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7mfn3y
|
market capitalization when it comes to purchasing a company.
|
Here is my understanding of market capitalization: outstanding shares x stock price = market cap. The market cap is in essence the value of the company.
Recently Humana announced they would be buying Kindred Healthcare for $4.1B. Kindred's market cap is $822M at the time of this writing. Wouldn't that mean that Humana is paying more than 4x what Kindred is actually worth?
I'm so confused. Please ELI5. Thank you in advance!
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/7mfn3y/eli5_market_capitalization_when_it_comes_to/
|
{
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"Often the buying company must pay a premium to the traded price, to acquire the company, but usually this premium is 20-50% of the pre-offer share price. \n\nOne thing that isn't in the market cap but is usually part of the purchase price is the assumption of debt. If Kindred owed roughly $3.3 billion to its creditors, the purchase price could be $4.1 billion with only $800 million going to shareholders. The idea being the purchase of two otherwise identical businesses, one financed by mostly equity while another financed by mostly debt should probably have the same purchase price. \n\nI didn't see the deal press release, but did find an article with this:\n\n > Kindred, which had $7 billion in revenues last year, has been weighed down with *$3.2 billion in long-term debt.*\n\nSo Humana is paying $800ish million for the equity in Kindred Healthcare, but also will have to repay Kindred's creditors $3.2 billion. It's fairly common to include both of these when reporting the amount spent on a merger. \n\nWhoa, thanks for the gold!",
"There are many different ways to value an asset, be that a house, a single square of toilet paper, or a company. At any given moment, the different ways to value an asset can be equal or vastly different. However, the actual price of something at any given time is the intersection of supply and demand.\n\nIn terms of valuation there are many ways to value something.\n\n* There's **replacement cost**: how much money would I need to spend to replace this exact asset at this particular moment in time with another of the same quality. Car insurance companies use this when valuing your car in case it gets 'totaled'. A car is totaled when the cost to repair it is greater than the cost to buy a similar car (before the damage) on the open market. This is why a 15 year old car with 250k miles on it can be totaled after a fender-bender. A insurance company would prefer to pay the $900 to buy a comparable copy of your car versus what it would cost to repair it.\n\nLet's look at a bottle of water as an example. I can buy a bottle of water at a gas station for $1.19. If I walk out of a gas station after purchasing a bottle of water and it gets stolen, the replacement cost of that bottle will be another $1.19 plus the effort it takes to go back inside and retrieve another one.\n\n* **Market Capitalization** is exactly what you described. The number of outstanding shares times the price per share. For public companies, this price is the aggregate of all publicly available knowledge about a company's value. In layman's terms, this means that across however millions of shareholders a company has, their collective average valuation of that company at any given picosecond is the market capitalization at that moment.\n\nSince a Market Cap is the crowdsourced valuation of a company, it will include things that don't affect other types of valuations. Wall Street's perception about who's running a corporation, where the company is incorporated, how many (and how serious) pending lawsuits it may be exposed to all affect how people perceive a company's current value (or, more importantly, how they think it will be valued in the future). \n\nThis is why companies like Tesla have a huge market capitalization relative to the value of their physical assets. People *think* Tesla will be more valuable in the future than it is today, so its market capitalization is nearly equal to a physically much larger car manufacturer like General Motors. \n\nUsing our water bottle example, Market Capitalization would be like getting a million people into a room and asking everyone how much each would pay for one water bottle ($1.19). Then taking their average price to determine the value of 100,000 water bottles ($119,000).\n\n* There's also **intrinsic value** which takes into account how a company generates cash. Value investors calculate a company's intrinsic value and compare it to the market cap to see if a company is over or undervalued at any given time.\n\nIf I own a 100 water bottles, using the market capitalization method I have $119 worth of assets. But, if in real life I am selling those bottles for $2 each, my assets are worth much more than what my market cap is suggesting. My intrinsic value, in this example would be much higher than $119 because the cash I generate from my assets is higher than what the market gives me credit for.\n\nFinally, we come to price in the real world. Buyers of public companies almost always need to pay more than the market cap for a number of reasons.\n\nOne, you need to convince the target's shareholders to actually sell their stock. Remember, a company's current price is the aggregate of the collective knowledge of its shareholders. This means that a company's shareholder are, at any given time, happy with their expectation of prices. No one would continue to own a share of a company if they *think* the price was going to get worse, they all continue to own shares because they think the price will increase. So, to purchase all of the shares of another company, you have to buy them for more than what the average shareholder thinks they're going to be worth.\n\nSecond, a market cap is the valuation of a company given all publicly available information. Publicly available is a key distinction. All companies have trade secrets, secret product development pipelines, and their own secret sauce that only they know about and control. The secret sides of a company are sometimes called 'goodwill' on a balance sheet because its made up of things that aren't able to be easily valued. \n\nIn pharmaceuticals, the difference between physical value and goodwill can be extreme and nearly impossible to valuate. The cure to the common cold could make a small lab of five researchers worth billions of dollars. But, if they fail to get their promising drug past FDA regulations, they're literally worthless.\n\nFinally, there are a host of other reasons to pay more for a company. Maybe you're paying gobs of money for a company because you don't want your competitor to purchase them. Maybe they have a key patent to a widget that you want to include in your next gadget and without the rights to that widget, your gadget is worthless. Or maybe you're under intense pressure from your own shareholders to grow your company and Company Z is up for sale.\n\nThis gets us to supply and demand and real price. Humana is spending $4.1 billion on Kindred because Kindred is worth $4.1 billion to Humana. All of Humana's internal valuations of Kindred's product line, services, people, patents, and more sum up to $4.1 billion (or more). Kindred's selling to Humana because their internal valuation of all of those things is $4.1 billion (or less).\n\n\n\n\n"
]
}
|
[] |
[] |
[
[],
[]
] |
|
10vgn7
|
If everyone had a self-driving Google car, would there be a problem with interference between all the radars and lasers?
|
askscience
|
http://www.reddit.com/r/askscience/comments/10vgn7/if_everyone_had_a_selfdriving_google_car_would/
|
{
"a_id": [
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48,
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"text": [
"Probably not. Google “phase-sensitive detection” and you'll see how it's actually quite easy to recover your own signal from a sea of noise.",
"Follow up question: \n\nIf there were a sea of self-driving Google cars that somehow had to report each others positions to each other actively, rather than simply updating the positions of nearby cars inside their local memory, how would that be done? Would **that** cause a problem with interference between all the signal updates? "
]
}
|
[] |
[] |
[
[],
[]
] |
||
6ivo3l
|
the difference between interpreted and compiled computer languages?
|
I'm teaching myself code right now and this subject has come up here and there. I feel like I understand general qualities of the two languages but don't have a fundamental understanding of what they truly are.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/6ivo3l/eli5_the_difference_between_interpreted_and/
|
{
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"dj9f8wj"
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22
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"text": [
"Compiled languages are translated directly into the machine code that the processor can execute. It would be like taking a cookbook written in Greek, and getting it translated to a cookbook written in English. Once you have the translated cookbook, you can then follow the recipes (as can everyone else that reads English).\n\nInterpreted languages are translated on the fly. It would be like having a professional Greek interpreter sitting next to you, and you'd go \"ok, what next?\" and the Greek guy would be \"Add half a cup of broth\" and so on. The upside is that you didn't have to wait for him to translate the whole damn book, and if the original author makes changes to the book in Greek, you don't have to go retranslate it. The downside is that now whoever wants to use the recipe book has to have the Greek guy sitting next to them.\n\nCompiled languages are usually faster to run, but they require a \"build\" step which can be time consuming, and is effectively when the translation to machine code is done.\n\nInterpreted languages don't usually require a 'build' step, but they usually don't run quite as fast, because they need to have the interpreter there, translating everything as the program runs."
]
}
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[] |
[] |
[
[]
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3sxehv
|
why do manufacturers print "best before: see bottom" instead of the actual date?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3sxehv/eli5_why_do_manufacturers_print_best_before_see/
|
{
"a_id": [
"cx17u8h"
],
"score": [
4
],
"text": [
"It could be a case where the label is printed well before the product actually gets canned/boxed, so you cant put a date on the label as you don't know when it will actually be put on a product. So it directs you to where the date will be put during the final canning/boxing process."
]
}
|
[] |
[] |
[
[]
] |
||
7auxmh
|
Have humans/organisms caused an increase on the overall mass of Earth? ie man made objects or birth of organisms?
|
askscience
|
https://www.reddit.com/r/askscience/comments/7auxmh/have_humansorganisms_caused_an_increase_on_the/
|
{
"a_id": [
"dpd27to",
"dpd2i18"
],
"score": [
8,
42
],
"text": [
"The Earth (and everything on it) has not really increased in mass, other than meteorites coming in and lighter gases going out.\n\nYes, there is a lot more people, animals and plants than in the beginning. That's life, basically turning dirt and sunshine into people.",
"Since all organisms on earth are created from the earth, (air, water, minerals) it is simply a redistribution of mass. We actually have reduced the mass by sending probes away from earth. Some is replaced by the constant in fall of inter solar dust and meteors but organisms do not add mass."
]
}
|
[] |
[] |
[
[],
[]
] |
||
2ho1ys
|
why in most us universities do they make you share a room with a roomate?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2ho1ys/eli5_why_in_most_us_universities_do_they_make_you/
|
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"text": [
"It's cheaper, and uses less space. I'm getting shafted enough already on rent in this two-person dorm room, I can't imagine what it would cost for everyone to have their own room. ",
"They get twice the amount of money for one room. Economics is down the hall. ",
"more people in the same living space equals greater profits per unit\n",
"Because not having a roommate would be a tremendous waste of a bunkbed.",
"Because then the dorms would all be 75 stories high.\n\nYou have a refrigerator, right?\n\nIt has 5 shelves, give or take a few.\n\nDo you just put one thing on each shelf? Fuck no, you fill that fucker up.\n\nSame thing with college. You get a roommate for 2 reasons. First, they want you to socialize, and with a random person, you will socialize.\n\nSecond, they want to be able to house everyone.\n\nIF you want a private room, you can get one, tell your parents to fork over more money so you can fap on your own time."
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[]
] |
||
9ed2cb
|
Possibly the defining characteristic of Julius Caesar's legendary status as a general was the speed with which his army was able to operate- what accounted for this? What was he doing that other Roman generals weren't? Do we know how he was able to pull this off?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/9ed2cb/possibly_the_defining_characteristic_of_julius/
|
{
"a_id": [
"e5o6cst",
"e5o7foq"
],
"score": [
60,
22
],
"text": [
"This has been asked before:\n\n_URL_0_",
"Refer this [earlier thread](_URL_0_)\n\nExcerpt from /u/Teizke : \n\n > He was in fact a believer in *forced/loaded marches* as seen in his campaigns mainly in gaul. He was able to do this because he was so charismatic and loved by his troops. He would often *sever[e] his baggage train* in order to march faster which is a very risky move that can result in the cutting off of the armies. It almost always worked out for him but more often than not for other commanders \n\n/u/XenophonTheAthenian\n \n > Both posters here correctly mention that Caesar would often march with no baggage and often resorted to forced marches, but they neglect Caesar's use of night marches, which was a key feature of his strategy of movement ......\n\n > Caesar's marches were always rather quick, since he marched for longer than most armies\n\n[Plus of a couple of famous marches that they were more like dashes/flanking manoeuvres that left a large portion of the army to catch up and left even the vanguard tired and having to rest after they got there...]\n\n > ... It's worth noting that not all Caesar's troops got there at the same time--it seems that a significant portion of his army fell out of the march and continued as best it could, to be collected over the course of the next couple days and allowed to rest.\n"
]
}
|
[] |
[] |
[
[
"https://www.reddit.com/r/AskHistorians/comments/2zre9o/how_did_caesar_move_his_troops_so_quickly/"
],
[
"https://np.reddit.com/r/AskHistorians/comments/2zre9o/how_did_caesar_move_his_troops_so_quickly/"
]
] |
||
6d355p
|
why is devil's food cake not just called devil's cake?
|
I understand the name refers to the texture and decadence of the type of cake but why does the name include the word "food" if it's cake?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/6d355p/eli5_why_is_devils_food_cake_not_just_called/
|
{
"a_id": [
"dhzhknx"
],
"score": [
4
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"text": [
"there's two kinds of cake. \n\nthe first one along was called \"[angel food cake](_URL_0_)\". \n\n\nthen someone added chocolate to it, and made it into \"[devils food cake](_URL_1_)\". \n\n\nbecause the second one was \"devilishly good\"\n"
]
}
|
[] |
[] |
[
[
"http://allrecipes.com/recipe/7324/angel-food-cake-i/",
"http://allrecipes.com/recipe/25570/devils-food-cake-ii/"
]
] |
|
2iovsy
|
why does alaska have so many lakes?
|
I was looking at a map of alaska, near Alpine Alaska, and I noticed tons and tons of small lakes. Why are there so many up there?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2iovsy/eli5_why_does_alaska_have_so_many_lakes/
|
{
"a_id": [
"cl42dlr"
],
"score": [
4
],
"text": [
"Glaciers receded during the ice age and tore up the land. Check out what most of the Canadian landscape looks like vs the lower 48 for a clearer example. Tons of tiny (and not so tiny) lakes everywhere. "
]
}
|
[] |
[] |
[
[]
] |
|
ttvlj
|
Ancient Rome, Marriage, Sex
|
I recently have discovered the huge differences between Roman norms and modern Western norms for sexuality. There were a few discrepancies I could not find the answers to for the Principate era, once I explain what I think I know.
Everything in Roman society came to *virility*, in the sense that a man (*vir*) had to be masculine in order to perform his duties. The *pater familias* essentially owned everyone in his family, and any crime against a child or woman legally committed the crime against the *pater*. Married women, unmarried women, and boys were considered "sacred" and could not engage in sex. Young men, however, could engage in relations with *infames* (prostitutes, actors, gladiators) or slaves, or they take a *concubinus*. When a man married, he had the same abilities except having a *concubinus*. Punishments were finally formalized with Augustus' *Leges Juliae*, which continued to allow divorce but even allowed the husband to kill the adulterer.
If the *pater familias* died, would his sons become *patres familias* of their respective branches? Were married women not allowed extramarital sex, even with slaves or *infames*? Was a man subjected to social degradation if he was the "bottom" only when he was a full Roman citizen or even when he was a freedman (and not legally considered an *infamis*)? Were all men taken as *concubinus* or *puer* considered *infames*? What were the common punishments for when a husdand was found cheating, and the same for a wife?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/ttvlj/ancient_rome_marriage_sex/
|
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"text": [
"I'm actually a little skeptical about how much different their sexual norms were. For example, many say that sex between men and boys was acceptable but there's a scene in The Satyricon where a tutor brags about trying to seduce his underage male student but if the father caught him, he'd be killed. There's a lot of other stuff I periodically stumble over that I can't recall off the top of my head. I probably need to start taking notes when I do.\n\n > If the pater familias died, would his sons become patres familias of their respective branches? \n\nI think so and the Wikipedia article seems to back it up. \n\n > Were married women not allowed extramarital sex, even with slaves or infames? \n\nNo. I really don't think so. A father and/or husband might let it slide if the whole world didn't know about it. But if it became public, they may feel pressured to do something. This seemed to be the case between Augustus and Julia regarding her adultery scandal.\n\n > Was a man subjected to social degradation if he was the \"bottom\" only when he was a full Roman citizen or even when he was a freedman (and not legally considered an infamis)? \n\nYes. Even if there were no legal punishments for certain acts, there were social pressures. It was not okay for a man to cheat on his wife in any respect. \n\n > Were all men taken as concubinus or puer considered infames? \n\nSocially probably. Legally, it depends. Homosexuality was frowned upon but there doesn't seem to be many if any laws against it. Though the individual pater familias would deal with such situations in their own way. Though it seems that an adulterous wife was more damaging to family honor than a son who had a boyfriend.\n\n > What were the common punishments for when a husdand was found cheating, and the same for a wife?\n\nThis would probably fall under the authority of the pater familias and would depend greatly on the situation. If it was the pater familias himself, the social damage would be the punishment; his whole family would probably be pissed for dishonoring the whole family. In honesty, this is much triangulation on my part. I don't know off hand of any written accounts detailing such a specific situation with a man. With a woman, Augustus had Julia exiled, though I think that was considered rather severe.\n\nEdit:\n\nThanks for posting this because it lead me to reading the Wikipedia article about infamia and helped me piece together some things I'm working on. I had read that Caligula had lifted the law that forbade slaves from testifying in court to help with his majestas trials. And in Antiquity of the Jews, Josephus talks about how an actress was used to testify against a senator. Her ability to testify is most likely because all laws forbidding infames from testifying were lifted. It's just really interesting seeing that these things are interconnected. It's these moments right here why I love studying history. I'm having a mini-orgasm in my brain.",
"I'm on my phone so I'm just going to answer your last question here, and come back later for the rest. \n\nIn Roman law and morality adultery is defined only as sexuality relations between a married woman and a man who is not her husband. Therefore, a married man can have sex with anyone - male or female - except women married to another man. The punishment for adultery therefore is usually on the married woman, and is traditionally handled by a family council of her parents, grandparents etc headed by her paterfamilias or guardian (although as Richard Saller demonstrated in the 1990s the life expectancy of the Roman man was such that many women would be under the power of a guardian such as a service brother or family friend). Legally and technically the punishment was death, but due to the private nature of the judging body its very unclear how often women were actually executed for sexual crimes. It's probably pretty rare. \n\nThis was a pretty brief summary, but I will get back to the rest of your questions later :) \n\nNb. Qualifications are m.phil and phd in late roman and early christian marriage and sex ideologies :) ",
"[relevant master thesis](_URL_0_) (.pdf-Warning)\n\n[relevant literature](_URL_1_)\n\nThere's always the question of the effectiveness of moral legislation. It is often the case throughout history that morals are legislated, often more than once over a period of some years. This *usually* indicates that the legislation wasn't very successful, otherwise it would only take one law to change the behaviour. But as you normally can't change human behaviour and social problems with moral legislation or changes in technology, this kind of legislation is usually an indicator of what the ruling class thinks *should* be, and not of what *actually is*.\n\nToday's example would be the fight against \"piracy\" on the internet - there's legislation galore, but the effect is negligible.",
"Ok, so to the rest of your questions.\n\nIf the pater familias died, would his sons become patres familias of their respective branches?\nThis rather depends on family circumstances, and - again drawing on Peter Saller's demographic work - many children lost their paterfamilias at a young age and became sui juris (without guardianship/legally competent), but generally yes you are correct. \n\nWere married women not allowed extramarital sex, even with slaves or infames? \nI sort of answered this, in that married women having sex with ANYONE other than their husband was the only legal (and mostly, moral) definition of adultery. The best example of the moral ideaology of this is in the story of Lucretia as told by Livy and Ovid as the reason for the Roman removal of their kings. In that story, the prince of Rome Tarquinus Superbus takes a fancy to Lucretia - the wife of one of his friends - and tries to rape her. When she fights him off, he threatens to kill her and a male slave, place them naked in the bed together and claim that he had found them committing adultery. At the threat of this, she stops resisting and lets him have his way with her. Then she told her father and husband everything and killer herself. Fun. This story underpinned a lot of the way Romans thought about themselves, and they really really did think that rape was better than consensual adultery. Also, that the punishment for adulterous women and then non-free men they were found with was immediate death if they were caught in the act. \n\nWas a man subjected to social degradation if he was the \"bottom\" only when he was a full Roman citizen or even when he was a freedman (and not legally considered an infamis)?\nUmmm...not really my area of expertise. Mostly because Roman ideas about what we now call homosexuality are so different from our own they are hard to analyse really (to paraphrase Halperin \"Homosexuality and heterosexuality are modern, western bourgeois terms...nothing resembling them can be found in classical antiquity). But broadly, yes. Romans were pretty disgusted by the idea of homosexual intercourse, and especially \"bottoms\" who were viewed as soft and wet like women (related to Roman medical ideas of sex, that women required regular injections of semen to keep their wombs damp and working basically, so any man who received semen was viewed as literally and figuratively wet). \n\n\nWere all men taken as concubinus or puer considered infames? \nAgain, not my area. But basically yes. Unless they were emperor in which case it was totally cool until they were dead ;)\n\nHope that helps. If by some chance you want academic research on this I totally recommend Peter Saller's Patriarchy, Property and Death (1994). It's got lots of impenetrable demographic tables but absolutely groundbreaking work on the role and potestas (power) of the paterfamilias and what those power relationships were ACTUALLY like. On Roman homosexuality Amy Richlin has written on it: her article in the Journal of The History of Sexuality (4/3 1993) is really excellent as a brief overview and on the legal aspects. The classic text is Craig Williams \"Roman Homosexuality: Ideologies of Masculinity in Classical Antiquity\" although more recently his thesis has been criticised. On Roman marriage in general, Percy Corbett's little 1930s book \"The Roman Law on Marriage\" has yet to be bettered really on the legal side but the absolute authority on the matter is Susan Treggiari's monster work \"Roman Marriage: Iusti Coniuges from the Time of Cicero to the Time of Ulpian.\" \n\nEnjoy!"
]
}
|
[] |
[] |
[
[],
[],
[
"http://dspace.library.uvic.ca:8080/bitstream/handle/1828/3341/Staging%20Morality.pdf?sequence=1",
"http://books.google.de/books?id=Ejwhh6cXwoQC&pg=PA136&dq=augustus+moral+legislation&hl=en&redir_esc=y#v=onepage&q=augustus%20moral%20legislation&f=false"
],
[]
] |
|
ae80ed
|
Is there any consensus among historians on why Britain, in particular, became the birthplace of the Industrial Revolution?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/ae80ed/is_there_any_consensus_among_historians_on_why/
|
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"This is a difficult question and my reasoning could be subjective in many aspects, I will cite my sources to justify my reasoning. For the industrial revolution to occur, people such as land and business owners had to be incentivised to invest in newer technology, otherwise there would be no reason to invent.\n\n**Starting the Revolution:**\n\nThat incentive came with the [British Agricultural Revolution](_URL_0_) (Which I will try to summarise), which saw rich people acquire the communal land which peasant farmers often used. The most efficient method of farming until the 1700's was the three year crop rotation plan, which saw a plot of land divided three, two used to grow crops and one given a years rest to revitalise the soil, usually occupied by grazing animals of perhaps another farmer (Grazing animals generally boosted the crop productivity of the plot).\n\nThe Second Viscount of Townsend, Charles Townsend served as the British ambassador to the Netherlands from 1709-1711, where he observed Dutch farmers using a four year plan of wheat, turnips, barley and clover, where the turnips would re-nitrate the soil doubling the productivity of the plot, and clover would be used as pasture resulting in high yields for the next few years. When he came back to Britain, he popularised the widespread use of the technique. It's important to note that the technique was used in Britain, just not widely.\n\n[Enclosure](_URL_5_) was essentially the privatisation of the communal land which the farmers used. As an analogy, imagine you and a few other people each control a small plot of land, each of you plant crops by hand because it would not be cost effective to acquire technology to help as your revenues simply aren't high enough and your plot is too small to make it worthwhile. Now a wealthy individual acquires the land which you and a number of others use and merges them into one farm. it would be simply too hard for that individual to seed it all by hand, so they employ the use of technology, specifically the [seed drill, refined by Jethro Tull](_URL_2_) in 1700.\n\nSomeone is using technology, food output is dramatically increasing population, and suddenly you and those few other people are out of work, resulting in massive amounts of urbanisation throughout the 1700-1800's, travelling to cities to work in textile (England monopolised cloth into Europe from the 1500s) and steel mills, as well as coal mines for very small wages (pretty much, lots of people are very cheap to hire) - it's no coincidence that some of the most [populous cities in Britain](_URL_1_) are built atop of [coal](_URL_4_) and iron fields and had a large manufacturing sector.\n\n**Sustaining the Revolution:**\n\nWealth and materials are required for invention;\n\nImperial preference was employed by the British upon her colonies - free trade within the empire, and tariffs when trading outside the empire. Now I must direct you to historian and politician *Shashi Tharoor's Inglorious Empire,* where he, although not the main point of the book, argues that \"Britain's industrialisation was built on India's de-industrialisation.\" for two thousand years India had been the producer of exquisite cloths, originally produced in Bengal, which sent wealth from Europe and the Middle East to India through trade. With the \"colonisation\" of India, she could no longer export her manufactured goods favourably (Britain banned the importing of Indian cloth, putting many out of business), and became an exporter of raw materials and an importer of manufactured goods, now including British textiles which soon overwhelmed the Indian markets and sent hundreds of years of wealth in the region back to Britain, as well as endless amounts of raw materials. Wealth and raw materials being siphoned to Britain also applies to her other colonies, but I'd argue that India was the most important, being the populous, industrialised and \\[formerly\\] wealthy - the Jewel of the Empire. (**Edit:** This said, please read the important points u/ReaperReader has mentioned below)\n\nBritain maintained political and economic stability, her heartland being protected by The Channel from foreign threats such as Napoleon.\n\n**Why not ...?**\n\nIberia lacked resources. Spain primarily produced goods with high retail value, like sugar, and gold to finance wars in Europe rather than to build economic power. They also suffered political instability following their bankruptcies. While they were an agricultural economy, they really lacked the incentive (slavery, very little industry).\n\nFrance had a religious intolerance, and many great thinkers were protestants. There was a bit more religious freedom in Britain, in the case of Denis Papin, he left France for Britain and ended up inventing the precursor to the pressure cooker (Originally used to create fertilisers such as bone meals). They also suffered political instability through the 1700s.\n\nIt's very well a possibility that the [Dutch](_URL_3_) could've hosted the revolution. The Republic of the Seven United Netherlands were the first to industrialise after Britain, however they had a relatively small population and high wages.\n\nIndia (Various princes). The fall of the Mughals created regional instability and the East India Company's invasion didn't help the situation financing themselves with Indian plunder.\n\nChina had stability wealth and population, but the people were not concerned with increasing economic output, was more concerned with philosophies and culture, nor had the thinkers of the time.\n\nTo sum it up, a population boom and high urbanisation made allowed the production of enough goods and made them large enough for businessmen/farmers to invest in inventions, high amounts of wealth, materials and need for better efficiency increased the output of ideas and inventions, as well as the fact that Britain was highly educated and had public libraries."
