [
"They develop from the same system, like your toenails, and probably develop at different rates, like your toenails. Source: familiar with cherries and toenails and 6 year olds.",
"It's the different ripeness of the individual fruit, since fruit become sweeter as they ripen. Ripening is the process of breaking down starch into sugars. This happens at the same time other stuff inside the fruit is breaking down, like the cellulose that makes them firm, so they get squishier as they ripen. Fruit on the same tree do not ripen at the exact same rate, so when a cherry is very sour it is typically unripe. It depends on factors like exposure to sunlight, position on the tree, how many other fruit are near it, when it first started forming, etc. Fruit may also first become ripe at a smaller size compared to each other. Fruit ripen because softer, sweeter fruit are more attractive to the animals that will eat and spread the seeds of the plant. [ URL_0 ]( URL_0 ) is a pretty in-depth article if you want to know more!"
],
"score": [
4,
4
],
"text_urls": [
[],
[
"https://kids.frontiersin.org/articles/10.3389/frym.2018.00016"
]
]
} | [
"url"
] | [
"url"
] |
numje5 | how early manually operated elevators worked | Ok so in the beginning there were no computer chips, and so the elevators had to be controlled via a dial manually inside the elevator, requiring an elevator operator, right? 1. Where was the power source? Was it on the lift or at the top of the shaft. If it was at the top of the shaft, how was it controlled, and if the motor was in the lift, then how was it powered? Was it via batteries, was there a set of switches that let you control the motor at the top of the shaft, or whatever? Was this constantly shifting wires/ pipelines dangerous? 2. How did they know where to go? Was there some kind of pipe where they could shout orders? I know that on every floor there's a button I can press, but what did they do when there was no button to press? How did they know where to go? | Technology | explainlikeimfive | {
"a_id": [
"h0yd41l"
],
"text": [
"Elevators work like a pulley, there’s actually two shafts. In one shaft is the elevator, in the other shaft is a counter weight that weighs similar to the elevator. Both hanging on a cable. Then a motor just spins that cable which does as much force as you’d think because of the counter weight, you don’t have to lift the whole weight of the elevator. For how the operator controlled it, there was a lever connected to a circuit that would tell the motor to rotate one way or the other, causing the elevator to move up or down."
],
"score": [
4
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
numqf1 | Why bugs always die on their back ? | There are multiple explanation online that varies from their center of weight, to relaxing position, weak legs, chemicals that hits their nerves... But nothing seem to be a definite answer, specially to answer why they turn on their back before dying at first. | Biology | explainlikeimfive | {
"a_id": [
"h0ycdcy",
"h0ycn4r"
],
"text": [
"When they get old, they don't have as much strength and dexterity. If they fall over onto their backs they can't right themselves back up. Yes, bugs too are susceptible to \"I've fallen and I can't get up\".",
"They’re top-heavy. The same way you would fall to the ground, likely into your front, if you suddenly fainted, bugs roll onto their backs. Your centre of gravity is high up in your abdomen if you’re biologically male and a little lower if you’re biologically female. This is how you can balance to stand upright. Unless you actively *keep* yourself upright, you fall. It is the same with bugs. A bug’s centre of gravity is very high on their body. When they are dead or dying, they roll like a Land Rover."
],
"score": [
9,
4
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
nunh8l | What determines the life span of an animal species? Why does a wolf only live for 10 years but a tortoise can live for 100? | Biology | explainlikeimfive | {
"a_id": [
"h0yeyr0",
"h0yedu7"
],
"text": [
"There are a variety of reasons. One important one is metabolism. Flies have a very “quick” metabolism. They live fast, need lots of energy, fly around real fast, and die young. They burn fast and bright like a cigarette. Turtles have a much slower metabolism. The speed at which they metabolize food and do other processes is slower. They walk slower. Digest slower. Grow slower. Die older. Like a slow burning cigar. In the eyes of nature, as long as the fly and turtle reproduce, then their lives were equally successful despite the vast difference in lifespan.",
"Each creature evolves to have the lifespan which is most efficient in its particular ecologic niche. Living longer isn't necessarily \"fitter\"."
],
"score": [
12,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
nunx67 | How do what know what happens when we sleep? How did we discover sleep cycles etc? | Biology | explainlikeimfive | {
"a_id": [
"h0yh9e6"
],
"text": [
"we used machines to measure the electricity in your brain. The output would change based on activities. Every time anyone sleeps, it switches to a different wave frequency. And when they're awake, it is in another different frequency. Once we figured that out, the rest was easy."
],
"score": [
4
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
nunz3c | How did the Antikythera machine actually work? | I know there were cogs that predicted eclipses but how do cogs predict eclipses?? | Technology | explainlikeimfive | {
"a_id": [
"h0yimps",
"h0yi2w9"
],
"text": [
"There's a fantastic YouTube channel where a guy is re-creating the machine by hand using only tools and methods available at the time. It's called Clickspring. He goes into a lot of how the machine works. Basically, all celestial motion is circles, and those circles happen at different rates. The earth rotates on its axis once per day, the moon rotates around the earth once every 30 days, the Earth goes around the sun once every 365.25 days, and the Earth has an axial tilt of 23.4 degrees. That means that depending on where the Earth is in its revolution around the sun, the sun will appear higher or lower in the sky. So what we need to find is a situation where the moon is between the earth and sun, the sun is at the right height at that time of day, and the observer is on the side of the Earth that's facing the sun. By using gears sized proportionally to each of those rotation times, you can track the movement of the Earth, Sun, and Moon in relation to each other at any point in time, then its just a matter of turning a drive gear an appropriate amount for the passage of time, and you can observe when the conditions for an eclipse will be met.",
"The machine modelled the movements of the earth and moon around the sun do that future alignments could be predicted. The cogs modelled the relative speeds of rotation."
],
"score": [
7,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
nuok5r | How can birds stabilize their heads so well? | Biology | explainlikeimfive | {
"a_id": [
"h0yq4nj"
],
"text": [
"The same way we stabilise our eyes so well. Our ears have balance organs inside them, in something called the vestibule. The fastest reflex in the human body is called the vestibulo-ocular reflex (VOR), and makes our eyes twitch when we move. Try walking or running along whilst filming a video on your phone. Things look fairly normal as you look with your eyes. But the video will look like it's jumping all over. This is because the VOR moves your eyes to stabilise what you see. Birds do a similar thing. But instead of just pointing their eyes in a different direction, they move their heads. I don't know if this is because it's better that way because of how their eyes are positioned, but that's the jist of it."
],
"score": [
3
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
nuokc4 | Why are brain wrinkles good | I understand it’s because a wrinkly brain has a higher surface area than a smooth one. But why is surface are better than volume? What make a surface neuron more influential then an internal neuron when determining intelligence? | Biology | explainlikeimfive | {
"a_id": [
"h0yl0fx",
"h0ym3ff"
],
"text": [
"Grey matter is the part of the brain that contains the most neurons and governs higher cognition. As it turns out, grey matter grows in a thin layer around the brain. So, increasing the brain's surface area, increases the amount of grey matter and thus intelligence. It is not known why grey matter only grows on the surface, and not completely through the brain.",
"for 99% of history brains were fairly simple balls of nerves. Automatic stuff to keep a simple animal breathing and reacting to stimulus. At some point something ended up going \"hey, what if we put a dense layer or nerves right around the outside\" and that worked super well for making complex behaviors but since it was around the outside everything started having to make more outside. If some guy was in charge of redesigning the brain they wouldn't do it that way. But brains evolve weird, you basically die if you mess with what was there already so a lot of brain evolution is \"don't touch this thing that works, make a new part\" and the new part ended up being a skin around the outside instead of going back to change the inner parts to be more advanced. So all the parts that make you breath and have your heart beat are all more internal and bottom and back to the brain, the complicated thinking parts are on the outside top and front"
],
"score": [
13,
6
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
nuoqku | What happens after you pass the sound barrier. Does vehicle control return to normal? | Physics | explainlikeimfive | {
"a_id": [
"h0yn45v"
],
"text": [
"Yes and no; weird effects related to unequal shock formation around the various surfaces of the aircraft (e.g. Mach Tuck) do tend to go away as you get beyond Mach 1. At the same time, though, if the aircraft is not designed to fly past the sound barrier, it's entirely possible that you won't be able to get normal control without slowing down as all of your control surfaces are in the \"shadow\" of the shock waves being produced by the aircraft."
],
"score": [
6
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
nuoxuk | How do sinkholes happen and not get noticed before building stuff like houses or streets on top of it? | Earth Science | explainlikeimfive | {
"a_id": [
"h0ynlds",
"h0ymzml"
],
"text": [
"If a hole is near the surface, you could do a test that is similar to sonar to find it, but this rarely happens because they cannot penetrate very far down. Another option is to bring a geotechnical company out and drill a bunch of test Boeing’s to see what the Stone is like (which happens anyways with most major construction) but even these will miss things because the Boeing’s are spaced out by dozens of meters, leaving plenty of space for stuff to hide. In generals sinkholes are only predicable by region. ie if you build in an area that has bedrock that is known to commonly get sinkholes (or just smaller holes in general which can wreck foundations even if the surface doesn’t cave in, the building can start to sink). You have a better chance of encounter a sinkhole. These areas typically have bedrocks with stones like limestone, that can dissolve from rain/acidic rain over decades. That’s the real problem with sink holes, even if you did do major testing a verified that there were no sinkholes or issues with the bedrock you’re building on. In 10-20 years there could be a sinkhole forming without anyone knowing, and 25-50 years, which is a common life span of a building/road/parking lot, you can have a sinkhole many feet across that is bout to collapse. The bedrock can just slowly dissolve out from underneath you. Edit: source, I work for a Foundation Engineering company that deals with sinkhole affected areas in the Northeast USA.",
"The hole wasn't there when they built the building. Something caused the hole, and it happened after the building was built. For example, you can get sinkholes around water pipes if the pipe springs a leak. The water washes the soil away from the pipe, causing a sinkhole."
],
"score": [
10,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
nupvf1 | - What is the "falling thing" people apparently experience when trying to sleep? | I keep seeing it popping up, whether that be in memes or comments. I don't think I have experienced this ever. Is this some sort of genetic thing? I tried searching it on Google, and the first result mentioned something like > What causes falling sensation while sleeping is the natural disengagement of the astral body - and I just stopped reading when it mentioned astral body. Is this just another thing we have no idea about or is there something to this? | Biology | explainlikeimfive | {
"a_id": [
"h0yt7t1",
"h0yt94r",
"h0z7i5k"
],
"text": [
"Our body relaxes our muscles when we sleep so we don't act out our dreams, however if your body relaxes all it's muscles just before you pass out it can feel like you're falling, which jolts you awake again.",
"This is likely referring to hypnic jerks. These are involuntary muscle spasms. They are often caused by excessive caffeine intake or anxiety, but can just as often be nothing more than a dream.",
"Try a military sleeping method. Breathe in for 4 seconds, hold it for 7 seconds and breathe out for 8 seconds. Do this continuously with your eyes closed until you feel as if you're asleep. Before I had tried this, I had never experienced falling asleep either so I hope that this helps!"
],
"score": [
22,
9,
3
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
nuqc0z | Why do antiseptics such as alcohol burn on open wounds? | Other | explainlikeimfive | {
"a_id": [
"h0yxdom"
],
"text": [
"They mess with the heat detecting cells in your skin, the things that let you know if somethings too hot. it reduces the threshold that sets them off to slightly below your body temperature. So your own body temperature is detected as being hot enough to burn you."
],
"score": [
4
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
nuqu68 | - Why are biological females finished physically/emotionally maturing before biological males? | And for that matter, is this even true? I was always told that females were done maturing before males when I was younger and I was wondering if there’s a scientific reason for this if it’s true. | Biology | explainlikeimfive | {
"a_id": [
"h0yyc1u",
"h0z7czi"
],
"text": [
"Probably because a species survives better when the females can reproduce earlier than later. Men of age 12ish all the way until they die can bust nuts so that’s never gonna be a problem.",
"The average ages at which girls go through the various stages of puberty are slightly lower than the average ages at which boys go through them, but it's not a huge difference, and there is a lot of variation between individuals. I'm not sure anyone knows why this difference exists - puberty is a complicated process and much of it is not fully understood. There have been a number of studies which have found that the age of onset of puberty is actually decreasing over time in various countries - again, it's not clear why this is, but most people think it probably has to do with changes in nutrition over time. I suppose it's even possible that the difference between girls and boys is also a culture-specific thing that has to do with male-female differences in diet, exercise, obesity rates, etc. As for emotional maturity, that's a very subjective concept, so I don't think you're going to reach a clear answer there. I see you're already getting a variety of answers suggesting reasons why the difference might be an evolutionary adaptation - please take them with a huge pinch of salt. First of all, it's very easy to come up with seemingly neat explanations for why some trait evolved the way it did. Often you can think of several equally plausible explanations for the same trait. Working out whether any of them are actually correct is often very difficult. But there's a deeper problem, because it's not even clear that this male-female difference *is* an evolutionary trait. It may be a result of environmental factors, or it may be a consequence of how puberty works at a fundamental level - i.e. maybe there is no change that could be made to our genes that would alter the male-female puberty age gap without also altering loads of other things. (if you want an analogy for that last idea: perhaps it would increase our evolutionary fitness if we could shoot lasers out of our eyes, but we're not going to evolve like that because it would require massive fundamental changes to our biology, not just a few tweaked genes here and there)"
],
"score": [
9,
5
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
nur729 | What is Cyclic Voltammetry and what does it aim to do? | Title says it all | Chemistry | explainlikeimfive | {
"a_id": [
"h0z2tj6"
],
"text": [
"It's been a long time since I've done this so forgive me any errors or omissions. You have some substance in a solution. Then you stick electrodes into it and apply voltage to it. You slowly increase the voltage to some set amount over time, then once you get to the max you slowly decrease it back down. The whole time you're measuring how much current flows, which in turn tells you about how much resistance the solution you're analyzing has at each level of voltage. This is generally done by some computerized set up or machine that controls the voltage and measures the current/resistance and plots it on a graph [like this]( URL_0 ). It's also generally done several times in a row. So you might go from 0V to 12V (or -9V to 9V or whatever) then back to 0V then back to 12V for several repetitions. This is where the word \"cyclic\" in the name comes from. So what's the point? Well we're measuring the electrochemical properties of whatever's in the solution. If you get nice smooth line instead of something like that picture I linked above, there's not much interesting going on chemically, it only really tells you about what the electrical resistance of the solution is. In that picture I linked, the substance is undergoing some kind of chemical reaction as the voltage goes up and down, specifically an oxidation-reduction reaction. Those two humps (one hump is oxidation, the other is reduction) going up and down tell you what at what voltage the reaction occurs. The size of the humps (peak current) tells you a bunch of stuff about the reaction that I can't exactly remember at the moment. There's a number of other things you can measure with this technique (and I'm surely forgetting most of them). One of the interesting ones though is that you can keep running the experiment for a long time having it constantly sweep back and forth. Then you can count how many sweeps it takes until the humps in the graph diminish in size by some appreaciable amount. This gives an idea of how many times the substance your measuring can react back and forth (this is a reversible reaction after all, though if you only get one sweep it means the reaction is not reversible). So, for example, you might be testing some material you want to use for a battery. This measurement gives an idea about how many times that battery could recharge."
