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{ "a_id": [ "e4cch3e" ], "score": [ 3 ], "text": [ "I'll try. Libet instructed his subjects to make a small wrist movement whenever they felt like it. He also instructed them to note the time on a clock regarding the moment they first became aware of deciding when to move. Of course they were all wired up to have their brains activity recorded. \n\nTurns out that Libet consistently found an electrical spike called the readiness potential (RP) 200ms before the subjects reported becoming aware of their decision to move. This strongly suggests that at least some of what we assume to be free and conscious decisions are actually pre-decided unconsciously.\n\nLibet himself didn't interpret the results as a refutation of free will, and has argued against those who have. He believes that we have free will in the form of veto power over unconsciously directed decisions. Critics say that even this \"free won't\" is nevertheless a product of unconscious activity and effectively the equivalent of free will.\n\nOthers have followed up on Libet's work and have found even greater lag times between the RP spikes and subjects' conscious awareness of having made a decision." ] }

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{ "a_id": [ "ehuiazt", "ehuqnt9", "ehvbtzr" ], "score": [ 8, 3, 3 ], "text": [ "As I understand it, getting something into orbit is more about going sideways really fast than going up really high. You have to go a bit up to get above the atmosphere but then go mad fast in the same direction as the Earth is spinning.. That spin gives a nice like speed boost.\n\nPut those 2 needs together and you get a curved flight path.", "Going to orbit (ie: where satellites and stations are) require going up a few hundred kilometers but also going \"sideways\" **extremely** fast (7.6 km/s for the ISS). \n\nThis sideways acceleration is what makes going into orbit so hard and is why rockets curve after take off. (They begin by going straight up to get out of the dense part of the atmosphere first)", "The flight path you see is called a gravity turn. Basically the bottom part of the atmosphere is *much* more difficult to punch through than the top part.\n\n\nFor the first part you go pretty much straight up to get through the thick part atmosphere (it's so hard to get through that there comes a point where going faster will just waste fuel due to the stacking effect of friction) \n\n\nOnce you've punched through that barrier (If you watch NASA launches, I think they call it passing the point of maximum dynamic pressure or something like that) you can begin to tilt the rocket and accelerate, with the end goal usually being to have the rocket end up travelling parallel to the ground outside of the atmosphere. You just don't want to tilt it too fast, or air resistance will fold your rocket in half and you will not go to space today. That's why the turn appears to be very gradual." ] }

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{ "a_id": [ "dpiuftk" ], "score": [ 9 ], "text": [ "I'm a librarian and an archivist. First off: contact your library. If librarians only advised on issues we were personally subject experts on we'd have to shut down right now. You think I answer questions about eunuchs all day? Of course not. Librarians are familiar with how to find anything, that's what we're trained on, not subject expertise. I can just as easily answer your question as help someone find car repair manuals for a 1988 Honda Accord, having no expertise in either, it is the same essential task to us. Also you're almost certainly going to need ILL with this, since it sounds like your school doesn't support a strong East Asian program? And you'll probably need help working with ILL because we don't typically teach it to freshman library instructional classes, usually just grad students. \n\nSecond: this is way too much for a freshman, slow your roll! No one expects a freshman to be churning out original archival research in a language they don't fluently read! There would be way less college graduates if so. I do archives instructionals with freshman and they typically are me presenting a single document (in English) carefully selected to relate to their classroom topics, and a worksheet with questions like \"Who wrote this document? Who did the writers intend to read or use this document?\" etc. [Talking this level](_URL_1_) is what I expect from a freshman, as an archivist working with freshmen. \n\nWhat you can reasonably use at your level (though this is somewhat advanced for a freshman, but not crazy advanced) is translated published primary source collections. [Here is a good guide to what these are and how to find them.](_URL_0_) The main words to use when searching are \"sources\" and \"documents.\" [This example search turns up what you should be looking for.](_URL_2_) " ] }

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[ [ "http://guides.library.illinois.edu/c.php?g=489191&p=3344216", "https://www.library.illinois.edu/village/primarysource/mod1/index.htm", "http://www.worldcat.org/search?q=su%3ATaiwan+Sources.&qt=results_page" ] ]

{ "a_id": [ "co8rx20", "co8s302", "co8uamz", "co8uogs", "co8vun5", "co8wp8a", "co8xoe6" ], "score": [ 70, 3, 16, 2, 2, 10, 2 ], "text": [ "salt is good for not dying in car crashes and car crashes are worse for cars then salt.\n\nSome places use other things, but salt is really cheap compared to most alternatives, although sand is pretty good.", "No other options that are as effective and not extremely expensive.\n\nWhile sand/gravel can improve traction, it's not really effective in eliminating the ice like salt is. Part of our problem is that we overuse salt because we think more salt = more melting, and that isn't the case. Our overuse has basically ruined our natural waters, and we're only now exploring other options (cheese!) because we have to before we kill off all natural water fish/vegetation. ", "In Minnesota and North Dakota, they tend to use sand, not salt. In these states, though, it is cold enough that the salt cannot actually melt the snow, and so it refreezes and you end up with black ice on the roads, which is counterproductive. In other states whether there is snow but not so cold, wet asphalt is better than gritty snow for traction and so salt is favored for safety. Most people who live in states where salt is used, and by the way also in coastal cities, know that washing the car a couple times a week is critical.", "Not everyone uses salt; where I am, we use sand and dirt - not because of the refreezing issue, but because it's a semi-desert environment and I think the salt is ecologically problematic. \n\nHaving lived in New England where they do use salt, I can say that it is REALLY much better at dealing with ice than sand is. It's a little bit of a pain to have to wash your car's undercarriage, sure, but it's better than sliding all over the road, wrecking and/or dying. ", "If it's above 10 °F, salt is very effective at melting snow and ice. It's also very cheap. There are other chemicals that make good de-icers, propylene glycol comes to mind. They use propylene glycol to de-ice aircraft, but it's not practical as a road treatment because it's more expensive and the runoff is more harmful to the environment than brine. ", "Used to work in the salt industry (yes, it's a thing).\n\nSalt is one of the cheapest substances on earth. As in, you'd be getting ripped off if you paid more than $150 per metric ton. (In fact, the largest component of salt's price is actually shipping. Yes, it costs more to transport salt than it does to produce it.)\n\nSalt does its job (lowering the freezing point of water) incredibly effectively and is ludicrously abundant in nature.\n\nIts crystalline structure can also be manipulated in order to have sharper edges that reduce bounce. So that allows it to stick evenly to critical surfaces such as roads.\n\nYes, there are alternatives. Usually salt/gravel mix or sugar beet based solutions. Those have less of an environmental impact when the spring melt washes it into the drain. This is more used in places where balance of water salinity for the safety of aquatic life is important. Propylene glycol, a water displacer, is even used in some places where it's so cold that salt won't work effectively.\n\nBut salt is by far the cheapest, most effective solution for preventing the icing of roads. And your government wants above all cheap and effective solutions that reduce winter accidents and keep people safe. They don't care as much about the finish on your 1994 Honda Prelude.", "yeah, salt is bad for the metal components of cars.\n\nDo you know what else is bad for cars? skidding on ice and crashing.\n\n" ] }

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{ "a_id": [ "chbw4a2", "chbwk32" ], "score": [ 4, 5 ], "text": [ "Keep in mind \"America\" can mean everything from northern Canada/Alaska to Cape Horn at the southern tip of South America and these lands (in the north) did have humans on them far before the Vikings landed. Remember that there was a land bridge during the last glacial period (more than 10,000 ago) and it is generally thought that peoples who lived on what is now called Asia simply walked across to what is now Alaska. They probably then migrated slowly south. \n\nThe Wikipedia article is fairly straightforward: _URL_0_\n\nTL;DR: People have been in the Americas for many thousands of years, most likely having come from Asia by land.\n\nSource: I'm a human geographer. \n\n\n", "2 things:\n\nTo this day, the colonisation of the pacific islands stands as one of the most brillant feats of navigation. The time scale you describe speaks far more to the excellence and motivation of the Pacific islanders as navigators than it does to any ability of the Europeans. Cook established through his first contacts with Pacific islanders that they could navigate extraordinarily accurately using simply the stars and swells on the ocean as guides. The use of wave patterns in particular is not unlike the way waterstriders use triangulation to locate floating objects. It seems Pacific islanders used similar methods to locate new islands.\n\n2 - There were other Europeans between the Vikings and Columbus, such as the Basque." ] }

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[ [ "http://en.wikipedia.org/wiki/Settlement_of_the_Americas" ], [] ]

{ "a_id": [ "d02squu" ], "score": [ 3 ], "text": [ "Modern websites, especially popular ones are not a standalone computer running a webserver. They're usually part of a full network of servers. \n\nFront end web servers that receive a request from users. Web caches that store commonly requested pages and data. Databases and file servers for a lot of the back end data.\n\nSo front end webserver can be programmed to follow this sequence:\n\n1. check if page is available in the web cache, use that if possible. \n2. if web cache is unavailable or slow to respond query database and file server, use that if possible \n3. Fall back to an error page of \"overloaded\" or \"down for maintenance\"" ] }

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{ "a_id": [ "cx29unz", "cx2asq5", "cx33ky9" ], "score": [ 8, 3, 2 ], "text": [ "This is commonly done and is sometimes called *rolling over* a loan. The problem is that the amount due will keep increasing due to interest charge, and eventually it will be so large that no one will be willing to loan you that much.", "If you are doing this responsibly (*refinancing*, *consolidating*, or *rolling over* loans: explained later), there is nothing problematic, and is perfectly acceptable. On the other hand, if you are just doing this to keep ahead of the loan collectors, this will hurt your credit rating, and eventually result in nobody wanting to loan you money.\n\n\nRegarding those three cases:\n\nRefinancing a loan is when you take out a new loan that is more favorable to you than the old loan: often because interest rates have come down (if your old loan was at 3%, and you can get a new one at 2.75%, that's good for you), but there are other reasons as well.\n\nConsolidating loans is where you take out one big loan to cover several other loans. For example, if you have a car loan, a mortgage, and a student loan, you might take out a new mortgage to pay off all three other loans, so now you only have one (larger) loan to pay off.\n\nRolling over a loan is when you switch who you are borrowing money from. Maybe the bank you had your loan with has been treating you badly, or maybe you want all your business to be with the same bank, or maybe you've moved and don't want to be paying your car loan to a company in another state, or whatever. So you borrow money from one bank, and use it to pay off the other bank.", "Getting a loan lowers your credit score. When your credit score gets too low, nobody's going to loan you more money.\n\nIf you try to borrow from loan sharks, you'll quickly realize that the amount of money they expect in repayment is *far* greater than what a bank charges. You'll quickly run out of sharks willing to lend you the money you need." ] }

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{ "a_id": [ "dcpe3v7", "dcpe6fu", "dcpek8o", "dcpevzr", "dcpjuyi", "dcpjxge", "dcpm9ib", "dcpmkiu", "dcpp6wt", "dcpqicm", "dcpqmwe", "dcpqvsk", "dcprnl9" ], "score": [ 295, 18, 7552, 7, 13, 1585, 2, 5, 17, 3, 2, 2, 2 ], "text": [ "In short, divers have two main ways to ‘jump in’ from a scuba dive boat:\n\nThe Giant Stride Entry (requires a stable platform from where to step off; common in larger boats)\n\nThe Backward Roll Entry (preferred technique when the boat is smaller, less steady, and lacks a secure platform or ladder)\n\nPlus, think about this: walking around in fins is difficult and you're carrying the weight of a scuba tank (not light)- it's easier to roll backwards off the boat than to walk to the edge and stride off. ", "One method is to take a step off the boat into the water - this works well when your boat has a platform that you can step straight off of into the water. If you're trying to enter the water over a gunwale going forwards, your flippers will get in the way, making it difficult to smoothly enter the water. Instead, divers sit on the gunwale, which allows them to smoothly lean back into the water, rather than making an awkward forward step over the gunwale.\n\nSitting on the gunwhale also helps ensure you won't hit your tank or head against anything as you enter the water.", "If they don't go back first, they go feet first. Both for several reasons.\n\n1. Out of the water, the tank is **heavy**. Imagine doing a belly flop while wearing a backpack full of cinder blocks. You hit the water, then the pack hits you. Ouch.\n\n2. Hitting the water face first means you get the mask smacked into your face. Ouch again.\n\n3. Some kinds of SCUBA gear will have bits extending behind your head. Going face first means you have a good chance of smacking the back of your head on them. Not fun.\n\n4. When you hit the water, you are less concerned about landing on the guy that is already in the water than you are about the next guy in line landing on *you*. Going back first means you can see what's going on above you and move if needed.\n\n5. Lastly, sometimes shit happens and you need to quickly ditch your gear. If you are face down, you have to get out from under the stuff after you undo the buckles, risking getting something getting caught in a stray loop. Face up means everything is below you, thus much less risk of getting snagged.", "When walking from shore, it's easier to walk backwards with fins on. \n\nWhen sitting in a small boat you usually face inward while underway, and it's easier to just fall backwards over the side than to turn yourself around.\n\nPerhaps another reason is that hitting the water face first could dislodge your mask or regulator.", "I understand what you meant, in fact most people did but divers can be dicks... So we have two different kinds of entries when diving. \n\nThe first is called a 'giant stride entry' which is what is says on the tin. You take a big stride into the water. This is typically off of the back of a big hard boat or from a shore entry with a drop below. Don't hop in because you're likely to hit your cylinder on the entry point and knock yourself clean out (I've dragged a couple of people out who have done this.)\n\nThe second, which is the one you're on about, [is typically out of a rigid hulled inflatable boat (RHIB.)](_URL_0_) The reason we roll off backwards is because the boat will rock like crazy if you try to stand up in heavy dive gear. It's pretty low in the water and you're also less like to knock any gear off as you enter. Everyone needs to go at the same time or you risk clocking someone in the face with your cylinder.\n\nThe super fun entries are negative entries using RHIBs off of big boats in strong currents - you roll into the water as a group with no air in your jacket and head straight down. Feels like being a navy seal.", "In the PNW we very rarely use the seated back roll entry technique unless entering the water from a boat like a zodiac or similar. Usually we use a giant stride entry when entering from boats or docks. But the reason for the seated back roll is because when you're diving you have a lot of heavy and loose gear, and you want to be in control of it all and yourself the whole time. The seated back roll (SBR from now on) is really good for wrangling your hoses and accessories in front of you where it can all be held onto while at the same time holding the clasp of your weight belt. It also allows you to lead with the hardest heaviest and least fragile part of your body and gear: the tank. If say, a log floated up next to the boat while you were managing all your gear and getting ready to take a dip, and you didn't see it, when you roll backwards, your tank shields you from the blow of hitting the log from a small height with sometimes nearly 100 lbs of gear on top of you. It also serves to propeller you away from the boat quickly and with little effort. This way, you clear the boat, which may be bobbing up and down on rough seas, as well as allow someone else to enter behind you. It also serves to, usually, orient you facing the boat when you surface so you can signal the boat that you're OK and do not need assistance. Also, if the seas are you specially rough, your tank breaks the water for you so you don't get smacked in the face with an upswell right as the boat breaks the crest of the previous wave and you fall face first into it (no fun). \n\nTl;Dr - it's easier and safer than the alternatives sometimes. \nSource - am PADI Divemaster, out of teaching status Master SCUBA Diver Trainer. Yes, I know, we have the best \"ranks/titles\"", "Most are correct. One additional reason is because it's nearly impossible to walk forwards with flippers on your feet. Source: am PADI diver and can't walk forwards with flippers on my feet. ", "Actually most SCUBA divers dont usually enter the water backwards, and ill get to that in a second.\n\nBut first the answer to your question. I assume that the entry technique you are referring to is when the diver rolls backwards of the side of a smaller boat.\n\nIn that case it is because when geared up you are crazy top heavy, and most people are not super graceful on land when in full gear. Couple that with a small and rolling boat, and you must be able to put your gear on and drop in to the water without standing up. It also minimizes the risk of people dropping in on top of each other, as divers will each drop from a different spot on the boat, and once they hit the water they can see the boat and get out of the way of the next diver. As a side note doing \"negative\" (non floaty) entries from small boats in rough waters makes you feel really cool.\n\nHowever there are many other entry techniques which are also very common. In a lot of places people dont dive of boats in the first place, and when shore diving you would just walk out into the water, or do a \"giant stride\" if there is a dock or something. A giant stride is common from bigger boats and is just a fancy word for stepping of the boat forwards.\n\nOf course there are tons of ways to get in to the water, and a part of being a good diver is to choose an appropriate one for the situation. When diving of my familys sail boat for example I usually make my gear buoyant and throw it down first before going in after it, since the entry is quite high and there is not much room up on the back. A favourite entry of mine as an alternative to a giant step, is to do three quarters of a flip forwards and land on the tank (on my back). But that is only with people I know, it looks kind of uncontrolled and is not a favourite with DMs and boat crew, its good fun tough.", "Simple explanation for a five year old: \n\nBecause it's easier to sit on the side of the boat and fall backward into the water than it is to lift your feet with fins, stand on the narrow side wall of the boat, balance yourself for a second without falling back into the boat, and then jump forward into the water.", "We only do that on boats where it's not practical to jump into water feet first, like on inflatable boats. Space in these boats is scarce and the two big tubes on the sides are hard to step over (especially with fins, in a thick suit, and with 25kg of gear on our backs). Standing on the tubes is dangerous as they are slippery, unstable and not flat , so it's easier (safer) to sit on them and fall backwards. Generally speaking, in an inflatable you avoid standing up when you have your gear on anyway.\n\nWith any boat that has a big platform in the back, it's much easier to jump feet first.", "Everyone here is giving you fantastic information without actually answering your question. \n\nThe reason scuba divers don't go in face first is the risk of blowing out the glass in your mask. Secondary to that would be the risk of your regulator (breathing apparatus) being knocked out of your mouth.", "Not sure where everyone gets the idea that face first entry would hurt your face or rip your mask off.\n\nI am a disabled diver, certified through HSA and when doing boat dives I do a modified sit roll sometimes face forward, others side roll and my mask and regulator stay on. I hold it both hands but as a low level quad my fingers don't work so I'm just pressing my hands to my face.\n\nThe only thing is we must make sure to tuck chin to chest to avoid getting hit in the back of the head by the tank .", "I do the seated back roll from small boats out of convenience because of the heavy gear. I do mostly shore dives however which typically involve just walking on in." ] }

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{ "a_id": [ "efhumyz", "efhwsur" ], "score": [ 6, 2 ], "text": [ "So... look at the sky. \n\nNow. With your hand make a circle \nNow through that circle, focus on only the sky you can see in the perimeters of your hand. Imagine zooming in almost endlessly, finding millions of different cosmic clusters just in those small confines. \n\nNow pick another random part of sky. Do it again and voila! You found a new galaxy.", "not all galaxies are created equal - some are a lot larger/brighter than others\n\nit's like not being able to see a firefly a meter away from you because it has a stadium spotlight behind it, which even if it doesn't dazzle or blind you, still masks the presence of the closer object" ] }

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{ "a_id": [ "eke19jh" ], "score": [ 4 ], "text": [ "Well seeing as how humans are mammals. And mammals are animals. And we have have one. \n\nYes other animals do too" ] }

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{ "a_id": [ "d6hbomw", "d6hlw1x", "d6hxp2i" ], "score": [ 120, 10, 4 ], "text": [ "Your metabolism's job is to regulate the temperature of your body. \"Metabolizing\" food is basically like setting it on fire in your body and using the heat for energy. \n\nIn the extreme heat, your body temperature is already high. So your body doesn't burn the energy it has as aggressively (your metabolism slows down) so that you don't overheat. This decreases your appetite.\n\nIt's also why you have less energy and feel wiped out after a hot day. You still needed that energy, but your body converted less to avoid overheating. Basically put you in low power mode.", "Your body is a heater. It stays at 98.6°F like *all the time*. To keep it hot, you put food in it. If it is cold outside, you need more food. If it is hot, you need less.", "TIL that people in texas are fat, because of heat-induced-slowed-metabolism, rather than because heat makes things expand..." ] }

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{ "a_id": [ "cjsmf2t" ], "score": [ 5 ], "text": [ "It's when it's turned to stone after millions of years. The wood becomes buried underground where it's preserved because of the lack of oxygen, and as water flows through the ground on top, the minerals enter the wood and replace the organic material. Eventually all of the organic material is replaced by mineral, and the wood is now stone which has kept its original structure." ] }

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{ "a_id": [ "cjd98se", "cjd9y97" ], "score": [ 13, 2 ], "text": [ "I guess I'd tackle this question by first addressing what \"in the texts today\" means. Biblical versions in modern languages are translated from what's called *critical editions* of the NT. A critical edition is produced by taking the earliest manuscripts of the NT we have, comparing their texts and--through certain (quite complicated and contentious) processes--determining the common \"archetype\" for these manuscripts, which is thought to be close(r) to the original texts. (Big caveat on the term \"original text\" [here](_URL_0_), if you're looking to get waaay into some hardcore stuff.).\n\nMuch more could be said about this process, but the salient point is that the \"texts today\" are really based on manuscripts (or reconstructed texts) from the 2nd-5th centuries--which doesn't lie *too* far away from the time of their original composition. (Though there are many other texts--for example the Homeric works, etc.--for which the earliest manuscripts are ~1,500+ years after the time of their original composition, and yet are almost certainly very close to the \"original\" texts.)\n\n_____\n\nThe question is then this: if we can reconstruct, with good confidence, what the NT texts looked like in, say, the (mid-to-late) 2nd century, *how do we know that the texts weren't changed in the time between their original composition (in the mid-1st to early 2nd century) and then*? \n\nThere are some general methods for determining this. One of the main ways in that interpolations into the texts are often times *disruptive* to their style/vocabulary/syntax/flow, etc. Perhaps if one were unscrupulous enough to actually attempt to alter these texts, they were at the same time careless enough to not spend a lot of time making sure it wasn't an obvious intrusion into these elements of the text.\n\nBut there are other cases in which there is no consensus as to whether something is a secondary interpolation or not. Some of the most hotly-debated passages here include things like 1 Corinthians 14:34-35 and 2 Corinthians 6:14-7:1. People can be trigger-happy about proposed interpolations, though; and you can find discussion/analysis of tons of proposed interpolations in books like William Walker's *Interpolations in the Pauline Letters*. \n\n____\n\nFinally: there are a few instances in the Hebrew Bible where what we think of today as a single \"book\" was originally a shorter original work, with later redactors then taking another (later) related work and adding it to the original one, so that it's almost like a \"collection\" of books within a single one. For example, in the Wiki article for the book of Isaiah, you can find this:\n\n > The scholarly consensus which held sway through most of the 20th century saw three separate collections of oracles: Proto-Isaiah (chapters 1–39), containing the words of Isaiah; Deutero-Isaiah (chapters 40–55), the work of an anonymous 6th-century author writing during the Exile; and Trito-Isaiah (chapters 56–66), composed after the return from exile. While one part of the consensus still holds – virtually no one maintains that the entire book, or even most of it, was written by one person – this perception of Isaiah as made up of three rather distinct sections underwent a radical challenge in the last quarter of the 20th century.\n\n(The book of Enoch is another great example of this, with the divisions between the separate works that comprise the \"one\" book even more obvious.)\n\nHowever, proposals of a similar process taking place in the NT have not held large sway. Yes, it's virtually uncontested that, say, the author of the gospel of Matthew copied large sections of the gospel of Mark; but this is merely a *utilization of another source*--it's not like Matthew is just Mark + another autonomous work tacked onto it.\n\nPerhaps the most comparable thing in the NT is in the composite nature of things like the [Second Epistle to the Corinthians](_URL_1_): that this \"single\" epistle was actually several separate letters that were then compiled into one \"collection.\"", "We rely primarily on [Alexandrian Text-type](_URL_8_), as it is the oldest we have. It is older than [Byzantine Text-type](_URL_9_), which is what was used in Orthodox churches, and for the King James translation.\n\nThe oldest types of texts we have are [papyri](_URL_1_). The oldest one we have of those is [Papyrus 52](_URL_4_). However, it is just the corners of a page.\n\nProbably one of the oldest texts you would consider a \"book\" would be the [Codex Sinaiticus](_URL_5_), and the [Codex Vaticanus](_URL_2_). These are both [uncials](_URL_10_), which are generally more complete than the papyri. There are also more recent [lectionaries](_URL_11_) and [minuscules](_URL_12_).\n\nMany manuscripts were found in [Oxyrhynchus](_URL_3_) about one hundred years ago. As koine said, we currently use a critical edition of the New Testament, with the most popular being the [Novum Testamentum Graece](_URL_6_). You can look more at how the New Testament manuscripts are [categorized here](_URL_7_). And you can see a list of [textual variants here](_URL_0_). Some variants will be noted in your Bible translation. A major one is the ending of Mark. There are two endings known, both of which are later additions to the text. The first verse also has some controversy as to whether it contains a later addition.\n\n/u/koine_lingua, if I made any mistakes, please tell me/correct me." ] }

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[ [ "http://www.reddit.com/r/AskHistorians/comments/2c8iw2/how_close_to_the_original_texts_is_the_new/cjdeb86", "http://en.wikipedia.org/wiki/Second_Epistle_to_the_Corinthians" ], [ "http://en.wikipedia.org/wiki/Textual_variants_in_the_New_Testament", "http://en.wikipedia.org/wiki/List_of_New_Testament_papyri", "http://en.wikipedia.org/wiki/Codex_Vaticanus", "http://en.wikipedia.org/wiki/Oxyrhynchus_Papyri", "http://en.wikipedia.org/wiki/Rylands_Library_Papyrus_P52", "http://en.wikipedia.org/wiki/Codex_Sinaiticus", "http://en.wikipedia.org/wiki/Novum_Testamentum_Graece", "http://en.wikipedia.org/wiki/Categories_of_New_Testament_manuscripts", "http://en.wikipedia.org/wiki/Alexandrian_text-type", "http://en.wikipedia.org/wiki/Byzantine_text-type", "http://en.wikipedia.org/wiki/List_of_New_Testament_uncials", "http://en.wikipedia.org/wiki/List_of_New_Testament_lectionaries", "http://en.wikipedia.org/wiki/List_of_New_Testament_minuscules" ] ]

