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jr1od | When did males start growing beards and why don't great apes have them? | I understand great apes have facial hair below the chin, but I've never seen an ape with a mustasche. When did the ability to grow hair above the upper lip develop? I found a post saying that is was selected for sexuality, but when and why did it start?
Also, why didn't women develop facial hair? | askscience | http://www.reddit.com/r/askscience/comments/jr1od/when_did_males_start_growing_beards_and_why_dont/ | {
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"Women have facial hair. It is not typically as dense as men's, and obviously in many cultures it is shaved/tweezed/waxed/bleached so you never see it. ",
"Orangutans have reasonably sized [beards](_URL_0_) and this one has a bit of a mustache too.\nAnd I'm sure they aren't the only ones.",
"This is a very interesting question, and it is difficult to put a finger on what exactly is the driving factor behind facial hair.\n\nIt's usually considered a secondary sex characteristic that our females loved back in the day. Beards are typically associated with wisdom and age, across many cultures. It's possible that back in the day, subconciously or conciously human females were attracted to those with dark colored beards (not white and whispy).\n\nFrom a Wikipedia article about androgenic hair in general (body hair, including facial hair):\n\n > Androgenic hair provides tactile sensory input by transferring hair movement and vibration via the shaft to sensory nerves within the skin. Follicular nerves detect displacement of hair shafts and other nerve ending in the surrounding skin detect vibration and distortions of the skin around the follicles. Androgenic hair extends the sense of touch beyond the surface of the skin into the air and space surrounding it, detecting air movements as well as hair displacement from contact by insects or objects.\n\nMuch like the dwarves in Artemis Fowl.\n\n > Cambridge University zoologist Charles Goodhart believed men have long preferred the \"hairless trait\" in women, ever since the existence of the \"hairless trait\" occurred in our hairy forebears 70,000-120,000 years ago during the last episode of global warming. Goodhart argued that humans are relatively hairless today compared to our ancestors because women who were sexually selected for their \"hairless trait\" passed it on to both their male and female offspring.\n\n > Markus J. Rantala of the Department of Biological and Environmental Science, University of Jyväskylä, Finland, said the existence of \"androgen dependent\" hair on men \"could be\" explained by \"sexual attraction\" whereby hair on the genitals would trap \"pheromones\" and hair on the chin would make the chin appear \"more massive\".\n\nThe purpose behind facial hair is probably no longer relevant, although it may impact us on a subconscious level. There are plenty of people I know who just plain hate beards and find it unattractive.\n\nA lot of things we may just never know...Cool topic though!\n\n_URL_0_",
"Women have facial hair. It is not typically as dense as men's, and obviously in many cultures it is shaved/tweezed/waxed/bleached so you never see it. ",
"Orangutans have reasonably sized [beards](_URL_0_) and this one has a bit of a mustache too.\nAnd I'm sure they aren't the only ones.",
"This is a very interesting question, and it is difficult to put a finger on what exactly is the driving factor behind facial hair.\n\nIt's usually considered a secondary sex characteristic that our females loved back in the day. Beards are typically associated with wisdom and age, across many cultures. It's possible that back in the day, subconciously or conciously human females were attracted to those with dark colored beards (not white and whispy).\n\nFrom a Wikipedia article about androgenic hair in general (body hair, including facial hair):\n\n > Androgenic hair provides tactile sensory input by transferring hair movement and vibration via the shaft to sensory nerves within the skin. Follicular nerves detect displacement of hair shafts and other nerve ending in the surrounding skin detect vibration and distortions of the skin around the follicles. Androgenic hair extends the sense of touch beyond the surface of the skin into the air and space surrounding it, detecting air movements as well as hair displacement from contact by insects or objects.\n\nMuch like the dwarves in Artemis Fowl.\n\n > Cambridge University zoologist Charles Goodhart believed men have long preferred the \"hairless trait\" in women, ever since the existence of the \"hairless trait\" occurred in our hairy forebears 70,000-120,000 years ago during the last episode of global warming. Goodhart argued that humans are relatively hairless today compared to our ancestors because women who were sexually selected for their \"hairless trait\" passed it on to both their male and female offspring.\n\n > Markus J. Rantala of the Department of Biological and Environmental Science, University of Jyväskylä, Finland, said the existence of \"androgen dependent\" hair on men \"could be\" explained by \"sexual attraction\" whereby hair on the genitals would trap \"pheromones\" and hair on the chin would make the chin appear \"more massive\".\n\nThe purpose behind facial hair is probably no longer relevant, although it may impact us on a subconscious level. There are plenty of people I know who just plain hate beards and find it unattractive.\n\nA lot of things we may just never know...Cool topic though!\n\n_URL_0_"
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5ldxhw | When and where did people start using beds with legs, as opposed to some sort of mat for sleeping on the floor? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/5ldxhw/when_and_where_did_people_start_using_beds_with/ | {
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"While you may get answers here, this question may be worth x-posting to our sister sub, /r/AskAnthropology "
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95x3mp | Why did the dutch nationalist/fasists suport the german invasion instead of remaining loyal to the queen? | In may 1940 germany invaded the netherlands as part of case gelb. The dutch army was forced to surender after 5 days of fighting. At wich point the nsb was prompt to declare the queen and her goverment who had fled to londen day's before traitor's. My question is why would a nationalist/fasist orgnisation suport invaders who killed dutch troops over their own goverment and country?(Sorry for the bad english its not my native language. =D)
edit: the title should say ocupation not invasion. | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/95x3mp/why_did_the_dutch_nationalistfasists_suport_the/ | {
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"The position of the NSB (Dutch national-Socialist party) in regards to the German invasion was twofold. On one hand Anton Mussert (the leader of the NSB) welcomed the invasion, as he hoped that Hitler would install him as the leader of the Dutch territories but on the other hand he could not be seen as openly welcoming the German forces.\n\n\nMussert was contacted by the *Abwehr* (German military intelligence) in december 1939, in order to ascertain what the NSB would do in case of an invasion. Mussert stated that the NSB would not 'stab Holland in the back' by demanding the party members to desert in case of an invasion. The *Abwehr* concluded after the invasion of Norway, where National Socialist Quisling had actively supported the German invaders, that Mussert ‘must be able to pose as [the nation’s] “saviour in time of need” ’, not appear to have betrayed it to the enemy.'\n\n\nWhen the invasion begun, however the NSB members were seen as enemies and several were incarcerated. Mussert tried his best to dispell this, even ousting some party members who had assisted in the invasion. This didn't convince the Dutch populace, though, and NSB members were largely shunned and seen as traitors.\n\nDenouncing the fleeing cabinet members and the queen as traitors was in line with Musserts ambition to be named the *Reichskommissar* for The Netherlands. Mussert hoped him and his party would be installed as the new governement. But for all his efforts he got few results. Arthur Seyss-Inquart was to be the *Reichskommissar* and Mussert wasn't even invited to his inaugural adress. Even though the NSB grew during the German occupartion, the party never got enough goodwill under the populace to be considered useful by the Germans (in terms of governement, they were seen as a good recruiting platform for the SS). Mussert was seen as too much a Nationalist, not enough National Socialist by the Germans.\n\n\nMussert, at his post-war trial, maintained that he had always intended to act as a guadrian of the Dutch values under the Nazi opression and that him remaining as the last Dutch politician to stand between the populace and the oppresive German regime. He did try his best to have The Netherlands remain 'independent' (this meant 'not annexed' ,with an own governement) but he had to bow down to many German demands only to have a 'shadow cabinet' with no formal authority.\n\n\nSo: you see that Musserts position was rather twofold. He wanted to gain power under the German rule, but he also wanted to be seen as a 'saviour of the Dutch people'. Things never really turned out the way he wanted, though and he became a sockpuppet for the Germans even though he tried really hard.\n\n\nSources: \n\n* Slaa, R te, and E Klijn, *De NSB: ontstaan en opkomst van de Nationaal Socialistische Beweging, 1931-1935* (Amersfoort, 2009).\n* Stokes, LD, 'Anton Mussert and the NSB: 1931-45', History 56 (1971), 387–407.\n* Pollmann, Tessel, *Mussert & Co : de NSB-leider en zijn vertrouwelingen* (Amsterdam, 2012)."
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8nkgg6 | Is there an underlying physical limitation of the bandwidth of wireless links? | Or can you just keep throwing up more antennas with wider channels?
If we abandoned all other broadcast medium, is there a upper limit of frequencies we could use? | askscience | https://www.reddit.com/r/askscience/comments/8nkgg6/is_there_an_underlying_physical_limitation_of_the/ | {
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"There is no bandwidth limitation per se, but there is an underlying physical limitation on the amount of information that can be transmitted over a given channel (a channel being the mathematical abstraction of everything that happens to a signal in between the transmitter and receiver). In order to explain why such a thing exists we first have to talk about the channel's [capacity](_URL_3_), why it exists, and how it relates to data rate in the end. \n\n#What is the capacity of the channel?\n\nThe capacity of a channel is the amount of information/per symbol we can pass through a channel. To be a little bit more concrete we shall consider the [*binary symmetric channel*](_URL_6_) (denoted BSC(p) where p is the probability of bit flip). For a BSC(p), the transmitter may choose one of two symbols (say {0,1}), to transmit over the channel, and likewise the receiver will receive one of two symbols (say again {0,1}). If the transmitter sends a 0, the probability the receiver receives a 0 is 1-p, while the probability the bit is flipped is p. For this channel the capacity of the channel is 1-H(p) where H(p) is the entropy of a Bernoulli(p) random variable (that is - p log(p) - (1-p) log(1-p) ). This makes sense, as when p = 0, then no errors in transmission will occur and thus the capacity is 1 - H(0) = 1 bit of information per symbol. On the other hand when p =.5, the output does not correspond to the input (that 1 and 0 are always equally likely of being received regardless of the input), and here the capacity is 1-H(.5) = 0 bits per symbol.\n\n#How does this relate to the data rate?\n\nThe data rate can be expressed as the information/second = (information/symbol) (symbol/second). We have already discussed the information/symbol, on the other hand symbol/second is determined by the bandwidth. More specifically, without going into all of the mathematics of it, the maximum symbols/second is twice the bandwidth, as determined by [Nyquist-Shannon sampling theorem](_URL_2_). \n\nSo considering the factors from the channel, and the available bandwidth gives us an understanding of the maximum number of bits/second that can be transmitted across a given channel. One famous example [AWGN](_URL_7_) channel, for which the capacity is 2^(-1) log(1 + P/N) (where P is the signal power and N the noise power) leading to a maximum data rate of B log(1+P/N). This result is so well known it has its own name: [Shannon hartley theorem](_URL_8_).\n\n#Back to underlying limitation\n\nNow, at this point one may ask about the signal power and noise power the following question. Does using a larger bandwidth incur more noise? The answer is yes. Staying with the AWGN channel, in fact the noise power grows linearly with the bandwidth, or N = μ B, for some real number μ. More specifically, μ represents the noise variance per sample. \n\nIn either case, we can now represent the maximum data rate as B log(1 + P/(μ B)), which has a maximum as B grows to infinity, and in fact it converges to P/μ (log e). \n\n#Does this hold true for all channels?\n\nAWGN is essentially the best model (or base of the model) for all for all practical EM channels. But, to be clear, the AWGN is actually the worst possible channel in terms of power for data rate. In specific, the channel capacity of the AWGN channel has a smaller capacity than all other channels. \n\nFurthermore there are also exist channels other than point to point channels. What if two transmitter want to transmit to a single receiver? Or what if one transmitter wants to communicate with two receivers? There are many different types of multi-user channels such as these, and many we do not know the capacity. Among the few cases that the capacity is known is the scenario with multiples transmitters talking to one receiver. This is called the [multiple access channel](_URL_5_), and the capacity region is in general only achievable by [CDMA](_URL_1_). In contrast the capacity region of one transmitter to many receivers is still an open question. This type of channel is known as a [Broadcast channel](_URL_0_).\n\n##What about quantum?\n\nThankfully, one of the most approachable books on this subject was made freely available, and if you are interested [check out *From Classical to Quantum Shannon theory* by Mark Wilde](_URL_4_).\n",
"There are limits on the frequencies based on the absorption, and based on practical considerations. Clearly you don't want to use something that is absorbed within a meter of air (like short-wavelength UV), and you also don't want to use something that is blocked by a sheet of paper or two (like visible light, for example).\n\nAntennas should have a length comparable to the wavelength to work properly, and you want an electronic circuit to be able to generate the necessary frequencies. For visible light this is extremely challenging already, for x-rays and gamma rays you can't even build a suitable antenna (as you don't get structures smaller than an atom)."
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"https://arxiv.org/abs/1106.1445v7",
"http://circuit.ucsd.edu/~yhk/ece255c-win14/lect04.pdf",
"https://upload.wikimedia.org/wikipedia/commons/thumb/b/b5/Binary_symmetric_channel.svg/1000px-Binary_symmetric_channel.svg.png",
"https://en.wikipedia.org/wiki/Additive_white_Gaussian_noise",
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b9qsb7 | if earth's inner layers are essentially super hot metal, and some sections are liquid, how does it keep from solidifying through loss of heat? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/b9qsb7/eli5_if_earths_inner_layers_are_essentially_super/ | {
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"A lot of radioactive elements sank to the center when the Earth was still fully molten, and their high concentrations in the center generate a huge amout of heat as they decay.\n\nThis is the primary source of Earth's inner heat today. The heat from formation alone isn't sufficient to keep it liquid for all these millennia.",
"Heat generated by the decay of radioactive elements in the Earth's make-up helps keeps things warm but, overall, the Earth is losing the residual heat it started with, and will eventually cool off and solidify. So the end answer is \"nothing\" is keeping it from solidifying, the process is just a very long one that is being delayed by the internal generation of heat.",
"Only the [outer core of the Earth is liquid](_URL_0_). Mostly the earth is rigid.",
"Because it's an absolutely massive amount of material (somewhere in the neighborhood of 1.603 x10\\^24 kg) and heat is constantly being generated by the decay of radioactive elements. Eventually the core will solidify, but this will take roughly 91 billion years, and the sun is going to turn into a red giant and blast the Earth into a charred ball or rock long before that happens. "
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9mcffw | Contemporary Bubonic Plague | What do we think of today caused the bubonic plague? Why did it stop/what they could've done better with their med tech knowldge? Is it true that prices went down and wages went up because of the smaller population? How did it affect the culture of the next few generations? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/9mcffw/contemporary_bubonic_plague/ | {
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"There is a strong consensus that Yersinia Pestis was the pathogen responsible for the medieval Pandemic referred to as the \"bubonic plague\" or \"Black Death.\" Twigg and various scholars (primarily in the 1970's) claimed that this particular pathogen was not responsible because the pandemic spread too quickly and blamed Anthrax and other sources, but their work was largely built on medical research which was outdated in the 1970's or has been refuted since. One of the effects of the post 9/11 fear of biological attacks by terrorists was a glut of funding for research into Y. Pestis, which discovered that both the pathogen and it's various vectors (fleas, rodents) are much more robust that Twigg assumed in making his argument.\n\nRecently archaeologists have been able to empirically refute these \"alternative pathogen\" theories by doing genetic analysis of the tooth pulp of skeletons recovered from plague pits (mass burial sites) from both the 6th and 14th century pandemics. Repeatedly confirming that the victims died from some strain of Y. Pestis.\n\nLocalized outbreaks continued for centuries after the initial pandemic, eventually ending as rodent and human populations became disease-resistant or because or changing climactic conditions. The reasons are not well understood.\n\nWhat could they have done better? In the fourteenth century very little. Most of the population lived in rudimentary one-room houses in which their animals and livestock often lived or slept. Y. Pestis can infect a wide range of animals (dogs, cats, pigs, chickens) and can be transmitted by both fleas, common lice. Without modern housing or sanitation medieval humans had little way to prevent exposure to or the spread of the disease. Fourteenth century medicine was mostly superstition, and for the tiny minority of people that could afford a \"doctor\" the medical care they could receive would have no medical benefit or be genuinely harmful (e.g. bloodletting).\n\nIt is true that real wages increased (effectively doubling) and prices for some things went down. The mortality rate is contested, but for England, where we have the best data, it is believed 55-60% of the population died in the initial Pandemic (1347-1351). In real terms this caused a massive shift of economic power from landholders to laborers, in a sense the wealthy were now competing for labor, rather than the usual situation where labor competes for jobs. This famously caused Edward I to issue the statute of laborers in 1351, establishing wage controls and attempting to restore the economic power of the nobility. \n\nThe sixth century plague pandemic caused the East Roman/Byzantine Emperor Justinian to issue a remarkably similar edict on wage and labor controls, also in response to economic changes caused by a Yersinai Pestis pandemic.\n\nHow the plague affected the culture goes beyond my knowledge."
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tsnwk | Does you brain function differently when ketones are the main source of energy, than it does on glucose? | Or are there any noticeable effects? | askscience | http://www.reddit.com/r/askscience/comments/tsnwk/does_you_brain_function_differently_when_ketones/ | {
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"Google Scholar had a few references to ketogenic diets that predate Dr Newport's claim that extra virgin coconut oil cures Alzheimers, but the studies relate to epilepsy in children. Snopes said it was unproven.\n\nFast until your breath has that smell of nail polish remover and see for yourself if your brain is better. Mine is different in a bad way when hungry.\n[some critical comment] (_URL_0_)"
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7q7nj1 | Where do animals get water from in the winter in places where everything is frozen over, and there is no snow available to eat? | askscience | https://www.reddit.com/r/askscience/comments/7q7nj1/where_do_animals_get_water_from_in_the_winter_in/ | {
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"Funnily enough eating snow is actually very expensive in terms of metabolism. Meaning it's normally a waste of time! (Another reason to not eat the yellow snow)\n\nUsually it varies from animal to animal. Polar bears for instance use a chemical process to help break down fat into water. That's why seals are the main course, they strip the blubber off and leave the meat to the scavengers.\n\nPenguins on the opposite end are designed with drinking salt water in mind. A gland behind their eyes filters the salt out of their blood and expels it through their nose.\n\nSo there's no catch all answer, but usually\n\nA) they extract enough water from what they eat\n\nB) They adapt to drinking saltwater, which usually doesn't freeze in subzero conditions"
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2mwzzr | different led types (led, oled, amoled, p-oled), their status (common in mobile devices, r & d only) | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2mwzzr/eli5_different_led_types_led_oled_amoled_poled/ | {
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"LED's are light emitting diodes. Diodes are a device made of semiconductors that only allows electrical current through one way. A light emitting diode is a diode that while allowing current through the one way emits light at the same time. \r\r\rOrganic scientifically means anything that contains the element carbon. A few exceptions being pure carbon (diamond, graphite, soot) and the gases it makes with oxygen (carbon monoxide and dioxide) and maybe a few other i can't recall off the top of my head. Note this isn't the \"food\" definition of it, things scientifically organic could be very deadly and completely artificial. \r\r\rHistorically LEDs have been inorganic. Things like gallium arsenic for example make traditional LEDs. The semiconductor of choice depends entirely on what colour you want. \r\r\rMore recently we have been able to make LEDs out of organic semiconductors. An OLED is an organic LED. LED could potentially mean either inorganic or organic. \r\r\rPOLED is a polymer organic LED. This is a OLED, but the particular organic semiconductor being used is a polymer. A polymer is a long chain like organic molecule, they are plastics. \r\r\rAs for what R & D and what's in use, i can't tell you. All those terms are to broad, there is some of both in each. All i can tell you is there is probably more research going on with OLEDs than inorganic LEDs. \r\r\rAMOLED is a type of screen, not a type of LED. AM is active matrix, it means how the computer controls the screen. The screen itself is made of OLEDs. Hence, AMOLED. OLED screens are ones made from OLEDs. \"LED\" screens are really LCD screens with LEDs for back lights rather than a florescent bulb. "
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25f0l7 | What actually happened to the Roman Ninth Legion that "vanished" from present day Scotland in the second century? | _URL_0_
This thread piqued my interesting, and I immediately thought of you guys, hoping I could gain some insight on the disappearance of Legio IX Hispana. | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/25f0l7/what_actually_happened_to_the_roman_ninth_legion/ | {
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"It's important to remeber that IX Hispana was always under strength since its near destruction during Boudicca's revolt (Annals 14.29) so that by the campaigns of Agricola, it numbered only 1000 under Lucius Roscius Aelianus (CIL 14, 3612). Because of this it almost saw destruction once again in Caledonia during 83/84AD. Little more is known until it's construction of a gate way at Eboracum fortress which is dated to 107-108AD (RIB 1,665). then due to the legions absence during the construction of Hadrians Wall some consider it to not even be in Britain. Some evidence even tells us that a legate of the legion in 121AD was buried in 127AD in Petra after serving as governor of Arabia Petraea (CIL 3,87). It seems likely that the legion was not destroyed in Britain, but possibly in the Second Jewish Revolt or one of the Armenian Campaigns.\n\nEdit* Tiles found in Noviomagnus on the Rhine suggest the legion was transferred to Germania around 121AD before being moved to the East.",
"Lurking dilettante wannabe here ( enough with the caveats) Is this thread about the Lost Eagles of Varus or is that another Roman Legion mystery?"
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9tasu0 | What is the optimal number of blades a plane's propeller could have? | I recall seeing planes with different number of propeller blades, different sizes and types. Is there really an optimal number, and if so, does it depend on the plane's size and functionality? Is this number different for helicopters? Are there different propeller blade types for different purposes (eg. high speed, high altitude, etc.)?
Quite a lot of questions, but I don't know anything about the subject. I'd be grateful if someone could tell meg the basics, so I'd have an idea how all this works. | askscience | https://www.reddit.com/r/askscience/comments/9tasu0/what_is_the_optimal_number_of_blades_a_planes/ | {
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"It depends on the plane's function, attributes, specifications, etc. There's no one optimal size; if there was, every aircraft would use it. Generally, fewer blades are more efficient because as the blade turns, it at least partially passes through the disrupted airflow of the blade \"ahead\" of it. Additional blades can also increase the parasitic drag of the propeller.\n\nIf you're trying to increase the thrust produced by the propeller, you can increase the length of the blade but this has drawbacks. As the blade grows longer, the tip travels faster. At a certain point, the tip speed can approach the speed of sound, causing the efficiency to drop because of how transonic air behaves compared to subsonic air. Longer blades are also floppier than short blades, requiring them to be stiffer which adds weight. You also have practical considerations like ground clearance.\n\nThe other way you can increase thrust is by adding additional blades, but as noted above this also has drawbacks. So you end up having to balance these factors based on what your aircraft has to do. An example you can look at is the C-130 Hercules. The first block of aircraft had four 3,750 hp engines, each with a three-bladed propeller. They later upgraded the engine to 4,600 hp and added a four-bladed propeller."
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5d57rl | Mansu Musa and gold in Europe | Hey, I have a question about Mansa Musa of Mali. Did he introduce a lot of gold to Europe, since I've seen European maps with Mansa Musa and lots of gold on it? Or did he just show Europe more gold? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/5d57rl/mansu_musa_and_gold_in_europe/ | {
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"Emperor Musa went on hajj in 1324, and on his hajj he visited Cairo before continuing on to Mecca. He was not the first Malian monarch to make this hajj, nor was he the last. But, by the vagaries of fate, he is remembered for the particular wealth he brought with him on his pilgrimage.\n\nOur earliest source describing this hajj comes from the syrian scholar Shihab al Umari, who wrote his account twelve years after the fact, based on interviews with people in Cairo who interacted with the Malian monarch. [Here is an excerpt from al-Umaris account](_URL_0_) which concerns the extent of the *mansa's* wealth, and details his visit to the Mameluke sultan in Cairo. Since al-Umari's account is second hand and comes years after the event it relates, we should keep in mind the possibility that the story was embellished in the intervening years.\n\nIn this period, Italian city states like Venice were engaged in trade with Mameluke Egypt. These merchants would have heard the tale of the *mansa's* immense wealth, and spread the rumor to European ports on the Mediterranean shore. Emperor Musa holding a gold nugget is first depicted on the Catalan Atlas, which was produced in 1375, some fifty years after the hajj and 38 years after al-Umaris account.\n\nI don't know of any scholarship or numismatics that has tried to directly link gold that ended up in Europe as the gold that came from Mali in 1324. Again, he wasn't the only one to bring gold. In fact, Arab sources make particular note of the wealth in gold of the monarchs of Ghana in the 9th-11th centuries, and mention other Malian monarchs bringing caravans of gold with them.\n\nRather, the mere rumor of immense wealth in a far off land was enough for *Mansa* Musa and Timbuktu to be remembered in Europe."
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16wbgq | why can't kim dotcom be prosecuted for his new site? | What's the big deal about this? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/16wbgq/why_cant_kim_dotcom_be_prosecuted_for_his_new_site/ | {
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"He can't be persecuted because he is operating entirely within the domain of a country in which he is breaking no laws. He was able to be persecuted for the old one (illegally) because it was a .com, which falls under jurisdiction of the USA. "
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1rql8y | Whole, negative, and rational exponents all have intuitive meaning. What does it mean when raising a number to an irrational or transcendental number? | For example raising a base (B) to a whole number (N) "means" to multiply B by its self (N) times.
b^n = b*b*b*b...*b
Raising (B) to a negative integer (-N) just "means" to take the inverse of B raised to (N).
b^-n = 1/(b^n)
Raising (B) to a rational number (N/M) "means" to take the the Mth root of B^(N)
b^(n/m) = mthroot(b^n)
So is there an intuitive way to understand what it "means" to raise a number to an irrational or transcendental number like pi? My original thought was no because the previous three meanings/explanations are algebraic statements and irrational numbers and transcendental numbers are not algebraic numbers. However; this is only partial true. The sqrt(2) is irrational and algebraic, but I still have no real understanding of what 2^sqrt(2) means.
Any insight is much appreciated.
As a side note I fully admit that I say "meaning" a lot in my question which is really not a mathematics term so maybe I am asking more of a philosophical question. | askscience | http://www.reddit.com/r/askscience/comments/1rql8y/whole_negative_and_rational_exponents_all_have/ | {
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"No need to distinguish transcendental numbers from irrational numbers—transcendental numbers are irrational so if we can figure out what exponentiation by irrational numbers means, we're done. Incidentally, the following treatment of this question is essentially taken directly from Principles of Mathematical Analysis by Walter Rudin, which is undoubtedly the biggest introductory analysis textbook out there. It's important enough for Rudin to have written the entire first chapter about it, so, good question.\n\nIn order to sort it all out, let's remember what irrational numbers are for in the first place. You may be familiar with the old proof that the length of the diagonal of the unit square is not rational. Often this is referred to as a \"proof that √2 is *irrational*\" but that's actually not quite right. It proves that there is no number √2 in the rational numbers, but maybe that just proves that √2 doesn't exist *at all*.\n\nThis is the perspective that we take when we talk about constructing the real numbers from the rational numbers. The proof that there is no square root of 2 in the rational numbers tells us that the rational numbers have a \"hole\" where √2 should be. That means that the rational numbers are inadequate to perform one of the tasks we would like a number system to do: measure lengths. In particular, it is impossible to measure the length across the diagonal of the unit square—that's no good. We want a number system that fills in the holes.\n\nSo suppose that we don't know anything about the real numbers, and all we know about is rational numbers. Our rational number system works for a lot of things, but it fails at being good for measuring lengths, since there are some lengths which correspond to holes in the rational numbers. We want to plug the holes. In order to do this, we must first determine where the holes in the rational numbers are. Intuitively we know that there's a hole at √2, but there are two problems with putting it this way. The first problem is that, since √2 isn't a rational number, and we haven't constructed the real numbers yet, √2 isn't an object that we can point at and say \"there\". Second and more importantly, √2 is only one hole. Are there more? Probably. Do we know where they are? Probably not.\n\nA way to deal with this is to rephrase the problem of finding the holes entirely. Instead of looking for individual holes å la proof that √2 is not rational, we can try to identify a particular property of the entire set that would eliminate holes. Another way to say that there is a hole at √2 is to say that the set S of all rational numbers r such that r^(2) < 2 has no *least upper bound*. That is, for any rational number that is an upper bound of S, you can find a smaller rational number which is also not in S (exercise: prove this), so there is no least upper bound of S. The fact that there exist bounded sets of rational numbers with no least upper bound is exactly equivalent to the fact that there are these \"holes\", and it gives us a better way to talk about the property of having or not having holes. If a set F has the property that every bounded subset of F has a least upper bound, we say that F has [the Least-upper-bound property](_URL_2_). The idea, then, of the construction of the real numbers, is to form a set which has all the properties that we like from the rational numbers (they're ordered, they have all the arithmetic operations that we like, etc.) as well as the Least-upper-bound property. The irrational numbers correspond exactly to the \"holes\".\n\nThis might seem convoluted, but this is what you need to understand if you want to understand what is meant by *any* arithmetic operation on real numbers. Like, forget exponentiation, what does it even mean to *add* π+e? Certainly not the same thing that it means to add 1+1. I don't really know what it would mean to take π apples and e apples and put them in a bag and count what you end up with. \n\nSo anyway, I won't go over exactly how this is done (there are two main approaches: [this](_URL_1_) and [this](_URL_0_)), but suffice it to say, the real numbers are (necessarily) what you get when you sort out a way to build a system that has all the nice properties of the rational numbers along with the least upper bound property.\n\nThen you can think of any real number as the least upper bound of some bounded set of rational numbers. So √2 is just the least upper bound of the set of all rational numbers r such that r^(2) < 2. A little tedious mathematical maneuvering that I'll hand-wave over shows that this implies that 2^(√2) is the least upper bound of the set of all 2^r such that r is rational and r^(2) < 2. More explicitly, we might say that 2^√2 is the limit of the sequence {2,2^(1),2^(1.4),2^(1.41),...}.",
"*a*^(*b*) = e^(*b* log *a*)\n\nThe exponential function is well-defined for any real (or complex) exponent, so this will work for *a* > 0. There's no good way to do this for negative *a*.",
"Since every real is defined (or can be defined) as a limit of a sequence of rational numbers, you can use continuity to define exponentiation to an irrational power as the limit of the power of the base to successively closer rational exponents.\n\nThat's how I interpret it, anyway.",
"This is a great question and it's not at all obvious.\n\nOne thing to note is that we need to precisely define what \"real numbers\" are. There's generally two main constructions that define the reals: as Dedekind cuts or as equivalence classes of Cauchy sequences of rational numbers (you can find more info about both of these [here](_URL_0_). Let's stick with Dedekind cuts. In this construction, the number sqrt(2) is represented by the set of rational numbers less than sqrt(2).\n\nOne thing that's not hard to show is that exponentiation, on the rationals, is strictly increasing. That is, if p and q are two rationals, and p < q, then 2^p < 2^q. So if you let p be in the Dedekind cut for sqrt(2) (ie, p is rational and p < sqrt(2)), and q be rational and q > sqrt(2), it follows that the set { 2^p | p < sqrt(2) } is bounded above by 2^q.\n\nSo we define 2^sqrt(2) to be the least upper bound of the set {2^p | p < sqrt(2) }. This is in fact equivalent to the other definition given in this thread, ie, the limit of any sequence of 2^(p_n) where p_n is a sequence of rationals approximating sqrt(2)."