],
"score": [
3
],
"text_urls": [
[
"https://en.wikipedia.org/wiki/Cyclic_voltammetry#/media/File:Cyclovoltammogram.jpg"
]
]
} | [
"url"
] | [
"url"
] |
nuraz0 | Why do long-haired people shed so many individual hairs everyday and yet they don't go bald? | Biology | explainlikeimfive | {
"a_id": [
"h0z1jw8",
"h0z3mhx",
"h0z1g0l",
"h0zwzdm"
],
"text": [
"You shed just as much as they do. Theirs is just, perhaps, more noticeable given the length.",
"They shed the same as people with short hair. But most of the hair lost in long hair daily is not due to falling out but due to breakage (because it’s easier to damage) and there’s simply more of it, so you see it.",
"Because each strand of hair goes through a growth cycle which ends with it being shed. If they are shedding some hairs every day, they are also starting to grow some hairs everyday, so they get replaced at about the same rate as they are lost.",
"My wife has hair almost to her butt and sheds like a wookie. It's just more noticeable than us short hairs. They don't actually shed more."
],
"score": [
23,
9,
6,
3
],
"text_urls": [
[],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
nus1xy | How do scientists interpret what some animals see | You get taught that animals see different colors. I was reading a book about animal senses and I thought how do we know what some animals see? | Biology | explainlikeimfive | {
"a_id": [
"h0z6va3"
],
"text": [
"When we dissect their eyes, we see similarities to our own eyes. We have structures called rods that are sensitive to low-light and peripheral vision and cones that are sensitive to colors. Humans have 3 cones (Red, Green, and Blue light sensitivity). Dogs have 2 cones. Blue and Yellow light sensitivities. So they don't see reds and the greens are yellow-y, not having a specific green cone."
],
"score": [
4
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
nus6q0 | What's the big deal about MIDI 2.0? | Why is the update to MIDI so important? What are the implications? | Technology | explainlikeimfive | {
"a_id": [
"h0zewaw",
"h0znl30"
],
"text": [
"MIDI 2.0 will enable a number of features currently not possible with 1.0, in particular, the MIDI signal can now be 2-way on the same cable, where previously you needed individual \"in\" and \"out.\" Because of this feature, the additional feature of \"profiles\" is possible. For example, if you plug a physical mixer into your DAW, the DAW can ask the mixer what it is, and the mixer can tell it \"I'm a Mixer!\" And the DAW will automatically map the faders, knobs, and buttons in your on-screen mixer to the appropriate corresponding items on the hardware. Another thing worth mentioning, 2.0 will be 32-bit, enabling better resolution of note velocity and even +/- cent tuning, per pitch. This enhances the \"realism\" of human expression when trying to capture it digitally. There are more features worth listing but hopefully this gives you an idea :) TL;DR the 2.0 update increases data resolution and provides quality-of-life improvements to everyone who uses MIDI.",
"Currently the implementation of MIDI 1.0 and the various revisions date back to around 1983 when the specifications for MIDI was implemented allowing various instruments to talk to one another, however the 1.0 protocol is only able to support up to around 34 notes of polyphony before you get drop off, but can be stretched, but usually only has around 2 or 4 different pressures of velocity that can be supported. Currently MIDI 1.0 is either 8-bit or 16-bit of information which is why some keyboards just are loud no touch control, while some are pretty good. MIDI 2.0 will allow two-way communication so two instruments no longer have to run in \"Master and Slave\" configuration usually in midi 1.0 your keyboard is the Master and the computer is the slave, accepting the information while the MIDI keyboard sends the signals. MIDI 2.0 will allow bi-lateral transmission between instruments and computers. So it should actually be able to support USB C, that said if you look at instruments such as the DX7 and its various revisions you will see that they have a MIDI in, MIDI Out, and Passthrough so it can be the master instrument controlling another MIDI enabled instrument, or be the slave following the another instrument or just allow you to dazy chain instruments together. Also this should allow much better things such as pitch control, the new DAWs for MIDI 2.0 should allow instruments and the program to communicate easily by requesting information to assign it. It also will allow the use of subharmonics allowing instruments to pull of feats that are not heard in western music by allowing each key to serve as a pitch bend in some. From what I heard it should make after-touch a more common add on."
],
"score": [
6,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
nus7j2 | Why does food's taste fade away the more we chew it? | Biology | explainlikeimfive | {
"a_id": [
"h0za847"
],
"text": [
"This phenomenon varies between different food types. Put simply, as you chew, your saliva dissolves the food in your mouth to help you swallow it. The first thing your saliva touches is the outer layer of your food. In the case of prepared meals like steak and pasta, the main flavor is on the outermost layer of your food, as you chew and swallow the saliva in your mouth it takes the flavors (herbs, spices, salt, seared crust etc.) down with it and you taste more of the remaining meat or wheat in these examples, which don't taste as flavorful without that outer seasoning. This is also why if you don't like the flavor of broccoli or peas, they taste worse the more you chew them, since the seasoning washes down with your saliva and the vegetable taste starts coming out. You'll notice that this doesn't happen with fruits, ice cream, or chocolate etc. since in those cases all layers of what you're eating have the same flavor."
],
"score": [
25
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
nusnyc | What is animal instinct ? | What is it ? Where is it stored ? Where does it come from ? How is it passed on from parent to sibling ? | Biology | explainlikeimfive | {
"a_id": [
"h0zze2k"
],
"text": [
"Instincts are complex innate behaviours, reflexes are simple innate behaviours. For instance, when a human baby is dipped underwater, it immediately holds its breath. That's a reflex. When a sea turtle hatches from its egg, it heads straight for the ocean. That's far more complex than just holding your breath so we consider it instinctual behaviour. The behaviour of complex living organisms is largely governed by brain chemistry and hormones in particular. When you find yourself in a surprising situation, it's a hormonal response that causes you to feel afraid, aggressive, overjoyed or any other emotion. And your behaviour will result from that. I'm sure you've heard of the fight or flight response in the face of something scary for instance. Something surprises the organism and the brain immediately gives a response that causes the organism to respond with aggression or fear. So now that we understand that brain chemistry can determine how an organism behaves. We're also closer to understanding how instinctual behaviour is \"stored\" or passed on from parent to sibling. Take those hatching sea turtles for instance. Sea turtles immediately head for the ocean by heading towards the brightest patch of the horizon in their field of vision. If they keep doing that, they'll find the quickest route to the water. There are many possible reactions a baby turtle could take after hatching: * It could lie still and rest after the exertion of hatching * It could start looking for food to replenish its energy after hatching * It could set off in a random direction * It could follow the scent of water (and risk ending up in the wrong body of water rather than the ocean) But lots of animals are hanging around for the express purpose of feasting on the hatching baby turtles. So natural selection means that the lazy turtles, the lost turtles, the wandering turtles are the first to die. And the turtles whose brain chemistry urges them to get moving, to head towards the light on the horizon and to get into the water are the ones that survive the most. The turtles who survive the most pass on their genes the most. Evolution simply means that for baby turtles, those whose brain chemistry urges them to rush for the ocean fastest are the best young survivors. And over time that means that every single turtle that hatches has the overwhelming desire to race to the water. That's instinct. And that's how instinct is stored and passed on. They are chemical balances in the brain that produce behaviour that is so beneficial to survival that pretty much every member of a species has it. Because all others die."
],
"score": [
4
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
nusqeu | why does our brain play tricks on us? Shouldn't it "protect us" by not scaring us? | I''ve posted this in another sub too but thought maybe I get a more detailed info about our brain here. Basically I read on the good old internet that if you stare for a period of time into the mirror that your brain will start playing tricks on you and scare you. Well I wanted to see for myself, indeed it did happen. A few times I thought I've seen someone behind me for a split second, or that my face moves even tho I didn't move a muscle etc. Why would our brain do that to ourselves since it could harm us by making us panic therefore it being bad for our brain? Is there any reason that our brain does that? I'm quiet certain it's not to protect us is it? Additionally does this maybe explain why people say they seen bloody marry or other ghost storys connected to mirrors? That our brain for some reason plays tricks on us? Since if we go into the bathroom and we expect to see bloody marry by doing that ritual that our brain tricks us and makes us see it just cause we expected it to be there? Maybe Im thinking too far Why does our brain do this? Shouldn't it do the opposite and protect us from it? | Biology | explainlikeimfive | {
"a_id": [
"h0zbfky",
"h0zbvd0",
"h10mozz"
],
"text": [
"I'm sure someone will give you a more detailed answer but to simply explain what our brain is up to: Or brain is wired to protect us from physical danger and harm, but it can cause us psychological distress while doing so. So when you're staring into a mirror, as you get used to the view in front of you, your brain start scanning for threats around you, and since the greatest threat cash come from behind you where you can't directly see, in a reflective surface your brain gets more active making sure there are no threats behind you. Now if in this situation you start to panic, small things like a dark spot in your vision from increased blood pressure can be taken as a threatening shape that you saw in your mirror. And since your brain can't fully process what it saw, it can make you think of ghosts of macabre images to match what you might have glimpsed at.",
"Which is more protective, getting scared by something that turned out not to be there, or not getting alerted when something was there? The first situation is a slight spook, the second is death-by-tiger. We evolved to err on the side of getting spooked, so no, the brain shouldn't \"protect us\" by not alerting us at the slightest hint of a threat.",
"To add to what others have said (correctly) about risk/reward (better to recognise 9 false risks and 1 real then 0 false risks and 0 real when it's there), it's also helpful to think about how we process our senses, particularly vision. Our brains are amazing pattern recognising machines. They take signal which is just light hitting certain cells in the eye, turn it into electric codes, then produce a coherent image. When information is missing, it fills in what it expects to keep a coherent conscious image of the world. For example, your field of vision contains a blind spot (where the optic nerve leaves the eye), and your peripheral vision is in black and white. We notice neither of these things because the brain uses a combination of information from our two eyes and our expectation/previous knowledge to construct a single, unified visual representation. The brain has a variety of patterns of light it looks for which are useful for building up the single image from the information it's getting. This is why we are so susceptible to visual illusions. Your brain is not tricking you - it is trying to make sense of incomplete (and sometimes contrasting) information. What you perceive is essentially your brain's best guess at what's going on. So in terms of these mirror tricks you're talking about, it's a combination of heightened attention to risk (especially if you feel as if you're in danger) and your brain interpreting light patterns. *It* is being tricked, not tricking you."
],
"score": [
14,
6,
4
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
nusuhz | How do cicada eggs survive over a decade? Wouldn't they be eaten or washed away by then? | Biology | explainlikeimfive | {
"a_id": [
"h0zcftc"
],
"text": [
"The eggs don't. The eggs are laid on tree branches and hatch after 6 weeks. It is the young cicadas which drop to the ground and burrow, attaching themselves to tree roots, that survive for long periods."
],
"score": [
10
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
nutcuw | Why do dolphins and whales die when they hit land if they have to come to the surface to breathe? | Biology | explainlikeimfive | {
"a_id": [
"h0zej9z",
"h0zei8r",
"h1036hq"
],
"text": [
"They’re so heavy that when the water isn’t supporting their weight, their lungs get crushed and they die. Basically, they’re too heavy to live on land. Which is why people work so hard to get them back in the water. Check out the concept of a buoyant force for more information.",
"The water helps support their weight (think how when you go swimming you feel lighter). Without the water to support them, they literally crush themselves so they can't breathe in.",
"A few reasons. First is that they evolved in water with the water supporting their weight, and on land, that's not happening, so the weight of their bodies actually crushes them. They also overheat because the water isn't keeping them cool like it normally would."
],
"score": [
68,
27,
4
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
nuttsb | If you trap a beam of light inside a perfect mirror sphere, where does it go? | Physics | explainlikeimfive | {
"a_id": [
"h0zhegs",
"h0zh75l"
],
"text": [
"Yes, but the reality is that real mirrors aren't perfect, so if you do that for a real mirror sphere, it will end up eventually being absorbed by the mirror and turned to heat. Each bounce will cost around 1% of the light being turned to heat even with extremely good reflectors. Also, you'd never be able to view it, because any device put in to view it would also absorb photons.",
"In a \"perfect\" mirror sphere...it would simply bounce around, ad infinitum. However, there's no such thing as a \"perfect\" mirror. Some light will always be absorbed, and the light would eventually (read: in a unbelievably quick manner) cease to be (inside the chamber)."
],
"score": [
11,
7
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
nuu790 | How do nucleotides work in mechanical terms | Biology | explainlikeimfive | {
"a_id": [
"h0zlepv"
],
"text": [
"I'm not entirely convinced you know what a nucleotide is. Because nucleotides *don't* self-replicate. They're the components DNA is made of and DNA doesn't self-replicate either; it's just information storage. Proteins ultimately do all the \"acting\", including the replicating of DNA."
],
"score": [
3
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
nuudpd | why do digital thermostats have both heat and cool settings, as opposed to a singular temperature control | (e.g why does 70 degrees on “cool” feel colder than 70 degrees on “heat”)? | Technology | explainlikeimfive | {
"a_id": [
"h0zm7e5",
"h0zmbir",
"h104alq",
"h0zmc8g",
"h10wwou",
"h0zt77m"
],
"text": [
"Depends on the thermostat, but generally cool is connected to an AC unit while heat is connected to a furnace. When heat is on the temperature might go above the selected temperature and when cool is on it might go below the selected temperature. It would be extremely inefficient to make the temperature be exact since a house has a pretty large volume. Thus the heating/cooling system is more of a greater than/less than system.",
"Instructing the system to repeatedly cycle between heating and cooling modes to maintain a narrow temperature range would consume A LOT of electricity/fuel as the system would potentially be running nearly constantly. While on a hot summer day, you really don't want to run the heater just because the AC ran a little longer than necessary.",
"There are two interesting parts to this answer. The first is covered by most of the other comments, in that it would be impractical to maintain the temperature at exactly one degree (e.g. 70). Instead it makes more sense to have a cool setting - \"keep it at least as cool as 70 degrees\", and hot setting - \"keep it at least as warm as 70 degrees\", to allow a little wiggle room. The other portion not covered in the other comments (at least so far) is that how cold or hot it feels is based on more than just the absolute temperature. Other interesting factors include things like direct sunlight, air flow, humidity, and air pressure. Besides the seasonal differences you may have for these that make you feel like 70 in the winter feels different than 70 in the summer, AC also serves as a dehumidifier, contributing to an AC induced 70 feeling different than a heat induced 70.",
"The same reason why analogue thermostats have them. \"Heat\" turns on the furnace and \"cool\" turns on the AC unit. Which is the same reason why one feels colder than the other. On heat the thermostat is trying to reach its sets temperature so the vents are blowing hot air. On cool the opposite it happens. In order to reguajte the temperature of the whole house the thermostat is place away from vents. So a room may be cooler or warmer than the set temperature when the thermostat turns off.",
"When you're cooling, the air conditioner is also dehumidifying the house. When you're heating, the heater does not dehumidify. This is why the same temperature will feel different.",
"70 is the goal temp, but HVAC systems use much cooler or much hotter air to efficiently get the temp to that level. An AC might blow 40 degree air, while a furnace blows 100 degree air. Each does do until the hot/cold air mixes with the ambient air to hit the desired temp. Also, an AC turns on and cold until temp drops to 70, while a furnace turns on to warm until it heats up to 70."