{ "a_id": [ "cn5t6y7" ], "score": [ 2 ], "text": [ "Disclaimer: I liked Generation War, for what it was, a piece of entertainment; and fairly decent combat scenes.\n\nNow, with that out of the way, I do agree there needed to be a huge suspension of disbelief. My eyebrows merged with my hairline when the 'Token Jewish Friend' made his first appearance. This was unheard of; the Series begins prior to Barbarossa so you wouldn't risk much more than negative attention from the regime at that time, but association or hiding of Jewish persons later on would be a death sentence. It wasn't just farfetched it was insulting; It *really* did seem like it was an alleviation of German guilt. \n\nOthers have taken issue with this as well. Poland did not take well to the depiction of the RKA. There has been arguments that there was heavy anti-semitism before and after WWII in Poland, but the series depicts them as so *collectively* anti semitic that it accomplishes nothing more but to say \"See look, we weren't the only ones!\" Its intellectually dishonest, and the Polish Newspaper \"The Catholic Weekly\" wrote a [good review](_URL_0_) (Use a good translator there) that echoes these sentiments and has some nuggets of info on the actual RK.\n\nIf I could inject my opinion here; I don't think the producers of Generation War meant to deliberately alleviate German guilt, however, based on how it was recieved abroad and the general touchiness of the subject, it certainly appeared that way. As a piece of entertainment, *of course* you need to be able to sympathize, empathize and relate to the main characters - so they become essentially decent people. The 5 main characters are meant to represent ''the typical Germans'' however, so its one big foggy looking-glass. " ] }

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[ [ "http://tygodnik.onet.pl/swiat/oprawcy-mimo-woli/xr8st" ] ]

{ "a_id": [ "dm3rl5t" ], "score": [ 2 ], "text": [ "I can specify for Early Medieval rather than necessarily High Medieval, although there is some considerable overlap. In essence, the answer boils down to the fundamental values of medieval kingship. A medieval king has three major responsibilities: to defend his people, to justly uphold the law, and to maintain the faith. In particular when dealing with early medieval kingship, such as in Anglo-Saxon England, it was vitally important for a king to be seen as a brave and competent military leader. This is why, for example, Harold Godwinson fights on foot in the middle of the battle line at Hastings in 1066.\n\nIt may seem dangerous to have your heirs alongside you in a battle, but symbolically, it could almost be *more* dangerous for them to be seen to be avoiding battle, and thus be weak. The *Anglo-Saxon Chronicle* portrays a long tradition of heirs taking part in conflict, either alongside their fathers and brothers, or often leading armies independently. According to Asser's *Vita Ælfredi*, King Alfred, for example, was initially unlikely to be a king, and trained for priesthood, but as his oldest brothers were killed, he begins accompanying his older brothers into battle and learning to be a military leader.\n\nAlfred's own son, Edward, campaigned extensively alongside his father in the 880s and 890s, and according to William of Malmesbury, his grandson and future King of England, Æthelstan, was raised in the Mercian court of his aunt Æthelflæd, and accompanied her military campaigns against both the Welsh and the Vikings. During Æthelstan's reign, his brothers and heirs Edmund and Eadred both take part in the Battle of *Brunanburh* alongside the king, and the *Anglo-Saxon Chronicle* describes them leading the charge into the Viking lines.\n\nWhere this tradition is not in effect, it can cause issues. The reign of Æthelred II \"the Unready\" is beset by issues, many of which stem from the fact that he takes the throne as a child and only comes of age to rule independently in the 980s, a decade after his accession. Lavelle (2002) and Roach (2016) both suggest that many of the political problems in Æthelred's reign begin after the deaths of his late father's ministers, who had been largely administering the kingdom. These men were widely respected as experienced leaders, and had fought and campaigned together, and the young Æthelred lacked the experience, symbolism or practiced charisma of leading men into battle." ] }

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{ "a_id": [ "c3taxkv", "c3tbbxd", "c3tcrw3" ], "score": [ 3, 3, 2 ], "text": [ "What's more discouraging is the more common scenario, where you think you're going to lose 10 pounds a week and then gain 1 because you don't realize how hard dieting is.\n\nThe Biggest Loser, like all TV, is about entertainment. A realistic diet program would have half the people losing no weight and maybe the best 1% losing 2 pounds a week; that would be incredibly uninteresting to watch.", "I'd imagine they lose said weight under very close supervision by health professionals. A contestant suffering health issues from rapid weight loss would be a huge liability for the network so the contestant's dietary and physical activities are probably very heavily scrutinized.\n\nSome random dude doing it at home won't have such supervision and would likely be far slower to react to negative consequences should they arise, so they prescribe a far more gradual approach to weight loss.", "It's much easier for morbidly obese people to lose significant amount of weight since there's more to lose to begin with. When you weight 400+ it's not impossible at all to lose 10 pounds a week. Those people normally get very little exercise and eat a lot of calories, so any change in lifestyle will result in weight loss. For example, you will gain one pound for every 3500 calories you consume, so if a fat person normally consumes 5500 calories a day and now you are making him eat only 2000 calories a day, he will lose several pounds within one week. If he exercise on top of that he will likely to lose more. \n\nNotice that weight loss will become harder and harder as you get thinner. On the show no one can lose more weight the second week than they did for the first week, and a person approaching his ideal weight will have to work extra hard to lose the last several pounds. His body is used to the workout routine and diet, so he will need to workout even longer or eat even less to break the plateau. " ] }

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{ "a_id": [ "ff87xou", "ff891px" ], "score": [ 2, 3 ], "text": [ "Because of the segregation of the races way back when it was societally acceptable to publicly oppress certain peoples.", "1. Wealth distribution and property values make a self-feeding cycle. More money in one neighborhood means better upkeep of buildings and infrastructure. This increases property value, which in turn encourages developers to invest more money into high-end developments.\n\n2. Cities (and states and countries) have a different attitude and approach to wealthy and poor areas. This is why government housing (projects) and industrial zones still exist and are built in poor areas, while nicer areas become zoned for parks, schools, and high-end businesses and residences.\n\n3. Natural economics means the liquor stores and pawn shops continue popping up in bad areas, while designer clothing stores and fancy cupcake bakeries open in good areas." ] }

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{ "a_id": [ "cjyurfo" ], "score": [ 5 ], "text": [ "[Andalusian Cadence!](_URL_2_) Also known as the Diatonic Phrygian Tetrachord--sometimes written as i-bVII-bVI-V (or, in the key of A, the descending sequence A, G, F, E)\n\n [the Dorian tetrachord--](_URL_1_) A popular melodic pattern of Ancient Greece[5] offers a possible starting point for the Andalusian cadence. A sequence more or less close to the Greek tetrachord structure might have been known to the[ Moors in Southern Spain](_URL_0_) and spread from there through Western Europe. The French troubadours were influenced by the Spanish music." ] }

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[ "https://www.youtube.com/watch?v=5pidokakU4I" ]

[ [ "http://en.wikipedia.org/wiki/Andalusian_cadence", "http://en.wikipedia.org/wiki/Descending_tetrachord", "http://www.wnyc.org/story/worlds-most-used-musical-sequence/" ] ]

{ "a_id": [ "c8jsiu8", "c8jujwv", "c8k082s" ], "score": [ 6, 2, 2 ], "text": [ "Because the earth is a whole lot heavier than the moon. Even an asteroid large enough to crash and knock out a moon-sized piece of the Earth would barely change the orbital speed of the Earth. Think of it like standing on the highway and throwing a rock as hard as you can at an oncoming semi-truck. Then you wonder why the truck didn't slow down. Sure, you probably made a dent in the metal wherever you hit it, and it slowed down *a little*, but not nearly enough to send it hurdling into the sun (ok, the analogy falls apart there). Also, because of the mathematics of orbital mechanics, orbits can change considerably and still remain stable, so even if something so large were to hit us that our momentum changed by a considerable amount, the Earth wouldn't get \"knocked out\" of its orbit", "[This is why](_URL_0_)\n\n...Please don't remove this for being a quasi-joke, it really is the answer!", "Who's saying it didn't get 'knocked' out of its previous orbit to some extent?\n\nThe Earth-Moon system are now on an orbit which is the combination/sum (for lack of better terms) of the combined orbits of the proto-Earth and proto-Moon. Both objects were almost certainly on relatively similar orbits.\n\n\n\nAlso remember that it takes a *frightening* amount of energy to move a given mass up or down the gravity well of a solar system. To move the mass of the proto-Earth substantially out of its previous orbit would have taken a staggering impact.\n\nThe 'Mars-sized' object that struck the proto-Earth, was not on some drastic comet-like orbit, likely rather on a similar intersecting orbit with a more glancing/gradual blow. Had the orbit been drastically different and the speeds and impact angles so much greater, the resulting explosion would have been a lot more catastrophic. Even then, the leftover mass that didn't reach escape velocity would have eventually returned to the Earth/Moon system, impacting one body or another and settling in the combined orbit." ] }

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[ [], [ "http://www.youtube.com/watch?feature=player_detailpage&v=jgizA0R6Ncs#t=29s" ], [] ]

{ "a_id": [ "e01zmue", "e020lgm", "e025pbu", "e02752q" ], "score": [ 38, 16, 123, 3 ], "text": [ "Haven’t experienced it myself, but I thought they purposefully gave abnormal/weird tasting foods to chemo patients because patients start to associate their shitty nauseous feeling with what they ate and they don’t want patients to develop an aversion to normal foods. ", "Chemo kills tastebuds. Also, some chemo drugs are metallic and result in a metallic taste. Also, chemo sucks balls. ", "\"Everything changed for me\" \n\n\"I'll never forget the day that everything tadted like tofu. Everything tasted like nothing.\"\n\nSource, wife who went through chemo last year. \n\nTastebuds are fast turnover cells that regenerate and die quickly. Chemo kills the tastebuds before they can develop and mature. What taste you lose is specific to you individually. \n\nSource, same wife who is also a doctor. ", "Huh... I find this interesting....\n\nMy dad was just diagnosed, and one of the reasons was he said everything tastes terrible to him. He went from eating like royalty all the time, to only wanting beefaroni, and oatmeal.\n\nThe doctor said the cancer can release enzymes that change the way food tastes, but once the chemo starts he will be back to normal.\n\nHow is that possible? Can someone explain that?" ] }

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{ "a_id": [ "ds0n7jg", "ds0oc2w", "ds0oh3q", "ds0pqig", "ds0pul2", "ds0q6v2", "ds0qftv", "ds0qp7u", "ds0qvke", "ds0r43j", "ds0ruob", "ds0rz39", "ds0s3ik", "ds0s63s", "ds0sbfd", "ds0sup3", "ds0w2c4", "ds0w323", "ds0wegq", "ds0xvfy", "ds0y4qn", "ds0z5p7", "ds10cfs", "ds10cr5", "ds10fbv", "ds10qk8", "ds11dsf", "ds11ht2", "ds13p2b", "ds148kb", "ds17x4q", "ds1a06n", "ds1jjme", "ds1ww93", "ds07pw3", "ds084u9", "ds0a5pd", "ds0aoxl", "ds0cw0l", "ds0ehwj", "ds0gbkx", "ds0guz4", "ds0hq5g", "ds0hu9v", "ds0i87a", "ds0igpc", "ds0iyi1", "ds0j8cb", "ds0k7rm", "ds0koob", "ds0kq4d", "ds0l3ll" ], "score": [ 26, 64, 16, 13, 4, 3, 54, 11, 48, 39, 3, 13, 3, 4, 7, 10, 2, 3, 5, 2, 3, 2, 3, 3, 3, 8, 2, 4, 3, 3, 2, 2, 2, 2, 1468, 88, 66, 72, 1248, 92, 59, 278, 303, 509, 37, 18, 764, 4, 66, 128, 17, 280 ], "text": [ "Awesome! I'm looking forward to many enlightening discussions of the cultural significance of Legend of Zelda: Ocarina of Time!", "Don't forget the year the British formally handed over Hong Kong to China. That should lead to some interesting questions and plenty of good Rush Hour references. ", "Now we can talk about the *Second* Congo war! (or at least year 1 of it)", "1998 actually starts to feel recent(and a year ago I would not have said the same about 97). Probably because I was a teenager. Yanks win get back to the WS. Ocarina of time is released. Phil Hartman died and that bummed me out since his character on the Simpsons was always so enjoyable. ", "Happy New Year!\n\n^What ^is ^“is”?", "Happy New Year everyone! \n\n(I'm not a contributor but let me say this: big thanks to everyone answering and moderating the sub - keep up the great work, you often make my day! )", "I did not have historical relations with that year.", "I was in the museum of the world longest suspension bridge this summer. \n\ntldr: don't build a bridge there", "If I’m currently on the West Coast, do I have to wait another five hours to post questions about 1998?\n\nEDIT: NEVERMIND, Tubthumping came out in 1997. It’s been fair game all year and I haven’t asked!", "Finally! I can have a question answered that's been burning in my mind for 20 years!\n\nWhat exactly is the function of a rubber duck?", "Not much people will ask about new about Israel. But that’s no prob. I’ll just be here.", "Did Tennessee's national title in 1998 set the Vols up for the decade plus run of failure they've experienced by giving Cutcliffe a chance at being a head coach and increasing fanbase expectations to an untenable level?", "Aww man I feel old now. I'm history.", "Hey everyone, looks like the mods are all out drinking! Feel free to shitpost away! HNY", "*Say, one thousand nine nine nine, ask those questions, any time*\n\n*We gonna party with historians reprobate, like it's Nineteen Ninety Eight!*", "What is the definition of \"is\"? Did we ever actually find out? Did anyone even really care since we apparently never did find out?", "May 2018 is just a month - it will be impossible for to that to be a year. \n\n/s", "I feel old reading this...", "Thank you for the starting gun. Drat! I didn't get the first 1998 question with [Did President Clinton's oral sex change US attitudes towards oral sex?](_URL_0_)! Beaten by\n\n~~/u/MaesterMagoo on Hong Kong~~ Happened in 1997, so that wasn't a new 2018 question.\n\n/u/jimjay: [Hugo Chavez was elected in 1998 - how did someone who had tried to lead a coup and overthrow democracy end up getting elected?](_URL_1_)\n", "I'm officially history!", "Ask me about my first divorce!", "Does Viagra rhyme with Niagara?", "1998, the year I graduated from High School.\n\nI don't feel any older...what happened?", "Woot! I do have a lot of questions about the asian market failure, hoping for good answers!!\n", "So did we ever figure out who exactly wanted to know if that guy was Jimmy Ray?", "Oh good. Now I can finally get to the bottom of who’s responsible for Smash Mouth", "Pretty excited about the questions of nuclear tests of india and Pakistan in 1998.", "Fun fact: in 1998 I was 20. So I'm about to double my age. ", "Oh man, the year half of this subreddit apparently graduated high school, and I... Ate solid food? *Maybe* started walking?", "It makes me feel old that the year of my birth can now be “history.”", "Is there a similar subreddit that has similar moderation/perspective for more recent events?", "The true origins of the Attitude Era can start to be fully unraveled. ", "Historians, how many hours did I spend playing Sim City that year? ", "I'll have whatever relations with 1998 that I want, thank you very much.", "To be fair, you have to have a very high IQ to understand Askhistorians comments. The historical analysis is extremely subtle, and without a solid grasp of Critical Theory most of the posts will go over a typical reader's head. There's also the mod team's nihilistic outlook, which is deftly woven into their content curation - their personal philosophy draws heavily from Pyrrhonic literature, for instance. The flairs understand this stuff; they have the intellectual capacity to truly appreciate the depths of these stickied comments, to realize that they're not just warnings against shitposting- they say something deep about LIFE. As a consequence people who dislike the Askhistorians mod team truly ARE idiots- of course they wouldn't appreciate, for instance, the humour in Automod's existencial catchphrase \"[deleted]\", which itself is a cryptic reference to Abelard's epic *Logica nostrorum petitioni sociorum*. I'm smirking right now just imagining one of those addlepated simpletons scratching their heads in confusion as /u/sunagainstgold's genius unfolds itself on their computer screens. What fools... how I pity them. And yes by the way, I DO have a complete Subreddit Rules tattoo. And no, you cannot see it. It's for the ladies' eyes only- And even they have to demonstrate that they're within 5 karma points of my own (preferably lower) beforehand.", "С Новым годом! Happy New Year! Жаңа жылыңызбен! ", "Happy New Year, everyone at AskHistorians!\n\nDoes this mean I can ask questions about the Good Friday Agreement, then?\n\n:D", "Since you mentioned it.. wasn't N*sync's manager revealed to be a child molester? Did he ever abuse any of the members of the band?", "Excellent, my knowledge of Starcraft can finally come of use", "I actually am pretty interested in the antitrust case against Microsoft and the international space station though. Please people, ask lots of questions about those.", "Yesssss, we can do the East Africa bombings. We're getting closer to the 21 Year Rule. You could say that it's the looming tower before us. [Everything that has transpired has done so according to my design.](_URL_0_)", "you're kidding, Martin you lazy piece of..... *grumbles off into the distance*", "I'm now a historical object!", "Only a few more years until the 9/11 questions flood in. I hope you are all ready for that day.", "I have little to contribute in this subreddit but the answers from here are one of the best reads from anywhere as I have general interest in history... erm in general, so I wish everyone great holidays and more good questions and good answers in here for me to read! (selfish but true :) )", "Thank you all for your hard work and being the best subreddit on reddit. ", "Does that mean we can discuss Clinton’s impeachment from December 1998, but NOT the 1999 Senate trial? ;)", "Happy new year everybody! May the new year bring everyone happiness.", "1998?! That isn't history. I mean it was only like 5 years....fuck. I'm old aren't I? ", "Hi,\n\nWhat is the definition of is?", "Thanks for making me feel old! My fav podcast has a 50 year role, and academic historians generally shy away from topics if the political records haven’t been released yet (we’re in the 70s now). I though my lifetime was free from historical analysis, guess not. ", "What was the cultural impact in 1998 when The Undertaker threw Mankind off Hell In A Cell and plummeted 16 ft through an announcer’s table? " ] }

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[ [], [], [], [], [], [], [], [], [], [], [], [], [], [], [], [], [], [], [ "https://www.reddit.com/r/AskHistorians/comments/7ncz6b/did_president_clintons_oral_sex_change_us/", "https://www.reddit.com/r/AskHistorians/comments/7nb39r/hugo_chavez_was_elected_in_1998_how_did_someone/" ], [], [], [], [], [], [], [], [], [], [], [], [], [], [], [], [], [], [], [], [], [], [ "https://imgur.com/gallery/Zv4Go4v" ], [], [], [], [], [], [], [], [], [], [], [] ]

{ "a_id": [ "ek4ijfy", "ek4w7kb" ], "score": [ 2, 3 ], "text": [ "Animals that can see stars see the same stars we do, but they don't all see them the same way. Bees and reindeer can see ultraviolet light, and there are a few species of mantis shrimp that can see colors and waves no other creatures on Earth can see.", "There are two reasons why they see the same stars.\n\n1. Pretty much every star gives off light in the visible spectrum.\n\n2. Pretty much every animal can see the visible spectrum. \n\nSo effectively, we all see the same stars. The only reason some animals might see more or less is their sensitivity to a star's brightness. Some stars that are just barely fainter than our sensitivity to light will be visible to more sensitive animals and vice versa. Stars might also look a little different if animals are colorblind to certain regions of the spectrum relative to others, but they will continue to be visible." ] }

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{ "a_id": [ "epe5rcs" ], "score": [ 7 ], "text": [ "We don't exactly know, unfortunately.\n\nThere were legitimate reasons for English people not to accept her as queen. When William I died in 1087, William Rufus immediately went to London to be crowned at the Tower; when William Rufus died in 1100, Henry I immediately went to London to be crowned at the Tower. When Henry I died in 1135, Matilda ... stayed in France, where, despite her role of heir presumptive to the English throne and former Holy Roman Empress, she was the countess of Anjou. She was pregnant at the time, and since her previous pregnancy had been quite dangerous, it's likely that she didn't want to risk the travel. That's fair, but as her cousin Stephen of Blois *did* cross the Channel and had himself crowned in London just a few weeks after Henry's death without any real reaction from her, it seemed quite natural for people to consider him the rightful king. He persuaded the Archbishop of Canterbury that Henry had forced his unwilling barons to swear the oaths acknowledging her as heir, and that he'd repented of it on his deathbed, so the Archbishop performed the coronation and Stephen effectively had God's mandate to rule. There was no opposition at the time.\n\nMatilda's husband had begun fighting for Normandy (which was an English possession at the time; remember, it was William I's home turf) soon after this, but Matilda didn't get involved in presenting herself as the rightful ruler of England until 1139. She appealed to the pope and Stephen counter-appealed and won. Turning to military means, she enlisted the help of her brother, Robert of Gloucester, and made his county her base. She would basically take over southwestern England - which is not the part with London in it. Once she captured Stephen in early 1141, however, she was broadly allowed to have become queen, with the backing of religious authorities that had previously supported her cousin, and that's when she decided to get herself crowned in London to get the divine stamp of approval. She moved to take the city with soldiers, but was met by Stephen's forces, under his wife's command; when she succeeded, she was at first welcomed, but then, as you know, the Londoners turned on her and she was forced to escape.\n\n*The Lioness Roared: The Problems of Female Rule in English History* lists the reasons given by primary sources, chronicles of the period: Henry of Huntington said that God caused the city to rise up; the Worcester chronicler wrote that the citizens asked her to let them live under \"the excellent laws of King Edward\" rather than her father's \"oppressive ones\" and she refused; the author of the *Gesta Stephani*, overall not a fan of hers, demanded a tax they didn't want to pay. The author, Charles Breem, interprets these criticisms as discomfort with a queen taking on masculine hardline authority, instead of acting with forgiving gentleness and compromise. This was not just a simple \"women shouldn't do men things\" - Stephen's wife directed his soldiers in protecting and retaking London, and the chroniclers were clear that this was brave and virtuous of her - but in large part there were people using \"this is not appropriately-gendered behavior\" as a justification for issues they already had. In this case, whatever the specifics, the Londoners didn't really want Matilda in the first place, and they probably wouldn't have been happy if she *had* released Stephen or taken a very publicly gentle stance." ] }

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{ "a_id": [ "ds0w4xl" ], "score": [ 2 ], "text": [ " > Time crystals, can this idea be simplified?\n\nThink about a salt crystal, it has a regular cubic structure which repeats in each of the three spatial dimensions. You can imagine a 3D lattice with each axis having a repeating sequence of atoms bonded together.\n\nNow imagine that time is a dimension just like the spatial ones. A crystal in the dimension of time would have a repeating structure over time; basically it would cycle between states in a regular fashion. A \"time crystal\" then is a form of matter which cannot exist in a static equilibrium and instead cycles between states over time." ] }

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{ "a_id": [ "cse3yj1", "cse3ynb", "cse47fr", "cse6vm7", "cseewza" ], "score": [ 37, 8, 2, 3, 3 ], "text": [ "Sounds like low blood sugar. You may have a prediabetic condition. It would be good to see a doctor.", "Hmm I don't think this relates to the majority of people. Seems like a personal condition. I would for sure get it checked out if you feel that you need to. Could be related to diabetes. But I am not a doctor.", "Your body has nothing to sustain it so its breaking down at a faster pace, causing you to get heated and tense, hence the shakiness. It's also related to low blood pressure. ", "I get this exact same feeling also, it is horrible. It comes on fast and you feel like you are sweating and breathing heavy and heart pounding. I would like to know why ( I know it's low blood sugar for me, but why can't I just feel hungry instead). I sometimes don't even feel hungry when it happens. I am in good shape, and go to the gym regularly, pretty skinny. Weight 167/5'11. \n\nMy stepmom is diabetic (type 2 though) and one time I was feeling this way I borrowed her blood tester and my blood sugar was about 47. I checked it a few more times to see where my threshold was when this would happen and it was always around 50 or less.\n\n I don't know why my bloodsugar tanks like that all of a sudden. I tried to be on a clean diet for a while because I wanted to see what kind of results I could get from the gym but I found that even if I am full, my bloodsugar gets low unless I eat carbs or sugar. I cannot physically survive on non fat/sugar free foods without having the shakes happen.", "Thanks everyone for the advice I really appreciate it. " ] }