]
}
|
[] |
[] |
[
[
"http://www.bbc.co.uk/history/british/empire_seapower/agricultural_revolution_01.shtml",
"https://about-britain.com/tourism/main-cities.htm",
"http://www.bbc.co.uk/history/historic_figures/tull_jethro.shtml",
"https://cpb-us-e1.wpmucdn.com/sites.northwestern.edu/dist/3/1222/files/2016/06/The-Industrial-Revolution-and-the-Netherlands-Dec-1999-279qng9.pdf",
"https://www.nmrs.org.uk/mines-map/coal-mining-in-the-british-isles/collieries-of-the-british-isles/coal-mines-england/",
"https://www.britannica.com/topic/enclosure"
]
] |
||
1gs16v
|
what are farm subsidies and how do they work?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1gs16v/eli5_what_are_farm_subsidies_and_how_do_they_work/
|
{
"a_id": [
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"text": [
"Farmers get government payments for planting a crop, or for not planting any crops. People who own farm land and say they are \"actively engaged\" in farming the land they've never even seen get government payments, too. Some of them live in Manhattan and Beverly Hills.\n\nIt used to be that you got the payments no matter how much money you made or how much of that money came from actual farming. Now the rules are different and if you're a farmer who makes more than $750,000 a year, you don't get any payments. And if you have another job and 2/3 of your money comes from *that* job instead of your part-time farming job, your payments get cut, too.\n\nFarmers can sell their crops to the government and get a guarantee of a certain price even if that price is more than what they could get if they just sold it to anybody else.\n\nFarmers get to buy cheap insurance for their crops in case all the crops DIAF because the government pays for part of the insurance premiums. Let's call it Farmercare.\n\nThe subsidies make it so the farmers don't go broke every year there's a flood or a drought or plague of locusts, and you don't have to pay $3.50 for your $1 cheeseburger.\n",
"Farmers can be their own worst enemy.\n\nThey want to grow as many crops as they possible can. The problem is when they all have a good year, there is an oversupply, prices plummet, and they all lose out.\n\nThe gov't tries to fix this with subsidies. They either pay farmer not to grow when it looks like there will be an oversupply, or they guarantee a minimum price for the crops, and make up any difference with tax money.\n\nThis might be a good idea to help out Farmer Bob and his family, but many farms are owned by corporations, who don't need the help, and are better able to manipulate the system. There are people who get paid millions in gov't money to not grow crops.",
"Okay, so for years the United States produced more cotton than any other country. So anyone in other countries who wanted cotton would end importing it from the United States.\n\nAll was well, and the cotton farmers had a great time, since everyone was paying top dollar for their cotton.\n\nNow, for a number of reasons that I'll explain when you're older, other countries suddenly were able to grow and sell cotton for cheaper than the United States. This was very bad news for American cotton farmers, who couldn't compete with the cheap cotton coming from other countries.\n\nSo, the cotton farmers said Help! Please, government, can you do something? Our business is in danger, and as you can see, the United States relies on all the business the cotton trade brings in! Please do something! \n\nSo, the government says \"Well, you're right, this cotton industry is too big to fail. What we'll do is we'll pay you some money each year so that you can lower the prices of your cotton.\" This way, people don't start buying Brazilian or Egyptian cotton, the US cotton is cheaper for them.\n\nThis is sorta short-sighted though. The government is propping up a business that can't keep itself afloat, and everyone who pays taxes ends up paying a bit of their money each paycheck so that US cotton is cheaper than imported cotton. \n\nNow this has happened in other industries as well. Wheat, corn, oil, and a bunch of other things are all heavily subsidized, so that your bread and gasoline are cheaper and so that you don't have to buy imported goods, keeping the money inside the country, and creating jobs for Americans. This is of course silly and unsustainable.\n\nThis causes other weird stuff like for instance if one year everyone grows too many pigs, the price of pork will drop too low, so sometimes the government will come in and pay the farmers to kill their pigs and bury them, so that they don't suddenly flood the market with cheap pork, putting some people out of business.\n\nNow, it gets even weirder. Since sugar is so hard to produce in America, and it's so easy to grow in the tropics, instead of subsidizing American sugar, we put tariffs on imported sugar. That means, there's an extra tax on sugar that you get from other countries. That combined with the fact that corn is subsidized by the government means that people who make sweet foods have switched away from using real sugar, and instead use high fructose corn syrup. All kinds of weird things like that happen when the government artificially interferes with the prices of goods.\n\nNow, to make things *even* weirder, back to the example of cotton.. All of the sudden Brazil, who we trade with a lot, says \"Hey, you guys are subsidizing your cotton so it's too cheap, so we are unable to sell our Brazilian cotton. Do something about that or we won't trade coffee (for example) with you!\"\n\nThe sane thing to do might be to lower the subsidies given to US farmers, but those are written into contracts that couldn't be broken at the time, so what they did instead is subsidize Brazilian farmers! That's right, the some of the tax dollars that US citizens pay off of every check goes to Brazilian cotton farmers so that they can lower the prices of their cotton, so they can compete with the unfairly low prices of US cotton! Imagine that!\n\n",
"_URL_0_ chapter 13. might have to read 1 and 2 and maybe 3 to get a premise though. great read",
"Okay. So everyone needs to eat, and we need to do it almost every day. So we have farmers who grow us food. In the last little while it's become clear that it would be sorta cheaper to just buy food from some poor places and spend our time doing other things, or use factory farms to produce meat instead of crops because meat is delicious. The problem with this is if there's a huge crisis, or a war, or whatever, the people selling us food might not want to sell us any at all, no matter what the price. They have to eat too. So it's a pretty good idea to always grow food in your own country. But the farmers can't live off the food they grow because foods so cheap, so the government pays them to grow food so they can compete with other farmers and still buy things in their country at their country's prices. This ends up with the US having like retarded amounts of corn, so they started using corn for everything, animal feed, chips, and eventually sugar. This is why there's so much HFCS in foods. It's not because it's better than sugar, it's because there's tons of food laying around and you can't just add corn to ice cream, but you can just add sugar to ice cream. This causes health problems not because its HFCS but because it's stupid amounts of sugar to put into bread/drinks/everything you ever eat.\n\n\nIt's all for national defence.",
"Here it is for five year olds:\n\nIf you have too much of something, like corn or any other farmed thing, the price of corn will go down because there's so much corn and not enough people to buy it all!\n\nSo the government says to the farmer, \"Hey farmer! I think you've done your job too well, can you please stop farming corn?\"\n\nBut the farmer says, \"If I stop farming corn, I'll make no money!\"\n\nSo the government says, \"Okay, we will give you money to live off of so that you won't make corn, or as we like to call it in fancy government words, a *subsidy*.\"\n\nThis keeps corn at a normal price. Now everybody is happy!",
"Most of the current laws are reauthorizations of laws written in the 40s. Why were they written then? The problem at the time was a bunch of hungry rural americans. The solution we came up with was cheap calories. To make cheap calories come about, the government encouraged farmers to \"plant to the fences\" meaning grow a lot of food. To do this, the government offered to pick up the tab if prices dropped below a certain point, insuring farmers of their income, and encouraging them to crank out lots of cheap food. Every 5 years the Farm Bill generally renews this policy. Except now, the problem is not a bunch of skinny starving Americans, it's obesity. Yet, our Farm Bill makes sure the cheap calories keep flowing. So subsidies keep the food cheap and abundant which boosts profit margins for companies like Kraft and offers unhealthy choices to Americans. ",
"A farm subsidy is money paid by the government to farmers in order to supplement the high risk they take in producing something that is critical to national security: our food supply. \n\nFarming is one of the most risky jobs you can have. You put everything you have into the field in the spring, you work from dawn til dusk every day cultivating the crop, then in the fall you harvest and hope to recoup your cost plus enough to live on until next spring. Now consider the number of things that can go wrong along the way: pests, drought, floods, hurricanes, tornados, etc. In addition to that, if everything goes well, you can still have a problem in the event of a bumper crop (everyone produces too much) because the market is flooded and prices drop. Now if it were just the production of Sham-Wows or something trivial, we might just say let them fail. However, food is a national security issue. A nation cannot survive without it. Therefore, the government subsidizes the farmer to make sure that, even in the event disaster strikes, he will still be ok. ",
"There are many kinds of subsidies. One of the biggest and most important is crop insurance. \n\nIf your vegetables are thirsty, it is easy to grab a hose and spray them with water. Farmers have giant areas of land too big for hoses and have to rely on rain and big sprinkler systems to water their crops. If it doesn't rain for a while, they can run out of water and their crops might die. If it rains too much, the land becomes very soft and the crops can fail over or get sick. If it rains a lot during harvest, the farmers may not be able to get to the food they worked so hard to grow before it rots. If it is too windy or a major storm occurs the crops can be killed. If there is a fire, the crops may burn. Farming is very risky, but we need farms to grow the food we eat, so the government has programs to help the farmers out when their crops have trouble. Farming is very expensive. A single corn combine can cost more than a nice house. Without help a farmer might not be able to plant his crops again the next year.\n\nAnother program pays farmers to not grow crops.\n\nIt sounds strange, but land needs to rest. Growing food is hard and wears land out. But farmers need all their land to grow enough food to pay their bills. So sometimes the government pays the farmers so the land can rest and grow food better in later years. Sometimes the government pays farmers so the land can rest for a long time and provide homes for native plants and animals.\n\nA third program pays farmers so they can compete with farmers in other countries who can grow crops easier.\n\nSome crops like to grow in different areas. Corn likes to grow in the United States, but coffee likes to grow in parts of South America. Sometimes when farmers have been growing a crop for many years, another area will start growing the same crop, and sell it for less money. When that happens the older group of farmers lose money and can't afford to keep growing the same crop. But changing crops is expensive. The farmer needs to buy seed and equipment, and then sell his old equipment. This equipment can cost more than a house, and if everyone is changing, then no one will want to buy the old stuff. A farmer could find himself stuck with expensive tractors he can't use and unable to afford what he needs for the new crop. The farm could go out of business. To keep that from happening sometimes the government will step in and pay the farmer so he can afford to keep growing the old crop and not lose business.\n\nWhen this happens the new farmers complain and the different governments start to fight and argue."
]
}
|
[] |
[] |
[
[],
[],
[],
[
"http://mises.org/books/economics_in_one_lesson_hazlitt.pdf"
],
[],
[],
[],
[],
[]
] |
||
7dtsbs
|
Do we know anything about siege weapons and siege warfare in Native American societies?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/7dtsbs/do_we_know_anything_about_siege_weapons_and_siege/
|
{
"a_id": [
"dq0hkvd"
],
"score": [
2
],
"text": [
"While waiting for further comments, check out [this earlier thread](_URL_0_) on warfare and sieges in the New World."
]
}
|
[] |
[] |
[
[
"https://www.reddit.com/r/AskHistorians/comments/3g8fp5/do_we_know_anything_of_large_scale_native/"
]
] |
||
15kbey
|
How long would it take for Earth's orbit to be affected if the sun were to suddenly blink out?
|
askscience
|
http://www.reddit.com/r/askscience/comments/15kbey/how_long_would_it_take_for_earths_orbit_to_be/
|
{
"a_id": [
"c7n7odk",
"c7n7wse"
],
"score": [
2,
3
],
"text": [
"Approx the same time as us finding the lights going out, as gravity (they now say) travels the speed of light. I think this is about 8 minutes. ",
"The effect of gravity does travel at the speed of light, so the earth would cease to orbit, and travel in a straight line after 8 minutes 20 seconds."
]
}
|
[] |
[] |
[
[],
[]
] |
||
78v14a
|
What is the biochemical mechanism by which smoking reduces bone density?
|
Is it the increase in blood CO2, a result of cellular interactions with nicotine, a secondary effect of pulmonary damage, or what? And what about the other effects of smoking, aside from the more obvious ones like carcinogenesis and respiratory system stress?
|
askscience
|
https://www.reddit.com/r/askscience/comments/78v14a/what_is_the_biochemical_mechanism_by_which/
|
{
"a_id": [
"doy6wq8"
],
"score": [
3
],
"text": [
"From the national institute of health, \"Analyzing the impact of cigarette smoking on bone health is complicated. It is hard to determine whether a decrease in bone density is due to smoking itself or to other risk factors common among smokers. For example, in many cases smokers are thinner than nonsmokers, tend to drink more alcohol, may be less physically active, and have poor diets.\"\n\nOr in other words no one knows for sure."
]
}
|
[] |
[] |
[
[]
] |
|
3e1c20
|
Do human skeletons retain their death pose?
|
We see it in the movies all the time, especially when there is pirate treasure, or ancient Egyptian tombs being opened: a skeleton of some poor unfortunate who died trying to get the treasure. The skeleton is typically intact, somehow maintaining the pose they died in. Then the ingenue touches it, and it collapses.
Does this really happen, or does the skeleton fall apart into a pile of bones as the body decays?
|
askscience
|
http://www.reddit.com/r/askscience/comments/3e1c20/do_human_skeletons_retain_their_death_pose/
|
{
"a_id": [
"ctazzmz"
],
"score": [
4
],
"text": [
"Rigor mortis would likely change the position, and as tendons dry up they would pull the skeletal structure into different positions; you've almost certainly seen this in fossil imprints where a creature's head is bent backwards. Consider [this](_URL_0_) image.\n\n\n"
]
}
|
[] |
[] |
[
[
"http://i.imgur.com/7UCbmep.jpg"
]
] |
|
6aqv5h
|
why do media organizations ask for user permission before sharing submitted content from twitter but not reddit?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/6aqv5h/eli5_why_do_media_organizations_ask_for_user/
|
{
"a_id": [
"dhgrem0"
],
"score": [
2
],
"text": [
"If you submit a link to Reddit, it's from an external source/site. Just because you shared it doesn't mean it's yours so there is no reason to ask permission from anyone on Reddit. You'd ask the owner of the original source of the link.\n\nText posts and comments are easier to use under fair use - especially since you can paraphrase the original post. You can't paraphrase a video or photo of an important event, so they explicitly ask permission for things like that.\n\nEither way, I commonly see Reddit and Reddit usernames referenced in online news/articles as sources."
]
}
|
[] |
[] |
[
[]
] |
||
6aceth
|
A good source for causes WWI?
|
Hi,
Looking for a good source (preferably a podcast as I have a hard time concentrating on reading) for the causes, course, and results of WWI.
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/6aceth/a_good_source_for_causes_wwi/
|
{
"a_id": [
"dhdh0n0"
],
"score": [
2
],
"text": [
"Definitely make sure to check out the /r/AskHistorians Booklist, [which has an extensive section on this!](_URL_0_) If you find yourself better suited to listening, many of those books should be available as Audiobooks."
]
}
|
[] |
[] |
[
[
"https://www.reddit.com/r/AskHistorians/wiki/books/wwi"
]
] |
|
1lps7x
|
How did the vacation practices of Western Europeans differ from Eastern Europeans during the Cold War?
|
Did they visit other communist countries, visit non-communist countries, go camping, etc.?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/1lps7x/how_did_the_vacation_practices_of_western/
|
{
"a_id": [
"cc1p4fz",
"cc1s4y9"
],
"score": [
2,
2
],
"text": [
"Not sure about the rest of Eastern Europe, but in the Soviet Union, you couldn't easily travel abroad without a special permission or a work assignment. Especially to non-communist countries. However the USSR was a large enough country that there were still plenty of places to vacation within the country. The Black Sea coast was known for its summer resorts, as well as the Baltic. One could take a cruise up and down the Volga river to see historic central Russia. The Caucasus Mountains and Central Asia were good places to hike. \n\nMore locally, it was popular to go a nearby forest and collect berries, mushrooms, etc, usually as a day trip on a weekend. Some of the better off people had \"dachas\", or summertime shacks in the countryside. A dacha would usually have a small plot of land attached to it where one could do some gardening. So during the summer people who had them would be at their dacha on weekends. Children would often spend their summers at a summer camp. ",
"In Yugoslavia most people went to the seaside or lakes / mountains, usually during summer. Croatian and Slovenian middle class were wealthy enough to build summer homes, but most workers got a week or two off at a vacation complex their company owned.\n\nI remember getting an extremely cheap room or bungalow at a hotel my mom's company owned. Wealthier companies even had real hotels, like the ones western tourists visited. Poorer folks used nearby rivers and lakes.\n\nWinter vacations were reserved for people who lived near a winter resort or had enough money to go to Austria or Slovenia for a week. Part of the vacation ritual was going to Graz or Trieste for shopping, but such trips mostly lasted just a day."
]
}
|
[] |
[] |
[
[],
[]
] |
|
q0sgr
|
the difference between gaelic, welsh, breton, and manx
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/q0sgr/eli5_the_difference_between_gaelic_welsh_breton/
|
{
"a_id": [
"c3truwz",
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"score": [
6,
2
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"text": [
"Since you are five, let's pretend that English, [Gibberish the language game](_URL_1_), and Pig Latin were all languages you knew. They are all pretty closely related, but you can pretty much immediately understand Pig Latin and English since there really isn't much difference. Gibberish on the otherhand is still based on English but there are many more syllables so it's much harder to understand. Now you speak Pig Latin. Your neighbors on the other hand speak Gibberish but never learned English. You can probably listen and catch onto some of the words but if you don't know the bits of grammar it probably won't make sense to you. The same would be true of all the languages you listed. In that they all came from a common source, however, they are different based on the area where the developed. In this case, it was your house and your neighbors house.\n\n[Here's an example of someone speaking Gibberish if you are interested.](_URL_0_)\n\nMore like you are fifteen: there are two branches of Gaelic, Brythonic and Goidelic Gaelic. They would have all come from a Proto-Celtic language. I'm assuming when you say plain old Gaelic that you are referring to Irish Gaelic which is of the Goidelic branch. Breton and Welsh are the only two languages of the Brythonic branch of Gaelic. There were other Gaelic family languages that are no longer spoken. \n\nThe big difference between the two is that Brythonic languages generally were spoken in Southern Great Britain as well as small enclaves on mainland Europe, whereas, Goidelic languages tended to be spoken in northern Great Britain and Ireland. That is other than the obvious bit about the vocabulary being different. Since you are five, Goidelic languages will share more common words and vocabulary with each other. Whereas Brythonic languages will have the same. However, Goidelic and Brythonic langauges will have much less in common with each other.\n\nBack to the geography based differences. Those that speak the Brythonic languages are Celts but they are not Gaels. Those that speak Goidelic languages are both Gaels and Celts. ",
"Bretons are people that hail from the north-western region of High Rock and are the most gifted humans in the field of magic, due to their past close relations with elven kind."
]
}
|
[] |
[] |
[
[
"http://www.youtube.com/watch?v=GT_HROSuI90",
"http://en.wikipedia.org/wiki/Gibberish_%28language_game%29"
],
[]
] |
||
tk2gy
|
Why do pigeons walk the way they do?
|
I would think its their bone structure and connections from the neck and feet but what's the real reason?
|
askscience
|
http://www.reddit.com/r/askscience/comments/tk2gy/why_do_pigeons_walk_the_way_they_do/
|
{
"a_id": [
"c4nbbzn"
],
"score": [
2
],
"text": [
"[The head bob allows them to hold their head still (relative to their surroundings\\) for as much time as possible](_URL_0_). This probably makes them better able to observe their surroundings. "
]
}
|
[] |
[] |
[
[
"http://blogs.telegraph.co.uk/news/peterwedderburn/100000937/why-do-hens-and-pigeons-walk-with-bobbing-heads/"
]
] |
|
28c5sj
|
how come native americans never built empires like cultures on other continents?
|
South America had Incas and Mayans. Asia had Mongols and the Chinese Dynasties but, North America never had great cities or monuments.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/28c5sj/eli5_how_come_native_americans_never_built/
|
{
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7,
5,
5,
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6
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"text": [
"See also, [The mound builders](_URL_0_)",
"Near St Louis is Cahokia. There are Mounds several stories high that were built by a large civilization. Several thousand Indians thrived there. \n\n_URL_0_\n\nMore information : apparently it was one of the largest civilizations between 600-1400AD",
"It's been awhile, so please be patient, but I do recall that one of the biggest reasons was a lack of sufficient surface iron. North America was every bit as competitive as Europe and the Mediterranean, but while that region had plenty of rich surface deposits of iron that could be worked at low temperatures (see Norway as an example, I believe), the metal deposits in North America were buried deeper, and those that were above ground were not as rich, which meant that they were beyond the reach of refining with stone-age technologies, and therefore not worth the effort of anyone even bothering to look at the ore to see if it was at all useful.\n\nGold was there and plentiful, but too soft to be useful for tools or weapons. Lack of easy iron meant no technological advances requiring metal. Native Americans had progressed quite far in nearly any technology that didn't have metal as a prerequisite.",
"There were several large cities in pre-Columbian North America, and there were also several widely-distributed cultures. By some definitons these would qualify as \"empires\". Wood and mud were the primary building materials however so very little of them currently remains.\n\nCheck out each of the cultures here: _URL_0_\n\nHaving said that, large cities aren't intrinsically \"better\" than smaller or nomadic societies. There are certainly advantages, depending on the situation, to any one of those lifestyles.",
"There is a large element of false information in your statement. True, the North American natives were not as advanced as the Incas, but they were not as backwards as they are in holywood movies. The reason is this: when columbus showed up, he spread desease. . A dark ages caused by the plagues followed, then, 200 years later, Europeans started settling in the eastern US, by which time the cleared farmland was overgrown and the villages were gone. When Lasalle went through the Confederate areas in the 1500s, he reported finding empty villages and unplanted but cleared farmlands. Ask yourself why primitive savages could teach the pilgrims what crops to plant or how to cure scurvy. The Americas were a little behind eurasia because of a lack of pack animals and less heterogeneous trade opportunities, but they were coming along.",
"The Mayans aren't in South America, they are in central and North America. They are also preceded by the Olmecs. The Aztecs are in North America too, and were an empire.\n\nAnother problem is that you cannot evaluate cultures as evolving along a single line that leads to empires. The Northwest coast people had very sophisticated cultures and large populations, but they never developed agriculture because they didnt need it. Farming from the central Mexican region spread all the way up the Mississippi and led to the Moundbuilders mentioned else where. "
]
}
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[] |
[] |
[
[
"http://en.wikipedia.org/wiki/Mound_Builders"
],
[
"http://en.m.wikipedia.org/wiki/Cahokia"
],
[],
[
"http://en.wikipedia.org/wiki/List_of_pre-Columbian_cultures#Northern_America"
],
[],
[]
] |
|
j0ktm
|
In evolution, why do certain traits develop that seem helpful but not essential to survival?
|
For instance, I'm Arab and I have pretty thick eyebrows. I'm sure this is due to the heat in the Middle East and essentially is a way to keep sweat out of my eyes.
Now this trait is very helpful but doesn't seem essential to survival. Why would people with thinner eyebrows (that get sweat in there eyes) die off? It doesn't seem like a big enough issue to slowly kill off people.
There are many other small characteristics like this, that seem helpful but not essential.
Thanks in advance!
Edit: I don't just specifically mean the eyebrows thing, I'm talking about everything else too!
|
askscience
|
http://www.reddit.com/r/askscience/comments/j0ktm/in_evolution_why_do_certain_traits_develop_that/
|
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"It can sometimes be deeper than this.\n\nFor example Cystic Fibrosis is a genetic disorder that shortens life span significantly. Why then do 1 in 25 people in Britain carry the recessive allele? Surely evolution would have killed it off?\n\nThe answer is that Not so long ago (in the evolutionary time scale) Britain was ravaged by the Black Death. If you are a CF carrier you have a significantly thicker layer of mucus than people with no CF gene. This made the virus that caused the Black Death was less likely to make it into the body. This meant that actually if you were just a carrier you were more likely to survive this deadly disease. And because this disease killed so many people in Britain the results of nature's selection for it (even though it shortens life spans when there is no respiratory disease) is still observable.\n\nI know that CF isn't in the category of things you are asking for but I am just saying sometimes it takes a deeper look into the subject.",
"The gene site that controls for eyebrow thickness would also control for other phenotype (physical) features. Their cumulative effect would be a significant advantage to the survival of the individual. Also, we're not just talking a few hundred years of evolution here- it can take thousands of years for these traits to be selected for and observable.\n\nAlso, I think eyebrows aren't just a sweat filter (?) but also like eye lashes filter dust and dirt that carry bacteria. I dont know about this part.",
"1) It could have been useful in the past.\n2) Dumb luck (ie the people with this trait could have had other awesome traits).",
"*For want of a nail the shoe was lost.*\n\n*For want of a shoe the horse was lost.*\n\n*For want of a horse the rider was lost.*\n\n*For want of a rider the battle was lost.*\n\n*For want of a battle the kingdom was lost.*\n\n*And all for the want of a horseshoe nail.*\n\nSmall advantages can add up over time. Imagine you are your thick eyebrowed ancestor, competing against his thin eyebrowed cousin centuries ago. You see slightly better because you wipe the sweat out of your eyes less often, but otherwise you both are pretty much the same. How does your life unfold?\n\n* Perhaps your keener vision makes you a celebrated hunter, while your cousin is merely average.\n* You attract the healthiest women to be your mate, while he has to settle for what's left. \n* You see the lion sooner, and protect your goats, while he loses a few. \n* You have more food and milk, enough to raise many healthy children your healthy wife bore you. His underfed children are sickly, and not all survive.\n\nRemember, it's not just about survival, it is about survival and reproduction. You both might live to a ripe old age, but over time, there will be more thick eyebrowed children and grandchildren running around.",
"There is a tendency to search for \"Just So\" stories when it comes to evolution. Thick eyebrows may have evolved \"for a reason\" as you mention, but it is more likely to occur because of random drift of traits. Someone got a \"hairy eyebrow\" random mutation in a gene, and it had no selective advantage or disadvantage in itself - but the person who got the trait had innumerable offspring for other reasons, so now the trait is fixed in the population.",
"small statistical likelihoods of surviving can actually be exaggerated in a fairly small number of generations. let me show you an example of this with numbers. let's say gene A has a 99% chance of surviving, and makes up the whole population. Gene B has 100%. i will oversimplify by saying that survivors have 2 kids asexually (this means the population will explode, but i will be looking at percentages).\n\nstart with 100 animals, all with A, and 1 with B.\n\nafter n generations, there will then be 100(2(.99))^n with A and 2^n with B. Let's look at the percentages after some generations,\n\nn,\t % with A,\t% with B\n\n0,\t 99.0, 1.0\n\n1,\t 99.0 , 1.0\n\n10,\t 98.9 , 1.1\n\n100,\t 97.3 , 2.7\n\n500,\t 39.7 , 60.3\n\n1000,\t 00.4 , 99.6\n\nyou can see after 7-800 generations, A is basically gone, and that was with a 1% increase in survival rate.\n\nAlso, sexual selection can play a huge role in things like this surviving. Someone with eyes full of sweat could be less attractive. A peacock's feathers is a good example of this. once it starts being sexually selected, it snowballs because if don't want to mate with a big-tailed bird when the rest of the population does, you will mate with a small-tailed one, then have small-tailed kids, and hence very few grandchildren because the rest of the population wants big tails. After a while, birds have completely ridiculous tales that probably make them far more likely to die, but it's selected anyways. \n\nIt's is theorized that sexual selection played a big part in developing a sense of humor in people. it's clearly a turn on for girls, and it could have originated as a sign that the person is smarter, then sexual selection took over and much of our brains is designed to make us funny, which doesn't really help survival.\n\nsorry for the rambling, did i come close to answering the question? basically it could have been a slight change in survival rates getting exaggerated, or sexual selection could have been responsible for this, or a little of both."
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7wl1ae
|
When the brain receives a nerve signal from the skin, how does it differentiate between a heat signal, a cold signal, a pain signal, a pressure signal etc?
|
Is it "code-based", like different levels/durations of charge?
Is it "structure-based", like the pain-detecting nerves are connected to a pain-detecting piece of brain?
