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1u2ce3
|
When will the Andromeda Galaxy be close enough to be visible to the naked eye? How big would it be in the night sky?
|
In reference to this post/picture: [Andromeda's actual size if it was brighter](_URL_0_).
At what point in time will the Andromeda Galaxy be close enough to be visible to the naked eye, perhaps not as bright as this picture depicts it. And, how big would it be in the night sky?
Thanks.
|
askscience
|
http://www.reddit.com/r/askscience/comments/1u2ce3/when_will_the_andromeda_galaxy_be_close_enough_to/
|
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"Andromeda is visible to the naked eye now, in decent light conditions. It has an apparent magnitude of 3.4. It is more than six times the width of the moon in the sky, but the full diameter is not bright enough to be seen.",
"I do not know when it will be visible to the naked eye, however NASA has a great image showing different stages of what the collision will look like as it happens (as seen from earth, of course) over the next 7 billion years (which may be a moot point as our sun has less than that much time left to it if I recall correctly), which is half of your question answered:\n\n_URL_0_\n\nAnd this youtube video has a beautiful simulation of the collision (just not from an earth view):\n\n_URL_1_"
]
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[] |
[
"http://i.imgur.com/EpuhHJa.png"
] |
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[],
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"http://science.nasa.gov/science-news/science-at-nasa/2012/31may_andromeda/",
"http://www.youtube.com/watch?v=PrIk6dKcdoU"
]
] |
|
ptrs1
|
How did Newton derive the Law of Universal Gravitation?
|
I just learned the Law of Universal Gravitation in my physics class, and I understand well what it means and how to use it to calculate gravity...but how did Newton derive it? I've done some Googling around but I can't find any solid step-by-step proof of it.
|
askscience
|
http://www.reddit.com/r/askscience/comments/ptrs1/how_did_newton_derive_the_law_of_universal/
|
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"Observations demonstrated that the planets in our solar system orbited the Sun in ellipses. Newton discovered through his investigation (IE invention) of Calculus that a body undergoing acceleration proportional to the inverse square of their distance would travel in an ellipse. He then made a mental leap and realized that observable natural laws we see on Earth also are obeyed in the heavens, and thus concluded that the process that causes an apple to fall to the ground is the same force that keeps the Moon in orbit around the Earth and the planets in orbit around the Sun. He then reasoned that every particle in the universe acts on every other particle with this force, meaning that the force between two objects must be related to each of their masses.\n\nIt was this series of mental leaps that led to his deduction of the law of gravitation. There was very little theoretical derivation involved; it was mainly an assertion which turned out to be demonstrably accurate. The gravitational constant G was not known for nearly a century afterwards when it was finally empirically measured. No known first principle derivation can produce G, so it remains an empirical observation.",
"I think we'll never know his exact train of thought. Looking in the Principia isn't very helpful, since it's all written in lemma/theorem/corollary style math. I don't know if he wrote about the less rigorous version of how he got to the idea.\n\nIf you wanted to try to guess at it, without knowing the answer, you could probably come up with something that looks similar to Newton's equation. Once you decide that *there exists an attractive force between massive objects*, which I think is the big intuitive leap, you look around and say, well these two apples aren't hurtling towards each other, they hurtle towards the earth. This force should be proportional to the masses, so that bigger masses apply more force. It could be the square of the masses, but why complicate matters from the start? Next, since the earth is round, and the planets move around the sun in ellipses (known by Newton's time), it is reasonable to suppose that this force emanates radially from a mass, equally in all directions. If this force fell on the points of a sphere of radius r, it would be spread over an area of 4 pi r^2. Therefore, the same object would have a lesser effect farther away, as the lines of force it was emanating would be less dense, and this drop off would be inversely proportional to r^2.\n\nFortunately, using his new mechanics and the calculus, this simplest law that takes into account observations turns out to be the correct one, as Newton showed by reproducing all known planetary motion from one universal law. It worked so well that it took a few centuries before scientists found the holes and plugged them up with General Relativity.",
"Exactly how Newton derived gravitation can be found in his Philosophiæ Naturalis Principia Mathematica. \n\nHowever, from a more approachable standpoint: you can take Kepler's Laws of Planetary Motion, which are based on observation, and derive the Newton's inverse square law. It is a fairly standard homework problem for intermediate mechanics level physics students. \n\nEssentially, you start with Kepler's 1st law - make sure to include the radial and tangential unit vectors - and take two time derivatives. You will get an acceleration that has a piece in the radial direction (r-hat) and a piece in the tangential direction (theta-hat). Newton makes the assumption that the force between two celestial bodies acts only on the line between them, i.e.: only in the r-hat direction. Therefore, the terms in the theta-hat direction must equal zero. \n\nBy setting these to zero you get an expression that expression that is equivalent to conservation of angular moment. dL/dt = 0 & L = r^2 d(theta)/dt. You can leverage this new found constant into the rest of the second derivative to arrive at the inverse square law.",
"Newton actually modified Kepler's Laws of planetary motion which had previously assumed that the Sun was immovable.\n\nBecause for every action there is an equal and opposite reaction, Newton realized that in the planet-Sun system the planet does not orbit around a stationary Sun.\n\nInstead, Newton proposed that both the planet and the Sun orbited around the common center of mass for the planet-Sun system.\n\nNewton simply changed this to include centre of mass as a consideration.\n\nNewton defined the force on a planet to be the product of its mass and the acceleration. What he changed was Kepler's assumption that: \n\nA) Every planet is attracted towards the Sun.\n\nB) The force on a planet is in direct proportion to the mass of the planet and in inverse proportion to the square of the distance from the Sun.\n\nHere the Sun plays an unsymmetrical part which is unjustified. So he assumed Newton's law of universal gravitation:\n\nA) All bodies in the solar system attract one another.\n\nB) The force between two bodies is in direct proportion to the product of their masses and in inverse proportion to the square of the distance between them.\n\nThe gravitational constant that he posited was not calculated till much later.\n"
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57rts5
|
can the body repair a rupture of a spinal disk?
|
what happenes in the body when you rupture a disk in your spine and can the body repair or heal itself? what can happen if this condition is left untreated?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/57rts5/eli5can_the_body_repair_a_rupture_of_a_spinal_disk/
|
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"So I ruptured the disk in my neck. The doctor explained it like this:\n\nThe disk is like a krispy Kreme doughnut. When it ruptures the jam inside spills out. It could split on the inside or on the outside. On the outside is not such a problem. However on the inside it can directly apply pressure to the nerves it surrounds. After a while this jam can 'dry' out and can retract back inside. This is painful for obvious reasons.\n\nNow the non ELI5 bit. See a doctor if you can. If you loose feeling or get pins and needles in a limb see one immediately. This is, according to my doctor 'really bad'. Now I just had extreme pain, we are talking screaming and being taken away in an ambulance high on ketamine bad. The 'jam' was only 2.6mm according to the scans. It has healed but is weaker and occasionally happens again to a less serious degree each time. "
]
}
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[] |
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89finh
|
Have there ever been a situation where a booming city or town went "out of business"?
|
Edit: Please ignore the title typo!
I'm not talking about an ancient city that was wiped out or something along those lines, I'm thinking of a situation where maybe a city was built around a valuable resource that was either made to be obsolete or diminished to nothing and the town could no longer afford to continue to operate (or operate on the level it previously did).
If a city no longer had enough tax payers would civil servants need to be fired? Would government need to be made smaller? Would they need to merge with other nearby municipalities?
It doesn't have to be this exact scenario but something like this.
A less severe scenario I was just reading about would be Schenectady NY which used to house the headquarters of GE and many other large factory jobs. It was once a city of about 100,000 people in the 1930s and has since diminished to about 60,000 because of all of the jobs leaving the area.
So I'm interested in learning about stories similar to this but much more drastic.
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/89finh/have_there_ever_been_a_situation_where_a_booming/
|
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"This sort of thing is THE hallmark (not just A hallmark!) of the Intermountain West. Towns frequently burst into existence around the discovery of an ore body with precious metals. But precious metals being what they are, they are typically rare, and so while an ore body might seem promising, it was a finite resource and typically limited at that. This resulted in a rush to the new location with people eager for an opportunity to strike a claim, find a job, or to provide essential services. This often resulted is a sudden rise in population and the building of a lot of structures. When the ore was exhausted, the population would just as suddenly dwindle. Buildings were often hauled away to the next boom - or they fell victim to a harsh environment.\n\nIf the community was sufficiently long-lived and promising, it might succeed in establishing itself as the seat of county government, with the promise of a few jobs when the boom subsided. That said, seats of government can be moved - and they frequently are - so even this source of revenue and employment was vulnerable, and some communities went from shadows of their former selves to complete oblivion.\n\nThere are hundreds of instances of all of this in the vast uninhabited outback of Nevada, the seventh largest state in the nation (with roughly 87% of its land under federal management). In the nineteenth century, Hamilton was home to an important mining boom and became the county seat of White Pine County. It yielded that title to Ely, which retains it to this day. Dayton prospered as a result of it being able to offer milling to the Comstock Mining District, but as the mines failed, so did Dayton. It retained the title of Lyon County seat until its courthouse burned in 1910 (locals maintain it was arson caused by someone who wanted to move the seat of government). Dayton subsequently dwindled, although it has enjoyed a recent resurgence as a bedroom community. Yerington took the seat of government, and it retains that title.\n\nAustin in central Nevada became a boomtown with such promise that everyone thought it would overtake Virginia City, which was suffering a slump (Virginia City's mines prospered for an astounding two decades before it also crashed). An entrepreneur even moved Virginia City's International Hotel to Austin in the mid 1860s, and Austin became the seat of government for Lander County (building what is likely the nation's last Greek revival courthouse, erected in 1872). Its mines quickly failed. It lost a part of Lander County to neighboring Eureka County (experiencing another mining boom-bust cycle), but it retained its government for nearly another century until Battle Mountain was able to take the seat of Lander County government.\n\nOne of the most dramatic examples of this phenomenon involved Goldfield, often put forward as the site of the last gold rush in the continental US. Shortly after the turn of the century, thousands flooded into remote south-central Nevada and established the town of Goldfield, which quickly took the title of Esmeralda County government from Hawthorne (which had earlier taken it from failing Aurora, now a ghost town). At one point Goldfield had about 25,000 people and was the largest city in Nevada. Its mines failed within a decade, and eventually Hawthorne began a fight to regain its seat of government: although its mines had also failed, it was able to claim other means of support. Ultimately, the Nevada government split the enormous Esmeralda County to form two new counties, so both places could have the benefit of county government. Goldfield and its diminished Esmeralda County declined until that enormous piece of real estate (rivalling the size of some smaller states) had only a little more than 300 residents.\n\nThis cycle of boom and bust has resulted in what may be a record for the most times that \"largest community in the territory/state\" has been exchanged: That title has moved from Dayton (AKA Chinatown) to Mormon Station (AKA Genoa) to Carson City to Virginia City to Reno, to Goldfield, back to Reno, and finally (or so far!!!) to Las Vegas. That's eight times that the title has moved; whether that is record could be contested here, but it is certainly remarkable.\n\nThis is a pattern throughout the mining West, caused by an industry with resources located in remote, often inhabitable land, where cities boomed into existence because of the attraction of wealth, and then just as quickly disappear. Two state parks are dedicated to this phenomenon: California's Bodie State Park and Nevada's Berlin State Park both commemorate the nineteenth-century quest for wealth and ingenuity that it took to scrape together an existence where nature provided little - together with the inevitable abandonment of the towns when it was no longer possible tor resist the effects of gravity.",
"I spent some time as a youth in a small town in Missouri named \"Excelsior Springs\" which I've always thought of as a great example of a boom town.\n\nThe town of Excelsior Springs was formed around several fresh water springs in the area that all had different alleged \"healing properties.\" Within a year of the town being officially founded by two men named Flack and Wyman in 1880, almost 200 homes had been built in the area.\n\nBy late 1881, schools, an opera, and several hotels (including [this famous 1888 hotel I worked at briefly](_URL_0_) ) were being built. No other city in Missouri had ever seen as much growth as Excelsior Springs in a single year by this point. It continued to expand, building a golf course and becoming a destination for a few US Presidents.\n\nNow before I continue, what made/makes Excelsior Springs springs so unique is their incredibly diverse and dense combinations of different minerals found in the waters. For example, there are only 4 springs in Europe that have relevant levels of Iron and Manganese, and the only two in the United States are located in Excelsior Springs. There are over 20 different springs with different levels of types of minerals, making it one of the most dense areas of mineral-enriched spring water in the world. This was the primary reason for the idea of the waters' healing properties, and the explosive growth of the town.\n\nIn 1963, with help from national organizations like the Arthritis and Rheumatism Foundation, legislation was passed that prevented many of the clinics that had opened in the area from advertising the spring water as \"cures.\" In addition, the Saturday Evening Post published an article called [The Hucksters of Pain](_URL_1_) which destroyed a lot of the credibility of the springs' healing properties.\n\nA combination of modern medicine, the dying of 3 railroad nodes in the area, and former citizens leaving the city for greener pastures essentially killed off the city by the 1970's. You could say their main source of revenue... *evaporated*\n\nIt still exists today, and the Springs are still a tourist destination, but the amount of abandoned Art Deco buildings and boarding houses still seen today are both beautiful and indicative of a lost age for the small town.\n\n\n",
"I'll answer this from a slightly different angle, in how these towns entertained themselves, using three ice hockey teams as examples:\n\nThe Upper Peninsula of Michigan, was the home of the first openly professional ice hockey league during the early 1900s, a direct response to a mining boom, particularly copper, that occured. The governing bodies in Canada refused to allow professionals, but the US was a little more lax on amateurism (at least in regards to hockey, at that time), so the International Hockey League was formed in 1904, based in several towns that grew due to the mining industry (and Pittsburgh, as it had an arena with artificial ice, I believe the first to do so). But with the 1907 crash in commodities, and the subsequent legalisation of professionals in Canada at the same time, the IHL folded up; however most of the top ice hockey players of the era played at least a few games in the league during this time period, giving it some added notoriety. Just a small note about the impact of boom-towns and what happens around them.\n\nThe Klondike Goldrush also saw the formation of an ice hockey team in Dawson City, Yukon, though several years after the goldrush had ended. The team, the Dawson City Nuggets, are most known for their 1905 Stanley Cup challenge, in which they travelled across Canada, travelling variously by train, dog sled, boat, and walking, until they reached Ottawa and played the strongest team in the country, the Senators (known unofficially as the Silver Seven). The Nuggets would proceed to lose the two-game series 9-2 and then 23-2, the latter being the largest margin of victory in a Stanley Cup game.\n\nA similar situation happened with the Ontario town of Kenora, known as Rat Portage until 1905. It experience a minor boom when the Canadian Pacific Railway built a stop there in 1877, lasting until about 1908. They established a hockey team, the Thistles, comprised entirely of local players, and competed for the Stanley Cup four times between 1903 and 1907, winning in January 1907. With some 5000 people in the town at the time they were, and remain, the smallest city/town to win the Cup, and after losing it in March 1907, the shortest holders of the trophy. The economic downturn, and advent of professionalism spelt the end of the team, which folded in 1908.\n\nThere are probably more examples I could add, but the above three are the most famous ones in hockey, and show both the rise and fall of boomtowns and their economies. All of them happened for simple reasons: these rapidly-growing towns/regions had an influx of people (mainly young, single men) who suddenly had a lot of disposable income, and they needed entertainment. Sports proved to be a great answer to that, especially as betting was a huge part of sports culture in the early 1900s (and far more open and prominent than today). Of course once the economic upswing ended in these places, the teams died out, just as quickly as they arrived, and they are now largely footnotes, somewhat insignificant in the overall status of hockey today (while the IHL helped push forward professionalism in Canada, it was arguably only a matter of time before that happened).\n\nSources:\nInterestingly enough, there are several academic papers on this very topic (at least for the IHL and the Thistles; nothing on the Nuggets that I know of, yet):\n\n* Daniel Mason, *The Origins and Development of the International Hockey League and Its Effects on the Sport of Professional Ice Hockey in North America* (1994). Mason wrote his MA thesis on the IHL, which has come to be regarded as the major source for the league. He later published a condensed form as a journal article, \"The International Hockey League and the Professionalization of Ice Hockey, 1904-1907\" in *Journal of Sport History*\n\n* John Wong, *From Rat Portage to Kenora: The Death of a (Big-Time) Hockey Dream* another article in *Journal of Sport History* looks at the economic impact of the Thistles, and how it shows the rise and fall of these boomtowns.\n\n* For the overall impact of all three, I'd suggest:\n* Michael McKinnley, *Hockey's Rise from Sport to Spectacle* (2000). Not an academic work, but thorough (even though he lifted a passage in the book from somewhere else; yes, plagiarised), and goes over these three examples in particular.",
"(1/2)\n\nWell I'm pretty late here but I thought I could maybe add something about buccaneer or pirate \"boomtowns\" in the 17th and early 18th centuries. The economic impact of theft at sea could be very important, not just to those whose wealth was stolen and not just to the thieves themselves but also to thriving communities in port side towns who set themselves up to benefit from this plunder, in many ways far more than the buccaneers and pirates ever did. These port side towns known today as \"pirate havens\" thrived on this sometimes huge influx of stolen plunder that the buccaneers brought back with them from their raids and usually recklessly spent ashore on alcohol and prostitution, or cheaply fenced to enterprising merchants. \n\nAlthough their glory days are long gone, the names of some of these major havens in the Caribbean like Tortuga, Port Royal and Nassau still live on and conjure up images of drunken and debauched pirates rampaging through the streets. Of course something like this has always been a stereotype of sailors in all eras but the added impact of huge amounts of stolen plunder made these piratical and violent sailors especially extravagant and important. However, as European nations increasingly grew to have more peaceful and mutually beneficial trading relations with one another in the late 17th and early 18th century, those governments that had once given tacit or explicit support to the buccaneers as lawful privateers began to turn on them and outlaw them as pirates. And with that crackdown on piracy, those port side towns that had once thrived on it also quieted down faded away into obscurity. I believe the last real \"pirate haven\" came to an end in 1718 with the British capture of Nassau in the Bahamas, although by then the era when buccaneers could readily rely on real safe-havens offered by complicit local governors had already disappeared at least several decades earlier.\n\n**The heyday of Tortuga and Port Royal**\n\nOne of the first notorious pirate havens in the Caribbean was the island of Tortuga off the north coast of Hispaniola (modern Haiti). Although claimed by the Spanish, it was first taken over and settled by French adventurers in about 1625 who survived by hunting wild cattle and pigs in the wilderness and then selling the hides and smoked meat to passing ships (the apparatus on which they smoked the meat was referred to as a *boucan* and this is where the words bacon and buccaneer come from). Despite only numbering a few dozen at first and despite being attacked and driven away several times by the Spanish, the French settlers on Tortuga and nearby Hispaniola always returned and quickly grew in number. By the early 1630s they were striking back at their Spanish attackers by undertaking acts of piracy against passing Spanish ships using small boats. By the 1640s and 1650s, the buccaneers had grown bolder and they were joined in Tortuga by hundreds of English and Dutch privateers who banded with them to attack the Spanish, either by capturing Spanish ships at sea or raiding coastal towns. \n\nBy the 1660s, buccaneers in Tortuga had reached the height of their power and frequently sacked large Spanish towns along the Caribbean before returning to Tortuga to spend their loot. The former buccaneer surgeon Alexandre Exquemelin writing in 1678 describes a typical return voyage of buccaneers under their ruthless leader Francois l'Olonnais after sacking the Spanish towns of Maracaibo and Gibraltar in 1666:\n\n > Having divided the spoils, the buccaneers set sail for Tortuga, where they arrived with great joy a month later. For some the joy was short-lived -- many could not keep their money three days before it was gambled away. However, those who had lost what they had were helped by the others. A short time previously, three ships had arrived from France with cargoes of wine and brandy, so liquor was very cheap. But this did not continue for long: prices quickly went up, and soon the buccaneers were paying four pieces of eight [equivalent to about $200] for a flagon of brandy. Tortuga at that time was full of traders and dealers. The governor got the ship laden with cacao for a twentieth of what it was really worth. The tavern-keepers got part of their money and the whores took the rest, so once more the buccaneers -- including l'Olonnais their chief -- had to consider ways of obtaining more booty. (Exquemelin, 104)\n\nAlthough the governors and merchants in Tortuga benefited tremendously from all this, their ultimate control over things was often tenuous and nominal at best. The buccaneers tended to be strongly independent and violently ready to oppose government regulations. The French governor of Tortuga, Jean le Vasseur, was killed by the buccaneers in 1653 after a dispute. In 1669 when Bertrand d'Ogeron, the French appointed governor of Tortuga, attempted to impose trade restrictions and tariffs on the buccaneers living on the island, the buccaneers rose up in arms and shot at him in his boat. Then a group of them planned to attack the governor's fortress and kill him, only being dissuaded when two fully armed French warships showed up to intimidate the buccaneers into retreating to the woods. The French soldiers landed and burned down the buccaneers' houses but then negotiated and agreed to the buccaneers' demands of free trading rights.\n\nThese towns were often extremely violent places because pirates themselves were engaged in a very violent business. Exquemelin describes how buccaneers would frequently get into quarrels and kill each other or fight to the death in duels. The behavior of later pirates in the 1720s in a base they had established in Madagascar was described by one observer like this:\n\n > When we bartered with the Pyrates at Ranter-Bay for Provisions, they frequently shewed the Wickedness of their Dispositions, by quarrelling and fighting with each other upon the most trifling Occasions. It was their Custom never to go abroad, except armed with Pistols or a naked Sword in their Hand, to be in Readiness to defend themselves or to attack others. (Downing, 115)\n\nDuring this same time in the English town of Port Royal in Jamaica, the situation was no less violent and chaotic. Captured from the Spanish in 1655, Port Royal quickly became an alternate base for buccaneers to freely spend their loot. As in Tortuga, the settlement in Jamaica was under constant threat of Spanish invasion to recapture the island and this contributed to it becoming a refuge for buccaneers who were longstanding enemies of Spain. As in Tortuga, the English, French and Dutch buccaneers came there to recklessly spend their loot on alcohol and women before departing again to bring back more. This was vividly described by the former buccaneer quoted earlier in his 1678 book *The Buccaneers of America:*\n\n > Captain Rock sailed for Jamaica with his prize, and lorded it there with his mates until all was gone. For that is the way with these buccaneers -- whenever they have hold of something, they don't keep it for long. They are busy dicing, whoring and drinking so long as they have anything to spend. Some of them will get through a good two or three thousand pieces of eight in a day -- and next day not have a shirt to their back. I have seen a man in Jamaica give 500 pieces of eight to a whore, just to see her naked. Yes, and many other impieties.\n\n > My own master often used to buy a butt of wine and set it in the middle of the street with the barrel-head knocked in, and stand barring the way. Every passer-by had to drink with him, or he'd have shot them dead with a gun he kept handy. Once he bought a cask of butter and threw the stuff at everyone who came by, bedaubing their clothes or their head, wherever best he could reach.\n\n > The buccaneers are generous to their comrades: if a man has nothing, the others will come to his help. The tavern-keepers let them have a good deal of credit, but in Jamaica one ought not to trust these people, for often they will sell you for debt, a thing I have seen happen many a time. Even the man I have just been speaking about, the one who gave the whore so much money to see her naked, and at that time had a good 3,000 pieces of eight -- three months later he was sold for his debts, by a man in whose house he had spent most of his money. \n\n > ... but to return to our tale. Captain Rock soon squandered all his money, and was obliged to put to sea again with his mates.... (Exquemelin, 81-82)\n\nThis \"Captain Rock\" mentioned here was known by the nickname Rock Braziliano and was originally a Dutchman. He was known to be incredibly violent and Exquemelin goes on to describe how in the early days of Port Royal he would get drunk and prowl the streets with his henchmen, attacking random people who got in his way and hacking off their limbs or killing them with his cutlass. Apparently the governor and any law-keeping forces in Port Royal were too afraid to do anything or arrest him. In fact, they probably not only feared violent retaliation from Braziliano's own crew (who were probably capable of killing the governor just as French buccaneers had done in Tortuga) but more importantly if they made an example of him that it would scare off other buccaneers from using Port Royal as a safe-haven. That would not only deprive Port Royal of its main source of revenue but leave the town virtually defenseless against Spanish attacks.\n\nPort Royal was grew to be referred by contemporaries as \"the wickedest place on earth\" and the \"Sodom of the New World\" one English clergyman wrote this description:\n\n > This town is the Sodom of the New World and since the majority of its population consists of pirates, cutthroats, whores and some of the vilest persons in the whole of the world, I felt my permanence there was of no use and I could better preach of the Word of God elsewhere among a better sort of folk. (Talty, 139-40)"
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[],
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"https://www.elmshotelandspa.com/",
"http://connection.ebscohost.com/c/articles/18086891/hucksters-pain"
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5mxjni
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why does your body temperature increase when you're nauseous and or vomiting?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5mxjni/eli5_why_does_your_body_temperature_increase_when/
|
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"text": [
"Body temperature doesn't increase because you're nauseous or vomiting.\n\n It rises so it can kill the intruder, like bacteria. \n\nVomiting happens so the body can get rid of the bacteria. I assume the main reason for vomiting is that the body tries to get rid of the material that has the intruder in it. Like spoiled food.\n\nIt also happens even if you ingest safe substance because the body doesn't know it's safe. "
]
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698f5i
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why do kids and some adults jump up and down when excited or happy?
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[deleted]
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explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/698f5i/eli5_why_do_kids_and_some_adults_jump_up_and_down/
|
{
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"text": [
"Have you never done this? Never gotten so excited and filled with energy you just have to move? It's an energy release. We're also social animals and this is a way to express our excitement. \n\nPlus it's good for ventilation, moves the air around."
]
}
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[
[]
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415cpk
|
Did the U.S. Government encourage people to move to the suburbs during the Cold War in order to avert catastrophic population losses from nuclear attacks?
|
I'm reading [this article](_URL_0_), and it says:
> Postwar suburbanization and the expansion of transportation networks are occasionally overlooked, but weirdly crucial facets of the military-industrial complex. While suburbs were largely marketed to the public via barely concealed racism and the appeal of manicured “natural” landscapes, suburban sprawl’s dispersal of populations also meant increased likelihood of survival in the case of nuclear attack. Highways both facilitated suburbs and supported the movement of ground troops across the continental United States, should they need to defend it (lest we forget that the legislation that funded much of the U.S. highway system was called the National Interstate and Defense Highways Act of 1956).
It seems to suggest that the Cold War-era U.S. Government encouraged people to move to the suburbs and built highways, in part because it would mean that not so much of our population would die due to nuclear attacks on our cities.
Is there any truth to this? Is it even possible to know?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/415cpk/did_the_us_government_encourage_people_to_move_to/
|
{
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"cyzw5lv",
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"text": [
"I've never found any evidence suggesting it did.\n\nKathleen Tobin has written [an article](_URL_0_) claiming that policymakers' fears of atomic attack was a significant factor in population dispersal. I find it to be an astonishing piece of rhetorical sleight-of-hand, using a few magazine articles discussing the *concept* of dispersion to prove that it was federal policy—despite the absence of a single federal law or regulation on the subject.\n\nAs for the role of Interstate highways, those were proposed long before the Cold War, and throughout the years of congressional debate, military strategists repeatedly testified that they didn't need any particular routes or geometric specifications, always saying that highways built to promote commerce would also serve their needs. To Pres. Eisenhower, the public-works and job-creation aspects of the system were about as important as defense aspects. I am not aware of any serious civil defense or military rationale that was part of Congressional debate. The words \"and Defense\" were added to the name of the \"National System of Interstate Highways\" in conference committee, almost as an afterthought, and played no role in congressional voting. See *Congressional Record* 102, Part 8, pp. 10991-10997. The definitive source on this history is Rose, Mark H. *Interstate: Express Highway Politics, 1939-1989.*",
"There were definitely a lot of government _discussion_ about the value of dispersion, from the point of view of civil defense (ameliorating damage from a nuclear attack). An article that discusses them in some detail is Peter Galison's \"War Against the Center\" (2006). In the 1950s, for example, the Bureau of Commerce directed planners in metropolitan areas to move new industry outside of city centers. Project East River, in 1952, studied the problems of dispersion specifically as civil defense issues, and the ways in which you could encourage it to happen (e.g. by making it a consideration in federal loans, insurance, and contracts). There were also some cases of specific federal agencies (like the Atomic Energy Commission) having their headquarters being located outside of assumed target areas (in this case, the AEC was moved to Germantown, MD, rather than Washington, DC). Apparently there were some tax incentives put into place for moving industry out of prime metro areas in the early-to-mid 1950s. \n\nSo there was urging, there was planning, there were many pamphlets and studies. Is this why dispersion and suburbanization actually _happened_? That, I think, is a harder argument to make. There are lots of other reasons (economic and social) that can be more directly attributed to those movements. I am not sure (and Galison's article does not indicate) whether these more heavy-handed inducements (other than the aforementioned tax benefits) actually were put into place. "
]
}
|
[] |
[
"http://www.nextgov.com/big-data/2016/01/70-percent-global-internet-traffic-goes-through-northern-virginia/124976/"
] |
[
[
"https://pdf.yt/d/ngRmM9OYAqvydrAi"
],
[]
] |
|
ec8io3
|
how are roads on steep cliffs built?
|
Whenever I am driving through the mountains I always end up on a road going along the middle of a steep cliff and I've never understood how the road crews and engineers built the road on the first place.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/ec8io3/eli5how_are_roads_on_steep_cliffs_built/
|
{
"a_id": [
"fb9tvhn"
],
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"text": [
"Dynamite. I remember going on a hike somewhere in Utah and there was a trail that was originally going to be turned into a road but they just left it unfinished and made it a trail instead. You could see where they drilled the holes and were going to blow the cliffside. It takes a lot of precision to keep it somewhat level and prevent the whole side of the cliff from just crumbling. To level the road, they'll just use all the dirt and small rock debris to make a flat surface, then pour asphalt over it"
]
}
|
[] |
[] |
[
[]
] |
|
16xr8c
|
Why is it so hard to distinguish between something that is cold versus something that is wet?
|
askscience
|
http://www.reddit.com/r/askscience/comments/16xr8c/why_is_it_so_hard_to_distinguish_between/
|
{
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"c80cfw8"
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"text": [
"Gonna take a shot here.\n\nAn object feels cold because we're feeling heat transfer away from our skin. This is dependent on both the temperature difference between our skin and the object, and the heat insulation/transmission properties of both. The faster heat transfers, the colder a contact feels.\n\nWater has a very high specific heat and transfers heat quickly, so a small temperature difference still transfers heat quickly as opposed to touching something like titanium with a large difference, since titanium transfers very slowly. A wet object with a ten degree difference will feel colder than titanium with a twenty degree difference.\n"
]
}
|
[] |
[] |
[
[]
] |
||
2u06kt
|
If I lived in the USSR during the purges, were there any choices or steps that I could take to guarantee my survival, and to what extent could this not require moral compromises like denouncing innocent neighbors?
|
For example: imagine if I volunteered myself and my family to work on a farm in a remote area. Might we avoid being denounced if we isolated ourselves in this way?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2u06kt/if_i_lived_in_the_ussr_during_the_purges_were/
|
{
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"text": [
"There wasn't anything that would guarantee survival, but there were things you could do to increase your chances. Even in the worst years, 1937-1939, the number of people who were \"repressed\" (contemporary term for those that were arrested and either deported, imprisoned, or executed) was between 1.5 and 2 million -- about 1% of the total population of the country. So your chances to survive we're pretty good -- unless you were one of the priesthood, or a relative of former czarist civil servants or officers, or rich, or Jewish, or a supporter of the wrong political movement du jour, or, funnily enough, being a communist party member -- in 1936-39 arrest rate among those was 50%!\n\nGenerally, not being one of the above, and not getting yourself noticed (e.g. making political statements in front of others, having a business or trading \"under the table\", being in someone's way (always a good chance of being denounced)), you would have very good chances to survive, above 99.9% I would say.\n\nSources: born there and know history; Conquest's \"The Great Terror\" (1990), Rogovin \"The Party of the Executed\" (in Russian). ",
"If you were brave, in decent health, and had the resources, you could have done like the Lykov family and [fled into the Siberian wilderness](_URL_0_).\n\nOf course, this was not easy, by the Lykov account, and most of the family did not survive to old age. On the other hand, they lasted altogether for several decades, which might have been more than if they stayed.",
"I hadn't intended to write so much on this so apologies if it comes across as somewhat disjointed. It started out as a reply to /u/Impstar2 but ended up rambling well beyond that.\n\n**Repression Deaths**\n\nJust a note on the figures. There's obviously been a huge amount of debate and controversy on these over the past few decades but the trend, as I can see it, has tended to favour lower numbers to those popularised by Conquest. \n\nThis debate became particularly acute when Getty *et al* published, in English, the official NKVD archival figures of 682,000 executions for 1937-38. Now, nobody accepts these numbers literally but they serve as a lower boundary to the estimates and are more useful than the previous estimates and guesswork that had informed Conquest's work.\n\nWith this in mind, today's estimates for 1937-38 (in English language literature) typically tend to range from 1-1.2m deaths. But, as I say, this is still a pretty contented area. Going beyond deaths and into the broader category of 'victims of repression' is even more difficult.\n\nThe important point is that while these numbers are high, and are higher when you add in Gulag figures, they do not represent a cull of the Soviet population in general. Soviet citizens would know about the purges but there was little to fear unless they were in one of the below victim groups.\n\n**Victims**\n\n/u/Impstar2 is right to point out the degree to which the elites suffered. The ranks of Communist functionaries was particularly gutted. There is a great story of two young graduates and junior party members (Ponomarenko and Chuyanov) being called up to party offices in Moscow only to be immediately packed off to the regions as the new heads of the Communist Party in Belarus and Stalingrad, respectively. In many ways this was a clean sweep of the pre-Purge party leadership.\n\nBut the Purges weren't an entirely elite affair, as was once thought. The majority of deaths were products of the 'mass operations', Order 00447 being justly infamous. In addition to those with suspect class backgrounds, at high-risk were those labelled 'socially harmful elements' (eg homeless, beggars, prostitutes, 'hooligans'), the intelligentsia and petty criminals. In addition, the 'national operations' targeted a range of suspect national minorities.\n\nAnd, of course, there was pure bad luck. Getty provides the example of Turkmenistan in 1938 where \"a fire at a factory became an occasion to meet 'quotas' for sabotage by arresting everybody who happened to be there and forcing them to name 'accomplices' (whose number soon exceeded one hundred persons)\". He also notes that \"it was always possible to round up people having the bad luck to be at the marketplace, where a beard made one suspect of the 'crime' of being a mullah.\"\n\nBut, while there is still debate on how far down the terror reached into society, for most people who never appeared on the state's radar there was, other than bad luck, little to fear. Workers in high-priority industries or with in-demand skills were relatively unscathed by the repression. (The draconian labour laws to tighten labour discipline didn't begin to appear until late 1938.) Workers were also protected to a degree by their enterprises, who were loath to lose skilled labour.\n\nEven those that were at risk could sometimes survive by moving (so called self-dekulakisation) and getting work elsewhere. (Occasionally the neighbouring village was far enough, the Soviet state apparatus being uncoordinated enough that this sometimes sufficed.) This was after all a society continually in flux.\n\n**Sources**\n\nMichael Ellman's *Soviet Repression Statistics* is a nice summary of the 1990s literature on the topic, particularly the repression deaths. \n\nThe key post-Soviet paper on repression is Getty *et al* *Victims of the Soviet Penal System in the Pre-War Years*, which gave rise to a range of related polemics and articles. That also serves as the reference for 'bad luck'.\n\nThe story on rapid promotion during the purges came from Shelia Fitzpatrick's *Education and Social Mobility in the USSR*.\n\nFor general discussion around the purges and the nature of its victims, see Paul Hagenloh's *Stalin's Police* and Gerland and Werth's chapter on mass violence in *Beyond Totalitarianism*.\n\nThe note on 'self-dekulakisation' came from Mark Edele's *Stalinist Society.* Also useful, in understanding the reactions of ordinary people, is Sarah Davies' *Popular Opinion in Stalin's Russia*."