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{ "a_id": [ "cewjh54", "cewk7hx", "cewswwy" ], "score": [ 7, 7, 3 ], "text": [ "[By developing this.](_URL_0_)\n\n\nAlso by [capturing one of them,](_URL_2_).\n\nWhat was known was that the thing could turn like a beast and climb like a Valkyrie. It was very maneuverable and fast. Nothing the US had could come close to it. However once the US captured one they found that it could turn great but when forced to roll it performed horrible. Also if you dove and made them chase you the engine of the Zero would stall out. With this knowledge strategies where adopted. Once the F6F came into the picture it was game over.\n\nAlso of note was that like with almost EVERYTHING in military terms the best pilots/soldier wins. The Japanese had pilots that where REALLY good and experienced that flew the Zero's. Once they started losing them they where not able to refill their ranks fast enough and keep the staffed long enough before the US killed them. This led to a feedback loop of great planes being staffed by worse and worse pilots while the US got better and better pilots.\n\nEdit: Also to Add to Backgrinders comment [Joe Foss](_URL_1_) a Marine Pilot ripped 4 Zero's apart in one pass to show you how vulnerable they where. Also I may be incorrect but Zeros did not have resealing gas tanks so one bullet = bad news.", " It should be noted here that superior is a bit of an awkward word choice in your first question. The Zero was a fine aircraft, and provided superior performance in some ways, but it was inferior in others. The Zero was designed with extended range operational capacity first and foremost, so it was a very, very light aircraft. This contributed to making it particularly fast and agile, because speed is determined largely by power to weight, and a lighter mass means you can turn quicker with the same amount of force on the control surfaces. \n\n The lighter weight also meant compromises though, primarily in defensive armor. Zeros were highly maneuverable and trouble one on one, but they were easy to knock down as well. Tough and durable is exceptionally important in combat, the Zero was neither of these things. Think of it like in American Football. It isn't much use being the fastest guy on the field if one hit knocks you out and you can't play the rest of the game.", "**The outbreak of war**\n\n/u/backgrinder gave an excellent look at the compromises in the Zero’s design. I would like to expand on that portion of the answer, as well as add some other details. The Zero was indeed designed for excellent range. The Japanese knew that being able to fly a long distance would be of great importance in any war they ended up in. As such, the Zero was built with the demand that it be able to fly a very long way. It was able to fly nearly two thousand miles without refueling. The Brewster F2F Buffalo and the Grumman F4F Wildcat—the Zero’s main competitors at the beginning of the war—were able to fly only about a third of that distance. To get this range, the main thing that had to be done was lose weight. This did indeed lead to excellent maneuverability. \n\nSo, why did the American planes not have this range and maneuverability? Design choices led to very different solutions to the same problems of naval aviation. The US Navy demanded rugged planes that could survive the rigors of hard landings onto pitching flight decks. To get reliable and rugged aircraft, you add things like more bracing, redundant systems, and heavier landing gear. Also, with the Wildcat features like pilot armor and self sealing fuel tanks were added. All of this added weight, which had costs of its own. As has already been mentioned, range and maneuverability were restricted. However, there were advantages as well. Stability and speed in a dive were improved. Also, the same rugged characteristics that allowed good peacetime reliability meant that more battle damage could be absorbed by a plane before it became crippled or destroyed.\n\n**Thatch weave**\n\nThe ability to absorb damage is a good thing, but if that’s all you can do you’re still going to end up losing a fight. One on one, the Zero was able to get onto the tail of an American plane and destroy it. American pilots could not hope to climb or turn with a Zero, and individual brilliance was not enough to turn the tide. A new approach was needed.\n\nEnter John Thatch of the United States Navy. He tested out a new system that bears his name, [the Thatch weave.](_URL_0_) The wikipedia page has some good diagrams of how this innovation works. Instead of working one on one, American pilots flew as a team. Pair(s) of planes would weave through the sky. If enemy pilots attacked one element, the other would soon be on their tail. Now, the rugged nature of the Wildcat could be used to full effect. When they came under attack, they could absorb a few moments of fire while their teammate got into position to attack the pursuing plane. This tactic was employed to good effect at Midway, and it was soon picked up by the Cactus Air Force on Guadalcanal. The Thatch weave allowed for much greater success against the Zero. Since it had no pilot armor or self-sealing fuel tanks, the Japanese planes could not simply absorb battle damage and would quickly be destroyed. However, if the weave was not executed perfectly US pilots were quite vulnerable. Any mistake would leave US pilots very much alone in a plane that could not hope to match the acrobatics of their opponent.\n\n**Attrition and training**\n\nOne sometimes overlooked element of the Pacific theater was attrition. The Japanese entered the war with a cadre of highly experienced pilots. These men had been in combat for years before Pearl Harbor, and had learned a number of lessons that only combat can teach. In their incredible Zero fighters, they were able to fly circles around less experienced opponents. Those same Zeros would catch fire or succumb to damage quite easily, and unless the pilot was over friendlies he had very little chance of rejoining the war. Further, the lack of pilot armor meant that these highly experienced pilots were vulnerable to a single stray bullet that could end their career—or their life. There were dramatic losses of experienced pilots such as the Battle of Midway, and there was also slow attrition in the skies surrounding Guadalcanal and New Guinea. On the other side of the coin, American pilots received relatively lavish training and their more survivable aircraft allowed men to return home when a Zero would not have been able to.\n\n**Planes at the end of the war**\n\nThe development of the Hellcat was detailed by /u/pmaj82. The development of succeeding waves of fighters is the final part of how the Zero was countered by the US. The F6F Hellcat could match or beat the Zero in every aspect except range. It was rugged and survivable like the Wildcat, but with greatly added speed, rate of climb, and agility. And the Hellcat wasn’t alone. It was joined by the Chance Vaught F4U Corsair. (I like just *saying* that phrase. Chance Vaught F4U Corsair, try it!) These planes were as iconic to the Pacific theater as the P-51Mustang and P-47 Thunderbolt were in the European theater. In addition, there were Mustangs deployed in the Pacific as well, primarily due to their incredible range and high altitude capability making them ideal escorts for the B-29 Superfortress. \n\nNow, the technical capabilities of these planes is somewhat obvious. The less obvious event that went hand in hand with their success was the *production* of these fighters. American aircraft production dwarfed that of the Japanese. The American economy was able to produce huge numbers of highly advanced aircraft, and was agile enough to switch production from prewar designs to those designed during the war. While most of the other combatants in WWII were able to upgrade existing airframes during the war with more powerful engines and improved subsystems, the US was able to field entirely new fighters with seeming ease. Then, the US was able to make these new planes in the thousands. Paired with giving their pilots sufficient training, this prodigious rate of production resulted in a highly capable force that was able to island hop all the way to the doorstep of the Japanese home islands. Along the way, the Zero was first supreme, then contested, and finally driven from the skies by a succession of planes, tactics, and pilots." ] }

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[ [ "http://en.wikipedia.org/wiki/Grumman_F6F_Hellcat", "http://www.ibiblio.org/hyperwar/USMC/USMC-C-Aces/index.html", "http://www.history.com/news/the-akutan-zero-how-a-captured-japanese-fighter-plane-helped-win-world-war-ii" ], [], [ "http://en.wikipedia.org/wiki/Thach_Weave" ] ]

{ "a_id": [ "c4af7kp" ], "score": [ 4 ], "text": [ "**Entropy** is the amount of energy in a system that is not available to do work - that is, it is \"waste heat\" that isn't useful. We know from thermodynamics that entropy is a measure of how likely a particular process will happen. Because a process that produces more randomness in the system is statistically favored, we say it has higher entropy. And while it is possible to increase the amount of order in the system (think of water freezing), we can only do this by using another process that produces even more entropy than you lose. This is the Second Law of Thermodynamics: the amount of entropy in the universe will always increase (ΔS_universe > 0).\n\nFor your class, just imagine that each substance in your chemical equation has a temperature-dependent amount of \"randomness\", which we track as the variable \"S\". A change in entropy is written as \"ΔS\". Entropy is a \"state variable\" - practically, this means that the value of S doesn't depend on how the substance arrived in that state (the path didn't matter, just the destination).\n\nEntropy is measured in units of energy/temperature (i.e. Joules/Kelvin).\n***\n**Enthalpy** is a measure of the total energy of a system. For your class, you can just visualize it as the amount of \"useful work\" a system can do. We track it as the variable \"H\", which we can't directly measure. Because of this, we are ever only interested in \"ΔH\", the change in the energy of the substance. Enthalpy has units of energy, usually expressed per mole of material (Joules/mol). Like entropy, it's also a state variable, which will be important when we get to Hess' Law.\n\nEvery chemical equation has a \"ΔH_rxn\", which is the amount of heat absorbed or released by the reaction. If the system has less energy than before, ΔH is negative, and heat has gone from the system to the surroundings (\"exothermic\"). If it has more energy, ΔH is positive, and heat has gone from the surroundings into the system (\"endothermic\"). We can measure ΔH directly by using a calorimeter (you've probably used one in your class experiments).\n\nEvery substance has a \"ΔH_formation\", which is the ΔH of the reaction used to form it from its elemental parts. For example, ΔH_f of methane (CH4) comes from the reaction C + 4H -- > CH4 (notice we're using elemental hydrogen, not hydrogen gas). You can think of ΔH_f as \"the amount of energy in this particular compound\".\n***\n**Hess' Law** is what makes that last paragraph useful. Remember how I said enthalpy is a state variable? That means that it doesn't matter what reaction path we take to form a particular compound - ΔH will be the same no matter what. This allows us to use ΔH_f's to compute the ΔH of any reaction we want!\n\nImagine the combustion of methane: CH4 + 2 O2 -- > CO2 + 2 H2. We want to know how much energy is released or absorbed (ΔH_rxn). We could use a bomb calorimeter to measure it directly, but your school was forced to sell all its lab equipment due to budget cuts. But it's okay! Visualize all the atoms of the reactants breaking apart into all their separate C's, H's, and O's. Because this is the opposite of a formation reaction, we can write ΔH = -[sum of ΔH_f_reactants]. Now imagine all those letters recombining to form the compounds on the other side of the equation; this is a formation reaction with ΔH = [sum of ΔH_f_products].\n\nNow for the big finish - since enthalpy is a state variable, it didn't matter that we took two steps instead of one! So just add the enthalpy changes of the two steps together:\n > ΔH_rxn = [sum of ΔH_f_products] - [sum of ΔH_f_reactants]\n\nSo using Hess' Law is really just playing accountant. First, use the table in the back of your textbook to find ΔH_f for each of the compounds in your reaction. Then, sum together all the heats from the products and subtract those of the reactants. Don't forget to multiply each term by its stoichiometric coefficient (two moles have twice as much heat as one).\n\nHope all that helps!" ] }

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{ "a_id": [ "cszrg8h" ], "score": [ 14 ], "text": [ "If we were lined up just right then they could probably see a transit of Venus and Earth. Essentially a mini-eclipse as the planets crossed the disk of the sun. The problem with Jupiter and Saturn is their years are so long they would take a long time to be confirmed. Jupiter takes 12 years to go around the sun, so you'd need to be observing for at least 36 years to confirm a transit. (2 times to determine a year length and a third to confirm it was a planet and not a large sunspot)\n\nAs for seeing the planets directly, nope. The glare from the sun is way too much. If you look at the list of exoplanets which have been directly observed, they are very far out (most are more than Pluto distances away) and much larger than Jupiter. Also the planets are relatively young, so they are hotter and are seen because of the energy emitted by the planet, not reflected from the star.\n\n_URL_0_" ] }

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[ [ "https://en.wikipedia.org/wiki/List_of_directly_imaged_exoplanets" ] ]

{ "a_id": [ "dc7az4t" ], "score": [ 3 ], "text": [ "Most pills are basically small molecules designed to disolve and go right in. Most food is large molecules that need to be broken down first." ] }

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{ "a_id": [ "dd8g5xd", "dd8gpl1", "dd8kxnc", "dd8lj4n" ], "score": [ 6, 12, 2, 7 ], "text": [ "That's about it. Nutrients. Granted, you could get the exact same nutrients from food, too. The placenta is there to provide nutrition to the *baby*, not the mother, and even then usually only before birth.\n\nEating one's own placenta isn't terribly uncommon in the animal world, but that has more to do with the fact that resources can be very scarce than the fact that the placenta is somehow some miracle food.", "Despite the belief of the many health benefits of eating your placenta, there is no conclusive evidence that placentophagy provides any substantial nutritional value. In fact the preparation process (cooking the placenta or drying it for encapsulation) removes a large portion of its nutrients by reducing protein hormones and other things. \nSome suggest that the health benefits perceived by people who consume their placenta is caused by the placebo effect. \nEating your placenta will provide you with about enough caloric energy and nutrition to make it to your next meal in the day (which is the most likely reason wildlife can be observed performing this practice as well). ", "If you're a dirty hippie that believe in that kind of shit, you might get some sweet placebo (placent-ebo?) effects. Otherwise, no, there are no actual benefits. ", "Midwife's assistant here.\n\nPeople use several arguments to justify consumption of their placenta. I will note that in my experience most mothers pay a doula or other person to dehydrate and encapsulate their placenta and consume it gradually in pills after birth rather than snack on it raw, though some people make a post partum smoothie with raw placenta. \n\nHere are the common reasons I here for consumption of placenta post partum;\n\n\"All mammals eat their placentas after birth.\" While true, this is most likely done to keep away predators. \n\n\"It helps prevent post partum depression.\" This is not proven. Anecdotally, it seems to have the placebo effect, and what are placebos best at treating? You guessed it, depression.\n\n\"It helps increase milk supply.\" I take issue with this argument. The birth of the placenta is what signals to the mother's body that it's time to amp up milk production. It signals the release of prolactin. If any parts of infarcts of the placenta are retained in the uterus it will negatively impact a mother's milk supply, so I don't see how re-ingesting placenta would help milk supply. \n\n\"It's ancient Chinese medicine.\" This isn't necessarily a good reason to do something. I think this is self explanatory. \n\nHere is a study that explores common reasons for placentophagy and the science behind it.\n\n_URL_0_" ] }

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[ [], [], [], [ "https://www.nichd.nih.gov/news/releases/Pages/062615-podcast-placenta-consumption.aspx" ] ]

{ "a_id": [ "dqwvb0x" ], "score": [ 5 ], "text": [ "Oh, yes! I have [an earlier answer](_URL_0_) on \"Renaissance women\" bouncing off the idea of Leonardo da Vinci as a \"Renaissance man\" that might interest you. :D\n\nBut that post was narrow in scope to intellectual/polymath types. There were so many more ways that individual women made an impact! Religious leaders claiming gifts of ecstatic prophecy like bitter archrival nuns Domenica dal Paradiso and Dorotea da Lanciuole played active, even leading roles in post-Savonarolan religious politics--their feud spanned a decade and involved the entire city's mendicant community. Catherine of Genoa was a mystic who, more quietly, dictated her teachings to a circle of students.\n\nWomen also involved themselves in the flourishing art scene. Catherine of Bologna is probably the most famous one today. Antonia Pulchi was a playwright, composer, and lyricist of religious dramas and music that were performed in her native city of Florence.\n\nAnd then, of course, there were the aristocrats and politicians. Even though women were barred from holding formal office and in Italy, specifically, were almost never heads of household, as mediators and as proxies for male relatives they wielded a surprising amount of indirect influence and direct power. Alfonsina Orsini ruled Florence from 1517-1519 during yet another period of *male* Medici exile from the city.\n\nThere are two important points to raise here. First, nearly all the standout women from Renaissance Italy we can point to were not married: they were nuns, tertiaries (informal nuns), or widows. With the intellectual/humanist women in particular, the sad pattern is a father providing his daughter the best education possible, she flourishes as a young woman author/philosopher/theologian--and as soon as she marries, ceases public literary activity.\n\nSecond, when we talk about \"Renaissance\" Italy, we are necessarily speaking primarily or exclusively of the upper crust. There are some women among the tertiaries who would have had a more middle class background. But in general, \"the Renaissance\" and its developments were an urban and elite phenomenon. We don't hear about peasant widows making great art or writing religious plays for their village confraternity.\n\nNevertheless, there are some really excellent stories based around phenomenal--for good or ill--women to come out of 15th-16th century Italy. And thanks to the literary grounding of its elite society, we can tell those stories in quite a bit of depth today." ] }

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[ [ "https://www.reddit.com/r/AskHistorians/comments/5riw8w/leonardo_da_vinci_is_often_cited_as_an_example_of/dd7za52/" ] ]

{ "a_id": [ "dprxow0" ], "score": [ 9 ], "text": [ "The Saudis had long backed and had long-standing connections with traditionalist forces in North Yemen. In the 1962-70 North Yemen Civil War (really a proxy war) they backed the Zaydi Shia Mutawakkilite Kingdom of Yemen against the Egyptian-backed Yemen Arab Republic. The death of Nasser in 1970 helped bring an end to the hottest phase of the Arab Cold War and Saudi Arabia recognized the victorious Yemen Arab Republic and worked in coordination with various factions in North Yemen, preferring it over the Marxist South.\n\nYemen's unification in 1990 came at a precarious time. The overall Cold War was ending with a Soviet collapse and Saddam Hussein's invasion of Kuwait threatened to rip apart the Middle East. The president of the newly re-united Yemen, Ali Abdullah Saleh, backed Saddam in sharp contrast to the rest of the Gulf States.\n\nPartly as a result of that the GCC countries split from Saleh, and flirted with the secessionist movement in 1994. As it happened, the 1994 Civil War so brief that I'm not sure you should quite read into it the way the wording of your question suggests.\n\n[Saleh claimed US support](_URL_2_) but it wasn't a major break from the rest of the US' GCC partners. \n\nSaleh won so quickly that the war couldn't become the kind of protracted proxy conflict that characterized the North Yemen Civil war decades prior, or for that matter that characterizes the conflict in Syria today.\n\nThe other motivating issue that remains relevant are accusations that Saudi Arabia is concerned about the potential power of a united Yemen on its southern border. The population of Yemen is at least equal to Saudi Arabia, and that's only if you believe the official Saudi population figures, which are dubious and likely inflated.\n\nYou're not likely to find much in the way of concrete discussion/documentation of any of these factors from Saudi officials, however. Saudi Arabia remains one of the most opaque polities in the world, these Carnegie Endowment articles would be a good overview though:\n\n_URL_0_\n_URL_1_\n" ] }

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[ [ "http://carnegie-mec.org/diwan/62405", "http://carnegie-mec.org/diwan/60627", "https://books.google.com/books?id=WCyiAwAAQBAJ&pg=PA505&dq=us+support+to+yemen+1994&hl=en&sa=X&ved=0ahUKEwjkwO6CyrzXAhXBRCYKHeTvCPUQ6AEIQjAF#v=onepage&q=us%20support%20to%20yemen%201994&f=false" ] ]

{ "a_id": [ "dknyox6" ], "score": [ 4 ], "text": [ "Synchronous call - I'll drop you off at the store and wait her until you come back\n\nAsynchronous call - I'll drop you off at the store and periodically check to see if you are done\n\nMost calls are synchronous because the caller usually wants something right now and can't really proceed without it.\n\nBut if what the call is doing is low priority, can take a long time, or is outside the control of the system, asynchronous calls make more sense. The drawback is they require extra logic to periodically check to see if the call has completed, or if it fails to complete." ] }

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{ "a_id": [ "c90m1bp", "c90ve8j" ], "score": [ 2, 2 ], "text": [ "can't be sure of the exact method, but at the very least you can be sure that Google Maps was not relying on the IP address of your http request to determine your location. ", "In modern web browsers on some types of computers, a mechanism is provided to web developers to determine your location (with your approval). This has nothing to do with how your computer is connecting to the web site. \n\nBasically, the web site asks your browser for your current location (in longitude and latitude). The browser asks your permission (which may have been given previously) and then asks your computer operating system for the location information. \n\nYour operating system uses various techniques to determine its location:\n\n- cell phones, tablets, or other hand held devices may have GPS services available. \n- many devices (phones, tablets, and desktop computers) use wifi to determine location. In a nutshell, they have access to a database of hundreds of thousands of know wifi access points and their locations. By comparing the relative strengths of every access point the computer can \"see\" it can determine your position. \n\nYour operating system tells the browser where you are, and it tells google. " ] }

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{ "a_id": [ "cpiqswk", "cpisivh" ], "score": [ 2, 2 ], "text": [ "The best why I can describe this is how a computer works. A computer processes data and displays that data on a screen. A single core computer is of like the windows 95 or 97 version. The more cores you have the better the computer processes data. This is kinda like what IQ means. IQ isn't how smart you are, it's how well you can process information. The Questions in an IQ test are to specifically to see what you can process and if you can come up with the right answer in a fast enough time. So basically some tasks require a deeper thinking. Those with high IQs can process high amounts of information or the core of a problem at a better rate than someone with a low IQ. Think of someone with mental disabilities. It takes them a while to do a simple task that would be a normal task for someone without those disabilities. ", "Presumably a mental task that requires more effort recruits from more \"areas\" of the brain. For example, a simple discrimination task, such as is this a boy or girl, recruits the visual pathway and then continues down through the ventral pathway towards the temporal and limbic structures so you can then discern whether it is a guy or girl. \n\nHowever asking the persons ethnicity, job, age, and other identifications takes longer (read: effort) as the mental task recruits additional neurons/areas of the brain. Mental effort, which is the emotional byproduct of waiting for information to compute and be integrated, is dependent on several factors. Some of which such as, distance between recruited areas, myelination, and if those connections have been recruited before (long-term potentiation/neuroplasticity). \n\nEdit: which theoretically could be computed using biophysical models of circuit theory (e.g., membrane potentials, conductance, resistance, capacitance)" ] }

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{ "a_id": [ "d81em6h", "d81ffk2", "d81fvjo" ], "score": [ 3, 5, 3 ], "text": [ "In a car meant to take regular, no. In a luxury or sporty car designed for premium/super, yes. \n \nEngines use gasoline by igniting it, high octane gas ignites at a higher temperature than regular octane does, so it can withstand more compression. \n \nWith modern cars, there is no real negative to adding high octane in a car not designed for it. As for any pros, the gas has a slight chance of being better quality; however, going to say a Shell and getting regular compared to a regional company will also be higher quality. \n \nWith cars made for high octane, using low octane used to result in engine ping, but now it just results in slower acceleration.", "Higher octane fuel is more stable at high temperatures and pressures than lower octane fuel. In an engine, there is a thing called 'Knocking' that can happen if you squeeze/heat fuel too much, and it's basically the fuel spontaneously combusting instead of being ignited by the spark plug.\n\nWhy is that a problem? Well in a diesel engine it isn't, because they are designed for it. A gasoline engine, however, is not built for it (literally: less metal, thinner walls, etc). When the fuel spontaneously combusts, two bad things can/do happen.\n\n1. The explosion happens too soon, the piston is in the wrong position.\n2. The explosion starts in the wrong spot, and so it puts stress on parts of the cylinder from directions they were not built to handle.\n\nThis can cause tremendous damage to an engine. Higher octane fuel prevents this premature detonation.\n\nedit: The engineers know what your engine will do under normal operation. IF your engine says it needs 87 octane, you do NOT need higher octane fuel to prevent knocking unless you install a turbo or some other compression/temperature modification to the car.", "A car engine has four \"strokes\" as the piston head moves up and down inside the engine:\n\n* An intake valve opens and the piston moves down, drawing in air and fuel\n\n* The intake valve closes and the piston moves upward, compressing the gas mixture\n\n* The spark plug fires, driving the piston down to produce power\n\n* The exhaust valve opens and the piston moves up, pushing out the exhaust.\n\nDuring the second stroke—compression—the fuel/air mixture is heated substantially. That's what happens whenever you rapidly compress a gas. This compression and associated heat increase is an important part of making a car's engine powerful and efficient.\n\nThere's a danger during that stoke, though: if you compress the fuel/air mixture too much then it could get hot enough that the fuel ignites on its own. This premature ignition is bad for the engine and is bad for efficiency. It's referred to as engine knock or pinging and is something to avoid. Modern engines even have a sensor to detect if it's happening and they'll put some extra fuel into the cylinder to cool things off (the fuel has to be turned from liquid to vapor, which takes energy. You might expect more fuel to be more energy, but there isn't enough air to burn it so you get no extra power from the extra fuel. Pressing the gas pedal gives you more fuel *and* more air, hence more power). If your engine's anti-knock system is dumping extra fuel into the cylinder then that's going to kill your efficiency.\n\nDue to the possibility of engine knock you want to be sure that you have a fuel that can resist autoignition. That's what octane rating describes. That's *all* the octane rating describes.\n\nAn engine is designed to cause a certain amount of compression on its compression stroke. That amount of compression is fixed due to the geometry of the engine. The engine designers will then determine how high of an octane rating is necessary to prevent knocking and will publish that information in the car's handbook. If you put that grade of fuel into the engine then it shouldn't knock (and shouldn't have to take countermeasures against knock), so there is zero benefit in paying more for higher octane fuel.\n\nMost cars are designed to accept the lowest grade fuel that's sold, typically about 87 octane (aside: different countries use different scales; I'm referring to AKI, the scale used in the U.S., which is an average of RON and MON). High performance cars look to get as much power out of the engine as possible, so they often are designed to compress the fuel/air mixture more, therefore requiring a higher grade of gasoline to prevent knock. Check your car's manual and it'll tell you what grade of fuel to use.\n\nA final variable to consider is altitude. If you happen to be at a very high altitude then you can get away with a lower octane rating since the lower density air will also deter knock. Gas stations in high altitude areas will often sell 85 octane fuel which will run fine in a car designed for 87 octane at sea level. Keep this in mind if you're filling up in a high altitude region but are planning to drive to a much lower elevation on that tank of gas." ] }

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{ "a_id": [ "c9orj61", "c9ozmll" ], "score": [ 76, 10 ], "text": [ "Hi there, since this is a crosspost linked to a very popular video on Reddit at the moment, I figured I should welcome some redditors unfamiliar with AskScience.\n\n Welcome to AskScience! We have a few specific rules on this subreddit, you can find them on the sidebar that way --- > \n\nIn a nutshell, please do not respond with personal anecdotes or speculations. Please stay on topic, even though you might have a funny tangent to get that sweet sweet karma (you can post that [joke here instead](_URL_0_)!).\n\nThanks\n\nAskScience Mod Team", "The water, under pressure from the weight of the ice above it, is shooting out of cracks in the ice, and the air temp is cold enough to instantly freeze the water. The new ice lands on top of the other ice, increasing the weight of ice and therefore the water pressure. The water jets out and freezes, and the cycle repeats. " ] }