]
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"http://en.wikipedia.org/wiki/Least-upper-bound_property"
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33pljl | Which loses its fizz faster: A soda bottle standing upright or a bottle that's lying on its side? | Will the soda lose fizz slower if it only has contact with the air that's the area of the neck of the bottle, or will nothing change? | askscience | http://www.reddit.com/r/askscience/comments/33pljl/which_loses_its_fizz_faster_a_soda_bottle/ | {
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"Assuming both bottles are completely sealed there will be no difference in the long term as the volume of the head space should be same and thus the amount of CO2 that escapes into that space will be the same. In the very short term the sideways bottle will lose (a small amount of) carbonation faster as the gas-liquid interface is much bigger when laying down, thereby increasing the speed that the transfer from liquid to gas can happen.\n\nThere could be some factors such as the bottle cap being a better nucleation site that the rest of the bottle which would also favor the upright position for carbonation retention, but again that should not effect the equilibrium state.\n\nIf for some reason the seal on then bottle isn't perfect then it could swing the opposite way. Gas is likely to escape an imperfect seal faster than liquid, so in the upright bottle you may lose significantly more CO2 to leakage and thus lose the carbonation in the bottle faster. However if the seal is very poor and the bottle is on its side you may lose a significant amount of the liquid, and while the remaining stuff might still be well carbonated it is probably not the outcome that you want."
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39j4tf | could a hacker theoretically breach a bank and erase all the debt the banks have on file? | Could a hacker erase all records of mortgages and credit and if so what would the bank do? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/39j4tf/eli5_could_a_hacker_theoretically_breach_a_bank/ | {
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"Technically, yes, but realistically, no.\n\nMost companies have back up centers located in different physical locations.\n\nThey also have back up tapes (think VHS tapes, but the size of N64 cartridges) for storing computer data. These are take out of the backup machine and stored, so they cant be accessed virtually.",
"Not unless he breached the bank HQ and then stole the information to access the databases, wherever they are, (and don't forget the backup databases).",
"It is very unlikely to impossible to erase all the debts because it is persisted all over the internet at this point. Many larger businesses are using cloud backup solutions, in some cases you can even save a virtual copy of your entire network and access it over the internet in the case of an attack that wipes out the office, This includes workstations, servers, voip solutions, and more.\n\nRedundancy is the rule with important data\n\n",
"We keep the original loan agreements in the vault. It would be a pain in the ass, but it could all get sorted out. \n\n",
"Theoretically? Maybe.\n\nPractically? No way in hell. There are simply too many backups and copies of the data in multiple locations, both virtual and physical.\n\nAt the very least, a bank (or really any business with vital digital data) has their servers, an on-site backup (HDDs or tapes) and an off-site backup. You can't hack in to them and delete all the data.",
"I think you'd probably wipe out the bank before you were able to wipe out all traces of debt at that bank. As in the bank would go out of business due to the massive data loss it was experiencing and trying to recover from while the attack continued against all their backups, hard copies etc.\n\nNot sure what happens if a bank goes under though. Does maybe a bigger bank buy all the debt and then you're screwed anyway?"
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361704 | What Made the Nazi Military So Powerful? | This seems like it would be a common question, but everything I found in searches talks about how the Nazis gained support within Germany. They don't explain how a nation that was impoverished following the first world war and forced to disband much of its military managed to take over Poland and France, march on the Soviet Union, AND bomb Britain.
Shouldn't they have been at a significant disadvantage? Why didn't the many countries they attacked have an easier time fending them off? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/361704/what_made_the_nazi_military_so_powerful/ | {
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"After WWI, Germany was economically devastated. There were restrictions placed on their military strength and reparations that were forced to be paid with the stipulation that if they were not paid, Britain and France would seize German lands and divide them as a result of secret treaties not made public after WWI. (On a side note, the US would pay the reparations for Germany in an effort to maintain peace when Germany was unable to pay due to rapid inflation). Germany was in chaos with returning soldiers organizing into different revolutionary sects and open conflict on the streets. The Nazi party organized and specifically targeted the poor and disaffected - poor people who could not afford to eat and middle class families that had lost their savings. Only the mega-rich were able to make any money or could afford to live relatively normal lifestyles. Hitler and his Brownshirts (who were like the security force during rallies and such) presented to the German people not only organization and a greener pasture ahead, but promised jobs and economic stability, earning popular support enough that he was given a position in government in an effort to control him. Despite the limitations on the military, after gaining dictatorial power, focused most of German production on military strength because he knew what he wanted. He had a plan to reconquer lands that he felt had no right to exist such as Czechoslovakia and Poland. He felt that these countries were part of Germany and should be returned to the Reich. They produced tanks at an unprecedented level. Unexperienced Germans \"volunteered\" in the Spanish civil war to learn flying techniques and maneuvers and utilized this experience in the air. France was organized defensively and when the Germanys invaded, they simply bypassed French fortifications and cut off those who were fortified. The speed and efficiency that the Germans exhibited with their mechanized divisions was unorthodox and devastating. When you're asking how it happened, you have to take into account the goals of Hitler, the reluctance of Britain and France (who were arguing amongst themselves at the time) to get into another war, the deception and strategy of the Nazis in professing peace while at the same time manipulating countries like Czech and Poland into submission, their u-boats which were very successful early on, the blitzkrieg strategy, etc. Also, keep in mind that Russia was a German ally when it all started. Russia helped in the invasion of Poland and was sending supplies to Germany up until the day before Germany invaded Russia. Many believe that had the Germans continued onto Moscow instead of diverting to focus on supplies and pausing long enough to allow logistics to catch up, the Germans would have handily defeated the Russians by toppling their government and maybe have been able to resist American and British forces. There are so many what-might-have-happened-ifs, but I don't think you're asking about those. To answer your question of how it was possible: The Nazi party devoted almost ALL of their focus on developing their military with the purpose of invading their surrounding countries and their equipment, strategy, and tactics were far superior when the war began. ",
"The simple fact of the matter is that Germany was never in as bad a position after WWI as is commonly believed.\n\nThe Hyperinflation, which stemmed partially from wartime financial decisions of the German government and partly from deliberate attempts to sabotage reparations, was largely under control by 1924. Thanks to the Young-Dawes Plan, Germany now had access to foreign loans and enjoyed immense economic prosperity from 1924-29. Following the Great Depression, the German economy was stabilized by the efforts of Hjalmar Schacht, utilizing Keynesian methods. Hitler used the opportunity to begin a massive armaments programme, part of Goering's Four Year Plan, which placed Germany in an advantageous position in 1939 compared with it's neighbours.\n\nBy 1933, the population of Germany was c. 65 million, the same as the much larger German Empire in 1914. The incorporations of the Saarland, Austria, Sudetenland and Czechlands into Germany between 1935 and 1939 ensured that the population in 1939 was much larger than in 1914, and Germany had a much larger industrial base, which was geared towards war. \n\nIt also helped that the German military had hardly been curtailed by Versailles. 115 000 men was still a large army and to this could be added the 'Black Reichswehr', a clandestine organization that kept tabs on the right wing Freikorps paramilitaries, so as to call them up in case of war. The General Staff was dispersed through the so-called Troop Office and various other organizations, such as the Reichs Archiv, where former officers wrote apologist histories of the First World War. After the Treaty of Locarno in 1926, Germany began cooperating with the USSR: German officers trained at Soviet Academies, German pilots trained in the USSR, and German aircraft and tank designs were tested in the USSR. Hans von Seeckt, essentially the chief of staff of the German Army, sought to build up the Reichswehr as a professional force which would form the nucleus of a new German Army in the future. All of these efforts ensured that when conscription was reintroduced and the formation of the Wehrmacht was announced, Hitler's generals did not need to start from scratch.\n\nPoland was no match for Germany militarily in 1939; they found themselves in a two front war with the Germans and the USSR, with attacks all along their border from the Baltic to Slovakia. No support was forth coming from Britain or France, but this did not prevent the Poles from putting up staunch, heroic resistance. The Polish campaign cost the Germans c. 50 000 casualties, 1/4 of all their tanks, 285 aircraft lost and c. 280 more damaged.\n\nFrance was attacked half a year after the Polish Campaign. In this case, the Luftwaffe was able to attain air superiority, and so the movement of the German Army Group A through the Ardennes went largely undetected. The French and British were expecting the main thrust through Northern Belgium as in 1914, and were surprised when they had a large German mechanized force in their rear, and had no strategic reserves. Even still, the Battle of France was a costly affair for the Germans: c. 158 000 casualties, 795 AFVs destroyed, c. 1300 Aircraft lost.\n\nThe Battle of Britain, suffice to say, was a failure. The German Navy was reeling from Norway, and the Luftwaffe was inefficient at Anti-shipping operations, so the Royal Navy was a formidable barrier to invasion. The German army lacked the specialized equipment and the training to carry out an amphibious landing. Above all, the RAF was NEVER as close to defeat as the Germans OR the British believed. The losses the RAF suffered could be replaced relatively easily, but German aircraft production lagged behind, and the losses the Luftwaffe suffered were unsustainable. What comes to mind is the dark humour of Luftwaffe pilots, who announced the approach of British aircraft by saying, \"here come the last of the Spitfires, AGAIN!\" Above all, the losses incurred by the German bomber force in the BoB and the Blitz left it hamstrung for Operation Barbarossa.\n\nTo make a long story short, Barbarossa was a failure; spectacular gains were made and losses inflicted, but the USSR survived. From 1942-43 the Red Army gradually got back on it's feet, and by 1944 the war in the east, and in general, was lost for the Germans."
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3d675x | why can you still have gps and wifi on when you're on a plane but not standard cellular network connection | I'm assuming it has something to do with how the data is sent and received? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/3d675x/eli5_why_can_you_still_have_gps_and_wifi_on_when/ | {
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"Well, GPS is a receive-only technology. A constant signal is broadcast from all of the GPS satellites. The signal contains a timestamp, all of the satellites have their times precisely synchronized, and the location of the satellites are known. So based on the delay between signals from multiple satellites, your GPS device can triangulate its own position. The satellites are just up there broadcasting, with no knowledge that your phone -- or any other GPS-enabled device -- even exists.\n\nWiFi is managed by way of short-range radio signals. When you're on a plane with WiFi, the receiver that is communicating with your phone (and unlike GPS, it both sends and receives data from your phone) is right there in the plane with you. The plane will then have either a ground-radio-based or satellite-based communications link that connects their WiFi to the rest of the Internet.\n\nSo what about your cellular network connections? Well, cell towers are designed to deal with phones on the ground, so their transmitters are directional, and don't really point up towards airplanes. And if you *are* able to connect to one, you'll be moving past towers much more quickly than they're designed to handle, so you'll still risk a spotty connection as the network hands you off between cells."
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5lb3j4 | Why has the US seemingly always supported right-wing dictatorships in opposition to communist ones? | Mostly for central and south america, it seems every time the communist boogeyman would rear its head the CIA would try and install the most brutal despot they could find as long as they swore to kill lots of communists.
Why not try and get these countries on e.g. US-aligned european-style social-democracies to draw them away from communist lure instead? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/5lb3j4/why_has_the_us_seemingly_always_supported/ | {
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"The wars and military operations to which you are referring were, for the most part, secondary to the larger 'conflict' which framed much of the later 20th Century known as **The Cold War**. (I'm sure you know this, just so we are on the same page). A significant European contingent of states were likewise party to military pacts arrayed against the Communist world and its satellites.\n\nThe US supported right-wing allies primarily as a counter-balance to Communist or 'leftist' expansion in areas they sought to influence, such as Central America. This was a block against the supposed *domino theory* which states that one successful change in ideology within a state can cascade through a region. \n\nThat being said, while many of these conflicts look similar in a macro sense they are all subtly different in a micro sense. Is there one instance which you are particularly interested in here? Then either myself or someone else could give you some more specific context!\n\nFor a good primer on Reagan-era activity in this sphere I would suggest:\n\n **T. Carothers: In the Name of Democracy - US Policy toward Latin America in the Reagan Years**.\n\nIt provides a country-by-country background to US activity in promoting right-wing governments and undermining left-wing influence.\n\nEdit: Text. "
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7splj1 | why do you hear yourself breath louder when you have headphones in with no music playing? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7splj1/eli5_why_do_you_hear_yourself_breath_louder_when/ | {
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"You are blocking your ears from hearing things outside your body, so your ears are hearing the sounds resonating within your body easier. That's why you hear your heart beat and stomach rumble easier with your ears covered.",
"There are two types of conduction for hearing. Air conduction and bone conduction. Air conduction is the sound waves traveling through your ear canal. Bone conduction is the passage of sound to the inner ear through the bones of your skull. When you put headphones in you block out air conduction. The only thing you can hear is the sound conducting through bone. This will likely be something like your heart beat or air moving in and out of your lungs. ",
"Adding to the other answers, your ears have a sort of automatic gain control. That's why you hear faint sounds when it's quiet, but not when normal house noises are going on. When you block outside sounds with the inactive headphones your ears become more sensitive and hear the bone-conducted sounds of your body."
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dqtj1o | Anyone know any books about the Filipino-Spanish Society during the Spanish Colonization of the Philippines? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/dqtj1o/anyone_know_any_books_about_the_filipinospanish/ | {
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"What aspects are you interested in? What do you mean by “Filipino-Spanish society”? Do you mean Filipino people under colonialism or do you mean the very small Spanish population running the colony?"
]
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bxetd9 | what are the technological/physical limitations regarding smartphone camera advancements? will we ever see them match traditional ones? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/bxetd9/eli5_what_are_the_technologicalphysical/ | {
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"Small lens size limits light entry, so no, will probably never match the quality of a traditional SLR"
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3a9o7n | How did the laws of war come to be? How did certain ways of killing others in war come to be seen as so inhumane it can't be allowed even in a war? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/3a9o7n/how_did_the_laws_of_war_come_to_be_how_did/ | {
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"This is actually a somewhat broad question and you could get many possible answers. I'll only discuss one thing and allow others to pipe in.\n\nIn 1863, Abraham Lincoln signed a set of rules on wartime conduct that his troops were going to follow. This was called informally the Lieber Code.\n\nIt was named after a German-American named Franz Lieber who had fought in the Battle of Waterloo when he was fighting with the Prussian Army. Lieber ended up as an academic and eventually was a professor at Columbia. \n\nAnyway, him and several other guys got together and came up with this code. It addresses several things that would later be incorporated in The Hague Conventions and Geneva Conventions.\n\nIt's starting point is that the means must be justified and codified so that soldiers don't end up making terrible choices in the fog of war. You have to begin with the end in mind and that your goals in war must be reflected in your conduct. It explicitly banned a few things. Here are a few:\n\n1. You can't kill POWs.\n\n2. Torture can't be used to get a confession.\n\n3.Poison can't be used.\n\nThat's just some, but you can see how those became part of later war conventions. Lieber also differentiated between POWs and Guerilla fighters. POWs needed to have uniforms, a command structure, and a capacity to hold other POWs. Without that, the Guerilla fighters would be executed, though Lieber didn't really endorse that. But similar rules made it into The Hague Conventions and Geneva Conventions.\n\nThe Lieber Conventions also outlined the treatment of occupied territories and the status of slaves, escaped slaves, and returned slaves. \n\nIt did a lot more than that, but that's just the basics. The Code wasn't really put into that much use during the Civil War as some Union generals and Confederates didn't really consult it. It's importance became more evident when the Europeans adopted quite a bit of it later and it worked it's way into future conventions and whatnot.",
"I second /u/GregPatrick: the law of war has developed many times in many different places, such that there are many ways to answer this question depending on which culture and era you highlight. One thread you might take a look at is [this discussion](_URL_1_), about nine months ago, about \"just war\" theory and \"illegal wars\" in Roman history, especially towards the end of the Republic. In brief, Roman tradition held that certain rites be followed before a war could be lawfully commenced. But these \"rules\" were mostly honored in the breach. This of course is about \"just war\" theory, which overlaps with but is not the same as \"war crime\" theory. \n\nFor _war crimes_, consider this thread that [expands upon](_URL_0_) GregPatrick's comments about the Lieber Code and the Geneva Convention. \n\nAn interesting topic that someone with WW2 flair might discuss in greater depth is the public idea of war crimes, and how those ideas evolve during actual war. For example, there's a [recent Radiolab episode](_URL_2_) about American public opinion of war crimes during World War II. And I believe there's also some controvery, for example, about whether Churchill was prepared to use mustard gas in the event of a German landing. Since that is outside my specialty, I pose it only as a recommendation for someone to follow-up on if they want. ",
"The first line of thinkers in this tradition exist within the Roman and Greek society. Cicero, Plato and Aristotle wrote about the moral issues facing leaders and soldiers when they go to war. \n\nA lot of it also comes from the Christian Tradition of Just War. Important first authors on the tradition were St.Augustinus and Thomas Aquinas.\n\nIt was thought out to find a balance between warfare and the christian pacifist origins.\n\nThe first important secular thinker on just war and the 'laws of war' was Grotius. He also wrote a lot about international lawmaking.\n\nOutside the Christian tradition there are a lot of other examples of 'laws of war'. \n\nSun Tzu for example stated that a general should treat is prisoners wel. This was more out of a pragamtic vision since Sun Tzu saw it as a way to gain more manpower. More important here are Mo Tzu and Mencius who wrote about the injustices facing people and the necessity at times of taking up arms. \n\nIn Indian society there are discussions to be found about ethics of war in The Laws of Manu and The Bhagavad Gita.\n\nAnother example from the Talmudic law from the 12th century involves sieges. It said that the besieger should leave space open from the siege so the civilians could flee from the city.\n\nAs you can see the laws of war developed separate in every society. So im not so sure how they did develop, but i would think that a lot comes down to religious authors.\n\nsource: Moral Constraints on war\n\nif anybody has any questions on just war theory ask away. I just wrote a casestudy for my thesis using just war theory."
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5uykvx | What evolutionary pressure is there for people with good looking faces? | Why are some faces considered attractive? Why are people with certain faces more likely to survive? | askscience | https://www.reddit.com/r/askscience/comments/5uykvx/what_evolutionary_pressure_is_there_for_people/ | {
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"One theory is that more symmetric (but not perfectly symmetric) faces are seen as more attractive because asymmetric faces may indicate some prior injury or disease. For example, [Moller (1992)](_URL_4_) ( < - pdf!) suggests that parasitic infection leads to increased asymmetry. Body and facial symmetry may therefore also be a marker of genetic quality because it reflects ability to stave off disease. For reviews see [Thornhill and Gangestad (1999)](_URL_1_) ( < - pdf!), [Zaidel, Aarde, and Baig (2005)](_URL_0_) ( < - pdf!) and [Moller and Thornhill (1998)](_URL_2_) ( < - pdf!). In the last article they review findings of facial symmetry preference in some insects and birds as well.\n\nIn male faces, cheekbone visibility also seems to be important, perhaps as a cue to symmetry ([Scheib, Gangestad, and Thornhill 1999](_URL_3_)).\n\nSee the introduction of [Perret et al. (1999)](_URL_5_) ( < - pdf!) for a number of other citations on facial symmetry preference. ",
"Those traits don't **necessarily** make people more likely to survive, just more likely to reproduce-- which is still an evolutionary advantage. Reproductive advantages don't always align with what's \"best for the species\". For example-- why do moose grow big antlers and fight over mates?\n\nYou could argue that the offspring will be larger and stronger, which is good for their survival and the species. But this isn't an in-debatable truth. The reality is that the fighting moose get to mate because they win the fights, and the next generation will be better fighters as well because they got genes from the parents that won the fights. Is it really \"worth\" spending all that effort growing antlers? Maybe it wouldn't be, but the circumstances of moose genetics and \"society\" favor it. ",
"Might be worth mentioning that natural selection and sexual selection are two distinct concepts in evolutionary biology. It's probably safe to say that most of the time, sexual selection is closely related to natural selection, in that sexually appealing characteristics directly reflect fitness and health. But some sexually appealing characteristics can actually harm an animal's chances of survival, such as in the case of certain birds with unnecessarily long tails. These absurdly long tails don't aid them in flight in any way that we know of, and they are more likely to be caught by predators. But females prefer the longer tailed males, presumably because they were able to make it to sexual maturity in spite of their handicap. Personally, I suspect that sometimes desirable traits are uselessly exaggerated because they've been selected for so many times. \n\nSo basically, a lot of what makes a person attractive is just a direct display of their fitness level, and it means something to us on a subconscious level. But there are other characteristics that in no conceivable way relate to survivability, or might even harm out chances of survival, and it is of course a lot more difficult for us to pin down why we find such traits desirable. "
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"http://invibe.net/biblio_database_dyva/woda/data/att/c264.file.08484.pdf",
"https://www.researchgate.net/profile/Randy_Thornhill/publication/23276452_Bilateral_Symmetry_and_Sexual_Selection_A_Meta-Analysis/links/0c960526ac8a9d19b5000000.pdf",
"http://rspb.royalsocietypublishing.org/content/266/1431/1913.short",
"http://onlinelibrary.wiley.com/doi/10.1046/j.1420-9101.1992.5040691.x/pdf",
"https://pdfs.semanticscholar.org/380e/533a545a83b75c0c8d9c81f0b9a9c8563da5.pdf"
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4fn5fi | why the saudi government would have backed an attack on the us? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4fn5fi/eli5_why_the_saudi_government_would_have_backed/ | {
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"In a word, Wahabbism. That's the ultra-conservative sect of Sunni Islam that preaches seriously strict interpretations of the Quran, and intolerance for anybody or anything that isn't them. It has been the religion of the top members of the Saudi royal family for some time now, and since the 1960s or so, it's been spreading throughout Saudi Arabia, Egypt, and other places. \n\nGoing all the way back to the early days after 9/11, there have been persistent, troubling signs that either prominent members of the Saudi government--or even the government itself--have been actively supporting anti-US terror groups because of their Wahabbist beliefs. \n\nShortly after 9/11, when US intelligence officers were working with their Saudi counterparts, they were rather startled to find that a lot of the Saudi security guys had Osama bin Laden screen savers on their office computers.\n\nEarly on, a top Al Qaeda guy was captured, and a commercial-level bank card from a leading Saudi bank was found on him. This was unprecedented, no terrorist before or since has been caught with such a thing. The CIA peed itself like an excited puppy and said, \"wow! This is really significant, it could help us bust open their entire finance network!\"\n\nSo they stuck it in a file and ignored it for several years.\n\nWhen they pulled it out some time later, and sent in an agent to make some discreet inquiries, they found that shortly after the AQ guy was captured, members of the Saudi state security came into the bank and made every record of the card disappear.\n\nAnd after all this and more, the official position of the US is to stick its fingers in its ears and go, LA LA LA. I can't heeearrrr youuuuuu!\"\n\n",
"To placate the fucking retarded clergy that brainwashes the population to prevent it from revolting against the royalty.",
"I think it's important to note that the government per se did not back 9/11, but that some people IN the government may have. That's a pretty significant distinction.\n\nEdit to add that the Pakistani government is far more guilty of this sort of thing than Saudi Arabia.",
"The government wouldn't have. People in the government very well could have, because by-and-large outside of the actual very tip-top of the royal family the folks who make up the government don't like the united states very much. Saudi Arabia is actually one of the most conservative, if not the most conservative/extreme Islamic government in the world. The US and Saudi governments are only on good terms because we give them TONNES of money to keep down their population and dominate their region militarily and they sell us bunches of oil.",
"They don't. Some members of the Saudi government probably have funded them, but the Saudi government has not directly funded terror attacks.\n\nIf Obama punched your dad, it does not mean that the American government punched your dad. It means an individual has punched your dad. It is highly embarrassing for the government because of Obama's actions and you may want to sue him and/or the state, but it does not mean the U.S. government is acting against him!",
"The ruling Saudi royal family are followers of a very dogmatic religious sect ([Wahhabism](_URL_0_)). A chief complaint of these folks is the presence of foreign (American) bases in the holy land (Saudi Arabia contains Mecca, Islam's most holy city). Herein lies some ambivalence. They want us out, but they also wanted us in to protect them from Saddam Hussein. He's gone now, but Iran which favors a competing version of Islam remains a worry.",
"There is a view (read Machiavelli) that causing problems for the powerful is something that the less powerful should do to ensure that the powerful are distracted.\n\nIn this case, by \"encouraging\" the 9/11 attacks the Saudis would (1) disrupt the US, (2) drive the US closer to the kingdom, and (3) get rid of Saddam Hussein, someone who made everyone in the region nervous. If they were lucky, there'd be some spillover into Iran as well.\n\nAs someone said, the royal family is large, and doesn't speak with one voice. There are lots of factions, just like in the Pakistani ISI. Given the Saudi history of financing everyone in the Middle East, it's not out of the question that a group of Saudis were financing the operation. They may not even have known what they were financing; maybe they were told that the strike was to be against Israel.\n\nThe truth, whatever that is, may never be known.",
"So the US would go to war and they could sell oil?",
"Saudi's could theoretically have wanted to involve the US military in dealing with their middle Eastern enemies. This included extremist, anti-royalty forces in Afghanistan. A good chess strategy typically involves letting your opponent believe they're making a decision for themselves.",
"Uggg....instead of spending billions or trillions on stupid wars, why can't we just wage economic war on the middle east. With a trillion dollars, I would hope that we could create alternatives to oil, which might lower the importance of the middle east, say a few thousand notches.\n\nOh, but then that might affect US oil companies too. \n\nNevermind-",
"The most basic answer? To draw the US into a war with Iraq. Cause the terror attack, misinform the government and make them take down your closest economic and business (oil) rival in the process.\n\n\n",
"Are you familiar with the Amish? The solitary group of Christians that live primarily in the north east US and shun outsiders. \n\nWahhabi Islam is what you get when you cross the Westborough Baptist Church and the Amish. Wahhabism is a cancer fueled by Western money that has been metastasizing in Saudi Arabi for decades. It is a diving force behind Sunni extremism around the world.\n\n*I'm going to use the Amish as a metaphor here. I love the Amish. I'm not overly concerned with any Amish seeing this and getting upset because...well...they don't use technology. Except during rumspringa, but that's another ELI5.*\n\nImagine the Amish had a penchant for violently opposing anyone who didn't live like them. They support very strict punishments for anyone who uses technology and permit harsh and sometimes violent punishment of women who do things like show their hair in public. Now imagine these Amish extremists had lots of money and influence within governments all along the East Coast. A few generations of families in important positions all over. Family is important, after all, and few groups have larger families than the Amish. These powerful and wealthy Amish families have influence with other old world religious groups as well, such as the Mennonites and Quakers. These families protect each other and close up around one another when threatened by outside groups. \n\nWithin these groups there are more extreme groups who want to force the entire world to live a romanticized pure lifestyle such as that lived by their ancestors. Some of the powerful elders in the community wish for this too. They see the evils being made available to the youth by outsiders from the West Coast in places like San Francisco, Hollywood and Las Vegas, and they see it as their religious duty to stop these threats. Using their religion as a shield of peace and purity they speak out against what they see as Satan's minions in schools they build in poor areas around the world...but that's just the top layer. Smoke and mirrors. What the elders really want is control and power like they had long ago before they turned in their swords for plows. They use these schools to indoctrinate illiterate youth to their version of faith and they use disenfranchised young men as weapons to strike against their enemies. They use the influence to spread their hateful message far and wide infecting other places the West Coast deals with. They cannot openly strike against the West Coast because it holds too much influence around the world, so instead they use the radical extremists within their remote communities and the youth in these poor countries as pawns in a terrible and bloody conflict.\n\nFortunately for them the government's of the West Coast are so connected to the goods and services provided by their Amish families many are willing to let some offenses and crimes go unpunished in the name of continued partnership. In other instances the Governments of the West and East Coasts team up to fight against a common adversary that threatens to interfere with the economic interests of the West Coast. Heck, the Amish wouldn't even exist like they do now if it weren't for a guy from Texas who knew he could make a fortune selling Amish goods around the world. The Amish could take advantage of these relationships. And they did. \n\nSome of the groups of elders provided money and support to the most extreme elements of their faith. These groups had been fighting smaller and easier groups they opposed in places the people who live in the West Coast didn't care about. They had built a worldwide network of groups that hated the West Coast and they financed terrorist training camps in those places. In some cases these enemies fight each other in proxy conflicts in far off places using third parties. Eventually, a few dudes with ties to senior members of the governments of the East Coast were able to get a bunch of hard core Amish believers together to strike a blow to the heart of what they saw as against god and good Amish values.\n\nNone of the senior Amish government officials can be directly linked to planning the attack that followed, of course, but the money trail is there. It's classified, because otherwise elements of the governments of the West Coast would be shown to have known those ties existed. Intelligence agencies knew something was coming, but so many things were all happening at once it was difficult to sort through, and the CIA and the NSA don't start wars independently or react to threats militarily no matter what that YouTube video you watched says. That's the job of the President and Congress. It wouldn't have mattered anyway though. Political will didn't exist to do anything of any value prior to the attack. An attack on the same location by the same group happened a dozen years earlier but nothing was done except to launch some cruise missiles against some of their training camps.\n\nIn the end everyone is responsible, but no one is accountable. It's all dark politics and dark money and dark power. A shadow game played at night where the winners get rich and the losers get dead. \n\ntl;dr There's a reason we have a wall of separation between church and state in the US. Now all we need to do is create a wall of separation between money and politics. Unfortunately, Islamic countries fueled by Western money don't have any walls. "
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c5h5el | why do some blood tests need to be done from a specific arm, when blood in the body circulates so quickly? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/c5h5el/eli5_why_do_some_blood_tests_need_to_be_done_from/ | {
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"They don't need to be done from a specific arm. The arm is usually just the easiest and most convenient way to draw blood with a minimal amount of fuss.",
"Blood tests don't need to come from a specific arm.\n\nIf you're having multiple draws performed, they may switch arms between the draws to reduce the amount of punctures in a single arm (though it's preferable to get all the necessary blood from a single draw). And if they're testing for an infection that could involve a diagnosis of sepsis, they'll draw from both arms to compare the two and see if the infection is system-wide. And it may just be that a person has veins that are easier to find and draw from in one arm.\n\nBut there are no blood tests that need to be from a specific arm. They don't even need to be from an arm at all.",
"ICU RN here, and I have no idea what you’re talking about. Outside of blood cultures (which need to be gathered from two separate sites), there’s no reason to specify which limb a blood draw comes from unless there’s a disease process/procedure that would lead to an increased risk for infection (things like radical mastectomies after breast cancer where lymph nodes are removed)."
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19f7zc | Does a lightning bolt or strike have a thickness? Or is it one electron thick? | A friend and I were wondering about this today. Does lightning have a thickness? Do we know? | askscience | http://www.reddit.com/r/askscience/comments/19f7zc/does_a_lightning_bolt_or_strike_have_a_thickness/ | {
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"It has a thickness.\n\nThe lightning bolt is a channel of hot ionized gas created through an electrical discharge. Depending on the discharge this channel can be tiny (e.g. piezo sparks) and typcial thickness in real lightnings is 1-4 cm\n\n_URL_0_"
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6gckhq | clean energy and electric cars are great and all, but crude is refined into many many other things. how are those other industries preparing for the day that there isn't enough oil in the world to meet demand? | Edit: Could be flaired as either economics, engineering, or chemistry... I couldn't decide. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6gckhq/eli5_clean_energy_and_electric_cars_are_great_and/ | {
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"There will always be enough oil to meet demand, thats the fun part about supply and demand.\n\nAs we deplete the easy oil reserves the price of oil will increase and we'll tap into the more expensive to drill reserves. As those run low, we'll tap into even more expensive reserves increasing the price more, and the cycle will continue.\n\nAt each stage, as the prices goes up it'll become more economical for companies to switch to other sources which reduces the demand for the oil and stretches the time of the reserves. Eventually the price gets crazy high so we only end up using a tiny amount of really hard to get to oil so it lasts forever\n\nWe'll never run out of oil, we'll just run out of reasonably priced oil",
"Clean energy and electric cars mean more oil is available for other purposes like making plastic. Even if we eventually run out of oil there's even more coal which could be used with some more effort. Or we could recycle existing plastics."