Or something else entirely?
|
askscience
|
https://www.reddit.com/r/askscience/comments/7wl1ae/when_the_brain_receives_a_nerve_signal_from_the/
|
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"It is in part structure- and code-based. In addition, it is also signal-based. Below is a rather simplistic description of what goes on without discussing how it happens. May be able to provide one later if you are interested. Unfortunately my lunch break today was rather short.\n\nI'll try to illustrate this by a rather simplified system of three nervecells, where the first one reaches from skin-surface to the spinal-cord. There are different types of these \"first-order\"-neurons: some are only responsible for \"reporting\" on pain, some do vibrations, pressure or stretch. Temperature and pressure can, if stimulated very strongly or over pro-long time also signal pain (code-based). \n\nWhat a specific neuron detects will depend on its set of membrane-proteins, which can be activated by for instance mechanic stimulation or by presence of a molecule. When the receptor is activated, this will lead to a generation of a signal, that will move from the \"skin-end\" of the cell to the \"spinal-cord-end\" of the same cell. Also the structure of this end of the neuron affects which type of signals it will respond to. If you want to look them up, you can search for Ruffini-and Pacinian endings, Meissner- and Merckels corpuscules and nociceptors.\n\nHere, it will release neurotransmitters in order to activate the second cell in the series. This 2nd order neuron stretches from the spinal cord all the way up to the brain. On its way, it can give off collaterals to other spinal cord regions, which can be involved in processes such as pain modulation. A 2nd order neuron will usually terminate somewhere between Medulla oblonggata and Thalamus. Here, it can It will, just like the 1st neuron, signal to a 3:rd one to carry the signal further. The 3:rd order neuron will be mainly responsible for your to be aware of where the sensation occurs, by projecting to the somatosensory cortex and to more associative areas, which will make it possible to analyse what you think of said sensation and what you think you should do about it. (Some part of your experience will also depend on activation of amygdala, but I am not sure if this can occur directly via 2nd order neuron or via 3:rd order).\n\n",
"Different neurons in the skin are used to detect different sensations, and the frequency of the signals they send determines the intensity of the sensation. Different parts of the brain take in different signals so we can distinguish different sensations from each other",
"I have just a minor addition. In your title, you mentioned heat and cold signals, but we don't actually feel either. What we feel is the rate of heat leaving or entering our body, not the temperature of the object. This is why the metal part of your seatbelt might be painful in summer while the nylon part is not even though both are the same temperature -- the metal has much higher thermal conductivity and thus transfers heat to your skin much more swiftly.",
"So as others have pointed out there are specific pathways that signals from nerves take to get to your brain. While this does play a part in the overall sense perceived there are a myriad of other factors at play here. Things like receptive fields, top-down control, hi-pass filtering, and receptive maps all play a part in the generation of a specific stimulus.\nFirst off the area of your brain that encodes for sensations from your skin and inside your body is the somatosensory cortex. This area is where all the information regarding your sense of touch ends up, it also contains topographical maps of your body which aids in the localization of particular stimuli. By this I mean that the neuronal pathways and axonal projections from particular parts of your body all cluster together, so the neurons associated with your fingers are separated from the neurons associated with your face. This helps with localization of sensations as the area that's activated when you get punched in the face is different than the area that gets activated when you stub your toe or prick your finger. \nBesides the localization of senses, These neurons also all encode for different types of stimuli through the usage of Receptive Fields (RFs). RFs are essentially the preferred stimulus that a neuron encodes for. So in your skin in particular you have different cell types that are all adapted to respond to different signals. there are a few primary receptive neurons in your skin, These are called pacinian corpuscles, ruffini corpuscles, Merkel's disks, free nerve endings, and Meissner corpuscles. These cells all respond to touch based sensations but are adapted to respond best to different specific stimuli. For example, Merkel's disks respond best to touch and pressure whereas free nerve endings respond best to pain, temperature, and crude touch. These specific stimuli are their RFs and when they are activated by these stimuli they send a strong signal on to the brain. Because of this strong signal that is sent to the brain from a specific receptive cell, the brain is able to encode for a particular sense based on these factors and the location in the brain the stimulus ends up. \nThis brings us into the concept of sensory maps (SMs). SMs are ordered arrangements of RFs in a particular region of the brain. These respond to stimulus quality and spatial maps (the area the sense was generated). For touch based sensations these are located in the somatosensory cortex. Through the activation of these SMs your brain is able to designate what a specific sense is. So a hot feeling is sent to a SM that is specific to RFs for hot feelings. Same thing with pain and touch. \nIt should also be noted that the receptive fields in your primary receptive cells are small and simple. They activate optimally to basic concepts like hot, cold, stretch, pain, and touch and start on single pathways. Once these signals reach your brain however, emergent RFs come about (these are RFs that your primary receptive cell may not be encoding for) and the signal grows as it synapses onto other neuronal pathways. This is why you feel as many different senses as you do, and are able to describe each sensation greater than just saying something hurts or is cold.\nWhile the location in the brain a signal ends up is the way your brain is able to encode for different stimuli, there are other factors that can affect your sensory perception. High-pass filtering is huge in helping determine what signals are actually encoded for and what signals aren't. High-pass filtering occurs in your thalamus and it acts as a buffer to all incoming stimuli. It does this by only allowing stimuli that have a great enough action potential to pass through to a SM in your somatosensory cortex. This eliminates all of the noisy signals that you body picks up on, but aren't important enough to actually perceive. Things like pain have large action potentials so it will almost always be able to get to its designated SM whereas something like pressure from sitting might eventually be cut off, causing you to not really perceive sensorily.\nThere is also the concept of Top-down control of your nervous system. This is basically saying that your brain is what determines everything and the rest of your nervous system is just there to send signals to it so that it can decide what to do with them. This concept gets especially interesting when thinking about phantom limb syndrome (PLS). This occurs in people who have suffered an amputation but still feel stimuli from the affected limb despite the fact that it isn't there anymore. This relates to top-down control because it means that your peripheral nerve cells aren't actually responsible for encoding for a sense, as if that was the case sufferers of Phantom limb would not still feel pain/sensation in the lost limb. \nThere is a ton of other things that affect how your brain encodes for particular stimuli from your skin such as the protein receptors that get activated under the effect of certain stimuli as well as the proximity of neurons to other neurons causing signals to jump around and cause stimuli to be felt in areas besides the affected area. But the big thing that decides how you feel is the area of the brain that a signal eventually ends up in, and how this particular area encodes for a particular stimuli. \nHope this answers your question and then some. Also sorry for any grammatical mistakes and please do correct me if you see something I said that was wrong"
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qnbjl
|
Skim, 1%, 2%, whole milk? Soy milk? Almond milk? Coconut milk? Nutritionally speaking, what's the best kind of milk to drink?
|
askscience
|
http://www.reddit.com/r/askscience/comments/qnbjl/skim_1_2_whole_milk_soy_milk_almond_milk_coconut/
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"Are we talking about long-term health or general nutrition? Steroids can be administered to cows in the US, the same is true for antibiotics in cases other than curing disease (or preventing it from spreading) - both these things are prohibited in the EU for health reasons. I tend to agree with the European notion if only because I believe that these things encourage anything less than best practice. Antibiotic abuse is the major cause for the emerging problem of antibiotic resistance and growth hormones can lead to hormonal imbalance and cancer, especially in young boys. \n\nCheck out _URL_0_ for some more info about that trade dispute between the EU and the US.\n\nNutrition-wise: the most important principles of a healthy diet are moderation and variety. I know of no research that suggest that there are advantages of skim milk over whole milk, or vice versa, so the most important thing to keep track of is that your bodyweight doesn't fluctuate heavily; if you enjoy drinking whole milk, just make sure that you keep those extra calories in mind.",
"On a similar note, is there any evidence that bovine steroids/hormones present in milk are harmful to humans when consumed? \n\nI would assume that most of these steroids and hormones would be broken down by stomach acids before they are absorbed (if at all) by the body.",
"Lactose seems to have a negative effect when taken in large doses for adults, leading to Ovarian and Prostate cancer. From a purely dietary standpoint, milk does little to help you lose weight.\n\n_URL_2_\n\n_URL_0_\n\n_URL_1_",
"It all depends on if you want more protein, want less calories, or less sugar.\n\nNon Fat Milk: Calories: 90 Fat: 0 Protein: 9 Sugar: 12\n\nSilk Light Soy Milk (Vanilla): Calories: 50 Fat: 2 Protein: 6 Sugar: 2\n\nSilk Pure Almond Milk (Plain): Calories: 60 Fat: 2.5 Protein: 6 Sugar: 7\n\nSilk Pure Almond Milk (Unsweetened): Calories: 35 Fat: 2.5 Protein: 1 Sugar: 0\n\nSilk Pure Almond Milk (Vanilla): Calories: 90 Fat: 2.5 Protein: 1 Sugar: 15\n\nBlue Diamond Almond Milk: Calories: 40 Fat: 3 Protein: 1 Sugar: 0\n\nSilk Chocolate Milk: Calories: 120 Fat: 1.5 Protein: 5 Sugar: 19\n\nSo Delicious Coconut Milk (Unsweetened): Calories: 50 Fat: 5 Protein: 1 Sugar: 0\n\nSo Delicious Coconut Milk (Vanilla): Calories: 90 Fat: 5 Protein: 1 Sugar: 7\n\nLiving Harvest Hemp Milk: Calories: 130 Fat: 3 Protein: 4 Sugar: 15\n\nTempt Hemp Milk Original: Calories: 100 Fat: 6 Protein: 2 Sugar: 6\n\nTempt Unsweetened Original: Calories: 70 Fat: 6 Protein: 2 Sugar: 0\n\nTempt Vanilla Hemp Milk: Calories: 120 Fat: 6 Protein: 2 Sugar: 9\n\nRice Dream Oat Rice Milk: Calories: 130 Fat: 2.5 Protein: 1 Sugar: 12\n\nPacific Organic Oat Milk: Calories: 130 Fat: 2.5 Protein: 4 Sugar: 19\n\nI personally believe, for children growing a little fat with protein is perfect for youngins. Which is why I would recommend just normal milk, skim milk hardly has any fat content, so I would even suggest looking into skim milk because it has some fat content and a good amount of protein.",
"In relation to Calcium I can tell you that you require 1500-2000 mg (1.5-2 grams) a day, making Calcium the highest requirement micronutrient/mineral required. All types of milk generally have the same amount of Calcium in them.\n\nHowever, this is due to the addition of Calcium in Soy/Almond/Rice/Coconut milk, as non-dairy milk has very little to no Calcium in it already. Soy milk being the exception, it does actually have a significant amount of Calcium (but still up to 5-6 times less than dairy milk).\n\nMilk often has Vitamin D added to it, as Calcium uptake has been shown to be enhanced by Vitamin D (When consumed at near the same time. This is has been shown with Iron and Vitamin C as well).\n\nOther nutrients are generally a wash. (I.e. B12 is marginally higher soy, omega-3's are about the same usually. Note that Omega 3's from fish are healthier than those from flax/milk. [1]) My studies didn't me far beyond Calcium, but Phosphorous was mentioned (~25-30% DV in Dairy milk to 0-10% in Non-Dairy milk), the K / Ca element balance is important to your body (although they are found in ion form in your body, in case anyone cares).\n\nSome proponents of soy milk argue that it is not a wash, and soy milk has significantly more micronutrients than milk. I haven't much research on this, besides looking at 2-3 comparisons, none of which seemed very conclusive. (I.e. It didn't pertain to my area of research, so pubmed/JSTOR were left untouched). A more full answer might be found if you kept this in mind =)\n\nIn terms of fat, for a NA diet, Skim Milk wins out by a long shot. In almost all households you will already be eating enough, if not too much, fat. I am simplifying the concept of \"fat\" here because I have to leave for lab work =(\n\nAs a side note, what napmeijer said is unfortunately **wrong**. Antibiotics are used on many dairy cows to destroy their resident bacterial flora, this causes none of their intake of food to be feeding bacteria, and thus is more efficient feeding. In the U.S. up to 50% by weight of all antibiotics are fed to farm animals. It has very little to do with disease. It should be noted that while Europe has better antibiotic regulations than NA has, by far, no cutting edge antibiotics are used, and very little health concerns have risen from antibiotic use in animals\n so far, although the potential danger is there.\n\nOn the whole skim milk is \"healthier\" in that on an already balanced diet, it is preferred to drink skim milk. However, if your diet is lacking in fats, then milk with more fats can supplement it nicely. \n\nTL;DR: Milk choices should be personalized, but skim is \"healthiest\". \nFollowed by soy.\n\n[1] You can research Alpha-Linoleic Acid if you wish =)",
"According to [dietary recommendations](_URL_0_) put out by the Harvard School of Public health, you should be consuming 1-2 servings (at MOST) of dairy products per day. And those dairy products should be low in fat. These dietary recomendations are formed with actual science, as compared to the crap that the USDA releases. \n\nThe USDA's recomendation of 1000mg/day of Calcium is widley disputed by the scientific community. [Here](_URL_1_) is a video from the Harvard Director of the School of Public health discussing the issue.",
"Speaking as the son of a dietician and nutritional therapist:\n\nRegardless of what type of milk you're drinking, the nutritional benefits of milk are limited. Whether you're drinking 1%, 2%, skim or whole, after the homogenization and pasteurization of milk happens, the substance of milk is mostly sugar and water. As mentioned by others, lactose is poorly metabolized in the body. If you wish to continue drinking milk, whole organic milk is best for nutritional needs such as saturated fat (NEEDED FOR HEALTHY CHILDREN) and for the ethical considerations (cows not living in shit their whole lives). However, you still are mostly drinking poorly metabolized sugar-water with very few benefits (often the Vitamin A and D added to milk is synthetic and also poorly absorbed in the body). \nMy suggestion to you is to drink RAW organic milk for the maximum benefits of milk, which contain fantastic enzymes and vitamins which have not been destroyed by pasteurization or homogenization. The living bacteria in the raw milk also helps digest the lactose for us. \n\nMany raise concerns about Raw milk's potential to give the imbiber disease and other contagions. This is a noted concern with drinking raw milk; however, raw milk is a living ecosystem that should prevent the proliferation of harmful bacteria much like our own immune system does. The bacteria in raw milk can be considered a pro-biotic in some cases. Moreover, concerns launched against raw milk's consumption are petty and generally illogical, considering the drastically more common infection of pasteurized milk and other foods like spinach and peanut butter--and we still continue to eat those. People have drunk raw milk for hundreds of years prior to pasteurization laws; with mandated cleanliness, concern for contagion is relatively small if you have an ethical dairy farmer. \n\nThe sale of raw milk is prohibited in many states. In such states you can acquire raw milk with a license from a physician or purchase it for pet consumption. Because it is prohibited in most states, unless you can get a hold of it, I'd advise not drinking milk at all and instead drink almond or coconut milk.\n\nCoconut milk is the preferred choice of the two nut milks because of its higher fat content and medium chain fatty acids (which numerous studies have linked to increased metabolism and brain function--I don't have time to find right now). Many think coconut milk is too thick and the taste is a bit unpalatable and so choose to drink almond milk instead. My family only drinks coconut milk and raw milk--we have never once gotten ill from the raw milk (and in fact, when we started when I was a teenager, my acne coincidentally started to disappear.) If you do choose to try raw milk, drink in small amounts first otherwise the bacteria in the milk can instigate a die-off in your GI tract and you may get an upset stomach. \n\nSoy milk is a blight on humanity. Because of the touted benefits of soy as a \"health food\" it has also become a cash crop worldwide. As such, most soy is farmed quite unethically and usually comes from Monsanto's own stock of seeds. Nuff' said at this point. However, soy has also been implicated in serious hormonal health problems and even delays/inhibits sexual maturation in males (rats studies exist supporting such, and humans are being studied now). For more information you can read a lay summary of recent research in Mary G. Enig's \"The Whole Soy Story\"\n\n\n\n\n",
"It depends less on the milk and more what's been done to the milk. Commercially manufactured non-organic milk will almost certainly come from cows being fed grains like low-grade corn, and then antibiotics to counteract the adverse effects of this diet. \n\nCows are ruminoids, which means they are meant to eat highly fibrous diet (grass, hay). When fed corn, they may become ill, but get fatter faster. This is now the industry standard.\n\nTheir milk, butter, fat, meat, etc is thus a byproduct of corn (which already makes up the bulk of the American diet, since it is so cheap to produce in mass quantities and so easily processed into myriad other food-like substances, and shows up in many of our processed foods). \n\nFat is not inherently unhealthy. The ideas of the 70's that we need to cut fat from our diets to be healthy is reductionist science at its most dangerous. What we really need to cut from our diets are highly processed, additive-laced foods. Though I know we all love our Gushers.\n\nYour regular milk from your regular store, because of your regular cow's regular diet, has become something like a processed food – processed by a machine ill-equipped to handle the fuel it has been provided. \n\n*The answer*\nSo your best bet is probably grass *finished* organic cow's milk. (\"Grass fed\" regulations are not strictly enforced, and can simply mean that the cow was once fed a handful of grass. Grass finished ensures at least a half diet of grass, during the grazing months. \"Organic\" may be redundant here, since it's the antibios that make a cow non-organic, and the corn that makes them need the anti bios). Unpasteurized (raw milk) usually requires a very healthy, very clean cow. If you can find a good farmer at a farmer's market who sells raw milk, it is delicious.\nSoy milk is fine, but we already get beaucoup soy in our diets, since it is the second-most highly produced farm product in the US. And it is also often highly processed, with a lot of additives (like sugar). Ditto almond milk.\n\nTL;DR Buy a cow and put it in your backyard. ",
"Tangential. [This paper](_URL_0_) found that higher midlife tofu consumption was independently associated with indicators of cognitive impairment and brain atrophy in late life. Could we reasonably assume that soy may produce similar effects? I realize a different study is needed, but if someone in this thread could comment on it, I'd appreciate it.\n\nA followup criticized some aspect of the analysis, but when the author's complied with the recommended adjustment they still found that it was an independent risk factor for cognitive impairment."
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"http://en.wikipedia.org/wiki/Beef_hormone_controversy"
],
[],
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"http://pcrm.org/search/?cid=1021",
"http://pcrm.org/search/?cid=993",
"http://pcrm.org/search/?cid=157"
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"http://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/pyramid/",
"http://media.nutrition.tufts.edu/Seminars/FriedmanWeekly/Mar3/mar3.html"
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nkfoc
|
Is the lack of snow in North America an effect of Global Warming?
|
Recently' there has been a major lack of snow in the United States. Just a simple question is that is this a effect of global warming?
EDIT: I did mean effect. Sorry.
|
askscience
|
http://www.reddit.com/r/askscience/comments/nkfoc/is_the_lack_of_snow_in_north_america_an_effect_of/
|
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3,
2
],
"text": [
"Two things.\n\n1) The lack of snow, if anything, would be a symptom of global warming not a cause. AKA more heat = less snow.\n\n2) The local weather is influenced far more by local meteorological trends (highs, lows, fronts, etc.) than by global warming. It's like dipping a cup into the ocean trying to find a specific fish, you're just looking at too small of a sample to find it. So no, the lack of snow in the US would be better explained by other phenomena than by global warming.",
"You really cant make any claims based on 'recently'. It would not be unheard of to have a stretch of little snow or warmer winters without a general long term warming trend. There does look to be a distinct warming trend, but its still a little too brute force to say 'directly because of global warming, yes' when looking at 'recently'.",
"Probably not. Even though there is a warming trend to the climate, there are still weather-related events on top of that, and weather is much more difficult to predict than climate. For example, there's currently a [La Niña advisory](_URL_0_) in effect. It's predicted that:\n\n > During December 2011 - February 2012, there is an increased chance of above-average temperatures across the south-central and southeastern U.S. below-average temperatures over the western and north-central U.S. Also, above-average precipitation is favored across the northern tier of states, excluding New England, and drier-than-average conditions are more likely across the southern tier of the U.S. (see 3-month seasonal outlook released on 17 November 2011).\n",
"Climate change mainly deals with long-term averages. It's impossible to attribute short-term phenomena to climate change and not local meteorological processes. It's only when you look at larger time scales that you find a significant trend.",
"Two things.\n\n1) The lack of snow, if anything, would be a symptom of global warming not a cause. AKA more heat = less snow.\n\n2) The local weather is influenced far more by local meteorological trends (highs, lows, fronts, etc.) than by global warming. It's like dipping a cup into the ocean trying to find a specific fish, you're just looking at too small of a sample to find it. So no, the lack of snow in the US would be better explained by other phenomena than by global warming.",
"You really cant make any claims based on 'recently'. It would not be unheard of to have a stretch of little snow or warmer winters without a general long term warming trend. There does look to be a distinct warming trend, but its still a little too brute force to say 'directly because of global warming, yes' when looking at 'recently'.",
"Probably not. Even though there is a warming trend to the climate, there are still weather-related events on top of that, and weather is much more difficult to predict than climate. For example, there's currently a [La Niña advisory](_URL_0_) in effect. It's predicted that:\n\n > During December 2011 - February 2012, there is an increased chance of above-average temperatures across the south-central and southeastern U.S. below-average temperatures over the western and north-central U.S. Also, above-average precipitation is favored across the northern tier of states, excluding New England, and drier-than-average conditions are more likely across the southern tier of the U.S. (see 3-month seasonal outlook released on 17 November 2011).\n",
"Climate change mainly deals with long-term averages. It's impossible to attribute short-term phenomena to climate change and not local meteorological processes. It's only when you look at larger time scales that you find a significant trend."
]
}
|
[] |
[] |
[
[],
[],
[
"http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.html"
],
[],
[],
[],
[
"http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.html"
],
[]
] |
|
2805yu
|
How big is the area of sky we look at during the day?
|
askscience
|
http://www.reddit.com/r/askscience/comments/2805yu/how_big_is_the_area_of_sky_we_look_at_during_the/
|
{
"a_id": [
"ci65cru"
],
"score": [
8
],
"text": [
"**It depends on your height and how far into the sky you are looking.** I assume you mean \"Due to the atmosphere we can only look so far\", this I'll not be able to clarify for you. Part of your question can be answered with math though. \n\n\nIf we assume you are at sea (the most uniform horizon) and your elevation is 0, then you'd be able to see 180 degrees of sky because your line of sight is tangent to the bending of the earth. However, the earth is not 2D, it's 3D, so if we draw a line through the centre of the earth, through you and up into the sky, we can establish the 2D environment by saying you look at 90 degrees at a time, times 360 degrees all around you. (if we say it's 180 and then all around you, we'd be counting the same space twice), so it's 90*360 degrees of space. \n\nThe moment you stand up things get a bit more complicated, because you'd be able to see further into the horizon, thus, more of the sky. Luckily, the angle at the horizon is 90 degrees to the centre of the earth, so it's super simple to calculate. [Nicely illustrated by the drawing in this article (beware, his calculations are very approximate and based on false information)](_URL_4_). \n\n[I use this calculator](_URL_2_) and [This article shows the average distance to the centre of the earth](_URL_1_) at 6371km [(same as wiki says)](_URL_3_)\n\nIf you are in a boat standing up, let's say your elevation is 2m\nthen you'd be able to see the horizon 5.05km away. I plot in 6371 as side b, and 6371.002 as side c (and angle C at 90 degrees). Your angle of sight between the centre of the earth and the horizon is then what's here called \"Angle 3\", (which is actually angle B). At two decimals it's 89.95 degrees. Now imagine the line going straight up from the centre of the earth and into the sky above you and you are looking due east. There is 180 degrees between these lines going through you but 89,95 of those are earth, so the remaining 90.05 is sky. Now take this and spin a circle, you get the additional 360 degrees. The higher you get the closer the angle between the centre of the earth and the horizon get's to 0, without ever reaching it. So the higher you are up, the more of the sky you'll be able to see. (+ maybe you can see further into the atmosphere).\n\nEdit: Athhmosphere..\n\nEdit 2: [Here is a calculator for sphere surface area.](_URL_0_). you can clearly see an airplane which I believe fly at a height of approximately 10km. If you plot in 10000m as your radius, the surface area is 1256640000m^2. If we assume your elevation is 0 you just divide it by 2 and get the surface area of the sky, which is 628320000m^2 which is 628320km^2 so well over half a million square kilometers. Note: I believe you're able to see much further."
]
}
|
[] |
[] |
[
[
"http://www.calculatorsoup.com/calculators/geometry-solids/sphere.php",
"http://www.universetoday.com/48919/distance-to-the-center-of-the-earth/",
"http://www.csgnetwork.com/righttricalc.html",
"http://en.wikipedia.org/wiki/Earth_radius",
"http://blogs.discovermagazine.com/badastronomy/2009/01/15/how-far-away-is-the-horizon/#.U5oytLFAcSM"
]
] |
||
2sliik
|
If humans can see ants at our current sizes, would we be able to see germs, cells, etc. if we were ant size?
|
Saw [this](_URL_1_) posted by u/dudelikeshismusic in [this thread](_URL_0_) and I was curious if it was possible for ants (or ant sized humans) to see cells, or cell nuclei or other really small/microscopic things that we normally cannot see.
Not sure if this is the right section of r/askscience but I figured it was the most fitting.
|
askscience
|
http://www.reddit.com/r/askscience/comments/2sliik/if_humans_can_see_ants_at_our_current_sizes_would/
|
{
"a_id": [
"cnqvxv4",
"cnqzuzq"
],
"score": [
5,
8
],
"text": [
"Yes, but they can see only slightly smaller objects than we can. Camera resolution is limited by the [aperture diameter](_URL_0_). The bigger the aperture the better angular resolution. That's why astronomers like huge telescopes. On the other hand smaller camera can focus on closer objects. Both of these effects cancel each other when you are are talking about smallest possible object camera can see, but ants have a few other advantages. First of all their eyes have larger aperture relative to their bodies and they may be able to see UV light which has shorter wavelenghts.",
"When we say we \"see\" something, we mean that we can \"[resolve](_URL_0_)\" the object, i.e., we can clearly identify the object as being at that position with that brightness etc. If the object is not resolved, then depending on how poor our resolution is compared to the object's size, it will range anywhere from appearing blurry to looking like nothing against the background.\n\nSo to see smaller and smaller objects, we need to be able to resolve these small objects. A fundamental limit imposed by physics is that the resolution of any system (eye, camera, telescope) is limited by the size of the \"aperture\", or collecting area for the light. So the larger the aperture, the better your resolution, and you will be able to see smaller and smaller things\n\n**To finally get to your question:** If we shrunk down to the size of an ant, our eyes would also shrink, so our resolution would get comparitively poorer. So it's unlikely we will be able to see things an order of magnitude smaller than us like cells, or organelles in a cell or whatever. The best way to do that is to get a larger aperture. So use a microscope, or grow a larger eye."
]
}
|
[] |
[
"http://www.reddit.com/r/AskReddit/comments/2skk1s/what_fact_about_the_universe_blows_your_mind_the/",
"http://htwins.net/scale2/"
] |
[
[
"http://en.wikipedia.org/wiki/Airy_disk"
],
[
"https://en.wikipedia.org/wiki/Angular_resolution"
]
] |
|
1lf2aq
|
why is it illegal to use milk crates for other things aside milk?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1lf2aq/eli5_why_is_it_illegal_to_use_milk_crates_for/
|
{
"a_id": [
"cbyksht"
],
"score": [
2
],
"text": [
"I didnt know that. At my job we go into the dairy cooler and grab milk crates for other purposes every day."