],
"score": [
84,
41,
11,
4,
3,
3
],
"text_urls": [
[],
[],
[],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
nuuj3f | Why do mortgages go 15 or 30 years? | Car loans have gone from 48 month payment terms to 60 months, to 72, even 120 months. Why are mortgages typically for 30 years? Do people really pay 30 years without moving to pay off the notes? Since housing prices are going up and wages aren’t keeping up, why aren’t there 40 or 50+ year mortgage repayment options to make payments more affordable? Thank you! | Economics | explainlikeimfive | {
"a_id": [
"h0zlw50",
"h0zl96j",
"h0zlpph",
"h0ztez5",
"h0zlra7"
],
"text": [
"There's an article on why 30 years: [ URL_0 ]( URL_0 ) summary: the original system was terrible (you only paid interest, then owed all the money, so people took out another loan, repeat this failure cycle), so the government stepped in. 30 years turns out to be affordable-ish monthly payment, but it's already pushing the boundaries of the risks lenders are willing to take on so there aren't longer terms typically available. As far as moving: no, people don't always life there for 30 years. Typically what happens is either: 1. The money from selling the house pays off the remainder of your mortgage all at once. So a new mortgage from the new owners pays off your mortgage 2. People rent it out for more than their mortgage taxes etc.",
"Because a 50 year loan would be very high risk. Maybe if the mortgage company makes you buy life insurance to go with it…",
"Balancing of risk between the supplier of the loan and the consumer of the loan. Short term mortgages skews the risk to the consumer whereas long term mortgages skews the risk to the supplier.",
"Mortgages are fairly standardized so they can be bundled and bought/sold easily by investors. Those are the time frames that seem to work best and thus were chosen as standard confirming mortgaged the government would back.",
"There are 40+ mortgages, the maturity date is up to your bank to negotiate. It's up to the banks to decide if they want to allow for long term mortgage. If they are now starting to shorten the maturity periods, it likely due to it being preferable to give you 30 years and allowing for refinancing once close to the maturity dates."
],
"score": [
13,
11,
8,
3,
3
],
"text_urls": [
[
"https://www.marketplace.org/2018/10/31/why-do-we-have-30-year-mortgage-anyway/"
],
[],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
nuvrng | When did smiling become a happy trait/facial expression? | Biology | explainlikeimfive | {
"a_id": [
"h0zt83q"
],
"text": [
"Even newborns can smile when they're happy. It appears to be somewhat innate to us. Naturally we have cultivated much social language around how and when to smile, but the gesture itself is instinctual."
],
"score": [
8
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
nuvrwj | Why does a lever work? | So i know a lever has two sides, the effort and the load. If the effort side is longer it means the angle is larger, but then it requires less force to push the load side. Does a lever work because the weight you are manipulating has been equally divided between the whole swing distance of the "effort" side of the lever? Am I thinking about this correctly? | Physics | explainlikeimfive | {
"a_id": [
"h0ztv67"
],
"text": [
"You're definitely on the right track. If the effort side of a lever is longer, then you are actually moving the load a shorter distance! So you are accomplishing less work. This means it takes less force. Or seen the other way, you are moving the lever farther, so you are doing more work even if each bit of work takes less force."
],
"score": [
6
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
nuw6l0 | How can IP Address be used to determine the location of the device? | I’ve seen social networks being able to track my device’s location “through my IP address,” and other websites’ privacy policy stating that they collect data such as IP address to determine your location. How does it work? | Technology | explainlikeimfive | {
"a_id": [
"h0zvaxv",
"h10y8oz"
],
"text": [
"Blocks of IPs are assigned to specific internet companies. Those companies publish Geolocation data for each of their network blocks detailing the general idea where the IP is located.",
"A little more clarification as this will undoubtedly become a bit more confusing as you think about it more. The location is returning to you is the location of your ISP. If you are in a smaller suburban town a few miles out of the city, the website will still think you're in that city because that's where your ISP is. When you commit a crime online and the police track your ip, they look up the ISP that IP is leased to and get a warrant to get the customer address of that IP address from your ISP and come for you. That is the only way to get a real, physical address from an IP."
],
"score": [
13,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
nuw98g | How does Apple’s “spatial audio” or other “3D audio” work when there are only two speakers? | Technology | explainlikeimfive | {
"a_id": [
"h10295h"
],
"text": [
"Humans locate sources of sound in space through frequency response cues (i.e., the bass/midrange/treble balance; for example, noises heard from far away will sound more muffled due to air absorbing the upper treble), the difference in time it takes for a sound to reach one ear before the other, the way the sound changes as you move your head around, and the difference in loudness between ears. Headphones and earphones can only simulate the last one and (to a much lesser extent) the first one because instead of letting sources of sound interact with your outer ear and other body parts naturally, you're piping sound directly into each ear. However, those interactions can be turned into a mathematical model by measuring how sound changes as you move a sound source around either a real or dummy human head (called a *head-related transfer function* or *HRTF*). You can apply this HRTF to audio digitally to simulate listening to something from speakers or live when listening to headphones. Also, sound bounces around real rooms, whether it's a home theater or an auditorium, which creates its own changes in when and how sound waves reach the ears. This can also be simulated through digital processing."
],
"score": [
3
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
nuwsw4 | why is cancer increasing in young people? | Is it just because we dont die of other things first? | Biology | explainlikeimfive | {
"a_id": [
"h0zyz3i",
"h10h8q8",
"h102srn"
],
"text": [
"The largest reason why it's increasing for young people is that our techniques and technology for the detection of cancer have improved significantly thanks to all the money thats been going in to cancer research for the past few decades. So we're catching it earlier and more accurately. Even the non harmful benign cancers are being caught sooner. The other reason is an increased awareness of cancer. People have been educated on what skin cancer looks like and that any unusual lumps really should be looked at by a doctor and not dismissed as something you can ignore.",
"Research suggests that millennials are twice as likely to develop some cancers as baby boomers were at the same age, and obesity is the likely culprit. Research has found that the incidence of several cancers is on the rise among younger adults in the United States.",
"There’s some evidence that prolonged/constant exposure to specific chemicals in plastics (BPA, phthalates, dioxins) might be contributing to increased cancer risks. Mostly through ingesting the chemicals after the plastic has been heated up and transferred into food/drink. The science is still out and studies are still ongoing and currently inconclusive... but I’m inclined to believe that has something to do with increased cancer diagnoses. It should be noted, however, that less people (relative to population) are actually dying from cancer these days. In terms of young people- I haven’t heard about a specific increase there. But yes, mostly the cancer rates are increasing because people are living longer and not dying of other things first. Majority of cancer cases are in people over the age of 60."
],
"score": [
74,
23,
16
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
nuxm9v | How can sunburns and sun exposure cause permanent skin damage if your skin is constantly replacing itself? | Recently read something about how a few bad sunburns when you're young can cause a large increase in cancer later in your life. How can you develop cancer several decades after you're burnt if your skin cells are constantly dying, falling off, and regrowing? | Biology | explainlikeimfive | {
"a_id": [
"h102zso",
"h106rjj",
"h102x93",
"h110wf4",
"h10om94",
"h1176bi",
"h10y75f",
"h10e90h"
],
"text": [
"One of the best ways to think about it is not as \"sun burn\" but as a radiation burn. The skin is constantly replacing the top layer but more severe burns penetrate deeper into the skin and surrounding tissues. Sometimes this can damage the skin all the way to the lowest skin layers and when the tissues heal scarring forms as the skin cannot adequately regrow across the urn.",
"Your skin is like a layer cake. The frosting is constantly sloughing off and being replaced, and the first layer sometimes takes damage but it can grow back. Getting a sunburn is like microwaving the cake.",
"Basically the sun sends out UV rays which go through our bodies, hitting the skin the hardest. These rays can damage the DNA in a cell, causing it to grow improperly. If enough get damaged in this way then it can present itself as a growth, or tumor. If a cell that tells skin how to make itself gets damaged, the same thing happens but more aggressively.",
"First of all the top layer of the skin is constantly replaced, but the lower layers aren't. This is why tattoos are permanent, and why superficial burns can heal completely but deeper burns won't. Also, the skin regenerates itself by dividing the cells. When a call divides it makes a copy of itself. If a cell's DNA is damaged then the new cells that come from that cell will have the same damaged DNA from then on, until that cell line dies. The UV rays damage DNA. Most of the time the DNA can be fixed or the cell dies. Some of the damage can't be fixed and the cell doesn't die, so any further copies of this cell will contain the damaged DNA. And sometimes this damaged DNA causes the cells to divide forever and become cancer.",
"We had a saying during Navy Nuke school: Good Daughters, Bad Daughters, Dead Daughters, No Daughters. When your cells are exposed to ionizing radiation, it can cause mutations. When that cell reproduces, it can not pass on the mutation (Good Daughter), it can reproduce, but the daughters die (Dead Daughters), the cell could die (No Daughters), or it can pass the mutation on (Bad Daughters). Cancer would be Bad Daughters, cells that mutate and then pass those mutations on.",
"The longer you are exposed to the sun, the more the plans for rebuilding get faded and harder to read. Over a long period of time, skin cells begins to have errors as the dna structure is mutated/damaged by radiation.",
"The sun's radiation is filtered through our atmosphere and a fraction of it reaches the ground level where we live. Of this, some is filtered through our skin too but a fraction reaches the ground level of our skin called the basal layer. When the sunlight hits the basal layer its either absorbed by pigments called melanin or its absorbed by other sensitive cells. When its absorbed by sensitive cells it can cause the burning sensation. This basal layer doesn't replace itself as quickly as the outermost layer of 'dead skin'. Interestingly, we only get exposed to a small percentage of the sun's energy. Imagine how burned you would get if you were on top of a mountain or high up in the atmosphere! Also, sunscreen works by adding an extra layer of filters at the top layer of your skin.",
"Human skin consist of three layers. The outermost layer called epidermis and responsible for protecting body from environment including UV lights. Epidermis have 5 more layer within. The ability of renewal of skin comes from this 5 layer. The deepest layer contains melanocytes which provides melanin to skin and basal cells. Basal cells duplicate and grow outwards and while going out they get less and less supply from body and slowly dies. But the basal cells are always there are functioning. Sunburn cause damage basal cells and melanocytes because UV lights are something called ionizing radiation. UV lights produces ions which interfere with duplication on cell nuclei of said cells. Little amounts of sunlight damage often can be tolerated but in sunburn situation cells are dying from nuclear damage from UV not from the sun heat. The basal cells are the type of cell that does the replacing process. But they aren’t replaced and thus the damage from sun exposure builds up entire life."
],
"score": [
41,
14,
8,
7,
6,
3,
3,
3
],
"text_urls": [
[],
[],
[],
[],
[],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
nuxuib | How does my tv service provider determine which channels I get? | Technology | explainlikeimfive | {
"a_id": [
"h104uy9"
],
"text": [
"Essentially all channels flow (or can flow) to your box at all times and you get only the filtered ones, depending on what you’re paying for. The TV box has a chip in it that acts as a filter. Your TV provider creates a custom config for the device (your very own filter) they put at your place, in-line with your service plan. To know which device is yours, they rely on the on-site tech that installs it to enter its ID in the system next to your name."
],
"score": [
3
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
nuy7vv | How do phone calls work? | Like …. I get the premise of the receiver and the sound is transmitted via radio waves…. But when you say it out loud?? We somehow trap our physical sound inside radio waves which you can’t physically see or touch and that transmits almost instantaneously and someone can then hear it ??? HOW | Technology | explainlikeimfive | {
"a_id": [
"h108ihb"
],
"text": [
"To break it down at a general level: 1. Your voice makes the air vibrate. 2. The air makes a microphone vibrate. 3. The microphone turns the vibrations into electrical “vibrations”. 4. The phone interprets the electrical signal digitally. At this point, it’s sort of like an MP3 file. 5. The digital audio gets sent to the other phone. 6. The other phone plays it back just like a music file (and it’s almost exactly the inverse of steps 1-4!)"
],
"score": [
8
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
nv1s13 | How are status pages for major CDNs and major backbone providers designed to be up even though the provider is down? | Technology | explainlikeimfive | {
"a_id": [
"h10zfwq",
"h10m0m1",
"h110s2l",
"h11u5jz"
],
"text": [
"The computational requirements for a status page are extremely low compared to a full website such as e.g. reddit or facebook. It's extremely cacheable, lightweight, and read-only. There's no user authentication or policy enforcement logic. It's also, for obvious reasons, hosted on separate infrastructure from the main site. Furthermore, even during an outage event, a status site is going to receive less traffic than the actual site, since only a more savvy subset of the users will bother checking the status page.",
"The most obvious way to implement this is to host the status page with a competitor using completely independent infrastructure. Another trick which can be implemented is that if any part of the status page fails in some way it will just fail by showing the service as failed. So for example with todays fastly issue when the front end servers worked but the backend network had issues the frontends can be configured to show a status page with everything failing if they can not find the back end servers. This obviously does not work if there is any errors very early in the pipeline but at that point it is likely a problem with the clients network provieder anyway and the status page would be of no help.",
"A park you visit could be closed, but the signs at the perimeter and leading to it will still be there. It's much like this. The status pages are kept specifically in heavily redundant places, sometimes reside in multiple places, so that they can always be reached, and not at the same physical location as the site itself.",
"I can answer this as it's my job. I manage a large CIRT (Critical Incident Response Team) who provides critical incident services to over 45 companies, I believe its the largest CIRT in the western world at least. I see from a lot of your comments that you are looking at internal hosting solutions, **dont**, look at the already established industry tools in place, consider something like [statuspage]( URL_0 ) (and also take a look at ops genie, its magnificent)."