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[ "http://www.reddit.com/r/videos/comments/1db0cy/ice_needles_flowing_out_of_minnesota_lake_as_it/" ]

[ [ "http://www.reddit.com/r/videos/comments/1db0cy/ice_needles_flowing_out_of_minnesota_lake_as_it/" ], [] ]

{ "a_id": [ "cbtdwt4", "cbtm9d3" ], "score": [ 2, 2 ], "text": [ "Go to a quality site like _URL_0_, create a portfolio (used to be free, now it might require basic membership of around $7 a month, not sure), and set the parameters (such as how much the assumed cost is per transaction fee, account value, etc...)\n\n\nNow, this imaginary portfolio will be tracked and charted as though it was real. Spend a few months learning about the stock market, and buying and selling the money in this portfolio as you think you should. \n\n\nAs you learn and develop new strategies, create new portfolios and test them in a the same fashion. After a few months, you can see EXACTLY how successful the different strategies were... review what worked and what didn't.\n\n\nTHEN, and only then, open a real account and put it on the line. I would recommend Scottrade.\n\n\nIf you figure out a formula that works, the HARDEST THING IN THE WORLD is to stick to it. Don't get greedy... it is easier than you think. Stick to your plan, or stop, scrap the plan in its entirety and re-evaluate before continuing.\n\n\nSOURCE: Used to daytrade a LOT... as in, highest volume year had a 40 page transaction report on my tax return with almost $4 million in trades.", "I hope you're not American, cause if you are, you need more money" ] }

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[ [ "Smartmoney.com" ], [] ]

{ "a_id": [ "ccq75o8" ], "score": [ 3 ], "text": [ "There are a couple of diagrams [here](_URL_0_) that illustrate the direction and *relative* magnitude of tidal acceleration over the surface of the earth.\n\nNote that I would not describe this exactly as \"the moon's gravity tugging on the Earth's surface water.\" This can at least potentially be misleading; for example, consider the example presented in the link above: what would be the effect on the tides of a *second* moon, on the opposite side of the earth (at the same distance)? Would the gravitational \"tugging\" of the two moons \"cancel\" the tides, or increase them? (Answer: the latter.)\n" ] }

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[ [ "http://possiblywrong.wordpress.com/2012/11/17/if-the-earth-had-two-moons/" ] ]

{ "a_id": [ "c2j5lme", "c2j5s2e", "c2j6ele", "c2j6gqr", "c2j6l9c", "c2j5lme", "c2j5s2e", "c2j6ele", "c2j6gqr", "c2j6l9c" ], "score": [ 5, 2, 11, 2, 3, 5, 2, 11, 2, 3 ], "text": [ "Honestly an ELI5 is just going to tell you want to think. There numerous lists and sites out there which go over his stance (as well as others) on individual issues.\n\n[Use the search](_URL_0_), there are 20 threads on Paul here. Check r/libertarian too.", "[Wikipedia](_URL_0_) has a great article that I actually just read today. Very basic and informative.", "In a nutshell, \"Mind your own damned business.\"", "Video introductions: _URL_0_", "Here is a more recent intro site that lays out major issues: _URL_1_\n\nAlso, for a more detailed introduction about a particular issue, you can check out the online version of his new book, Liberty Defined: \n_URL_0_", "Honestly an ELI5 is just going to tell you want to think. There numerous lists and sites out there which go over his stance (as well as others) on individual issues.\n\n[Use the search](_URL_0_), there are 20 threads on Paul here. Check r/libertarian too.", "[Wikipedia](_URL_0_) has a great article that I actually just read today. Very basic and informative.", "In a nutshell, \"Mind your own damned business.\"", "Video introductions: _URL_0_", "Here is a more recent intro site that lays out major issues: _URL_1_\n\nAlso, for a more detailed introduction about a particular issue, you can check out the online version of his new book, Liberty Defined: \n_URL_0_" ] }

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[ [ "http://www.reddit.com/r/explainlikeimfive/search?q=ron+paul&restrict_sr=on" ], [ "http://en.wikipedia.org/wiki/Ron_Paul" ], [], [ "http://www.ronpaulintro.com/" ], [ "http://libertydefined.org/", "http://learnpaul.weebly.com/" ], [ "http://www.reddit.com/r/explainlikeimfive/search?q=ron+paul&restrict_sr=on" ], [ "http://en.wikipedia.org/wiki/Ron_Paul" ], [], [ "http://www.ronpaulintro.com/" ], [ "http://libertydefined.org/", "http://learnpaul.weebly.com/" ] ]

{ "a_id": [ "d8wzw0z", "d8x13r7", "d8x1w2y" ], "score": [ 14, 2, 3 ], "text": [ "_URL_0_\n\n > Latent heat of vaporization.\nIt's generally accepted that water always boils when it reaches exactly 100 Celsius. This is not entirely the case, but we'll assume that it's true for the explanation since it illustrates the point.\nOnce water hits 100 degrees, all heat added to the system no longer raises its temperature; instead the extra energy allows water molecules to break free from the surface tension and escape into the atmosphere, even if the atmosphere is already saturated with water. This is what we characterize as the state change from liquid to gas.\nThis extra energy is not added symmetrically to the collection of liquid; rather, it's transferred as radiant or conducted heat from one or multiple directions. The thin layer of water closest to the heat source absorbs the energy and creates a localized state change into a gas, which can then be reabsorbed by the water and the energy distributed, or can rise as a bubble with more gaseous water and escape the liquid. The more energy you add at the boiling point, the more water that turns to a gas, and the more violent the boil. Convection then replenishes the water against the heat source, which absorbs sufficient heat to vaporize and the cycle continues.\nIf you have a sufficiently hot source and a sufficiently small amount of water, you can flash boil an entire collection of water, like if you throw a cup of water on a lava flow or hot fire - nearly all of the water vaporizes at once. However, this requires a great amount of surface area for the water to contact the heat source, and a very large heat differential between the two.\n\ncourtesy of /u/techadams", "Two reasons:\n\n* The water does not reach boiling temperature all at once - it is heated from somewhere, and the water closer to the source of heat reaches it first. It forms bubbles of steam, and then you get all the incredibly complex circus of fluid dynamics going.\n* It takes a considerable amount of extra energy to go from water at 100°C to steam at 100°C, the [enthalpy of vaporization](_URL_0_) - this makes the whole process \"jerky\".\n\nThe two points together result in the familiar \"boiling\" process with bubbles", "With regards to the Maxwell Distribution, the molecules at the water's surface boils first, then as those molecules leave, the next layer of water molecules boils off and so on. " ] }

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[ [ "https://www.reddit.com/r/explainlikeimfive/comments/2vxexu/eli5_why_doesnt_all_of_the_water_turn_into_steam/" ], [ "https://en.wikipedia.org/wiki/Enthalpy_of_vaporization" ], [] ]

{ "a_id": [ "cgmblsa" ], "score": [ 2 ], "text": [ "Cartilage transition happens in 4 zones, with details [here](_URL_1_).\n\nAll parts of the cartilage is important for load distribution, but where a transition from cartilagenous histology to more bone-like histology appears at the *tidemark* zone. A really good picture of this can be found [here](_URL_0_) showing the transition from more pliant non-calcified cartilage to the hardened calcified cartilage." ] }

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[ [ "http://ard.bmj.com/content/59/12/F1.medium.gif", "http://www.wheelessonline.com/ortho/articular_cartilage" ] ]

{ "a_id": [ "eincfd9" ], "score": [ 3 ], "text": [ "The water you drink travels through your digestive system to get absorbed by cells lining your small intestines and large intestines. These cells pass the water on into your bloodstream, and hence water circulates as blood around your body.\n\nBlood vessels supply the cells in your body with water, oxygen, and other nutrients via diffusion and through other channels. These nutrients are essential for every cell in your body to perform their function \n\nSimilarly, cells in your lacrimal glands (which produce tears) and salivary glands (comprising submandibular, submental, and parotid glands) will use these nutrients as well, and they function to combine water with other substances to form tears and saliva respectively." ] }

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{ "a_id": [ "clwbp6a" ], "score": [ 91 ], "text": [ "There's a very interesting theory about this, called the sperm (or semen) displacement theory. It goes a little something like this.\n\nWay back when, humans, and in particular, human males, weren't so much into the pair-bonding thing, and women regularly had sex with multiple men. This meant that the sperm in the woman's vagina (which can live for a few days) wasn't necessarily 100% yours. Larger penises with coronal ridges (that is, a long shaft with a slightly wider head) created a \"vacuum scraper\" that essentially allowed the most recent male mate to scrape away the semen from the previous mate. Larger penises achieved this more effectively than smaller penises, giving them the selective advantage necessary to become a relatively common trait among human males." ] }

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{ "a_id": [ "czaihgs", "czbchh8" ], "score": [ 4, 2 ], "text": [ "No. You'll burn extra fuel getting up the hill, but you won't save that much going down the other side, because your engine will be (at least) idling, which consumes some fuel.", " In my personal experience of driving a manual transmission car around Colorado I can actually get better fuel economy driving in mountainous terrain then I get driving on flat land. " ] }

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{ "a_id": [ "c2zhq1z", "c2zomij", "c2zhq1z", "c2zomij" ], "score": [ 3, 2, 3, 2 ], "text": [ "0-4ish: pre-school, this is optional but is correlated with higher socioeconomic status and attending is shown to be a good predictor of future success.\n\n5-11: kingergarten (grade 0) and grades 1-6, this is called elementary or primary school.\n\n12-13: middle school, or junior high school. grades 7-8\n\n14-17: high school or senior high school, grades 9-12, with years referred to as freshman, sophomore, junior, and senior. These schools are separated differently depending on the school districts. My schooling has grades 0-6 in one school and 7-12 in another school. This is compulsory until the age of 16.\n\n18+ is university, which typically starts with about 4 years of an undergraduate program, and usually culminates with a bachelor of science or a bachelor of arts, but there are also other programs, such as 5 year engineering programs which end with a masters, or other vocational programs like nursing, etc. Some people decided to go to community college first, which are typically local to each county, and have 2-year programs that reward an associates degree, which can later be applied to the first two years of a 4-year program at a university. Community colleges also have vocational programs like the trades (carpentry, electrician, mechanic), and may have other programs like nursing.\n\nAfter you have a 4-year degree, you can choose to pursue higher (postgraduate) education. Most masters and doctorate programs are examples of postgraduate education.\n\nIn the sciences, most candidates pursuing PhDs are fully funded by their university, and some receive a Masters degree along the way. PhD programs typically take about six years and must include original research.\n\nIn engineering or the liberal arts, you can go for a masters or PhD but these programs are less likely to be funded. A masters usually takes 2-3 years.\n\nThere are also the professions, such as medicine, dentistry, and law, which have their own separate schools and processes, but are still likely to be part of the major universities. These programs are all very expensive, and can be extremely competitive to get into. A typical MD will graduate with $250,000 in debt.", "Something small to add onto what DoubleSidedTape said.\n\nThe specifics of the earlier years very quite a bit even among public education based on state.\n\nIn some cases grades 6 and/or 9 are even considered part of a middle school.\n\nI don't know if colleges and universities have any specific \"rules\" for the name, but if so it would likely be tied to whether they offer masters or above education, which is as far as I know always associated with schools called \"universities\".\n\nAlso, unlike our british counterparts, we don't \"go to university\", that just sounds strange to most americans.", "0-4ish: pre-school, this is optional but is correlated with higher socioeconomic status and attending is shown to be a good predictor of future success.\n\n5-11: kingergarten (grade 0) and grades 1-6, this is called elementary or primary school.\n\n12-13: middle school, or junior high school. grades 7-8\n\n14-17: high school or senior high school, grades 9-12, with years referred to as freshman, sophomore, junior, and senior. These schools are separated differently depending on the school districts. My schooling has grades 0-6 in one school and 7-12 in another school. This is compulsory until the age of 16.\n\n18+ is university, which typically starts with about 4 years of an undergraduate program, and usually culminates with a bachelor of science or a bachelor of arts, but there are also other programs, such as 5 year engineering programs which end with a masters, or other vocational programs like nursing, etc. Some people decided to go to community college first, which are typically local to each county, and have 2-year programs that reward an associates degree, which can later be applied to the first two years of a 4-year program at a university. Community colleges also have vocational programs like the trades (carpentry, electrician, mechanic), and may have other programs like nursing.\n\nAfter you have a 4-year degree, you can choose to pursue higher (postgraduate) education. Most masters and doctorate programs are examples of postgraduate education.\n\nIn the sciences, most candidates pursuing PhDs are fully funded by their university, and some receive a Masters degree along the way. PhD programs typically take about six years and must include original research.\n\nIn engineering or the liberal arts, you can go for a masters or PhD but these programs are less likely to be funded. A masters usually takes 2-3 years.\n\nThere are also the professions, such as medicine, dentistry, and law, which have their own separate schools and processes, but are still likely to be part of the major universities. These programs are all very expensive, and can be extremely competitive to get into. A typical MD will graduate with $250,000 in debt.", "Something small to add onto what DoubleSidedTape said.\n\nThe specifics of the earlier years very quite a bit even among public education based on state.\n\nIn some cases grades 6 and/or 9 are even considered part of a middle school.\n\nI don't know if colleges and universities have any specific \"rules\" for the name, but if so it would likely be tied to whether they offer masters or above education, which is as far as I know always associated with schools called \"universities\".\n\nAlso, unlike our british counterparts, we don't \"go to university\", that just sounds strange to most americans." ] }

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{ "a_id": [ "dcnod7n", "dcnr175" ], "score": [ 2, 5 ], "text": [ "Quick little answer here: \nThe reason for the seasons is because of the angle of the sunlight hitting the earth. When it is summer, the lift is hitting more directly than in winter. Back to different seasons for different hemispheres: because the earth is tilted, when the sun's light hits the earth directly in one hemisphere it will hit less directly in the other. This is also why the equator's seasons are less extreme.", "you seem to be confused - the days do not get longer at just one end of the day. both sunrise and sunset get earlier and later at roughly an equal rate. the closer you are to the poles, the more drastically they change, and the closer you are to the equator the less they change. \n\nthe graphs below help demonstrate this. go to the link, and slide your mouse along the big blue graph with the red line. underneath you will see the sunrise and sunset times growing and shrinking together. (those jumps near the beginning and end is when daylight savings comes in). i chose london and melbourne as the cities to use as examples, both relatively far north and south respectively. \n\n_URL_1_\n\n_URL_0_" ] }

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[ [], [ "https://www.timeanddate.com/sun/australia/melbourne", "https://www.timeanddate.com/sun/uk/london" ] ]

{ "a_id": [ "e0f07e5" ], "score": [ 2 ], "text": [ "It you'd classify them as a \"gang\" (I would) Blackbeard's pirates are interesting." ] }

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{ "a_id": [ "cayp215", "caypiuf", "cayq4bb" ], "score": [ 10, 2, 3 ], "text": [ "I think the easiest way to explain it is: 1/9 = 0.111..., and 9 x 0.111... would be 0.999... for the same reason that 4 x 111 = 444. So we have 9 x 1/9 = 0.999..., and 9 x 1/9 = 9/9 = 1. So we have 1 = 0.999...", "First, we must define what \"0.9999...\" means.\n\nThe '...' at the end means that you should take the limit of the behavior before that. So we want the number that is reached by starting with 0.9, and then 0.99, followed by 0.999, 0.9999, 0.99999... etc. The number we want is the number that this process has as a limit (if such a number exists).\n\nWell, now we need a second fact: if two numbers aren't the same number, then there has to be a definite distance between them. That is, if you give me the two numbers, I must be able to tell you a positive number such that they are at least that far apart.\n\nBut what about the limit of 0.9999... and 1?\n\nWell, if you give me a distance, I can find some number of 9s in a row such that 1 minus that number is less than the distance you gave me. So we can't name a distance between the limit of 0.9999... and 1!\n\nSince we can't say they have any distance between them, they're the same number.\n\ntl;dr: \"0.99999....\" is a statement about a process, like \"3 - 2\", and is just another way to specify the number \"1\".", "I am going to assume you know that:\n\n1/3 = 0.3333...\n\nand \n\n2/3 = 0.6666...\n\nso adding them together you get\n\n1 = 0.9999...\n\njust like you suspected." ] }

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{ "a_id": [ "ddwyo3y" ], "score": [ 2 ], "text": [ "It's steam and it's most likely blowoff from the steam heating system. Power plants generate excess steam and instead of dumping it into the air, they pipe it all over the city to heat buildings. " ] }

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{ "a_id": [ "clc53ui" ], "score": [ 2 ], "text": [ "I'm probably going to offend you in saying this, but this sounds a *lot* like a homework question. If so, we can provide you with good sources, but we can't answer it for you." ] }

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{ "a_id": [ "dnuz27j", "dnv2b59" ], "score": [ 10, 3 ], "text": [ "Typically such a person believes he has been treated unjustly by society, so he is striking back at society in general -- which includes basically everyone.\n\n_URL_0_", "They may believe that they have been mistreated by society as a whole and want revenge, even on strangers. They also may feel like their life was pointless so want to do something that makes them notorious, even in an extremely negative way." ] }

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[ [ "https://www.psychologytoday.com/blog/saving-normal/201405/the-mind-the-mass-murderer" ], [] ]

{ "a_id": [ "c1mg7ba", "c1mg9gi", "c1mgh1c" ], "score": [ 3, 8, 8 ], "text": [ "This should be a last resort (you dont realy ever want to be in a situation where you are in the water). I have seen people say grab onto something which can keep you afloat, a log or part of the surrounding infrastructure still above the water level (try to get out of the water). There are also reports of people out to sea surfing the waves back inland. Due to its long wavelength trying to dive under the break/wave front is impractical, you will be underwater for a very long time (also due to the debris).\n\nEdit: first part of the question\nSpeed and power/momentum also being caught off guard", "I'm not sure that swimming skills would help much. Someone looking at tsunami videos [estimated](_URL_0_) the velocity of the recent tsunami in Japan over land near the Sendai airport at 5-6 m/s. World-caliber swimmers go about 2 m/s during a race -- but that's in nearly-perfect conditions. In a tsunami, you'd be wearing clothes and swimming in extremely rough water.\n\nSo you wouldn't have much choice about where you'd be going, you'd be in rough (and possibly very cold) water with tons of debris and unpredictable currents, you'd be weighed down with wet clothing, and you might be submerged at unexpected times. If you hit something stationary, it'd be like you swam into it twice as fast as an Olympic swimmer goes. Imagine hitting a pool wall like that, and then getting pinned there (the water's still coming!) while debris comes your way at that same speed and the water level possibly continues to rise -- that probably wouldn't end well.\n\nIf you absolutely couldn't avoid the wave, I'd say you'd probably want to find something large and buoyant and hope for the best. You really wouldn't want to swim for it.", "I got dumped out of a raft on a rafting trip. I have no idea how fast the current was but it was August so, relatively speaking, current wasn't too fast and the water was the warmest it was going to get. We had been given directions on what to do if we ended up in the water: assume a sitting/reclining position with feet pointed downstream and rest with feet against a rock if you happened to find yourself at a calm point in the river. I was wearing t-shirt, shorts, Tevas and a float vest.\n\nFalling in the water was the biggest shock. The lower temp just inches below the surface caused me to gasp and I didn't breathe normally for the rest of my short ordeal. I remembered to point my feet downstream but the rush of the current seemed very strong. Between trying to control my breathing and being carried along by the current, I couldn't see anyone else in the river or try to look for the aforementioned calm spot toward which I could maneuver for rescue.\n\nDespite wearing the vest, the water pushed my head under several times. I remember looking up at the sun through a few inches of water and wondering how I'd get my head up to take a breath. Suddenly, the water would push me up long enough to breathe, then it would push me under again. This how people drown: silently. There's no time or energy left to scream for help.\n\nI finally managed to push my feet up against a rock toward which I drifted in the middle of the stream. I tried to stay put, hoping that another raft would be along to pick me up. But the water pushing up against me from behind was really strong. I didn't have the strength to keep pushing back with my legs in order to maintain position. So I let go. Luckily, the rapid gave out shortly after that and I floated in calm water until a raft came by.\n\nTl;dr: There's very little chance you could survive what's sure to be a freezing cold ocean wave flowing at maximum force even if you could keep your fully-clothed wits about you. Which you can't." ] }

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[ [], [ "http://www.abangan.org/2011/03/rough-tsunami-wave-speed-calculation.html" ], [] ]

{ "a_id": [ "dodn7si" ], "score": [ 2 ], "text": [ "If you wanted a picture of every building from exactly overhead you would need to fly exactly over every one. That is a ton of flying, it is much easier just to fly where you can see them." ] }

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{ "a_id": [ "dkw0pwl", "dkw0rxb", "dkw8m5w" ], "score": [ 2, 7, 4 ], "text": [ "There is no reason for luxury cars to make the sacrifices in performance to give them good gas milage as their buyers can easily afford gas. ", "People who can afford and purchase luxury cars aren't usually concerned by mpg. Also these cars often serve as a status symbol, so the bigger the engine, the more expensive and exotic the car is, you look \"better\" with that car. Whereas cheaper cars are aimed towards people who commute, and have to go from A to B while spending the least, so it's a great selling point to be able to travel more for less.", "It's a matter of priorities. Some people want 400 horsepower and 0-60mph in 5 seconds, and are willing to take the poor fuel economy trade-off to get that. Others, especially those with limited budgets, prioritize ongoing costs in addition to purchase price... so they're willing to forego performance to get the good fuel economy. They're fine with 100 horsepower and 0-60 in 12 seconds to spend half as much per year on fuel." ] }

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{ "a_id": [ "ceqm2hj", "ceqo44o" ], "score": [ 5, 2 ], "text": [ "random chance and recognizing false patters. \nHow many faces do your eyes shift to in a full room? 10? 20? A hundred? How often do you catch people's eyes just at the right time? Maybe once? It's not that it happens that often, its that when it does happen, its memorable.", "It's theorized that the Sclera (the white part) of our eyes aids in non verbal communication. Humans are very social animals and in my interpretation of the theory we have evolved socially and visually to make eye contact with each other.\n\nIn other words when you notice someone looking at you out of your peripheral vision you're compelled to look at them. While our white Sclera make it easier to tell if someone is looking your way. \n\nhere is a very small reference for the topic:\n_URL_0_" ] }

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[ [], [ "http://en.wikipedia.org/wiki/Sclera#Role_in_communication" ] ]

{ "a_id": [ "clw6dbt", "clw6qtl", "clw8xxl" ], "score": [ 2, 3, 2 ], "text": [ "The process of making computers is in fact very very expensive, but because they are mass produced the price of an individual computer is relatively cheap.", " > Shouldn't it take a lot of effort to put all of the transistors in the right places?\n\nTransistors aren't \"put in place\". All of the billions of transistors are created together at the same time, using a technique called [photolithography](_URL_0_). In simple terms, CPUs are manufactured in a manner similar to how you would develop a photograph from a piece of film.\n\nYes, it's expensive, but most of the expense is in the development of new processors, and the equipment needed to manufacture them. That cost is spread out across all of the millions and millions of processors that are sold.", "This is the central insight of \"Moore's Law\".\n\nMaking semiconductors (\"transistors\") turns out to be a process where the fixed costs do not correlate to the variable costs. In other words, most of the cost of a chip is the machine that makes all the chips not the individual components of a single chip.\n\nThe technology to make chips smaller and faster keeps improving by doubling about 18 months so the value of the chips made by the machines built 18 months ago is forced to decline.\n\nMaking the smallest, fastest chips is the most expensive part of the industry. But the machines to make larger, slower chips are still working (until they so become obsolete nobody has any reason to buy what they can produce and they're scrapped). That means that the price of a given performance level always declines over time.\n\nIf the price between \"smallest/fastest\" and \"previous smallest/fastest\" becomes too great, consumers will just opt for the previous generation. That puts an upper limit on what chipmakers can charge for the current generation. That limit has remained essentially unchanged since the 1970s. You pay about as much for the highest-end intel CPU today as you would have paid for the highest-end chip in the 70s. But today's chips have doubled in speed and density every 18 months for 40 years so they're billions of times better." ] }

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[ [], [ "http://en.wikipedia.org/wiki/Photolithography" ], [] ]

{ "a_id": [ "c9uf9hc" ], "score": [ 2 ], "text": [ " > that doesn't answer why a smooth brain wouldn't be able to hold the same amount of grey matter with a similar volume to a wrinkly brain.\n\nYour head can only get so big before your neck can no longer support it. So in order for more neurons to fit in the skull, the increase in surface area must be in wrinkles rather than over a smooth area. " ] }

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{ "a_id": [ "dsa4vhz", "dsa50ag", "dsa52ce", "dsa73e7" ], "score": [ 3, 2, 12, 9 ], "text": [ "They have those sensors at the doors and security tags on items. When you checkout they remove or disable the security tag. So when you walk out the alarm doesn’t sound. ", "They have a tiny chip inside them (RFID), and it gets magnetized at the factory. When you buy the item, there is a demagnetizer built into the scanner which deactivates the tag. \n\nThat's why often there is a big sticker saying \"DO NOT PUT CREDIT CARDS HERE\" as the credit cards have a similar magnetic stripe on the back and the demagnetizer will accidentally demagnetize them thinking they are the RFID tags.", "Most theft detectors rely on one of two mechanisms. Small tags and large tags.\n\nLarge tags get removed by the cashier, and are either attached in a way that damages the item if you try and force it open or locked in a larger and more cumbersome package.\n\nSmall tags are usually small magnetic stickers, and are demagnetized during the checkout process. You may see in some stores that there is a large circle on the counter that the clerk slides everything across. That's for small tags.\n\nWith the tags demagnetized, you can pass through the theft detectors without setting off alarms.", "There are a few methods, I'll describe one of the more common ones.\n\nThe item being protected has a small circuit in it, about the size and shape of a postage stamp. It is essentially a radio receiver, and when a certain frequency is applied to it, it emits an echo that can be detected. That's how the alarm part works. \n\nWhen that same radio frequency is applied with high intensity the circuit becomes overloaded and shorts out, permanently damaging it so it no longer echoes. That's how the deactivation works." ] }