]
}
|
[] |
[] |
[
[]
] |
||
3lgsem
|
What is the evolutionary advantage of the poppy plant to produce morphine?
|
askscience
|
https://www.reddit.com/r/askscience/comments/3lgsem/what_is_the_evolutionary_advantage_of_the_poppy/
|
{
"a_id": [
"cv66oxw"
],
"score": [
31
],
"text": [
"Alkaloids like morphine, nicotine, caffeine, and many more act as [insecticides](_URL_0_) for the plant in nature. Their effects on us are a bit of a natural accident."
]
}
|
[] |
[] |
[
[
"http://mentalfloss.com/article/55372/addictive-drugs-are-actually-pesticides"
]
] |
||
6fpibt
|
why do companies pay ceo's so much money?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/6fpibt/eli5_why_do_companies_pay_ceos_so_much_money/
|
{
"a_id": [
"dik26bt"
],
"score": [
4
],
"text": [
"1) CEOs spend a lot of time working, so they need to be compensated. They are held responsible for the company, so 24/7 they are on the hook and often answer calls in the middle of the night, skip weddings and kid's soccer games, and don't have meaningful time off. \n\n2) There are only so many experienced CEOs. There are millions you could hire to fry chicken at KFC, but only a handful of individuals who have experience running multinational corporations that employee tens of thousands of people. A small pool means more negotiating power for those in it. "
]
}
|
[] |
[] |
[
[]
] |
||
tqswh
|
Could a diamond be considered a massive molecule?
|
askscience
|
http://www.reddit.com/r/askscience/comments/tqswh/could_a_diamond_be_considered_a_massive_molecule/
|
{
"a_id": [
"c4oxmyb",
"c4oy0xc"
],
"score": [
4,
2
],
"text": [
"I's technically not considered a massive molecule, as it doesn't have an identifyable shape or size. They tend to be better described by how other crystalline structures form: in \"cells\" that are repeating patterns of with the same structure that can be joined together and repeated. \n\nIt does depend on your definition of a molecule though, if you're taking the meaning as a number of atoms with intra-molecular bonds then you could consider it a molecule.",
"Since diamonds are made of just carbon in a certain lattice, there is no diamond \"molecule\", so to speak. If you were to find the smallest possible unique unit that makes up a diamond, it would be a single carbon atom. So using the term molecule when talking about diamond is not a very useful term. "
]
}
|
[] |
[] |
[
[],
[]
] |
||
ccfg05
|
so what exactly is the connection between nazism and the composer richard wagner?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/ccfg05/eli5_so_what_exactly_is_the_connection_between/
|
{
"a_id": [
"etmhm30",
"etmi00w"
],
"score": [
6,
2
],
"text": [
"Wagner wasn’t a Nazi, because he died in 1883, before Hitler was even born. But in his time, Wagner was a virulent anti-Semite. \n\nHitler and the Nazi Party loved Wagner, however, and the composer and his beliefs conflated with Nazism and anti-Semitism. \n\n[BBC source ](_URL_0_)",
"I've asked this question to some people and most assume that it's because he was a nazi that apparently turned over several jewish members in his orchestra group a some point. Problem is he died a a half dozen decades too early to do.\n\nNo the main reason is because at one point Hitler went to a concert that was playing his music and he wrote about it in his mein kampf book. After gaining office he liked to suggest and request that a lot of people play Wagners music and stuff as a symbol of german pride and because Hitler liked wagners music.\n\nFrom there a lot of nazis just kinda played records of wagners music and that's a bad thing because nazis are bad."
]
}
|
[] |
[] |
[
[
"http://www.bbc.com/culture/story/20130509-is-wagners-nazi-stigma-fair"
],
[]
] |
||
7lmn7m
|
Do we know exactly what would've been hit had the cold war gone hot?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/7lmn7m/do_we_know_exactly_what_wouldve_been_hit_had_the/
|
{
"a_id": [
"dro2836"
],
"score": [
2
],
"text": [
"Not exactly. First of all, the targets, strategies, and capabilities varied by time period. So the answer for 1962 is not going to be the same for 1983, for example. Second, the exact targets have tended to be classified. Occasionally there are ways to glance at that information, e.g., a list of possible targets in the USSR used for weapon requisition purposes [was released by the US recently that gives some impression of what kinds of things they considered a target](_URL_0_). But it did not indicate priorities, how many weapons would be assigned to each target, the type or size of the weapons, the method of delivery, etc. \n\nWe do have a pretty good guess as to what the US thought the USSR would target if the USSR was using US targeting strategies, though. Note this is several leaps from knowing what the Soviets would do. But the US assumed the USSR would target all nuclear facilities (counterforce), any airfields that could be converted to military use (almost all of them), large power plants, sites of heavy industry, and so on. So that's a pretty big list in and of itself. \n\nWe do have some indications about some of the historical war plans for the US. Generally not to the detail of specific targets but bulk information about how many targets, how many megatons assigned, whether you could choose not to target China or not (in the early plans, you could not), and so on. \n\nIt's necessarily a speculative game in any case — war is chaotic and contextual. We can see the rough outlines of what it might look like. "
]
}
|
[] |
[] |
[
[
"http://blog.nuclearsecrecy.com/2016/05/09/mapping-us-nuclear-war-plan-1956/"
]
] |
||
no123
|
why does certain bacteria cause food poisoning that makes you expel basically everything in your digestive system?
|
How does bacteria cause that to happen? I just can't seem to grasp the concept. I have had food poisoning a couple times, but I can't seem to understand how just bacteria can cause that powerful of a reaction.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/no123/eli5_why_does_certain_bacteria_cause_food/
|
{
"a_id": [
"c3al4x1",
"c3al4x1"
],
"score": [
2,
2
],
"text": [
"Some bacteria, as a byproduct of their metabolism, produce a toxin. This toxin and its source, when detected by our bodies is *gotten rid of* as quickly as possible via explosive bowel movements. ",
"Some bacteria, as a byproduct of their metabolism, produce a toxin. This toxin and its source, when detected by our bodies is *gotten rid of* as quickly as possible via explosive bowel movements. "
]
}
|
[] |
[] |
[
[],
[]
] |
|
ch8plg
|
Where would you have to be standing on Earth such that you were furthest away from the Earths centre?
|
[deleted]
|
askscience
|
https://www.reddit.com/r/askscience/comments/ch8plg/where_would_you_have_to_be_standing_on_earth_such/
|
{
"a_id": [
"eusc03g"
],
"score": [
8
],
"text": [
"The summit of [Chimborazo](_URL_0_), Ecuador."
]
}
|
[] |
[] |
[
[
"https://en.wikipedia.org/wiki/Chimborazo"
]
] |
|
39o6fq
|
why is identifying as another gender ok but identifying as another race crazy?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/39o6fq/eli5_why_is_identifying_as_another_gender_ok_but/
|
{
"a_id": [
"cs502md",
"cs5087d"
],
"score": [
2,
2
],
"text": [
"_URL_0_\n\n_URL_1_\n\n_URL_3_\n\n_URL_2_\n\n",
"Duplicate of other posts\n\n_URL_0_\n\n_URL_1_\n\n_URL_3_\n\n_URL_2_\n"
]
}
|
[] |
[] |
[
[
"http://www.reddit.com/r/explainlikeimfive/comments/21pfov/eli5_if_people_can_determine_their_own_gender/",
"http://www.reddit.com/r/explainlikeimfive/comments/39nsxd/eli5_why_is_rachel_dolezal_identifying_as_black/",
"http://www.reddit.com/r/explainlikeimfive/comments/38g7kf/eli5_how_come_transgender_exists_but_not/",
"http://www.reddit.com/r/explainlikeimfive/comments/39lx5k/eli5_why_dont_we_recognize_a_person_who_wants_to/"
],
[
"http://www.reddit.com/r/explainlikeimfive/comments/21pfov/eli5_if_people_can_determine_their_own_gender/",
"http://www.reddit.com/r/explainlikeimfive/comments/39nsxd/eli5_why_is_rachel_dolezal_identifying_as_black/",
"http://www.reddit.com/r/explainlikeimfive/comments/38g7kf/eli5_how_come_transgender_exists_but_not/",
"http://www.reddit.com/r/explainlikeimfive/comments/39lx5k/eli5_why_dont_we_recognize_a_person_who_wants_to/"
]
] |
||
1y2tl6
|
What force balances gravity when I spin a belt/cord/rope above my head in a circular motion?
|
Why does the belt/cord/rope's end remain horizontal despite gravity?
|
askscience
|
http://www.reddit.com/r/askscience/comments/1y2tl6/what_force_balances_gravity_when_i_spin_a/
|
{
"a_id": [
"cfgwr27",
"cfh3rjd"
],
"score": [
7,
2
],
"text": [
"Good question. This is a problem often addressed in a first year mechanics class. It is the tension in the string which balances the force of gravity, and that tension is determined by the string's weight and how fast the string is spinning - spinning faster means more tension, according to the centripetal force law. For low tension (spinning slowly) the centripetal force is small compared to the weight of the string, so the string is close to parallel to the direction of the gravitational force (perpendicular to the floor). For high tension (spinning fast) the centripetal force is large compared to the weight of the string, so for the component of tension in the opposite direction to gravity to balance out gravity, the string needs to be spinning close to, but not quite, perpendicular to the gravitational force. Try it for yourself - spinning the string faster and faster (in a safe way!) will cause it to become closer and closer to horizontal.",
"The thing at the end of the rope's inertia and the force you are applying to it with your hand at the center of your spinning rope circle. If you let go of the rope, it will just fly off in one direction as per its inertia and fall down as per gravity.\n\nYou keep pulling it back, preventing it from going where it wants to go - flying away and falling down. \n\nThe rope will end up slightly tilted down in proportion to the ratio of gravity to the force you keep applying to the rope. And you are lifting it, with a small upward force applied to the rope. You don't really notice that you're still carrying the weight of the rope because most of your energy is going into the spinning action. It's a lot more tiring than just holding a rope.\n\nMeanwhile, you may also be applying little nudges to the rope as you swing it that include a bit more of upward push to balance out gravity. Making it seem to travel almost horizontal in a perfect circle with no droop. There is a very good chance your spinning rope is slightly tilted as you keep applying those little upward nudges at the same time in the cycle, subconsciously.\n\nSee if there's a difference between spinning a rope from below, and spinning a rope from above. Try spinning the rope while consciously trying hard to **only** apply force side to side in an even circle at a steady speed with no nudges.\n\nI think this is \"felt\" more consciously using a hula hoop. If you don't have good skill in timing those upward nudges against gravity to keep the hoop up, along with the side to side motion your hula hoop will fall."
]
}
|
[] |
[] |
[
[],
[]
] |
|
b2qiec
|
why objects smaller than the wavelength of visible light can't be seen by a regular microscope
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/b2qiec/eli5_why_objects_smaller_than_the_wavelength_of/
|
{
"a_id": [
"eiuq2o9"
],
"score": [
8
],
"text": [
"Imagine that you are tasked with building a realistic statue of a man. The only materials allowed are Legos. Done well, the statue will look fairly realistic. Now, build the same statue with concrete blocks. Can it even resemble a man? No, the pieces are too big. It's the same with light. If you are trying to resolve an image of something, what you are using must be smaller than the object being imaged. The closer the imaging medium's size approaches the size of the object, the resolution diminishes and disappears entirely when the sizes match. Electrons have a smaller wavelength than visible light, and therefore electron microscopes can resolve smaller objects."
]
}
|
[] |
[] |
[
[]
] |
||
2qax14
|
how do they count all those bees when news headlines say 37 billion dead bees?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2qax14/eli5_how_do_they_count_all_those_bees_when_news/
|
{
"a_id": [
"cn4g2zz",
"cn4insg"
],
"score": [
7,
3
],
"text": [
"They send people out to count them all\n\nJust playing, Basically, they (whoever released the information) judge how many bees died by what they know about bees, and what they can observe. Bees act a certain way, weigh around a certain amount, etc. They would most likely find the rough area of where the bees died, and how close to each other they are on the ground. this would give you a rough amount, say, 37 billion. The headlines are estimates, and generally are exaggerated. I don't have many facts to back up my information, its mainly speculation based on the scientific method. I hope I made sense.",
"I can guarantee that people aren't counting dead bees on the ground and extrapolating from there. It's much easier to estimate based on dead hives. The big bee die-off lately is based on beekeepers' numbers.If a hive typically carries 30k bees (depending on the time of year), and beekeepers are reporting 30-80% hive loss, simple math can come to a total estimate. \n \nBasically, remember that bees are just barely individuals. The health of the hive is the important part. We don't care about individual bees dying, but rather whole hives dying, which is what has been happening lately. "
]
}
|
[] |
[] |
[
[],
[]
] |
||
98k741
|
Do magnetic and/or electric field have any influence on time and space?
|
According to Einstein, gravity has influence on space and time. Does magnetic field have influence on time and space? Does electric field have influence on time and space?
|
askscience
|
https://www.reddit.com/r/askscience/comments/98k741/do_magnetic_andor_electric_field_have_any/
|
{
"a_id": [
"e4gp2bj",
"e4gq7lg",
"e4guroa"
],
"score": [
42,
117,
17
],
"text": [
"Yes, all energy contributes to the stress-energy tensor and the curvature of space-time so that includes energy in the electric and magnetic fields",
"As other people have pointed out, the answer is yes, but there’s something in the way you phrased the question I want to focus on. You said that gravity curves spacetime, and wondered if other forces do as well.\n\nIt’s much more accurate to think of matter and energy as curving spacetime, and this effect is *itself* gravity. Gravity *is* spacetime curvature. So in that sense it’s on a different footing than the other forces.\n\nAll of the forces are carried by fields - for example, the electric and magnetic forces are carried by the electromagnetic field - and fields have energy, so they do curve spacetime, which is to say, they gravitate. \n\nEDIT: I should add this effect is absolutely tiny unless the strength of the electric or magnetic field is absolutely enormous. \n\nEDIT EDIT: Probably the most famous (theoretical) example of this effect is a charged black hole. The spacetime curvature around such a black hole is different than for an uncharged one. That is to say, charged and uncharged black holes gravitate differently. This is *in addition to* the electromagnetic force that charged black holes have. ",
"I'll provide two different explanations in case you find one more helpful than the other. The first one is mine, and the second one is quoted below from a Scientific American article. While mine speaks a little bit more loosely with certain definitions, it has been a useful way for me to think about some things.\n\n**My explanation:**\n\nOne of the important things in physics to remember is that energy is equivalent across forms. By this I mean, electrical energy can be converted into mechanical energy and so forth. Joules was one of the big pioneers in this field and that's why \"Joules\" are used as a universal unit for energy. Another important thing to remember is that Einstein's special relativity paper showed that all forms of energy contribute to the mass of a body. This is often stated as the \"mass-energy equivalence,\" and people often point to the equation E = mc^2 to discuss this issue (although I would point out that the equation is actually E = γmc^2 , where γ is based on the velocity of the body; but that is a slightly different issue). \n\nAs was realized by Newton, mass causes gravity, and it makes sense that this would somehow be true in general relativity as well. However, in special relativity, we already know that mass and energy are related, so logically it should be energy, not mass, that causes gravity. As we know, however, energy is just one component of a four-component four-dimensional momentum, so perhaps we should be including momentum as well. (Sidenote: this last sentence is a bit of a jump, but it relates to the \"γ\" value in Einstein's equation above, and its derivation might take us off the rails. However, if you're curious, this wikipedia article gives a good in-depth summary of the issue: _URL_0_).\n\nIn fact, it turns out that not only do the momentum and energy come into the equations, but also the way they are flowing or being transferred plays a role as well. The whole source is not just the energy, or even the energy and the momentum, but something nastier that should properly be called the \"stress-strain-energy-momentum tensor.\" But, because even physicists can’t get their mouths around this phrase, it is more commonly called the stress-energy tensor or \"energy-momentum tensor\" or even just the \"stress tensor\" (or sometimes, just Tμν). In Einstein's field equations for general relativity, the stress–energy tensor is the source of the gravitational field, just as mass density is the source of such a field in Newtonian gravity. While the stress-energy tensor contains many components (sixteen in all), just one of these components, the time-time component, is the actual energy density (which is proportional to the mass density).\n\nThis is where your question is answered. The time-time component of the stress-energy tensor accounts for the electromagnetic field having an influence on the space-time continuum, thereby causing gravitational fields under general relativity.\n\nIf you'd like a slightly more detailed coverage of this issue for an undergrad level understanding, this [lecture paper by Eric Carlson](_URL_2_) is a very good overview in my opinion. I would also recommend his slides titled \"General Relativity\" for one of his undergrad courses ([found at the bottom here](_URL_1_)). To really get the full experience, put the slides in presentation mode and click your way through.\n \n**Scientific American explanation:**\n\nThis [article in the Scientific American by Charles Torres](_URL_3_) provides a better detailed answer in layman's terms than I could probably provide. I've quoted the article below:\n\n > Electric charges and magnets do indeed \"distort space,\" but this happens on a couple of levels.\n\n > First, a word of background. According to the current best theory of gravitation, which is contained in Albert Einstein's famous general theory of relativity, a gravitational field represents a curvature of space-time, rather than a distortion of it. Anything that carries energy, momentum and stresses is a source of a gravitational field, that is, a curvature of space-time.\n\n > Electric charges and magnets are manifestations of certain types of matter, most particularly electrons. Since matter carries energy (via Einstein's famous relation that energy is mass times the speed of light squared), such objects will have a gravitational field and so they will distort space-time. So one way in which a charge or a magnet will distort space-time is by virtue of its matter. That answer may not sound too impressive, but there is more. . . .\n\n > You see, electromagnetic fields themselves carry energy (and momentum and stresses). The energy density carried by an electromagnetic field can be computed by adding the square of the electric field intensity to the square of the magnetic field intensity. As another example, a beam of light (produced from, say, a laser) consists of an electromagnetic field, and it will exert a force on charged particles. Thus the electromagnetic field carries momentum. Because an electromagnetic field contains energy, momentum, and so on, it will produce a gravitational field of its own. This gravitational field is in addition to that produced by the matter of the charge or magnet.\n\n > A simple example of the gravitational (or space-time curvature) effect of electric charges arises in the \"Reissner-Nordstrom\" solution to Einstein's gravitational field equations. This solution describes the gravitational field in the exterior of a spherical body with non-zero net electric charge. (The solution describing the special case in which the net electric charge is zero is the famous \"Schwarzschild solution\" to the gravitational field equations.) From the Reissner-Nordstrom solution, it is clear that the motion of test particles in the gravitational field of the spherically symmetric body depends on whether or not the body carries a charge. Just as the Schwarzschild solution can be extended to describe the famous phenomenon of a \"black hole,\" the Reissner-Nordstrom solution can be extended to describe a \"charged black hole.\" For an electrically charged black hole, the gravitational field of the hole includes a contribution due to the presence of an electric field.\n\n > I do not know (and I doubt) whether this aspect of gravitational theory (that electromagnetic fields produce gravitational fields) has been directly tested by experiment. The difficulty is that the gravitational field produced by a typical electromagnetic field you can produce in a laboratory is predicted to be very, very weak. A better place to look for gravitational effects due to electromagnetic fields would be in astrophysical objects carrying a significant net electric charge. Unfortunately, to my knowledge, such objects are expected to be hard to come by. So while the answer to the question is definitely \"yes\" according to theory, the experimental status of this effect appears to be somewhat open.\n\n > If you want to read more about some of these ideas, you might try Space, Time, and Gravity, by Robert Wald (University of Chicago Press, 1992). This book is aimed at non-specialists. For a more detailed mathematical treatment, you can consult any text on the general theory of relativity."
]
}
|
[] |
[] |
[
[],
[],
[
"https://en.wikipedia.org/wiki/Four-momentum",
"http://users.wfu.edu/ecarlson/modern/index.html",
"http://users.wfu.edu/ecarlson/modern/gr.pdf",
"https://www.scientificamerican.com/article/do-electric-charges-and-m/"
]
] |
|
jxbn3
|
Can rocks evaporate?
|
I think of rocks as if they're pieces of ice of a different composition. When they melt they turn to lava...but can they turn to a gas state?
Thank you, everyone.
|
askscience
|
http://www.reddit.com/r/askscience/comments/jxbn3/can_rocks_evaporate/
|
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"Technically when rocks melt (as in a volcano) they become magma (underground) and only lava when it reaches the surface.\n\nTo vaporize rock you would need to raise the heat way higher than what can occur naturally in a volcano. But yes, it would be possible to vaporize the rock. Since 'rock' is not a single material, but a host of materials, you would end up with different gasses released at different temperatures.\n\nI have no idea what the vaporization point for, say, a pahoehoe type lava would be. The lava itself is usually around 2000 F - so it would have to be much much higher than that (I would guess in excess of 20000 F).",
"The process you're thinking of is called sublimation, a transition from solid to gas. The best-known example is dry ice, which sublimates quickly under ambient conditions. Iodine also sublimates, but as far as I know (and I'm no geologist), there are no rocks that do it under normal conditions.",
"Sulfur does. In thermal vents around volcanoes, you can find deposits of sulfur that has sublimed from below and been deposited in the cooler upper regions of the vent. \n\nHere's a [picture](_URL_0_) of it.",
"Technically when rocks melt (as in a volcano) they become magma (underground) and only lava when it reaches the surface.\n\nTo vaporize rock you would need to raise the heat way higher than what can occur naturally in a volcano. But yes, it would be possible to vaporize the rock. Since 'rock' is not a single material, but a host of materials, you would end up with different gasses released at different temperatures.\n\nI have no idea what the vaporization point for, say, a pahoehoe type lava would be. The lava itself is usually around 2000 F - so it would have to be much much higher than that (I would guess in excess of 20000 F).",
"The process you're thinking of is called sublimation, a transition from solid to gas. The best-known example is dry ice, which sublimates quickly under ambient conditions. Iodine also sublimates, but as far as I know (and I'm no geologist), there are no rocks that do it under normal conditions.",
"Sulfur does. In thermal vents around volcanoes, you can find deposits of sulfur that has sublimed from below and been deposited in the cooler upper regions of the vent. \n\nHere's a [picture](_URL_0_) of it."
]
}
|
[] |
[] |
[
[],
[],
[
"http://sciencefilm.de/detail.php?rubrik=%&id=220016&lang=en&q=&qrubrik="
],
[],
[],
[
"http://sciencefilm.de/detail.php?rubrik=%&id=220016&lang=en&q=&qrubrik="
]
] |
|
j1lr1
|
Is there significant risk of infection from fecal
bacteria if there is an open cut on the anus?
|
Logically I want to say yes, but experience would seem to prove the opposite.
|
askscience
|
http://www.reddit.com/r/askscience/comments/j1lr1/is_there_significant_risk_of_infection_from_fecal/
|
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"This sounds like something you should see a doctor about.",
"Yes. There is increased risk of infection anywhere a wound can become contaminated. It's not a guarantee of infection, especially for a young and healthy person with a small cut. But an older or sick person with a large wound is at significant risk, especially so if they are unable to keep the area clean without help.",
"Yes. Gut colonizing microbes are the most common organisms in perianal abscesses and anal fissures are frequently infected with the same bugs.",
"While this isn't the exact area of my research, I searched around on pubmed to see if this appears to be a well studied problem, and I found very little information, suggesting that infection with fecal bacteria of these kinds of wounds is not a common concern, or it is understudied or possibly irrelevant to treatment. On wikipedia I did find one [statement](_URL_3_) suggesting that infection with bacteria from the gut could occur and cause problems such as ulcers that will not heal. While I didn't find an articles specifically backing the wikipedia statement up, in general as your skin is your body's first line of defense against infection, any cut in it would place you at a higher risk. Still, it may be interesting to note that even if they are not infected, these sorts of injuries can continue to progress for months and worsen over time requiring increasingly specialized care ([source, NSFW](_URL_0_)).\n\nWhile I didn't find much suggesting anal fissures could become infected, I did find quite a few sources that suggested bacteria and viruses could cause fissures and absesses (see previous source). Some of the bacteria included among those that could cause infection were E. coli and Bacteriodes, organisms commonly found in the gut which usually are not pathogenic. This seemed to me to suggest that there may be a possibility that some wounds could become infected with these organisms after they occur, though again, there was not specific source for this. Other causes of anal fissures include stds such as Treponema pallidum (causes syphillus) and organisms that typically infect other areas of the body such as [Mycobacterium tuberculosis](_URL_1_).\n\nIt is also interesting to note that even without breaks in the skin, gut microbiota can cause disease. While rare, in some instances, bacteria can [translocate](_URL_2_) across the intestinal mucosal barrier. More commonly, bacteria, especially E. coli, from your intestines can enter your urethra causing a urinary tract infection.\n",
"I would say no, people who have [anal fissures](_URL_0_) [wikipedia link but NSFW] consistently pass fecal matter over an open cut and to my knowledge have a very low risk of infection. I'd be interested to hear from an expert on this as well.",
"I don't have expertise in these, but I have had an Anal Fissure before, and I asked my doctor this exact thing. He told me there was literally no problem of infection from fecal bacteria. ",
"Unlikely. Most microorganisms in and around that area are members of your normal microbiota, which are (in most cases) not harmful to your body. I would only be concerned if you were on some specific antibiotics that only target the intestinal tract. "
]
}
|
[] |
[] |
[
[],
[],
[],
[
"http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2710774/?tool=pubmed",
"http://www.ncbi.nlm.nih.gov/pubmed/9195814",
"http://www.sciencedirect.com/science/article/pii/S0140673603124890#SECX6",
"http://en.wikipedia.org/wiki/Anal_fissure#Causes"
],
[
"http://en.wikipedia.org/wiki/Anal_fissures"
],
[],
[]
] |
|
71qz7l
|
Did dinosaurs, like reptiles of today, molt or shed their skin?