],
"score": [
80,
15,
5,
3
],
"text_urls": [
[],
[],
[],
[
"https://www.atlassian.com/software/statuspage"
]
]
} | [
"url"
] | [
"url"
] |
|
nv1uzz | How does DNA matching work? | Recent story about Colin Pitchfork (first person convicted of rape using DNA analysis) got me wondering how this works. How is DNA coded in a way which allows you to match it up with another sample? When you look at it under a microscope or something there aren't exactly letters and numbers for each part of it. | Biology | explainlikeimfive | {
"a_id": [
"h10rdpq",
"h10odvf"
],
"text": [
"In addition to the more old-fashioned analog method of testing the length of particular bits of the genome through gel electrophoresis, more modern methods that actually sequence the sample DNA *do* actually yield a (massive) string of letters. These letters, A, T, C and G, represent the four nucleobases (adenine, thymine, cytosine and guanine) that encode information in DNA. The chemistry behind how a bunch of small molecules can encode huge amounts of information is something for a different post, which I'm sure has been asked and answered on this sub before. All you need to know is that similarly to how a computer can store information as a long string of zeroes and ones, DNA does something very similar but with 4 possibilities per place along the string instead. And just like you could have a computer compare two strings of binary information and calculate a % match, you can do the same with sequenced DNA.",
"The most common technique is to use various enzymes that split up the genes at specific points. Then the genes are forced through a gel by an eletrical field. Shorter genes go through the gel faster then the longer genes. If you power it off when the genes are half way through the gel and then use some fluorizing light to identify the genes they will form certain bands depending on their lengths. The theory here is that different genetic materials will be different enough that it is cut in different locations and therefore be of different lengths. By using different enzymes you get a different pattern again. Each set of DNA gives a unique fingerprint that you can compare. It should be noted that this system is not perfect by any means. Even though no two non-twins have the same DNA this test can make two different sets of DNA look the same by pure chance, just like two fingerprints may look very similar to each other just by chance. These tests also use DNA amplification techniques first so it is possible that a small sample like a single dead skin cell may just happen to be the one to get amplified and tested against. So a DNA match might mean that the suspect were on the same subway as either the victim or the criminal within the last few days."
],
"score": [
16,
8
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
nv1zaq | Why do brains differ in the abilities to store and process information despite the conditions we grew up with? Even amongst siblings you can see that one may be way smarter than the other | Biology | explainlikeimfive | {
"a_id": [
"h111ka5",
"h10texj",
"h10qlfz",
"h10qxeu"
],
"text": [
"Think of it like a phone. Your phone can't really change. You bought it and thats how it is. This is nature. You're born and that's how you are. Your cells are arranged a specific way. Nurture is like adding different apps. You can add different apps and influence how your phone works and what it is good at doing. So say a person is born with many neurons hooked up just right, like a high end smart phone. They have the capacity to possibly do more naturally. But if you only put useless apps on a great phone, that's it's limit. Conversely, a cheap phone can still be good if it has the capability to run the apps you want. People are very unique, even siblings or twins. Twins can be almost the same person biologically, but the way they grow up, their friends, their life experiences influence them to behave differently. Imagine one twins friend is always mistaken for the other. Perhaps she grows to resent this because it makes her feel less unique. So she grows up trying to be different. Twin A isn't bothered by this and does well in school, makes good friends, etc. But twin B is annoyed and tries to act differently. She makes different friends, maybe bad influences that lead her to make bad choices like skip school or such. So twin A is now getting better education and making better choices. Eventually, twin A is in college to become a doctor, but twin B dropped out of school. Even though they're almost the same biologically, they're very different. Conversely, imagine 2 different people who lived similar lives. These people could end up similar or different. Perhaps one had dyslexia that made learning more difficult. But because of this they tried even harder and overcame their struggle and ended upbas a doctor, while the other was naturally gifted and didn't struggle but also became a doctor. Life is a lot of small parts that add up.",
"Basically, \"What's the effect of genetics on intelligence?\" This one opens a can of worms. The people who think the answer is \"next to none\" are very adamant about that position. Basically, though, *some* of the difference in intelligence is genetic, and even siblings do not have the exact same genes.",
"URL_0 As with many other highly heritable complex traits, the genetic polymorphisms underlying normal-range intelligence differences remain elusive. One possible explanation is that many mildly harmful, lineage-specific, rare genetic variants ('mutation load') might be responsible for the heritability of intelligence.",
"Depends how many times child was dropped, If parents are obv not very smart, or challenged. Or purely on how many times the child’s been dropped."
],
"score": [
20,
7,
6,
3
],
"text_urls": [
[],
[],
[
"https://www.nature.com/articles/nrn2793"
],
[]
]
} | [
"url"
] | [
"url"
] |
|
nv3bbx | - why can’t you feel the sun damaging your eyes when you stare into the sun? | Biology | explainlikeimfive | {
"a_id": [
"h112nge",
"h11t050",
"h10u48c",
"h12c8t4"
],
"text": [
"Retinas don’t have pain receptors. Corneas do, but similar to when you get a sun burn and it doesn’t hurt right away, the corneas don’t start hurting until a bit later when the keratitis sets in.",
"? It hurts like hell to look at the sun! At least it does for me. I assume it hurts for others.",
"There are some parts of her bodies that don't have any pain receptors, the nerve endings that make us feel pain. Our lungs are similar which is why people don't feel lung cancer growing until it pushes into something else.",
"Why can't you feel the sun damaging your skin when you sit in the sun? It feels hot, but it doesn't hurt......yet. The sun damages dna through radiation. Radiation damage doesn't trigger pain receptors, only the eventual side effects of that damage might (large quantities of cell death causing blistering, skin peeling, fatigue, etc) Radiation damage in the eyes will eventually cause pain when cell death starts to happen in the cornea. Some parts of our body don't have pain receptors. The retina is one of those places, so if damage is done to the retina, it doesn't hurt. Bright light triggers pain for most people, but interestingly we aren't quite sure why, or what nerves are being tickled into giving us that pain sensation. That is why staring at the sun during eclipses, when there is no bright light to trigger immediate pain but still DNA damaging uv rays, is especially dangerous."
],
"score": [
45,
26,
9,
6
],
"text_urls": [
[],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
nv3bf4 | Time Is Relative | Physics | explainlikeimfive | {
"a_id": [
"h112fel",
"h114jj5",
"h12fewz",
"h110bop",
"h10zqus",
"h116l8b",
"h10vdtz",
"h10xy3v",
"h11xayi",
"h10zwdj",
"h11wnhb",
"h110fgi",
"h11upvi"
],
"text": [
"The simplest way I can think to describe it is not entirely accurate, but most people “get it” when I explain this way. Think of time itself as occurring at the speed of light. It’s then easy to see why, in a universe where nothing can move faster than light, traveling near the speed of light would make time appear to be slow, because you’re basically keeping pace with time itself. If a car is traveling at 100mph and it drives by while you’re standing still, that car seems really fast. But if you’re driving at 99mph and that same car passes you at 100mph, the relative speed of that car is only 1mph. The concept is similar to this, though as I said, not entirely accurate because with light and time, nothing *can* go any faster than light. For what it’s worth, light doesn’t have anything to do with the speed of light. The speed of light should really be called the speed of causality. Light is just the most common and apparent thing that moves at that speed.",
"This is the thought experiment that allowed Einstein to begin conceptualizing his work (or, at least this is the story that gets told) Einstein was walking home from his job as a parent clerk, when he hopped on the trolley in his city (I forget which at this point in his life, forgive me) As he was riding home from work he looked at the clocktower and imagined the hands being exactly where they were when he was looking at them, but then imagined his boxcar moving at the speed of light. He realized that, if he was able to move at the speed of light in his boxcar, those hands on the clocktower would never move again, from his point of view. He would be moving just as fast as the light that carries the information that tells us 'the minute hand just moved', therefore that information could never catch him and update him upon the current position of the hands. They would basiclly be frozen in time until he slowed back down I would love to link a Carl sagan video , I hope that's ok and doesn't get my comment removed Carl Sagan, the wordsmith of astrophysics and my personal [hero]( URL_0 ) Because this comment is getting some traction I implore anyone interested to watch [this]( URL_1 ) -- brilliant channel to learn",
"\"If there was an easy way to explain this, it wouldn't be worth the Nobel Prize.\" -Richard Feynman. But maybe this will help. First, let's lay a little groundwork. Imagine you're standing in a field, and there are two people each exactly 40 feet away from you, one on your left and one on your right. Each has a dog on a leash! The dogs are super excited to see you and both people let their dogs off the leash at exactly the same time. If both dogs run toward you at the same speed, they will both reach you at the same time. But you REALLY like dogs and don't want to wait! So you start running TOWARDS one of the dogs! What happens? Well, you reach that dog earlier. Because you covered some of the distance yourself. And the other dog arrives LATER because, since you ran away from it (and toward the other dog) you ADDED some distance between you. That should be relatively (lol) straightforward. So let's add a small wrinkle. Imagine I'm standing at a train station. There's a train coming, but it doesn't stop here. You're on the train. The only thing special about this train is that it happens to be travelling close to the speed of light. Then two bolts of lightning hit the platform, one to my left and one to my right. Both are exactly the same distance from me, so the light from each bolt arrives at my eyeballs at the same time, **I see the two strikes happen simultaneously.** Same as how, if you had stayed still, both dogs would have reached you at the same time. But the lightning bolts strike JUST as you are passing by. So that, for a moment, we are exactly opposite each other. If I was looking straight ahead when the lightning bolts hit, I would see you across from me in the train. What do YOU see when the lightning bolts hit? Well, the train is moving. It's moving TOWARD one bolt, and AWAY from the other. Just like in our example, you ran TOWARD one dog and AWAY from the other. So...like in our example, you are going to REACH the light from one lightning strike EARLIER than the other because the train moved toward it. Therefore **you SEE the light from one bolt BEFORE you see the light from the other bolt.** Which of us is correct? I saw two bolts of light hit the platform at the same time. You saw one bolt hit, then the other. Einstein proved that...there is no test you can perform, no test you could EVER perform, that would resolve this contradiction. I saw a simultaneous event, you saw one bolt hit, and then the other. Because you were moving close to the speed of light when this happened. In fact this means...**there is no such thing as simultaneity**. ANY TIME one person perceives two different events happening at the same time, another person in another frame of reference might see one happen before the other and there is NO WAY to tell which is \"correct.\" It's just that we don't notice this unless one of us is traveling very close to the speed of light. It's still true, it just almost impossible to measure in our normal lives. The only solution is...time is different for us. We are experiencing time differently, and in fact we are experiencing space differently as well. Your train would appear shorter, to me, than it does to you. At this point I fear my explanation would get very esoteric and not in the spirit of an ELI5 but hopefully this was at least interesting and not confusing.",
"**\"The faster you move through space, the slower you move through time.\"** Which means, relative to a \"stationary\" observer (technically there's no such thing, but this is ELI5), the faster they observe you moving, the slower you appear to be experiencing time - i.e. for every hour that passes for you, it might look like they only experience 1 second. The reasoning for this is that the Universe wants to keep the speed of light *constant* regardless of how fast you're moving. In other words, the headlights of a ship travelling 0.5c aren't going to have photons travelling at 1.5c. In order to do this, the Universe warps both space *and* time (which is why you get length contraction as well as time dilation). The mathematics of this get a little complicated, but there's a quantity called the *spacetime invariant interval* (which kinda looks like Pythagoras' Theorem in 4D) that has to stay the same no matter how fast you're going. Since the speed of light can't change, all the other values (x, y, z, t) do! Now this is more or less just *special relativity* (the one with the trains and the spacecraft and has to do with how fast things are going). *General relativity* is a bit more complicated, and it's the one that talks about how gravity (like planets and black holes) warp space and time. For that, you could consider that: **\"When gravity stretches space, it also stretches time.\"** This has to do with the fact that space and time are actually part of the same thing, spacetime, so changing one also changes the other. It's also why down here on earth, clocks tick slightly slower than they do on the ISS or a GPS satellite. If we didn't program relativity into our satellites, your phone wouldn't be able to get you closer than about 2km! The mathematics of this are *far* more complicated (even I don't fully understand them), but intuitively this visual works great!",
"The illustration which impressed this upon me is this: imagine person A is standing in a train car with glass walls and bounces a rubber ball off the floor, and back into their hand. This is observed by person B standing stationary on the platform the train is rolling past. Both observe the ball to travel down, bounce, travel up and be caught in the same time. However, person A observes a vertical motion down, then up, while person B observes a V-shaped trajectory. The vertical component is the same height for person B, but the ball also translates laterally while falling down, then further translates as it climbs back up. Now, the time is the same, but the distance for person B is longer. Therefore the ball travels faster from the perspective of person B. Since B is stationary, let's flip the perspective: from the perspective of person A, the ball will travel slower since it covers less distance in the same timeframe. The same ball, doing the same thing, viewed from different perspectives travels at a different speed.",
"Speed of light is a constant. That means it can’t change. It is also the fastest speed anything can go. Let’s do a thought experiment! You’re standing in a room and have a laser pointer. You flash the laser pointer to the ceiling (pointing it upwards like this | ), and measure how fast it gets there. It took one second. Suddenly the room travels 99.9% the speed of light sideways. You make the experiment again: you flash the laser pointer to the ceiling (pointing it upwards like this | ) and measure how fast it reached the ceiling. Still 1 second. HOWEVER! Since you’re also traveling sideways, from an outside perspective (if someone was standing outside the room, and saw it fly by), the light doesn’t look like it’s traveling straight up! From the moment the light left the laser pointer, not only did it travel upwards, it also traveled sideways along with you and the room you’re in. If someone watched your room traveling by, light would not have traveled a straight line upwards like this | but rather in a slant like this /. This means, from an outside perspective the light would have to travel a longer distance to reach the ceiling, namely up AND sideways. But it took 1 second for the light to reach the ceiling during both experiments! How can that be? First one may think: “easy! The light traveled faster of course!” But that’s impossible because as I stated in the beginning, the speed of light can’t change. It traveled just as fast the second time as the first. But something have to change to get the same result twice! And something did change! time. So what I happening here? Well, for the experiment to work, light can only travel a longer distance, in the same time, if time itself changes! So if it took one second when standing still, and one second while traveling sideways, it must mean that the one second is slower while traveling sideways! And the faster you’re traveling sideways, the slower time has to get for the light to be able to reach the ceiling in one second, as it’s traveling further sideways as well. Conclusion: if you’re traveling sideways at the speed of light, the time it takes for the light to reach the ceiling (your one second) have to be so slow, that it stops. So from your perspective, traveling at the speed of light, time stands still! Bonus: nothing can travel faster than the speed of light. Not even events, or gravity. That means, with light, comes time as we see it as well. It takes 8minutes for light to get from the sun to earth. That means if the sun disappear in an instant, it will take 8 minutes for the change to reach us. We wouldn’t know that the sun disappeared or its gravity went way for 8 minutes, because from our perspective, it wouldn’t have happened yet! Crazy thoughts!",