]
}
|
[] |
[] |
[
[],
[
"http://www.smithsonianmag.com/history/for-40-years-this-russian-family-was-cut-off-from-all-human-contact-unaware-of-world-war-ii-7354256/?no-ist"
],
[]
] |
|
8skrco
|
how does 50% sodium salt exist?
|
As sodium is a fundamental ingredient to the molecular structure of salt with a 1:1 relationship, how does Morton or other salt companies create the same amount of salt but with something like 50% less sodium?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/8skrco/eli5_how_does_50_sodium_salt_exist/
|
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"text": [
"Well since salt is 50% Sodium and 50% Chloride technically speaking all salt is 50% sodium.",
"They displace sodium chloride with potassium chloride. It doesn’t taste exactly the same, which is why light salt tastes a bit strange.\n\nSource: _URL_0_",
"\"Salt\" is the name of a wide variety of compounds. Sodium Chloride is table salt, but other like potassium iodide are also salt.\n\nLow sodium salt is just a salt that uses no or less sodium. ",
"We call NaCl \"salt\" like we call ethanol \"alcohol\"; there are many kinds of both salt and alcohol, but most people are only familiar with a few of them. \n\n50% sodium salt is just regular NaCl mixed with another salt, usually KCl. It's a bit ironic that people without sodium-sensitive medical conditions turn to it for health reasons because KCl can actually be harder to get rid of, especially for diabetics, and can be *more* detrimental to health than NaCl. This is a very common theme; chemistry illiteracy is so rampant that people often run from something relatively harmless to embrace something else that can be worse."
]
}
|
[] |
[] |
[
[],
[
"https://www.mortonsalt.com/home-product/morton-lite-salt-mixture-2/"
],
[],
[]
] |
|
1gnc53
|
If only one photon goes through a double-slit, is there an interference pattern on the other side?
|
I've read this in the novel Improbable and have a few questions about it.
Most importantly: Do we know for sure that this happens?
And has the photon, which is a particle *and* a wave, therefore multiple positions?
Also, why would this change when the photon is observed?
|
askscience
|
http://www.reddit.com/r/askscience/comments/1gnc53/if_only_one_photon_goes_through_a_doubleslit_is/
|
{
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"calv29z",
"calwdt2"
],
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12,
7
],
"text": [
"Yes. Have a look [here](_URL_0_) for more information. \n\nIt's not so much that the photon has multiple positions as that its position is not known accurately. This uncertainty in the position allows the photon's wavefunction to interfere with itself, because its probability distribution is spread over both slits.\n\nIf you observe the photon going through one slit, you lose your interference pattern because there's no longer any probability that the photon went through the other slit.",
"Whether the photon has got multiple locations depends on which interpretation of quantum mechanics you follow. Which means that the question isn't answered by quantum mechanics, as \"having one position\" isn't covered by the equations (as /u/YouGotTheTouch said, it is a \"political affiliation of a banana\" kind of question if you only look at the equations). Why it changes also depends on the interpretation.\n\nIn the Copenhagen interpretation, the photon behaves like a wave and passes through both slits simultaneously, interacts with itself, and then behaves like a particle when it is observed. The reason that i starts behaving like a particles is that its wave function collapses.\n\nIn the many-world interpretation, different versions of the photon passes through different slits in different worlds. These worlds can interact, to a certain degree, forming the interference pattern. However, once the photon is detected, the world where is has been detected in one place cannot interact with the worlds where it was detected at another, so while one version of you sees one outcome and another version sees another, the two version of you cannot communicate. This decoupling of the worlds is the reason why it stop \"behaving like a wave\" (it never really did in the many world interpreation).\n\nIn the de Broglie-Bohm interpretation, the photon is always a particle, so it travels through one slit. However, it is affected by a wave function, which can travel through both slits. The wave function then interacts with itself, causing the particle to show an interference pattern. Here, it was always a particle with a definite position, and its speed is deterministically determined by the position of every particle in the universe.\n\nedit: typo"
]
}
|
[] |
[] |
[
[
"http://en.wikipedia.org/wiki/Double-slit_experiment#Interference_of_individual_particles"
],
[]
] |
|
4d1w8x
|
Why can you rename, or change the path of, an open file in OS X but not Windows?
|
askscience
|
https://www.reddit.com/r/askscience/comments/4d1w8x/why_can_you_rename_or_change_the_path_of_an_open/
|
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"text": [
"The Windows filesystem identifies files by their paths (including the file names)—if you change a file’s path, applications and the operating system will perceive it as a new file with no connection to the original.\n\nThe OS X filesystem identifies files by an independent file ID, which remains fixed if the file is moved or renamed.",
"Another aspect of the problem is that Windows has something called a *share mode* on open files—basically, an application can open a file in *exclusive* mode meaning that no other program can do anything with the file. It is not possible to circumvent the share mode. This is extensively used in Windows and part of the reason why you have to reboot to apply updates.\n\nUNIX-like systems (like Linux) only have *advisory* file locking which can be ignored by other processes if they decide to. Once a lock is violated, the process is notified of that circumstance and can proceed to handle the case. A rogue process cannot lock up critical files with no way out.",
"I believe the explanation for this goes back from DOS (which was partially based on Unix and CPM). Open files are stored via FCB (file control blocks) which is an older system but was changed to file handles. These handles are nothing but integers that uniquely identifies the current file along with its complete path. \n\nIf a certain program or task if holding up a file handle for write mode, it locks any changes to the file from other users/tasks. This includes its current file system path.",
"In Windows, the file is like your full name, and in unix like os it's like your social security number.\n\nIf you change your name, nobody knows you're you anymore. But if you change your name, you can still be identified by your social security number.\n\nIt's like a photograph of you wearing specific clothes versus a DNA imprint.\n\n",
"The question is incorrect.\n\nWhile all these other answers do point out valid differences between Windows 95 and Linux, the [thing is that you actually can.](_URL_0_) It just depends on the lock level - if the lock level is too high (likely because the application cares about the path not changing) the file can't be moved.\n\nThe reason is simple: regardless of how the file system represents a file, both Windows and Unices (Mac, Linux, BSD, etc.) represent a file as a handle once you open it. The filename is only used to create that handle - it can change afterwards, it no longer matters.\n\nAs for NTFS, the on-disk representation has similarities to Linux. The argument about inodes only applies to FAT - i.e. Windows 9X.",
"I'd just like to mention that, for some reason, you can change the filename of a video while it's playing in PotPlayer, and even move it to another folder, without having to stop the video. ..no idea why it works though.",
"The big question I want answered... how come on either operating systems you have: \n\n* New\n* Save\n* Save as...\n* Close\n\nbut never a \"Rename\" option. It seems like such an obvious option. I suspect 75% of the time, when I use Save As I have to go and delete the old file, because really I just wanted to rename. "
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[
"http://pastebin.com/B5m3a0RM"
],
[],
[]
] |
||
2ehyhn
|
Is it just complete coincidence that the outline of the moon fits nicely inside that of the sun during an eclipse? And if so, what an amazing coincidence it is...
|
askscience
|
http://www.reddit.com/r/askscience/comments/2ehyhn/is_it_just_complete_coincidence_that_the_outline/
|
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"text": [
"It's only a co-incidence for here and now. A billion years ago the moon was a lot closer (tides would have been a bitch). In a billion years it will be a lot farther away.",
"The fact that the Moon and Sun are very similar angular sizes in our sky is indeed a complete coincidence. The Moon has retreated somewhat from the Earth over time, and earlier on it would have fully covered the Sun, including most of the corona.",
"Exactly like you said it's an amazing coincidence. Moon was much closer at the beginning and it will be further away in the future. So it will be seen smaller than the sun in the sky. It's getting away about 3.78 cm per year. \n\nSo not only it's a coincidence that they are about the same size, it's a coincidence that we live in a time that they are. "
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
x4i66
|
If someone died and had their brain preserved, could we map their entire neural network?
|
Do we have the technology to analyze every synapse and neural connection, or is that only possible while they are living?
|
askscience
|
http://www.reddit.com/r/askscience/comments/x4i66/if_someone_died_and_had_their_brain_preserved/
|
{
"a_id": [
"c5j3zko"
],
"score": [
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"text": [
"Yes, but a dead brain may look very different than a live brain. \n\nCurrently, in vivo techniques (MRI, PET, CT, etc...) do not have the resolution required to do this. Serial block imaging along with automated taping lathe ultramicrotome and heavy duty custom neural imaging software can reconstruct every synapse and connection, but the data file would be in the petabyes. \n\nEssentially, here is how this works: a brain is frozen in a big block of ice, and a VERY thin blade shaves off a very small section at a time. Something in the micrometer range. After every time a piece of brain is shaved, an electron microscope takes an image. From there, computer software can reconstruct the brain in 3d and trace individual neurons and their connections. It is an exciting time for the field of connectomics. \n\nCheck out these links: \n\n[Quest for the connectome](_URL_0_)\n\n[Sebastian Seung's](_URL_1_) I am my connectome. His [faculty webpage at MIT](_URL_2_) is also a great read. \n\nEdit: Also to further answer your question, this cannot be done in an alive human. In alive people, the best resolution we can get is 1.5-2 mm, which contains thousands of neurons and other types of cells (such as glial cells)"
]
}
|
[] |
[] |
[
[
"http://www.guardian.co.uk/science/2012/may/07/quest-connectome-mapping-brain",
"http://www.ted.com/talks/sebastian_seung.html",
"http://bcs.mit.edu/people/seung.html"
]
] |
|
odd4w
|
What percentage of lift is generated by the shape of an airplane wing and what percent is generated by the angle of attack?
|
10 degree angle of attack, Clark Y airfoil with aspect ratio of 6. _URL_0_
|
askscience
|
http://www.reddit.com/r/askscience/comments/odd4w/what_percentage_of_lift_is_generated_by_the_shape/
|
{
"a_id": [
"c3gca2v"
],
"score": [
2
],
"text": [
"Well, depends what kind of wing it is, first of all. Secondly, speed, pressure altitude, temperature, etc. Tons of variables to consider here aside from the shape of the airfoil and the AoA.\n\n\nWould be a good question for [/r/AskEngineers](/r/AskEngineers) or [/r/aviation](/r/aviation)."
]
}
|
[] |
[
"http://en.wikipedia.org/wiki/File:Lift_drag_graph.JPG"
] |
[
[]
] |
|
1lnt5k
|
Is everything at least a tiny bit soluble in water?
|
Wikipedia, without citation, states:
> [The extent of solubility ranges widely, from infinitely soluble...such as ethanol in water, to poorly soluble, such as silver chloride in water. The term insoluble is often applied to poorly or very poorly soluble compounds.](_URL_0_)
Which leads to two questions:
1. Would a solution of water at a high enough temperature and pressure in a closed system contain enough energy to split the covalent bonds connecting (for example's sake) at least a single carbon atom in a diamond molecule matrix, hence making it at least a tiny bit soluble?
2. Even at STP, is there enough *variation* in the energy contained within a water solvent--the rational being similar to how a pot of boiling water does not boil off all at once--to break at least a single carbon atom in a diamond molecule matrix (that presumably has variable energy contained within the structure itself)?
Thanks!
|
askscience
|
http://www.reddit.com/r/askscience/comments/1lnt5k/is_everything_at_least_a_tiny_bit_soluble_in_water/
|
{
"a_id": [
"cc147f8"
],
"score": [
5
],
"text": [
"Enough energy isn't the problem, there's more than enough in a macroscopic amount of water, it's the probability of having enough energy in one spot (e.g. a single carbon atom) to cause the reaction you want (the carbon atom dissociating). The probability of that decreases exponentially with the (energy required)/(absolute temperature), so it's never an exactly zero probability except for the fictional situation where the substance would be at absolute zero. But since it's exponential, it also means it quickly becomes an astronomically small number if the energy required is large. \n\nThe equation in question that describes this is the Boltzmann distribution.\n"
]
}
|
[] |
[
"http://en.wikipedia.org/wiki/Solubility"
] |
[
[]
] |
|
4ul7wc
|
How does physics address the situation in Zeno's arrow paradox? (This is not the same as the Achilles and tortoise paradox)
|
[deleted]
|
askscience
|
https://www.reddit.com/r/askscience/comments/4ul7wc/how_does_physics_address_the_situation_in_zenos/
|
{
"a_id": [
"d5qw998"
],
"score": [
9
],
"text": [
"Velocity cannot be determined by the position of the arrow at one given instant of time. So you can't say \"at an instant in time, the arrow is still and not moving\". You have no idea whether the arrow is moving or not moving. You need at least two positions to calculate its average velocity over the time elapsed. As the time elapsed goes to zero, the average velocity goes to the exact instantaneous velocity."
]
}
|
[] |
[] |
[
[]
] |
|
3s6vio
|
how does preloading games on apps such as steam work?
|
I understand that it gives you a download before the game is released so you can play as soon as it is released. I don't understand how once you have the game files it can still restrict you from playing. Is there another final component to download or..?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3s6vio/eli5_how_does_preloading_games_on_apps_such_as/
|
{
"a_id": [
"cwulsgj"
],
"score": [
6
],
"text": [
"Two ways:\n\n1. The game files are encrypted, and the decryption key is given only when the game is released.\n\n2. Most of the game files are assets such as music, textures and models. The actual game executable is relatively small. Preloading downloads these assets but not the executable."
]
}
|
[] |
[] |
[
[]
] |
|
6i9e1k
|
Are there any nuclear fusion processes that don't give off excess energy?
|
Take hydrogen fusion in a star, for example. Under intense gravitational pressure, two hydrogen atoms shack up and become helium. Much like a newlywed couple that moves in together, they don't need two toaster ovens - in fact they don't even have the space, so the excess luggage is discarded (one helium atom consists of less energy than two separate hydrogen atoms, because their spare toaster oven was ejected in the form of photons).
Is there any scenario in which two elements will fuse together 'perfectly' and not require shedding off some spare energy? Or does fusion always require some overcoming of, perhaps, a natural repellent electric charge that, when overcome by pressure, will result in an ejection of energy?
|
askscience
|
https://www.reddit.com/r/askscience/comments/6i9e1k/are_there_any_nuclear_fusion_processes_that_dont/
|
{
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12
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"text": [
"Yes, many fusion reactions don't release energy, but *take* energy instead. Generally, fusion of two heavy nuclei will be endothermic."
]
}
|
[] |
[] |
[
[]
] |
|
bxgaim
|
when you google a certain store or restaurant and it gives you a bar chart of peak times, where does the data come from?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/bxgaim/eli5_when_you_google_a_certain_store_or/
|
{
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"eq6c1rf",
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"text": [
"When you have Google Maps, you can turn on location tracking to help Google learn certain tasks. For example, it will learn where your home and work are, and what route you usually take to get there, so then it will send you a message when it's time for you to leave for work based on current traffic. \n\nWhen you have location tracking enabled, Google can use GPS to determine that you're probably at a particular store or restaurant if you linger in that location for a while. So if Google notices that around 6pm, not many phones are announcing their location at a particular restaurant, but at 7pm, a lot are, then at 8pm, not many are pinging again, they can surmise that 6pm and 8pm aren't very busy, but 7pm is. \n\nRepeat that over weeks and weeks and they can build a pretty good idea of how busy a restaurant or store will be at any given time.\n\nIf you use google Maps, you can even look at where Google thinks/knows you have been. Go to Menu > Your Timeline and it will show a history if you have location tracking enabled. For instance,[ here's some of my tracking from yesterday.](_URL_0_) I didn't have to do anything or even confirm I was at those places. Google Maps just knew from my GPS.",
"If you have an android device or Google maps, they track your location 24/7. \n\nIf you're curious, Google lets you sign in and see the data they collected on their \"Google Maps Timeline\": [_URL_0_](_URL_0_) \n\nIt's incredible. Time-stamped, accurate to a few feet, going back YEARS. \n\nSo, when you see those peak usage times, that's essentially a count of android phones inside the store at certain times.\n\nThey do something similar for the Google Maps traffic. Track the speed of phones, and you know the speed of traffic, live.",
"Simply put. Google knows where you are because you use Google apps and opted in for location tracking. So based on that data, they can predict the busy times by how many people are at that location at a given time."
]
}
|
[] |
[] |
[
[
"https://imgur.com/iFiaD3R"
],
[
"https://support.google.com/maps/answer/6258979?co=GENIE.Platform%3DAndroid&hl=en"
],
[]
] |
||
jvijf
|
Why do we get frustrated?
|
What is the evolutionary advantage of being so frustrated that you are willing to shake a baby?
|
askscience
|
http://www.reddit.com/r/askscience/comments/jvijf/why_do_we_get_frustrated/
|
{
"a_id": [
"c2ffz8w",
"c2ffz8w"
],
"score": [
10,
10
],
"text": [
"Just because we do it, doesn't mean there is an evolutionary advantage or that it is even related to evolution.\n\n\n\nWe get frustrated because we are inherently selfish beings who want to succeed. Failure to succeed or proceed at a pace we like causes frustration.",
"Just because we do it, doesn't mean there is an evolutionary advantage or that it is even related to evolution.\n\n\n\nWe get frustrated because we are inherently selfish beings who want to succeed. Failure to succeed or proceed at a pace we like causes frustration."
]
}
|
[] |
[] |
[
[],
[]
] |
|
7qlr9j
|
why can we listen to music at a loud volume, but once it cuts to a commercial or someone talking, it sounds a lot louder?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/7qlr9j/eli5_why_can_we_listen_to_music_at_a_loud_volume/
|
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"text": [
"Unfortunately certain media volumes are not regulated - television shows themselves might be at a uniform volume, but there's nothing forcing advertisers to make their commercials quieter or the same volume as the show / radio / video / etc.\n\nIt could be used as a tool to hype up someone's memory (evidence suggests that being startled helps you remember something better), or because they want to advertise to the largest audience possible and that might include people who are hard of hearing :\\",
"You know how at the loud volume of your music the music itself has variations in loudness?\n\nSome sounds are louder some are softer.\n\nSo, without changing the volume of your speakers you can encode and change the volume of the music.\n\nAdvertisers know this and just make their sound super loud.\n\nIts illegal in most media in the US. There is a max encoded volume for television commercials, at any rate.",
"What we are experiencing when we percieve the commercials as louder is called compression. \n\n\nWhen watching a movie, the audio is quite dynamic - some sounds are quiet, some are loud, and some are very loud. \n\n\nPeople making commercials don’t need dynamics, they want to be heard. So they apply compression, which means that the difference between the quiet and the loud sounds are diminished, often by a LOT. This gives a fat, dense sound which sounds louder than it actually is, since the audio is less dynamic, but also because the compression also applies to the frequencies of the sound, boosting the low and the high ones generally. \n\nBut, yes - commercials are also louder, since they use compression to get as even a signal as possible, and then turn it up close to max.\n\n\nIf applied poorly, compression can result in what’s known as ”ducking” - for example a commercial with a speaker voice that’s tweaked and compressed on its own, but then you apply too much compression on the main track, so that when the speaker pauses, the background noice or music rushes up to meet the required intensity. This often happens on radio, since they apply their own dynamic range compression, to compensate for differences in volume between albums and songs. Distortion and lack of dynamics are other wanted or unwanted side effects. \n\nGenerally, music is getting more and more compressed, more loud, and less dynamic. \n\nNine Inch Nails were known for producing really loud and compressed albums, but nowadays they don’t really stand out. Arcade Fire and Godspeed you black emperor are other bands that have been quite sucessful in using lots of compression, audio quality wise. ",
"Because it is perceptibly louder, so you pay attention to the commercials.\nThis doesn't mean the volume has gone up, it's that it's been produced in such a way that you take notice when the music stops, for example, vocals in a song must coexist with the music, if your volume is 50 db, then the guitar, keyboards, bass, drums and vocals all sum up 50 db, each one contributes a little bit to the overall volume, but when the announcer comes up and you only hear that voice, then that voice can take up the whole sound spectrum up to 50 db. It can be louder because there is no music to compete with or it is really low.\n\nThe amount of volume hasn't changed but the voice is now louder than the vocals in music which means we now perceive it to be louder.\n\nJust like there are optical illusions, this is an example of an audio illusion. There's a whole field of study devoted to it called psycho acoustics."
]
}
|
[] |
[] |
[
[],
[],
[],
[]
] |
||
4xtleh
|
Can ohms law be applied to any circuit?
|
askscience
|
https://www.reddit.com/r/askscience/comments/4xtleh/can_ohms_law_be_applied_to_any_circuit/
|
{
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"d6iuw4p"
],
"score": [
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],
"text": [
"No, Ohm's law is a special case. In general, the relationship between the voltage you apply across a given circuit element to the current that flows through it (or current density to electric field) is not linear.\n\nFor example, see diodes, transistors, operational amplifiers, etc."
]
}
|
[] |
[] |
[
[]
] |
||
1s8gmg
|
How long did it take for Poland's post-WWI borders to be established?
|
The Polish state was established via the Treaty of Versailles, but how long did it take until the borders Poland had before WWII were established? I remember reading about plebstices and some about the war with the Soviets but could someone with knowledge of the subject elaborate?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/1s8gmg/how_long_did_it_take_for_polands_postwwi_borders/
|
{
"a_id": [
"cdv8qfs"
],
"score": [
3
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"text": [
"The Versailles Treaty in 1919 assigned to Poland the territories of Poznan (Great Poland) and Gdansk Pomerania (is Germany and the West also known as Western Prussia or Danzig Corridor) and decided that Upper Silesia and southern part of the Eastern Prussia will be plebiscite territories.\n\nGreater Poland was already controlled by local Polish authorities since the uprsing in December 1918; Pomerania was taken over in July 1919.\n\nThe Prussian plebiscite took part in July 1920 and was quite a disaster for Poland who only won a few villages.\n\nUpper Silesia was finally was divided after 3 Polish uprising and a plebiscite in October 1921.\n\nPolish southern borders were created after heavy disputes (sometimes open conflict) with Czechoslovakia over the former Duchy of Teschen/Cieszyn and Spis(z) and Orava regions. The conflict was somehow resolved in 1920 with the arbitration of the Western Powers, on terms that were rather unfavorable to Poland. Some very small border changes were later made in 1924.\n\nPolish eastern border largely defined by the March 1921 Riga Peace Treaty with the Soviet republics of Russia, Ukraine and Belarus (USSR not yet existing)\n\nThis didn't include the important areas of Vilnius and Eastern Galicia through. Vilnius was taken over by a \"rebellious\" (actually acting on the orders of Polish supreme leader Józef Piłsudski) Polish general in 1920; for some times it functioned as an \"independent\" state of Middle Lithuania before it was officially annexed in 1922.\n\nEastern Galicia was captured by Poles in 1919 but its legal status was complicated: Western allies only consented to Polish administration for the period of 25 years, not incorporation. Polish ownership was offically recognized in 1923.\n\n\n"
]
}
|
[] |
[] |
[
[]
] |
|
e9ec7i
|
Has there been a change in how academic history is written over the years?
|
I was reading a few different threads recently, and a similar concept of "it's not about the (quality) of the older sources per se, it's about how they're read". This was sort of in reference to misrepresentations, mistakes or just general "bad" history.
It got me thinking: reading primary/secondary/etc. Sources is a skill to be developed (or so I think), but has there been a shift over time in how sources are written? Are there generational (or even uhh, decade-tional?) differences one needs to keep in mind when reading a historical account of an event?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/e9ec7i/has_there_been_a_change_in_how_academic_history/
|
{
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"fajmoly"
],
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"text": [
"There have been overall shifts, but there is also a \"horizontal\" diversity in the approach taken by historians, based on different theoretical models. Today, almost any good academic history will contain a section discussing its methodology. Academic history essentially consists of writing _narratives_ which are then critiqued, rejected, amended and so forth in the broader historiographical discussion.\n\nOne broad shift that I always think of is from the Rankean paradigm of figuring out history \"as it really was\" based on identifying the most reliable sources or harmonizing diverging narratives. This kind of presupposes that a history should always represent what a historian think is, overall, the most plausible account of everything. The problem is that this generally leads to a prohibitively broad scope (or more likely, vastly suboptimal criteria for choosing how to read sources), and therefore, historians will often deliberately write histories from a particular perspective. For example, Richard Payne's \"A State of Mixture: Christians, Zoroastrians and Iranian Political Culture in Late Antiquity\" re-examines the notion of the zealous, theocratic Sasanians oppressing their Christian and Jewish minorities by reading the traditional Armenian and Aramaic martyrdoms as situated in an Iranian political context, and discussing how the Sasanian Empire could be understood as a pluralistic society under a supreme monarch, submission to whom was paramount. For instance, this perspective suggests that Khusrau II's pilfering of the True Cross from Jerusalem was not merely intended to humiliate his Christian adversaries, but also to yield a glorious trophy for his Christian subjects and a banner for his legitimacy among the Christians of the Eastern Mediterranean he intended to subjugate.\n\nThis reading has various advantages, such as highlighting potential tensions between a more pluralistic monarch and religiously conservative high nobility and clergy, and yielding a potential explanation of the dissolution of noble support for Khusrau at the zenith of his empire's power. But it isn't necessarily the most plausible or palatable narrative in all regards - it has a tendency to gloss over real religious violence and persecutions as a necessity to uphold the barriers Payne takes as essential to this \"state of mixture\". However, Payne's monograph is far more useful in this form as a point of reference, than would be the likely outcome of an attempt to consider _every possible angle and implication_ of _every single source_ to highlight _every single possible implication of interest_.\n\nSo yes, the era a history is written in should absolutely be taken into account, but writing will differ not just based on time but also on the individual historian and their preferences, whether they have a degree in history or something like philology, and so forth. Ultimately, you should look at the historian's argument for reading a source in a particular way, as well as why what that reading yields might be interestikng. In most cases, you are unlikely to find a single monograph that is a truly satisfactory account of an era; studying the actual historiography and differences between accounts is necessary to get a strong understanding."
]
}
|
[] |
[] |
[
[]
] |
|
couvu4
|
What happened to Supersymmetry?
|
I haven’t been following Supersymmetry at all but I have noticed that it’s not mentioned quite as often as before.
|
askscience
|
https://www.reddit.com/r/askscience/comments/couvu4/what_happened_to_supersymmetry/
|
{
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"text": [
"A little background info first: in particle physics you begin with the so-called \"Standard Model\". It's kind of like the periodic table of the elements, cataloguing and grouping the known fundamental particles. It's not just a table though, it's also a mathematical model that predicts how all particles behave. It predicts what you'll see when you smash, say, protons together (as they do at the LHC). Then you go smash the particles and see what actually happens. The prediction is called the background, and anything different is called an excess. Excesses are an indicator the SM might be overlooking something, a suppersymetric (SUSY) particle for instance. \n\nThe most recent LHC upgrade promised to show all sorts of new excesses but there really wasn't anything. Each time we upgrade to higher energy and don't see any evidence of SUSY, the SUSY models have to be changed and eventually you start running into problems like, say, violation of conservation of energy. The models are getting flimsier. It's becoming harder for SUSY to hold it's promises of unification and a potential explanation of dark energy. There are many different models theorists have made that use SUSY. The most prevalent is the minimally supersymmetric model or MSSM, and it's taken quite a beating from the lack of excess.\n\nThe hot thing in High Energy Physics (HEP) now is neutrinos which are known to exist but not much else is known about them. A great deal of effort is being expended just to determine their mass. All that's known right now is that it's between zero and the mass of an electron.",
"To add to the excellent answer of u/cynfwar:\n\nWhile SUSY is running out of steam for phenomenological purposes, its still of interest for mathematical physicists. SUSY is in some sense a very strong symmetry: it helped in providing exact solutions for many observables in an idealised version of the Standard Model called 'N=4 Super-Yang-Mills theory' (SYM). Having those exact solutions is very valuable because it helps in checking the validity of the approximative tools used in the Standard Model and also to develop new tools which might just radically change the way we do quantum field theory. \n\nIn case you want to read up on this more, I'll list just a few (decreasingly specific and increasingly esoteric) new tools that have been developed with a lot of influence from the SUSY community: spinor helicity variables, the CHY formalism, the amplituhedron and the AdS/CFT correspondence. While the former two of those are actively being used to study the properties of real life quantum field theories as QCD and electroweak theory, the latter are still in development and it is unclear if they will ever be of any use to interpret collider measurements and the like. \n\nStill, those techniques are very interesting on their own: they shed some light on the connections between different quantum field theories, the fascinating duality between gauge theories and gravity and the underlying geometrical concepts of physics. All this progress wouldn't have been possible if not for SUSY."