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2ysvh2 | did cocaine for the first time a couple of days ago. i was wondering how does cocaine get into your brain and how is it that it takes so little time. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2ysvh2/eli5_did_cocaine_for_the_first_time_a_couple_of/ | {
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"its water soluble. when you insuffilate it into your nose, the teeny tiny capillaries will absorb the drug directly into your blood stream. any mucous membrane in your body will do this (example: benzos that are sublingual dissolve under your tongue and are absorbed through the membrane into the little capillaries) as long as the substance is water soluble. you know it is water soluble if you can pretty much just ingest it without doing anything fancy, like infusing THC with a fatty substance in order to eat it because THC is fat soluble, not water soluble. ",
"Cocaine is water soluble meaning that it can be absorbed very easily into your body. It is also extremely easy to develop a dependency on it to the point where trying it once could get you hooked. Be wary.",
"As for the how it acts so fast, cocaine is water soluble and the mucous membranes of you sinuses will absorb it directly into your blood stream, little to no filter required. \n\nOn a related note, I once coughed a shot of Everclear into my sinuses and went from having no previous drinks to shithammered, incapacitated drunk in about 20 seconds, and it felt like my veins were on fire. 0/10 would not recommend."
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46wzp8 | what's the point of a gated community if they just open the gates at night? | At least in my area, there are many residential complexes/communities that are gated, but late at night they open the gates. Doesn't opening the gates like that defeat the whole point of having a gate in the first place? If it doesn't, then why not? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/46wzp8/eli5_whats_the_point_of_a_gated_community_if_they/ | {
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"I don't think they *normally* open the gates at night. I have a friend who lives in one of these and in his gated community they have on site security who patrol around, and the front gates are opened by a wireless key every resident has.\n\nFor things like Pizza there is a special code or something.\n\nInterestingly I believe I remember reading somewhere that crime rates are often higher in gated communities as all the valuables are gated into one convenient area... ",
"It still narrows the ways to get in and out (which could be more easily monitored by camera for instance), and particularly if there is a single entrance it prevents traffic from using the streets just to drive through. Fewer people driving by scoping out, the thought goes, the fewer chances for crimes of opportunity, burglary, etc",
"They normally open the gates during rush hour. Something like from 5pm to 7pm. This is to keep the gate area from getting congested by the large amount of people trying to get through the gates in that time frame. Imagine hundreds of cars each having to stop at the gate for 30 seconds to let the gate open. It would take people forever to get home."
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3tweyv | how do satellites communicate with thousands of individual devices at once? | If I'm carrying two GPS devices, each one is engaged in its own communications with a satellite (afaik). If all of the communications are wireless, I'm guessing they're broadcasted in every direction, so how are all of these communications routed (how does device A distinguish its communications from device B?) and are the satellites really processing all thousand requests at once? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3tweyv/eli5_how_do_satellites_communicate_with_thousands/ | {
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"Satellites are just big radio stations in the sky, its a one-way communication just like when you listen to the radio in your car, and everyone else on the radio does too. Your GPS is just a listening device, pretty much everything any consumer would ever use regarding satellites is just a listening device, you don't broadcast it back, you just hear the song playing on the radio",
" > How do satellites communicate with thousands of individual devices at once?\n\nSatellites don't communicate with any devices at all. GPS is a completely passive technology. Each satellite broadcasts its ID and a timestamp, like a sort of high-tech lighthouse. If you know where each satellite is (your GPS receiver has that data built in), and how far away each satellite is (your GPS receiver uses the delay between the timestamps sent out from each satellite to calculate the distance), then you can calculate your exact position.",
"GPS isn't a good example for this, because, as stated by others, GPS is a broadcast service that isn't dependent on devices being able to communicate with the satellites.\n\nHowever, there isn't anything stopping a communication device (including satellites) from engaging in two-way communication with multiple devices.\n\nIt can be handled a couple of ways. Basically, the communication device can use multiple frequencies, \"talking\" to a different device on each frequency, or the communication device can switch back and forth between talking to all the different devices very, very quickly.\n\nRadio is radio; your WiFi router at home can connect to more than one computer/smartphone/etc at a time.",
"GPS\n-\n\nWith GPS, as mentioned, it's a \"broadcast\" setup: there's no individual communication with devices, the satellite just broadcasts and your GPS device listens.\n\nOther radio communications\n-\n\nWhere there truly *are* multiple devices using the same communications system, we use a combination of several things\n\n1. Multiple channels/frequencies. In your home router you can choose which WiFi \"channel\" you use. Your router may have 2.4GHz and 5GHz bands, or \"MIMO\" (multiple in, multiple out) antennae. This means we are splitting our communication band into smaller bands. If we split our WiFi into 12 channels, we can have 12 different devices with no interference (in theory)\n\n2. Mutiplexing. There are a few techniques for this, which I won't go into, but the basics idea is to split your transmission between devices: eg if I have 10 devices, I might spend 1/10th of a second transmitting to/receiving from each device, each second. Over a whole minute, each device gets 6 seconds total. This is called **Time Division Mutiplexing** and there are lots of different approaches. There are other techniques for multiplexing, such as Frequency Multiplexing, which are used more rarely.\n\nSatellites do the exact same things, usually at the same time: they will use several frequencies and multiplex on those frequencies. This is one of the reasons satellite communication is slower than most other communication: because lots of people are sharing one satellite."
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8tdnc1 | Why did medieval european chroniclers and clerks write in intricate and flourished calligraphy? | Hi everybody,
So I’ve been studying english medieval history in the twelfth and thirteenth century. Looking at say for example a genuine copy of a royal writ, or magna carta and then a digital transcript of the same latin. I can not discern any of the words from the calligraphy. Was this intentional? Is this just my modern ignorance? Or did the literate person of the day simply learn throughout their whole life that that was how letters were written. Moreover, is anybody aware of when we started to transition to clearer fonts like on a computer or in handwriting? Thanks and sorry for any incoherence!
Examples:
_URL_0_
_URL_1_ | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/8tdnc1/why_did_medieval_european_chroniclers_and_clerks/ | {
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" > I can not discern any of the words from the calligraphy. Was this intentional? Is this just my modern ignorance? Or did the literate person of the day simply learn throughout their whole life that that was how letters were written.\n\nI had to do paleography during my PhD, and this kind of text *is* readable, it just takes an awful lot of practice to get used to. The added complication to modern eyes are the added abbreviations and contractions to the Latin thrown in by the scribes which make it all the harder to discern what letters logically follow on. To scribes trained in this script from an early age, the style would be far more readily recognisable."
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"https://images.google.co.uk/imgres?imgurl=https%3A%2F%2Ferenow.com%2Fpostclassical%2Ftheplantagenetsthekingswhomadeengland%2Ftheplantagenetsthekingswhomadeengland.files%2Fimage011.jpg&imgrefurl=https%3A%2F%2Ferenow.com%2Fpostclassical%2Ftheplantagenetsthekingswhomadeengland%2F89.html&docid=EPPjbQgD770VIM&tbnid=50uRxj6yiq7DkM%3A&vet=1&w=980&h=606&hl=en-gb&source=sh%2Fx%2Fim",
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2dog47 | Are there any uncommon forms of bacteria or an organism that once enters your body, increases physiologically functioning rather than cause disease? | I already know about the existence of "good" bacteria throughout your body, but are there any uncommon contractible organisms or bacteria that enhance functioning? | askscience | http://www.reddit.com/r/askscience/comments/2dog47/are_there_any_uncommon_forms_of_bacteria_or_an/ | {
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"I cant find the link. But there are indeed bacteria that help in increasing metabolic functions there are studies that even show that there is a correlation between amount of a specific bacteria and Kwarishokers or Krohns disease but trick is finding which caused which. Some bacteria help prevent harmful bacteria to be colonized in the gut like C.difficle, its one of the reasons why fecal transplants are becoming more popular. Overall, yes your microbiome is a very important aspect of your body and the bacteria in your body outnumber the cells in your body 10:1"
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429cep | Relative (adjusted) cost of paper in 17th century England? | So I was watching this documentary on the history of the Calculus, and this fellow was reading from Liebniz' and Newton's respective notebooks, and I was noticing the impossibly small size of their script relative to my ponderously wasteful use of scratch paper. This got me to wondering what the cost of paper would have been back then, and also what folks would have used to work out their problems as they went. Chalkboards?
Thanks. | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/429cep/relative_adjusted_cost_of_paper_in_17th_century/ | {
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"In the incunable age, i.e. from the inventing of the printing press to ca. 1500, a book printed on paper without a binding sold (in Venice) for a price approximately equivalent to the daily salary of a skilled laborer, so say $100-200 modern dollars. Napkin math: 300 page text gives us somewhere between 20 to 75 sheets of paper (depending of how it was folded, octo to bifilium). Let's say the price is for a quarto, so each sheet becomes 4 leaves or 8 pages, which means we need 38 (large) pieces of paper to make our book. Splitting the difference on the price gives about $150 for the book, and if we guesstimate 20% of that is from materials, that gives us $30 modern dollars for those 38 pages, or just under $0.80 a sheet. \n\nThis is pretty cheap, and substantially cheaper than parchment. It gives us a useful baseline to talk about the cost of material and labor, but we must also realize there was a wide range of prices for materials across time and space. Paper costs mostly depended on the prevalence of linen clothing. Tree-fiber paper would wait until the 19th century. Before this, paper was made from linen rags, and thus the cost of paper were tied to their availability. If you lived somewhere where people wore a lot of wool, you'd probably pay more for paper.\n\nHowever, for both parchment and paper, the cost of materials was not usually a factor that dictated script size. Despite the high cost of vellum, medieval manuscripts had very wide margins (though they are often now found trimmed). Although helpful for note-taking, this was an aesthetic choice. Scribal abbreviations certainly shortened the overall length of a text, but they were designed to save the scribe's hand, not material cost. Even parchment manuscripts produced under the *pescia* system in medieval Paris - essentially medieval textbooks - do not show concern for wasted space, though they might use lesser quality materials. \n\nBasically, if you knew how to write, you were almost certainly wealthy enough that the cost of materials was not a particular problem. \n\nFor scratch, sometimes people used the margins of books, sometimes they used chalk, and sometimes they used wax spread over wood. "
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2p27bv | why can large files like video games be stored and used on a single disc while presumably much smaller things like seasons of shows take multiple discs | just thinking, after buying all of A:TLA | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2p27bv/eli5why_can_large_files_like_video_games_be/ | {
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"Because shows aren't small. A good quality video can easily push over a gig per hour of play, plus the menus and extras and commentary and all the other useless shit, those discs fill up fast. ",
"I don't think the other answers capture the main difference at all.\n\nIn a recording of a TV show or movie, what the disc is storing is every single frame of video, at 30 fps. That adds up fast.\n\nIn a video game, every frame you see is dynamically rendered in 3-D. The data to generate each character, each building, etc. may be large - but it doesn't take any extra disk space to redraw those characters in each new position, from every angle - that's all rendered on the fly.\n",
"You could actually fit more than 3 episodes of Seinfeld on a DVD if you wanted - they can easily take a full 4 hours of video.\n\nIt's just that the companies selling the DVDs would rather place them on more discs so that customers don't feel like they're getting ripped off spending $60 on content that had already aired on TV for free.\n\nYou also need to consider that DVD compression is going to be *far* less efficient than the compression you're used to seeing if you download shows from pirate sites. Pirates are using modern video codecs that expect to have powerful CPUs to play them back. The video compression in the DVD standard is based on the capabilities of 1995-era embedded processors. 20 years of improvements in CPU power & algorithms makes a big difference."
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56itpu | how does akinator and other genie games really operate? i get it's based on narrowing it down but it has guessed obscure characters in less than ten questions. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/56itpu/eli5_how_does_akinator_and_other_genie_games/ | {
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"It has a large database of characters and answers that are true for them (contributed by users of the website) and by asking questions that roughly split the possible characters into equal groups (50/50 split), means that it only takes ten questions to narrow down 1024 into one character and twenty questions to narrow down from 1048576 characters to one character."
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4cl6yc | How progressive and democratic were pirates, really? | Its my understanding that pirate ships were democratic enterprises were captains and undertakings were voted on, and women and black men were welcomed as equals. This sounds wonderful, is it true? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/4cl6yc/how_progressive_and_democratic_were_pirates_really/ | {
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"This is a huge question and the answer to it formed a large part of my [doctoral thesis](_URL_0_), particularly chapter 2.\n\nIn legitimate early-modern seafaring there existed two distinct chains of command: within the ship (the *internal* chain) the captain held sway, with command passing down through the ship's officers; but in almost every instance there also existed a higher chain of command outside the ship (the *external* chain), consisting of the vessel's owners, in the case of merchant or privateer ships, or the in the case of Navy ships, the higher chain of commodores and Admirals, extending ultimately to the government and the monarch via the Lords of the Admiralty.\n\nHowever, pirate ships faced the problem of not having any form of external command to direct things like the appointment of officers or the course of actions the ship took. De facto ownership of the pirate ship fell to the crew themselves, effectively placing the *external* command hierarchy uniquely within the confines of the ship. This created an intriguing dichotomy whereby the captain held command over the crew on *internal* matters, but was subservient to the crew on *external* matters. Or, put a different way, as members of the crew the rank-and-file pirates were at the bottom of the chain of command, but as de facto owners of the vessel they were *also* at the top of the chain.\n\nSo, for example, the crew might choose the captain of their ship in their position as owners, just as the owners of a legitimate vessel would, but having chosen him generally had to obey his commands in their position as crew, just as the crew of a legitimate vessel would.\n\nThus, on the face of it, pirate crews appeared to be highly democratic.\n\n**But here's the kicker**. On very few pirate vessels were the *entire* crew considered to be owners.\n\nMuch has been made of the clause in Bartholomew Roberts' articles that states '*Every man shall have a vote in affairs of the moment*', but of all the surviving articles Roberts' is the *only* one to contain such a clause, and there is strong evidence that 'every man' did not actually include *every* man bound by the articles. Roberts' company included a large number of slaves, a few boys, and a number of forced conscripts, none of whom were probably allowed to vote. Former soldiers in the company were looked down upon and only given a quarter share in any proceeds, which, while not evidence that they couldn't vote, does suggest that not all men were equal. Thomas Davis, a forced man in Bellamy's company, gave evidence at trial that sheds light on the extent of the franchise in practice:\n\n > When the company was called together to Consuls, and each Man to give his Vote, they would not allow the forced men to have a Vote. There were one hundred and thirty forced Men in all, and Eighty of the Old company; and this examinate being a forced Man had no opportunity to discover his Mind.\n\nThat is to say, only 38% of Bellamy's company had the right to vote. In colonial Massachusetts the right to vote was extended to anywhere between 28.4% and 77.6% of the adult male population, so pirate companies begin to look less and less like beacons of democracy. On p. 132 of my thesis (linked above) there is a table showing the extent of the franchise in 14 pirates companies, 1704-1724, in which the number of voters ranges from 18-87%, in an analysis which is likely to overestimate the number of voters rather than underestimate.\n\nIn some companies, like John Gow's, there is no evidence of any formal voting taking place at all. John Philips was described as 'so arbitrary as to be hated by his own crew,' and one of Gow's articles states,\n\n > That every Man shall obey his Commander in all Respects, as if the Ship was his own, and we under Monthly Pay\n\nPerhaps one of the biggest issues is that even when a vote was taken, there was no guarantee that it would be adhered to. For example, the company of a pirate ship commanded by William Mason in the Atlantic voted on whether to sail East for the Indian Ocean or West for the Pacific. The officers all voted for the East and the men (the larger party) voted West, but since everyone capable of navigating had voted for the East, that was the course they took.\n\nThe status of both women and black men on pirate ships of the 'golden age' could easily fill a whole post each: here's the short version. Only four women are known to have been members of pirate companies in the period, and while three of them seem to have been more or less 'equal', that's a statistically insignificant number. The status of black men varied enormously: those who were useful and spoke English might well become free members of the company, though I've yet to find an example of a black man receiving a share of the profit; the rest were generally treated as slaves, to be put to work on the arduous tasks like pumping or sold for profit."
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l1ag3 | iambic pentameter | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/l1ag3/eli5_iambic_pentameter/ | {
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"When we speak, there's usually a natural rhythm to how we say the words. Some syllables get more emphasis and some get less.\n\nAn *iamb* is just a non-emphasized syllable followed by an emphasized syllable.\n\nFor example, say the sentence \"I ate the food\" out loud. If you speak like most English speakers, you put the emphasis on the words \"ate\" and \"food\" -- those words are a little louder than \"I\" and \"the\" in that sentence. So that sentence is actually two iambs in a row!\n\nIambic pentameter is a pattern (or a *meter*) used when writing poetry. Each line of a poem written in iambic pentameter is made of five (that's where the \"penta-\" comes in) iambs in a row. Like, \"I **ate** the **food** out**side** my **school** to**day**.\" (MSchmahl's example)\n\nThe other kind of 2-syllable patterns are a *trochee* (an emphasized syllable followed by a non-emphasized syllable), a *spondee* (two emphasized syllables in a row), and a *pyrrhus* (two non-emphasized syllables in a row).\n\nThere are other meters, but iambic pentameter just happens to be fairly easy to write and sounds pleasant to us so it's common.\n\nNext time you read or listen to a poem, try figuring out whether it's in iambic pentameter!\n\n[Edit: corrected example]",
"I never understood this concept at all before this ELI -- thanks everyone! Upvotes for all, on the house!",
"When we speak, there's usually a natural rhythm to how we say the words. Some syllables get more emphasis and some get less.\n\nAn *iamb* is just a non-emphasized syllable followed by an emphasized syllable.\n\nFor example, say the sentence \"I ate the food\" out loud. If you speak like most English speakers, you put the emphasis on the words \"ate\" and \"food\" -- those words are a little louder than \"I\" and \"the\" in that sentence. So that sentence is actually two iambs in a row!\n\nIambic pentameter is a pattern (or a *meter*) used when writing poetry. Each line of a poem written in iambic pentameter is made of five (that's where the \"penta-\" comes in) iambs in a row. Like, \"I **ate** the **food** out**side** my **school** to**day**.\" (MSchmahl's example)\n\nThe other kind of 2-syllable patterns are a *trochee* (an emphasized syllable followed by a non-emphasized syllable), a *spondee* (two emphasized syllables in a row), and a *pyrrhus* (two non-emphasized syllables in a row).\n\nThere are other meters, but iambic pentameter just happens to be fairly easy to write and sounds pleasant to us so it's common.\n\nNext time you read or listen to a poem, try figuring out whether it's in iambic pentameter!\n\n[Edit: corrected example]",
"I never understood this concept at all before this ELI -- thanks everyone! Upvotes for all, on the house!"
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4jen2z | Has a presidential candidate ever selected a Vice President from a different party? | This is not intended to be a political discussion, I'm just genuinely curious.
| AskHistorians | https://www.reddit.com/r/AskHistorians/comments/4jen2z/has_a_presidential_candidate_ever_selected_a_vice/ | {
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"The only one I can recall off the top of my head is when Lincoln (Republican) chose Andrew Johnson (Democrat). Johnson was a Democrat who supported the war effort. Other folks will likely give more detailed responses, and other possible cross-party tickets. "
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11n8w2 | If a hotter object has higher average energy and emit more light, where do LEDs, for instance, fit in? | I watched this video: _URL_0_
I found it quite interesting. Planks constant gets me though. What I don't get though is with LED's for instance. They have a higher efficiency and emit more light than incandescent lights, as they give of less heat (I thought wasted energy). But if heat = higher energy = bigger packets of light, then why are LEDs so cold, yet so bright?
I think I am confusing Frequencies, Energy and Temperature. Could someone kindly break this down for me?
PS: Are packets another term for Photons at different energy levels? | askscience | http://www.reddit.com/r/askscience/comments/11n8w2/if_a_hotter_object_has_higher_average_energy_and/ | {
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"Black body is a continuous emission of energy based on heat. But things like LEDs are materials that allow for specific transitions between energy levels for electrons. And as the electrons drop between those levels they emit specific (or at least a fairly small band around a specific) frequency of light.\n\nDifferent mechanisms doing different things.",
"LEDs operate in a completely different way from incandescent bulbs. Lightbulbs, as you said, work via blackbody radiation-- the hotter they are, the more power they output, and the higher the frequency-peak is. \n\nLEDs work by making electrons fall from high-energy states to low-energy states; when this happens, a photon is emitted that makes up the energy difference. If you use the right semiconductor material, this is a very efficient process, and very little energy is transferred to the material in the form of heat."
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eqb21y | why does everyone here hate emojis so much, when they seem to be proliferating on all other platforms? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/eqb21y/eli5_why_does_everyone_here_hate_emojis_so_much/ | {
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"Reddit has an entirely unique culture compared to most other popular platforms, which gains it popularity with some and hatred with others, the ELI5 answer is that emojis are seen as a lesser form of meme on reddit. \n\nReddit culture is fairly conservative with memes, preferring lennys and simple \":)\" to emojis."
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26dxe8 | Why did Dutch become a separate language but Swiss German didn't? | I have a feeling the answer has more to do with the history of the two countries than with any linguistic reason, so that's why I'm posting my question here instead of Asklinguistics.
As far as I know, both are just as incomprehensible to a standard German speaker and both are spoken in different countries, so why did the Dutch decide to call their dialect a separate language, but the Swiss didn't? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/26dxe8/why_did_dutch_become_a_separate_language_but/ | {
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"I am afraid the reason is linguistic. According to [Pijnenburg](_URL_0_) (pdf in dutch, the second chapter) the reason why Dutch diverted from German is twofold, the [high German consonant shift](_URL_1_) didn't happen in dutch and the dutch dialectcontinuum was influenced by oldfrankish. High german did follow the consonant shift and low german was influenced by oldsaxon, not oldfrankish.\nFor knowledgeable comments I advise you to post this question in /r/asklinguistics.\n\nOf course history does have something to do with how the languageborders are determined, an interesting remark by Pijnenburg was the influence the administration of the bishopric of Utrecht had on the language of especially the current province of Overijssel, since Utrecht (in the frankish dialectcontinuum) ruled that area, then called Oversticht. Utrecht's civil servants wrote in middledutch, while the area was part of the lowergerman dialectcontinuum. The local Overijssel dialects are still called nedersaksisch, lowersaxon."
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1gsk7w | What are your opinions on Hagarism and Patricia Crone's work? | Specifically, I'm asking for /r/AskHistorians opinions on *Hagarism: The Making of the Islamic World* and *Meccan Trade and the Rise of Islam,* both by Patricia Crone, and Hagarism in general. So, thoughts? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1gsk7w/what_are_your_opinions_on_hagarism_and_patricia/ | {
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"Crone wrote Hagarism when she was a grad student, which was extremely gutsy since the book essentially refuted the whole of Islamic studies at that period. Crone herself has repudiated the book's central premise but it is still very important and useful. Crone advocated that we should not trust Islamic sources from the 9th, 10th, and 11th centuries to tell us the reality of what happened in the 8th or 7th centuries since later adherents of Islam might want to legitimize the accepted practices of their time or change history to accommodate political and social behaviors. In that sense, her work is very valuable in its analysis and study of the contemporaries of Islam, and the few Arab sources we have as well. We ought to look at what Islam's neighbors were saying about Islam but also realize that many of them deliberately misunderstood or misinterpreted Islam as well (Byzantines purposefully mistranslated the Arabic phrase 'Allah u Akbar' to mean 'praise Aphrodite').\n\n\n\n"
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15ceiz | Did the stranglehold the Soviet Union had on Eastern Europe hinder its ability to compete economically with the Western nations today, or are their economic shortcomings merely a result of a historically unstable region? (X-post, was told to post here) | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/15ceiz/did_the_stranglehold_the_soviet_union_had_on/ | {
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"Very interesting question. I have always wondered this and assumed it was because of no capitalism for 45 years. While talking about something else, on of my history profs did mention that the Balkans has always been and economically depressed place. They were under the Ottoman Empire, so were not very open to new technologies and ideas and they had very simple economies. They didn't have the openness and market driven economies of the Western European nations. But that would only apply to some of the Communist countries.",
"First, Eastern Europe is huge. Although there's no consistent definition, it's quite a bit larger than Western Europe. So when you refer to it as a \"historically unstable region,\" it's not clear which part you mean. It's not at all clear to me that Eastern Europe is any more historically unstable than Western Europe. \n\nI'd like to answer your question, but I also need to know what \"economic shortcomings\" means. Are we measuring GDP? Economic growth? Resiliency against the '08 crisis? Are we going to compare Eastern European nations with Germany? Or are we going to compare them with Greece and Spain? Are we going to normalize the results by economic status in 1990, or should we not take that into account?\n\nIn order to have a reasonable discussion, some of these terms need to be specified. Without any more information, I'll say that yes, communism had a negative effect on economic development both during the communist-era and the post-communist period, and that, generally speaking, lack of stability affects all national economies, in Eastern and in Western Europe and everywhere else. So I suppose the answer is both. I reject the term \"hinder ability to compete economically\" - by definition every country economically competes with every other country. Eastern European nations are however, on average, less economically developed than those in Western Europe, for an entire wealth of reasons.\n\n",
"Just to contribute pure anecdotal evidence, if you go to some of the great cities of Eastern Europe - Prague, Budapest, Bucharest, Warsaw, etc, especially the ones that weren't too badly damaged by WWII - you will find some stunning architecture (often imperial) that matches anything you can find in the great cities of Western Europe. Budapest, for instance, has the incredibly gorgeous Parliament building and a number of impressive cathedrals. Though they may not have had the empires Western Europe had, they certainly were capable of shining on their own right. \n\nThat (almost) everything after WWII and the advent of communism does not quite match up suggests to me that Eastern Europe can't be said to be behind because of any inherent property of the region (which is, as other commenters have posted, loosely defined in any case). It's far more likely that it's the result of stifled economic, political, and social growth from totalitarian policies of the regimes there.",
"increasecapacity is certainly right, that the question lumps countries and regions of a very broad range together, which all have their different histories and conditions. It's also not clear, what \"historically unstable\" means in this context.\n\nHaving said that, it is true that Eastern Europe, whether we're talking about the Balkans, Eastern Central Europe or easternmost Europe, was economically behind in comparison to Western Europe even before the advent of communism. But there were large differences even between those nations, which would become part of the eastern bloc. There were worlds in between Romania and Poland for example and they still are today."
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fdgedc | what is the precise biological mechanism that leads to teething | I have a very painful wisdom teething right now and I want to know why my body thinks it’s a good idea to grow teeth even though there is no space left for new ones. Also, why does it grow in short bursts over several months instead of all at once ? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/fdgedc/eli5_what_is_the_precise_biological_mechanism/ | {
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"Evolution. The human jaw used to be more than large enough to hold all those teeth, but as our jaw size shrank, things got crowded. I've had all four of my wisdom teeth pulled, as well as four other molars and four bicuspids. Only 20 teeth in my mouth, but they fill all of the available space."
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s43uu | Are we "smarter" than our ancestors or is this an artefact of bias towards the current zeitgiest? | I suppose I would like an answer from a cultural anthropologist or science historian but any input is welcome. It seems that the great discoveries of the past (talking 150+ years ago) took a long time to arrive at and were mindblowing while now they seem to happen on a weekly basis and are almost casually accepted. Have we culturally evolved into "smarter" humans (i.e. more willing to accept a plausible scientific memetic) or is it just a function of time (exponentially increasing discoveries based on increasing previous discoveries)? This question may be a bit too classically philosophical for this subreddit but I suspect that a scientist will have a more profound explanation than a philosopher. | askscience | http://www.reddit.com/r/askscience/comments/s43uu/are_we_smarter_than_our_ancestors_or_is_this_an/ | {
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"You partly touched on your answer - its not that were smarter, and in any case its notoriously hard to define 'smartness' or 'intelligence'. Its that we are the result of an accumulation of knowledge. The general consensus is that while other animals have culture (learning, customs, traditions etc.) that are past down from one generation to the next there isn't always an accumulation of traditions or knowledge or at least its very hard for these traditions to accumulate. In some primates accumulation of traditions or culture has been shown but its still unclear why it is not to the same extent as we see in ourselves. \n\nWhereas in humans it appears we have the ability to do this on much larger scales - we are able to individually and collectively store more knowledge. Scientist sometimes refer to this as 'cumulative culture' [This may offer you some more explanation](_URL_1_) although the source is not great - it gets to the point. Anatomically modern humans have been around for about 200,000 years, but around ~60,000 years ago we appeared to have gone through a 'cultural revolution' - art, artifacts, tools become more elaborate, intricate and symbolized. \"By the beginning of the [Upper Paleolithic](_URL_0_) period (50,000 BP), full behavioral modernity, including language, music and other cultural universals had developed.\" Its not entirely clear what caused this, in any case it looks like if you picked a random human from that time they should be able to do anything we do now - they would be able to understand math, biology, physics, economics, learn languages etc. if they were taught (just as we are taught).\n\nI have to counter argue that we really have only begun to scratch the surface of what animals are capable of, and our methods of testing and assessing their intelligence, cultural capabilities and other soci-cognitive skills are really improving. In the end we are finding out that animals can do plenty of things we can so far we just appear better at some things - like cumulative culture."
]
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[
"http://en.wikipedia.org/wiki/Upper_Paleolithic",
"http://scienceworld-frontiers.blogspot.ca/2012/03/cultural-ratchet-present-in-humans.html"
]
] |
|
yd33h | How effective would strapping dry ice to a fan be at cooling down an area? | And, also, would the CO2 kill me? | askscience | http://www.reddit.com/r/askscience/comments/yd33h/how_effective_would_strapping_dry_ice_to_a_fan_be/ | {
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"Air conditioners work so well because they take all of the heat from the air and put it outside. You need to put a lot of work into the system(the room you're in) in order to remove all the energy that is in the room with you(the hot air). Dry ice strapped to a fan would give you a nice cool breeze if you were standing right in front of it, but there isn't enough energy stored in the dry ice to cool down the entire room. If you did have enough dry ice to cool the room down you'd be better off spending your money on a small window A/C unit. \n\n Also, you'd be okay with very small quantities of dry ice, but for the quantity you'd need to cool an entire room, you would need a good ventilation system, which would in turn require you to get more dry ice.",
"Building off of McDirty20, the latent heat of sublimation of dry ice is 246 BTU/lb, so in that transition from solid to gas, 1 lb of dry ice has 246Btu's of cooling capacity (EDIT: this is assuming dry ice sublimates at 1 lb/hr, which may be an incorrect assumption). A typical window A/C unit has about 12000Btu's/hr capacity.\n\nSo you'd need about 48lbs of dry ice every hour to match the cooling capacity of a window A/C... at around $1.00/lb, that'll get really expensive really fast. "
]
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[],
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|
1c1wfn | What was life really like in Japanese-occupied Taiwan and Korea? How did they differ? | Disclaimer: I am from Vietnam. Everything I write here is what I have learned from history lessons and Chinese sources. Please do not take offence at any inaccuracies - they are what I am here to correct.