"I'll focus on special relativity since that address the question and is much easier to explain than general relativity. So the key idea behind special relativity is that the speed of light is constant for all observers, and that physics works the same for all observers. I.e we should be able to have a single theory that works for everyone no matter where/when/how fast they are (this is the relativity part). So what happens if the speed of light is constant? Well we can work it out by conducting a thought experiment (Einstein was very fond of these). Imagine we create a 'light clock' which works by bouncing a photon between two plates which are a meter apart, every time the photon hits a plate we count it and using that and the speed of light we can work out how much time has passed. When you are stationary relative to this clock then the photon is going to be moving one meter per bounce, light travels at \\~3x10^(8) meters per second, so if we count 3x10^(8) bounces then one second has passed. Now imagine you start moving relative to this light clock, or rather this clock starts moving relative to you. The photon will now appear to be bouncing 'diagonally' as it also has sideways velocity of the box, as well as it's original up/down bouncing. In classical physics this doesn't change anything, but remember the speed of light must be constant. From your perspective it's speed must still be \\~3x10^(8) , but since it is now travelling diagonally it is covering a distance slightly over a meter, so it will take slightly longer between bounces. From your perspective it takes longer than a second for 3x10^(8) bounces to happen, while for someone stationary relative to the box it still takes a second. The only way to reconcile this is that time must actually be passing differently for both parties. Changing your relative velocity has changed how fast time appears to be passing in that reference frame from your own. Another way to think about it is with someone holding a flashlight in a vacuum, they measure the light as moving at c relative to themselves, as do you. Every second a photon emitted from them gains 1 light second of lead. Now imagine they accelerate up to 50% of the speed of light relative to you. From your perspective since they are now moving half as fast as the emitted photons, the photons only gain half a light second of lead on them each second. But from their perspective the light is still moving at c, so gains a 1 light second lead in a second. Again the solution is that for each observer the definition of the second has changed, they are observing different times.",
"Basically, everything is moving at the same speed in space-time. If you move faster in space, you must move slower in time. If you put all your points into moving in space and attain light speed, you will not move in time.",
"Here's a relevant comment from /u/his_savagery which is *related* to your question, OP asked about relative speed of light. It is one of the easier explanations I've seen so I've saved it. > Wow, OP. You've asked the very same question that Einstein asked himself to come up with one of the most revolutionary ideas in physics! > You are correct that speed is relative. If I'm walking up an escalator at 2 m/s and the escalator is moving at 5m/s then my speed relative to a person standing still at the bottom of the escalator is 7 m/s, but to someone else on the escalator who is standing still and waiting patiently for the escalator to transport them to the next floor my speed is 2 m/s. > But light travels at the same speed from all perspectives. Say a spaceship is traveling at 90% the speed of light. If I shine a torch from the back of the spaceship to the front and someone on the ground can see through the spaceship's window, then the light from the torch will appear to move at the speed of light to both of us. But the escalator example would suggest that to the person on the ground, it should be traveling at 90% of the speed of light + the speed of light i.e. at 190% of the speed of light. So how can it appear to move at the speed of light to both of us? Well, if the person on the ground is looking through the window and everything in the ship (including not only the beam of light from the torch, but the people inside the ship) is moving in slow motion, then the beam of light can appear to move at the speed of light. > Mind blowing, eh? To solve the paradox, time must be relative! Time inside the ship appears to be slowed down to the person on the ground, and conversely everyone outside the ship looks like they're running around like ants to the people inside. Actually, there's a bit more to it than that, since distances are affected too. But thinking about it like this is a good starting point I hope it helped you understand it too, even if your question wasn't specifically aimed towards *speed* (directly).",
"here's a less accurate analogy: imagine light as a row of photons, an imagine each photon is a frame in a movie. photons are passing you at the speed of light, so you see each frame, chronologically. if you also move forward in the same direction, then you see the frames slower, since they are slower relative to you. and if you reach the same speed, then you only see the same photon - as if time stands still. If you go faster, you should be able to see photons that have already passed you - as if traveling back in time. of course, mathematically its a lot more complicated that this. \\- I have no analogy for the mass increase, and I don't think I understood the length difference properly, either.",
"It might help to think of it from a different perspective: instead of asking why is time relative, ask instead whether time is absolute. Intuitively, we think that space and time is absolute. In other words, we would imagine that 1 meter would always be measured as 1 meter *no matter who measures it*, whether this observer is not moving or moving extremely fast. Likewise, intuitively, we feel that time passes by constantly for everyone, at a rate of 1 second per second universally. This means that when I experience 1 second pass by, I expect to observe 1 second pass by for all observers, including those that are moving or stationary. Now, lets ask whether or not this is actually true. It turns out (and there are historical bits of evidence leading up to it) that, when we tried to find out what this absolute space was, the experiment failed! And it lead us to ask what *is* exactly constant for all observers, and it turns out that it is the speed of light itself. Just as a quick refresher, speed is the space traversed in a given time. And so if the speed of light IS constant, but absolute space is not, then time itself but stretch and squish if the speed of light is indeed constant (and, as far as we know, it is!). What does this look like? The an example is to imagine sitting at a train station watching someone on a train moving at 99% the speed of light. You then turn on the lights at the station and you watch the light zoom off at 100% the speed of light and overtake the train, but from your perspective, it looks slow, since the light is only 1% faster than the train. Now what does the person on the train see? Well, they instead see the light zoom of at 100% the speed of light ahead of them. So what gives? You on the train station watching the train sees the light overtaking slowly, but the person on the train itself sees it rushing off into the distance. The answer is that when you look at the watch of the person on the train, you would see that his watch is ticking *a lot* slower than yours, and by the time that person's watch ticks of 1 second, the light has travelled ~~300~~ 300,000 km ahead of the train (the distance light travels in 1 second). And so the better way to think about time dilation (and space contraction), in my opinion, is to look at it via the speed of light being constant. Once you fully accept that it is the *speed* of light that the universe cares about, then it naturally follows that space and time have to warp to keep it constant. There is a lot more nuance in the theory but this should suffice for an introductory level.",
"like you're actually 5: You're moving really fast, everyone else is not, so because you're moving very very fast, faster than you can imagine, time slows down for you. Everyone else is going the same speed they were before, so time does not slow down for them.",
"I think the place to start with this, is to say that this whole idea is based on a bunch of experiments which people have done that produced unexpected, weird results. And the best ideas we have about the “why” behind those results is really not “Explain Like I’m 5” material, it is more like “Explain Like I’m 25 and studying physics in college.” So let’s just talk about some of the weird things people observed. The main topic here is “relativity” which is basically the idea that your perspective on the physical world is just as “real” as anyone else’s. If you watch a train pass by, it looks like you are standing still and the train is moving. However, to a person riding the train, it appears that they are standing still and the whole world is moving around the train. Which perspective is correct? Is the train moving, or the earth moving? Relativity says that _both_ are actually true at the same time; for the person on the ground, the train _is_ moving; for the person on the train, the ground _is_ moving. This feels weird to us, because we’re used to thinking of the Earth as standing still all the time, but if you do precise experiments from the train, the results you get will claim that the world is moving around the train. This idea by itself doesn’t cause many problems, but it produces weird results when it interacts with other rules. The big problem is with the speed of light. We have measured the speed of light very precisely, and for the most part it is always the same. In particular, it is the same for people who are in motion relative to each other; if you stand on the ground next to a train track and do an experiment to calculate what the speed of light is, and someone else does the same experiment at the same time on a train that is passing by, you will both get the same number. If you think about it, this is actually _very_ weird. We expect velocity and momentum to add up in a rational way. If you are jogging at 5 MPH next to a train track as a train passes by at 25 MPH, a person on the train will see the world passing by at 25 MPH, and will see you passing by at either 20 MPH if you’re running the same direction as the train or at 30 MPH if you’re running the opposite direction. Now, if you shine a light at that train as it travels away from you, and you and a person on the train measure the speed of that light, you would expect your measurement to be 25 MPH different from the measurement the person on the train gets, but that’s not what happens - you both will get the exact same number. Also, that light you shone at the train will be a slightly different color for the person on the train than it is for you. It turns out that the color of light indicates how much energy that light is carrying; red light has a certain amount of energy, green light has more, and blue light has still more. So, the person on the train _should_ observe a difference in velocity for that beam of light, but they do not; instead, they see a difference in color, and this difference is proportional to the difference in velocity that they expect to see. It is as if the universe “knows” that light is supposed to always travel at a certain speed, and it borrows energy from the color of the light to make up for the difference in velocity. The next weird problem is also connected to the speed of light: as far as we know, nothing can go faster that the speed of light. There are some special cases, but in general this is true. Now, let’s say you are on a train traveling across the earth at 75% the speed of light, and your friend is on a different train which is traveling at the same speed in the opposite direction. If you try to measure how fast your friend’s train is moving, we expect that you would measure it to be 150% of the speed of light. Thanks to Relativity, we know that your perspective is objectively “true”; it looks to you like you are standing still, and the earth is flying by at 75% of the speed of light, so your friend’s train should appear to be traveling at your speed plus their speed, right? Well, no. What actually happens is, you will measure his velocity to be substantially less than the speed of light, and it will also look like his train is shorter and weighs more, and it will also look like time is traveling more slowly for him than it is for you. Why does this happen? The simple version is, the mass that an object has, and the space that an object occupies, and the speed at which the object is moving, and the passage of time around the object, are not separate, independent qualities - they all connected to each other. This is why physicists sometimes use the word “spacetime” instead of just “space” and “time” - they know that space and time are connected, and are talking about a situation where that might matter. When we had that ray of light we shone at the train, the universe “borrowed” energy from the color of the light to make sure the speed was “right”; the same thing is happening here. The universe needs to ensure that the other train isn’t moving faster than light. According to Relativity, if it _looks_ like it’s moving faster than light from your perspective, then it really is doing that, and that’s not allowed. So to prevent this, the universe “borrows” again. The universe wants to “fix” the velocity of the other train, to bring it below the speed of light, so it “borrows” from the other train’s velocity, size, and flow of time, and moves what it borrowed into the other train’s mass. So the total all still adds up correctly, but the velocity is now below the speed limit. And yes, this is only true from your perspective, but it is objectively _true_ - if your friend measures his train, and you measure his train from your train, you will get different numbers."
],
"score": [
5259,
643,
508,
150,
142,
77,
58,
35,
17,
7,
6,
5,
4
],
"text_urls": [
[],
[
"https://youtu.be/_pEiA0-r5A8",
"https://youtu.be/msVuCEs8Ydo"
],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
nv4kv8 | kW and kWh difference | Can someone please explain the difference between kW and kWh? Thank you! Edit: thank you for all the responses, I appreciate you taking time to respond! | Physics | explainlikeimfive | {
"a_id": [
"h112jb0",
"h114eph",
"h11a2eb",
"h112ea4",
"h112oq3",
"h122795"
],
"text": [
"A kW is an amount of power, specifically 1000 Joules every second. A kWh is a kilowatt, multiplied by an hour. 1000 J/s \\* 1h = 3 600 000 J So a kWh is an amount of energy. Specifically it is the amount of energy used by a 1kW device every hour.",
"The difference between kW and kWh is the same as the difference between miles per hour and miles.",
"To use a water analogy: kW is a rate and kWh is a quantity. kW would be analogous to gallons per second. kWh would be analogous to gallons. Different faucets in your house will expel water faster or slower. Your kitchen sink will expel 0.025 gallons per second while your shower might expel 0.1 gallons per second. If you let each of those run for a minute you'll find that they will expel a different amount of water (shower more, faucet less). In your daily life you'll most likely encounter kW and kWh referring to electricity consumption. An appliance you own would be rated in kW (how quickly it will consume electricity) and you can use that to figure out how much electricity (and therefore how much $$$) it will use if you leave it on all day, half a day, for an hour, etc.",
"kW is power. kWh is energy. Watts is a measure of a single point in time. A device or system is, at any given point in time, using a specific amount of power. Energy is a measure over time. It's how much power you've used over a specific period of time",
"kW (kilowatts) is a measure of how fast electricity is flowing into something, like your house. kWh measures how much of that electricity has flowed into your house total. Think about it like your water. You can run your taps at all sorts of speeds (in this case, your kW), but if you want to know how much water you've used, you also need to know how long you've run those taps for (your kWh). You can work this out just by multiplying the water (or electricity) flow rate by the amount of time (hence why its kWh and not kW/h). This is because Watts is actually already a rate - of energy! Measured in Joules per second. So by taking some amount of kilowatts and multiplying is by how many seconds (or hours) you've used it for, you're just calculating the energy you've used.",
"* Let's say I can eat 2 [Whoppers]( URL_0 ) a second. This means my rate of consumption is 2 Whoppers, or 2 Whops, or 2W, which in turn makes for 7200 Whoppers an hour (2 per second x 60 seconds in a minute x 60 minutes in an hour). * Let's say I buy a festival-sized box of Whoppers from the store, which contains 7200 Whoppers. We can say that this box contains 2 Whop-hours (2Wh) of candy - because at a consumption rate of 2Whop, it will take me 1 hour to finish it. * Note that if I was feeling a little under the weather and could only manage 1Whop, then a 2 Whop-hour box would last me 2 hours, and if I was hungry and sustained a rate of 4Whop, then a 2 Whop-hour box would only last me .5 hours, or 30m. * Let's say my graduating class can, in total, consume 2000 Whoppers every second (7.2 million Whoppers an hour). That is, they consume 2 kiloWhops, or 2kW. * In order to keep them happy for 4 hours, we would need a crate of Whoppers which contains 8 kiloWhop-hours, or 8kWh - that is, 28.8 million Whoppers (2000 x 60 x 60 x 4). Fun fact: 7200 Whoppers fills about 12.5 U.S Gallons, weighs about 37.5lb, and contains about 1.35 million kCal. Also, as it turns out, humans need about .3 Whopper-Gallons per day to maintain a healthy weight."
],
"score": [
40,
10,
10,
9,
4,
4
],
"text_urls": [
[],
[],
[],
[],
[],
[
"https://en.wikipedia.org/wiki/Whoppers"
]
]
} | [
"url"
] | [
"url"
] |
nv5309 | what is a partial refund ? | So recently I bought this shoes that had deflects and i wanted a return ( this was on ebay) then the buyer says if i want a partial refund. So i need to know what it is. The value of the shoes is £40. | Other | explainlikeimfive | {
"a_id": [
"h1157jy"
],
"text": [
"A partial refund is like haggling. Basicly they're saying they'll give you a discount by returning some of the money and you keep the item for a cheaper price."