]
}
|
[] |
[] |
[
[],
[]
] |
|
11fc51
|
After the Big Bang, why does matter only exist in pockets of galaxies? Why is it not more 'homogeneous'?
|
Or is the universe more homogeneous than we think it is? Why isn't there more 'stuff' in the huge space between galaxies?
|
askscience
|
http://www.reddit.com/r/askscience/comments/11fc51/after_the_big_bang_why_does_matter_only_exist_in/
|
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"text": [
"Gravity. If there's any initial fluctuation at all, everything condenses down to points and filaments under gravity.\n\nHere's a cool video of a calculation exploring how this happens. Dark matter's role in large-scale structure formation in the universe is a big topic in computational astrophysics right now.\n_URL_2_\n\nMore here:\n_URL_0_\n_URL_1_",
"This is actually a phenomenally cool question. giant_snark does a great job explaining what happens once gravity takes over, but what triggers that?\n\nSmall quantum fluctuations that are completely random existed when our universe was only a fraction of a second old. Then, suddenly, the universe expanded by 50 orders of magnitude (that number is impossible to wrap your head around). This cooled the universe tremendously, and \"locked in\" the quantum fluctuations in temperature generated by quantum movements of the quarks. The temperature differences resulted in density differences, and thus gravity could start taking over.\n\nYou can actually still see this today in the [CMB](_URL_0_) Those temperature differences were determined 13.7 billion years ago.",
"The Universe is uniform on the largest scales - that is, if you average over a few hundreds of millions of light years. On smaller scales, things like galaxies formed from tiny overdensities that grew and then collapsed under their own gravity. As the Universe expands, even a region just slightly denser than its surroundings will expand at a slower rate than average, and eventually turn around and begin to contract, until the pressure exerted by gas balances it out and stars and galaxies start to form.\n\nThe cool thing, though, is where those overdensities come from. The best answer we have is in something called *cosmic inflation*, our idea of the very earliest moments of cosmic history. The idea is that for the briefest of moments, not even a trillionth of a trillionth of a second, just after the Big Bang, the Universe expanded at an accelerating pace (much like it's doing today, in fact, though the acceleration was far greater then).\n\nWe didn't come up with inflation for any reasons to do with structure formation, though. In fact, we came up with it for essentially the opposite reason - we wanted to understand why the Universe was so *smooth* and spatially flat, and why we don't see exotic particles like magnetic monopoles (particles with just a magnetic north or south pole, but not both). Inflation has a tendency to smooth over any inhomogeneities and curvature and leave everything dark and featureless, with particles like monopoles being diluted so heavily that most observable patches of universe don't even contain a single one.\n\nSo it was pretty amazing when it was realized that inflation also explains, quite naturally, where the matter we *do* see comes from, and why it makes the inhomogeneous structures we see. The matter comes from the energy left over from inflation; as long as the energy driving inflation interacts with matter, which seems quite reasonable, then when inflation ends that energy will decay into matter and radiation.\n\nBut most exciting, inflation ties the small scale physics of quantum mechanics with the large-scale structure of the Universe. Quantum physics tells us that on the smallest scales, there's uncertainty in position and momentum, and so the density of matter on small scales fluctuates. Normally, these fluctuations average out with each other and die off in a fraction of a second. During inflation, though, the Universe is expanding so quickly that before those fluctuations could die off, they were expanding to be larger than the observable universe, so they couldn't communicate with other fluctuations! Thus they were left \"frozen in,\" quantum weirdness made bigger than the observable universe, leaving the Universe more dense in some regions and less dense in others. When inflation ended, these fluctuations all started to come back into contact with one another, eventually leaving the Universe with a patch of over- and underdense regions. It's the overdense ones that collapsed under their own gravity to form the galaxies and galaxy clusters we see today.",
"visualize it like a few drops of oil floating on water, even though the oil could spread out thinly and cover the entire surface area of the container of the water, the oil will coalesce into tight droplets due to intermolecular forces, gravity is the binding force on a larger scale"
]
}
|
[] |
[] |
[
[
"http://cosmicweb.uchicago.edu/filaments.html",
"http://en.wikipedia.org/wiki/Structure_formation",
"http://www.youtube.com/watch?v=8UzVi8MJolo"
],
[
"http://apod.nasa.gov/apod/image/0302/sky_wmap_big.jpg"
],
[],
[]
] |
|
1o2m99
|
Why did France (West Francia) end up more unified than the rest of the Holy Roman Empire (East Francia)?
|
Was this influenced by the invasion of the Normans? Was terrain a significant factor? Did the successors of Charlemagne have drastically-different methods of rule?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/1o2m99/why_did_france_west_francia_end_up_more_unified/
|
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"text": [
"During what era? Because France wasn't particularly unified until Richelieu.",
"By West Francia and East Francia I am assuming you mean the kingdoms controlled by Charlemagne's descendants? After Charlemagne's death his son, Louis the Pious (co-emperor with Charles) took over and kept the kingdom intact for the most part. After Louis' death his three sons split the Empire. This was accustom of Frankish boys to split their father possessions. Since Louis was claimed the legitimate heir to Charlemagne's throne he was the only one to receive his father's blessing and the kingdom (he did rule in a kind of co-emperor deal, but he was the head honcho if you will). Since Louis had four boys, three who were \"legit\" they split their grandfather's empire. Lothair was named Emperor but after a series of rebellions and negotiations each took an equal piece based on economic means. They were not split by geography but by what the land, cities, and import/exports were worth. Charles the Bald received the western portion of the Empire, Louis the German received the Eastern Part, and Lothair I (eldest) received the lands between the two and that stretched to Rome. He was also named Emperor and King of the Franks. The brothers often quarreled trying to dispel one another and seize each others lands. Louis almost obtained the Western portion but was stretched too thin along his eastern border and in Western Francia. \n\nThe reason why the German part of the Frankish empire dissolved after Louis the German's death was because of his sons, nephews, and the rival duchies on his borders like the Slavs and Magyars. So it was a political and cultural differences as to why the German portion couldn't remain together, remember their sons get their possessions. As for the Western Frankish Empire his sons had a buffer zone from those rivals but also had the support of strong rulers. \n\nsources: [Struggle for Empire: Kingship and Conflict under Louis the German](_URL_1_)\n\n[Early Carolingian Empire: Prelude to Empire](_URL_0_)\n\n\nAlso the label France is just for geography reasons. But for the medieval period it should labeled Frankish Kingdoms or Gaul depending on when and where you're referring.",
"West Francia was not more unified than East Francia. East Francia did deal with the Magyar threat, but the Vikings devastated West Francia and helped to destabilize it. Basically the West Frankish Kings could not stop the vikings from pillaging at will, so they paid them off with ridiculous sums of silver, which bankrupted the Crown, which they then tried to pass off to the rest of nobility to collect. This goes on for 150 years or so of summer raids and destabilizes the government almost from the start, because nobility and ordinary citizens had no faith in the central government to protect them. Things were not much more centralized in East Francia, but it was the first major government in mainland Europe to really come together into a unified authority after Charlemagne, under Otto I in the early 10th century. As someone else suggested, West Francia did not really unite until after the 100 Years War.\n\nSource: Birth of the West, by Paul Collins",
"Semantics aside, the HRE was less unified because the power of local landlords (particularly castellans) was disproportionate. A rich family would control and tax their own lands, and if they had a castle the emperor couldn't really control what they did. Geography played a big part in this, but I think the emperor being unable to control local powers is really the big reason.",
"Paradoxically, it is because initially, power was much less centralised than in the East (with the Ottonians). The process of unification in France went from a totally shattered area in term of power distribution, slowly amalgamating itself, to one dominant player who took it all.\nIn Germany, it went from a powerful central power that kept being checked by growing regional ones. The main thing is that the German side loaded itself with the title of Emperor, and thus kept having imperial dreams for the longest time. For the Emperor, East Francia (Germany) was not a goal, just a step, a power BASE.\n\nThe French kings never really had such ambition: their one and only goal was to unify under their direct rule (the domain) their whole kingdom. For the French kings, France was the goal to achieve. They went at it for generations and generations, through marriage, wars, and acquisitions. It was a more modest goal and they got lucky to have one family rule (Capetians) for the longest time ever.\n"
]
}
|
[] |
[] |
[
[],
[
"http://www.amazon.com/Early-Carolingian-Warfare-Prelude-Empire/dp/0812221443",
"http://www.amazon.com/Struggle-Empire-Kingship-Conflict-Conjunctions/dp/0801475295"
],
[],
[],
[]
] |
|
5sv01u
|
How are the wave functions of antiparticles related to those of their "normal" counterparts?
|
This might be a kind of simplistic view of how wavefunctions work, but are wavefunctions of particles and antiparticles a sort of "complex negative" of each other, allowing the particles to cancel each other out and emit their energy as photons?
How does one mathematically describe particle/antiparticle annihilation?
|
askscience
|
https://www.reddit.com/r/askscience/comments/5sv01u/how_are_the_wave_functions_of_antiparticles/
|
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"text": [
"When you're talking about particles and antiparticles, you're generally outside the regime of standard one-body, nonrelativistic quantum mechanics. So the notion of a wavefunction is sort of abandoned.\n\nInstead you replace them with field operators. There is a mathematical operator denoted by \"C\" which is the \"charge conjugation operator\". It turns a particle into its antiparticle.\n\n > How does one mathematically describe particle/antiparticle annihilation?\n\nYou'd use quantum field theory. For example to calculate the probability of electron/positron annihilation into two photons using perturbation theory, you'd sum over a bunch of Feynman diagrams. The lowest-order contributions look like [this](_URL_0_).",
"To describe particles properly you have to give up on the idea of wavefunctions and use fields instead. A field is an object with a value at every point in spacetime, and quantum fields are described by Quantum Field Theory.\n\nBasically you have a field for every particle-antiparticle pair. So you'd have the photon field (a.k.a. the EM field), or the electron-positron field. Particles like photons which are their own antiparticle are described by real fields, meaning the value of the field is a real number. Particles with distinct antiparticles like electrons and positrons are described by a complex field, so the field value is a complex number.\n\nHowever, it is *not* the case that the standard field corresponds to the particle and the conjugate field corresponds to the antiparticle. To see where particles and antiparticles come from you have to see how a field is actually constructed, which is a bit in-depth. Essentially, we use things called annihilation and creation operators (*A* and *A*\\*), which destroy or create a particle with some fixed given momentum. Importantly, they say *absolutely nothing* about the position of the particle (you can view this as a manifestation of the Heisenberg principle). So to get a value for a field, we basically do a Fourier transform and take a sum over all possible momenta:\n\n > ϕ = ∫d*p* 1/sqrt(2*E*) [*A*(*p*)e^(i*p**x*) + *A*\\*(*p*)e^(-i*p**x*)]\n\nThat is the definition of a (scalar) real quantum field. However, when we do this for a complex quantum field, we find that there are two separate sets of annihilation and creation operators: *B*, *B** and *C*, *C**. The field is then:\n\n\n > ψ = ∫d*p* 1/sqrt(2*E*) [*B*(*p*)e^(i*p**x*) + *C*\\*(*p*)e^(-i*p**x*)]\n\n > ψ* = ∫d*p* 1/sqrt(2*E*) [*B*\\*(*p*)e^(i*p**x*) + *C*(*p*)e^(-i*p**x*)]\n\nEach pair of operators corresponds to a unique particle. These are interpreted as the particle and the antiparticle. Why you end up with two sets of operators is a bit in-depth, but it's essentially an emergent property. If you know any solid state physics, it is similar to how phonons arise from considering the sum of the oscillations of each individual point in a lattice.",
"While for a full treatment of particles and antiparticles, you need to use quantum field theory and move beyond wavefunctions as /u/RobusEtCeleritas says, within the context of the Dirac equation (which, in fact, led to the prediction of antimatter in the first place), we can formulate wavefunctions for matter and antimatter.\n\nThe Dirac equation can be used to describe electrons and positrons both relativistically and quantum mechanically. In the standard formulation of the Dirac equation, the wavefunction has four components, two corresponding to the electron and two corresponding to the positron (the antimatter partner of the electron).\n"
]
}
|
[] |
[] |
[
[
"https://upload.wikimedia.org/wikipedia/en/f/f4/Feynman_Diagram_of_Electron-Positron_Annihilation_v2.png"
],
[],
[]
] |
|
2j7lhy
|
why do we grow hair in specific places?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2j7lhy/eli5_why_do_we_grow_hair_in_specific_places/
|
{
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"cl93nu8",
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],
"score": [
12,
7
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"text": [
"Hair in armpits and groin is a dry lubricant, hair on your head is sun protection, men's facial hair is a sexual marker. ",
"I actually had this question in my head, so I'll add on about something else which has been bothering me:\n\nWhy does the hair in our head have such a specific \"shape\"? It stops around your forehead but extends down your sideburns, goes around your ears and forms sharp edges around the back of your head. And it's the same for most people. How is this regulated?"
]
}
|
[] |
[] |
[
[],
[]
] |
||
ah5zu9
|
How did soldiers know the names of enemy weapons and equipment?
|
This may be a simple answer, but I've always wondered how in the middle of a war soldiers would know the names of equipment of their enemies. Taking WW2 for example, how did they know that the MG-42's were actually called that by the Germans? Was it from POWs? Or did the Germans publish the names of their equipment in literature that the Western powers could get access to?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/ah5zu9/how_did_soldiers_know_the_names_of_enemy_weapons/
|
{
"a_id": [
"eec6xrn"
],
"score": [
6
],
"text": [
"u/kieslowskifan has an answer to this! \n\n_URL_0_ "
]
}
|
[] |
[] |
[
[
"https://www.reddit.com/r/AskHistorians/comments/aetyc7/how_did_allied_forces_discover_the_names_of/"
]
] |
|
dtclmy
|
when you suck on an m & m, why does it feel smooth, then rough, then smooth again?
|
If you haven't tried it before, try it now. Go on, you deserve it. Notice how it feels smooth, then feels rough, and then the rough kinda licks off? Yeah, please ELI5 why this is.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/dtclmy/eli5_when_you_suck_on_an_mm_why_does_it_feel/
|
{
"a_id": [
"f6vw004"
],
"score": [
8
],
"text": [
"The smooth part is likely the candy glaze, the rough would be the actual shell of the m & m and then the chocolate."
]
}
|
[] |
[] |
[
[]
] |
|
2jsdk8
|
During the Spanish Reconquista, did much of the Muslim population convert to Catholicism?
|
Or was Muslim population driven out or killed?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2jsdk8/during_the_spanish_reconquista_did_much_of_the/
|
{
"a_id": [
"cley5bb",
"clf4omh"
],
"score": [
4,
6
],
"text": [
"Follow up question, during Muslim Iberia what per centage of the population stayed christian?",
"Different states treated the Muslims differently.\n\nCastile and it's possessions were known to be extremely aggressive towards Muslims and Jews. However, for most of the period of the Reconquista, this was in the form of a heavy tax burden placed on non-Christians, similar to the Jizya (the Muslim tax on non-Muslims) in place earlier, although probably much heavier. However, prior to the completion of the campaigns, this monetary contribution was probably more beneficial, as it encouraged conversions in the same way the Jizya did; that is, without having to resort to costly and dangerous population purges. The key thing is that any attempt to avoid the heavy (often crushing) burdens placed on them was harshly punished. This was an easy way to target individuals. In addition, huge swaths of land were appropriated by incoming Castilian nobility, which was often still worked by the formerly Muslim peasantry. This gave landowners another important leverage over those that worked their land.\n\nIn Aragon, things worked a little differently. Initially attempts were made to incorporate much of the existing leadership structure of the conquered areas of Catalonia and Valencia, but a revolt in the 13th century by Muslim leadership put the kibosh to that. However, within the coastal cities relatively lax treatment was available to Muslims and Jews, as these populations and their trading relationships were seen as very valuable.\n\nIn both Castile and Aragon, things changed drastically in the very end of the 15th and early 16th centuries. Muslims and Jews were given the option of conversion of expulsion, and this is when the Spanish Inquisition earned it's reputation. Paranoia about falsely converted Muslims and Jews was what gained them that. \n\nI am not as familiar with Portugal however. It does seem that in the early 16th century they too took a harsher tone against Muslims by expelling all Moors, but I am not as certain as to the levels of persecution prior to that. It is important to note that Portugal completed their own Reconquista far before Castile.\n\nAs for the ultimate fate of the Muslim population of Spain, most of them would be descendents of the original inhabitants there before the invasion by the Caliphate who had converted over the centuries, and probably not all that ethnically different from their northern neighbors. The Muslims in leadership positions were the ones who would be the ones most likely to be expelled on sight or killed. Southern Spain has a population with higher 'Moorish' blood origins, likely thanks to greater intermingling of the population with North Africa's due to proximity as well as time spent under their rule (leading to the distinct 'Andalusian' ethnic/cultural group."
]
}
|
[] |
[] |
[
[],
[]
] |
|
80x47m
|
how and why did apa become the standard for referencing sources?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/80x47m/eli5_how_and_why_did_apa_become_the_standard_for/
|
{
"a_id": [
"duyvp19"
],
"score": [
2
],
"text": [
"In research papers for publication, it's usually *not* standard (at least in most of the journals I am familiar with), partly due to the simple reason that in printed material *words cost money.* It's more common in review articles, perhaps because in primary research articles the other sources are just used for background while in reviews *most* of the content comes from other places so it makes more sense to show more of the citations. \n\nAlso, APA format has been around longer than computers, and citation-managing software specifically. Nowadays, you can automate citations in a word processor and auto-adjust the numbering pretty easily. But back in the day of typewriters and early word processors, if you wanted to number things you had to *manually* number things. So if you decide to add in another reference later, you would have to manually re-number *everything.* And if you're working with 30, 40, 50+ references... you get the idea. "
]
}
|
[] |
[] |
[
[]
] |
||
23khvf
|
is a 200hp car two times faster than a 100hp car?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/23khvf/eli5_is_a_200hp_car_two_times_faster_than_a_100hp/
|
{
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"text": [
"No, it just has twice as much health",
"Most likely not. The horsepower is a rating of the power output of the engine, but the power consumption of a car doesn't usually scale linearly with speed. For example, aerodynamic drag is approximately proportional to the ~~fourth~~ third power of speed, and rolling resistance is quadratic.",
"No.\nThe faster you go, the more wind and rolling resistance you generate. This number goes up exponentially, not linearly. \n\nSimplifying it a lot, it looks like the horsepower needed to overcome just air resistance increases by a power of 3, plus a bunch of funny constants we're going to ignore for this example. Ignoring all the constants to simplify to the meat of the equation, you'll get something like Horsepower Needed = Speed ^ 3. The numbers this gives are way off from realistic, though, so we'll just adjust by a factor of 10000 to get normal looking numbers, giving us \n\n Horsepower Needed = (Speed ^ 3) / 10,000\n\n Again, this isn't the real formula, just an order approximation. \n\n\nPunching in a few numbers with this *extremely* simplified version of things, you'll get: \n\n 100hp = max 100mph\n\n 340hp = max 150mph \n\n 800hp = max 200mph\n\n 1500hp = max 250mph \n\n\nIf you're a bit older than five, go ahead and read here: [linky](_URL_0_)"
]
}
|
[] |
[] |
[
[],
[],
[
"http://phors.locost7.info/phors06.htm"
]
] |
||
4xkant
|
why do actors tend to put themselves as "executive producers" & "producers" after being in a television show for a while?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4xkant/eli5_why_do_actors_tend_to_put_themselves_as/
|
{
"a_id": [
"d6g4l6u",
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],
"score": [
8,
2
],
"text": [
"This indicates they are not only acting in the show, but taking a stronger creative or production role *behind the scenes*. They are working on MAKING the show in addition to appearing on screen, but not every actor makes this change.",
"It may be just a prestige title, but it may also reflect that when they renegotiated their contract they got some % share of the shows profits."
]
}
|
[] |
[] |
[
[],
[]
] |
||
a1dbzg
|
Is there a historical consensus about the girls who started the accusations of the Salem Witch Trials? Were they put up to it by others? Were they psychopaths? Did they actually believe they were being afflicted by witchcraft?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/a1dbzg/is_there_a_historical_consensus_about_the_girls/
|
{
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"eaq17dm"
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"text": [
"To add to what the others have said, those accusers who had suffered from the conflict with neighbouring Indians had had their lives upended. Those who were orphaned were now living with relatives or friends of their late parents, and those whose families had been displaced lost whatever livelihoods they had previously worked. Their prospects, both for marriage and the rest of their life, were greatly diminished. They could provide little in the way of a dowry, a vital part of arranging a beneficial marriage, and their newfound benefactors (if they had them) had other priorities than their new wards. It is perfectly understandable to look at their situation from their perspective, and feel resentment and anger towards the events that had led to their diminished position; this was the problem. They had been taught that feeling this way made them perfect recruits for the Devil’s cause. He could use their resentment to slip through their defences of faith and use them to further his diabolic aims. \n\nRichard Godbeer suggests that while these first accusers may have genuinely believed that they were the victims of the Devil, their ‘possession’ gave them a legitimate method of expressing their grievances in a society that disapproved of such self-pity. It’s hard for a modern perspective to understand how firmly held beliefs in magic and the Devil were. In other trials, some individuals willingly handed themselves over for the crimes they believed they had committed. Alexander Sussums of Long Melford, Essex had volunteered to be searched by a witch finder during the East-Anglian panic, out of a genuine belief that he had been a witch for over a decade and a half. Through his guilt and negativity, combined with a genuine belief in the power of the Devil and his mother’s reputation for witchcraft, Sussums convinced himself that he too was a witch. Such was his conviction that he actively sought out the man who could, and did, order his arrest and trial for capital crimes (although he was eventually pardoned). Of course, with a society as deeply strained as 17th century New England, there were definitely accusations driven by more mundane motivations, but it is very likely that at least some of the young women who declared their possession did so out of a genuine belief that they were the victims of the Devil.\n\n* Anderson, Virginia Dejohn, 'New England in the Seventeenth Century', in Canny, Nicholas (ed.) *The Oxford History of the British Empire: Volume I: The Origins of Empire*\n* Godbeer, Richard, ‘Witchcraft in British America’, in Levack, Brian (ed.) *The Oxford Handbook of Witchcraft in Early Modern Europe and Colonial America*\n* Hansen, Chadwick, ‘Andover Witches and the Causes of the Salem Witchcraft Trials’, in Levack, Brian (ed.) *The Oxford Handbook of Witchcraft in Early Modern Europe and Colonial America*\n* Le Beau, Bryan F., *The Story of the Salem Witch Trials*\n* Levack, Brian, ‘State-Building and Witch-Hunting’, in Oldridge, Darren (ed.), *The Witchcraft Reader*\n"
]
}
|
[] |
[] |
[
[]
] |
||
2qsztg
|
No Irish Need Apply - how badly were Irish discriminated against in 1840's - 1930's America?
|
I was listening to the song 'No Irish Need Apply' and decided to look it up. There's newspaper ads that show that 'No Irish Need Apply' was a thing, but I keep seeing references to a paper by Richard Jensen (retired Professor of History, University of Illinois, Chicago) saying they didn't exist, and that all the evidence is anecdotal.
Did they, and to what extent were the Irish discriminated against in 1840's - 1930's America?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2qsztg/no_irish_need_apply_how_badly_were_irish/
|
{
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"cn9jzar",
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],
"score": [
6,
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],
"text": [
"I am not a historian, but the Library of Congress has a good overview with source documents [here](_URL_0_).",
"As a follow up question, how about in the same period in Great Britain?"
]
}
|
[] |
[] |
[
[
"http://www.loc.gov/teachers/classroommaterials/presentationsandactivities/presentations/immigration/irish5.html"
],
[]
] |
|
8mgbye
|
How Are The Chauvet Cave Drawings Still There?
|
I was reading about the Chauvet Cave drawings in France, which are around 30k years old. From what I've read it seems they were made with charcoal from fires. So my question is, how are they still there? Why havent they been removed from erosion or something? Even if they were in some cave far away from wind and water; in 30k year I would think earthquakes or something would damage them.
|
askscience
|
https://www.reddit.com/r/askscience/comments/8mgbye/how_are_the_chauvet_cave_drawings_still_there/
|
{
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"text": [
"Yes, they are. It's amazing they are still preserved - there are likely countless of other drawings from the period that weren't.\n\nAccess to the drawings is very limited. Here's an account from 2015 by a reporter who was granted rare access: _URL_0_",
"I don't know much about this cave in particular, but I will try to give a bit of an answer. Preservation is very hard and there are few environments that can preserve perishables (like textiles, baskets, or in your case drawings). Such environments can be waterlogged such as bog bodies, frozen like Otzi, or incredibly dry like sand in a desert or certain caves. Caves can be dry enough that micro-organisms do not flourish and preserve perishables for thousands of years. \n\nAs far as earthquakes, some areas just aren't as prone to earthquake activity. There are probably cave drawings that were in caves that suffered earthquake damage, but they simply didn't get preserved. As for anything else knocking the pigment off the walls, animals don't have much incentive to go back that far into a cave. They can get sufficient shelter much closer to the mouth of the cave.\n\nAlso, just a nitpick is that the pictures seem to be made with ocher which is a better pigment than charcoal."
]
}
|
[] |
[] |
[
[
"https://www.smithsonianmag.com/arts-culture/only-handful-people-can-enter-chauvet-cave-each-year-our-reporter-was-one-them-180954981/"
],
[]
] |
|
4it3h5
|
the tingling sound in total silence
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4it3h5/eli5the_tingling_sound_in_total_silence/
|
{
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"text": [
"It's your ears trying to make up for that lack of sound you're not hearing. Same thing goes for the tingling/numb feeling you get when your appendages fall asleep ",
"One form of what you're talking about is tinnitus, ringing in the ears which can be a result of age-related hearing loss, over-exposure to loud sounds (such as at frequent loud concerts or a construction job), or even sometimes brain injuries/tumors. Killing off the hair cells in your ear through loud noises leads to spontaneous activity of the neurons they're connected to, which is interpreted as sound. However, you might be referring more generally to the idea of hearing slight ringing or \"tingly\" noises in total silence even in people without tinnitus, something which often happens particularly after exposure to loud noises for a length of time.\n\nNeurally, this tingly sound doesn't have a definitive explanation, but one perspective is as follows. Essentially, neurons in the ear, like most neurons (i.e., the auditory nerve) are firing regardless of whether you are hearing sounds; they just fire more in response to loud noises. The brain knows this, and so it tends to interpret overall firing rates (and some more complex patterns, etc. of firing) relative to a baseline, no-noise firing rate as 'sound.' However, this isn't a perfect process, so even in the absence of any sounds, there is some activity that might be interpreted as ringing by the brain.\n\nThis explanation isn't complete, and I'm not an expert on auditory neuroscience. Maybe someone who is can add to it!",
"The rushing, almost roaring sound you hear is your blood flow, which is why when you \"flex\" your ears it gets louder.",
"they have drugs for tinnitus now. if u are willing to have ED, hypertension, and bloody stool. my answer was no, but to each his own.",
"Can everybody just chill out with the tinnitus diagnosis? Tinnitus is comparatively rare, and what OP is talking about sounds like what basically everybody who's ever been in a silent space has noticed."
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[]
] |
||
3plvye
|
why is the metric system so perfect in regards to water mass versus weight?
|
I'm not entirely sure how to word this but basically i'm wanting to know how and what the metric system is designed or based around.
Mainly the fact around 1sq cm equals 1 gram of water and this obviously transfers to 1sqm equals 1 ton etc etc
so i this just pure universe coincidence that weights and sizes mesh so perfectly or was it originally based off water weight?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3plvye/eli5why_is_the_metric_system_so_perfect_in/
|
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"text": [
"It's originally designed this way. Units in the SI system are all defined by certain basic quantities, like a liter of water or one Kelvin, or one meter and so on.\n\nex: a kilocalorie (a calorie to all dieters) is the amount of energy required to raise the temperature of one liter of water by one kelvin.\n\nSo it's right there in the definition of the unit.",
"Because it's the way the creators designed it. If you were half way around the world and needed something to reference weight to you could just take a known volume of water.",
"I am not completely sure and the history is very complicated but I believe that the metre as a totally arbitrary measure came first. Then the gram was based on the weight of water at freezing point that would fit in 100th of a metre cubed.",
"The meter was original intended to be one ten millionth of the distance from the equator to the north pole along the earth's surface. (In practise it was the distance between 2 scratches on a certain iron bar kept at a lab near Paris, as you can't just measure the distance from the equator to the north pole whenever you want. Eventually they decided that the scratches on the bar was the definition of the meter, not just a local secondary estimate of a meter. And swapped the iron bar for one of a platinum-iridium alloy that was less subject to corrosion and thermal expansion. But it took a long time to decide on these things.)\n\nOnce they had the meter, more or less, they then picked the unit of weight so that it had the relationship you mentioned, that one gram is the weight of one millionth of a cubic meter of water. So that is not a coincidence at all.\n\nBut, it is not very practical to use two scratches on a 3 foot long iron bar to construct a very precise thimble, and then get ultra pure water to exactly fill that thimble at a certain temperature. So while the gram was inspired by the weight of a cc of water, that was not the actual definition of the gram, or at least not for more than a few years, they quickly switched to using another hunk of metal instead, and decided a gram was one thousandth of that.\n\nSo no, not a coincidence.\n\nBut there is one natural coincidence in here though. A competing definition (or inspiration) for the length of a meter was the length of a pendulum whose swing was exactly one second. The pendulum based definition and the earth-distance based definition happen to be very close to each other."
]
}
|
[] |
[] |
[
[],
[],
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|
g63l6
|
Are 98% of the atoms in the human body replaced every year?
|
In my World Religions class, the teacher presented an article that stated that 98% of atoms in the human body are replaced every year. This was to spark a discussion about whether "we are this body" or whether we have some kind of spirit soul.
The direct quote from the article is:
> Studies at the Oak Ridge Atomic Research Center have revealed that about 98 percent of all the atoms in a human body are replaced every year. You get a new suit of skin every month and a new liver every six weeks. The lining of your stomach lasts only five days before it’s replaced. Even your bones are not the solid, stable, concrete-like things you might have thought them to be: They are undergoing constant change. The bones you have today are different from the bones you had a year ago. Experts in this area of research have concluded that there is a complete, 100 percent turnover of atoms in the body at least every five years. In other words, not one single atom present in your body today was there five years ago.
This seems incredibly unlikely and comes across as BS to me.
Is either this, or the "cells in your body are replaced in 7 years" statement true?
|
askscience
|
http://www.reddit.com/r/askscience/comments/g63l6/are_98_of_the_atoms_in_the_human_body_replaced/
|
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"text": [
"I looked around for an answer to this, but I couldn't find the original article cited, which was in Annual Report for Smithsonian Institution in 1953.\n\nThis article, I think, sums up the discussion of it though: \n\n_URL_0_",
"It seems to have some good basis in experiments conducted by some dude called Paul Aebersold back in the fifties:\n\n_URL_0_ (Note the date on the article: 1954!)\n\nI'm not surprised that it's a high percentage (the watery bits of your body should be cycled through quite rapidly), though I am surprised that it's quite as high as 98%.",
"I'm not sure but I think he probably means 98% of cells rather than individual atoms. I'm not sure about the percentage but generally, through mitosis, we replace most of the cells our body uses. Now this doesn't really have to do with any type of \"soul\" or anything like that because we don't replace the cells all at once. It's a process that's happening constantly from the time your born to your death. ",
"You may find [this interview from NPR](_URL_0_) relevant:\n\n > KESTENBAUM: McCarthy did some research and he found this article from a Smithsonian Institution publication from 1953. So this is the beginning of the Atomic Age. And the article described these experiments where researchers fed to people radioactive atoms. Or they injected them with radioactive atoms. And then using radiation detectors, they could watch the atoms as they moved around. So they'd watch them go up one arm, into the heart and down the other arm.\n\n > Mr. McCARTHY: You can follow it through their body. Does it get excreted through urine, or is it excreted through their sweat or through feces or, you know, what happens to it? Does it end up in their fingers or in their eyeballs, or you know? So you can follow where these atoms go.\n\n > [...]\n\n > KESTENBAUM: A lot of the atoms get incorporated into our bodies. The article says the atom turnover is quite rapid and quite complete. In a year, 98 percent of the atoms in us now will be replaced by other atoms that we take in, in our air, food and drink. So that means 98 percent of me is new - every year.\n\n > [...]\n\n > KESTENBAUM: Still, this means that in a very real sense, we are not the people that we were a year ago. We're this collection of atoms that hang out together for a while and then they go on to do other things - sort of a momentary cloud of organization.\n\n > So what is me? Am I still me if my parts have been replaced?\n\n > Professor DANIEL DENNETT (Director, Center for Cognitive Studies, Tufts University): Well, of course, the question goes way back to ancient philosophy.\n\n > KESTENBAUM: This is Daniel Dennett. He's a philosopher at Tufts University. Remember, he says, the old joke about Abe Lincoln's axe?\n\n > Prof. DENNETT: There it is in the glass case and it says, this is Abe Lincoln's axe. So I say, that's really his axe? And he says, oh, yes, but, of course, the head has been replaced twice and the handle three times.\n\n > KESTENBAUM: There's also a modern atomic version of this puzzle that really gets to the heart of things.\n\n > Prof. DENNETT: We imagine that your rocket ship has landed on Mars and you have to get back from Mars to Earth by teleporter.\n\n > KESTENBAUM: Here's how the teleporter works. It dismantles you, atom by atom, (unintelligible), you know, records the precise location of every carbon, every hydrogen, every phosphorus, and it sends that information to Earth, (unintelligible), where a receiver transporter reconstructs you, (unintelligible) out of new atoms.\n\n > Prof. DENNETT: And you step out of the teleporter receiver on Earth, is that really you? I say, of course, it's you.\n\n > KESTENBAUM: Okay, that's clear enough.\n\n > But now imagine, he says, instead, the teleporter on Mars doesn't take you apart - it doesn't disassemble you - it just scans your atoms, do-dot-dot-do-do(ph), leaving you intact.\n\n > Prof. DENNETT: So now you're - there's a you that's stranded on Mars and there's a you that's back on Earth. Which is the real you?\n\n > KESTENBAUM: Well, it's pretty clear to me. That there's - that I have David 1 and David 2.\n\n > Prof. DENNETT: Yeah. And does one of them have some sort of special priority? Is one of them sort of realer, more you than the other?\n\n > KESTENBAUM: Yeah. What does my wife do?\n\n > Prof DENNETT: Exactly. Yes.",
"Heavy metals, such as Lead and Mercury, accumulate in animals bodies, particularly our bones. We get these heavy metals from our diet and our environment. Being that they are there for the rest of the animal's life, I would say that the above statement is false. I would also look at the source for the article. Is it from a scientific journal or is it from a newspaper? \n",
"Three things:\n\n1. When you get down to particles the size of atoms or smaller, they're [completely indistinguishable](_URL_0_). This means that two identical atoms could switch places and there would be no way to tell. Everything would look exactly the same as if they hadn't swapped. Atoms don't carry a label that lets you tell this one from that one. Thus it doesn't really make sense to talk about atoms being replaced. (This is actually the origin of some of the quantum weirdness.)\n\n2. The phrase \"studies at Oak Ridge\" is actually really vague. I poked around a little bit and couldn't find that research (maybe someone else can track it down). Unfortunately, it's not uncommon to see bogus research attributed to a legitimate institute like this. Also, the conclusion drawn, that 98% of the atoms in a human body are replaced every year, doesn't sound like the result of a physics experiment. At best, it's probably an *inference* based (probably very loosely) on another result.\n\n3. I also poked around a little to try to find the origins of that \"cells replaced every 7 years\" conjecture. Again, all I could find were quotes citing other quotes without actually citing any original research. Both of these assertions are starting to look to me like the [10% myth](_URL_3_). Such claims are really no more than old rumors often based on a [gross misreading](_URL_2_) of legitimate research.\n\nEdit: looks like [drhu](_URL_1_) tracked down an article that talks about the original research. It seems they tracked different isotopes of atoms, which *is* a way of distinguishing (at least somewhat) between particles.",
"It might be true, but using this as evidence for a soul is cheap. I much prefer the proverb: a man cant cross a river twice, as it won't be the same river, nor the same man. \n\nSee, the same effect can be used to prove the spiritual stuff you can't prove, or it can be a great tool to make us think about the ever changing world. ",
"\"Soul\" and \"Spirit\" are curse words for me on /r/askscience"
]
}
|
[] |
[] |
[
[
"http://stevegrand.wordpress.com/2009/01/12/where-do-those-damn-atoms-go/"
],
[
"http://www.time.com/time/magazine/article/0,9171,936455,00.html"
],
[],
[
"http://www.npr.org/templates/transcript/transcript.php?storyId=11893583"
],
[],
[
"http://en.wikipedia.org/wiki/Identical_particles#Distinguishing_between_particles",
"http://www.reddit.com/r/askscience/comments/g63l6/are_98_of_the_atoms_in_the_human_body_replaced/c1l6cvo",
"http://scienceblogs.com/builtonfacts/2010/04/the_worst_physics_article_ever.php",
"http://www.snopes.com/science/stats/10percent.asp"
],
[],
[]
] |
|
34qxqd
|
Why are White House meeting minutes recorded and kept?
|
This occured to me after watching a cold war documentary. Obviously it's extremely useful for historians, but why minutes are kept? Is there a law that mandates that? And for what reason?
ps: I posted the same question a year ago and didn't get any answer :(
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/34qxqd/why_are_white_house_meeting_minutes_recorded_and/
|
{
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"cqxj05o"
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"text": [
"[Here is a paragraph from the University of Oregon Holden Leadership Center on record keeping during meetings:](_URL_0_)\n\n > As you can see, the role of a secretary is more than \"just taking minutes\". The secretary is in effect, the historian. What he/she records will be referred to by current members as a reminder of finished and unfinished business, what needs follow-up and what actions were taken. It will also be kept for future members to read to gain an understanding of where the organization has been and why. Many organizations make it the secretary's responsibility to notify the membership about upcoming meetings-time, date, location-as well as any important items to be discussed.\n\nMany business meetings, particularly important ones, will keep minutes with a stenographer, and government business meetings are no exception. Minutes of a meeting are useful for the principals to later refer to as an aide-memoire, to reference in the event of a later dispute of what was said by whom; for sharing with non-attending staff, possibly even for eventual publication for some types of organizations, there are a wide variety of reasons why minute-keeping is a common practice. Minutes are kept for many meetings, whether the governing board of the local floral society, all the way to the highest government councils, committees, and cabinets.\n\nWhat is more interesting, is that in the modern era, there exists a delicate balance between keeping minutes or particularly audio and audiovisual recording of important meetings and deliberate obfuscation of such records. The infamous White House audio taping system was used to fix Nixon's responsibility, \"what did you know and when did you know it\" during the Watergate crisis and was instrumental in forcing him from office.\n\nWatergate and the role of the taping system in bringing down a Presidency was definitely noted by later politicians of all parties. Part of the art of modern government is to keep the President and other important and public figures from being pinned down to a position, or to having learned a particular bit of knowledge. This permits \"plausible deniability\" in the event of a crisis. The leader can be vague or deny knowing about the decisions that led to the crisis, and on occasion, a convenient subordinate can be thrown to the wolves of the media or the legal system.\n\nLook at the controversy over the use of personal, non-governmental email by some well-known public officials. Government records are almost always preserved and archived, and they are subject to subpoenas during judicial or congressional investigations. In the event of a scandal or crisis gone bad, without good records, a leader can testify with a high degree of vagueness or ignorance: \"Of course if I had warning that this terrible event might happen, I would have taken action to prevent it.\"\n\n"
]
}
|
[] |
[] |
[
[
"http://leadership.uoregon.edu/resources/exercises_tips/organization/keeping_minutes"
]
] |
|
2shcvj
|
Do LED lightbulb work in extreme cold temperatures?
|
I could not find a definitive answer whether they can be used for outdoor lighting. By extreme cold, it would down to -40F.
|
askscience
|
http://www.reddit.com/r/askscience/comments/2shcvj/do_led_lightbulb_work_in_extreme_cold_temperatures/
|
{
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"text": [
"The operating temperature of the LED will depend on the design of the device, typically -40F is at or below the lower limit of silicon devices, (this will generally be shown on the device datasheet).\nLithonia Lighting OFLR 6 MO 's datasheet quotes its minimum ambient temp as -40C."