Hello Historians,
I am confused regarding the Japanese occupation of both Korea and Taiwan.
For the longest time, I've been under the impression that Japanese occupation of these two places was relatively benevolent:
* The Imperial government devoted vast amounts of capital to develop their economies.
* Their people were given largely the same rights as Japanese in the home islands.
* Koreans and Taiwanese even served voluntarily in both the Imperial Diet and the IJN/IJA, at least in China.
When I observe or ask Taiwanese people about this time in history, they largely acknowledge these things as facts. However, when I observe or ask Korean people about this time in history, there is strong denial and near universal hatred of the Japanese.
Westerners seem to accept the modern Korean story as fact, but are completely unaware of the Taiwanese story. Mainland Chinese tend to dismiss Korean grievances as exaggerations or outright lies. Really, I would like to know the facts. There is a lot of misinformation about the subject circulating around East Asian internet users.
Thank you. | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1c1wfn/what_was_life_really_like_in_japaneseoccupied/ | {
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"I personally do not have a history of Colonial Korea to give you, as I am not in possession of the literature necessary to do so at this time; however, I can point you in the right direction, if you have access to a library.\n\nThere is a great primary source collection called *Under the Black Umbrella: Voices from Colonial Korea, 1910-1945* authored by Hildi Kang. It's a very balanced approach to the subject, as it gives you accounts of both those who *were* oppressed by the Japanese and those who were not.",
"Hello! Taiwanese person here. While I'm not a true historian, I've been recently getting into my country's history during the occupation. Certainly, I can say that many Taiwanese will regard Japan's rule in a much higher regard than the Chinese's after the Kuomintang fled to Taiwan in 1949. \n\nAs for life during the occupation, things were only in a happy democratic state starting at what is referred to as the Dōka period (assimilation/integration) starting around the 1920s which in the entirety of the empire the electorate of the Lower Diet had been extended to all adult males. This period also added that Taiwan be considered an extension of the homeland. \n\nDuring the Kōminka movement in the mid-1930s as Japanese militarism was on the rise, locals were forcibly \"Japanized\" to an extent, in which their lives became highly similar to that of any other Japanese. During the war, Taiwan was an important airbase in the early stages and many Taiwanese did indeed serve in the armed forces.\n\nAs a personal addition on my part, my great-grandmother had lived under the occupation and her house was demolished by an American bombing raid during the war. I'd also recommend reading *George E. Kerr's Formosa Betrayed*, it provides a much better insight into how Taiwanese felt before, during and mainly after WWII than I have presented. My grandfather just received an original copy last year.\n\nLastly, I apologize because I actually met a Korean lady last week who was born in 1934 and provided incredible insight into life under the occupation, but I've largely forgotten what she told me (mainly because our conversation began with ways to treat acne, since she was a cosmetologist) - but at the very least she did mention it in kind terms, despite the fact I know many Koreans were used as laborers (more than a few had been working on the airfield at Guadalcanal).\n\nI do hope this helped."
]
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[],
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|
3p9iz4 | I just read that Homo erectus used and controlled fire. How do we know that? | I understand how we know they used tools. But fire? What evidence of fire could have possibly survived that long? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/3p9iz4/i_just_read_that_homo_erectus_used_and_controlled/ | {
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"Hi, questions on early humanoids are worth x-posting to our sister sub /r/AskAnthropology ",
"The most commonly used evidence of fire is remnants of charcoal, burned earth, or burned bone, that can either be dated directly, or dated in relation to objects of known age nearby. The chief issue with the extremely early dates for fire use ( > 600,000 years ago) often associated the *H. erectus* is that the evidence of those fires is difficult to distinguish from naturally occurring brush or forest fires. After several hundred thousand years a burning stump and an intentionally managed, but not re-used, cooking spot tend to look the same. Richard Wrangham is perhaps one of the most vocal advocates for the early appearance of fire, and he maintains cooking drove cognitive, social, and biological changes in our genus that eventually prompted the emergence of anatomically modern *H. sapiens*. His detractors claim the early hominin use of fire vs. naturally occurring processes isn't clear enough, nor is there sufficient evidence of early consistent, controlled use of fire needed to cook foods (and drive evolutionary change in our species).\n\nBy ~200,000 years ago, hominins begin constructed hearths, and routinely re-use cooking space, which leaves much better evidence of consistent, controlled use of fire. If you are interested in Wrangham's work [*Catching Fire: How Cooking Made us Human*](_URL_0_) is an accessible introduction into the fire and cooking debate."
]
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"https://books.google.com/books?id=BVzV9reo0bYC&dq=catching+fire+how+cooking+made+us+human&source=gbs_navlinks_s"
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|
6irsw7 | what is the difference between a "culture" and a "subculture" | I've asked my sociology professor twice and am still confused. He says it isn't arbitrary but he also says that it depends on which sociologist you ask for whether something is or isn't a subculture.
Would someone please explain what the difference is and how one culture can have many cultures but not all cultures within that culture are "subcultures"? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6irsw7/eli5_what_is_the_difference_between_a_culture_and/ | {
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"Just guessing here, but isn't a culture bound to geological locations and subculture not?\nExample: western culture, Japanese culture, are bound to the western world and Japan.\nRock n roll subculture can be found in every part of the world, but doesn't form a whole location wise",
"A subculture resides within a dominant culture. \n\nThe simplest example is probably the African-American subculture existing within the larger North American culture.\n\nSo you can see both are characterized by larger patterns: both eat at McDonald's, shop at Walmart, and watch the NFL on Sundays.\n\nBut then there are things that distinguish the African-American subculture, like the droopy jeans and hilarious content on twitter. "
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jd5kg | why big banks are considered evil. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/jd5kg/eli5_why_big_banks_are_considered_evil/ | {
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" Imagine your parents are saving up money to buy a house. The house is very expensive and your parents don't have all the money that is needed at the moment to pay for the house. The bank says, oh thats ok, you just pay us a little bit every month until you make the full payment and you can move in right now. You don't even have to pay us anything for the first three months. Your parents say \"Wow! Thats great\" and trust the bank to do this. This debt that your parents pay to the bank every month is called a mortgage. The standard length for a mortgage in the US is about 30 years.\n\nHowever, the bank purposely didn't tell your parents that the money they must pay each month will get bigger and bigger. Also the bank will charge your parents something called interest. Interest is more money that your parents have to pay the bank for borrowing their money. So even though the house may have only been worth 200,000 dollars, the bank can add on fees for borrowing that may mean your parents have to end up paying 300,000 dollars to the bank. Your parents think that they would pay the same amount of interest every month, but the interest goes up every month too. The bank intentionally does not tell your parents about this and they have to work very hard and pay a lot more money because the bank was being mean and they trusted the bank too much.\n\nIf your parents' piggy bank runs dry, and they can no longer pay the bank. The bank will kick you out of your house and you will no longer have a place to live. All because the agent for the bank was acting very friendly, but tricked them into signing a piece of paper that would make them lose thousands. \n\nThis is one of the main reasons why many people in the united states hate banks and think they are mean and want to steal their hard-earned money.\n\n",
" Imagine your parents are saving up money to buy a house. The house is very expensive and your parents don't have all the money that is needed at the moment to pay for the house. The bank says, oh thats ok, you just pay us a little bit every month until you make the full payment and you can move in right now. You don't even have to pay us anything for the first three months. Your parents say \"Wow! Thats great\" and trust the bank to do this. This debt that your parents pay to the bank every month is called a mortgage. The standard length for a mortgage in the US is about 30 years.\n\nHowever, the bank purposely didn't tell your parents that the money they must pay each month will get bigger and bigger. Also the bank will charge your parents something called interest. Interest is more money that your parents have to pay the bank for borrowing their money. So even though the house may have only been worth 200,000 dollars, the bank can add on fees for borrowing that may mean your parents have to end up paying 300,000 dollars to the bank. Your parents think that they would pay the same amount of interest every month, but the interest goes up every month too. The bank intentionally does not tell your parents about this and they have to work very hard and pay a lot more money because the bank was being mean and they trusted the bank too much.\n\nIf your parents' piggy bank runs dry, and they can no longer pay the bank. The bank will kick you out of your house and you will no longer have a place to live. All because the agent for the bank was acting very friendly, but tricked them into signing a piece of paper that would make them lose thousands. \n\nThis is one of the main reasons why many people in the united states hate banks and think they are mean and want to steal their hard-earned money.\n\n"
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4kaio6 | Japan usually had an isolationist policy towards foreigners, but what did they think of Europeans when they first made contact, and how has that viewpoint evolved since then? | Were the Japanese people distrustful towards Europeans? Were they racists? Just looking for more insight, thanks! :) | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/4kaio6/japan_usually_had_an_isolationist_policy_towards/ | {
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"Here is the earliest known Japanese account of the Portuguese:\n\n\"They eat with their fingers instead of with the chopsticks such as we use. They show their feelings without any self control. They cannot understand the meaning of written characters... They have no fixed abode, and barter things which they have for those they do not, but withal they are a harmless sort of people.\"\n\nAccording to \"Giving Up the Gun: Japan's Reversion to the Sword\", this type of account was typical. Japanese in this time regarded the Portuguese and other Europeans as culturally inferior, reflected by the Japanese word for Portuguese (And later other Europeans) in this time: Nanban, which meant barbarian from the South.\n\nDespite this, trade with Europeans brought in some foreign influences from Japan, such as new foods, loan words, art, furniture, and the Christian religion. This continued from the arrival of the Portuguese in 1543 until the Sakoku Edict of 1633, which strictly limited trade with Europeans (And other areas). The only Europeans allowed to trade after this were the Dutch, who could trade only through the artificial island of Dejima in Nagasaki harbor.\n\n Oda Nobunaga was adoptive of foreign influences and encouraged conversion to Christianity. However, later, this changed with Toyotomi Hideyoshi who was far more distrustful of Christianity and foreigners. Both of these things were seen as a threat and distrust of foreigners grew in government. Toyotomi wrote that: \n\n\"1. Japan is a country of the Gods, and for the padres to come hither and preach a devilish law, is a reprehensible and devilish thing ...\n2. For the padres to come to Japan and convert people to their creed, destroying Shinto and Buddhist temples to this end, is a hitherto unseen and unheard-of thing ... to stir the canaille to commit outrages of this sort is something deserving of severe punishment.\" (From Boxer, The Christian Century in Japan)\n\nThe Tokugawa Shogunate also saw Christianity as a threat, having a negative view of foreigners, and eventually banned the religion from the country, persecuting those who practiced it, most notably after the Shimabara Rebellion in 1638. This type of attitude towards foreigners continued until the Fall of the Tokugawa Shogunate. After that, during the Meiji Restoration, Europeans were no longer seen as inferior. \n"
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yes4w | tort reform | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/yes4w/eli5_tort_reform/ | {
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"\"Tort\" is when a person who has a responsibility to you screws it up really badly. For example, let's say your doctor accidentally cuts off your leg. That's a tort.\n\nNow, when there's a tort, you compute \"actual damages.\" For example, let's say that after he cuts off your leg, another doctor shoves him aside and sews your leg back on. The surgery to repair it costs $527,000. The actual damages, in that case, would be $527,000.\n\nWhen that happens, you can normally sue doctor legchopper for $527,000 - that's the amount you'll need to pay the bill, which is his fault. You're suing for \"actual damages.\"\n\n\"Tort reform\" is when congressmen put a limit on damage payments. For example, let's say that the congressmen decide that a doctor is never responsible for more than $100,000, no matter how badly he screwed up. So yeah, he made you lose $527,000, but you can only sue him for $100,000. When they don't have to pay the full amount of the actual damages, that's tort reform.\n\nThe two sides of the argument are:\n\n* You just received a bill for $527,000. Why shouldn't you be able to hand the whole thing over to the idiot who caused the problem?\n\n* Doctors have to buy a ton of insurance because of this sort of risk. That insurance is very expensive, and it adds to the cost of medical care, which is high already. If they didn't have to pay, medical care would be cheaper.\n\nNow, the biased part of the post: if we make medical care cheaper by forcing you to pay for your own $527,000 surgery, we aren't really making it cheaper. We're making it cheaper for most people, by putting the cost on the poor souls who get their legs accidentally cut off.\n"
]
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d69te2 | What kind of dances did Romans have? Were there dances that the higher classes were expected to know like ballroom dancing in the 18th and 19th centuries? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/d69te2/what_kind_of_dances_did_romans_have_were_there/ | {
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"Upper-class Romans were typically spectators, not performers, of dance.\n\nAt least some elite Romans, in fact, considered participating in a dance nothing less than shameful. Cicero, for example, is at pains to explain why one of his clients - accused of being a dancer - would never stoop or shimmy so low:\n\n\"Cato calls Lucius Murena a dancer....you ought not \\[O, Cato\\] rashly to call a consul of the Roman people a dancer...**For no man, one may almost say, ever dances when sober**, unless perhaps he be a madman, nor in solitude, nor in a moderate and sober party; dancing is the last companion of prolonged feasting, of luxurious situation, and of many refinements.\" (*Pro Murena* 1.6)\n\nIt was perfectly legitimate, however, for elite Romans to dance in certain religious contexts. Only patricians, for example, could be *Salii* \\- the dancing priests of Mars. Twice a year (probably), 24 of these men would put on a stylized version of ancient armor and process through the city of Rome, pausing at intervals to perform an elaborate dance while clashing their shields and singing ancient songs. The dance itself (the *tripudium*) seems, like the Pyrrhic dances of ancient Greece, to have evolved from military exercises. Plutarch gives a disappointingly brief description: \"the dance is chiefly a matter of step; for they move gracefully, and execute with vigor and agility certain shifting convolutions, in quick and oft-recurring rhythm\" (*Numa* 13).\n\nRoman women might also dance in ritual contexts. A traditional (and therefore respectable) example was the \"rope dance\" at least occasionally performed to honor Juno. As described by Livy:\n\n\"Then the seven and twenty maidens in long robes marched, singing their hymn in honor of Juno the Queen...From the gate they proceeded along the Vicus Iugarius into the Forum. In the Forum the procession halted, and passing a rope from hand to hand the maidens advanced, accompanying the sound of the voice by beating time with their feet.\" (27.37.12-14)\n\nOther sacred dances were less reputable. The *Galli* \\- the eunuch priests / devotees of the Anatolian goddess Cybele, whose worship had been imported to Rome in the third century BCE - were known for their ecstatic dances, which often seemed disturbingly exotic and indecorous to the Romans. Their fascination and otherness are captured by a passage from Lucretius:\n\n\"The Galli come: and hollow cymbals, tight-skinned tambourines resound around to banging of their hands; the fierce horns threaten with a raucous bray; The tubed pipe excites their maddened minds in Phrygian measures; they bear before them knives, wild emblems of their frenzy, which have power to panic with terror of the goddess' might the rabble's ingrate heads and impious hearts\" (2.614f)\n\nUnless they happened to be part of a priestly college, however, elite Romans were almost exclusively spectators of dances. Roman banquets often featured professional dancers - male, female, or both - who would perform carefully choreographed pieces for the pleasure of the diners. Spanish dancing girls seem to have been especially popular in the late first and early second centuries. Juvenal, with characteristic sourness, condemns those who indulge in such things:\n\n\"You may look perhaps for a troop of Spanish maidens to win applause by immodest dance and song, sinking down with quivering thighs to the floor...\" (11.162-4)\n\nMost Romans, however, seem to have had no problems with immodest dance or quivering thighs. \n\nOutside of banquets, the Romans were very fond of watching pantomime, a ballet-like entertainment in which a highly-trained masked dancer (usually male) performed an episode from mythology as a stylized dance, to musical accompaniment. Pantomime was sometimes criticized:\n\n\"The pantomime dancer, \\[a Cynic philosopher\\] said, was a mere appendage to flute and pipe and beating feet; he added nothing to the action; his gesticulations were aimless nonsense; there was no meaning in them; people were hoodwinked by the silken robes and handsome mask, by the fluting and piping and the fine voices, which served to set off what in itself was nothing.\" (Lucian, Of Dancing 63)\n\nBut many appreciated the talent and range of the star pantomimes, who could imitate episodes from the madness of Ajax to the love of Venus and Vulcan to Saturn devouring his children (I would have liked to see that one). \n\nElite Romans, in short, knew and appreciated a great variety of dances; but they very seldom polished the dance floor themselves."
]
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1t6lmn | What group of people determined the constellations we use today, were there different constellations for different groups of people? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1t6lmn/what_group_of_people_determined_the/ | {
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" > What group of people determined the constellations we use today\n\nAssuming you mean the constellations used by the scientific community, I'll let someone else handle the development of the International Astronomical Union's official constellations, and their largely Mediterranean and Middle Eastern origins. Those are the constellations your likely most familiar with, barring a few exceptions (most Americans would recognize the Big Dipper as a constellation, for example, but to the IAU it's part of Ursa Major). Instead, I'll focus on your second question.\n\n > were there different constellations for different groups of people?\n\nYes, different cultures had and have their own sets of constellations, though their are sometimes similarities - both coincidental and due to the sharing of ideas across cultures over time.\n\nTo give you an example from the eastern portion of North America, the stars around the Big Dipper / Ursa Major as also usually associated with a bear, as it is in parts of Europe. However, the bear is usually being hunted in Eastern Woodland astronomy, and there is disagreement over which stars are the bear, which are its hunters, and which are its den. \n\nSo for the Mi'kmaq, the constellation is the Endless Bear Hunt, with the bowl of the Big Dipper being the bear, the stars of the Big Dipper's handle and others all the way to Arcturus and a little way beyond are the hunters (a flock of birds, including two owls, a blue jay, a pigeon, and a chickadee carrying a pot). They block the bear's path to its den, which is composed mainly of the stars of the Northern Crown.\n\nThese stars form a nearly identical constellation for the Haudenosaunee (Iroquois), though the hunters are human, not birds, and fewer in number (usually three). The chickadee's pot may either be one of the hunters' pot or his dog. Rather than being the bear's den, the Northern Crown is the net the hunters throw at the bear. The three hunters with a dog interpretation is also shared by the Meskwaki (Fox).\n\nThe Lenape (Delaware) have a different interpretation of the bear hunt using these stars. The Northern Crown is the bear's head, rather than being the den or the net, and is detached form its body. Its body is nearby, trying to catch up with its missing head (with apocalyptic results if it were ever to succeed). Another set of nearby stars represents the bear's den, while a fourth set represents the monstrous beast the pursues the bear. The exact identity of the body, the den, and the monster is debatable. \n\nWhen these stars aren't associated with bears, the next most common interpretation is they represent [the Fisher](_URL_0_). This is the interpretation favored by the Anishinaabe and the Cree. The bowl of the Big Dipper is the Fisher's body; the handle is its tail. The little star that other's associated with a hunter's pot or dog is an arrow that struck the Fisher and killed him.\n\nAnother possible exception in the east is the constellation *Hotci'li pi'la*, the Boat Stars. This is one of the constellations of the Alabama, who were part of the Creek Confederacy during the colonial era. The constellation is described as being a large boat trailed by smaller boats, which ferry the Sky People to and from the earth. While ethnographic sources are explicit about which constellation this is, it has been associated with the Big Dipper - the large boat being the bowl and the smaller boats being the handle. \n\nSource:\n\n[Stars of the First People](_URL_1_)"
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ao6gup | when disconnecting a circuit (i.e. a car battery), why is it better to pull the negative side before the positive? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/ao6gup/eli5_when_disconnecting_a_circuit_ie_a_car/ | {
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"In a car its more because you want to disconnect the chassis first. Less chance of a short if all the metal in the car isn't part of the circuit.",
"Basically, if you take power off first and it touches any part of the engine / body it will complete the circuit (all parts are earthed) and it’ll spark like a mo’fucker. Take the earth off first and you remove that problem.",
"Batteries have little gremlins called electrons that always flow from the negative side to the positive side. \n\nWhen these gremlins travel to the places they’re supposed to, they’re well behaved. If they travel to places they shouldn’t be, they wreak havoc. \n\nNow, if you take off the positive side first and accidentally touch it to any metallic part of the car, the little gremlins will flow from the negative side to the positive side and into a place they shouldn’t be, therefore causing damage because of their penchant for bad behavior. \n\nBy disconnecting the negative side, you make sure the little gremlins can’t travel out of the battery. Therefore touching the positive side to another part of the car will not harm it because there aren’t any gremlins there to cause harm. ",
"The black wire (negative) is connected to every metal part of the car, so if you're taking off the red wire (positive) first, and your wrench slips and touches any metal part of the car, it will complete a circuit and throw up sparks. It can even start a fire. If you're taking off the black wire first, and you slip, nothing happens, because that side is already connected to the car. After you take the black wire off the battery, then the battery isn't connected to the car any more, so then you can take off the red wire without any sparks.\n\nFor many decades now, engineers have designed circuits so the negative side is connected to the chassis, or case, or frame, or whatever (usually called the \"ground\"), just so there won't be any confusion. There are still a few really old cars (they switched around 1956) and farm tractors with positive ground, but you're not likely to ever work on one without knowing that."
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10n8gx | in space, it always seems that we are shown traveling on a 2d plane. what happens if you leave earth and go straight "up" or "down"? | All pictures of our solar system have this neat, perfect linear illustration of the plants lined up. So we take off from Earth to travel "sideways" or linear to get to the moon, to send our probes and such to planets, but what if you left from the North or South Pole and traveled straight from there? What is out there? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/10n8gx/in_space_it_always_seems_that_we_are_shown/ | {
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"Our planets are all mostly on the same plane, which is nicely convenient for illustration purposes. If you go any other direction, it's pretty darn empty. And it will take a while to run into the [Oort cloud](_URL_0_). Beyond that is way more empty before another solar system.",
"Everything. Everything is out there.\n\nFirst, let's explain about the solar system. There is a very good reason that the planets are (mostly) lined up so well. The planets and asteroids around our sun started out as a huge dust cloud that was swirling around the sun. Over a very, very, VERY long time, the dust clumped up and accumulated into the bodies we have in the solar system today. Since the dust cloud was all swirling around one way, the planets are, too.\n\nNow, we get to what happens if we travel up or down from the \"disc\" of the solar system. What's there is the rest of the universe. See, like the planets, our solar system is moving along in our galaxy, which is just a huge cluster of stars. The galaxies themselves are also moving around within the universe. So, what you'll find if you move straight up or down from the plane of our solar system really depends on when you go and how quickly you'll move. \n\nFor the most part, you'll find a whole lot of nothing. That's just because the universe is so incredibly, indescribably big. However, you'll also run into different galaxies, nebulae (which are basically just massive clouds of gas, but are much prettier than they sound), black holes, comets, all of the things that are out there.\n\n[here](_URL_0_) is a good picture of our galaxy, and our solar system's place in it. The solar system faces about 60 degrees up from the center of the galaxy (it's tough to explain easily, but the best picture I can find to demonstrate is [this](_URL_1_)), so you would wind up leaving the galaxy pretty quickly. From there, who knows what you'll come across. Eventually, if you go far enough, you will likely see every type of thing there is to see.\n\nI hope this answers your question."
]
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376o4b | How can sexual selection work at species which have a 50:50 ratio of genders? | Hello scientists!
So I am an amateur in evolution theory and specialized on it in my A-levels (Abitur) and red a little bit of Richard Dawkins.
Although there are still a few basics of evolution I never understood 100% of (especially when we look at the human evolution).
Sexual selection is probable the most important selection method out there. Evolution always works by someone getting disadvantage in reproducing or surviving until he can reproduce.
All mammals do have sexual dimorphisms. How could they develop?
When we look at races that use to live in couples like humans; my crucial point is:
Let's say sexual selection started and for example the women preferred to choose taller men. So the good looking women started to take tall men as partners. And what happened when all tall men were taken? The remaining women had no choice but take those as partner who were not tall. So the tallness would have never been selected by evolution.
Where am I wrong?
(illoyal women betraying the small partners? Even if so, that can't explain how female characteristics are selected. Females always know their child is theirs)
This is just one example.
I get why sexual selection works when there are for example 1000 drones and one bee queen. She chooses the fittest drone to pair.
But how can this work with a 50:50 ratio? Everyone who feels to noble to take a partner without the preferred characteristic will stay single, therefore won't get children and will be terminated by evolution :)
I know I have an error in the logic. Please find it.
| askscience | http://www.reddit.com/r/askscience/comments/376o4b/how_can_sexual_selection_work_at_species_which/ | {
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"It might be a really important one, but it's not the only factor.\n\nHumans can now walk to the supermarket for food, but this wasn't always the case.\n\nIf you couldn't hunt properly, you or even your group would have less food and you might not get enough and die before reproducing.\n\nIf you were susceptible to diseases you might catch a disease and die before reproducing.\n\nBut you must also remember that this is about populations and not individuals.\n\nSay you had an individual with a disadvantage. However, where other individuals with this disadvantage died before mating, this individual found a way to live and mate with it's disadvantage. You might be inclined to think that the disadvantage will now propagate through the population. However, if it's offspring also had the disadvantage then there's no guarantee that they can cope with it just as well as their parent could. So it's more likely they'll die before mating.\n\nSo just like what the commenter before me said, it's about many many generations. And low chances of success turn into almost no chance at all.",
"Lets look at more obvious cases before humans.\n\nTake [Cock-of-the-rocks](_URL_0_), for instance. These are highly dimorphic birds with elaborate courtship rituals in S American rainforests. In their specific case, males endlessly parade and court females in leks. Despite this enormous investment in time and resources, very few males mate at all, but those who do mate with several females. So in this scenario, the advantage of being in the top 1% is obvious.\n\nIn humans, you have to take a more nuanced situation. First: although we *do* show a degree of sexual dimorphism, in comparison with highly dimorphic species our divergences are slight - we are *slightly* dimorphic. Then, just because a man and woman pair together does not necessarily imply they will breed. In fact, a significant proportion of people do not form lifelong bonds or successfully reproduce. Furthermore, just because our currect society is based on couples forming a nuclear family does not imply that was always the case. There is a long history of alternate social structures in humanity which could have denied access to reproduction to large numbers within a population: harems, polyandry, etc.\n\nAlso keep in mind that the most desireable mates (desireable, as defined by sexual selection) get picked first. This in itself gives a huge advantage in allowing \"the sexiest\" to get first crack at dividing available resources to meet the needs of their children. It also gives them a potentially longer breeding history, by starting earlier. These are significant advantages allowing their offspring to outcompete that of the \"less sexy\" segment of the population which might have to enter the breeding game later and after the best quality resources were already appropriated by the offspring of those bearing favored characters.\n\nThe way this problem is usually tackled in human is by looking at th eresults wihin populations. What are the traits which have *locally* been selected as attractive? You may want to refer to the quite well written work by C Darwin on that subject (The Descent of Man, and Selection in Relation to Sex), to get a feel for how this works.",
"Nearly all animals have 50:50 sex ratios. But not everybody actually has sex. In many species (for example, herd animals where one male is dominant, or prides of lions) only a few males breed while most females do. There's sexual selection to be the one that breeds.\n\nBut what about humans and other species where individuals organisms are in pairs? Well, that sort of mating system _does_ tend to reduce sexual selection. For example, compare sexual dimorphism in [dik diks](_URL_1_) which are monogamous, and [kudu](_URL_0_) where males compete for access to female herds. Humans also exhibit reduced sexual dimorphism...we are less dimorphic in size than many primates, and male humans lack the elongated canines that are common in other male primates. \n\nBut sexual selection still exists. First of all, humans aren't perfectly monogamous....historically, polygamy has been relatively common, for example, with some men taking several wives. People also sleep around, so the most attractive sometimes get extra mating on the sly. This sort of thing happens at least occasionally in most species. But even in a situation where everyone is perfectly monogamous, you can still have some sexual selection. This is because attractive individuals will get their pick of mates: as the best looking, they can get the best while the less attractive are passed over by those and get stuck with less high quality mates. This means the most attractive are more likely to have the most offspring, because they are reproducing with a partner that has, on average, better genes/health/territory/whatever. This isn't as strong selection, but it's still there."
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35zwzd | what did locke mean by 'property' in life, liberty, property? | I've read it's physical property. I've also read it's dignity - and that's why Jefferson changed it. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/35zwzd/eli5_what_did_locke_mean_by_property_in_life/ | {
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"It really just means property, the pursuit of happiness also means acquiring property but it's a more broad statement, also meaning the right to do what you like to be happy. ",
"Locke had this idea that you own your property by creating it. There are resources in the commons, like flowers in the meadow, trees in the forest, water in the rivers. And you can appropriate things from the commons by mixing your labor with them. So no one owns the water in the river. But if you go and fetch a bucket of water, that water belongs to you, because you labored to create it. You don't own the trees, but if you cut one down, that one belongs to you, because you mixed your labor with the tree. "
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7gyhb5 | The collapse of the Western Roman Empire is perieved as the end of an era and the beginning of another, but how did life for the average European farmer change after the fall of the Roman Empire? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/7gyhb5/the_collapse_of_the_western_roman_empire_is/ | {
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"Although there's certainly more to say, especially with regards to agricultural productivity in late antiquity and the fall of the Empire's impact on the mediterranean \"common market\" for agricultural goods, we've actually gotten a number of questions about the end of Rome recently that might give you a cleared idea about life during the end of the Roman Empire. \n\n[This discussion](_URL_0_) led by u/Iguana_on_a_stick examines life in \"Roman Cities\" after the end of the empire, and might give you a clearer idea of what post-Roman society was like. u/shlin28 wrote [this other answer](_URL_1_) on the specifics of the city of Rome after the empire ended."
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"https://www.reddit.com/r/AskHistorians/comments/4dclc7/what_exactly_happened_to_the_city_of_rome_after/d1qhl1q/"
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3a7mt3 | Why do Chinese cash coins have square holes? | I know the holes are there so the coins can be strung together for ease of use. But is there any particular reason the holes are square as opposed to round? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/3a7mt3/why_do_chinese_cash_coins_have_square_holes/ | {
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"hi! it may be worth x-posting this one to the coin collectors in /r/coins or /r/Numismatics ",
"So the best answer i could find on the webs states that the real reason was likely practical: Ancient Chinese coins were cast/poured into moulds, not stamped or milled. If you've ever casted, you know that you get flash, which is material that overflows through the casting molds' joining space. In order to make a uniform coin, after the casting, the coins were put on a dowel or rod so that many of them could be filed down at once. This rod was square in order for the coins to stay stable and not roll while being filed. \n\nOlder round Chinese coins did have round holes in them as well, and one effect of this was that the money could be stored on strings. \n\nThere are a variety of philosophical meanings assigned to the \"square hole, round coin\", but these appear to be an after effect from the practical filing needs\n\nOn a side note, I am not a fan of Wiki as a source, but the [Wiki page](_URL_1_) on \"Ancient Chinese Coinage\" is a clearing house of every type of Ancient Chinese coin, all the way back to their \"spade money\", and cowrie shells! A dedicated numismatist put this together....\n\nSources:\n\n^[1] Encyclopedia of Chinese Symbolism and Art Motives by C.A.S.Williams, 1960, NY\n\n^[2] The Passing of Korea by Homer Hulbert 1906 (? date questionable)\n\nvia:\n\n[This website](_URL_0_) Sources listed above confirmed via google books search and other text searches."