],
"score": [
4
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
nv5c7e | How do polygraph tests tell the difference between a lie and genuine anxiety? | Like - if it's based on a person's physiological responses, isn't it possible that a response to a question like "did you murder your hamster" would register as a lie due to the increase in heart rate and blood pressure cause of anxiety associated with being accused of something? | Other | explainlikeimfive | {
"a_id": [
"h116kbd",
"h11abrm",
"h11y7hp",
"h11xt7w",
"h11a0jo",
"h119j04",
"h12a3m0",
"h120e2y",
"h11wldg",
"h11fvhz",
"h12kt9b",
"h11ap3t",
"h11uf7s",
"h13mxhz",
"h126zgc",
"h12d314",
"h13l45i",
"h12b0nw",
"h11vyt6",
"h125ywm",
"h12hdha",
"h11xhca",
"h12bdc0",
"h12q2g9",
"h12p3ex",
"h122hgh",
"h12em7g",
"h13mpub",
"h13l0lo",
"h118hbi"
],
"text": [
"They don't. According to the American Psychological Association, “There is no evidence that any pattern of physiological reactions is unique to deception. An honest person may be nervous when answering truthfully and a dishonest person may be non-anxious.” It has never actually been shown in a controlled test that a polygraph machine can detect lies. Even the creator of the machines stated that they were bunk. They're purely a prop for interrogators.",
"Polygraphs are mostly nonsense; they simply test \"stress\" - and even then it's interpreted by the examiner. The only thing they really do are make guilty people feel scrutinized, with the hope that they'll confess under the pressure.",
"Never under any circumstances take a lie detector test. It will never prove your innocence but will always be used against you if you fail. It is completely inaccurate and useless. EDIT: Exception is if it's required for a very high paying job.",
"I volunteered to take polygraph tests as part of my Police Foundations course, so that they could teach newly polygraphers. In our round of testing, they would give you 2 cards from a deck, and the administrator would have to figure out which 2 cards you had. (And you were encouraged to lie) They would ask mundane questions, and then slip in questions like “is you card red, is your card a face card”. They couldn’t get a good reading on me, and said that I either cope really well under pressure, or that what ever mental gymnastics I was doing was throwing off the readings. In the main scenario, one of the group being tested was instructed to steal a wallet, while others witnessed or had 0 role to play. I was a witness who was instructed to lie about not seeing the wallet. The polygrapher could tell that I didn’t steal the wallet, but had no clue as to whether or not I actually witnessed the “crime”. Pretty neat experience, albeit stressful considering they really try and make you feel bad about every little thing you have ever done in your life. (Pirating music/movies, watching porn, malicious thoughts)",
"From the [ URL_1 ]( URL_0 ) home page: The dirty little secret behind the polygraph is that the \"test\" depends on trickery, not science. The person being \"tested\" is not supposed to know that while the polygraph operator declares that all questions must be answered truthfully, warning that the slightest hint of deception will be detected, he secretly assumes that denials in response to certain questions -- called \"control\" questions -- will be less than truthful. An example of a commonly used control question is, \"Did you ever lie to get out of trouble?\" The polygrapher steers the examinee into a denial by warning, for example, that anyone who would do so is the same kind of person who would commit the kind of behavior that is under investigation and then lie about it. But secretly, it is assumed that everyone has lied to get out of trouble. The polygraph tracings don't do a special dance when a person lies. The polygrapher scores the test by comparing physiological responses (breathing, blood pressure, heart, and perspiration rates) to these probable-lie control questions with reactions to relevant questions such as, \"Did you ever commit an act of espionage against the United States?\" (commonly asked in security screening). If the former reactions are greater, the examinee passes; if the latter are greater, he fails. If responses to both \"control\" and relevant questions are about the same, the result is deemed inconclusive. The test also includes irrelevant questions such as, \"Are the lights on in this room?\" The polygrapher falsely explains that such questions provide a \"baseline for truth,\" because the true answer is obvious. But in reality, they are not scored at all!They merely serve as buffers between pairs of relevant and \"control\" questions. The simplistic methodology used in polygraph testing has no grounding in the scientific method: it is no more scientific than astrology or tarot cards. Government agencies value it because people who don't realize it's a fraud sometimes make damaging admissions. But as a result of reliance on this voodoo science, the truthful are often falsely branded as liars while the deceptive pass through. Perversely,the \"test\" is inherently biased against the truthful, because the more honestly one answers the \"control\" questions, and as a consequence feels less stress when answering them, the more likely one is to fail. Conversely, liars can beat the test by covertly augmenting their physiological reactions to the \"control\" questions. This can be done,for example, by doing mental arithmetic, thinking exciting thoughts,altering one's breathing pattern, or simply biting the side of the tongue. Truthful persons can also use these techniques to protect themselves against the risk of a false positive outcome. Although polygraph operators frequently claim they can detect such countermeasures, no polygrapher has ever demonstrated any ability to do so, and peer-reviewed research suggests that they can't.",
"They don't, at all. It might as well be a Magic 8-Ball while the interrogator acts like it is science.",
"Another fucked up bit of trivia: although polygraph tests can’t be used as evidence in trial (unless all parties consent as some others have mentioned), they can be used as the basis for probationary decisions. So if you fail a polygraph test your PO can determine that you violated your probation whether you actually did or not.",
"They don't, which is why lie detector tests are considered pseudoscience and are inadmissible in courts of law. Other commonly accepted pseudosciences: - Chiropractic - Magnet Therapy - Accupuncture (some people might like the endorphin release, but evidence is weak for treatment of anything) - Most of Chinese \"medicine\" - Reflexology",
"They were invented by the guy who created Wonder Woman as a part of his male fantasies involving BDSM. They were snatched up by the FBI because they loved the idea...not because it was ever verified to work.",
"They're just like police dogs. It's just a tool for cops to create evidence from thin air so they can convict you whether you are guilty or not.",
"I want to second u/rhombiodus here and say - they don’t. But what you suggested is essentially how they are supposed to work. The idea is they get a reading of your heart rate, breathing rate, etc. when you are answering normal questions truthfully (is your name yoteachcaniborrowpen?) Then, they ask you the ‘real’ questions (did you strangle Mr. Body?). The idea is that lying is stressful, which causes your heart rate and breathing rate to ‘spike’. So you look for these spikes compared to the easy questions, and say ‘lie’ or ‘not lie’. It’s utter BS. There was a 400-page plus report commissioned by congress that was put together by tons of experts in the field that concluded there was no evidence whatsoever to support polygraphs. It’s not admissible in court. The only reason it’s still around is to threaten people into confessing and use it against you if you refuse one - because the fact you refused IS admissible (AFAIK). Source: psych prof",
"It’s complete bullsht and based on the belief one has the machine will work. It’s a tool used by the people using them to achieve an end result...there is a reason they are no longer accepted as evidence in a court of law",
"People think I’m lying anytime they ask a super serious question. Like if someone asks “did you brush your teeth?” I’ll say yes, they’ll give me a hard stare and I can’t help but break out in a big grin. WHATS WRONG WITH ME?!",
"It's not a lie detector, it's a stress detector. they start by questionning you on common things; non stressful questions. Is your name Joe, etc. And while doing that, they check your physiological reactions (heart rate, sweating, breathing, etc). Then they move on to ask you questions about the thing they want to check (ie: did you kill Bob?). They do so with the assumption that if you are truthful, you won't really be *more* stressed out. And that if you are lying, you will be *more* stressed out, and therefore have physiological reactions that are different than when you are honest. But keep in mind this whole thing is also an interrogation: the polygraphist could try to get you to confess by suggesting or indirectly implying you failed the polygraph. \"Any reason the polygraph would show you are lying?\" Is a type of question that might throw off some lying people into thinking some kind of red light flashed on the machine. And then they will start talking and backtracking their story and boom: the story is broken. It's not rare for people leaving a polygraph to feel like the polygraphist think they are lying, to feel lile they failed the test. That's part of the strategy to push a lying person to talk more, to overjustify to the point of contradicting themselve.",
"I have taken one, it was a waste of time. The results came back \"inconclusive\". I asked, well am I lying or not?",
"The real bag of laughs here is that the guy who INVENTED the polygraph says it's nothing to do with lie detection, it's just some experiment he was doing and the US government jumped all over it and decided without any scientific input that it was a magic lie detector machine",
"They don't. Convicted murderers have passed the tests with ease despite being guilty of their crimes. It's a physiology response detector first and foremost, if you happen to get nervous easily (like when you're being accused of a crime that anyone would be nervous when confronted with) there's a good likelihood of you exhibiting some form of response.",
"I watched a video from a former CIA agent there are no physical signs that someone is lying to you there are only physical signs that someone is in distressed or is stressing.",
"They dont. Its just a kind of present day voodoo aimed at convincing stupid people that it can detect their lies. It cant and has no validity in court. Some criminals aren't very bright.",
"They don't. Lol my friend's crazy boyfriend bought one to see if she was cheating on him and we used it to ask each other goofy questions. She asked me if i ever ate my poop, i said no, and it said i was lying. Lol so... Yeah, definitely not very good at telling the truth.",
"They can't. I failed a polygraph when applying for a job at the police station, because I randomly freaked out and got anxiety at the question \"have you ever received or moved stolen goods\". I can't explain it, I've never been involved in any sort of stolen good in my life. I crushed every other part of the interview, but a week later I received a letter in the mail stating that I would not be selected to continue on in the hiring process. 🤷♀️",
"As others have said, they really don't. It's absolutely not a hard science at all. Occasionally they're just used as a simple intimidation tactic. Good cop / Bad Cop stuff ... except instead of having bad cop yell \"I KNOW THAT YOU'RE LYING,\" you have the machine do it. \"THE MACHINE KNOWS THAT YOU'RE LYING.\" In that setting, you might as well hook the subject up to an etch-a-sketch. There's no useful data coming out. You're just trying to get the person to confess. However, sometimes they are used and you actually do want to get some useful information. So you make a whole day of it. Or evne 2 or 3 days, potentially. It can be a hell of a process. To start with, you acclimate the person. Spend a while with them hooked up to the machine, and asking questions that aren't really important. Start with simple stuff: \"Where were you born, what year did you graduate high school, what was your first pet's name, etc.\" Turn it into a conversation. It helps to create a baseline, because even simple conversation is more tense when you're hooked up to weird machines, in a strange room, with strange people asking you questions. From there you start asking awkwardly probing questions that aren't really important, but are designed to illicit an emotion response. \"Have you ever had homosexual thoughts (assuming the subject isn't openly gay). Have you ever taken prescription medication that wasn't yours. Have you ever shoplifted or stolen from any of your jobs. How would you rate your own dick: small/medium/large.\" You'll certainly get some kind of a reaction from some of those questions, and again, it's used as a baseline. You're not being accused of anything (yet) they're just getting a reading for what makes you squirm, and how that shows up on the machine. From there, they can start getting into more specifically probing questions and use all of the previous responses to try and gauge a reaction. Of course... it's all easy enough to muddy by simply putting a rock in your shoe. Pressing down on the rock will cause your body to react internally. Doing this during the \"baseline\" portion will prevent them from having a useful comparison. And there are other ways to muddy the results. Even just crossing your legs, clenching up your butt-cheeks hard enough or holding your breath can register on the machine. Of course... of course... a muddy result can also be useful data itself. It tells you that the person is probably doing this on purpose, and trying to hide something. You're not going to get a printout with exactly what they're trying to hide, but you know that they're hiding something, and smart enough to try and deceive you. And that's good to know.",
"The short answer is they don't. Polygraph tests are known for being unreliable at best and downright wrong at worst. You could hook one up to a houseplant and scream at it for a while and still get results.",
"Polygraphs do absolutely nothing but track vital signs. That’s it. They don’t do anything else. Anybody who makes a claim otherwise is misinformed, lying or doing it because it advantages them in some way. A polygraph is absolute snake oil.",
"they don't. this is why they are inadmissable in court. only scumbag pigs try to use them on poor/stupid people. the same basic concept as belarus recently used to get their false confession to parade for the media after hijacking a passenger jet.",
"They don't, not really. I'm not an expert but I have had several polys and been told on each occasion I am effectively untestable. The ELI5 is that it measures your physiological responses, so imagine it just can tell how fast your heart is beating. Now imagine when you lie your heart beats just a little faster. There's lots of stuff that makes your heart beat a little faster. One of those things is actually the process of deciding what your answer is. So, if I said to you \"have you ever stolen anything\" and you haven't, but in your head you quickly go through your personal history to make sure you never stole anything before you say \"no\". Well, that is going to make your heart beat a little faster. It will look identical to a lie. Anyone who especially truthful or has any sort of guilt complex is going to be exceedingly difficult to test. Edit to say: A lot of responses are calling it pure bunk and equating it to astrology and such. I would argue this isn't true. I was given pretty thorough access to the results of my tests, given a psychological evaluation to see why it was difficult to test me and the people involved explained the whole process to me much like I did in the ELI5 portion of my answer. They're detecting tiny changes is heart rate, conductivity of the skin (I believe and I think to detect sweat) and breathing. One of the controls we did was for me to write down the numbers 1 through 9 on a card leaving out the 4. Then the person giving the test wrote in the 4. They asked me to always answer yes to all questions and then asked if I wrote each number. Obviously the 4 was a lie. It was pretty clear on the results where the answer to the 4 was. So, it may not be a hard science, but there is at least some veracity to it.",
"They don't. They are used as an interrogation prop in which the interrogated subject believes they can detect a lie. There is a reason polygraph test aren't admissable in court.",
"They don’t. Which is why they aren’t accepted as true lie detector tests. They’ll have you answer spare questions to calibrate the test. But even still, this doesn’t work 100% of the time.",
"They can’t. Literally. Which is why polygraph tests are inadmissible in court. It’s as bad as the ancient and bizarre theory behind phrenology. They are only used to pressure suspects because based on TV and films, some people think they are even remotely accurate.",
"There is some correlation between physiological responses and lying/guilt. But it's pretty loose and you can have similar responses for a variety of different reasons not at all related to lying. As someone else said, they're a prop for the interrogator who's doing the real work. All the sensors and belts and gadgets are mostly props to make you nervous and admit things you might not otherwise. And the interrogator is literally just there to fuck with you and get you to talk."