]
}
|
[] |
[] |
[
[]
] |
|
2gzm63
|
why didn’t the Ancient Egyptians conquer the rest of North Africa to the west of them?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2gzm63/why_didnt_the_ancient_egyptians_conquer_the_rest/
|
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"The Western/Libyan Desert is 1000 km north to south and 1000 km east to west and largely blocks access out of the Nile and Nile Delta.\n\nAs we saw in the WW 2 desert campaign, the Western Desert makes even mechanized and motorized maneuvering problematic.",
"From a geographic stand point most of the land immediately west of the modern day country of Egypt is mostly desert. The Ancient Egyptian empire was almost primarily based around the Egyptian river and would have been fertile and habitable land. Anything outside of that would be illogical and extremely difficult to live in.",
"Before modern nation-states, the control of such large barren areas was very rare and often only nominal. If you go due west from the heart of ancient Egypt, you run into the \"Great Sand Sea', which is exactly what it sounds like. Places like this have no pre-existing infrastructure to conquer, and there is no way to build a meaningful infrastructure either; there is simply nothing to support a sedentary population. \n\nThe only parts of North Africa that could have conceivably been conquered would have been along the Mediterranean coast. But why did they not conquer these areas then? Well, the Egyptians were not a particularly naval people, and he only large seagoing ships that the Egyptians used were for commerce. Also, inhabitable land along the north-African coast is somewhat segregated, thus discouraging any king of land invasion. The closest arable land west of Egypt would have been on the Marj Plain, near modern-day Benghazi. Between there and Alexandria, there's a whole lot of desert to dissuade invaders. \n\nAlso for what it's worth, the Libyan Berbers who inhabited this area weren't wilting daisies. They were so aggressive in fact, that they managed to install a dynasty in northern Egypt, the Bubasites, for 200 years. So perhaps it was not just geography that suppressed the ability to conquer North Africa."
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
2y5uju
|
how does keeping an avocado seed with the raw avocado 'meat' keep it from browning?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2y5uju/eli5_how_does_keeping_an_avocado_seed_with_the/
|
{
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"[Here's a pretty good write-up of why Avocados turn brown](_URL_0_)\n\nIn short, it's the exposure to oxygen that makes the flesh turn brown. Keeping the stone (seed) with the meat does not prevent this in any way.\n\nFun fact about avocados: the trees release enzymes preventing ripening of the fruit, once they're picked they lose the enzymes. This allows the fruits to stay \"fresh\" on the tree far longer. \n\n",
"It doesn't. Exposing the meat to air will oxidize it and turn it brown no matter what. However, oil can help slow browning and acids will denature the enzymes responsible for oxidation."
]
}
|
[] |
[] |
[
[
"http://www.compoundchem.com/2014/08/03/why-do-avocados-turn-brown-the-chemistry-of-avocados/"
],
[]
] |
||
dfmq7e
|
why are tiff files so large?
|
I have a Panasonic G85 that produces 18MP raw files. But if I edit in PS, even without adding layers, the resultant tiff files are around 150MP. Where is all this extra data coming from?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/dfmq7e/eli5_why_are_tiff_files_so_large/
|
{
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"1. TIFF (also known as TIF), file types ending in .tif\nTIFF stands for Tagged Image File Format. TIFF images create very large file sizes. TIFF images are uncompressed and thus contain a lot of detailed image data (which is why the files are so big) TIFFs are also extremely flexible in terms of color (they can be grayscale, or CMYK for print, or RGB for web) and content (layers, image tags).\nTIFF is the most common file type used in photo software (such as Photoshop), as well as page layout software (such as Quark and InDesign), again because a TIFF contains a lot of image data.\n\nSource: _URL_0_",
" > 18MP \n\n > 150MP\n\nI'm guessing that the first is actually meant to read MP, while the second should probably read \"MB\"? Because \"MP\" means \"MegaPixel\" (million pixels), while \"MB\" means \"Mega Bytes\" (million/ 2^(20) bytes).\n\nSo let's take a look at how much that actually is: \n150/18 = 8.333…\n\nSo for every pixel, there are eight and a bit bytes used. Let's just call it an even eight and attribute the rest to metadata (when was the photo taken, what were the iso, shutter etc. settings, maybe GPS coordinates, etc.).\n\nDepending on your colour scheme (RGB/ CMYK/ RGBa/ …) and bit-depth (8-bit/ 16-bit/ 24-bit (\"true colour\") / …), this leaves between one and two bytes per pixel and colour channel. That actually sounds very reasonable. Heck, it isn't even enough to give you true-colour RGB - that would need 3\\*3=9 bytes per pixel (three colour channels, each of which having a precision of 24 bits = 8 bytes).\n\n & #x200B;\n\nThe reason other formats like jpeg or png will generally produce far smaller files is that they utilize (lossy) compression, which simply means that they don't save a colour value for every single pixel but instead try to save space by doing thing like saving \"the next five pixels all have this colour: \\[…\\]\" (very simplified)."
]
}
|
[] |
[] |
[
[
"https://www.ivanexpert.com/blog/2010/05/the-5-types-of-digital-image-files-tiff-jpeg-gif-png-and-raw-image-files-and-when-to-use-each-one/"
],
[]
] |
|
ebnkco
|
how do we develop crushes on people?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/ebnkco/eli5_how_do_we_develop_crushes_on_people/
|
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"you see someone you find attractive and then you get a bone bone and decide that you want to make a hooman with them",
"Lots of different reasons. Most influential factors include:\n- Proximity: You’re more likely to have a crush on someone who you have multiple classes with each day than you are to have a crush on someone who lives across the country.\n\n- Pheromones: Chemical signals, so to speak, that indicate a good genetic match or a person who is ovulating, to name a couple examples (there’s been a study where people use unscented soaps and deodorants and wear the same white t-shirt to bed every night for a week and then different people come to the lab and sniff the shirts to decide which person they find most attractive based on pheromones more or less. Heterosexual men prefer the shirts of women who are ovulating, and also like the smell of shirts worn by homosexual men the least)\n\n- Similar Levels of Attractiveness: This applies a bit more to the kind of person you actually end up in a relationship in as opposed to a crush. But a person tends to pursue people who are about the same level of attractiveness as they themselves are. This way, you protect your ego because you perceive the crush to be less likely to reject you. There are obviously exceptions to this (20 year old women dating wealthy 70 year old men, as an extreme example)\n\n- Admirable Qualities: That person has some sort of qualities that you would like to adopt in yourself or associate with your internal image of your ideal self. A person who is socially awkward and anxious and wishes they weren’t, for example, might have a secret crush on the outgoing, friendly person who strikes up conversations with the people who look like they could use a friend. This has a limitation: our egos come first - we don’t want people who we perceive as being so much better than ourselves that we feel inferior.\n\n- Time: The more time you spend with a person (similar to proximity), the more you start to really pay attention to a person. Think of the experiment where complete strangers stare into each other’s eyes for minutes at a time, and by the end of it, they feel a bit more comfortable with them even if they never exchange words. \n\n\nThere are a looooot more but these are the most commonly observed in lab settings\n\n\nSource: Psychology of Relationships and Intimacy class in college; also have a degree in psychology.\n\nEdit: Pressed enter between each bullet for better readability"
]
}
|
[] |
[] |
[
[],
[]
] |
||
29qo5i
|
why charities with similar goals don't merge to become more effective?
|
I saw today on my Facebook newsfeed of a video for I already forgot the name but a charity that provides clean drinking water to poor villages in Africa.
I am all for the cause because everyone in the world should have clean water at a bare minimum. That said, I know I have seen at least 2 other charities with the same goal.
Why do these charities not merge, combine funds and resources, and provide more marketing campaigns and build more wells?
The only thing that comes to mind is el hefe of each charity wants his final say in how things are done and/or some want to push their agenda (be it a political/religious/etc affiliation). Please tell me it is not that ignorant? There has to be more reasons, right?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/29qo5i/eli5_why_charities_with_similar_goals_dont_merge/
|
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"That would require a lot of profit sharing for the lawyers and executives. Charities more proficient at throwing celebrity endorsed, wine and cheese events aren't going to share their spoils with the smaller outfits holding three legged races at a park.\n\nAbove all it's about paying the bills and lining their pockets. Whatever is left over goes to build wells, cancer research, etc.",
"Merging companies (and yes, non-profits are companies) requires a lot of work. First, just because two companies do the same thing does not mean that they could merge easily. What if one is a Catholic charity, and the other is non-religious? Is the new charity religious or not? Which of the two Presidents is going to be in charge? Are you going to fire a bunch of staff? If not, how is it more efficient to have 1 big company with twice as many workers?\n\nCompanies merge when it makes some financial sense. Since non-profits are not in it to maximize value, they don't have to worry about being the biggest and best.",
"Corruption is a big one, lots of charities run at the minimum spending to be called a charity and you don't know which ones are/to what degree profiteering unless they show you their books.",
"Because most these non profit charities actually rake in a lot of money that goes to CEOs and higher ups. They aren't about to lose money like that.",
"I was talking to a well to do person who wanted to found a charity that did what the Red Cross did. I asked her why she didn't make a donation, volunteer or apply for a job. She didn't want to \"work for another organization\". She wanted to be the CEO.\n\nIn this case, it was her personal ego and desire to have her name be on the marquee.",
"The simple answer is that they don't become more effective by merging. Mergers of all kinds tend to cause bloat within companies. Non-profits rely on being nimble, quick to act, and flexible to changing needs and conditions. As they become too large, they are less able to do all of those things.\n\nAnd then they have larger infrastructure to maintain, which takes money away from where it is needed.",
"[Sometimes they do.](_URL_0_)\n\nProper answer: Some charities that raise money for the \"same\" thing might be focusing on different aspects of it. If the issue is big enough multiple charities might be able to do this very well without getting in each other's way.",
"Because everyone would lose their jobs.",
"I work full time for a not for profit organization so I can tell you my point of view. I'll try to explain why your question, to me, sounds a lot like 'why don't all grocery stores and restaurants of the world merge together to be more efficient and make more money'...\n\nThe biggest reason is that we often we have different 'specialities'. For example one might be very adept at mobilizing students as volunteers; or be very specialized to deliver programs to a specific audience (specific age group, type of community, etc). Everything in the organization (staff, resources, mentality, values) etc could be geared towards that. Trying to merge might end being like trying to merge a restaurant and grocery store.... it might not really be more efficient. \n\nAlso I'll add that most NFPs I have worked with are really driven by the passion of the people working there, and that has to be considered a resource, too. Where I work, and pretty much any other NFP that I have had the inside scoop on, we make a lot less money than if we worked in equivalent jobs in the for profit sector. So we are motivated by different things than money. Often it's the belief in our cause or a love of the methods through which we work towards our cause. I'm motivated by our program and all its side benefits (the personal growth our volunteers go through) as much as I like the outcome of our work. If my organization merged with another one that used a totally different approach and I lost that aspect of things, I might not stick around for my job, which I think would be a loss for 'the cause'. I guess I'm just trying to give another example of another benefit of having different means to the same end... motivating people / harnessing their passion is important for NFPs because salary is not going to cut it (even more so if your are working with volunteers)! \n\nThrough my work, I often meet people who work/run other not for profit organizations with similar goals. Usually we explain our organizations to each other and then we try to see if we can partner. For example I might be able to provide a pool of trained/keen/screened volunteers to deliver a resource that they have created but don't have the manpower to deliver themselves. Whenever we create a new program, we look carefully at what already exists so that we don't duplicate anything. I think everyone finds their niche and develops their expertise accordingly. Sometimes I do encounter smaller group that have just started a new program that is really similar to what we do, and I feel they are reinventing the wheel (often students... who had a good idea and didn't take the time to research if other similar programs existed). I usually offer to bring them under our umbrella, sometimes it works, but sometimes running their own thing (as volunteers) is their motivation so it's important to them to continue on their own. When you are working with volunteers, the time they donate is a scarce resource (like money) and if they'll donate more by having ownership of their own initiative, then it might be more efficient to let them lead their own thing.\n\nAnyways, I don't think it's a bad thing overall that we don't all merge together. A little healthy 'competition' is a good thing like it would be for any companies. We are all competing for funding from government, corporations, and individuals, and it makes us try harder!\n\nPS. It really frustrates me when people say that NFPs are ways of lining their pockets. I know there have been some bad apples but there are bad apples in everything. Where I work and any other organization that I hae first hand knowledge of, our salaries are very low compared to what we would make in industry, and the CEO's salary is extremely reasonable. We are audited every year and there are a lot of regulations in place by the government (in my country anyways). I'm really sad that some bad apples are giving a bad reputation to the sector and potentially hurting us all.",
"higher-ups won't get most of the money that's used for \"administration\""
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[],
[
"http://en.wikipedia.org/wiki/Age_UK"
],
[],
[],
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] |
|
22s0k5
|
why are endorphins not used as the ultimate drug?
|
At the end of thr day drugs are taken so thr user will feel better, why don't we see people injecting this or any other happy hormones?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/22s0k5/eli5_why_are_endorphins_not_used_as_the_ultimate/
|
{
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"They are. Heroin and opioid/opiate narcotics are basically just synthetic endorphins. ",
"Endorphins can't cross the blood-brain barrier. Injecting or injesting them won't actually do anything, because they won't get to the receptors on which they exert their \"feel-good\" effect."
]
}
|
[] |
[] |
[
[],
[]
] |
|
5birw9
|
if pre-election polling is mostly done by phone interviews via landline, and the number of landlines is declining among most demographic groups, why are they still fairly accurate?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5birw9/eli5_if_preelection_polling_is_mostly_done_by/
|
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"text": [
"It is not accurate that \"... poling is mostly done by phone interviews via landline\". Actual polling companies call cellphones and have non-phone ways of reaching people. \"Polls\" limited to landlines are badly disguised political activism.",
"I forget which election, but I believe it was Wilson. The polls were heavily in his opponents favor, however Wilson won by a decent margin. This was due to the fact that only rich people had phones, and therefore only rich people were included in poles. ",
"[NPR Politics Podcast - Polls](_URL_0_) \n\nCheck out this podcast. They talk to a Pollster from Pew Research Center about this very subject. ",
"If you know the demographics of the population you're polling, and you know the demographics of the actual people you get ahold of on the phone, you can then weight the results to adjust for the polling discrepancy.\n\nExample: Lets say your polling population is 50/50 men/women. You then call a bunch of people to actually poll them, and realize the people who pick up the phone are 25/75 men/women. Since you know the population should be 50/50, you count each male response twice to account for the polling discrepancy.\n\nIn practice it's more complicated, but the principle is the same, and the adjustment methodologies are documented for any legitimate poll. (So they can be peer reviewed)"
]
}
|
[] |
[] |
[
[],
[],
[
"https://itunes.apple.com/us/podcast/npr-politics-podcast/id1057255460?mt=2&i=377528353"
],
[]
] |
||
6rgsbx
|
What makes meth labs so dangerous?
|
It's widely known that meth labs are practically ticking time bombs, but what actually causes the explosion?
|
askscience
|
https://www.reddit.com/r/askscience/comments/6rgsbx/what_makes_meth_labs_so_dangerous/
|
{
"a_id": [
"dl5p8o4"
],
"score": [
10
],
"text": [
"because they're attempting to replicate processes that are normally carried out in a _URL_2_, but without the design of engineers, construction with appropriate materials or operation by trained experts. Instead they're copying instructions from the internet or passed down orally, using whatever is cheapest and available and running the processes without necessarily understanding the details, especially the energies, of the reactions.\n\nI'm not interested in looking up the specific synthetic steps involved, but I expect at least a few of them are exothermic, meaning that when that reaction happens, one of the products is heat. If that reaction happens faster than expected, then you get lots of heat, all at once, and if that happens in a liquid solution like water, the liquid turns to gas, and expands violently, as in _URL_1_\n\nThere's nothing intrinsically dangerous about making meth, or any other pharmaceutical, but some of the reactions can be quite dangerous, even putting aside the potential for violently energetic reactions. One scary example: _URL_0_"
]
}
|
[] |
[] |
[
[
"https://en.wikipedia.org/wiki/MPTP#Discovery_in_users_of_illicit_drugs",
"https://www.youtube.com/watch?v=7MxsKkAnLC0",
"https://en.wikipedia.org/wiki/Chemical_plant"
]
] |
|
19knsp
|
What is the affect of aging on sex cells in humans, and how is DNA preserved to pass on to offspring?
|
This might be an oversimplification but if aging is a result of sustained DNA damage during cell division, how is the DNA in reproductive cells preserved to pass on to offspring?
|
askscience
|
http://www.reddit.com/r/askscience/comments/19knsp/what_is_the_affect_of_aging_on_sex_cells_in/
|
{
"a_id": [
"c8oxcdo"
],
"score": [
3
],
"text": [
"The [germ cell line](_URL_2_) is separated from the rest of the developing organism early in development, and is kept in a state of minimal cell division and protection from metabolic damage. There is still degradation of the genetic material in [males](_URL_1_) and [females](_URL_0_), but it doesn't become an issue until past the age of 40."
]
}
|
[] |
[] |
[
[
"http://link.springer.com/chapter/10.1007%2F978-0-85729-826-3_3?LI=true",
"http://humupd.oxfordjournals.org/content/10/4/327.short",
"http://en.wikipedia.org/wiki/Germ_cell"
]
] |
|
26hc0e
|
Can anyone identify the markings on this rock in my front yard? (Buffalo, NY)
|
_URL_0_ This has been in my yard since the house was built 100 years ago in North Buffalo. What is this, a cornerstone, headstone? It's just sitting in the middle of my yard almost as it isn't mean to be moved. It's about 6 inches by 6 inches.
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/26hc0e/can_anyone_identify_the_markings_on_this_rock_in/
|
{
"a_id": [
"chre35z"
],
"score": [
3
],
"text": [
"You'll probably get more help over at /r/whatisthisthing, the appropriate subreddit for these kinds of questions."
]
}
|
[] |
[
"http://imgur.com/zWX6WZW"
] |
[
[]
] |
|
19x933
|
how did the golden eye disk hold a full game and an emulator with 10 games only on 12mb?
|
If an album is like 80 mb how do they have all the textures and a.i and music, plus this emulator I just read about?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/19x933/eli5_how_did_the_golden_eye_disk_hold_a_full_game/
|
{
"a_id": [
"c8s51qg",
"c8s5514",
"c8samuj"
],
"score": [
3,
3,
2
],
"text": [
"It is a game contained in a ROM and the emulator is what allows you to play access the ROM. There is not as much data as you think.",
"I'm pretty sure the music is synthesized. The music actually stored on the cartridge is basically just the musical notes it should play, instead of having the actual sound data. The console then has a built in sequencer that reads the notes and plays them. The music files aren't thus very large at all.\n\nThe textures are very low quality, and probably take up most of the 12 megabytes. \n\nI'm not sure what you mean by emulator, but that is just additional code that probably doesn't take up a lot of space.",
"because older games like that kept lists of instructions on how to play the music, and how to draw the video, instead of storing the already processed and ready video and sound. The instructions lists take a lot less space than the methods we use to store video these days. Modern Mp3 files, and videos are completed music and video that have already been processed, and take up a lot more space."
]
}
|
[] |
[] |
[
[],
[],
[]
] |
|
2msxdo
|
how do the big torrent uploaders like yify, eztv, etc, not get caught?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2msxdo/eli5_how_do_the_big_torrent_uploaders_like_yify/
|
{
"a_id": [
"cm7p0wu",
"cm7srgj"
],
"score": [
11,
6
],
"text": [
"There can be many reasons:\n\n- hiding behind a VPN or TOR or another proxy, or all of those; remember that there still are countries where piracy is not regulated by law\n- initial seeding from a remote server\n- actually living in a country with no laws against piracy\n- all of the above\n\nI also doubt that they are *that* heavily hunted for. The authorities have much bigger Internet problems like hacking, fraud, drug trade. ",
"Well actually those are not the actual source of the pirated content. The content usually comes from scene groups like KILLERS, DIMENSION for tv shows, RELOADED, SKIDROW for games etc. I'm not really sure if torrent is the first platform these original files appear in. The ones OP mentions are just known uploaders on public trackers like The Pirate Bay. You won't find those on private trackers. \n\n\n\nOP, you'll have a better chance of getting good answers to your question if you ask it in /r/Trackers"
]
}
|
[] |
[] |
[
[],
[]
] |
||
5kuu9h
|
what is the difference between "_url_1_" and "_url_0_"? i know that they are one and the same, but in general i want to understand how the domain name works.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5kuu9h/eli5_what_is_the_difference_between/
|
{
"a_id": [
"dbqu86j",
"dbqwtjq",
"dbqwx6x",
"dbr2iun",
"dbr33b3"
],
"score": [
10,
9,
2,
3,
3
],
"text": [
"_URL_0_ is what is called a subdomain. _URL_1_ is called a subdirectory. Pretty much the same on the server side except that a subdirectory is within a domain's directory while a subdomain is outside a domain's directory, yet has its address response to the initial domain. The reason that those particular two respond to the same place is that both addresses go to the same server location.\n\nresource: I work in websites and hosting. ",
"\nThere are two protocols here:\n\n- The Domain Name System (DNS for short) resolves a text domain name, like \"_URL_3_\", to a numeric IP address, like \"10.234.56.7\".\n\n- The Hyper-Text Transfer Protocol (HTTP for short, or HTTPS if you use the Secure version) allows you to request websites from a computer at an IP address.\n\nIf you type \"_URL_3_\" into your browser, first the browser will add the transform the URL into \"_URL_0_/\". The missing parts added are \"http://\" which specifies the protocol, and \"/\" which specifies a resource. It will ask your ISP's DNS for the address of \"_URL_3_\", be informed by the DNS server that the address is 10.234.56.7, then send an HTTP request to 10.234.56.7 for the \"/\" resource.\n\nIf you type \"_URL_2_\" into your browser, again the browser will transform the URL, this time into \"_URL_1_\". The resource part \"/mail\" was already there, so only the \"http://\" protocol part needed to be added this time. It will ask your ISP's DNS for the address of \"_URL_5_\", be informed by the DNS server that the address is 127.77.88.99, then send an HTTP request to 127.77.88.99 for the \"/mail\" resource.\n\nGoogle has programmed their servers to have both of these URL's do the same thing. For example, \"_URL_1_\" may use an HTTP redirect to tell your browser it should ask for \"_URL_0_\" instead (an HTTP redirect is a reply a website can send to your browser to tell it to request a different URL and change your address bar to match). Another common use for redirects is to redirect the HTTP version of the website to the HTTPS version.\n",
"When you buy an internet name (domain name), you would buy \"_URL_3_\". Once you own that, you can use it for different servers, like _URL_2_, _URL_0_, _URL_1_ or whatever you want. www._URL_3_ would traditionally be used for your companies main web server, but in fact you can set it up anyway you want.\n\nEverything after the slash indicates a different directory or application on that server. So maybe on your server you have a /mail folder, maybe a /games folder or whatever you want.\n\nIf you want to go beyond ELI5, you can use technologies like URL rewriting or BigIP iRules or host name bindings where you can parse domain names however you want and the guidelines I wrote above can be bypassed.\n",
"Breaking up the `_URL_0_/mail` URL a bit:\n\n- `_URL_0_` determines *which server you contact* (specifically, you're looking for the server that corresponds to the `www` subdomain registered under the `google` domain, which is registered under the `com` top-level domain.\n\n- `/mail` determines which document you ask the server for (and if this part isn't specified, you effectively just ask for `/`\n\nOf course, since Google owns both `_URL_0_` and `_URL_2_`, they can make both URLs lead to the same page anyway, but this is the difference. One says \"Give me the `/mail` document from the server located at `_URL_0_`, and the other says \"give me the `/` document from the server at `_URL_2_`\".",
"As a web site creator, here is my understanding:\n\nImagine two servers. One is the main site server and the other is a dedicated mail server both of which are wired together. A browser request for \"_URL_0_\" will route the request to the main server and redirect it to the mail server. Where as the \"_URL_1_\" request goes directly to the mail server without the need for passing through the main server. Both methods will use the same IP numbered address.\n\nThe reason for the two variations is because we humans would not remember to enter the numbered IP address and which of the two methods used is determined by the person who programmed the link used to access it. If it was Google staff member it likely would be the direct method. But if it was programmed by another web site they likely would use the main server redirect because they were unaware that a dedicated server exists."
]
}
|
[
"mail.google.com",
"www.google.com/mail"
] |
[] |
[
[
"Mail.google.com",
"Google.com/mail"
],
[
"http://mail.google.com",
"http://www.google.com/mail",
"www.google.com/mail",
"mail.google.com",
"http://mail.google.com/",
"www.google.com"
],
[
"ftp.google.com",
"yomama.google.com",
"mail.google.com",
"google.com",
"www.google.com"
],
[
"www.google.com",
"www.google.com/mail",
"mail.google.com"
],
[
"www.google.com/mail",
"mail.google.com"
]
] |
||
l1bnx
|
what exactly happened to gandalf after the snafu at moria?
|
This was always one of those plot points I could never really wrap my head around. I understand that he became Gandalf the White, but did he die? Did he have some sort of epiphany? Is he the same person?
The books confused me and then when I saw the movies I was even more confused.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/l1bnx/eli5_what_exactly_happened_to_gandalf_after_the/
|
{
"a_id": [
"c2oyukp",
"c2oyzqm",
"c2oyukp",
"c2oyzqm"
],
"score": [
5,
3,
5,
3
],
"text": [
"He slays the beast. He dies. While dead, he does things in the afterlife which he never talks about. He is reborn as the white, for I imagine his bravery, valor, and just doing the right thing.\n\nHe then gets taken away by the eagle, taken somewhere where he gives advice, and such, I believe it was to the cliff of the birds.",
"The fall did not kill him or the Balrog. When they landed, the Balrog fled from Gandalf, but he chased it through the myriad of twisting tunnels below ground. After a few days, he finally found and killed it, but not before suffering mortal wounds himself. His spirit went to \"*a place beyond space and time*\", but he was resurrected and returned to Middle Earth, ostensibly because he was needed to defeat Sauron. The books never tell exactly what happened...",
"He slays the beast. He dies. While dead, he does things in the afterlife which he never talks about. He is reborn as the white, for I imagine his bravery, valor, and just doing the right thing.\n\nHe then gets taken away by the eagle, taken somewhere where he gives advice, and such, I believe it was to the cliff of the birds.",
"The fall did not kill him or the Balrog. When they landed, the Balrog fled from Gandalf, but he chased it through the myriad of twisting tunnels below ground. After a few days, he finally found and killed it, but not before suffering mortal wounds himself. His spirit went to \"*a place beyond space and time*\", but he was resurrected and returned to Middle Earth, ostensibly because he was needed to defeat Sauron. The books never tell exactly what happened..."
]
}
|
[] |
[] |
[
[],
[],
[],
[]
] |
|
8mktot
|
Did ancient Israel abolish or prohibit slaveowning in any way after the Exodus from Egypt? Was it socially frowned upon to own slaves?
|
This has less to do with the historical truth of the Exodus and more the Israelite society allegedly being founded by ex-slaves. After whatever event freed the Israelites from Egyptian rule, how was slavery perceived in the society and amongst its people? How was it treated legally?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/8mktot/did_ancient_israel_abolish_or_prohibit/
|
{
"a_id": [
"dzomol0"
],
"score": [
12
],
"text": [
"EDIT: Just to be clear, not a historian, but I’ve been reading this book for the past ten years, I think I know a little bit about it.\n\nThe Law actually says a lot about slaves and servants and how you were to treat them. How well they followed it or if they followed it all is questionable whether you believe the Bible (That’s a heavy theme of the Old Testament) or not but we can look at what they thought they were supposed to do.\n\nAmong fellow Israelites the law was explicit about keeping one another out of poverty, helping the poor, forgiving debts Ect. But not everyone cooperates. So if you could not afford to pay a debt, pay for your land, pay for a dowry, or if you couldn’t even take care of yourself, you could sell yourself, or your children and become a servant.\n\nBut this was not permanent. The law gave you two outs. You could work for seven years then you were free to go. If you married while in service and had kids, the owner kept those. And if you were Female, you had to marry into the family, if you could. But other then that, you were free. You could even go back to your own land or your husbands land if you were working off a Dowry. \n\nInteresting though if you didn’t want to leave, you could become an Indentured servant, from Exodus 25.\n\n“But if the servant declares, ‘I love my master and my wife and children and do not want to go free,’ then his master must take him before the judges. He shall take him to the door or the doorpost and pierce his ear with an awl. Then he will be his servant for life.“\n\nBasically if you treated your slaves well, they could stay on and become basically a family member. It’s was a good incentive to be nice to slaves. \n(And there were laws in place to prevent people from like forcing slaves into indentured servitude without consent but that’s another story)\n\nThe other way to be free was called the year of Jubilee. The idea was that every fifty years, all debts just stopped. If you sold land to someone, you got it back. If you owed someone money, you were covered. And if you were a Israelite slave, you were free. Period. And as cool as it sounds (If completely unpractical for a more advanced civilization) I can say for certainly, I doubt this was ever observed due to Ocupation and quarreling before the exile. And afterwards, land was fairly scarce.\n\nForeigners weren’t quite as lucky. If someone came to live in your land peacefully, you weren’t allowed to enslave them. The law said that you should incorporate Foreigners into your land and basically make them Israelites. People you were fighting though were fair game. Though most of the time, the law said kill everyone and take none for slaves. Like the invasion of the promised land, and they didn’t want the natives to breed with the Israelites so they didn’t turn to idols. The Old Testament acknowledges this didn’t happen basically at all. And Foreign slaves were not under the seven years rule, I don’t believe. Luckly the law was pretty lax about becoming an Israelites. Basically be circumcised and respect Passover. So a foreign slave could become an Israelite and become free by extension.\n\nTreatment of slaves was pretty good according to the law. You were to respect slaves as people, feed and give them space, and refrain from sexual relations. Indetured servants were to be treated as family. And punishment for mistreating slaves ran from heavty fines to freedom for the slave.\n\nI’ve been mostly pulling from Leviticus, Exodus, Joshua, and the all important, Spurgeon’s commentaries."
]
}
|
[] |
[] |
[
[]
] |
|
rtfag
|
Someone I met got me curious... in the early days of America, mineral surveyors would cross the country looking for metal deposits. How exactly did the bore into rocks and test things without modern equipment?
|
As the title explains, prior to air hammers and hollow drills, how did men effectively bore through rocks to get samples using their muscles and (I assume) some rough implements? If there is some good reading on the subject, that would be perfect.
|
askscience
|
http://www.reddit.com/r/askscience/comments/rtfag/someone_i_met_got_me_curious_in_the_early_days_of/
|
{
"a_id": [
"c48jsp1"
],
"score": [
9
],
"text": [
"A lot of it boils down to understanding the geology itself. If you can recognise evidence of (for example) a large igneous porphyry body you might take a good guess at there being workable amounts of copper mineralisation.\n\n\nAlternatively, simple techniques such as panning for heavy minerals in stream beds can tell you that there's economically viable mineral deposits somewhere upstream."