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47kh5d | How enthusiastically did “ordinary” Germans join Nazis in antisemitic discrimination and violence before 1939? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/47kh5d/how_enthusiastically_did_ordinary_germans_join/ | {
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"While I can't exactly answer how enthusiastic they were about it but I can write something about ordinary Germans joining in active measures of discrimination and violence before 1939.\n\nGenerally, people higher up in the Nazi party were not fond of spontaneous pogroms. People like Hitler, Himmler, and Werner Best saw themselves as proponents of what they called \"rational anti-Semitism\", meaning that to them the alleged Jewish threat had to be encounter not with violence on the streets but with an overarching political program. That didn't mean though that they were against using violence in the streets when it suited their program.\n\nThe first attempt at rallying the public against the Jews by the Nazi party was a boycott of Jewish businesses in 1933 but that was in essence a failure and it was not until 1938 and the November pogrom that there was to be some kind of Reich concerted action against Jews. During the pogrom of 1938 however, a lot of people joined in and over 400 Jews died during the night and many synagogues all over the country burned.\n\nAnother area where ordinary Germans joined into the discriminatory policy is \"Aryanization\", meaning the theft of Jewish property by the state and its redistribution to the German populace. It's hard to gauge just how many people pofited from it but the number is somewhere in the high thousands if not ten thousands.\n\nThirdly, we have what Michael Wildt describes as low key anti-Semitic action as a reaffirmation of the Volksgemeinschaft (the German racial people's community loosely translated). In his book on the subject, he describes that outside the urban centers small anti-Semitic actions could serve as a affirmation for the community partaking in them. He describes such things as a village crowd getting hold of a German-Jewish mixed couple, shaving their heads and parading them through the street as \"race defilers\". These things seem to have been rather common in German provincial areas, especially during the first half of the 1930s.\n\nFurthermore, with the addition of more and more discriminatory measures, most Germans participated or at least accepted them like separate benches for Jews and Germans, separate shops etc. etc.\n\nSources:\n\n* Frank Bajohr: „Arisierung“ in Hamburg. Die Verdrängung der jüdischen Unternehmer 1933–1945. Christians, Hamburg 1997.\n\n* Saul Friedländer's books on the Jews and the Third Reich.\n\n* Michael Wildt: Volksgemeinschaft als Selbstermächtigung. Gewalt gegen Juden in der deutschen Provinz 1919 bis 1939. Hamburger Edition, Hamburg 2007."
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8limtg | what are the differences between regionalized, decentralized, and centralized states? | I recently saw [this map](_URL_0_) on wikipedia and I saw no explanation or examples of how these systems of government differ. They are all supposedly decentralized, with certain responsibilities being removed from the federal state, but to what extent and how they all differ is not explained. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/8limtg/eli5_what_are_the_differences_between/ | {
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"Centralised vs decentralised (I'm using British spelling) is about how much power the central government is vs how much power the parts of the country have.\n\nIn a highly centralised country, there is one government for the whole country that makes nearly all the decisions. In a decentralised country, the different parts of the country (e.g. states, provinces, cantons) have their own governments which make most of the decisions themselves, and the government of the country as a wholr is only responsible for a limited number of things such as defence and foreign relations.\n\nA related concept is federations vs unitary states. \n\nA federation is a country like the USA, where the constitution guarantees that the constituent parts of the country can run themselves, and the federal government is only responsible for things set out in the constitution.\n\nA unitary state is where the central government holds all the power.\n\nThis is where a regionalised state comes in. A country which is a unitary state is not necessarily very centralised. The central government can create autonomous governments for regions of the country. The difference between this and a federation is that the central government still has ultimate power, the regional governments only have the powers that the central government lets them have.\n\nThe UK is an example of this. It's a unitary state, meaning the UK Parliament in theory holds all the power. But Scotland, Wales and Northern Ireland have their own governments which the UK Parliament has given powers to. In theory the UK can overrule or abolish these governments (although it would be politically very difficult).",
"Think about all the services that a government can provide to their population. Now those services can be provided by the federal government or province/state. The more the province/state provide the more the country is decentralised, the more those services are provided by the federal government, the more centralised the country is.\n\nFor example, here in Canada, the federal government have little direct impact on the everyday lives of the population (to a certain extend). The federal government take care agriculture/fisheries, immigration, defence, inter-provincial infrastructure, public safety, etc. \n\nBut it's the Provincial government that take care of the health services (hospitals, clinics, ambulance, etc), education, infrastructure inside the province, social services, culture, energy, etc. \n\nCompare that to the UK. The Health care system is for the whole country, it's the same for education. It's a more centralised states.\n\nThe US is in the middle. Both the federal government and states have their hands in health care, but education is a state affair.\n"
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1shvel | The extent of the Jewish involvement in the October Bolshevik Revolution, and in Government in the period immediately following it. | Is anyone here an expert in this area? I'd love to hear some well informed answers.
Thanks! | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1shvel/the_extent_of_the_jewish_involvement_in_the/ | {
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"I'm not an expert in that specific area, but I can dig up some sources. [This party census](_URL_1_) says that slightly over 5% of party members in 1924 were Jewish. Wikipedia cites [this source](_URL_0_) for other figures, but unfortunately I can't read Russian. A cursory google translate gives a figure of 7.1% in 1922. Given the number of Jews in Russia, those figures aren't terribly surprising. [This source](_URL_2_) says 364/23,000 were Jews pre-revolution, because more Jews were Mensheviks, not Bolsheviks.",
"I've attempted to answer here:\n_URL_2_\n/what_was_the_role_of_the_jews_in_the_bolshevik/\n\nI would add that many jews, holding top-level offices in Soviet government have tended to de-emphasize their nationality, as per Marxism and Bolshevism class is much more important than nationality. \n\nTo the point that [Lazar' Kaganovich](_URL_0_) - being as ethnic jewish as it gets - refused to sign Anti-fascist Jewish Committee memo: \"I'm not a Jewish politician, I'm a member of Politburo\".\n\n**Sources**\n\n1. [Russian: Emmanuil Ioffe - \"Unknown Lazar Kaganovich\" (excerpts from interviews with L. Kaganovich)](_URL_1_)"
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bkiuwf | Why isn't the Ummayad Caliphate talked about like the Roman and Persian Empires? | It was as big or bigger than both of the aforementioned empires and it played a signifigant part in European history (Not to say that if something isn't European it isn't important, it's just that a lot of written history is rather euro-centric) in the muslim conquest of Iberia. What is the reason for this ommision? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/bkiuwf/why_isnt_the_ummayad_caliphate_talked_about_like/ | {
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"I’d wager that It really depends on the classes you take. In high school, I learned fuckall about anything that wasn’t western Europe or the US (including barely anything about Persia) simply because my high school’s curriculum, or at least the AP curriculum, was structured that way. But in university, there are plenty of courses offered at my school that talk about European-Muslim relations during the early modern era, and so on. It just depends on where you take classes I suppose. Individual teachers might also be biased due to their own courses of study or their backgrounds. I wouldn’t simply say that the Ummayad Caliphate is underrepresented in academia... Especially in higher education.",
"If you mean the Umayyad period specifically (661–750 CE), keep in mind that it was relatively short-lived. And it can be overshadowed by what came before it (the initial rise of Islam) and what followed (the ‘Abbasid “golden age”).",
"A combination of Eurocentrism, Anglocentrism, and general ignorance.\n\nIt's often not taught in schools because they tend to focus almost entirely on European and colonial/postcolonial American history. The things that Americans and Europeans see as \"their\" history and fit the narrative they want to tell. At least from the perspective of an American history curriculum, pre-United States history only matters insofar as it acts as a prologue to United States history/\n\nThings like the Umayyad conquest of Spain are left out due to Anglocentrism. At least in America, they want to tell the history they see as their history. Spain does factor into that until Columbus comes in and discovers America. which sets the stage for colonization, which sets the stage for English colonization, which sets the stage for the United States.\n\nAs for why it's not \"talked about\" in popular discourse, that's because it's not part of \"popular history.\" The Romans (but not the later Eastern Romans or the earlier Kingdom of Rome), the Greeks (but again, not the Greek speaking Eastern Romans), the English (but not the pre-Anglo Saxon Britons), the Colonial Americans (but not the Native Americans), the Crusaders (but not the Islamic defenders) all get movies, and TV specials, and pop history books written about them. So what they did, and how they lived their lives are pretty well known to the general public.\n\nBut the Umayyads don't get this same treatment. They tend to only get discussed in academia or in specialist historical works. So, most people don't really know who they were, what they did, or how they lived. They aren't aware how big the Caliphate got, and the impact it had on history. They probably aren't even aware that an \"Umayyad Caliphate\" existed and how it differed from any other Arab state.\n\nSadly, it's a self causing cycle. Arab history isn't taught in schools, so it doesn't become part of our popular histories. No one knows about it, so no one thinks to teach it in schools. So, because of that, one of the largest and most important empires in world history is completely unknown in the west outside of academia."
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gfo77 | Any counter arguments to the "evolution doesn't make sense mathematically" argument? | I just posted the question over in r/evolution, and didn't get much of a response. I've heard this argument before, and was wondering if anyone has a math based counter argument. | askscience | http://www.reddit.com/r/askscience/comments/gfo77/any_counter_arguments_to_the_evolution_doesnt/ | {
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"Could you elaborate on what the argument is against evolution making sense mathematically? ",
"Math is a language to express ideas. You can make simple evolution models just fine using math. Very complex simulations (anywhere near a real situation) are impossible to run on modern computers.\n\n\n[Here's](_URL_0_) an evolution simulation using colors.",
"Look, based on your question, I have no idea what you're talking about. Maybe you could be a little more specific. Evolution does make sense mathematically. What is the discrepancy?",
"Now I understand your question. All these arguments are based on the idea that the first self replicating organism that sprung from the \"primordial ooze\" was highly unlikely. That is true. But it wasn't impossible and we are here today, so I guess it happened!",
"I can think of several arguments, from the snarky to the more metaphysical. \n\nSnarky: This type of thinking is exactly why Mathematicians make terrible chemists!\n\nMore meaningful: Chemical reactions and self-organizing systems don't operate by random chance, therefore treating them as if they do is inappropriate. To use the math terminology, their lemme isn't true, therefore their argument is baseless. ",
"Here's something tricky about their argument: they're calculating the probability of a *specific* sequence occurring by chance, not the probability of just any old sequence. Indeed, if you mix together amino acids, you'll probably get a lot of different kinds of proteins. They're making the assumption that the most ideal form (i.e. working copy in their language) of any protein would occur immediately, and not through trial and error or evolution. Plus, they're making the assumption that there is no external driver (e.g. evolution or some kind of feedback mechanism) to the construction of those proteins. They're asking the question: what is the possibility of a working copy of a gene (necessary for survival of the host organism) arising by chance from a mix of amino acids? Their math is correct, but they've ignored some very basic assumptions in order to make their point. There are three kinds of liars: liars, damned liars, and statisticians.",
"I think that I know what you are talking about. People make arguments that the chances of randomly getting the right DNA sequence to make a viable cell are so astronomically small that evolution would take trillions of years or more.\n\nThe essential problem with this argument is that evolution is driven by natural selection, which greatly changes the probability of creating viable mutations.\n\nThe process of natural selection is NOT equivalent to just picking mutations at random over and over again. In fact, it has such amazingly high performance compared to random selection that it is an often used technique in mathematical optimization.\n\nAs an example, consider the problem of trying to find the optimum travel path between the 500 largest US cities that minimizes the total distance traveled. There are an unimaginably large number of possible paths and this is an exceptionally different problems.\n\nYou can just select paths at random and compute your mileage, but you can grind through trillions of such solutions without getting anything good.\n\nYou can also mimic natural selection by computing 50 or so random paths, and then keeping the 25 best paths with the lowest mileage. You then mutate the 25 best paths randomly to get another set of 50 paths, and repeat the process. After just 1000 or so \"generations\" of pathways, you will start to see very good solutions to the problem emerge.\n\nThe bottom line is that natural selection will approach near optimal solutions at a blindingly fast pace.",
"\"Yes it does\"",
"Evolution makes lots of sense mathematically. There are tons of _real_ mathematicians doing real mathematical research on mathematical biology, computational genometics and related fields, and getting real results. \n\n",
"Another short answer, permutation of others: The problems with this approach lie in **assuming the existing state must be the only viable state and there is only one path to it**.\n\nThis assumption ignores all the viable alternatives and also all the possible but still working mis-steps on the way to our current state.\n\nAfter all the argumentation is not very much different from presuppositionalism. If you presuppose that there was the one path to the NOW that had to be taken to arrive at a working NOW ... than the odds are staggering high. But the odds of any event that is taken out of context are astronomic - the odds of me sitting here would be 1 in 6 billion if we just ignore that I have a history of stumbling around in this area ..."
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"http://www.freewebs.com/scikidus/evolution/index.html"
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3mkil5 | why do smart people "look smart"? | More specifically: what is it about the facial expression and particularly the eyes of intelligent people that makes it easy to tell that they're intelligent? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3mkil5/eli5why_do_smart_people_look_smart/ | {
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"The eyes that follow a person's movements and respond to speech and show engagement are my first clue. I once knew a lady and didn't like her very much, but the first thing I noticed about her was her intelligent eyes. From that point on, I regarded her with caution and tried to consider what she was trying to achieve from interacting with me. This was a good call, since a few months after that encounter, she tried to stage a coup of the board of directors at my place of employment and failed. If I would have gone along with what she said, I probably would have gotten in trouble. "
]
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dyx8s0 | What are some small events in the American Revolution that Historians still disagree on? | I’m not talking about big overarching questions like what the actual cause of the revolution was. Im more interested in small, seemingly irrelevant events that people still can’t come to a concensus on. | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/dyx8s0/what_are_some_small_events_in_the_american/ | {
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"Perhaps the most interesting is the mysterious death of Jane McCrea. Jane was the daughter of a Presbyterian minister from New Jersey, and in July 1777 was living with her older brother outside Saratoga, New York. \n\nHer brother was called up by the local militia, and her fiance was a loyalist posted at the recently re-captured Fort Ticonderoga, so she made her way towards British lines. \n\nWhile resting in the home of another loyalist, Sara McNeil, an Indian scouting party attached to General Burgoyne's advancing forces raided the village of Fort Edward, killing a patriot family and taking Jane McCrea prisoner.\n\nWhat happened next became the stuff of folklore, and even repeated exhumations of McCrea's remains for forensic analysis have been unable to resolve the conflicting accounts.\n\nThe warriors who scalped her, and the official British stance, said that McCrae was struck by a Patriot musketball and killed while being marched back to the British camp. Her Indian escorts, wanting to claim their reward for capturing an alleged Patriot, decided to scalp her and take her hair as proof rather than carry a corpse several miles. Her fiance, and many others, believed she had simply been murdered by an overzealous scouting party. \n\nThe Patriot cause immediately seized on the incident as proof that the British could not uphold their promises to protect the Loyalists from raids and reprisals, and the sensationalized story struck a blow to Burgoyne's civilian base of support at a crucial time of the war. \n\nIn 2006 a research team, with the blessing of Jane's closest living relative and a court order, exhumed her grave for forensic examination. Most of her bones were intact and showed no signs of injury, but her skull was missing (likely looted during her first reburial in 1822) as were most ribs. With no signs of injury on the remains, even the best modern science cannot conclusively say if Jane McCrea was the unfortunate victim of a stray Patriot musket ball or of a native's hatchet during a British-sanctioned raid.\n\nEDIT: I reread the actual 2006 report today, not just the summary I had saved, and apparently Sara McNeil's remains were reburied with Jane in 1822, causing no small challenge for the forensic team."
]
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5o22h2 | Are there animals that nurse or feed each others young? | Examples of kangaroos sharing pouches, birds sharing food with other babies. Mammals feeding birds? | askscience | https://www.reddit.com/r/askscience/comments/5o22h2/are_there_animals_that_nurse_or_feed_each_others/ | {
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"Plenty of examples in domestic animals like dogs and also some found in wild animals too. Some examples:\n\n_URL_1_\n\n_URL_0_"
]
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"https://www.buzzfeed.com/stacylambe/16-animals-taking-care-of-other-animals",
"http://www.mirror.co.uk/news/world-news/surrogate-dogs-adopted-pigs-26-3731138"
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1xtg2c | monsanto's patent on broccoli | What did they actually patent? What does their patent mean to us, what does it mean to farmers? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1xtg2c/eli5_monsantos_patent_on_broccoli/ | {
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"They patented a specific strain of broccoli. It doesn't mean anything to us or to farmers, since it's just that strain; the broccoli you buy at the grocery store isn't affected.\n\nSome people thought that they patented *all* kinds of broccoli, but this isn't the case.",
"In effect, Monsanto's patents are similar to patenting software. The are patenting a small amount of instructions for getting a plant to grow. They do not patent the entire computer, nor do they patent the operating system. That is to say that they do not patent the entire plant, nor do they patent the bits core to a plant. In this case, what is patented is a particular strain of broccoli that is able to grow in more areas than normal broccoli. The computer equivalent of this would be like patenting a piece of software like MS Paint. There are other image editing softwares out there, but Paint might be the best one to use in a particular instance.\n\n\nAs far as what this means to a farmer, it gives them the option of paying a little extra to grow a crop that can potentially give more profit at the end of the year. On the consumer end, we might actually see a drop in broccoli prices, but likely we will not notice any real change.\n\nSide note: GMO discussion does not play into this at all. This technology was not used in the development of this broccoli strain."
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2ibn9p | why does plaque feel fuzzy on my tongue? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2ibn9p/eli5why_does_plaque_feel_fuzzy_on_my_tongue/ | {
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"Do you mean bacteria on teeth plaque or trophy and medal plaques?"
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3t434q | Why is there no Asian Sahara? | I understand that subtle wobble in the tile of the earth is the likely cause of the Sahara becoming desert. This is a huge area of catasrophic change - is there any evidence of similarly massive regional climate change at the same time elsewhere? | askscience | https://www.reddit.com/r/askscience/comments/3t434q/why_is_there_no_asian_sahara/ | {
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"Air and ocean currents in the Indian Ocean supply South Asia with vast amounts of rainfall. There is a desert to the Northeast of the Himalayas when those clouds run into the mountains and dump their moisture on the Southern and Western slopes."
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aypszp | How did Europe go from slavery to serfdom in Late Antiquity / Early Middle Ages? | I understand this was asked similarly [before](_URL_0_), but you can see that the answer did not touch this point specifically. What economical / social / political causes allowed for the shift between being able to sell a person and working on a field of land a few days a week to pay the landlord? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/aypszp/how_did_europe_go_from_slavery_to_serfdom_in_late/ | {
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"It's been about a year since I did anything on this topic so forgive me for any mistakes I make in terms of the Historiography or nuances on the topic. The shift away from systems of slavery occurs far later than one might expect, it is around the year 1000 Pierre Bonnaisse (**1**) identities slavery as having ended in France, although we must remember even after the shift towards serfdom slavery still existed into the high middle ages in the form of galley slavery and eventually economic chattel slavery imported from Syria by the Genoans.(**2)** \n\nThe nature of the shift away from slavery towards serfdom occurs slowly over a long time making it a favoured topic by the Annales school, contemporary studies look more towards the ideas of \"unfreedom\" and \"freedom\" which are far more useful terms in deriving information about the transition. I'll largely base this off my reading of Alice Rio's book *Slavery after Rome.*(**3**)\n\n**What is Medieval Slavery:** In brief I don't think medieval slavery is so much to do with selling or buying people as later slavery is, but to do with cultural ideas of debt and punishment. Slavery took different forms such as:\n\nCapture and resale: Typically a goal of Viking/Islamic raids and unsurprisingly disliked in Christian sources (*Life of St.Wulfstan* for example).(**4**) Western Christians also partook in this form of slavery too, but as a bi-product of conquests like the expansion of Charlemagne's empire into Slavic lands or the instability of the Heptarchy period in England, slaves takenin this way were moved and planted on estates as labourers.(**3**) However, this form of slavery shouldn't be emphasised too much as it is typically seen on Scandinavian, Islamic and Pagan peripheries and remains unsourced in western documents.(**3**)\n\nDebt: A favourite term of economist David Graeber, this explains slavery on local levels where figures may willingly sell themselves into temporary slavery in order to pay off unpayable debts to someone else in the community.(**3**) I'm not hugely familiar with the impact of this on ones family but I would imagine they also become slaves until the debt is payed. This is where \"unfreedom\" becomes useful as people in this position are subservient and slaves, but still partake in the community and can have ambiguous social statuses, in general however they're unfree.(**5**)\n\nPunishment: Very similar to debt slavery this was paying off a debt to legitimate legal authority via temporary enslavement.(**3)**\n\n**Why Did Slavery \"end\" in Medieval Europe:** \n\n**Feudal Impact:** The \"feudal revolution\" led to a shifting role of the general peasant and in general symbolised a shift from paying tribute to those above you but towards a system of obligation that is feudalism. Seen in the ideas of the school Auxerre and King Alfred the Great there's a general shift towards the notions of \"three orders\" and mutual obligations in the 9th century which eroded some of the practical and social reasons for slavery.(**6)** Lords are quite likely to grant manumission/freedom to slaves and even grant them property to live on which allows them direct access to their labour, rather than having the intermediate access via a slave owner.(**7**) This may have been to do with the collapse of the Carolingian empire with Charles the Fat in 888 into many polities as the more personalised feudal politics that followed encouraged a shift away from slavery for aforementioned reasons.(**8**) In England we can see this following the Norman Conquest of 1066 which largely ended the collapsing practice for good, in the *Doomsday Book* we see a lot of examples of slaves freed by their new lords and added to the general collective of serfdom who incidentally may have become increasingly \"unfree\" as a result.(**9**)\n\n**Church Impact:** Surprisingly church impact was initially limited in the ending of slavery and permitted rural slavery beyond the nobles (in England) as they couldn't as effectively monopolise the labour of serfs as effectively as the nobles.(**10**) Guy Bois was increasingly cynical about the church's role in ending slavery, citing examples such as St.Augustine who called it a \"temporal punishment\" and their Christian pushing of acceptance of ones place in this life as all could be redeemed in Heaven.(**11**) Nonetheless the church doubtless had social impact, in England and France it shows an increasing intolerance towards slavery towards the millennium, something that likely took a while to come into effect (the works of *Aelfric of Eynsham, Wulfstan of York and Wulfstan of Worchester* in the context of England).\n\n**Social Impact:** As mentioned before, debt slavery (alongside penal and self sale) were common in early medieval communities but one could remain a slave and generate a social standing within a village. One of the most important sources for this is the example of the *Judgement of Courtisols* in 847, in which serfs in Chalons-sur-Marne vouch for the serf status of several slaves in the village (until some village elders attest against it).(**12**) This implies the status of slavery in a social context was malleable and in the absence of personally aware authority people could work or earn their way out of slavery, something that plausibly occurred in times of chaos (which paradoxically may have created more slaves too such as after the Danish invasion of England in the early 11th century).\n\n**Conclusion:** In conclusion the question is incredibly difficult to answer, the end of slavery in the early middle ages is more of a transitional period towards general serf-ly \"unfreedom\" more than any form of mass liberation or radical shift in thinking. This is a rather Anglo-centric answer unfortunately, although I don't know much about the ends of slavery in places beyond England or France, ultimately, it is just important to recognise that slavery was malleable and transitionary, rather than enshrined institutionally to any serious degree, the names for \"serfs\" and \"peasants\" in of themselves vary and aren't codified, it is dependent upon local social relations to function. \n\n**General Sources (I don't know how to cite on Reddit):**\n\n1. Bonnassie, P., *From Slavery to Feudalism in South-Western Europe,* Birrell, J., (tran.), (Cambridge, 1991).\n2. Phillips, J.R.S., *The Medieval Expansion of Europe*. 2nd ed., (Oxford, 1998).\n3. Rio, A., *Slavery After Rome: 500-1100,* (Oxford, 2017).\n4. Coleman, William of Malsmebury (ed.), *Life of St. Wulfstan.*\n5. Greaber, D., *Debt: The First 5000 Years,* (New York, 2011).\n6. Alfred of Wessex's and school of Auxerre's respective translations and interpretations of *Boethius*\n7. Pelteret, D. A. E., *Slavery in Early Medieval England,* (Woodbridge, 1995).\n8. Bois, G., *The Transformation of the Year 1000: The village of Lournand from antiquity to feudalism,* Birell, J., (trans.), (Manchester, 1992).\n9. Hincmar of Riems, The Judgement of Courtisols."
]
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71n1dg | why do many people get easily spooked by small animals that don't actually pose a thread? | Inspired by this post: _URL_0_
I could totally imagine that kid being like a 30 year old. Why is it that a seemingly large portion of people get easily freaked out by harmless animals? I'm guilty of this too but it just feels like things like squirrels, bugs, ducks, etc. tend to startle people a lot. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/71n1dg/eli5_why_do_many_people_get_easily_spooked_by/ | {
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"In the old days, small animals were common causes of disease. You could get a deadly flu from a chicken, or rabies or plague from a rat.",
"a)They are not life threatening but they can still hurt you. And no one wants to get hurt.\n\nb)People get startled because they're not expecting. Jump scare doesn't need a scary object. A gust of wind blowing a door shut can still startle you when you're not expecting. And animals aren't predictable when you're not familiar with them. Same reason why people are scare of and stay away from mental disfunctional people (sorry, I actually don't know what to call this, basically crazy people) in public because you don't know what to expect."
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2t0jjr | Today is the 80th anniversary of the introduction of tighty-whities. What were mens undergarments like before 1935? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/2t0jjr/today_is_the_80th_anniversary_of_the_introduction/ | {
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"I did a quick run-down of the [history of men's and women's underwear](_URL_0_) in a previous post, but there's definitely room for someone more versed in 19th century fashion to expand!"
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"http://www.reddit.com/r/AskHistorians/comments/265b9n/when_did_people_start_wearing_underwear_did_men/"
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ampbk5 | Why does our Sun have so many planets compared to other stars/solar systems? | Our star has eight planets and numerous dwarf planets. On Wikipedia, I read that most stars only have 0 or 1 exoplanets. Is the difference:
a) our Sun is simply a statistical anomaly
b) other stars likely have similar numbers of exoplanets, but we can only detect large ones
c) related to something unique about our Sun?