],
"score": [
12507,
821,
624,
304,
237,
58,
54,
52,
38,
19,
16,
15,
15,
9,
6,
6,
6,
5,
5,
5,
5,
5,
4,
4,
4,
4,
3,
3,
3,
3
],
"text_urls": [
[],
[],
[],
[],
[
"https://AntiPolygraph.org",
"AntiPolygraph.org"
],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
nv5cq1 | The Pole in the Barn Paradox | I studied about this paradox and encountered some problems: • What are the observations when both the front and the back door of the barn are closed? •When both the doors are open. •When the back door is closed but front door is open. •And finally, the conclusion from this paradox. | Physics | explainlikeimfive | {
"a_id": [
"h11972t",
"h11av4v",
"h11ltij"
],
"text": [
"This is the sort of paradox you get when you only half commit. You shorten the pole you carry though the barn by treating it as an object within the theory of relativity. You keep the barn as is by treating it as if it was an object obeying newtonian laws. You can't do that. You have to treat both hypothetical object as is they existed within the same theory. Otherwise you get nonsense. You can't say that you for example open the 2nd door and close the 1st one as soon as the pole reaches it. That is pretending that you have a pole flying through your barn at near relativistic speeds, but that you can see and react and send commands at faster than light speeds. \"At the same time\" is not a thing that exist when you are dealing with relativity. If your barn is 100m long than anything happening at one end can't affect the other end before 100m /c time has passed. For 100m that is about a third of a microsecond and we normally treat is as \"at the same time\", but normally we also don't deal with relativistic poles flying through barns.",
"URL_0 The problem is that \"at the same time\" doesn't mean the same thing in both frames of reference (pole runner and observer).",
"The key thing with the Pole/Ladder in Barn 'Paradox' is that events don't have to happen at the same time for everyone. There is no such thing as simultaneity. ---- Due to Special Relativity if something is moving relative to you it is squished in the direction of relative travel from your perspective. For example, something travelling at 3/5ths the speed of light, will only appear 4/5ths the length it \"should.\" So if we run a 5m long ladder through a 4m long barn, and it is moving at 3/5ths the speed of light compared to the barn, from the barn's perspective the ladder will only be 4m long, so there will be an instant where it is entirely in the barn. But SR is symmetric(ish). From the ladder's perspective it is the barn moving at 3/5ths the speed of light. So the 4m long barn will only be 3.2m long from the ladder's point of view - at no point will the ladder be entirely within the barn. Wikipedia has some great diagrams for this. [This shows things from the barn's perspective]( URL_0 ); the ladder is squished by SR, so there is an instant where it is entirely within the barn. [This shows things from the ladder's perspective]( URL_2 ); the barn is squished by SR, so there is no point where the ladder is entirely within the barn. The key thing to realise is that *times* are also different for the ladder and the barn. We can't deal with this just thinking about space, we need [the full Minkowski diagram]( URL_1 ) (from the barn's perspective). There is a lot going on here, so let's break it down: * the blue x/t-axes represent space and time from the barn's perspective. The origin O is the entrance of the barn, when the front of the ladder reaches it. The blue shaded area is the barn. * the red x'/t'-axes represent space and time from the ladder's perspective (skewed by how fast it is going). The red shaded area is the ladder. * Point A is when and where the front of the ladder hits the back of the barn. Point D is when/where the back of the ladder reaches the front of the barn. B is where the back of the ladder is when A happens *from the barn's perspective*, so AB is the ladder at that point in time; the ladder is entirely within the barn. But C is where the back of the ladder is when A happens *from the ladder's perspective*, so when the front of the ladder reaches the back of the barn, the ladder is the line AC (not AB). Events A and B happen at the same time for the barn, but at different times for the ladder. Similarly A and C are the same time for the ladder but different times for the barn. D - the point where the back of the ladder reaches the front of the barn happens *before* A for the barn, but *after* A for the ladder. We can also see (although not marked on that diagram) that when the back of the ladder reaches the front of the barn (so the bold red line starts at D) the front of the ladder will be a long way out the other side of the barn (off to the top-right of A). -------------- So what happens if we start closing doors? We *could* close both the front and back doors at the same time, very briefly. *But only from the barn's perspective.* Going back [to the original diagram]( URL_1 ), we could leave the back of the barn closed until the front of the ladder reaches it at A, and then open it. And we could close the front of the barn when the back of the ladder reaches it at D. From the barn's perspective, D happens before A (time going upwards for the barn, horizontal lines represent things happening at the same time). But from the ladder's perspective A and C happen at the same time (lines parallel to that line represent things happening at the same time, time goes up-and-right). So D happens some time after A. From the ladder's point of view, the back of the barn opens before the front of the barn closes and all is good with the world. There is plenty of time where both doors are open for the ladder, even if there is no time both doors are open for the barn. What about keeping doors closed? If we close the back door, we'll need to slow down the ladder so it comes to a stop. If we do this gently, from the barn's perspective the ladder will return to its normal length (so we'd 'see' the back of the ladder start slowing down before the front does - 'stretching' the ladder, and it won't fit in the barn). If we leave the back door shut and let the ladder smash into it, then our idea of solid objects breaks down. The \"knowledge\" that the barn is closed can't travel faster than the speed of light. So the back of the ladder won't learn that the front has stopped until some time later (marked as point F [on this diagram]( URL_3 )). After the front of the ladder hits the back of the barn (event A) the front moves from A to E. From the barn's perspective, during that time, the back of the ladder moves from B to F (where the back of the ladder comes crashing to a halt). But from the ladder's perspective the back of the ladder moves from C, through D and B, to F. The ladder is going to get crushed as the back slams into the front, collapsing it down. Also, we probably blow out the back of the barn. The energies involved are going to be massive. Don't try this at home."
],
"score": [
5,
3,
3
],
"text_urls": [
[],
[
"https://www.youtube.com/watch?v=YVhI45\\_WzJ4"
],
[
"https://en.wikipedia.org/wiki/File:Ladder_Paradox_GarageScenario.svg",
"https://en.wikipedia.org/wiki/File:LadderParadox1_Minkowski.svg",
"https://en.wikipedia.org/wiki/File:Ladder_Paradox_LadderScenario.svg",
"https://en.wikipedia.org/wiki/File:Junk1.png"
]
]
} | [
"url"
] | [
"url"
] |
nv5ddp | how is endometriosis not a form of cancer? | The cells act similar to cancer, it sure as hell feels like dying, and there's no cure. What is the qualifier that makes it not cancer? | Biology | explainlikeimfive | {
"a_id": [
"h11fp81"
],
"text": [
"Cancer cells are undifferentiated/ immature cells. Endometriosis is caused by mature differentiated uterine wall cells."
],
"score": [
9
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
nv5dgb | What's the difference between rationalism, empiricism and nativism? | Other | explainlikeimfive | {
"a_id": [
"h117hhd"
],
"text": [
"Rationalism is focused as \"reason\" as the source of knowledge, empiricism focuses on experience and sensory inputs as the source of knowledge and nativism is a derivation from the latin word for being born and apparently is some anti-immigration policy? Not sure what that has to do with the other unless you've heard about all of that in the right wing context in which case \"rationalism\" means \"I am smart and if you don't agree, then you're not smart\", \"empiricism\" means \"I've seen it ones so it must be that all the time, also don't ask to many questions where I seen it\" and \"nativism\" means \"despite my family likely having immigrated into whatever country I'm currently in, I'll pretend as if I have much more of a claim to live here than other people\". Hope this summarizes it."
],
"score": [
6
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
nv6fv7 | how knife throwers make sure the blade hits the target instead of the handle | I mean, if the knife is balanced, there should theoretically be an equal chance for every angle of the knife to hit the target, not just the sharp part, right? Is it just “it only has time for about half a rotation” and take the distance and speed into account? | Physics | explainlikeimfive | {
"a_id": [
"h11fg6w",
"h11h9zt",
"h11fbba"
],
"text": [
"It is actually, as far as I am aware at least. There’s specific technique to knife throwing, and most of what I’ve seen in the past has been relatively consistent with other things. It’s similar to the idea that flipping a coin isn’t really truly “random”. With enough practice, and properly controlled conditions, you could get whatever result you wanted. With knife throwing I’ve always seen things say “Make sure you do steps 1, 2, 3, while being X feet away from your target, if you knife is blade heavy, hold it from the handle, of its handle heavy, hold from the handle.” etc.. It also probably does more than half a rotation in a normal throw depending on how far away you are.",
"Throwing knives typically are not balanced, they tend to be much heavier on the point end. Google pictures and you'll find examples of what I mean. Aside from that, it's technique that gets it to stick. Knowing the knife itself, the distance away from the target and number of rotations is key. Doesn't work like in the movies where the guy can throw any knife he picked up off the ground and hit another guy square in the back who's running away from them.",
"So basically when throwing a knife you have to take distance and how many rotations are going to happen into account some people can get the perfect half rotation always stick others have multiple full rotations but the biggest thing in my experience is know how far you're throwing it and how many times it will turn. It's been a long time since I threw knives but I always based it around essentially how many paced away from the target I was. Also throwing knives are weighted heavier on the blade end generally they aren't balanced the same way regular knife or sword is."
],
"score": [
5,
3,
3
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
nv6gbr | Why do people all have different voices? | Biology | explainlikeimfive | {
"a_id": [
"h11em57",
"h11ece0"
],
"text": [
"The sound of your voice is determined by: * The shape of your throat * the shape of your mouth * The shape of your nose * The shape of your face * The amount of fat you have in your neck * The amount of muscle you have in your neck * The tension in your throat * The way you learned to speak All of which can vary from person to person.",
"Voice is produced by vocal cords and the shapes of the airways and mouth above them. Everyone has unique and slightly different cords and airways, because they grow biologically, therefore everyone gets a unique voice."
],
"score": [
27,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
nv6mto | Why are our vocal folds unable to work properly when inhaling? | Biology | explainlikeimfive | {
"a_id": [
"h11h060"
],
"text": [
"\"Properly\" is the enough adverb here. \"Differently\" would be more accurate. Your vocal cords/folds are evolved to work best when air is flowing past them *OUT* of your body, but they still work when air is flowing *IN*."
],
"score": [
6
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
nv7rer | why do fish or other underwater creatures yawn in a similar way to humans? If they breathe through gills shouldn't yawning be done more by flairing their gills wider instead of opening their mouth? | Biology | explainlikeimfive | {
"a_id": [
"h11lmmk",
"h11ubil"
],
"text": [
"They aren't really yawning, they're just breathing. Gills are where the water goes out, not in. Fish breathe in water, then force it through their gills to take in oxygen",
"Fish do not yawn, at least not the way we do. They do open their mouths sometimes, but that is typically to attract mates or deter aggressors. Stickleback fish open their mouths sometimes very wide and move their bodies in a way that looks like stretching. Meanwhile Siamese fighting fish seems to be yawning upon seeing another fish, sometimes even of its own species. However, then it jumps into an aggressive attack, which kind of shows that it is not really yawning, even if it looks like that for us. Siamese fighting fish may look like they are yawning, but they are actually just warning their competitors about an incoming attack."
],
"score": [
121,
25
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
nv8hgb | How do flavors work? | I was sharing a can of bacon flavored pringles at work with some coworkers and we got into discussing the different types of "weird" flavored chips we've eaten. Cheeseburger flavor, taco flavor, and oven roasted chicken flavor, pizza flavor, etc. How the heck do they manage to get the chip to taste like a cheeseburger? Bread, cheese, meat, and all? How? | Biology | explainlikeimfive | {
"a_id": [
"h11qgvf",
"h11py26"
],
"text": [
"The seasoning powder is made with combinations of dried ingredients like spices, dehydrated vegetables, or dried and powdered vinegar or sour cream. Some of these come from natural sources and others are artificially made. Something like a bacon cheeseburger flavour would be made by mixing salt with some powdered beef stock, pork stock, smoke flavouring, and powdered cheese. A taco flavoured chip might have the same beef stock with some Mexican spices, tomato powder, and powdered cheese.",
"Flavor all comes down to two basic things (as far as I'm aware): chemical composition, and temperature (this affects the movement of the molecules). If a scientist is able to break down the general composition of a cheeseburger to the basic elements and then create a flavor powder that contains most of the more important chemicals, then with a little bit of psychological suggestion people will taste what they are told it's supposed to taste like. Generally speaking, the more complex flavors like oven roasted chicken or pizza you wouldn't associate with those foods if you were blind tasting the product. For the oven roasted chicken you might think it's chicken broth flavored and for pizza you might think it's tomato and cheese flavored."
],
"score": [
7,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
nv8yd7 | What happens when photons are absorbed or emitted from atoms? | Physics | explainlikeimfive | {
"a_id": [
"h11son6"
],
"text": [
"The photon is not really a carrier of energy. It is the energy itself. A photon has no mass, there is nothing that could disappear to begin with."
],
"score": [
11
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
nv9mc7 | How do we know the universe is ever expanding? | Physics | explainlikeimfive | {
"a_id": [
"h11yiax"
],
"text": [
"Doppler effect. When the source of a wave is travelling away from you, the waves stretch out causing a shift down. That’s why the sound of a car horn changes as it drives past - the sound waves are getting longer and therefore the pitch is changing. The same thing happens with light waves - if the source is travelling away from you, the wavelength of light stretches until it drops below the visible spectrum. If this didn’t happen, then you wouldn’t see individual stars at night - the night sky would be full of stars from all over the universe."
],
"score": [
5
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
nv9umd | If time is relative, do drivers live longer? | If time is relative and when you move faster time slows down, does it mean that people who drive cars will live longer than people who always walk? I actually laughed out loud while typing this but I am really curious. | Physics | explainlikeimfive | {
"a_id": [
"h11yw94",
"h11yn4q",
"h11zm6m",
"h121fb4"
],
"text": [
"Yes and no - they won't experience themselves as having lived longer, however, they will have aged less than people who didn't travel. So time travel into the future is possible - if you travel at near light speed into space and back again, you could come back to a world in which everyone you knew is dead",
"It’d only be a fraction of a second over a lifetime. You’d also have to take into account their health and you’d need to assume there was no earlier accidental death due to the mode of transportation.",
"First of all, the math says that even if you lived in a car moving at highway speeds all your life, you might live for 2 minutes longer than were you not. That's an incredibly small difference in the grand scheme of things, and your odds of being killed in a vehicle crash vs being killed as a pedestrian more than make up for that. Being in a car is the more dangerous of the two by a pretty significant margin. Second, remember that time is relative to who's measuring in. You in the car experience time normally as far as you're concerned, and the person walking experiences time normally as far as they are concerned. In the faster vehicle it looks like the rest of the world speeds up around you as you go faster. Everyone else thinks you will live slightly longer, but nothing changes from the way you see it. Edit: \"slows down = > speeds up\" pretty sure this is the correct version now.",
"If you had two identical people who led otherwise identical lives and would have died at the exact same moment, in theory the one who drove would live for a few microseconds longer than he otherwise would have. In practice, this has some problems anyway, but the bigger issue is that other differences that people have would cause any difference this made at the speeds we drive at to be insignificant. To put this into a bit of perspective, let's take a page from r/theydidthemath and just look at the two numbers we'd care about, and a few others to give it context: The speed of a car driving on the highway at 65 miles per hour is going at roughly 30 meters per second. The speed of light is 299,792,458 meters per second. This means that at highway speeds you're traveling at 0.000001% the speed of light. For context, the earth's diameter at the equator is 12,741,981.1 meters. Assuming that you could track a photon across a path in equatorial orbit at the surface of the planet, in 1 second it would complete ~23 laps and be in the middle of its 24th. Going at highway speed, it would take you 424,732 seconds, or 7,079 minutes, or 118 hours, or almost 5 full days days of non-stop driving. In that time, that photon could have done nearly 10 million laps. Time dilation is a function that is based on an exponential formula, and as such it is only really noticeable at all - Given 30m/s as the velocity, I plugged in 80 years of nonstop movement at that velocity [into this calculator]( URL_0 ) and the answer was the same number of seconds I started with. Not even a single second of difference at that speed. If you plug in half of the speed of light, you end up with the relative time being about 92 years. So you really do need to ratchet up your speed quite a bit to see results."