]
}
|
[] |
[] |
[
[]
] |
|
66feuh
|
cryptocurrency mining. what is the process and why is a gpu required?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/66feuh/eli5_cryptocurrency_mining_what_is_the_process/
|
{
"a_id": [
"dgi402n"
],
"score": [
2
],
"text": [
"Currency has value in part because it is rare. If you can get however much of it you want, it becomes worthless. Imagine you can just print off $100 bills from home and they count as real dollars. Why, then, would I sell you, I dunno, a used book for $5? I can just print off $100, so why do I want your $5? Or even $500? Or even $5000? I don't need your dollars, I can have as many as I want whenever I want.\n\nLikewise, cryptocurrency derives value in part because of its rarity. You can't just *have* bitcoins. But like real dollars, bitcoins still have to come from *somewhere*. You may be thinking \"dollars come from the US mint\" but that isn't really true. Physical paper dollars come from the US mint, but the underlying *value* of a dollar comes from the goods and services you can use the dollar to purchase. Those goods and services take time and resources to acquire, and the dollar value it takes to purchase the goods and services is assigned based on how much time and the cost of those resources. Take the simplest example: gold.\n\nYou want gold, it's shiny, it's malleable, it doesn't tarnish, it's an important part of electronics, etc. *I* want food, for obvious reasons. I don't know how to farm and I don't have the tools or land for farming. I *do* have the tools and expertise to find gold. The opposite is true for you: you have farming stuff, but no gold-getting stuff. So I will trade my time getting gold, which to me has less value than food, and trade you my gold for your food. Everyone wins, and it's not complicated until you start adding in a bunch of other people all trading for different resources and you need a way to keep track of who owes what to whom, and that's where currency is useful. Assuming nobody is just stamping out money, the amount of currency you have in the system depends on how much of the resources are available and how much time it takes people to get it. If there's a lot of gold to go around, you need more dollars to represent that gold. And getting gold takes *time* and *tools*.\n\nBack to bitcoin: you have to have a way for your cryptocurrency to enter the system. But you can't just dump it in, because then you'll have more currency in your system than you have absolute value in the system, and the currency will be worth less. You also can't just hand it out to people, because that isn't fair, and those people can horde the cryptocurrency and create artificial scarcity, and control the currency such that it's a hassle to use and nobody wants it, which also makes it worth less (although in both cases, perhaps not worthless). You have to have a way for the currency to enter the system *slowly* to keep up with the demand for it, and control who gets it, and give the currency inherent value by making it - like gold - hard to obtain.\n\nThe solution is \"mining\" it. The cryptocurrency is obtained by having your computer \"mine\" it by solving very long, difficult math problems. This takes a lot of time - the problems aren't simple 1+2, they're incredibly complex functions that take even fast computers a very long time to complete. It also takes resources: you can solve more problems with a faster computer, but that means you have to invest in a faster computer. It solves the cryptocurrency dilemma perfect, though, for those reasons: you are investing time and resources, which are inherently valuable, into the cryptocurrency, which makes *it* valuable. And anyone can do it.\n\nGPUs or graphics processing units are useful because they attack computing by using a *lot* of small, efficient processors rather than the traditional CPU (central processing unit) way of doing it, which is to have a few very powerful processors. CPUs solve problems by having a few core processors, like *maybe* eight, doing thousands of processes each second. A GPU has thousands of processors instead, and they each do a few processes each.\n\nGPUs are useful for crypto mining because you can work on many different functions simultaneously, and the functions can be broken down into smaller, easier problems that can be solved in parallel. Compare that to a normal CPU that would solve one of the functions much faster, but has to solve *just that one* function, in its entirety, before moving onto the next one. It's the difference between having a tiny group of miners that work really fast and nonstop, but are all in the same mine, and having thousands of miners that are kind of ok at mining but you have hundreds of them in each mine and you have hundreds of different mines."
]
}
|
[] |
[] |
[
[]
] |
||
8u2m40
|
if a 213g potato has .2g of fat, 4.3g of protein, and 37g of carbs, what is the other 171.5g?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/8u2m40/eli5_if_a_213g_potato_has_2g_of_fat_43g_of/
|
{
"a_id": [
"e1c2hfc",
"e1c2mfb"
],
"score": [
3,
22
],
"text": [
"Net carbs? If yes, most of the rest is fiber",
"Water, fibre, and other things that humans don't digest into energy."
]
}
|
[] |
[] |
[
[],
[]
] |
||
24pyyq
|
Gigantic Black Holes in galaxy centers keeps 'devouring' matter. Why doesn't that eventually result in whole galaxies being consumed and merging into single immense 'holes' with all galactic mass inside them?
|
Doesn't adding matter to a black hole increase its gravitational 'pull'?
If the sun for example magically doubled its mass wouldn't the planets be pulled closer and closer?
|
askscience
|
http://www.reddit.com/r/askscience/comments/24pyyq/gigantic_black_holes_in_galaxy_centers_keeps/
|
{
"a_id": [
"ch9nepf",
"ch9rrrw"
],
"score": [
3,
2
],
"text": [
"The planets don't fall into the Sun because they basically \"keep missing\" when they fall towards it, hence going around in elliptical orbits. Matter around a black hole is essentially the same. The gas and dust orbiting a black hole carries angular momentum with it that must be conserved and hence it will orbit around the hole in a disk, always missing the black hole and never falling into it. Of the entire accretion disk it is only a small fraction that eventually falls into the hole. Even if more matter fell into the hole, the rate of accretion would eventually stop when the luminosity created by the infall gets so high that the radiation pressure counteracts the infall motion. This limit is known as the Eddington luminosity. One of the big misconceptions of black holes is that they are cosmic vacuum cleaners that just go around in a galaxy and suck up everything they encounter, but this is vastly untrue. In fact, only very little mass actually enters a black hole.\n\nAlso, if the Sun's mass was doubled somehow, the period of the planetary orbits would get a lot shorter according to Newton's law of universal gravity and Kepler's laws, but they wouldn't necessarily fall into the Sun unless they could somehow lose their angular momentum like if the Earth was moving through a cloud of gas, which it isn't.",
"A black hole of mass M has no more gravitational pull than any other object of mass M. So basically, whether the center of the galaxy has M kilograms of stars or M kilograms of black holes, the gravitational pull is the same. "
]
}
|
[] |
[] |
[
[],
[]
] |
|
41klye
|
Not quite connecting the whole Franks, Alemanni, Charlemagne, Holy Roman Empire, and France thing.
|
From what I thought was right before, the Franks settled in Gaul and the Alemanni conquered a lot of central Europe/ northern and central Italy/ Frankish Gaul and made the Holy Roman Empire under Charlemagne. Now I'm learning that Charlemagne was ruler of the Franks, but that means the Franks made the HRE. But the Franks made France right? So why did the French hate the German peoples if the Franks (future French) made the HRE? And how do the Alemanni fit into this?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/41klye/not_quite_connecting_the_whole_franks_alemanni/
|
{
"a_id": [
"cz3honu"
],
"score": [
3
],
"text": [
"Charlemagne, at his death, ruled an Empire encompassing modern day France (sans Brittany), the Pyrenees, Austria, Switzerland, the low countries, the northern half of Italy, and the majority of modern Germany. After his death, his son Louis I came to power, then died leaving his three sons to divide up his Empire, which they did in 843 with the Treaty of Verdun. Charles the Bald was given West Francia (modern France without Provence or Brittany), Lothair (the eldest) was given a strip of land encompassing the low countries, Burgundy, Provence, and northern Italy, and Louis the German was given the eastern territories (East Francia). [Here](_URL_0_)'s a map to clarify things. East Francia and parts of Lotharingia developed into the Holy Roman Emperor.\n\nThe traditional dislike between the French and the Germans come from more recent sources (such as the Napoleonic wars, the Franco-Prussian war, and the two World Wars)."
]
}
|
[] |
[] |
[
[
"https://upload.wikimedia.org/wikipedia/commons/4/42/Partage_de_l'Empire_carolingien_au_Trait%C3%A9_de_Verdun_en_843.JPG"
]
] |
|
6sdq4x
|
Can bees tell the difference between their own hive's honey and another hive's honey?
|
askscience
|
https://www.reddit.com/r/askscience/comments/6sdq4x/can_bees_tell_the_difference_between_their_own/
|
{
"a_id": [
"dlcertl",
"dlctx09"
],
"score": [
8,
3
],
"text": [
"Well they certainly know the difference between their hive and other hives, even if there are several of them adjacent to each other. \n\nHoneybees will also rob other hives of their honey if food is scarce. This is intentional; they are not mistakenly at the wrong hive, and the host hive will try to repel the invaders. As far as if they would \"know\" the difference between their own honey and another hives if you placed this in containers near the hive, there is no way of knowing. Bees are pure genetics, I don't think there's really much going on in their brains besides the various primal instincts that allow the hive to survive. You would need one tiny MRI machine seeing how the brain lit up to answer this. ",
"I feel like, as sensitive to smell as they are and as much as they rely on pheromones, they must have some way of identifying their own honey. That said, they may just be identifying their own hive and hive-mates, rather than the honey itself.\n\nAdditionally, I think bees are \"smarter\" than we give them credit for. Have you seen the bumblebees being taught to roll a ball to a specific place?\n\n_URL_0_"
]
}
|
[] |
[] |
[
[],
[
"https://youtu.be/exsrX6qsKkA"
]
] |
||
4z2wxw
|
if you sweat salt does that mean your body needs more salt or it already had too much?
|
If that's a sign the body needs more then why is it that drinking salt water can kill you, but adding salt to water won't?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4z2wxw/eli5if_you_sweat_salt_does_that_mean_your_body/
|
{
"a_id": [
"d6sf77n",
"d6sp09j"
],
"score": [
8,
2
],
"text": [
"One of those pesky \"electrolytes\" all these sports drink companies are trying to sell us on buying, salt (or sodium, if you prefer) is necessary for proper bodily function.\n\nSea water has a an average content of about 35 parts per thousand, so for every liter (1000ml) of seawater, you've got 35 grams of salt.\nThe reason it's harmful to drink seawater is because the human kidney is only capable of making urine that is LESS salty than 35 parts per thousand, so you'd have to urinate more liquid than the content of the seawater. Your body literally dehydrates faster than you can drink it.\n\nYou can drink small amounts of seawater occasionally, so don't worry if you get a little in your mouth when you're swimming at the beach. Just don't make it a habit.\n\nWhen you add a little salt to some water, you're adding much much less than that, so it's not a problem. Neither is having some salt in your food, because we take in so much more water per day than is required to filter out the salt. Even your food as water in it!\n\nEDIT: I forgot to answer the main question!\nYes, your body needs salt. And yes, when you sweat, a small part of that is salt. \nYou get all you need from the foods you eat, even if you don't eat processed foods that are high in sodium, so don't worry about it.\nIt doesn't mean your body had \"excess salt\", nor should you worry about trying to put extra salt on your food later to compensate. ",
"I don't know if this will help you out, but once I was training for a half marathon. I didn't hydrate well during a 20k run once and had sweat a lot during the run. At the end of it, I could brush off the salt crystals which had formed on my skin. About 30 minutes after that my leg muscles started cramping like crazy. The pain was more intense than just delayed onset muscle soreness or lactic acid build up. I limped back to the building I was training in and just knew I needed salt water. It was part instinct and part basic medical knowledge I had that told me I needed specifically salt water. I managed to get my mitts on a package of salt and mixed that into some water. 15-20 min later, the cramps eased off. The water tasted horrible, but was absolutely necessary.\n\nI'm sure pro athletes have a perfect routine that works for them with regards to electrolyte balance during their events, and I learned my lesson with regards to my requirements during long runs in a hot environment."
]
}
|
[] |
[] |
[
[],
[]
] |
|
1h1t5v
|
How does the body build tolerance to caffeine?
|
In addition to building tolerance to its mental effects, how does the body become tolerant to its diuretic effects?
|
askscience
|
http://www.reddit.com/r/askscience/comments/1h1t5v/how_does_the_body_build_tolerance_to_caffeine/
|
{
"a_id": [
"caq23ga"
],
"score": [
10
],
"text": [
"By regulation of the number of receptors sensitive to caffeine on the cell membrane.\n\nCaffeine functions by inhibiting adenosine receptors in the brain, which we believe is involved in our biological clocks. After prolonged exposure to caffeine, the cell tries to return to homeostasis by *increasing* the number of adenosine receptors present on each cell's membrane to compensate for caffeine's effects. This results in the need for more caffeine to achieve the same effect on the brain as before, and can lead to withdrawal symptoms once the baseline caffeine level is removed.\n\nOf course, there's more to it than that, but that's the crux of the idea."
]
}
|
[] |
[] |
[
[]
] |
|
6su659
|
Why are there nuclear-powered subs and aircraft carriers but no nuclear-powered airplanes?
|
askscience
|
https://www.reddit.com/r/askscience/comments/6su659/why_are_there_nuclearpowered_subs_and_aircraft/
|
{
"a_id": [
"dlfrkyo",
"dlftga2"
],
"score": [
36,
16
],
"text": [
"This was experimented with a bit in the '50s by both the Americans and the Soviets. The main issue is that to protect the crew from radiation you need a lot of heavy shielding, and this makes it difficult to fly. \n\n_URL_0_",
"Power to weight ratios. Naval vessels are massive, with displacements of thousands of tonnes. The reactors powering such vessels are themselves massive, with weights in the many hundreds of tonnes. That weight comes from the combination of the fuel, the reactor control and cooling components, and the heavy radiation shielding.\n\nNuclear powered aircraft have been researched however, with several different designs. The molten salt reactor design, for example, came out of US Air Force research on a nuclear reactor light enough to power an airplane. There's also the hair raising concept of a nuclear powered RAMJET, as in [project pluto](_URL_0_). The problem with all of these designs is that if you don't have the luxury to add enough weight for shielding and containment then you generally have a very \"dirty\" aircraft. Either one that radiates the crew a bit (MSR) or a drone aircraft that leaves a trail of nuclear fallout in its wake (SLAM/Pluto)."
]
}
|
[] |
[] |
[
[
"https://en.wikipedia.org/wiki/Nuclear-powered_aircraft"
],
[
"http://www.merkle.com/pluto/pluto.html"
]
] |
||
kq793
|
Physics problem that has been plaguing me since high school.
|
Hypothetical situation. Lets say you have a fighter airplane that flies at a maximum velocity of (just throwing numbers out there) 100 m/s. This plane can fire missiles, which travel at 200m/s. If the plane is flying at 100m/s and fires the missiles, the missiles would travel faster than 200m/s, right?
Ok. So what happens if the same missiles are equipped on a jet fighter that can travel 500m/s. If the jet fighter is flying at 500m/s and fires a missile, will the missile now be able to travel faster than 500m/s or would it trail behind the jet fighter, kind of like when you throw a ball out the window of a moving car (I know its an entirely different phenomenon). I don't know how air resistance would play into this, assuming there is or isn't any. Also, assume the missile is loaded under the wing of the aircraft (not in some tube that could jam).
This hypothetical situation has seriously been giving me headaches for about 10 years because I simply can't wrap my mind around it. I'd appreciate some clarification!
|
askscience
|
http://www.reddit.com/r/askscience/comments/kq793/physics_problem_that_has_been_plaguing_me_since/
|
{
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18,
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"text": [
"The question at hand is: What causes the speed limit on the motion of the missiles? Is it air resistance (as is the case for airborne missiles)? \n\nIf so, then firing a missile (limited to 200 m/s velocity in air) from a jet (traveling at 500 m/s in air) will cause the missile to fly backward at 300 m/s from the perspective of the jet pilot. Imagine throwing a beachball from the window of a rapidly moving car. The air catches it going \"above its speed limit,\" and drags it back down pretty quickly. \n\nIf all of this is happening in outer-space, where there is no air resistance, whatever speed limit is imposed won't be with respect to the air, so you're the pilot will likely see the missile move forward in the expect fashion. ",
"Remember that the missile is not travelling at 200m/s relative to the plane as it is released, or it would probably rip a wing off with it!\n\nThe missile will detach and fire. Its initial speed will be that of the plane, but if it cannot maintain this speed then it will slow down.\n\nObviously in reality missiles are far more aerodynamic and have much higher thrust/weight ratio than a plane so the missile is likely to have higher speed!\n\nEDIT: To add to this, consider 3 phases:\n\nPhase 1, Missile attached to plane, travelling at the same speed as plane\n\nPhase 2, Missile detaches and reduces in speed due to air resistance\n\nPhase 3, Missile fires and its speed increases upto and beyond that of the plane (for a real world missile).",
"With no air resistance:\n\nFighter travelling at constant 100 m/s fires missile. Missile gets up to 200 m/s relative to fighter. So missile looks like its going 300m/s, measured by someone on the ground.\n\nFighter travelling at constant 500m/s fires missile. Missile gets up to 200 m/s relative to fighter. So missile looks like its going 700m/s, measured by someone on the ground.\n\nThis assumes that the fighter is not accelerating. If the fighter is accelerating, and there is no air resistance, then the fighter will go faster. Air resistance determines the \"maximum speed\" of fighter jets and missiles. So yes, **air resistance is of crucial importance**.\n\nIf there were no air resistance, the fighter could theoretically get up to 8,000 m/s, like the space shuttle (if it had enough jet fuel). And the missile would go even faster. I assume that the maximum speed of the missile is based on how much fuel is inside it.",
"Thanks for the replies everyone! Love this subreddit. My mind can rest easy - I had forgotten that the velocities can just be added to each other (assuming no air resistance). If there's air resistance, the missile will lag behind the plane. Many future headaches avoided. ",
"It will help your understanding of many physical systems to consider, in this case, that the top speed of a missile is not an intrinsic property of the missile, nor is the top speed of an aircraft. Consider instead more intrinsic properties: that a missile or jet aircraft has some intrinsic maximum thrust (force), and its shape endows it with certain drag and lift properties. A missile launched from an aircraft traveling at 100 m/s will accelerate if its intrinsic thrust force can overcome the drag at that speed. Maximum speed in these cases is reached when the drag force increases to match the thrust force, whatever speed that may be.",
"The jet has the power to take the rocket to 500. Once dropped, the rocket engine kicks in to accelerate it toward 700. but the second its dropped from the jet, it no longer has the added power of the jets engine. Once the rockets engine reaches max power, it slowly losses the momentum of the +500 boost of the jet. Since the rocket engine is only capable of 200 it is not capable of maintaining a speed above that. Once the momentum of the jets initial 500 boost wears off the rocket slows to 200.",
"The question at hand is: What causes the speed limit on the motion of the missiles? Is it air resistance (as is the case for airborne missiles)? \n\nIf so, then firing a missile (limited to 200 m/s velocity in air) from a jet (traveling at 500 m/s in air) will cause the missile to fly backward at 300 m/s from the perspective of the jet pilot. Imagine throwing a beachball from the window of a rapidly moving car. The air catches it going \"above its speed limit,\" and drags it back down pretty quickly. \n\nIf all of this is happening in outer-space, where there is no air resistance, whatever speed limit is imposed won't be with respect to the air, so you're the pilot will likely see the missile move forward in the expect fashion. ",
"Remember that the missile is not travelling at 200m/s relative to the plane as it is released, or it would probably rip a wing off with it!\n\nThe missile will detach and fire. Its initial speed will be that of the plane, but if it cannot maintain this speed then it will slow down.\n\nObviously in reality missiles are far more aerodynamic and have much higher thrust/weight ratio than a plane so the missile is likely to have higher speed!\n\nEDIT: To add to this, consider 3 phases:\n\nPhase 1, Missile attached to plane, travelling at the same speed as plane\n\nPhase 2, Missile detaches and reduces in speed due to air resistance\n\nPhase 3, Missile fires and its speed increases upto and beyond that of the plane (for a real world missile).",
"With no air resistance:\n\nFighter travelling at constant 100 m/s fires missile. Missile gets up to 200 m/s relative to fighter. So missile looks like its going 300m/s, measured by someone on the ground.\n\nFighter travelling at constant 500m/s fires missile. Missile gets up to 200 m/s relative to fighter. So missile looks like its going 700m/s, measured by someone on the ground.\n\nThis assumes that the fighter is not accelerating. If the fighter is accelerating, and there is no air resistance, then the fighter will go faster. Air resistance determines the \"maximum speed\" of fighter jets and missiles. So yes, **air resistance is of crucial importance**.\n\nIf there were no air resistance, the fighter could theoretically get up to 8,000 m/s, like the space shuttle (if it had enough jet fuel). And the missile would go even faster. I assume that the maximum speed of the missile is based on how much fuel is inside it.",
"Thanks for the replies everyone! Love this subreddit. My mind can rest easy - I had forgotten that the velocities can just be added to each other (assuming no air resistance). If there's air resistance, the missile will lag behind the plane. Many future headaches avoided. ",
"It will help your understanding of many physical systems to consider, in this case, that the top speed of a missile is not an intrinsic property of the missile, nor is the top speed of an aircraft. Consider instead more intrinsic properties: that a missile or jet aircraft has some intrinsic maximum thrust (force), and its shape endows it with certain drag and lift properties. A missile launched from an aircraft traveling at 100 m/s will accelerate if its intrinsic thrust force can overcome the drag at that speed. Maximum speed in these cases is reached when the drag force increases to match the thrust force, whatever speed that may be.",
"The jet has the power to take the rocket to 500. Once dropped, the rocket engine kicks in to accelerate it toward 700. but the second its dropped from the jet, it no longer has the added power of the jets engine. Once the rockets engine reaches max power, it slowly losses the momentum of the +500 boost of the jet. Since the rocket engine is only capable of 200 it is not capable of maintaining a speed above that. Once the momentum of the jets initial 500 boost wears off the rocket slows to 200."
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[]
] |
|
141c9n
|
what is the impact of palestine being promoted to "non-member observer status" in the un?
|
Will this lead to any change in the Israeli-Palestine conflict?
What does the future look like now for Palestinians?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/141c9n/eli5_what_is_the_impact_of_palestine_being/
|
{
"a_id": [
"c791om8"
],
"score": [
2
],
"text": [
"It's not a full UN membership but it's a more symbolic move since it gives them more status than before. They are now on the same level as the Vatican and Switzerland (until a few years ago). \n\nIf they now try to join the international criminal court, this status of theirs will give them more 'points' in their favor. That's quite important.\n\nAlso, they can now go to many UN meetings. So mostly it's a step forward."
]
}
|
[] |
[] |
[
[]
] |
|
1igbw4
|
What were Pinkerton agents duties, roles, etc. in 1890-1912?
|
Hi Historians. I stumbled upon this question while playing bioshock Infinate. The search on Pinkertons didn't give me an answer, so my question is as follows.
In bioshock infinate, the main character refers to himself as a former Pinkerton agent. This is brought up a few times, mostly around the times where we see factory workers. The character says at one point something along the lines of how he was called in to keep workers in line. Is this something a Pinkerton Agent would do? What was the role of a Pinkerton?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/1igbw4/what_were_pinkerton_agents_duties_roles_etc_in/
|
{
"a_id": [
"cb46bhu"
],
"score": [
7
],
"text": [
"Pinkertons were part of a huge private detective agency that was essentially the Black Water of the 19th century. One of the Pinkerton's specialties was strikebreaking. Employers would hire the company to provide thugs that would stop strikes in progress, and this is arguably what Pinkertons are most famous for. So yes, that is definitely something a Pinkerton would do."
]
}
|
[] |
[] |
[
[]
] |
|
3e0noc
|
How would one derive electricity from post-fusion plasma?
|
I know how fusion works, my question though is how to change from high energy plasma to electrical current.
|
askscience
|
http://www.reddit.com/r/askscience/comments/3e0noc/how_would_one_derive_electricity_from_postfusion/
|
{
"a_id": [
"ctam2fs",
"ctb6akd"
],
"score": [
7,
2
],
"text": [
"Boil water.\n\nThat is how pretty much every power plant makes electricity. Its easy to make heat with nuclear or fossil fuels. You use the heat to boil water, which makes a lot of pressure, and you use the pressure to turn a turbine, which is geared to a generator.",
"its my crude understanding that the Polywell systems (which get like, no funding, and are unlikely to be progressed any time soon because the Tokomak projects have the bigger rice bowl and more aggressive protectors) do it directly.\n\nPolywell reactors unlike Tokomak reactors are able to achieve the temperatures to undergo Proton-Boron Fusion (in theory at least, see above no money = no progress) the result would be pure alpha radiation which in effect are high kinetic (very hot) helium ions traveling perpendicular to the magnetic containment. this would induce current into the containment field. so in practice all you would need to do is power up the fields and start the reactor up and once running you could draw power off the containment field.\n\nthe system would run much more thermally efficiently because it directly converts the heat into current instead of doing it via thermal transfer and steam turbines. it would also be much smaller system, contained into the actual reactor core, coils and whatever control circuitry it needed. i believe the 100MW plant that was planned, but not funded, would be about 1 cubic meter give or take some engineering constraints.\n\npractically every other system is simply a steam engine."
]
}
|
[] |
[] |
[
[],
[]
] |
|
zf2wr
|
Why does adding more components to a transistor increase clock speed?
|
I am always hearing about components on transistors getting smaller and that this is increasing the clock speed (okay, its tailed off these days).
It seems strange to me that adding more components would increase clock speed, as I'd think that you just need a few components and make them work very fast.
|
askscience
|
http://www.reddit.com/r/askscience/comments/zf2wr/why_does_adding_more_components_to_a_transistor/
|
{
"a_id": [
"c640mpq",
"c640uaz"
],
"score": [
3,
5
],
"text": [
"First, they aren't referring to adding more components to a transistor, rather they are talking about increasing the number of transistors on a chip or the density of transistors on a chip.\n\nIncreased transistor count doesn't necessarily lead to a higher clock speed, but as we increase the number of transistors, we are also packing them tighter, which does allow for a higher clock speed. One factor which limits clock speed is the distance between the sections on a chip. As the chips get better, we can make those sections smaller, and we can increase the clock speed. We are also increasing the number of transistors.\n\nEDIT:\n\nIt should be noted that clock speed doesn't fully tell you how powerful a processor is. Clock speed is merely how long one cycle on the chip is. Modern chips are multicored and multithreaded and occasionally have multiple adding units. More transistors means that you can do more, even if clock speed isn't increased.",
"At the level of fundamental physics, the speed of transistors is limited by physical effects. Among other effects, the smaller a transistor is, the less electrical charge you have to move around to make it turn on and off. That means you can turn it on and off more times per second when it's smaller.\n\nIn addition to faster speeds, having smaller transistors means that you can add new circuits to the integrated circuit 'chip'. This might be more memory (higher amounts of cache memory), or duplicate processing units (2, 4, 8 cores, etc). It can also be additional function that used to be outside the processor. Many current processors now incorporate graphics processing on the same die.\n\nHaving the extra functionality in one IC not only gives you more processing for the buck, but it reduces the number of chips and amount of system interconnects required to build a complete computer, which reduces cost. If you compare the number of chips on motherboards from ten years ago with the number now, you'll find fewer chips, and those old motherboards required add-on cardsfor graphics, USB, and more.\n[EDIT] for clarity"
]
}
|
[] |
[] |
[
[],
[]
] |
|
j3e4d
|
why can't a state just print more banknotes to create more money? [li5]
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/j3e4d/why_cant_a_state_just_print_more_banknotes_to/
|
{
"a_id": [
"c28sqpp",
"c28src5",
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],
"score": [
23,
7,
2
],
"text": [
"Think of a rare baseball card. If there's only 10 of them in existence, then everyone would want them and they would be willing to trade hundreds of chocolate bars for it. \nNow think if they printed 990 more of that rare baseball card. Now everyone has one, and no one is willing to trade a chocolate bar for it.",
"Money stands for things. A dollar stands for a dollar's worth of bread, or gold, or land. We invented money so we don't have to swap chickens and stuff to buy things. It's a lot easier. \n\nNow. Paper money used to be backed up by gold. The U.S. had, say, a billion dollars of gold, and so it put out a billion dollars of paper money. The paper dollar was a promise that you could go get a dollar in gold. Today, there isn't enough gold to back up all the paper money in the world. So paper money is a promise that the government can pay you back. Using dollars says that you believe in the government. That you believe the people of the United States will be rich enough and hardworking enough - and lucky enough! - to always pay back their loans.\n\nNow, if you keep printing dollars, then it's like making too many promises. If you promise that you'll wash the dishes, you can't promise to mow the lawn at the same time. People start to think you're lying. And then they don't believe in your promises as much. The same thing happens to money. If you print a whole bunch of dollars, without making the government run better or showing that people are working harder and making more money, then that's the same as breaking a promise. People won't use dollars - or they'll say it's not worth as much. \n\nSo printing too many dollars won't make more money. It will make money worth less. ",
"By printing more money, you devalue it."
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
3mvqaq
|
what is the "sharing economy"?
|
A good example would be ride share programs like Uber (vs. traditional taxi services). How is Uber not just another taxi service?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3mvqaq/eli5_what_is_the_sharing_economy/
|
{
"a_id": [
"cvij9ed",
"cvijtse"
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"score": [
6,
3
],
"text": [
"Instead of being full time taxi drivers anyone with a car and a license can hop on and be an uber driver.\n\nSimilarly, Airbnb allows individuals to host people in their homes as a hotel would.\n\nThe \"sharing\" idea is that personal assets (cars, homes, etc.) are utilized to provide services for a fee instead of assets that are wholly dedicated to providing those services.",
"Benjamen Walker's podcast 'Theory of Everything' did a great three-part series on this, called 'Instaserfs'. Opinions differ, but their angle is that it's startups convincing freelance casual workers that minimum-wage gigs are in some way empowering.\n\nPodcast here: _URL_0_"
]
}
|
[] |
[] |
[
[],
[
"https://toe.prx.org/2015/06/instaserfs-i-of-iii/"
]
] |
|
3557k4
|
is hemp realistically a great replacement for many materials (plastics and papers) or has this been over emphasized by those seeking legal marijuana?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/3557k4/eli5_is_hemp_realistically_a_great_replacement/
|
{
"a_id": [
"cr15rfy"
],
"score": [
3
],
"text": [
"Hemp is a decent replacement for a broad range of things. You won't see paper companies switching from wood to hemp just because it's legalized. \n\nAlso hemp contains almost none of the active ingredients that recreational marijuana has (you can't get high off of it)."
]
}
|
[] |
[] |
[
[]
] |
||
3k2yr9
|
what's a military formation?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3k2yr9/eli5_whats_a_military_formation/
|
{
"a_id": [
"cuudigv",
"cuui7ft"
],
"score": [
3,
2
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"text": [
"Any set of soldiers marching under one command, usually in a regular form.\n\nAlready Egyptians did so that the they had the less experienced at the front, and the more experienced at the back, to prevent retreat and fill in gaps. The ancient Greeks invented the phalanx. The enemy can do more damage if they can strike multiple soldiers or go behind them and hit them for the side or back. If the soldiers form an unbroken line, no one can get through and the enemy can face the formation only from the front, which is strongest. The shields are locked together, so there is one long armored wall. But, some of the soldiers are struck and killed, so there will be holes in the line. If there is already another line behind it, the gap is easily filled.\n\nThe formation is psychologically effective against unorganized fighters, but degenerates into a pushing match in phalanx-to-phalanx combat.\n\nClosed formations were used also even in the firearms era. But, he machine gun made them useless as an actual fighting formation. Still, soldiers are taught to walk and move about in formation in military drill. It creates a sense of an organized force and develops discipline.",
"It can also apply to vehicles, such as tanks, planes, or ships.\n\nSimplified:\n\nThink of the \"line of battle\" used by British and French fleets during the Napoleonic wars; all the ships spaced out nose to tail, guns pointing sideways (a ship's sides could fit more guns than the front). If ships broke formation and became positioned side by side, one of them would get in the way of the other's guns.\n\nOr world war 2, when allied bombers over Europe would fly in squad formations, and several squads formed into bigger formations. This would allow the defensive machine gunners in each bomber to \"cover\" each other from Nazi fighter planes, and also reduce the time over hostile flak cannons. If you fly one at a time over hostile AA, it's gonna be easy to pick you off. If you all fly to the target independently, the lack o f coordination is going to cause a collision. Ergo, fly in a formation.\n\nBack to infantry: you grunts at Waterloo might be facing direct cannon fire, or cavalry charges. Best thing to do in case of cannon is to form a side-by-side skirmish line so that if cannon balls come at you they hit one guy at most. \n\nBut then what if you get charged by bojack horsemen? Each one of you standing unreinforced is going to probably get cut down by a fast-moving cavalry saber. Best thing to do in that case is form a square. That way, no matter what direction the very mobile cavalry charges from, it's repulsed by disciplined musketry. \n\nThe faster your unit can change formations, the likelier y'all are to survive on the battlefield."
]
}
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[] |
[] |
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[],
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5jbikq
|
Why was Dwight Eisenhower made Supreme Allied Commander during WWII despite the United States entering the war after other nations?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/5jbikq/why_was_dwight_eisenhower_made_supreme_allied/
|
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"I asked a similar question a few months ago that I think might get to the heart of what you're asking. Hopefully this helps? The response I got was fantastic! (all credit to u/goodmorningdave)\n\n_URL_0_"
]
}
|
[] |
[] |
[
[
"https://www.reddit.com/r/AskHistorians/comments/4fo56f/why_was_eisenhower_chosen_over_other_more_field/"
]
] |
||
45efsd
|
AskScience AMA Series: We study neutrinos made on earth and in space, hoping to discover brand-new particles and learn more about the mysteries of dark matter, dark radiation, and the evolution of the universe. Ask us anything!
|
Neutrinos are one of the most exciting topics in particle physics—but also among the least understood. They are the most abundant particle of matter in the universe, but have vanishingly small masses and rarely cause a change in anything they pass through. They spontaneously change from one type to another as they travel, a phenomenon whose discovery was awarded the 2015 Nobel Prize for Physics.
Their properties could hold the key to solving some of the greatest mysteries in physics, and scientists around the world are racing to pin them down.
During a [session at the AAAS Annual Meeting](_URL_0_), scientists will discuss the hunt for a “sterile” neutrino beyond the three types that are known. The hunt is on using neutrinos from nuclear reactors, neutrinos from cosmic accelerators, and neutrinos from man-made particle accelerators such as the Fermilab complex in Batavia, Ill. Finding this long-theorized particle could shed light on the existence of mysterious dark matter and dark radiation and how they affect the formation of the cosmos, and show us where gaps exist in our current understanding of the particles and forces that compose our world.