Thanks! | askscience | https://www.reddit.com/r/askscience/comments/ampbk5/why_does_our_sun_have_so_many_planets_compared_to/ | {
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"It's mostly B. With our techniques we can mostly detect planets that are massive enough to make their stars wobble, or big enough to make a dent in their brightness AND do so fast enough for us to detect the pattern. This is why most exosystems found so far are so similar, yet so different to ours. Detecting planets like our trans saturnian ones would be almost impossible with either technique (brightness dip too small, orbital period too slow)\n\nEdit: Thank you for the silver!\n\nEdit 2: I went and looked for the original comment I'm quoting down below, and I haven't found it yet but I did find another thread which I found interesting back at the time. It touches up on the subject of our current bias for detecting exoplanets in certain configurations of solar systems rather than things more akin to our own: [check it out!](_URL_0_)",
"The answer is almost certainly b. Since they are too dark to be directly imaged, the existence of dim and distant objects such as exoplanets has to be inferred through crunching data. It just so happens that big objects are easier to detect, which is why the current list is all massive planets.\n\nAs our detection methods improve we'll start finding smaller and smaller things around other stars for certain.\n\n \n\n\nThere's no reason not to suspect all star systems have millions of satellites of various sizes and categories. We just can't 'see' them yet.",
"a) it might be but we dont know yet! We are only just at the beginning of exoplanet observations and there are many things we thought we knew that are being questioned. Things that often get spoken about in popsci as if they are solved are in fact nowhere near to being complete and often have a few big hurdles left (a couple of examples are core accretion has a big problem with the pebble accretion scale as well as explaining the population of hot Jupiters around young stars, the nebular hypothesis has problems explaining the misalignment of hot Jupiters and more generally the misalignment of protoplanetary disks). These questions have came about due to increasing observations and we are finding the variety is so large that we still do not have enough data points.\n\n & nbsp;\n\nOne interesting idea that has came out of exoplanetary surveys is that there may be two populations of protoplanetary disk. One of which can result in a planetary system and one that can not.\n\n & nbsp;\n\nb) this is very important. Along side this is our detection ranges in that we have a bias in detection of planets < 1AU from the star. If we consider an identical system to ours and then think about how many of our planets we would observe then we end up fairly typical! We would likely observe our system as a single plant (or at a push a two planet) system also. I would guess we are above average on the number of planets in the system but not by much (and would also not be surprised to be wrong). But it is important to note that this would be for a specific type of system! Not all protoplanetary disks will produce planets at all.\n\n & nbsp;\n\nc) the sun is fairly typical for its size as far as we can tell. We know a bit more about stars than planets, we a lot more.",
"Many systems are binary systems - the 2 stars don't leave much space for planets to form and will have swallowed most of the matter in the vicinity.\n\n0-1 exoplanets is the number we have been able to deduce so far from very limited data.\n\nA decade ago it was mostly 0.\n\nAll those star systems could have a dozen planets - just too small or in orbits that don't \"wobble\" the light from it's star in a way that we can detect yet.\nIt's easier to notice a Jupiter sized gas giant than a Venus sized rock.\n\nWe can't even be sure about the number of planets in our own system.\n",
"We detect planets overwhelmingly using two methods, Radial Velocity (looking at how the star wobbles during the orbit of an exoplanet) and Transit (looking at how the star dims when the planet goes in front of the star, only possible for systems that are aligned *just* right.)\n\nBig and fast is the name of the game for these detections. Massive planets produce more visible wobble in their star, big planets dim their star's light more. Planets in lower, warmer orbits produce a signal that repeats faster, so you can wait only weeks to confirm your object instead of years.\n\nFor systems where we only know of a few somewhat small inner planets, it's quite possible that there are gas giants in the outer solar system that haven't been detected because they orbit too slow. On the other hand, many systems in which we only see a single Jupiter-like planet in a Jupiter-like orbit are examples of what aliens would see with our technology if they looked at the Sun, so we might expect a solar-system-like inner system and more gas giants in the outer system.\n\nFor more information about how solar systems form and how common systems like our own are, I recommend this video series from planetary scientists Allessabdro Morbidelli and Sean Raymond, called Modeling the Origin of JOvian planets: _URL_0_",
"We have a few methods for detecting exoplanets, and each one only works for certain types of exoplanets. A quick review of the methods:\n\n \\- **Astrometry**: In a star-planet system, the planet doesn't exactly orbit around the star. Rather, both planet and stars orbit around the mass center of the system. Usually the star is so massive that it \"looks\" like the planets orbit around the star, because the mass center is so close to the star that it's actually inside it. This is the case of our solar system, for example. However, in other solar systems, there are planets massive enough (relative to the star) to have a mass center far from the star. Thus, by precisely measuring the position of a star through several years, we can infer the presence of very massive exoplanets (and even then, only those with long orbital periods, that is, far from the star), usually no more than one. This doesn't mean that there aren't other exoplanets in that system, but they are not massive enough to affect the mass center.\n\n\\- **Fotometry**: We measure the brightness of a star over time. When a planet crosses in front of the star, we see a dip in its brightness. We can then infer its mass, size, orbital period and distance to its star. This requires the planets to be VERY close to their stars (usually we see orbital periods of only days). If the planets are further away from the star, it's likely that they don't cross between the star and the Earth, and we don't see any decrease in light intensity. Think of it as seeing a very far eclipse, it can only be seen from certain spots each time. The further the planet is from the star, the less likely we are to be able to see it. This planets are usually small (or they wouldn't be so close to their star).\n\n & #x200B;\n\nTL;DR: We can only detect very large planets far from their star or small planets very close to their star. Most exoplanets probably neither, and are thus undetected.",
"While I don't know the exact numbers, there is also the \"many stars are binary\" ([Sun Likely Has a Long-Lost Twin](_URL_1_) / [New evidence that all stars are born in pairs](_URL_2_))\n\n > “Within our picture, single low-mass, sunlike stars are not primordial,” Stahler added. “They are the result of the breakup of binaries. ”\n\nIt appears that young star systems are often wide binary (500 AU separation) and then either migrate closer (for example, Alpha Centauri A and Alpha Century B are 11 AU apart). This makes having planets a more complicated endeavor.\n\nOur Sun 'got away from' its twin and maintained its planets rather than becoming a closer binary system and possibly ejecting its planets.\n\nLow mass stars (red dwarves) - which are the majority of stars out there - are a different story for the percent in binary systems.\n\n---\n\nFrom Wikipedia, [Binary Stars : Research Findings](_URL_3_) from [Stellar Multiplicity](_URL_0_)\n\nMass range | Multiplicity Frequency\n:-- | :--\n≤ 0.1 M☉ | 22% +6% / -4%\n0.1 - 0.5 M☉ | 26% ± 3%\n0.7 ± 1.3 M☉ | 44% ± 2%\n1.5 ± 5 M☉ | ≥ 50%\n8 ± 16 M☉ | ≥ 60%\n≥ 16 M☉ | ≥ 80%\n\nSo the sun isn't an anomaly, nor is it unique... but it appears to be in the minority of stars. Thus, mostly B, but there's a bit of A in there too.",
"Follow up question:\n\nThere is an option d) of which I genuinely don't know how important it is, postselection. The chances of an individual planet having life are very small, so wouldn't we expect life to occur more frequently in solar systems with more planets, making it a more likely situation for life to find itself in?",
"Probably B. \n\nBut I think that as we discover more exoplanets we’ll recognize that our current planetary configuration is pretty unique. Granted, we haven’t searched much, but the location of Jupiter and Saturn in our solar system (actually, all the largest planets) outside rocky ones in the habitable zone seems to be of much importance in the search for life since they shield us from asteroids and other debris. ",
"Think about this: Our own Uranus takes approx 80 years to orbit our Sun, and the technology we presently use to determine the existence of exoplanets is based on a planet's orbit dimming the hoststar's light. Using this current technology, over the decades we will find many new stars and discover that most of the stars we already monitor have more bodies orbiting them than previously thought.\n\nNew telescopes are arriving but we can't speed up the process of a planet's orbit around it's hoststar. Definitely the technology will see vast innovations over the coming years. \n\nMaybe one day our scientists will somehow be able to detect an orbiting planet's \"trail\"... ",
"Other's have answered your question. I posted a link below that goes into more depth on all this.\n\nBut! you want to think about something nuts? \n\n\nSo say they've found some exoplanets. now ask yourself, given the tools we have, how would we you be able to make predictions on what elements are present on said exoplanets? Like you hear things like \"oh this star has an exoplanet that appears to have an atmosphere\". like da fuq? how do you figure that out by just looking at the light gathered by a telescope.\n\nWhen I read about that, it blew my mind that people were able to work out the science for that.\n\n[_URL_0_](_URL_0_)\n\n\" In order to do that, we obtain what is known as a planetary [transmission spectrum](_URL_1_), which is acquired using light that streams through its atmosphere. Because of the size discrepancy, it’s virtually impossible to differentiate between the planet and the star, so we record the spectrum of the star before and during a transit—If the planet has no atmosphere, it will block the same amount of light at all wavelengths; If it does, gasses in it will absorb additional light. The two numbers are then divided and you get the planet’s atmospheric transmission spectrum.\n\nAgain, this is no easy feat given the fact that the light blocked by the planet is a mere percentage of the star’s total output. However, it is doable. When light interacts with atoms and molecules in the exoplanet’s atmosphere, it absorbs certain wavelengths on the spectrum, and those wavelengths are indicative of certain elements on the spectrum.\"",
"People always underestimate the number of stars in the universe. Its not hundreds of billions. Its a billion quadrillion.\n\nIf one in a thousand stars has a planet similar to Earth...its still quintillions ..not just billions or trillions.\n",
"We mostly detect exoplanets because they pass between their star and us, and the light of the star changes a tiny bit.\n\nThink about what that means.\n\nIf the planet is too small to change the light enough, we don't see it.\n\nIf we are looking at the wrong time ( and that's once every few centuries in some cases ), we don't see it.\n\nIf the planets orbital plane is wrong, we don't see it.\n\nThe amazing part isn't that we know of so few exoplanets. The amazing part is that we know of so many.",
"The answer is b).\n\nImagine we were instead inhabitants of Tau Ceti e, or some other nearby exoplanet, and the Sun is just one of many bright stars in the sky. And imagine that this hypothetical planet had the same exact technology/astronomy as we currently do. How many planets would our Tau Ceti-ans have currently discovered around the Sun?\n\nThe answer is probably one - Jupiter. That's because our searches with Radial Velocity (the doppler wobble method) is so far only sensitive enough to detect the orbits of Jupiter-like giant planets. Saturn would likely be too small and on too long an orbit to detect, and Earth produces far too small a signal (\\~100 times smaller than Jupiter).\n\nEven in the unlikely chance that the Sun and its planets happened to align edge-on with Tau Ceti so that the planets cross their star or \"transit\" (a \\~0.5% chance for Earth), none would probably have so far been spotted. That's because only a few thousand stars have been surveyed with the sensitivity to detect Venus & Earth-like planets (with Kepler), and those were all relatively faint stars covering < 2% of the sky.\n\nSo if you looked up the hypothetical Tau-Ceti-equivalent-wikipedia for \"known exoplanets\", it would say \"Sun - G2 dwarf, 1 exoplanet\". But of course that does not mean exoplanet systems do not have \\~8 planets in.",
"It's mostly b). An often understated fact is that if all solar systems were like the Solar System, Kepler would have found very few, if any planets. Almost every planet that has been found to date has an orbit closer to it's star than Earth is. Kepler has found many systems with multiple planets, but often even if the planets all orbit in the same plane, planets further from the star have less chance of transiting. You can do statistics to try and estimate how many extra planets you missed, but it requires some assumptions. If these assumptions are valid, then interestingly, a) many stars have multiple planets, but b) there are almost certainly some with only single planets.\n\nTo find small planets in larger orbits will require different techniques, or the patience to observe for many decades. Thankfully, the gravitational microlensing technique can be used to find small, distant planets far from their stars without waiting for them to orbit (it can even find planets that have been ejected from their solar systems by gravitational interactions). NASA is working on a flagship mission that will use microlensing to find over 1000 planets, with more than 100 with masses smaller than Earth. Most of these planets will have orbits in the 1-10 AU range. The mission is called WFIRST and will launch in the mid 2020s.",
"One additional reason: If our sun had 0 planets you couldn't be asking this question and if it had only a few it would also be much less likely that intelligent life could have developed on one of them. So the chance to sit in a system with more planets than the mean, however unlikely that is, is automatically higher.",
"As stated elsewhere, the answer is B. \n\nHowever, an important thing to think about is how do you define a planet. If it's anything orbiting a star then our solar system has thousands if not millions of planets. So that isn't a helpful definition. What's the cut off for size or mass to be considered a planet? If we look at planets on the scale of Jupiter, then our solar system has two maybe three. \n\nAs of now, detecting exoplanets is really difficult. There most certainly are more planets around other stars. ",
"Primalily, (b), and in addition, we have only done this for a few years. Jupiter takes 12 years for an orbit, so we might need up to 24 years before ~~we~~**aliens** would have enough data to find it.\n\nThe first planets found was big and close to the star. As time goes by, we are finding more and more distant planets.\n\nToday we can measure doppler shift of the star down to 4m/s. For comparison, Jupiter causes the sun to wobble 152m/s, so easily detectable.\n\nSaturn causes a wobble of 2.8m/s over 30 years, so not detectable with todays accuracy. (actually 2014. maybe this is better today)\n\nEarth causes a wobble of 9cm/s...\n\n( The dimming of the star due to occultation by the planet, and direct observation of extrasolar planets has different measurement limits, and it all is changing fast.)\n\nBTW: the fact that we can measure doppler shift changing 4m/s over many years in actually incredible: \n- The earth (or satellite observatory) is spinning at many km/s. \n- The earth rotates around the sun at 30km/s \n- Our solar system has a relative movement compared to local stars of 20km/s \n- and finally, we are rotating with our galaxy at 230km/s. \n\nThe star we are observing is moving at some unknown speed.\n\nAll in all, pretty spectacular observation and math.",
"We can detect large exoplanets close to their star due to their gravity. We can detect planets that go between us and their star (extremely rare. Look at how rarely Venus passes in front of the Sun). We can directly image very few very large planets. With our current technology one would be unable to detect planets around the Sun when looking at it from the Alpha Centauri system. \n\nThe Sun doesn't seem to be an anomaly among single suns of it's type but we don't yet know very well what a \"typical\" planet system looks like, especially with planets which take years to orbit which we need to be extremely lucky to detect",
"It doesn't. Our Sun is very average, and likely has a typical number of planets. Just 30 years ago, many people debated if there were any planets at all beyond our solar system as we had no evidence of any (although most astronomers thought there would be many). We have only in the blink of an eye begun to detect planets. And only in the last few years begun to detect smaller planets. Soon (with new telescopes and methods) we will even begin to detect planets the size of Earth and smaller in large numbers. We will find out that our Solar System is nothing special, and that there are many millions of other star systems very similar to ours.",
"Mostly b but perhaps a bit of c!\n\nOur most sensitive method of detecting exoplanets has been to spot them eclipsing their hosts (using Kepler and now TESS, this is the method responsible for about 90% of exoplanet detections). We can only observe planets this way who's ecliptic is aligned with ours. Otherwise from our perspective there are no eclipses. \n\nThe odds of this go down with the radius of the planet (fatter planets have wider ecliptic angles that will still cause observable eclipses. This is similar to the reason there are so many more lunar eclipses than solar eclipses on Earth) and the distance of the planet from the host star (imagine trying to kill two birds with one stone. This becomes more plausible the closer the birds are to begin with unless one bird is right in front of you but this is never true of exoplanets.). \n\nNow even given all this, it's still hard to detect even Jupiter-size planets this way with our current method because we've only been doing it a few years. It takes Jupiter 12 years to get its big butt around the sun so if we are looking for Jupiters like ours we have to be looking at least that long and much longer for the outer planets. Also at those distances the odds of alignment are way down so the number of detected planets goes down too.\n\nEarth sized terrestrial planets face their own difficulty, namely their eclipses are harder to detect because they block out less of the light from the host star. So you might need to have a computer identify a bunch of marginal maybe-eclipses at regular intervals to confirm a smaller planet, meaning more years of observation. But this gets complicated when you consider a system of planets. \n\nTake our own Solar system for example. An alien civilization pointing a telescope at Sol would only spot our planets using eclipses if it sat along our ecliptic plane. To identify the inner planets it would need to see many eclipses over a decade or so (assuming their tech was similarly sensitive to ours for this illustration) and solve for the association of each one to a set of 4 independent eclipsing solutions to determine we have 4 inner terrestrial planets. We've performed similar feats, but there's no telling how many we've missed. Planets tilted in the ecliptic plane might exhibit eclipses sporadically, complicating the solution, or perhaps multiple solutions can't be separated if the planets are tidally locked. The aliens would need to keep observing for 100 years or so more to spot the remaining gas giants.\n\nSo in terms of b, at present we are most sensitive to large planets very near their host stars. But this brings up point c. Our Sol is not unique, but it is unclear just how rare our setup here is. Observations have proven that gas giants in extremely close orbits are quite common around stars in the Milky Way. Think Jupiter 5x closer to the sun than Mercury, orbiting every few days. This seems to be one of Nature's preferred stable configurations of planets around stars. But this is not our configuration. \n\nIt is suspected that such \"hot Jupiters\" fall into their inner orbits from larger origin distances, casting any terrestrial planets out of the system during the migration. In fact the Milky Way may be littered with these rogue planets drifting through space alone, lacking any semblance of daylight. Needless to say our configuration is not compatible with hot Jupiters, and such systems may represent the majority, making our system rather rare. In fact, leaving Jupiter right where it is may be key to the stability of the orbits of the inner planets.\n\nBinary star systems pose a separate issue. About half of all star systems are binary or multiple star systems. In such configurations planets in stable orbits are possible, but far less likely than in single star systems. And multi-planet configurations around binaries are probably infinitesimally unlikely (though that won't stop us from looking!). \n\nFinally there's Sol's type to consider. A Population-I G-type star perfect for hosting planets. Pop-I means our star is more than a second generation star. Pop-III stars are the very first generation. They must exist but they have never been confidently observed. Chances are they were giant dinosaur stars which only existed for a short period at the beginning of the Universe. Pop-II stars are still around, and formed from the waves put out by the explosions of Pop-I stars. These stars can be smaller and live longer, but they are always metal-poor, meaning they do not have sufficient material to host rocky planets. They simply didn't have the rocks to build them while they were forming. Pop-I stars are stars formed from the explosions of Pop-II stars or other Pop-I stars. They have metallicities similar to our Sol and the potential to form rocky planets. We do not know of any significant star population more metallic than our Sol, and it is likely that the Universe is too young for there to be such a population yet.\n\nThe G-type of Sol puts it squarely in a special range of stellar mass with a radiative core and a convective mantle. This configuration makes our star quite stable in it's energy output. Strong radiation from nuclear burning is filtered through a thick mantle and radiated out into the photosphere from a much milder hot plasma ocean at the surface. This is helpful for the creation of rocky planets undergoing gravitational collapse and requiring a certain amount of stability in the circumstellar disk. It's also especially helpful for the development of life, which likely has a hard time getting a foothold under the harsh radiative conditions from a more intense stellar energy source. \n\nG-stars are rather rare themselves, although not as rare as giant O, B and A stars. But these stars have much shorter lifetimes than our Sol, so short that they explode before their planets have had time to settle down, scattering more rogue planets throughout the galaxy in the process with hot, molten cores. \n\nThe most common types of stars, M-stars, are quite small and cool. \nRocky planets can form around these stars but the formation zone is smaller and the planets are either fewer in number or more crowded. Gas giants around M-dwarves face a similar challenge, and it is far less likely for M-dwarf stars to host systems similar to ours because a Jupiter-sized planet in a more crowded configuration would almost certainly be unstable and start bouncing it's neighbors into interstellar space. Additionally, since the star formed from less-than-average material it has less material to spare for gas giants.\n\nLife it seems may have a harder time developing in M-dwarf systems as well because these stars lack a radiative core, transitioning straight from the nuclear burning zone into a convective envelope. This makes them fairly mild most of the time, but prone to eruptions of nuclear burning material which periodically overshoot the convective envelope. These are called flare-stars. It is possible that these regular flares hinder not only life but planet formation itself, which is a type of gravitational collapse and may fail to occur amid perturbations caused by flares.\n\nSo to summarize, it is currently difficult to detect systems like ours, but systems like ours may be much rarer than this difficulty can account for if large planetary systems are severely skewed to single, population-I, G-type hosts. There is currently only 1 system known other than our own to host 8 planets, Kepler-90, along with several 6-7 planet systems. The fact that we can see these at all with our limited observation time suggests there are many systems like ours. But many is a relative term considering the hundreds of billions of stars in our Milky Way, and such systems may still be considered extremely rare in this context.",
"B is mostly right. There are two primary ways to detect an exo-planet. Either an occulation will reduce the brightness of the star, allowing us to infer that a planetary sized object passed in front of it, and also determine an approximate size, and through the use of tracking red/blue shift on the light of the star as it \"orbits around the planet\". Each of these methods requires at least one full orbit to properly detect an object, and two full orbits to confirm it's not some other anomaly. That works great for planets that are relatively close to the star and large, since they'll provide multiple opportunities for detection in the last 25 years since we've been actively monitoring for them. However, Jupiter's the nearest of our large gas giants and it takes 10 years to orbit the Sun. Also, the further from the star, the less impact it will have on the star's orbit or its brightness, requiring more sensitive detection technology as well as more opportunities for confirmation. Not only that, more planets will create a more complicated orbital pattern, taking longer to unravel and determine multiple smaller planets in a system with a few large ones, especially if the larger ones are closer to the star. \n\nAs far as it goes, it would appear that for a star like ours, we should be safe in estimating a similar number of planets, on average. As we gather more data, those assumptions can be modified. Remember, 30 years ago, we didn't know about ANY exo-planets, nor did we know about the existence of the Kuiper belt beyond Pluto and Charon, and that's our own Solar system. Detecting objects that small orbiting another star will be far more complicated and time consuming.",
"Honestly its option B mostly, but at the same time it’s not. The method that has been used the most since the explosion of Exoplanets in the mid 2000s is the transit method. When an object goes in front of a light source it can alter its output of light. If a scientific instrument has a sensitive enough light detector it can sense this light change when a planet passes in front of it. The more sensitive the instrument the smaller the object it can sense like our own planet. So far the Kepler Telescope sole objective is doing this job using the Transit Method. The reason why we don’t really kind that many planets around a Star is not so much the fact that we are special but if we look at our own solar system we can see why we don’t see that much. It takes 365 Earth rotations to make a full orbit around our parent Star. Therefore if some Alien species was doing the same to our Star using the transit method it would take them anywhere from a year to the next day to detect us. So the kian problem is time, Neptune is the farthest planet and takes 164 years to orbit the Sun once, so the chances of catching a far out planet like Neptune is slim to none. So we will probably never truly be able to detect every planet around a Star and make sure that’s it. It could take a maximum of 164 years to catch every planet around our solar system alone. Hopefully, this answers your question if not the astronomers of Reddit will cast their judgment on me.",
"As it has already been explained, our sun is not atypical, it's just that it's difficult to detect planets from light years away. One important reason that I have not seen mentioned yet is that our detection methods work the best when the plane of ecliptic of an exoplanet is aligned with our point of view and the exoplanets star. It's not a given that the exoplanet will ever cross in front of its star, blocking its sunlight. Most likely it's only a small fraction of exoplanets that fall into that category."
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"https://www.youtube.com/watch?v=cVe-V_UjB28"
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"https://arxiv.org/abs/1303.3028",
"https://www.space.com/37186-sun-long-lost-twin-nemesis.html",
"https://news.berkeley.edu/2017/06/13/new-evidence-that-all-stars-are-born-in-pairs/",
"https://en.wikipedia.org/wiki/Binary_star#Research_findings"
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"https://futurism.com/how-do-we-know-what-planets-are-made-of",
"http://www.wired.com/wiredscience/2010/01/direct-spectrum-exoplanet"
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7brswi | How is my daily life affected by quantum mechanics? Is it? | askscience | https://www.reddit.com/r/askscience/comments/7brswi/how_is_my_daily_life_affected_by_quantum/ | {
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"All chemistry is based on quantum mechanics, how electronic orbitals work and interact in chemical reactions, how folowers get their colour. And if we didn't have all this amazing chemistry biological compounds (DNA, sugars, proteins etc.) would not exist and life would not possible.\n\nSo the fact that you were able to type out this question is in some way all thanks to quantum!",
"Computers, microchips, transistors, lasers, Solid-State harddrives, flash memory, DVD/CD/Blu-ray players, LED lights, LED monitors, modern chemistry, nuclear power (and weapons), cancer radiation therapy, X-rays, MRIs, PET scans, etc. (and this is a real etc, I could keep listing all day) are quantum technologies. They are technologies that exist because we understand quantum mechanics and their operation is fundamentally quantum mechanical in nature.\n\nWe call the 50s and 60s the \"Space Age\", but really it was the \"Quantum Age\". Nearly every invention of the digital age is powered by quantum mechanics."
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5paq93 | How often did lower nobles within the same kingdom wage war against each other? | It is often depicted in fiction that Barons, Counts, and Dukes within the same kingdom would wage open war for titles or honor. How historical is this? What are some examples of monarchs' responses? How did the practice of vassals warring against each other change from Charlemagne's time to the renaissance? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/5paq93/how_often_did_lower_nobles_within_the_same/ | {
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"Follow up: Did the structure of the Holy Roman Empire help or hinder member states going to war with other members?"
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dl92y3 | What happened to dukes, counts and barons in England? Do they still own vast tracts of land? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/dl92y3/what_happened_to_dukes_counts_and_barons_in/ | {
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"While precise estimates are hard to come by- the simple answer to your question is yes. \n\nThe primary reason we do not know for sure is the UK Land Registry (wherein land owners are named) does not cover the whole of Britain. Ownership of land only needs be declared if the land is sold and a new buyer takes it, so land that existed before its establishment often is owned by unknown people. \n\nGiven it has remained in these mysterious hands for so long it is a reasonable assumption that this land is in the hands of noble families. \n\nThe undeclared amount of land in the UK stands at 17%. If it is owned by nobility that would make landownership by nobles in the UK about 47% of the whole country, just shy of half of it all. \n\nWhat we do know is in the hands of our Dukes?\n\nThe Boughton estate belongs to the Dukes of Buccleuch, who also happen to be the largest aristocratic land owners in the UK (they own about 240,000 aches of land in Scotland); the Dukes of Westminster own more of Britain than the Queen does- crucially the land is run via Grovsenor Estates, the private family company which manages their estates; their fortune was built upon owning huge swathes of land that became London (Mayfair and Belgravia), but now own properties in the United States, Canada, Sweden, China, Japan and more. \n(I believe a surprisingly large chunk of Washington DC belongs to the Duke of Westminster). \n\nThe Queen is a mammoth land owner- she does NOT own 6.6 billions ached as has been incorrectly reported several times; this land is run via Crown Estates and includes large portions of London, most of the still in use palaces; large parts of Scotland; and most of Britain’s off shore wind farms. \nAs Duchess of Lancaster (the title of Duke of Lancaster always goes to the reigning monarch these days) she owns quite a bit of land in the industrial north-east, while the title of Duke of Cornwall always goes to the heir of the throne (in this case HRH Prince Charles) and includes areas like Dartmoor, the Isles of Scilly and of course Cornwall). \n\nShe also privately (not as monarch) owns we believe a horse farm in Kentucky and a chunk of Park Avenue in NYC. \n\nWe don’t exactly know- but the British Embassy in Washington (the largest Embassy in the US) is located next door to the Vice Presidents residence I believe and that is owned entirely by the monarch. \n\nBeyond that? Other noble land owners? \nThe 8th Earl of Mexborough owns 20,000 aches; the Duke of Beaufort owns 20,500 mostly in Wales; the 4th Earl of Iveagh owns 20,665 aches of farmland mostly in Suffolk (fun fact- the Earl of Iveagh family surname is Guinness- yes THAT Guinness); the Dukes of Bedford around 22,500 aches (slightly less than the Italian Count Vighignolo who owns 25,000 aches of Norfolk and is the largest foreign noble landowner); the Tempest family are not aristocracy but they have held land since Norman Times and rock in around 25,500 acres; the Earls of Lonsdale have about 35,000 acres mostly in Cumbria. \n\nAnd as I said- these are just the ones we know about. \nHope that answers your question about the land anyway."
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2rolwz | If all the clouds across the globe condensed into the ocean, how much liquid water would be produced? | Also, how much would the seas rise? | askscience | http://www.reddit.com/r/askscience/comments/2rolwz/if_all_the_clouds_across_the_globe_condensed_into/ | {
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"According to [this website](_URL_0_):\n\n\"One estimate of the volume of water in the atmosphere at any one time is about 3,100 cubic miles (mi^3 ) or 12,900 cubic kilometers (km^3 ). That may sound like a lot, but it is only about 0.001 percent of the total Earth's water volume of about 332,500,000 mi^3 (1,385,000,000 km^3 ), as shown in the table below. **If all of the water in the atmosphere rained down at once, it would only cover the globe to a depth of 2.5 centimeters, about 1 inch.**\"\n\nUsing the table in the website, the atmosphere has 12,900 cubic km. \n\n[This site](_URL_1_) says the surface area of the oceans are 361,900,000 sq km. \n\nThis would mean sea levels would rise 3.56 cm (1.4 inches) if all the water in the atmosphere went into the oceans. You can also get to this number by taking their land amount and adding 30% since ~30% of the Earth is land. "
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8x3idn | Is there a particular reason why the America’s were so much less developed compared to Europe & Asia? What caused Europe to develop empires, explore, advance technology, and all those things, whereas those in America were distinctly tribal and not up to par with their European counterparts? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/8x3idn/is_there_a_particular_reason_why_the_americas/ | {
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"Hi! While more can always be said on the subject, you should check out the [\"Technology and Civilization in the Americas\"](_URL_0_) section of the FAQ, where your specific question has previously been discussed."
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"https://www.reddit.com/r/AskHistorians/wiki/nativeamerican#wiki_technology_and_civilization_in_the_americas"
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a01sgj | i watched a video about a girl who survives being hit by a car because she can't feel pain, therefore, not bracing for impact. if it's more ideal to relax, why do humans automatically tense up/brace for impact? what is the most optimal way to survive a crash? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/a01sgj/eli5_i_watched_a_video_about_a_girl_who_survives/ | {
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"This is also why the drunk person usually survives a DUI collision relatively unharmed while the other party has injuries. ",
"I was hit from the side by a van that ran through a red light, thank god i didnt see it coming and brace. Bracing readies your muscles for either fight or flight, which is useful for if there is a threat. However tense muscles are obviously less flexible and therefore are injured far easier",
"its rather simple to imagine, take a water ballon (an analog for a human)....drop on the floor from 3 feet, squish, watery inside can flex and ripple taking impact. \n\nnow freeze that water ballon (analog for a human who has tensed up).... drop on floor from 3 feet, crack, soild inside takes 100% impact force instead of dissipating it",
"“Why do humans automatically tense up”\n\nLarge fast moving metal vehicles did not exist during hominid evolution. Human (and animal) behavioral responses to cars probably evolved as reactions to predator attacks."
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29ww2s | Energy can be converted into matter and vice-versa. Can energy be converted into antimatter? | askscience | http://www.reddit.com/r/askscience/comments/29ww2s/energy_can_be_converted_into_matter_and_viceversa/ | {
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"The terms \"matter\" and \"antimatter\" here are a bit misleading, because what we call \"matter\" in this context is just *ordinary* matter. Antimatter comprises the complementary antiparticles of ordinary matter, but antimatter is itself a form of matter. So converting energy into matter could mean converting it into antimatter just as easily as converting it into ordinary matter.\n\nThis is especially demonstrated in the process of pair production, where a high-energy photon (a gamma ray) interacts with a nucleus, spontaneously converting into a particle and its anti-particle counterpart, the classic example being an electron and a positron (the anti-electron). Typically these pairs will, due to their opposite electrical charges, pull each-other together once more and annihilate, forming a gamma ray once again.",
"Not only you can but in fact you simply will produce antimatter whenever regular matter is being produced, otherwise you would be creating electrical charge out of nothing, which is forbidden by a charge conservation law.",
"Absolutely. There's nothing special about matter vs. antimatter, except that the particles we're made of we call matter, and their opposites we call antimatter. Physics, however, makes no such distinction :)",
"Anti matter isn't really that special. It is, for most intents and purposes, the exact same as matter. The fact that we are made of matter seems to be the result of a proverbial coin flip that occurred right after the big bang.\n\nIn quantum electrodynamics, we have only one process. Two fermions (for example, an electron and/or a positron) interact with one photon. You can have any combination of these three particles at this interaction as long as the interaction conserves charge. (Electron has -1, positron has 1, photon has 0.)\n\nIE you can say we start with one electron and it collides with a photon and scatters off in another direction. Or you can say that a photon splits into an electron and a positron. Or a positron and electron collide and turn into a photon. \n\nSo, yes, you can turn energy (photons) into antimatter."