|
askscience
|
https://www.reddit.com/r/askscience/comments/71qz7l/did_dinosaurs_like_reptiles_of_today_molt_or_shed/
|
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"It depends on the dominant integument (body covering) of the dinosaur in question. \n\n**Feathers:** There is good evidence to indicate that feathered theropods with pennaceous (vaned) feathers molted as they grew, much in the same way that birds do today. Although hatchlings of the oviraptorosaur *Similicaudipteryx* bore pennaceous tail feathers at birth ([Xu et al., 2010](_URL_4_)), immature specimens have a peculiar \"ribbon-like\" feather morphology that drastically differs from the feathers of adults. These represent molting feather germs undergoing development, and look identical to the same kind of feathers in modern birds ([Prum, 2010](_URL_2_)).\n\n**Scales:** The ancestral state of dinosaurian scales probably would have been relatively close to crocodilian integument in molecular composition (i.e. the specific alpha- and beta-keratin structure that they were composed of). See the work of Greenwold and Sawyer (e.g. [Greenwold & Sawyer, 2013](_URL_1_)). Crocodiles do not molt in the same way that squamates do, where the entire integument is replaced at once. Thus, it would be reasonable to assume that the same held true for early dinosaurs.\n\n**Secondarily-derived scales:** Some molecular ([Dhouailly, 2009](_URL_0_)) evidence indicates that the reticulate and scutellate scales on the feet of birds, non-avian theropods, and possibly ornithischians ([Cuesta et al., 2015](_URL_3_)) may have been secondarily derived from feathers (or protofeathers). If this was indeed the case, and applied more generally to scalation across the entire body - a highly speculative assumption - it may be possible for some molting (incl. replacement of filaments with filament-derived scalation) to have occurred.\n\n",
"In the absence of fossils of shedding skin, the best we can do here is form a hypothesis. We do this by using what's called an extant phylogenetic bracket, which is kind of tricky to explain but very intuitive once you see it in action.\n\nBasically, you form the bracket by looking at closely related living (aka extant) taxa on either side of the extinct taxon in a phylogenetic tree. A trait that is present in both extant taxa is probably ancestral for the group, so unless it was secondarily lost, it would be present in the extinct taxon you're interested in. \n\nI realize that that explanation is kind of obtuse, so here's an example: lots of people are interested in the behavior of extinct dinosaurs. Well, luckily for us, we have 1) birds, which are dinosaurs who are very much extant, and 2) dinosaurs' closest living relatives, crocodylians. Dinosaurs, crocs, and some other groups like pterosaurs form a big group of reptiles called [Archosauria](_URL_1_). So we're actually bracketing archosaurs here, but for our purposes, we'll look at dinosaurs. Crocs and birds may seem very dissimilar, but one similarity they have is that they show parental care for their young (to varying degrees depending on species). Using a phylogenetic bracket, we would hypothesize that extinct dinosaurs would also show parental care for young. The cool thing is that we've been able to test that hypothesis with some really amazing fossils like [this](_URL_3_). \n\nSo, what does that mean for dinosaurs shedding their skin? I think it's important to note that skin is a living organ that's constantly regenerating beneath the surface. The question isn't whether those dead skin cells are coming off, it's what they look like when they do. Crocs shed their skin in pieces. It's not like a snake; it kind of peels off and falls away in small sections. Birds are obviously quite different in appearance to crocs, but their skin does something kind of similar. I looked briefly for a decent source on this and didn't find one, although when birds shed, it's even less conspicuous and the skin flakes are even smaller. Some behavioral stuff like preening is going to be a factor, too. So they're kinda similar but with differences, but based on how birds and crocs shed, we'd hypothesize that extinct dinosaurs didn't shed their whole skin nearly intact like snakes, but that it'd peel away in smaller pieces. \n\nNow, the complication here is that there is considerable variation in dinosaur morphology, including in their integumentary structures (fancy name for hair/feathers/quills/etc. that grow out of the skin). Feathers are the big one, and they really get cranking in Coelurosauria, a group of theropod dinosaurs. That's not the end of it, though, because there are integumentary structures in other dinosaurs like [*Tianyulong*](_URL_0_) and [*Psittacosaurus*](_URL_2_). We don't really have modern analogs for some of these structures. Given that incredible variation, I'm sure there was variation in how they shed their skin! \n"
]
}
|
[] |
[] |
[
[
"http://onlinelibrary.wiley.com/doi/10.1111/j.1469-7580.2008.01041.x/abstract",
"http://onlinelibrary.wiley.com/doi/10.1002/jez.b.22514/full",
"http://www.nature.com/nature/journal/v468/n7320/full/nature09480.html?foxtrotcallback=true",
"http://www.sciencedirect.com/science/article/pii/S0195667115000373",
"http://www.ivpp.cas.cn/qt/papers/201403/P020140314381809346593.pdf"
],
[
"https://en.wikipedia.org/wiki/Tianyulong",
"http://www.ucmp.berkeley.edu/taxa/verts/archosaurs/archosauria.php",
"https://en.wikipedia.org/wiki/Psittacosaurus",
"http://news.nationalgeographic.com/news/2004/09/0908_040908_dinoparents.html"
]
] |
||
1a48vy
|
Ants and bees have queens that are physically very different and serve very different roles than the rest of their group...how genetically different are they?
|
Do all female ants have unactivated genes that can cause them to become queens?
|
askscience
|
http://www.reddit.com/r/askscience/comments/1a48vy/ants_and_bees_have_queens_that_are_physically/
|
{
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"text": [
"It is how they are treated and fed during development. They have the full set of genes, unlike the drones, but they are not genetically different from their sisters.\n\n\n",
"Queens are genetically identical to their sister workers. I am not entirely sure about ants but bees are fed a special substance called royal jelly which causes them to develop the way they do. \n\nThe trick is that while they are genetically identical they are *epigenetically* very different. Epigenetics strictly speaking means anything that changes an organisms phenotype (appearance, behavior etc) without changing its genotype. More recently it has come to mean chemical modifications to chromatin - the DNA/protein complex that packages the genome inside the cell. Some epigenetic modifications cause the chromatin, and therefore the genes contained therein, to be compacted and shut down, while others cause it to open up and allow for gene expression. Royal jelly contains epigenetic modulators that cause the developing queen larvae to have a different gene expression pattern from worker larvae.\n\nThe other important part of royal jelly is growth factors - small signaling proteins that encourage growth and development. During embryonic development they are produced by the organism itself, and left to their own devices bee larvae will grow into a normal bee using their own growth factors. The royal jelly is enriched for extra growth factors and allow the larvae to develop into a much larger animal. \n\nThere is a japanese scientist who published a paper in Nature about a year ago about the active components of royal jelly which effect the development of queen morphology. Its a remarkable paper partly because its just good research and partly because its a single author paper. He did it all by himself. No one does that any more. Here's the link to the paper, which you won't be able to read unless you can get journal access, but you might be able to get the gist of it if you google the author's name and look at his lab website. \n_URL_0_"
]
}
|
[] |
[] |
[
[],
[
"http://www.nature.com/nature/journal/v473/n7348/full/nature10093.html"
]
] |
|
62a2u4
|
how do countries divide payments for sending mail by post?
|
Let's say I'm in Canada and want to send a letter to someone in Australia. I buy correct postage in Canadian stamps and send it on its way. How does Australia get its share of the money from the stamps to deliver the mail on their end? Both Canadian and Australian postal workers need to get payed. How are the costs split up?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/62a2u4/eli5_how_do_countries_divide_payments_for_sending/
|
{
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"text": [
"They are not, as the countries themself have little to do with it (unless we are dealing with state-postal-service - but they usually are still another entity).\n\nLets stay within your canada- > australia example.\n\nYou buy stamps from the Canada Post Corporation. put them on your evenlope to australia and give it one way or another to Canada Post. \n\nIn case of \"Canada post\" - > \"Australia post\" both have an explicit long term contract within the [international post corporaton](_URL_0_) and Australia post keeps record of how much mail (or packages) they delilvered for Canada post. How often they demand the money i dont know. \n\nWhile Australia post would not (paper)stamp your letter again, they will add their ink stamp for tracking.\n\nHow the mail gets there is differnt from contract to contract (UPS flies to the country and to the nearest/cheapest hub of the other company if they for example are not allowed to deliver letter-mail in that country, and DHL and La Poste have a joint-venture exchange point AFAIK)\n\n\n\nOther postal companies will have diferent contract-constellations to make it work. (DHL with itself in case of Germany- > USA for example)\n\nsource: Grandfather was in Deutsche Post (which became DHL), Father was in german division of UPS"
]
}
|
[] |
[] |
[
[
"https://en.wikipedia.org/wiki/International_Post_Corporation"
]
] |
|
cfsisu
|
why do cucumbers taste so mild while you're eating them, but taste so strongly when you burp afterward?
|
It's all I can taste when I burp for hours after eating a cucumber!
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/cfsisu/eli5_why_do_cucumbers_taste_so_mild_while_youre/
|
{
"a_id": [
"euc6nim"
],
"score": [
7
],
"text": [
"It's the cucurbitacin in them. It's a chemical that they have to help prevent certain animals from eating them (too much and there wouldn't be any to make more-hey nature!)\n\nIt's mostly in the stem end so if you don't eat that part it will cut down on it too. Also can deseed them and they will help prevent excess gas from coming up. Also the \"American\" slicing cucumbers have more in it and the Asian/English types have less."
]
}
|
[] |
[] |
[
[]
] |
|
ns3vc
|
how do password hashes work?
|
How do password hashes work? How can there be a 'one way function? ' It doesn't make sense to me. Why can't someone look at exactly what we should done to convert something to a hash and then do the same process backwards? Also, what's to stop someone from essential 'brute-forcing' hashes by starting with a and going through all the alpha-numerical symbols for 12 characters or so, and then have a just compare any given password to the compiled list of hashes?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/ns3vc/eli5_how_do_password_hashes_work/
|
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"text": [
" > Also, what's to stop someone from essential 'brute-forcing' hashes by starting with a and going through all the alpha-numerical symbols for 12 characters or so, and then have a just compare any given password to the compiled list of hashes?\n\nThis is called a [rainbow table](_URL_1_). And if you just did something simple like one pass of md5 to make a hash, you could easily find out what the password is from a hash just by [googling it](_URL_2_). This is why you don't just do md5 once. You would use a hashing algorithm (like md5 or better yet SHA256) hundreds of times on the same password. \n\nYou would also use random [salt](_URL_3_) and store it with the hash. A salt is not an encryption key, and having the salt won't allow you to decrypt the hash. It is just some random text you append or prepend (or both) to the original password to make the result more unique. \n\nWhat the uniqueness of the salt and multiple passes of the hashing algorithm add are more time to generate all the combinations. This also prevents one rainbow table from being used for every password in your database. You would need to generate the table for each password which takes time. You want to add as much time as possible, such that the time it takes to brute force one password would take years (preferably centuries).\n\nThe number of alpha-numerical combinations of 12 length is ~3,226,266,760,000,000,000,000 ((26 + 26 + 10)^12 ). And a even rainbow table that size with just basic one pass md5 and a computer that could calculate a billion md5s a second would take a 100,000+ years to generate the whole table.\n\nSo, lets say you have a password. What you do is run it through your hashing algorithm, 1,000,000 times with a random salt appended each time. This process takes a half second to complete on your server. The user doesn't notice since the compute time isn't that long. You store the result, along with the randomly generated salt in your DB. Then the next time the user comes to log in, you take the new password they entered to check and run it though the same process. First you grab the salt from the DB though and use it as the same salt to run the 1,000,000 passes of your hash. If the resulting hash matches, the entered password is correct.\n\nWhat this has accomplished is two things. First, it slows down the server side validation of a password. A person trying to brute force their way into your server by sending random passwords to be validated would have to wait a half second each time to get an answer. Second, if your database and code was compromised and someone wanted to brute force their on their own super fast machine, they would know your hashing method (1,000,000 sha256 with random salt) and resulting hash, but that would get them nothing really. They'd still need to generate all possible combinations until they matched the password. Most importantly, they'd need to through the whole table out for each password they wanted to crack. As in, if they generated all 8 length combinations to guess the first password, they couldn't use all those generated hashes for the second. \n\nThis whole process will take them a really long to even crack one 8 character length password. Lets say they're machine can do the hashing of one guess in 0.00001 seconds (50,000 times faster than your server). It would take them ~70 years for one password. \n\nThe best thing to do if you are planning to generate your own client login system is to use an already built library for generating and validating hashes. For php, there is the (poorly named) [phPass](_URL_0_).\n\nSo is it one-way then? Well, the hash is. But using a hash on a password is not really one-way. Since passwords generally have an upper bound on length (say < =12 characters for reasonable password use) it makes it such that the space that a hash is mapping probably one have any collisions. Meaning, a generated hash for a password probably won't match another different password (i.e. the hash is unique to the password). But hashing algorithms aren't specifically designed for use in password encoding. \n\nThey are generally designed for checking data integrity and can take any length string. md5 for example can take a whole harddrive (say 1TB in size) and spit out a 32 length hexadecimal string. It can take an infinite length string and boil it down to a 32 length hexadecimal string. In that scenario, you couldn't take the md5 hash and run through some magic and get the harddrive image. There are millions of strings that would match that hash that are less then a TB is size. So in that sense, the hashing algorithm is \"one-way\".\n\n\n\n",
"You've stumbled across something big, actually. We have no idea if one-way functions exist, its one of the \"big picture\" unsolved problems in computer science. \n\nWhat we do have, however, are functions that given current levels of technology might as well be one-way, because computing the inverse would be ridiculously difficult for our hardware (effectively impossible). So we usually take \"one-way\" to mean these, unless otherwise specified.\n\nDo they get \"outdated\", then, as hardware improves? Yep. They also get broken when really smart people work out indirect or non-obvious attacks, flaws in the algorithm that weren't foreseen or weren't considered important.",
" > Also, what's to stop someone from essential 'brute-forcing' hashes by starting with a and going through all the alpha-numerical symbols for 12 characters or so, and then have a just compare any given password to the compiled list of hashes?\n\nThis is called a [rainbow table](_URL_1_). And if you just did something simple like one pass of md5 to make a hash, you could easily find out what the password is from a hash just by [googling it](_URL_2_). This is why you don't just do md5 once. You would use a hashing algorithm (like md5 or better yet SHA256) hundreds of times on the same password. \n\nYou would also use random [salt](_URL_3_) and store it with the hash. A salt is not an encryption key, and having the salt won't allow you to decrypt the hash. It is just some random text you append or prepend (or both) to the original password to make the result more unique. \n\nWhat the uniqueness of the salt and multiple passes of the hashing algorithm add are more time to generate all the combinations. This also prevents one rainbow table from being used for every password in your database. You would need to generate the table for each password which takes time. You want to add as much time as possible, such that the time it takes to brute force one password would take years (preferably centuries).\n\nThe number of alpha-numerical combinations of 12 length is ~3,226,266,760,000,000,000,000 ((26 + 26 + 10)^12 ). And a even rainbow table that size with just basic one pass md5 and a computer that could calculate a billion md5s a second would take a 100,000+ years to generate the whole table.\n\nSo, lets say you have a password. What you do is run it through your hashing algorithm, 1,000,000 times with a random salt appended each time. This process takes a half second to complete on your server. The user doesn't notice since the compute time isn't that long. You store the result, along with the randomly generated salt in your DB. Then the next time the user comes to log in, you take the new password they entered to check and run it though the same process. First you grab the salt from the DB though and use it as the same salt to run the 1,000,000 passes of your hash. If the resulting hash matches, the entered password is correct.\n\nWhat this has accomplished is two things. First, it slows down the server side validation of a password. A person trying to brute force their way into your server by sending random passwords to be validated would have to wait a half second each time to get an answer. Second, if your database and code was compromised and someone wanted to brute force their on their own super fast machine, they would know your hashing method (1,000,000 sha256 with random salt) and resulting hash, but that would get them nothing really. They'd still need to generate all possible combinations until they matched the password. Most importantly, they'd need to through the whole table out for each password they wanted to crack. As in, if they generated all 8 length combinations to guess the first password, they couldn't use all those generated hashes for the second. \n\nThis whole process will take them a really long to even crack one 8 character length password. Lets say they're machine can do the hashing of one guess in 0.00001 seconds (50,000 times faster than your server). It would take them ~70 years for one password. \n\nThe best thing to do if you are planning to generate your own client login system is to use an already built library for generating and validating hashes. For php, there is the (poorly named) [phPass](_URL_0_).\n\nSo is it one-way then? Well, the hash is. But using a hash on a password is not really one-way. Since passwords generally have an upper bound on length (say < =12 characters for reasonable password use) it makes it such that the space that a hash is mapping probably one have any collisions. Meaning, a generated hash for a password probably won't match another different password (i.e. the hash is unique to the password). But hashing algorithms aren't specifically designed for use in password encoding. \n\nThey are generally designed for checking data integrity and can take any length string. md5 for example can take a whole harddrive (say 1TB in size) and spit out a 32 length hexadecimal string. It can take an infinite length string and boil it down to a 32 length hexadecimal string. In that scenario, you couldn't take the md5 hash and run through some magic and get the harddrive image. There are millions of strings that would match that hash that are less then a TB is size. So in that sense, the hashing algorithm is \"one-way\".\n\n\n\n",
"You've stumbled across something big, actually. We have no idea if one-way functions exist, its one of the \"big picture\" unsolved problems in computer science. \n\nWhat we do have, however, are functions that given current levels of technology might as well be one-way, because computing the inverse would be ridiculously difficult for our hardware (effectively impossible). So we usually take \"one-way\" to mean these, unless otherwise specified.\n\nDo they get \"outdated\", then, as hardware improves? Yep. They also get broken when really smart people work out indirect or non-obvious attacks, flaws in the algorithm that weren't foreseen or weren't considered important."
]
}
|
[] |
[] |
[
[
"http://www.openwall.com/phpass/",
"http://en.wikipedia.org/wiki/Rainbow_table",
"http://www.md5rainbow.com/2ab96390c7dbe3439de74d0c9b0b1767",
"http://en.wikipedia.org/wiki/Salt_\\(cryptography\\)"
],
[],
[
"http://www.openwall.com/phpass/",
"http://en.wikipedia.org/wiki/Rainbow_table",
"http://www.md5rainbow.com/2ab96390c7dbe3439de74d0c9b0b1767",
"http://en.wikipedia.org/wiki/Salt_\\(cryptography\\)"
],
[]
] |
|
3j17ec
|
In WWII were there any reports of either military or civilian injuries or deaths caused by anti-aircraft weaponry, or any type of air based weaponry, missing a target and falling back to the ground?
|
When I watch documentaries on WWII bombing raids or even patrol missions they always talk about the unimaginable amount of ammunition shooting upwards at the planes. Did any of that ever fall back and hit people? Even in dogfights things like shell casings or debris from hit planes causing injuries?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/3j17ec/in_wwii_were_there_any_reports_of_either_military/
|
{
"a_id": [
"culg09k"
],
"score": [
6
],
"text": [
"hi! there's always room for more input on this, but you'll be interested in several previous posts on the impacts of anti-aircraft weapons and dogfights...\n\nAnti-aircraft\n\n* [What happened to all the stray bullets fired in the skies during WWII? (Or any war for that matter)](_URL_4_) - featuring /u/defrost\n\n* [Are there any statistics regarding WW2 flak as a source of friendly fire (civilian or otherwise)?](_URL_0_) - featuring /u/astrogator \n\n* [How dangerous was WW2 anti-aircraft Fire to people on the ground below it.](_URL_1_) - featuring /u/the_alaskan (post also links back to the above post)\n\n* [Did any shell fragments from flak cannon defense ever cause injury or damage for people on the ground?](_URL_5_) - featuring /u/when_ducks_attack \n\n* [Did anti-aircraft guns cause more damage to the city they were trying to protect?](_URL_3_)\n\ndogfights\n\n* [I imagine dogfighting between two planes would create a huge ammount of stray bullets travelling a good distance. Are there recorded cases of civilians or soldiers dying because of them?](_URL_2_) - contains links to several more posts\n\nMost/all of these posts are locked now, so if you have follow-up questions, ask them here & post the relevant user by including their username"
]
}
|
[] |
[] |
[
[
"https://www.reddit.com/r/AskHistorians/comments/3egffb/are_there_any_statistics_regarding_ww2_flak_as_a/",
"https://www.reddit.com/r/AskHistorians/comments/3ha9f8/how_dangerous_was_ww2_antiaircraft_fire_to_people/",
"http://www.reddit.com/r/AskHistorians/comments/211nhd/i_imagine_dogfighting_between_two_planes_would/",
"https://www.reddit.com/r/AskHistorians/comments/25psoe/did_antiaircraft_guns_cause_more_damage_to_the/",
"https://www.reddit.com/r/AskHistorians/comments/1115kx/what_happened_to_all_the_stray_bullets_fired_in/",
"https://www.reddit.com/r/AskHistorians/comments/2sp8qt/did_any_shell_fragments_from_flak_cannon_defense/"
]
] |
|
55s4wh
|
airport economics
|
I have no idea how it works... Do airlines pay airports to run flights there? - or vice versa? Does any of my flight ticket$ go to the airport? Where exactly are the airplanes kept and how is that paid for? How are terminal slots distributed to airlines?
In general looking for a good synopsis of the economic interactions between: airport, airline, + customer.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/55s4wh/eli5_airport_economics/
|
{
"a_id": [
"d8d805g",
"d8d9ot3"
],
"score": [
6,
2
],
"text": [
"Couple things:\n\n- Retail space. Airports generate a ton of money from retail. Renting space to specific stores/shops, selling products directly, etc. I would not be shocked to learn that franchise set ups inside airports are also owned by the airport directly (like burger king and mcdonalds)\n\n- Flowage fees for fuel placed into the aircraft\n\n- Usage fees from airlines for access to gates, the number of passengers they move through the airport, usage of terminals, etc.\n\n- Land leases to places like rental car companies and retail space outside of the airport but may still be on airport property\n\n- Landing fees\n\nThey can also generate revenue through federal funding to infrastructure and such.\n",
"Here's a nice video [with a breakdown of the costs](_URL_0_). On a short flight (the video uses JFK to IAD--New York to Washington DC). For a full plane, per person:\n\n* fuel is $2.50\n* Crew is $1.50\n* Airports get $13.50\n* Taxes and government fees are $15.60\n* the depreciation of the aircraft is $11\n* maintenance is $14\n* overhead is $10\n* insurance is $0.25\n\nThese add up to about $70 in total costs per person for a short flight that's likely to be full most of the time (the costs start zooming up if the plane isn't full or close to full). \n\nAirports also get from passengers: things like rent from retail services (compare the price of a typical fast food meal at the airport to near the airport to get an idea of the rent impact) and parking fees for airport affiliated parking services or taxi surcharges from car services. "
]
}
|
[] |
[] |
[
[],
[
"https://www.youtube.com/watch?v=6Oe8T3AvydU#t=38"
]
] |
|
40wi4d
|
the falcon9 landing. why is it cool? what does it get us closer to doing?
|
Yah. What direction is it a step in? What kinds of things can it lead to in 5-10 years.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/40wi4d/eli5_the_falcon9_landing_why_is_it_cool_what_does/
|
{
"a_id": [
"cyxo4x1"
],
"score": [
2
],
"text": [
"As you can probably imagine, one of the most expensive aspects of space travel is building a rocket to get there. SpaceX has been working to make re-usable rocket technology at an unprecedented scale, and the Falcon 9 landing tests are part of that goal.\n\nIf SpaceX are able to land their rocket boosters for safe retrieval, they can save a *lot* of money and resources.\n\nWe can already get to space. This would mainly make it easier and cheaper to do so, which might open up other opportunities that otherwise wouldn't be feasible."
]
}
|
[] |
[] |
[
[]
] |
|
fkvcg5
|
why do some noises produce a physical reaction in people?
|
When I hear scratching on a blackboard or polystyrene it gives me chills. Why does this happen?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/fkvcg5/eli5_why_do_some_noises_produce_a_physical/
|
{
"a_id": [
"fkv56mb"
],
"score": [
7
],
"text": [
"Well, your body reacts to sounds by using your brain to resurface earlier instincts. For example, sudden high pitched sounds (such as writing on a chalkboard) will make you feel stressful and \"wriggly\" because your primal brain tells you to run from the nonexistent predator or natural danger that is suddenly screeching near or at you. Interesting fact- us humans are so horrible, that clanging, metallic sounds resemble war, and can cause legitimate, unexplainable (by them) fear in some people."
]
}
|
[] |
[] |
[
[]
] |
|
abiy0x
|
how does putting food in hot oil fry it (like, how does the actual frying process happen)? also, what are those bubbles, is it water that leaves the food due to the high temperature or something else?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/abiy0x/eli5_how_does_putting_food_in_hot_oil_fry_it_like/
|
{
"a_id": [
"ed0ozm2"
],
"score": [
4
],
"text": [
"Oil is active as a heat stabilizer and heat transfer fluid. As the oil heats various components begin to break down or evaporate (boiling does this rapidly). This takes energy and holds the temperature relatively even as the oil evaporates or smokes. This means that your food is cooked at a relatively stable high temperature evenly across the entire surface, which is what gives it the \"fried\" consistency (coupled with the residual oil).\n\nThe bubbles are steam. Usually."
]
}
|
[] |
[] |
[
[]
] |
||
22kmi5
|
Was lacrosse really used to settle national disputes? Are there other examples of sports settling national disputes?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/22kmi5/was_lacrosse_really_used_to_settle_national/
|
{
"a_id": [
"cgo5di5"
],
"score": [
3
],
"text": [
"There are a lot of lacrosse-related metaphors regarding warfare, and warfare-related metaphors regarding lacrosse. Many of the preparations undertaken by ball players have close or identical analogues among wartime preparations. The association between the two has deep roots and grew increasingly stronger in the late-1700s and early 1800s. At that time, actual warfare became less common in the Eastern Woodlands and men required a new venue for acquiring prestige formerly associated with military service.\n\nThis relatively recent shift in metaphoric emphasis has obscured other aspects of the game. At the time of Contact and for quite some time after, it was employed as a medicine game. More importantly for your question, though, a game between two villages was a huge social event and the subject of considerable gambling, with all manner of prizes up for grabs. Though the sum total of exchanges could be staggering, they usual involved many small personal wagers. However, the leaders of villages or nations might wager for higher stakes on behalf of their constituents.\n\nA famous example of this is recorded in Horatio Cushman's [History of the Choctaw, Chickasaw and Natchez Indians](_URL_1_). The incident was related to Cushman from the well-respected Creek-by-birth, Choctaw-by-adoption elder Stonie Hadjo, through an intermediary and concerns an 18th Century disagreement between the Creeks and the Choctaw over a particularly lucrative hunting ground. The Creeks claimed it because they had been the ones to discover that a large population of beavers had established themselves in the area, while the Choctaw claimed it because it was within their general territorial claim. To settle the dispute, a ballgame was held. Thousands of people of each nation gathered to observe the game.\n\nThe Creeks won the game, but during the celebration, a Choctaw player and a Creek player exchanged insults which escalated into a brawl and into an all out fight that lasted the rest of the evening and picked up briefly the following morning. The leaders of the respective sides got a hold of the situation and quickly entered into peace negotiations. They matter was laid to rest then, and the Choctaw granted ownership of the disputed lands (which turned out not to be as lucrative as everyone thought anyhow). Hadjo regarded the post-game fight as worse than any actual war fought between the Choctaw and the Creek before; five-hundred people allegedly died during the fighting, the majority of whom Hadjo considered to be the most promising young men of their generation. They were buried near the ball field while the peace talks were on-going, and in 1832 their graves were looted for the silver that had been buried with them.\n\nFor more information about lacrosse, its social context, and some other famous lacrosse games, see [American Indian Lacrosse](_URL_0_) by Thomas Vennum."
]
}
|
[] |
[] |
[
[
"http://books.google.com/books?id=ySIIyex5nboC",
"http://books.google.com/books?id=qdrsAAAAIAAJ"
]
] |
||
18bpu5
|
Why do we only look for radio waves in SETI research?
|
The recent Kepler telescope search of 86 exoplanet systems came up with nothing. It seems to me that it is just as likely that an alien intelligence might, due to completely different sensory organs, invent an entirely different way of communicating that we have. If an alien species evolved without the ability to detect sounds as one of it's senses, is there even any reason to use radio? Microwaves, X-rays, directional lasers, pheromones, infrared, even quantum entanglement are all possible alternatives.
