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g13hec | During the ww2, do any of belligerent dispose some sort of "night vision equipment" to help night combat? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/g13hec/during_the_ww2_do_any_of_belligerent_dispose_some/ | {
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"I can speak about Soviet night vision equipment.\n\nDevelopment of night vision devices began in the late 1920s, but there was no prototype produced before 1940. The initial goal was to create night vision driver's observation devices so that tanks could drive at night, rather than fight. Trials in the winter of 1940 showed that the concept had some promise and development continued. Requirements composed in March of 1941 had a second scope for the commander. The goal was still the same, to drive at night with a speed of 10-20 kph (due to realistic expectations of the range of the vision), but there was also a provision for an IR signal lamp for nighttime light signals. However, by May 29th there was already talk of an IR scope for the gunner as well with a range of 200 meters.\n\nThe experiments for a driver's device were still the most promising. By August of 1942 a satisfactory device was developed that allowed the driver to see large objects from 50 meters, vertical items such as a person or a pole from 35 meters and road features from 12 meters. Clarity in complete darkness was similar to observing with the naked eye in moonlight. An experimental batch of 25 devices was produced and sent to the 26th Tank Corps for field trials. Trials showed that it's possible to drive at a speed of 12-15 kph with hatches closed when using the devices, and a human figure can be seen from 30 meters away in motion or 50 meters away when stationary. There were specific complaints made about several features of the devices, even though the concept was deemed promising. The chief of the GABTU ordered 60 more improved devices in order to conduct wider trials. \n\nThe 26th Tank Corps used the devices in battle until the spring of 1943, when they had to be destroyed during a breakout from encirclement. They were still judged to be far from perfect, especially in use during nighttime attacks. No significant improvement was made to Soviet tank-borne night vision devices during WWII and as far as I'm aware they were never used in battle again.\n\nSources\n\n_URL_6_\n\n_URL_3_\n\n_URL_4_\n\n_URL_0_\n\n_URL_5_\n\n_URL_1_\n\n_URL_2_"
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"http://www.tankarchives.ca/2019/10/night-vision-driving.html",
"http://www.tankarchives.ca/2019/10/night-driving.html",
"http://www.tankarchives.ca/2020/01/night-vision-conclusions.html",
"http://www.tankarchives.ca/2016/12/pre-war-night-vision.html",
"http://www.tankarchives.ca/2013/10/night-vision.html",
"http://www.tankarchives.ca/2019/10/night-rider.html",
"http://www.tankarchives.ca/2015/06/pre-war-night-vision.html"
]
] |
||
b0ljvb | Why didn't Japan have to pay reparations for World War II when Germany did? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/b0ljvb/why_didnt_japan_have_to_pay_reparations_for_world/ | {
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"What makes you think they didnt?\n\nPost war reparations from Japan took two main forms, very similar to what was extracted from the European Axis. The first being cash or free goods and services to both former combatant nations, and former Allied POW's, or the confiscation of money or other financial assets held overseas. The compensation for forced labor by POW's was actually then coordinated by Japan making payments to the Red Cross for distribution.\n\nThe other was the literal transfer of physical assets like remaining machinery, vessels, vehicles, and the like from Japanese control to other parties. Either taken from Japan itself, or whatever was left in newly free nations that was owned by a Japanese company or the govt, was no longer their property. \n\nThe process and parties Japan would be expected to pay and the general amounts were mostly hammered out in 1951 in the Treaty of San Francisco. It both officially ended US military rule in Japan, codified the expectations of the new Japanese govt with respect to honoring things like the decisions of the War Crimes Tribunals, and UN mandates, etc, as well as the financial aspect. \n\nOver the course of the 1950's then Japan concluded agreements with nations like The Philippines, Vietnam, and Indonesia to work out payment in either cheap loans, outright payments, or goods and services as a result of occupation of those territories. Though the value of Japanese assets in the former occupied nations that was transferred tended to be worth more than the new monetary compensation which was stretched out over 20 years of payments essentially. To put some hard figures out the payments for Burma, The Philippines, Indonesia, and South Vietnam totaled about 1Billion USD collectively in 1950's dollars. \n\nWhile for assets held abroad in one form or another\n\n > According to the Japanese government’s research, as of August 1945, the total amount of Japan’s assets abroad was US$23.7 billion, including: US$4.391 billion in Korea; US$2.658 billion in Taiwan; US$9.158 billion in North East China; US$3.465 billion in North China; US$2.295 billion in Central and South China; US$1.751 billion in other areas. _URL_1_\n\nIt should also be noted that there were exceptions, the USSR was not a party in San Francisco, nor was the PRC. China and Japan would not formally settle claims until the 1970's and a Joint Communique between the two was released wherein China renounced claims.\n\nThere were several other notable issues that were not covered specifically which have since caused tension, notably Comfort Women from occupied nations and any compensation due them directly and specifically. While the framing of long term or low interest loans as 'quasi reparations' would be a sticking point at times, especially as relates to South Korea. That also doesnt mean that private citizens have not occasionally bring new court cases against either Japan itself or private companies for compensation, and while most of the time Japan has been able to point to followup treaties with nations that barred further new claims, occasionally a court will side with the person bringing the suit and these cases can drag out for a decade or more. Nor was this only from Asia, Western POW's have brought cases occasionally as well.\n\n[Text of the Treaty of San Francisco](_URL_0_) if you would like to read it. \n\nI would give this wonderful article compiled by the Library of Congress a look through it examines much of both the process, and context or various forms of payment from Japan, and their challenges afterwards. _URL_1_"
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147g5h | Are there example of inter-species cooperation in nature? | Humans have domesticated animals rather successfully and often those animals get along rather well, without which, traditional farming would be much more difficult. Additionally, I keep seeing examples on reddit of animal which would in nature most likely never interact socially getting along quite well (mostly cats and dogs). Is this a result of domestication or is this a natural occurrence as well?
Edit: I realize I seem to have been misunderstood. My question was more about inter-species friendships, such as between a dog and a cat, or a cat and a pet rodent of some sort. | askscience | http://www.reddit.com/r/askscience/comments/147g5h/are_there_example_of_interspecies_cooperation_in/ | {
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"It has happened in ants, some species of ants farm aphids as a food source. _URL_1_\n\nEdit: Also some other cases if you are interested: _URL_0_",
"There are many examples of this. It's called a symbiotic relationship, synergy, or mutualism. A great example of this is the relationship between the nitrogen fixing bacteria, Rhizobium, and any legume, such as pea plants and clover. The legumes provide a stable environment for the bacteria inside their root nodules, whilst the bacteria fix the nitrogen in the soil so the plant can use it.\n\nA more visible example is the relationship occasionally seen between small predators, such as a Lynx and birds of prey. The bird spots the prey for the Lynx (the bird usually scares it away on its own, whilst the Lynx has trouble finding it) then the lynx hunts and kills the prey and they both share the meal.",
"Cleaning Fish!\n_URL_0_",
"There's a video on YouTube which shows dogs and baboons in a rubbish dump in India. The baboons kidnap puppies and raise them as pets, which later become guard dogs for the baboon troop. Arguably that is because the dogs have some history of human selection in the past, though.\n\nIn general, I don't think it's common (for animals as opposed to things like bacteria). The best known examples (cleaner fish, ants/aphids) have been mentioned. There are also cleaner birds, which work on crocodile teeth.",
"Moray eels and grouper fish have been observed cooperatively hunting. [link](_URL_0_)\n\nEDIT: the videos in that old article seem to be broken :(",
"Some primate species have been known to forage together. Sometimes, it's species who have diverse diets, like a ripe fruit-eating group will hang out with a leaf-eating or non-ripe fruit-eating group. These interspecies groups will respond to each other's alarm calls, even though those calls are not in the vocal repertoire of both. ",
"Yellow Watchman Goby and Tiger Pistol Shrimp work together in long lasting pairs in many reef environments. The Goby provide sharp eyes and act as a warning of incoming predators for the blind shrimp. They share the shrimp's burrow and sometimes even food.\n\n > \"The costs of the shrimp are that they cannot live without the guidance/protection of the goby. Because they are blind, they are completely reliant on the goby’s guiding and their protection. The goby in return cannot burrow a hole properly. Without the shrimp, they would have to find alternative methods of a home. In most places in the ocean world, an empty hole would be hard to find. The goby is almost completely reliant on the shrimp for finding a home.\"\n\nSee: _URL_0_",
"I would say any symbiotic relationship will work here. \nI study coral so this is my favorite:\nCoral/algal (symbodinium) symbioses. Coral are animals that harbor dinoflagellates in their cells. So basically there are plant cells inside the animal cells. Tropical corals live in shallow, relatively clear water. They are exposed to plenty of light, so if they can use it why wouldn't they? Having a symbiotic relationship with dinoflagellates provides corals with products of photosynthesis (sugars essentially) to use for energy. The coral provides carbon and nitrogen to the symbiont, as well as protection and a substrate to live in/on. It is mutually beneficial. There are plenty of complicated and confusing interactions that I have left out of this process, but generally it is interesting and mutualistic. "
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tp169 | what is 4chan and 9gag? | ... | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/tp169/eli5_what_is_4chan_and_9gag/ | {
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"4chan is a forum, comprised of unadulterated core of the internet. There are no rules in 4chan. It's the Internet, unrated, XXX edition. What you may see there may scar you for life.\n\n9gag is a website that takes funny content from reddit and rehosts on their website with a 9gag watermark. Redditors hate 9gag and hating on 9gag will garner you with karma."
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1ue0gr | why can't the hpv be cured? | While cancer and other deadly diseases can be cured in this day and age, why is it not possible to get rid of HPV (or the herpes virus) for good once you've contracted it? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1ue0gr/eli5_why_cant_the_hpv_be_cured/ | {
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"If i'm not misstaken you can get HPV vaccine... that is a cure.",
"There are exactly zero viruses that we know how to cure. Influenza? Nope. Chicken Pocks? Nope. HPV? Nope.\n\nWhen people give you medicine for viral infections its either an antibiotic (might treat symptoms, extremely bad idea) or a medicine specially designed for treating the symptoms. That's it. The medicine makes you more comfortable while your body defeats the virus. Because we simply don't know how to do it yet.",
"HPV is a virus. It's very hard to cure viral diseases - the drugs we have that kill viruses are very expensive, unreliable & often hurt the patient more than the virus will. All we can really do is take care of symptoms & wait for the body to clear the virus out. Most of the time, this happens quickly (like a cold or a flu). It can take several years with HPV & in some cases , like herpes, the virus might never really go away.\n\nIt isn't fair to say we can \"cure\" cancer - our best solution to getting rid of cancer involves trying to cut it out and hoping we don't miss anything or poisoning your body & hoping it kills the cancer without killing you."
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32fvn3 | How do we imagine stuff we've never seen before? | askscience | http://www.reddit.com/r/askscience/comments/32fvn3/how_do_we_imagine_stuff_weve_never_seen_before/ | {
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"Imagination and sight are two domains working in paralel. \nYou can imagine only that what you have seen (all kinds of shapes/colors), for it was alrerady associated (preserving the structure (pathways) of a specific picture corresponding to reality). But as new research shows the way the brain organizes its visual sense remains intact even in people blind from birth, and the pattern of functional connectivity between the visual area and the topographical representation of space (up/down etc.) can develop on its own without any visual experience. Here: _URL_0_\n\nBlindness from birth does not eclude imagination.\nI think they experience shapes and objects in imagined / projected 3D worlds same as we, what differs is the actual organization of their associations (method) with the real world inputs (other senses)"
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3dlqjc | Has anyone used game theory to attempt to explain sexual selection? | I've been reading other posts about sexual selection and in particular peacock tails, and the responses are usually in the form of "Here are a list of hypotheses that may explain what we observe, but we're not sure which, if any of these, are actually at work".
It seems like there's no clear theory as to why sexual selection exists, meaning an explanation which can be tested, or can be used to predict future situations or undiscovered data.
The extremes of sexual selection seem to be the opposite of an evolutionary stable strategy. I can see that from the male perspective, if the current landscape is dominated by females that prefer an elaborate trait, then possessing that trait can increase your chance of breeding so much that it offsets the fitness cost of having that trait. However, females in this landscape would greatly benefit from a mutation that prefers less elaborate traits.
Should a peahen prefer a less elaborate tail, she will have more males to choose from. Her female offspring will also prefer less elaborate tails and her male offspring will be less burdened by elaborate tails. This mutation should be hugely advantageous in the current situation. Why is there not a balancing force pushing peafowl back to a camouflaged state? How have these species become stuck in a positive re-enforcement loop that supports these costly traits?
Has anyone used game theory or evolutionary simulations to attempt to explain this? | askscience | http://www.reddit.com/r/askscience/comments/3dlqjc/has_anyone_used_game_theory_to_attempt_to_explain/ | {
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"In our game theory lecture the prof. talked about peacocks and mentioned the [Handicap principle](_URL_0_).",
"I think your issue is claiming the females male offspring will be less burdened. If she mates with a male without an elaborate tail then her male children won't have elaborate tails themselves. This means that they won't be as able to find females because a vast majority of females require males to have a large tail. This would seem to indicate that any female that doesn't conform to the standard preferences would be disadvantaged as about half of their offspring would have difficulty finding mates and any male without a large tail would be even more quickly eliminated by the females selection. This would mean that a large rapid shift would be required to make going against the common preferences viable. Also large random events may also be responsible for the development of sexual selection systems as a large random change in preference would be required.",
"In answer to your title, yes, there are scientists who have devoted their careers to this.\n\nThe most widely accepted theory of how peacocks got their tails is that the genes for a male having a beautiful tail, and the genes for a female liking the beautiful tail are linked (on the same chromosome) so they are inherited together. Therefore a peahen will have the gene which predisposes her to like the males fancy tail, but also a gene that if she were male, would give her a fancy tail. Conversely the cock will have the gene which, were he female, would predispose him to like the fancy tail. The theory goes that this led to a runaway evolution of fancy tails.\n\nYour idea is that a mutation in the female gene, causing them to prefer a plain tail, might be advantageous. However, if the theory outlined above is correct then this would work, as the female would have produce offspring which would prefer plain tails (in the case of the females) but possess fancy tails (in the case of males). Clearly this gene would not survive as the females would struggle to find a mate. Otherwise, simultaneous mutations would have to occur in the male and female genes, which is unlikely.\n\nExamples of runaway evolution such as this are rare; few species possess features which are such a liability except in the ability to attract mates.\n\nI would recommend reading Richard Dawkins' \"The Blind Watchmaker\", he discusses the specific example of peacocks in detail. ",
" > It seems like there's no clear theory as to why sexual selection exists \n \nThere's a long history and a very robust *body* of theory here. \nIt's a very important topic in the evo literature actually. \n \n\n\n\n > However, females in this landscape would greatly benefit from a mutation that prefers less elaborate traits. \nShould a peahen prefer a less elaborate tail, she will have more males to choose from \n \nBut the males will be of lower quality. \n \nThat's for a couple of reasons. \nFirst is that those extreme secondary sex characters are usually honest indicators of health. Any parasitism or disease stops the production of the most attractive traits. \nSo choosing the male with the best tail is also choosing the healthiest male. \n \nSecond is that choosing a male with a less attractive tail would make her male offspring less sexy. \n'Sexy sons' are part of the reason to choose sexy males. Her offspring will be more attractive to the other females, so her inclusive fitness is increased by choosing the best tail. \n \nSo if she preferred less elaborate tails she would be choosing unhealthy males that will also create less fit male offspring. \n \n \n > Why is there not a balancing force pushing peafowl back to a camouflaged state? \n \nThere is actually. Natural selection balances sexual selection for the \nshowy traits in males and sex specific expression allows NS to prevail in females. \n "
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1ykwfp | Does body temperature change when you're sleeping?. | askscience | http://www.reddit.com/r/askscience/comments/1ykwfp/does_body_temperature_change_when_youre_sleeping/ | {
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"Body temperature can naturally fluctuate up to a degree Celsius or more throughout the day. It varies with your circadian rhythm, amongst other factors. Tends to be lowest in the middle of the night or early morning.\n\n_URL_0_\n\nSecondary source: I measure body temps as my job."
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zrgv2 | why is interference with digital tv signals so seemingly mysterious and unpredictable? | I have two digital TV's in my house. Both are hooked up to a wall socket (with a splitter leading to two long RF cables) which is connected to an internal roof antenna with an amplifier and all the usual stuff connected to a powerful antenna.
Then yesterday, a problem cropped up. Basically, the "Secondary" TV stopped getting a signal, at all, and the first TV got a signal, but it was choppy and laggy, breaking up and distorting.
After trying a few different things, oddly my best solution was to unplug the splitter completely from the wall socket (with the two RF cables still attached), and the primary TV then received a perfect signal (keeping in mind it's NOT PLUGGED IN), and the secondary TV still didn't work.
After a bit of fiddling today, I discovered that one of the RF cables I had (there were multiple, joined with gender benders, for each TV) was obviously the source of the problem. Swapped it out and everything was fine, on BOTH TV's.
**My question is : Why is interference with DTV's so complicated? And at a really basic level, what is at work when (and everyone can relate to this), for example, you flick a light switch, or you just *close the fridge*, and your DTV momentarily distorts/gets interference?**
| explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/zrgv2/eli5_why_is_interference_with_digital_tv_signals/ | {
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"I'm not so great at explaining things, but here's my attempt:\n\n\"Digital\" signals are transmitted between the source and destination as analogue transmissions (voltages on a wire, radio waves, etc). The source will typically add redundant information to the stream when it converts from digital to analogue, and the destination can then use this extra info to reconstruct the signal if it's corrupted slightly.\n\nThe practical upshot of this is that the transfer from source to destination can be perfect, even if the connection is poor. However, if the connection becomes so bad that the destination can't rebuild the signal, then the transfer suddenly goes from being perfect to really bad.\n\nIn answer to your other questions:\n\nYour first TV worked without being plugged in because the wire itself was picking up the signal. An antenna is just a section of wire after all.\n\nSwitching other devices in your house on or off will cause the mains voltage in your house to bounce, this normally shouldn't be a problem because your digibox should be able to cope with it. If it can't however then the bounce will stop the digibox from working until it goes away.\n\nSource: Master's degree in electronic engineering."
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9n182k | Can old plastics spontaneously explode? | I was listening to the 99% Invisible podcast, at about 19:30 someone (Emma McClendon?) says the following (my transcription, please forgive any errors).
I did a few Google searches but couldn't find anything more.
"This is what people need to realize, plastics sometimes age
in such a way that they are attempting to go back to a gas or
they want to go back to a liquid.
So that means that if you feel your sneaker sole that you've had for a
really long time begins to stick to the floor you should get rid of
it because it is what we would call weeping or other terminology.
It's going back to it's liquid state. It's toxic, you don't want to touch it.
**Same with something if you keep a plastic comb or barrette or
a Tupperware container, you never know, in an airtight drawer,
say you don't open it for years,
and then you open it and you find shards it means that it exploded.
It literally combusted at some point and you will smell it.**
These things are giving off noxious fumes.
And again we don't tend to see this because we see plastic as disposable but that's what this stuff is doing in these landfills."
_URL_0_ | askscience | https://www.reddit.com/r/askscience/comments/9n182k/can_old_plastics_spontaneously_explode/ | {
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"Plastics will degrade/decompose over time. How quickly depends largely on the type of plastic, and the conditions of use/storage. Generally, any extreme conditions (heat, humidity, pH, etc.) will be harsher.\n\nThat being said, the majority of plastics you would run into are likely to break down first into smaller chains (I don't know how much background you have, but plastics - polymers - are long chains of repeated \"building blocks\"). There can be off-gassing or degradation to other organic molecules, but few if any of them would be explosive.\n\nIt's an oversimplification, but aside from combustible gasses or liquids (methane or many organic solvents, for instance) most explosive organics are nitrogen-rich materials, in particularly higher conjugated nitrogens such as azides. However, such byproducts are not particularly stable, so polymers are very unlikely to produce them by normal degradation processes.\n\nMore likely, the cited example would be an airtight container that burst due to the pressure from off-gasses. They are also unlikely to smell \"noxious\", as most strongly smelling gasses have sulfur, or possibly some nitrogen complexes. Few consumer polymers contain enough sulfur to lead to such problems, so any smell would most likely be things like CO2, ethylene, etc.\n\nWhat also happens with many plastics is embrittlement. It's what it sounds like, plastics can become very brittle - often accelerated by UV exposure, for instance. This can cause them to shatter for no apparent reason, if for instance manufacturing processes were not ideal. Perhaps there are stress concentrations in the plastic from being formed, that become untenable once too much ductility is lost. Then, they will crack. Or, the brittle plastic is under increasing pressure from gas buildup inside, and shatters. The exact options are actually fairly broad, so it's hard to give a catch-all explaination.\n\nBut, plastics don't \"attempt\" to become liquid or gas. They simply degrade, as can all molecules. Hell, water can and does spontaneously \"degrade\" into H+ and OH-, O2 can spontaneously form O3 and then decompose again... All materials tend to try to form the most stable state and configuration available to them, including Tupperware.",
"The only thing I can think of that's remotely like what the interviewee is describing is celluloid, aka nitrocellulose. This was a very early plastic used in the 19th century: it was often used as imitation ivory or tortoiseshell to make things like billiard balls, combs, and buttons. Later on it was used to make movie film.\n\nNitrocellulose is highly flammable, and in a refined form it goes by the name \"gun cotton\", and was used to make smokeless powder for firearms. There are old stories of saloon owners in the Old West writing to the manufacturer thanking them for the new imitation ivory billiard balls, but complaining that when struck hard they sometimes caused a loud bang that tended to startle the trigger-happy guys at the bar. \n\nThere are urban legends of celluloid buttons and combs also blowing up, but I can't find confirmation that that actually happened or was even possible.\n\nThe expert in the interview may be inflating this very specific problem with one historical plastic into an overall property of plastics in general.\n\n_URL_2_\n_URL_1_\n_URL_0_"
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"http://mentalfloss.com/article/64247/first-plastic-billiard-balls-routinely-exploded"
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swie5 | Can someone explain to me how and why mass increases with speed? | I was watching a video about the LHC and they were saying that the mass of the particle by the time it reached the 4th stage in the LHC was something like 25,000 times the mass of the particle before acceleration. How does an object add mass? Why are mass and speed linked in such a way. Am i confusing mass and weight? Does the particle weight 25,000 times more? Is the mass that the particle adds caused by it somehow absorbing the energy that is used to accelerate it? | askscience | http://www.reddit.com/r/askscience/comments/swie5/can_someone_explain_to_me_how_and_why_mass/ | {
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"They are considering relativistic mass which sounds fancy, but isn't used often by the physicists I know because it leads to confusion and questions exactly like yours. :P\n\nThe idea of relativistic mass is that it's the hypothetical rest (not moving) mass of an object that has the same energy as the lighter real object which is moving at high speeds.\n\n > m(relativistic) = E(of object)/c^2\n\nFor instance, the relativistic mass of a particle of light with a wavelength of 1 nanometer would be 2.2\\*10^-30 grams. So a hypothetical object with a rest mass of 2.2\\*10^-30 grams would have the same energy content of a 1 nm light particle.\n\nTherefore, a better way to imagine this is to consider the full energy equation:\n\n > E^2 = p^2 c^2 + m^2 c^4\n\nAs you add energy to a particle, like at the LHC, it's the momentum of the particle which increases indefinitely while the mass stays the same."