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nigtf | Is it actually possible to set the atmosphere on fire? | I've heard it spoken about in some science fiction publications, but it sounded a little silly. Is there any truth to this? | askscience | http://www.reddit.com/r/askscience/comments/nigtf/is_it_actually_possible_to_set_the_atmosphere_on/ | {
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"There isn't anything in the atmosphere that would serve as a fuel. For a fire to occur, you need at least two chemicals, an oxidizer and a fuel, that form a product that is at a lower energy state than the fuel and oxidizer had previously been. So, for example, hydrogen will burn in oxygen because the product of their combustion is water, which is at a much lower energy level. The difference in energy between the reactants and the product is the heat given off by the fire.\n\nNow, if you just mix hydrogen with oxygen (or gasoline or wood with oxygen) nothings happens. Why is this? It is because an energy barrier needs to be overcome before a reaction can occur. You need to input a certain amount of energy to break the intermolecular bonds that hold the fuel and the oxidizer together before they will have the ability to react with each other. When they do react, they release even more energy than was necessary to get over that energy barrier. Some of this energy is released as heat, and some of it is absorbed by other molecules of fuel and oxidizer so that they may react with one another. A spark or sunlight or lightening can provide that initial energy necessary to start a fire, and after that it's self sustaining.\n\nWhat about nitrogen oxides? Aren't those the products of oxidation of nitrogen? Might they be set on fire? Well, yes and no. Oxides of nitrogen will form at very high temperatures, but they have a higher energy level than the initial reactants did. So once the energy barrier necessary for their formation is overcome, they won't release enough energy to cause more nitrogen oxides to form. Thus the reaction would not be self sustaining, and there would be no fire.\n\nOther possible fuels, like methane and hydrogen, which are present in the atmosphere, cannot be set on fire because they are too sparse. There simply can't be transported to the fire by diffusion quickly enough to burn. That is, if I light a match, I will burn some of the methane in the air, but the energy will be absorbed by the surrounding gasses such that there isn't enough energy available to the nearby methane to coax it into igniting.",
"I think there's a boat being missed here. The question was: Is it POSSIBLE to set the atmosphere on fire. This is not contingent on current conditions, ratios, or forecasts. So I'll address that question.\n\nNobel Prize-winning physicist [Luis Alvarez](_URL_0_) postulated one way that a significant portion of the atmosphere could be set ablaze. In fact, he says it happened once.\n\nBefore jumping right into that, let's look at the [Fire Triangle](_URL_1_) to see what we need to start a fire. O2? Check. Heat? Check. The only thing missing is fuel.\n\nBut how could we possibly get enough fuel into the atmosphere to make a firestorm that engulfs the Earth in a blaze that reaches miles high into the atmosphere and in fact radically changes the contents of the air for millions of years to come?\n\nDr. Alvarez has the answer. An [Impact Event](_URL_3_). If a heavenly object impacted the Earth with such speed and devastation so as to kick up tons upon tons of dust and vapor... suddenly the fire triangle is complete.\n\nTrillions of particles that leave and re-enter the atmosphere would burn up on their way back down. This would set off a chain reaction. Heat touches off the now-omnipresent fuel in the presence of O2... and you have a global firestorm.\n\nHow long it would burn depends on the size of the impact, the ferocity of the hurricanes generated by the impact, and the state of the atmosphere prior to impact. According to Alvarez, analyses of fluid inclusions in ancient amber suggest that the oxygen content of the atmosphere was very high (30–35 percent) during the late Cretaceous period. This high O2 level would have supported intense combustion. We would likely get a different 'mix' with today's O2 ratios. We may have to wait until O2 levels climb back up to get a really good firestorm! But for all intents, it would still look like, feel like, and in essence BE an atmosphere on fire.\n\nAfter the fire goes out, we have an [impact winter](_URL_2_), photosynthesis grinds to a crawl, and the O2 levels drop like a stone.\n\ntl;dr Possible with massive impact event to kick fuel into the atmosphere.",
"Side question: was there ever any legitimate concern among scientists that a nuclear bomb would ignite the atmosphere, or was this more along the lines of the Large Hadron Collider possibly destroying the universe? I.e. an idea that didn't have a strong scientific basis being popularized and sensationalized in the media. Any combustion scientist could tell you why you can't ignite the atmosphere, so I can't imagine this taking more than a five minute phone call to allay any fears. Come to think of it, a group consisting of the smartest people in the world could probably figure it out on their own in a few minutes.",
"There isn't anything in the atmosphere that would serve as a fuel. For a fire to occur, you need at least two chemicals, an oxidizer and a fuel, that form a product that is at a lower energy state than the fuel and oxidizer had previously been. So, for example, hydrogen will burn in oxygen because the product of their combustion is water, which is at a much lower energy level. The difference in energy between the reactants and the product is the heat given off by the fire.\n\nNow, if you just mix hydrogen with oxygen (or gasoline or wood with oxygen) nothings happens. Why is this? It is because an energy barrier needs to be overcome before a reaction can occur. You need to input a certain amount of energy to break the intermolecular bonds that hold the fuel and the oxidizer together before they will have the ability to react with each other. When they do react, they release even more energy than was necessary to get over that energy barrier. Some of this energy is released as heat, and some of it is absorbed by other molecules of fuel and oxidizer so that they may react with one another. A spark or sunlight or lightening can provide that initial energy necessary to start a fire, and after that it's self sustaining.\n\nWhat about nitrogen oxides? Aren't those the products of oxidation of nitrogen? Might they be set on fire? Well, yes and no. Oxides of nitrogen will form at very high temperatures, but they have a higher energy level than the initial reactants did. So once the energy barrier necessary for their formation is overcome, they won't release enough energy to cause more nitrogen oxides to form. Thus the reaction would not be self sustaining, and there would be no fire.\n\nOther possible fuels, like methane and hydrogen, which are present in the atmosphere, cannot be set on fire because they are too sparse. There simply can't be transported to the fire by diffusion quickly enough to burn. That is, if I light a match, I will burn some of the methane in the air, but the energy will be absorbed by the surrounding gasses such that there isn't enough energy available to the nearby methane to coax it into igniting.",
"I think there's a boat being missed here. The question was: Is it POSSIBLE to set the atmosphere on fire. This is not contingent on current conditions, ratios, or forecasts. So I'll address that question.\n\nNobel Prize-winning physicist [Luis Alvarez](_URL_0_) postulated one way that a significant portion of the atmosphere could be set ablaze. In fact, he says it happened once.\n\nBefore jumping right into that, let's look at the [Fire Triangle](_URL_1_) to see what we need to start a fire. O2? Check. Heat? Check. The only thing missing is fuel.\n\nBut how could we possibly get enough fuel into the atmosphere to make a firestorm that engulfs the Earth in a blaze that reaches miles high into the atmosphere and in fact radically changes the contents of the air for millions of years to come?\n\nDr. Alvarez has the answer. An [Impact Event](_URL_3_). If a heavenly object impacted the Earth with such speed and devastation so as to kick up tons upon tons of dust and vapor... suddenly the fire triangle is complete.\n\nTrillions of particles that leave and re-enter the atmosphere would burn up on their way back down. This would set off a chain reaction. Heat touches off the now-omnipresent fuel in the presence of O2... and you have a global firestorm.\n\nHow long it would burn depends on the size of the impact, the ferocity of the hurricanes generated by the impact, and the state of the atmosphere prior to impact. According to Alvarez, analyses of fluid inclusions in ancient amber suggest that the oxygen content of the atmosphere was very high (30–35 percent) during the late Cretaceous period. This high O2 level would have supported intense combustion. We would likely get a different 'mix' with today's O2 ratios. We may have to wait until O2 levels climb back up to get a really good firestorm! But for all intents, it would still look like, feel like, and in essence BE an atmosphere on fire.\n\nAfter the fire goes out, we have an [impact winter](_URL_2_), photosynthesis grinds to a crawl, and the O2 levels drop like a stone.\n\ntl;dr Possible with massive impact event to kick fuel into the atmosphere.",
"Side question: was there ever any legitimate concern among scientists that a nuclear bomb would ignite the atmosphere, or was this more along the lines of the Large Hadron Collider possibly destroying the universe? I.e. an idea that didn't have a strong scientific basis being popularized and sensationalized in the media. Any combustion scientist could tell you why you can't ignite the atmosphere, so I can't imagine this taking more than a five minute phone call to allay any fears. Come to think of it, a group consisting of the smartest people in the world could probably figure it out on their own in a few minutes."
]
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[],
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"http://www.nobelprize.org/nobel_prizes/physics/laureates/1968/alvarez-bio.html",
"http://www.hantsfire.gov.uk/firetriangle.htm",
"http://en.wikipedia.org/wiki/Impact_winter",
"http://www.newworldencyclopedia.org/entry/Mass_extinction#Theories"
],
[],
[],
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"http://www.nobelprize.org/nobel_prizes/physics/laureates/1968/alvarez-bio.html",
"http://www.hantsfire.gov.uk/firetriangle.htm",
"http://en.wikipedia.org/wiki/Impact_winter",
"http://www.newworldencyclopedia.org/entry/Mass_extinction#Theories"
],
[]
] |
|
1ab6i3 | Why was the WWI Armistice on 11/11 at 11:11? | Why were the elevens important? The teacher gave me a hint that it was about a secret society. | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1ab6i3/why_was_the_wwi_armistice_on_1111_at_1111/ | {
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"It's not a secret society... Conspiracy theorists love to claim that secret societies such as the illuminati have influenced major events in history. \n\nThis would likely be a question for one of the experts like Panzerkampfwagon or NMW to answer. However, until they do, I would suggest that 11:00 was chosen because it is easy to remember and it gave time for the troops to be told.\n\n*edit: Actually... 11:11 sounds dodgy. I am relatively certain that the armistice came into effect at 11:00 not 11:11... Do some independent research on the topic and you will see that the theory of a conspiracy of secret societies has no leg to stand on.\n\nHope that helps...\n"
]
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[]
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2q7te4 | what is an aneurysm | I head Vegeta off, Dragon Ball Z abridged, say to Nappa he had an aneurysm out of sheer stupidity. Since then I've always wondered what it ment | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2q7te4/eli5_what_is_an_aneurysm/ | {
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"dictionary [dik-shuh-ner-ee] \n\nnoun, plural dictionaries.\n\n1. a book, containing a selection of the words of a language, giving information about their meanings, pronunciations, etymologies, inflected forms, derived forms, etc., ",
"An aneurysm (in the medical field) refers to a balloon-like bulge in the wall of an artery. Aneurysms can occur in any artery of the body, but they are most commonly found in the brain because they cause symptoms when they press on your brain matter. Aneurysms can be very dangerous because if they rupture, they cause a hemorrhage. This is especially dangerous in the brain because it causes a cerebral hemorrhage, more commonly known as a hemorrhagic stroke. "
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3qfj5q | When did Harvard become the most prestigious university in America (and maybe the world)? | Other than when it was the only university in America, obviously.
Also, not just when but HOW | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/3qfj5q/when_did_harvard_become_the_most_prestigious/ | {
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"I'm going to go on a limb and actually attempt to answer this question despite people's objections over the definition of prestigious.\n\nHarvard's prestige may have a large part to do with how old it is. For much of colonial New England's history, if someone of means wanted to get a higher education, the only options were to go to Harvard or back to England. \n\nFor obvious reasons, Harvard become a popular option for the rich and powerful of New England society. This cycle feeds itself as new up and comers in the system attempt to form connections with the existing establishment.\n\nBoth Roosevelt presidents can claim Harvard as their alma mater. The Roosevelt family is the closest you can come to naming blue blooded American royalty. The shear number of American and world leaders, justices, business men, etc that have passed through Harvard over the centuries is an inertia that is difficult to overcome.\n\nThis also feeds into another of Harvard's inherent advantages in the prestige department: their endowment. Because of the aforementioned individuals, Harvard gets more donations and can quite literally afford to acquire anything they want. The best facilities, or outbid on acquiring world class faculty. Harvard has a larger endowment than any other American institution of higher learning. On paper, their endowment also dwarfs Oxford's, however Oxford's other assets are more difficult to access."
]
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[]
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|
1ooc5v | Was there any notable resistance by white people against Apartheid in South Africa? | I was reading some articles on wikipedia on Apartheid and there seemed to be resistance by white people against Apartheid in South Africa. I was wondering on what scale it was, if they used force or violence, who the notable figures were, if and how they cooperated with the black/coloured resistance or the ANC and, in general, whether the "white resistance" had an important role or impact? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1ooc5v/was_there_any_notable_resistance_by_white_people/ | {
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"Yes, and, to my knowledge, most of the prominent resisters (rather than the everyday resisters) were communists. Among the most prominent white resisters will always be [Joe Slovo](_URL_6_) (head of the South African Communist party 1984–1991, and a minister in Mandela's first government). He started his political career in a [white-led anti-apartheid social movment](_URL_10_). He was later a prominent member of [Umkhonto we Sizwe](_URL_0_), the armed wing of the ANC. When going through lists of White anti-Apartheid activists, you realize that almost all of them were also Jewish: in addition to Slovo, [Harry Schwarz](_URL_2_) (non-violent resister and prominent member of the legitimate non-Apartheid white parties), [Denis Goldberg](_URL_9_) (a communist involved with armed resistance), [Helen Suzman](_URL_3_) (from 1961-1974 she was the only member of parliament unequivocally opposed to Apartheid), [Helen Joseph](_URL_1_) (another important early activist), [Lionel Bernstein](_URL_12_) (another Jewish communist who ended up imprisoned for his political activism), [Arthur Goldreich](_URL_4_) (who was involved with military resistance and training), and [Ruth First](_URL_8_) (Slovo's wife who was assassinated via a letter bomb sent by the regime while she was teaching in exile in Mozambique). \n\nThe [1956 Treason Trial](_URL_11_) basically aimed to get rid of all major anti-regime opposition. To give you a sense of what the opposition looked like (quoting Wiki):\n\n > In December 1956 many key members of the Congress Alliance were arrested and charged with treason, including the almost entire executive committee of the ANC, as well as the SACP, SAIC, COD. 105 Africans, 21 Indians, 23 whites and 7 coloured leaders were arrested.\n\nAt the famous [Rivonia Trial](_URL_5_) which arrested 19 ANC leaders, six of those leaders were Jews (including some of those listed above), two were Indian, one was of mixed race, and the rest I believe were black. Of the 10 actually tried (including Nelson Mandela), three were Jewish, one was Indian, one person was of mixed race, and five were blacks. Another Jew was on the initially listed on the indictment, but removed before the trial began. \n\nSo yes, there were, but for the most part they were Leftist Jews associated with the Communist Party who cooperated extensively with the ANC (and in fact, were regularly tried alongside ANC members, especially in the early period). That's for more overt resistance. I know there were lots of more subtle acts of resistance, but I can't really list any off the top of my head. One prominent white, non-Jewish opponent of Apartheid was [Adolph Malan](_URL_7_) (at least, I think he was not Jewish)."
]
} | [] | [] | [
[
"http://en.wikipedia.org/wiki/Umkhonto_we_Sizwe",
"http://en.wikipedia.org/wiki/Helen_Joseph",
"http://en.wikipedia.org/wiki/Harry_Schwarz",
"http://en.wikipedia.org/wiki/Helen_Suzman",
"http://en.wikipedia.org/wiki/Arthur_Goldreich",
"http://en.wikipedia.org/wiki/Rivonia_Trial",
"http://en.wikipedia.org/wiki/Joe_Slovo",
"http://en.wikipedia.org/wiki/Adolph_Malan",
"http://en.wikipedia.org/wiki/Ruth_First",
"http://en.wikipedia.org/wiki/Denis_Goldberg",
"http://en.wikipedia.org/wiki/Torch_Commando",
"http://en.wikipedia.org/wiki/Treason_Trial",
"http://en.wikipedia.org/wiki/Lionel_Bernstein"
]
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|
25bbfn | why can some people smoke and never get addicted, while other are addicted for life? | If nicotine is the factor which makes cigarettes addictive, and all the big brand cigarettes have it... Why is it some people can smoke today but then quit without having to deal with cravings at all by the next week?
I understand mind over matter etc. but what is the bigger factor mind or matter? and whats going on biologically? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/25bbfn/eli5_why_can_some_people_smoke_and_never_get/ | {
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"Not everyone is equally susceptible to addiction to cigarettes. I can chain smoke for a few weeks and then just stop for a few weeks without it being an issue. I'm not sure why that is true for me but its possible it may be because I was around second hand smoke a lot as a child.",
"I'll weigh in on this.\n\nI've been suffering from axillary hiperhydrosis (overactive armpit sweating) for around 15 years now since I was a young teen. I can only smoke maybe two cigarettes, at night, after I've had some alcohol before bed. This is attributed to the fact that if I just smoke a cigarette for no reason it will aggravate my condition and it's just incredibly uncomfortable; I'll sweat until the \"nicotine high\" fades away maybe 20 minutes later. So because of this, it makes it no more enticing for me to smoke a cigarette during any other common point of the day. Thus, I don't really get \"hooked\" on constant smoking as a normal \"everyday smoker\" would. \n\nEquating in the alcohol factor, this is because it supresses my sweat glands and my overall body activity, so smoking a cigarette can actually be a bit pleasing at the end of the day after a few beers. Thus, just like susceptibility, it's different for every human being. It's a plethora of biological factors.\n\nEDIT: words",
"It's weird, I have a friend that smokes socially when drinking and will have one if someone offers, but they don't go out their way to buy them daily as far as I can tell. Never understood that. ",
"I smoked cigarettes for about 5 years, probably a little more than half a pack of Newports a day. I started because I noticed that those that smoked had more breaks, all of my buddies smoked, and I had a lot of time to kill (hurry up and wait nature of the army.). I quit smoking the day I finished my contract.\nI have tried to pick it up again here and there, but I just take a puff and throw the rest away. Tastes disgusting, and smells bad to me now. Except black and minds, those smell good. "
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29r7n6 | why are electric cars and hybrids, which have more powerful motors, quieter than power drills and blenders? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/29r7n6/eli5_why_are_electric_cars_and_hybrids_which_have/ | {
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"They have space for more sound dampening. Your car is quieter than a lawn mower for similar reasons.",
"The power tools and such might be using brushed motors which are notoriously louder than the brushless design I would imagine a serious car would use. "
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gqjhs | If I had eyespots instead of eyes, what would I see? | I'm currently in Zoology and we did experiments with protists where we covered half of their dish with a black cloth, etc and watched them migrate to and from lit areas.
I know that they don't really "see" per say and that "sense" would be a better term, but I'm still really curious...
* How sensitive are their eyespots?
* Can they tell the difference between different wavelengths of light?
* I know some protists are photosynthetic (eg Euglena), so would they be able to tell the difference between let's say green light and red light?
* How about their sensitivity to light intensities? If I had a dim light and a dimmer light, would they be able to sense the difference between them? | askscience | http://www.reddit.com/r/askscience/comments/gqjhs/if_i_had_eyespots_instead_of_eyes_what_would_i_see/ | {
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"It seems you have access to most of the things to be able to run some experiments and answer some of these questions yourself. I'm sure your teacher/prof would support you in such a project.\n\nHow about modifying the experiment you did by shining lights of different wavelengths at different areas of the dish? That way you will be able to find out which wavelengths they are attracted to or repelled by.\n\nThe ones that are photosynthetic should be able to \"tell\" the difference between light that is absorbed by their chloroplasts and light that isn't absorbed. Only the type of light that powers their photosynthesis will result in them producing sugars."
]
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2hkszs | When I rub my hands with hand-sanitizer, how do germs leave my hands? | askscience | http://www.reddit.com/r/askscience/comments/2hkszs/when_i_rub_my_hands_with_handsanitizer_how_do/ | {
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"They don't leave your hands (immediately). The alcohol just kills them and breaks them open. \n\nThey fall off at a later point through friction or when your actually wash your hands in water."
]
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[]
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||
11ez0r | Without mass production, how did Rome supply it's vast armies with weapons and armor? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/11ez0r/without_mass_production_how_did_rome_supply_its/ | {
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"By the use of production en masse of course. \n \nDedicated assembly line production with individual workers and work teams focussed on repetitive single tasks didn't really originate with Henry Ford. \n \nThe [Flavian Amphitheatre](_URL_0_) (aka *the* Colosseum) took nearly a decade of continuous labour to design and build starting with the draining, infilling and relevelling / compacting of 6 acres of lake. \nThe subsequent quarrying and shaping of 100,000 cubic meters of stone for the outer wall and the mining, smelting and fashioning of 300 tons of iron clamps to bind them were obviously big jobs, as were transportation, laying, tile making, etc., etc., etc. \n \nThe romans *had* mass production, just not mechanised. \n \nGlassblowers and smiths were artisans at the apex of small armies of wood cutters, charcoal makers, miners, refiners, stokers, bellow monkeys, and (of course) beer & wine makers. \n \nGetting tossed down the salt mines was a grim punishment for those that didn't fall in line and a useful source of salt and human urine for tanning all those hides for all that leather for all those soldiers.",
"Mass non mechanized production with the primary source of labor being slaves! ",
"The Romans used mass labour in forms of smithy's woodcutters etc.\n\nThe best example of pre industrialized mass labour is in England and Wales during the 100 Years War with France. Hundreds of thousands of arrows were produced every year by counties all across England and Wales.",
"It sounds like this question should be \"without assembly lines and interchangeable parts, how did Rome supply its vast armies with weapons and armor?\" \n\nIs that right?",
"I'll just leave this here. [Industry of the Roman Empire](_URL_0_)\n\nTL;DR\nRoman industrial production (especially metal production) at the height of the Empire was not to be exceeded until around 1750 - the beginning of the Industrial Revolution. \n\nEdit: Also, Romans certainly had mass production, so the question should be tailored more towards modern industrial practices, or something like that.",
"This has always been something I wondered as well. Every writer in medieval history seems to emphasize how swords and mail were very expensive, and only the elite could afford them.\n\nYet when we look at Republican Roman history, almost every soldier had a sword and some armor. Even the velites, who were skirmishers, possessed a sword that would mysteriously become impossible for them to own a thousand years later."
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axadua | how are our phones so resistant to bugs, viruses, and crashing, when compared to a computer? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/axadua/eli5_how_are_our_phones_so_resistant_to_bugs/ | {
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"Both Iphone and Android are based from Unix/Linux based systems. In short, these operating systems have much stricter rules on what is allowed to run, or who is allowed to run something. The user isn't even allowed to access most features themselves. In order to get a virus on a phone the way you could with a Windows PC, you would have to basically intentionally run the code on your own and possibly root/jailbreak your phone.",
"Phone OSes came about in a different era of architecture and design (and security awareness) than most OSes. Phone hardware is far more tightly controlled that that of a PC, which can support thousands of different options of each component. Even Android, which is relatively \"open\" as a specification, still has a specification that's far tighter than any PC specification. Even the software distribution is much tighter, as app developers have to submit their apps for testing and certification before they can be published. Yes, Android has \"alternative\" app stores, but those are largely overrun with buggy, virus laden software. There is no such control point for software on a PC.",
"Bugs because the hardware combinations are more limited ~~then~~ than PCs\n\nViruses? They're still vulnerable, less so because the O/S is very locked down always. The user *almost* never has \"root\" control of anything, unlike a windows system where if you have the password you can force through risky things to install if you have no idea what you're doing.\n\n\\*Also phone app stores are the only official way to install onto your phone, those apps are screened by Apple and Google. Sideloaded apps are far more rare and you have to work at getting that done knowingly\n\nAndroid and iPhone are both based off of Unix Like systems→Linux (droid)/BSD(apple) - There's no normal admin account that just gets to do whatever, everything is compartmentalized and locked down making only very rare exploits the likely vulnerabilities.\n\nCrashing? Same as bugs, limited combinations mean a manufacturer can ensure no weird hardware will cause problems and the OS doesn't have to be change much, minor driver differences at best.\n\nMost phones use the same family of chipsets for radios/wifi; screens. Samsung makes tons of shit for apple phones, they need each other. Until recently everyone uses qualcomm\n\nSidenotes:\n\n1. YES I know this isn't quite eli5\n2. For all those grammar enthusiasts, yes I know the difference between then and than, I'm glad someone found a way to backhandedly comment my \"seeming\" intelligence yet complete feeble-mindedness due to a minor lazy grammatical error. Marvelous!",
"Extremely controlled environment. \n\nThe Google/Apple/Amazon store only allows apps that are guaranteed* to work on the hardware their customers have. Those that have incompatible hardware cannot download the apps through the store. \n\nWith great effort, you still can install the program manually and your phone will start crashing and bugging out. \n\nComputers can have any mix of parts that may or may not work as intended by the developers, and be running drivers that may or may not be updated. \n\nSince there's no universal store to buy all your apps from (and probably shouldn't be) developers have to just take a guess at what their user will be installing software on, and hope that they actually read what was and wasn't compatible. \n\nNobody does, and the list isn't complete, so you run into bugs. ",
"Does your phone run Windows?",
"Phones are slightly more stable because when you buy a phone, you get a package that got finetuned to run fine in this exact state. Usually the manufacturer of the phone also customized the operating system and other software running on it. Results may vary depending on how much care the manufacturer put into this process.\n\nThen there's also other control mechanisms to prevent you, the owner of the phone, from changing fundamental configurations. This also helps a bit in preventing you or other people to make your phone do things not intended by the manufacturer - you could call this safer if you want. However, the operating systems of phones are not generally safer than those of computers.\n\nA computer is much more customizable, many more combinations of software and hardware have to work together, and if it's your own computer you usually have all rights, including the rights to do something that damages the way your system should work.",
"because they limit the user in what they can do. on an windows pc you can download and run any .exe you find. in android you have to specifically enable third party apps via hidden menu's before you can do that. on iphone thats basically impossible. this makes it way harder to deliver malicious apps because they have to go through an distributor instead of directly to victims. the operating systems are also limited in what they can do, a lot of niche things the majority of people won't use but are super powerfull. ",
"In addition to what others said, I'll add that most PC viruses spread via email attachments or by clicking bad links. Both are those are mitigated heavily on phones because an evil EXE file, for example, simply won't do anything on a phone - it literally cannot open.",
"I used to be a mobile developer, doing mostly Android but also some iOS development.\n\nApps on a phone are a lot more sandboxed than what you would get on your PC. An android app, for instance, does not have direct access to the storage spaces of any other app on your phone; as far as that app is concerned, using only its own power, you have nothing else on your phone except this app. No matter how hard it tries, it can't escape the little bubble that it's in.\n\nIn order to allow the apps to talk to other parts of the phone, they use \"private methods\" or internal APIs, commands supplied by the OS to let apps access stuff. So, for instance, if your app wanted to access the camera on your Android phone, it would need to go through an API called Camera/Camera2. This is part of the Android OS, and written by Google. There are libraries that wrap this functionality up and make life easier for developers, but in the end all calls must go through that API. \n\nWhat this does is mean that the Android OS can essentially control everything the app does. This is why apps have to ask \"permission\" to access things like the camera; there is only 1 way in/out to the camera (that Camera2 API call), and it can be closed/opened using the little permission toggle. All other permissions work the same way.\n\nThis is very different than Windows, where access to hardware is open to any application that can talk to the hardware drivers, and where any storage on the machine is accessible, as long as it isn't write protected or encrypted by the OS or some other means. \n\nWindows is the wild west, while your phones are highly controlled themeparks. ",
"These days the malware and viruses are right out in the open like [Uber's \"God Mode\"](_URL_1_) spying on you and [Facebook undermining a Presidential election](_URL_0_).",
"They aren't, the systems are just more scrutinized\nCellphone ecosystems are simply easier control in each phase.\n\nTake a peak:\n\n_URL_0_\n\nEdit: typo ",
"Here's is a better ELI5:\n\nYou have two houses.\n\nPC house is large, and has lots of big doors and windows. Many are unlocked, because the family living there wants to be able to go where they please, when they please, and do what they want. This freedom also means burglars can also get into the house easier if the family is not protected. Good families buy alarms systems and security guards (virus protection, firewalls etc).\n\nAndroid is a smaller house, and it's not owned by the family but just rented to them, and it was built with a lot more locked doors and windows the family can't open at all. Neither can burglars. The family gave up some freedom to go where they want and do what they want for more security. Now the family can rip out those locks (root/jailbreak) and get more freedom, but are again at higher risk.\n\nApple house is pretty much a prison. ",
"While others have done a good job explaining why this is true, I'm going to point out that it's not as true as you think it is.\n\n**First of all, phones have plenty of bugs.** Apps have plenty of bugs. Phones crash occasionally. Users just don't notice as much!\n\nMobile OSes started with power usage as a major concern and extremely limited multi-tasking. As such, their app development SDK insisted that 3rd party apps allow the OS to kill them at any time (to save battery) and provided a design pattern to allow \"tombstoning\". The app gets a brief notification that it's about to be killed and can write a little bit of state, then it's shut down. Well-designed apps write this tombstone data ahead of time in case they're killed without warning. When you \"switch back\" to the app, it may actually be started from scratch. It just pretends that it just picks up where it left off.\n\nWhen an app crashes or freezes on a desktop OS, the OS tries to give it a chance to resume working. This make it very noticeable when an app freezes, you get a spinning wheel, then the app UI disappears (and Windows gives you a crash notice). On a mobile OS, the app just crashes, restarts, and picks up where it left off. Sometimes, mobile apps get stuck in a crash-resume-crash loop, but are generally designed to count the number of start attempts and delete the \"resume\" data and start fresh.\n\nWhen a mobile OS crashes, it can do the same thing. Just reboot while the user isn't looking and pick up where it left off because the user isn't watching the individual app windows disappear.\n\n**Secondly, the virus game has changed since the days of Big Internet Worms.** There didn't used to be profit in malware, and so the goal was notoriety. Now, there's a shit ton of profit to be made in stolen user data, cryptocurrency mining, etc. The goal of modern day malware is to be unobtrusive and stay unnoticed, while the goal of famous Windows viruses was to do as much damage as possible. There is plenty of malware on phones, and the most insidious of all are apps that use 100% approved APIs and get the users to grant them permission to their hardware.",
"You mean when compared to a PC running Windows and not Linux or MacOS?\n\n",
"I'd come at this from the other perspective: who says they are?",
"Honestly, they aren't really. The main difference is that an operating system like Windows will let you install just about any piece of software you find on the Internet, while your phone restricts you mostly to a curated app-store that tries to weed out malicious programs. You can sideload apps onto phones, especially Android phones, and in those cases they are just as likely to be infected as any computer.\n\nWe also replace our phones every year or two, but most people keep the same computer for 5+ years, which gives them a lot more time for hardware/software degradation.\n\nA properly maintained PC should have almost identical reliability to a properly maintained phone or tablet device.",
"Simple: Simplicity of OS and hardware compared to a PC.\n\nSimpler: Walled Garden in the case of Apple products: the very thing many people complain about.\n\n**For Apple**, this also includes controlling BOTH hardware design and software design plus implementing critical technologies other platforms still don't really have like:\n\n* Apple designs both hardware and software so it has a level of control over how the device operates that Intel, Microsoft and Wintel vendors could only dream about. Similarly Android can never have the same control over behavior that Apple has because it also splits HW from SW. This is inherently more secure.\n\n* Apple can customize SW to match desired or designed HW features **it has designed**, and it conversely customize HW to match desired or designed SW features, Examples are the security/encryption processors and the motion processors that cooperate with the A-series CPU/GPU chips. Again, split-HW/SW architectures can only dream of this kind of control. So the security/encryption processor stores all thumb-prints, facial recognition and passwords inside of it - you can't hack it out short of opening the device, unsoldering the chip, using a lot of expensive equipment to destructively reverse engineer the chip and there's still a good chance doing that would destroy the data forever. iOS and macOS are designed to exploit this security processor now.\n\n* Use of a Unix-based OS - all networking was originally invented on Unix and similar minicomputer OSs, NOT on PCs - it makes a difference. Unix is generally more security and Windows historically shot itself in the foot by being \"backwards compatible\" which created most of the security problems. Android is a new OS so it's largely untested and Google isn't exactly the most trustworthy companies anyway when it comes to privacy and security.\n\n* Use of a particular variety of Unix called Mach which has a microkernel - the philosophy of which is minimize what is given privilege and put as much as you can into lower privilege user memory spaces. This includes stuff like file systems and hardware drivers. There are SOME kernel drivers but those are minimized and developers are strongly discouraged by Apple from writing kernel drivers. Usually you don't really have to unless you aren't a good programmer.\n\n* Sandboxing all apps so no app has direct memory access to any other apps memory or to kernel (OS) memory without going through special controlled interfaces. Every app lives in it own little virtual machine space where it has to ask \"Mother May I\" to do anything outside that space.\n\n* Declaration of what OS and hardware features you will use (disk, cameras, microphones, etc.) as part of the software BEFORE it's even accepted into the App Store. So you must declare what \"Mother May I\" questions you will EVER ask before start coding or submitting your app to the Apple Store\n\n* Having fairly tough guidelines on what can or can not be in the App Store. For example you can't just say \"I want to access all things all the time\" in the above credentials - that's not allowed and your App will be rejected if you try to do that.\n\n* Curating and reviewing every App to assure they meet the guidelines and rules\n\nStrictly some bad stuff that can still wiggle through but compared to Windows or Android or Linux, it's fairly minimal. This is part of why malware species are several orders of magnitude (1 order = 10x, 2 orders = 100x, etc.) higher on Wintel than Mac or iOS.",