There is also the idea that we are applying human paradigms to alien minds. What if, on an alien world, there is no long-range communication as we know it? What if all beings shared a hive mind?
Also, why do we assume that these civilizations would be broadcasting into space the way we do? What about directional bursts?
I understand that not every one of these options can be tested for, but even so where does "no radio, no ET" come from and why?
EDIT Has anyone looked for ET signals using anything besides radio?
|
askscience
|
http://www.reddit.com/r/askscience/comments/18bpu5/why_do_we_only_look_for_radio_waves_in_seti/
|
{
"a_id": [
"c8de883",
"c8dezpy",
"c8dfi5b",
"c8dki6a",
"c8dnhdf"
],
"score": [
12,
5,
3,
6,
3
],
"text": [
"We assume that life is like us, because we have to. We're aware that life could take any form we can or can't imagine, but we don't know how to look for life we can't imagine, and while we might be able to look for life we can imagine but is very different from us, it's smarter to look for life like us. Why? Because we know that life like us is possible and has appeared at least once in the universe. We have no evidence that any other kind of life is possible or present. We're looking for what is the most likely, given the data available to us.\n",
" > It seems to me that it is just as likely that an alien intelligence might, due to completely different sensory organs, invent an entirely different way of communicating that we have. If an alien species evolved without the ability to detect sounds as one of it's senses, is there even any reason to use radio? Microwaves, X-rays, directional lasers, pheromones, infrared, even quantum entanglement are all possible alternatives.\n\nHere's the thing: We're already capable of sending detectable radio signals to the nearest stars. We can't do the same with any EM frequencies higher than radio (maybe microwave). Pheromones are slower than c. Quantum entanglement requires you to transport a particle to somewhere in the first place, and it can't transmit information.\n\nRadio is far and away the easiest way to send signals across interstellar distances. It's also the easiest to detect. That's why we're looking for it.",
"What do you mean \"came up with nothing\"?\n\n",
"\"If an alien species evolved without the ability to detect sounds as one of it's senses, is there even any reason to use radio\"\r\rYour misunderstanding the word radio. Just because we use radios, the devices, to transmit info we send and interpret as sound doesn't mean radio transmission, the light wavelength, can only transmit info interpreted as sound. ",
"The old Wired Storyboard podcast has an episode about this called [Hunting for Extraterrestrial Intelligence With Geoff Marcy](_URL_0_) That covered this very question and was very interesting. I can't speak with any level of expertise on it, but from what they said that they're now looking for laser based communications and will likely look into other methods of communication. Most of it has to do with what we can comprehend and what we're capable of detecting. We have to work off of the assumption that to some extent the evolutionary process that resulted in us, might have happened similarly elsewhere in the universe and have similar communication methods. However, the recognize that it could go beyond this too. "
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[
"http://www.wired.com/underwire/2012/11/storyboard-seti-geoff-marcy/"
]
] |
|
2jnc3p
|
How did the Mexica (aka Aztecs) deal with the umbilical cord after birth? Was there any cultural significance attached to it or was it merely disposed of?
|
I wanted to do the question for Mesoamerica, but alas our rules say no. And with the recent trend of medical related questions associated with the Mexica I thought I'd add another.
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2jnc3p/how_did_the_mexica_aka_aztecs_deal_with_the/
|
{
"a_id": [
"cldd0ce"
],
"score": [
88
],
"text": [
"Aztec births were a highly ritualized affair involving spirituality and midwifery. When the umbilical cord was removed it was preserved and when a son reached adulthood he would bring his to a battle field and bury it. A daughter would bury hers next to the family's hearth. There is an illustrated book called the Florentine Codex, I believe, that describes most (if not all) practices in regards to birth and raising children. \n\n[Edited for link] (_URL_0_)"
]
}
|
[] |
[] |
[
[
"http://www.wdl.org/en/item/10096/"
]
] |
|
bu12d9
|
Interested in the Three Kingdoms
|
Hey so I'm wondering what would be the best material or something of value to know more about the Three Kingdoms of 14th-Century China. After Total War Three Kingdoms came out, and replaying my guilty pleasure Dynasty Warriors 4, I realize I don't have firm understanding of ancient Chinese history. I just want to try to have a better understanding of that time period.
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/bu12d9/interested_in_the_three_kingdoms/
|
{
"a_id": [
"ep5t8m8",
"ep5uxpu"
],
"score": [
6,
6
],
"text": [
"I would suggest you read (assuming your an English speaker) the book itself! There are many translations available, the one I read was the translation by [Robert Moss](_URL_0_). Also there is the actual historical text that the novel was based on, Records of the Three Kingdoms by Chen Shou, for that I would recommend checking out any university libraries in your area. \n\n\nAnd also I'll ping /u/cthulhushrugged for a better answer.",
"There are primary sources on the Three Kingdoms... literary Chinese is a must-know since as far as I can tell, very few documents from the Han and the 3 Kingdoms have been extensively translated into English. Secondary sources are much more accessible. I strongly recommend the *Cambridge History of China, Vol. 2* which spans 220 AD to 589 AD for a baseline of understanding. You could also look into finding an English translation of the Official Histories (*San Guo Zhi* for the 3 kingdoms)... but again, as far as I know those don’t exist and only abridged or heavily edited versions of them are available. Some are currently in the works, but god knows how long those will take. If you have access to specialist resources, then maybe you could get some usage out of them. If all else fails, just read *Romance of the Three Kingdoms*, a 14th century novel that draws upon the official history and which has been translated. Finding source documents from 2,000 year ago is very difficult, so secondary sources will be your friend here. Search library catalogs for bibliographies on books surrounding the “Six Dynasties” era of Chinese history and you should have a good jumping off point from there."
]
}
|
[] |
[] |
[
[
"https://www.amazon.com/Three-Kingdoms-Chinese-Classics-Volumes/dp/7119005901/ref=sr_1_2?keywords=three+kingdoms+robert+moss&qid=1559060470&s=gateway&sr=8-2"
],
[]
] |
|
29wzwf
|
What were preparations like in the dsys/hours/minutes before an attack on a castle or city back in medieval times?
|
I originally asked this in ask history and got a good amount of upvotes, but no response. A user suggested I post it here.
Where did people go, congregate. What defenses were raised, were people conscripted, etc.?
Edit: Sorry for the typo.
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/29wzwf/what_were_preparations_like_in_the/
|
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"It's useful, I think, to first differentiate fortifications into three basic types. These are the fortified town, the baronial castle, and the ducal/royal castle. The three really only have in common the fact that they are fortified places of strategic importance; the way in which they are constructed, manned, and function in peace and war differ dramatically. I want to make this very clear: everything I speak about below applies to 11th-13th century England and France, and should not be taken as definitive in regards to any other area or period.\n\nThe fortified town is just that - a town which has been reinforced with walls of some variety. These could be permanent fortifications, ranging from masonry walls reinforced with towers and gatehouses at the high end of the scale, to simple timber palisades at the low end. The penultimate fortified town of medieval Europe was probably Constantintople, which was defended by some twelve miles of walls, four on the land face, and eight on the sea face. Some had no permanent walls, but in times of crisis were hurriedly encircled with jury-rigged ramparts of earth, timber, and stone, sometimes in as little as two weeks. Regardless of their scale and sophistication, fortified towns suffered from the same problem: they were not purpose-built military installations, but population centers around which defenses had been thrown up. Generally, this meant a weaker geographical position, many entrances which must be defended, and a long circuit of walls. The longer the stretch of walls, the more men are needed to defend them. Though it may seem counter-intuitive, a city with a garrison of 500 men may well be weaker than a castle with 50, because those 500 are less concentrated. A small or unimportant town might be forced to rely wholly on a local militia of artisans and merchants; a more important city, like Rouen or Paris or Poitiers, might have the benefit of a permanent royal, ducal, or comital garrison.\n\nThe second fortification we will talk about is the baronial castle, though that term is unfortunately imprecise. These are fortifications of local, rather than regional, importance, belonging to mid-level aristocrats referred to variously as castellans, barons, vavasours, and lords; the regionally, but not nationally powerful men. The majority of castles were of this type, and they could be very numerous, with eight, ten, or more in a given county or shire, spaced every few miles, this being the area which a small mounted garrison could exert control over. This is a dedicated military fortification, generally sited on a site of strong natural strength - most commonly, a ridge, hill, or man-made mound called a motte. It varied with time and military technology, but could range from a simple wooden hall surrounded by one or more timber palisades, to a stone keep (a very large tower) surrounded by palisades or stone curtain walls, to, in the most lavish cases, a series of two or three interconnected stone courtyards, with towers and gatehouses. But it was also an aristocrat's court, where a lord and his household of knights and servants lived (though it was not uncommon for a magnate to have two or even three such castles, in which case those not resided in would be more purely military structures). In event of siege, it would be defended by the aforementioned household, supplemented by landed knights owing service to the lord and the free peasants of the nearby area. These castles, owing to their small size, inadequate garrisons, and lack of stockpiled provisions, tended to fall very quickly to determined besiegers.\n\nThe third variety is the royal or ducal castle. This is more what people think of when the term castle is mentioned. Besides being generally larger and more modern than the typical baronial castle, it is a fort, not a home, and almost always defended by a permanent, often quite large, garrison under a commander appointed by and answerable to the king or duke. It was very frequently constructed at great expense and with great care, almost always to defend a strategic point, such as a river crossing, an imposing height, or a threatened frontier. Thus we can say that these castles, rather than being locally important, were very often regionally important; their possession or loss determined the possession or loss of the wider region. With the funds of the crown to back them, these generally were kept very prepared for siege, with huge stocks of food; Chateau Gaillard survived 7 months of siege before being forced to surrender, not by lack of food, but by the compromising of its last remaining defensive wall.\n\nThe immediate defensive measures were quite similar among them all. Get in as much food and drink as possible; reinforce any weaknesses in the walls, often with wooden hoardings; get every able-bodied freeman available under arms. Then get ready to wait for as long as it takes a relieving army to arrive, the food to run out, or the defenses to be breached and surrender compelled."
]
}
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[
[]
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8sip51
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How did Rome get buried?
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Hi guys. I went to Rome a while ago and some tour guides kept saying that, being surrounded by hills, Old Rome got buried by rain carrying sediment from the hills. So now most ruins are completely buried. How exactly did this take place gradually, though? I understand that after 2000 years that much would build up, but when it started getting noticeable, wouldn't the Romans take steps to stop it? This may be a stupid question and I may be misunderstanding something. I just don't quite see how this process took place.
Edited your to tour. Oops!
|
AskHistorians
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https://www.reddit.com/r/AskHistorians/comments/8sip51/how_did_rome_get_buried/
|
{
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"e0zvm49"
],
"score": [
5
],
"text": [
"I didn't know /r/askhistorians did guides (I'd definitely hire some of the mods for private tours!) \n\nIt's definitely not a stupid question, how indeed does a city fall to ruin and get buried under the ground when people still occupy it?\n\n\nThis isn't exactly asnwering about Rome but /u/Pachacamac answers why ruins happen and get buried in cities with people living nearby.\n\n_URL_1_\n\n\n/u/gpodolec answers more specifically why rome gradually went to ruin\n_URL_0_"
]
}
|
[] |
[] |
[
[
"https://www.reddit.com/r/AskHistorians/comments/5g2xnx/after_the_roman_empire_collapsed_did_rome_become/",
"https://www.reddit.com/r/AskHistorians/comments/17je7i/archeologists_are_always_digging_up_ancient_ruins/"
]
] |
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422bvb
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what does it mean when a drug (cocaine, heroin) is cut?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/422bvb/eli5_what_does_it_mean_when_a_drug_cocaine_heroin/
|
{
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"cz71fti",
"cz71gfw",
"cz71gxh"
],
"score": [
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2,
2
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"text": [
"It means it's been cut *with* something in order to stretch the supply. Kind of like if you have half a can of soda, and you fill it up with water. You now have a full can, but it's much weaker soda. And if you sell it like that, whoever bought it might be pissed.\n\nWith drugs, it's not unusual to have them cut with something that's even *less* healthy than the drugs. ",
"Cutting means to dilute the drug by blending it with an inert non-drug ingredient (flour and powdered milk are common for light colored drugs along with potentially less healthy things like baby powder or powered drywall/sheetrock). ",
"It means it is mixed with another drug. This is done mainly to save money, so that people buy 1g of something but they are actually getting .9g of it and .1g of something else that's cheaper. \n\nIt can also be done to produce a different effect or to make a product more addictive."
]
}
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[
[],
[],
[]
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uxkgp
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Do castrated people lose their libido?
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Since libido seems to be a testosterone/estrogen-based drive, does the dip in production eliminate a eunuch's sex drive?
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askscience
|
http://www.reddit.com/r/askscience/comments/uxkgp/do_castrated_people_lose_their_libido/
|
{
"a_id": [
"c4zgg7m"
],
"score": [
5
],
"text": [
"Yes. Your testicles are a driving force in testosterone production, which is key to having any sort of sex drive for males. Steroid users often use faux testosterone to get bigger, causing their body to stop making its own. So when they get off a cycle the have to block estrogen production and wait for natural testosterone to return. And hope they're T levels are in check with their estrogen levels. Thus normal libido.\n\n"
]
}
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[
[]
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3f3zyw
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When will earth lose the moon?
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The moon is moving away from the earth at a rate of 4 cm per year. How long before it escapes our orbit? What will happen to it then?
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askscience
|
http://www.reddit.com/r/askscience/comments/3f3zyw/when_will_earth_lose_the_moon/
|
{
"a_id": [
"ctl99z4"
],
"score": [
27
],
"text": [
"We will not lose the Moon. It will recede as it exchanges energy with the Earth by slowing our rotation. Eventually the recession will stop when the Earth becomes tidally locked to the Moon and one side of the Earth will always face the Moon. \n\nThe opposite process has already happened and the same side of the Moon faces the Earth. When this happens to the Earth, one day will take several \"now\" months, that is how slow we will rotate. This process is very slow due to our greater mass, the Sun will be long dead before this happens."
]
}
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[] |
[] |
[
[]
] |
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agt8aj
|
why do so many older people who are otherwise competent struggle to use computer technology (such as copying and pasting or attaching a file to an email)?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/agt8aj/eli5why_do_so_many_older_people_who_are_otherwise/
|
{
"a_id": [
"ee8wjoa",
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"score": [
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"text": [
"Something about technology scares them. It's so different than how things were when they were younger that they assume something horrible will happen if they do something wrong. They have heard so many \"horror stories\" from their contemporaries that they have just given up. \n\nCombine that with the fact that it's just harder to teach someone who's, say, over 70, something entirely new, and you have the situation we're all in now. They are capable of learning, they just choose not to try. Frustrating, indeed.",
"Biggest obstacle is they tend to use the computer very rarely. It's just not part of their mindset. They get news and entertainment from the television. Communication is through telephone, postal mail, or a walk down the street. \n\nThis lack of skill makes them nervous about breaking it. They grew up with announcements all the time about how your car, dryer, hot water heater, and the like could break down or even kill you if they weren't used and cared for properly. Elderly people also tend to be embarrassed/ashamed about their lack of skill so avoid facing that as much as possible.\n\nIf you happen to be in the position of helping an elderly relative in using their PC here are some tricks I've learned:\n* DO NOT TOUCH THE MOUSE OR KEYBOARD. Tell them how to do something, and only take control if they ask you to. It's **very** tempting to just do it yourself to speed things along, but they learn better if they actually do it themselves rather than just hear it. \n* Remind them (and yourself) that they're not incompetent, ignorant, a failure, whatever just because they don't know how to use a computer. They've accomplished a lot in their lifetime, and lots of people are uncomfortable with computers.\n* Reassure them that it's very hard to break a computer, and (usually) very easy to fix one.\n* let them move at their own pace\n* finally, don't touch the controls. Even if an error message or something comes up. They need to have the confidence that they can handle little hiccups like that. \n",
"The real answer here has to do with learning: specifically skills and generalization.\n\nA skill is something we can define. It can be broad but can be broken down into smaller categories, and the more specific the better. \"Use a computer\" describes both my grandmother and a programmer. It isn't until you get into more complex things and more complex ways of measuring use that we can see differences. Both my grandmother and a programmer can send e-mails but the programmer would understand more about the client and could write them faster.\n\nWhen we generalize a skill, we transfer what we already know to another area. If you can use a typewriter with a QWERTY setup then you can use a keyboard, though you don't immediately start off knowing every button or shortcut.\n\nIn short: people know what they know.\n\n**The biggest issue** is the layman's view on intelligence, being smart, or as you put it, being competent. You're asking why someone you perceive as competent (already subjective) would possibly fail at any given task. Same reason you're competent but if you were given a task you haven't done or don't need to do as often you would fail. There are remote villages around the world that do basic tasks you could never do, and they would consider you incompetent. People think that someone who doesn't speak their mother tongue are illiterate, when really they just aren't fluent. This is a major issue that doesn't get tackled. It's like if you think someone's an idiot and therefore define everything they do by those terms, when really you're taking a biased view and stereotyping it.\n\nWhy **should** someone who's competent not struggle to use computer technology in that case? I'm competent. I have a masters and live a full life. Doesn't mean I can do absolutely anything I want to. I would still have to learn how to do new things. There are going to be very smart people being born for a hundred years but if they never learn to drive stick, let's say, why would they suddenly know how to do it for no reason?"
]
}
|
[] |
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[
[],
[],
[]
] |
||
9ctn48
|
why do companies doing an ipo need to "secure $x billion from y investors" and need z investment companies to "sponsor" them?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/9ctn48/eli5_why_do_companies_doing_an_ipo_need_to_secure/
|
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"text": [
"They are sponsors in that they have committed to pay at least some amount of money to buy shares of the company. If there was no secured funding, the private owners of the company might have no bidders at all. The secured funding also sets a floor on the price so that they don't get unlucky and sell the whole company for peanuts. \n\n In addition, there are many rules in place for IPOs so that ordinary investors don't get defrauded by the current owners of the company or other bidders. If they weren't in place, the first bidders might pay 1 cent per share while everyone else paid much more.",
"It has to do with the logic of investing.\n\nWhen you invest in a company, you are gambling that they are gonna turn a profit and pay you back more then you invested.\n\nKeyword: Gambling.\n\nThere is ZERO guarentee that you are not throwing your money away. Have you been following MoviePass? Some people paid $20/share for stock. You can pick it up for about 2 cents a share today. Legally those people have very, very little ground to stand on. They are simply out that money. When MP declares bankruptcy it becomes even more difficult.\n\nWhen a company goes public typically that is the last tier of people given the opportunity to invest. So, as a joe schmoe investing seems like a smarter idea if there are already a bunch of people firmly committed with the company.",
"Finding the \"price\" of a stock before that company goes public can be very difficult. There often is limited historical information available and while the company needs to provide LOTS of disclosure for an IPO it's obviously not everything. So there's always uncertainty.\n\nYou are correct when you say that stock buyers give the company money for a share when the company is going public. The stock buyers can then resell that share to other buyers on the open market without the company being involved. \n\nOnly most people want a bit more security when they make that first buy from the company. And this is a service that investment banks provide under the role of \"sponsor\". The sponsor sets the initial price of the IPO and in so doing they agree to purchase a certain number of shares at that price.\n\nSo effectively, 1 second before the actual IPO happens, Goldman, Merrill and Morgan Stanley all buy a certain number of shares at the IPO price. It's their way of signalling to other buyers that the price is fair, they basically put their money where their mouth is. Those investment banks hold those shares for a short period of time then they resell them on the open market. Now, this can happen with all or a part of the total shares the company is selling on day 1. So sometimes the investment bank and the company are both out there at the same time selling their shares to the general public.\n\nThis leads to one of the main criticisms of the IPO process. It's all guided by an investment bank who's incentive is actually to underprice the shares. That way they won't wind up stuck with the shares that they purchase ahead of the IPO. When that happens the investment bank who advises the company has an incentive to provide advice that is counter to the companies actual interest. So the investment bank and the company negotiate to set the IPO price and the market takes over after that. When a companies stock goes up immediately after an IPO it's the investment bank who's the big winner, not the company itself.\n\nNow onto your first question. Often times larger shareholders can provide benefits that the general public cannot, particularly confidence in the company. So other investors can look at people who have agreed to buy large blocks of shares as a way to gauge the companies health without doing a detailed deep dive into the companies financials. In this case, Tencent is known in the gaming industry and them putting money into Meituan is a vote of confidence. It's like a celebrity endorsement. \n\nIt's also worth pointing out that the large investment banks also play a role in bringing these large share purchasers in. Often it's the investment bank that brings the 2 parties together. As such it's often the investment bank's own shares that are sold to the large investor to reduce the investment bank's own risk on the deal.",
" > Why do they need to secure billions from 5 investors? \n\nThey don't \"need\" to. They \"plan\" to. Those are different things.\n\n > Shouldn't the money be coming from the stock buyers? And why are Merrill Lynch \"sponsors\" of the IPO?\n\nThere are no stock buyers (not \"public\" ones, anyway) until after the IPO. Somehow, you have to get from \"no publicly traded stock\" to \"yes publicly traded stock\". The sponsors are how you usually bridge that gap. They buy the stock before the IPO, then sell to the public upon the IPO."
]
}
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[] |
[] |
[
[],
[],
[],
[]
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5f1yh5
|
why do some electronics not turn on while charging?
|
If it's not a full computer, it doesn't work while plugged in. My electric razor, an old mp3 player, my watch, even my battery powered vacuum. Why can't it work while it's charging, especially if it's already full and I just didn't bother unplugging it?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5f1yh5/eli5_why_do_some_electronics_not_turn_on_while/
|
{
"a_id": [
"dagtlyg",
"dagvpqt"
],
"score": [
7,
2
],
"text": [
"Simply put, those things don't have a circuit that diverts power to the device as well as the battery. \n\nBatteries can't charge and discharge at the same time. When you plug something like your phone in, it has a circuit which directs the required power to the phone and the rest to the battery to charge. Some devices are simpler and the power can only go to the battery. ",
"Two possible reasons. \n\n1. Some cheap low power chargers don't have isolation from the AC line and use a capacitive dropper instead of a transformer. For safety reasons, they isolate the user while charging by disconnecting the battery from the device. \n\n2. More commonly, the charger is not powerful enough to power the device and charge a dead battery at the same time. The vacuum would fall into this category."
]
}
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[] |
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[
[],
[]
] |
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18ulji
|
Why do things like glue, sticky notes and other adhesives like that become "unsticky" when it's cold?
|
Pretty much it. I know it has to do with bonds, but, why cold?
|
askscience
|
http://www.reddit.com/r/askscience/comments/18ulji/why_do_things_like_glue_sticky_notes_and_other/
|
{
"a_id": [
"c8i5xqp"
],
"score": [
3
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"text": [
"Most glues conform to the shape of whatever they are bonding to. If there are microscopic ridges on a surface the glue would fill them This increases surface area for chemical bonding and attraction which is the primary way the glue sticks.\n\nWhen its cold the glue can contract and it may not conform to the surface anymore if it contracts at a different rate than the material its bonded to. Also the glue will harden and may not be able yield when the material its bonded to puts a stress on it or vice versa. "
]
}
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[
[]
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5oy5bb
|
why are sodas made with such strong acids?
|
I've read before that the reason that, for example, a can of Coke has ~46 grams of sugar is because if it had less, you wouldn't be able to taste the sweetness over the sour/bitter taste of phosphoric acid.
So why are they made with such high concentrations of phosphoric and citric acid? What does that do for the soda? If they used less, surely they'd need far less sugar?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5oy5bb/eli5_why_are_sodas_made_with_such_strong_acids/
|
{
"a_id": [
"dcmyhh5"
],
"score": [
4
],
"text": [
"As far as I understand it, the do it to equalize the sweet taste of sugar. Now, you asked why they even add as much sugar in the first place.. sugar sells. Your body reacts to sugar well comparable to how it reacts to heroin, although significantly less drastic. You have the feeling of happiness and being energized. If they didnt add that sugar, coke would sell a lot less. If your body notices a lack of sugar or wants more of the energy/happiness, it usually forces you to drink coke or eat something sweet. \n\nCompare it to salt/umami tastes in chips. The umami is really beneficial for your body, it would normally carry lots of nutritients and minerals. The bad thing is, that umami in chips is usually just the pure taste without the extracts that you would have in natural umami taste.\n\nWell I drifted off-topic here, but in general, sugar makes you lets you more likely grab a coke than water/another soda, acid is used to equalize the sweetness."
]
}
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[
[]
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48c1ep
|
Besides Allied interception of Japanese plans throughout the Pacific theatre, what caused the demise of the Imperial Japanese Navy and its forces?
|
The Japanese appeared to have an impressive fleet throughout the war, with ships ranging from:
* destroyer classes *Fubuki* (including the type 2/3 classes, *Ayanami* and *Akatsuki*) and *Akizuki* to the super-destroyer *Shimakaze*
* cruiser classes such as the *Takao, Mogami, Tone* classes
* battleship classes *Kongo, Fuso*, and the flagship *Yamato* class
* Aircraft carrier classes *Soryu, Shokaku*, and the more modern *Taiho*
This surface fleet combined with submarines such as the Type B1 class and the *Sentoku I-400* class sounds like an incredibly powerful force on paper - what factors excluding Allied codebreaking and communications interception caused the demise of the Japanese fleet?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/48c1ep/besides_allied_interception_of_japanese_plans/
|
{
"a_id": [
"d0iigcr"
],
"score": [
7
],
"text": [
"Allied codebreaking and other SIGINT ultimately had relatively minor impact compared to the sheer quantitative, qualitative, and technological advantages that the US Navy had over the Japanese one. \n\nThe authors of Shattered Sword have a [certain webpage](_URL_0_) in reference to just how massive the Allied advantage was in the Pacific. Simply put, by 1945, the US would have been able to deploy something along the lines of 30 modern CVs, 9 modern CVLs, and over 120 CVEs, against 14 Japanese CVs (of which 1 was arguably even close to the quality level of the US ones), resulting in anywhere from a 2.5 to 3 to 1 disparity in aircraft capability. In addition, the US aircraft were far superior to anything the Japanese could put into the air, and the US could replace their plane and pilot losses, which Japan simply could not due to a combination of poor logistics and a strict naval aviation training regime that made pilot training extremely difficult. \n\nThat was just carriers. The US Navy was larger than the rest of the worlds navies, combined. And the US models were the best in the world. In the Battle off Samar, 7 destroyers and a handful of escort carriers, which didn't even have torpedoes for their aircraft, bloodily repulsed a sortie by the main battleline of the Japanese navy, including almost all of their battleships and remaining heavy cruisers.\n\nI talk more about this [here](_URL_2_), [here](_URL_1_), [here](_URL_3_) and [here](_URL_4_)."