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{ "a_id": [ "c6iyquk", "c6iyv89", "c6j0pe6" ], "score": [ 8, 65, 3 ], "text": [ "Entropy is the disorder of a system. The universe is moving toward more disorder, or entropy. \n \nWhat does \"disorder\" mean? Well, chemical reactions that take place without any energy create more entropy, or chaos. For example, when you mix baking soda and vinegar, you don't have to stir the mixture, or heat it, or even shake it, it just starts fizzing up and carries out the reaction. \n\nThis reaction increases entropy. What used to be two orderly substances, the solid baking soda and the liquid vinegar, is now all over the place, broken into multiple parts of gas and liquid, and generally more chaotic. You start with two substances and end up with three. One of which is a gas, and gasses are chaotic because they go everywhere, unlike liquids and solids whose molecules are somewhat bonded to each other.\n\nIf a reaction does not increase entropy, it requires energy. So if I wanted to make a cake, I can't just throw all the ingredients in a bowl and produce a cake. I need to heat it, or apply energy, to cause the reaction. This is because this reaction decreases entropy by taking five or six separate ingredients and turning them into just one finished product. Going from six separate parts to one decreases the chaos of a system. If I threw all the ingredients into the air it would make a really bad mess and create disorder. Cake thrown in the air would be much easier to clean. \n\nEntropy is just the disorder of a system. ", "Here we have a cardboard box, about the size of a shoebox, filled with coins. Not a ton of them, just enough so that the all lay flat on the bottom of the box.\n\nThere are three possible states for that box to be in: all coins heads-side-up, all coins heads-side-down, and the other thing where some of the coins are heads-up and some are heads-down.\n\nImagine the box starts out in the all-coins-up state. We put the lid on and shake it. Without opening the lid, what state do you expect the box to be in?\n\nThe answer is obvious: Some of the coins will be heads-up and some will be heads-down. Why? Because the all-heads-up and all-heads-down states correspond to *exactly one arrangement of coins* each, while there are *many* arrangements of coins that correspond to the some-up-some-down state.\n\nThe \"all-up, all-down, some-of-both\" states are what we call *macrostates.* They're the states we care about, the ones we can easily observe. The individual position and heads-up-or-down-ness of all the coins comprises what we call a *microstate.* It's a state that is normally invisible to us, hidden from view, either because we just don't care about that much detail, or because that much detail is practically impossible for us to measure.\n\nEntropy is, in a sense, how many microstates correspond to a particular macrostate. In this example, the all-heads-up and all-heads-down macrostates each correspond to just a single microstate; that's a very low-entropy condition. But the some-of-each macrostate corresponds to *many* microstates, making that a high-entropy condition.\n\nWhen we started out, all the coins were heads-side-up, but when we put the lid on the box and shook it, the system moved from a low-entropy state to a high-entropy state.\n\nIn nature, systems always tend to move from low-entropy to high-entropy states. In the most abstract sense, this is just because of pure dumb luck: There are more combinations of coins that add up to \"some of each\" than either \"all up\" or \"all down,\" so *pure random chance* dictates that we're far more likely to go from the all-up state to the some-of-each state than the other way around … and furthermore, that as we continue to shake the box, we're far more likely to *stay* in the some-of-each state, because the odds against getting all the coins to land heads-side-up are enormous.\n\nIn reality, this use of pure-dumb-luck-based statistics to describe complex systems is a mathematical approximation. After all, things like the motions of molecules in a bathtub of water aren't really random. They're actually the product of a *huge* number of very simple interactions … but that's the thing. When you take something that's fundamentally simple but that becomes vastly complex because of sheer scale, that thing tends to behave very much like a purely random system governed by dumb luck. So it turns out those dumb-luck-based statistical approximations are actually incredibly useful and predictive.\n\nSo basically, entropy can be thought of as a way of quantifying just how likely or unlikely it is that a complex system will evolve in a particular way. If the evolution you're imagining is from a low-entropy state to a high-entropy state, in general that's pretty likely. If it's the other way around, from a high-entropy state to a low-entropy state, then in general that's probably not going to happen. The more complex the system you're thinking about, the better statistical methods tend to be for predicting the evolution of that system over time.", "Disorder is easy. Order, on the other hand, requires work.\n\nEntropy is the overall natural tendency towards chaos, towards disorder.\n\nSay you spend about 1 hour cleaning your room. You have put work into your room, to make it orderly.\n\nLet's wait a week.\n\nLo and behold, your room is even messier than before! Why? Because disorder is easier to maintain than order. Disorder does not need to be maintained. Your room will get messy on its own. Your room will not get clean on its own.\n\nOrder requires work. Disorder simply happens without intervention.\n\nNow apply this to the universe. The universe is very stubborn, and doesn't like cleaning its room. In fact it never does. It's got a lot of space, so why should it? It's just gonna keep getting messier and messier, for an amount of time our monkey brains cannot comprehend. \n\n/how a professor explained it to me, I thought it was a cute analogy" ] }

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{ "a_id": [ "dihpwk4", "dihq2iv" ], "score": [ 3, 3 ], "text": [ "It's an inverse relationship - the less you want your SO to know you ate it, the more it stains.", "Different fabrics have different molecular structures. These structures allow the colors to take different effects, and they bind with the fabric differently. [These](_URL_0_) can show you what effects the dye can have across a variety of fabrics, and how well they bind or how they react with detergents." ] }

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[ [], [ "https://www.teachersource.com/product/927/forensic-supplies?gclid=CjwKEAjwgtTJBRDRmd6ZtLrGyxwSJAA7Fy-hacyGoELBYKRJp516i-I9I0sOo6qoVsRdPz3e7q8sihoCsB_w_wcB" ] ]

{ "a_id": [ "c3frius", "c3frmsu" ], "score": [ 5, 4 ], "text": [ "Supply and demand work hand in hand to regulate price in an economy. When a new iPhone comes out, the demand for it is high, so Apple can charge a high price for it.\n\n But if Apple overestimates the number of iPhones it could have sold, it will flood the market with surplus iPhones (the supply of iPhones exceeds the demand for them) and they will have to drop the price to convince people to buy these iPhones.\n\nPrice elasticity of demand is a measure of how much the demand of a good changes in comparison to its price. Say Apple starts charging $1000 for new iPhones. The demand would drop drastically because no one wants to pay that kind of money for a cell phone. So the iPhone has an elastic demand.\n\nBut if your city starts charging you 3 or even 5 times for water, your demand will not change much (in fact you may start using exactly what you need and stop wasting water - this will be your true demand since you did not need that excess water). So water has a price inelastic demand.\n\nMarginal cost is the cost of producing each additional good. Say Apple opens a new iPhone manufacturing plant. The cost of producing the first iPhone will be in millions of dollars (the land, building, machines, labor etc), but the next unit will be much cheaper (plastic, glass, processor, microphone, speaker etc). Over a period of time, Apple can produce iPhones for dirt cheap and this is when they start making profit. If that first iPhone sold for $500, Apple lost millions. But when they sell their 1 millionth iPhone, they made a huge profit.\n\nA producer is called a monopoly when it and only it is capable of providing a certain good or service. If tomorrow Samsung/Motorola/Nokia all disappeared and Apple was the only manufacturer of smartphones, it would have a monopoly in that market segment. Governments everywhere try their hardest to prevent monopolies because these are generally not healthy for a free market at all. Microsoft had a near monopoly in the Operating System (and the internet browser segment) market for a long time. You can \neasily google the anti-trust charges against them in several countries and the lawsuits they have fought and lost.\n\n", "Well, I'm not brilliant. Credentials: second year student, economics is a significant part of my degree.\n\nLet's start with the easiest: the definition of 'marginal cost'. In economics, the 'marginal cost' of something is the cost to acquire another unit of that something. Also, it's the rate of change of costs (if your course has any mathematics in it at all, it's the derivative of cost with respect to the good).\n\nThe 'price elasticity of demand' is a little more complicated but still easy to explain. Elasticity is the response of one variable to another. The 'X elasticity of Y' is the change in Y as a result of the change in X. So, if you say something has a price elasticity of demand of -.1, that means that for a 1% increase in price, you'd lose 10% of demand.\n\nA monopoly is when one firm supplies the whole market, so every customer has to go to that firm to buy the product. Almost always, monopoly prices are greater than the equilibrium price of perfect competition, or even duopoly or oligopoly, however there are some firms that operate a 'productive' monopoly in that their vast resources are plowed into research to keep prices low because the 'barriers to entry' (the initial start-up costs of getting into the market) are low. Considering it's an anti-trust course, I imagine you'll see monopolies which are monopolies due to anti-competitive practices, such as engaging in price wars to drive out competition when it does arrive.\n\nSupply and demand is key to micro. It's too difficult to ELY5 all the things about S+D without either an unduly lengthy explanation or a diagram. I'll tell you what the different components are, though and tell you that the intersection is usually the best outcome for everyone. The supply curve (or function, or whatever) represents the cost for suppliers (in aggregate) to provide a certain quantity of goods. The slope of the line is the marginal cost to supply (i.e. how much, as above, it costs to supply an extra unit of a good). This curve is almost always upward-sloping, though it can bend backward. The demand curve, which usually slopes downward, represents the quantity of goods that will be bought by consumers across a series of prices. When the two intersect, that is the price where the magic happens. Everyone goes home happy. The suppliers are making profit and every consumer who wants the good at that price gets it, without any shortages. There is a lot more to it, certainly things about market failure where the magic doesn't happen but that's the basic supply and demand graph in words.\n\nI'd like to point you to a good website of audiovisual slideshows that I found that will take you through all of your questions in a simple manner. _URL_0_ Ignore the crazy photo of the guy in an aquarium. That's just how he rolls. Also, try Khan Academy and YouTube for further details." ] }

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[ [], [ "www.kevinhinde.com" ] ]

{ "a_id": [ "c9ylity", "c9ymh5r", "c9ymmso", "c9ymtv9" ], "score": [ 3, 22, 3, 5 ], "text": [ "The fact that there are no answers yet just further confirms to me that it doesn't matter and I can keep wearing them indefinitely.", "A few different reasons, actually. One, the most prominent, is that your eyes will build up protein deposits on the contacts. The solution you clean them in helps with this, but any solution powerful enough to clean the lens completely is going to be powerful enough to physically break down the lens itself.\n\nAlso, soft lenses will begin to change shape over time to fit your eye, which means their ability to adjust your vision degrades. Hard contact lenses do not have this problem, they will actually slightly reshape your eye, but you lose a lot of the comfort and ease of soft lenses.\n\nContacts are a lot like motor oil in a car. Even if you don't use it, the material that makes it up will eventually just break down and deteriorate over time, but having them in your eye accelerates this process.", "Your eye doesn't like to have things in it. In fact, it's evolved defenses to help get rid of bits of things that get into it. Your eye will attach calcium and proteins to those bits and then use your tears to flush them out.\n\nContact lenses have to be made very carefully and out of the right materials so that your eye won't think that they shouldn't be there. Depending on the materials used and how carefully the lens is made, it will pick up more or less protein and calcium.\n\nLess expensive two-week contacts aren't as good at keeping the proteins off, so they build up over time (and make your lens feel scratchy on your eye). Cleaning them helps take some of that buildup off, but over time they get more and more covered (if you look at really old lenses, you can sometimes see bumps or cloudy areas--these are proteins and calcium).\n\nThese buildups can also block the very small holes in the lens that let oxygen reach your eyeball, which can lead to infections or other damage.\n\nAlso, another part of your eye's defense is the chemicals in your tears that kill germs and break down bits of stuff that make their way into your eye. Less expensive contacts aren't always as durable, so between the chemicals in your tears and the wear and tear of cleaning them they are more likely to tear. If they tear in your eye, little bits of contact can get stuck in the corner of your eyes (or further) and make your eyeball get red and irritated. The sharp edges of the tear can even scratch the outer layer of your eye (the cornea) and give germs a place to grow, leading to infection.\n\n**tl;dr** - Cheaper lenses build up gunk faster and can tear in your eye, possibly leading to infection.", "Soft contacts are sponges, which is why soaking them in the solution helps clean them out. Just the same why they recommend you use different eye drops from regular contactless eyes. As you wear your contacts, a couple things are happening that aren't in the contact's favor:\n\n * You blink. \n\nIt happens, you can't really do anything about that, but you do. And blinking across this soft sponge causes friction. This even happens when you sleep and experience REM cycles. The friction wears on the contacts REALLY slow (It would be a long long long time before you manage to wear through them) but its tiny scuffs and scrapes that, while not harmful to your eye, further expose the lens to contaminants.\n\n* You build up protein. \n\nDon't expect to do any bench presses with your eyeballs anytime soon, it's not the fun kind. This is really evident when you sleep with them in and your eyes get crusty. Being a sponge, the lens sucks that stuff up and while letting it soak helps wash that out, it gets less and less effective with time.\n\nThe difference in extended wear contacts and more disposable types is really the quality of that sponge and how long it will hold up to the conditions. If you don't remove them before too long, you *can* damage your eye, but it isn't always obligatory to remove them *within* the stated period.\n\nElevators recommend a carrying load a bit lower than it can actually hold specifically so you don't inadvertently test it and get hurt." ] }

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{ "a_id": [ "cn1h5q5", "cn1j1jg", "cn1op4i" ], "score": [ 3, 3, 3 ], "text": [ "They have plenty of methods. Let's go with gas chromatography:\nVaporize your liquid and inject it into a gas chromatograph (a long column coated with an inert substance). The test substance moves through the column, interacting with the inert coating, causing the various chemicals inside it to separate out (as some \"stick\" to the coating and move slowly through it, while others just flow right through). \n\nA detector at the end senses when each component comes through, and compares the time with the time of other chemicals on a database (for example, chemical x took 7.03 seconds to emerge, which matches up with chemical A on the database - therfore x is A). \n\nIt's not 100% accurate, since some chemicals will take 7.031 seconds and others 7.029, so if both are present, one will \"hide\" behind the other and it'll be difficult to distinguish between them. But the guys who do this are pretty smart, so they'd figure chemical x is more likely to be carbon than uranium (using completely random examples there). ", "Some methods for determining the identity of unknown samples include:\n\nMass spectrometry- fragments and separates samples based on mass. The pattern of fragmentation shows the likely functional groups attached to the molecule and determines the mass of the parent molecule. This method is usually coupled with gas liquid chromatography to further purify and separate the sample. \n\nFourier Transform Infrared Spectroscopy- blasts the sample with different wavelengths of infrared light, causing different bonds to vibrate. Bonds will vibrate at certain wavelengths based on what they are attached to (functional groups) and by bond type (single, double, triple bond). This information allows the functional groups of a molecule to be clearly identified. \n\nNuclear Magnetic Resonance Spectroscopy- if an organic (carbon-based) molecule is suspected, this method is often used to determine at what frequencies a hydrogen or carbon nucleus resonates in a magnetic field. Depending on what the C or H is attached to, different characteristic frequencies can be seen. This method shows the functional groups of a molecule and also the bond connectivity (what group is attached to what part of the backbone). \n\nI really oversimplified a lot of the explanations, but I hope this isn't still too confusing. Basically, my point is that there are a ton of different techniques with different merits that can be used to find the identity of an unknown substance. ", "A lot of what happens when you send a sample for analysis is they run the unknown sample through the magic box and then they compare those results to results previously obtained from other pure standard versions of known compounds. The vast majority of toxicology especially in criminal forensics/illegal drug testing works like this. Only when the known standards fail do they use the nuts and bolts NMR spectroscopy etc. previously described to try to deduce the actual chemical structure of the molecules of interest." ] }

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{ "a_id": [ "cm52b37" ], "score": [ 2 ], "text": [ "So, this really depends on where in colonial America you are talking about. It's really important to understand that there were deep geographical differences in colonial America. In New England, during the eighteenth century, the literacy rates were upward of 90%. This has a lot to do with the Puritan influence in New England, which required that everyone be able to read the Bible. The literacy rate in the South was lower, being around 80% in South Carolina, for instance. This does not include slaves, however, so if you are including the entire population, the numbers are lower. So, most people probably would have been able to read the pamphlets you're talking about. \n\nMany people, however, may not have actually read it. Colonial America was still very rural and agricultural, which meant that it took a little while for literature to penetrate into the countryside. And the language may well have been obtuse to most people. By and large, these pamphlets were directed at what we might think of as the middle and upper classes, which were in the minority then as they are today. It's a mistake to think that, just because they may not have read it, people weren't familiar with the ideas. People were talking about these issues at the common level. \n\nThere is an argument, however, that the ideology of the revolution was not as influential in kicking of the whole thing as the economic problems. Woody Holton has argued that the elite of Virginia, like Washington and Jefferson, didn't really want a revolution, but were pushed into it by the lower classes. Essentially, the new taxes and laws that Great Britain passed hit the lower classes disproportionately hard, and that the lower classes were the ones really pushing for revolt, rather than the idealistic upper class. While I personally find his argument incredibly persuasive, there's little doubt that the revolutionary ideals trickled down to all levels of society. There's even quite a bit of evidence that the American Revolutionary ideas even got as far as the slaves in Haiti.\n\nSources: F. W. Grubb, \"Growth of Literacy in Colonial America,\" Woody Holton, *Forced Founders*, T. H. Breen, *Marketplace for Revolution*." ] }

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{ "a_id": [ "f2brwbp" ], "score": [ 5 ], "text": [ "The term is usually used when white women(mainly from higher economic classes) fight for gender equality while not being invested/interested in fights that other women face, like racism for women of color, homophobia for queer women and transphobia for trans women." ] }

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{ "a_id": [ "ckw9siy" ], "score": [ 15 ], "text": [ "It depends on the recording.\n\nMost modern music is made by recording instruments individually and mixing them together, with plenty of effects and some electronic instruments added in. There's actually no realistic way to listen to this music since the composite sound never existed on its own to be recorded. Asking how to get a realistic representation of this music is like asking what kind of TV gives you the most realistic representation of The Simpsons. \n\nSome recordings are made with stereo microphones in a sound field. Many classical and jazz recordings are made this way. Since these are recordings of real sounds, it's possible to achieve a more realistic reproduction. Since the microphones intercept the sound field, speakers that reproduce that sound field will be your best bet for a realistic listening experience.\n\nHeadphones aren't usually good for realism for stereo recordings because they wrap the sound field around your head and you lose location information. The sound appears to come from the center of your skull, and it moves when you move your head. \n\nThe most realistic recordings however, are meant to be listened to with headphones. They are called binaural recordings. Binaural recordings are made with a dummy head that has microphones embedded in the ears. This captures all of the subtle details that result from the shape of a person's head and ears. Good binaural recordings are scarily realistic when listened to on quality headphones." ] }

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{ "a_id": [ "c1jxx5n" ], "score": [ 7 ], "text": [ "Yes, that is what the adaptive immune system is all about.\n\nFor many things exposure to bacteria is necessary for a proper development. Things like immune function and GI development are often used as examples (in mice and zebrafish) as sterile (no germs) raised individuals lack the development seen in ones with regular exposure.\n\nAdditionally a paper last year showed that after feeding a soil living bacteria to some mice their serotonin levels in creased and they did better on a maze or memory task then mice who were not fed the bacteria. The effects lasted for 2 weeks after the bacteria had been wiped out (hinting at an enzyme or mRNA mediator)" ] }

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{ "a_id": [ "d8moasb", "d8mwv1a", "d8my0lh" ], "score": [ 2, 2, 6 ], "text": [ "I'm not a scientist. \n\nIt's some thing about blocking body langauge, expressions, or the popularity of an inexspensive prop in horror flicks. Clowns and Geishas seem to have similar issues with thier heavy make up on. \n\nHumans are use to seeing a constant flow of face changes to help figure out what the other person is communicating. When facial clues are taken away and you now have to guess if the other person is a threat, I can see why it would make people uncomfortable. ", "There is a concept called the uncanny valley, where something looks human, but isn't quite there. While this is usually applied to robotics and the realness of video game renderings, it can also apply to masks and costumes. After all a corpse looks exactly like any other human being, except the stillness, un natural posture, and lack of expression. In the case of masks there is furthermore the inability to read the expression of the person behind them. To a lesser degree this applies to any partial covering of the face, especially the eyes. This is one of the reasons why people with dark sunglasses may be more intimidating. ", "There is a great video from Vsauce about the \"uncanny valley\": _URL_0_\n\nBasically, things that don't look at all like humans don't cause any special emotions by themselves. As things begin to look more human, they become more \"friendly\", and \"ususal\". \n\nImagine a curve in a graph going up, and up... Until it drops drastically at a point where something very closely reassembles a human... Although it isn't. That is the uncanny valley. Masks, clowns, corpses, statues, robots, toys - all of these have the potential to look very similar to a person, and yet there's something not quite right. So your mind is prepared to trust the thing as a person... And then it takes a few steps back when it realizes it was deceived." ] }

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[ "http://d28xhcgddm1buq.cloudfront.net/product-images/blank-masks-white-full-face-adult-3_260.jpg" ]

[ [], [], [ "http://m.youtube.com/watch?v=PEikGKDVsCc" ] ]

{ "a_id": [ "cbrrh5v", "cbrtmw9", "cbrvxxj" ], "score": [ 11, 210, 8 ], "text": [ "Older threads: _URL_2_\n\n_URL_0_\n\n_URL_1_", "Psychiatrist here. No. You can rest, but you cannot substitute for sleep. In fact, if you can't sleep, just laying there after a while is countertherapeutic, as you start allowing your brain to do other activities in bed at night instead of sleeping. Good sleep hygiene involves getting up after you've tried sleeping, doing a non stimulating activity for a while until you are tired again (NOT reddit or TV or video games which compel further use... Open ended stuff like reading a long novel or working on athe soothing craft project.) then try to sleep again. Rinse. Repeat. \n\nOne of the best resources for sleep hygiene that I've come across and give to all my patients.:\n\n_URL_0_", "Mythbusters recently did a Deadliest Catch special where they tested [napping on long shifts vs no sleep at all](_URL_0_). They found that taking 20-minute naps doubled their scores vs no sleep in the tests. At the end of the myth Tory said that \"it's not so much that you actually fall asleep, but what it did do is allowed my body and mind to rest\", which makes sense because on average it takes 10-20 minutes to actually fall asleep.\n\nSo, at least based on what they tested, yes resting but not sleeping does help you focus/think better, but it's in no way a substitute for actual sleep." ] }

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[ [ "http://www.reddit.com/r/askscience/comments/jfkav/whats_the_difference_between_sleeping_for_6_hours/", "http://www.reddit.com/r/askscience/comments/y4kgv/does_a_persons_body_still_become_rested_if_only/", "http://www.reddit.com/r/askscience/comments/zvcrz/if_a_person_lays_in_bed_eyes_closed_not_moving/" ], [ "http://umm.edu/programs/sleep/patients/sleep-hygiene" ], [ "https://en.wikipedia.org/wiki/MythBusters_%282013_season%29#Crab_Napping" ] ]

{ "a_id": [ "c4un4zt", "c4uogpy" ], "score": [ 6, 2 ], "text": [ "It's all about density. \n\nAs an object enters water, it displaces some of the water proportional to its *volume*. For example, a cube one meter per side will displace exactly 1 cubic meter of water when fully submerged.\n\nHowever, as you submerge an object, the water pushes back up on it, and it turns out that the force that the water exerts is exactly equivalent to the *weight* of the amount of water that the object has displaced.\n\nSo if an object can managed to displace enough water to match the weight of the object, and if it can do this before it is totally submerged, it will simply stop sinking. It will float.\n\nNow, ships may seem kind of odd, because there's a lot of steel construction, and still obviously sinks, being much denser than water. However, most of the volume of the ship is actually air, so the entire ship taken as a whole is actually less dense than water, and thus it float.", "the force that pushes an object to the surface of the water is equal to the weight of the displaced water. if something displaces enough water that it outweighs the object, the object will float. A cruise ship weighs a lot, but it also displaces a ton of water. a pebble doesn't weigh much, but it also doesn't displace much water at all." ] }