],
"score": [
42,
17,
7,
7
],
"text_urls": [
[],
[],
[],
[
"https://www.omnicalculator.com/physics/time-dilation"
]
]
} | [
"url"
] | [
"url"
] |
nv9x8p | why do blacker skin tones get less sunburns(in general) than whiter ones (when the blacker colours would absorb more light) | shouldnt the darker tones absorb more light (hence heating up and burning more?) | Biology | explainlikeimfive | {
"a_id": [
"h11yhyz",
"h11yr79",
"h126sev"
],
"text": [
"Darker skin tones have more melanin than lighter ones, meaning they're better protected from the sun. But melanin isn't immune to all UV rays, so there's still some risk. A Centers for Disease Control and Prevention (CDC) study found black people were the least likely to get sunburned.",
"That is exactly what prevents sunburns. The darker skin, higher melanin content, absorbs more of the damaging UV instead of letting it pass to the squishy flesh beneath.",
"so like others said, melanin is the key here. melanin is produced by specialized skin cells, and creates a \"shield\" around the nucleus of the neighbouring skin cells, protecting the DNA. People with darker skin tend to live in places with a lot of sun all year round (around the equator) and need the extra protection against sun damage. white people, on the other hand, have less of those melanin-producing skin cells because they live in places with less sun (far from the equator). But why not go the default of protecting against the sun? because darker skin is less effective in making vitamin D from UV rays, and people who live in the north need all the vitamin D they can get, so their skin was optimized for vitamin D synthesis :) loll i get nerdy about science, sorry if that was a lot!! edit: optimized by evolution, ofc"
],
"score": [
10,
9,
4
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
nva0k3 | As to what the smoke you see coming off houses/poles/cars in nuclear bomb footage? | Every time I see footage of a nuke going off, there are the really cool but really confusing shots of objects turning into “smoke”. Is this the paint vaporizing off? Or the actual object vaporizing? Or, could it be something else? Thanks. | Physics | explainlikeimfive | {
"a_id": [
"h11zhxe",
"h120b96"
],
"text": [
"Burning stuff, be it wax, paint, dust, ... The energy density of the light from such a blast is so high that anything which blocks even a little of it will likely be heated beyond it's ability to dissipate the heat.",
"Follow up question: In the footage, you can see a blast wave travelling in one direction, then reversing. What's happening there? [ URL_0 ]( URL_0 )"
],
"score": [
14,
7
],
"text_urls": [
[],
[
"https://www.youtube.com/watch?v=wgpo0qAfwDk"
]
]
} | [
"url"
] | [
"url"
] |
nval77 | How the value of a nation's currency is determined? | Like why can't some country say something like "our country's currency value will be 200 times that of US dollars " . And who determines this value or how it is determined. And why it constantly changes. | Economics | explainlikeimfive | {
"a_id": [
"h124fgi",
"h122yky",
"h123ina",
"h1254zt",
"h124nb5"
],
"text": [
"\\ > \"our country's currency value will be 200 times that of US dollars \" They do. This is called \"pegging\" and is a fairly common practice. However, it does come with risks: if the currency you're pegging to changes in value in a way that's harmful to your economy, there's not much you can do about it.",
"The value of money is determined by the demand for it, just like the value of goods and services. When the demand for Treasurys is high, the value of the U.S. dollar rises. The other way is through foreign exchange reserves. That is the amount of dollars held by foreign governments.",
"Sure, Randomistan could say \"our currency is now: 1 of ours to $200USD.\" But if that value isn't realistic, no currency traders will engage in transactions and Randomistan will be screwed. And no/minimal tangible goods traders would trade with them either. If Randomistan tries to price their currency way out of what it should be, no one will sell them food/oil/raw materials/etc. at the price they want, and vice versa. Picture your street with a bunch of garage sales. Got a bunch of them all selling KidToy1 at $3, except that one guy down the street with an overgrown lawn and rundown house is selling KidToy1 for $25. Who's going to buy it from him at $25 when they can get it for $3 next door?",
"Anyone can print out some shoddy custom bills on their printer and claim they are worth 200 times the USD. The problem is to find someone who actually wants to buy these bills at your high price. The traditional way of doing this is to build a strong economy built around this currency and produce a lot of valuable goods that you export to other countries. But in order to export these goods people need to buy your currency using for example USD in order to buy the products they want from your country so they can export it. But be carefull because people might want to import goods into your country and they will have to offer a better price in order to get their hands on USD to buy things abroad. However the more modern way of making a currency highly valuable is to post about it on reddit claiming it is going to be the peoples currency to fight against the evil millionare. This is a very fast way of getting to be one of those evil millionares yourself as you were the one who made the currency in the first place or at least bought a lot of it early on and are able to sell it at a much higher price. If you are clever though and already a super billionare with your own space project then you can just mention the currency on twitter and see the price go up as all the gullable followers want to get rich too, so you sell the currency to them and then in your next national public speaking event you talk trash about the currency so you can buy them again at a low cost. This is of course all tax free since you are using offshore proxy accounts. I am not saying anyone have ever done something like this but that would be a very good way of making money.",
"> Like why can't some country say something like \"our country's currency value will be 200 times that of US dollars \" . They can. But to what end? Let's say you have some country whose unit of currency is the *foo*. Right now, 1 foo = 1 dollar. And let's say that 1 foo/dollar can buy 1 apple. This country wants its money to be 200 times the value of the dollar so it decides to come up with a new currency, the *bar*. 1 bar = 200 foo = 200 dollars. Everyone exchanges their foos for bars. But what has changed? If I had 200 foos before, I now have 1 bar. But I'm just as \"rich\" as I was before. I can't buy any more apples than I could have before. It'd be like if you went to your bank and exchanged 10 one dollar bills for 1 ten dollar bill. It doesn't make you ten times richer, you've just swapped one currency for another. > And who determines this value or how it is determined. In a free market, the value of the currency is determined, more or less, by supply or demand. The value of an object in currency is determined by how much of that currency people are willing to give up in order to obtain that object. Theoretically, a government could ban all export/import, forcibly set all prices and wages, but then you've completely removed yourself from world economics and your nation's currency really wouldn't have a comparison since it is completely isolated. Not to mention that such an economy would be doomed to fail. > And why it constantly changes. Because supply and demand changes, the cost of materials and labor changes, technology makes things cheaper but then produces more advanced more expensive products, natural and man-made events affect supply chains, hurt or promote businesses. The economy is a dynamic system that is always changing because people and the world is always changing."
],
"score": [
24,
22,
15,
11,
3
],
"text_urls": [
[],
[],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
nvaoe4 | what does Carl Jung mean when he talks about the "Shadow Self" | Other | explainlikeimfive | {
"a_id": [
"h12fya7"
],
"text": [
"The shadow self usually refers to the hidden parts of our personality that we reject either because we find them repulsive or because society does and we are ashamed. As a person with a Bachelor's in psychology I do have to say there is not a lot of evidence for this mainly because in the modern form it's not testable and in the original Jungian form it doesn't appear to be true. If you need I can edit this with references that will help if needed."
],
"score": [
5
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
nvc0vq | How do phones (and other devices) show the exact date and time even after being switched on after a while? | My phone was switched off since the past hour and I switched it on right now and I realised how normal it was for It to show me the exact present time and date and I wonder how. | Technology | explainlikeimfive | {
"a_id": [
"h12d5ye",
"h12c6wx",
"h12clmd",
"h12t308"
],
"text": [
"It has a battery-backed clock on the inside. You don't *have* to sync your time with the internet, and you don't always have an internet connection. If you don't, the phone still keeps relatively decent time while it's on. How? There's a circuit somewhere in the phone that serves as a clock. It might even be part of the CPU. One neat thing we figured out a long time ago is certain crystals vibrate at predictable frequencies when you run electricity through them. That's why you see a lot of watches say they have a \"quartz movement\". Both watches and computers take advantage of this. So basically a tiny quartz crystal gets installed in a thing that can count how many times it vibrates. Then some electricity is applied. The person who designed the circuit set it up so once the right number of vibrations happens, a \"tick\" happens. That \"tick\" might be once per second, but usually it's much faster so smaller amounts of time can be measured. The smallest amount of time that can be measured is whatever one vibration of that crystal takes. So even when your phone is \"off\", it's probably still running a tiny circuit that updates the clock. This only takes a teeny tiny amount of electricity. Many simple watches can go 3+ years on one battery charge. So your phone can stay off for a long time before that clock circuit drains the battery. PCs have this too. If you open most cases, you'll find a small watch battery attached to he motherboard. This is used to keep the clock running even when there is no power. There's also a battery inside some early Game Boy games like Pokemon Crystal that had a clock. By now many of the batteries have run out and those clock-based features don't work anymore if you turn off the game! Pretty much anything that has an \"off\" state and keeps the time is likely using a small battery-backed quartz clock to do so. These clocks aren't always the most accurate, though. Very accurate ones are more expensive. That's why computers tend to sync with an internet time source. My last PC could be as much as 5 minutes wrong if it went a day without internet connectivity.",
"Even when turned off, there is still a little bit of power being used to keep some fundamental operations of the device running, one of them being the system clock.",
"Turning your phone off does not cut the power to everything in your phone. Mostly just the screen and main processor. There's still a lot going on after you've powered it down.",
"There are a few different ways: * Some devices like TVs are never completely \"off\" - even when you turn the TV \"off\", there are some circuits that are still powered, such as a \"realtime clock\" chip. * Some devices like computers will have their realtime clock chip powered by a watch battery, so even when you unplug the device it will still keep track of time. * Some devices like your phone or your TV's cable box will just connect to a network and ask a dedicated timekeeping service what time it is. * GPS navigation devices get their time from the GPS satellites every time they connect."
],
"score": [
7,
5,
3,
3
],
"text_urls": [
[],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
nvc77w | If all human cells contain the same DNA, then how come your eye cells and your bone cells are different? | Is it something encoded in the DNA itself, or something on the side that makes cells different? | Biology | explainlikeimfive | {
"a_id": [
"h12d1il"
],
"text": [
"The DNA is like a complete list of instructions for the entire body. Each cell doesn't use all of those instructions though, they just focus on the instructions for the particular part they are meant to be. So while your eyes have a copy of the code to make every cell in your body in them, they are only using the part that makes eyes."
],
"score": [
14
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
nvcbv6 | Why do trucks tires need less air pressure than bicycles? | Physics | explainlikeimfive | {
"a_id": [
"h12hmzw",
"h12hy42"
],
"text": [
"It has to do with how wide the tire is and how much of the tire is touching the ground. This is a simple way to think of it: **Low pressure + high surface area = high pressure + low surface area** Bike tires don’t have much contact so they need a lot of pressure, because all of your weight is being focused on the two points of contact that are your front and back wheel, both being less than 2 inches wide. Truck tires have a lot more contact so they don’t need as much pressure. There’s also a lot more of them, some having 18 wheels total. This makes the weight be spread evenly, and since there’s so many, the weight is distributed evenly. Each wheel has to carry less weight for every added wheel. The wheels are also nearly a foot wide each, giving them much more surface area. URL_0",
"A typical road bicycle and rider weighs, say, 100kg. All of that weight rests on two tiny contact points of around 1cm sq each. That's 50kg on 1cm sq. A biggish truck may weigh around 40000kg and rests on perhaps 12 tyres with contact area of maybe 10x10 cm each. Total contact area =1200 cm sq. That's around 35kg per cm sq. So the pressure needed to support the weight on a road bicycle tyre is typically higher than on a truck tyre."
],
"score": [
15,
4
],
"text_urls": [
[
"https://www.quora.com/Why-does-a-bicycle-tire-have-a-much-higher-inflation-pressure-than-that-of-a-car"
],
[]
]
} | [
"url"
] | [
"url"
] |
|
nvcgl7 | When homeless shelters are set up in countries following natural disasters, what happens to those who were already homeless when the disaster occurred? | and if they’re allowed to use shelter, what happens when everyone gets relocated to new homes? | Other | explainlikeimfive | {
"a_id": [
"h12giz1"
],
"text": [
"Since you didn't specify one country there is no right answer to this. I can answer for mine, which is Germany. Here the first priority after a natural disaster is the safety of the people. The government would book hotel rooms or if there are none available build emergency shelters, for example repurposed gyms. The homeowners will be insured and use the insurance payout to either repair their home or get a new one. There is no organized relocation effort. For the homeless there will be the regular welfare that is always accessible to them. The problem here is that homelessness in Germany is seldomly the lack of funds, but comes from other reasons like distrust of the government or serious mental illness. They will most likely stay homeless."
],
"score": [
6
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
nvctbe | What is the difference between different kinds of 'oil'? | There's the oil from the oil wells which is inflammable but it's not in the form of petrol or diesel, which is also decided from the same oil, but petrol isn't oily to the touch the way regular cooking oil is. But cooking oil isn't as inflammable, irrespective of whether it comes from sunflowers, or groundnuts, or coconuts or some other source. However, the oil on our skin is oily, but again not inflammable. Help me wrap my heart around all these different 'oils' - and why some are more oily to the touch vs those that are not, and why some are inflammable vs those that are not. | Other | explainlikeimfive | {
"a_id": [
"h12j28e"
],
"text": [
"Oil is chains of hydrocarbons. Biological oil is fat where each hydrocarbon chain have a lipid acid end and three of these lipid acids is connected to a glyceride molecule. They have a lot of the same properties as mineral oil but are still distinct. The other major factor in the property of oil is the length of the hydrocarbon chains. Shorter chains is lighter which means they catch on fire much easier, flows much faster, etc. The shortest of these oils are natural gas which is technically the same thing but just very light. The longer the hydrocarbon chains the heavier the oil. They have a hard time catching fire (diesel) and runs much more slowly. Eventually they become tar, butter, pitch or tallow. The lubricity of each oil is a lot more complex. All oils are in general slippery but there are a lot of variations. The oils are not always straight hydrocarbons but often have kinks and loops and stuff which change their property. And small trace elements of esters or sulphur compounts can make the oil even more slippery. Oil wells generally contain a mix of different lengths of hydrocarbons while vegitable oil or animal fat is generally a lot more consistent. When we destill and process the oil from the wells this too becomes far more consistent. As for the flamability heavier oils like cooking oil or diesel is hard to burn in open air but if you heat it up enough it will catch fire. The easiest way though is to use a whick which helps it evaporate from the heat of its own flame. This is how old oil lamps worked and how a candle works. You can even make the oil in your skin into a candle if you want to."
],
"score": [
5
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
nvdupz | Why does rain fall in tiny droplets and not all at once? | What determines the size of a rain drop? | Physics | explainlikeimfive | {
"a_id": [
"h12n2pq",
"h12opm0"
],
"text": [
"Rain is restricted to drops of water that fall from a cloud. Larger drops do not survive as the process of surface tension which holds the drop together is exceeded by the frictional drag of air and therefore larger drops break apart into smaller ones.",
"In addition to what the other guy said, moisture has to form around something, it can't just appear out of the air (it doesn't just rain in your bathroom during a shower, the mirror gets damp and water droplets form there instead). If you had a planet with literally just water and not a speck of anything else, it would never be able to rain no matter the moisture. In our case though, each raindrop has to from around a spec of dust or bacteria floating around in the atmosphere. Eventually the raindrops get too heavy from all the water, and they fall before more can build up. This cycle continues until the moisture in the clouds is exhausted."
],
"score": [
14,
10
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
nved94 | What makes gummy type candies give them different textures? | Candies such as Gummy worms, Gummy bears, Sour Patch Kids, Gummy sharks, Sour Punch etc. What is in them that give different firmness, longevity, and/or elasticity? | Chemistry | explainlikeimfive | {
"a_id": [
"h12sc5k"
],
"text": [
"The real answer is \"Trade Secrets\". The \"technology\" to make most gummies isn't patentable, as the core techniques have been around pretty much since sugar was invented. Some of the effects you can achieve with simple manipulation of sugar over specific times at specific temperatures. Check out how to make [Turkish Delights]( URL_0 ) for a super basic primer. That will get you a good deal of the way there. They can also thicken juice with Fruit Pectin or Gelatin. The more you add, the more it gels. Again, manipulate this sugary gelatin at the right time and texture and you'll eventually hit their target. I know this is a vague answer, but you've asked a REALLY big question. Better to just go binge some [Gourmet Makes]( URL_1 ) for more specifics."
],
"score": [
6
],
"text_urls": [
[
"https://www.thespruceeats.com/turkish-delight-521388",
"https://www.youtube.com/watch?v=fEMxFSjmo5Q"
]
]
} | [
"url"
] | [
"url"
] |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.