]
}
|
[] |
[] |
[
[
"http://www.combinedfleet.com/economic.htm",
"https://www.reddit.com/r/AskHistorians/comments/2ijyh8/what_kind_of_training_did_imperial_japanese_navy/cl2umdy",
"https://www.reddit.com/r/AskHistorians/comments/3gyzs2/osprey_publishing_pacific_war_megathread_contest/cu2vczy",
"https://www.reddit.com/r/AskHistorians/comments/22oyi9/was_the_attack_on_pearl_harbour_a_gamble_by_the/",
"https://www.reddit.com/r/AskHistorians/comments/22ihye/did_the_japanese_victory_at_the_battle_of/cgn7sq5"
]
] |
|
x1jzq
|
how does one secure venture capital funding?
|
I don't have an idea or plans to do so, I'm just wondering how this process takes place normally. The information I found online seems to be hype.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/x1jzq/eli5_how_does_one_secure_venture_capital_funding/
|
{
"a_id": [
"c5ierev",
"c5ixs1e"
],
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7,
2
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"text": [
"Hype might not be the right word- but there is a significant preference to high-growth companies (usually young ones, since the maturity phase is relatively unlikely to lead to a high (risky) ROI-1). A mere business plan is usually not good enough unless you've discovered an untapped market or |the market is monopolistic * (low barriers to entry-2, basically). Competition often makes it too unpredictable for funders to just accept a business plan- initial results are greatly valued. After that, get someone with connection or approach companies yourself (your business career is truly aided by years of solid networking)- have a good presentation where you not only show some passion / strategy, but also give them some cold hard numbers and be the prize. (their initial offer will usually be near the minimum of what they're willing to give)\n\nFurthermore I suppose it's probably also important whether you want to give them equity (stock) or just have them be a glorified bank (debt).\n\n\n-1ROI = Return on investment, e.g. if they're going to invest 25.000, and their analysts say you've got only a 50% survival rate and no real assets to lay claim on if you do perish, they're going to want a lot more than a 25.000 return.\n\n-2barriers to entry = how easy it is for a new player to enter a market, compare a farmer's market (near perfect-competition, easy as shit) to e.g. the PC market (oligopoly, hard as shit). The uncertanties of competition will be very dominant in oligopolies.\n\n\nIt's a little late, so I might've been a bit incoherent, but these are some of the basics.\n\n\n*edit: Perfect competition, not monopoly. Dayum. Edit #2 Why the fuck would a venture capitalist fund a business in perfect competition? This is stupid, I apologise. (Made this post at like 04:00, wasn't thinking too straight.)",
"You put together a convincing case, and go ask for it. But you'd better know your shit, and have done your homework.\n\nThe trick is not just in building a convincing case, but identifying a viable business to base all this on. You have some idea, and you put together a plan for developing your idea. You identify who your customers might be, and how you will go about getting their money. You project things forward a bit, and anticipate assorted costs and difficulties, and upsides. You anticipate growth.\n\nBut let's turn it around. The venture capitalist is a gambler, evaluating your proposal, and trying to find flaws and so on. They aren't going to just write you a check, they will need convincing first, then there will need to be a series of constraints and evaluations along the way. They may only need to have a hit once in every ten investments, but they are still very careful about giving away money."
]
}
|
[] |
[] |
[
[],
[]
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6sx80m
|
how can companies like amazon afford to price things at such low margins?
|
Its common to see things on Amazon for prices listed much lower than on their manufacturer's site.
How can Amazon be so profitable with this mindset?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/6sx80m/eli5_how_can_companies_like_amazon_afford_to/
|
{
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],
"score": [
5
],
"text": [
"Amazon's margin is ~15%, it's not low. Really what you're seeing is that many manufacturers place their MSRP high enough that the moderate traffic mom and pop shop in a major city can sell it at MSRP and still make rent, and they can afford to mark it down for various sales. [Thus most industries have 30-40% gross profit margins](_URL_0_).\n\nAmazon however has worked out awesome shipping rates (due to volume), and has no sales people, and always operates from warehouses, usually located in the sketchy part of town, not main st. Their costs are much lower than most stores, and instead of marking things down on sales, they really just take the actual cost, add their ~15%, and sell it as is, which for many industries is a very large percent off MSRP."
]
}
|
[] |
[] |
[
[
"http://research.financial-projections.com/IndustryStats-GrossMargin.shtml"
]
] |
|
2se5nw
|
why can't we use waste gas to create more energy?
|
So, everyone is complaining about how environmentally harmful power stations are because of their waste gas. Why don't we use those waste gases though? I don't really know how to explain what I mean to say since english is not my mother language but take a look at my [awesome paint image](_URL_0_) and you'll understand what I mean.
Thanks
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2se5nw/eli5_why_cant_we_use_waste_gas_to_create_more/
|
{
"a_id": [
"cnolgxs",
"cnom4ky"
],
"score": [
3,
3
],
"text": [
"The 'gas' emitted from power stations is the bi product of combustion of their fuel, which could be gas, coal, whatever. A hefty amount of that is water vapour.\n\nFor a gas to be able to turn a turbine then it has to be expelled under pressure, which is of course how power stations work, usually by steam turbines. But the emissions from the plants are not usually under any significant pressure, not enough to turn a turbine anyway, so to attempt to put a turbine on the top of the chimneys would be pointless.",
"I am an engineer who works for a company that designs power plants. The most popular plants being built right now are called combined cycle power plants, it is a combination of using gas turbines and steam turbines. \n\nThey work by having one or multiple industrial (power) gas turbines that produce electricity at around 30% efficiency. Meaning that only 30% of the energy in the fuel, mainly natural gas, is used to produce electricity. The waste gas of a gas turbine has a lot of energy in it. Typically the temperature is between 1000 - 1200 F. This is where the \"combined\" portion comes into play. The hot waste gas is sent through a Heat Recovery Steam Generator (we call them HRSG, pronounced \"her-seg\"), where high pressure steam is generated and sent to a steam turbine to produce more energy. By including the HRSG and steam turbine the overall efficiency goes up to around 50%. \n \nWhether or not a company wants a combined cycle or just leave it at using gas turbines only (simple cycle) comes down to a number of things. A major factor is the cost of the combined cycle.\n\n_URL_0_\n"
]
}
|
[] |
[
"http://imgur.com/3MKIAFc"
] |
[
[],
[
"http://en.wikipedia.org/wiki/Heat_recovery_steam_generator"
]
] |
|
86gjhj
|
why are smartphones vertically oriented screens by default and design, yet all other forms of screens and displays are all designed horizontal?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/86gjhj/eli5_why_are_smartphones_vertically_oriented/
|
{
"a_id": [
"dw4vby2",
"dw4vco4"
],
"score": [
10,
3
],
"text": [
"Have you ever tried holding your phone horizontally with one hand to use it?",
"Smart phones go into people's hands and a vertically oriented screen is much easier to hold and operate than a horizontally oriented screen. Just try holding a phone horizontally with one hand and see how it works out."
]
}
|
[] |
[] |
[
[],
[]
] |
||
210d62
|
Do Religious Scholars Take the Gospel of Judas Seriously?
|
When it was first translated and published, it made headlines, but now it's kind of disappeared. Do people still study it? Why hasn't it made a larger impact?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/210d62/do_religious_scholars_take_the_gospel_of_judas/
|
{
"a_id": [
"cg8hols",
"cg8jwwd",
"cg8nyy5"
],
"score": [
20,
8,
5
],
"text": [
"The Gospel of Judas gets a good deal of action in academic circles devoted to the study of ancient Christianity, as /u/anoldhope mentions. (Take a look around [JSTOR](_URL_2_) or [Google Scholar](_URL_3_), for instance.) In fact, it gets just as much scholarly attention as any of the many [other ancient, non-canonical gospels](_URL_6_).\n\nAs for GosJudas' lack of \"impact\" in modern religious practice, that depends on several factors. (**N.B.:** I am a Christianity scholar, so I will limit my discussion to modern Christianity.) \n\nIn Christianity, the focus has historically been placed on the canonical New Testament, and any books outside that canon were treated with scorn and condemnation. \n\nMany modern Christians (specifically those from conservative traditions) maintain the same scorn towards these other Christian texts. Other modern Christians (usually, those who are more progressive) do not actually feel any animosity towards ancient, non-canonical Christian literature, but still neglect it, because of the longstanding focus on the canonical NT. Finally, a somewhat smaller portion of modern Christianity actively embraces non-canonical literature (as exemplified by the *[New New Testament](_URL_1_)*.)\n\n**Further reading:**\n\n-On the varieties of ancient Christianity, see Bart Ehrman's books *[Lost Christianities](_URL_0_)* and *[Lost Scriptures](_URL_5_)*.\n\n-For a conservative Christian reaction to the Gospel of Judas, which typifies the tradition's views on non-canonical gospels in general, see Albert Mohler's blog post, [\"From Traitor to Hero? Responding to 'The Gospel of Judas.'\"](_URL_4_)\n\nEDIT: Fixed a typo.",
"Scholars still study it. In fact, I gave a paper (partially) on it at an academic conference not much more than a year ago. :P\n\nI think it probably *has* made a bigger impact than you'd think. The general public tends to be pretty gullible to sensationalism - of the Dan Brown variety or whatever. I'd imagine some non-Christians (and New Age-y types who see some \"spiritual\" truth in Christianity) probably have some notion that this is a text which is a viable alternate to the \"orthodox\" gospels...and they may think that Big Bad Orthodoxy suppressed it (for theological/political motives or whatever). In other words, they may have some idea that this gospel represents a \"truth\" on the same level as (or perhaps higher than!) the one that the other *canonical* gospels do.\n\nIt's certainly made less of an impact among conservative Christians. I suspect that once these people have some notion that this represents a challenge to their beliefs that needs to be confronted, they'll investigate the context in which this gospel emerged and - well - *discover the context*. \n\n(I guess I should say that I'm an atheist/antitheist - I'm just trying to delve into the psychology and sociology of its reception.)\n\nBasically, people who look into the context of GJudas will find that it's a product of a particularly idiosyncratic Christian tradition that was quite far removed (temporally, ideologically, geographically, etc.) from the circles that wrote the earliest canonical gospels. Hell, the extant fragments of Judas aren't even in the same *language* as the NT (although many these Coptic texts are hypothesized to be translations of Greek originals). \n\nOne last note: even though this gospel may be thought of by some as a \"competitor\" to orthodox Christianity, when you actually think about it, there are obvious major elements here that represent a sort of apologetics for a strand of \"orthodox\" Christianity, in a way. As opposed to the (potential) embarrassment of the Messiah himself being betrayed by one of his own disciples, instead, in GJudas, you find the idea that *this was Jesus' plan all along*.",
"You may also want to post this question in[/r/AcademicBiblical/](_URL_0_)"
]
}
|
[] |
[] |
[
[
"http://www.amazon.com/Lost-Christianities-Battles-Scripture-Faiths/dp/0195182499",
"http://www.amazon.com/New-Testament-Combining-Traditional-Discovered-ebook/dp/B008LQ1B44",
"http://www.jstor.org/action/doBasicSearch?Query=gospel+of+judas&acc=on&wc=on&fc=off",
"http://scholar.google.com/scholar?hl=en&q=gospel+of+judas&btnG=&as_sdt=1%2C16&as_sdtp=",
"http://www.albertmohler.com/2006/04/07/from-traitor-to-hero-responding-to-the-gospel-of-judas/",
"http://www.amazon.com/Lost-Scriptures-Books-that-Testament/dp/0195182502",
"http://en.wikipedia.org/wiki/List_of_Gospels"
],
[],
[
"http://www.reddit.com/r/AcademicBiblical/"
]
] |
|
faqhp6
|
the difference between pressure and compression?
|
As I understand it fluid can't be compressed, but they can be pressurized. How is this possible? What's the difference?
I get how a fluid can be pressuring a tank containing air. But what about, as an example, in a pump where there is no air?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/faqhp6/eli5_the_difference_between_pressure_and/
|
{
"a_id": [
"fizrald",
"fizsbma",
"fj0wq2h"
],
"score": [
10,
7,
2
],
"text": [
" > \tAs I understand it fluid can't be compressed\n\nAnd that is where you went wrong, any fluid can be compressed. Any material at all can be compressed of course.\n\nFluids are often said to be incompressible because they take a lot of force to compress even a little bit, but it is a simplification which isn't strictly accurate. Many engineers new and old take such simplifications to heart and don't understand which are approximations to make calculations easier under normal conditions.",
"pressure is force per area and compression is a change in volume. Air which is a fluid can absolutely be compressed and pressurised. But water which is a fluid can be pressurised and can also be compressed but at very miniscule amounts so it's just taken as not compressed at all. Liquid is pressurised by fitting as much of it as possible into a tank and seeing how hard it is pressing against the walls.\n\nIn a pump, it is pushing liquid as hard as it can. So if you were to stand in front of that jet of liquid, it is how painful it will be. So the pressure is determined by how much force is used to push out the water to cause that pain.",
"Pressure is a force over an area, whereas compression is squeezing of something. Compression is a byproduct of pressure.\n\nHowever when it comes to a tank, how the pressure is applied will determine if you get compression or expansion.\n\nPositive pressure inside of the a tank will cause it to expand. Negative pressure inside of a tank (otherwise known as a vacuum) will cause it to compress/collapse."
]
}
|
[] |
[] |
[
[],
[],
[]
] |
|
3wbe02
|
Did ancient people really get captured by marauding bands of slavers?
|
[deleted]
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/3wbe02/did_ancient_people_really_get_captured_by/
|
{
"a_id": [
"cxv42wm"
],
"score": [
3
],
"text": [
"Yes, certainly. If you want a good real-life version of the Gladiator scene we have Julius Caesar's capture by pirates. These pirates would capture people and sell them as slaves, often to rich Romans. \n\nHowever, if they happened to catch an important person, such as Caesar, they ransomed them instead of forcing them to work as some agricultural slave (or being forced to fight in the arena!). These important captives were much more valuable being ransomed than simply being sold as a slave. Poor people had no such luck.\n\n[Here](_URL_0_) you can read Plutarch's version of the incident."
]
}
|
[] |
[] |
[
[
"http://www.livius.org/sources/content/plutarch/plutarchs-caesar/caesar-and-the-pirates/"
]
] |
|
6qr25h
|
how do other countries come to know if a nation has conducted a missile test?
|
Nuclear and non-nuclear.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/6qr25h/eli5_how_do_other_countries_come_to_know_if_a/
|
{
"a_id": [
"dkzceum"
],
"score": [
2
],
"text": [
"In the case of North Korea, the US probably has a satellite pointed at the country 24/7 to detect missile launches. Maybe some other detection equipment based in Japan and South Korea too"
]
}
|
[] |
[] |
[
[]
] |
|
679wce
|
Are there any examples of positive cooperation between the Soviet Union and the USA during the Cold War?
|
Many of us know about the many conflicts between the two great powers, from regional wars to the nuclear arms race to chess matches. But what about positive, cooperative moments... were there any?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/679wce/are_there_any_examples_of_positive_cooperation/
|
{
"a_id": [
"dgq6vc8"
],
"score": [
2
],
"text": [
"There was the Apollo-Soyuz Test Project that led to a joint US-Soviet space mission in 1975. ASTP's value in terms of scientific or engineering progress was extremely questionable, but it certainly qualifies as a \"positive, cooperative moment.\" One could argue that that first instance of working with the Russians in space helped lay the groundwork for the International Space Station. "
]
}
|
[] |
[] |
[
[]
] |
|
5gt3dv
|
Is it known who shot down the plane that triggered the Rwandan genocide?
|
On April 6, 1994 a plane carrying Rwandan president, Juvénal Habyarimana and Burudian president, Cyprien Ntaryamira was shot down triggering the Rwandan genocide.
I have read many conflicting accounts as to who is believed to have been responsible.
I thought this was wrapped up after reading an article some years ago [clearing current President Kagame's Tutsi forces](_URL_1_) from the assassination, but then saw something this year [indicating France still believes Kagame's forces](_URL_2_) might have been involved.
I know [there is a book](_URL_0_) that investigates France's role in the Rwandan genocide, like continuing to supply weapons to the Hutu-dominated army, and that there is bad blood between France and Kagame's government today.
But what is the prevailing opinion amongst historians on who is responsible for the downing of that airplane back in 1994?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/5gt3dv/is_it_known_who_shot_down_the_plane_that/
|
{
"a_id": [
"dav2r4n"
],
"score": [
68
],
"text": [
"I asked a similar question a week ago! If I may ask a follow up question, why was it that so much of the world almost seemingly refused to get involved and even turned blind eye to the Rwandan Genocide? \n\nWhy did countries like the U.S. And Europe and even local surrounding countries abstain from trying to stop the violence occurring? "
]
}
|
[] |
[
"https://www.amazon.com/Silent-Accomplice-Frances-Rwandan-Genocide/dp/1780767722",
"http://www.bbc.com/news/world-africa-16472013",
"http://www.bbc.com/news/world-africa-37613315"
] |
[
[]
] |
|
4vedlc
|
What were ancient Roman parties like? Describe the most opulent/crazy one.
|
[deleted]
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/4vedlc/what_were_ancient_roman_parties_like_describe_the/
|
{
"a_id": [
"d5yqw2o"
],
"score": [
2
],
"text": [
"You should read the feast of Trimalchio. It's not about orgies and is more satire and mocking of the extravagance of Roman elites.\n\nIn this case it is mocking the faux sophistication of Trimalchio (a former slave who has now become quite wealthy) as he hosts a dinner party but repeatedly commits mistakes which actual educated cultured Romans would notice but of which Trimalchio is oblivious of.\n"
]
}
|
[] |
[] |
[
[]
] |
|
3za2p6
|
how do thermal optics pick up heat signatures from such large distances away?
|
Weapon sights, tanks, aircraft etc.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3za2p6/eli5_how_do_thermal_optics_pick_up_heat/
|
{
"a_id": [
"cykdy7p",
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"cykhl43",
"cykjnu6",
"cyklet1"
],
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8,
3,
2,
2
],
"text": [
"if i understand this correctly, its basically just shifting the infra red spectrum so it can be seen. (electronically, with a sensor and a screen)\n\n_URL_0_\n\n\nits always there, we just are not equipped to see it.\n\n\nlife would be weird if we could see somewhere up to fm frequencies.\n\n\n_URL_1_\n\n\nsuprisingly eli 5",
"All objects are glowing all the time due to the temperature they are at. It just so happens at room temperature they are too cold to emit light we can see. If you heat an object, it will eventually glow a colour you can see. You can see a candle or light bulb or molten metal or the sun. You can see these glowing from a large distance away, as can a camera designed to see what a human sees. All thermal optics are is cameras that pick up light we can't see, they can see heat signatures from distance the same way you can see a candle from a distance. In fact, they can do it better as their optics can be better designed for range the same way a camera with the right lens and sensor can see far away better than you. ",
"When I pick up a warm cup of tea, I don't feel that it's warm until my hand is only a centimetre or two away. This is not because the warm teacup is only radiating heat to a distance of a few cm, it's because I, as a human, lack the sensory system to sense the heat at a greater distance. \n\nIt turns out that radiation in the infra red spectrum travels quite a distance - much like light does! It can be reflected, hidden and even focused! \n\nThermal imagers are electronic devices that are very sensitive to wavelengths in the infra red spectrum, and after processing, the data from these imagers can be presented to us as an image that Humans can see. They just show us what was already there, even though we couldn't see it.\n\nIf you have the means, pick up a thermal imager for your mobile phone. There are a few models available - I have experience with a model from FLIR Systems called the FLIR One. They cost a few hundred bucks, which is historically unprecedented for this kind of technology.",
"Every object on earth emits thermal radiation, from your toes, to a generator, or in this case the enemy soldier. The job of an infrared detector is to receive this radiation and convert it to an image for the user to see. Being able to view an image at a distance relies on a) the resolution of the detector (the more pixels, the more accurate the readings) as well as b) the Field of View of the imager. Typically a camera used on a tank, for example, would have a very narrow FOV as to measure at a distance. \n\nSource: I'm a certified Thermographer. ",
"To ELY5: Heat can be visible as long wavelength infrared light. Much like a visible light camera, infrared cameras use a lens which is coated with special materials that allow it to bend, or refract, this long wave length infrared light onto a sensor that detects the long wavelength infrared as heat. The camera can then render this heat image as a series of light or dark areas on a normal LCD or OLED display or using various colors. \n\nDetailed explanation: \nHeat is visible as long wavelength infrared. Infrared light, like visible light can be bent by a lens and focused. This is actually a really interesting question because some materials are transparent to visible light, but opaque to infrared light and some lenses focus visible light but don't focus far infrared light. \n\nInfrared refraction is achieved with a somewhat normal lens shape, but by doping and coating the lens with materials like silicon, zinc oxide, germanium, etc, which change the materials index of refraction and cause it to refract long wavelength red light better. \n\nThe thermal imaging sensor can then get a very clear view of the 10-1000 nano-meter light arriving, and it can then render this in visible light using the LCD or OLED display. \n\nJust like regular light cameras, the smaller the opening that light passes through, the smaller and cheaper the lens can be made with the ultimate being a pinhole camera which has no lens at all. But the more sensitive the camera, the more light/infrared light it must let in which means larger diameter lenses, which means more elements and perfect tolerances to make sure all the light or infrared light arrives at the same time to the sensor. "
]
}
|
[] |
[] |
[
[
"https://upload.wikimedia.org/wikipedia/commons/thumb/f/f1/EM_spectrum.svg/2000px-EM_spectrum.svg.png",
"https://www.youtube.com/watch?v=FjHJ7FmV0M4"
],
[],
[],
[],
[]
] |
|
2mkma8
|
What were the attitudes of Orthodox Russian rulers towards the Crusades and the Crusaders?
|
I understand that the Russian Grand Princes of the 11th and 12th century had connections with the Byzantine Greeks, and that they interacted with Eastern European Catholics. I'm just curious as to the opinions of Russian Princes towards the crusades. Did they agree with the idea of a "Holy War" that the crusaders followed, or did they see it as a foolish venture?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2mkma8/what_were_the_attitudes_of_orthodox_russian/
|
{
"a_id": [
"cm58pm9"
],
"score": [
9
],
"text": [
"As a follow-up, how Christianized was late 11th century Russia? Was Orthodox Christianity the religion of the majority of people west of the Urals?"
]
}
|
[] |
[] |
[
[]
] |
|
1mte1t
|
why do i feel depressed at random times for no reason?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1mte1t/eli5_why_do_i_feel_depressed_at_random_times_for/
|
{
"a_id": [
"cccfx2h"
],
"score": [
4
],
"text": [
"You have no history under this name. Are you male, female, have a family history of depression, etc? I don't think any one can say much about you specifically without more info. That and you should see a doctor as \"medical\"advice really shouldn't be given on redit."
]
}
|
[] |
[] |
[
[]
] |
||
595k0n
|
why u.s. conservatives are so against abortion but generally the first to gripe about families with multiple children on welfare.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/595k0n/eli5_why_us_conservatives_are_so_against_abortion/
|
{
"a_id": [
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"score": [
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5,
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"text": [
"It generally goes to a perception of responsibility. A key conservative principle is that people should be responsible for their own actions and behavior. And children are a part of this; if a woman becomes pregnant, she should carry the child to term and ensure for its future. If you have children, you should be able to support them. That is the key conservative view on this.",
"Because they are honoring a set of principles:\n\n1. the fetus deserves protection as a living thing.\n2. it's not fair to others to create economic advantage for some without the hard work put in by the rest of us.\n\nYou too have principles that result in \"tension\" - where upholding one leads to pushing against another. For example, I believe as an entrepreneur that I ought to be able to create a company like I want to and hire people that I want to hire and pay them what I want to. I also believe we need to have an organized system of immigration - these things are total odds. I also believe that we need to protect rights of those who have been historically screwed and that I shouldn't be allowed to only hire white men like myself beyond some point. Tension. Part of political life. \n\nYou're asking of those you disagree with to meet a bar of consistency based entirely on your framing of the issues. These are independent considerations based on primary principles to one audience, and thinking of it as \"stupidity\" doesn't further our ability to find common ground.\n",
"I don't agree with them, but it is based on a consistent view (or principle) that people should be self sufficient and personally accountability for their decisions. The idea is that if you made the choice to have unprotected sex, you should bear the consequence of that choice. Aborting the fetus (which most conservatives, especially religious conservatives, consider to be a child) is an immoral out for the decision you made in the first place. As for welfare, it is entirely consistent to believe people should be accountable for their own lives to believe that a family should work and take care of themselves, rather than have government take care of them. Again, this is not my personal view, but I understand the position.",
"There is the belief that a fetus is living at the moment of conception (and in some cases, even before, so contraceptives can be forbidden - this is generally not a view expressed by most political conservatives though.) This view is usually driven by a religious belief - many conservatives view the status quo as being better than uncertain change, and family roles as being the most important to a stable society.\n\nThe economic aspects boil down to a few basic principles.\n\n* Economic outcomes are determined by the person, people should be given the opportunity to succeed but shouldn't be prejudiced in one way or another by government support.\n\n* The government should be small and efficient; a welfare state often isn't. \n\n* The belief that welfare is used by people that are leaches on society, and that it is a negative to society.\n\nA lot of these policies make sense when you think about the motivations, but they rarely work in practice.\n",
"A conservative would say to not take on/perform a task you are incapable of seeing through. More simply put, if you are not prepared for the possible outcomes, do not take the risk i.e. if you can't take care of a kid, don't go around having promiscuous, unprotected sex. Terrible analogy coming up here, but you wouldn't encourage someone to take on car payments from a dealership if you, in fact, knew they could not afford it. The same principle applies here, except it's a living, breathing person and should therefore be taken even more seriously than a car. People want all the benefits of sex but none of the responsibility. That ideology pretty much permeates throughout most of American culture in everything we do, which is why we, as a country, are so fucked. The very same ideology is why conservatives are mostly against welfare. Too many people reaping the benefits of it with zero responsibility. Everyone else deals with the responsibility/repercussions of it. In terms of abortion, the defenseless child, who has zero choice, deals with the repercussions. It comes down to selfishness at the end of the day, and people being sick and tired of it.",
" > Don't post to argue a point of view.\n\nThis post has been removed. Possibly try /r/nostupidquestions, or if you want to have your view changed try /r/changemyview.",
"These types of questions about conservatives always show up on reddit. It really shows how little understanding people have for the conservative mindset. \n\nWith conservatives, it's all about the principle of the matter. They don't see things like welfare as a means to an end. Dr. Thomas Sowell does a good job of explaining any questions someone might have about modern American conservatism. \n\nThis video sort of explains your question. \n_URL_0_\n"
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[],
[
"https://www.youtube.com/watch?v=2GklCBvS-eI"
]
] |
||
acuypg
|
why do certain bugs and glitches appear on seemingly random occations in some programs?
|
What I mean is that there should be a trigger for such events.