This AMA is facilitated by the American Association for the Advancement of Science ([AAAS](_URL_4_)) as part of their [Annual Meeting](_URL_1_)
**Olga Mena Requejo**, IFIC/CSIC and University of Valencia, Paterna, Spain
[Searching for Sterile Neutrinos and Dark Radiation Through Cosmology](_URL_3_)
**Peter Wilson**, scientist at Fermilab, Batavia, Ill.
[Much Ado About Sterile Neutrinos: Continuing the Quest for Discovery](_URL_2_)
**Kam-Biu Luk**, scientist at Lawrence Berkeley National Laboratory, professor of physics at the University of California, Berkeley, and co-spokesperson for the Daya Bay neutrino experiment in China
**Katie Yurkewicz**, Communications Director, Fermilab
**We'll be back at 12 pm EST (9 am PST, 5 pm UTC) to answer your questions, ask us anything!**
|
askscience
|
https://www.reddit.com/r/askscience/comments/45efsd/askscience_ama_series_we_study_neutrinos_made_on/
|
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"How exactly do you detect neutrinos? I was under the impression that while known they are one of the most elusive particles. ",
"How exactly can neutrinos shed light on the nature of dark matter? Is there any hypothesis that scientists want to test regarding the connection between the two, or is the research more exploratory at this stage? ",
"How can a sterile neutrino ever be detected, my understanding was that a normal neutrino only interacts via the weak force (and gravity) and a sterile neutrino doesn't interact via weak force. Also in wat way could a sterile neutrino be involved in dark matter? Thanks in advance for you time :)",
"What is dark radiation, and how is it different from normal radiation.",
"How dense does an object have to be such that neutrinos would interact with it? Like neutron star dense?",
"The properties of neutrinos could shed light on the existence of dark matter, but how would this tie up with the news that gravity waves have been detected, which also promises to shed light on dark matter? \n\nHow does gravitational-wave astronomy intersect with the field of neutrino astronomy?\n\nEdit: I see also that Joseph Weber, whose earlier claims to have detected gravity waves were rejected, later worked on neutrino scattering.",
"What is the difference between the \"flavors\" of neutrinos? Thanks!",
"I read somewhere that a supernova releases a lot (90%+) of its radiant energy in a short burst of neutrinos. When a huge amount of energy like this is converted into neutrinos, would the sheer number of particles mean enough interaction to cause an effect noticeable without an advanced detector? (Assuming you could survive close enough to a supernova to observe any interactions).\n\nAlso how does this connect to gravity waves? Actually can you just put the gravity waves team on the phone please?\n\nPeople these scientists have been generous enough to come here andanswer your questions, please keep it related to their field.",
"What is your day to day job like and how do you go about getting it?",
"I was under the impression dark matter was only hypothesized, what discoveries has made its existence more than speculation? ",
"It is currently unknown whether neutrinos have a regular or inverted mass hierarchy (e.g. do the electron, mu, and tau neutrinos get heavier with each generation, or not?). Do your expected results differ based on which hierarchy turns out to exist?",
"Is there any significance of the recent findings of gravitational waves on your research?",
"Will it one day be possible to create a walkie-talkie like device (even if it's directional) and beam data from NYC to Tokyo straight through the Earth using neutrinos? \n\nI'm assuming that if this were possible, banks and other financial centers would jump on it simply for the arbitrage opportunities by connecting computers together faster than can currently be done using around the world cables or satellites.\n\n",
"My very basic understanding is that neutrinos are just one possible \"ingredient\" of dark matter. Is it the most plausible particle in the composition of dark matter or are there other, perhaps more abundant particles, that also contribute? \n\nAlso, if your kid is crying for no good reason, do you still call them a WIMP, or is that off-limits now?",
"I've heard of Dark Matter and Dark Energy, but I've never heard of Dark Radiation before. What is Dark Radiation?",
"Aside from the better understanding of the composition of our world, in what ways could this breakthrough affect the day to day lives of regular-non-astrophysicist individuals like myself?",
"Hello! Thanks for posting. \n\nHow likely is it that dark matter is a whole zoo of new particles that we haven't or can't discover? How does it not interacting with much indicate that it is one type of particle if possible?",
"I have read that neutrinos bring validity to the theory of the elastic Big Bang (don't know the correct name) but the theory is that the universe will eventually start to retract back into what people belive to be the singularity only neutrinos prevent such drastic collapse and are the driving force behind the universe switching from contraction to expansion. Do you have any input on this? Maybe can you elaborate on the role neutrinos play in such a theory? I'm sorry if I cannot better articulate my position but I am not well studied in physics.",
"Experimental neutrino detectors generally involve large and elaborate detectors in tanks (except one, I believe sits on the sea bed) sitting down big holes.\n\nWill it ever get easier to detect such weakly interacting particles?",
"What do you think of the possibility that you are largely on a wild-goose chase when you are hunting for dark energy, matter and perhaps even black holes?\n\nAre you open for the possibility that there are some fundamental building blocks in current understanding -- and thus taught curriculum -- of Physics that are sufficiently flawed to always produce errors when interated enough in the realm of micro and the realm of macrocosmos while still being accurate enough in mundane life to avoid suspicion?\n\nOr is entertaining such ideas the modern equivalent of heresy?",
"What are your personal guesses for *δ^(CP)*?",
"Thanks for doing the AMA! :) I have a few questions for you:\n\n1) We know that the flavour Neutrino states are superpositions of the mass states. But we can measure how much of each mass state the flavour states contain. Why can't we then say that the mass of the flavour states is simply the sum of the mass states? \n\n2) This is a bit philosophical, but do you have any theories as to why Nature only involves left chirality in the weak interaction? :)\n\n",
"What explains the definite discovery of neutrinos, yet the elusiveness of Dark Matter in being discovered?",
"Not a physicist, so excuse the layman's terminology:\n\n* Why does gravity interact with everything (neutrinos, dark matter, normal matter), whilst those things rarely interact with each other ?\n",
"Would it be possible, if you had many, many neutrinos, to disrupt normal matter to the point it would be dangerous for life?\n\nI know neutrinos only interact with gravity and the weak force, but the weak force is responsible for changing the flavor of quarks. My understanding was that when a neutrino strikes a proton, the weak force turns the proton into a neutron and emits an electron.\n\nSo, theoretically, if you had an extraordinarily enormous number of neutrinos, could they be dangerous? I imagine if you had enough of these weak iterations, you could turn non-radioactive matter radioactive, or cause damage to life through beta decay.",
"Hey actually watched the cosmos episode where they talk about neutrinos. And I didn't know earth made them how is that possible?",
"Do you have any research relationship with the research facility in Soudan, MN?",
"How does a neutrino compare to a lepton, inflaton, and other virtual particles? When neutrinos (or inflatons) change, how it conservation of energy preserved?",
"How do neutrinos oscillate between flavours? It seems impossible if they have different masses, but if their mass was the same surely they'd be indistinguishable anyway.",
"Do you ever use fractal math/geometry for finding smaller particles?",
"What have you gleaned from your experiments and observations that could explain what dark matter is? What is your hypothesis as to why there is so much more dark matter in comparison to visible matter in the universe? Thank you.",
"Is dark matter somewhere near of being detected? Or is it something that won't happen in the near future (from this lifetime to say, a few decades in the future) ",
"Is it easier or harder to detect neutrinos from man-made sources versus natural sources? My understanding is that the universe is practically saturated in a flood of the little buggers - how can one distinguish man-made neutrinos from all the rest?",
"What kind of mysteries could neutrinos solve?",
"Hello. Thanks for doing the AMA. I come from a southern state of India where a recent proposal (The INO) for a neutrino observatory was almost cancelled due to opposition from the public. Ignorant poloticians fear mongering since it was nuclear and very illiterate public combined with some whacky conspiracy theories brought down everything. \n\nMy question is this. How do i explain the tech and why we need it in very simple terms to these people? These are people with no education and not even the most basic understanding of physics. What should be my approach as someone trying to answer the question,\n\n What good is it gonna do for us now. Better spend the money trying to solve our plight rather than doing this. \n\nAny suggestions on dealing with ignorant politicians and activists who hold a huge sway over the people will also help a ton.",
"Something I've mused over for a little while and I thought you might find it interesting.\n\nIf we agree that form begets function(or vice-versa, take your pick): Then it strikes me as an interesting observation when I compare the structure of Dark matter distribution with the structure of mycelium, the nervous system, and, of all things, internet architecture.\n\nWhy this strikes me as interesting is that this type of web/node structure seems primarily to be employed when information(I'm using this loosely) is being passed from location to location.\n\nIs this a line of thinking your team has been down before? If yes/no would you care to share your thoughts on this despite being a little off topic?\n\nIt's one of those things that got it self lodged in my head and I find myself thinking about it a couple of times each year.\n\nref for dark matter structure assumptions: _URL_0_",
"My Physics professor studied Neutrinos down in Antartica with a bunch of other scientists; my question is, why go down to Antartica to study them, what is the benefit?",
"Thanks for a great AMA! We had a great time!",
"Is there any evidence for neutrino oscillations where MORE (instead of fewer) neutrinos are measured than expected (without oscillations) or even better experiments that observe a full cycle?",
"Physics Undergraduate at Arkansas Tech University here,\n\nWould you fly me to where ever you are so that I can do incredible research like you are doing now with you this summer? \n\n\"Yes\" you say?\n\nFantastic! Have your people call my people. \n\nIn all seriousness though, the opportunity to do undergraduate research with you all this summer would be incredible and I love and appreciate your work.",
"So I'm Curious- if we as the scientific community are looking for another form of neutrino- a particle that makes up what we consider dark matter and gives off this dark radiation, have we officially agreed on what makes up dark matter (100%)? Have we done any experiments to place an object or instrument into a location we believe is dark matter to take a measure of what we find? Or is this all still based on observing and measuring the gravity and emitted energy from these dark matter locations? \n\nDark matter confuses and intrigues me, so I'm mostly curious as to what we actually know."
]
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"https://aaas.confex.com/aaas/2016/webprogram/Paper16884.html",
"https://aaas.confex.com/aaas/2016/webprogram/Paper16885.html",
"http://t.sidekickopen35.com/e1t/c/5/f18dQhb0S7lC8dDMPbW2n0x6l2B9nMJN7t5XZsQK2V-W1p81NR1p1klTW2z8P1C56dvDDdhQHrz02?t=http%3A%2F%2Fwww.aaas.org%2F&si=5841448254046208&pi=10d8c60e-50ac-423d-e77b-887b7b3f004a"
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c84ty8
|
what do people who speak different languages hear when someone speaks english?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/c84ty8/eli5_what_do_people_who_speak_different_languages/
|
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"It sounds just like what you hear when you hear someone speak in a language you don’t know. You can tell they are saying something that means something because their voice is controlled and their body language will tell you they are not just making up sounds like a crazy person. When I hear American English vs United Kingdom English, American English sounds like the mouth is more open so the words are more full sounding. There is a great video online that demonstrates what English sounds. The video uses a mix of English words and gibberish, but sounds like how an American English speaker would. This is what English would sounds to someone who doesn’t know English. The video can be found [here](_URL_0_) ."
]
}
|
[] |
[] |
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||
2eu1oj
|
why do people donate to different cancers (breast, prostate, etc), won't one cure lead to cures for all the others?
|
[I thought of this question after seeing this chart.](_URL_0_)
Isn't cancer just cancer? And if there isn't just one cure, then which one is most important to uncover the cure for all the others, let's put our focus there first?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2eu1oj/eli5_why_do_people_donate_to_different_cancers/
|
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"Cancer is actually a term that broadly describes a group of diseases, not just one, where there is uncontrollable cell growth that invades other parts of the body. What this means is that there are a number of different causes as to *why* the cells become cancerous, requiring different types of research to find different causes (i.e. caused by DNA damage in gene A, as opposed to being damaged in gene B, etc). \n\nFor your second question, there is not a most 'important' one to uncover to cure the others. It's like comparing apples to sheep, cancers are different and can even vary between people. While it's possible that the cures may be connected and have the potential to shed light on other types of cancer, this is absolutely not a 100% guarantee. ",
"[This comic sort of sums it up](_URL_0_).",
"Firstly, you have to understand that Susan G Komen is a scam-they aren't raising money for a cure, they're raising money for \"awareness,\" which is a fancy way of saying you're paying them to tell people that breast cancer sucks. Oh yeah, and they're aggressive with lawsuits and very corrupt, that too. ",
"My understanding is that cancer, being that it is an uncontrollable and often random outburst of cell growth, is like a mutation. The cells mutate, get confused, and start screwing things up in other areas of your body. Because of this cancer is not a one-size-fits-all sort of ailment, and therefor has no one-shot quick cure. As /u/TheSeventhCircle said, within the different types of cancer its specific characteristics can change on a person to person basis. That's why finding a \"cure for cancer\" is actually not accurate at all because it isn't a disease or virus, it's your own body attacking itself. Granted it may be possible to find specific causes of it outside of things like exposure to harmful elements (IE a smoker getting lung cancer, an outdoors man getting skin cancer, etc.) which would lead into a more comprehensive understanding of what it is, and therefor a potential cure for its varying forms. However since it is so varied and diverse, I doubt say focusing on curing breast cancer would lead to a breakthrough in the curing of prostate cancer. They're just too different.\n\n\nIn regards to that chart, it is very curious that cancer receives the highest amount of awareness and charity funding where heart disease is forgotten. Perhaps instead of the heartwarming (lol) cancer story in the movies they should show heart disease instead, as that may actually be curable (even though, like cancer, it is an umbrella term). ",
"To put it simply, different cancers are caused by different things. You wouldn't ask is disease just disease? Why won't one cure for disease cure all other disease?",
"Asking why there's no cure for cancer is like asking why there's no cure for having allergies. There's more than one thing that people can be/are allergic to, just like there's more than one thing that might cause cancer."
]
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21gngu
|
Effects Of Shakespearean/Elizabethan Theater on the London Society?
|
I have been looking for articles and information on the effects theater had on Elizabethan London society and I cna't seem to find anything trustworthy, I really need some help!
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/21gngu/effects_of_shakespeareanelizabethan_theater_on/
|
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"**Clothing**\n\nThe major theaters served as fashion runways, setting popular trends in clothing. Costumes were elaborate, expensive, and often borrowed from or donated by local tailors, cobblers, and jewelers. These clothiers could then advertise that they were producing the clothes being worn in the most fashionable theaters in town. And in late 1500s - early 1600s England, fashion was serious business:\n\n > In these days a wondrous excess of apparel had spread itself all over England, and the habit of our own country, though a peculiar vice incident to our apish nation, grew into such contempt, that men by their new fangled garments, and too gaudy apparel, discovered a certain deformity and arrogancy of mind whilst they jetted up and down in their silks glittering with gold and silver, either imbroidered or laced. The Queen, observing that, to maintain this excess, a great quantity of money was carried yearly out of the land, to buy silks and other outlandish wares, to the impoverishing of the commonwealth; and that many of the nobility which might be of great service to the commonwealth and others that they might seem of noble extraction, did, to their own undoing, not only waste their estates, but also run so far in debt, that of necessity they came within the danger of law thereby, and attempted to raise troubles and commotions when they had wasted their own patrimonies\n\n* [A Complete History of England: IV. The history of Queen Elizabeth I](_URL_1_), written by Edward, lord Herbert of Cherbury in 1706, page 452.\n\nSee also:\n\nStephenson, Henry Thew. The Elizabethan People. New York, Henry Holt and Company, 1910. Shakespeare Online. 20 Feb. 2010. (accessed March 27, 2014) _URL_3_\n\n**Language**\n\nThere was no dictionary of the English language prior to 1755. In the Elizabethan period, London was teeming with foreign trade and with it came linguistic influences from many far-flung cultures. English was a fluid, dynamic language and the plays of the period are famous for their wordplay. Theaters of the day became laboratories for language with new words being adopted, adapted, or invented to convey the emotions of the characters. Shakespeare alone is believed to have invented (or at least been the first to write down) some 1,300 common words.\n\nSee [The Development of Early Modern English](_URL_2_), by Marta Zapala-Kraj, 2009.\n\n**Thought/Society**\n\nIn *Hamlet* Act 3, Scene 2, Shakespeare describes acting (and by extension, the purpose of theater) as being an art \"whose end, both at the first and now, was and is to hold, as ’twere, the mirror up to nature, to show virtue her own feature, scorn her own image, and the very age and body of the time his form and pressure\".\n\nShakespeare's plays reflect the society they were written for. England was in a period of transition between its Medieval past and its Renaissance future and the growth pangs of that transition were being played out on stage. Among Shakespeare's greatest influences on the art of theatrical storytelling is the heavy use of the soliloquy as a means of allowing the audience to listen to a character's most intimate thoughts. As we listen, we meet people who are simultaneously progressive and old fashioned. They have complex, multi-faceted personalities and think of themselves as unique individuals defined as much by merit and personality as by social class. We hear superstition wrestling with science, urban sophistication clashing with provincial wisdom, and numerous variations on the eternal human question: \"Given the knowledge of our own mortality, what should we do with the time that we have to be alive?\"\n\nSee:\n\n[Shakespeare's Philosophy](_URL_4_), by Colin McGinn, 2009.\n\n[From Shakespeare to Existentialism: An Original Study : Essays on Shakespeare and Goethe, Hegel and Kierkegaard, Nietzsche, Rilke, and Freud, Jaspers, Heidegger, and Toynbee](_URL_0_), by Walter Arnold Kaufmann, 1980"
]
}
|
[] |
[] |
[
[
"http://books.google.com/books?id=wvKRUSdUsnkC&printsec=frontcover&dq=From+Shakespeare+to+Existentialism&hl=en&sa=X&ei=57szU7GIAaazsQSBzYHYCA&ved=0CC0Q6AEwAA#v=onepage&q=From%20Shakespeare%20to%20Existentialism&f=false",
"http://books.google.com/books?id=HGZZAAAAYAAJ&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false",
"http://books.google.com/books?id=lp0phazoyIsC&printsec=frontcover&dq=the+development+of+early+modern+english#v=onepage&q=the%20development%20of%20early%20modern%20english&f=false",
"http://www.shakespeare-online.com/biography/elizabethanclothes.html",
"http://books.google.com/books?id=TtgnbxfshI0C&printsec=frontcover&dq=shakespeare's+philosophy&hl=en&sa=X&ei=P7szU6HtCcPgsASm74GQAQ&ved=0CDYQ6AEwAA#v=onepage&q=shakespeare's%20philosophy&f=false"
]
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|
28f7b4
|
why do they need so much money for cancer research?
|
What exactly does the money for Cancer go towards?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/28f7b4/eli5why_do_they_need_so_much_money_for_cancer/
|
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"Scientific research costs money - hiring scientists, buying highly specialized equipment, buying the supplies, chemicals, etc... It can cost thousands of dollars to buy a milligram of a single antibody you need for your experiments.\n\nSuccess is also not guaranteed in research, so you can spend millions of dollars over several years and fail in what you're trying to do. Much of research is exploratory, and so lots of scientists are researching a bunch of different things all at the same time.\n\nAssuming your research is \"successful\", turning a research discovery into a marketable product (it needs to make more money than it costs to produce, it needs to be produced on a way larger scale than what was developed in the research lab) is an incredibly hard and costly endeavor. ",
"For some charities, the money is directed almost entirely to research. For example, the Multiple Myeloma Research Foundation has received an A+ rating from _URL_0_ judging by [these criteria](http://www._URL_0_/criteria.html). \n\nOther charities aren't so dedicated to actual research, and instead often are categorized as 'awareness' charities. Now, that's not to say that they weren't started in an attempt to do some good, or that they aren't doing good now, but they're not really helping. Everyone is aware of breast cancer now, but the goal of many of these is to make sure that people get mammograms and do self checks. Why these things aren't part of regular health care exams is an entire other kettle of fish. Groups like the American Breast Cancer Foundation are these sort of groups. Unfortunately only about 25% of their raised funds go to actually help people get exams. The rest is spent on continued fund raising, and that includes pay for their employees and the board.",
"Because the human body is stupidly complex and research on how to keep it from killing itself is really finnicky.\n\nAlso, \"Cancer\" isn't just one disease. There are like, a bajillion different types of cancer with a scrillion different genetic and chemical causes and preventors.",
"Not to cancer research but to the next years marketing campaign.\n\nTo the artists who are hosting the events and who are getting credit for 'their help beating cancer'.\n\nTo the TV commercials and marketing companies. (taking away the biggest chunk)\n\nTo events for cancer survivers. (money must get spent)\n\nTo pay for poor patients chemo and treatment. (okay for me)\n\nTo psychologic assistance for patients and familie. (still a bit okay)\n\nTo everything but cancer research. (not okay)\n\nEdit: but this is an unpopular reality so will get downvoted"
]
}
|
[] |
[] |
[
[],
[
"charitywatch.org",
"http://www.charitywatch.org/criteria.html"
],
[],
[]
] |
|
2hmvoj
|
Unlike in Europe, where the tradition is still to build in brick and concrete, why does the US construct buildings using cheap building materials?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2hmvoj/unlike_in_europe_where_the_tradition_is_still_to/
|
{
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"text": [
"What cheap building materials are you talking about in particular?",
"I'm assuming you are asking about why houses in tornado or hurricane zones are constructed out of wood. Hurricanes and tornadoes are extremely destructive and no building material can hold together in the path of a F4 or F5 tornado. In fact concrete and brick blocks can cause even more damage if they end up flying. So instead, buildings in Tornado Alley are required to have underground tornado shelters that can keep its occupants safe in a tornado. \n\nI don't know where you got the idea that buildings in the US don't have strict building codes. ",
"(On my phone, so will add sources later.) In California, at least, unreinforced masonry construction has been banned since 1933. This is because wood buildings flex in earthquakes but stay standing; unreinforced masonry, like brick or stone, falls down. Because of this, most new buildings less than six stories are wood-framed, and everything taller is steel framed or made of reinforced masonry or reinforced concrete. \n\nedit: it's the Field Act of 1933 and Garrison Act of 1939.",
" > Unlike in Europe, where the tradition is still to build in brick and concrete\n\nWhat do you mean by \"in Europe\"? I'm from a European country where pretty much all houses are made of wood. ",
"It's also a lot about which materials are abundant in a region. \nWhen you live in a wooded region like Canada it's only logical that many buildings are made of wood. \nBut, when you take the Netherlands as an example, there aren't a lot of forests left but there is an abundance of clay which can be made into bricks. \nOn a side note it also has a lot to do with the popularity of the Chicago school in the USA. If I recall correctly this style focused a lot more on concrete instead of bricks. \nThe Chicago school was however not widely adopted in Europe. "
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[]
] |
||
5x3m2p
|
what is a car engine really doing when it is "warming up"?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5x3m2p/eli5_what_is_a_car_engine_really_doing_when_it_is/
|
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" Well, first off you don't need to warm up the engine of a modern car. They are designed and built to such a fine tolerance you can simply turn them on and drive under normal operating conditions year round.\n\n As to what they are doing they are literally warming up, or getting hotter. Since the engine is made of metal which expands slightly when heated the parts of the engine will expand a bit, and the main engine components (the block and head, or lower and upper part of the engine) will expand enough to float off each other a bit when they get fully heated. \n\n This isn't a worry because the parts have a gasket between them designed to make a proper seal so no oil or radiator fluid leak out. This has been a problem in the past, some engines from the 70's and 80's that leaked notoriously did because newer materials expanded at unpredictable rates. We are well past the days of those exotic (for the time) alloys and early aluminum head/cast iron block hybrids. ",
"they are \"warming\"!\n\nChemical reactions inside the motors are more efficient when happen in a range of temperatures. this is usually especially true in diesel motors.\nMoreover there are other fluids (oil for example) which are less viscous when warmer than ambient temperature, and when it happens motors work better.",
"You are letting the temperature of the engine increase.\n\nIn very cold temperatures, this allows the lubricant to heat to a point it flows more freely before the engine is operated at higher RPMs. \n\nBut mostly it is so the engine will be warm enough to transfer heat to the heater, and warm up the rest of the car."
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
3d3ywm
|
how can i avoid mosquito bites?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/3d3ywm/eli5_how_can_i_avoid_mosquito_bites/
|
{
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"Source: I live in the south, and I have visited north east Arkansas which has more mosquitos than air at times. In Texas we have mosquitos that are so large they look like baby wasps. You can clearly see they have black and grey stripes on them. When you smack them on your arm it's a bloody mess. I have a friend that contracted West Nile while at work and I hate itching so I like to avoid them. In order of most to least effective or important:\n\n* Stay indoors around sunset. You will learn that there is a peak time where it's time to seek shelter, just as it starts to cool off. No amount of Deet is going to ward them all off during that time.\n\n* Keep some Deep Woods Off nearby at all times. You don't necessarily have to wear it all the time, but when you get your first bite go ahead and hose down with it. Don't spray it in your face, but be sure and get your back, and the backs of your legs and arms. They love behind the knees. Be careful of overly powerful deet products. I once was handed a DEET wipe that claimed \"maximum strength\". Putting it on my skin made me sick almost instantly and I was not in a place where I could wash it off or remove it effectively.\n\n* Never allow anything to collect water around your living space. Outdoor standing water = mosquito breeding ground. They look like tadpoles in the water but in reality they are satan's spawn. turn over all buckets, or other things collecting water.\n\n* Citronella products can be effective to a point but you have to be close to them. ThermaCELL appliances seem to kinda work but they are expensive and cumbersome. When I go camping I have four cheap hurricane lamps ($5.00 each at Walmart) that I power with citronella lamp oil (~$10.00 for 64oz Walmart). The lamps burn very efficiently if you keep the wik short and they do an ok job of creating a bug free zone. I also just like the look of old timey lamps.\n\n* Wind is your friend. I don't have two ceiling fans on my back porch just for cooling. They are mostly to keep the bugs away. If they can't fly, they can't get you. If you can get in front of a good fan you are not going to be getting bit by mosquitos (as much). \n\nHurricane Lamp:\n_URL_0_\n\nCitronella Lamp Oil:\n_URL_1_"
]
}
|
[] |
[] |
[
[
"http://www.amazon.com/Stansport-Hurricane-High-Lantern-12-Inch/dp/B000K6FI7E/ref=sr_1_4?ie=UTF8&qid=1436783105&sr=8-4&keywords=hurricane+lamp",
"http://www.amazon.com/TIKI-Brand-Citronella-Torch-Fuel/dp/B001UTGPCC/ref=sr_1_2?ie=UTF8&qid=1436783156&sr=8-2&keywords=citronella+lamp+oil"
]
] |
||
3mpskz
|
The German Schlieffen Plan was in development for years prior to the breakout of WWI... how well was the plan kept secret? Was the invasion of Belgium genuinely a surprise to the other European powers?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/3mpskz/the_german_schlieffen_plan_was_in_development_for/
|
{
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"Debates over whether or not the idea of a \"Schlieffen plan\" actually existing aside, the Plan itself was kept fairly secret, with wargaming of scenarios based on it being few in number, and knowledge of the actual plan being restricted to high ranking war ministry and General Staff members.\n\nThat being said, to an extent the French and the Russians had guessed German intentions before. The French formulated Plan XVII with the expectation that the Germans would invade through southern Belgium (ie south of the Meuse) and Luxembourg, avoiding the bulk of the country while also avoiding most of the French fortress line. Hence Plan XVII envisioned placing two French armies inside Alsace-Lorraine via offensives to threaten the German advance from the south, while three armies to the north parried and reversed the main German attack. Likewise, the Russians promised to mobilize '800 000 men' to be sent against presumably weak German opposition, in support of the French, while two thirds of Russia's mobilized forces would move against Austria-Hungary. \n\nWhen the German invasion actually came, it was certainly a surprise for France, Britain and Belgium. The French did not expect an invasion of Belgium on such a wide front, and with all of Germany's reserve divisions committed. The British were shocked considering that the invasion encompassed the whole country; had the invasion taken place as the French believed it would, the chances of British involvement would have been greatly reduced. Few were also prepared for the ferocity of the German attack: in spite of Belgian civilians having been told to avoid altercations and largely heeding this advice from their government, the invading Germans lashed out at 'francs-tireurs' real or largely imagined, and c. 5600 Belgian and c. 900 French civilians were murdered, and tens of thousands of homes destroyed. Dinant and Lueven (including it's university library) were almost completely raised. \n\n* *War Planning in 1914*, Holger Herwig and Richard Hamilton\n* *Helmuth von Moltke and the Origins of the First World War*, Annika Mombauer\n* *Catastrophe*, Max Hastings\n* *Belgian Atrocities 1914: A history of denial*, John Horne and Alan Kramer\n* *The War that Ended Peace*, Margaret MacMillan"
]
}
|
[] |
[] |
[
[]
] |
||
1a0fgj
|
Was WWI a true good guy vs bad guy war?
|
WWII obviously had major tyrannical figures that have become today's embodiment of evil, but i don't see that within WWI. I feel that early 20th century Germany was just growing and industrializing at a rate which European empires feared.
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/1a0fgj/was_wwi_a_true_good_guy_vs_bad_guy_war/
|
{
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"text": [
"Okay, no. No, no, no, no. No war is ever a \"good guy vs. bad guy\" sort of thing from a historical perspective, though individual nations by and large choose to cast the war they're fighting in that sense. You can bet World War II was seen by citizens of the Axis powers as a \"good vs. evil\" affair, just as certainly as you can bet that they didn't see themselves on the \"evil\" side.\n\nThe truth of the matter is that history really is, to raise the old cliche, \"written by the victors\". Or at least by those left alive to write it. Retrospect allows us to see the horrors of the Holocaust or the unspeakably brutal after-effects of the Eastern or Chinese or Philippine Fronts, but it's probably safe to say that the majority of German conscripts fighting at, say, Kursk, were not there so that their leaders could continue to exterminate millions of innocent civilians in frighteningly efficient fashion.\n\n**tl;dr: No war is ever \"good vs. evil\"; individuals and nations just choose to cast it that way.**",
"The truth is that WW1 wasn't fought over anything in particular. Perhaps the only belligerents that had any real reason to go to war were the Serbians who wanted to remain free of direct Austro-Hungarian control and the Austro-Hungarians who wanted to control the Serbians (in a manner of speaking). The other parties had a variety of reasons which I'll cover below.\n\nWar had been coming for a long time before the actual event. The arms race between Great Britain and Germany resulted to the development of the Dreadnought and increased tensions between the two nations. The intricate treaties and alliances saw Germany surrounded by Triple Entente powers. Obviously this left Germany feeling threatened and coupled with the existing German military tradition, preparations for war were inevitable. \n\nFrance had territorial ambitions. It had been humiliated by Germany in the Franco-Prussian War and was forced to cede the territories of Alsace-Lorraine to the Prussians. Russia is probably the more interesting. It had no real interest in joining the war and only did so because of Serbia's plea that Russia aid its Slavic brethren. Following German unification, Russia feared German military intentions and so agreed to an alliance with France, encircling Germany. \n\nItaly really had no reason whatsoever. It had initially been aligned with Germany and the Austro-Hungarians but withdrew when hostilities broke out. It eventually joined the Entente and spent most of the war getting its butt handed to it. The British were part of the Entente but only entered the war after Germany violated Belgian neutrality. I don't recall reading anything about it, but I suspect the British were also suspicious of German colonial ambitions and with the High Seas Fleet, Germany had the naval power to threaten British colonial possessions abroad.\n\nThe Ottoman Empire only entered the conflict after initial hostilities had broken out and only did so because war would have provided a nice distraction to its domestic issues of which it had many. The Empire also didn't really care who it allied with, it approached the Russians but refused Russian demands that would have effectively placed parts of the Ottoman Empire under Russian control, the British also refused. Germany on the other handed needed an ally in the Middle East. The Ottomans could threaten British interests which would tie up British forces (which it did) and also had the potential to threaten Russia (which it did to some extent).\n\ntl,dr: the reasons that the different belligerents entered the war were varied and all served national interests. None can be labeled good or evil.\n\nEdit: a word"
]
}
|
[] |
[] |
[
[],
[]
] |
|
5xjmhj
|
Would it be right to say that semiconductors are produced by doping?
|
I'm doing some research on semiconductors, and I've gotten onto the subject of doping. It appears that doping creates the p-n junction found in semiconductors. Since this seems to be a vital part of semiconductors, would it be right to say that doping is the process in which semiconductors are produced?
|
askscience
|
https://www.reddit.com/r/askscience/comments/5xjmhj/would_it_be_right_to_say_that_semiconductors_are/
|
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"No, not all semiconductors are doped. There are also [intrinsic semiconductors](_URL_0_), where pure materials act as semiconductors. For example, a pure chunk of silicon is an important example of such an intrinsic semiconductor. ",
"Doping is a necessary process for many *applications* of semiconductors, but the materials are semiconductors without doping as well.",
"What doping does in those systems is create conditions under which a junction between two semiconductors can be made to conduct electricity. In other words, it can be switched between a zero state, or a one state. But without the doping, the materials used, like silicon, are semiconductors on their own. Being a semiconductor means simply that the electrons living inside those materials can never have certain values of their energy. Imagine they can have any value between 0 and 1 (in some unit of energy), or any value between 2 and 3, but they can't have values between 1 and 2. That part of the energy spectrum is known as the energy gap. Basically, if you put electrons in all states from 0 to 1, you cannot put another one in a state of energy 1.0001, for example. The next available energy for that extra electron is 2, so you have to provide one entire unit of energy to bring that electron into your material.\n\nThat's precisely what happens when you transport electricity: you connect metallic cables to your sample, and you apply a voltage to bring electrons from your battery, through one cable, into the sample, then out through the other cable and back to the battery. But if you need to provide 1 unit of energy, and your battery can only provide, say, half a unit, then you cannot bring electrons into the sample (there are no states for those energies!), and current can't pass through it. That's what being a semiconductor is all about.",
"It doesn't necessarily have to be doped. Doping allows the creation of diodes, certain types of transistors and devices. A semiconductor is defined by having a specific bandgap. Insulators are materials that have a large separation between the valence and conduction band so it would be difficult for electrons to get excited and move into the conduction band. Conductors usually have lots of electrons in the conduction band and the valence band can overlap the conduction band meaning it'll easily be conductive. For semiconductor it's somewhere in between and a few electrons can reach the conduction band. \nThe most basic is semiconductor is silicon based and you can manipulate its behavior by adding dopants such as in the diode or silicon mosfet. \nOne example is a transistor that doesn't have to use doped material is a Gallium Nitride High electron mobility transistor (HEMT). Essentially you have a small layer of AlGaN on top of GaN and due to the lattice mismatch it causes a stress on the interface which causes a piezoelectric polarization thereby creating a 2 dimensional electron gas channel like with regular silicon mosfets. ",
"Semiconductors are simply materials which *can* be doped to make Electronic Devices based off of those materials. Usually doping(in Silicon based devices) involves using Silicon which has been laced with impurities to produce the pn junctions you speak of. Silicon by itself is an intrinsic semiconductor and it's not capable of being used as is in devices. \n\nNowadays, for MOSFETs(Metal Oxide Semiconductor Field Effect Transistors), we use Compound Semiconductors which are made out of different materials altogether. For example Gallium Arsenide (GaAs) is used because it can give us better conduction characteristics and produce faster devices. Another one, as has been pointed out below is AlGaN(Aluminum Gallium Nitride) which is used in cases where we need extremely high mobility (speed of movement) of electrons.\n\nKeep in mind that MOSFETs form the basis of Very Large Scale Integrated circuits which are the basis of chip fabrication technology today.\n\n\n\nSo what does it mean to be an intrinsic semiconductor?\n\nYou can take a pure silicon wafer and it's still considered a semiconductor. Mostly this regular silicon can't be used as it is because we need a charge imbalance to induce current flow. This is done by doping two pieces of silicon and joining them to form the pn junction you talked about. I hope the internal process of doping is something you've understood well already.\n\n\nA device with only 1 pn junction is a diode. We can alter the doping concentrations of the p and n type substrates (surfaces) to produce different devices. For example Zener diodes use imbalances in doping concentrations to produce the reverse breakdown characteristics they use to control voltage.\n\n\nWe can keep adding these junctions and tweaking their doping to form more intricate and useful devices. A common purpose device with 2 pn junctions is a Bipolar Junction Transistor (BJT). An SCR(silicon controlled rectifier) is a device which has 3 pn junctions. These are old devices compared to the technology we have today. I'm currently doing my undergrad in Ee so these are the devices I'm mostly familiar with.",
"Most of the time you actually say semiconductors are \"grown\". It's weird, I know - when I started working in a lab a few years ago and started describing the process to people I knew, everybody was confused because the word \"grow\" seems to imply something alive, but it's actually also the technical term for creating semiconductor crystals.\n\nIt's because semiconductors are created by very slowly adding material to a crystal so it appears to slowly increase in size, or grow. In the case of silicon crystals (the most well-known semiconductor in everything from desktop computers to solar cells) there's literally a huge (like 30cm diameter) cylinder of solid silicon crystal slowly being pulled from a vat of liquid silicon and cooled, causing the liquid to freeze to the crystal. It's like making salt crystallize out of water but really really precise.\n\n\"Doping\" is basically the process of mixing in some trace impurities during growth so they get mixed into the semiconductor and modify the material's electronic properties. You can even dope a semiconductor after growth by shooting impurity atoms at it at such a high speed they embed themselves in in the surface of the crystal.\n\nIf you don't dope the semiconductor (if it's pure), it's known as \"intrinsic\", because all the mobile charge carriers (electrons AND holes) are thermally excited from the material itself, rather than in doped \"extrinsic\" semiconductors, where the mobile charge carriers (either electrons OR holes) are excited from the dopant impurity atoms which are kind of \"external\" - not part of the base material."