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4fw0hl | Why is the Sin 0i/Sin 0r ratio is equal to the refractive index of a material? | Hi, I was covering sine's law in my science class and could not figure out how this ratio is equal to the refractive index. Thank you! | askscience | https://www.reddit.com/r/askscience/comments/4fw0hl/why_is_the_sin_0isin_0r_ratio_is_equal_to_the/ | {
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"This only works if the index of refraction in the material where the incident beam travels is 1 (which would be the case, to very good accuracy, if the incident beam is traveling in air). You can see this via Snell's Law."
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h52fl | What happens when a black hole "finishes"? | So I was reading an article on misconceptions about blackholes and the author was talking about "active" black holes. So my layman's understanding of black holes (and please correct me if I'm wrong) is that they are a point with intense gravitational pull that suck things into its center to create something incredibly dense. The things that aren't sucked into its center get spun around the black hole just as they would around any other gravitational center in space. So what happens when a black hole is finished sucking things into its center? Do they ever finish? | askscience | http://www.reddit.com/r/askscience/comments/h52fl/what_happens_when_a_black_hole_finishes/ | {
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" > So what happens when a black hole is finished sucking things into its center? Do they ever finish?\n\nThe \"sucking\" is nothing more than the force of gravity. Black holes have mass, and are generally the result of a star going supernova and then collapsing back on itself. So long as the black hole has mass, it will continue to exert gravitation force on things just like any other star. It can't \"stop sucking\" any more than the sun or the earth can.\n\nThe thing that makes black holes unique is the strength of the gravitation field. As you get closer to a planet or star, the force cause by gravity increases. However, once you reach the surface and start \"digging\" into the body, the force begins to drop again, since the shell of material above you cancels itself out (the stuff directly above you exactly counterbalancing the stuff on the opposite side of the planet/star from you).\n\nA black hole, though is **extremely** dense, so you can get much closer to its \"surface\". In fact, you can get so close that the force of gravity is strong enough to capture light and not let it out (this is an oversimplification, but it's close enough to give you an idea of what's going on).\n\n----\nThe other way I could interpret your question has to do with time dilation, and whether or not material falling into a black hole every actually reaches the center. I *believe* that the answer to that is \"no\", but I'm not an astrophysicist, so take that with a grain of salt.",
"I think what you're thinking of is [Active Galactic Nuclei](_URL_0_). And that's usually when a very *large* amount of matter is falling into the black hole at that point in time. But the black hole is never \"finished\" as you're saying. Sometimes there's just more stuff around them.\n\nThey do evaporate away but it's over insanely mind-bendingly long time scales."
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2nwkkw | how does dominos pizza tracker work? or is it not even real? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2nwkkw/eli5_how_does_dominos_pizza_tracker_work_or_is_it/ | {
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"They have buttons to press on their display screens that tell them what to make. In theory it's real and shows the real names of the people that are really logged in. But how real it actually is depends on how much you trust a bunch of teens to actually take it seriously and keep logged in as the right people and to not just mash the button at whatever time keeps them from getting in trouble regardless of what's actually happening. ",
"Former Domino's driver here.\n\nThe system watches everything, from when the order is logged, to when it's cleared from the make line (into the oven) to when it's dispatched by the driver. Then it goes by the estimated time for delivery. I never got any feedback on how accurate it was."
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11xjjp | Is there anything advantageous about the position of our solar system within the Milky Way Galaxy? | Earth is within the solar system's "Goldilocks Zone." Earth is neither too close, nor too far from the sun's radiation for liquid water to exist here. My question is: Would a solar system like our own be able to exist at a distance significantly further from or closer to the center of our galaxy? Is there some limiting factor such as cosmic radiation, with respect to the possibility of the existence of life?
| askscience | http://www.reddit.com/r/askscience/comments/11xjjp/is_there_anything_advantageous_about_the_position/ | {
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"I'll give one example. We would have no luck trying to find a location for our solar system near the core of the galaxy. Stars are much more densly packed near the center, 0.2 stars per cubic parsec where we now are located versus 10 million stars per cubic parsec when you are within a parsec of the center [[source](_URL_0_)]. High energy phenomenon in a variety of wavelengths are common in these parts as well. The implications are pretty clear, but some content in the link provides more insight about the environment of the center of the galaxy.",
" > We are one of the 30B lucky ones out of the 100B stars in our galaxy\n\n[Dr. Lawrence Krauss](_URL_0_)"
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rfji7 | 100-year-old light bulb? | Today, I learned that there is a [light bulb](_URL_0_) that has been glowing continuously for over a century. How is this possible? Why don't regular, more advanced light bulbs last as long? | askscience | http://www.reddit.com/r/askscience/comments/rfji7/100yearold_light_bulb/ | {
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"Low power (about 4 watts), robust carbon filament and a lack of thermal expansion/contraction cycles since it's left on.\n\n4 watts isn't very bright (60 watts is a \"normal\" incandescent bulb), cheaper and easier to make filaments are used in modern bulbs and we turn our lights on and off.",
" > How is this possible? \n\nIf a light bulb is run at a sufficiently low temperature, it can last a very long time. Works for people too.\n\n > Why don't regular, more advanced light bulbs last as long?\n\nIf you took a regular, store-bought light bulb and ran it at 1/2 or 2/3 normal voltage, it would last just as long as that famous bulb -- maybe even longer.\n\nThe only reason light bulbs typically last only 1000 hours is because they're run at very high temperatures. This is why we didn't consider incandescent lights for the Space Shuttle during my time as a NASA engineer -- they're not reliable enough.\n"
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9f04e3 | If grasses evolved relatively recently, what kinds of plants were present in the areas where they are dominant today? | Also, what was the coverage like in comparison? How did this effect erosion in different areas? For that matter, what about before land plants entirely? Did erosive forces act faster? | askscience | https://www.reddit.com/r/askscience/comments/9f04e3/if_grasses_evolved_relatively_recently_what_kinds/ | {
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"I'm not the best suited to give an in-depth explanation, but I would note that angiosperms as a whole are relatively recent in the evolutionary timeline of plants, which have been around for about 480 million years.\n\nThe first flowering plants diverged from gymnosperms about 200-250 mya, and angiosperms became widespread about 120 mya (so about the last quarter of the entire existence of the plant kingdom).\n\nPoaceae (the family that contains grasses) was originally thought to be around 55 million years old, but older fossil evidence keeps turning up. Plant structures associated with grasses have been found in fossilized dinosuar feces dating back to 66 mya, and revised dating of the rice tribe and fossil evidence of mammals with apparent grass-feeding adaptations have pushed the origins of Poaceae back to around 100-120 mya, about the same time that flowering plants became widespread.\n\nAs far as the make-up and distribution of plant communities prior to the emergence of grasses/grasslands/angiosperms in general I really don't know. Nor do I know much about erosion and soil formation at the time plants first began to colonize land.",
"That question is kinda hard to answer, here’s my attempt as a plant ecologist. Grasslands today exist where grasses can outcompete pretty much everything else, or that are too inhospitable for other vascular plants. Without competition from grasses, shrublands and woodlands would likely have been able to establish in many of these places, other places that were too harsh likely would have been barren except for a covering of moss, lichen, or cryptogamic crust. Marshes, wetlands, meadows etc that are dominated by grasses and grasslike plants either would have instead been dominated by mosses, ferns, and horsetails or trees and shrubs that can tolerate wet feet, or just open water, maybe with aquatic plants/green algae.",
"I've read that ferns likely occupied the niches that grasses do in modern times. Grazing dinosaurs ate ferns which were harder to digest than grasses are for modern grazers. Not sure what hypothetical consequences came from that. I'll have to do some searching to find the source of that info. ",
"I'll give my two cents with the two examples I know, the African savanna and the Australian outback, they have similar stories. \n\nThe savanna/outback used to be home to jungle/rainforest. The thing about rainforest is that it is a self-perpetuating cycle. There is a huge amount of evaporation, called transpiration, that comes from the leaves of the plants in a rainforest, this causes a lot of water vapour to form above the rainforest, which makes it rain, which feeds the plants which move the water to the leaves which transpirates. \n\nMost of the African and Australian continent used to be rainforest but became grassland over thousands of years due to 2 factors. The first is mechanical destruction. The african rainforest was destroyed by elephants. Less rainforest means less rain which means the rainforest will not grow back. Grass grew back after being trampled because it didn't rely on such delicate conditions. Then the grass caught fire. Natural grass fires burn grasslands down to stubs, but grasses have evolved for this to be as painless as possible and grow back quickly. They also burn all the trees that were competing with the grass. Evolution can be really smart sometimes. So you get savanna. In Australia the source was a bit different. Natural fires helped but what was possibly the biggest source of rainforest loss was the indigenous people burning the forests to hunt animals. Nowadays there are some trees that must be burned to reproduce.\n\nTl:dr: Thick rainforest and jungle, at least in Africa and Australia.",
"[Grasses evolved about 60-120 million years ago](_URL_1_) and this estimate is under constant revision in the face of new fossil evidence.\n\nBut many plants which could casually be called \"grass\" are not actually grass, yet occupy many of the same ecological niches.\n\nSedges, for example. I could not quickly find a source of estimates on the earliest sedges, but [the phylogenetic tree in this wikipedia article](_URL_0_) suggests that sedges (Cyperaceae) are more basal than grasses (Poaceae). So I would imagine them to have been around earlier. Emphasis on the word \"suggesting\".\n\nA solid answer may not be available due to lack of good fossil evidence. Even though there are fossils of both families, and these can be dated, how do you know if you have found the oldest fossils of both? You can only start to be confident after a great deal of effort.",
"Ok. As an ecologist who isn't totally across the history or the details...\n\n & #x200B;\n\nGrasses have been around for maybe 100 million years. But grasslands as a widespread, dominant ecosystem is relatively recent (last 10-20 million years).\n\n & #x200B;\n\nThis has coincided with a general drying trend globally. Grasses can handle extreme dry conditions better that trees, by just dying and reseeding, or re-sprouting. Their fibrous root systems can handle soil drying and cracking a lot better than trees, which can be damaged from shifting soil. A lot of grasses are fine with fire, for similar reasons to drought. Adding to that was the coevolution of grasses with grazing animals. They tend to eat everything, but importantly they don't kill the grasses. Having low/ground-level growing tips is the key here.\n\n & #x200B;\n\nThis dynamic of grazing animals and huge grasslands is relatively new. In Australia (where I'm from) before this dynamic much of the continent was covered with forests! Even rainforest. So at ground level there was generally a lot less growing. Ferns, mosses other small herbs, some understorey shrubs. But not in the ground covering layer we expect in a grassland, or with anything like the growth rate. \n\n & #x200B;\n\nThe soil in forests is largely protected by the amount of organic matter from fallen branches and leaves, and the interception of wind and rain by the forest canopy. The depth and friability of forest soils mean there is a lot less runoff driven erosion.\n\n & #x200B;\n\nBefore land plants is getting a little out of my knowledge, but erosion must have been far higher! Imagine the dust storms with nothing holding the soil. But I'll have to leave the details of that to someone else..."
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8obnqq | Can Pilot Wave Theory be expanded to incorporate relativity? What are the current barriers to its expansion? | askscience | https://www.reddit.com/r/askscience/comments/8obnqq/can_pilot_wave_theory_be_expanded_to_incorporate/ | {
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"The fundamental problem in combining pilot wave theory and relativity is that:\n\n* Pilot wave requires each particle's motion to be determined by the motions of every other particle's motions in the whole universe at that instantaneous moment. This is why pilot wave is called a deterministic and nonlocal theory.\n\n* In relativity, there is no such thing as a universal time, so there is no such thing as a shared instantaneous moment.\n\nIn essence this implies that for unmodified pilot wave to function you can't just know what the universe is doing \"now\", but also what the universe will be doing in the future to even solve for what \"now\" is supposed to look like.\n\nTo illustrate consider two observers trying to solve for the motion of an electron in a box. One observer A is at rest relative to the box, the other B is moving.\n\n* A can solve for the electron's motion if they know how the pilot wave is behaving now.\n\n* B can also do this, but their \"now\" relies on events that can change the pilot wave that haven't happened yet for A. The reverse is true as well. \n\nIt's actually even worse because neither A and B can agree on the order of many events, but wouldn't the pilot wave change if two external events happened in a different order? And on top of this difficulty, A and B must predict the same behavior for the electron. We must agree on what happens right?\n\nThis is a serious problem. There are efforts to fix this and make a relativistic pilot wave, but I'm not really qualified to comment on them, but from a light-reading on them, they do not look very satisfying. "
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2uf1hk | why to the label wood 2"x4"/ 2"x6" / 2"x8" etc when the true measurements are irregular and actually 1.75"x3.5" and so on | *they | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2uf1hk/eli5_why_to_the_label_wood_2x4_2x6_2x8_etc_when/ | {
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"That is the original dimensions of the rough cut lumber. Older houses actually have 2\" x 4\" 2x4s but later they began to plane 1/4\" off each side for nicer wood, as a result, everything is 1/2\" smaller then what we call it.",
"It's actually 1 1/2\" x 3 1/2\".\n\nThe explanation saying the wood shrinks as it dries does not make sense as all dimensions up to at least 12\" are 1/2\" short of the real number. If this were a case of shrinkage, the larger dimensions would shrink more.\n\nI've heard for years that 2\"x4\" are the rough cut sizes, and in fact I've seen wood of that dimension in an American house from the 1920s. The surfaces of those studs and joists are very rough, lending credence to the other thing I've heard, which is that the wood is rough cut to 2\"x4\" (etc), then finished down to the size that's 1/2\" under the whole number.",
"In addition to what people have already said, it's good to know that the amount milled off of one-bys and two-bys is slightly different. \n\n[Example](_URL_0_) ",
"Thanks, I thought it was probably something like that.\nAs far as wood use from a tree I found this a while back that is a pretty cool representation. _URL_0_"
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6v3nro | Was there any pushback to Sykes–Picot Agreement in the West? | It just on its face seems like such a bad idea, did folks warn of possible issues at the time? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/6v3nro/was_there_any_pushback_to_sykespicot_agreement_in/ | {
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"There was absolutely opposition to the agreement in the West. For the most part it took on one of two, similar yet different, forms: one was the outrage at the British Administration for violating the Arab's right to self-determination, and the other was opposition in light of the British not using their influence to obtain *more* from the Arabs.\n\nTwo advocates for Arab self-determination were T. E. Lawrence and Woodrow Wilson. It's widely known that Woodrow Wilson advocated very strongly that each nation, especially those under imperialist overlords, had a right to act independently and govern themselves. During the War, the British convinced the Arabs to rebel against the Ottoman Empire by promising them independence, which was seen by Wilson as an act of goodwill. When the secret agreement was published, he was offended at the encroachment of his ideals for pure political gain. Following the war, his office administered the King-Crane Commission as a last-ditch effort to investigate how a division of the Middle East should take place as though to minimize disaster. However, while originally observed by the other members of the Great Four (Italy, Britain, and France) the Commission was subsequently ignored and the Sykes-Picot Agreement was followed during post-war negotiations instead.\n\nSimilarly, T. E. Lawrence, following his awareness of the agreement, felt that his direct support for the Arab rebellion was based on lies. Held a disdain for the agreement which was showcased in his autobiography. Lawrence knew about it when it was drawn up, due to his involvement with the rebellion, and came to a moral crossroads when it was signed. He struggled with whether to continue to lie to his Arab allies or reveal the truth. In the end, when it was published, Lawrence begrudgingly pushed forward and helped the Arabs in their, now seemingly empty, campaign. As he wrote in *The Seven Pillars of Wisdom*, \"I had to join the conspiracy and assure the men of their reward. Better we win and break our word than lose.\"\n\nDetractors from a pro-British standpoint included William Reginald Hall, the then-Director of Naval Intelligence for Great Britain. He actually was involved in the review of the agreement's draft, but he berated it for ignoring the possibility of including a \"Jewish home\", as well as strategic importance of railroads through Palestine and Egypt, into the agreement. Similarly, Henry McMahon, the British High Commissioner in Egypt at the time, felt betrayed by his superiors that the deal had taken place: he was at the forefront of negotiations with The Sherif of Mecca, Hussein bin Ali, over British support for Arab independence following the war. He too felt betrayed, as the agreement undermined all of his office's work, on top of making him look like a liar to Hussein and his supporters, who would become local leaders following the war.\n\nThere were no doubt individuals in other notable positions that opposed the agreement for treating the Arabs unequally, or for disrupting good British-Arab relations, but at the time the agreement was seen by the majority of the West as a means of maintaining good infrastructure (the British) or expanding influence (the French). \n\n----\n\nSources:\n\n- Barr, James. *A Line in the Sand: Britain, France and the Struggle for the Mastery of the Middle East*. New York City: Simon & Schuster, 2012\n- Smith, Charles D. *Palestine and the Arab-Israeli Conflict: A history with documents*. New York City: Bedford/St Martins, 2016.\n- Lawrence, T. E. *Seven Pillars of Wisdom: A Triumph*. London: Anchor, 1922.\n- Danforth, Nick. \"The Middle East That Might Have Been\". *The Atlantic*, February 13, 2013. Retrieved from _URL_0_"
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2amh62 | History of international trade: where did the actual exchanges take place? | It's easy to research where the trade routes were for any given period of time. I wanted to know where goods were exchanged. Specifically, how organized was this process? Did all villages on the trade routes have markets and all of the exchanges took place there? Was it more of an exchange of goods, or was there a common currency (eg: gold)? Did the end-user purchase the item directly from the traders who traveled on the trade routes, or were there just as many middlemen as exist today?
If someone could point me to any references about how trade historically took place, I would also love to read it! | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/2amh62/history_of_international_trade_where_did_the/ | {
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"It depends on what type and scale of trade you are talking about. Some types of trade aren't really done from a profit motive, and are more accurately termed \"exchange\". A classic example is the so-called \"Kula Ring\" famously described by early anthropologist Branislow Malinowski, in which the Trobriand Islanders would exchange items to partners who are well known and for reasons of cementing personal bonds rather than gaining economic advantage. Lest we think this is something only weird islanders do, think of Christmas or other gift exchange holidays, in which items are exchanged personally from face to face interaction.\n\nBut if you mean in terms of economic exchange from profit motives, historically this has frequently been done at set market times or fairs. Peddlers, for example, would typically travel a set route corresponding to different market centers, For example, in a workshop in Pompeii the owner had scratched on the wall plaster the schedule for the market fairs in the towns in the surrounding region. This person would thus be able to travel to nearby towns in the knowledge that when he arrives there he could sell his wares from some sort of ephemeral stand.\n\nWhat you are really interested in, I suspect is more large scale affairs. For example, I study the trade between India and Rome, which was largely carried out on large ships travelling between the Roman Egyptian ports on the Red Sea and the ports along south India. We know from literary sources that these ships would make frequent stops along the way and engage in \"tramp trading\" in smaller ports along the way. How did this work? From comparative evidence it is likely that the members of these villages, which would frequently be fishing dependent, would simply sail or row out to meet the larger trading vessel (which could not approach the coast) and engage in barter in that way. They might carry, for example, a load of food or water supplies and exchange it for wine.\n\nHow the trade was conducted when the ship reached its destination is a bit murky. The traditional view, still somewhat bafflingly supported by some scholars like Whitaker, is that the trade was entirely within the hands of \"princes\", that is the local rulers who engaged in it purely to obtain high prestige items. This has no support, but it is likely that local authorities were involved in organizing trade in some way. For example, at the Gujarati port of Barygaza it is said that local ships would go out to help guide the Roman vessels through the shoals, and goods would be led up to a warehouse to be stored before being sold. It is quite likely that these goods would be sold at an auction or through some sort of dealing between merchants. Facilitating this would be Roman merchants who resided year round in India.\n\nAll of these large networks (such as the \"Silk Road\") were really groups of middlemen, depending on your point of view. A glass bowl travels from Italy to China through innumerable different hands by being absorbed into preexisting trade routes."
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8el93g | chimerism and how it happens in humans. | Asking due to [this comment](_URL_0_) from a /r/showerthoughts post. Credit to /u/yumyumsmoothie for the post mentioning Chimerism.
| explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/8el93g/eli5_chimerism_and_how_it_happens_in_humans/ | {
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"I heard about this case also, and just did a little research. Basically, two separate fertilized eggs merge together, and the DNA is combined. Certain parts of the body have different DNA. [Here](_URL_0_) is an interesting article on it.",
"Chimerism describes technucally two bodies who are combined into one. With plants you can do that quite simply: cut off a branch from tree A, cut one off of Tree B, connect branch A with Branch B and they will most likely continue to grow as one even though they have different DNA's. I do not know if Chimerism is possible in Reptiles/Amphibians/Birds (species that lay eggs) but it would be definately more difficult... in mammals such as Humans it happens in the womb, when the Organisms seemingly \"merge\" together at an early or sometimes even a bit later stage. Chimerism can only happen if you would have gotten twins but they merged into one",
"Two eggs are fertilized in a woman to make two embryos. Then, for some reason, the embryos fuse (they might not technically be embryos--they might be at an earlier stage, like blastocyst or something) and become one embryo. The embryo then grows into a person, like normal. But since it is made of half one set of genetic material, and half another, the resulting person (or animal) is made up of two different genetic sets. It could be the left side of a person's body is from one set of genes, and the right side from another. Or the top half from one set of genes, and the bottom from another, or a more convoluted mixture not easily separable into right side/left side, but rather certain organs from one set of genes, others from another. In Lydia Fairchild's case, we see reproductive organs from one set of genes, external body parts (skin, hair) from another. \n\nIt's thought that some cases of people with different color eyes could be due to chimerism, and of hermaphrodites (where, say, the left half of the body has masculinized traits and the right side feminized traits). \n\nIt's still pretty early after the discovery of chimerism, so it's hard to say how common it is. It requires some extraordinary amounts of genetic testing to uncover it and there is seldom a call to do that."