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{ "a_id": [ "c8kenso", "c8kgcbb" ], "score": [ 26, 4 ], "text": [ "I feel like there has been a bubble of references to the Indus Valley/Harappan civilization (just called \"IVC\" from here on) this week. Was there a documentary on it or something? Regardless, I'm glad you brought the question here because there is an enormous amount of disinformation on it. The IVC exists in the center of a Venn diagram of nationalism, orientalism, and lack of good information. That even the greatest experts on the topic have difficulty answering very basic questions means that statements taken out of context, uninformed and incautious speculation, and outright falsities spread very quickly.\n\nI need to qualify this because, generally speaking, when people talk about the IVC they do so divorced from other cultures at the time. Our ignorance of it is not so much greater than that for, say, Minoan Crete, where we face many of the same issues, and we know considerably more about the IVC than about, say, the Sanxingdui Bronze Age culture of Sichuan (in fact, we only know marginally more about pre-Zhou Bronze Age China in general). The reason scholars stress their ignorance of the IVC is because we lack the crucial element of greater cultural context. We may not know much about the Minoans, but we know a great deal about the context of the eastern Mediterranean and can make inferences about that. Our ignorance about pre-Zhou China is profound, but we know a great deal about what came after. The IVC exists in a vacuum. People have made heroic attempts to connect it to later accounts in Iron Age Indian literature, like the Vedas and Upanishads, but to no real avail. Every solution raised by this method contains so many difficulties that most scholars choose to simply avoid it altogether. The IVC exists almost within a vacuum, and the paltry connections found to contemporary Mesopotamian civilizations leave us with frustratingly little.\n\nPeople also often look at its seemingly impressive advances as divorced from other advances at the time. The IVC's city planning and sewage system were quite impressive, but such things were far from unheard of at the time--the Minoan colony at Akrotiri has city planning and sewage as well. The IVC may have had more \"advanced\" in these matters, but such things are rather difficult to prove when looking at 3500 year old brickwork. Oftentimes therefore the statements about the impressive IVC remains come with the implicit suggestion that the rest of the work was just hitting themselves over the head with rocks to pass the time, which I think is [just a](_URL_0_) [trifle](_URL_1_) [unfair](_URL_2_).\n\nThis is not to deny the impressive scale of the IVC. Something very remarkable and very interesting was going on in the Indus Valley during the bronze age. But it is unfair to the civilization to throw unwarranted speculation and hyperbolic figures at it, or to co-opt it either for our political, nationalist, or ideological advantage or our orientalist fantasies.\n\nNow, to answer your question, the IVC is usually said to have collapsed due to a confluence of climatic and other natural factors, which may have exacerbated social stresses caused by, or leading to, internal or external conflict. This is archaeologist speak for \"hell if I know\".", "The most commonly-accepted possibility for the decline of the IVC is due to climate change. Much like India today, the IVC depended on the monsoons for agriculture (seasonal storms that occur around summer due to the warm, moisture-laden air from the Arabian Sea and Indian Ocean making their way over the subcontinent). However, by the time of the IVC's decline, the monsoons started weakening as the general climate started getting much cooler and drier. \n\nAnother factor is that the IVC was highly dependent on the river systems in that area, such as the Indus River, and the Ghaggar-Hakra river system (it has been suggested, but not universally accepted, that this river system might be the same as the Vedic Saraswati [cognate with Avestan Harahvati/Haraxvati] river). The Ghaggar-Hakra is still an intermittent river-system that is fed by rains and not by Himalayan glaciers. So a lessening of rainfall could have lead to it drying up or being an unreliable source of water. What is interesting is that maps showing IVC sites show a clear pattern of being along the Ghaggar-Hakra river system. So this leads some credence to the theory that the drying up of the rivers that the IVC relied on, could have led to their decline." ] }

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[ [ "http://en.wikipedia.org/wiki/Great_Ziggurat_of_Ur", "http://en.wikipedia.org/wiki/Knossos", "http://en.wikipedia.org/wiki/Shang_Dynasty#Bronze_working" ], [] ]

{ "a_id": [ "f5vgvx0" ], "score": [ 2 ], "text": [ "The elastic, chewable properties of bubble gum come from the other ingredients, such as polymers, plasticizers, and resins that act as stabilizers. These ingredients give bubble gum its texture and elasticity.\n\nWhen gum is made, these ingredients are in a \"sleeping\" state and when you start chewing your saliva and teeth \"wake them up\" causing the gum to become more like rubber." ] }

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{ "a_id": [ "cuskmzk" ], "score": [ 3 ], "text": [ "[Dolby](_URL_0_) is a company which designed a system for surround sound. When something says Dolby surround sound, it simply means that it uses that companies technology." ] }

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[ [ "http://www.dolby.com/" ] ]

{ "a_id": [ "f8e4uja", "f8e54ww", "f8etp4t" ], "score": [ 13, 4, 3 ], "text": [ "I’ve taken more genetics courses and read more genetics papers than I care to admit to, but I’ve never heard of such a thing. DNA/RNA is one of the basic necessities of life. Are you sure you didn’t read a paper that was extrapolating the idea of DNA-less life?", "There's a bacterium called [GFAJ-1](_URL_0_). Some researchers claimed that it can use arsenic instead of phosphorus in the DNA backbone, which sparked a lot of controversy. That might be what you're thinking of.", "As has been said, all life that we know of depends on DNA/RNA, and shares a common ancestor that itself depended on DNA/RNA (and largely shared its genetic mechanisms with us as they are highly conserved, and already had our genetic code).\n\nThere is presently no evidence of life that doesn't operate this way. Not that it is impossible, we just have never encountered anything like that." ] }

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[ [], [ "https://en.wikipedia.org/wiki/GFAJ-1" ], [] ]

{ "a_id": [ "d07lamn" ], "score": [ 3 ], "text": [ "According to John Man^1 it was called this as Genghis's family was known as the 'Golden Clan', and the Mongolian word ord/orde meant a palace, or for the Mongols a tent. Hence Batu's (initial leader of the khanate) apparent use of a gold coloured tent as his 'palace', and the shift of ord/orde to horde led to the khanate being called the Golden Horde.\n\nWorth noting that initially it was known as the Khanate of Qipchak^2 (named after the nomads who previously inhabited that area) and according to David Morgan the popularization of Golden Horde came about later.\n\n---\n\n^1: The Mongol Empire, John Man\n\n^2: David Morgan, The Mongols" ] }

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{ "a_id": [ "ckb6pyr", "ckb9u4f", "ckbaxup", "ckbgn0b" ], "score": [ 789, 199, 2, 20 ], "text": [ "This recording of Thomas Edison from 1906 is full of \"uh\" as conversational filler or \"verbal disfluency\". It doesn't sound much different than speech today. I'll see if I can find an earlier recorded example \n_URL_0_ ", "All of this has only discussed English conversion fillers, which is what I assume is what you're mainly interested but maybe you'd like to know about other languages as well. In Turkish, among the most common are *şey* (\"thing\") and *yani* (\"that is\"). One can tell that they predate the massive language reform of the 1930's, which attempted to get rid of all words with foreign etymologies--şey and yani were both originally Arabic words. In fact, yani is still used as a space filler in Arabic, at least as far as I can tell from eavesdropped conversations at airports, and if it was borrowed into Ottoman Turkish a space filler, I can imagine it has been used as one for quite a long time (actually, I looked it up. The Turkish etymologist Sevan Nişanyan notes that it was already in use ~1300 with the meaning \"that is to say\", so it is a pre-Ottoman borrowing into Turkic languages, though maybe not in the specific space filler sense).\n\nGeoffery Lewis, in his book *the Turkish Language Reform*, recounts that şey's banning was unlikely because şey is:\n\n > a word without which many Turks would find difficulty in conversing, for it is what comes automatically to their lips when groping for a word or a name, or thinking what to say next. It is used much like the English 'what-d'you-call-it' or the French *chose* and, as a sentence opening, like 'Well now' or 'I'll you what', or 'Il-y-a une autre chose qui est celle-ci'. Atatürk wanted it abandoned as it was a borrowing from Arabic (Had that happened, an English analogy would be the inhibiting effect of a ban on 'y'know' or 'basically).\n\nEventually, as Lewis recounts, one of the reformers was able to win Atatürk over with the argument:\n\n > 'Don't do it, Pasha!' I was saying, 'If a miracle were to occur and all the dead Turks in Anatolia could suddenly be resurrected, the first word to come out of their mouths in unison would be *şey*. That's how Turkish *şey* is.'\n\nWhich, I think indicates just how ingrained it was in Late Ottoman daily speech.", "Is conversation fillers the right term?", "I'm not seeing any responses to the words such as like, you know? So all I know is 1800's English literature, where the 'extra' words and phrases are such as \"wouldn't you agree\" used rhetorically as our \"isn't it\" or \"y'know\". Also \"verily\", \"are we not\". That's all that spring to mind right now. They also did use ums and ahs then but fiction rarely wrote conversational place holders, preferring very correct grammar. Reading transcripts or affadavits from the time would help answer this because they are word for word. Also I think Hansard was established by the late 1800's. That's a written record of what is spoken in Parliamentary discussions. Hope I've helped a bit." ] }

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[ [ "http://www.nps.gov/edis/photosmultimedia/upload/EDIS-SRP-0158-06.mp3" ], [], [], [] ]

{ "a_id": [ "cl49h9f" ], "score": [ 3 ], "text": [ "The Mesopotamians didn't really use \"currency\" as such, which we can define as a centrally issued object having the function of store of account, medium of exchange and measure of value. In short, they did not have coins. But they did have standardized systems of weights and measures that, in practice can fulfill one or the other functions of currency. In Sumerian documents for example you will see value expressed in units of silver even if no silver is involved in the transaction. Currency in the form of coinage does not really come into being until the Iron Age in Anatolia, and it was taken up by the Persian Empire." ] }

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{ "a_id": [ "dgda09v", "dgdaghw", "dgdksqs" ], "score": [ 3, 10, 3 ], "text": [ "If someone wants it they'll buy it. If someone else wants it more they'll pay more for it. Eventually you've got an expensive work of art. As for why people want it, preferences are impossible to determine across a population.", "Usually it's based on the body of work of the artist.\n\nFor example, by the end of his work life Joan Miró was placing a single stripe of paint on a canvas and these are very prized even though *anybody* could place a stripe of paint on a canvas.\n\nLike he'd stare at the canvas for a while and then in one fluid movement put a single stroke down and he'd love it and everyone else would love it.\n\nThis is because he spent his whole life evolving from being a talented painter that you'd probably call \"normal\" (i.e. he made pretty pictures with paint) to becoming a more and more abstract painter.\n\nHe kept reducing the complexity of his forms to see how to express emotions and form in an ever increasingly abstract way so that after decades of doing this he had developed a kind of language of form that was uniquely his.\n\nSo if you're aware of his progression and have an understanding of how to \"read\" his abstraction you can see how his single stripe of paint has meaning and is different and special compared to a stupid stripe of paint that just *anyone* could do.", "This is what we mean when we say \"market forces\". So there is no single person or organization that decides what is worth what. A thing is worth as much as someone else is willing to pay for it. That dot sold for what it did because someone else was willing to pay that much for it. There is no central authority that sets prices for art.\n\nThe question is, why would someone pay that much for a dot painting. And the answer is complex. Could be that they really liked the dot and really hated money, but likely not. A better answer is that they felt, given their experience in buying art, that this particular painting by this particular artist was worth that much money. This feeling was based on other paintings by that artist and how much other people have paid for them, along with a general feeling about what the future value of that artist's paintings is going to be. \n\nArt has no intrinsic value. Meaning, you can't break it down and sell it for parts. Art is only worth money because other people are willing to pay for it. If people all of a sudden decided that Pasco's paintings were all worthless, you'd not be able to sell them at all. The price of art is 100% based on other people's perceptions." ] }

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{ "a_id": [ "e4ye8ow", "e4yeb1d", "e4yel55" ], "score": [ 4, 20, 7 ], "text": [ "They don’t deliver within 24 hours to every nation. I live in Singapore (just moved from USA) and it takes a minimum of 2-3 days to ship prime items from the USA. There are few items stocked locally that allow for true one-day shipping.\n\nThe cost of international shipping is also paid for by the prime customer. The 2-3 days shipping I mentioned would cost anywhere from $16 USD to $30 USD. The cheapest option would take 2 weeks (for my location).\n\nBut for the few items stocked locally (eg fire tv sticks) you can get same day delivery.", "It can't and it doesn't\n\nAmazon prime provides free *two day* delivery for *many* items in *many* locations. There are a fair number of locations where Amazon Prime gets you free *three to five day* shipping rather than two day\n\nAmazon does not proclaim that you can get any item anywhere in the world within 24 hours.", "They can't\n\n1-day delivery is only available for a small subset of items and only in certain areas. \n\nAmazon maintains a number of warehouses and logistics affiliates across the globe. Its most popular items in urban areas are stocked locally for fast delivery to Prime customers. If you order a set of tractor tires to Tahiti, it's gonna take a while." ] }

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{ "a_id": [ "d62l9tp", "d62lmhg", "d62lokd", "d62mzun", "d62p34n", "d62ufrp", "d639nkc", "d63gg4x" ], "score": [ 61, 6, 102, 28, 3, 28, 15, 9 ], "text": [ "Something to keep in mind is that's a bit of an older post, and one that was written when the rules of the subreddit were still being hashed out. But that said, I would offer the simplest explanation that I can: \n\nWhat's the point of passing moral judgment on past societies? And how much time do we have to waste on doing it? To quote a professor of mine from a historiography class, \"if I'm writing a book about the Holocaust, how many pages do I have to spend detailing how awful it was? Don't the facts of the Holocaust speak for themselves?\" \n\nThat's not a morally nihilistic stance, it's a pragmatic one that allows us to present events in their context without getting bogged down in determining the relative moral scale of past tragedies. We have a rueful term for questions that get asked here along the lines of \"was genocide X worse than ethnic cleansing Y,\" -- we call it playing genocide Olympics, because it's an exercise that's fruitless, and to be frank somewhat masturbatory. The point of writing history, after all, is to explain events and ground them in their contemporary context, not pass judgment on how good or bad past events were. ", "Hi Historian in training and longtime lurker here,\n\nFrom what I was taught it is because otherwise we would judge everyone to be bad in some sense of the word. For example, Thomas Jefferson is idolized in the United States,but he also owned slaves. He wrote the American constitution and is considered a great man. Does the fact that we owned slaves factor in if he was a good person or not? In our modern view we say that this is morally reprehensible and that it makes people immoral, but at time it was more than standard, his handling was even considered radical. \n\nTake for example Gay marriage today. It would absolutely not have been allowed one or two hundred years ago, but today we are for it. Are we better than those of a hundred years ago? You cannot judge the people of the past by the ideals of the present. Our ideals and morals are not universal nor are they native to our species. They are a learned experience and if those in the past did not grow up exactly as we did, maybe something we consider obvious would never occur to them. If you are taught all your life that blacks are evil, you will think that. Does that make you intrinsically evil? No it just means you were raised with different morals. \n\nThat is why as historians we cannot judge the past by our morals because it would alter our perception of the past and undermine the deeds of the past. One day something we consider normal may be looked down on as evil. \n\nHopefully I understood your question and answered it well. Apologies if my English is less than stellar, I'm not a native speaker.", "Presentism does not facilitate or encourage an answer to (one of) the main historical question(s): \"Why did these people do what they did?... what led them to that train of thought and chain of actions?\"\n\nHistory seeks understanding and comprehension, and that is best achieved in many cases by viewing the world *not* through the hind-sight of 21st century righteousness, but by trying to view and understand people and events in the contexts of their own times, places, and actions.\n\nSure, it's easy enough to say, \"but Naziism was bad.\" Pretty low fruit, that. But what about... other historical questions? What happens if and when we start breaking off from the Modern Western morality spectrum altogether?\n\nWhat happens when we start asking why Genghis Khan felt justified in doing what he did? Is a 21st Century \"well, killing is bad and inhumane\" presentist viewpoint going to help or hinder that answer? Or how about if we ask into An Lushan's justifications for killing 2/3 of the Chinese population in the 8th century? Or Alexander the Great's justifications for invading half of Asia?\n\nPresentism isn't helpful because it is essentially a moral judgement. That's not helpful to history because history seeks to understand *how* and*why*, rather than seeking to place arbitrary blame against those who are no longer capable of explaining or defending themselves or their actions, in many cases. \n\nJudging an ancient battlefield or political tangle from a modern perspective will render judgement, to be sure... but in doing so it will warp what actually happened and *why* it happened beyond any actual comprehension or meaning.", "I don't think that historians in general (or in this sub specifically) actually do embrace moral relativism or nihilism. The OP of that thread, who you're quoting there, is not a flaired user, nor do they seem to be particularly qualified to discuss the subject. For comparison, [here](_URL_0_) is a user flaired in Spanish colonialism discussing Columbus and arguing that his actions are \"absolutely indefensible\" due to his violence, slaving, and genocide. This does not seem relativistic or nihilistic to me. For another example, look at the posts by users who study slavery in this subreddit, who are some of our best and most erudite flairs. People like /u/freedmenspatrol, /u/sowser, /u/dubstripsquads, and others do an excellent job of understanding the ideology, culture, and mentality of antebellum southern slaveowners, but understanding the mindset of American slaveowners does not equate to rationalizing away the abhorrent system of slavery. \n\nAlthough historians are capable of and sometimes do make moral judgements on their subjects, there's also a limit to the utility of doing so. For a much more trite example than slavery or imperialism, the killing of the French prisoners at Agincourt is an infamous episode in medieval history. When discussing this event, does it actually add to our understanding of medieval combat and of the Hundred Years War to insert a footnote saying that stabbing wounded and disarmed prisoners is, in fact, a Bad Thing? The most interesting aspect of that event is that it was specifically not condemned by its contemporaries and was considered an acceptable part of warfare. Is it \"morally nihilistic\" to point out that medieval soldiers in 1415 would sometimes kill their prisoners without it being considered a war crime? I don't think we need an addendum to every book on premodern warfare explicitly stating that the murder, sexual violence, and theft that occurred during the sack of a city were morally bad things. ", "Follow-up question:\n\nI think /u/jschootiger gets to the nub of the issue\n\n > The point of writing history, after all, is to explain events and ground them in their contemporary context, not pass judgement on how good or bad past events were.\n\nI'd largely agree with that, however I wonder if there are uses of history that *do* involve passing this kind of judgement. For example, if we want to hold up a historical figure as an inspiration or an exemplar, does this require some judgement of them by contemporary standards?\n\nIf so, are invocations against presentism also linked to a decline in this sort of history? (If it is declining - \"great man\" history is, but maybe other figures are now exemplars.) Or are the warnings simply about making sure you pay attention to context? ie. it took a much stronger character to condemn slavery in the 18th century US than it does today, so we should make allowances for people.", "Given my specialty, I can share some thoughts on my approach to the subject:\n\nI hope it is pretty obvious from my work in general and my posts here that I absolutely abhor the Nazis and what they did. They were criminals who committed horrible deeds by any moral standard. And they knew it, which is why they went to great lengths to hide it. And yet, on some level they did what they taught was right and necessary. That doesn't mean that it was objectively necessary and right when in fact it was the very opposite of that, but my job as a historian is to explore what factors lead to them thinking they were right and necessary. In my opinion my explaining of these factors does not portray that as right but rather is a contribution to how we can on some level recognize the factors leading to people thinking that doing something obviously wrong by any standard, i.e. committing genocide, in order to prevent similar factors and tendencies growing strong in contemporary society.\n\nTaking one concrete and slightly different example from my line of work, I hope I can also show some problems that are associated with making moral judgement calls: The Judenräte. I describe them [here](_URL_0_) but in essence, the Jewish councils were set-up by the Nazis to help them administer the Ghettos. On a regular basis, they had to make-up the lists of people who were to be deported to their deaths. Different Jewish councils approach this in different ways but here the perfidy of the Nazi system becomes obvious: They forced their victims to assist in their own murder. After the war was over, many members of these Jewish Councils, provided they had survived as well as those who didn't, were called traitors and collaborators. As were the Jewish members of the Sonderkommandos in the Camps, i.e. the people who had to clean the gas chambers of bodies and burn them.\n\nThe thing is, in 99.9% of all cases, I am confident in my moral judgement of the Nazi perpetrators. In the case of the Jewish councils however, I am entering a massive grey area morally where I feel confident in describing the moral dilemmas they faced but less confident in making a moral judgement call on their actions. They were people put in a morally impossible situation by genocidal maniacs and making a definitive moral judgment call on them is something that I don't feel I am able to do. I can describe the circumstances, I can analyze the historical factors and describe the dilemma they faced but I don't think that it is my place to morally condemn them. I can emphasize what could have been done differently in certain cases based on what others in the same situation historically did but that also is not the same as making a moral judgement.\n\nI also don't think that qualifies as moral nihilism or relativism. It's merely that sometimes historians need to acknowledge that some historical situations were so impossible or difficult that it is best not to make the definitive judgement on morally correct actions.\n\nPresentism imo is related but something different: Presentism is the projection of current concepts in way that makes historically little sense. To exemplify: When ratheists try to portray certain of their scientific heroes as atheists beacons or reason and rationality but fail to acknowledge that for someone like Galileo a world view without God would simply be unthinkable. Or to pick an example of a discussion recently in the area of studies of Nazi Germany: There was recent discussion whether in an effort to make German language more gender neutral, if it is necessary to write not of Wehrmachtsoldaten but of Wehrmachtsoldat_innen. The _ and female word ending usually used to signifying that peoples' gender identities are open to their own definition. Using both male and female endings to describe them as well as the _ to leave open an empty space for those who either reject male and female as identities or see themselves somewhere in between. While generally a nifty concept if you are into that, in the case of the German Wehrmacht it makes no sense because by its very organizational ethic, it was a very very male organization that instilled its members with values and ethos that was in gender terms codified as male. Thus, leaving room for alternate identities without empirical evidence that they existed and with an organization whose ethos is strongly codified as male makes imo little sense and obscures an important factor in why they did what they did rather than clearing it up.\n\nAdditionally and in connection to some of the examples you mentioned: As historians frequently do in this sub in connection to slavery, we as historians are absolutely entitled to making moral judgement calls. We can also go a step further even: We can show that not only was it wrong what historical actors did at the time but also show that it was understood as wrong at the time. There were actors who justified slavery in many places of the world,but there were also actors who from the very beginning of the system of slavery objected to it on the grounds that owning other people is wrong.\n\nSimilar to the Nazis who were obviously aware that murder was wrong, they too had the perspective of what they did was wrong as we can infer from their arguments and the arguments of their opponents. Why they were not convinced by these arguments is an interesting historical question. I mean, concerning the so-called New World, we have the writings of Bartolomé de las Casas pretty much right after the Spanish incursions start, who strongly objects – with different justifications and different system of thinking – to the system the Spanish established there. As historians, we also have the duty to emphasize these arguments and point at them in order to be able to fully appreciate and portray actors' contingency.", "I draw a line between methodological neutrality / relativism (I prefer the word 'symmetry'), and moral judgement. When I study the past, I must keep an open mind and suppress my modern preconceptions if I hope to understand why people in the past acted the way they did. This is in some ways a hopeless cause - I can never fully escape my own prejudices - but there is value in entering as much as possible into the experiences, perceptions, and values of people in the past to try to see things from something close to their own perspectives.\n\nBut that doesn't mean I leave my moral judgement behind. The ability to judge and learn from events in the past and present is an important part of being human, especially when used alongside openminded credulity. The important skill historians train ourselves to develop is to hold that judgment back until we've given the data / facts / sources a chance to speak, as much as they can, for themselves. Then we insert ourselves, and start making sense of things, and this often includes our own moral prejudices.\n\nI study human burials in the early middle ages, and one grave in particular sticks in my mind. A young girl, maybe 16, was buried face-down, perhaps with her hands and feet tied together. Her thigh bones were scarred from her muscle's tearing, the kind of injury women receive when they try, and fail, to fight off a rapist. And one of her legs had a healed knife wound from where someone had pressed a blade into her thigh to make her cooperate. Her wounds suggest multiple assailants: she was gang raped. And about six months later (judging from the healing of her injuries), she was dead and dumped, face forward, into a grave. There's no evidence she was wear any clothes when she was buried.\n\nPart of my job as a historian is trying to enter into the minds of the people who did this to her: her rapists, the people who buried her, the possible causes of her death. One theory is that she became pregnant, and her community killed her out of shame. Perhaps she was a slave, raped after she was captured, and buried once she was used up. Maybe she killed herself, in response to the trauma. Maybe her community starved after losing a war, and she was one of the casualties. We can keep going, and imagine the kind of mentality that would normalize these behaviors, where rape is a normal part of war, or where women can be enslaved and killed with so little seeming compassion. A society where shame killings are considered good and honorable, something that earned her father or brother respect. And so on.\n\nAll of that can help me, dispassionately, understand her world. And I try my best to leave my modern assumptions about rape, violence, and the value of human life behind me when I do this, because I want to understand what happened in the past on its own terms, and not merely interject my own prejudices into the sixth century.\n\nBut none of that for one minute makes me feel that her rape and death was ok. And I dearly hope that whoever did this to her died with a spear in his belly. My methodological scholarly dispassion helps me understand the past, but it doesn't keep me from judging it.\n\nAnd just as there's value in understanding the past from its own moral perspective, seeing questions of right, wrong, and normalcy through other people's and culture's eyes, there's also value in allowing the past to shape our own understanding of the moral world of the present. This young woman reminds me that rape and violence against women continues to be a horror of the present, that war continues to hurt women and children more than anyone else, that sex slavery is still a great struggle, and I need to open my eyes to these tings and fight against them now, for people who haven't yet become a footnote in an archaeologist's report.\n\nSo methodologically, I try to keep my morals to myself. I need to understand before I can judge. But once I understand the past, I lift that barrier and let it interact with my present values, because if the past cannot help us learn to be better humans in the present, history has very little value.", "Just to tack on small addendum to other responses: relativism can be a _methodology_ even if you don't embrace it as a _philosophy_. That is, one can say, \"you do better _history_ if you adopt a relativist stance in your relationship to the past (with regards to writing history), but you can believe whatever you want with regards to the rest of your life.\" This is a way that historians of science, for example, deal with epistemological relativism — we tend to write histories of debates over truth without trying to over-privilege the side that we now believe is correct, because that ends up being a very impoverished account (it becomes the scientific equivalent of \"history written by the victors\"). But in our private lives very few of us as probably truly epistemological relativists — I do believe that many scientific claims are to some degree essentially true, and lead my life as such. \n\n(To make it concrete: one might write about the dispute between Boyle and Hobbes over the existence of a vacuum or not without taking the stance that Boyle was \"right\" and Hobbes was \"wrong,\" instead looking at the different ways in which they marshal different types of logic and evidence and rhetorical techniques to make their points. But outside of that specific mode, I do believe vacuums exist.) \n\nPersonally with regards to moral relativism I make a distinction between \"historian mode\" (I am talking about people in the past on their own terms) and \"today mode\" (where I am really trying to engage with something in the present), even if they are muddled. If I was in pure historian mode talking about slavery I wouldn't bother condemning it as evil because it's not really here or there. But if I'm talking to people who believe that the Constitution was a totally perfect document and are using that to justify certain policies over others I might bring up that it had slavery baked into its DNA, and I would happily explain why slavery was an evil thing if I were pressed. (Though to be honest, I'd also mention that its evils were in fact recognized in its time, as well, so to say it is an awful institution is not _merely_ passing a present-day judgment on it. Maybe that is my historian instinct, but I generally find that if you want to find someone condemning something awful in the past, you can usually find that person, even if their opinion isn't the one that was the most dominant.)" ] }