]
}
|
[] |
[] |
[
[
"https://en.wikipedia.org/wiki/Intrinsic_semiconductor"
],
[],
[],
[],
[],
[]
] |
|
4isofh
|
what are the "loudness wars", why are they happening, and why should anyone care that music is getting louder?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4isofh/eli5_what_are_the_loudness_wars_why_are_they/
|
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"Music is getting compressed so it sounds louder. Before this you're set your volume to your preferred level and would hear everything from quiet notes to very loud and distinct drum hits. Now the quiet notes are louder, the mid range is louder, and consequently the formerly loud and distinct drum hits are just barely louder than everything else.\n\n[This](_URL_0_) video demonstrates it better than any written description really can.",
"There isn't as much of an issue with it today, so we might be able to say the the war is over, or at the very least, a truce.\n\nLouder tends to sound better. Why? Not really sure, but it is probably just something to do with biology.\n\nThis fact is very important in mixing music because a big issue that is run into constantly is that you will tend to find things to be better the louder they get. It is very easy to trick yourself into thinking that you skillfully EQ'd a track, but in reality, all you did was increase the volume.\n\nNow, the big factor in the loudness wars is compression. The sort of compression we are talking about in essence will make softer sounds louder. If you compress a signal enough, you can make a whisper the same loudness as a yell. This is what is called as reducing the dynamic range, as in the range of loudness is reduced. It may have been previously from -50 to 0 db, but after some heavy compression it is now -20 to 0 db.\n\nYou can see this in the photo below. Where there used to be peaks and valleys, it is just a straight line.\n\n_URL_0_\n\nSo, we can certainly come up with many negatives as to why this is bad. An obvious one is the philosophical question of \"compared to what?\", in that if everything in a song is the same volume, isn't the song neither loud nor soft?\n\nThat is honestly my biggest issue with poorly compressed music. There is never a point where it just hits you. What should be an epic buildup or a sudden spike reduces itself to be less of a surprise. The soft parts are never soft, the loud parts are never loud.\n\nBut, more importantly, there is a very big reason as to why music needs more of this sort compression now compared to before, and that reason is that we listen to music everywhere. \n\nPortable devices are relatively new, and the idea of listening to music on bike rides, on the train, when shopping, when working out, when doing work, riding the lawn mower, and so on was soon to follow. \n\nBut a big problem arose, and that was that while you were at the gym listening to your favorite song and a soft part came on, you couldn't quite hear it because of that noisy elderly couple chatting in the corner, so you turned it up to hear it... and then the loud part came on and you are frantically looking for the volume knob before you blow your eardrums.\n\nThis is a big problem because not only is it annoying to have to constantly adjust the volume, but it can actually do harm to your ears. A decent deal of compression can help this a lot by reducing the dynamic range just enough so that the soft parts are loud enough to hear over that noisy elderly couple, but soft enough to be distinguishable from the loud part. The goal is essentially to have it all audible, retain dynamics, and not have the listener have to touch the volume knob.\n\nYou might be wondering why portable music changed this. Well, it is because you used to have to listen to music in spaces where there wasn't much noise to overcome. You might pop in a record at the silence of your home. With advances in technology, we know listen to music in less suitable places to hear all the details.\n\nWith that said, there is an interesting selection process in how certain genres of music tend to be selected for their venue. Rock music tends to work for hockey stadiums because it is loud, simply, and punchy; whereas classical in the same stadium would softly garble on a sock.",
"People who make the music think that YOU think everything sounds better louder. And they keep trying to outdo each other to sell records. Because of this, they are sacrificing dynamics (highs and lows) for something that's consistently \"loud\". To me, it's also boring and rather tiring especially when it's done obnoxiously. \n\nI have heard it said that the loudness wars are almost over. Since most music is streaming through YouTube and Spotify and they control the loudness... the actual loudness of the recording doesn't matter as much anymore except if you're listening to a cd. And people think their music should probably be loud if they want to get it on the radio, but that's not true because the radio compresses and limits and EQs the music beforehand anyway. \n\nSource : the mastering show (podcast). ",
"It has ruined every single band ever... From Metallica, to my favorite, Parkway Drive. \n\nI saw Parkway Drive perform their new album live and damn near shit myself. There is NO reason a band should sound THAT much better live. \n\nTheir new album has a dynamic range of 5. Fucking embarrassing. ",
"Go listen to an old recording of money for nothing. The dynamics are great. Listen to it loud. If your sound system is bad, it's going to sound bad. If it's good it's going to sound good.\n\nWith the terrible and compressed mixes of today, and compressed in the sense that the dynamics are compressed, a bad sound system will sound a little better and a good one a lot worse than it could. Your ears will get tired faster and stuff like snare drums will sound weak and disappear into the mix.",
"Loudness Wars: The war part. People discover that the audience remembers \"louder\" as \"better\". Some things get louder (like the average volume of Television Commercials).\n\nSo the producers started mixing their tracks \"hotter\" so they'd stand out in play. Most stations mixing on CDs at the time wouldn't spend much time tweaking levels for every song played.\n\nAlso then at parties those tracks would \"pop\".\n\nNow why \"louder is worse\". In both encoding and electronics performance you get lower quality output. The long explanation is skipped here but basically if you run components near their limits they kind of just don't do as well.\n\nSo anyway, If you take, say a classic Police CD and anything modern and play the CDs back-to-back the total difference is amazing.\n\nSo the same song recorded at the \"natural volumes\" will be in the meaty part of the performance and output curves for the decoders and such. (hence the other stuff about compressing signals and such.)\n\nAlso, if people stopped being dicks about the volume, then it would be easier to play music."
]
}
|
[] |
[] |
[
[
"https://youtu.be/dcKDMBuGodU"
],
[
"http://housepital.nl/mastering/wp-content/uploads/2014/01/loudness_war.jpg"
],
[],
[],
[],
[]
] |
||
2dodx1
|
How would a Christian church service have differed in Rome in 500, 1000, and 1500 CE?
|
Who would be there? Would they be speaking to a congregation? Was there interaction from people other than the clergy? How long would it last and how often was it? Etc.
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2dodx1/how_would_a_christian_church_service_have/
|
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"I can only give some descriptions on the changes throughout history. The essence basically remains the same throughout history: the mass of the catechumens and the eucharistic liturgy proper. Initially Mass was offered only on Sundays and feast days, but as more feast days were inserted, daily masses began to be offered.\n\nChanges were made throughout history: additional prayers, or changes in the order of prayers. But the Canon of Mass, the core eucharistic prayer in the eucharistic liturgy, has more or less been the same in Rome since Pope Gregory I (600 AD) to 1500 AD. Elsewhere there is more variation, and only unified by Pope Pius V in 1570 after the Council of Trent.\n\nThe liturgy in 500 AD compared to 1000 and 1500 AD was simpler, with fewer prayers, graduals, and no Credo, just to mention a few. It should therefore be shorter, but since the medieval ages sometimes did not have sermons, the length could be the same. A Tridentine mass (after 1500s) could reach 3 hour long in high mass form with a sermon.\n\n",
"If you're curious, the liturgy of John Chrysostom (4th century) is still performed in Eastern Orthodox churches today every Sunday morning with very little difference, except a few: Pews wouldn't have been there; catechumens would be standing in the back, in the narthex, and would leave after the catechumen prayers mid-way through; non-Christians would also leave mid-way through, before the eucharist; men and women would be on separate sides of the aisle. Besides these minor differences though, attend pretty much any Eastern Orthodox Sunday morning liturgy and it's word-for-word (translated) the same one done in the fourth century as written by John Chrysostom."
]
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[],
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28sb8s
|
why can hospitals charge $50 a pill for tylenol, but i can buy a whole bottle at the store for $5?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/28sb8s/eli5_why_can_hospitals_charge_50_a_pill_for/
|
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"My local hospital charged $25000 (to insurance) for the birth of my daughter, a three day affair. That's a lot, but my daughter was severely breached, and my wife needed an emergency c section. They'd both likely be dead if we didn't go to a hospital.\n\nSo if the choice is ludicrous prices or death, what choice do you have?",
"I'm sure the large amount of people that use the ER as a doctors office and don't pay have something to do with it.",
"You're not just paying for the tylenol. You're paying for the nurse to give it to you, to make sure it's the right thing, for the diagnosis from the doctor to give you the tylenol, for anything any of the techs have to do for you, for the bed you're sitting in, for the air conditioning, for the TV, for the electricity, for the hospital administration and record keeping. You're paying for all of it. Going to the hospital for a tylenol is a very silly thing to do.\n\nIt's the exact same reason you get charged $1.99 for a coke at a restaurant, when you can get a whole two liter for $0.99 at the store. You're not just paying for the soda, you're paying to have it brought to you, with ice and a straw, in a social setting, with food available, by a server. Same idea.",
"Because doctors are struggling and don't make enough.",
"Because they can.",
"Because of greed.",
"because insurers haggle over bills. starting way over your target price and negotiating down to where you wanted to be initially is haggling 101.",
"In Denmark... it would cost you about 0$, if it was given to you in the hospital, and you did not have to go buy it at a pharmacy... although, the treatment, the bed, the electricity, the nurse, the doctor.. would add up to the huge sum of 0$... And really... I don´t have a problem with paying for others, because I know that if I (god forbid it) need treatment someday, other will pay for me. I just hope America starts to realise this. Both on healthcare and school system",
"The rationale is that in a hospital, at least two highly trained \nprofessionals have to review whether you should be given that \npill, and a third needs to double check that it's the proper pill,\ngiven at the proper time.\nGiven the rate of 'medication error' problems this isn't as\nridiculous as it appears on the surface.\n\nFor Tylenol, this is ridiculous most of the time, (but \nappropriate in some instances).\n\nStill I agree, = it's bill padding.",
"Insurance companies, Medicaid, Medicare, and people who visit the ER without insurance don't pay $50 a pill. Insurance pays a reasonable amount, Medicaid and Medicare pay about 70% of the pill's cost, and uninsured ER patients pay nothing. Hospitals have to make up the difference somewhere or they'd go out of business.",
"They have to make up the cost from people that don't pay.",
"I am a nurse and I have worked both in a hospital setting as well as a doctor's office setting. This is my understanding of why tings cost so darn much when billed thru a hospital or clinic.\n\nWhen you pay what seems like an exorbitant amount for something like a Tylenol what you are really paying for are things that can't be added to your bill, but you use while in the hospital. Things like electricity, water, staff time, cost of maintaining and upgrading the building/infrastructure, and to help offset things that we can't bill the actual cost because it is too ginormously high.\n\nYou are also paying to of set the cost of what insurance companies write off. For example when I bill a specific code it costs $20 dollars. Insurance A's contract with my hospital reimburses us $10 and requires that we write off the remaining $10. Insurance B's contract pays $15 and we write off $5. Insurance C's contract pays $5 dollars and we write off $15 dollars, and so on and so forth. \n\nSince we can't very well call the electric company and say sorry we didn't get as much reimbursement as we expected this month, what happens is every so often (usually once a year) someone/some committee from the finance department looks are what we need to charge to A)remain competitive with other area hospitals, and B) still be able to pay our bills.",
"Hospital finances are complicated. Bills can vary wildly depending on who is paying the bill. For example medicare sets the \"reasonable and customary\" fee and then generally insurance companies try to negotiate something like that for their members. The only people who would ever see a $50 for tylenol would be the uninsured mostly because the charge is built once and just not adjusted.\n\nWhy would you get an insane number like that? Well insurance companies may reduce the bill by 80% so if the hospital wants $10 for that tylenol they charge $50. Generally though a bill is tied to a Diagnosis Related Group DRG, which more or less says if you have x problem the hospital gets $5000 because it should take 2.1 days. This is just like the mechanic who says a transmission costs $1500 and takes 6 hours. If it takes 3 then yay if it takes 7 then boo. \n\nA big part of hospitals are hidden expenses. Compliance with the myriad of regulations isn't free. Electronic medical records cost plenty and most hospitals gain nothing from them. Safety officer isn't cheap, infectious disease nurses, dietary counseling, diabetes counseling, housekeeping, executive salaries and IT is a big cost. Certain procedures are big dollar losers (mid 5 figures) but physicians have patients who need them so the hospital takes a fat loss to make them happy so they'll do more profitable procedures there. \n\nSo hidden but very real expenses and a complicated billing system make a pretty opaque process. An opaque process can drop crazy bills. ",
"Even different pharmacies have different pricing on prescriptions within the same city. From what I learned, Costco ALWAYS has the lowest pricing compared to Walgreens/other drug stores. I almost had to pay 500 dollars a month for 30 pills, luckily at the end I managed to get insurance and the cost went down to 5 dollars.",
"The average cost of a stay in the ICU for somebody who need ventilated is about $31,000 - $42,000 (over a typical 14 day stay). Poor/homeless/uninsured people receive these treatments, some of whom make multiple emergency room visits per year, and have no way of making their payments. Hospitals inflate prices for insured people and people who can pay for healthcare in order to turn a profit. If you use a hospital, you're payment plan is paying for your care AND the care of the people who had no way of making payment.\n\nEDIT: [source](_URL_0_)",
"They're free in Canada"
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1j0x0z
|
How long does it take for a nerve signal to travel from a blue whale's tail to it's brain?
|
Considering how large a blue whale is, I was wondering if the speed at which nerve signals take to cross it's entire body is significantly different to that of humans.
Now obviously the brain would take a while to process anything that it receives, but I'm just interested in how long the actual nerve signal takes to get to the brain.
Although it'd be interesting to know just how a blue whale's brain deals with all the extra body mass it has and controlling it, do you just need a bigger brain to deal with it all?
Thanks for your time! :D
|
askscience
|
http://www.reddit.com/r/askscience/comments/1j0x0z/how_long_does_it_take_for_a_nerve_signal_to/
|
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"Assuming an optimally myelinated fibre, nerve impulse speeds in humans are circa. 100m/s. So if there were 1 fibre travelling the distance of the blue whale, about 0.3s. \n\nI don't know much about whale physiology, but I very much doubt there is a single axon travelling the whole whale. Instead it will be punctuated with synapses which dramatically slow down the total time taken to traverse the whale.\n\nReflex arcs are faster due to fewer synapses, but will also go via the spinal column rather than the full distance to the brain - so it's an unfair comparison!"
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|
1jp59x
|
why would someone want to jam gps receivers?
|
I can obviously see the benefit of being able to jam military GPS, but why would someone want to drive around jamming GPS, other than to be a jerk? TIA!
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1jp59x/eli5_why_would_someone_want_to_jam_gps_receivers/
|
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"The usual reason is people who are commercial drivers who want to do something they aren't allowed to do (take a detour to visit a relative, for example) but their commercial vehicle logs or transmits the vehicle's information to their boss. The vehicle usually gets its location, time, and current speed from GPS, and either logs this information periodically to a recording device or transmits it to the boss/company via the cellular network.\n\nJamming the GPS intermittently as well as when \"needed\" for clandestine activity, and it looks like mechanical GPS / equipment failure.",
"In addition to location data, GPS also provides precise timing data for some applications. If this timing is disrupted, it can usually make whatever it's supporting useless. This can include things from automated toll collection systems to stock exchange trading algorithms. Generally, the people disrupting them do so because they have something to gain by the system's failure."
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4adjfs
|
is there a fixed amount of money/assets in the world?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4adjfs/eli5is_there_a_fixed_amount_of_moneyassets_in_the/
|
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"no it wouldn't. because you can create money out of nothing. aka interest. the amount of money is always going up basically due to interest. ",
"Money roughly approximates the total amount of wealth in the world.\n\nEvery time someone pulls a rock out of the ground, encourages a plant to grow, or composes a hit single, wealth is created, and eventually, money will be created to reflect this.",
"Money is an arbitrary abstraction of wealth. There is no limit to how much money is in the world."
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3tfjyc
|
how do processors work? how is a simple silicon chip able to perform calculations?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3tfjyc/eli5_how_do_processors_work_how_is_a_simple/
|
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"This is a complicated topic built on very simple ideas. If you go step by step you should be able to wrap your head around it.\n\n**What is a semi-conductor?** Starting all the way down at the atomic level. In pure silicon crystals, the atoms are neatly arranged, and all have their outer electron shell full, so it won't conduct electricity because all the electrons are nice and cosy. By adding impurities into the crystal, we make two types of semiconductors,: P and N. N (negative) has more electrons, so it's willing to give them away and P has fewer electrons (positive) so it's glad to take in electrons.\n\nYou [put a chunk of N next to P](_URL_4_) and you have a diode. Pass electric current (aka a flow of electrons, but in the other direction) through it in the P-N direction, and the electrons will flow freely. however if you pass current in the N-P direction, the part where the two semiconducting materials meet will become \"full\" of electrons, like natural silicon crystals, building a wall between the N and P where electrons don't want to move, and any new electrons will hit that wall and won't be able to move forward, instead they'll just keep building that cosy wall.\n\nSo we can force electricity to only pass one way through a circuit, pretty cool...now what?\n\n**What is a transistor?** By [sandwiching semiconductors](_URL_3_) in an N-P-N or P-N-P way, and attaching electrodes (wires), we have a component that will behave differently depending where the electron flow comes from. This was first used as an amplifier (like a transistor radio), But can also be [used as a switch](_URL_1_).\n\nDepending which part you put current in, what comes out of the transistor will either be current or no current.\n\n**Logic circuits.**\nNow that we have this little thing that can switch depending on if it has current or not, we can string a bunch of them together in various ways to make boolean logic circuits. boolean just means you either have yes or no, or, in binary, 1 or 0.\n\nHere's a [NAND gate](_URL_0_), meaning *not and*, as you can see it pretty much looks like a transistor, because it is! You have two inputs, and if A has current (A=1) and B has current (B=1), it will put out a 0 (because it's a *not and*).\n\n[Here's a basic XOR, *exclusive or* gate](_URL_2_), meaning that A need to be 1 or B needs to be 1 for Q to be 1, but if A and B are both 0 or both 1, Q will be 0. This is just one way basic AND or NAND gates can be strung together.\n\nNow slap a few billion of these together in a CPU and you have a logic machine that can do all kinds of calculations.\n(sorry for the brief ending, I ran out of time, hope you learned something)\n\nEDIT: thanks to all the other people explaining boolean arithmetic on a higher level. Teamwork, yay!\n\nEDIT2: Fixed some links and hopefully cleared up the confusion between electron flow and current.",
"You have transistors the size of about 70x70x70 atoms. So even in a tiny chip you can have a fucktonbazillion of the basic elements.",
"There is nothing simple about it. Processors are quite possibly the most complicated thing mankind has ever invented. Learning how one works is a semester long 300 level EE class that's not a lot of fun. \n\nTo understand how a processor works you have to understand what its purpose is. The processor's job is to take data from memory (RAM), storage (hard drive), user inputs (mouse/keyboard) and then perform an operation on that data and output new data to memory, storage, or output devices (screen, speakers, etc). And at the end of the day, it's mostly just moving data from one place in memory to another. \n\nThe operation that the processor performs is a list of \"instructions\" called a program or algorithm. This is not high level code, every single instruction corresponds to a direct action taken by the processor circuitry. It's important to understand this, because at the instruction (or \"machine\") level, you are forcing a bunch of switches into position directly with a sequence of high and low voltages. \n\nNow when I say \"a bunch of switches\" I really mean a couple million logic gates. Logic gates are the simplest digital circuits and implement the boolean expressions AND, OR, and NOT. We use these operations to define and build more complex ones like addition and negation, even bit shifting (move all the bits to the left or right). Once we have those operations, we have subtraction (negation then addition), and multiplication (repeated additions and shifting). We can build up and implement all these operations in a special circuit that forms the basis of the processor called the **ALU** or Arithmetic Logic Unit. (We also have a thing called an FPU or Floating Point Unit, the ALU works on fixed point numbers, where we need an FPU for the floating point numbers). \n\nThe ALU usually has three inputs and one output. Two data inputs and an instruction input. Think of it like a calculator. It takes two inputs, does the operation you tell it, then gives you the output.\n\nSo the question is, where do the data inputs come from, where does the output go, and what is telling the ALU which operation to perform? The answer is the **registers** and **control unit.** Registers are tiny chunks of memory that hold onto a single \"word.\" If you have a 32 bit processor that means the registers are 32 bits \"wide.\" If you have a 64 bit processor then the registers hold 64 bits. Most processors have 16 registers. \n\nThe control unit is a bit more complex because it's the \"brains\" of the processor. It takes the instruction from the program and controls switches between the registers and the ALU. A simple code example might help you understand this:\n\n ADD $r0, $r1, $r2\n\nThis is an assembly instruction that tells the control unit to switch the data pathway so the ALU inputs are registers 0 and 1, the ALU instruction is \"ADD\" and the ALU output is switched to register 2. \n\nSo to recap, we have the ALU, registers, and control unit. The control unit handles the internal \"data path\" or the routing from the registers to the ALU, and the takes instructions from the program to send instructions to the ALU. \n\nThis is all well and good, but we're still only inside the processor. We haven't talked about how the processor accesses data from the user, memory or hard drive, or how the program is treated by the control unit. \n\nThis all has to do with memory. The processor generally has a special register called the \"stack pointer.\" It stores an \"address\" or location in memory where data lies (which is why it's called a \"pointer\" it \"points\" to data). It's the responsibility of the program to keep track of memory. Usually all the data the processor will ever need is in memory. \n\nIt also has a special layer of memory called the \"cache\" of very fast access memory. It's like RAM but costs a couple hundred bucks a gigabyte so you're lucky to have a few megabytes in the chip. In the cache we store \"program\" memory, which is the list of instructions to be executed. It is important to understand that the program memory holds the instructions as machine code *in order.* The processor has another pointer called the \"program counter\" which points to the location in program memory where the current instruction is stored. At the end of an instruction execution the processor increments the program counter so it then accesses the next instruction in program memory. What's really cool though is that like the stack pointer, the processor has direct access to the program counter which means it can execute instructions that changes its value. This is how we do things like loops in programming, you just reset the program counter to the start of the loop. You can also skip around in program memory, which is how you do things like functional programming. And because you're using very fast, random access memory for this there's usually no performance hit. \n\nLastly, I'm sure you're wondering how the processor knows to go to the next instruction. It's pretty simple, you use a clock. Each time the clock ticks, the program counter increments and this forces the control unit to execute the next instruction. You might be wondering what happens if it gets messed up and the control unit doesn't successfully execute the instruction in that clock cycle. It's called a \"hazard\" and it's really bad so people put lots of effort into writing code that's free of hazards and processor architectures that make them near impossible to happen. \n\nYou may also be wondering, is that really it? It's just a super complicated way of moving data from one place to another and *maybe* doing some math with it? And the answer is yes, that's it. Think about it, when I'm typing this the motherboard firmware is moving the data of the last key pressed and the action of the key being pressed (two data words) into memory, and Chrome is looking for the \"Key is pressed\" word, then the processor jumps to the instruction saying \"load last key pressed\" and moves it into the \"display\" program to show \"these bits at these locations.\" The whole thing is just moving data around. \n\n",
"I think the OP meant how they fundamentally compute things, not how they are made.\n\nThey are not complicated in how they work, their engineering is but the actual mechanism for calculation has been known since about 400 BC apparently. Doing it quickly was the problem. Since the time of the clock, mechanical computation has been known but the capabilities were held back until the advent of the transistor.\n\nSo how a processor works:\n\nA processor is a collection of light switches (or gears and values in a mechanical system) that are arranged into logical gates like AND, OR, XOR, NOT, etc. If you have ever played with Minecraft with mods like RedPower you know about those cool redstone gates.\n\nUsing those gates you can load information into registers. Think of them as little bowls you put marbles in representing bits.\n\nYou then dump the contents of those bowls into a channel that runs the marbles into those cool little gates and you get a result.\n\nYou can make a basic 'computer' with nothing more then Legos and a few marbles. Clockwork computations have been around since the 12th century. The big advancement, attributed to Babbage was the idea of a programmable calculating device. (See also Turing Complete Systems) but that is another discussion.\n\nSo back to the marbles. Depending on what marbles you pick depend on the route the remaining marbles take.\n\nIf the first marble is red, turn left. If the first marble is blue, turn right. Swallow that marble and pass the rest on.\n\nNow if we go left we take the marbles in the first bowl say (1 for red, and 0 for blue) 101101 and run them to a XOR gate. The next bowl (register) also goes 101001. At this point we now have 01101 and 01001 at the XOR gate. As the marbles pass the XOR gate the output becomes 00100 and those marbles roll into the third bowl.\n\nThis is basic computation. Turing, Babbage, Von Neuwmann, and others built modern processing to give us the ability to design complex routines that allow us to route those marbles around to a bunch of different gates, run some gates and routes concurrently, and even more complex stuff, but at the very core, it is very basic fundamentals. A few specialized components like addition, subtraction, multiplication, and division are collections of gates. More complex systems are usually built up from fundamental gates grouped and working together. The deepest principle is Boolean Logic or Binary Logic. Flipping light switches more or less.\n\nThe cool thing is we do this every day as part of a processor already. When you go to the grocery store and there are two lanes for groceries. The cashier rings up your stuff and it goes to one lane but if there is a special code (e.g. that bar that separates your stuff from the next person in line) then a switch is thrown and the remaining stuff gets processed down a different path. \n\nBy chaining tens of millions of those fundamental gates you can do complex calculations but again, the fundamentals are so basic you can build the basic parts on your own. It's shrinking them down and linking them together that is the hard part.\n\nAny basic book on Logic Circuits, a basic breadboard, and a electronics kits < $100 bucks and you can build nearly all the fundamental circuits used in a modern processor with a few exceptions.\n\nFor fun look up the 8086 processor (which has been recreated in minecraft on several occasions) as a good look at how modern processors work.\n",
"These answers are good, but let me try relating it to an actual 5 year old.\n\nImagine the processor is like a type of giant choose your own adventure book. It's a gigantic book, and though you might only have 32 or 64 choices to make at the beginning of the story, each unique set of choices you make at the start results in a different ending. All the billions of possible endings are already written into the processor when it's made, so all the hard work is done for you. You just choose a beginning and it (nearly) instantly gives you the ending. \n\nNow, the way the story is actually written into the processor is like a maze with special gates. When a part of the story reaches a gate, the gate automatically decides which way that part of the story will go, sometimes adding more stories to send through the maze. What comes out of the maze is the final ending, or the result of what you asked the processor to do.\n\nIn reality, each choice you make at the beginning is really an on or off electrical switch (like a light switch). So for instance, you can give the processor two numbers (say 2 and 4) and ask it to add them. This means your story choices would be 2, 4 and add. The trick here is, there is a special language/code you have to know, that lets you write any number, letter or request with just the on/off switches. This is called binary, and the book/processor is already written to understand it. \n\nSo you tell the processor 2, 4 and 'add' in its special on/off switch language and it tells you how that story ends, or in this case, the answer to your problem, 6.\n\nEdit: Rereading the question, I think and explanation of the silicon base was asked for.\n\nThe book/processor is written onto a silicon chip. The silicon is special because a maze can be drawn onto it, where electricity/stories can only travel through where the maze is drawn. The special gates are created with silicon, which has a special ability to only let electricity through under certain circumstances. These circumstances are what we use to build the book and decide which story parts go where next in the maze.",
"Everyone in this thread might enjoy reading [this](_URL_0_).\n\nA thread from /tg/ on 4chan where an anon suggests making a pocket computer out of shrunken zombies acting as simple AND/OR gates. We lovingly termed it Skeletron A.I.\n\nHilarity ensues.",
"Suffice it to say that binary numbers have exact analogies to all your usual mathematical operations. And it has been rigorously proven that any arithmetic operation with binary number can be expressed in some sequence of basic logic operations on the individual bits of the numbers.\n\nThe complexity of a CPU comes from organizing and synchronizing multiple circuits that all do relatively simple things.\n\nUnderstanding how a CPU adds two number is easy. But when you think about some instruction stored on a hard drive that is then loaded and inserted into the cpu and then the how the result is written... The cpu turns into a giant switchboard of circuits that can appear almost completely beyond comprehension.\n\n\n\n\n**Micro Architecture**\n\nOn the most basic level,a CPU reads and stores data from storage, it reads instructions (code) from memory, and it executes those instructions.\n\n\nYou can think of an instruction as a key that plugs into a slot, the instruction turns the slot and like one of those coin smushers at tourist attractions a result is returned on the other side. The CPU has multiple hard-wired circuits that compute specific instructions and each one has its own slot. For every instruction in your program there is a dedicated electronic circuit that will do the work. For efficiency, many of the actual physical circuits are shared between these \"slots\" and countless other little tricks to optimize as much as possible.\n\n The instruction itself consists of an operation code (*opcode*) that selects which slot the key should engage with, and it may pass additional information in the instruction through the door to the circuit inside.\n\nA very simple CPU could only have instructions that do mathematical operations with integers, typically then the instruction processing element is called the [Arithmetic Logic Unit](_URL_0_) and you can read the following page on how logic is used to implement [Addition](_URL_5_ )\n\n\nThis is the architecture view of the CPU\n\n**Architecture**\n\nAround this basic kernel of digital computation are hundreds of additional supporting electronic circuits that make this puppet show run.\n\nThe CPU/ALU discussed above has a clock connected to it, every fraction of a nanosecond it reads the next operation and then the logic executes it. How 32/64 bits of information representing an instruction gets into the CPU core is a very complex process involving multiple circuits that are responsible for: tracking which instructions are loaded, which are about to be loaded, loading instructions from memory.\n\n Most modern CPU's have a tiny amount of memory located on board called the [cache](_URL_10_) that stores instructions and data directly on the CPU silicon. This lets us \"ignore\" how the data actually got there (e.g. exactly how you communicate to a hard drive) because the [Memory Management Unit](_URL_7_), the [DMA Controller](_URL_1_), along with other supporting circuits take care of the logistics of getting data to the core.\n\nThousands of human-years have been put into optimizing each individual subcircuit as well as optimizing combinations of them to perform work faster. \n\n**Silicon**\n\nSo far these are all abstract concepts, the final connection to the physical comes in understanding that the most basic logic elements can be implemented as electronic circuits, and that the electrical properties of silicon based transistors make them very reliable and very fast and therefore a natural choice for implementing a massive synchronized computer. \n\nMost modern processors are implemented using the [CMOS](_URL_6_) Process, which uses a specific type of transistor called the [MOSFET](_URL_3_) to perform the electrical lifting to concretely represent this abstract logical machine. Earlier logic systems using resistor and bipolar transistors includes [TTL](_URL_2_) and [RTL](_URL_8_). \n\nCMOS has been the de facto standard for the lowest level of the electronic design since the 70's and is entirely responsible for the exponential progress of microprocessors, primarily because the logic circuits are simple, consume low power, can switch very fast (compared to other logic families), and can be made very very small. MOSFET transistors are also very simple to make using the deposition-etching paradigm used in manufacturing crystals (effectively a MOSFET is 2 overlapping bits of silicon)\n\nIt may surprise you to find out that it is mathematically proven that *every* logical operation can be rewritten to use a (more complicated sequence) of a single logical operation. In CMOS it is very common to express all logic in terms of [NAND](_URL_11_) gates, using what is called [NAND Logic](_URL_4_). \n\nTo see why NAND is so important we need to look at detail of CMOS technology, where using MOSFETS the NAND gate is the most compact (only 4 transistors) and lowest power of all logic gates you can create [CMOS NAND](_URL_9_).\n\n\n**Press a button and see it blink**\n\nThe Complexity of the CPU comes from absolute synchronicity across thousands of different subcomponents and subcircuits, but at the lowest level most circuits are relatively simple, accomplishing a single task and then stacked together like legos. The genius of a computer architecture comes in organizing a collection of well understood circuits into something that works synchronously together. Additionally, \n\n\n",
"Processors are made up of millions of transistors.\n\nTransistors are just miniature electronic relays. (a switch that is either on or off when power is either applied or removed)\n\nWith one relay you can make a 1 bit storage device (1=turn the relay on, 0 = turn the relay off) for code and data.\n\nWith two relays you can make a 1 bit adder circuit.\n\nBasically that is it, the first processors were made out of relays, the most complicated calculation you can think of can be implemented with millions of 1 bit adders and 1 bit storage devices and a list of instructions (stored in the 1 bit storage devices which connect the adders to specific data in a certain sequence).\n\nSubtract, you invert the input, multiply is a bunch of adds, divide is a bunch of adds and subtracts, sqrt(x) is just a bunch of multiples and divides, same for cos(x) (uses Taylor series) etc\n\nEverything else, pipelines, caches, floating point units etc are just made to speed things up (and are made out of transistors)\n\n1 or 0 that is all you need",