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3nrmv7 | when drinking, why don't liquids flow straight down instead of us having to swallow them? | Tried Wiki - couldn't get through the Latin medical terminology. When you drink something, you make an active decision to swallow the liquid already held in your mouth, why isn't this automatic so that the drink flows straight down? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3nrmv7/eli5_when_drinking_why_dont_liquids_flow_straight/ | {
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"It gives you the chance to hold something and breath without swallowing. Imagine if the substance was blood, poison, or saltwater: would you really want to swallow? By the same token, say your mouth is full of water and you try to breathe through your nose; do you want that water going into your lungs?\n\nIt's all to keep things from going where they're not supposed to go.",
"Multiple mechanism, I'm not totally aware of those though I have some ideas. Having to do that is a very good security against ingesting something you don't want. It also gives you the ability to choose wether you are breathing or swallowing something. \n\nAnother good part is that it allows you to be able to swallow even if you are laying down or with your head hanging down. If you had just a tube, simply bending to touch the floor could result in your stomach's content coming back inside your mouth. Not very nice.\n\nI suppose many people can probably give you more reliable explanation on the subject though",
"Because otherwise it would go into your lungs. the act of swallowing closes your flap (epiglottis) so that whatever you're swallowing goes to your stomach.",
"You said that the decision to swallow is active- and that isn't entirely true. It's a reflex triggered by a physical stimuli and requires there to be something in the back of your throat for it to happen. \nAt the junction between your trachea (the tube to the lungs) and your esophagus (the tube to the stomach) is a flap called the epiglottis. The epiglottis is always covering one opening and not the other. When you are breathing, the epiglottis is covering the opening to your esophagus (which prevents stuff from your stomach from getting out, but that's for another post). But when you have enough of a substance in the back of your throat, your swallowing reflex is triggered which 'flips' the epiglottis to cover the trachea so that the contents of your mouth can travel to your stomach instead of your lungs, temporarily stopping your ability to breath. \n\nWhile you can make the active decision to push the contents of your mouth to the back of your throat with your tongue, whether or not you swallow isn't actively decided by you. When you are holding a liquid in your mouth, you are actually preventing the swallowing reflex from being triggered, not actively deciding not to swallow. Try it out- flatten your tongue and let your drink flow to the back of your throat. You can't help but swallow! If this reflex didn't exist, you would drown in your own saliva. \n\nTLDR; because of your swallowing reflex. ",
"It *is* automatic, once it makes it past your epiglottis. Peristalsis occurs no matter what you put into your esophagus (including liquids), but you have to make the conscious decision to swallow it so it can make it past your epiglottis.\n\nIn a nutshell, the back of your mouth contains one opening that goes two ways- your throat, and your lungs. One of these has to be closed for food to even go to your throat, otherwise you get foreign substances in your airway (which is bad; for one, liquid in your lungs can cause pneumonia or outright kill you by dry drowning). You make the conscious decision so you eat (or in this case drink) instead of inhale.\n\n**tl;dr**, you have one opening in the back of your throat that goes two ways-- your digestive system and your respiratory system. Since you don't want to inhale food or drink, it requires an active decision to close your airway so food and drink goes the right way."
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4b83wk | why does the ethernet cable from the router to the modem need many conductors when the coaxial cable from the modem to the "internet" only need 1(plus sheath)? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4b83wk/eli5_why_does_the_ethernet_cable_from_the_router/ | {
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"Your modem (modulator-demodulator) changes the digital signals being carried by the Ethernet cable into an analog signal which is more appropriate for traveling long distances and needs only a single conductor. ",
"Ethernet *used to be* coaxial in the days of 10base2. It was a pain: you had to use at least BNC tee pieces for every machine and make sure the ends of the run were properly terminated. Token ring was worse, if you broke the ring it just stopped working. \n\n10/100/1000baseT use multiple twisted pairs which gets them a decent bandwidth, fairly simple connectors to assemble (coax can be a pain, it's heftier than cat5/cat6 and there are more restrictions on things like minimum bend radius) and also gives other options like power over ethernet and common wiring so you can flexibly soak wire buildings for networks, phone and alarms with significant cost savings.\n\nTl;dr coax cable is a pain to use in quantity. ",
"Think of coaxial cables as the equivalent of fiber optic cables for radio waves. The radio waves travel through the cable and they can't escape past the metal jacket. Coaxial cables are good for transmitting over long distances. However, the cables and the transceivers on either end are more expensive.\n\nEthernet cables send digital signals directly. They use twisted pairs of wires to reduce interference but it does not work as well as coaxial, so you find it used in shorter-distance applications.",
"When current travels down a metallic conductor, it creates a magnetic field surrounding the conductor. This field takes energy to establish, which comes from the signal being transmitted. The longer the conductor, the more energy is lost. If the signal travels down a long enough conductor, eventually so much energy is lost creating the magnetic field the signal can no longer be detected. There are several strategies for reducing this loss.\n\nOne strategy is to use two conductors carrying the same signal in opposite directions. The two conductors generate the same field, but with opposite sign. If the two conductors are close enough together, part of the magnetic field of each is cancelled out due to the opposite sign. This reduces the energy lost to the field. This works a bit better if the wires twist around one another. Two conductors arranged in this way are called a twisted wire pair. Ethernet cable has 8 wires arranged in 4 twisted pairs.\n\nThis \"self cancellation\" of the magnetic field in twisted pair cables is incomplete because the magnetic field of the two conductors does not completely overlap. The centers of the two wires are offset from each other due to the width of the wires.\n\nIt is possible to arrange a cable with two conductors so that both conductors have the same center. To do this, one conductor must surround the other. This is what we call coaxial cable. The central wire is surrounded by the sheath, and both have the same center, the axis of the cable. Both the central wire and the sheath are conductors. Both carry the same signal, in opposite directions. Since the center of the magnetic field generated by both is at the center of the cable, the self cancellation of the two fields is nearly perfect.\n\nThus a coaxial cable has a lot less loss than a twisted wire pair. Bandwidth is the opposite of loss, the lower the loss, the higher bandwidth of signal the cable can carry. You need several twisted pairs to get the same bandwidth as a single coax cable.",
"Coaxial cable carries the same radio-frequency signals that otherwise could go through the air. Channeling the signal through the cable is just a more efficient means of transmission. The cable company's transmitter is similar equipment to a TV or radio station, just with less amplification. For uploading, the modem on your end does the same.\n\nRadio frequency means that the transmitter mixes the signal with a carrier wave, and the receiver extracts the signal using the same carrier wave. Many signals can be carried on different carriers on the same cable, but they need expensive equipment to combine all their customers' signals, and you need a somewhat expensive modem to extract your particular signals from the mix. You wouldn't want to need a cable modem in every internet-connected device.\n\nEthernet is designed to run for shorter distances, and to connect to simpler, cheaper circuits. Only one data stream can be carried at any moment, and the router divides time on the cable between your different devices. The usual transmission protocol is called 1000BASE-T:\n\n* **1000** is the total capacity in megabits per second (Mbps).\n* **BASE** stands for baseband, as opposed to radio-frequency. The signals are carried as digital pulses of varying voltage, not mixed with a carrier wave. So no modem is needed.\n* **T** stands for *twisted pair*, as opposed to coaxial. Coaxial geometry is higher quality, so it could be used just as well, but when wiring an office building one wants to avoid the expense.\n\nOK, so both systems send signals over pairs of conductors. Why does Ethernet use 8 conductors instead of 2? Really, just because of tradition. In the old days, you could put four phone lines on four twisted pairs, and the wires and connectors for this became commonplace.\n\nToday, four pairs carry four times the data as one pair, which is good because 1000 Mbps is a lot of information. The preceding standard, 100BASE-T, only relied on two pairs, potentially leaving half the cable unused. Essentially, 8 conductors instead of 2 is just the difference between having 1000BASE-T and having \"250BASE-T\" (not a real thing).\n\n---\n\nTL;DR: Coaxial cable allows sending signals to different customers simultaneously. It can do this because it is higher-quality and more expensive. Common \"ethernet\" cables have the same number of conductors as the pre-ethernet cables they evolved from. But the extra conductors do help to improve their capacity.",
"Completely different transmission method. Also cat5/6 can transmit data at a much higher rate than coax, but no where near the distance of coax."
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48orfm | us serving sizes | can someone explain how US food products determine how much a serving size is? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/48orfm/eli5_us_serving_sizes/ | {
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"The FDA has serving size guidelines, which are codified in [21CFR101.12](_URL_0_). Manufacturers are not required to use those sizes, but they usually seem to when it's a bulk product, or, for single-serving packages, try to get close-ish to the guidelines by dividing the package into whole fractions.",
"Depending on the food group and some other factors, this is governed by either the USDA or the FDA. The manufacturer indicates the category they believe that food/drink/etc falls into and if the government agrees, they use the standard serving size for that category. There's some leeway though. For example, cookies have a reference amount customarily consumed (RACC) of 30g, and the manufacturer could round to the nearest number of whole cookies as long as they still indicate number of grams and such.\n\nAFAIK the reference categories and amounts are still based on surveys from 1978 and 1988, because those were the last two surveys before the USDA helped implement the whole serving size practice in the early 90's. They're a compromise made by whatever task force was in charge between the amount the average American at the time (over 4) actually ate in one sitting, and the amount they *should* eat.\n\nThey started updating the values a little more than 10 years ago, idk how far along they are.",
"They can pretty much just make it up. That's why for things like soda, the serving size can depend on the size of the package.\n\nThe serving size for cooking spray is a 1/4 second spray. That way they can legally call it \"fat free\" even though it's 100% fat. The serving size is less than half a gram and they round the grams of fat to the nearest whole number - zero. "
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a0xba3 | Is there any difference between the light that a flashlight makes to the light that the sun makes? | askscience | https://www.reddit.com/r/askscience/comments/a0xba3/is_there_any_difference_between_the_light_that_a/ | {
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"Generally yes. The color of light is determined by the length/frequency of the electromagnetic waves that make it up, and light from LED bulbs and incandescent bulbs have a [different pattern of wavelengths/colors](_URL_0_). I can't speak to the exact accuracy of the graphs in that image, but that gives you a general idea.\n\nThere are light bulbs that are designed to be closer to the \"full spectrum\" light we get from the sun, but I assume that none of them are exactly the same pattern. ",
"Greetings from /r/flashlight. /u/ridcullylives has already shown some spectral graphs that give a sense of how some different light sources compare to sunlight, but I'll elaborate some.\n\nOne characteristic used to describe differences between different light sources we would describe as \"white\" is correlated color temperature or CCT. You may have encountered this when shopping for lighting or manually adjusting the white balance on a camera. CCT is the temperature an object that emits light solely because it is hot (a blackbody radiator) would need to be in order to produce light of a similar color. Visually, this is mostly a measure of blue/yellow balance. Solar radiation is close to blackbody radiation with a color temperature around 5900K, however filtering through the atmosphere lowers the color temperature.\n\nAnother characteristic is red/green tint deviation. This is usually undesirable in a white light and rarely advertised. Most LEDs on the market have a small green deviation, probably because human vision is most sensitive to green light, and the lumen, the unit of total light output used for rating the output and efficiency of light sources, is calibrated to human visual sensitivity. That means excessive green is a \"free\" boost to efficiency.\n\nA third important characteristic is how closely the spectrum matches that of a blackbody radiator of the same color temperature. The oldest measure of this in common use is color rendering index (CRI). This is based on the average difference in color reproduction with eight standardized colors between the test light source and either real blackbody radiation or an idealized model of it (it's difficult to produce blackbody radiation at very high temperatures). CRI tops out at 100 and can be negative. The newer IES TM-30-15 standard contains several more sophisticated measurements of color rendering in comparison to blackbody radiation, but CRI is the only metric likely to be advertised on a flashlight.\n\nSo, a flashlight with a light source that's 5000K CCT and 100 CRI would be almost indistinguishable from direct sunlight at noon on summer solstice say... 30 to 60 degrees north of the equator. If you can find a flashlight like that, **please** post it to /r/flashlight so we can all buy it. We can get close with LEDs though; many LEDs guarantee CRI over 90 and come in a variety of color temperatures. A flashlight using one of these **will** advertise it, while an LED flashlight with unspecified CRI will usually be in the high 60s to low 70s.",
"I haven't seen it said yet, but there is one significant aspect not addressed. The individual photon are not in any meaningful way different or unique.\n\nI won't go into detail since there are many great explanations already, but the key difference between a flashlight and the sun are *quantity* of photons released and *proportion* that each wavelength comprises.\n\nThe quantity, holding all else equivalent, is essentially indistinguishable if the flashlight and the sun are held at appropriate distances (in this case, the sun will be much, MUCH farther away).\n\nThe proportions of wavelengths, however, is what determines \"temperature,\" hue, etc. This is where the sun and a flashlight differ. Note that each photon of 470nm wavelength (blue) is exactly the same as every other photon of 470nm wavelength, so only by the ratios of each wavelength can we differentiate sources."
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332qmq | there are more and more posts about how other countries have much better education systems than the us, so why does the us seem to have the greatest scientific advances? | Sorry if I sound like a condescending asshole. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/332qmq/eli5_there_are_more_and_more_posts_about_how/ | {
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"When they talk about education system they usually arent talking about higher education like universities.. We have a metricfuckton of universities and dont forget about private corporations who have small armies of scientints and huge resources",
"Because if you have a PhD you can go straight to the front of the immigration line.\n\nEdit: Los Alamos National Laboratory in the city of Los Alamos new mexico has the highest per capita of PHDs in the country I've 'never' met an American one. I'm sure that's just chance but, it illustrates the point.",
"Most of the problems in the US education are related to poverty. Children from middle and upper class households in the US get an education at least equal to any other country. We just spend a lot less money on poor people in general.\n\n_URL_0_",
"There are two reasons that I can point to for this. The first is that despite the US lagging behind in education up through high school, it still has by far the best university system in the world. [This list](_URL_0_), while controversial, is absolutely dominated by American universities. \n\nThe second is that the US has the [largest public research and development budget of any country](_URL_1_), with China being a close second. ",
"1: We have a very strong intellectual property rights system that is reliably enforced. When an inventor secures a patent, that patent can be used to extract licensing fees even from really big companies. That makes the value of patenting something in the US very high, and ensures that inventors in the US feel like their time is being rewarded. Those rewards spur innovation.\n\n2: We have a very good system for company formation and for returning rewards to investors who provide the capital for new companies to form. This rewards inventors who try to commercialize and invention and provides an incentive for people to risk money & time to attempt it.\n\n3: We have the best higher educational system in the world. No other country even comes close. Our top universities have an unequaled track record at producing innovative thinkers who translate their ideas to practical knowledge. Those universities attract the smartest talent from all over the world, not just from the US. We make it possible for anyone, from anywhere to attend a US university; we have no limits on admission based on country of national origin.\n\n4: The US has a historical narrative of celebrating and rewarding innovation. Our national story is interwoven with threads like the Wright Brothers, Ford, Gates & Jobs, etc. Unique among nations we celebrate our inventors about as much as we do our priests, politicians, generals and celebrities. That creates an interest in invention and an understanding of why it matters at all levels of our society.",
"As others have said, our basic lower education (K-12) is not horrible, just not as good as some other countries. Our universities are very good and we have people from all over the world trying to get in. My husband teaches music theory at the undergrad and graduate levels. He has had students and colleagues from every continent. \n\nIt goes the other way too. We have a friend who teaches physics. He was one of the many hundred people from all over the world who worked on finding the Higgs-Boson particle. \n\nEinstein was German. The Curies were French (Pierre) and Polish (Marie). The Russians sent the first man to space. We have made a lot of advances in the US, but the whole world has made advances as well."
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c93pwp | how is the universe expanding, but it's not expanding *into* a larger containing space? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/c93pwp/eli5_how_is_the_universe_expanding_but_its_not/ | {
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"Well I guess you cannot. Similarly to the statement that big bang is when time began. There was no time \"before\". Quotes because it does not make sens to use before it there was no time.\n\nUsing balloon analogy you can imagine that for 2D creatures living on balloon (they have no mean to comprehend 3D) their 2D world is simply expanding. It is not expanding into any 2D space they can comprehend.\n\nI am no expert, this Is just a way I understand this.",
"We cannot, this is one of the greatest questions ever bestowed upon mankind, there are many theories; some of which being an empty void of dark matter/dark energy. But we truthfully have no idea what is beyond the observable universe. We can only see up to 13.8 billion\\~ light years with current tech, the James Webb Telescope will surpass this by hopefully a minuscule fraction more, albeit, it will be used to see objects we have already seen via the Hubble but at a higher level of clarity than we have ever been able to achieve before. Anything beyond is simply so red-shifted that we will never know, this is also a scary thought, the universe is theorized to be expanding at a FASTER rate than we previously predicted and it is speeding up, for all we know there could be absolutely anything out there, things that we cannot even begin to comprehend.",
"Imagine a two-dimensional piece of a grid paper that stretches to infinity in all directions. This grid paper is all that exists and nothing can exist outside of it. Now, imagine that each individual grid is getting bigger and bigger. If you are a dot on the grid, you are not moving and expanding, but the distance between the gridlines is getting larger.\n\nIf you try to draw a line between the grid lines, it will start to take longer to draw from one side to the next. So the \"metric\" we use to measure the distance between the grids is changing.\n\nIn the universe, this is called metric expansion of space.\n\nEdit: You are correct that the balloon analogy doesn't work, because it is asking us to imagine that an object expanding into another space. Unfortunately, there is no exact analogy that will work here because we aren't talking about an object or a space, we are talking about *all objects and spaces*. At the least, human brains weren't evolved/designed to understand things on this scale, so the best we can do is come up with incomplete analogies or mathematical models.",
"Imagine that our universe is a bubble of air underwater, and it is rising to a lower depth. In this analogy, the bubble expands due to the lowering of hydrostatic pressure. We don't know exactly what the water is in this analogy (what lies beyond the observable universe) neither if there are other bubbles around (if there is a multiverse). \nWhat you're asking, whithin this analogy, is how our bubble didn't bump into other bubbles. There are no evidences to that ever happening, and if it ever comes to happen (after enough time for it's light get to us) would be clear signs of it in the Cosmic Microwave Background (due to a very likely temperature difference between our bubble and the other one at the time both became transparent to photons).",
"People keep talking about a balloon, but there really is no proper analogy. That one seems pretty good though. The problem is, there just is no reasonable answer because we cannot know right now. \n\nMy theory is that the concept of space is literal nonsense outside of our universe. “Distance” and “size” are only coherent concepts within our universe, created by the laws of our universe. Outside, we could expand forever, and nothing would change.",
" > How can we make sense of this?\n\nTo paraphrase Neil deGrasse Tyson, the universe is under no obligation to make sense to us.\n\nIt is our job to make sense of it.\n\nThe universe *is* expanding. Any two points in the universe are slightly further apart now than they were a minute ago (although the actual stuff may not be moving apart, if bigger things are holding it together, or pulling it inwards).\n\nWhat is it expanding into? That involves discussing what is outside the universe.\n\nExcept at the moment there is no clear framework with which to discuss \"outside the universe.\" The concept of \"outside the universe\" doesn't really make sense in the same way that \"north of the North Pole\" doesn't make sense. Sure, we can expand our definition of \"north\" to give \"north of the North Pole\" meaning, but we have to come up with that new definition and show it is reasonable before we can really justify using it.\n\nSo maybe the universe isn't expanding into anything, it is just expanding internally.\n\nMaybe that doesn't really make sense to us, but that's *our* problem, not the universe's. The idea of relative or curved spacetime doesn't really make sense until you get used to it (doing the maths helps a lot), ideas of wave-particle duality, or \"cat states\" or all sorts of other things are hard to understand when you first meet them (or even after you've spent a few years studying them). But that doesn't mean they're not real; it just means we need to spend a bit more time trying to make sense of them.",
"Don't think of the balloon analogy as us being inside the balloon, but on the surface of the balloon. \n\nWe're 2d, but expanding 3 dimensionally into an environment. So what are we expanding into? No idea. The answer is probably an equation that doesn't make a lot of sense anyways. Like n-dimensional matrix algebra.",
"You might find it easier to think of it more like the definition of \"distance\" is changing. That is: it's effectively the case that \"1 metre\" is becoming a smaller bit of distance in the universe than it used to be.",
"The classic analogy I’ve heard is the “Raisin bread” example. If you’re baking a pound cake of some kind, you know it starts as batter, and expands into your cake. Imagine the galaxies in the universe as raisins or chocolate chips in the batter. As it bakes, they all stay in the cake (our universe) and don’t move locally, but the space itself expands around them. The universe is a pound cake, there’s nothing outside the space as far as we know, but the cake itself can get bigger.",
"Ignore that the balloon is 3-dimensional and suppose the entire universe is just the surface of the balloon. Creatures in this universe can only move along its surface. They can't jump off of it or go below. Then the universe is 2-dimensional and there is ever more space between things as time goes on. Moreover, there is no center of this expansion (remember, the center of the balloon is not part of the universe. The entire universe is the surface). Of course, our universe isn't 2-dimensional. It's 3-dimensional. All the balloon analogy is saying is it is the space between things that is expanding as if more space is being created where there is space.",
"Did someone already post this?\n\n[_URL_0_](_URL_0_)",
"The following is not scientifically accurate, but it might help you visualise it better than a balloon.\n\nThink of the event horizon of a black hole. As you get closer to the event horizon, time slows down. Every second takes a minute, an hour, a day, until eventually time stops completely from the outside perspective.\n\nSpace works the same way. The edge of the universe is an event horizon for space. The closer you get to the edge, the more distance it takes to get any closer still, until eventually distance ceases to exist from an outside perspective. Every millimetre is a thousand light-years.\n\nExcept instead of the event horizon being a centre point like a black hole, it's the surface of a sphere and you're inside it. It's not so much that 'beyond' doesn't exist, it's just effectively infinitely far away. The universe 'expanding' just means that the distortion isn't noticeable until you're that bit closer to the surface of the sphere. The opposite of a black hole expanding and the event horizon getting bigger.\n\nTL;DR - Limits are weird."