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[ "https://www.reddit.com/r/AskHistorians/comments/uo4zh/meta_lets_have_a_serious_talk_about_howard_zinn/" ]

[ [], [], [], [ "https://www.reddit.com/r/AskHistorians/comments/3iqsbc/what_is_the_truth_about_christopher_columbus_how/cujhgyz" ], [], [ "https://www.reddit.com/r/AskHistorians/comments/4ltzee/is_this_description_about_judenrats_in/d3q8rif" ], [], [] ]

{ "a_id": [ "e98zt5s", "e992yqd", "e99hkkw", "e99if0t", "e99ishn", "e99orlp", "e99t4t8", "e99toxx", "e99v2d6", "e99wmer", "e99wouy", "e99ybg5", "e99zkqa", "e9a3fi8", "e9a4z9b", "e9a6uf5", "e9a797w", "e9agx6q", "e9ah59f", "e9aj2kf", "e9ak2d5" ], "score": [ 207, 3715, 2562, 25, 338, 9, 7, 27, 2, 19, 24, 13, 10, 10, 2, 2, 3, 3, 5, 3, 4 ], "text": [ "It's going to be difficult to tell you the exact consequences because we just don't know. Everyone is different, but there have been studies done about sleep debt and the adverse effects it has on our health. The negative effects of sleep deprivation are *not* simply cognitive. I think your argument is solely about not messing up your circadian rhythm, which can be a valid concern. But basically skipping an entire night of sleep is not good for you and you should avoid doing it whenever possible. ", "During sleep, the brain clears away toxic waste products which accumulate during the day. One of these products is beta-amyloid, the protein involved in Alzheimer's disease. It's been found that a single night of sleep deprivation greatly increases beta-amyloid ([source](_URL_0_)). In the long run, it could potentially increase Alzheimer's risk.", "Notes taken from a Brandon Marcello, Ph.D. seminar: \n\n* Not getting enough sleep leads to increased risk of injury and reduced pain threshold; greater susceptibility to sickness; reduced physical and psychological performance; reduced motivation, learning ability, and memory; increased anxiety, irritability, and mistakes; increase in body fat percentage; reverting to old habits; poor justment of distance, speed, and/or time.\n\n* Most of the Rapid Eye Movement (REM) cycle occurs in the final 2-3 hours of a night's rest. Missing ~25% of your total sleep one night may have a larger than 25% negative impact on your mind and body. \n\n* Getting enough sleep improves motivation; recovery of muscle strength; sprint speeds; muscle glycogen (stored energy in muscle); cortisol (stress) regulation; motor skill development; memory consolidation.\n\n* Sleep debt simplified: if you need 8 hours and get 7 hours, that means you accrue 1 hour of sleep debt. Need to get 9 hours to repay that 1 hour of debt. Sleep debt can build up over time to *(30 hours? I failed to write this down)*.\n\n* After extending time in bed to 10 hours per night for several weeks, collegiate swimmers showed improvements of +8% 15meter sprint speed; +20% reaction time off the block; +10% turn time efficiency; +19% kickstrokes.\n\n* During sleep, the brain will get rid of waste products and clean out toxic proteins which can impair healthy aging of the brain and cause brain related diseases such as Alzheimer's and other neurological disorders.\n\n* Sleep Myths: you can get too much sleep; naps are bad; 8 hours of sleep is ideal *(everyone is biologically wired to require different amounts of sleep)*; older people don't need as much sleep *(they need more because they usually awaken more frequently)*; storing up sleep for the week ahead; alcohol helps you sleep.\n\n* Sleep/Nutrition Interaction: sleep deprivation alters the ability of the body to metabolize and store carbohydrates for recovery, as well as use for a later time; reduces glycogen levels.\n\n* Ask yourself: what is detracting from your sleep quality? Noise? Light? Pain? Temperature? Priorities? Stress? Alcohol/Drugs/Food?\n\nStudies: Predicting Major League Baseball (MLB) Player Career Longevity via Sleepiness Measurements, Validation of a Statistical Model Predicting Possible Fatigue Elementas in Major League Baseball, Chronic lack of sleep is associated with increased sports injuries in adolescent athletes, Sleep patterns of U.S. Military academy cadets (2003), Effect of 1 Week of Sleep Restriction on Testosterone Levels in Young Healthy Men\n\nSeminars: One More Reason to Get a Good Night's Sleep (Jess Iliff), Why Do We Sleep? (Russell Foster)\n\nBooks: The Promise of Sleep (William Dement, M.D., Ph.D.), Take a Nap! (Sara Mednick, Ph.D.), The Sleep Revolution (Arianna Huffington)", "if your interested in sleep related things hidden brain podcast did a great two part episode on the effects of missing sleep \n\n_URL_1_\n\n_URL_0_", "This is an npr podcast about a guy who set a world record for going 11 days without sleep. He’s interviewed at the end and discusses his experiences. Then they bring in a neuroscientist to talk about the negative effects. Pretty crazy! [eyes Wide Open](_URL_0_)", "You never really \"make up\" lost sleep. Some research I came across once indicated your body can keep an accurate log of sleep deprivation for up to 15 days potentially and sleeping extra doesn't ever \"make up\" for sleep lost.", "Ive also been traveling the last months \n\nI had some nights without sleeping and always noticed (using the mi band) that on the next day I always have near the double of the deep sleep time compared to a regular night.. so for sure the body \"compensates\" in the short term but in a long term for sure is not that good ", "How does one know how many hours of sleep is efficient? Do 8 hours apply to everyone or is that an average?\n\nThe reason I ask is because even with no distractions/alarm clocks, I wake up around 6-7am and this only gives me about 6-7 hours of sleep. I so far don't feel like I'm poorly performing any differently than I would. \n\nI want to sleep 8 hours, but I seem to default to 6-7, and sometimes I wonder if sleeping more than that makes me groggy. \n\n & #x200B;", "While I didn’t conduct the study, I’ve performed extensive data analysis & published on a sleep deprivation study. The only way that it would likely be seriously detrimental is if something happened (e.g., a car accident because you were tired). These things are much more likely if you are very tired, but still overall unlikely. \nHowever, this study was done only with healthy adults; these are serious physical risk for someone with compromised health. Me, I’d take the day off if I had serious heart issues, and I wouldn’t get behind the wheel of a semi. ", "Some good information here. \n\nI am an amputee from a bad car wreck and suffer from intense chronic pain. And I will tell you that the disruption of sleep is the biggest problem for me. It is not uncommon to go 48 hours plus without sleep. My whole life goes to hell when I am not sleeping due to pain or my head injury. ", "Hello! Neuroscience major here.\nFirst of all, your wake/sleep rhythm is dictated by two cycles that work together to sync up and fluctuate at the same time: the circadian rhythm and homeostasis.\nNow, the circadian rhythm normally stays consistent and even, even when you skip a night’s sleep. It fluctuates and regulates your body temperature and helps produce slow brain waves (delta usually) to initiate sleep.\nBUT! Homeostasis is the equilibrium process of your sleep. There’s this thing called the Process H, which means that as soon as you wake up in the morning, you accumulate a kind of pressure that will lead you to go to sleep around 10pm. You can imagine it as a graph, X being the number of waking hours and Y the % of accumulated pressure, that slowly rises until 9pm then rapidly drops as the night goes on (the pressure wears off because you’re recuperating and sleeping). And it starts all over again the next day. \nNow, imagine that same graph when you take a 1h nap around 2pm. The pressure drops around 2pm and the graph is unstable — you won’t have enough pressure to go to sleep tonight, and your quality of sleep will be significantly lowered. Delta waves will be scarce and deep sleep will make up probably only 5-10% of your sleep. See how one hour of napping has a snowball effect?\nNow, imagine the same thing but for one night where you don’t sleep at all. You will lack delta waves and produce too many alpha and theta waves, keeping you awake but uncomfortable. \nThe worst thing is, you can never “make up” for an all nighter. Sleeping 12 hours the next day will only worsen things, because of Process H. The only way to even it out is to stick to a strict waking and sleeping time for a few days and to not exceed 8 hours of sleep for each subsequent night. ", "There is a statistically significant increase in your odds of having a heart attack on any day you are deprived of just one hour of sleep, and while I can't find the source to quote it, Freakanomics claimed it was a 30% increase in daily risk ([this site claims a much smaller, but still significant, risk](_URL_0_)).\n\nRegardless of the exact increase, and regardless of whether the cardiac arrest is fatal or merely an instance of risky, permanent damage to your heart, it's obvious that no amount of sleep \"later on\" will compensate for this.", "Is there a correction between mothers that breastfed and alzheimers? Because they are definitely getting less than 7 hours a night on a regular basis. The reason I ask about breastfed vs formula is that in theory formula fed babies can be fed by others, allowing some of the sleep debt to be repaid. ", "Nothing good. As with most things, doing it once won’t kill you, but if you make a habit of it there are extremely serious and long term effects on your health. Hugely increased risk Alzheimer’s disease and most cancers being the ones I’d worry about. \n\nIt’s also worth noting that it’s impossible for the human body to catch up properly on sleep debt. A human needs approx 8 hours a night - if you get 0, there is no chance of you getting 2 nights worth of sleep (16 hours) the next night. The human body does not work that way. \n\nIf you’re interested, I’d recommend picking up a copy of Matthew Walker’s “Why We Sleep”. It’s not just “why” but also “how” and what”. ", "Last year I had to miss a night’s sleep twice a week. \n\nThe main consequences I remember were feeling very cold and dizzy all the time. \n\nAlso after eating dinner on the first day I had no urge to eat again even 24 hours later. \n\nWhen I did finally sleep it was just a normal nights sleep. ", "Wish I could remember the source, but went to a lecture by a neurologist who said (iirc) that you can run ok on getting poor sleep one or two nights, but to maintain ok brain function you need a GOOD sleep by the third night at least.\nI'm sure individual differences apply though\n\n.. Edit: in your situation I'd def prioritise not mucking up your circadian rhythm over getting a few hours now. I'd go to bed earlier than usual bedtime (maybe 2-3hrs earlier), but not too different. ", "Weekend sleep-ins may counteract the effects of lack of sleep during weekdays - Adults under the age of 65 who get 5 or fewer hours of sleep may have a higher risk of death compared to those who get 6 or 7 hours. However, individuals who then sleep longer on weekends had no raised mortality risk.\n\n_URL_0_", "On a similar note, are there any consequences to purposely waking up during the night ever day? I set an alarm 1-2 hours before I have to wake up, just so I get the feeling of being like 'Hell yeah I don't have to get out of bed' and then I go to sleep again for 1-2 more hours.\n\nI've done it for years", "Is there a correlation between sleeping less and wanting to eat junk? I find sometimes, like at the moment, when I get 4-5 hours sleep I just crave fast food and junk all day, whilst when I sleep more I’m happy with fruits and nuts and good meals.", "Haha oh brother... I used to work nights. It’s the worst. Don’t listen to anyone who tells you otherwise. \n\nThere is no making up for a full night of sleep lost - no matter how much you sleep the next day or no matter how used to it you are. It’s honestly just unnatural. ", "I listened to a Joe Rogan podcast with Matthew Walker about sleep and it totally blew my mind. I ended up buying Matthew Walker's book, \"Why We Sleep\". Highly recommend the podcast if you don't like reading, even if you don't like Joe Rogan. Walker is extremely informed, well-spoken, and they cover a variety of topics (all sleep related). " ] }

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[ [], [ "http://www.pnas.org/content/115/17/4483" ], [], [ "https://www.npr.org/2017/11/13/563831137/the-swiss-army-knife-of-health-a-good-nights-sleep", "https://www.npr.org/2017/11/06/562305141/eleven-days-without-sleep-the-haunting-effects-of-a-record-breaking-stunt" ], [ "https://open.spotify.com/episode/4qvflb0HMWckOuXRhwNhFC?si=PzEtL8ONREiqsfvZ7tVGrA" ], [], [], [], [], [], [], [ "https://www.health.harvard.edu/blog/daylight-saving-time-fall-back-doesnt-equal-sleep-gain-201311016836" ], [], [], [], [], [ "https://www.reddit.com/r/science/comments/8ligfu/weekend_sleepins_may_counteract_the_effects_of/" ], [], [], [], [] ]

{ "a_id": [ "c4tbl6v", "c4tc99c", "c4tem8c" ], "score": [ 10, 6, 2 ], "text": [ "The post-WW1 Reichswehr did not generally agree with the bounds of the treaty of Versailles, but its commanders (like Hans von Seeckt) did their best to abide by the letter of the law while maintaining the basic structure of a capable army.\n\nFor one thing, the General Staff was officially abolished, but went underground as the Truppenamt (Troop Office) for most of the interwar years. The army itself was limited to 100,000 men, which von Seeckt organized into 7 divisions. When the prewar officer corps was severely purged to a significantly smaller number, the army generally chose to retain men born within a certain time period, neither too old nor too young, with an eye toward expansion once the 'unjust' treaty was done away with. The junior officers and NCOs of the interwar Reichswehr were eventually to serve as an elite cadre around which the later Wehrmacht would form.\n\nAs for the French and British, they had other priorities during the interwar years, and were none too keen on another European war. Some people within Britain (including, arguably, Edward VIII) did not regard Hitler as a threat in the prewar years. The German military did expand, secretly at first, but later openly when no protests came. The Rhineland was reoccupied with only the slightest complaint from France and Britain, so it's no real surprise that the Germans believed they could get away with anything. Until the French and British made good on their guarantee of Polish independence, those Germans were right. The Allies did nothing about the Anschluss of Austria, the Czech cessation of the Sudetenland, and eventually Neville Chamberlain came home after the total annexation of Bohemia with a piece of paper bearing Hitler's signature proclaiming \"Peace in our time!\".", "Britain would not have been capable of going to war in say, 1938, because it could not depend on the support of its colonies (Canada, Australia, NZ, etc.) The most militarily useful colonies were by this time all self-ruled, had all experienced the horrors of WWI, and didn't want to enter another European war. Only when it became clear how bent on domination of Europe Hitler was, and the reality of the threat to Britain, did this change.", "Just as a side note, and on a point of semantics, but you probably don't mean England: instead use the United Kingdom or the UK or Britain when referring to the country as a whole.\n\nIt's sort of like referring to the US as Texas, or Germany as Bavaria. While a large part of the country, England is only one region of the UK." ] }

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{ "a_id": [ "cl0yt5m", "cl1b16g" ], "score": [ 28, 3 ], "text": [ "The answer to your question lies somewhere between \"no\" and \"we can't know\". \n\nIf the [no-hair conjecture](_URL_0_) holds, there's nothing you can know about a black hole except for its mass, angular momentum and charge. You're not allowed to know anything about the mass distribution within the black hole, and hence if there is a surface in there. In general relativity, the general assumption is that there is no surface, just a spacetime singularity. We don't yet know how this fits with quantum mechanics, but we'll have to wait until a theory of quantum gravity is established. ", "I hope that [this](_URL_0_) is true. The experiments in the next few years (maybe until 2020) will show whether or not this theory is right.\n\nFor those who don't want to read the paper: \n > A first finding is the deviation of the redshift compared to standard GR. The\ncalculated redshifts are not infinite any more but approach finite values near the\nSchwarzschild radius. \n\n > As a second important result we obtained an anti-gravitational effect for radii\nsmaller than half of the Schwarzschild radius, assuming the particular values\nB = 2m^2 and B = 2.2m^2\n. For other values of B the scenario is similar, i.e., for\nr smaller than a given distance, anti-gravitation appears. As a consequence, heavy\nmass objects can not contract to a point at r = 0. The origin of this effect will be\nfurther discussed in a forthcoming paper.\n\n\nI don't know if you know this, but your question is actually very important for the understanding of gravitation itself. In General Relativity black holes are singularities and you can't get infomation from inside the black hole, because light cannot escape the black hole. What this paper says is: \"black holes\" are no singularities. Black holes must have a mass destribution, because mass can't be compressed into one point due to the \"anti-gravitational\" effect described in the paper. So to answer your question: If this paper is true, black holes do have a surface.\n\nBut if the standard General Relativity is true, then we do not know, because there is no information from radii smaller than the Schwarzschild radius.\n\nPS: I want to point out that this paper isn't proven yet. It will be (dis)proven in the next few years, so thats a very interesting topic." ] }

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[ [ "http://www.wikiwand.com/en/No-hair_theorem" ], [ "http://arxiv.org/pdf/0812.1738v1.pdf" ] ]

{ "a_id": [ "d88z1id" ], "score": [ 25 ], "text": [ "As far as Classical Greece goes, much of it was an indigenous development within the confines of that historical period, but it does build upon earlier foundations, which are also Greek, but not considered part of Classical Greece, namely Mycenaean and Kretan architecture. Mycenaen architecture largely seems to have been an indigenous development as well, and appears in such similarity to the very inception of architecture in the neolithic that it is amply clear that it would rather have developed from neolithic precursors than external influence. If I recall correctly, however, there are some theories which trace its origin to the Balkans - I'm not sure about the merit these theories deserve. \nMinoan, that is Kretan, culture was subject to Egyptian influences, which reflected in aesthetics and architecture, although Krete remained very distinct from Egypt in both fields. " ] }

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{ "a_id": [ "c84v024" ], "score": [ 5 ], "text": [ "The two surfaces of a typical cell membrane have very different lipid compositions because they need to have different physical properties. For example the outer surface of a mammalian cell's plasma membrane has mostly charge-neutral lipids, and thus presents am inert surface to the outside world. Good for preventing unwanted interactions, perhaps. The inner surface has many negatively charged lipids which are the site of interaction for proteins that need to interact with the inner cell surface. The proteins that flip lipids across the bilayer are called flipases (seriously)." ] }

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{ "a_id": [ "cbh2juc" ], "score": [ 2 ], "text": [ "Evolution selects the individuals who are most fit for their environment. This is not always the most physically imposing specimen (ask the T-Rex how that worked out) but rather one who is able to survive under the given circumstances.\n\nSince humans are a highly social species our \"circumstance\" consists largely of other humans and our mental capacity is far more valuable to our survival than pure physical might.\n\nThe average IQ has been increasing over the decades so it would appear we're going in the right direction. Brute strength is no match for human ingenuity.\n\nIf it's any consolation, the *homo* genus has been selecting intelligence over strength for several million years, this isn't a new phenomenon." ] }

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{ "a_id": [ "e4o1he2" ], "score": [ 5 ], "text": [ "same way it's generated during the rest o the year. big ass diesel generators and wind turbines. \n\n_URL_0_" ] }

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[ [ "https://scienceroadshow.wordpress.com/2013/01/26/power-up-what-keeps-mcmurdo-going/" ] ]

{ "a_id": [ "dv0s5di", "dv12fvl" ], "score": [ 68, 7 ], "text": [ "[Ring Species](_URL_0_) sounds like what you're asking about. From the page:\n\n > a ring species is a connected series of neighbouring populations, each of which can interbreed with closely sited related populations, but for which there exist at least two \"end\" populations in the series, which are too distantly related to interbreed", "Likely in the Equus genus (horses, zebras, wild asses, donkeys). A horse-donkey offspring is a mule, and is sterile since the horse has 64 chromosomes and the donkey 62; the mule has 63.\n\nThere are zebra hybrids with others of the Genus Equus, but not sure if they're fertile or sterile." ] }

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[ "https://en.wikipedia.org/wiki/Ring_species" ]

[ [ "https://en.wikipedia.org/wiki/Ring_species" ], [] ]

{ "a_id": [ "c37ktne", "c37lx1m", "c37ktne", "c37lx1m" ], "score": [ 6, 2, 6, 2 ], "text": [ "Yes, absolutely. When planning the orbit of a spacecraft, the gravitational fields of the Moon, the Sun and even the other planets can be taken into consideration. For an Earth orbiter, the non-spherical shape of the Earth also significantly affects the orbit. Solar radiation pressure is another major component of the force model.\n\nThe higher the orbit of the spacecraft, the more significantly the Moon (and Sun) will affect the orbit. Similarly, accounting for the non-spherical gravity field of the Earth is more important the lower your spacecraft's orbit.\n\nAs a source, I picked an low Earth orbiter, ICESat, which measured the topography of the ice sheets, oceans, and the globe in general:\n_URL_0_\n\n\"ICESat’s repeat groundtrack orbit was designed using a disturbing force model that includes only the Earth geopotential. Though the third body effect from the Sun and the Moon was neglected in the orbit design, it does in fact disrupt the repeatability condition of the groundtrack and consequently implies orbit correction maneuvers. The perturbations on ICESat orbit due to the third body effect are studied as a preliminary work towards including these forces in the design of the future ICESat-II repeat groundtrack orbit.\"\n\nWhile ICESat's orbit may have been planned without considering the Moon's gravity, for precise orbit determination, an accurate force model-- including the Moon's gravity-- is vital.\n\nedit:\nThe force on a spacecraft can be divided into components: the force due to the Earth's gravity plus the force due to the Moon's gravity plus...\n\nF_total = F_earth + F_moon + F_sun + ...\nIt's a continuum, with the importance of each component depending on where the spacecraft is. On one hand, you have ICESat, whose orbit was planned without even considering the moon...on the other hand, you have spacecraft like Artemis, whose orbit doesn't even exist, can't even be approximated, without considering the Moon's gravity: _URL_1_", "You are correct that theoretically the answer is \"yes.\" Now, the question \"is it noticeable\" is up to the debate of \"noticeable by who?\"\n\nHere is what I can tell you. In my field of Aerospace we have several levels of orbit propagation that we use according to accuracy needs ranging from simple two body propagators to propagators that account for drag, radiation pressure, all of the planets and even some large asteroids. That being said, the simple and mid range propagators only start to noticeably deviate from the super complex ones for orbits run out for days to weeks. The most popular of the mid range propagators are the [SGP4 propagators](_URL_0_), which are two body propagators, and treat the sun and moon as perturbations to that orbit. SGP4 loses about 2 km of accuracy per day or propagation. (this is the propagator wolfram alpha uses when you ask it when the next time you can see the ISS)\n\nIt is more noticeable for high orbit satellites, but not because the force of the Moon's gravity is so much stronger, but because other forces, such as drag, are weaker. \n\nYou are on track when you ask about the effect being accumulation. Yes, the pull from the moon is weak, but it is rhythmic and always the same direction. These effects add up. However, satellites have regular corrective burns, so during their lifetime the effects are not cumulative. However, after the satellite is shut off, if it is left in orbit or pushed up to the \"graveyard belt\" those effects will start to build. \n\nI hope this helps answer. Sorry if I started to ramble at times... it is just a very large and somewhat open ended question. ", "Yes, absolutely. When planning the orbit of a spacecraft, the gravitational fields of the Moon, the Sun and even the other planets can be taken into consideration. For an Earth orbiter, the non-spherical shape of the Earth also significantly affects the orbit. Solar radiation pressure is another major component of the force model.\n\nThe higher the orbit of the spacecraft, the more significantly the Moon (and Sun) will affect the orbit. Similarly, accounting for the non-spherical gravity field of the Earth is more important the lower your spacecraft's orbit.\n\nAs a source, I picked an low Earth orbiter, ICESat, which measured the topography of the ice sheets, oceans, and the globe in general:\n_URL_0_\n\n\"ICESat’s repeat groundtrack orbit was designed using a disturbing force model that includes only the Earth geopotential. Though the third body effect from the Sun and the Moon was neglected in the orbit design, it does in fact disrupt the repeatability condition of the groundtrack and consequently implies orbit correction maneuvers. The perturbations on ICESat orbit due to the third body effect are studied as a preliminary work towards including these forces in the design of the future ICESat-II repeat groundtrack orbit.\"\n\nWhile ICESat's orbit may have been planned without considering the Moon's gravity, for precise orbit determination, an accurate force model-- including the Moon's gravity-- is vital.\n\nedit:\nThe force on a spacecraft can be divided into components: the force due to the Earth's gravity plus the force due to the Moon's gravity plus...\n\nF_total = F_earth + F_moon + F_sun + ...\nIt's a continuum, with the importance of each component depending on where the spacecraft is. On one hand, you have ICESat, whose orbit was planned without even considering the moon...on the other hand, you have spacecraft like Artemis, whose orbit doesn't even exist, can't even be approximated, without considering the Moon's gravity: _URL_1_", "You are correct that theoretically the answer is \"yes.\" Now, the question \"is it noticeable\" is up to the debate of \"noticeable by who?\"\n\nHere is what I can tell you. In my field of Aerospace we have several levels of orbit propagation that we use according to accuracy needs ranging from simple two body propagators to propagators that account for drag, radiation pressure, all of the planets and even some large asteroids. That being said, the simple and mid range propagators only start to noticeably deviate from the super complex ones for orbits run out for days to weeks. The most popular of the mid range propagators are the [SGP4 propagators](_URL_0_), which are two body propagators, and treat the sun and moon as perturbations to that orbit. SGP4 loses about 2 km of accuracy per day or propagation. (this is the propagator wolfram alpha uses when you ask it when the next time you can see the ISS)\n\nIt is more noticeable for high orbit satellites, but not because the force of the Moon's gravity is so much stronger, but because other forces, such as drag, are weaker. \n\nYou are on track when you ask about the effect being accumulation. Yes, the pull from the moon is weak, but it is rhythmic and always the same direction. These effects add up. However, satellites have regular corrective burns, so during their lifetime the effects are not cumulative. However, after the satellite is shut off, if it is left in orbit or pushed up to the \"graveyard belt\" those effects will start to build. \n\nI hope this helps answer. Sorry if I started to ramble at times... it is just a very large and somewhat open ended question. " ] }