"If you're looking for a thorough but easy to follow explanation I'd recommend \"Code\" by Charles Petzold. It's a fantastic book and gives you a good basic understanding of computer architecture.",
"The best explanation I ever found was this: _URL_0_\n\n",
"Computerphile: How computers do math demonstrated with dominoes. \n\n_URL_0_\n",
"OP if you want a book that breaks it all down and is easy to understand check out the book [Code by Charles Petzold](_URL_0_)",
"Don't know if it has been posted before, but numberphile has made an [awesome video]( _URL_0_) that explains the inner workings of a processor with dominoes. ",
"Apparently this isn't an ELI5 question. I'm a CS major and it would still be hard to describe in a few sentences. \n\nThe bottom line is there are 1-2 billion transistors in a cpu, which results in a practically infinite amount of combinations of on or off. When a computer looks at all of these on and off switches it is able to do cool things, which answers the first part of your question. Translating binary into cool things is more complicated.",
"On the silicon chip are millions of tiny transistors - like tiny switches. These are arranged in configurations to make logic gates, which the manufacturers \"wire\" together to make more complex logic circuits which can follow 'instructions' held in the memory (more chips attached to the CPU). \n\nThink of it like the way pinball machines work - when the steel ball hits switches or goes through gates, it causes lights to flash, buzzers and bells and actuators etc. to be triggered, and maybe increments your score. Each switch or gate is input into a logic circuit, and the output might be to flash a light or activate a buzzer.\n\nInside the CPU, the \"wiring together\" of these logic circuits allow operations like arithmetic, or tests to be done, and also most important, the \"decoding\" of instructions stored in memory and then operation on data, also stored in memory.\n\nEach instruction is stored in memory as a number, encoded in binary (number base 2), and each number, known as an opcode, specifies a particular operation for the cpu to carry out. There are instructions for loading data from memory into special memory on the cpu called registers, and for loading data from registers into normal memory; instructions for making decisions, and instructions for performing arithmetic, and so on. Today's cpu's can perform millions of these instructions per second.\n\nExamples of instructions (not real ones, just for illustration). The pretend opcodes and their data are the number to the left. Apologies for the formatting:\n\n 5510 0001 load memory location 1 into register a\n 5511 0002 load memory location 2 into register b\n 0212 add register a to register b\n 3112 0100 compare register a and 100\n 9801 if greater, jump to end\n 5611 0003 store register b in memory location 3\n end:\n ....\n ....\n\nUsually these instructions are not written directly by humans, because they're pretty hard to write this way - we use more human friendly languages, called \"high level languages\" instead. However, people can and do write these directly sometimes, and they usually use \"mnemonics\" - short abbreviations that describe the operation required, instead. We call this low-level language \"assembly code\".\n\n\n\n",
"The answer is that they do not perform calculations in the way you think. That is what we see as being the \"result\" of what happens. what a processor does is route electrons through various types of logic gates. You provide input, example, your fingers touching the number pad on a calculator. That input is taken and broken down into logical steps that are performed by the processor. The processor generates output. The output is then translated into numbers that you see on the display. ",
"All of them miss very important levels.\n\n1. **Level 1: The Silicon.**\n\n A semi conductor is a material which can pass an electrical signal or not. Most semiconductors are \"yes or no\" devices (Diodes), but you can place semiconducting material together in a way that you have pins: An input, an output and a control. This is called a transistor, and you can control the level of electrical signal that passes through it. For our purposes, there is a kind that operates in the \"switching zone\", called a MOSFET. This is a voltage controlled voltage device, and turns on or off.\n\n By placing two of these in series between a voltage source and ground, the midpoint can be controlled to be switched to voltage source, ground, floating, or short the source and ground together.\n\n We arrange so that the input to one of these two MOSFETS is the opposite of the input to the other, so one input switches the output to high, or low voltage.\n\n This is the most simple logic gate, either a Buffer (delay) or Inverter (turns a high signal into a low signal).\n\n2. **Level 2: Logic Gates**\n\n A logic gate is a combination of MOSFETS in a manner that has a predictable and known response to input. Multiple inputs can be added. There are SIX kinds of non trivial gates able to be made with two inputs and one output. AND, OR, XOR, NAND, NOR and NXOR. These gates outputs depend if input A AND B are high, A OR B are high, A and not B (exclusive OR). The output can also be inverted for NAND, NOR and NXOR.\n\n3. **Level 3: Metastable circuits.**\n\n This is slightly complicated. In short, if you have two NOR gates, and wire the output of each to one of the inputs of the other you get something that looks like [this](_URL_1_). It doesn't look like that at all. That is an abstraction. The real circuit diagram is more like [this](_URL_0_)\n\n Abstractions are important here. Real silicon are not perfect ideal switches, but we moved up from level 1 to 2 by imagining they were. We moved from level 2 to 3 by ignoring that the switches need resistors and power and ground and various other electronic bits.\n\n But at our current level of abstraction, we have a latch. You can set it on, or reset it off. This output state will stay constant but not really. It can get confused and into bad states. So by taking two latches and putting them one after the other, we can get something called a D FLIP FLOP. The mechanics of this flip flop get rather complicated, but it basically breaks down to this:\n\n A D Flip Flop is a collection of logic gates with one input and one output. The Flip Flop also takes a \"CLOCK\" signal, a square wave. When the clock signal rises from low to high signal, the signal present on the input is then expressed as the output. At all times OTHER than the rising edge, the output is independant of the input.\n\n We have a one bit memory cell.\n\n4. **Level 4: Registers and computation.***\n\n A register is a collection of single bit memory cells that can be read out in parallel or sequential fashion. Sequential registers are not really needed atm, so we'll use parallel. Easiest way to imagine them are a bunch of coins, heads up or down in a line.\n\n See the abstractions? We went from silicon to switches, to logic gates, to memory cells, and now we're operating completely independently of the actual material of the computer. If you had enough coins, the right rules and time, you could run hello world on your kitchen table.\n\n So, a register is a memory element of fixed size, usually, 8 bits. This memory element can be connected to the input of a computational block depending on various signal switching.\n\n Lets talk about computational blocks and binary representation.\n\n Binary is a base two numerical system. It has the representation 0b00000111, which is '9' in decimal. Binary maths looks a bit weird, but behaves like normal maths.\n\n 0b00000111\n +0b00000101\n ----------\n 0b00001100\n\n 1+1 = 10. 10+10+10 = 110.\n\n Starting at the least significant bit, you go, \"Bitn input A, NXOR Bitn input B\", and put that in the same spot in the output. You then go \"Bitn input A, AND Bitn input B\" and if that is true, that is your carry signal, and that goes to your next bit. The next bit up is very similar, except you NXOR the output with the previous carry, and you decide if any 2 or more of the previous carry and your two input bits are one to form the next carry.\n\n So now we have an adder. It can add two binary represented numbers. We can also build a subtracter or multiplier with much more complicated logic gates. But the important thing is while it is complicated, we have the abstractions and tools that let us do it.\n\n5. **ALU, Control Unit, General Purpose Registers, Special Purpose Registers**\n\n Now the big boys come in. Arithmetic Logic Unit This is a configurable computational block that can perform a number of operations. It takes one input which tells it what to do, and two inputs to operate on, which are also loaded into General Purpose Register. It executes the known operation and that is placed in the output General Purpose Register.\n\n So where does does the 'what operation to do' come from? The Control unit is a large collection of logic which takes an encoded instruction. This instruction might say \"Add Register 1 and 2 and put it in 1.\" The control unit will then switch so that registers 1 and 2 are connected to the input to the ALU, and register 1 is connected to the output. It will also set signals so that the ALU does an addition.\n\n How does the Control Unit Know what do do? It reads an instruction from what is known as \"Program Memory\", usually disk. Where to read from in the memory is controlled by the instruction count register, one of the special purpose registers, which increments whenever the Control Unit has finished its previous instruction. The new memory location is then loaded into another of the Special Purpose registers for execution.\n\nSo, here we are.\n\nFive levels in, and we have:\n\n* Silicon can allow or deny electrical signals to pass through it.\n* These switches can be used to create basic logic.\n* This logic can be combined into persistent memory.\n* This memory can be fed into special logic to operate on the contents of the memory.\n* Memory contents can be operated on with special logic to control the operations on memory and how they are executed and stored.\n\nWHEW!\n\nBUT WE\"RE NOT DONE.\n\nWe're not at MACHINE CODE level. This is the most basic level. I haven't covered data memory, buses, program memory, programming, or a swathe of other, equally complex things.\n\nBut, as someone who has done a Electrical Engineering degree, and built transistors on doped silicon, and used logic gates to build adders, and then use VDHL with FPGAs to make a basic, rudimentary CPU, then learnt C to use on an ATMEGA 8, and now works for a multi national software company....\n\nGood question.\n\n**There is no explaining like you were five. Best I can give is \"explain like you're a high school graduate\".**",
"Very hard to Eli5 it, but essentially it works like a lot of switches that are really really tiny, but it's not a simple silicon chip, it's almost as complex or more complex than most factories. Here's one zoomed in: _URL_2_\n\nAt this scale it's still not easy to understand because the pieces are still too small to see, if you get close enough this is what you see:\n\n_URL_1_\n\nIn the second image there are about 5 or 6 transistors showing just in the picture, everything is made of silicon but it's kinda carved out in an intrinsic way, step by step.\n\nIn the first image you can see about 42,000,000 transistors.\n\nThe calculations are made just like any other machine with switches to change modes and values: _URL_0_\n\nthe advantage of the processor is that it's easily reprogrammable to do different stuff",
"Found [this video](_URL_0_) some time ago and I think the topic is very well explained",
"I'd like to make a book recommendation to anyone interested in an approachable in-depth explanation of simple logic processing: Code\n\nIt's seriously the best book I've read on the subject.\n\n_URL_0_",
"This isn't really a subject that can be covered in a way that an actual 5 year old can understand because the fact of the matter is that a lot of very smart people who make processors maybe don't understand every single bit of it either.\n\nBut to do my best anyway, I will explain here the basic workings of a Register Transfer Machine, which contains some of the basic functionality of a computer and lots of the basic components.\n\nYou need only one component to start off with but you will eventually need lots of this component strung together in somewhat complicated ways to do complicated things. This component can be made of whatever you like but when it is 'on' an electrical current will pass through it, and when it is 'off' no electric current will pass through. Generally we use transistors for this job nowadays but before that, we used vacuum tubes. I will say transistor in the next bit when I mean this component.\n\nLogic gates are the next level of complexity. Generally, they are made of between 2 and 8 transistors. The job here is that I will put in electrical signals, which will either be a high voltage or a low voltage, from outside the logic gate and the circuit should put out a high or a low voltage depending on the input voltages and the arrangement of the transistors. The simplest logic gate is the 'not' gate which takes one input: if the input voltage is high, the output voltage should be low; if the input voltage is low, the output voltage should be high.\n\nTwo other important logic gates are 'and' gates and 'or' gates; these both take two inputs. An 'and' gate will output a high voltage only when both its inputs are high. On the other hand, an 'or' gate will output a low voltage only when both its inputs are low.\n\nThe reason these gates are called logic gates are because they are analogous to logical statements where high voltage is analogous to saying something is true and low voltage is analogous to false.\n\nAt the next level are basic composite components. These are made up of ~5 logic gates(so between 10 and 40 transistors) and 'adder' circuits (circuits that can 'add' the value of two inputs) will come under this heading. I won't explain an adder circuit as these are readily available to see online elsewhere but these are important to the working of a processor and good examples of how we can combine logic gates to make more useful composite components.\n\nOne really important composite component is the multiplexor. The goal of the multiplexor is that I have two input voltages and I want to filter one of them out and simply look at the value of the other. but I want to be able to change which input I am looking at. To do this, I have a third input called a control. When the control is low, the multiplexor will match the value of the first input. When the control is high, the multiplexor will match the value of the second input. It might not be immediately obvious why this is useful but eventually, this will be important in something called addressing in the finished machine. This is also a component that goes into something called registers.\n\nBefore going into registers, I will explain that there exist components called flip-flops. Simply, these components have an input and a connection to a clock. When I say clock, I just mean an electrical input that changes value regularly at precise time intervals. When the clock \"ticks\"(changes value), the output of the flip flop may change to match the input. Until the clock ticks, however, the output of the flip-flop will remain the same, no matter if the input changes.\n\nThe goal of a register is to be able to give the signal for this register to accept a high or low voltage and then, until I give the signal again, constantly output the high or low voltage given before. Registers are made up of a flip-flop and a multiplexor. The flip-flop stores the value that we want the register to put out. The multiplexor decides whether we should update the value of the register or keep the signal the same. The way it does this is that we connect the output of the flip-flop into the first input of the multiplexor and leave the second input of the multiplexor open to accept new values. This way, while the control on the multiplexor is low, the flip-flop's value will feed-back into itself. When the control is high, the flip-flop(and so the register circuit as a whole) will take the value of the second input.\n\nRegisters are really important in the operation of processors, they are used to store values used in calculations as well as the results of those calculations.\n\nThe final thing to explain is that a Register Transfer Machine is made up of three components: a register file, containing a bank of register units to contain values to be used in calculations and the results of said calculations; an arithmetic or logic unit, collections of circuits to be used to calculate results (including adder circuits); and a series of connecting wires called 'buses'; there are three buses: data bus, address bus, and control bus. Data buses, unsurprisingly, carry the actual values of the registers and calculations. Address buses indicate which registers to use to get input values and which register to store the result in. Control buses decide which operation to perform.\n\nIn early machines, I might manually change values on the control and address buses to achieve the desired calculations but this quickly becomes tedious and highly inefficient. So, instead, I create a control unit which generates these signals for me.\n\nAnd fundamentally, that's how a processor works.",
"\"simple\" silicon chip\n\nMicroprocessors are the most complex manufactured item in the history of mankind",
"Simple answer: By giving it electricity.\n\nImagine a CPU is a bowl of spaghetti, but starts with one strand and splits into millions at the other end like a tree.\n\nBut it's a metal tree so you can put electricity through it. It has 2 states, powered and unpowered, or on and off, or 1 and 0. \n\nNow, imagine that when this tree makes a branch, each branch splits into a 1 and a 0 branch (one sends power and the other doesn't). \n\nWhen you look at the other end of the strand (millions of ends) you see tons of 1's and 0's. Because not all the power got all the way to the end of each path.\n\nNow imagine that this end with millions was a specific pattern, not random. So that when you applied power, the million ends created a system of 1's and 0's that actually meant something in a language you made up.\n\nLike the first 8 branch endings was 01001010 and that translated into a letter 'H' or something. \n\nNow attach a bunch of these trees together, powering them off and on really fast with a timing switch. \n\nYou then have a bunch of 'places' to hold 'data' in the form of characters. Just by powering something on and off really fast.\n\nSo when you look at the millions of trees with millions of branches, imagine some are looped up in a way that they continue to hold the same 1's or 0's no matter what the state of the original power timing. That is sort of like memory.\n\nNote: This is simplified to the point of probably being wrong. But the concept is there.\n\nEdit: \n\nWhoops forgot the obvious at the end. Memory means you can store numbers or data, and if you can store data (like a 5 and a 7) and a character (like a + sign). You can also connect the loop branches so that 00000001 goes up by 1 binary calculation (to 00000010) each time it loops. Also you can connect the loop branches to 'send' a pattern of 1's and 0's to another bunch of places (it can then 'load' and 'save' data to other places).\n\nSo in this example you input 5 and 7 (or load them from some place you used earlier) and send 5 into the 'addition' loop for 7 loops, and each time 5 goes up by one because that is all those branches do when the power is on. So when 5 is looped 7 times, you unload it's new value to another place and have 12 stored. Thus performing a calculation. ",
"You could have just googled it \nBut you had to get 2000 upvotes didn´t you? \nActually, that seems to be the whole point of this sub",
"Lets dive right into the magical land of data.\n\nWhats the symbol for five? 5. Whats the symbol for ten? 10. But wait, isn't that the symbol for one and zero? Right, so in our numbering system, when we get to the number ten, we write the symbol for one and zero. There is no symbol for ten, we simply recycle the ones we already have. Because of this, we call our numbering system \"base-ten\", or \"decimal\". \n\n\"Ones and zeros\",\"true and false\", and \"on or off\" are all terms you have probably heard before. What these all are referring to is a *different* kind of numbering system. For our decimal system, we write a '10' when we get to ten, but for binary, we write a '10' when we get to two. There is no symbol for two in binary, exactly how there is no symbol for ten in decimal. \"On\" or \"off\" simply refers to '1' or '0' in binary.\n\nJust to make sure that makes sense (as its super important):\n\n01 = one;\n\n10 = two;\n\n11 = three;\n\nMake sense? Cool (if not google \"binary\").\n\nOk, now for something completely different, but related.\n\nTheres something in computer theory called a \"logic gate\". It's a device. It has two inputs, and one output. The only input it accepts is \"on\" or \"off\", and the output is the same, \"on\" or \"off\". You might see the relation to binary.\n\nA logic gates output is based on its input. An example of a logic gate is a \"AND\" gate. When both of the inputs are on, the output is on. Otherwise, the output is off. \n\nYou still with me? Don't worry, the cool stuff is coming soon.\n\nAnother logic gate is the \"NOT\" gate. The NOT gate has one input. If the input is off, the output is on, and vice versa. The output is *not* the input. Get it? \n\nNow, if we put the input of a NOT gate on the output of an AND gate, we get a NAND gate. Creative, I know. We nerds don't get out much. Anyways, try to figure out what the output would be for all the four different possible combinations of the two inputs for the NAND gate.\n\n[Anyways, heres what a NAND gate looks like drawn.](_URL_1_) \n\nNow, you have probably heard of computer memory right? [**ta da!**](_URL_0_)\n\nIt's not going to make total sense at first, but that diagram shows a memory-holder-thingamajig. Look at it for a while and try to figure out what it does. Basically it holds a \"bit\" of memory. You could say that a bit is like one digit of a binary number. You line a bunch of these in a row, and you can start holding numbers.\n\nBut what do you *do* with those numbers?\n\nThis is where it gets cool. You do math with those numbers. This next device is called an \"[*adder*](_URL_2_)\". \n\nThe gate on top is called an XOR gate, its output is on if only one of its inputs is on. If there both on or off, then the output is off. \n\nNow, make it a [little more complex](_URL_3_) and you can add multiple bits at the same time, by linking the last ones \"Cout\" to the next ones \"Cin\".\n\nCool, now we have a basic calculator. How can we turn this up to 11 and make a computer?\n\nCode. \n\nNow, you know what data is, and so code is easy to explain. Its just data. Thats all it is. Really. \n\nThe reason why its different then other data though, is because the CPU interprets it as *instructions.*\n\nIf we wanted to do math for example, and we got to decide the instruction definitions we could use a system like;\n\n 00000001 = *add* a number to another number;\n\n 00000010 = *subtract* a number from another number;\n\nWith this, we can set what logic gates are being used based on data. \n\nNow, real quick, memory is organized on a computer by something called memory addresses, basically they just allow the CPU to ask for memory at a specific location.\nGenerally speaking the addresses are sized by \"bytes\" which is just another word for \"eight bits\". So if we wanted to access memory location five or whatever we could store that as '00000101'.\n\nLets go back and add some more to our table;\n\n00000011 = move this data into some location;\n\nCool, now we can say something like:\n\n\"add the number at location #5 in memory to the other number at location #7 in memory.\"\n\nBy breaking it down into:\n\n (add) (memory address #5) (memory address #7)\n\nWhich is really just\n\n 00000001 00000101 00000111\n\nPretty sweet right?\n\nBut hold on, how does the CPU know where to get its instructions?\n\nOn the cpu, Theres a tiny amount of memory, it does various things, such as hold something called the \"instruction pointer\". The instruction pointer holds the address of the next instruction, and increments itself after every instruction. So basically, the cpu reads the instruction pointer, fetches the next instruction, does it, adds one to the instruction pointer, and then goes back to step one.\n\nBut what happens when it runs out of instructions?\n\nLets go back to our table. Last time, I promise:\n\n 00000100 = set instruction pointer to address\n\nBasically, all this instruction does is set the instruction pointer to a number. You ever wonder what an infinite loop is on a computer? Thats what happens when an instruction pointer is set to instructions that keep telling the instruction pointer to set itself to that same set of instructions.\n\nThats computers in a nutshell.\n\n**tl;dr** I need to get laid.",
"I know I'm late to the party, but [I learned about computers from this 90s cartoon, The Magic School Bus Gets Programmed.](_URL_0_)",
"Imagine you and your spouse agree to turn on the light switch near your front door when either of you gets home, so that if one of you comes home and sees that the switch is on, that means that the other is already home.\n\nOn = home, off = not home.\n\nThis is a binary state. In a computer, if a circuit is on, it is represented as a 1. If it is off, it is represented as a 0. the circuit being represented as 1 or 0 it therefore called a \"bit\" (**bi**nary in**t**eger)\n\nNow imagine you replace that 1 switch with a switchboard that has 8 switches in a row. Your spouse and you can communicate a lot more information now. In fact, you can communicate **255 times** as much information. Instead of just 1 and 0, you now have 8 switches.\n\nSo information can range from\n\n[00000000] (your spouse is not home) to\n\n[00000001] (Your spouse is home) to\n\n[11111111] (Your spouse has been kidnapped by ninjas and needs you to be a bad enough dude to rescue them).\n\n255 configurations.\n\nIn a computer, when 8 bits are clustered together like this, they are called a byte. This is a basic computing concept. You can apply this concept in the context of storage, or of a CPU, and so on.\n\nNow as for how these are used to make calculations, remember the basic concept binary; either a switch is on or off. There is a nifty little type of device called a logic gate that uses binary in a very clever way. In concept, a logic gate is a little circuit that has two inputs and one output, and the output depends on the input.\n\nThere are 7 types of basic logic gates (AND, NAND, OR, NOR, XOR, XNOR, NOT). To explain the underlying idea of what their function is, I will explain only one, the AND gate. The AND gate's function is to output \"on\" if both inputs are \"on\" i.e. if both inputs are \"1\", the output will be 1, but if either or both of them are \"off\" i.e. 0, then it outputs \"off, 0.\n\nHow can the AND gate tell if both are on? Because it is physically wired that way. Here's an MSPaint example of how that effect can basically be achieved:\n\n_URL_0_\n\nIf either is \"off\" (because the circuit is broken) then current can't flow through the output, meaning the output will show as off. So the AND gate will be 1 if the first **and** the second inputs are on.\n\nThe other types of logic gates are (in terms of how they output 1)\n\nNAND: **N**ot **AND** (Both inputs are not simultaneously 1)\n\nOR (one **or** both inputs are 1)\n\nNOR (neither input is 1)\n\nXOR: e**X**clusive **OR** (only one of the two inputs are 1)\n\nXNOR (either both are 1 or both are 0)\n\nNOT, also known as an inverter, is a special one that gives the opposite output to its input. It only has 1 input (usually the output from one of the other types of logic gates).\n\nWith a combination of logic gates, you can create a more complicated logic gate called adders, and these can then be used to output the answers to mathematical inputs.",
"im taking a class on this and its complicated. and its still not explaining what we use today, just what was used and the basics of a simple processor implementation. there are still jumps in logic from electric signals to actual code that i dont understand. this is a complex topic and you might not be ok with the simple answers here, i wasnt when i asked these questions when i was 5. so, these answers are just the beginning.",
"imagine a gigantic plinko game... but one that's rigged so that if you drop balls at the top in a specific pattern, they'll switch a bunch of gates along the way down and always come out the bottom in another pattern. \n\nit's like that. you drop 0110 and 1100 into the top, 10010 pops out the bottom. expand that to millions of switches per second and getting \"hello world\" to pop out in 11010110010 form gets to be quite simple :)\n\na processor is a tiny box full of tiny switches that turn inputs into outputs like a microscopic sized epically huge plinko board.\n\nso... \"magic\" :) ",
"Eli5: imagine if you had a hundred light switches, and a hundred people, each person on each switch. all these people are standing randomly across earth. At one end, there is a light bulb, and at the other, there’s a power source. Every time the power source gets to a switch, the person will decide to flip the switch or not. If a certain combination of people switch their switches to ON, the light will turn on. Now instead of just having earth, one light, and a hundred switches; imagine there is a whole galaxy of earths. millions of lights, billions of switches. Now shrink that into the size of a penny. That’s a processor. It takes the different power sources, puts them through a few switches, and a light comes on, or turns off. That’s it. ",
"I have a midterm on this exact concept tomorrow! Reddit just made me study! There might be a god! As the ultimate procrastinator who uses reddit to distract himself I find this pleasantly ironic. ",
"There is no way to ELI5 this. The closest thing is maybe to show one of those water droplet based \"computers\" that I can't seem to find a link to right now. "
]
}
|
[] |
[] |
[
[
"https://upload.wikimedia.org/wikipedia/commons/5/58/Nand-gate-en.svg",
"http://i.imgur.com/pAFEsit.png",
"https://upload.wikimedia.org/wikipedia/commons/thumb/f/fa/XOR_from_NAND.svg/300px-XOR_from_NAND.svg.png",
"http://i.imgur.com/bdu5kOQ.png",
"http://www.circuitstoday.com/wp-content/uploads/2009/08/semiconductor-diode-p-n-junction.gif"
],
[],
[],
[],
[],
[
"http://suptg.thisisnotatrueending.com/archive/12936417/"
],
[
"https://en.wikipedia.org/wiki/Arithmetic_logic_unit",
"https://en.wikipedia.org/wiki/Direct_memory_access",
"https://en.wikipedia.org/wiki/Transistor%E2%80%93transistor_logic",
"https://en.wikipedia.org/wiki/MOSFET",
"https://en.wikipedia.org/wiki/NAND_logic",
"https://en.wikipedia.org/wiki/Adder_\\(electronics\\)",
"https://en.wikipedia.org/wiki/CMOS",
"https://en.wikipedia.org/wiki/Memory_management_unit",
"https://en.wikipedia.org/wiki/Resistor%E2%80%93transistor_logic",
"https://en.wikipedia.org/wiki/NAND_gate#CMOS_version",
"https://en.wikipedia.org/wiki/CPU_cache",
"https://en.wikipedia.org/wiki/NAND_gate"
],
[],
[],
[
"https://www.youtube.com/watch?v=lNuPy-r1GuQ"
],
[
"https://www.youtube.com/watch?v=lNuPy-r1GuQ"
],
[
"http://www.amazon.com/Code-Language-Computer-Hardware-Software/dp/0735611319/ref=sr_1_1?ie=UTF8&qid=1447965649&sr=8-1&keywords=code&pebp=1447965653247&perid=0R8F3TKN8XGJBT2VGJW7"
],
[
"https://youtu.be/lNuPy-r1GuQ"
],
[],
[],
[],
[
"https://upload.wikimedia.org/wikipedia/commons/1/14/Transistor_Bistable_interactive_animated_EN.svg",
"http://sub.allaboutcircuits.com/images/04173.png"
],
[
"http://petapixel.com/assets/uploads/2014/11/008.jpg",
"https://i.ytimg.com/vi/Fxv3JoS1uY8/maxresdefault.jpg",
"http://www.tayloredge.com/museum/processor/1999_Pentium4.jpg"
],
[
"https://www.youtube.com/watch?v=cNN_tTXABUA"
],
[
"http://www.amazon.com/Code-Language-Computer-Hardware-Software/dp/0735611319"
],
[],
[],
[],
[],
[
"http://en.wikipedia.org/wiki/Flip-flop_\\(electronics\\)#mediaviewer/File:SR_Flip-flop_Diagram.svg",
"http://en.wikipedia.org/wiki/NAND_gate#mediaviewer/File:NAND_ANSI_Labelled.svg",
"http://en.wikipedia.org/wiki/Adder_\\(electronics\\)#mediaviewer/File:Half_Adder.svg",
"http://i.stack.imgur.com/0rqZz.png"
],
[
"https://youtu.be/TnSLR8lUses"
],
[
"https://i.imgur.com/oxvX0Vy.png"
],
[],
[],
[],
[],
[]
] |
||
2b229e
|
why do my teet hurt when i eat sugary candy (taffy, tootsie rolls...)
|
I bit into a doughnut with sprinkles today. I got a sprinkle right in between two teeth and my mouth lit on fire.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2b229e/eli5_why_do_my_teet_hurt_when_i_eat_sugary_candy/
|
{
"a_id": [
"cj10b9u",
"cj10ef0",
"cj11e05"
],
"score": [
3,
2,
3
],
"text": [
"Sounds like cavity creeps",
"Almost certainly a cavity. Your saliva dissolves the sugar and the liquid sugar mix can get into the smallest of places, so it may only be a really really tiny cavity, but still something to get checked out.",
"Hey sugar tits!"
]
}
|
[] |
[] |
[
[],
[],
[]
] |
|
ainsgc
|
Intelligence documents from WWII and after from my Grandfather
|
Recently my Grandmother gave me a box of paperwork that she has kept secret for many years for my Grandfather (who passed away 20 years ago) relating to WWII and afterwards which is a lot of intelligence information, a lot is in English but also a lot in Italian, German, French and other.
I believe recently the date came when it was available to be released into the public realm but i have no idea who may benefit from this stuff. She has kept it secret and after talking with her has been a burden on her because of the importance of some of the information and documents.
Who in the UK would be the best place to seek help and advice in looking through the materials and finding out the importance of it?
Thank you in advance!
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/ainsgc/intelligence_documents_from_wwii_and_after_from/
|
{
"a_id": [
"eepz4ke",
"eeq6tfn"
],
"score": [
3,
2
],
"text": [
"First and foremost it's amazing that they've been kept. Please do what you can to make sure they don't get damaged and do what you can to minimize the damage. Original documents are often a wonderful treasure trove to many historians. Often even mundane documents can lead to some critical insight that nobody would have suspected at the time or even a century later. So please make sure they stay safe until they can be properly inventoried/scanned/saved.\n\nIt is also possible that they are of little actual value outside of the connection to your grandfather. Still better safe than sorry. Scanning the documents (provided the scanner itself does no damage) would probably be a good place to start as it preserves what is there.\n\nNot sure about the UK, if this were the US I would probably look at whatever preservation/museum that the particular unit he served in might have. I know the several army, navy, and air force units in the US have museums and archives at their home bases. That might be a place to start in the UK as well.\n\n ",
"If there's a local museum or historical society it might be worth contacting them to see if they can help or direct you somewhere. I'd definitely advise giving them a quick read through to see if there's anything particularly interesting in there that you can mention."
]
}
|
[] |
[] |
[
[],
[]
] |
|
1pi2xf
|
what does it mean when someone is "in shock"?
|
The vid on the front page of the guy busting his leg base jumping, everyone was saying "oh he's calm because he's in shock" and I see that term thrown around a lot. What exactly does it mean? Is there a medical definition or is it just colloquial or what?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1pi2xf/eli5_what_does_it_mean_when_someone_is_in_shock/
|
{
"a_id": [
"cd2io40",
"cd2iqqd",
"cd2n2pj",
"cd2p4yj"
],
"score": [
6,
2,
14,
3
],
"text": [
"The term \"shock\" is used very frequently in the medical world. It is when the organs within a person's body aren't getting enough oxygen. If a person is in shock for too long, the organs lacking oxygen will be permanently damaged, possibly leading to death.\n\nEdit: Just to be clear, I haven't seen the video mentioned by the OP. I'm referring to the term \"shock\" strictly as it is used in a medical environment. ",
"Shock is a legitimate problem and can be life threatening if not treated properly and quickly.\n\nThere are a number of causes that can trigger it, but it is basically a significant drop in blood pressure. Anxiety, chest pain, confusion, heavy sweating, shallow breathing, passing out, lack of response to trauma... all can be symptoms of shock.",
"Nobody has given a unified answer so I will try. Basically there are two kinds of shock that somebody could be referring to.\n\n/u/upvoter222, /u/someanonymousaccnt have alluded to **physiological shock**, a condition you are unable to maintain a blood pressure to the extent that it becomes life threatening. There's a huge list of causes but the familiar terms **septic shock** and **toxic shock syndrome** fit into this category.\n\nWhen you talk about somebody appearing calm after suffering some calamity, this probably refers to some form of **[dissociative episode](_URL_1_)**, which is psychological response to overwhelming pain / emotional stress / other psychological stress. Some people describe the experience as being *dream-like* or as if they were watching it *happen to somebody else* and not to themselves. Dissociative episodes are one of the symptoms of **[PTSD](_URL_0_)**, though having an episode does not necessarily mean you have PTSD. It's also an effect of certain medications. This is what I think /u/redleadereu and /u/rafflecopter are referring too.\n\nIn your example, he could very well have both: physiologic shock from blood loss and psychological shock from pain.\n\nEDIT: grammar",
"Shock is best defined as a state of hypoperfusion. Basically, in a normal state, your body moves blood around, through its network of arteries and veins, and delivers oxygen. Heart, Veins/Arteries, and Blood equal Pump, Pipes, and Pepsi. There is a problem with one of these three when a person is in shock... \nHypovolemic shock: Not enough blood. You are bleeding out. \nSeptic Shock: Systemic infection causes massive dilation of pipes, leading to relative hypovolemia. \nCardiogenic Shock: For some reason (there is a bunch) your heart isn't pumping effectively. \nNeurogenic Shock: A severe injury to the brain causes the vessels in the body to dilate, (usually below a certain point, as related to injury location). This dilation again causes a relative hypovolemia state. \nAnaphylactic Shock: This is a sever allergic reaction, which causes a massive dilation of vessels, leading to again, a relative hypovolemic state. \nPhyscogenic Shock: A shock of various causes, this can usually occur when people are scared or witness something they deem horrible or whatever. This is only temporary. Usually these people may feel dizzy, lightheaded, faint, feel the need to vomit. Best guess is it results from a rapid increase in sympathetic tone. ( basically, your fight or flight system just kicked into overdrive ) \nAlong with that, True shock can be either \"compensating\" or \"decompensating\". Compensating shock is when your body has this things happen, you are in a state of hypoperfusion, but your body is holding its own. For example, your heart rate increases, your body shunts blood to the core, you basically are dealing with the situation. At this point, a person's blood pressure usually rises. Decompensated shock is when these mechanisms start to fail. Your body can no longer keep up with the demands. Your heart can only beat so fast for so long. It is at this point that people's blood pressure usually begins to decline. This is when shit gets real. \n\nAs far as people dealing with pain, it is mainly due to the compensatory mechanism of releasing catecholomines. You're body says \"oh, shit, this is bad...\" and you get flooded with adrenaline and things. \n\nEDIT: I spelled shit wrong, and my grammar sucks. Sorry. "
]
}
|
[] |
[] |
[
[],
[],
[
"http://en.wikipedia.org/wiki/Posttraumatic_stress_disorder",
"http://en.wikipedia.org/wiki/Dissociative_disorder"
],
[]
] |
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