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9ylvtl | gauge theory | I heard about it for the first time from Eric Weinstein on Joe Rogan’s podcast, but it all kind of went over my head. Every explainer video I’ve found goes into some pretty complex math - so if it’s possible to explain like I’m 5, reddit please help me. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/9ylvtl/eli5_gauge_theory/ | {
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"I'm going to give this a red hot go for that sweet Karma. \n\n\nGauge theory: The first thing to take from this is the word gauge refers to a measurement, and isn't some dudes last name tied to a complex formula. Gauge can refer to things such as thickness, a space between objects, a measurement, or amount of something within a parameter, lets say number of jelly beans in a jar, or number of threads in your bedsheet. \n\n\nA general feature of all modern theories is that the fundamental fields cannot be directly measured, such as Electromagnetic field, gravitational field, of the forces between particles. However, some of the properties of the equation CAN be measured such as to derive a value for something that cant in itself be quantified. \n\n\nAn example would be perfect sphere lead balls that are equal in every way shape and form, but you do not know the diameter. You can take the amount of balls required, the elemental mass of lead, the formula for volume of a sphere from a given diameter and work backwards to obtain your answer. \n\n\nIn field theories, different configurations of the unobservable fields can result in identical observable quantities. A transformation from one such field configuration to another is called a **gauge transformation;** the lack of change in the measurable quantities, despite the field being transformed, is a property called **gauge invariance**. Since any kind of invariance under a field transformation is considered a symmetry, gauge invariance is sometimes called **gauge symmetry**. Generally, any theory that has the property of gauge invariance is considered a gauge theory. \n\n\nThen, you basically look at gauge theory as a constraint in physics - all changes induced by a gauge transformation have to cancel each other out when written in terms of observable quantities. \n\n\nFor an application in Gauge theory, consider the following: For example, in electromagnetism the electric and magnetic fields, **E** and **B** are observable, while the potentials *V* (\"voltage\") and **A** (the vector potential) are not. Under a gauge transformation in which a constant is added to *V*, no observable change occurs in **E** or **B**. \n\n & #x200B;"
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fupjio | why isn't there a pattern in prime numbers? | I have always wondered, even though prime numbers can be understood by a fifth grader. We were never able to crack the inherent pattern in them. I don't understand how something could just be random in Mathematics. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/fupjio/eli5_why_isnt_there_a_pattern_in_prime_numbers/ | {
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"They have a kinds of pattern, because numbers that aren't prime numbers have a pattern.\n\nEvery second number after 2 is not a prime. Every third number after 3 is not a prime. Every 4th number after 4 is not a prime and so on. The numbers that aren't primes have a pattern of your can call it that",
"There are. There are buckets of patterns in prime numbers. [Matt Parker](_URL_0_) will happily show you one.",
" > I don't understand how something could just be random in Mathematics.\n\nWhat does random mean to you? Mathematics is perfectly capable of treating \"probability theory\", modelling randomness, in a deterministic way.",
"The prime numbers are at the heart of Number Theory, the most complicated branch of mathematics. In short, while there are various patterns (mentioned above), learning about primes is the current focus of many of the most brilliant minds on the planet. There isn’t a unified theory about primes.",
"Prime numbers are indeed just one of those things with no clear pattern which are difficult to compute in many aspects (finding next prime? determining if a large number is indeed prime, etc). In fact, that property is what common methods of encryption, such as those used on the web, rely on to be secure. A good article about that here: _URL_0_"
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2me1fg | Could there possibly be any solar systems that have a supermassive "planet" at the center instead of a star? If not, why are there always stars at the center? | askscience | http://www.reddit.com/r/askscience/comments/2me1fg/could_there_possibly_be_any_solar_systems_that/ | {
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"Well, the thing that defines such a system is the large mass of gravity at the center. If you have a large enough mass it will collapse in on itself and become a gas giant. There's always more gas around then there are rocks so the idea of having a large terrestrial center would be pretty far-fetched. Once the central object becomes massive enough fusion can begin. There are some almost-stars that are called brown dwarfs that never underwent any kind of nuclear fusion. Jupiter is a mini version of a brown dwarf. These systems would have no sunlight because there will be no Sun to create light. I guess its possible that you could have terrestrial planets orbiting a brown dwarf, but the fact that brown dwarfs don't shine any light out means they are incredibly hard to find in the first place.",
"Brown dwarfs and lone planetary objects probably do often have smaller bodies orbiting them.\n\nSince these bodies are fairly small, the planets can't be too massive or it'll be closer to a binary system than a \"star\"-planet system.",
"I think that people didn't interpret your question pretty well. \n\nThe answer is yes. It would be a planetary system (like Earth and Moon, or Jupiter and its moons) that is rogue. It is in interstellar space. In that case, such thing is possible. However, it wouldn't be called a *solar* system",
"Similar but bifferent question.\n\nIf there were rocky bodies orbiting a massive rogue planetoid, could they generate or receive enough heat to sustain liquid water? I know that europa has liquid oceans under the ice, but don't know if this is entirely due to tidal forces. Could there be a similar situation with water at the surface?",
"Supermassive? Depends on what you mean. The same mass as a star? By definition: no. Cosmologists define \"stars\" by mass. Any object above a certain mass is considered a star. Even if it were solid iron and of the lowest possible \"star-level\" mass, it would be a brown dwarf.\n\nRelevant wikipedia section:\n\n > The defining differences between a very-low-mass brown dwarf and a giant planet (~13 Jupiter masses) are currently being debated. One school of thought is based on formation; the other, on the physics of the interior."
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3cgwpu | why do many democracies have a president? | Why don't countries highest power lie in the senate, so that the whole country(the highest-clearance actions) doesn't lie in one person's hands? Also, why the fuck does the opinion of one person determine whether nuclear weapons will be used? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/3cgwpu/eli5_why_do_many_democracies_have_a_president/ | {
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"Because it just doesn't work practically to have a country led by 100+ people. When another country wants to communicate with it, who would they talk to? One of the 100? Wouldn't that de facto make that one guy the leader?\n\nTo the second part - because if we get launched against, we can't wait for 100 people to debate and decide whether to counterattack."
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6igkfs | how do craft like voyager and pioneer propel themselves through space? are the using the gravity of the bodies they pass by to slingshot along, or do they use thrusters of some sort and propel themselves along? a combination of both? | The idea of zooming around in space fascinates me and I wonder how it works. Are all the "directions" pre-programmed before the mission or are there people on Earth giving inputs? So many questions! | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6igkfs/eli5_how_do_craft_like_voyager_and_pioneer_propel/ | {
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"They travel at constant velocity in a straight line because that's what Newton's law tells them to do. There is no friction, nothing stops them. They will continue moving at constant speed forever. Unless they encounter massive objects. The trajectory can be altered by the presence of celestial bodies, though.",
"Initial thrust of the Earth Rockets and ion thrusters.\n\nSpace is an (almost) perfect vacuum. There is basically no friction, no inherent force Fire a rocket into space and it will go at that speed for basically forever (unless you put some other force that changes it's trajectory). When we launch a deep space probe out of Earth's orbit, the vast majority of it's momentum came from that original rocket thrust.\n\nSometimes for fine maneuvering or to get probes to the planets/places we want them to fly to, our probes either equipped with a tiny engines called an Ion Thruster. Basically these engines use magnets to accelerate a small amount of matter, ions. This does not provide much thrust. If you put an ion thruster on your car, I doubt it could even overcome the friction set forth by the Earth's atmosphere/the ground to make your car move forward. However, as I said before, there is no friction in space, so even a tiny ion engine, with time, can alter the trajectory of a probe to get it where it needs to go. Remember, space probes can take months if not years to get to their destination, so even a lowly little ion engine is enough. ",
"The Voyager and Pioneer spacecraft specifically were accelerated by their launch vehicles which put them in space and on course. After that, they don't need any sort of propulsion because in space there's nothing to slow them down. They have small thrusters that use hydrazine to control which whey they point and to make minor course corrections, but they have no engines as you think of them, ion or otherwise. Pioneer 10 got a gravity assist when it flew by Jupiter but this was unnecessary since Jupiter was its only target. Pioneer 11 and Voyager 1 got gravity assisst at Jupiter to get it them to Saturn, and Voyager 2 used gravity assists at Jupiter, Saturn, and Uranus to fly by Neptune. Once they flew past the outer planets, their velocity was pretty much locked in. They're headed where they are headed at the speed they're at unless they encounter some force in deep space.",
" > How do craft like Voyager and Pioneer propel themselves through space?\n\nWe're used to stuff coming to a stop if it isn't being 'pushed' any longer here on Earth. But that's misleading. \n\nThe *normal* state of things is that if you give something a push, say accelerating it up to five miles per hour, it will travel at 5 miles per hour *forever* or until some other force acts upon it.\n\nOn Earth however, we have that other force ready to hand. The Earth and its atmosphere will exert drag. So if you are moving across the surface of the Earth, say in a car, your wheels are moving across the ground, and your body is slamming into the wind, and all of this is working against your movement, slowing you down until you and the ground are moving at the same speed. To keep going, you burn fuel to propel yourself.\n\nIn space, there's basically no atmosphere, and no ground. By and large, the effects on a craft are going to be minimal. Give it a push, and it will keep going. Unless you send it close to some other massive object, it's unlikely to deviate much, and there's so much empty space in space, that it will only get near another massive object if you *plan for it to do so.*\n\nSo stick a rocket on your ship, bring it up to speed x, and it will keep going x in the same direction for a very long time. "
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9c8rjs | All ancient peoples discovered and used fermentation to brew alcohol except native Americas. Why didn't they discover the process? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/9c8rjs/all_ancient_peoples_discovered_and_used/ | {
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"Not to discourage any further answers, but you'll want to read these older posts about the development of alcohol and other fermented beverages in the Americas:\n\n[Before contact with Europeans, were there any fermented alcoholic beverages (beer, wine) being consumed by Native Americans, and if so, what were they like?](_URL_2_)\n\n[What types of pleasure drugs were used in the Americas prior to European colonization and how prevalent were they?](_URL_0_) \n\nBoth by /u/400-rabbits\n\n[Did Native Americans ever produce alcohol?](_URL_1_) by /u/Pachacamac\n\n[Do we have recipes for the fermented chocolate drink favoured by the Maya?](_URL_3_) by /u/Mictlantecuhtli\n\n[What did ancient Native Americans drink?](_URL_4_)"
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"https://www.reddit.com/r/AskHistorians/comments/14lq6l/did_native_americans_ever_produce_alcohol/c7ec9u8/?st=jlk8o7f5&sh=509b9d95",
"https://www.reddit.com/r/AskHistorians/comments/1ya99h/before_contact_with_europeans_were_there_any/",
"https://www.reddit.com/r/AskHistorians/comments/5mtfz9/do_we_have_recipes_for_the_fermented_chocolate/dc7edwg/?st=jlk8nwkb&sh=0f5950da",
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dhe2aq | why are most coins in the world circular? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/dhe2aq/eli5_why_are_most_coins_in_the_world_circular/ | {
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"It is a convenient shape, for stacking, for machines (counting and vending). A circle is the same size in every orientation you take it",
"In addition to the other points people have made, round shapes don’t poke you, don’t poke holes when in you pocket or purse. Also sharper corners would wear down over time.",
"It's like that for a few reasons.\n\nIn the older times, coins would be stamped and formed by pressing a bit of metal, so it ended up in a shape that would resemble a circle (imagine pressing a bit of dough with a stamp, the corners will be rounded, or it'll be completely circular.\n\nCurrently we have circular coins for either cultural reasons (they've always been like that) and because it is convenient.\n\nA circle is a very convenient because it has no corners which may be weaker, it has only one orientation when flat, so it can be stacked and carried easier and it certainly doesn't poke you.\n\nAlso, it can contain sizable detail inside of it without using as much material as a square coin would. A number for example of equal size on two differently shaped coins would consume less material on a circular one (unless it's shaped around the number).",
"It is a security measure.\n\nCoins used to be a specific amount of precious metal, gold, silver, or copper usually. People used to \"clip\" coins, shave off a little bit of the metal to keep then try to spend the coin at its full value. You do that enough times and all those little slivers can add up. \n\nCircular coins make this harder to do, as the round shape makes clipping more obvious and you can only take a small amount. Later, ridges called *milling* were placed on the edge of the coin to make clipping every more apparent.",
"There are some modern coins that aren't circular...?",
"Judging from [this picture of a Roman coin](_URL_0_), that appears to be (roughly) the shape you get when you squeeze a bit of silver in a press.",
"All of those reasons, plus you also get the most area for the least material, so you have plenty of surface to imprint your security image on. \n\nAs metals have become more expensive than the currency they represent coins have got smaller to save on material and the circle is the most efficient use of material to get large area from less material.",
"In 1969 the heptagonal 50 pence coin was introduced in the UK. \n\n\nA pressure group, the 'anti-heptagonists' protested against it. \n\n\nTheir leader Essex Moorcroft said \n\n\n\" I have founded the society because I believe our Queen is insulted by this heptagonal monstrosity. It is an insult to our sovereign, whose image it bears.\" \n\n\n [_URL_0_](_URL_0_)",
"I bet you posted this after todays certain post, huh. \n\n[_URL_0_](_URL_1_)",
"Square coins kept getting stuck in medieval vending machines. \n\nImagine you're at the Roman Colosseum and you get up to buy a non gluten, dairy free, vegan hot dog quickly before the next Christian gets slaughtered only to be stuck trying to get your square drachma into the machine before you miss the big event.",
"We have a saying. Money needs to roll! ( we need to spend money) We can't fucking roll money if they are square or triangle now can we? The guy who invented the triangle way back when was stoned to death by circular shaped stone things by the inventor of the stone wheel.",
"European coins used to be round for the same reason pizzas are round. If you want to create a roughly uniform shape from a ball it's far easier to make it a flat disc. As european coin making frequently relied on making coins from blanks that had been repeatedly hammered to make them flatter the round shape was the easiest to produce. \n\n\nChinese coins tended to be slightly thicker, very small and fully cast. To get around the problems with casting and later keeping them from getting lost chinese coins had a square hole in them. This square hole allowed them to be securely mounted while the mold-edges were filed away, and then you could thread them on a string to prevent them from getting lost.",
"Because a cylinder shape (which is what happens when you stack coins) is the best shape for filling up as much space as possible while keeping the items in question safe. A square, on the other hand, has a puncture load on every corner. It's the same reason soda cans are cylindrical.",
"Some answers here are incorrect.\n\nIt's not for security reasons, as shaving a circular coin is not particularly harder than a square one, and they were circular long before people stopped weighing them in transactions. The risk of the coin containing less silver or gold than it should was never a real concern as weighing is easy. Having a recognizable mint pattern on it was more about guaranteeing the composition of it.\n\nIt's also incorrect that they were pressed. [Plenty of ancient molds have been preserved](_URL_0_), and we can see it's not the case.\n\nIn reality it's probably because a a circular coin retains its shape better over time (corners chip easily).\n\nIt's also another layer of authentication. The most important feature of a coin is that you can easily see its authentic, which makes transactions quicker and more reliable. If I see the [Athenian owl](_URL_1_), I can safely assume I'm looking at an actual Athenian drachma made of silver. I can weigh it if I think it's a bit worn, but generally speaking it makes things easier.\n\nIt's easier to chip out a rectangle or a triangle out of a piece of metal, than it is a circle, so that's another aspect of guaranteeing authenticity - that this coin came from a real mint."
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7vul05 | At what temperature do Bose-Einstein Condensates and other exotic states of matter exist? | All I can seem to find is that "Bose-Einstein Condensates exist in very low temperatures whilst plasma and quark-gluon plasma exists at very high temperatures." Does anyone know exact temperatures that these states of matter exist? For example, does a BEC only occur in temperatures ranging 1 – 10 kelvin or 1 – 10 nanokelvins? What order of magnitude of temperature (i.e. 10,000 K, 100,000 K — not too sure if I'm using the right terminology here) would plasma or quark-gluon plasma exist? Thanks! | askscience | https://www.reddit.com/r/askscience/comments/7vul05/at_what_temperature_do_boseeinstein_condensates/ | {
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"Helium-3 and -4 both form Bose-Einstein condensates, as do the electrons in a superconductor.\n\nHe-4 transitions at around 2-3K if I remember, and He-3 is a bit lower, which is because He-4 is a boson while He-3 is a fermion and has to pair up to form a BEC. In a superconductor the electrons pair up to form bosons and condense into a BEC, so any transition temperature you find will give you a pretty accurate measure. The highest temperature superconductors are now well over 80K, which is where you can cool with liquid nitrogen.\n\nPlasmas I can't really comment on, but it's thousands of Kelvin at which the coldest plasmas form.",
"for the respective \"plasmas\" you'd have to look at the temperature that correspond to the typical energy scale for the respective binding energy (electromagnetic force that binds electrons to the nucleus maybe 10s of eVs, and strong force which binds quarks to form nucleons, ~GeV). but if you type them into wikipedia it tells you the temperature (quark gluon plasma ~10^(12) K - 10^(13) K, which rougly aligns with the estimate of GeV). 10 eV is roughly 100.000 K"
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25ew6u | What plans, if any, did the Confederate States of America have - or discuss - for expansion into Latin America? | I know about groups like Knights of the Golden Circle from before secession, and I know that the Constitution of the CSA included provisions regarding future expansion, but I haven't seen much about post-secession.
Did Confederate leaders still plan to annex (or discuss annexation of) additional territory for the expansion of slavery? Were they too busy dealing with the Civil War to put much thought or effort into plans for future expansion? What, if anything, did they have to say on the subject? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/25ew6u/what_plans_if_any_did_the_confederate_states_of/ | {
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"None that I know of, however, Southerners before the war had long had pipe dreams of an America that would extend to Panama. All of these new territories would be slave states. More realistic were attempts to gain Cuba as a slave state. One southerner, Walker, established a slave country in Nicuragua by an invasion of the sons of Southern slavers. This regime was overthrown quickly. The Slavers tried to strong arm one of the weak antebellum presidents (Pierce or Buchanan, I forgot which) into forcing the \"purchase\" of Cuba via a secret document called the Ostend Manifesto. It would have worked too, if the document wasn't leaked to the public. The Northern states raised holy hell about a new slave state, and one that would be wrangled from another power at that (insert irony about the Spanish-American War here), and thus the Ostend Manifesto was dropped to maintain the peace."
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mlrui | how "e" raised to "i times pi" is -1. how can you raise a real number by an imaginary number and get a real number? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/mlrui/eli5_how_e_raised_to_i_times_pi_is_1_how_can_you/ | {
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"It happens because of how closely related the exponential and trigonometric functions are.\n\ne^*ix* = cos x + isin x.\n\nIf you're okay at calculus, [this site](_URL_0_) has a pretty good in-depth explanation.",
"Imagine the real line going sideways and the imaginary line going up and down. Each complex number can be thought of as a point somewhere in this infinite square - where it is left and right tells you the real value and where it is up and down tells you the imaginary value. Together, these define the complex numbers. Now, -1 is a complex number as well as a real number, it just has up and down value 0 (so it's 1 to the left on the horizontal line). Another way to represent a complex number would be to say how big it is (i.e. how far from the middle where both of those lines meet) and starting from the right, how far around you go. This is given by r (how big it is) and theta (we'll just use T) how far around you go. You can translate between these two kinds of representations like so: z = r(cos(T) + i\\*sin(T)) - this tells you the left-right position and the up-down position using r and T.\n\nRaising e to the power of a complex number has a special definition, but if you were to only use complex numbers that were also real numbers it would work out the same as the regular definition for the reals. Here is the special definition for complex numbers:\n\nLet z = x + iy be a complex number. Then e^z = e^x \\* e^iy and e^iy is defined to be cos(y) + i\\*sin(y). In fact, if z=iT for some angle T in radians, e^z = e^iT = cos(T) + i\\*sin(T). But this is just the same as the representation of a complex number which is 1 big and goes around T far. \n\nSo if T were pi (as in we're looking at e^i\\*pi ) it would be a complex number which is 1 big and goes around pi far. Since pi is half a circle and we're going around starting from the right, this means we land 1 far to the left of centre. That's just the real number -1.",
"It happens because of how closely related the exponential and trigonometric functions are.\n\ne^*ix* = cos x + isin x.\n\nIf you're okay at calculus, [this site](_URL_0_) has a pretty good in-depth explanation.",
"Imagine the real line going sideways and the imaginary line going up and down. Each complex number can be thought of as a point somewhere in this infinite square - where it is left and right tells you the real value and where it is up and down tells you the imaginary value. Together, these define the complex numbers. Now, -1 is a complex number as well as a real number, it just has up and down value 0 (so it's 1 to the left on the horizontal line). Another way to represent a complex number would be to say how big it is (i.e. how far from the middle where both of those lines meet) and starting from the right, how far around you go. This is given by r (how big it is) and theta (we'll just use T) how far around you go. You can translate between these two kinds of representations like so: z = r(cos(T) + i\\*sin(T)) - this tells you the left-right position and the up-down position using r and T.\n\nRaising e to the power of a complex number has a special definition, but if you were to only use complex numbers that were also real numbers it would work out the same as the regular definition for the reals. Here is the special definition for complex numbers:\n\nLet z = x + iy be a complex number. Then e^z = e^x \\* e^iy and e^iy is defined to be cos(y) + i\\*sin(y). In fact, if z=iT for some angle T in radians, e^z = e^iT = cos(T) + i\\*sin(T). But this is just the same as the representation of a complex number which is 1 big and goes around T far. \n\nSo if T were pi (as in we're looking at e^i\\*pi ) it would be a complex number which is 1 big and goes around pi far. Since pi is half a circle and we're going around starting from the right, this means we land 1 far to the left of centre. That's just the real number -1."
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aobfq2 | why is sexual isolation not reversible? | When speciation occurs over time and two species that used to be able to reproduce can no longer reproduce to make a viable offspring.
I don’t think this process is reversible, and I was wondering if anyone could explain why it isn’t (if that’s truly the case) | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/aobfq2/eli5_why_is_sexual_isolation_not_reversible/ | {
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"When the two populations have experienced enough different mutations that their offspring are not viable it is extremely unlikely that later mutations are going to sync up such that later offspring are viable. It isn't technically *impossible* but so unlikely as to be dismissed.",
"It is possible for reproductive isolation to be reversed. The likelihood of it recombining gene pools of previously isolated metapopulations (species) relies on a lot of stuff: intensity of selection, response to selection, generation time, gene expression rate, etc. I have not encountered any examples of this from sympatric speciation (reproductive isolation), but the same selective pressures and what not from above can combine two metapopulations if the source of reproductive isolation is removed. A lot of genes go \"dormant\" and come in handy for hypothetical situations like that. This is all a gross oversimplification, though the general idea stands."
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3wk3or | why did some animals become mainstream pets? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3wk3or/eli5_why_did_some_animals_become_mainstream_pets/ | {
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"They were the easiest to tame and domesticate. Also, some had actual uses beyond \"companion\".",
"Dogs that liked to be around humans did better than those who didn't. Eventually dogs lived in our villages and ate our garbage in exchange for offering us some protection.",
"Pets are a fairly recent development. In the meaning of keeping an animal for poor enjoyment, rather than usefulness. Apart from birds, which have been kept for much longer for pure enjoyment. Most of what we keep as pets now used to be kept as working animals. And food (rabbits). Keeping rodents and reptiles/spiders as pets is even newer. \nWealth and more leisure time is probably the biggest factor. We now have the money to feed animals that we have no need in keeping and the leisure time to spend time with them for fun.",
"Like a king charles cavalier spaniel. I can picture one of those mother fuckers purched on a throne in the 15th centur the same way he plops himself on the high pillow my parents place for him in the middle of the couch. He knows who the boss is and he doesn't give two squirts of piss about you if you ain't it. "
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1cptii | What is the temperature at which heavy elements will undergo fission? | In astronomy, I learned about the CNO fission cycle which happens in a star after helium is used up. This leads to a star core comprised of heavier elements. At what point will say, gold, undergo nuclear fission?