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[ [ "http://repositories.lib.utexas.edu/handle/2152/6840", "http://www.universetoday.com/87044/artemis-spacecraft-curlicuing-their-way-to-lunar-orbit/" ], [ "http://en.wikipedia.org/wiki/Simplified_perturbations_models" ], [ "http://repositories.lib.utexas.edu/handle/2152/6840", "http://www.universetoday.com/87044/artemis-spacecraft-curlicuing-their-way-to-lunar-orbit/" ], [ "http://en.wikipedia.org/wiki/Simplified_perturbations_models" ] ]

{ "a_id": [ "ccospeg", "ccosrqq", "ccou1fx", "ccov67o", "ccoxgr1" ], "score": [ 7, 2, 2, 4, 2 ], "text": [ "I'm not sure, but I think it's either with a green screen or a custom built movie set\n\nEdit: here's an example of what amazing things you can achieve with a chroma key (green or blue screen) and some talented artists: _URL_0_", "Movie sets and animation. ", "They build sets and in the case of larger outdoor scenes, supplement those sets with green screen elements. The West Wing, for instance, was shot in a fairly accurate recreation of The West Wing...", "As someone who has worked in a government building and done film work, I can say you dont want to film in a government building. They are largely boring and hard to light.", "They filled two movies ever in the UN and it was a big deal - the Alfred Hitchcock one and the movie with Naomi Watts" ] }

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[ [ "http://www.youtube.com/watch?v=clnozSXyF4k" ], [], [], [], [] ]

{ "a_id": [ "cv55ier" ], "score": [ 2 ], "text": [ "Hate to be needy, but Ill ping some of the relevantly flaired users:\n\n/u/JoelWiklund /u/BeondTheGrave /u/British-Empire" ] }

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{ "a_id": [ "cm854dg", "cm85bqm", "cm85dri", "cm85e8q", "cm86ovz", "cm93pke" ], "score": [ 28, 9, 5, 3, 30, 4 ], "text": [ "From Wiki:\n\nThe first hints of a subsurface ocean came from theoretical considerations of tidal heating (a consequence of Europa's slightly eccentric orbit and orbital resonance with the other Galilean moons). Galileo imaging team members argue for the existence of a subsurface ocean from analysis of Voyager and Galileo images. The most dramatic example is \"chaos terrain\", a common feature on Europa's surface that some interpret as a region where the subsurface ocean has melted through the icy crust. This interpretation is extremely controversial. Most geologists who have studied Europa favor what is commonly called the \"thick ice\" model, in which the ocean has rarely, if ever, directly interacted with the present surface.\n\nThe best evidence for the thick-ice model is a study of Europa's large craters. The largest impact structures are surrounded by concentric rings and appear to be filled with relatively flat, fresh ice; based on this and on the calculated amount of heat generated by Europan tides, it is predicted that the outer crust of solid ice is approximately 10–30 km (6–19 mi) thick, including a ductile \"warm ice\" layer, which could mean that the liquid ocean underneath may be about 100 km (60 mi) deep. This leads to a volume of Europa's oceans of 3 × 1018 m3, slightly more than two times the volume of Earth's oceans.", "Here is what I found on NASA's website: \n\n > Why do we think that Europa has a subsurface ocean?\nThere are several strong pieces of evidence that suggest an ocean exists on Europa:\n\n > The magnetometer aboard the Galileo spacecraft detected signs of an induced magnetic field near Europa's surface, clear evidence for a conductive substance less than about 30 kilometers (about 20 miles) or so below. This is strong evidence for some amount of salty liquid below the surface. But the Galileo spacecraft was not designed specifically to test the hypothesis of a subsurface ocean on Europa. To know for sure whether Europa has an ocean, a spacecraft would need to carefully measure the tidal fluctuations of Europa's surface as it orbits Jupiter. This would require a spacecraft to either to go into orbit around the moon or make repeated flybys with the right geometries.\n\n > Europa's surface features (including bands, ridges, chaos terrain, and multi-ringed impact structures) suggest that there is warm, mobile, glacier-like ice at relatively shallow depths that sometimes has reached the surface. The presence of an ocean would make Europa's frozen surface flex more under its daily tides, cracking and warming the ice, to help explain its strange surface geology. For example, Europa's bizarre curved fractures (called cycloids) probably owe their origin to cracking in response to the flexing of Europa's icy shell on the very rapid time scale of its 3.55-day rotation. Creating large fractures in this way this requires large tides, best facilitated by liquid water. Also, Europa's multi-ringed impact structures suggest that Europa's largest impact scars punched all the way through the ice shell into an ocean.\n\n > Judging by the pattern of the satellite's large-scale fractures, the surface of Europa may have \"slipped\" relative to its interior (processes called \"nonsynchronous rotation\" and \"polar wander\"). A subsurface ocean would greatly facilitate this slipping, allowing the ice shell to slide over the fluid ocean. Such slipping would be much more difficult if the ice shell was in direct contact with rock.\n\n[Source](_URL_0_)", "In the beginning it was closeup photographs by the voyagers, or possibly pioneer 11 I don't remember if it came close enough to europa to take pictures, that showed surface features that suggested the ice moved and reacted to tides. they wern't sure at that point but it seems likely there was a liquid layer beneath the surface.\n\nIT's worth noting that even today it's not proven that there is a liquid ocean beneath the ice, but all our observations thus far including some high resolution photographs are consistent with a liquid layer beneath the ice. There is also evidence, from the interaction of europa with jupiter's magnetic field, that there is a conductive layer beneath the ice, and it is surmised that this is most likely to be a salty liquid ocean. \n\nNot sure what the calculations you're referring to are...", "Forgive me, I may not give the best answer but I will do my best.\n\nWe don't have any actual proof that there is liquid water on Europa, although we are pretty sure that it is there. This is based on a few different observations. One being our observation through the Hubble Telescope of enormous water vapor plumes. If I remember correctly they think they are made from regular volcanic like plumes like those in our oceans. There were also tests performed with the Galileo orbiter that had something to do with the magnetic field on Europa and Jupiter which suggests that there might be a salty (and therefore conductive) ocean under the crust. There is also something called tidal acceleration (if i remember correctly) that would heat up the water closer to the rocky surface of Europa. \n\nI hope I answered your question, and sorry it couldn't be more specific. ", "The short answer is that geologists sat down and created models to show how the surface features could be created by tidal movement. \n\nA person I've had the pleasure of working with over the years is, quite literally, the top authority in the world on this specific subject. He was the one who discovered this. I was just chatting with him, and he provided this insight as well: \n\n\"The real smoking gun was that the magnetometer on Galileo measured a dipole during close flybys of Europa. If Europa has an ocean (with salts) then an induced magnetic field should be detectable. And it was\" \n\nI'm trying to see if he can create an account and provide a more detailed answer. ", "How could there not be liquid oceans underneath miles of ice?\n\nWater is most dense as a liquid, therefore with that much ice creating enormous pressures underneath, the water would necessarily turn into a liquid, no?" ] }

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{ "a_id": [ "cm3afik" ], "score": [ 156 ], "text": [ "Romans wrote a lot of BS about 'the Germanic tribes', mostly because they defined 'Germans' as 'those who are not like us and who live outside the borders of the empire'. This definition lumps quite a lot of people together, while still throwing in loads of cultural bias as well.\n\nIt is much more interesting to look at 'people who lived outside the Empire' outside of their classification as 'Germanics'. We then see that settlements change over this time period. In the centuries BC (and up to 200 or so), the regular person would live on his own farmstead, within viewing distance (or walking distance) of his neighbours. A farmstead would have its own fences, wells, and outbuildings and would generally be mostly self-sufficient, though some regional specialisation (some areas focused on cattle raising, some on cereal cultivation etc.) did take place. Some areas that were particularly suitable for resource exploitation (close to forest for suitable timber, or close to iron ores for iron mining, or near the sea for salt extraction, or near a peat bog for peat digging) did have this 'industry' as a household activity 'on the side', but this is secondary to the main function of the household as a farm.\n\nAround the 2nd century or so, the village (collection of farmsteads) becomes more popular. While villages did exist in the earlier period as well (but were not the norm), the village of the late roman period becomes more common and more formalised. We now see a collection of these farmsteads. Archaeologists have tried to make statements about elite dominance within these farms on the basis of the size of the stable (and hence the capacity for cattle, and hence wealth), but this is very difficult. Generally, it seems that farms within a village were 'equal'. This does not mean that everyone within the village was equal, just that everyone lived in the same kind of house. It is also later, in the Migration period, that the size differences between households within a village gets more expression, and the larger farmstead collects also more small outbuildings, including a temple and more craft workshops. The first of these is Gudme in Denmark around the year 200, but by 400 these kind of places exist in many regions.\n\nParallel to this, you should also keep in mind that in the south of 'Germania', in modern Southern Germany and Austria, village organisation had already taken place in much earlier periods, including task differentiation between households.\n\nWe can see no traces of nomadism in Germany, the Netherlands and Denmark in this period. They did travel to cattle grazing grounds in the summer, but this type of seasonal movement, called transhumance, is restricted to cattle herders, and not common within society in general. It is also highly regulated and occurs within fixed 'grazing areas', relatively close to the stationary 'home base', and not at all 'migratory'.\n\nFarms (and hamlets) also did move around within a landscape, so a field that in one decade might have been used for grain, might become a building plot a decade later, and grazing lands 30 years after. However, this cycle of rebuilding the farm (related to pest control) also happens within a local area." ] }

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{ "a_id": [ "c9dua0a", "c9dufj4", "c9dvkaq", "c9dvzik", "c9dyqhk", "c9dz7sc", "c9e0705", "c9e08cx", "c9e1i9d", "c9e25zd", "c9e3v9l" ], "score": [ 117, 12, 4, 53, 15, 4, 3, 24, 5, 2, 2 ], "text": [ "Miniaturizing the fancy lenses on SLR cameras would be a lot of work—they require extremely precise optical glasswork and tons of fiddly mechanical gizmos for focusing and such.\n\nThe really insurmountable difference between big cameras and small ones, though, is sensor size. The sensors used in digital cameras have tiny electronic \"photosites\" which convert photons into electrons. Making these smaller has a serious adverse effect on the quality of the images you can produce, for physics reasons.\n\nThere's nothing magical about the 35mm size, of course. That just happens to be the size of the imaging region of standard photographic film, so lots of equipment was made to that standard for a very long time. When digital SLR cameras hit the scene, photographers and manufacturers wanted to keep using their old lenses, so they kept the same physical layout and just replaced the film with a digital sensor of comparable size.", "The physical size of a lens is dictated by the diameter of the image circle it has to produce to completely cover the sensor. SLR sensors are fairly large and so the lenses also have to be large. Full-frame SLR sensor has dimensions of 36x24 mm, and most lenses (esp. professional ones) tend to be compatible with this standard. There are some more subtle reasons for large lenses, but this is the basic one.", "You want high performance? You better use a large sensor. Or, rather, the size of each individual pixel needs to be large.\n\nSmall pixel sizes have poor performance. They are more vulnerable to noise and other issues.\n\nWhen you want all the performance you could get, there's no choice but to use large sensors. With that come large lenses. That's all.", "Super simplistic analogy:\n\nDon't forget that when you take a photo, you are building something using light (photons) and the more photons that you can collect, the greater the detail (quality).\n\nA lens with a large diameter, like an SLR lens, allows much more light to be collected simultaneously as opposed to the tiny diameters of those lenses used in mobile devices.\n\nThe software & hardware of a mobile device really does a great job of compensating, but that's just it though, it's still compensating at best. Even if the SLR designs were scaled down to mobile device sizes, it seems doubtful that they would be able to truly replicate the efficacy of full sized lenses.\n\nSource: decade of photographic sales, development, and processing\n\n*Edits for clarity*", "Looking at the comments there has been a lot of focus on the sensor size, but another important consideration is the optical properties of the lenses themselves. The most basic characteristics of lenses are the Focal Length and the Aperture Diameter. The ratio of focal length to aperture diameter is called the f-number (f-number = FL/AD). \n\nThe f number in turn determines the optical resolution of the light focused by the lens, a higher f number results in less light hitting the sensor, lower resolution but high \"depth of focus\" and a smaller f-number results in more light hitting the sensor, higher resolution and smaller depth of focus.\n\nThe ratios involved here have real physical constraints that determine lens size. A telephoto lens by definition has a high focal length, so to have a high focal length lens for a high resolution camera you need a low f-number. To get a low f-number you need a large aperture diameter! \n\nAn example of why everything is so big:\nSay you have a 135mm telephoto lens on your sweet SLR so you can take pictures of giraffes humping in the Serengeti. Your high resolution camera wants an f-number of something like 2.2 to get piercingly clear images of giraffe coitus. Some quick math gives you an aperture diameter of 61.36mm which for the American giraffe enthusiasts out there, is 2.42in. There's just no getting around physics when you need shockingly clear photos of even-toed ungulate mammal reproduction.\n\n\n ", "As others noted before me, larger lens apertures and larger sensors (with bigger pixel sites) physically let more light into the system and more easily differentiate (sharply focus) light, respectively. At some point you also run into the **[diffraction limit](_URL_0_)**, where angular resolution is limited by the diameter of the lens opening (bigger lens = sharper limit), so tiny cameras' theoretical image granularity get hit by CMOS/CCD and fundamental optical limits.\n\nThat being said, why can't you have a really broad lense and sensor that were really thin? Refractive optics just aren't fundamentally there. Professional-grade lenses often use 10-20 different layered lens elements internally to provide minimal distortion and best frame-wide focus at a range of focal depths and optionally focal lengths (i.e., zoom). Using more exotic glass types for minimized color-dependent focal lengths (**chromatic distortion**) or aspheric lens surfaces (more expensive to grind) get lenses that are closest to their best in a wider range of conditions/settings, but perfection isn't even theoretically possible.\n\nWhat's on the horizon that could change this? Well, **[metamaterials with negative refractive indexes](_URL_2_)** allow some theoretically better and flatter lenses, but real examples of these tend to work better at sub-visible light frequencies and only for certain narrow 'color' ranges. Something I would bet might be closer is **[light field processing](_URL_1_)**, whereby an array of small lenses can have their input computationally processed to simulate a larger aperture lens at multiple focal depths *simultaneously*. Think of small lenses tiling a surface like the compound eyes of an insect. There have been large-scale (~1 m^2 arrays of webcams) demonstrations of this being used to do fancy things like see through foliage, but I am unaware of someone seriously proposing something like a thin, 1\" square lens array and data processor that could realistically replace a normal 'fat' lens/sensor combo.", "I'm willing to bet smaller sensors are the way to go in the future. Using the human eye as an analogy we have pretty small lenses compared to most cameras but we have millions of light sensitive nerves that can work very well with the amount of light that is captured.", "Lots of people talking about sensors, not enough about the lenses themselves. The scientific reasoning for this relies heavily on some knowledge of the [fourier transform](_URL_0_). \n\nThe image at the lens is focused toward the sensor. Physically what happens is a specific phase correction (read: time delay) is applied to the inbound light rays based on the material of the lens, the curvature of the lens, and the thickness of the lens. However, due to the finite aperture size, some of the information of the image is truncated (IE, only some of the generated light rays are captured by the camera.) Mathematically, this means the frequency domain information of the light is being *convolved* at the lens with the fourier transform of the geometrical shape. For a circular lens, this is the sombrero function (circular sinc.) In laymans terms, this means that the image itself is being smeared in the frequency domain, and the degree of this smearing is dependent on the size of the sombrero function. By fourier transform intuition, a broader lens collects more light, loses less information and causes less smearing of the image at the lens' focal distance (where the detector is placed.) \n\nThis is why huge lenses take stunning photos, it's why mobile cameras (small apertures) take crappy photos. You can improve the sensor all you want - at the end of the day, the lens size is mathematically limiting how crisp the sharp edges (the high frequency components) of the image will be.\n", "It has to do with the diffraction limit, which defines how small of a bright circle each point of light makes. The smaller the diffraction limit, the tighter the circle, and the sharper details that you get. \n\nThe formula for calculating the diffraction limit as an angle is \n\nLimit Angle ~= 1.22 * (wavelength) / (diameter of aperture)\n\nFor visible light which we'll ballpark around 409nm wavelength, the diffraction limit of an aperture of 5mm (roughly a cell phone camera lens size) has a diffraction limit of 1x10^-4 degrees. This seems pretty good, but for the sensor a few millimeters behind the lens, for a field of view of 20 degrees this only gives you about 200000 distinguishable points of detail in each dimension, assuming your optics are perfect (which they're not going to be).\n\nLet's up the lens, then, to a 5cm aperture (roughly DSLR size). Doing the calculations, the diffraction limit is decreased tenfold, to 1x10^-5 degrees. For that same 20 degree field of view, you can now fit in 2 *million* distinguishable points. This is why digital SLR cameras with their larger lenses are theoretically able to capture more detail in a scene. As far as the fancy depth-of-field effect, where a digital SLR camera can kind of isolate a subject in its own focus plane and everything else seems out of focus, that has to do with the change in focal length of the target object creating details larger than the diffraction limit, which makes them blurry. I'm sure someone else could explain the math of that better than I could though, but in general the larger your aperture the more tight your depth of field will be.\n\nWhy stop with digital SLRs though? Let's go for Hubble, with its giant 2.4m aperture. If the optics were perfect and there were no atmospheric distortion, doing the calculations again we get 2x10^-7 as the smallest resolvable angle. That means that if Hubble were pointed at the earth and we're in our perfect physics world with no atmospheric distortion, it could theoretically see details as small as 11cm from its orbital height of 569km.", "Plus - Isn't 35mm the focal length and not necessarily the physical size?", "35mm isn't necessarily the standard for lenses. 50mm lenses are cheap and common which are the closest to the human eye. Cheap dslrs typically are bundled with lenses with a range of 18-135mm. 35mm sensors are considered \"full-frame\" for dslrs, but the majority of DSLRs normal people will buy are actually cropped, and the frames are much smaller than 35mm. If you shrunk the size of the frame, you'd shrink the size of the depth of field. " ] }

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[ [], [], [], [], [], [ "http://en.wikipedia.org/wiki/Diffraction-limited_system", "http://en.wikipedia.org/wiki/Light_field", "http://en.wikipedia.org/wiki/Negative_index_metamaterial" ], [], [ "http://en.wikipedia.org/wiki/Fourier_optics" ], [], [], [] ]

{ "a_id": [ "cle7f0d", "cle7mwo" ], "score": [ 8, 4 ], "text": [ "Rewriting any code that's locked to a particular system to work for the other ones. The OS has 'toolboxes' for things, but each OS's is a different. You have to rewrite to use the other tools. ", "They rewrite code that is designed specifically for Windows. For example, if they port Portal 2 to Mac and Linux (they actually have done this; this is hypthetical), they will have to rewrite the sound playing files to use Mac/Linux methods, and create the window to be for Mac and Linux. Some things, though, are universal, such as image files and in most cases the base code (like what will happen when the player attempts to walk into a portal and how fast the player moves, etc.)." ] }

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{ "a_id": [ "dgz9r3i" ], "score": [ 3 ], "text": [ "By the Archimedes' principle, a buoyant body (that is, stationary without expending energy to remain that way) submerged in water, is equal in mass to water of equal volume to the part of the body submerged underwater. For fully submerged bodies, that means it's mass is equal to the mass of the water of equivalent volume.\n\nSince a blue whale can remain stationary underwater, it follows this principle. By approximating the volume of the whale, we can calculate it's mass by calculating how massive is water of equivalent volume. In open ocean, exact volume calculation could be difficult, but a reasonable estimation is possible with visual means.\n\nFor more controlled environments such as a large swimming pool (not applicable to a blue whale, but applicable to orcas or dolphins), a more precise volume approximation may be done using another law attributed to Archimedes, the Equal Displacement rule, stating that a body submerged in water displaces an equivalent volume to its own. By measuring the height of the water with and without the animal, we can calculate the animal's volume, and then proceed with the Archimedes' principle above to calculate it's mass." ] }

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{ "a_id": [ "c30n9jq", "c30n9jq" ], "score": [ 9, 9 ], "text": [ "Hi there! I use this at work. I'll give it a super ELI5 shot:\n\nImagine your friend wrote a paper in Swahili and gave it to you. Cool, but you don't speak Swahili. So what he did was also send you the phone number to a guy who *does* speak Swahili. You call him up, he comes over, and he reads the paper aloud to you. That's how TrueCrypt works.\n\nPaper in Swahili - HDD with encrypted data **written down**. This is the important part, that it's only written down in encrypted format.\n\nGuy who speaks Swahili - TrueCrypt. For the purposes of this analogy, we'll say that lots of people speak Swahili, but only if you call them up using that exact phone number will any of them actually talk to you. He can turn the Swahili into data you can use. This is TC turning encrypted data into useful data 'on-the-fly' as it says in that document.\n\nPhone number - Code that you use to \"mount\" the TrueCrypt volume.\n\nGuy reading it aloud - Loading the encrypted data into RAM. Notice that the guy is reading it aloud to you and it's going into your head. This means that there is **no** decrypted copy in long-term storage anywhere. This is important. It's not like the guy copies the paper into a language you do understand and leaves it for you. With this, you *have* to have a Swahili-speaker to use it, and there is no decrypted copy anywhere but in your head (and his, but his memory sucks).\n\nNow, what about the other way? Sure. When you write to a TrueCrypt encrypted volume, you're dictating in English to a guy who writes it down in Swahili. Only if you have the phone number to get this guy again can you get it back out. Same deal, there is no unencrypted copy anywhere.\n\nBasically, TC is a magic door that makes everything passing through one-way gibberish, and turns everything passing through the other way from gibberish to useful data.\n\nDid that help at all?", "Hi there! I use this at work. I'll give it a super ELI5 shot:\n\nImagine your friend wrote a paper in Swahili and gave it to you. Cool, but you don't speak Swahili. So what he did was also send you the phone number to a guy who *does* speak Swahili. You call him up, he comes over, and he reads the paper aloud to you. That's how TrueCrypt works.\n\nPaper in Swahili - HDD with encrypted data **written down**. This is the important part, that it's only written down in encrypted format.\n\nGuy who speaks Swahili - TrueCrypt. For the purposes of this analogy, we'll say that lots of people speak Swahili, but only if you call them up using that exact phone number will any of them actually talk to you. He can turn the Swahili into data you can use. This is TC turning encrypted data into useful data 'on-the-fly' as it says in that document.\n\nPhone number - Code that you use to \"mount\" the TrueCrypt volume.\n\nGuy reading it aloud - Loading the encrypted data into RAM. Notice that the guy is reading it aloud to you and it's going into your head. This means that there is **no** decrypted copy in long-term storage anywhere. This is important. It's not like the guy copies the paper into a language you do understand and leaves it for you. With this, you *have* to have a Swahili-speaker to use it, and there is no decrypted copy anywhere but in your head (and his, but his memory sucks).\n\nNow, what about the other way? Sure. When you write to a TrueCrypt encrypted volume, you're dictating in English to a guy who writes it down in Swahili. Only if you have the phone number to get this guy again can you get it back out. Same deal, there is no unencrypted copy anywhere.\n\nBasically, TC is a magic door that makes everything passing through one-way gibberish, and turns everything passing through the other way from gibberish to useful data.\n\nDid that help at all?" ] }

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{ "a_id": [ "dfyt82l", "dfyw4a5" ], "score": [ 13, 6 ], "text": [ "For microwave you will have an increased time. \n\nThe food will have to absorb twice the energy. \nSome energy will be lost in the oven itself. Also microwaves are not good at penetrating water and will only be good at heating the top layers. So that can case some water to evaporate. (Lost heat)\n\nBut in general you will need to supply twice the energy to heat twice the mass of food. \n\nSome exceptions apply like tiny food stuff that only gets hit by very few waves and causes the loss to occur inside the over mostly. \n\nP.s.: I have no clue what a hot pocket is ;)\n", "Microwaves have a specific power output, like 1000w. How fast your food heats up depends on the total power output of the magnetron, and the percent of power absorbed by the hot pocket. The percent power absorbed is a function of average cross-sectional area in relation to the average orientation to the wave emitter. \n\nIf you double the amount of things, general rule of thumb is add 75% of the original time. If you double the volume of 1 thing it's more like add 150% of the time. \n\n" ] }

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{ "a_id": [ "dkd8okb", "dkddpaa" ], "score": [ 5, 17 ], "text": [ "You can not. There is no substance that exists that can bounce all light off of it. No matter what some photons are absorbed, and eventually all will be absorbed.\n\nYou can bounce light into a mirror sphere, but mirrors are not 100% reflective, so all light will be absorbed by the mirror fairly quickly.", "Optical cavities exist but you have to keep in mind that no mirror is perfect and even if, say, a mirror reflected 99.9% of light, given a 1 meter cubed box, light would reflect 300 million times a second. So that means that after 10 microseconds there'll only be about 1% of that light left.\n\nHowever, generally when we build an optical cavity we are continuously GENERATING new light within it and an optical cavity is a big part of, for example, the design of a laser. In this case it is by design that the light get out, rather than be reabsorbed and you don't want perfect reflection (though you do want really good reflection) but rather higher transmission than absorption" ] }

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