"Who wants to write malware when you could just build an app where a user pays you for the privledge of giving you all their personal data.",
"The viruses are too big to enter the phones\nPhones move around constantly, so the remaining viruses fall off .",
" They arent.\n\nPeople tend to replace their phone every year or 2 and buy top quality phones.\n\nGet a $200 phone or keep your phone for 5 years.\n\nYou will see",
"This is an excellent question OP and I am going to try to offer a partial answer - on security in phones. For a start, any mobile device which has a CPU, RAM, an OS, and an ability to connect with other devices is at risk. \n\nThis includes, cell phones, tablets, some cameras, some in car systems, etc. Those devices are not inherently resistant to security threats but are less of a target for some kinds of attacks (e.g. large scale malware and ransomware) because the people who initiate the attacks normally want to be paid and they can't make much by infecting or encrypting data on a phone (that is changing). \n\nAs well, people on phones tend to use apps much more than Web services, and so they are less prone to downloaded malware and some other kinds of attacks. However, phones are much more prone to phishing (email, text, MMS) of all types as phone users tend to take security less seriously than they should and often respond to phishing attempts without thinking it over. \n\nThe fact that most phones ship without security apps is a part of the problem, but the constant use of social media, texting, Cloud and other services from phones is really the bigger issue. People on phones often inter-mix personal data (useful to criminals for things like more phishing attacks, fraud, black mail, etc.) with work data (valuable to intellectual property thieves, corporate spies, nation state actors, etc.). Those people know that an average person is likely to have both types of data on their phone (e.g. business emails sent to the phone, docs stored from work via the phone, into a Cloud folder). \n\nSo, phones are a target and they are under attack. Most of the time, attackers want your data. That is worth more to them than the phone (some exceptions apply). They are less of a target for **some** kinds of attacks but the threats that are on the rise include:\n\n* phishing (as mentioned);\n* Social engineering (convincing users to share sensitive or private information with another person through manipulation);\n* Surveillance of the user and their location/transactions/shared contacts, etc. via text monitoring, audio tagging, metadata collection, GPS, and a lot more. Much surveillance is done because the user agreed to terms of service without understanding them. Some is done by malicious actors though. \n* Malware (on the rise, including to take control of the phone for things like crypto mining)\n* Malicious WiFi hotspots (someone puts up a hotspot so phone users will connect, and then scans their communications looking for something they can steal/use).\n\nComputers are prone to the same stuff, except that most PCs come with built-in security features, especially under Windows 10 and Mac OS X and from Intel (another whole story) and a lot of users install and run Anti-malware software, a basic firewall, etc. to help secure the PC. PCs get hit far more often than phones and the numbers are staggering, so manufacturers tend to take security seriously (e.g. Microsoft).\n\nThe protections in place on phones are unique though as follows:\n\n1. Apple implements security in iOS (running apps in controlled and secure \"sandboxes\"), uses encryption widely to protect user data (e.g. in iMessage) and in hardware (built in encryption hardware, etc. In a nutshell, Apple iOS is a closed system and that makes it much harder for attackers to figure out the inner workings and then plan/launch attacks\n2. Android, as an OS also forces apps to run in a controlled sandbox, runs a hardened kernel (the \"core\" of the OS). and support a bunch of encryption options (some run w/o user notice). Android is implemented on a ton of different hardware though and so things like device access hardware, file segregation, absence of bloatware, provision of security apps, and lots of other things is down the the phone manufacturer (e.g. Samsung) and some do security well (OnePlus) and some don't (you can google that :)\n3. Both also provide tools to find lost/stolen phones, lock the phone, check that apps are signed and from a known source, block apps, protect OS files, etc \n\nThings start to break down if:\n\n1. Users jailbreak their phone\n2. Side load apps from unknown sites (i.e. not Apple or Google)\n3. Don't use a password, facial recog., thumb print or SOMETHING to lock the phone\n4. Share their device with others who may not be careful and diligent about security of YOUR phone and data\n\nAll of those things put your phone at greater risk. \n\nA few tips on what you can do to improve phone security:\n\n1. Set up a phone login and use a strong PIN or password or switch to biometrics...(at least 8 characters for a PIN)\n2. Turn on phone tracing in case it is lost or stolen\n3. BACK-UP important info (e.g. contacts) from the phone to a PC or into the Cloud in case you need to restore it later\n4. Password protect any Cloud accounts with a strong (like 12+ characters) password\n5. Install a password vault so you do NOT save passwords in something like Note or EverNote (bad idea and password vaults are free or cheap)\n6. Install **all** vendor patches and updates, especially if they say \"Security enhancements\". This is a big issue in Android. Many vendors (looking at you Google) don't offer support for older phones. So, people who can't afford a new phone every 2-3 years are prone to newer attacks (because...no patches)\n7. Install anti-malware apps and set them up to auto scan apps, incoming data, etc\n8. Only install apps from reputable sources and check the security/privacy settings for all apps. If you are done with an app or have suspicions about how it is behaving (often hard to know), consider deleting it\n9. Don't use social media apps on the phone. Seriously, they all suck and all (especially some in the news lately) take your data ALL the time\n10. Read up on your phone's security features and apply those you understand (if not sure, read more)\n\nAll of this applies to phones and tablets. Also, I know I didn't fully answer your question so it comes down to this \"more attacks on PCs, because they are data rich and may provide a pay day so vendors offer more security some built in and some you buy\"...but things with phones are getting worse and because phones are the gateway to much more (Cloud, remote to home, banking, etc.) they must be secured. Long post, but I hope this helps. :) ",
"Most phones lock you down to only using their app store to acquire applications. The app stores are fairly secure and keep malicious software off of it. On a desktop, you have the option to get applications from anywhere you like. This can be a security issue if you're not careful. I believe Windows has made huge strides though and have added steps in preventing you from installing malicious software.",
"If you restrict what the user can do, then the user doesn't have the opportunity to break something.\n\nConsider this. If you went to Mcdonalds, and you were the only customer and you ordered a cheeseburger, the Mcdonalds (operating system) is very efficient at giving you what you ordered. Now if you added more features, like letting the customer pick what they can have on that cheeseburger, there's a chance that mcdonalds might get it wrong. \n\nNow if you had the customer order 15+ things on the menu and they ask for customization on all 15+ things, then you have even more chance of getting something wrong. \n\nBecause the customer is asking for so many things, let's say now you give the customer the ability to pour his own soda to speed things up and the customer drains all of the flavored syrup in the machine and now you can't get soda anymore.\n\nAnd because you're a Mcdonalds, you need to not just serve that one customer, but you may need to add customization for hundreds/thousands/millions of customers, you start allowing for a whole range of customization, well chances are somethign will go wrong.\n\nOn that note, it's dinner time and I'm going to Mcdonalds.",
"Ontop of other good answers \nThere are mainly only 2 main os for computers\nSo a programmer only has to make a few version to work and infect.\nFor phones their is ios and to many versions of android with each device having their own versions",
"Microsoft doesnt really care about the quality of their software, they have been a rent seeking company for a while now, and any change has to make a direct profit in order to maximize shareholder value. When a tech company is run by accountants its easy for competition to creep up which can do a much better job using modern practices.\n\nThey could have implemented virus scanning when downloading and opening a file like Google does, or allow third party software repos, or a number of things; they just dont care because it doesnt make them any more money, its just another job to cut in order to improve dividends.",
"How I thought it worked, was because fewer people were making viruses and bugs for phones. On top of that you have to download entire apps most of the time, which are controlled. Sure you can download files straight to your phone, but you need an app to read them. Most phones come with a photo viewer type app, and a music listener app, but I wish I could just read some epubs.",
"Your computer is a big outside sandbox that has one section for you and all the kids play in. If one of the other kids wanted they could put something in your sandbox of your not skilled enough to realize. This could destroy your sand castle.\nMobile devices are sandboxes that are made of plastic and lifted off the ground, additionally you have to play without actually touching the sand. Other kids cant put things in your sandbox because they can't touch it either.\n\nAs far as exploits go the big sandboxes that are all connected and just sectioned off, the owner has complete control over and could have his sand be destroyed if he makes the wrong friends. \nThe small off the ground secure sandbox is watched by your dad, he won't let you, or your friends destroy it. ",
"Your phone is more like an appliance (or multiple) than it is a computer. It’s always on, you use the screen to enter data (like a calculator or microwave). \nThe apps you install are carefully controlled by Apple A you only download stuff they’ve approved and that goes a long way to limiting risk. \nLike appliances which have been perfected over many years, the phone components and code inside have been perfected. This also means any risks have largely been addressed. \n\nYour pc is a bigger, more complex machine that can do a lot more than your phone and has many more ways to install code, and gives the user a lot more control to mess with it. Hence there is more risk. ",
"Let me **answer you with a question**:\n\n**When was the last time you installed a program on your computer that \"requested\" permissions for its functionality?** When did the program ask to read a file, to access settings, mess with the registry, run in the background, open windows, interrupt your work or similar? Probably never, right? You might get the \"You need administrative permissions\" popup once in a while, but that's it.\n\nIf you think about that observation you will realize it: while there are other factors, the truth is mobile operating systems[1] are built with much tighter restrictions on what their applications can do, and when. If you limit how much your application can do, you have a much easier time making sure it has no ill intentions.\n\nIn practice, and in slightly greater detail, applications built for the smartphone are really \"locked down\". For example, they can't see each other's files on iOS. It seems mind-boggling, but if you think about it, why should Windows Media Player have access to my word documents? On a mobile OS, apps can barely interact with one another -- and that's a good thing. That way they can't ill-intentionally get in each other's ways either.\n\nThis is a very simplified explanation and it lightly ignores other excellent things mentioned in this thread, but I thought that bringing this other question to you might help get the overall picture.\n\n[1] The Operating System (OS) is like the \"main program\" that commands other programs and gives them important functionality. Windows, MacOS, (GNU/)Linux, iOS, Android, etc.",
"To help. Lets start with a simple explanation.\n\nEverything is software utilizing hardware. All malware (virus) is just another application. The applications purpose is typically something unwanted.\n\nCrashes can be software (typically due to bugs) or hardware (possibly due to heat or component failure).\n\nThat being said: Over the years security features have been added into operating systems. Many of these features prevent installation of software without consent. One of the big issues with Windows is the fact that they keep legacy support. So even though they have the newer features by default they leave all the old unprotected stuff available for compatibility. \n\nPhone OS's were created at a point where viruses vectors are very well known. They were built taking these possibilities into consideration. Additionally, the delivery of new software to your phones is in controlled repositories. If you just randomly started downloading apps off of random sites the amount of malware on your phone would increase.\n\nTo sum it up: Hand-held computers running \"mobile\" OS's were created at a point in time when the technology was already long-in-the-tooth.",
"Because mobile OS (iOS and Android) were built in the 2000's with security in mind from the start. Unlike Windows and MacOS, where almost all users have permission to permanently modify the OS, mobile phones use the principal of least privilege [_URL_0_](_URL_1_), or, at least, a close approximation of it.\n\nIn addition to restricting what users can do, mobile OS's restrict what applications can do. They can't modify other applications, they can't (easily) change the underlying OS. They're allowed to change their own data, and, with permission, change your photos, call history, music library, etc.",
"In a normal computer, all your applications, by default, have access to all your files (and also the microphone and camera). Separating them is extremely rare, because, well, mainly because that's how it's always been.\n\nUnder Windows and OSX, you also typically obtain your software by downloading it from the software vendors web site.\n\nOn a phone, every app gets its own sandbox to play in (yes, that's actually the technical term). Also, the system will not let them access certain things like the camera without you giving permission. That means that even if you download malware, it can't really do much: It can't access data stored by other apps, access your camera etc. (Unless it manages to break out of the sandbox, which is not easy and requires an unpatched security issue in the sandbox.)\n\nYou also can't (easily) download random software off the Internet - and putting malware into the Play/Apple store means that Google/Apple *might* find it before you can infect many users (though the reviews are no guarantee!) This makes the initial infection much harder, since the attacker can't just tell you an ad telling you to download the newest flash player.\n\nAdditionally, the sandbox concept, combined with the fact that each phone has its own specific operating system and all phones of that type are exactly identical, means that it's very easy to know what the state outside of the sandboxes is supposed to look like. Thus, the phone can be built to make it very hard to change anything outside, making it harder for the malware to break out of its sandbox (and stay alive there even when the phone reboots). An operating system for a PC has to run on many different configurations of hardware, the user will install low-level drivers, and everything messes with everything, which makes it really hard to tell which changes were supposed to happen, and which ones were done by something malicious.\n\n\nNothing technical (aside from the driver issue that could be worked around) stops you from building an operating system for computers that works like the one on phones, except that it will be unknown, nobody will use it because it has no apps, and nobody will write apps for it because nobody uses it... there are attempts to make this work with existing software, but there isn't enough demand for secure solutions to make them work well, and the ones that build them typically target the ultra-paranoid, which results in very secure solutions that are impossible to use for the average person, eat lots of resources, don't allow you to do many things, etc.",
"They're no more resistant to bugs or viruses than compared to a computer, there's just less of an interest currently in exploiting them because it's harder and the payoffs are harder to make happen automatically.\n\nThey crash less because the people who built the hardware part of the phones also build the software that talks to the hardware (this is called a driver). This way the OS doesn't do anything the hardware can't handle and vice-versa. Your apps still crash more frequently than you'd probably believe, but they're way better at recovering from it.\n\nEventually I'm sure there will be a worm that spreads from phone to phone and scans for photos with a lot of skin in them. After that there will be one that tries to use your online banking apps in the background. Really it's just way harder to do that than install a bitcoin miner.",
"As someone who works in tech support for a cell provider my opinion is it's not that they are resistant, they are just way better at hiding it. Usually by the time any crashes or viruses become noticeable to the user the damage to the OS is already done and you have to wipe/reinstall the OS ",
"Viruses target industry. Why would you build a virus for Joe schmo using his phone to call the kids and use Google maps to get to the restaurant in the neighboring city.\n\nNo, viruses are built to target sensitive data such as military contractor designs and strategies, a law firms data, a companies patented information, etc. That stuff is stored in computers, not phones. Joe schmo using his windows computer to email the kids and check his fantasy football team is collateral damage because computer viruses are built and released. Joe schmos phone isn't collateral damage because there's not nearly as much to be gained from a virus in a cell phone, so there's less viruses out there for there to be collateral damage.",
"Phones don't need viruses, the users ignorantly installs apps that do anything the creator wants. Steal photos, turn on the camera, steal contacts, screenshots, keylogger, etc.\n\nEvery app you install has access to every part of your phone. There is really no need for most viruses. Even so, most every phone out there is compromised in some way.",
"Because the only place you can really download apps is from the App Store on an iPhone. Androids have more sources easily accessible which is why they’re more susceptible to viruses.\n\nThere’s nothing special about a Mac that makes it less likely to get a virus. It’s a combination of people having interest to develop a virus, and people actually downloading them.",
"It all comes down to the fact that Phones and desktops run different Operating Systems. I agree that a controlled environment for apps is a factor like others have pointed out. But it mostly depends on how well the vendors have tested their OS. The virus part heavily depends on how lucrative it is for hackers.\n\nAnd it can also be the other way round. For example I've got a Android phone with LineageOS and an Arch Linux Desktop. I need Anti-Virus Software for my phone, but not for my PC. And my phone crashes much more often than my desktop.",
"If you're on Android, they absolutely aren't.\n\nThe only thing safer about a phone than a PC is that the average user is less likely to mess something up with random app installations thanks to the existence of a curated app store. ",
"For simplicity's sake. Different operating systems need diiferent code to infect. Just like H1N1 doesn't infect slugs. Or if you speak a different language you can't manipulate someone.",
"Computers are designed to let you download any program that alters it in any way you want. Phones aren't. The apps you downloaded are meant to have very limited uses, and the ones you download from the store are specifically vetted.",
"Imagine a computer and an iPhone are like houses. \n\nYou only want to let your friends in, right? You don’t want bullies getting in so you? \n\nWell, if you have a house with 20 doors, you’d have to run around very fast to stop all the bad guys getting in! By the time you close one door, you have people coming though another! This gives the bad guys a better chance of getting into our house! \n\nBut.. if you only have 1 door, you can sit there all day, making sure only friends are allowed in! \n\nYour iPhone is the house with 1 door\nYour PC is a house with 20 doors\n\nThe PC = a house, is often a useful metaphor for teaching kids about computers.\n\nJust a good way to introduce the PC as an entity with access points, how there are good and bad connections, how certain people have access to certain rooms, and how mom (admin) is in charge and makes the decisions and can go in any room, regardless of whether it’s hers. Etc \n\nI find metaphors work well with kids, find something they know about already and draw parallels. "
]
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[],
[],
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"https://www.nytimes.com/2018/03/19/technology/facebook-cambridge-analytica-explained.html",
"https://www.theguardian.com/technology/2016/dec/13/uber-employees-spying-ex-partners-politicians-beyonce"
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"http://cve.mitre.org/cgi-bin/cvekey.cgi?keyword=android"
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"https://en.wikipedia.org/wiki/Principle\\_of\\_least\\_privilege",
"https://en.wikipedia.org/wiki/Principle_of_least_privilege"
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||
4y27lj | what exactly are laminar and turbulent flows and how are they utilized by swimmers? | I know that a laminar flow follows a smooth path where none of the molecules disrupt each other's path and that turbulent is where the path isn't smooth and so little whirlpool type-things occur in the fluid but i don't really understand how they work and how they are used by swimmers. I didn't think the swimmer could decide if the pool is going to be turbulent or not. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4y27lj/eli5_what_exactly_are_laminar_and_turbulent_flows/ | {
"a_id": [
"d6kcarx"
],
"score": [
3
],
"text": [
"The swimmer doesn't control the pool, of course, they only control their body. The water in the pool isn't flowing, if you take the people out it becomes quite still.\n\nRather, the swimmer is moving through the water, and water is flowing around their body. Good technique tries to keep that flow laminar, watch particularly the underwater kicks after a flip turn. In previous Olympics they allowed swimmers to wear suits made of a special fabric that repelled water, further reducing their flow resistance, but that's no longer permitted.\n\nSince their body can only produce a certain amount of energy, the goal of good technique is to convert as much of that energy as possible into motion. That means wasting as little of it as possible producing turbulence.\n\nOther swimmers produce some turbulence, and waves reflect off the walls. That's why swimmers prefer the middle lanes of the pool, the reflection effect is the least. Putting the fastest times there allows the fastest swimmers to face more uniform, calm water."
]
} | [] | [] | [
[]
] |
|
1yagrj | Has there ever been an offensive or invasion in which both armies left, and couldn't find the other? | Like, let's say Italy launches a navy with a landing force to hit North Africa. North Africa did the same to Italy, and upon landing, both nations can't find their enemy's main force. Also applicable to land offensives.
Just using Italy and North Africa because they're the best locations I could think of. | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1yagrj/has_there_ever_been_an_offensive_or_invasion_in/ | {
"a_id": [
"cfit94m"
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"text": [
"Sort of. Ancient armies used to keep screens a lot closer in than modern armies, usually within line of sitght of the main forces. this meant they had a very small footprint, maybe 4-5 miles wide while traveling, and sometimes they had to meander around a bit to find each other. The best example I can think of this is Alexander and Darius II heading to the battle of Gaugamela. They knew there was going to be a fight, and both sides were headed to it, but they actually passed each other up on the road heading to the showdown, and Alexander had to backtrack a bit to get the two armies aligned for a proper face off. \n\n This covers part of your question, it's a good example of two armies heading to a fight and missing each other, but they did find each other after a brief SNAFU. That is fairly typical for ancient battles, the two armies would often have to feel around a bit in situations where the defenders decided to meet the invaders out in the open instead of sticking to static defenses and waiting for them to show up. Scouting wasn't the same as it is now, and as I mentioned screening forces tended to stay much closer in, but eventually when two groups want to fight and are headed towards each other they manage to get it together."
]
} | [] | [] | [
[]
] |
|
cm8tbq | Why do Serotonin-Norepinephrine reuptake inhibitors reduce anxiety when Norepinephrine is an excitatory neurotransmitter? | As above. Why is it that SNRIs such as Effexor demonstrate efficacy in the treatment of anxiety disorders comparable to SSRIs when they also keep more Norepinephrine in the synapse? Is there some sort of downstream result of more norepinephrine that results in anxiolysis? (Neurogenesis, etc?) Could someone with actual education enlighten me?
Also, why is it assumed that more serotonergic activity = decrease in depression when novel antidepressants are often 5HT1A agonists, when the activation of this receptor suppresses serotonergic activity? | askscience | https://www.reddit.com/r/askscience/comments/cm8tbq/why_do_serotoninnorepinephrine_reuptake/ | {
"a_id": [
"ewgtn4f"
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"score": [
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"text": [
"You're not the only one to be confused. This phenomenon has been called [the Noradrenergic Paradox](_URL_3_). However, I will argue that it just looks like a paradox.\n\n[Noradrenaline doesn't cause anxiety](_URL_8_). Libet and Gleason had the chance to electrically stimulate the locus coeruleus (LC) in awake patients. The patients did not experience anxiety. Instead, they felt focused and \"sharp\".\n\nSo, what does noradrenaline (also known as \"norepinephrine\" for inane reasons) actually do?\n\nI'll sum up three theories and tell you why they're actually all the same theory wearing different hats.\n\n1. [Adaptive gain and optimal performance](_URL_4_). The LC-noradrenergic system maximizes utility by selectively promoting engagement or disengagement from tasks. In its low tonic mode, it promotes disengagement and exploration. In its phasic (burst) mode, the LC promotes engagement and exploitation. In its high tonic mode, the LC promotes disengagement and retreat. This is the classic Yerkes-Dodson relationship. And it's the same thing Csikszentmihalyi is talking about when he's talking about \"flow\". If an activity isn't rewarding enough the LC enters low tonic mode, you get bored, and you disengage. If an activity is too difficult the effort isn't worth it and you lose attention, again disengaging. If the cost-benefit relationship is optimal, you enter phasic mode and that's where the magic happens.\n2. [Network reset](_URL_0_). When there is a change in environmental imperatives, the LC-noradrenaline system interrupts ongoing processes to prepare you to respond to this change. In short, it triggers a network reset. When there are a lot of new imperatives, this is like the high tonic mode. When there is little, it's like the low tonic mode. A moderate level equals the phasic mode.\n3. [Unexpected uncertainty](_URL_5_). If you flip a coin and it lands heads, this isn't surprising. Sure, you can't be certain whether it will land heads or tails, but it's exactly a shock. This is expected uncertainty. If it landed heads ten times a row, then you might be surprised. This is unexpected uncertainty. It's the uncertainty you didn't expect. Just like the name implies. The idea here is that noradrenaline signals just that; unexpected uncertainty. Imagine seeing a movie where you can predict everything. It would be incredibly boring. Imagine seeing one where you can't predict anything. It would be worse than boring: it wouldn't make sense at all. The sweet spot is simply a state where everything is just the right amount surprising.\n\nYou might see that they're all the same already. The big difference between the first and last one is a philosophical one. The first assumes that biological systems maximize utility. The last assumes that biological systems minimize error. [These can actually be said to be the very same thing.](_URL_2_) Which makes it a lot of easier for us.\n\nNoradrenaline, then, signals surprise. [This translates to emotional intensity](_URL_7_).\n\nSurprise is neither good or bad but thinking makes it so. It can be good, because it could mean you found a treasure. It can be bad, because it could mean you found a threat. [Which was basically established already in 1962](_URL_6_).\n\nYou're still reading? Good!\n\nNoradrenaline, then, can just as well tell you that life is rich, vivid, and filled with interesting things as it can tell you that it's scary, confusing, and filled with dragons.\n\nWhich is why the noradrenaline-part of the SNRI equation can explain enhanced well-being. People who take antidepressants expect them to have a positive effect. This makes them appraise the noradrenergic stimulation in a positive light. Which improves their mood.\n\nNow, this is already pretty long so I won't get into your second question. Instead I'll direct you to [this paper](_URL_1_), which may clear things up for you."
]
} | [] | [] | [
[
"https://www.cell.com/trends/neurosciences/fulltext/S0166-2236(05)00243-2?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0166223605002432%3Fshowall%3Dtrue",
"https://www.boksem.nl/pdf/tops2009bc.pdf",
"https://www.frontiersin.org/articles/10.3389/fpsyg.2013.00710/full",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4780187/",
"http://www.people.vcu.edu/~mreimers/SysNeuro/Aston-Jones%20&%20Cohen%20-%20Nor%20Epi%20Function.pdf",
"https://www.cell.com/neuron/fulltext/S0896-6273(05)00362-4?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0896627305003624%3Fshowall%3Dtrue",
"https://psycnet.apa.org/record/1963-06064-001",
"https://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1003094",
"https://www.sciencedirect.com/science/article/pii/0006899394902747?via%3Dihub"
]
] |
|
135g6e | Does turning your heat on in your car while driving waste gas? | If yes, is it an amount that actually makes a difference or is it a few cents every hour. I'm just curious since winter is here! and i have always heard people argue both ways | askscience | http://www.reddit.com/r/askscience/comments/135g6e/does_turning_your_heat_on_in_your_car_while/ | {
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"text": [
"It is almost \"free\". Your engine normally has to rid itself of excess heat by transferring the heat to the environment. In the case of using the car heater, a fraction of that excess heat is funneled through the passenger compartment on its way out into the world. \n \nThere is a tiny bit of excess energy used when you turn on the heater, since you have to pump the coolant fluid through the heater core and run a blower fan to move the warm air into the passenger compartment and circulate it around. The difference in fuel consumption is trivial. ",
"_URL_0_\n\nMost cars heat up air by running it over hot water from the engine.",
"Also something that I have not seen mentioned:\nSome cars will engage the A/C compressor while the heat is on in order to \"dry\" the air, before heating it.\nMy ranger does this in most heating modes.",
"Watch this, it will answer every question. Top gear study involving a jaguar. _URL_0_",
"In relation to OP's question. Do we use gas when we use the A/C during summer?",
"You do not waste gas using your heater. Heat is pretty much free when dealing with an internal combustion engine - you just need to move it to the right place when it is cold outside. When it's hot outside you want to keep the heat away from you. \n\nWhen you turn on your heater, a valve opens letting engine coolant fluid flow into the cab of your vehicle to a component called a \"heater core\". This is essentially a small radiator, and when hot coolant flows over it it gets warm. Air then gets blown over the heater core and heat is transferred from your engine into your cab. You are actually helping cool your engine by doing this which is counterproductive when trying to warm up in the winter. This is why it takes forever to get heat - your engine has to get to operating temperature to transfer the heat from the engine into the cab. \n\nThe amount of fuel you use is proportional to the amount of drag the engine has to overcome to get you going. The biggest factor is wind resistance, then friction and other components that draw power from your engine such as alternators, power steering pumps and air conditioning compressors.",
"Depends. For the normal heat in your car, the other comments are probably right.\n\nFor heated seats, these work with an electric current which comes from the battery which is charged by the engine, so yes."
]
} | [] | [] | [
[],
[
"http://www.howacarworks.com/article/how-the-heating-and-ventilation-systems-work"
],
[],
[
"http://www.flixxy.com/audi-a8-diesel.htm"
],
[],
[],
[]
] |
|
1z1jqv | Combining magnets: Stack or spread? | I have in my possession a large quantity of tiny, disc-shaped magnets. My problem is basically that of making a refrigerator magnet to hold a heavy item. The individual magnets are too weak to hold it, so I'm trying to combine them.
My question is, should I stack the magnets end to end, or spread them side-by-side? I experimented with both, and it *seems* that stacking is slightly better, but I want to know for sure, and I want to know *why*.
| askscience | http://www.reddit.com/r/askscience/comments/1z1jqv/combining_magnets_stack_or_spread/ | {
"a_id": [
"cfptuff",
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"I have an answer! But I need to wait until I'm home to look at my notes from a magnetics course I took a few years ago for the specifics. But the basic idea is that the shape of the magnet plays a large role in the strength of the field on the surface and on the uniformity of the field. \n\nA magnetic material consists of many magnetic domains or groups of north/South poles. Exposure to a magnetic field can align these domains and depending on the type of material, this new orientation can \"stick\" (coercivity and susceptibility will explain this). Now think of these domains as lots of little arrows, when we have a short wide object like a disk for example, all the arrows are side by side such that you have a global North and South pole with respect to the whole disk. But think about how all these arrows that are side by side are internally repelling the adjacent arrows or domains since you have adjacent like poles. \n\nNow compare this to a tall narrow magnet. You have lots of arrows pointing in one direction in a chain of sorts and a few side by side. Therefore, by stacking them we can increase the length of these chains without adding more adjacent chains. However, there is a point where you have too many stacked magnets and you have diminishing returns therefore after about 3\" (neodymium) it is better to put them in parallel. Of course all of this is way oversimplified but it gives you a general idea. \n\nTldr: taller is stronger but there is a limit, best solution is use parallel short (2-3) stacks. \n\nSource: masters in magnetic field assisted finishing\n\n",
"To clamp heavy paper to the fridge? Or glue the magnet(s) to your heavy object, then stick it on the fridge with nothing between the steel surface and the magnets?\n\nIf gluing magnets to your object ...we can take a hint from rubberized magnet sheet, the kind which plummers and real estate companies give out as ads. Those sheets are polarized with mm-wide stripes of alternating NSNSNS. A sheet with all one pole is much, much weaker, and the Roto-rooter ad just slides right down the fridge front. With the polarized stripes we create a partly closed magnetic circuit through the steel fridge surface: shorting the N and S poles together. In the same way a horseshoe magnet lifts more than twice the weight of a single similar magnet pole, and NASA was freaking out about the extreme forces in Halbach Arrays a few years back.\n\nSo, first glue together many small separate stacks of disks (to form little cylinders,) then pack these cylinders in a checkerboard array of NSNS. Perhaps lay the array against a flat steel surface with wax paper, glue it all together, then pull it off the steel and remove the wax paper. That should convert the disks into a fierce magnet, even if it only was 2X2 or 3X3 square.\n\nIf you have some small pieces of sheet steel, you can cover them with these checkerboard arrays as a field-shorting backing. This makes the front of the array a bit stronger. If your disks are really tiny, get a big steel washer and try sticking them side by side NSNS around the ring. Stick that on the fridge. (Will you need a screwdriver to pry the thing off again?)\n"
]
} | [] | [] | [
[],
[]
] |
|
fu3cm | concerning infinite temporal regress | a multifaceted question here: I was talking to a teacher of mine and he brought up St. Thomas Aquinas and his 5 proofs for god. At least two of his arguments deal with the assertion that it's impossible to have infinite temporal regress (e.i.: an infinite past) and that there must be a beginning reference point (my teacher gives the argument that if there were an infinite amount of time in the past when would "now" exist?) and the argument then goes on to state that the beginning is called god.
now, putting aside the god arguments (which i think have a lot of 'argument from ignorance' and 'god of the gaps' problems with them) i'm more curious about the impossibility of an infinite temporal regress. Is this just an interesting logic problem or is there a real problem with understanding whether or not we can have infinite time going backwards as we can going forwards?
Another question that comes up is that if there was an infinite amount of time both forwards and backwards does that mean that time is cyclical?
Also do we have any ideas about what existed not only before the big bang but what exists outside the ever-expanding limit of the universe? | askscience | http://www.reddit.com/r/askscience/comments/fu3cm/concerning_infinite_temporal_regress/ | {
"a_id": [
"c1imx9x"
],
"score": [
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"text": [
"The biggest problem with gravity since it was first understood all the way up to the modern era is the fact that *the universe exists.* By all rights, it *shouldn't.* All matter and energy should have collapsed into gravitational singularity aeons ago.\n\nOf course, now we know that gravitation is not the only mechanism that changes the geometry of the universe. Metric expansion does as well, and that's how we can be here to wonder how we can be here.\n\nPart and parcel of the combination of metric expansion and gravitation is the unavoidable fact that the universe *had a beginning.* In fact, we can measure the amount of time that's elapsed in the cosmological reference frame since the beginning of the universe with a degree of precision that might seem startling at first. We know it to within about ten million years, which may sound like a lot, but is really very little on that scale.\n\nSo no. The universe cannot have existed for infinite time. If it had, it would look very, very different to us today than it does. And, again, we probably wouldn't be here to wonder about it.\n\nIf you want to postulate that it was a deity that sparked creation, go right ahead. There's no one who can say you're wrong.\n\nAs for your last two questions, I'm afraid they're both meaningless. There was no \"before the Big Bang,\" because the Big Bang was the beginning of everything, including time. And there's no outside-the-universe because the universe is infinite and thus has no outside."
]
} | [] | [] | [
[]
] |
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