EDIT: I meant fusion, not fission. As helpfully pointed out to me below. | askscience | http://www.reddit.com/r/askscience/comments/1cptii/what_is_the_temperature_at_which_heavy_elements/ | {
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"It's actually the [CNO *fusion* cycle](_URL_2_). There is a big difference between [fusion](_URL_1_) and [fission](_URL_3_). From the Wikipedia page, [here's](_URL_0_) a graph showing the relationship between temperature and fusion rate. Since, I'm not an expert in physics, someone else is going to have to explain this more in depth.",
"The temperature where the CNO fusion process kicks in is about 15-16 million Kelvins. See [this](_URL_0_) or [this](_URL_1_).",
"I recently read about what happens inside a star that undergoes nuclear fusion. Past helium it becomes complicated because some elements such as beryllium only last for tiny fractions of a second when they are fused so in order to become a heavier element they must quickly fuse again. The odds of this happening at any given time are tiny. However there are lots of atoms so it does happen.\n\nThe reason stars are able to burn for so long is because for any single hydrogen atom to hit another hydrogen atom hard enough to fuse is extremely tiny.\n\nAnyway gold will not fuse because in order for gold to fuse it will take energy away and would actually cool the star down. Iron is the limit and is the most stable. You can not derive energy from fusion past iron. You in fact lose energy fusing. The other elements are formed from a supernova blast which I can not remember exactly how it happens as it is somewhat complicated.\n\nThe star collapses very very quickly once all the silicon is converted in a star into iron in about a single day. The pressure keeping the star from collapsing disappears and matter falls inward and about 20% the speed of light and hits a wall harder than any wall in the universe and bounces back causing a massive shockwave that hits the matter falling downward and I think the shockwave slows down and builds up a layer of compressed matter that stops neutrinos from escaping quickly where normally they would fly through without interacting with normal matter. The neutrinos build up faster than they can escape and eventually this causes the star to explode like a bomb from the enormous pressure. This pressure derived from gravitational collapse is where further fusion can occur.\n\nIt takes these sort of extreme conditions to form the heavier elements.\n\nCorrect me if I am wrong on any of this."
]
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"http://upload.wikimedia.org/wikipedia/commons/d/d0/Fusion_rxnrate.svg",
"http://en.wikipedia.org/wiki/Nuclear_fusion",
"http://en.wikipedia.org/wiki/CNO_cycle",
"http://en.wikipedia.org/wiki/Nuclear_fission"
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"http://www.windows2universe.org/sun/Solar_interior/Nuclear_Reactions/Fusion/Fusion_in_stars/CNO_cycle.html",
"http://www.kcvs.ca/martin/astro/au/unit4/92/chp9_2.htm"
],
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|
35fhfh | If mockingbirds mimic sounds and calls from other birds, how do they attract mates? | askscience | http://www.reddit.com/r/askscience/comments/35fhfh/if_mockingbirds_mimic_sounds_and_calls_from_other/ | {
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"IIRC they attract mates by doing a series of different sounds/calls, the females go to the male with the most complex series of sounds. So basically they know to listen for a bizarre series of sounds inexplicably coming from just one tree, as opposed to listening for one particular song. Sorry I don't have a source for this, it's just what I remember from a field zoology course so don't quote me. "
]
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[]
] |
||
2zh69u | Which publication of the Diary of Anne Frank is the most historically accurate? | My daughter has a oral book report due next month about a person who had a significant impact on the world. Based on my daughters age and also her interests, she chose to complete her presentation about Anne Frank.
& nbsp;
I read a version of the Diary of Anne Frank several times when I was her age, however since then, there have been different variations released due to additional pages/documents being found including the pages found after her father Otto died.
& nbsp;
From what I can find, it appears there is an **A Version**, **B Version**, and **C Version**, however on Amazon, they are not listed this way. I do understand that there is a version that some parents feel is inappropriate for preteens to read, however I disagree with the parents who sought to censor this particular version. I appears this version is titled **“The Diary of a Young Girl: the Definitive Edition”**, which was published on the 50th anniversary of Frank’s death, however I'm not sure if another version has been released since then.
& nbsp;
**Does anyone know the title of the most complete/ historically accurate version of Anne Frank's diaries?** I do realize that a portion of her diaries have never been found, however **I would like to purchase the most complete and uncensored version**. | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/2zh69u/which_publication_of_the_diary_of_anne_frank_is/ | {
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"text": [
"OK, there is a lot here that needs to be addressed. \n\nThe three versions you discuss are the A, B, and C versions. The A version was the original diary that Anne wrote during hiding. The B version is a rewrite, also by Anne, of the first entries from the A version (interestingly, in the diary itself, Anne discusses this, when she mentions wanting to be a writer and wanting to send her diary off as a record of the war, as she had heard was requested by Education Minister Gerrit Bolkestein on Radio Oranje). The C version is the version compiled by Otto Frank after the war from the papers that were saved by Miep Gies after the Frank family was betrayed, arrested, and deported. Almost until his death, Otto Frank maintained that he had only lightly edited the diary, removing only some parts about Anne's physical development (this is the part that some folks get fussy about) and some especially nasty remarks about Anne's mother. In fact, Otto did much more than simple light editing, since he had duplicates of many of the entries (because B entries were rewrites of A entries, both by Anne) but he only included one or the other in the original published version (Het Achterhuis/The Diary of a Young Girl) - he can certainly be credited as an editor of the book, if not a co-author. \n\nAll of this is confused by the fact that five additional pages of the diary were discovered in 1998, after the publication by the NIOD Institute for War, Holocaust, and Genocides Studies of the complete Critical Edition in 1986 (in Dutch). The English translation of this original critical edition was only published in 2001, so after the discovery of the additional five pages, which meant that the English language critical edition was out of date before it was even published. A revised critical edition, which contains all of the texts, side by side for comparative reading, was published in 2003, in English (2001 in Dutch). You can find that edition on Amazon [here](_URL_1_). \n\nSource: [Anne Frank Foundation - Amsterdam](_URL_0_)\n\n"
]
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"http://www.annefrank.org/en/Anne-Frank/A-diary-as-a-best-friend/At-last-seriously-taken-as-a-writer/",
"http://amzn.com/0385508476"
]
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|
4q485i | How did tobacco altar old world society after it's new world discovery? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/4q485i/how_did_tobacco_altar_old_world_society_after_its/ | {
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"There's an excellent recent book about tobacco and China by the historian Carol Benedict, \"Golden-Silk Smoke: A History of Tobacco in China, 1550-2010.\" Like many other products found by Europeans in the Americas (ranging from large quantities of silver to hot peppers), tobacco made its way to China relatively quickly and began having all sorts of social and economic effects."
]
} | [] | [] | [
[]
] |
||
1tn6e0 | why does ordering something from a tv commercial takes so long to be received versus getting it from an online site ? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1tn6e0/eli5_why_does_ordering_something_from_a_tv/ | {
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"Because often times a large part of their profit is from overcharging you for the crappy shipping they use which in reality costs about 1/5th of what you paid. Additionally home shopping network, and others like it, are typically geared towards an older target demographic, those that aren't, for the most part, computer savvy... so they don't necessarily realize how big of a ripoff the shipping costs are. ",
"Many of the products sold through infomercials, especially information products, are not actually created until an order is placed. So, you may order a DVD set today but the next batch of orders are not created until the next week. It's a sort of 'standard' that the price of shipping should cover the entire cost of creating the product. So, if the DVD set is $30 and shipping is $5, that's generally what it actually costs to print the DVDs and the case they come in."
]
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[],
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89shhz | What changed that the commander of a Combat Air Group went from being a Commander rank to a Captain? | I was touring the USS Midway last week and I saw they had a list of all the people who where in charge of the CAG. Up until the 70s they were all Commanders. Afterwards, most were Captains. What changed? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/89shhz/what_changed_that_the_commander_of_a_combat_air/ | {
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"It was an intentional change to pump up the Carrier Air Wing's CO billet to 0-6. The change was phased in over a number of years that put the Carrier's CO and the CAG on equal footing as partners who both were direct reports to the Strike Group Commander. \n\nIn large part it was an acknowledgement of the power and importance of the embarked air wing as a separate and distinct asset from the ship itself. It also brought the organizational billet in line with the USAF, as they assigned at least a Colonel to lead Wings and a CVW is in reality a composite wing in USAF parlance. \n\nIt also came at a time when air wings were reaching what would become their max size in the post WW2 era. The air wings size had shrunk following WW2 by nearly 50% in some cases. The *Essex* and *Midway* class hulls could fit a lot, but jets continued to increase in size and wait, meaning by the mid 60's carriers might only have 50-70 at most aircraft embarked, and even then either a small number of large patrol aircraft or larger numbers of light daytime attacker or fighters in many cases. Doubly so when we consider many of the *Essex* hulls were re-designated as anti submarine carriers. However the newer super carrier hulls of the *Forrestal*, *Kitty Hawk/JFK*, and most of all the CVN's of the *Enterprise* and *Nimitz* classes changed the game. Once again carriers could embark huge mixed air groups of 90 or so jets. A super carrier air group of the mid 80's might have 2 F-14 squadrons, 2 A-7 Corsair II squadrons, an A-6 Intruder squadron, an EA-6B Prowler squadron, an S-3 Viking patrol squadron, and a helicopter squadron, along with E-2b Hawkeye and C-2 Greyhound detachments. While some squadrons on the smaller carriers in particular were also deploying with the first operational F/A-18 Hornet units. \n\nEven with the status of air wings again today having shrunk back to almost unprecedentedly small sizes, it easy to see why in the late Cold War how a billet in command of multiple squadrons and dozens of aircraft rated more than an O-5. Doubly so with Regan's famous 600 Ship Fleet drive under Secretary Lehman in the background. "
]
} | [] | [] | [
[]
] |
|
15qurk | Anti-abolitionists in the US cited economics as their most common argument against ending slavery. Did the US suffer any noticeable recession soon after the passing of the 13th Amendment? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/15qurk/antiabolitionists_in_the_us_cited_economics_as/ | {
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"text": [
"I would imagine this would be really hard to quantify since so much of the South'a economy was also recovering from the loss of life and and other reconstruction efforts after the devastation of places like those visited by Sherman and the Northern army.",
"The south was in depression after the Civil War only in part due to the destruction of slavery (the war was much more a cause). The first major economic downturn after the Civil War was the Panic of 1873 which had nothing to do with freeing the slaves.",
"the south was demonstrably poorer than the rest of the US well into the 20th century, and is still somewhat poorer, though it has been closing the gap rapidly in recent years. Part of the reason that LBJ was such a big supporter of the space program was his desire to spend a ton of money building a high tech southern economy, particularly in texas, which is why space shuttles launched from florida are controlled from Houston. But that poverty had at least as much to do with the direct damage of the civil war and 100 years of Jim crow suppressing black productivity as it did with freeing the slaves.",
"You can't use the time after the ratification of the 13th amendment as a tool to measure abolition/slavery's economic effects - the war had a much larger, lasting economic effect at this time and would distort the data.\nUltimately, you have to keep in mind that most slave-based systems are economically profitable, as was the US system of slavery, and that losing such a system will always have consequences as adjustments are made. \n\nI've made some recommendations here that can give you a decent background on the subject and perhaps give you some leads on more in-depth study:\n\n[Time on the Cross](_URL_2_)\n\n[Slavery and American Economic Development](_URL_0_)\n\n[The Political Economy of Slavery](_URL_3_)\n\n[Without Consent or Contract](_URL_1_)\n\n"
]
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[],
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"http://www.amazon.com/gp/search?index=books&linkCode=qs&keywords=0807131830",
"http://books.wwnorton.com/books/978-0-393-31219-5/",
"http://books.google.com/books/about/Time_on_the_Cross.html?id=ScpPBinpzwoC",
"http://www.amazon.com/gp/search?index=books&linkCode=qs&keywords=0819562084"
]
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||
9hg42u | Why did Ancient Egyptians really worship cats? Is this where the 9 lives saying originates? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/9hg42u/why_did_ancient_egyptians_really_worship_cats_is/ | {
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"text": [
"The problem with finding the origin of a folk belief like this one - that cat's have nine lives - is that when there is no clear answer, folklore typically invents one (the folk abhor a vacuum!). The idea that Ancient Egypt is the source of this belief is likely a bit of folklore in itself, caused at least in part by the understanding that ancient Egyptians revered the cat and are well known for their fascination with the afterlife.\n\n[This site](_URL_1_) attempts to answer the question presented here, but it has unsatisfactory explanations. It attributes the Egyptian source to the Encyclopedia of the Unusual and Unexplained: Superstitions, Strange Customs, Taboos, and Urban Legends - a site that does not inspire trust. Of use with the first site, however, is the observation that Herodotus, who is a contemporary commentator on Egyptians and cats fails to note anything about the multiple lives of cats: if this was such an important attribute of belief that we still remember it, one would assume the ancient Greek historian would have mentioned it. The site also notes the early reference to the cat's nine lives in Shakespeare's Romeo and Juliet, but that does little more than pin down an early occurrence - not that still earlier ones don't exist.\n\nThe [Wiki site](_URL_0_) on cats lends a bit of insight even though we all know that source is to be shunned. It suggests that \"In many countries, they are believed to have nine lives, but in Italy, Germany, Greece, Brazil and some Spanish-speaking regions, they are said to have seven lives, while in Turkish and Arabic traditions, the number of lives is six.\" We can't trust this source, but it raises a good question: if other cultures - particularly other European cultures have numbers other than nine for the life of the cat, we can assume that the folk tradition is a matter of multiple lives with no consensus on the exact number. In that case, we can set aside the idea that the number nine as significant and focus instead on the serial resurrection of the cat. We could return to the Egyptians as the source of that concept, but we would certainly need evidence rather than conjecture.\n\nKatharine Briggs, the esteemed British folklorist has a book titled Nine Lives: The Folklore of Cats. She was big on description and short on explanation. I don't have the book, but I suspect it won't explain this, and I suspect that your question can only be left unanswered."
]
} | [] | [] | [
[
"https://en.wikipedia.org/wiki/Cat#History_and_mythology",
"https://mythology.stackexchange.com/questions/1843/what-is-the-folkloristic-origin-of-cats-having-9-lives"
]
] |
||
7dpvmb | does temperature affect evaporation rate below boiling point? | I figure that water would evaporate faster as you get into higher temps, but is there some force at work that keeps the rate consistent below boiling point? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7dpvmb/eli5_does_temperature_affect_evaporation_rate/ | {
"a_id": [
"dpzkxvq"
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"score": [
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"text": [
" Water evaporates much faster at higher temps. Think of a clothes dryer. If the heat didn't speed the evaporation of the water in the clothes, there would be no need to warm the incoming air. Smear a drop of water on a cool surface and the same surface when it's warmed. It's easy to see the difference."
]
} | [] | [] | [
[]
] |
|
3bnoy2 | what is will power and where does it come from if emotion is based off of chemical interactions? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/3bnoy2/eli5_what_is_will_power_and_where_does_it_come/ | {
"a_id": [
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"text": [
"\"Will power\" is not a concept that modern psychologists really use -- it's kind of an inaccurate idea.\n\nA more accurate version is \"delayed gratification\". This means the ability to give up a short-term pleasure in order to obtain a larger long-term reward. Since our brain is motivated by *both* of these forces, they tend to compete with each other. Which one wins is determined by many variables."
]
} | [] | [] | [
[]
] |
||
4wov03 | is it possible for humans to procreate during zero gravity space flight? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4wov03/eli5_is_it_possible_for_humans_to_procreate/ | {
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"text": [
"Probably, sperm don't need gravity to travel. So a woman could probably get pregnant, but as far as after that, we just don't know. IIRC Vsauce did a video on this.",
"The short answer is, we don't know. Possible, maybe. The short term effects on the embryo, baby or the longer term health effects on the adult based on conception and possibly gestation of a human fetus in micro-gravity is unknown. \n\nWe may never know, because a large scale experiment would be unethical and expensive. Try in r/askscience, maybe they know about research on mammals such as rats in space."
]
} | [] | [] | [
[],
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] |
||
37twtw | If a tree lives to be 10,000 years old will it under go the same evolution of a series of 1000 ten year old trees of the same species? | askscience | http://www.reddit.com/r/askscience/comments/37twtw/if_a_tree_lives_to_be_10000_years_old_will_it/ | {
"a_id": [
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" A single tree cannot undergo evolution. Evolution is a process that can only be seen at the population level. A simple definition of evolution is: change in the genetic composition of a population over time [(Source)]( _URL_0_). So neither the 10,000 year old tree nor the 10 year old trees will, themselves, have undergone evolution.\nHowever, the population would have been different when the 10,000 year old tree was created. So the potential tree-parents would have changed between our trees of different ages. It may have been common 10,000 years ago, for trees of this species to have peeling bark ([like paper birch]( _URL_1_)). So our old tree has peeling bark because it was a common trait at the time of its creation. If you suppose that insect infestations became more common 9,000 years ago, that could have caused a selective pressure to have [firmer bark](_URL_2_). Our 10,000 year old tree was lucky that it didn’t get attacked by the insects but most trees were and trees with firmed bark were favored. So our 10 year old trees were created from a population of mostly firm barked trees and therefore most of them have firm bark.\n\nNote that at a timescale of 10,000 years most genetic changes in a tree population would be small.\n"
]
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"http://www.nature.com/scitable/definition/evolution-78",
"http://i.imgur.com/aylGhDL.png",
"http://i.imgur.com/d6kY0u8.png"
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||
aw870k | the indian “head bob” | I’ve seen a lot of references to the Indian cultural communication method colloquially know as the “the head bob”.
I’ve read that it means different things in different contexts... what are the main ones? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/aw870k/eli5_the_indian_head_bob/ | {
"a_id": [
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"text": [
"In America it is generally understood that rotating the head up and down means \"yes\" and rotation side to side means \"no\".\n\nHowever in India there are a lot more head movements with different meanings. Along with the two Americans are familiar with one might also indicate \"yes\" by rotating the head along the axis of sight. Also vigorously performing the yes or no head movements indicate that the decision is set.\n\nMoving the head down is calling someone over. Moving it upward is asking \"What is up?\" (Americans often recognize this as well). The same action may also be used to hit on girls as well as paired with a wink to indicate \"Carry on.\"\n\nHead wobble is also common both when enjoying music as well as an indication of respect and attention when being spoken to."
]
} | [] | [] | [
[]
] |
|
blh3oo | why is it princess eugenie and princess beatrice, but it's lady louise windsor and james, viscount severn? | Obviously there is Prince Harry and William as the grandchildren in the succession line, and all of the Queens children are Princes and Princesses (Charles, Anne etc), but why are two of her grandchildren Princesses, and another two are not? Both grandchildren from Andrew and Sarah are Princesses (Eugenie and Beatrice), but her grandchildren from Edward and Sophie are Ladies and Viscounts? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/blh3oo/eli5_why_is_it_princess_eugenie_and_princess/ | {
"a_id": [
"emocoig"
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"score": [
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"text": [
"This one's entirely up to personal choice. Whose choice, exactly, is not entirely clear, but when Prince Edward married, there was a royal press release that all of his children were to be styled as nobility, rather than royalty."
]
} | [] | [] | [
[]
] |
|
2m9liy | Can anyone point me toward some Norse elated books? | Edit: title should read "related" sorry.
I'm interested in expanding my knowledge about all things Norse. Currently I know very little but the concept of Vikings has always been fascinating to me. I'm hoping to find books relating to Norse culture, mythology, history, or warfare during the times when Vikings were most prevalent.
I don't know what books to look toward so some guidance here would be appreciated. I'm not looking for anything that's incredibly deep though because I am new to this subject and I want to taste several aspects of it in my leisure reading time.
Thanks for the help I do appreciate people taking their time to reply. | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/2m9liy/can_anyone_point_me_toward_some_norse_elated_books/ | {
"a_id": [
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"text": [
"Well, your best bet for a worm's eye view of Scandinavian society in the early middle ages (or, at least, a 13th century interpretation thereof) are the sagas.\n\nI would recommend highly the Folio Society's *The Icelandic Sagas*, as well as essentially anything published by Penguin. As far as the sagas themselves go, I've always been partial to *Egils saga*, *Brennu-Njáls saga*/*The saga of burnt-Njál*/*Njáls saga*, and *Laxdæla saga*. They give you a pretty good idea of what life was like for wealthy farmers in Iceland during the 9th-11th centuries.\n\nAs far as the mythology goes, get yourself anything written by Terry Gunnell or John Lindow - Lindow's *Norse Mythology: An encyclopedia* is a good reference. Also, you'll want both the Prose and Poetic Eddas.\n\nAs far as culture, I cannot recommend Stefan Brink and Neil Prices' *The Viking World* high enough, nor William Ian Miller's *Bloodtaking and Peacemaking.*\n\nI would strongly recommend keeping away from anything written by Jesse Byock about anything other than archaeology in Mosfellbær, as it's not really his strong suit and essentially everything he writes has been done before and far better by Miller or Anthony Faulks."
]
} | [] | [] | [
[]
] |
|
8528wz | How fast do clouds move in relation to the earth? What factors are there when measuring the speed of clouds? | Just looking at clouds on the chair lift this morning and during conversation with my friend we were discussing like what needs to be understood to know how fast clouds are moving. | askscience | https://www.reddit.com/r/askscience/comments/8528wz/how_fast_do_clouds_move_in_relation_to_the_earth/ | {
"a_id": [
"dvug8u8"
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"text": [
"They move at the speed of the wind at their altitude, typically tens of kilometers per hour. You can measure their angular velocity as seen from you, and you can determine their distance with triangulation if you have at least a second viewing point, combine both and you get the speed of the cloud. Radar can directly give you the speed."
]
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|
230qn5 | why is fluoride put in water marketed to babies if they are going to lose all of their teeth in a few years? | I've seen the "baby water" in the grocery store many times. I've checked it out, and it looks like the only difference is that it has more fluoride. Why do they add it if the babies potentially don't even have teeth yet, and are going to get a new set within a few years? Does it strengthen bones? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/230qn5/eli5_why_is_fluoride_put_in_water_marketed_to/ | {
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"text": [
"Because their teeth can still rot before they fall out, which can still be painful, and getting fillings as a child sucks. EDIT: Also consider the associated plaque, bone loss, and risk of infection associated with poor dental hygiene.",
"Yes it strengthens bones. Besides, human beings need a little bit of fluorine to live. Fluorine/Fluoride is necessary to ensure that bones mineralize normally.\n\nI don't see why people are worried about it. We need potassium, chlorine, sodium, copper, iron, and a bunch of other scary sounding elements to live, I don't really get why people pick out fluorine as the dangerous one. It's possible to get too high a dose, but in America, the amount of water you'd have to drink to get it would kill you far before the fluorine would.\n\nUnfortunately, in places like India and China, fluorine overdoses happen occasionally (around .5% of the population) It is a big public health issue, but in regulated developed countries, it's not a problem.\n\n_URL_0_",
"Their adult teeth are developing below the gumline. When the adult teeth develop, they'll incorporate small amounts of fluoride from your system if there's any there. This results in teeth made of fluoroapatite, a slightly stronger mineral than the hydroxyapatite that normally makes up the teeth - in particular, fluoroapatite is more acid-resistant.\n\nDrinking fluoridated water achieves this result to a small degree, forming a thin layer of fluoroapatite on the surface of the tooth. But it's not incorporated deeply into the tooth structure as it is if you're exposed to fluoridated water as a child."
]
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] |
|
efaqp2 | tears | What's actually happening when we blink back tears? If it doesn't flow down the face, where does it go? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/efaqp2/eli5_tears/ | {
"a_id": [
"fbzcgvm"
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"score": [
5
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"text": [
"You have small ducts in the inside corners of your eyes. If you can keep the tears from spilling over, the fluid drains out through those ducts into your nasal passages."