And if faults in the codes can appear at complete random, why?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/acuypg/eli5_why_do_certain_bugs_and_glitches_appear_on/
|
{
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],
"text": [
"The dont appear at random, but after a series of events / when the game is brought inr a certain state that triggers the bug.\n\nGames and programs are made so complex these days, that its nearly impossible to test each and every permutation / state the game can be in",
"not necessarly\n\nmore often than not a bug is merely an unforseen execution path that the programmer hasnt accounted for\n\nthey seem random, especially on larger program because more complex programs deal with so many variations of state and data that an unforseen result in somethnig seemgly innocuous can cascade into a full program crash if it happens in just the right spot.Them ost common sort of bug is what's called \" imporper validation\" aka checking if the input is what the program expect ot receive.\n\nat the end of it aany bug is merely a mistake by the programmer that wasnt accounted for, o such thnig as a \" random\" bug"
]
}
|
[] |
[] |
[
[],
[]
] |
|
1p7kgy
|
Was the Isthar gate and it's surrounding walls ever used in defence under a siege?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/1p7kgy/was_the_isthar_gate_and_its_surrounding_walls/
|
{
"a_id": [
"cd03uio"
],
"score": [
2
],
"text": [
"It depends on which Isthar gate you mean. Babylon had eight main gates, that were named after the closest temple to that gate. Babylon also fell to the Kassite and Assyrians after the time of Hammurabi, but before the rise of the Neo-Babylonian Empire. These attacks on Babylon are not well documented so it is uncertain if these attacks focused on the Isthar gate or not. However, it is the most likely axis of advance for an Assyrian army that was attacing Babylon. \n The Isthar gate that most people remember is the glazed brick Isthar gate that Robert Koldway excavated in the early 20th century. The glazed bricks from the lowest courses were well preserved and formed the basis for the rebuilt Isthar gate in the Pergamon Museum in Berlin. That gate was built during the reign of Nebuchadrezzar, circa 600 BC. That gate was at the northern end of the Processional Way inside Babylon. Nebuchadrezzar also had a large fortress built around the north side (outside) of that gate. So the artistacly famous Isthar gate was no longer part of the outer wall of Babylon. Also, when Nabonidus was the ruler of the Neo-Babylonian empire, he was less powerful than Nebuchadrezzer. Nabonidus' religious reforms were not that popular, the Persian king Cyrus was able to undermine Nabonidus' authority with a long term and successful propaganda campaign, and in 539 BC, when the Persians overran Babylon, they did so without a major fight. The Babylonians greeted Cyrus as a liberator, at least in the Persian sources on the fall of Babylon. So, the Isthar Gate at the Pergamon museum almost certainly did not withstand a siege. \nSource: John Oates \"Babylon\" "
]
}
|
[] |
[] |
[
[]
] |
||
28jjzs
|
why is a drone strike considered invariably worse than an f-16 pilot dropping a 500lb jdam?
|
In the exact same situation, why do a lot of people believe drone strikes to be worse?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/28jjzs/eli5_why_is_a_drone_strike_considered_invariably/
|
{
"a_id": [
"cibiqpi",
"cibirae",
"cibl1pp",
"cibolvy"
],
"score": [
7,
7,
10,
12
],
"text": [
"The more that people are removed from killing, the easier it is to lose ethical perspective. Currently, that doesn't seem to be an issue but imagine a world where drones had such good AI that people just had to press a button to kill someone--they'd become very detached from the killing. ",
"You don't send a fighter pilot into another country you are not at war with to bomb a village. that will just not happen, mostly because of the political concequences if the pilot gets stranded.\n\nFor some reason, the millitary is fine with doing the same with drones.",
"They wouldn't any different in that situation. However, armed drones are not used like F16's.\n\nDrones are the centerpiece of the United States assassination campaign against Islamic militants. Drones are typically not conducting missions in support of military operations like an F16 would, rather they are conducting surveillance and isolated strikes against suspects, who typically do not reside anywhere near an active battlefield.\n\nDrones are really just technology. I would imagine most people take more issue with the US running a global assassination program rather than the fact a UAV is doing it.",
"When the crossbow was first invented, it allowed a grubby peasant to kill a noble knight. For a while people, mostly those who relied on knights, labeled crossbows as \"dishonorable\", and try to discourage their use. Eventually, warfare adapted and moved on.\n\nThat is kind of where we are with drones. People are more comfortable with a standard air strike, because a pilot is at risk and there is some sense of \"fairness\". But because drones are new and spooky, complaints against them get more airtime."
]
}
|
[] |
[] |
[
[],
[],
[],
[]
] |
|
49rwo3
|
What is the Banach-Tarski paradox?
|
Re: _URL_0_
I don't understand the paradox here. Uncountable infinity divided by two equals uncountable infinity, that seems pretty obvious on the face of it. What makes this special?
|
askscience
|
https://www.reddit.com/r/askscience/comments/49rwo3/what_is_the_banachtarski_paradox/
|
{
"a_id": [
"d0uh7o8"
],
"score": [
51
],
"text": [
"Of course there exists a bijective function from the set of one sphere to the set of two spheres. That is, we can break up a sphere into uncountably many points, and rearrange the points into two sphere. So we're essentially forgetting everything about the first sphere, except how many points it has, and then artificially creating two new spheres because these have the same number of points. That's not super interesting. You can take a line segment and stretch it to get a line segment with double the length. While we're not breaking the line down into it's base points, we are distorting and skewing it. So that's not super interesting either. Both of these kinds of operations allow us to create volume, so it's not surprising when we get larger volumes.\n\nBanach-Tarski says that you can take a sphere, cut it up into five pieces, then using only rotations and translations (ie without stretching or skewing any of the pieces) we can put them back together in such a way that results in two spheres identical to the first in every way, doubling the volume. All of the geometry is preserved, yet we double what we started with. None of the operations that we use allow us to create new volume, we're just rotating and translating these pieces, yet we do create new volume. This *is* interesting.\n\nIt's a paradox because it *shouldn't* happen. It's even a surprise to people who know all the exact mathematical definitions. Rotations and translations do absolutely nothing to volume, yet Banach-Tarski proves that we can use rotations and translations to double volume. There's something nontrivial and paradoxical going on.\n\nThe issue is the existence of \"[Non-Measureable Sets](_URL_0_)\". These are sets that do not have a volume. Their volume isn't zero, they have no volume in the sense it doesn't even make sense to *talk* about their volume. They break the idea of \"volume\". We cannot write these sets out or construct them in any meaningful way, their existence is just guaranteed by of the [Axiom of Choice](_URL_1_). It should be noted that the existence of these kinds of sets is not a trivial result.\n\nWhat is happening is that we take the sphere and break it up into five non-measureable sets. While the geometry of the sphere is preserved in this, points in each piece do not move relative to each other, the instant that we break it into non-measureable sets we end up losing the information about the volume of the sphere. Using rotations and translations will then just preserve the non-measurableness of the sets. We then reassemble the pieces in a way that creates two spheres identical to the first. No rules were broken because the rotations and translations had no volume to preserve, and the five non-measureable pieces do not even remember their original volume so we are free to reassemble them in a way that gives us more volume than when we started with.\n\nBanach-Tarski is not just about sizes of infinity. That stuff is simple. Banach-Tarski is a nontrivial mixture of Measure Theory (which tells us what volume actually means), the Axiom of Choice (which is guarantees that we can choose elements in a specific way) and some nontrivial things in Group Theory (which tells us how to use rotations and translations)."
]
}
|
[] |
[
"https://youtu.be/s86-Z-CbaHA"
] |
[
[
"https://en.wikipedia.org/wiki/Non-measurable_set",
"https://en.wikipedia.org/wiki/Axiom_of_choice"
]
] |
|
d992ms
|
Why did clock and watch makers decide on only 12 hours instead of 24? How did a 12 hour clock face become standard?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/d992ms/why_did_clock_and_watch_makers_decide_on_only_12/
|
{
"a_id": [
"f1ljr4n"
],
"score": [
52
],
"text": [
"It has to do with the cost of building clocks and clock towers. 12 hour clocks are cheaper.\n\nI explained it in some detail in this previous thread [here](_URL_0_)."
]
}
|
[] |
[] |
[
[
"https://www.reddit.com/r/AskHistorians/comments/a3xkuh/whats_the_historical_reason_for_am_and_pm/"
]
] |
||
85e0he
|
To what extent did the Hittites make use of iron?
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/85e0he/to_what_extent_did_the_hittites_make_use_of_iron/
|
{
"a_id": [
"dvxdgt3"
],
"score": [
6
],
"text": [
"Iron is first attested in Anatolia in the third millennium BCE. An iron dagger with trace amounts of nickel was found in the \"royal\" tombs of Alaça Höyük (ca. 2300 BCE). Iron is better known, however, from Old Assyrian texts (2000-1750 BCE). During this time period, Assyrian merchants regularly traveled to Anatolia to trade textiles and other Mesopotamian products in exchange for precious metals. Iron was about forty times as valuable as silver in the Old Assyrian period. \n\nIn the Old Hittite period (1600-1450 BCE), iron was used especially for spears and sceptres during religious ceremonies, which served as symbols of the king's power. By the Middle Hittite period (ca. 1450-1350 BCE), the Hittites were also using iron for ceremonial axes, the king's lituus (a curved staff), and jewelry. An excerpt from the KI.LAM festival: \n\n > Then the palace spear-man takes the iron spear from the king and gives it to the palace official. \n\n > The first of the palace officials takes an iron axe from the last of the palace spear-men and gives it to the supervisor of the palace officials. The supervisor of the palace officials gives it to the king. The place on the axe where the engraving of the Storm God is, he turns that side toward the king...\n\nAttestations of iron in Hittite texts really take off in the Hittite empire period (1350-1180 BCE), however. By this time iron was also used for cult idols, knives, daggers, and swords. Its use for jewelry declined, suggesting the metal was not quite as rare and impressive as it had been. That it was now measured by the mina like copper rather than by the shekel like gold and silver (as it had been previously) supports this conclusion. \n\nThe Hittites sometimes referred to \"black iron\" (AN.BAR GE6), which is possibly meteoric iron. A ritual for the construction of a palace refers specifically to the use of meteoric iron. \n\n > They have laid foundations of silver and gold. The gold they brought from Birunduma. The silver they brought from Kazza. The lapis they brought from Mount Takniyara. The marble they brought from Kanisha. The jasper they brought from the land of Elam. The diorite they brought from the earth. The black iron of heaven they brought from heaven. Copper and bronze they brought from Mount Taggata in Alašiya.\n\nIron was worked by smiths (LÚ.SIMUG). The first step was to sort the raw material and purify it. The metal was then cast (*lahuwai*, \"to pour\") into ingots. Three types of iron are known - iron (AN.BAR), iron \"from the furnace\" (AN.BAR *ŠA* _URL_0_), and \"excellent\" iron (AN.BAR SIG5). \n\nIron does not seem to have been a significant metal for commerce and taxes. Andreas Müller-Karpe calculated the frequencies of metals in Hittite economic texts (\"Anatolische Bronzeschwerter und Sudosteurop\" in *Festschrift fur Otto-Hermann Frey zum 65. Geburtstag*, pp. 74-78). He found that 25% of taxes were paid in metal; of these taxes, 60%, 13%, and 8% were paid in copper, silver, and tin, respectively. Gold and iron had only one attestation apiece. \n\n**Further reading**\n\nMuhly, J.D. 1980. *The Coming of the Iron Age*.\n\nWaldbaum, Jane. 1978. *From Bronze to Iron. The Transition from the Bronze Age to the Iron Age in the Eastern Mediterranean*. \n\nYalçın, Ünsal. 1999. \"Early Iron Metallurgy in Anatolia.\" *Anatolian Studies* 49: 177-87.\n"
]
}
|
[] |
[] |
[
[
"KI.NE"
]
] |
||
8fn4sv
|
How are mineral seedbeds created?
|
[deleted]
|
askscience
|
https://www.reddit.com/r/askscience/comments/8fn4sv/how_are_mineral_seedbeds_created/
|
{
"a_id": [
"dy5im1i"
],
"score": [
3
],
"text": [
"A mineral seedbed is a growth medium that lacks significant amounts of organic matter.\n\nWildfire can create seedbeds like this by combusting all of the organic material out of topsoil, leaving behind a \"sterile\" mineral based layer for things to grow in. Areas with high erosion, desert climates, or limited existing vegetation can also have mineral seedbeds.\n\nSome plants thrive in this medium because they are readily available to use inorganic materials for growth. These plants have little competition in the seedbed until the ecosystem builds up organic material."
]
}
|
[] |
[] |
[
[]
] |
|
1xjifh
|
who benefits from sending computer viruses out into the world?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1xjifh/eli5_who_benefits_from_sending_computer_viruses/
|
{
"a_id": [
"cfbwfuq",
"cfbwht3",
"cfc6ynq"
],
"score": [
9,
2,
2
],
"text": [
"Depends on what it does.\n\nSome malware is designed to make the creator money. This includes things like the \"scareware\" programs that pop up, tell you that you have a virus and need to pay them $30 to clean it up. There are also viruses that try to steal your credit card information when you shop online, so they can sell that on the black market.\n\nOther malware is a \"just because\" type thing. Someone has found a flaw in the way the computer is programmed and wants to show it off. There's an immense personal satisfaction in creating something from nothing, and I'm sure the creators of malware that made the news like the Blaster worm are quite proud of their 15 minutes of fame, even if they personally were never identified. \n\nThen there's the espionage malware- stuff like Stuxnet that was designed specifically to infect Iran's nuclear reactors that was likely motivated by patriotism, and possibly sanctioned by one or more governments.",
"Believe it or not... [The mob](_URL_0_).\n\nMalware writers often sell their botnets (their network of infected computers) to organized crime who use it for financial crimes.",
"There's malware called \"ransomware\", what it does is encrypt a victims computer and demand a sum of money for the decryption key. Failure to pay will render the files inaccessible. It's making quite a lot of money considering it targets companies. Losing the company data is probably much more costly than the price of obtaining the encryption key."
]
}
|
[] |
[] |
[
[],
[
"http://allinnetworks.com/blog/225-virus-writing-and-organized-crime.html"
],
[]
] |
||
2ccj9e
|
why does the milk at the grocery store expire in 1-2 weeks but the milk at fast food places are good for over one month?
|
I buy a gallon of milk at the grocery store and it expires within a few days to two weeks (if I am lucky to find one this far out). But, I just went through the drive-thru for lunch and this milk doesn't expire for over a month from today. Why?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2ccj9e/eli5why_does_the_milk_at_the_grocery_store_expire/
|
{
"a_id": [
"cje3c6o"
],
"score": [
5
],
"text": [
"It's a different type of milk. You can get UHT milk/long life milk. It lasts longer and is fine for coffee etc but doesn't have the same taste as fresh milk. "
]
}
|
[] |
[] |
[
[]
] |
|
1qo9jk
|
i've deeply cut my finger, what is my body's immediate response to this and what exactly is my skin, muscle and other tissues doing during the healing process?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1qo9jk/eli5_ive_deeply_cut_my_finger_what_is_my_bodys/
|
{
"a_id": [
"cdes3qn",
"cdesegz"
],
"score": [
2,
2
],
"text": [
"Well, your immediate response is pain. The All severed blood vessels will constrict as much as possible to stop blood loss while other vessels proximal to the cut will expand, somewhat bypassing the affected area. \n\nDuring the healing process, as long as everything is bandaged up tightly and in the right place, your body will just repair/regrow new cells to replace the damaged ones and reconnect everything. I'm pretty sure you run into problems if a muscle is mostly/completely severed though. You'll get scarring, which is basically super-fast growing tissue your body makes to close up the hole in you so it can make repairs without (even more) risk of infection.",
"First your blood vessels near your wound tighten to reduce the flow of blood to where you cut yourself. Sticky blood cells called \"plateletes\" clump to eachother and then go to thes ides of your torn blood vessel, followed by clotting proteins holding the platelets in place over where you cut yourself (similar to a plug). The bleeding eventually stops due to blood clots(coagulation) and the \"plug\" becomes a scab. Scar tissue, not as strong as your original skin, will form but will fade eventually due to collagen.\n\nDuring all of this white blood cells are fighting off germs that have entered your blood stream. \n\nRemember, no one loves you as much as your body."
]
}
|
[] |
[] |
[
[],
[]
] |
||
2uwl6c
|
why is having netanyahu speak in washington so controversial?
|
Plenty of foreign leaders have spoken here. Why is this causing a fuss?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2uwl6c/eli5_why_is_having_netanyahu_speak_in_washington/
|
{
"a_id": [
"cocbvgx"
],
"score": [
3
],
"text": [
"I say this with a neutral point of view, not to make a point:\n\nThe Israel/Palestine conflict has led to a number of human rights issues and accusations of war crimes on both sides. Many people are opposed to the state of Israel's existence at all. The majority of foreign leaders who speak in Washington come from states that are universally recognized, and who are not openly associated with many of the terrible happenings in the Israel/Palestine conflict."
]
}
|
[] |
[] |
[
[]
] |
|
a9pa3j
|
What sort of influence did the arrival of European settlers have on the style of warfare practiced in the Natal? What did Zulu military technique look like prior to contact?
|
I asked this some time back, a previous time Africa was a theme, and never got an answer so figured I've resurrect it.
In any case, I certainly know little about Zulu warfare in the first place, and what I do is basically '19th century. My understanding is that their style of warfare underwent a veritable revolution under Shaka Zulu in the early 1800s, changing how the military was organized and implementing the famed 'Bull Horns'. I know that there is some debate on how much it can be said this was *influenced* by the contact with Europeans, and the extent to which that is true certainly interests me, but I'm also especially interested in what the 'before' was.
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/a9pa3j/what_sort_of_influence_did_the_arrival_of/
|
{
"a_id": [
"ecmdphe"
],
"score": [
3
],
"text": [
"To answer your first question:\n\nGuns were present in Natal from the time Shaka Zulu created the Zulu Empire - Shaka even hired/conscripted very small numbers of Europeans with muskets to fight for him, although never in decisive or significant numbers.\n\nThe primary Zulu weapons from the time of Shaka Zulu until the Anglo-Zulu War in 1879 were a throwing spear, the short assegai stabbing spear, and the heavy knobkerry club. The spears would be thrown when the Zulu charge was about 20-30 yards away from the enemy - then the warriors would drive the charge home to use their assegai and clubs.\n\nThe European transition away from flintlock and caplock firearms around 1850-1870 lead to a glut of surplus muskets flooding the world market. A large number of these ended up in Southern Africa by way of traders in Natal and Mozambique. The most common firearm in Zululand by 1879 was the trusty old Brown Bess flintlock musket - by thenb it was so cheap, it could be bought by a Zulu warrior for about the price of a sheep.\n\nThe Zulus did some skirmishing - the \"chest\" of the bull formation would sometimes be preceded by shooters who'd throw down generally inaccurate harassing fire. Other warriors with guns used theirs as a kind of replacement for the throwing spear - they'd fire their guns at short range and then charge in to use their assegai.\n\nI've written more about the subject of guns and Zulu tactics here: \n\n_URL_0_"
]
}
|
[] |
[] |
[
[
"https://www.reddit.com/r/AskHistorians/comments/a6es3u/how_powerful_were_the_zulus_militarily_did_they/"
]
] |
|
4mrdvm
|
why do older phones (like sony ericsson) not start up without sim-card?
|
You could still play games or take photos.
This may look like a double post, but automod messed with the first one after I failed to flair it in 60 seconds or so...
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4mrdvm/eli5_why_do_older_phones_like_sony_ericsson_not/
|
{
"a_id": [
"d3xr78f"
],
"score": [
6
],
"text": [
"Older phones' main functions were provided over the cellular network. They used the SIM to make and receive calls and send and receive text messages. Older phones did not have the concept of WiFi or Apps used for something other than communicating. Hence there wasn't a point of the phone unless it had a valid SIM.\n\nCurrent phones can be used for a plethora of activities like movie editing, recording, playing games, etc. and work over WiFi. So they can be used without a SIM. But at the same time, you cannot send messages or make calls while there's no SIM."
]
}
|
[] |
[] |
[
[]
] |
|
27nfmk
|
Why is it that there is a (approximately?) 50/50 chance of an offspring being male/female?
|
(Most likely grossly simplifying things here) The way I see it, there could be approximately 270 females to every male for the human species, assuming every male/female is fertile (9 months of gestation for a child, approximately 270 days, the male spends every day with a new female and hopefully impregnates her on that day). Obviously we are leaving out cultural ideologies. So why is it that there is an approximately 50/50 split between male and female births, if it could be more advantageous for the species to have more females than males. Are there any species where it is observed that it is more likely that one gender is born over the other?
|
askscience
|
http://www.reddit.com/r/askscience/comments/27nfmk/why_is_it_that_there_is_a_approximately_5050/
|
{
"a_id": [
"ci2jz4t",
"ci2m2jj"
],
"score": [
23,
6
],
"text": [
"[Fisher's principle](_URL_0_):\n\nImagine there exists a population in which the majority of individuals born are female. In this case, it's in a female's long term reproductive advantage to produce male offspring, because it's easy for males to find females to mate with, but hard for females to find males. The result is that any genetic mechanism that allows for females to produce more males than her sisters will tend to spread, and vice versa if males are common, leading to a balance at 50%.\n\nThis balance can be upset, however, if the reproductive value of the two sexes is not equal, i.e. if offspring of one particular sex are *a priori* more likely to have reproductive success even with an even sex ratio (in which case genetic elements that favored an increased frequency of that sex would tend to spread).\n\nAnother thing that can upset this are selfish genetic elements, or \"meiotic drivers\". These genes distort the process of meiosis so that they make it into greater than 50% of the gametes, and thus tend to rise in frequency in the population. They can arise either on autosomes or sex chromosomes, but when they arise on the sex chromosomes, they can impact the sex ratio of the population, even to the detriment of the population's long term well-being. \n\nMore broadly, the fact that an individual genetical element can gain a massive reproductive advantage from cheating during meiosis has led many to speculate whether much of the complicated machinery of genetic recombination is actually partially a defense mechanism to keep these kind of selfish genetic elements from exploiting meiosis. (good sources: citations 4, 12, 13, 15, 16, 19, and 25 in [this preprint](_URL_1_) written by some folks in my lab)",
"On a biological level its because the contents of sperm is created by splitting the chromosomal contents of a cell. So for each cell split, there are two sperm created, and one sperm has an x and the other has a y chromosome. So in each load there are equal amounts of x and y sperm.\n\nWomen of course are xx, so they always contribute an x chromosome, and the winning sperm then determines the gender, and there's always 50% of reach on the race."
]
}
|
[] |
[] |
[
[
"http://en.wikipedia.org/wiki/Fisher%27s_principle",
"http://biorxiv.org/content/biorxiv/early/2014/05/22/005363.full.pdf"
],
[]
] |
|
2crybk
|
Why did Roosevelt issue so many more executive orders in comparison to other presidents?
|
According to [this graph](_URL_0_) posted in /r/dataisbeautiful the number of orders issued by Roosevelt is way higher than any other president to ever be in office. Why?
|
AskHistorians
|
http://www.reddit.com/r/AskHistorians/comments/2crybk/why_did_roosevelt_issue_so_many_more_executive/
|
{
"a_id": [
"cjijidd"
],
"score": [
21
],
"text": [
"First, Roosevelt was in office for 12 years, so the orange bars (number per year) is a more useful measure. And before FDR, executive orders weren't always tracked that carefully.\n\nSecond, a lot of the government regulatory agencies that we now take for granted were *invented* as part of the New Deal. A number of FDR's orders were to set industry output and market shares in the desperate hope that central economic planning could help the nation recover from the Depression.\n\nThird, the exigencies of fighting a world war led to various military and home-front decrees. It's also useful to remember that Roosevelt spent five years before Pearl Harbor maneuvering the US into position to fight the war he could see was inevitable, preparations that isolationists resisted. A lot of those defense preparations and pre-1941 behind-the-scenes aid to Great Britain necessitated executive orders.\n\n[This opinion piece includes some useful historic background.](_URL_0_)"
]
}
|
[] |
[
"http://i.imgur.com/2L3LZh6.png"
] |
[
[
"http://www.forbes.com/sites/jimpowell/2014/01/30/how-president-obama-could-be-swept-away-with-his-executive-orders-that-defy-congress-and-the-courts/"
]
] |
|
7sor51
|
Late medieval/early modern urban geography (?) - how was the population spread in a country in the 1500s?
|
Apologies if this has been asked before - part of my trouble researching this on my own is I'm not sure exactly how to search for it? Beyond the Domesday Book, which is much earlier than I'm curious about but still helpful, not sure where to look.
Basically, I'm interested in a zoomed-out view of the distances and relationships between cities towns and villages in the 1500s, especially in England. I've got a lot of questions - like how far villages tended to be from each other, how much land in the country was simply unoccupied, population sizes and how they were divided between settlements and to what extent they moved... basically I'm really curious about learning more about this sort of thing, but the only books I have/can find are more specific (eg, village life in detail, but also treated more close up/in a vacuum).
Does anyone have sources or info on this sort of thing? Honestly, just a general search term for looking it up would be helpful at this point.
|
AskHistorians
|
https://www.reddit.com/r/AskHistorians/comments/7sor51/late_medievalearly_modern_urban_geography_how_was/
|
{
"a_id": [
"dt6synt"
],
"score": [
2
],
"text": [
"RenlyWHW:\n\nThere are a lot of questions here, but here are a few notes that might help. \n\nFirst, England's population distribution from 1550-1700 was somewhat unusual for Europe, given that London vastly outstripped every other city in size (it became what demographers call a 'primate city,' a city that vastly larger than the next city in a region/country). Spain, the Netherlands, and France, by contrast, had several large urban areas that were more balanced rather than a single sprawling metropolis and a bunch of small merchant towns, as in England. \n\nIf you are interested in population spread across counties, you might look at [this project being conducted at Cambridge] (_URL_0_), where they are figuring out population density at the ancient county level and, even smaller, at the parish level for a variety of dates including 1670. That will give you a sense of population density per square mile at a fairly granular level in different parts of the country. \n\nOne final note: not a lot of land in England by the seventeenth century was truly unoccupied (remember, the whole modern UK is only the size of Oregon; England alone is slightly more than half that). A combination of the expansion of sheep farming in the sixteenth century and the sale and destruction of the great royal forests in the seventeenth century meant that the areas that had been untouched were slowly eroded by farming and forestry. \n\nHope this is helpful!"
]
}
|
[] |
[] |
[
[
"https://www.geog.cam.ac.uk/research/projects/occupations/englandwales1379-1911/"
]
] |
|
3lltto
|
why are computer not used in sports games? for balls/strikes/safe/outofbounds etc...
|
To elaborate... refs arnt 100% accurate, why not just use computer software to determime exactly if the player was out of bounds or not... this technology already exists in baseball for strikes and balls, whats the point of the umpire?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3lltto/eli5_why_are_computer_not_used_in_sports_games/
|
{
"a_id": [
"cv7anki",
"cv7ao8x"
],
"score": [
3,
2
],
"text": [
"It's mostly tradition, umpires don't want to be out of a job, and people in general don't like change. But there can also be a deeper meaning.\n\nTake racewalking as an example, an olympic event where one must move as fast as possible without running, aka without ever having both feet off the ground at the same time. Race officials watch the racers at all times, and if anyone makes 3 mistakes in the run, they're disqualified.\n\nUsing high speed cameras, you can see that professional racewalkers actually do have both feet off the ground on most steps, but it's not detectable by human senses. If the human officials were replaced by robots, the entire sport would be completely changed.\n\nAnd after all, all sports are made of arbitrarily created rules, if you change the rules you can destroy the entire sport (although not many people would miss racewalking).",
"A computer can't make judgement calls. I can't speak for the role of an umpire (Never watched Baseball) but referees also determine whether players are adhering to proper sportsmanship. In rugby for example there are questions of whether tackles are made appropriately."
]
}
|
[] |
[] |
[
[],
[]
] |
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