]
} | [] | [] | [
[]
] |
|
3cu7ly | if rape is common in male prisons, why doesn't the public take it seriously? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/3cu7ly/eli5_if_rape_is_common_in_male_prisons_why_doesnt/ | {
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"I'm not sure how prevalent it is, but in general the public doesnt really care about the lives of prisoners.\n\nPrisons charge prisoners (and their families) ridiculous prices for essential items and completely rob them on telephone charges. What are they gonna do, shop around for a better prison?",
"Prisoners are not a very attractive group of people, so crimes against them don't attract much sympathy. It's sad, racist, and not a good reflection of our values.",
"I will assume you mean USA prisons? There are so many things wrong with the US prison for profit industry that the raping part seems like the iceing on the cake.",
"Crimes against males are often ignored or taken lightly. This includes domestic violence (pussy) and rape (lucky). That and the fact criminals are often painted as murderous raping monsters regardless of what crimes they actually committed. This doesn't help them in terms of gaining sympathy. ",
"It's because the media, including TV shows and movies, portray criminals as...well, TERRIBLE PEOPLE. And these terrible people are getting their karmic retribution in prison. \nAs an anecdote, I personally think it has something to do with the rules of law as seen in the Bible.",
"There are some good ongoing efforts being made to reduce (and eventually eliminate) prison rape. In 2003 Congress passed the Prison Rape Elimination Act, [wiki](_URL_0_), and some progress is being made on the issue. Not (obviously) enough and not with as much support as it might have, but it is something government money and attention is being spent on.",
"I read an ama from an ex con from a federal prison. Apparently it's mostly Hollywood drama as there are more than enough willing participants for those who want gay sex",
"The public doesn't care much about prisoners, and they also don't care much about male victims of rape. It's probably both of these things, as you would still hear outrage over a female prisoner being raped, and you would still hear some outcry over a male being raped.",
"It is because many consider any of the abuses that happen to criminals in prison to justified by the fact that they are criminals. They have forfeited their right to live in civil society and it is almost considered part of their punishments. ",
"Because we view prison rape as a form of retributive justice. However, it would most definitely be considered as both cruel AND unusual, so we let prisoners do it to each other, allowing prison systems to deflect blame."
]
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"https://en.wikipedia.org/wiki/Prison_Rape_Elimination_Act_of_2003"
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||
1e7nn8 | What was the first battle to be reenacted by actors? When was it? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1e7nn8/what_was_the_first_battle_to_be_reenacted_by/ | {
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"text": [
"Well, the Romans reenacted quite few battles at the Coliseum (built 72 C.E.), and I suppose they were reenacting battles before in other structures. I don't know that you could call the people in these events actors."
]
} | [] | [] | [
[]
] |
||
7isfdu | how did we come up with the asteroid theory for dinosaur extinction? | ELI5 | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7isfdu/elif_how_did_we_come_up_with_the_asteroid_theory/ | {
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"It's not the only theory but it's the one best explained by all the evidence. First, there's the 150km wide impact crater off the Yucatan peninsula. It was created by a roughly 10km wide asteroid impacting at 30+km/s and it's been date to 65 million years ago which is exactly when the dinosaurs became extinct. We know how catastrophic an impact like that would be so it already makes sense as the cause of the extinction. \n\nThere's also evidence of a large impact besides the crater such as ejecta layers in the rock, shock formations in the rock, melted rock from the molten impact site, and the high presence of certain rare elements that are only found in asteroids or deep within the Earth. This is all exactly what you'd expect to find in rock layers from the same time period, and there's a lack of evidence for other explanations.\n\nThe fossil record also indicates a sudden, catastrophic die-off rather than a slow decline in the number of fossils, which is what you'd expect from a sudden mass-extinction event.\n\n\n",
"Say that you find a dead body and you try to figure out what killed them. You examine the person and find a wound. You can look at the shape of the wound, and you can poke around inside the wound looking for any foreign material. You find small shards of glass, leading to the conclusion that glass was the murder weapon. \n\nYou have a mystery, you gather evidence, and you form a conclusion that can explain all the facts. \n\nWhen scientists began finding fossil relics, they found that the age of the rock that the fossils were embedded in could tell you when those animals walked the Earth.\n\nIt's a misconception that the oldest rocks are the deepest, because rock formations are displaced all of the time, and weathering and uplift, and many other geologic processes can sometimes bring old rock to the surface. But even before radio carbon dating, scientists could look at other things in the rock, seeds, plants, even pollen and insects, and get a general idea of how old the rock was. \n\n\nWell they found that dinosaur fossils tended to be located in rock layers that were millions of years old, however [at a certain point](_URL_1_), those fossils just stopped. In newer rock they found only smaller animal fossils like rodents and such, and in older rock they had megafauna like dinosaurs. So they could pretty much look at a layer of rock, and pinpoint the layer of rock between living dinosaurs, and dead dinosaurs. \n\nAnd much like finding those glass shards in the murder victim, they looked at what was inside these rock layers. They found some odd things. There were beads of glass there and glass usually forms in volcanic events and meteor impacts. They also found layers of rock that seemed to be made of ash. The final nail in the coffin of \"What killed the dinosaurs\" was a chemical analysis of the rock found large amounts of an element that is relatively rare on Earth, but common in asteroids; [Iridium.](_URL_2_)\n\nThis iridium dust was present in rocks all over the planet that were from that time period. So some how a rare element, mostly found in asteroids, managed to cover the entire earth in ash, all at the same time. Before this event you had dinosaurs and after the event you didn't. \n\nThe only thing they couldn't figure out was where was the crater? Surely something that big, that catastrophic left a crater behind right? And it turned out there [was a crater](_URL_0_), but that it was so large, we didn't even know we were looking at it. The crater was partially under water, and it was so large that you can't see it all at once because of the horizon; we didn't see it for a very long time. "
]
} | [] | [] | [
[],
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"https://en.wikipedia.org/wiki/Chicxulub_crater",
"https://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_boundary",
"http://www.pbs.org/wgbh/evolution/extinction/dinosaurs/asteroid.html"
]
] |
|
14z3hw | How did we know what note to tune our instruments to before we understood the physics of sound? | I was thinking- if we define a note as a vibration of an arbitraty frequency- then how do we know that a c note 300 years ago wasn't a vibration of, say 10 less hz? Against what universal did we tune our instruments to? did these vary from country to country, or city to city? | askscience | http://www.reddit.com/r/askscience/comments/14z3hw/how_did_we_know_what_note_to_tune_our_instruments/ | {
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"It varied from orchestra to orchestra. Before the 1800s tuning was usually based around instruments that were difficult to tune, like organs. (Since some of these organs are still around we can figure out what pitches they used.) But these varied from location to location.\n\nThere were actually some problems associated with this because orchestras that were slightly sharper than others sounded like they had more \"bite\" or were more \"brilliant.\" This led to a sort of \"pitch inflation,\" where orchestras would tune sharper and sharper so that they'd be sharper than competing orchestras. Things started getting out of hand in the mid-1800s, so orchestras collectively decided to standardize their tuning to a particular frequency.\n\nSee the [Wikipedia article](_URL_0_) for more.",
"Also, in the Indian tradition, there is no concept of fixed pitch. People used to tune their instruments to their voices, and till date, most people will tune their instruments to a harmonium, just because those buggers are a p.i.t.a. to retune. \nIt is important to keep in mind that music is not as much about specific notes as much as the difference between notes, hance the concept of musical interval. Using that metric, if we decided that tomorrow, concert A, rather then being 440hz was 540hz, music would still sound the same, albeit slightly sharper."
]
} | [] | [] | [
[
"http://en.wikipedia.org/wiki/Concert_pitch#History_of_pitch_standards_in_Western_music"
],
[]
] |
|
3p14ts | can a planet have two suns like tatooine? | And why is it possible? Does one sun revolve around the other? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3p14ts/eli5_can_a_planet_have_two_suns_like_tatooine/ | {
"a_id": [
"cw27z81"
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"score": [
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"text": [
"Yes. There are plenty of binary star systems in the known universe. However, the planets orbiting them might not be habitable, as temperatures would likely vary greatly due to how the planet orbits the stars."
]
} | [] | [] | [
[]
] |
|
17opg3 | envy--why exactly do others' accomplishments cause us to feel worse about ourselves? | It's a given that we feel worse when someone else has something we can't have.
My theory is that learning that there exists a person (whom we know) who has something we want "rubs in" the fact that we are missing something. But if missing something makes us feel bad, why don't we feel bad constantly, and not just when others remind us of it? If we don't always feel bad about missing something, do we really miss it/want it?
Btw, if this is in the wrong subreddit I apologize. I'm honestly just curious and trying to figure out the reasoning behind this experience. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/17opg3/eli5_envywhy_exactly_do_others_accomplishments/ | {
"a_id": [
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"While someone getting to have something that you can't have is certainly a part of it, I also think that respect is a major part of Envy. It makes sense that people get what they deserve, for better or for worse. It also makes sense that some people are a bit better at this-or-that than you. So it makes sense that some people get to have better things than you. \n\nHowever, what happens when you don't feel that someone deserves what they have? We all hear about how \"millionaires\" are a bunch of money-grubing jackasses. They spend time fighting to lower minimum wages for their corporations, while buying themselves a new gold-plated Ferrari every other month. Obviously, this gives the impression they aren't very good people, and they don't deserve all the nice things they have. \n\nThat, I believe, is the root of envy. You feel that you are better than someone, thus you deserve to have at least as much nice stuff as they do. Wither its envy over some asshole who's got a hottie for a girl, or some douchbag with a nicer car than you, the fact is that you don't respect the person you feel envy towards. Disrespect is the basis of envy. Its not so much about *what* someone has, its *who* has it. \n\nThats why almost no one minds that Bill Gates is richer than basically everyone. People respect him. He's a brilliant business man, he revolutionized an industry, and he is a major philanthropist. Its okay that he's richer than you. Compare that to the guy that cut you off in his new BMW, and the difference in respect is clear. \n\nFinally, this explains why the Holy Catholic Church considers Envy to be one of the Seven Deadly Sins. If you don't respect someone, how can you learn from them? Besides, if you Envy what they have, then you acknowledge that they have good tastes in their possessions. Envy stems from disrespect, and disrespect blocks self-improvment. "
]
} | [] | [] | [
[]
] |
|
36dcyw | what's the difference between silk produced by spiders, and silk produced by moth larvae? why don't we farm spiders for their silk? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/36dcyw/eli5_whats_the_difference_between_silk_produced/ | {
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"text": [
"Moth larvae will live happily in a box together, spiders however will kill and eat eachother. So it's much easier to farm moth larvae instead of having individually housed spiders producing the silk :)",
"Practicality and ease of collection.\n\nWe haven't figured out a simple and reliable way to get a spider to give us a consistent and unbroken silk fiber of the correct type (remember, spiders can change the silk they make to serve certain functions, like strong and stretchy structural silk, or sticky silk designed to capture prey).\n\nWith silk worms (moth larvae), they spin a silken cocoon out of a single strand of the type of silk fiber we need. By placing the cocoons in hot water, the bonds break down, and you can extract the single strand. It's a pretty easy process, and hundreds can be done simultaneously. \n\nSilk worms are easy to raise by the thousands (or millions!). They don't fight among themselves, they don't wander. There's also no risk of bites. Practicality wins out, using cocoons is far easier than trying to extract it from live animals."
]
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[],
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||
2hxq7v | is adblock plus detrimental to websites that rely on advertisements? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2hxq7v/eli5is_adblock_plus_detrimental_to_websites_that/ | {
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"text": [
"How to explain this for this subreddit..yes!",
"It really depends on the target audience.\n\nA website for grandmothers who quilt is unlikely to have many tech-savvy users that have AdBlock installed. The odd user who does isn't going to make much of a difference.\n\nA website like reddit has a target audience that is more familiar with technology, so the frequency of users who have AdBlock installed will be greater. This may seriously affect advertising revenue.",
"The answer is... it depends. \n\nAt first it seems as though the question is tautological. If a website *relies* on advertisements then anything that removes those advertisements is *by definition* detrimental. But that interpretation of your question lacks nuance.\n\nDepending on the type of advertisement, merely showing the ad might not be enough to generate any revenue. Some ads require the visitor to click on them, others require them to actually buy something. So for a user who never clicks on ads, Adblock doesn't harm website revenues in any way. Other ads may generate revenue on a pay per view basis, which would be negatively affected by Adblock. \n\nHowever, some websites use adverts that display in popup (or pop behind) windows. These popups are blocked by almost every modern web browser's default settings - no Adblock required. And what's more, nobody gives a second thought to it. There are no cries that popup blockers are somehow unethical or injurious to websites that rely on them for income. So it seems the issue is not a black and white one."
]
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[],
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||
1bmtki | What happens to all of the energy in a lightning bolt when it strikes the Earth? | askscience | http://www.reddit.com/r/askscience/comments/1bmtki/what_happens_to_all_of_the_energy_in_a_lightning/ | {
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"First of all the energy isn't \"in\" the bolt, the bolt is a sort of temporary wire between the earth and a cloud. The energy is in the imbalance of charge between the cloud and earth. A lot of the energy goes into ionizing the air. It takes a lot of voltage to separate electrons from the molecules in the air. Once the air is sufficiently ionized for a plasma channel to form energy goes into accelerating charge carriers and resistive heat loss. The current in this plasma also radiates energy in the form of electromagnetic waves (including the visible white-purple flash from the extremely hot plasma) and air pressure waves (thunder) due to the rapid heating. Once sufficient energy has been lost the air deionizes which results in a little bit more heat and possibly some more em radiation."
]
} | [] | [] | [
[]
] |
||
evpmfq | why, after building millions of cars and seeing that all of them rust, do automobile makers still not spray a rustproof coating or use stainless steel wherever appropriate? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/evpmfq/eli5_why_after_building_millions_of_cars_and/ | {
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"text": [
"Stainless steel is expensive and harder to work with. Spraying an undercoating at the factory costs money. They pass those savings onto the customer who hopefully will have a rusted out car in 6-10 years and buy a new vehicle."
]
} | [] | [] | [
[]
] |
||
cmsskv | why is the oil in the us so much cheaper than its european counterparts? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/cmsskv/eli5_why_is_the_oil_in_the_us_so_much_cheaper/ | {
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"text": [
"The US is one of the world's largest oil and gas exporters, and has a ton of domestic refining capacity. Combined with relatively low taxes on petroleum products, that makes oil cheap to buy in the US.",
"The government gives ~~corporate welfare~~ subsidies to the oil companies to drive down the price. Also, Euro countries probably charge a lot more in tax on fossil fuels.",
"We process our own oil (in addition to importing cheap oil) and export a fair amount of the refined products made from it to Europe. We also tend to have fewer taxes on it.",
"I assume you mean petroleum product that you burn instead of use for lubrication or the oil or oil that is used in food.\n\nThe main difference is the amount of tax on it. \n\nAt [_URL_1_](_URL_0_) you can find the tax for gasoline you ahve a 18.5c/gallon federal tas and the lowes state tax is Alaska 14.65c/gallon and the highets Pennsylvania 57.6 c/gallon. So the total tax is between 33.15 c/gallon and 76.1 c/gallon.\n\nA us liquid gallon is 3.78541l so the tax is $0.087/l to $0.201/l\n\nCompare that to for example Sweden where the tax is at 6.70 SEK/L that is $0.70/l. \n\nThen there is value added tax (VAT) I have not idea if in the US in states that have VAT it is added to the tax tax but it is in sweden with 25% so the total tax is $0.875/l. The VAT is also added to what the company that sell it charge\n\nThe result is that gasoline that cost on average 16,48 SEK/l in april 2019 of that 61% was tax. That is equivalent to $ 6.50/ gallon and $3.965 was tax. \n\nIt looks like the average us gas cost was $2.50 in March\n\nThe tax rate might not be as high in other countries in europe but it is higher than in the US.",
"It mostly has to do with taxes. The U.S. has relatively low gasoline taxes compared to Europe and elsewhere.",
"We produce and refine way more oil than Europe does, so there's lower shipping costs/import taxes/etc. We also have lower gasoline tax and lower business taxes in general",
"Also, don't forget that the US dollar is the reserve currency for the world. This gives it a substantial advantage in purchasing/selling on petroleum markets."
]
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[],
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"https://en.wikipedia.org/wiki/Fuel_taxes_in_the_United_States",
"https://en.wikipedia.org/wiki/Fuel\\_taxes\\_in\\_the\\_United\\_States"
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||
2evcv1 | how come tattooing doesn't cut skin off? | If a tattoo needle is constantly piercing your skin like a bajillion times a second, and making a (say....)circle, how come the skin doesn't peel/fall off?
Even shading for that matter. How does it not cut off skin if you're dragging this piercing object across your skin repeatedly? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2evcv1/eli5_how_come_tattooing_doesnt_cut_skin_off/ | {
"a_id": [
"ck3arri"
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"score": [
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"text": [
"Sometimes it does when done by a bad tattoo artist, but only with solid images. They go over the same area too many times, too deep. The entire patch of skin becomes one big scab and falls off eventually ."
]
} | [] | [] | [
[]
] |
|
45a5my | hindu deities, how are there so many versions of the same gods? | I am doing a research project on Hindu deities, and I am not understanding how some of the major gods are basically just versions of other gods. Ie: Durga is explained to be a fiercer form of Parvarti. I found a quote that reads "All Hindu gods and goddesses are the same god or divine energy." I am still not wrapping my head around how there are so many versions of one god, but they all have different names and different god or goddess titles. It is not a direct question, but any help would be appreciated. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/45a5my/eli5_hindu_deities_how_are_there_so_many_versions/ | {
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"text": [
"So, let's talk about you. You're a person, probably a student somewhere. No matter where you are or what you're doing, you're always you.\n\nBut! You're not always the same you. When you're at home with your parents you act one way. When you're at school in class, you act another way. When you're hanging out with friends you act a third way. You're still, well, *you* in all these situations, but your parents, your teachers, and your friends all have a different understanding of who *you* are based on how you act around them.\n\nIn this, *you* are the main entity, and the person that your parents know, your teachers know, and your friends know are all different manifestations of you. \n\nNow, scale this up to the level of Gods. There is the same divine essence, but depending on the context it may have different forms or titles. From its own point of view, it is unchanging. From the point of view of its worshippers, it might be quite different depending on the context.\n\nAnd to go one step further... *everything* could be considered a manifestation of this one divine essence, just interpreting itself from different points of view in different contexts.",
"All the Hindu deities are part of the same ultimate divine power, known as Brahman.\n\nThere are three main divisions from there, known as Brahma, Vishnu, and Shiva. These can be looked at in a similar way to the Christian Trinity. One being, three bodies.\n\nFrom there, it gets more complex and there are a thousand more divisions and fractals, each representing a slightly different aspect. For me, when I was studying them, the easiest way for me to picture it was each God as a different facet of the same gem. Each has its own qualities, but they're still all part of one Whole.",
"As in case of a musiccal band you need different instrument artists because we like patterns, curiosity and complexity and as individual artists they use different parts of the the body (as per the nervous system cycle different sensory and motor synapses. For Eg: In case of percussion: Synapses of Fingers/limbs and ears, In case of wind instruments: Synapses of Breathing pattern and finger/limbs and ears)\n\nLikewise, in case of Gods, each God is the epitome of his purpose/passion of life or skill (similar to @PenguinTod)\n\nFor Eg: Ganesha is for devotion, Karthikeya for valor on a broader spectrum of personalities but can be extrapolated to other finer finer qualities as in the case by @fumunculus for Parvati as Saraswati, Durga and Laxmi\n\n\n\n"
]
} | [] | [] | [
[],
[],
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|
1nsvnf | the sopranos; why after whacking someone killer always leaves the gun at the scene of the crime? script's stupidity? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1nsvnf/eli5_the_sopranos_why_after_whacking_someone/ | {
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"text": [
"Since the gun is not a legit purchase and may have the serial numbers removed, as long as they wiped it down there is generally no one to trace it to them.",
"If the gun can't be tied to you, and you've left no evidence on it (DNA, prints, etc) it makes more sense to leave the weapon behind. There's no chance you'll be caught with it later. ",
"Also could be a reference to the Godfather. When Michael Corleone kills Sollozzo he is specifically instructed to bring his arm down to his side and drop the gun."
]
} | [] | [] | [
[],
[],
[]
] |
||
1vzlnd | how can king trademark words like candy and saga, and what is to stop me from grabbing a dictionary and starting with a? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1vzlnd/eli5_how_can_king_trademark_words_like_candy_and/ | {
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"text": [
"Trademarks only cover uses that you can show could cause confusion to a consumer. So you can have Apple Computers and Apple Apple Company, and neither is infringing on the others' trademark.",
"To be fair, they're only trademarking them in regards to video games. You'd have to show that you're using the word in a particular context and that you got there first. It keeps another company from calling their game *Something* Saga, hoping to cash in on consumers thinking it's part of the King line of games that use \"Saga\".",
"The first part seems to be covered by other answers. In response to the second part: You'd need an actual product to begin trademarking. After that you could probably fill out the paperwork for nearly-unlimited frivolous trademarks, but you also need to be prepared to defend your trademarks repeatedly in court or they become fairly worthless. This is actually part of why companies sometimes seem to be needlessly picking on \"the little guy\" over trademark issues. If they decided to be lenient, that leniency could be used as an argument later by a more aggressive entity to show that the company's trademark has become obsolete."
]
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[],
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||
83kxo5 | what time do astronauts have on their watch? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/83kxo5/eli5_what_time_do_astronauts_have_on_their_watch/ | {
"a_id": [
"dviloz0"
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"text": [
"UTC.\n\nThis is mainly because this sleep schedule is convenient for most parties involves (mostly Russians and Americans). Its a compromise between American and Russian timezones, and fits fairly well for everyone else given that the exact opposite timezones are mostly found in the Pacific Ocean. \n\nEveryone should use the same timezone on the ISS of course since having half the station doing their thing while the other half sleeps of course leads to shitty sleep. "
]
} | [] | [] | [
[]
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3xgx35 | what is going on with the dnc and why is it so detrimental to a campaign? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3xgx35/eli5_what_is_going_on_with_the_dnc_and_why_is_it/ | {
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"From what I understand...\n\nThere was some sort of database error in the DNC (Democratic National Committee, the official name of the Democratic Party). In that error, one of Bernie Sander's staff accessed a part of the voter information database that should have only been accessible to Hillary Clinton's staff. Once the unauthorized access was discovered, the DNC banned the Bernie 2016 campaign from any use of the DNC databases. \n\nThis is detrimental because Bernie 2016 would need access to the DNC voter information--the party keeps a lot of information about a lot of different things. And if you're trying to target a certain advertisement or mailer to a certain demographic, you need that information.\n\nThe things that make this interesting are:\n\n- There's a Democratic debate tonight (Saturday 12/19), so Hillary, Bernie, and Ringo will be talking to each other tonight and things could get *awwkkkkkward*.\n\n- Some people believe that the DNC super-overreacted in shutting down Bernie's access just because one guy did a thing. Also, some people believe that the DNC leaked the story to discredit Bernie and sweep some support toward Hillary."
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21szqk | why can't we "drain" volcanoes before they explode? | I don't just mean the lava/magma, I mean also releasing the pressure inside. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/21szqk/eli5_why_cant_we_drain_volcanoes_before_they/ | {
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"Imagine you had a sealed pot, full of boiling water. You want to reduce the pressure inside the pot, but you can't turn off the fire. If you create a whole in the pot, releasing the pressure, then there's going to be a jet of steam. Doesn't matter where you make the whole, the pressure's going to come out, and come out with force. \n\nSame with a volcano. You could \"drain\" them (if you were willing to spend the money on drilling equipment) but the drain just becomes the volcano, just in a slightly different place. "
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8znz95 | why do many rivers tend to make an "s" pattern in the way they flow? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/8znz95/eli5_why_do_many_rivers_tend_to_make_an_s_pattern/ | {
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"Water will hit a rock while going slightly downhill and will go around the edge of the rock, and then continue along the original path. Alternatively it’ll hit a region of denser rock that is less erodible and so it will go around the edge before continuing on. ",
"Since it’s pretty well impossible for a river to be perfectly straight, there will be a small curve somewhere.\n\nThese tiny curves cause water to rush into them, which will cause more erosion of the bank in that spot. That erosion causes a larger curve, causing more erosion. This starts a feedback cycle that forces a river to get more bendy in a section. \n\nThen, when it gets really bendy, another effect arises. If there’s a sharp turn, the water will rush against the bank on the outside of the curve, which will slowly erode that section of bank. This can eventually basically cut a channel that bypasses the bend altogether. Then you have a sort of oval shape with two off-shoots. \n\nThe part that used to be the bend will be bypasses by the water, since it will tend to take the shortest path. Sand deposits carried by he river will pile up at the loop part, and eventually close the loop off, creating oxbow lakes. \n\nAt the end of that whole series of processes, the river ends up straight-ish again, with small curves. Then the process starts again. Look up oxbow lakes, there are some pictures and gifs that are really mind-blowing. \n\nBasically, the end result is that rivers switch back and forth between being bendy and straight. So there’s a natural average bendiness of rivers overall. "
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32dy2m | in a capitalistic country like the us, why are universities so expensive and without competition between each other? | I mean, with so many students looking for the best offer, I don't understand why doesn't any investor try to take a bite out of that market. To run a university is not cheap, but I don' think that's the point, studying in private universities in my country (Spain) cost usually around 6.000 €/year and, even if the costs are higher there (higher salaries to pay, etc. ), I don' see how that scalates so much.
Is there a lobby or such a thing in that field? If the only requirement to start up a university is capital, why don't we see massified affordable private universities trying to attract potential "consumers"? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/32dy2m/eli5in_a_capitalistic_country_like_the_us_why_are/ | {
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"Because universities are impacted. The demand is higher than the supply, so kids will pay what it takes to get it. We also have huge government aid programs that will fuck you when you're out, but allow you to go without worrying about the immediate cost. ",
"There are a *ton* of \"for profit\" universities in the US, these are different than \"private\" colleges. They are extremely competitive with each other. The students usually attend these universities because for various reasons they cannot attend a different school. They are often a very captive audience with little alternatives.\n\nThey also tend to pay for school in one of two ways, either a) a loan or b) \"scholarships\" which are usually govt sponsored and paid for programs\n\nHere's a small breakdown from: _URL_0_\n\n > On average, 86% of all funding at for-profit colleges are from federal tax-payer dollars. For-profit colleges enroll between 10 to 13% of college students, yet receive 25% of all federal financial aid dollars.\n\n > Specifically, for-profit colleges receive:\n\n > 25% of all Department of Education student aid funds, totaling $32 billion Education department grants and loans in 2009-10;\n\n > 37% of Post-9/11 GI Bill benefits, or $1.6 billion in benefits in the first two years of the program); and\n\n > 50% of Department of Defense Tuition Assistance Funds.\n\n\nSo basically, the schools have little reason to compete on cost, in fact raising tuition and costs are usually more profitable, since the students aren't really paying anyways, the cost is fairly irrelevant and will be paid to the maximum they charge, almost regardless of what the charge is. So you can simply charge more money and it will get paid, the only \"loser\" is the government.",
"A lot of these private institutions that are so expensive ($50,000/year) are so expensive because they have, for example, 20,000 applicants/year for 6,000 spots. Sure, some people are going to chose to go elsewhere because they are sensitive to the price, but plenty of other children will be thrilled to get into such an exclusive school and will finance it either with personal family wealth, scholarships, or debt. \n\nWe don't see cheaper universities at the same quality level of instruction because professors want to go to the most exclusive, highly regarded institutions as well. They want to make the most money and gain the most prestige possible. They also want to work in the best facilities, use the best labs, and all of these things cost money that high tuition supports. "
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c0b06a | How were Henry repeating rifles incorporated into Union ranks during the American Civil War? | How were soldiers with repeating rifles deployed on the battlefield, and how were they expected to fight? I know that soldiers were trained to operate as single, cohesive units, which meant they primarily fought elbow-to-elbow in tightly closed formations. Given the widespread use of Napoleonic tactics during the Civil War, how did repeating rifles affect the structure and tactics of infantry units during that time? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/c0b06a/how_were_henry_repeating_rifles_incorporated_into/ | {
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" & #x200B;\n\nMost all of the breech-loaders bought by the US Ordnance Dept. were given to cavalry units. There was no way they could have equipped millions of infantrymen with them, even if they had wanted to replace the millions of rifled muskets already in their hands. Because it is very awkward to load a muzzle-loading gun on horseback, cavalry was equipped with breech-loaders first. But the state militia units were under no such limitations, buying their own arms, and so some militia infantry had Henry rifles.\n\nThe Ordnance Dept bought very few Henry rifles: only 1,731 during the War. When assessed, in 1861, they were judged to be expensive and heavy. They also required special metallic cartridges, and the Dept. was already concerned about how it could supply the diverse ammunition for all the various breech-loaders it had already started to buy, the Sharps, Spencer, Burnside, Smith etc. But because of the state militia units equipped with Henry rifles, the War Dept. ended up buying about 4,000,000 cartridges for them anyway.\n\nThere does not seem to have been any great change in tactics in employing troops equipped with repeaters or breech-loaders. But their greater rate of fire certainly had an effect- as the War Dept itself would note, one solder that had the greater rate of fire of a breech-loader could equal a few equipped with muskets. One good example would be at the Battle of Franklin. Confederate Gen. John Bell Hood was already over-fond of frontal assaults against strong positions , but at Franklin his troops were badly mauled. The Confederate break-through around the Carter house on the first day of fighting was in part stopped by the 12th Kentucky and 65th Illinois militia units armed with Henry rifles."
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4cjlq1 | . why do many employers give their hourly employees sporadic, weekly-changing, temporary schedules? | So many employees assign new shifts every week. Wouldn't it be easier for everyone if they had set times each individual was meant to work? A schedule that didn't waver, have overlap, technical errors, over scheduling, and wildly differing hours (ex. Working night shift and then working morning shift)? Not to mention accidental no shows from when someone read the schedule wrong or forgot a shift. Can someone explain the benefits of this alternative scheduling that seems to be so wide spread? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4cjlq1/eli5_why_do_many_employers_give_their_hourly/ | {
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"I also work in the industry and we use an app (_URL_0_) where we employees can just swap shifts as we need to, without having to go through the manager every time (he just approves the swap on his app). We can also put in requests for shifts and requests for days off. This makes my life much more flexible and even though I still don't have a constant schedule it feels more like I'm in control of my life again. I also think my manager feels it is a lot easier to consider everyone's wishes like this and is much more willing to make sure people get what they want. ",
"This doesn't apply to all situations, but sometimes the person in charge of writing the schedule is either a total dick, or they can seriously clueless. I had one manager who took great glee in scheduling just about everyone to work the latest shift he could find for them the day before a day off, then he would schedule you to come in on an early shift after your day off; like I said, a total dick.",
"You are describing a few things.\n\nChanging from days to afternoons to nights and back again is often caused when the employer has a lot of employees with families. They want to make it so no one is stuck permanently on a shift that makes them unable to see their family because that is a fast way to lose an employee.\n\nOversheduling and overlap shifts are usually used when you have a job where you are interacting with people. They want the next shift already working when the previous one leaves so there is never an empty area and so that if someone is late, no one gets screwed over.",
"I'm one of those assholes. I hate having schedules that change constantly, and I do what I can to keep things stable, but there are a few factors I have to take into account. \n\nKeep in mind that every staff member has certain times they simply can't work. Because of this, if you change a single shift, you usually have to change everything. \n\n The biggest thing is that business will fluctuate based on local holidays and events. If I know there will be a school day off, I have to bring extra people on. This will change the rest of the week, since I want to keep everyone at as many hours as they have asked for. \n\nThe next is staff turnover. People come and go, and you have to make time to get people trained up. It helps to pair a newbie with a strong team member. That dices things up. \n\nFinally, I like to get a sense of how people work together. It helps to see if Susie and bob get along, but I also need to know if Matt and bob work well. And Susie will probably tell me she doesn't like working with Matt. Fine, I won't force her to. But that is just one more thing I have to keep in mind while scheduling. \n\nAt the end of the day, if you ask for 40 hours, or 20, or Fridays off, I will do anything I can to keep work from interfering with your life. That trumps having a stable schedule. Like I said, it isn't perfect, but getting your hours, having an enjoyable work team, and a good life balance trumps consistency. It is a balancing act. \n\nEdit: I also keep a log of every day, so I can look to see what last year was like so I can predict what might happen on any specific day. It helps to plan for weird busy times. It isn't perfect though. I hate overlap, but I really hate having employees who are swamped at work. I'd rather have 2 guys twiddling their thumbs than one girl in tears because she got swamped. ",
"While it can be nice having a fixed schedule, it just won't fit all people and all jobs - often the worst offenders here will be places like shops and restaurants that will have constantly changing staff with different needs, and staff holidays, illness, personal preference (often there will be preferred and disliked shifts, so it would be unfair to always give those to certain people) and customer demand will give constantly changing needs - why spend lots of time creating a nice fixed schedule when it will just get altered straight away?",
"Our work is project based, and as each project is tailored to our client, the hours and skills required vary. It is not unusual to have 7-15 projects going at once, but it does mean I cannot guarantee that someone who is working, for example 10-6 will always be able to work those hours forever and ever into the future.\n\nThat being said, I should also clarify that:\n\n*Right now, everyone knows their schedule for the next month, and I am figuring out what everyone's schedules will look like beyond that for another month or so. This tends to be an ongoing process.\n\n*There are TONS of scheduling software options out there which allow you to provide this info to employees electronically, 24/7. We use one of them. This takes away a lot of the 'I read the schedule wrong' kind of issue, as it is always available and very easy to check.\n\n*We are very up front about the need for this type of schedule when we recruit/hire. I would much rather someone decide they just cannot hack it and not pursue a career with us than to try and convince them it's 'not too bad' only to have them feel deceived and demoralized later.\n\n*We actually take pains to avoid the late shift/early shift scheduling - and if we have a dire need to do this (rare), then that's a conversation with someone about how to make it work best for them.\n\nI am seeing a lot of comments here about working late/early back to back and avoiding benefits, etc. etc. I have to say, a lot of the issues with this type of scheduling come down to a lack of communication -- either on the part of the employer or the part of the employee, or both. As an employer, I have to work to be sure both the software updates (to the schedule) and the communication (in person or by email, depending) are always happening. But I have also run into some (now former) employees who try to avoid talking about their schedule because what they really want is an \"I'll show up if I feel like it and you should accommodate it\" type of schedule (which no one at our company has, the owner included).",
"Many times there is an assumption of nefarious and evil intent in what we see. It is eaasier and probably just as correct that incompetance and lack of real business knowledge or leadership vision is the reason.\n\nSome managers or Hr departments think that it will give the store more flexibility to just call in who you need. busy day call in more people, slow day send people home. You save on hours and the store is more profitable. \n\nThe reality is that it is a short term win for a long term loss. It is a system that will degrade over time to the lowest levels of productivity because it is not a simple hours in hours out equation.\n\nFirst it allows managers at the store level to NOT have any leadership or forward thinking. They do not have to pay attention to what is going on around them, and results in reactive vice proactive management. It seems easy to say well it is a busy day so call more people in. Except it is already busy. Calling people in means the manager goes into the back and sits on the phone calling people instead of on the floor running things and providing help oversight. By the time people do show up it may be slow again. Meanwhile the customers get aggravated since the lines are long and no one is on the floor to help them with questions. Short term over long term. Short term saved a few hours. Long term customers won't come back.\n\nSecond thing overall. Employees will go down hill. You could start off with the best employees, but you will lose the good ones to other places where they have steady income and better hours. Eventually you will end up with only the employees that can't get a better job or employees that have zero experience and you are there first employer ever. Once they get to a point that they are pretty competent they will move to better pastures. The turnover rate is super high. Again this is seen by many as a plus since long term employees will by definition make more money. Experience and performance cost money. So you save money short term, but in the long term employees are not a good at the job or motivated as they could be. so in the long run it feeds back on itself and costs you.\n\nSo in reality is usually is not a \"bad person\" actually saying \"let's screw people over with this system\". It is usually someone saying \"we are losing money at all our stores, what can we do? Labor is one of our biggest expenses, cut labor. Trim down hours.\" It seems like a good bet, but in reality costs almost every company that does it. Sometimes they do it well and manage to recover, but in reality many just continue down hill since it is a short term fix, that has long term ramifications.\n\nThis applies to the question of why call in shifts. As far as changing every week. Sometimes it is the needs of the business. Holidays, big games, personnel training or turnover. Or a big one I ran into for larger workforces. The bigger the schedule and the larger the workforce, the more special requests you get. I can't work XXX night, I have class. My cousin is getting married Sat. I have to stay home and change my grandma's diapers on Wed and Thursday since the caregiver has those 2 days off. COncert on friday, I can't work friday night. (And if you think they will show up on Sat morning you're just as high as they were on Friday.) You have a huge list of demands and requests to meet.\n\nLots of valid reasons. Also lots of invalid reasons. I have known a couple people who used the schedule as more of a hammer to a find out who is \"loyal to the company\" or to show \"I run things around here, not you. You'll work when I tell you to work.\" The first list above is unavoidable, the second here is shitty managers. Some combination of the two is usually the reality. ",
" > Technology is speeding this transformation. In the past, part-timers might work the same schedule of four- or five-hour shifts every week. But workers’ schedules have become far less predictable and stable. Many retailers now use sophisticated software that tracks the flow of customers, allowing managers to assign just enough employees to handle the anticipated demand.\n\n_URL_0_",
"Employees don't usually stick to set hours though. Sickness including weekenditis, family problems eg being unable to get baby sitters, personal preferences etc usually build up to stop a set schedule from working. That said, a set rota or rotating rota works well when everyone actively wants it to.",
"On top of everything else mentioned about busy hours slow days, etc, Id like to point out that in a lot of places, managers are given hours. One week they might be allowed to schedule 250 hours. Next week they only have 200 hours to work with. \n\nWhere I work, we are expected to make above a certain $$/labor hour. The estimates are in large part based on what we made that week last year, which is kind of shit. Say half the team calls out this year. Our Dollars made / labor hour is going to jump way up. So that week next year they expect us to make a lot of money with very few people working, so maybe he only hands our manager 150 hours to use that week. Its obviously not enough hours, so he has to cut peoples hours or give a few people extra days off and have the people who are working come in at weird times to try to cover everything. \n\n",
"Employee scheduling isn't easy because there are so many variables. Employees have requested times off, shift preferences, number of hours per week/month. Then the business has cycles. They may be weekly or annual cycles which are easy to plan but sales and other factors can drive more customers in less predictable ways.\n\nThen you have people who call in sick at the last minute. If someone takes that shift, now you have to rearrange the entire schedule so they don't have overtime or too much overtime.\n\nDisclaimer: I'm the founder of a staff scheduling company: [time360](_URL_0_)",
"Scheduling hours is a very complex problem. \n\n_URL_0_\n\nThis is one of the unsolved problems in computing. The only way to find a solution is trial and error. Which means there will often been non-ideal solutions.",
"Because there's a fucking book out there on how to be a manager that says keeping a little anxiety in the workplace is a good thing and these deuschebag managers read that crap and follow it instead of talking to their employees.",
"They don't want employees to get used to / feel entitled to specific shifts. When you keep people in a state of constant flux, if you need them to come in for an odd shift, it won't be out of the ordinary.",
"I know a lot of hourly workers that *don't* have this issue. It really depends on how quick employee turnover is in those fields. Making a schedule that will work for everyone, and can still allow for covering of missed shifts (due to sick days or emergencies or whatever) takes a while to figure out and get down properly. \n\nIf you can't go a month without losing an employee, you'll never be able to make a good schedule. (Food service is easily the worst offender here.) There are also a lot of jobs with very low turnover, but these typically require some skill (Machinist, heavy machinery operator, etc.) that are also still hourly, but have very consistent and unchanging schedules. Maybe one persons gets goofed up for a week because someone else takes a vacation, but it doesn't mess up *everyone's* schedule, because when the employees are more consistent and reliable, the scheduling can be too. ",
"I ran a bar and restaurant. If it had been up to me, the schedule would have been set in stone. Less work on my end.\n\nThe reality is, though, many of the workers want to rotate around. Not only is there better opportunity for tips on busy weekends, but sometimes people want weekends off, too, so they can relax an party it up. Many people work these kinds of jobs because the hours are very negotiable. Sometimes they have kids and need to fix their schedule to another parent's schedule who can watch the kids, for instance. There was usually an agreement on an initial schedule, and then changes would periodically happen through the month. I had the rule that anyone could change their schedule so long as a) the shift was covered by a consenting worker b) the change was made outside of 24 hours c) everyone effected knew about it, including me.\n\nOther businesses could be different, but that's how the industry worked in my area."
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142eiv | My uncle has a collection of swords from WWII that his grandfather brought back from the war. Help me identify them for him. | He has had these for quite some time but hasn't ever identified them. We know they are German weapons. All help is appreciated.
_URL_0_ | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/142eiv/my_uncle_has_a_collection_of_swords_from_wwii/ | {
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"You should also try /r/whatisthisthing. They have a very good track record identifying historical artefacts.",
"We'd need clear pictures, and lots of them, of the hilts, grips, pommels, stampings on ricassos, marks in the fullers, etc. before we could even begin to start thinking of identifying these.",
"[not a historian]\n\nThe German student unions, in the beginning of the 20 century, still had academic dueling - it had impressive roots, which you can read about [here](_URL_0_) - and I take it that if these are swords of German officers, then they are also alumni of German universities, and the swords are their little mark of honour.\n\nI am of course not sure - especially given that the wikipedia article explicitly states that fencing (and student unions) were abolished during the Third Reich, and at least one of the swords has the Swastika and the Eagle of the Third Reich.\n\nHowever, comparing the swords to those illustrated in the Wikipedia article might illuminate the matter."
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mwb11 | how angel investing and venture capital works | I understand what they are there for, but how does the process work? Which one is ideal for what stage of a start-up's growth? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/mwb11/eli5_how_angel_investing_and_venture_capital_works/ | {
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"Angel investors are generally investing *their own money* in an organization, whereas a venture capital firm is investing *other people's money*, money that other people have invested in the venture capital fund.\n\nAs such, venture capitalists tend to have more money to invest, and therefore *do* typically invest more money than angel investors.\n\nBoth types of investors exchange money for shares in the company. Venture capitalists will often demand a seat(s) on the board of directors so that they can help manage the company; not so much with angel investors. Since the venture capitalist only has a certain amount of time to spend managing the companies in its portfolio, it limits the amount of companies they can invest in. So, they're more likely to invest in fewer companies; companies that are more likely to succeed.",
"Angel investors are generally investing *their own money* in an organization, whereas a venture capital firm is investing *other people's money*, money that other people have invested in the venture capital fund.\n\nAs such, venture capitalists tend to have more money to invest, and therefore *do* typically invest more money than angel investors.\n\nBoth types of investors exchange money for shares in the company. Venture capitalists will often demand a seat(s) on the board of directors so that they can help manage the company; not so much with angel investors. Since the venture capitalist only has a certain amount of time to spend managing the companies in its portfolio, it limits the amount of companies they can invest in. So, they're more likely to invest in fewer companies; companies that are more likely to succeed."
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3imvek | Will a standard oven cook food slower if there is more food in it, like a microwave? | I'm pretty sure it doesn't but I don't really know the facts to back me up and all three of my roommates think I'm wrong. Please enlighten us with science. | askscience | https://www.reddit.com/r/askscience/comments/3imvek/will_a_standard_oven_cook_food_slower_if_there_is/ | {
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"That depends on how good your oven is and how well the air circulates. Conventional ovens operate by getting to and maintaining a fixed temperature whereas microwaves emit a constant amount of energy. What this means is that in a microwave if you double the amount of food in there you need to roughly double the time spent cooking for the same results, nice and simple. The oven is a bit more complicated though.\n\nIn the simplest case you have a conventional oven preheated to the cooking temp and you put in your food. That food will absorb heat from the oven at some rate and the oven will need to put in more energy to maintain the temperature. If you put in twice the food then the oven needs to put in twice the extra energy. However, in contrast to a microwave oven there is really no need for this to necessarily take twice as long. If the heat added is fast and even then the cook time for twice the stuff is no more than the single serving.\n\nThis isn't quite the real world case though. Conventional ovens are relying on convection more than radiation, which means that putting more stuff in the oven can have significant heat transfer effects. You've probably noticed that when you stick two pizzas in there (top/bottom) they will cook significantly differently, and this is because the heat each is experiencing is different. Additionally conventional ovens only heat from the outside-in which means if you double the volume of your dish the middle might take much much longer to feel any of the heat seeping in from the outside, whereas microwaves can penetrate deeper especially if the outside is dry and inside is moist.\n\nSo in short there is no easy answer to this question. If using small foods and a convection oven (fan in the back to move air) the cook time could be independent of the amount of food, but more than likely you will see more complicated results that put it closer to a microwave's performance."
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|
43r4cx | what does it mean for a food to have 'anti-inflammatory' properties? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/43r4cx/eli5_what_does_it_mean_for_a_food_to_have/ | {
"a_id": [
"czk9ncf"
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"score": [
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"text": [
"It means that the food contains chemicals that can help to reduce inflammation.\n\nIt will not make you harder to set on fire."
]
} | [] | [] | [
[]
] |
||
90q6nj | King Richard I of England was known as 'Richard the Lionheart.' How did common folk know what a lion was? | Was the title bestowed upon him retroactively? I'm assuming that, since lions are not native to England/Western Europe, it would be difficult to conceive of a lion, unless of course, a "lion" referred to some other creature. | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/90q6nj/king_richard_i_of_england_was_known_as_richard/ | {
"a_id": [
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"score": [
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"text": [
"[This post](_URL_0_) from four years ago has some useful answers which might help you out."
]
} | [] | [] | [
[
"https://www.reddit.com/r/AskHistorians/comments/27m6po/how_did_the_three_lions_come_to_be_the_coat_of"
]
] |
|
8lzt42 | seeing as how electricity often takes the form of plasma in many instances of physical manifestation, would it stand to reason that all plasma could be utilized the same way if its heat energy were concentrated/channeled enough? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/8lzt42/eli5_seeing_as_how_electricity_often_takes_the/ | {
"a_id": [
"dzjq6s2"
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"score": [
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"text": [
"Electricity does not take the form of plasma, plasma is a state of matter where electrons and nuclei dissolve in a quantum soup example the sun.\n\nElectricity is electrons flowing through matter generally via the valence electrons.\n\nAlmost forgot to mention, high voltages can produce plasma (example lightening)"
]
} | [] | [] | [
[]
] |
||
4z25o4 | Could Nazi-Germany simply have stopped hostilities and be content with the signed treaties leading up to WW2? | After the remilitarization of the Rhineland, the Anschluss, the Munich agreement, taking Memel from Lithuania and the First Vienna Award were all accepted by the Allied powers, was it possible for Nazi-Germany to just stop pushing world tension and remain at that state for decades to come? In stead of invading Poland and causing a World War? Would the Allies have accepted Germany to stay in this shape forever, controlling Austria, the Sudetenland, Bohemia, Moravia and Memel? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/4z25o4/could_nazigermany_simply_have_stopped_hostilities/ | {
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"The same would go for states like Italy and the Soviet Union of course, could they have kept Albania and Ethiopia, and Bessarabia respectively forever?",
"Adam Tooze, *The Paperback of the The Wages of Destruction: The Making and Breaking of the Nazi Economy*, addresses it. The book is well worth reading, and it is well-regarded here.\n\nIt is his opinion that the German state was financially unstable due to economic problems -- what staved them off was first seizing Austria's state assets and reserves, then Czechosolvakia's state assets and production capacity, then Poland. But each step was follwed by expenses necessitating the next step.\n\nFurther, he states that it was Hitler's belief that, because America was a growing power, Germany had to have a broad base with lots of industry and resources just to match it, or else Germany would be enslaved and destroyed. And the only land that was available to Germany was Europe. Further, there were a few factors that came together around late 1939 that gave Germany a little brief advantage. So Hitler concluded that at some point he had to fight or die, and that moment was better/less bad.\n"
]
} | [] | [] | [
[],
[]
] |
|
7p87e1 | why do movie studios opt for cgi when it seems like practical affects would be cheaper, easier for actors to work with, and preferred by audiences? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7p87e1/eli5_why_do_movie_studios_opt_for_cgi_when_it/ | {
"a_id": [
"dsf85vl",
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"text": [
"Because CGI generally does look better the reason alot of people think practical effects are better is because we only notice bad CGI ",
"Practical effects are generally not cheaper. At least not in modernity. They are also very difficult on the actors. You are looking at hours of time applying the practical and hours of time removing it every day of filming. Some things (like Star Trek) could take up to 4 hours each side. On top of 6-10 hours of filming that is an insane amount of time. \n\nAnd also the modern methods that look best are a mix. You use practical and CGI together. "
]
} | [] | [] | [
[],
[]
] |
||
fx9gdm | why the sun feels hotter in some places than others? | I live in Rio and when it's 75°F and sunny it feels almost chilly; i've also lived in Houston, TX and when it's the same temperature it feels hot and the sun burns, even in winter. And it doesn't make senses because the sun is lower at the sky in Texas because of the higher LATITUDE. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/fx9gdm/eli5_why_the_sun_feels_hotter_in_some_places_than/ | {
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"Seems like a moisture and wind difference between the two. People normally say things like \"it's not the heat, it's the humidity.\" Which is true. Imagine taking a hot relaxing bath, now imagine that everywhere you go. It's hot, you sweat instantly, you feel like the sweat on you never goes away and everything in the air sticks to you. \nThis is because the moisture in the air in places like texas and Louisiana (where i live) doesn't need/have room for the moisture on your skin causingsweat to evaporate slower, so your body's cooling system can't really function as efficiently as it would in a dryer, breezier place.",
"Hard comparison to make. Rio has mountains so it's possible that the ground gets more shade during the course of the day resulting in less accumulated heat, also Rio is ocean adjacent. Cool air is rolling in from the sea.\n\nTexas is a large flat state, no natural structure to cast shade and it has very little coastline. It's not even ocean. Humidity can also be higher in Texas but I don't know about that in Rio.",
"There are various factors to consider: winds, geography, population, air pollution, humidity, etc. Here is a [link](_URL_0_) that compares Houston TO Rio. You can also click the hyperlink on the page to reverse the comparison. I can’t help but wonder if the average wind speed in Rio is higher which would help reduce the FEELING of heat.",
"Ozone layer depletion can change how hot the sun feels. I’ve visited Australia a few times and they have a thin ozone layer and I would get sunburned on a 70 degree F day in about 5 minutes.",
"The sun being even a few thousand kilometers closer or farther isnt going to effect how hot we feel, by the way. Else, we'd melt on mount Mount Everest or the moon, and our deep space explorers wouldnt function etc"
]
} | [] | [] | [
[],
[],
[
"http://www.houston.climatemps.com/vs/rio-de-janeiro.php"
],
[],
[]
] |
|
4mj4p9 | why does being in hot weather make some people irritable, the rain make people tired, and winter make people depressed? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4mj4p9/eli5_why_does_being_in_hot_weather_make_some/ | {
"a_id": [
"d3vvfle",
"d3vvw27"
],
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2
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"text": [
"The winter depression is probably linked to low levels of sunlight which will effect serotonin and vitamin d",
"When people are physically uncomfortable, they get irritable so they they feel encouraged to move to an environment that is comfortable.\n\n\nWhen it rains, that has a big effect on the atmosphere, it is darker, the barometric pressure gets low, it gets more humid etc. Energetically water and rain has a grounding effect.\n\nIn the winter people get depressed because of the lack of sunlight, and because the cold environment feels hostile and uncomfortable."
]
} | [] | [] | [
[],
[]
] |
||
p1j5f | How cold was it for the moon landings? | I hope this is a valid askscience question... I looked on google and found that the moon temperature has an enormous range, but how cold/hot was it when we landed on the moon? If it was extreme, how did they survive the temperatures(I don't know of many insulators that can withstand that type of cold)? | askscience | http://www.reddit.com/r/askscience/comments/p1j5f/how_cold_was_it_for_the_moon_landings/ | {
"a_id": [
"c3lr8po",
"c3lxcsr"
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"score": [
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"text": [
"Hey there friend!\n\n_URL_1_\n\nThe moon gets very cold, and very hot! This is why spacesuits are white - while the moon's surface absorbs about 80 - 85% of the sun's radiation, a space suit absorbs only 15%\n\nBelieve it or not, the greatest threat to a space man in a non-atmospheric environment it overheating from their own body temperature!\n\nIf you'll look at the wiki article I provided, you'll notice space suit designs often include a hydraulic system as a means of cooling the astronaut down.\n\n_URL_0_\n\nVacuums are confusing! However, according to kinetic molecular theory, a hot object would actually remain hotter longer in space than it would on earth!\n\nEventually, however, (and it could be a surprisingly long time!) the object would cool to 2.73 K, the constant temperature in a vacuum from cosmic backround radiation.\n\nShielding from the sun's rays, modest insulation, and the heat from our bodies allows us to not freeze or overheat on the moon.\n\n_URL_2_\n\nUnlike on earth, as the article states, convective cooling is not possible without an atmosphere with gasses to have undergo convection! Thus, a series of metal, foam and special reflective paints are used to insulate the spacecraft from radiation heating.\n\nHope that answers your questions!",
"I didn't see an answer to the op anywhere"
]
} | [] | [] | [
[
"http://en.wikipedia.org/wiki/Outer_space",
"http://en.wikipedia.org/wiki/Space_suit",
"http://en.wikipedia.org/wiki/Thermal_insulation#Spacecraft"
],
[]
] |
|
2m5ky8 | why do we have hair on our knuckles? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2m5ky8/eli5_why_do_we_have_hair_on_our_knuckles/ | {
"a_id": [
"cm15w5e",
"cm16xvk"
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"score": [
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2
],
"text": [
"We have hair on our knuckles , for the same reason we have hair on our arms/legs ( if you believe in evolution) . Now it doesn't really serve a purpose .. But it used to be part of our 'coat' .",
"That's a recessive trait called mid-digital hair. Anyone if I'm wrong please correct me, it's been almost 10 years since I learned about it. "
]
} | [] | [] | [
[],
[]
] |
||
7rzvju | how does a country’s military/businesses/etc transition when they are taken over by another in war? | [deleted] | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7rzvju/eli5_how_does_a_countrys_militarybusinessesetc/ | {
"a_id": [
"dt0u3l2"
],
"score": [
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],
"text": [
"It really depends on the war, the extent of the damage to that country (it may not have a functional military by the end), terms of the resulting treaty, etc. There's not a hard and fast rule when it comes to warfare: it's sorta the point where the rules all break down."
]
} | [] | [] | [
[]
] |
|
1ior40 | Some questions about radiation--what it is, and where it comes from | So AFAIK, there's 3 types of radiation: alpha (He nucleus), beta (electron) and gamma (photons/EM waves I think?). What is it that actually makes these things "radiation" and the substances that emit them "radioactive", as opposed to just normal electrons or EM waves?
And is that it, as far as radiation goes? Could individual protons and neutrons or smaller/larger nuclei be classified as radiation?
The last question I had is about ionising vs non-ionising radiation. Why are some types of radiation able to knock off electrons from atoms and others not?
Sorry if this is too many questions, too general, or if it's been asked before. It's something that really interests me, and I've tried wikipedia etc but there's some stuff I still don't quite follow. Any help would be appreciated :) | askscience | http://www.reddit.com/r/askscience/comments/1ior40/some_questions_about_radiationwhat_it_is_and/ | {
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"cb6nv2m"
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"text": [
"There are actually more types than 3. Alpha, beta, and gamma are the most common. You could include neutron, fission fragments, cluster decay and a few other rare ones. \n\nThe reason these particles are radiation and their sources are radioactive is that the initial systems are unstable. For example, some atoms have nuclei that have too many neutrons. In order for these nuclei to become stable, they need to shed a neutron or gain a proton. This can occur if the neutron undergoes beta decay. The neutron becomes a proton and emits an electron and an antineutrino. The nucleus can become stable or may need to beta decay again to become stable. An example of a beta decay isotope is strontium 90.\n\nThe electrons are the same as all other electrons, it is the source of the electrons the determines when we call them radiation and what type. For example, EM waves from electronic transitions in atoms we call x rays. When the EM waves come from nuclear transitions we call them gamma rays. Gamma rays can be more or less energetic than x rays and vice versa. \n\nYou can have proton or neutron radiation, neutron is far more common. For example, nuclear reactors emit tons of neutrons. There are high neutron fields near the core. You can have cluster decay from larger nuclei. For example, U-238 can decay by cluster decay. It can emit carbon-12. It is a rare form of decay, but it does happen.\n\nIonizing vs non-ionizing has to do with the energy of the radiation. Visible light is radiation, it comes from the decay of an unstable system. That system is electrons in higher orbitals decaying to a ground state. If the energy of the radiation is high enough, it can knock an electron off of an atom. That is ionization. The energy needed to do this depends on the atom, but at the lowest end of the spectrum for this is UV light. \n\nHope this helps. "
]
} | [] | [] | [
[]
] |
|
1jvexy | Was there any reaction from Catholics to the capture of Rome in 1870 and thus the destruction of the Papal States? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1jvexy/was_there_any_reaction_from_catholics_to_the/ | {
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"First, the vast majority of the Papal States had been lost by 1860 to Italian unification. Only Rome remained in papal hands, and then only because Emperor Napoleon III of France stationed troops there. The Franco-Prussian War (your 1870 date) put an abrupt end to that situation, and Italian troops siezed Rome. The pope (at this time, Pius IX) declared himself to be a \"prisoner of the Vatican\" and the issue remained largely unresolved for nearly 60 years. \n\nAs for reaction, it must first be pointed out that the pope losing control of the Papal States or Rome in particular was not a novel event. It had happened most recently in 1848. Through history, there were many times where the Papal States contracted violently, but most of the time they were restored after some interval of time. So, a situation like that of 1860 or 1870 was reasonably seen as a setback, not a final action. It was not unreasonable to think that this was a temporary situation, and Pius IX always thought that there would be a Catholic power that would come to the papacy's aid. They had in the past (largely out of self-interest that was temporarily aligned with the interests of the papacy, but sometimes out of legitimate piety).\n\nFor the interim, Pius IX barred Italians from participating in politics--*Non Expedit*. One had to choose between being Catholic and being Italian. Holding office and voting were both banned. This may seem like a harsh measure, and indeed in many ways it was. there were many Italians motivated by purely rational and wonderful things like national pride and economic growth and democracy and rights, but there were also concerted actions hostile to Catholicism. There were anticlerical sentiments--some of them violent. There were some that wanted to discard the past entirely, and this meant restrictions against the Church that were at least as strict as *Non Expedit*. The path to Italian unification was a troubled one.\n\n\"The Roman Question\" would linger until 1929, when it was settled in the Lateran Accords (or the Lateran Concordat). During that interval of nearly seven decades, there would be periods of antagonism by one side or the other, and periods of reconciliation. In the end, the papacy accepted being a small but independent nation that was neutral in foreign affairs and renounced any claim to the rest of Rome.\n\nI would be happy to answer any follow up questions that I have the answers to, so feel free to ask away!"
]
} | [] | [] | [
[]
] |
||
3ks47t | Aside from phrenology, what are other "disciplines" that were previously practiced but were eventually discarded/rejected? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/3ks47t/aside_from_phrenology_what_are_other_disciplines/ | {
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"Humorism, or the notion that human health depends on a balance of fluids (or \"humors\") in the body, was a predominant paradigm in health from the time of Hippocrates until the general acceptance of the germ theory of disease. It was believed that there were four humors: blood, phlegm, yellow bile, and black bile. Disease and mental illness arose from an imbalance in one's humors, and treatments ranged from the prescriptions of certain foods and drinks to increase one humor or decrease others, to bloodletting and other direct manipulations of the humors. \n\nAn 11th century poem attributed to John of Milano describes the symptoms of an overabundance of each of the humors (this is just an excerpt):\n\n > If Sanguin humour do too much abound,\n\n > These signes will be thereof appearing cheefe,\n\n > The face will swell, the cheeks grow red and round,\n\n > With staring eies, the pulse beate soft and breefe,\n\n > The veynes exceed, the belly will be bound,\n\n > The temples, and the forehead full of griefe,\n\n > Unquiet sleeps, that so strange dreames will make\n\n > To cause one blush to tell when he doth wake:\n\n > Besides the moysture of the mouth and spittle,\n\n > Will taste too sweet, and seeme the throat to tickle. \n > \n \n > \tIf Choller do exceed, as may sometime,\n\n > Your eares will ring, and make you to be wakefull,\n\n > Your tongue will seeme all rough, and oftentimes\n\n > Cause vomits, unaccustomed and hatefull,\n\n > Great thirst, your excrements are full of slime,\n\n > The stomacke squeamish, sustenance ungratefull, \n\n > Your appetite will seeme in nought delighting,\n\n > Your heart still greeued with continuall byting,\n\n > The pulse beate hard and swift, all hot, extreame,\n\n > Your spittle soure, of fire-worke oft you dreame. \n\n > \n > \tIf Flegme abundance haue due limits past,\n\n > These signes are here set downe will plainly shew,\n\n > The mouth will seeme to you quite out of taste,\n\n > And apt with moisture still to overflow,\n\n > Your sides will seeme all sore downe to the waist,\n\n > Your meat wax loathsome, your digestion slow,\n\n > Your head and stomacke both in so ill taking,\n\n > One seeming euer griping tother aking:\n\n > With empty veynes, the pulse beat slow and soft,\n\n > In sleepe, of seas and ryuers dreaming oft.\n\n > \n > \n > But if that dangerous humour ouer-raigne,\n\n > Of Melancholy, sometime making mad,\n\n > These tokens then will be appearing plaine,\n\n > The pulse beat hard, the colour darke and bad:\n\n > The water thin, a weake fantasticke braine,\n\n > False-grounded ioy, or else perpetuall sad,\n\n > Affrighted oftentimes with dreames like visions,\n\n > Presenting to the thought ill apparitions,\n\n > Of bitter belches from the stomacke comming,\n\n > His eare (the left especiall) euer humming.\n\nMood/personality descriptors based on the four humors are still in usage, though infrequently and largely divorced from the idea that one's fluids might actually be out of balance. If you've heard of someone being described as \"phlegmatic,\" \"sanguine,\" \"choleric,\" or \"melancholic,\" those terms arise from the four humors. In fact, the word \"humor\" itself as a modern synonym for \"comedy\" comes out of Renaissance comic plays -- specifically those of Ben Johnson -- in which characters represented exaggerated imbalances of the humors for comic effect.",
"According to John Quincy, in his book \"Lexicon Physico-Medicum\" (1767), doctors should refrain from the following practices...\n\n- Hanging a sign that says ABRACADABRA around the patients neck. Although this has been assigned curative powers by Serenus in his work \"Medicina Metrica\", Quincy condemns this as a trick and as laughable in modern medicine.\n\n- Amulets as medicine are often \"much abused\", but Quincy firmly states that a knowledgeable doctors \"will find no Reason to disbelieve the possible Efficacy of Amulets\". \n\n- Quincy states that Incantations when applied with Charms, although supported by Paracelsus and Helmont and other chemical enthusiasts, is delusional and should pursue a \"better Way of Reasoning\".\n\n- Necromancy that is espoused by some \"enthusiastic Physicians\" is purely a Juggle (deception), according to Dr. Quincy.\n\nA lot of things being condemned by Quincy in this mid 18th century medical book are what we would call sympathetic magic today, but I don't think they have that term back then. When Quincy gets really riled up, he calls them \"Jugglers\".\n\n",
"This is not a direct answer, but something to take into account: some successful and thoroughly empirical disciplines have fizzled out because they exhausted their subject matter. They're still taught to undergraduates, and they may be important as technologies, but fundamental discoveries are few are far between.\n\nIn my own field, language and literature, I'm thinking about classical rhetoric, analysis of rhyme and meter in poetry, Indo-European historical linguistics, philology and paleography, phonology and phonetics (except its relation with neurology and AI). \n\nI wouldn't put history in this category. New finds and new theoretical perspectives seem to keep this discipline alive. What do historians think?",
"I'm surprised this has not been mentioned yet, but eugenics was very popular in the Western world and was practiced all the way up until the 1970's, and was very popular among people all across the scientific world and the political spectrum. However, eventually scientific advances as well as moral concerns ruled most of it out, as the genetic sources of abnormalities are far more complicated than Eugenicists thought, among other reasons.",
"Psychoanalysis, as a medical discipline. In the 1950s, a majority of papers published in clinical psychology and psychiatry journals referenced psychoanalysis or its concepts. By the late 1970s, it was below 1%, and mostly negative. \n\nSome therapies (\"psychodynamic\") claim to be evolved from psychoanalysis but they either don't have much if any supporting evidence for their efficacy, are far removed in practice from historical psychoanalysis, or simply aren't any better than any form of talk therapy. \n\nThat's not to say it's not practiced anymore, far from it unfortunately, but it's declining. The theory is pretty much dead to science, as the huge advances in neurosciences in the past few decades usually contradict the unique claims of psychoanalysis. When they do, it's either the vaguest, unspecific notions (such as the unconscious) or those that aren't even original. "
]
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[],
[],
[],
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||
1zchpl | why i am i not hearing about anything being done about the comcast-tw merger? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1zchpl/why_i_am_i_not_hearing_about_anything_being_done/ | {
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"text": [
"It's in its early stages, it takes quite a while for two large companies to merge into one. "
]
} | [] | [] | [
[]
] |
||
5cbiaw | what us lean muscle? | Why do fitness experts and healthy food marketing harp on " lean muscle"? Is there other muscle? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5cbiaw/eli5_what_us_lean_muscle/ | {
"a_id": [
"d9viyad"
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"score": [
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"text": [
"There are 3 different types of muscle: Skeletal muscle, smooth muscle and cardiac muscle. Typically, lean muscle refers to skeletal muscle. Skeletal muscle are all the muscles that you have voluntary control of (your limbs, torso, back, neck, face, etc...) and act to move your body. \n\nSmooth muscle is found in many of your organs and has a variety of functions depending on where it is. Usually, it controls the diameter of hollow organs. One of it's most well known functions is to control your blood pressure by changing the diameter of your blood vessels. \n\nCardiac muscle (as the name suggest) is the muscle that makes up your heart. It is very similar to skeletal muscle, except it has special junctions in it that allow it to contract in synchrony so that your heart beats like a pump. "
]
} | [] | [] | [
[]
] |
|
6h9gn7 | how/why most stars are binary systems | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6h9gn7/eli5_howwhy_most_stars_are_binary_systems/ | {
"a_id": [
"diwklbx",
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"text": [
"Most stars are not. its estimated that 1/3 of the stars in the milky way are binary systems, but 2/3 are not. And since our methods for determining if a system is binary are flawed, the number may not even be that high.",
"The post has an article, which has a possible explanation right in it:\n\nEgg-shaped cores collapse into two centers\n\nThey concluded that the only way to explain the observations is to assume that all stars of masses around that of the sun start off as wide Class 0 binaries in egg-shaped dense cores, after which some 60 percent split up over time. The rest shrink to form tight binaries.\n\"As the egg contracts, the densest part of the egg will be toward the middle, and that forms two concentrations of density along the middle axis,\" he said. \"These centers of higher density at some point collapse in on themselves because of their self-gravity to form Class 0 stars.\"\n\"Within our picture, single low-mass, sunlike stars are not primordial,\" Stahler added. \"They are the result of the breakup of binaries. \"\nTheir theory implies that each dense core, which typically comprises a few solar masses, converts twice as much material into stars as was previously thought."
]
} | [] | [] | [
[],
[]
] |
||
73q0ap | if the wavelength of light corresponds to its energy, and space expanding lowers the wavelength of light, where does the light's energy go? | Edit: stretches the wavelength, not lowers it. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/73q0ap/eli5_if_the_wavelength_of_light_corresponds_to/ | {
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"Conservation of energy is not always true. Noether's theorem establishes a one-to-one correspondence between symmetries and conservation laws. The symmetry associated with conservation of energy is time-translation symmetry. In any system where this symmetry holds, energy is conserved. And in any system where this symmetry doesn't hold, energy is not conserved.\n\nAn expanding universe breaks time-translation symmetry, so on cosmological scales where the expansion of space is non-negligible, energy is not conserved.\n\nCosmologist Sean Carroll writes about it [here](_URL_0_)."
]
} | [] | [] | [
[
"http://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/"
]
] |
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